Patent Publication Number: US-2023152267-A1

Title: Cancer cell detection by monitoring changes in photoresponse of graphene/silicon schottky diode

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of International Patent Application PCT/IB2022/054230, filed on May 6, 2022, and entitled “CANCER CELL DETECTION BY MONITORING CHANGES IN PHOTORESPONSE OF GRAPHENE/SILICON SCHOTTKY DIODE”, which takes priority from U.S. Provisional Patent Application Ser. No. 63/298,666, filed on Jan. 12, 2022, and entitled “GRAPHENE/SILICON SCHOTTKY JUNCTION BASED DEVICE FOR CANCER CELL ANALYSIS”, which are both incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure generally relates to cancer diagnosis, and particularly, to a system and method for real-time diagnosis of cancer cells in a sample via monitoring photocurrent changes of a graphene/silicon schottky junction in the presence of the sample attached to graphene/silicon schottky junction and under light illumination. 
     BACKGROUND 
     Cancer has become one of the greatest challenges of global healthcare. According to the World Health Organization (WHO), cancer is now the second leading cause of death in the world. Glioma, a general term describing primary brain tumors, is the most frequently occurring tumor of central nervous system. Based on the level of malignancy, the World Health Organization (WHO) classifies gliomas as grade I to grade IV. Glioblastoma multiform (GBM) is designated as grade IV and is the most malignant and common primary brain cancer in adults (more than 60%). GBM is known as malignant and invasive cancer with high resistance to various treatments. Most of patients only have 14-15 months of survival after diagnosis and less than 5% will survive for 5 years. In more advanced stages of a diffusely invasive brain cancer, surgery cannot fully remove the invasive cells and this creates recurrence and increased mortality rates. Such an occurrence may be prevented if diagnosis is made possible in the earlier stages of tumor development, where the tumor cannot be visually distinguished. As seen from an increasing number of new cancer cases, and increasing death rates for different cancers of the nervous system, early diagnosis will play a vital role to control, help select the best treatment option, and eventually, decrease the mortality rate of such cancers in the future. 
     In recent years, nanotechnology has created rapid advances in development of various biosensors based on available solid state devices and nanostructures. Among these, carbon nanostructures (carbon nanotubes, graphene, graphene oxide, etc.) have been widely used as sensing platforms for different biological material. Biocompatibility and excellent electrical properties of these nanostructures, along with their low cost and high sensitivity, has prompted their application as both transducers, where they directly interact with target biomaterial, or templates, where they capture and immobilize biological transducers, such as proteins, DNA, RNA, etc. in various biosensors in different studies. However, most of the proposed sensors for cancer cells detection are suitable for biomarker detection. Whereas, there is a need to analyze cancer cells themselves. Furthermore, reliability and validity of results obtained by biomarker detection are the main problem that limits use of biomarkers as a diagnostic or analyzing variable in a clinical trial or in an epidemiologic study. 
     Hence, there is a need for a label-free and real-time sensor, method, and system to detect cancer cells. There is also a need for a highly precise and fast approach for detecting cancer cells in a sample acquired from a person suspected to have cancer utilizing a simply fabricated and non-expensive sensor. 
     SUMMARY 
     This summary is intended to provide an overview of the subject matter of this patent, and is not intended to identify essential elements or key elements of the subject matter, nor is it intended to be used to determine the scope of the claimed embodiments. The proper scope of this patent may be ascertained from the claims set forth below in view of the detailed description below and the drawings. 
     In one general aspect, the present disclosure is directed to a system for detecting Glioblastoma cancer cells. The system may include a biosensor, a light source placed above the biosensor, an electrical stimulator-analyzer device electrically connected to the biosensor, and a processing unit electrically connected to the electrical stimulator-analyzer device and the light source. 
     In an exemplary embodiment, the biosensor may include a semiconductor layer, an electrically passivating layer, two electrodes, and a graphene layer. In an exemplary embodiment, the semiconductor layer may include a silicon (Si) wafer and electrically passivating layer may include a silicon dioxide (SiO 2 ) layer coated on a first portion of the Si wafer. In an exemplary embodiment, the two electrodes may include a first electrode deposited on a second portion of the Si wafer and a second electrode deposited on the SiO 2  layer. In an exemplary embodiment, the graphene layer may be coated on parts of the substrate and the second electrode forming a graphene-Si Schottky junction between the Si wafer and the graphene layer. In an exemplary embodiment, a first side of the graphene layer may be in contact with the Si wafer and a second side of the graphene layer may be in contact with the second electrode. In an exemplary embodiment, the graphene-Si Schottky junction may be configured to put a sample thereon. In an exemplary embodiment, the sample may be in contact with the graphene side of the graphene-Si Schottky junction. 
     In an exemplary embodiment, the light source may include a light emitting device with a wavelength range of 300 nm to 1000 nm. In an exemplary embodiment, the light source may be configured to irradiate a light beam to the graphene-Si Schottky junction with the sample thereon. In an exemplary embodiment, the electrical stimulator-analyzer device may be electrically connected to the two electrodes of the biosensor. In an exemplary embodiment, the stimulator-analyzer device may include an electrical voltage generator and an electrical current sensor. In an exemplary embodiment, the electrical voltage generator may be configured to apply a voltage between the two electrodes and the electrical current sensor may be configured to measure a produced electrical current between the two electrodes responsive to the applied voltage. 
     In an exemplary embodiment, the processing unit may include a memory having processor-readable instructions stored therein and a processor. In an exemplary embodiment, the processor may be configured to access the memory and execute the processor-readable instructions to configure the processor to perform a method. In an exemplary embodiment, the method may include irradiating a light beam in a range of 500 nm to 900 nm to the graphene-Si Schottky junction with the sample thereon utilizing the light source, applying a first voltage of −1 V and a second voltage of −0.05 V between the two electrodes utilizing the electrical stimulator-analyzer device, measuring a first electrical current generated between the two electrodes responsive to the applied first voltage and a second electrical current generated between the two electrodes responsive to the applied second voltage utilizing the electrical stimulator-analyzer device, and detecting a presence of Glioblastoma cancer cells in the sample if a difference between the first electrical current and the second electrical current is detected to be more than 10 nA. 
     In an exemplary embodiment, irradiating the light beam to the graphene-Si Schottky junction with the sample thereon may include irradiating the light beam with a wavelength of 850 nm to the graphene-Si Schottky junction with the sample thereon. 
     In an exemplary embodiment, detecting the presence of Glioblastoma cancer cells in the sample may further include differentiating between T98G Glioblastoma cells and U87 Glioblastoma cells in the sample. In an exemplary embodiment, differentiating between T98G Glioblastoma cells and U87 Glioblastoma cells in the sample may include detecting a presence of T98G Glioblastoma cells in the sample if the first electrical current is less than 1 μA. In another exemplary embodiment, differentiating between T98G Glioblastoma cells and U87 Glioblastoma cells in the sample may include detecting a presence of T98G Glioblastoma cells in the sample if the first electrical current is more than 1 μA. 
     In an exemplary embodiment, the sample may include a biological sample containing biological cells acquired from a person suspected to have Glioblastoma cancer. In an exemplary embodiment, the sample may include a biopsied sample from a cancer-suspicious mass in body of the person, and combinations thereof. 
     In an exemplary embodiment, each of the two electrodes may include a gold (Au) film with a thickness in a range of 50 nm to 200 nm. In an exemplary embodiment, the graphene layer may include a monolayer graphene. In an exemplary embodiment, the system may further include a sample holder. In an exemplary embodiment, the sample holder may be placed around the graphene-Si Schottky junction. In an exemplary embodiment, the sample holder may include one or more sidewalls enclosing an area of the graphene-Si Schottky junction with the sample placed thereon. In an exemplary embodiment, the sample holder may be configured to keep the sample on surface of the graphene-Si Schottky junction, prevent the sample from flowing out of the graphene-Si Schottky junction, and prevent entrance of pollutants or external materials to the graphene-Si Schottky junction. 
     In one more general aspect, the present disclosure is directed to a system for detecting cancer cells. The system may include a biosensor, a light source placed above the biosensor, an electrical stimulator-analyzer device electrically connected to the biosensor, and a processing unit electrically connected to the electrical stimulator-analyzer device and the light source. 
     In an exemplary embodiment, the biosensor may include a semiconductor layer, an electrically passivating layer, two electrodes, and a graphene layer. In an exemplary embodiment, the electrically passivating layer may be coated on a first portion of the semiconductor layer. In an exemplary embodiment, the two electrodes may include a first electrode deposited on a second portion of the semiconductor layer and a second electrode deposited on the electrically passivating layer. In an exemplary embodiment, the graphene layer may be coated on parts of the semiconductor layer, the electrically passivating layer, and the second electrode forming a graphene-semiconductor Schottky junction between the semiconductor layer and the graphene layer. In an exemplary embodiment, a first side of the graphene layer may be in contact with the semiconductor layer and a second side of the graphene layer may be in contact with the second electrode. In an exemplary embodiment, the graphene-semiconductor Schottky junction may be configured to put a sample thereon. 
     In an exemplary embodiment, the light source may include a light emitting device with a wavelength range of 300 nm to 1000 nm. In an exemplary embodiment, the light source may be configured to irradiate a light beam to the graphene-semiconductor Schottky junction with the sample thereon. In an exemplary embodiment, the electrical stimulator-analyzer device may be electrically connected to the two electrodes of the biosensor. In an exemplary embodiment, the stimulator-analyzer device may include an electrical voltage generator and an electrical current sensor. In an exemplary embodiment, the electrical voltage generator may be configured to apply a sweeping range of reverse bias voltages between the two electrodes and the electrical current sensor may be configured to measure a set of produced electrical currents between the two electrodes responsive to the applied sweeping range of reverse bias voltages. 
