Au Gate Research Articles

Concentration gradients probed in microfluidics by gate-array electrolyte organic transistor

We propose a device architecture termed gate-array electrolyte gated organic transistor (GA-EGOFET) that quantitatively measures the solute concentration gradient created in a spatially inhomogeneous solution, for instance a (biological) fluid. The integrated H-cell microfluidics yields a diffusive concentration profile along the microfluidics channel according to the flow rate of the input streams. We demonstrate this concept by monitoring the formation of self-assembly monolayers (SAMs) on top of an array of parallel Au gate electrodes exposed to a different local concentration of alkanethiols. The deposition rate and the coverage both increase from the entrance towards the H-cell end. The voltage change at each gate is transduced in the transfer curve acquired with the specific gate electrode. For short chain length SAMs (n = 3), the trend of the current hints to a diffusion-limited surface reaction. For longer thiols (n = 6, 9), instead, the slower surface diffusion or incorporation in the more stable and compact SAM yields a current that is independent of the longitudinal gradient. The microfluidics/GA-EGOFET platform is viable for constructing dose curves in reproducible manner and for validating different electrode functionalization strategies where the deposition rates are different at each substrate site.

Design of a novel aptamer/molecularly imprinted polymer hybrid modified Ag–Au@Insulin nanoclusters/Au-gate-based MoS2 nanosheet field-effect transistor for attomolar detection of BRCA1 gene

Early detection of breast cancer, the first main cause of death in women, with robust assay platforms using appropriate biomarkers is of great importance for diagnosis and follow-up of the disease progression. This paper introduces an extra selective and sensitive label-free aptasensor for the screening of BRCA1 gene biomarker by taking advantage of a gate modified with aptamer and molecularly imprinted polymer hybrid (MIP) as a new synthetic receptor film coupled with an electrolyte-gated molybdenum disulfide (MoS2) field-effect transistor (FET). The Au gate surface of FET was modified with insulin stabilized bimetallic Ag–Au@nanoclusters (Ag–Au@InsNCs), after which, the immobilization of the hybridized aptamer and o-phenylenediamine was electropolymerized to form an aptamer-MIP hybrid receptor. The output characteristics of Apta-MIP hybrid modified Au gate MoS2 FET device were followed as a result of change in electrical double layer capacitance of electrolye-gate interface. The magnitude of decrease in the drain current showed a linear response over a wide concentration range of 10 aM to 1 nM of BRCA1 ssDNA with a sensitivity as high as 0.4851 μA/decade of concentration and a limit of detection (LOD) of 3.0 aM while very low responses observed for non-imprinted polymer. The devised aptasensor not only was capable to the discrimination of the complementary versus one-base mismatch BRCA1 ssDNA sequence, but also it could detect the complementary BRCA1 ssDNA in spiked human serum samples over a wide concentration range of 10 aM to 1.0 nM with a low LOD of 6.4 aM and a high sensitivity 0.3718 μA/decade.

Unamplified and Real-Time Label-Free miRNA-21 Detection Using Solution-Gated Graphene Transistors in Prostate Cancer Diagnosis.

The incidence of prostate cancer (PCa) in men globally increases as the standard of living improves. Blood serum biomarker prostate-specific antigen (PSA) detection is the gold standard assay that do not meet the requirements of early detection. Herein, a solution-gated graphene transistor (SGGT) biosensor for the ultrasensitive and rapid quantification detection of the early prostate cancer-relevant biomarker, miRNA-21 is reported. The designed single-stranded DNA (ssDNA) probes immobilized on the Au gate can hybridize effectively with the miRNA-21 molecules targets and induce the Dirac voltage shifts of SGGT transfer curves. The limit of detection (LOD) of the sensor can reach 10-20 M without amplification and any chemical or biological labeling. The detection linear range is from 10-20 to 10-12 M. The sensor can realize real-time detection of the miRNA-21 molecules in less than 5 min and can well distinguish one-mismatched miRNA-21 molecule. The blood serum samples from the patients without RNA extraction and amplification are measured. The results demonstrated that the biosensor can well distinguish the cancer patients from the control group and has higher sensitivity (100%) than PSA detection (58.3%). Contrastingly, it can be found that the PSA level is not directly related to PCa.

