bluuebunny/crossref_metadata_2025 huggingface dataset:
Enzyme-Based Nitric Oxide (NO) Releasing Surfaces: Nitric Oxide Synthase As a Source of Catalytic NO Release in Polymeric Films and in Electrospun Fibers
Authors: Bayachou Mekki , Gunesekera Bhagya , Wojciechowski Sarah
Published: February 2020

Nitric oxide (NO) is a key player at multiple physiologic fronts including the body’s immune response, neurotransmission, and cardiovascular processes. Among other effect on the cardiovascular system, NO is known to counteract platelet aggregation, and therefore has the ability to prevent the thrombosis cascade on the surface of blood-contacting medical implants and vascular grafts. Capitalizing on this property, NO-releasing surfaces have been proposed to counteract thrombosis on the surface of implanted devices or devices used as part of cardiovascular procedures. However, previous proposals using organic or inorganic sources of NO face the challenge that the amount of available NO is finite, which limits the long-term viability of implanted devices. We proposed the use of NOS enzymes, in alternating layer-by-layer thin film architecture, as the catalytic source of NO released using substrates of the NOS reaction in blood or plasma. We will summarize the performance of thin based on polyethyleneimine (PEI) including the effect of fabrication conditions on enzyme and loading and enzyme activity and subsequent effect on counteracting platelet adhesion from platelet-rich plasma. We will also describe and characterize membranes of electrospun fibers embedding nitric oxide synthase as a catalytic source of NO release. The NO-releasing membrane is to be used as a biocompatible platform for medical applications such as support-scaffolds for internal wounds. We will describe the process of formation of these NOS-based NO-releasing fibers. We will discuss the characterization of such material with methods including atomic force microscopy and enzymatic activity assay of encapsulated enzyme by monitoring levels of NO released over time. We will compare and contrast the results of PEI-based thin films with embedded NOS enzyme and electrospun fibers with encapsulated NOS.
Development of Electrochemical and Optical Based Biosensors
Authors: Gupta Vinay , Kaur Gurpreet , Paliwal Ayushi , Tak Manvi , Sharma Anjali , Tomar Monika
Published: February 2020

During recent years, rapid and highly selective determination of nucleic acid (in particularly, DNA) has gained much importance in the field of disease diagnostics, gene analysis, tissue matching, forensic and environmental protection. Various techniques have been employed for DNA detection like fluorescence, surface plasmon resonance (SPR), quartz crystal microbalance (QCM), piezoelectric, electroluminiscene, and electro-chemical. Among all these techniques, electro chemical and SPR based biosensors for nucleic acid detection have attracted researchers worldwide due to their high sensitivity, low detection limit, fast response time, wide detection range, good reliability, easy handling and portability. DNA based biosensors rely on the immobilization of a single-stranded oligonucleotide probe onto a surface to recognize by hybridization its complementary target sequence. The probes are typically short oligonucleotides that are capable of hybridizing with specific and unique regions of the target nucleotide sequence.  Due to formation of double helical structure between complementary strands, a change in current or SPR angle could be easily observed.

In the present study, an effort has been made towards the development of ZnO matrix based biosensors for the detection of Meningitidis using electrochemical (Amperometric) and SPR techniques. The surface plasmon modes have been excited at the ZnO-gold interface in the Kretschmann configuration using a right angled BK7 glass prism (np =1.517) with the help of a laboratory assembled system. The shift in SPR reflectance curve for increasing concentration of target DNA ranging from 10 to180 ng/μl were recorded which shows the promising application of SPR technique towards biosensing. The Sensitivity of the ZnO thin film using SPR is found to be about 0.031°/(ng/μl) with the minimum detection limit of 5 ng/μl.

Zinc oxide nanostructures possessing flower-like morphology have been synthesized onto platinized silicon substrate by simple and economical hydrothermal method. The electrochemical sensing response behaviour of the DNA bioelectrode (ssth-DNA/ ZNF/Pt/Si) has been studied by both differential pulse voltammetric (DPV) as well as impedimetric techniques. The fabricated DNA biosensor can quantify wide range of the complementary targets sth-DNA in the range 5–240 ng/μl with good linearity (R=0.98), high sensitivity (168.64μAng/μl/cm2) and low detection limit of about 5ng/μl.
Facile Hydrothermal Synthesis of in2O3 Nanoboxes for Electrochemical Sensing of Paraben
Authors: Rather Jahangir Ahmad , Qureshi Ahsanulhaq
Published: February 2020

Novel indium oxide (In2O3) nanoboxes have been prepared by template-less and surfactant-free hydrothermal synthesis. Synthesized In2O3 nanoboxes were characterized by X-ray diffraction (XRD) and field emission scanning electronic microscopy (FESEM). FESEM micrographs revealed highly uniform nanoboxes with smooth surfaces and XRD analysis confirmed that these In2O3 nanoboxes grown with a cubic crystal structure. The synthesized In2O3 nanoboxes were successfully immobilized on the surface of glassy carbon electrode for the detection of Parabens (butylparaben). Owing to the unique structure and intriguing properties of these In2O3 nanoboxes, the film electrode has shown an obvious electrocatalytic activity for the detection of butylparaben (BP), since it facilitates the electron transfer and significantly enhances the oxidation peak current and lowering of the detection limit of BP. The calibration plot of concentration versus peak current was found to be linear over the range of 0.14 µM to 2.4 µM. The detection limit (LOD) was estimated as 3s/m and was found to be 0.08 µM.  This sensor showed high sensitivity compared with other electrochemical sensors reported so far for the detection of BP.

