Chemical detection sensor system

A chemical detection sensor system comprises a support structure; multiple SERS chemical detection sensors supported by the support structure; multiple chemical reaction sensors, wherein each of the chemical reaction sensors is disposed for undergoing a state change in response to an occurrence of a chemical reaction at one of the SERS chemical detection sensors; a processor supported by the support structure for recording data representing occurrence of a chemical reaction at any of the chemical detection sensors in response to sensing the state change; and a power source for energizing the processor.

BACKGROUND OF THE INVENTION

In the 1970s, it was discovered that Raman scattering of analyte molecules, upon irradiation with optical energy, can be enhanced as much as 106to 107when the molecules are adsorbed on noble metals such as silver, copper, and gold. This phenomenon is known as surface enhanced Raman spectroscopy (SERS). A SERS structure generally includes a metal layer formed on a substrate and is used to detect the presence of an analyte by examining the emissions from the substrate when irradiated with optical energy. SERS emissions, or spectra, have been used to detect and identify trace organics and as a detection method in gas chromatography, liquid chromatography, and thin layer chromatography. Electro chemical SERS and SERS of chemically modified surfaces have been used to detect aromatic compounds and chlorinated hydrocarbons and other organic contaminants of environmental concern in the ppb to ppm range. SERS analysis generally requires bulky equipment and typically is performed in a laboratory setting. However, there are many applications in which it would be desirable to detect the presence of analytes in other than laboratory environments. A SERS sensor that is easily transportable and that may be used in the field would be desirable.

SUMMARY OF THE INVENTION

A chemical detection sensor system comprises a support structure; multiple SERS chemical detection sensors mounted on the support structure; multiple chemical reaction sensors, wherein each of the chemical reaction sensors undergoes a state change in response to an occurrence of a chemical reaction at one of the SERS chemical detection sensors; a processor supported by the support structure for recording data representing the occurrence of a chemical reaction at any of the chemical detection sensors in response to sensing the state change; and a power source for energizing the processor.

Throughout the several views, like elements are referenced using like references.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of a chemical detection sensor system includes multiple SERS chemical detection sensors that may be configured into an array. Each chemical detection sensor of the array is designed to react with a specific class of compounds and consists of a thiol-coated, SERS-active substrate. Thiol coatings are chosen that will chemically bond to an analyte that one is interested in detecting. Once an analyte binds to the thiol coating, the analyte may be identified and quantified by its characteristic Raman emissions. Thus, an array of SERS chemical detection sensors may be designed to detect one or more different classes of chemicals or analytes, depending upon the specific thiol coating employed.

An example of an expected spectral response is shown inFIG. 1, which shows SERS spectra of sulfate interaction with a cysteamine coated chemical detection sensor. Cysteamine has a quaternary ammonium group that forms an ion pair with sulfate ion. In the example described herein, the sulfate compound is the analyte. InFIG. 1, the evolution of the sulfate peak as it interacts with the coating is seen at a wavelength of about 1000 cm−1. The concentration response of the sulfate, shown inFIG. 2, may be used to quantify the amount of sulfate that reacted with the chemical detection sensor. In the example shown inFIG. 1, the cysteamine coating reacts reversibly with sulfate ion. It is desirable for the analyte to irreversibly chemically react with the coating on the chemical detection sensor so as to form a new compound, that may be detected and quantified by its characteristic Raman spectral emission.

The thiol coating on a SERS chemical detection sensor protects the SERS-active metal surface of the sensor from degradation due to oxidation. However, depending upon the thiol coating selected, the chemical detection sensor may be employed to detect chemicals of environmental concern such as: drugs, explosives, and agents used in chemical warfare. Because many chemical reactions occur in water, one or more of the chemical detection sensors may include a hydrogel layer to allow the thiol coating to chemically react with specific analytes. The hydrogel layer may be formulated to contain the needed reagents to facilitate reaction between the analyte and the thiol coating.

Each SERS chemical detection sensor is intended for a single use application. The chemical detection sensor system may be carried by a person who is conducting site inspections, left in a given area for a specified period of time, or mounted on a remotely operated vehicle such as a car, airplane, or robot. After exposure, the chemical detection sensor system may be taken into a laboratory where the individual SERS chemical detection sensors may be individually interrogated using a Raman-based spectroscopy system to identify the chemicals that have reacted with the thiol coatings of the various SERS chemical detection sensors. Interrogation of only those SERS chemical detection sensors that have undergone a chemical reaction may be determined by coupling a SERS chemical detection sensor to a particular chemical reaction sensor of the sensor array. If a chemical reaction occurs, the chemical reaction sensor associated with a specific SERS chemical detection sensor undergoes a state change that is indicative of a chemical reaction.