Binary THz modulator based on silicon Schottky-metasurface

We propose a metasurface THz modulator based on split-ring resonators (SRRs) formed by four interconnected horizontal Si–Au Schottky diodes. The equivalent junction capacitance of each SRR in the proposed modulator is much smaller than that of the previously reported metasurface counterparts with vertical Schottky junctions, leading to a higher modulation speed. To modulate a THz incident signal by the proposed metasurface, we vary the bias voltage externally applied to the Schottky junctions. Applying a reverse bias of VA = − 5 V to the Au gate, two LC resonances at 0.48 THz, and 0.95 THz are excited in the metasurface. Switching the applied voltage to VA = + 0.49 V, we diminish the oscillator strengths of the LC resonances, creating one dipole resonance at 0.73 THz in the transmission spectrum of the metasurface modulator. The modulation depths at these resonances are more than 45%, reaching 87% at 0.95 THz. The phase modulation for this THz modulator is about 1.12 rad at 0.86 THz. Furthermore, due to the particular design of the meta-atoms, the modulation speed of this device is estimated up to approximately several hundred GHz, which makes this device an appropriate candidate for high-speed applications in wireless communications systems based on external modulators.

Determination of sunset yellow in beverage based on solution-gated graphene transistors with multi-walled carbon nanotube functionalized gate electrodes

• A sunset yellow sensor based on solution-gated graphene transistor is proposed. • The sensor is modified by multi-walled carbon nanotubes and chitosan. • The sensor has a detection limit as low as 300 nM. • The sensor can be used for sunset yellow content in actual samples. Sunset yellow, one of the most widely used synthetic pigments in the food industry, may cause an adverse reaction in the human body due to its cytotoxicity and potential genotoxicity when overdosed. Developing a rapid, low-cost, and convenient detection method for the sunset yellow pigment is necessary. In this study, we report the fabrication of a highly sensitive and selective sensor for sunset yellow detection based on solution-gated graphene transistors (SGGT). To improve the performance of the SGGT-based sensor, we modified the Au gate electrode with multi-walled carbon nanotubes (MWCNTs). The detection limit of the MWCNT-modified SGGT sensor was 100 nM, and the linear range was from 300 nM to 100 μM. More importantly, the SGGTs sensor showed a selective response to sunset yellow. Finally, we demonstrated that the optimized SGGT-based sensor could detect the concentration of sunset yellow in Fanda soft drink. Therefore, we believe that the SGGT-based sensor with the reported effective modification can be used in the field of food safety and quality control, providing a promising platform for detecting many other analytes.

Comprehensive Schottky Barrier Height Behavior and Reliability Instability with Ni/Au and Pt/Ti/Pt/Au on AlGaN/GaN High-Electron-Mobility Transistors.

The reliability instability of inhomogeneous Schottky contact behaviors of Ni/Au and Pt/Ti/Pt/Au gate contacts on AlGaN/GaN high-electron-mobility transistors (HEMTs) was investigated via off-state stress and temperature. Under the off-state stress condition, Pt/Ti/Pt/Au HEMT showed abruptly reduced reverse leakage current, which improved the Schottky barrier height (SBH) from 0.46 to 0.69 eV by suppression of the interfacial donor state. As the temperature increased, the reverse leakage current of the Pt/Ti/Pt/Au AlGaN/GaN HEMT at 308 K showed more reduction under the same off-state stress condition while that of the Ni/Au AlGaN/GaN HEMT increased. However, with temperatures exceeding 308 K under the same off-state stress conditions, the reverse leakage current of the Pt/Ti/Pt/Au AlGaN/GaN HEMT increases, which can be intensified using the inverse piezoelectric effect. Based on this phenomenon, the present work reveals the necessity for analyzing the concurrent SBH and reliability instability due to the interfacial trap states of the MS contacts.