Figure 1
Nano-Asterisks of Vanadium Dioxide As Electrodes for TNT Detection
Authors: Cliffel David , Casey Matthew , Daniel Aaron
Published: February 2020

Vanadium dioxide (VO2) is a unique transition metal oxide that undergoes a first-order phase transition at approximately 340K from the insulating monoclinic phase (M) to the conducting rutile phase (R). This metal-to-insulator transition (MIT) results in a change in the resistivity and optical absorption of the material, which has made it useful in several electronic and electro-optic applications. Common synthetic techniques such as pulsed laser deposition (PLD), chemical vapor deposition (CVD), and magnetron sputtering allow for the synthesis of high quality films of VO2 for these applications. Recently, however, hydrothermal methods have been used for the synthesis of relatively large quantities of VO2(M) from inexpensive starting materials without the need for expensive instrumentation. While these hydrothermally synthesized VO2(M) particles are being developed for electronic and electro-optic applications, their applicability in other areas, such as catalysis and sensing, is the focus of research in our group. 

To make nano-asterisks of VO2, the amount of vanadium precursor present during a hydrothermal treatment was varied to produce several different morphologies of VO2(M) including plates, snowflake asterisks, and truncated asterisks.  Films of the particles were drop cast onto glass slides and four-point Van der Pauw resistivity measurements were used to determine the phase transition behavior of the particle films.  We observe resistivity changes of more than 2 orders of magnitude for drop cast films of VO2(M) nano-asterisks.  Additionally, BET gas adsorption theory was used to determine the surface area of the particles in order to evaluate their potential as electrocatalytic materials. 

The electrochemical reduction of 2, 4, 6-Trinitrotoluene (TNT) was investigated using films of vanadium dioxide, from both thin layer films formed by PLD and films composed of nano-asterisks particles. Three distinct reduction peaks were observed in the potential range -0.50 V to -0.90 V (vs. an Ag/AgCl reference electrode), corresponding to the electrochemical reduction of the three nitro-groups on the TNT molecule. Adsorptive stripping voltammetry was performed to achieve detection down to 1 µg/L (4.4 nM), revealing a linear response to TNT concentration. These results are the first describing the use of VO2 films as an electrochemical sensor for TNT, and open new avenues for further electrochemical research using this unique material.
Carbon Paste Biosensors Modified with Titanium Dioxide Nanoparticles for the Determination of Acids, Antioxidants and Glucose in Grapes
Authors: Garcia-Cabezon Cristina , Muñoz Raquel , Garcia-Hernandez Celia , Medina-Plaza Cristina , Blanco-Val Yolanda , de Saja Jose Antonio , Martin-Pedrosa Fernando , Rodriguez-Mendez Maria Luz
Published: February 2020

The use of quick, reliable and cheap sensors for the detection of chemical compounds represents an important need in the wine sector. Among the analytes that must be monitored and measured in order to guarantee the quality of final products and to verify that industrial processes are under control, glucose, phenolic compounds and acidity are the most important. Previous works have demonstrated that voltammetric electrodes chemically modified with electrocatalytic materials such as phthalocyanines or gold nanoparticles can be used to detect such compounds in musts and wines  [1]

Titanium dioxide nanoparticles TiO2 NPs have attracted much attention as catalyst support because of their large specific surface area, favorable surface chemistry, good biocompatibility, and electrocatalytic activity [2]. In this work carbon paste electrodes (CPE) modified with TiO2 NPs have been developed and used to analyze those components usually needed to establish the quality of grapes.

For this purpose, after optimization of the preparation method (proportion of TiO2, drying conditions, activation, etc), the electrochemical response toward organic acids (malic, vanillic and tartaric) and antioxidants (gallic acid and catechol) was evaluated.. It was demonstrated that the modified electrode produced higher peak currents than those achieved at carbon electrode alone, improving the detection limits. The linear range for the determination of phenolics and acids was in the range of  10−6 M at a signal-to-noise ratio of 3. The stability and repeatability of the biosensor was also discussed.

Biosensors consist of carbon paste modified with TiO2 nanoparticles combined with glucose oxidase was used to determine glucose. Similarly, the TiO2 electrodes were used to immobilize tyrosinase to detect phenolic compounds  The results showed that the modified biosensor was sensitive and stable in detecting glucose, indicating that TiO2 nanoparticles was a good candidate material for the immobilization of enzyme in glucose biosensor construction. Therefore the autocatalytic role of TiO2 nanoparticles was demonstrated on voltammetric sensors and biosensors. Finally, modified sensors and biosensors was applied to analysis of musts and allowed quantification of the acid and antioxidant capacity of the tested musts.

References

[1] C. Medina-Plaza, J.A. de Saja, M.L. Rodriguez-Mendez (2014) Biosensors and Bioelectronics 57, 276.

[2] S. Ashok Kumar, Po-Hsun Lo, Shen-Ming Chen 2008, Nanotechnology 19, 255501

 Figure 1. Voltammetric cyclic of graphite sensor (dotted line) and modified TiO2 NPS sensor (solid line) on catechol 10-3 mol.L-1 .