     In an exemplary embodiment, the processing unit may include a memory having processor-readable instructions stored therein and a processor. In an exemplary embodiment, the processor may be configured to access the memory and execute the processor-readable instructions to configure the processor to perform a method. In an exemplary embodiment, the method may include generating a set of photocurrents in a reverse bias regime through the graphene-Si Schottky junction with the sample placed thereon, measuring the set of generated photocurrents in the reverse bias regime through the graphene-Si Schottky junction with the sample placed thereon, and detecting a presence of cancer cells in the sample if a change in photocurrent within the reverse bias regime is detected. 
     In an exemplary embodiment, generating the set of photocurrents in the reverse bias regime through the graphene-Si Schottky junction with the sample placed thereon may include irradiating a light beam in a range of 500 nm to 900 nm to the graphene-Si Schottky junction with the sample thereon utilizing the light source and applying a sweeping range of reverse bias voltages between the two electrodes utilizing the electrical stimulator-analyzer device. In an exemplary embodiment, applying the sweeping range of reverse bias voltages between the two electrodes may include applying a set of voltage in a range of −1 V to −0.01 V between the two electrodes. 
     In an exemplary embodiment, detecting the presence of cancer cells in the sample may include detecting at least two photocurrent values of the measured set of the generated photocurrents being different with each other by a difference magnitude of more than 10 nA. 
     In an exemplary embodiment, the semiconductor layer may include a silicon (Si) wafer and the electrically passivating layer may include a silicon dioxide (SiO 2 ) layer coated on a first portion of the Si wafer. 
     In an exemplary embodiment, the sample may include a biological sample containing biological cells acquired from a person suspected to have cancer. In an exemplary embodiment, the sample may include a biopsied sample from a cancer-suspicious mass in body of the person, and combinations thereof. 
     In an exemplary embodiment, each of the two electrodes may include a gold (Au) film with a thickness in a range of 50 nm to 200 nm. In an exemplary embodiment, the graphene layer may include a monolayer graphene film. In an exemplary embodiment, the system may further include a sample holder. In an exemplary embodiment, the sample holder may be placed around the graphene-semiconductor Schottky junction. In an exemplary embodiment, the sample holder may include one or more sidewalls enclosing an area of the graphene-semiconductor Schottky junction with the sample placed thereon. In an exemplary embodiment, the sample holder may be configured to keep the sample on surface of the graphene-semiconductor Schottky junction, prevent the sample from flowing out of the graphene-semiconductor Schottky junction, and prevent entrance of pollutants or external materials to the graphene-Si Schottky junction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawing figures depict one or more embodiments in accord with the present teachings, by way of example only, not by way of limitation. In the figures, like reference numerals refer to the same or similar elements. 
         FIG.  1 A  shows an exemplary system for detecting cancer cells in a sample, consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  1 B  shows an exemplary biosensor with a sample holder, consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  1 C  shows an exploded view of an exemplary sample holder and an exemplary graphene-semiconductor Schottky junction with an exemplary sample thereon, consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  2    shows a flow diagram of an exemplary method for fabricating an exemplary biosensor, consistent with one or more exemplary embodiments of the present disclosure. 
         FIGS.  3 A- 3 I  show a schematic view of steps of an exemplary method for fabricating exemplary biosensor, consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  4 A  shows a flow diagram of an exemplary method for detecting cancer cells in a sample, consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  4 B  shows an exemplary flow diagram of an exemplary method for generating an exemplary set of photocurrents in a reverse bias regime through an exemplary graphene-semiconductor Schottky junction, consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  4 C  shows a flow diagram of an exemplary method for detecting Glioblastoma cancer cells in a sample, consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  5 A  shows a schematic representation of a shadow effect regime of operation of an exemplary biosensor, consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  5 B  shows a schematic representation of a charge transfer effect regime of operation of an exemplary biosensor, consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  6    shows an exemplary computer system in which an embodiment of the present disclosure, or portions thereof, may be implemented as computer-readable code, consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  7    shows a graph that illustrates current-voltage (I-V) characteristics of exemplary fabricated graphene/Si Schottky junction in dark and under illumination by different wavelengths of light, including 380 nm, 425 nm, 520 nm, 620 nm, 740 nm, and 850 nm with the same intensity of about 200 μW/cm 2 , consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  8    shows a set of diagrams illustrating current-voltage characteristics of an exemplary biosensor with and without T98G and U87 cell lines as specified in a top guide, in dark and under light illumination with different wavelengths of light, consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  9    shows a graph illustrating reverse photocurrent of exemplary biosensor in the absence and presence of different cancer cell lines for different wavelengths at diode voltage (V D ) of −1 V, consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  10    shows a graph illustrating current-voltage (I-V) characteristics of an exemplary graphene/Si Schottky junction (diode) under illumination with wavelength of 850 nm in the presence of human fibroblast cells and in a bare mode without any cells thereon, consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  11    shows a graph illustrating UV-Visible transmission spectra of PBS solutions containing T98G, U87, and human fibroblast cell lines, consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  12    shows a set of diagrams illustrating current versus time (I-t) characteristics with and without T98G, U87, fibroblast cells in dark and under illumination with lights of different wavelengths by applying V D  of −1 V as specified in a top guide, consistent with one or more exemplary embodiments of the present disclosure. 
         FIG.  13    shows a chart illustrating relative change of photocurrent versus wavelength with and without different cell lines at V D  of −1 V, consistent with one or more exemplary embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant teachings. However, it should be apparent that the present teachings may be practiced without such details. In other instances, well known methods, procedures, components, and/or circuitry have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present teachings. 
     Herein, an exemplary biosensor for cancer cells detection in a biological sample is described. An exemplary biosensor may comprise a mono-layer graphene/(n-type)Si Schottky junction. Furthermore, an exemplary system and method utilizing an exemplary biosensor are described for detection of cancer cells in an exemplary biological sample. An exemplary method may include putting an exemplary biological sample on an exemplary graphene/Si Schottky junction of an exemplary biosensor, irradiating a light beam onto an exemplary graphene/Si Schottky junction with an exemplary biological sample thereon, and monitoring photocurrent of exemplary graphene/Si Schottky junction while applying a reverse bias voltage regime (diode voltage (V D ) of less than zero) in the presence of an exemplary biological sample. In an exemplary embodiment, photocurrent of exemplary graphene/Si Schottky junction may be monitored by recording a set of reverse electrical currents respective to an exemplary applied range of reverse voltages. In an exemplary embodiment, each type of cancer cells may show a unique behavior of changes in reverse electrical currents versus an exemplary applied range of reverse voltages. In an exemplary embodiment, an exemplary method may further include comparing an exemplary set of reverse electrical currents versus an exemplary applied range of reverse voltages (an exemplary I-V set) associated with an exemplary biological sample with a plurality of reference I-V sets associated with a respective plurality of cancer cells and detecting a presence of a first-type cancer cells in an exemplary biological sample if an exemplary I-V set is identical to a first reference I-V set associated with the first-type cancer cells. In an exemplary embodiment, the plurality of reference I-V sets associated with the respective plurality of cancer cells may be generated as a calibration dataset for a plurality of cancer cell types utilizing a plurality of biological samples with known cancer type. An exemplary biosensor, system, and method may not only be capable of distinguishing two different cancer cell types, but may also be utilized easily to differentiate cancer cells from healthy human cells. 
     As used herein, “a reverse electrical current” and “a reverse voltage” may respectively refer to electrical current and electrical voltage in a reverse bias regime of an exemplary graphene/Si Schottky junction. An exemplary graphene/Si Schottky junction comprises an exemplary diode structure having a reverse bias regime and a forward bias regime in a current-voltage (I-V) diagram including a plurality of electrical currents generated within an exemplary graphene/Si Schottky junction versus a respective plurality of applied electrical voltages to an exemplary graphene/Si Schottky junction. In forward bias, a positive terminal of an electrical voltage generator device is connected to p-type or metallic material of an exemplary diode (herein, graphene side) and a negative terminal is connected to n-type material (herein, Si side) so that electrons are injected into n-type material and holes are transferred from Si to the graphene. Whereas, in reverse bias, a reverse process is applied and electrons must overcome the Schottky barrier to reach the conduction band of the n-type semiconductor. 
       FIG.  1 A  shows an exemplary system  100  for detecting cancer cells in a sample, consistent with one or more exemplary embodiments of the present disclosure. In an exemplary embodiment, system  100  may include an exemplary biosensor  102 , an exemplary light source  104 , an exemplary electrical stimulator-analyzer device  106 , and an exemplary processing unit  108 . In an exemplary embodiment, biosensor  102  may be electrically connected to electrical stimulator-analyzer device  106 . In an exemplary embodiment, light source  104  and electrical stimulator-analyzer device  106  may be electrically connected to processing unit  108 . 
     In an exemplary embodiment, an exemplary sample may include a biological sample containing cells. In an exemplary embodiment, an exemplary biological sample may be acquired from a person or an animal suspected to have cancer. In an exemplary embodiment, an exemplary biological sample may include at least one of a blood sample, a biopsied sample from a mass suspicious to be cancerous in a person&#39;s body, a cell line, a cell-containing liquid sample drawn from a living body, and combinations thereof. In an exemplary embodiment, an exemplary biological sample may include a sample acquired from a person suspected to have Glioblastoma cancer. As used herein, “Glioblastoma” is an aggressive type of cancer that may occur in brain and/or spinal cord. In an exemplary embodiment, exemplary system  100  may be utilized for detecting Glioblastoma cancer cells in an exemplary sample. 