Thermal Stability of HfO2|AlGaN|GaN Normally-Off Transistors with Ni|Au and Pt Gate Metals

Thermal Stability of HfO2|AlGaN|GaN Normally-Off Transistors with Ni|Au and Pt Gate Metals

Rapid Screening for COVID-19 Using Field Effect Transistor Biosensors

In this study, we have developed a platform for the rapid screening of the SARS-CoV-2 virus in saliva. Electrical double layer (EDL) gated field-effect transistors (FET) biosensor is applied in this research to detect the electrical signals in the sample. Nucleocapsid protein is used as the target protein since it is expressed abundantly during infection. The sensor illustrates a lower detection limit compared to recent methods, which shows the potential of our sensor to make a diagnosis in the early stages of the disease. Besides, additional pre-pretreatment is not needed. The sensor is a robust diagnostic tool for rapid screening of COVID-19. Introduction The coronavirus pandemic, also known as COVID-19, is caused by SARS-CoV-2 virus. COVID-19 causes severe acute respiratory syndrome and poses a significant threat to health internationally. The World Health Organization (WHO) declared this as a global pandemic. Symptom-based screening cannot be an effective strategy to identify individuals. The symptoms of mild patients are similar to influenza, which may easily lead to false negative confirmation of disease. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) is the most well-known method employed for the clinical diagnosis of COVID-19. But, this method is costly and needs a long time to get the result. Hence, a rapid and low-cost diagnosis method is urgently required. Experimental Sensor array fabrication The disposable sensor array chip consists of two gold electrodes. One electrode is connected to the gate voltage supply, defined as the reference electrode. The other one is connected to the gate metal, and considered as the sensing electrode. Functionalization of sensor surface Antibody against SARS-CoV-2 nucleocapsid protein is used as receptor in this study, which is immobilized on the gold gate electrode. Traut’s Reagent (Thermo Scientific, (26101)) introduces sulfhydryl (-SH) groups to the primary amines of antibody. The modified antibody can then covalently bind to Au gate electrode by Au-S Bond. The antibody(1.5mg/mL) and Traut’s reagent (14 mM) are mixed and incubated at room temperature for 1 hour. The mixture is then dropped on the sensor surface and incubated in 4 °C refrigerator for 12 hours. Electrical measurement The sensor array chip is inserted into a portable prototype device with FET LND150. 2V DC bias as the drain-source voltage and a short duration gate pulse are steadily provided. The difference between the two current drains is defined as current gain, which is used as the index in data analysis. Fluorescence experiment After the electrical measurement, the secondary antibody, anti-mouse IgG (DyLight® 594), is added to the sensor to conjugate with the primary antibody. The sensor array chip is incubated for 1 hour at room temperature, and the unbound molecule is washed away by 1X PBS. Fluorescence microscope, (LEICA DM2500 LED) is used to capture the fluorescence image with 100 ms exposure time and quantitative analysis is performed using imageJ software. Result and conclusion When infected with SARS-CoV-2, the body produces antibodies that bind specific to nucleocapsid proteins and other surface antigens to help eliminate the virus. SARS-CoV-2 virus nucleocapsid protein is abundantly expressed during infection and is one of the highly immunogenic proteins. Hence, nucleocapsid protein is used as the target protein in this study. We immobilized antibody for nucleocapsid protein on the sensor. Electrical signal changed as the concentration of nucleocapsid protein increased from 0 to 400 ng/mL. The limit of detection for N protein was established at 0.4ng/mL. Tests that can distinguish between IgM and IgG can provide information about the stage of infection, indicating how long the person has been infected with SARS-CoV-2. In this study, we developed a platform that can help to confirm the infection in patients quickly in saliva. N-protein testing can potentially help us track the spread of the disease and accurately detect the infected individuals so as to control further spreading of the disease. Figure 1

Switching and frequency response of ITO-gated GaAs OPFET models for VLC applications