Figure 1
Influence of pH on Morphology and Electro-Activity of Ternary Pt-Co-P/MWCNT Electro-Catalysts Towards Methanol Electro-Oxidation
Authors: Sun Junting , Wang Feng , Dou Meiling , Liu Jingjun
Published: February 2020

Methanol is widely investigated as anodic reactant in direct methanol fuel cell (DMFC) for its character of clean, convenient, and high theoretical density when compared with traditional fossil fuel and hydrogen. However, the sluggish kinetics of the methanol oxidation reaction (MOR) promotes the investigation of electrocatalysts to improve the reaction efficiency of the MOR process. Platinum is developed as the best catalysts for the MOR process, but poor anti-poisoning ability and the high cost severely limit its applications. Recent studies show that the amorphous metallic nanoparticles hold much promise for use as catalyst because of the surface-rich low-coordinate site, which could act as active site for catalyst [1].it was found that the incorporation of P into metallic alloy could form amorphous structure and lower the size of the nanoparticles, both of which are in favor of high electro-catalytic efficiency. Besides, the abundant valence electrons of phosphorous shows influence on magnetic and electro-catalytic properties of the metallic nanoparticles [2].

In this abstract, four supported Pt-based electro-catalysts prepared through impregnation method at different pH values were introduced for MOR. The difference of pH values for composition and crystallization of each electro-catalysts and their electro-catalytic activity was investigated through analyzing X-ray diffraction spectra (XRD), high-resolution transmittance electron micrograph (HRTEM), and cyclic voltammetry curves (CV). The XRD patterns show four obvious widening of diffraction peaks with the increase of pH value which indicates the decrement of particle size and the results are in accordance with our previous investigation. The CV tests show that the electro-catalyst prepared in high pH value perform a relatively high MOR activity comparing with others prepared in lower pH. The promotion of electro-catalytic activity for MOR is mainly due to the diminish of the particle size of electro-catalyst in high pH value which produce low-coordinate site on the surface of nanoparticle. The low-coordination sites show stronger adsorption towards small molecules which facilitate electro-oxidation of methanol on Pt-Co-P electro-catalyst.

Figure 1
Hybrid Bilayer Membrane As a Versatile Electrochemical Platform to Modulate Transport Kinetics of Small Molecules Across a Lipid Monolayer
Authors: Barile Christopher J. , Tse Edmund C. M. , Kirchschlager Nicholas A. , Li Ying , Zimmerman Steven C. , Hosseini Ali , Gewirth Andrew A.
Published: February 2020

We report our effort to gate molecular transport through lipids. To probe the kinetics of small molecule delivery in and out of a lipid layer, we monitored the electrochemical response of a redox-active moiety covalently attached to a self-assembled monolayer (SAM) on gold. We prepared the first synthetic dicopper electrocatalyst (CuBTT) on a SAM/Au system for the oxygen reduction reaction (ORR) through rational design based on an aminotriazole derivative discovered previously by our group. The kinetically sluggish ORR proceeds via multiple proton-coupled electron transfer (PCET) steps. By appending a monolayer of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) on top of a CuBTT-SAM to construct a hybrid bilayer membrane (HBM, Figure 1), we suppressed the ORR activity of CuBTT. This inhibition in ORR activity is due to the hydrophobic lipid interior which impedes transmembrane diffusion of the hydrophilic positively-charged protons.

In nature, membrane-bound proton carriers deliver protons across lipid bilayers via flip-flop diffusion. Inspired by biological systems, we recovered the ORR activity of CuBTT by incorporating an alkyl phosphate, mono-N-dodecyl phosphate (MDP), in the lipid monolayer of the HBM to facilitate proton transfer to CuBTT. We further discovered that this assisted proton transport behavior can be turned on and off by switching the pH of the bulk solution. This observation allowed us to build a pH-sensitive switch that modulates proton flux to a HBM-embedded ORR electrocatalyst.(1) We believe this HBM platform not only can provide valuable mechanistic insight into PCET reactions, but also lay the foundation for advanced bio-compatible electronics and nanocomputers.

The HBM electrochemical platform allows for the precise and independent control of both the thermodynamics and kinetics of proton transfer to a molecular catalyst. We are in the process of understanding the underlying mechanism of the assisted proton transfer process and in search of a quantitative structure-activity relationship between different proton carriers. Apart from studying related HBM platforms with different lipids and proton carriers, embedding redox and pH markers inside a HBM will provide valuable information about the internal environment of the system. We are also interested in controlling the kinetics of other small molecules through the lipid layer, which offers a unique electrochemical platform for drug screening processes.

References

1.         C. J. Barile, E. C. M. Tse, Y. Li, T. B. Sobyra, S. C. Zimmerman, A. Hosseini and A. A. Gewirth, Nat. Mater., 13, 619 (2014).

Figure 1
A Novel Real-Time, Mediator-Free, Non-Enzymatic Electrochemical Biosensor for Glutamate Detection
Authors: Yang Yu-Ping , Manfredi Anita , Daunert Sylvia
Published: February 2020

Glutamate is the major excitatory neurotransmitter in the brain, and an excess of glutamate can cause excitotoxicity, which is a common pathological process in many neurologic disorder such as stroke, brain trauma, and brain tumor. Therefore, monitoring glutamate in real time is of critical importance.  However, the existing methods for the detection and monitoring glutamate levels are limited.  Here in this work, we present a novel mediator-free, non-enzymatic electrochemical biosensor for real-time glutamate monitoring, based on immobilization of genetically engineered periplasmic glutamate binding protein onto gold nanoparticle-modified screen-printed carbon electrodes. Cyclic voltammetry is performed to determine the glutamate concentration in phosphate buffer solution (pH=7.4). The results show an excellent sensitivity with 0.1µM detection limit and the linearity was investigated in the 0.1µM-1µM range of glutamate concentration. The sensor was tested with common interfering substances such as aspartate, glutamine, serine, lysine and ascorbic acid, and exhibited high selectivity toward glutamate over those substances.