Referring toFIGS. 3A and 3B, there is shown a surface enhanced Raman spectroscopy chemical detection sensor system200for detecting chemicals of interest, wherein such chemicals may also be referenced herein as analytes. Chemical detection sensor system200includes a support structure203, such as a printed circuit board; a module202that houses an array of SERS chemical detection sensors and is supported by the structure203; multiple chemical reaction sensors205; processor206; optional global positioning system (GPS)208; optional clock210; and power source212, all or some of which may be supported by structure203. Power source212provides electrical power to each of global positioning system (GPS)208, clock210, and processor206via power line215. Each individual chemical reaction sensors205may be mounted in a fixing layer224formed on support structure203. For example, fixing layer224may be formed of an epoxy, or any other substance typically used for affixing electrical components to a support structure. Chemical reaction sensors205are positioned in fixing layer224which is mounted between module202and support structure203. Each chemical reaction sensor205is disposed to detect a change in state when the specific SERS chemical detection sensor204undergoes a chemical reaction with the analyte. State changes for each sensor205are presented on a signal line217coupled between each SERS chemical detection sensor204and processor206. By way of example, chemical reaction sensor205may be implemented as a thermocouple and/or a surface acoustic wave (SAW) device. When implemented as a thermocouple, chemical reaction sensor205is disposed for detecting the heat transfer either to or from the SERS chemical detection sensor204that is operably coupled to that particular chemical reaction sensor205. The heat transfer is caused by a chemical reaction between the SERS chemical detection sensor204and an analyte. When implemented as a SAW device, chemical reaction sensor205detects changes in the acoustic properties of a particular SERS chemical detection sensor204caused by a chemical reaction between the SERS chemical detection sensor and an analyte. Then processor206records an occurrence of a chemical reaction at one or more of the SERS chemical detection sensors204, based on sensing the state change that is detectable on one of the signal lines217. Optionally, processor206may also record the specific time and/or position of the sensor200based on clock signal214generated by clock210, and global position signal216generated by GPS208in order to determine the time and location of the occurrence of particular chemical reactions detected by sensor200. The clock signal214represents a time value generated by clock210, and global position signal216represents a global position value generated by GPS208.

The manufacture of a SERS chemical detection sensor204includes metal islands formed on the roughened surface of a transparent substrate such as transparent glass. When in contact with an analyte of interest and illuminated with appropriate excitation energy, a SERS chemical detection sensor will produce spectra having unique characteristics that are used to identify and quantify the amount of analyte detected. By way of example, analytes may include organic, metallic, and anionic contaminants. Referring toFIGS. 4 and 5, SERS chemical detection sensor204includes a specially roughened surface12of a transparent substrate14, such as glass, on which an adhesion layer15is formed. Adhesion layer15promotes the bonding of the metal islands16to the glass substrate14. The metal islands16are formed, as for example, by vapor deposition, on adhesion layer15to create a metal patterned substrate11, shown inFIG. 8. A thiol coating, or self-assembled monolayer18on metal islands16protects metal islands16from degradation, thereby extending the lifetime of chemical detection sensor204when exposed to air or aqueous environments from minutes or hours to months. The roughened surface12facilitates both a good SERS response and adhesion of the metal islands16to the substrate14.

In the fabrication of SERS chemical detection sensor204, transparent substrate14, such as a clear borosilicate glass slide, is carefully cleaned and prepared prior to having a metal film deposited on it. First, substrate14is immersed in a heated or boiling liquid reagent or reagents to remove any oils, metallic materials, and other contaminants that may be present on substrate14. By way of example, a transparent substrate14may be immersed in boiling nitric acid for about 30 minutes. However, other liquid reagents also may be used such as hydrofluoric acid, hydrochloric acid, potassium hydroxide. Next, substrate14is removed from the boiling nitric acid and rinsed in either deionized or distilled water. After the water rinse, substrate14is immersed in hot or boiling methanol for about 30 minutes, followed by immersion in boiling acetone for about 30 minutes. This procedure removes any remaining organic contaminants. Substrate14is then removed from the methanol and allowed to air dry, as for example, about 1 hour.