Visible-Light Communication (VLC) application such as traffic lighting requires high-speed data transmission wherein at the receiving end, a fast response and wide bandwidth photodetector should decode the sent data. High-speed detection is achievable through a photoFET such as Optical Field Effect Transistor (OPFET) while maintaining tremendously large photocurrent gain or sensitivity. In this paper, we investigate the switching and frequency responses of GaAs OPFET models (buried-gate front-illuminated, and generalized, models) with Indium-Tin-Oxide (ITO) gate. These responses have been contrasted to that with gold (Au) gate investigated in the previous work showing a considerable enhancement in the 3-dB bandwidth and an almost constant switching/amplification response. The effect of structural parameters on the switching and frequency responses of the buried-gate models has been studied. The switching parameters and the bandwidth-dependence upon the optical power have been analyzed. The attained responses suggest that the devices will serve good purpose in high-speed applications.

A sensitive platform for DNA detection based on organic electrochemical transistor and nucleic acid self-assembly signal amplification.

Highly sensitive detection of DNA is of great importance for the detection of genetic damage and errors for the diagnosis of many diseases. Traditional highly sensitive organic electrochemical transistor (OECT)-based methods mainly rely on good conductivity materials, which may be limited by complex synthesis and modification steps. In this work, DNA biosensor based on OECT and hybridization chain reaction (HCR) signal amplification was demonstrated for the first time. Au nanoparticles were electrochemically deposited on the Au gate electrode to increase the surface area. Then, the HCR products, long negatively charged double-stranded DNA, were connected to the target by hybridization, which can increase the effective gate voltage offset of OECT. This sensor exhibited high sensitivity and even 0.1 pM target DNA could be directly detected with a significant voltage shift. In addition, it could discriminate target DNA from the mismatched DNA with good selectivity. This proposed method based on HCR in DNA detection exhibited an efficient amplification performance on OECT, which provided new opportunities for highly sensitive and selective detection of DNA.

Performance Comparison of Low-Voltage non-Ionic Gel Organic Field Effect Transistors with Gold and PEDOT:PSS Gate Electrodes

Low-voltage non-ionic gel organic-field effect transistors (NIGOFETs) with two kinds of gate electrode materials namely gold (Au) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) formulation were fabricated in top-gate bottom-contact geometry to investigate the effects of gate electrodes on the electrical performance of the OFETs. In addition, three kinds of gate dielectrics were used for both types of transistors to understand the effects more thoroughly. As a result, it can be deduced from the data that NIGOFETs with Au gate electrodes (Au-NIGOFETs) display better performance considering higher mobility and on-to-off current ratio (ION/IOFF) as well as lower Subthreshold Swing (SS) of them. Besides, the threshold voltage (VTH) effects-free drain currents (IDS) of the Au-NIGOFETs surpasses those of the PEDOT:PSS formulation gated NIGOFETs (Pedot-NIGOFETs). This is probably due to having greater WF gate electrode (in our case Au) provides less injection barrier eventually leads to relatively unimpeded charge transportation. Nevertheless, Au-NIGOFETs interestingly proves to have further negative VTH and lower off-current (IOFF), which may be attributed to lower electrical resistivity (ρ) of the Au leading to denser charge carrier traps formation along with intensified charge carrier induction at the semiconductor-dielectric interface when the gate-to-source voltage (VGS) is less than VTH. However, because of the same reason, when VGS exceeds the VTH for example, IDS of Au-NIFOFET1 starts to increase in such a quick manner that enabling it to have higher ION/IOFF and lower SS.