Figure 1
Anion Transport Across Electrode-Supported Lipid Membranes
Authors: Tse Edmund C. M. , Barile Christopher J. , Gewargis John P. , Li Ying , Zimmerman Steven C. , Gewirth Andrew A.
Published: February 2020

We use a hybrid bilayer membrane as an electrochemical platform to study anion diffusion through a lipid monolayer. We first append lipid on a self-assembled monolayer that contains a covalently-bound Cu(I)/Cu(II) redox center. We then perform cyclic voltammetry using different anions in bulk solution and extract thermodynamic and kinetic information about anion transport. The voltammetry is affected by the scan rate and the identity of the anions, but not the bulk anion concentration. An increase in scan rate causes the HBM system to switch from a diffusionless regime to one controlled by anion diffusion. In the latter regime, we test six anions that exhibit a wide range of cathodic peak potentials and cathodic-anodic peak separation values, which reflect the differences in the thermodynamics and kinetics of anion diffusion across the lipid membrane.

We analyze the results using factor analysis and determine that anion transport quantitatively correlates to polarity and basicity, a relationship we formalize as the lipid permeability parameter. In addition, we discuss how our findings can be interpreted according to the two leading mechanisms describing ion permeability through lipids. Our results demonstrate that anion transport in a HBM is best described by the solubility-diffusion mechanism, not the pore mechanism.

Figure 1
Photocatalytic Nanocomposite Polymers for Enhanced Water Purification Applications
Authors: Rech Jeromy J , Hallenbeck Kathleen , Murray Jacob , Fernandez Michelle , Dial Courtney , Rago James , Keleher Jason J
Published: February 2020

The need for clean and drinkable water cannot be understated as it is the prerequisite for all human and economic development. Unfortunately, 780 million people do not have access to clean water, resulting in the death of over 2 million children every year. Literature has shown that photocatalytic nanoparticles enhance the chemical degradation of organic pollutants when exposed to UV light. The major limitation in this application is due to lack of availability of a UV radiation. This research developed a cellulose based nanocomposite film that uses visible light to degrade simulated organic pollutants through catalytic photo-redox reactions. Increasing the redox potential will also increase the potency of the nanocomposite, so various methods of enhancing electron transfer were implemented. Dye sensitization, surface modifications, and metal deposition on the nanoparticles were found to improve the transfer of electrons from the semiconductor to the pollutant. In addition to increasing the rate of reaction, Ag-functionalized TiO2 nanoparticles resulted in a synergistic antimicrobial effect, which eliminated E. Coli and S. Aureus from the water samples. Both dye sensitization and noble metal deposition showed a 25% increase in the amount of pollutant that was chemically degraded in comparison to unmodified TiO2. Additionally, surface modifications of the nanoparticles by covalently bonding new functional groups to the nanoparticle surface facilitate metal complexation, removing heavy metal ions from the sample.
Nano-Second Pulse Programming of Resistive RAM Devices and Its Benefits
Authors: Montesi Luca , Buckwell Mark , Mehonic Adnan , Hudziak Steven , Kenyon Tony
Published: February 2020

ReRAM devices have shown interesting results through traditional current v. voltage characterization involving the use of complex voltage sources with current compliance. While these results may be used to roughly estimate and display functionality, they do not allow for accurate estimate of switching time, injected power, small programmers and therefore interest to the industry. Given today’s constraints in terms of power and real estate, it is appealing to transition towards simpler pulse amplitude/width modulation strategies. We present a TiN/SiOx/TiN device which relies on intrinsic switching and is successfully programmed by means of nano-second pulses. This leads to a better understanding of the switching mechanism, non-redundant power injection, accurate power consumption estimates and the possibility of compact and efficient programming circuits. Issues involving high frequency transmission lines were taken into account. Dynamically changing impedance in the device under test leads to a need for careful consideration of pulse magnitude.
High-Performance SOFC Electrodes Synthesized By Novel One-Step Chemical Routes
Authors: Martinelli Antonio Eduardo , Macedo Daniel Araujo , Cesário Moises Romolos , Paskocimas Carlos Alberto , Fagg Duncan Paul , Nascimento Rubens Maribondo
Published: February 2020