     In an exemplary embodiment, biosensor  102  may include a substrate  103 , two electrodes  122  and  124 , and a graphene layer  126  coated on parts of surface of substrate  103  and two electrodes  122  and  124 . In an exemplary embodiment, substrate  103  may include a semiconductor layer  118  and an electrically passivating layer  120  coated on a first portion  117  of semiconductor layer  118 . In an exemplary embodiment, first portion  117  of semiconductor layer  118  may include a first half of semiconductor layer  118 . In an exemplary embodiment, semiconductor layer  118  may include a silicon (Si) wafer and electrically passivating layer  120  may include a silicon dioxide (SiO 2 ) layer coated on surface of a first half of an exemplary Si wafer. In an exemplary embodiment, semiconductor layer  118  may include an n-type Si wafer. In an exemplary embodiment, semiconductor layer  118  may have a thickness of about 500 μm. In an exemplary embodiment, electrically passivating layer  120  may have a thickness in a range of about 200 nm to about 1 μm. 
     In an exemplary embodiment, two electrodes  122  and  124  may include a first electrode  122  deposited on electrically passivating layer  120  and a second electrode  124  deposited on a second portion  119  of semiconductor layer  118 . In an exemplary embodiment, each of two electrodes  122  and  124  may include a gold (Au) film with a thickness in a range of about 50 nm to about 200 nm. 
     In an exemplary embodiment, graphene layer  126  may include a monolayer graphene film coated on parts of surface of electrode  124  and substrate  103 . In an exemplary embodiment, graphene layer  126  may cover parts of electrode  124 , electrically passivating layer  120 , and semiconductor layer  118 . In an exemplary embodiment, coated graphene layer  126  may form an exemplary graphene-semiconductor Schottky junction  128  between semiconductor layer  118  and graphene layer  126 . In an exemplary embodiment, exemplary graphene-semiconductor Schottky junction  128  may comprise a graphene-Si Schottky junction. In an exemplary embodiment, exemplary graphene-semiconductor Schottky junction  128  may be configured to be able to receive or have put on it an exemplary sample  129 . In an exemplary embodiment, a first side of graphene layer  126  may be in contact with semiconductor layer  118  and a second side of graphene layer  126  may be in contact with second electrode  124 . 
     In an exemplary embodiment, biosensor  102  may further include a sample holder.  FIG.  1 B  shows an exemplary biosensor  102  with a sample holder  130 , consistent with one or more exemplary embodiments of the present disclosure. In an exemplary embodiment, sample holder  130  may include a hollow enclosure. In an exemplary embodiment, sample holder  130  may include a hollow enclosure with a cross section of one of a circular cross section, a square cross section, a rectangular cross section, a triangular cross section, etc., for example, a hollow enclosure with a rectangular cross section as illustrated in  FIG.  1 B . In an exemplary embodiment, sample holder  130  may be placed on surface of biosensor  102  around a portion or the entire surface of graphene-semiconductor Schottky junction  128  so that sample holder  130  may enclose a respective portion or the entire surface of graphene-semiconductor Schottky junction  128 . In an exemplary embodiment, sample holder  130  may be configured to keep exemplary sample  129  on surface of graphene-semiconductor Schottky junction  128  and prevent exemplary sample  129  from flowing out of graphene-semiconductor Schottky junction  128 . For more clarity,  FIG.  1 C  shows an exploded view of sample holder  130  and graphene-semiconductor Schottky junction  128  with exemplary sample  129  thereon, consistent with one or more exemplary embodiments of the present disclosure. In an exemplary embodiment, graphene-semiconductor Schottky junction  128  may comprise a graphene side  142  and a semiconductor side  140 . In an exemplary embodiment, graphene side  142  may include a portion of graphene layer  126  coated on semiconductor side  140 , where semiconductor side  140  may include a portion of semiconductor layer  118  covered by graphene side  142 . In an exemplary embodiment, sample holder  130  may include a hollow cuboid with two open sides  135  and  136  respectively at top and bottom of sample holder  130 . In an exemplary embodiment, sample holder  130  may include one or more sidewalls, for example, sidewalls  131 ,  132 ,  133 , and  134 , enclosing a portion or the entire surface of graphene-semiconductor Schottky junction  128  In an exemplary embodiment, exemplary sample holder  334  may be made of plexiglass. In an exemplary embodiment, plexiglass may refer to a plastic material made from poly methyl methacrylate. 
     In another general aspect of the present disclosure, a method for fabricating an exemplary biosensor  102  is described.  FIG.  2    shows a flow diagram of an exemplary method  200  for fabricating exemplary biosensor  102 , consistent with one or more exemplary embodiments of the present disclosure. In an exemplary embodiment, exemplary method  200  of fabricating exemplary biosensor  102  may include forming a SiO 2  layer on a Si wafer (step  202 ), removing a first half of the SiO 2  layer from a respective first half of surface of the Si wafer (step  204 ), forming a first electrode on the first half of the Si wafer and a second electrode on a remaining second half of the SiO 2  layer (step  206 ), and coating a graphene layer on parts of the Si wafer, the SiO 2  layer, and the second electrode (step  208 ). 
     Furthermore,  FIGS.  3 A- 3 I  shows a schematic view of steps of exemplary method  200  for fabricating exemplary biosensor  102 , consistent with one or more exemplary embodiments of the present disclosure. In detail, in step  202 , a SiO 2  layer  314  may be formed on a Si wafer  312  as illustrated in  FIG.  3 A . In an exemplary embodiment, step  202  may include cleaning an exemplary Si wafer  312  as an example of semiconductor layer  118  and forming an exemplary SiO 2  layer  314  as an example of electrically passivating layer  120  on surface of exemplary Si wafer  312 . In an exemplary embodiment, Si wafer  312  may include an n-type Si wafer. In an exemplary embodiment, Si wafer  312  may be cleaned via a standard RCA cleaning method. In an exemplary embodiment, electrically insulating SiO 2  layer  314  may be grown on whole surface of Si wafer  312  using thermal oxidation in a quartz furnace. In an exemplary embodiment, Si wafer  312  may be placed in a quartz furnace, temperature may be slowly ramped up to about 1100° C. inside the quartz furnace, and Si wafer  312  may be held therein for oxidation under a constant flow of O 2  gas; thereby, resulting in forming an oxide layer on Si wafer  312  after a time period in a range of 20 minutes to 1 hour. 
     In an exemplary embodiment, step  204  may include removing a first half  311  of SiO 2  layer  314  from surface of a respective first half  310  of Si wafer  312  considering a hypothetical symmetric line  302  at the middle of SiO 2  layer  314  and a respective hypothetical symmetric line  304  at the middle of Si wafer  312 . In an exemplary embodiment, exemplary first half  311  of exemplary SiO 2  layer  314  may be removed using a standard photolithography technique through a two-step process shown in  FIGS.  3 B and  3 C . In an exemplary embodiment, removing exemplary first half  311  of SiO 2  layer  314  may include coating a first layer  316  of a photoresist material on SiO 2  layer  314  as illustrated in  FIG.  3 B , removing exemplary first half  311  of SiO 2  layer  314  along with a respective first half  313  of first layer  316  of the photoresist material thereon (considering a hypothetical symmetric line  302  at the middle of first layer  316  of the photoresist material) via a photolithography technique, and removing a remaining second half  315  of first layer  316  of photoresist material remained on a respective second half  320  of SiO 2  layer  314  as illustrated in  FIG.  3 C . In an exemplary embodiment, first layer  316  of the photoresist material may cover the entire top surface of SiO 2  layer  314 . In an exemplary embodiment, the photoresist material may include a cured negative photoresist polymer. In an exemplary embodiment, exemplary first half  311  of SiO 2  layer  314  along with a respective first half  313  of first layer  316  of the photoresist material thereon may be removed by etching and/or patterning SiO 2  layer  314  with first layer  316  of photoresist material thereon through a photolithography process. In an exemplary embodiment, remaining second half  315  of the photoresist material after applying photolithography technique may be removed using a NaOH solution. In an exemplary embodiment, exemplary first half  311  of SiO 2  layer  314  may be removed using a 10% Hydrofluoric acid (HF) solution through the photolithography process. In an exemplary embodiment, applying step  204  may lead to forming exemplary first half  310  of exemplary Si wafer  312  having a bare surface  318  and exemplary second half  320  of SiO 2  layer  314  remaining on a respective second half  319  of exemplary Si wafer  312  considering hypothetical symmetric line  304  at the middle of exemplary Si wafer  312  as illustrated in  FIG.  3 C . 
     Furthermore, step  206  may include forming two exemplary electrodes similar to electrodes  122  and  124 . In an exemplary embodiment, step  206  may include forming an exemplary first electrode on first half  310  of Si wafer  312  with bare surface  318  and forming an exemplary second electrode on remaining second half  320  of SiO 2  layer  314 . In an exemplary embodiment, step  206  may be done through four steps schematically illustrated in  FIGS.  3 D- 3 G . In an exemplary embodiment, step  206  may include coating a second layer  322  of the photoresist material on bare surface  318  of first half  310  of Si wafer  312  and on remaining second half  320  of SiO 2  layer  314  as illustrated in  FIG.  3 D . Moreover, step  206  may include forming two electrode sites  324  and  326  by removing two respective middle parts  321  and  323  of second layer  322  of the photoresist material as illustrated in  FIGS.  3 D and  3 E . In an exemplary embodiment, two electrode sites  324  and  326  may be formed by etching and/or patterning second layer  322  of the photoresist material using a standard photolithography technique. In an exemplary embodiment, two electrode sites  324  and  326  may include two openings through second layer  322  of the photoresist material, including a first electrode site  324  on surface of first half  310  of Si wafer  312  and a second electrode site  326  on surface of second half  320  of SiO 2  layer  314 . Step  206  may additionally include forming two electrodes  328  and  330  on respective two electrode sites  324  and  326  as illustrated in  FIGS.  3 F and  3 G . In an exemplary embodiment, forming two electrodes  328  and  330  may include coating an exemplary Au film  327  on remaining parts of second layer  322  of the photoresist material and two electrode sites  324  and  326  using a physical vapor deposition (PVD) technique and etching/patterning coated Au film  327  using a standard photolithography technique to form two electrodes  328  and  330  similar to two exemplary electrodes  122  and  124  of exemplary biosensor  102  of  FIG.  1   . In an exemplary embodiment, coated Au film  327  may have a thickness in a range of about 50 nm to 200 nm. In an exemplary embodiment, step  206  may further include etching all remaining parts of second layer  322  of the photoresist material away using acetone or a NaOH solution so that the photoresist material may be completely removed from structure of an exemplary fabricated biosensor. In an exemplary embodiment, an exemplary fabricated biosensor may be rinsed in acetone to remove the photoresist material before conducting step  208 . 