Referring toFIG. 6, cleaned surface12of substrate14is etched to provide surface12with a surface roughness having a maximum peak to valley depth of about 16,000, an average peak to valley depth of about 2,500, and a peak-to-peak periodicity of about 12.5 microns. The roughness of surface12and its periodicity may be measured using a Dektak3ST Surface Profiler (Vecco Sloan Technology). In contrast, commercial white glass generally has a surface having a peak to valley depth of about 200,000, an average peak to valley depth of about 43,700, and a peak-to-peak periodicity of about 100 microns. The combination of surface roughness and peak-to-peak periodicity of surface12provides SERS chemical detection sensor204with a greatly enhanced SERS response. In one implementation of an embodiment of a SERS chemical detection sensor204, surface12may be etched using a chemical etchant such as an HF based cream such as Velvet Etching Cream, manufactured by McKay International. Experience has shown that etching white glass for approximately 1 minute provides the surface roughness characteristics described above. Alternatively, surface12may be roughened using standard photo lithographic techniques.

After etching, structure14is rinsed with distilled or deionized water, followed by an ethanol rinse. The cleaned, etched substrate14is then derivitized in a silanization agent such as a 1:10 mixture by volume of (3-mercaptopropyl) trimethoxysilane (MCTMS) in ethanol for about 24 hours to form adhesion layer15on roughened surface12. As shown inFIG. 7, it is believed that the derivitization process causes a silane layer to bond to−OH functional groups believed to be present on surface12when substrate14is implemented as a transparent glass substrate. Substrate14was next rinsed in ethanol to remove unreacted (3-mercaptopropyl) trimethoxysilane and allowed to air dry. Adhesion layer15promotes bonding between roughened surface12and metal islands16.

When metal islands16are formed by vapor deposition, as shown inFIG. 12, one or more cleaned substrates14are positioned so that they each rest on both a stainless steel spacer84and on support structure82in a vapor deposition system80so that roughened surfaces12face upwardly at a slight angle a with respect to the horizontal. The angle may be in the range, for example, of about 3–5 degrees, and more preferably, 4.5 degrees. The purpose of canting substrate14at an angle with respect to the horizontal is to create “shadows” that prevent the deposited metal that comprises metal islands16from forming a continuous metal layer on roughened or discontinuous surface12. Discontinuities on the surfaces of metal islands16have that have been shown to enhance the SERS response of SERS chemical detection sensor204. By way of example, a metal such as gold, silver, or copper may be vapor deposited onto adhesion layer15to form metal islands16. In one implementation of an embodiment of chemical detection sensor204, gold islands were vapor deposited onto roughened surface12using material evaporated from an Aldrich, 99.99% pure gold wire. Vapor deposition system80may be implemented as a Vecco Model E.C. 200 vapor deposition system. As a result of the aforesaid processing, adhesion layer15durably bonds metal islands16to roughened surface12so that SERS chemical detection sensor204may provide an effective SERS response after being immersed in an aqueous environment for months.

After depositing metal islands16onto adhesion layer15a patterned metal structure11, as shown inFIG. 8, is created. Patterned metal structure11may be placed in a dilute ethanolic thiol solution at ambient temperature and pressure for a period of time, such as 24 hours. While metal structure11is immersed in the thiol solution, metal islands16react with the thiol to form a durable, self-assembled monolayer18on the metal islands16, as shown inFIG. 8. Thiol coatings may be selected which have an affinity for the analyte (organic compounds, metal ions, or anions) of interest. Moreover, detection limits in the ppb to ppm range are possible. TABLE 1 provides, by way of example, a list of examples of thiols and analytes that may be detected using such thiol coatings. However, TABLE 1 is not to be considered exhaustive.

An example of an application of chemical detection sensor system200is described with reference toFIG. 9for obtaining Raman spectra using fiber optic system50. Excitation light source52, such as a Spectra Diode Laser, Inc. Model SDL-5712-H1, generates a monochromatic coherent optical signal54having a wavelength of 852 nm that is focused into 200 nm diameter excitation fiber56. Optical signal54emitted from excitation fiber56is collimated by lens58, such as a 6.4 mm focal length plano-convex lens manufactured by Newport, Model KPX010R.16. Interferences due to fiber Raman emissions may be removed by band pass filter60(Chroma Technology Part No. 852BP) and dichroic mirror62(Chroma Technology Part No. 852RDM). Excitation light54focused by plano-convex lens63, having a 12.7 mm focal length, onto mirror64reflects excitation signal54to a specific SERS chemical detection sensor204of module202. The interaction of excitation signal54and SERS chemical detection sensor204in the presence of an analyte of interest generally results in emission of Raman scattering signals72that are reflected by mirror64to lens63. Scattering signals72reflected by mirror74are directed through long pass filter76, such as a Chroma Technology, Part No. 852REF. Lens78focuses the scattered Raman emissions72into a 365 nm diameter collection optical fiber80. Filter76blocks excitation signal54, thereby preventing excitation of Raman emissions in collection fiber80. Fiber80directs Raman emissions72to Raman system82which may be implemented as a Chromex Raman One Spectrometer. The Raman system82converts the Raman emissions72into a Raman spectrum84. The Raman spectrum84from Raman system82is displayed and analyzed on a PC workstation86.