The next generation of hydrogen-operated solid oxide fuel cells (SOFCs) will most certainly rely on high-performance ceramic and composite electrode materials manufactured from optimized routes.  La0.6Sr0.4Co0.2Fe0.8O3-Ce0.8Sm0.2O1.9 (LSCF-SDC, 50 wt.% SDC) and NiO-CGO (50 wt.% NiO) composite powders, usually employed to prepare SOFC electrodes, were synthesized by two novel one-step synthetic routes, namely microwave-assisted combustion and a modified polymeric precursor method, respectively. Powder characterization was carried out by XRD and TEM. Screen-printed electrodes with different microstructures, evaluated by scanning electron microscopy, were obtained on CGO pellets. The electrochemical performances for the hydrogen oxidation and oxygen reduction reactions were investigated by impedance spectroscopy in the temperature range of 650-750 °C using flowing humidified 10% H2 + 90% N2 gas mixtures for the anodes and pure oxygen for the cathodes. By using a three-electrode configuration cell, dc polarization measurements were also performed on selected electrodes. The results of the electrochemical characterization indicated a significant dependence of the area specific resistance (ASR) on the electrode microstructure, highlighting that the electrode resistance can be manipulated by microstructural design. The best ASR values obtained at 750 °C in pure oxygen (cathode) and hydrogen atmosphere (anode) were found to be 0.18 and 0.15 ohm.cm2, respectively. The one-step Ni-CGO electrode with improved microstructure showed an anodic overpotential of 91 mV at 750 °C for a current density of 322 mA/cm2, which is amongst the best results mentioned in the literature, demonstrating that the novel one-step synthesis routes are innovative chemical ways to prepare promising SOFC electrodes.
Electrodeposition of Highly Ordered CdTe Nanorod/Nanotube Arrays for Solar Energy Conversion
Authors: Liyanage Wipula Priya Rasika , Wilson Jacob Scott , Kinzel Edward , Nath Manashi
Published: February 2020

Research and development in the field of high efficiency solar energy conversion relies heavily on the fabrication of the photoabsorber materials as nanotubular or nanowire architectures, since these morphologies gives better photocurrent output with lese coverage of the active material. However, fabrication of the nanostructured semiconducting materials as vertically aligned, highly ordered nanowire or nanotubular arrays with precise distribution of size and shape over the entire region of interest is still a significant challenge to overcome. In this presentation, we will describe a straightforward approach for the fabrication of CdTe nanorod and nanotube arrays with a high degree of precision through confined electrodeposition on lithographically patterned nanoelectrodes. This technique has the potential of growing these nanotube/nanowire arrays over a significantly large area that can be scaled up to the industrial manufacturing scale. The desired nanoelectrode pattern was defined through electron beam lithography on indium tin oxide coated glass, which was used as a typical conducting substrate, and electrodeposition of the semiconducting material of interest (CdTe) on the nanoelecrodes was used to grow the nanotubes/nanowires. Nanosphere Photo Lithography technique was used to define nanorod/nanowire patterns over a significantly larger area (4 x 4 cm2). It is interesting to note that the measured photocurrent density of nanotube device created by this protocol exceeds that obtained from a thin film device fabricated under similar conditions by several orders of magnitude. The ability to tune the entire nanotube/nanorod diameter, length, shape, packing density, and nanotube wall thickness, make this method a versatile tool to fabricate and investigate the nano-structured photovoltaic devices and study their structure-property relationship. Additionally the ability to create uniform nanotube/nanorod arrays through one-step electrodeposition makes this protocol unique. The simplicity of this method opens up a window of opportunities to investigate the effect of morphology on the solar cell efficiency of different semiconducting materials. In this presentation we will discuss the growth of nanorod and nanotube arrays through patterned electrodeposition on nanoelectrodes, and discuss detailed investigation of their characterization and solar cell efficiencies along with future prospects for tuning the efficiencies even further.
Fabrication of Large Scale Molecular Junctions of Ag Nanowires By Mev Proton Beam Irradiation
Authors: Honey Shehla , Ahmad Ishaq , Riaz Saira , Naseem Shahzad , Maaza Malik
Published: February 2020

Here, we demonstrate a MeV proton beam irradiation induced nanowelding technique to fabricate X-, Y-, T and II-shapes molecular junctions between Ag nanowires, both suspended and deposited on substrates. High-resolution transmission electron microscopy, X-ray diffraction and Scanning electron microscopy revealed that the nanoweldings are nearly perfect, with the same crystal orientation. We further discuss various experimental aspects of this method which may potentially be used for developing complicated networks of joined nanowires. The high quality of the welding is attributed to the nanoscale sample dimensions, oriented-attachment mechanisms and mechanically assisted fast surface-atom diffusion.
Effect of Nano-Silver Ink Composition and Drying Behavior on Its Adhesion on Glass Substrate
Authors: Lai I-Hsien , Chou Kan-Sen
Published: February 2020

The adhesion of silver colloids to a glass substrate was investigated in this study.

The silver colloids first added nano-TiO2 particle by varying solid content and changed pH to 10 to make sure the solution dispersion well. The adhesion of silver colloids to the glass substrate after sintering was then measured according to both ASTM D4541 and ASTM 3359 standards. The results indicated that adhesion increased proportionally with TiO2 solid content; however, this enhancement effect was lessened when the solid content was above 8wt%. Sintering temperature was also beneficial in increasing adhesion to the substrate; however, the electrical resistance of the silver colloids after sintering increased with degree of solid content. This implied that TiO2 solid content simultaneously made adhesion and electrical resistance increased. Consequently, values of TiO2 solid content and sintering temperature were optimal when adhesion and electrical resistivity were balanced. Ultimately, using commercial software Origin to fit the TiO2 solid content and sintering temperature to get the optimum value of adhesion and electrical resistivity.
Novel Carbon Nanohybrids As Highly Efficient Magnetic Resonance Imaging Contrast Agents
Authors: Sun Baoyun , Cui Rongli , Huang Huan , Guo Xihong
Published: February 2020

Gadofullerenes derivatives had been proved to exhibit high relaxivities, even higher than that of commercial Gd-DTPA contrast agents. However, all reported gadofullerene contrast agents were based on the functionalized metallofullerene. In this presentation, we successfully constructed novel water-soluble carbon nanohybrids based on unmodified metallofullerene and graphene oxide, which exhibited high relaxivity and better brightening effect in magnetic resonance (MR) imaging in vivo. Gd@C82 was produced and isolated by the industrial-scale production line of metallofullerenes firstly established in Institute of High Energy Physics, Chinese Academy of Science (CAS). A “secondary spin-electron transfer” relaxation mechanism was proposed to explain how the encaged Gd3+ ions of carbon nanohybrids interact with the surrounding water molecules. This approach opens new opportunities in developing highly efficient and low toxic MRI contrast agent.