     Moving to step  208 , a graphene-Si Schottky junction similar to graphene-semiconductor Schottky junction  128  may be formed by coating a graphene layer on parts of surface of Si wafer  312 , remaining second half  320  of SiO 2  layer  314 , and second electrode  330 . In an exemplary embodiment, step  208  may include coating an exemplary graphene layer  332  on parts of surface of Si wafer  312 , remaining second half  320  of SiO 2  layer  314 , and second electrode  330  as illustrated in  FIG.  3 H . In an exemplary embodiment, exemplary graphene layer  332  may include a layer of graphene coated from a point  331   a  on surface of second electrode  330  to a point  331   b  on surface of Si wafer  312 ; thereby, forming a graphene-Si Schottky junction  333  (a graphene/Si bilayer  333 ) between graphene layer  332  and Si wafer  312 . In an exemplary embodiment, graphene-Si Schottky junction  333  (graphene/Si bilayer  333 ) may comprise a portion of graphene layer  332  on Si wafer  312  from points  331   c  to  331   b  and a respective portion of Si wafer  312  in a zone  331   d  between points  331   c  to  331   b  covered with graphene layer  332 . In an exemplary embodiment, graphene layer  332  may include a monolayer graphene film deposited on parts of surface of Si wafer  312 , SiO 2  layer  314 , and second electrode  330 . 
     In an exemplary embodiment, exemplary method  200  may further include placing an exemplary sample holder  334 , similar to exemplary sample holder  130 , around a portion or the entire surface of graphene-Si Schottky junction  333  as illustrated in  FIG.  31   . In an exemplary embodiment, exemplary sample holder  334  may enclose a portion or the entire surface of graphene-Si Schottky junction  333 ; allowing for keeping an exemplary sample, similar to sample  129 , on surface of graphene-Si Schottky junction  333 , preventing an exemplary sample from flowing out of graphene-Si Schottky junction  333 , and preventing entrance of pollutants or external materials to graphene-Si Schottky junction  333 . In an exemplary embodiment, exemplary sample holder  334  may include one or more confining walls, for example, walls  335 ,  336 ,  337 , and  338  around graphene-Si Schottky junction  333 . In an exemplary embodiment, exemplary sample holder  334  may be made of plexiglass including a plastic material made from poly methyl methacrylate. 
     Referring back to  FIG.  1   , exemplary system  100  may further include exemplary light source  104  placed above biosensor  102 . In an exemplary embodiment, light source  104  may be placed above graphene-semiconductor Schottky junction  128  of biosensor  102 . In an exemplary embodiment, light source  104  may include a light emitting device or a light emitting source with a wavelength range of about 300 nm to about 1000 nm. In an exemplary embodiment, light source  104  may include an array of light emitting diodes with a wavelength range of about 300 nm to about 1000 nm. In an exemplary embodiment, light source  104  may include one or more light emitting diodes (LEDs) or one or more light emitting lasers with an emission peak in a range of wavelength of about 350 nm to about 950 nm. In an exemplary embodiment, light source  104  may be configured to irradiate a light beam to an exemplary sample placed and attached on graphene-semiconductor Schottky junction  128 . In an exemplary embodiment, an irradiation wavelength of light source  104  may be adjustable using processing unit  108 . In an exemplary embodiment, light source  104  may be configured to irradiate the light beam with a wavelength in a range of 500 nm to 900 nm to an exemplary sample placed and attached on graphene-semiconductor Schottky junction  128 . In an exemplary embodiment, light source  104  may be configured to irradiate the light beam with a wavelength of 850 nm to an exemplary sample placed and attached on graphene-semiconductor Schottky junction  128 . In an exemplary embodiment, light source  104  may include one or more light-emitting diodes (LEDs). 
     Referring to  FIG.  1   , exemplary system  100  may include electrical stimulator-analyzer device  106 . In an exemplary embodiment, electrical stimulator-analyzer device  106  may be electrically connected to exemplary electrodes  122  and  124  of biosensor  102 . In an exemplary embodiment, electrical stimulator-analyzer device  106  may be electrically connected to exemplary electrodes  122  and  124  utilizing three respective electrically conductive lines  114  and  116 . In an exemplary embodiment, electrical stimulator-analyzer device  106  may include an electrical voltage generator and an electrical current sensor. In an exemplary embodiment, an exemplary electrical voltage generator of electrical stimulator-analyzer device  106  may be capable of applying an electrical voltage between two exemplary electrodes  122  and  124 . In an exemplary embodiment, an exemplary electrical current sensor of electrical stimulator-analyzer device  106  may be capable of measuring an electrical current generated between two exemplary electrodes  122  and  124  responsive to an exemplary applied voltage using an exemplary electrical voltage generator of electrical stimulator-analyzer device  106 . In an exemplary embodiment, electrical stimulator-analyzer device  106  may be configured to apply an electrical voltage between two exemplary electrodes  122  and  124  and measure an electrical current generated between two exemplary electrodes  122  and  124  responsive to the applied voltage. In an exemplary embodiment, electrical stimulator-analyzer device  106  may be configured to apply a sweeping set of electrical voltages between two exemplary electrodes  122  and  124  and measure a respective set of electrical currents generated between two exemplary electrodes  122  and  124  responsive to the applied sweeping set of electrical voltages. In an exemplary embodiment, electrical stimulator-analyzer device  106  may be electrically connected to processing unit  108  utilizing at least one of an electrically conductive line  110 , a wireless connection, and combinations thereof. In an exemplary embodiment, the wireless connection may include Bluetooth devices or Bluetooth modules, which may be embedded in electrical stimulator-analyzer device  106  and processing unit  108 . In an exemplary embodiment, electrical stimulator-analyzer device  106  may be further configured to send the measured electrical current or the measured set of electrical currents to processing unit  108 . 
     In an exemplary embodiment, processing unit  108  may include a memory having processor-readable instructions stored therein and a processor. In an exemplary embodiment, the processor may be configured to access the memory and execute the processor-readable instructions. In an exemplary embodiment, executing the processor-readable instructions by the processor may configures the processor to perform a method. In an exemplary embodiment, the method may include an exemplary method for detecting cancer cells in a sample described herein below. 
     In another general aspect of the present disclosure, an exemplary method for detecting cancer cells in an exemplary sample is described. In an exemplary embodiment, an exemplary method may be carried out utilizing exemplary system  100  described hereinabove.  FIG.  4 A  shows an exemplary flow diagram of an exemplary method  400  for detecting cancer cells in a sample, consistent with one or more exemplary embodiments of the present disclosure. In an exemplary embodiment, one or more steps of exemplary method  400  may be done utilizing an exemplary system similar to exemplary system  100  described hereinabove. Accordingly, exemplary steps of method  400  are described in context of elements of biosensor  102 . In an exemplary embodiment, method  400  may include putting an exemplary sample in contact with graphene side  142  of exemplary graphene-semiconductor Schottky junction  128  of biosensor  102  (step  401 ), generating a set of photocurrents in a reverse bias regime passed through graphene-semiconductor Schottky junction  128  (step  402 ), measuring an exemplary set of generated photocurrents passed through the graphene-semiconductor Schottky junction  128  in the presence of an exemplary sample (step  403 ), and detecting a presence of cancer cells in sample  129  if a change is detected in an exemplary set of measured photocurrents within an exemplary reverse bias regime (step  404 ). 
     In detail, step  401  may include putting an exemplary sample, for example, sample  129  in contact with graphene side  142  of graphene-semiconductor Schottky junction  128  of biosensor  102 . In an exemplary embodiment, exemplary sample  129  may include a sample including biological cells acquired from a person suspected to have cancer. In an exemplary embodiment, exemplary sample  129  may include at least one of a blood sample drawn from a person, a biopsied sample acquired from a person, a sample containing biological cells suspected to be cancerous, and combinations thereof. In an exemplary embodiment, exemplary sample  129  may include a biopsied sample from a mass suspected to be a cancerous tumor in a person&#39;s body. In an exemplary embodiment, putting exemplary sample  129  in contact with graphene side  142  of graphene-semiconductor Schottky junction  128  may include dropping or placing exemplary sample  129  inside sample holder  130  on graphene-semiconductor Schottky junction  128 . In an exemplary embodiment, putting exemplary sample  129  in contact with graphene side  142  of graphene-semiconductor Schottky junction  128  may lead to attaching/adhering exemplary sample  129  to graphene side  142  of graphene-semiconductor Schottky junction  128  due to dangling bonds of graphene. 
     Furthermore, step  402  may include generating an exemplary set of photocurrents in a reverse bias regime passed through graphene-semiconductor Schottky junction  128 . In an exemplary embodiment, generating an exemplary set of photocurrents through graphene-semiconductor Schottky junction  128  may be carried out utilizing electrical stimulator-analyzer device  106  and light source  104 .  FIG.  4 B  shows an exemplary flow diagram of an exemplary method  405  for generating an exemplary set of photocurrents in a reverse bias regime through graphene-semiconductor Schottky junction  128 , consistent with one or more exemplary embodiments of the present disclosure. In an exemplary embodiment, method  405  may include irradiating a light beam to exemplary sample  129  on graphene-semiconductor Schottky junction  128  (step  406 ) and applying a set of voltages in reverse bias regime to graphene-semiconductor Schottky junction  128  (step  407 ). 