FIGS. 10 and 11show Raman spectra of p-thiocresol chemisorbed on a thin film of gold formed on glass substrates, referenced as a “SERS chemical detection sensor” for convenience. The horizontal axis in each ofFIGS. 10 and 11represent the wavelength of the emitted spectra. The vertical axis in each ofFIGS. 10 and 11represents optical intensity or number of photons emitted at 1073 cm−1detected with a Chromex Raman One Spectrometer using a diffraction grating having 600 grooves/mm and binning three horizontal pixels. The detector was operated at −50 C, and had a 100 second CCD integration time. The SERS chemical detection sensors204were illuminated with an 852 nm DBR diode laser. Laser power at the sample was 63 mW. The element used to generate the curves inFIG. 10included a layer of gold having a thickness of151that was formed on a commercial white glass substrate. Curve90represents the number of photons generated from a SERS chemical detection sensor having a glass surface untreated with MCTMS. Curve92represents the number of photons generated from a SERS chemical detection sensor having a gold layer formed on a glass surface treated with MCTMS. Thus, fromFIG. 10, it may be appreciated that a SERS chemical detection sensor comprised of a gold layer formed on commercial white glass surface that is not treated with MCTMS exhibits a good SERS response, i.e., it emits a relatively high number of photons when illuminated as described. However, the gold film has very poor adhesion to such untreated surfaces and is very fragile. Treating a commercial white glass surface with MCTMS greatly improves the durability of the bond between the gold layer and the commercial white glass surface. However, the SERS response of the MCTMS surface results in a relatively poor SERS response as revealed by curve92ofFIG. 10.

Referring now toFIG. 11, curve94represents the number of photons emitted from a SERS chemical detection sensor204having gold islands formed on a transparent glass surface that is untreated with MCTMS and which is etched in accordance with the teachings herein. Curve96represents the number of photons generated from SERS chemical detection sensor204having gold islands16that is manufactured in accordance with the teachings herein. The SERS response at 1073 cm−1as represented by curves94and96are indistinguishable. However, the SERS chemical detection sensor used to generate curve94has very fragile gold islands which were not bonded well to the glass substrate, whereas the SERS chemical detection sensor204used to generate curve96has very durable gold islands. Thus, it may be appreciated that the SERS chemical detection sensors described herein each have metal islands durably bonded to a glass substrate and exhibit an excellent SERS response.

Another embodiment of a SERS chemical detection sensor204athat exhibits a good SERS response and is durable in an aqueous environment is manufactured using electrochemical techniques described with reference toFIGS. 13–16. Referring toFIG. 13, the fabrication of SERS chemical detection sensor204astarts by immersing substrate14a, such as clear, borosilicate glass in a heated or boiling liquid reagent or reagents such as nitric acid, hydrofluoric acid, hydrochloric acid, or potassium hydroxide, for about 30 minutes. Such immersion removes any oils, metallic materials, and other contaminants that may be present on substrate14a. Next, substrate14ais removed from the boiling reagent and rinsed in either deionized or distilled water. After the water rinse, substrate14ais immersed in hot or boiling methanol for about 30 minutes, followed by immersion in boiling acetone for about 30 minutes. This procedure removes any remaining organic contaminants. Substrate14athen is removed from the boiling methanol and allowed to air dry, as for example, about 1 hour.

Cleaned substrate14athen is derivitized in a silanization agent such as a 1:10 mixture by volume of (3-mercaptopropyl) trimethoxysilane (MCTMS) and ethanol for about 24 hours to form adhesion layer15aon substrate14a. Substrate14anext is rinsed in ethanol to remove unreacted (3-mercaptopropyl) trimethoxysilane and allowed to air dry.