Figure 1
Synthesis of an Extensive Family of Sc2o@C2n (n=35-47) and Chemical Insight into the Small-Size Species
Authors: Feng Lai , Chen Ning
Published: February 2020

An extensive family of oxide cluster fullerenes (OCFs) Sc2O@C2n (n=35-47) has been facilely produced for the first time by introducing CO2 as the oxygen source. Among this family, Sc2O@C70 was identified as the smallest OCF and therefore isolated and characterized by mass spectrometry, 45Sc NMR, UV-Vis-NIR absorption spectroscopy, cyclic voltammetry and DFT calculations. The combined experimental and computational studies reveal a non-IPR isomer Sc2O@C2(7892)-C70 with reversible oxidative behavior and lower bandgap relative to that of Sc2S@C2
(7892)-C70, demonstrating a typical example of unexplored OCF and underlining its cluster-dependant electronic properties. As for other OCF members, the related studies are still on the way.

Figure 1
Electric-Arc Synthesis of New and Uncommon Endohedral Metallofullerenes
Authors: Kime Brittany L , Stevenson Steven
Published: February 2020

During the last 30 years, minimal research has been successful for entrapping elements beyond the more common Sc, Y, La and 4f-block lanthanide metals.  Our goal is to expand the selection of metals that can be encapsulated.  Preliminary results indicate that new metallofullerenes can be produced successfully with our electric-arc, plasma reactor.  Key experimental parameters were metal selection, buffer gas, gap voltage, amount of current, chamber pressure, burn time, flow rate of added gases, and choice of chemically reactive atmosphere.  By manipulating these variables, we have produced new clusters in addition to conventional clusters in uncommon cages.  Upon their successful synthesis, efforts are currently underway to separate and isolate these new molecules utilizing non-chromatographic methods.
Carbon Nanodots - Towards a Comprehensive Understanding of Their Photoluminescence
Authors: Guldi Dirk M.
Published: February 2020

For the first time, a comprehensive report on the characterization carbon nanodots (CND), a novel class of nanocarbons is given.  Our microwave reactor synthesis provides mild and controlled conditions that afford CNDs with homogeneous and narrowly dispersed optical properties.  As such, they are well suited as a testbed for studies of the photophysics of carbon-based nanoscopic emitters, including electron transfer studies.  Our experimental work includes steady-state investigations, time-correlated single-photon counting, fluorescence up-conversion, and transient pump-probe absorption spectroscopy. It is rounded off by density-functional theory and semiempirical configuration-interaction calculations that provide significant additional insight.  This all leads to a sound understanding of the fundamental structure-property relationships for this novel type of material.
Chemically Functionalized Nanocarbons for Artificial Photosynthesis and Solar Energy Conversion
Authors: Imahori Hiroshi
Published: February 2020

Recently, we have conducted the regioisomer separation of hexyloxycarbonyl-substituted dihydronaphthyl-based [60]fullerene bis-adducts (C6BA) and applied the separated bis-adducts to PSCs for the first time.1,2 To reduce the plausible number of the fullerene bis-adduct isomers, a symmetrical dihydronaphthyl group was chosen as the substituent. We expected that symmetrical introduction of two long alkoxycarbonyl chains into the dihydronaphthyl groups would facilitate the isomer separation and purification. Indeed, repeated separations by HPLC equipped with a Buckyprep column afforded trans-1, trans-2, trans-3, trans-4, e, and a mixture of cis-2 and cis-3 (denoted as cis-2+cis-3) isomers. The LUMO energy levels of C6BA isomers estimated by cyclic voltammetry are 0.1 – 0.2 eV higher than those of the corresponding mono-adduct (C6MA) and [60]PCBM. However, the best PCE (1.44%) achieved by the trans-4 isomer of C6BA (denoted as C6BA–trans-4) in combination with regioregular poly(3-hexylthiophene) (P3HT) was lower than those of the corresponding mono-adduct C6MA and [60]PCBM-based PSCs (1.71 and 2.10%, respectively). The inferior efficiencies may be caused by the long aliphatic side chains, which disrupt the optimal packing and efficient electron transport of the fullerene molecules in the active layer. Hence, we decided to shorten the n-hexyl chain of C6BA to n-butyl and ethyl (C4BA and C2BA). We expected that we could systematically address the effects of alkyl chain length as well as substituent pattern of fullerene bis-adducts on the photovoltaic properties of PSCs.3 In this talk I will present an overview of our chemically functionalized nanocarbons for artificial photosynthesis and solar energy conversion.

[1] S. Kitaura, K. Kurotobi, M. Sato, Y. Takano, T. Umeyama, and H. Imahori, Chem. Commun., 48, 8550-8552 (2012).

[2] T. Umeyama and H. Imahori, J. Mater. Chem. A (Feature Article), 2, 11545-11560 (2014).