     In an exemplary embodiment, step  406  of irradiating an exemplary light beam to exemplary sample  129  on graphene-semiconductor Schottky junction  128  may include irradiating an exemplary light beam to biosensor  102 . In an exemplary embodiment, irradiating an exemplary light beam to exemplary sample  129  on graphene-semiconductor Schottky junction  128  may include irradiating an exemplary light beam to graphene-semiconductor Schottky junction  128  while exemplary sample  129  being on graphene-semiconductor Schottky junction  128  using exemplary light source  104 . In an exemplary embodiment, irradiating an exemplary light beam to graphene-semiconductor Schottky junction  128  with exemplary sample  129  thereon may include irradiating an exemplary light beam with a wavelength in a range of about 500 nm to about 900 nm to graphene-semiconductor Schottky junction  128  with exemplary sample  129  thereon utilizing light source  104 . 
     In an exemplary embodiment, step  407  of applying an exemplary set of voltages in reverse bias regime to graphene-semiconductor Schottky junction  128  may include applying an electrical voltage to graphene-semiconductor Schottky junction  128  in such a way that semiconductor side (Si side)  140  may be held at a higher voltage than graphene side  142 . In an exemplary embodiment, step  407  of applying an exemplary set of voltages in reverse bias regime to graphene-semiconductor Schottky junction  128  may include applying a set of voltages in a range of about −1 V to about −0.01 V to graphene-semiconductor Schottky junction  128 . In an exemplary embodiment, applying an exemplary set of voltages in reverse bias regime to graphene-semiconductor Schottky junction  128  may include applying an exemplary set of voltages in an exemplary reverse bias regime to graphene-semiconductor Schottky junction  128  in the presence of exemplary sample  129  on graphene-semiconductor Schottky junction  128  while irradiating the light beam to graphene-semiconductor Schottky junction  128 . In an exemplary embodiment, applying an exemplary set of voltages in reverse bias regime to graphene-semiconductor Schottky junction  128  may include applying a sweeping range of reverse bias voltages between two exemplary electrodes  122  and  124  utilizing electrical stimulator-analyzer device  106 . 
     In an exemplary embodiment, steps  406  and  407  of irradiating an exemplary light beam to exemplary sample  129  on graphene-semiconductor Schottky junction  128  and applying an exemplary set of voltages in reverse bias regime to graphene-semiconductor Schottky junction  128  may be done concurrently so that an exemplary set of photocurrents passing through graphene-semiconductor Schottky junction  128  may be generated. As used herein, “photocurrent” may refer to a photo-generated electrical current. In an exemplary embodiment, a photo-generated electrical current may be an electrical current with charge carriers generated due to light irradiation by converting photons to electrons. Herein, irradiating a light beam to an exemplary semiconductor material of graphene-semiconductor Schottky junction  128  may lead to generating a photocurrent passed through graphene-semiconductor Schottky junction  128 . In detail, when photons hit a depletion region of graphene-semiconductor Schottky junction  128  while conducting step  406  of irradiating an exemplary light beam to exemplary sample  129  on graphene-semiconductor Schottky junction  128 , an amount of energy may be absorbed to graphene-semiconductor Schottky junction  128  and may cause excitation of electrons and creation of electron-hole pairs. Exited electrons and created electron-hole pairs are charge carriers which may be separated (electrons go towards Si and holes towards graphene) due to an electric field (applied in step  407 ) in graphene-semiconductor Schottky junction  128 ; thereby, leading to generation of photocurrent in graphene-semiconductor Schottky junction  128 . 
     Referring back to  FIG.  4 A , step  403  may include measuring an exemplary set of generated photocurrents through graphene-semiconductor Schottky junction  128  in an exemplary reverse bias regime in the presence of exemplary sample  129 . In an exemplary embodiment, measuring an exemplary set of generated photocurrents through graphene-semiconductor Schottky junction  128  may include measuring a respective set of produced electrical currents between two exemplary electrodes  122  and  124  responsive to an exemplary applied sweeping range of reverse bias voltages utilizing electrical stimulator-analyzer device  106 . In an exemplary embodiment, an exemplary respective set of produced electrical currents between two exemplary electrodes  122  and  124  may include an exemplary set of generated photocurrents due to irradiating an exemplary light beam to graphene-semiconductor Schottky junction  128  while applying an exemplary sweeping range of reverse bias voltages to graphene-semiconductor Schottky junction  128 . In an exemplary embodiment, applying an exemplary sweeping range of reverse bias voltages between two exemplary electrodes  122  and  124  may include applying a set of voltages in a range of about −1 V to about −0.01 V between two exemplary electrodes  122  and  124 . 
     Additionally, step  404  may include detecting a presence of cancer cells in exemplary sample  129  if a change is detected in an exemplary measured set of generated photocurrents within an exemplary reverse bias regime. In an exemplary embodiment, detecting the presence of cancer cells in exemplary sample  129  may include detecting at least two electrical currents within an exemplary measured set of produced electrical currents being different with each other by a difference magnitude of more than about 10 nA. In an exemplary embodiment, exemplary sample  129  may be detected to be healthy or normal if all electrical current magnitudes of the measured set of produced electrical currents are the same. In an exemplary embodiment, exemplary sample  129  may be detected to be healthy or normal if a difference between magnitudes of each two electrical currents of an exemplary measured set of produced electrical currents is less than about 10 nA. 
     In an exemplary embodiment, step  407  may include applying two electrical voltages in an exemplary reverse bias regime between two exemplary electrodes  122  and  124 ; therefore, step  403  may include measuring two respective photocurrents generated responsive to exemplary applied two electrical voltages. Thereafter, detecting a presence of cancer cells in exemplary sample  129  (step  404 ) may include comparing exemplary two measured photocurrents respective to exemplary two applied electrical voltages with each other and detecting cancer cells in exemplary sample  129  if exemplary two measured photocurrents are different with each other by a value of more than about 10 nA. In an exemplary embodiment, exemplary two applied electrical voltages may include a first voltage of −1 V and a second voltage of −0.05 V. 
     In an exemplary embodiment, an exemplary method for detecting Glioblastoma cancer cells in an exemplary sample is described.  FIG.  4 C  shows an exemplary flow diagram of exemplary method  410  for detecting Glioblastoma cancer cells in a sample, consistent with one or more exemplary embodiments of the present disclosure. In an exemplary embodiment, one or more steps of exemplary method  410  may be done utilizing exemplary system  100  described hereinabove. Accordingly, exemplary steps of method  410  are described in context of elements of biosensor  102 . In an exemplary embodiment, one or more steps of exemplary method  410  may be similar to one or more steps of exemplary method  400  and/or exemplary method  405  described hereinabove. In an exemplary embodiment, method  410  may include putting exemplary sample  129  in contact with graphene side  142  of graphene-semiconductor Schottky junction  128  of biosensor  102  (step  412 ), irradiating a light beam with a wavelength in a range of about 500 nm to about 900 nm to exemplary sample  129  on graphene-semiconductor Schottky junction  128  (step  414 ), applying a first voltage of −1 V and a second voltage of −0.05 V between two electrodes  122  and  124  of biosensor  102  (step  416 ), measuring a first electrical current generated between two electrodes  122  and  124  responsive to the applied first voltage and a second electrical current generated between two electrodes  122  and  124  responsive to the applied second voltage (step  418 ), and detecting a presence of Glioblastoma cancer cells in exemplary sample  129  if a difference between the first electrical current and the second electrical current is more than about 10 nA (step  420 ). 
     In detail, step  412  may include putting exemplary sample  129  in contact with graphene side  142  of graphene-semiconductor Schottky junction  128  of biosensor  102  similar to step  401  of exemplary method  400 . In an exemplary embodiment, putting exemplary sample  129  in contact with graphene side  142  of graphene-semiconductor Schottky junction  128  of biosensor  102  may include putting exemplary sample  129  on graphene-semiconductor Schottky junction  128 . In an exemplary embodiment, exemplary sample  129  may include a sample drawn from a person suspected to have Glioblastoma cancer. 
     In an exemplary embodiment, step  414  may include irradiating a light beam with a wavelength in a range of about 500 nm to about 900 nm to exemplary sample  129  put on graphene-semiconductor Schottky junction  128  similar to step  406  of exemplary method  405 . In an exemplary embodiment, irradiating an exemplary light beam with a wavelength in a range of about 500 nm to about 900 nm to exemplary sample  129  may include irradiating an exemplary light beam with a wavelength of about 600 nm to exemplary sample  129  put on graphene-semiconductor Schottky junction  128 . In an exemplary embodiment, irradiating an exemplary light beam with a wavelength in a range of about 500 nm to about 900 nm to exemplary sample  129  may include irradiating an exemplary light beam with a wavelength of about 850 nm to exemplary sample  129  put on graphene-semiconductor Schottky junction  128 . 
     Furthermore, step  416  may include applying two voltages in a range of bias voltages between two electrodes  122  and  124  of biosensor  102 . In an exemplary embodiment, a first voltage of about −1 V and a second voltage of about −0.05 V may be applied between two electrodes  122  and  124  of biosensor  102 . In an exemplary embodiment, two electrical currents (photocurrents) may be generated due to the applied first voltage and the applied second voltage while irradiating an exemplary light beam in the presence of exemplary sample  129  on graphene-semiconductor Schottky junction  128 . In an exemplary embodiment, step  416  may include an exemplary process similar to step  407  of exemplary method  405 . 