Aptamer-based nanofilter interface for small-biomarker detection with potentiometric biosensor

In this paper, we report the concept of an aptamer (Ap)-based nanofilter interface for the suppression of nonspecific signals generated by interfering species in biological samples. As a model of the target small biomolecule, l-3,4-dihydroxyphenylalanine (l-DOPA) is used to demonstrate its electrical discrimination from dopamine (DA) despite their similar chemical structures using a DA–Ap nanofilter-coated Au gate field-effect transistor (FET). A Au gate electrode is employed to assess the electrical response of the FET to l-DOPA on the basis of oxidative reactions. In particular, the proposed nanofilter interface is based on the DA–Ap layer immobilized at the aryl-diazonium-based anchor monolayer, which is electrochemically grafted on the Au gate electrode via diazonium chemistry. As a result, the electrical signal from l-DOPA is clearly discriminated from that from DA at a concentration of 1 μM or higher using the DA–Ap nanofilter-coated Au gate FET. That is, DA is trapped by the DA–Ap nanofilter through the formation of complexes, the molecular charges of which are shielded by counter ions that are not in contact with the Au gate surface, whereas l-DOPA reaches and electrochemically reacts with the Au gate surface, generating an electrical signal regardless of the nanofilter. The surface properties of the DA–Ap nanofilter modified on the Au gate electrode are investigated by cyclic voltammetry, chronocoulometry, atomic force microscopy, and X-ray photoelectron spectroscopy. A platform based on the FET biosensor with the Ap-based nanofilter interface contributes to the electrical monitoring of small biomarkers while suppressing the nonspecific signals of interfering species in biological samples.

Quantum Dots-Sensitized High Electron Mobility Transistor (HEMT) for Room-Temperature Gas Detection

Introduction Nowadays there is an increasing demand for low power and low-cost gas sensors for a wide range of applications. With the advantages of miniaturization, low power consumption and good compatibility with the standard CMOS circuit, gas sensing field effect transistors (FETs) are the most attractive approaches.Since the first Pd gate field effect transistor gas sensor came into our insight [1], researchers have done a lot of work to materialize the device potential, starting with the choice of the sensing materials and sensor structure [2]. Due to the proximity of two-dimensional electron gas (2DEG) to the sensing surface and high sheet carrier concentration in the order of 1012~1013 cm−2, high electron mobility transistors (HEMTs) are extremely sensitive to the surface charge and variation in the environmental conditions, thereby enabling the sensing of the gases at low concentrations.In this paper, we demonstrate ppm level NO2 detection using AlGaAs/GaAs HEMT-based gas sensor with controlling gate and a PbS quantum dots sensitization layer. Experiment The HEMT structures in this paper were grown by molecular beam epitaxy (MBE) on GaAs substrate [3]. It was composed of an undoped 300 nm thick GaAs buffer layer, 15 nm thick In0.2Ga0.8As channel layer, 4 nm thick Al0.3Ga0.7As spacer layer, Si δ-doping layer, 25 nm thick Al0.3Ga0.7As barrier layer, and 30 nm thick GaAs cap layer. The sheet electron concentration of the HEMT was 2.3 × 1012 cm−2 with a mobility of 5.0 × 103 cm2V−1s−1 at 300 K.The sensing materials, PbS CQDs, were prepared by wet chemical synthesis technique according to previously paper [4], and the PbS quantum dots sensitization layer was formed as a sensing receptor on the exposed Au gate electrode using an electrohydrodynamic jet printer (HWK Co. Ltd., China).The CQDs capped with abundant oleic acid and oleylamine have stable dispersibility, a certain viscosity in the solvent and excellent solution processability, which makes it readily capable of being integrated with the electrohydrodynamic jet printing process at room temperature. The principle is to apply a high voltage power supply between the conductive nozzle (first electrode) and the conductive substrate (second electrode) and use a strong electric field force between nozzle and the substrate to pull the liquid out of the nozzle to form a droplet.Gas sensing characteristics were measured in a vacuum chamber probe station. The gas mixed in the mixing chamber flowed through the inlet of the chamber and out through the outlet. The flow rates of the gases were controlled by mass flow controllers (MFCs). Gas pressure and humidity in the probe station chamber remained constant for stable gas measurement. A series of electrical measurements of the fabricated sensors were carried out using the probe station and a semiconductor parameter analyzer (B1500A, Agilent Technologies). And the sensor response was defined as R=|Ig-I0|/I0, the I0 and Ig is the source to drain current in air and target gas atmosphere, respectively. Results and Conclusions The HEMT-type sensor showed high responsibility and excellent repeatability towards ppm level NO2. In this paper, extremely low concentration of the NO2 (0~25 ppm) was introduced, which shows a high response of 36.1% towards 25 ppm NO2 at room temperature, much higher than reported results [5-7], which even operated at a high temperature over 300 oC.In summary, through gate sensitization, the HEMT shows high sensitivity for ppm level NO2 detection at room temperature, the sensing performance can be both attributed to the receptor function of PbS quantum dots and the transducer function of HEMT. And the results of this paper will pave our future way for multiple target gas detection with in one chip.