[3] R. Tao, T. Umeyama, K. Kurotobi, and H. Imahori, ACS Appl. Mater. Interface, in press.
Chemically-Derived Graphene and Boron Nitride Heterostructures for Optoelectronic Applications
Authors: Behura Sanjay , Debbarma Rousan , Nguyen Phong , Sreeprasad Theruvakkattil Sreenivasan , Berry Vikas
Published: February 2020

Structural isomers, graphene and boron nitride (BN), are logical materials for two-dimensional heterostructures with properties controllable via interfacial, structural, compositional and chemical modifications. These heterostructures can leverage the combination of graphene’s ultrahigh carrier-mobility, ultrafast photodetection, sensitivity, tunable spintronics, strong/tunable optical absorption, carrier controlled interband/optical-transition, and quantum interference, and BN’s large band gap, high optical transmittance, UV-cathodoluminescence, thermochemical stability and thinnest electron tunneling barrier. We report on electrical, capacitive, optoelectronic and structural properties of macro-scale heterostructures of graphene and BN produced via an interfacial drying process. The talk will discuss the evolution of electronic band-structure, optical transitions, dielectric impedance, switching and UV quantum efficiency with change in the composition and structure of the heterostructure. The study of these facile heterostructures will lead to development of optoelectronic design concepts for future 2D flexible electronics.
Effect of Displacement Deposition on Platinum Deposition within Nanoporous Silicon
Authors: Koyama Akira , Fukami Kazuhiro , Koda Ryo , Sakka Tetsuo , Abe Takeshi , Kitada Atsushi , Murase Kuniaki
Published: February 2020

In the use of nanoporous electrode, the control of mass transfer within nanopores is crucially important to elicit their best performance. However, mass-transfer rate for ionic species through electrolyte solution within nanopores tends to be very low, so that only a limited proportion of the whole specific surface area contributes to electrochemical reactions. In the case of the metal filling within the porous silicon by electrodeposition, poor supply of metal precursor into the nanopores also causes a problem to induce a plugging at the pore opening. We have investigated the pore filling with platinum in an aqueous solution with tuning the hydration property of the surface of pore wall and platinum complex anions [1-3]. The important insight we have found is the surface-induced phase transition (SIFT: the concentration of the hydrophobic solutes near the hydrophobic surface becomes orders of magnitude higher than that in the bulk) in the nanopores plays an important role in electrodeposition of platinum within the nanoporous silicon. Our previous reports, however, focused only on the presence of platinum deposits in the porous layer corresponding to the various experimental conditions and didn’t elucidate the dynamic aspects of the penetration of platinum complex anions into the nanopores. We adopted the time developments of the mixed-potential measured during the displacement deposition of platinum within the porous silicon to find the peculiar penetration dynamics that could not be understood within the framework of simple diffusion. One of the typical observations shows the penetration is faster when the pore diameter is smaller and the anion size is larger. In this paper, we also discuss the effect of the pore depth on the penetration dynamics.

[1] K. Fukami, R. Koda, T. Sakka, T. Urata, K. Amano, H. Takaya, M. Nakamura, Y. Ogata, and M. Kinoshita, Chem. Phys. Lett., 2012, 542, 99-105.

[2] K. Fukami, R. Koda, T. Sakka, Y. Ogata, and M. Kinoshita, J. Chem. Phys., 2013, 138, 094702.

[3] R. Koda, A. Koyama, K. Fukami, N. Nishi, T. Sakka, T. Abe, A. Kitada, K. Murase, and M. Kinoshita, J. Chem. Phys., 2014, 141, 074701.
(Invited) Solution Processing and Device Integration of Two-Dimensional Black Phosphorus
Authors: Hersam Mark C.
Published: February 2020

Two-dimensional black phosphorus (2D BP) has emerged as a promising candidate for next-generation electronics and optoelectronics. As is common for new materials, much of the early work on 2D BP has focused on measuring and optimizing intrinsic properties on small samples under idealized conditions. However, real-world devices and systems inevitably require large-area samples that are integrated with dielectrics, contacts, and other semiconductors at standard temperature and pressure conditions. These requirements are particularly challenging to realize for 2D BP since its properties are highly sensitive to surface chemistry, defects, and the surrounding environment. This talk will thus explore methods for improving the uniformity of solution-based 2D BP with an eye toward realizing scalable processing of large-area thin-films. Specifically, methods for exfoliating black phosphorus in anhydrous organic solvents will be discussed such that the resulting 2D BP flakes show field-effect transistor mobilities and on/off ratios that are comparable to micromechanically exfoliated flakes [1]. In addition to solution processing, this talk will also report on the integration of 2D BP with dielectrics and other materials. In particular, atomic layer deposition of alumina dielectrics on 2D BP suppresses ambient degradation, thereby preserving electronic properties in field-effect transistors at atmospheric pressure conditions [2].

[1] J. Kang, J. D. Wood, S. A. Wells, J.-H. Lee, X. Liu, K.-S. Chen, and M. C. Hersam, “Solvent exfoliation of electronic-grade, two-dimensional black phosphorus,” ACS Nano, DOI: 10.1021/acsnano.5b01143 (2015).