     In an exemplary embodiment, step  418  may include measuring the two generated electrical currents utilizing electrical stimulator-analyzer device  106 . In an exemplary embodiment, measuring the two generated electrical currents may include measuring a first electrical current generated between two electrodes  122  and  124  responsive to the applied first voltage of about −1 V and a second electrical current generated between two electrodes  122  and  124  responsive to the applied second voltage of about −0.05 V. In an exemplary embodiment, step  418  may include an exemplary process similar to step  403  of exemplary method  400 . 
     Moreover, step  420  may include detecting a presence of Glioblastoma cancer cells in an exemplary sample if a difference between the measured first electrical current and the measured second electrical current is more than about 10 nA. In an exemplary embodiment, step  420  may include comparing the measured first electrical current with the measured second electrical current by calculating a difference between values of the measured first electrical current and the measured second electrical current and detecting the presence of Glioblastoma cancer cells in an exemplary sample if the measured first electrical current and the measured second electrical current are different with each other by a value of 10 nA or more. Furthermore, step  420  may further include detecting an exemplary sample being normal or healthy if a difference between the measured first electrical current and the measured second electrical current is less than about 10 nA. In an exemplary embodiment, an exemplary sample may be detected to be normal or healthy if the measured first electrical current and the measured second electrical current have the same magnitude. 
     In an exemplary embodiment, exemplary methods  400 ,  405 , and  410  may be utilized as fast and real-time methods for detecting cancer. In an exemplary embodiment, exemplary methods  400 ,  405 , and  410  may be done in less than about one minute. In an exemplary embodiment, exemplary methods  400 ,  405 , and  410  may be done in less than about 30 seconds. 
     In an exemplary embodiment, exemplary biosensor  102  may be utilized for detecting and differentiating biological cells by recording and monitoring changes in photocurrent generated in graphene-semiconductor Schottky junction  128  of exemplary biosensor  102  in reverse bias. In an exemplary embodiment, changes in photocurrent generated in graphene-semiconductor Schottky junction  128  of exemplary biosensor  102  in reverse bias may be explained and analyzed by an interplay of two different physical mechanisms of operation of exemplary biosensor  102 , each more prominent in a particular wavelength range. In an exemplary embodiment, exemplary two different physical mechanisms may include a first mechanism including a shadow effect regime and a second mechanism including a charge transfer effect regime. In an exemplary embodiment, an exemplary first mechanism of shadow effect regime may be activated when a light beam with a wavelength in a first wavelength range is irradiated to biosensor  102 , whereas an exemplary second mechanism of charge transfer effect regime may be activated while irradiating a light beam with a wavelength in a second wavelength range to biosensor  102 . In an exemplary embodiment, an exemplary second wavelength range may include higher wavelengths than wavelength of an exemplary first wavelength range. In an exemplary embodiment, an exemplary first wavelength range may include wavelength magnitudes of less than a threshold wavelength and an exemplary second wavelength range may include wavelength magnitudes of more than the threshold wavelength. In an exemplary embodiment, an exemplary threshold wavelength may include a wavelength of about 600 nm. In an exemplary embodiment, the threshold wavelength may include a wavelength of 520 nm for Glioblastoma cancer cells. In an exemplary embodiment, an exemplary second wavelength range may include wavelength magnitudes near infrared (IR) window between about 600 nm and 900 nm.  FIGS.  5 A and  5 B  show two schematic representations  500  and  520  of exemplary two respective different regimes of operation for exemplary biosensor  102 .  FIG.  5 A  shows a schematic representation  500  of an exemplary shadow effect regime of operation of exemplary biosensor  102 , consistent with one or more exemplary embodiments of the present disclosure. Moreover,  FIG.  5 B  shows a schematic representation  520  of an exemplary charge transfer effect regime of operation of exemplary biosensor  102 , consistent with one or more exemplary embodiments of the present disclosure. 
     In an exemplary first mechanism of shadow effect regime illustrated in  FIG.  5 A  while irradiating a light beam  502  with a wavelength magnitude in an exemplary first wavelength range below about 600 nm to exemplary graphene/Si Schottky junction  501  (similar to graphene-semiconductor Schottky junction  128  of exemplary biosensor  102 ), a main mechanism of operation of exemplary biosensor  102  may relate to an exemplary physical obstruction  510  of exemplary graphene/Si Schottky junction  501  made by exemplary adhered cells  506  and  508 . In an exemplary embodiment, a “first regime” or “shadow effect regime” refers to a wavelength of irradiation of about 600 nm or less. In detail, light beam  502  with a short wavelength of less than about 600 nm is not capable of passing through cells  506  and  508  adhered to exemplary graphene/Si Schottky junction  501 ; thereby, exemplary physical obstruction  510  exemplary graphene/Si Schottky junction  501  may be formed. In more details, exemplary physical obstruction  510  may decrease an effective surface area of exemplary graphene/Si Schottky junction  501  for photon absorption; thereby, resulting in decreasing a generated electrical current under illumination in exemplary graphene/Si Schottky junction  501 . As used herein, “an effective surface area” of an exemplary graphene/Si Schottky junction (similar to graphene/Si Schottky junction  501 ) may include a freely exposed surface area of an exemplary graphene/Si Schottky junction to irradiation, for example light irradiation. In detail, in wavelengths of less than 600 nm, exemplary adhered cells  506  and  508  may block an effective surface of an active region in exemplary graphene/Si junction  501 , and thus decrease a photocurrent produced in the presence of light irradiation to exemplary graphene/Si junction  501 . In details, some percentage of incident photons may be absorbed by exemplary adhered cells  506  and  508  so that absorption percentage in graphene/Si junction  501  may become less than when there is no cell. In more details, photons cannot reach to total surface area of graphene/Si Schottky junction  501  due to screening of graphene/Si junction  501  by exemplary adhered cells  506  and  508 , and consequently photon absorption by graphene/Si junction  501  decreases, leading to decreasing photo-generated current through graphene/Si junction  501 . In an exemplary embodiment, such screening of graphene/Si junction  501  by exemplary adhered cells  506  and  508  may be caused due to light absorption by exemplary adhered cells  506  and  508 . As a result, in an exemplary first wavelength range, a produced photocurrent is lower in the presence of cancer cells  506  and  508  relative to a bare exemplary graphene/Si Schottky junction  501 . In an exemplary first regime, physical shape and orientation of cells  506  and  508  on exemplary graphene layer may play the most significant part in generated photocurrent of exemplary biosensor  102 . For example, in an exemplary first regime of irradiating a light beam in an exemplary first wavelength range, exemplary biosensor  102  may show a lower photocurrent in the presence of U87 cell lines in comparison with a presence of T98G cell lines adhered to an exemplary graphene/Si Schottky junction  501 . 
     In an exemplary embodiment, an exemplary second mechanism of charge transfer effect regime is illustrated in  FIG.  5 B  while irradiating a light beam  503  with a wavelength magnitude in a second wavelength range more than about 600 nm to exemplary graphene/Si Schottky junction  501  and the start of the near infrared (IR) window in biological tissue. In an exemplary embodiment, “second regime” or “charge transfer effect regime” refers to a wavelength range of irradiation in which exposed cells to irradiation are almost transparent. In an exemplary embodiment, “second regime” or “charge transfer effect regime” refers to a wavelength range of more than about 600 nm. However, an exemplary second mechanism may not be dependent on physical obstruction of an effective surface area of exemplary graphene/Si Schottky junction  501 , as an exemplary second wavelength range falls within near infrared window in biological tissues, light may penetrate exemplary adhered cells  506  and  508  and reach exemplary graphene/Si Schottky junction  501 . In an exemplary second regime, charge may be transferred between cells  506  and  508  and graphene layer or a field effect of charged outer surface of cells  506  and  508  may locally alter work function of graphene layer by either adding electrons (increasing Fermi energy or lowering the work function) or taking electrons from graphene (lowering the Fermi energy or increasing the work function). Such change in the work function may results in local areas  512  and  514  under exemplary adhered cells  506  and  508  to have lower or higher Schottky barrier heights that either may facilitate or hinder charge transfer between graphene and Si layer. So, exemplary biosensor  102  may also show distinctive electrical behavior in the presence of respective distinct types of cancer cells adhered to exemplary graphene/Si Schottky junction  501  in higher wavelengths. For example, in an exemplary second regime of irradiating a light beam in an exemplary second wavelength range, exemplary biosensor  102  may show a higher photocurrent in the presence of U87 cell lines, while in the presence of T98G cell lines, exemplary photocurrent may remain constant, and lower than a photocurrent of an exemplary bare graphene/Si Schottky junction  501 . Accordingly, both exemplary two regimes of shadow effect and charge transfer effect can be used to differentiate between various cell lines using exemplary biosensor  102 . While an exemplary shadow effect in shorter wavelengths may give a measure of geometrical shape of adhered cells to graphene monolayer, as a produce photocurrent depends on physical obstruction of active area of an exemplary Schottky junction, an exemplary charge transfer effect can yield a measure of electrical interaction of cells with graphene monolayer and local changes in Fermi level of graphene. Therefore, both shadow effect and charge transfer effect may be utilized in exemplary biosensor  102 ; allowing for exemplary biosensor  102  being sensitive to presence of cells and at the same time, being selective (based on cell sizes, and physical properties, and electrical interactions of cells with graphene). 
       FIG.  6    shows an example computer system  500  in which an embodiment of the present disclosure, or portions thereof, may be implemented as computer-readable code, consistent with one or more exemplary embodiments of the present disclosure. For example, computer system  600  may include an example of processing unit  108  illustrated in  FIG.  1   , steps  402 - 404  of exemplary method  400  presented in  FIG.  4 A , and steps  414 - 420  of exemplary method  410  presented in  FIG.  4 B , may be implemented in computer system  600  using hardware, software, firmware, tangible computer readable media having instructions stored thereon, or a combination thereof and may be implemented in one or more computer systems or other processing systems. Hardware, software, or any combination of such may embody any of the modules and components in  FIGS.  1 ,  4 A and  4 B . 