A continuous metal layer17made from a material such as gold, copper, or silver, is vapor deposited onto adhesion layer15ato create a metal coated chemical detection sensor204a. The metal coated SERS chemical detection sensor204anext is subjected to electro chemical techniques described with reference toFIG. 14. Metal coated SERS chemical detection sensor204ais partially immersed in an electrochemical cell111that includes electrolyte101such as a0.1M solution of potassium chloride (KCl) held within fluid container101and electrodes105and108, and a working electrode113comprised of clamp106and the metallic layer17of metal coated SERS chemical detection sensor204a. Metal coated SERS chemical detection sensor204ais clamped to side102of fluid container104by metallic clamp106so that there is electrical continuity between clamp106and metal layer17. It is important that metallic clamp106not be immersed in the electrolyte101to prevent metallic ions from the clamp from contaminating the electrolyte. Also immersed in electrolyte101are counter electrode105and reference electrode108. Counter electrode105preferably is made of platinum wire107and platinum gauze109that is electrically and mechanically coupled to wire107. Electrode105is positioned so that gauze109is immersed in electrolyte101to increase the active surface area of electrode105in electrolyte101. Reference electrode108preferably is made of silver/silver chloride. Electrodes105and108, and clamp106are connected via wires110,112, and114, respectively, to potentiostat116. Potentiostat116maintains appropriate voltage levels at each of electrodes105and108, and, electrode113under the supervision of computer118via signal line120.

In the manufacture of SERS chemical detection sensor204a, the voltage, VW, of working electrode113is modulated from −300 mV to 1200 mV with respect to the voltage of reference electrode108for a predetermined number of oxidative-reductive cycles. An example of an oxidative-reductive cycle is shown, by way of example, inFIG. 15. Referring toFIG. 15, in an oxidative-reductive cycle, VWis held at −300 mV for about 30 seconds and then ramped to 1200 mV at a rate of about 500 mV/s. Next, VWis held at 1200 mV for about 1.3 seconds and then reduced to −300 mV at a rate of about −500 mV/s. Subjecting SERS chemical detection sensor204ato preferably 25 oxidative-reductive cycles of the type described above with reference toFIG. 15, transforms metal layer17into isolated metal islands16ahaving an average surface roughness of about 20 Å, thereby creating a patterned metal SERS chemical detection sensor204a, as shown inFIG. 16.

SERS chemical detection sensor204athen may be placed in a dilute ethanolic thiol solution at ambient temperature and pressure for a period of time, such as 24 hours, so that the metal islands16amay react with a thiol to form a durable, self-assembled monolayer18on the metal islands16. Thiol coatings may be selected which have an affinity for the analyte (organic compounds, metal ions, or anions) of interest. Examples of suitable thiol coatings are identified in TABLE 1, above.

Referring toFIG. 17, there is shown another embodiment of chemical detection sensor system200wherein each of the SERS chemical detection sensors204are fabricated in wells230formed in transparent substrate14, such as borosilicate glass. By way of example, wells230may have 2.0 mm×2.0 mm perimeters232and be spaced about 2.00 mm apart in a rectangular array as shown inFIG. 3. SERS Chemical detection sensor204includes a specially roughened surface12in each well230of glass substrate14. Then an adhesion layer15is formed over the roughened surface12. Adhesion layer15promotes the bonding of the metal islands16to the glass substrate14. The metal islands16are formed, as for example, by vapor deposition, on adhesion layer15to create a metal patterned substrate11, shown inFIG. 8. A thiol coating, or self-assembled monolayer18on metal islands16protects metal islands16from degradation, thereby extending the lifetime of SERS chemical detection sensor204when exposed to air or aqueous environments from minutes or hours to months. As described above, the roughened surface12facilitates both a good SERS response and adhesion of the metal islands16to the substrate14. Referring again toFIG. 17, a hydrogel layer234is formed over the self-assembled monolayer18and adhesion layer15. The hydrogel layer234should having a thickness sufficient to completely cover the self-assembled monolayer18, as for example, in the range of about 0.1 to 0.5 microns. The hydrogel layer234facilitates diffusion of an analyte towards the self-assembled monolayer of the SERS chemical detection sensor204and allows chemical reactions between the monolayer and analyte to occur in an aqueous environment. The hydrogel layer may contain additional reagents to facilitate the chemical reaction between the monolayer and analyte. Glass substrates having well structures suitable for use in conjunction with the disclosed embodiments may be obtained commercially from BioTrove in Cambridge, Mass.