[2] J. D. Wood, S. A. Wells, D. Jariwala, K.-S. Chen, E. Cho, V. K. Sangwan, X. Liu, L. J. Lauhon, T. J. Marks, and M. C. Hersam, “Effective passivation of exfoliated black phosphorus transistors against ambient degradation,” Nano Lett., 14, 6964 (2014).
Enhanced Charge-Transport Behavior on PbS Nanocrystals Capped with Atomic Ligands
Authors: Yoon Seongwon , Ha Jae Un , Cho Jangwhan , Chung Dae Sung
Published: February 2020

Colloidal nanocrystals (NCs) are promising materials with its unique electronic, magnetic and optical properties and therefore there have been tremendous research efforts. Among these application fields, especially in the case of electronic devices, the figure-of-merit parameter is charge carrier mobility because high mobility can guarantee prompt response of NCs-based devices against high frequency external signals. As-synthesized lead chalcogenide NCs are typically capped with insulating organic ligands such as oleylamine or oleic acid that impede the injection or extraction of charge carriers from individual NCs, resulting in very low charge carrier mobility. In order to enhance charge transport between adjacent NCs, long and insulating ligands have to be replaced with short and electronically transparent ligands. Traditionally, benzene dithiol or mercaptopropionic acid have been frequently used as such surface ligands to overcome low charge carrier mobility issues of colloidal NCs. However, the resulting devices usually rendered only limitedly enhanced mobility of < 0.1 cm2/Vs. Here we demonstrate the utilization of atomic ligands such as halide anion(X-, X : Cl, Br, I) as an electrically transparent ligands for lead chalcogenide NCs, to realize high charge carrier mobility over 0.5 cm2/Vs. The origin of such improved charge transport behavior as a result of introducing atomic ligands is fully discussed together with various characterization results.
Extreme Bottom-up in Through Silicon Vias by Leveler Pre-adsorption
Authors: Ishii Takao , Egoshi Haruki , Hayase Masanori
Published: February 2020

In the TSV copper filling process, combination of several additives, such as suppressor, accelerator and levelers, are used in the electroplating bath. Besides, strong agitation is often applied to achieve good bottom-up feature. From past studies, it is considered that levelers, which show strong suppression effect in the electroplating, have an essential role in the bottom-up feature. It is assumed that the bottom-up TSV filling is achieved based on diffusion-adsorption model, in which less suppression in the via bottom is caused by diffusional limitation of the leveler and preferential deposition happens around via bottom. However, in the practical filling process, in addition to the leveler, other additives are used, and the filling mechanism is not clear yet. In this study, only leveler is added in the plating bath, and the effect of leveler on filling feature is discussed.

Experimental

The leveler used in this study is a commercial product,and the composition is not opened. Besides, the product name is neither provided. At first, in order to grasp the suppression effect of the leveler, chronoamperometry was carried out with addition of only leveler in an acid copper sulfate plating bath ( 1M CuSO4 + 0.3 M H2SO4+ 1mM HCl ). It was assumed that initial adsorption of the leveler on plating surface has some impacts, and pre-immersion time before the plating start was varied. -520mV vs. MSE was applied with a rotating disk electrode at a rotational speed of 400rpm. Leveler concentrations of manufacture’s standard (x1) and 5 times concentrated one (x5) were examined. Figure 1 shows the results. Strong suppression was not obtained with standard leveler concentration, and suppression became stronger along plating time. Less current density at initial plating period was observed with longer pre-immersion. Stronger suppression was observed with 5x leveler concentration. From these results, it was supposed that suppression is limited by mass transfer of leveler. In order to clarify the diffusion-adsorption effect, TSV filling experiment with pre-immersion was performed. Figure 2 shows example results. With short pre-immersion, it is supposed that little leveler adsorbed inside the via, while strong suppression was observed on upper area of the via with 30min pre-immersion, and it was found that the leveler diffused deeper with long pre-immersion. Figure 3 shows an example result after some optimization. Extreme bottom-up was achieved with relatively high aspect ratio vias.

Figure 1
Dielectric Spectroscopic Detection of Early Failures in 3-D Integrated Circuits
Authors: Obeng Yaw S. , Okoro Chukwudi A. , Ahn Jung-Joon , You Lin , Kopanski Joseph J.
Published: February 2020

The commercial introduction of three dimensional integrated circuits (3D-ICs) has been hindered by reliability challenges, such as stress related failures, resistivity changes, and unexplained early failures[i]. In this talk, we will discuss a new RF-based metrology, based on dielectric spectroscopy[ii], for detecting and characterizing electrically active defects in fully integrated 3D devices.  These defects are traceable to the chemistry of the insolation dielectrics used in the through silicon via (TSV) construction.  We will show that these defects may be responsible for some of the unexplained early reliability failures observed in TSV enabled 3D devices.  While the immediate application has been in characterizing the reliability of prototypical 3D integrated circuits, the utility of this new technique could be extended to material characterization in general, for probing buried material interfaces in particular.

This low frequency RF technique could be optimized to compete favorably with other thin film metrology techniques, such as ellipsometry and FTIR, for mass production environments.  Unlike the current state of the art spectroscopic methods, this new method does not need ‘line of sight’ of the analyte, and can be used to interrogate buried structures and interfaces.

[i](a) K.N. Tu, Microelectronics Reliability, 51( 3), 2011, Pages 517–523; (b) Papers in MRS Bulletin special issue on “Material Challenges in 3D IC Technology”, 40(3), 2015

[ii] F. Kremer, A. Schönhals “Broadband dielectric spectroscopy” Springer, Berlin, 2003.