     If programmable logic is used, such logic may execute on a commercially available processing platform or a special purpose device. One ordinary skill in the art may appreciate that an embodiment of the disclosed subject matter can be practiced with various computer system configurations, including multi-core multiprocessor systems, minicomputers, mainframe computers, computers linked or clustered with distributed functions, as well as pervasive or miniature computers that may be embedded into virtually any device. 
     For instance, a computing device having at least one processor device and a memory may be used to implement the above-described embodiments. A processor device may be a single processor, a plurality of processors, or combinations thereof. Processor devices may have one or more processor “cores.” 
     An embodiment of the present disclosure is described in terms of this example computer system  600 . After reading this description, it will become apparent to a person skilled in the relevant art how to implement the invention using other computer systems and/or computer architectures. Although operations may be described as a sequential process, some of the operations may in fact be performed in parallel, concurrently, and/or in a distributed environment, and with program code stored locally or remotely for access by single or multi-processor machines. In addition, in some embodiments the order of operations may be rearranged without departing from the spirit of the disclosed subject matter. 
     Processor device  604  may be a special purpose or a general-purpose processor device. As will be appreciated by persons skilled in the relevant art, processor device  504  may also be a single processor in a multi-core/multiprocessor system, such system operating alone, or in a cluster of computing devices operating in a cluster or server farm. Processor device  604  may be connected to a communication infrastructure  606 , for example, a bus, message queue, network, or multi-core message-passing scheme. 
     In an exemplary embodiment, computer system  600  may include a display interface  602 , for example a video connector, to transfer data to a display unit  630 , for example, a monitor. Computer system  600  may also include a main memory  608 , for example, random access memory (RAM), and may also include a secondary memory  610 . Secondary memory  610  may include, for example, a hard disk drive  612 , and a removable storage drive  614 . Removable storage drive  614  may include a floppy disk drive, a magnetic tape drive, an optical disk drive, a flash memory, or the like. Removable storage drive  614  may read from and/or write to a removable storage unit  618  in a well-known manner. Removable storage unit  618  may include a floppy disk, a magnetic tape, an optical disk, etc., which may be read by and written to by removable storage drive  614 . As will be appreciated by persons skilled in the relevant art, removable storage unit  618  may include a computer usable storage medium having stored therein computer software and/or data. 
     In alternative embodiments, secondary memory  610  may include other similar means for allowing computer programs or other instructions to be loaded into computer system  600 . Such means may include, for example, a removable storage unit  622  and an interface  620 . Examples of such means may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an EPROM, or PROM) and associated socket, and other removable storage units  622  and interfaces  620  which allow software and data to be transferred from removable storage unit  622  to computer system  600 . 
     Computer system  600  may also include a communications interface  624 . Communications interface  624  allows software and data to be transferred between computer system  600  and external devices. Communications interface  624  may include a modem, a network interface (such as an Ethernet card), a communications port, a PCMCIA slot and card, or the like. Software and data transferred via communications interface  624  may be in the form of signals, which may be electronic, electromagnetic, optical, or other signals capable of being received by communications interface  624 . These signals may be provided to communications interface  624  via a communications path  626 . Communications path  626  carries signals and may be implemented using wire or cable, fiber optics, a phone line, a cellular phone link, an RF link or other communications channels. 
     In this document, the terms “computer program medium” and “computer usable medium” are used to generally refer to media such as removable storage unit  618 , removable storage unit  622 , and a hard disk installed in hard disk drive  612 . Computer program medium and computer usable medium may also refer to memories, such as main memory  608  and secondary memory  610 , which may be memory semiconductors (e.g. DRAMs, etc.). 
     Computer programs (also called computer control logic) are stored in main memory  608  and/or secondary memory  610 . Computer programs may also be received via communications interface  624 . Such computer programs, when executed, enable computer system  600  to implement different embodiments of the present disclosure as discussed herein. In particular, the computer programs, when executed, enable processor device  604  to implement the processes of the present disclosure, such as the operations in methods  400  and  410  illustrated by  FIGS.  4 A and  4 B , discussed above. Accordingly, such computer programs represent controllers of computer system  600 . Where an exemplary embodiment of method  200  is implemented using software, the software may be stored in a computer program product and loaded into computer system  600  using removable storage drive  614 , interface  620 , and hard disk drive  612 , or communications interface  624 . 
     Embodiments of the present disclosure also may be directed to computer program products including software stored on any computer useable medium. Such software, when executed in one or more data processing device, causes a data processing device to operate as described herein. An embodiment of the present disclosure may employ any computer useable or readable medium. Examples of computer useable mediums include, but are not limited to, primary storage devices (e.g., any type of random access memory), secondary storage devices (e.g., hard drives, floppy disks, CD ROMS, ZIP disks, tapes, magnetic storage devices, and optical storage devices, MEMS, nanotechnological storage device, etc.). 
     Example 1: Biosensor Fabrication 
     In this example, an exemplary biosensor similar to biosensor  102  was fabricated via a process similar to a process according to exemplary method  200  described hereinabove and schematically illustrated in  FIGS.  3 A- 3 I . An n-type Si wafer with approximate dimensions of 1 cm in 2 cm was used as an exemplary substrate. In a first step, the substrate was thoroughly cleaned using RCA#1 method (with NH 4 OH: H 2 O 2 : H 2 O solution and a volume ratio of 1:1:5), rinsed in deionized (DI) water, and dried. An insulating oxide layer was then formed on the substrate using an open chemical vapor deposition (CVD) quartz furnace similar to step  202  of exemplary method  200 . The substrate was placed in the furnace, and temperature was slowly ramped up to 1100° C. and held there for oxidation under a constant flow of O 2  gas. After approximately 40 minutes, a 500 nm thick silicon oxide (SiO 2 ) layer was formed on the Si substrate. In the next step similar to step  204  of exemplary method  200 , half of this oxide layer was removed using 10% HF acid solution, while the other half was covered with a cured negative photoresist. This photoresist layer was then etched away with acetone. To form metallic contacts similar to step  206  of exemplary method  200 , two square windows with approximate dimensions of 3 mm in 3 mm were formed using standard photolithography, where one window was placed on the oxide layer and the other on the bare Si substrate. Next, the substrate was placed in a physical vapor deposition (PVD) chamber and a 100 nm gold (Au) thin film was deposited on the substrate. The substrate was then rinsed in acetone to clear away the remaining photoresist layer, leaving only two metallic Au contacts. Similar to step  208  of exemplary method  200 , graphene mono-layers were deposited on 18 μm thick Cu foils, and then coated with a thin layer of polymethylmethacrylate (PMMA). Graphene layer of the appropriate proportions was cut from Cu/graphene/PMMA foil using standard scissors. This layer was then transferred into a beaker containing FeC 13  solution, where it floats on top of the solution as the Cu is dissolved away. The layer was then fished out using an RCA#1 cleaned glass slide into a beaker containing distilled water. The last step was repeated several times to ensure that there was no residue left from the FeCl 3  solution. In the final step, the graphene/PMMA layer was dip coated on the Si/SiO 2 /Au layer in a way that the graphene layer came into contact with the Au contact on the SiO 2  layer on one side and the Au contact on n-type Si on the other side. After this step, the substrate was left to dry out to improve the adhesion of the graphene to the substrate. Finally, the PMMA layer was dissolved using acetone, and the sensor was annealed in an oven at 150° C. for two hours. 
     Example 2: Cancer Cells Detection via Monitoring Photocurrent of Graphene/Silicon Schottky Junction of an Exemplary Biosensor 
     In this example, a method similar to exemplary methods  400  and  410  utilizing a fabricated biosensor (similar to biosensor  102 ) of Example 1 hereinabove was used to detect and differentiate Glioblastoma cancer cells from each other and from normal (healthy) cells. Glioma cell line U87MG (IBRC C10982), Glioma cell line T98G, and healthy human fibroblast cells were provided and STR DNA Profiling Analysis was performed to authenticate of Glioma cell lines. Cells were cultured in Dulbecco&#39;s modified Eagle&#39;s medium (DMEM) supplemented with 100 U/ml penicillin and 100 g/ml streptomycin plus 10% fetal bovine serum (FBS). Cells were incubated at 37° C. in a humidified atmosphere containing 5% CO 2  until 90% confluency was reached. In order to coat exemplary fabricated biosensors similar to sensor  102  by cells similar to each of steps  401  and  412 , approximately 1.2×10 6  of each cell lines and human fibroblast were suspended in 1 ml phosphate buffer saline and poured gently on the biosensors which were placed on the bottom of 6 respective well plates in duplicate. The plates were incubated at 37° C. in a humidified atmosphere containing 5% CO 2 . Controls of cell growth and confluency were wells which were coated by each of the cell lines and human fibroblast. By the time the control wells have reached 90% confluency, the cell coated biosensors were removed from each well and were used in photocurrent tests. Silicon epoxy containers were used to isolate exemplary graphene layers of the biosensors and to act as a barrier to hold an exemplary solution containing the cells. All biosensors were characterized in dark and also under irradiation by different wavelengths of light before the addition of cells. The cells were added to the epoxy containers that were created to hold the cell solution, and during tests, these wells were filled with PBS solutions. These tests were carried out similar to steps  404 - 408  and/or  414 - 420  and repeated in the presence of different cell lines, and changes in photocurrent were recorded for comparison. High quality commercial 3W LEDs were used as light sources with peak intensities in 380 nm, 425 nm, 520 nm, 620 nm, 740 nm and 850 nm for irradiating a light beam to cells adhered to an exemplary graphene/Si Schottky junction of an exemplary fabricated biosensor similar to each of steps  401  and  412 . 