Functionalization of Polymeric Nanofilter Biointerface for Small Biomarker Sensing

We propose a polymeric nanofilter biointerface with a multilayer that suppresses nonspecific signals caused by interfering species such as proteins and small biomolecules for potentiometric biosensors. In a previous work, we successfully prevented small biomolecules from reacting with the Au electrode using a polymeric nanofilter with a single polymeric layer, resulting in the suppression of nonspecific signals in an extended-Au-gate field-effect transistor (FET). In this study, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) is additionally employed as an antifouling nanofilter layer to suppress the nonspecific adsorption of proteins on the Au gate surface. We precisely graft the polymeric nanofilter on the Au electrode via diazonium chemistry and activators regenerated by electron transfer surface-initiated atom transfer radical polymerization (ARGET SI-ATRP). By impedimetric analysis, we found that the charge transfer resistance (R CT) of the Au electrode with the PMPC-based nanofilter hardly changes even when human serum albumin (HSA) is added onto the electrode. That is, the PMPC-based nanofilter effectively contributes to the prevention of the nonspecific adsorption of proteins such as HSA.

Enhancement Mode Flexible SnO2Thin Film Transistors Via a UV/Ozone-Assisted Sol-Gel Approach

The effect of ultraviolet/Ozone (UV/O 3 )-assisted annealing process on the structural, chemical, and electrical properties of sol-gel-processed SnO 2 films is investigated in this study. Via the UV/O 3 -assisted annealing processes, mixed-phase SnO 2 films composed of amorphous SnO 2 and polycrystalline SnO were obtained. Furthermore, the XPS spectra indicate an increase in the SnO 2 /SnO ratio and a substantial decrease in the number of -OH groups (serving as trap sites). This results in an increase in the conductivity and field-effect mobility of the films. The field-effect mobility of the UV/Ozone-assisted 300 °C-annealed SnO 2 thin film transistor (TFT) increases considerably (by $\sim 500\times$ ), yielding a device with a field-effect mobility of 3.09 cm 2 /Vs. In addition, flexible SnO 2 TFTs with Al 2 O 3 insulator and Au gate on Polyimide substrate fabricated via gate electrode engineering shows a decreased conduction bandgap offset, compared to the SnO 2 TFTs on SiO 2 , and enhancement mode operation properties (normally off at zero gate voltage) with a field-effect mobility of 1.87 cm 2 /Vs.

Gate/insulator-interfacial-dipole-controlled current conduction in Al2O3 metal-insulator-semiconductor capacitors

Electric dipoles at a metal-gate/Al2O3 interface are found to control the current conduction in negatively biased Al2O3 metal-insulator-semiconductor (MIS) capacitors by effectively increasing the Al2O3 electron affinity near the gate and thereby reducing the barrier height against electron field emission from the gate. By carrying out space-charge-controlled field emission analysis, the Al2O3 effective electron affinity in Al-gate capacitors was found to be larger than that for the Au gate by 0.38 eV, and the value for the Ni gate was similar to that for the Au gate. The cross-sectional transmission-electron-microscope images of the samples revealed the presence of an approximately 3-nm-thick layer intervening between the Al gate and the Al2O3 film. This layer is likely to have formed Al/Al2O3 interfacial dipoles that caused the aforementioned shift of the Al2O3 effective electron affinity. It was also confirmed that the conventional Fowler–Nordheim tunneling analysis yields remarkably erroneous results under the presence of these dipoles. These findings not only form the basis for investigating the band alignment of metal-gate MIS capacitors, but also alert us to a possibility of unexpectedly large leakage currents in negatively biased metal-gate MIS field-effect transistors.