FIGS. 18 and 19show an embodiment of a SERS chemical detection sensor system200includes a module202having multiple SERS chemical detection sensors204of which one or more may that include a pH sensor242. The pH sensors242are electrically coupled via electrodes243to electrical interconnect254. In turn, interconnect254is electrically coupled via signal line254to processor206. SERS chemical detection sensors204of module202further include a hydrogel layer234formed in well230of transparent substrate14. An end247of pH sensor242is coextensive with sidewall233of well230so that pH sensor242is in direct physical contact with the hydrogel layer234. When a chemical reaction occurs at any one of SERS chemical detection sensors204, the pH level of the hydrogel layer234of that particular SERS chemical detection sensor204changes. The occurrence of a change in the pH level of the hydrogel layers of any of pH sensors242is recorded by processor206. By way of example, electrodes243may be fabricated from electrically conductive materials such as aluminum, silver, copper, and gold. Electrodes243may also be made of electrically conductive polymers. An electrical insulating layer256, which may consist essentially of silicon dioxide, is formed over each pH sensor242and its associated electrodes243to secure and maintain the position of pH sensors242in the module202. BecauseFIG. 19provides an elevation view of SERS chemical detection sensor204, only a single electrode243is shown associated with each SERS chemical detection sensor204. However, it is to be understood that one or more electrodes243may be coextensive with side wall233of each SERS chemical detection sensor204.

In another embodiment of SERS chemical detection sensor system200, electrodes250may be directly coupled to processor206, so that the processor may determine the electrical conductivity between electrodes250of a particular SERS chemical detection sensor204. The electrical conductivity of hydrogel layer234may change when a chemical reaction occurs in any of SERS chemical detection sensors204. Such change in the electrical conductivity may be sensed as a change of state of the conductivity of the hydro gel layer234by processor204and recorded. Generally, each of SERS chemical detection sensors204includes a pair of electrodes250.

Another embodiment of a chemical detection sensor system200is shown inFIGS. 20 and 21wherein each of SERS chemical detection sensors204includes a thermocouple271that is operably coupled through interconnect254to processor206via signal line260. When a chemical reaction occurs at any one of SERS chemical detection sensors204, the temperature of the hydrogel layer234of that particular SERS chemical detection sensor204changes, i.e., changes state. The temperature change is sensed by a thermocouple272and recorded by processor206. Referring toFIG. 19, there is shown a cross-sectional view of SERS chemical detection sensor204that includes a thermocouple271formed on transparent substrate14which preferably is coextensive with the sidewall233of well230so that thermocouple271and the hydrogel layer234are in direct physical contact, thereby facilitating heat transfer from the hydrogel layer to the thermocouple. By way of example, thermocouple271may be fabricated from two dissimilar electrically conductive materials that define wire connects274and276that are in contact with each other at sidewall233. An electrical insulating layer256, which may consist essentially of silicon dioxide, is formed over thermocouples271. Generally, the number of thermocouples271is cardinally related to the number of SERS chemical detection sensors204of module202. From the above, it may be appreciated that pH sensors242, electrodes243, and thermocouple271all comprise elements of various types of a chemical reaction sensor205.

Another embodiment of a chemical detection sensor system200is shown inFIGS. 22 and 23wherein each of SERS chemical detection sensors204includes a chemical reaction sensor205that comprises a light emitting diode (LED)270and photodetector272attached to transparent substrate14opposite self-assembled monolayer18. By way of example, the light emitting diodes270and photodetectors272may be fabricated in substrate14using photo lithographic techniques. Electrical power to the light emitting diodes270and photodetectors272is provided by power source212through interconnect254A via signal line215. LED270emits an excitation light signal280that is directed towards self-assembled monolayer18. When a chemical reaction occurs at any one of SERS chemical detection sensors204, the light signal282that is reflected off of metal islands16may have different wavelength characteristics than those of excitation light signal280. The difference in the wavelength characteristics between excitation light signal280and light signal282is believed to be due to a plasmon effect that occurs at the self-assembled monolayer. It is believed that the plasmon effect results from the change in molecular weight of the thiol that comprises the self-assembled monolayer when a chemical reaction occurs there. Photodetector276may be selected to be sensitive to a narrow band about the wavelength of light signal282that results from the occurrence of a particular chemical reaction at the self-assembled monolayer18of a specific chemical detection sensor204. Upon detection of light signal282, photodetector276generates a signal276that is provided to processor206via interconnect254B. Signal276indicates whether photodetector276, and hence chemical reaction sensor205has undergone a state change. Processor206then stores information that represents the occurrence of a particular type of chemical reaction at a specific chemical reaction sensor204.

Obviously, many modifications and variations of the chemical detection sensor system described herein are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the chemical detection sensor system may be practiced otherwise than as specifically described.