       FIG.  7    shows graph  700  that illustrates current-voltage characteristics of exemplary fabricated graphene/Si Schottky junction in dark and under illumination by different wavelengths of light, including 380 nm, 425 nm, 520 nm, 620 nm, 740 nm, and 850 nm with the same intensity of about 200 μW/cm 2 , consistent with one or more exemplary embodiments of the present disclosure. It may be seen that under illumination in reverse bias (part  702  of diagram), exemplary biosensor shows a significant increase in current by increasing irradiated light wavelength in a direction illustrated by arrow  701  from 380 nm to 850 nm, while forward bias (part  704  of diagram) remains largely unchanged. A change in the reverse bias current increases as wavelength increases towards red and IR region (for λ more than 650 nm). Accordingly, cancer diagnostic tests were confined to a reverse bias regime of an exemplary graphene/Si Schottky contact, where it acts as a broadband photodetector, and changes in photocurrent were recorded. 
       FIG.  8    shows a set of diagrams  800  illustrating current-voltage characteristics of an exemplary biosensor with and without T98G and U87 cell lines as specified in top guide  801 , in dark and under light illumination with different wavelengths of light of 380 nm (diagram  802 ), 425 nm (diagram  804 ), 520 nm (diagram  806 ), 620 nm (diagram  808 ), 740 nm (diagram  810 ), and 850 nm (diagram  812 ), consistent with one or more exemplary embodiments of the present disclosure. As may be seen, in wavelengths longer than 520 nm, a better distinction between cells may be obtained. For easier comparison of data represented in  FIG.  8   ,  FIG.  9    shows a graph  900  illustrating reverse photocurrent of exemplary biosensor in the absence and presence of different cancer cell lines for different wavelengths at diode voltage (V D ) of −1 V, consistent with one or more exemplary embodiments of the present disclosure. It may be seen that below 520 nm for wavelengths (λ) of 425 nm or less, photocurrent is lower in the presence of both cell lines relative to bare Schottky junction without any cells. Whereas, above 520 nm and the start of the near IR window in biological tissue, exemplary biosensor shows a higher photocurrent in the presence of U87 cell lines, while in the presence of T98G cell lines, the photocurrent seems to remain more or less constant, and lower than the photocurrent of the bare Schottky junction. Such changes and differences in reverse regime behavior may be used to differentiate between the two cell lines U87 and T98G. As a result, for U87 cells and T98G cells, in a shadow effect regime, there is a greater current decrease for U87 cells in comparison with T98G cells. As wavelength increases and charge transfer effect becomes more dominant in IR window, these two cells switch places and lower reverse current belongs to T98G cells. This means that T98G cells have induced depletion regions on graphene monolayer and therefore, created higher Schottky barriers in graphene monolayer. Specifically regarding  FIGS.  5 A and  5 B  described hereinabove, in an exemplary second regime of irradiating a light beam in an exemplary second wavelength range, exemplary biosensor  102  may show a higher photocurrent in the presence of U87 cell lines, while in the presence of T98G cell lines, exemplary photocurrent may remain constant, and lower than a photocurrent of an exemplary bare graphene/Si Schottky junction. 
     Healthy human fibroblast cells were also tested to determine behavior of an exemplary biosensor in the presence of healthy cells.  FIG.  10    shows a graph  1000  illustrating I-V characteristics of an exemplary graphene/Si Schottky junction (diode) under illumination with wavelength of 850 nm in the presence of human fibroblast cells (curve  1002 ) and in a bare mode without any cells thereon (curve  1004 ), consistent with one or more exemplary embodiments of the present disclosure. As seen in  FIG.  10   , in the presence of human fibroblast cells, there is a drastic change in current-voltage characteristic curve of an exemplary biosensor and a rectifying Schottky junction behavior is almost completely diminished (curve  1002 ) in comparison with a rectifying behavior of exemplary biosensor without cells (curve  1004 ). This is further confirmed in relative change of photocurrent, where an increasing behavior may be seen for electrical currents generated within reverse bias regime in the presence of healthy human fibroblast cells (curve  1002 ) in comparison with an approximately constant electrical current within reverse bias regime in the presence of cancer cells ( FIGS.  7  and  8   ) or in the absence of any cells (curve  1004 ). 
     As described hereinabove referring to  FIG.  4   , a diagnostic behavior of photoelectrical properties of an exemplary biosensor in the presence of cancer cells may be monitored in an exemplary second range of wavelength magnitudes more than about 600 nm.  FIG.  11    shows a graph  1100  illustrating UV-Visible transmission spectra of PBS solutions containing T98G, U87, and human fibroblast cell lines, consistent with one or more exemplary embodiments of the present disclosure. As may be seen from  FIG.  11   , there is a sudden increase in light transmission for both T98G and U87 cells for wavelengths larger than 600 nm in an exemplary second regime or charge transfer effect regime (the start of the near IR window). There appears to be no prominent qualitative difference between the transmission spectra of the two T98G and U87 cancer cell lines. Therefore, the main mechanism behind different photoresponses of an exemplary biosensor in the presence of these two Glioblastoma cell lines is due to an electrical interaction between the cells and the graphene monolayer. 
     To better demonstrate sensitivity and selectivity of an exemplary biosensor, amperometric tests were performed under a reverse bias voltage of −1 V.  FIG.  12    shows a set of diagrams  1200  illustrating current versus time (I-t) characteristics with and without T98G, U87, fibroblast cells in dark and under illumination with lights of different wavelengths of 380 nm (diagram  1202 ), 425 nm (diagram  1204 ), 520 nm (diagram  1206 ), 620 nm (diagram  1208 ), 740 nm (diagram  1210 ), and 850 nm (diagram  1212 ) by applying V D  of −1 V as specified in top guide  1201 , consistent with one or more exemplary embodiments of the present disclosure. An exemplary biosensor with no cells, and exemplary biosensors with U87 and T98G cell lines behave as a standard Schottky junction with small dark currents and a high photocurrent. 
     To better quantify the results, relative photocurrent change (RPC) in the reverse bias is plotted in  FIG.  13   .  FIG.  13    shows a chart  1300  illustrating relative change of photocurrent versus wavelength with and without different cell lines at V D  of −1 V, consistent with one or more exemplary embodiments of the present disclosure. It may be seen that in the absence of cells and in the presence of U87 cell line, there is an increase in the RPC with increasing wavelength. However, the T98G cell line shows an increase in the RPC from shorter wavelengths to 520 nm, but starts to show a decrease in the RPC from 520 nm to 850 nm. In a context of a hypothesized shadow effect and charge transfer effect, the initial increase of the RPC from 380 nm to 520 nm is expected due to the shadow effect of both cell lines. This increase in RPC is a part of the signature behavior of the broadband Si/graphene Schottky junction. However, the subsequent decline of the RPC in the case of T98G cell line, as the wavelength enters into near IR biological window, suggests that these cells create depletion regions with higher Schottky barrier heights. Therefore, although the light in the IR window reaches the active area below the adhered cells, the high Schottky barriers there effectively prohibit any electron emission from graphene to Si. 
     On the other hand, the U87 cell line in the IR window shows a marked increase in RPC relative to the device with T98G cells. This suggests the existence of local regions with lower Schottky barriers where the cells have adhered to the graphene. This increases the electron emission from graphene to Si in these regions. The different behavior of the two Glioblastoma cancer cell lines can be used to identify and differentiate between U87 and T98G cell lines. 
     It should also be noted that the T98 cell line comes from a 61 years old male patient, which has no tumorigenic ability. Tumorigenicity is the tendency of cultured cells to develop benign or malignant growing tumors when injected to an immunologically unresponsive animal. U87 cell line is reported to come from a male patient of unknown age, which has tumorigenic ability. U87 cells were significantly more invasive, compared to the T98G cell line. 
     While the foregoing has described what are considered to be the best mode and/or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that the teachings may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all applications, modifications and variations that fall within the true scope of the present teachings. 
     Unless otherwise stated, all measurements, values, ratings, positions, magnitudes, sizes, and other specifications that are set forth in this specification, including in the claims that follow, are approximate, not exact. They are intended to have a reasonable range that is consistent with the functions to which they relate and with what is customary in the art to which they pertain. 
     The scope of protection is limited solely by the claims that now follow. That scope is intended and should be interpreted to be as broad as is consistent with the ordinary meaning of the language that is used in the claims when interpreted in light of this specification and the prosecution history that follows and to encompass all structural and functional equivalents. Notwithstanding, none of the claims are intended to embrace subject matter that fails to satisfy the requirement of Sections 101, 102, or 103 of the Patent Act, nor should they be interpreted in such a way. Any unintended embracement of such subject matter is hereby disclaimed. 
     Except as stated immediately above, nothing that has been stated or illustrated is intended or should be interpreted to cause a dedication of any component, step, feature, object, benefit, advantage, or equivalent to the public, regardless of whether it is or is not recited in the claims. 
     It will be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein. Relational terms such as first and second and the like may be used solely to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “a” or “an” does not, without further constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. 
     The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in various embodiments. This is for purposes of streamlining the disclosure, and is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter. 
     While various embodiments have been described, the description is intended to be exemplary, rather than limiting and it will be apparent to those of ordinary skill in the art that many more embodiments and embodiments are possible that are within the scope of the embodiments. Although many possible combinations of features are shown in the accompanying figures and discussed in this detailed description, many other combinations of the disclosed features are possible. Any feature of any embodiment may be used in combination with or substituted for any other feature or element in any other embodiment unless specifically restricted. Therefore, it will be understood that any of the features shown and/or discussed in the present disclosure may be implemented together in any suitable combination. Accordingly, the embodiments are not to be restricted except in light of the attached claims and their equivalents. Also, various modifications and changes may be made within the scope of the attached claims.