Impact of metal gate electrodes on electrical properties of Y2O3/Si0.78Ge0.22 gate stacks

Electrical properties of Y2O3/SiGe metal-oxide-semiconductor (MOS) capacitors with Al, Au, W and TiN gate electrodes have been evaluated in order to study the impact of the metal gate electrodes on Y2O3/SiGe interface properties. It is found that MOS capacitors with TiN gate electrodes can provide better Y2O3/SiGe MOS interfaces than those with Al, Au or and W gate stacks after post metallization annealing (PMA) at each optimized temperature. The physical origins of interface trap density (Dit) reduction are examined from the viewpoint of the composition and the quality of interfacial layers (ILs).

Stable operation of water-gated organic field-effect transistor depending on channel flatness, electrode metals and surface treatment

The main purpose of this study is to clarify the factors for the stable operation of a poly(3-hexylthiophene) (P3HT)-based water gated organic field effect transistor (WG-OFET). To this end, the influence of the surface morphologies and electrode metals on the transistor properties were investigated. The experimental results indicated that a flat surface improved the on/off ratio and switching repeatability. Treating the surface with a lipid membrane was found to reduce hysteresis loops in the transfer curves probably due to the reduced number of carrier traps. The Au gate electrode effectively lowered the threshold voltage. Consequently, stable transistor operation with a low threshold voltage of 35 mV was achieved by employing a gold gate electrode and lipid membrane treatment. These results suggest that WG-OFETs with an ultra-thin lipid membrane have great potential for sensor applications, and in particular for sensing water-soluble analytes.

Effect of Electrochemically Grafted Aryl-Based Monolayer on Nonspecific Electrical Signal of Field-Effect-Transistor-Based Biosensor

In this study, we demonstrate the use of a monolayer film electrografted via diazonium chemistry for controlling the potential response of field-effect transistor (FET)-based sensor. A 4-nitrobenzenediazonium salt is electrografted on an extended-Au-gate FET (EG-Au-FET) with using a radical scavenger by cyclic voltammetry (CV), resulting in the formation of a monolayer. In particular, the surface coverage of the aryl-derivative monolayer on the Au gate electrode gradually increases with increasing number of potential cycles in CV. That is, the denser the surface coverage of the grafted monolayer, the smaller the potential response of the EG-Au-FET. Thus, a platform based on such a monolayer film electrografted via diazonium chemistry is suitable for controlling the potential response based on the interference of low-molecular-weight biomolecules in biosamples.

Control of Potential Response to Small Biomolecules with Electrochemically Grafted Aryl-Based Monolayer in Field-Effect Transistor-Based Sensors.

In this paper, we demonstrate the use of a monolayer film electrografted via diazonium chemistry for controlling the potential response of a field-effect transistor (FET)-based sensor. 4-Nitrobenzenediazonium salt is electrografted on an extended-Au-gate FET (EG-Au-FET) with or without using a radical scavenger by cyclic voltammetry (CV), resulting in the formation of a monolayer or multilayer. In particular, the surface coverage of the aryl-derivative monolayer on the Au gate electrode gradually increases with increasing number of potential cycles in CV. Here, Au exhibits a strong catalytic action, resulting in the oxidation of organic compounds. Uric acid is used as a low-molecular-weight biomolecule for interference. The denser the surface coverage of the grafted monolayer, the smaller the potential response of the EG-Au-FET because the redox reaction of uric acid with the Au gate surface is suppressed. On the other hand, the effect of the aryl-derivative multilayer on the suppression of the potential response was smaller than that of the monolayer because the electrogenerated aryl radicals did not react with the Au surface but with the grafted species, resulting in an exposed part of the Au surface among the grafted aryl molecules. Thus, a platform based on such a monolayer film electrografted via diazonium chemistry is suitable for controlling the potential response based on the interference of low-molecular-weight biomolecules in biosamples.