Field-effect Transistor Sensor Research Articles

Laser-induced multi-doped graphene extended-gate field-effect transistor sensor for enhanced detection of cystatin C

In this study, we amplified the capabilities of laser-induced graphene (LIG) by developing a multi-doped LIG extended-gated field-effect transistor (EG-FET) sensor. This sensor integrates a multi-doped LIG EG electrode array as a disposable sensing component with a standard MOSFET for reusable transduction. The multi-doped LIG was synthesized using a dual-approach: initially, by using a MnCl2-doped polyimide (MnCl2-PI) film through precursor compounding, and subsequently, by employing a CO2 laser to respectively in situ generate MnO2 nanoparticles and gold nanoparticles (Au NPs) via direct laser conversion. By incorporating the resultant multi-doped LIG (Au NPs/MnO2/LIG) as the EG electrode, we boosted its electrical efficiency and provided ideal sites for the papain immobilization. This facilitated the selective binding of protein complexes with cystatin C (Cys C), allowing for precise measurement. Notably, the sensor exhibited a robust linear correlation across a concentration range from 50 ag/μL to 0.25 ng/μL and achieved a detection limit of 50 ag/μL. These advancements not only address traditional limitations of LIG applications but also highlight the potential of LIG-based EG-FET portable devices for accurate and early screening of chronic kidney disease (CKD).

Fabrication of Graphene-based Ammonia Sensors: A Review

Abstract: Graphene gas sensors have gained much scientific interest due to their high sensitivity, selectivity, and fast detection of various gases. This article summarizes the research progress of graphene gas sensors for detecting ammonia gas at room temperature. Firstly, the performance and development trends of the graphene/semiconductor Schottky diode sensor are discussed. Secondly, manufacturing methods and the latest developments in graphene field-effect transistor sensors are reviewed. Finally, the basic challenges and latest efforts of functional ammonia gas sensors are studied. The discussion delves into each sensor type's detection principles and performance indicators, including selectivity, stability, measurement range, response time, recovery time, and relative humidity. A comparative analysis is conducted to highlight the progress achieved in research, elucidating the advantages, disadvantages, and potential solutions associated with various sensors. As a result, the paper concludes by exploring the future development prospects of graphene-based ammonia sensors.

Drug evaluation platform based on non-destructive and real-time in situ organoid fate state monitoring by graphene field-effect transistor

3D organoid models have been widely used in drug evaluation because they effectively mimic physiological conditions and cell–cell interactions. However, current organoid-based drug evaluation heavily relies on invasive methods like qRT-PCR and immunofluorescence quantification, which disrupts the organoid’s structure and physiological function during the evaluation process. Therefore, it is urgent to develop a non-destructive drug evaluation platform to continuously monitor organoid fate. Here, a non-destructive and real-time in situ platform based on field effect transistor sensor (NDRS-FET) was developed to monitor organoid fate and obtained accurate drug evaluation by conducting the dynamic models. Using liver organoid as the model, the transition kinetics of liver organoid fate in response to candidate drug compounds were recorded by the NDRS-FET platform. OSM, FH1 and BG45 were successfully identified as effective regulators of liver organoid fate. Compared to traditional methods, the NDRS-FET platform could not only accurately capture the drug effect on organoid in real time, but also reduce the intergroup deviation among samples, providing more accurate and reliable tool for drug development and screening.

Integration of highly sensitive large-area graphene-based biosensors in an automated sensing platform

Graphene-based biosensors, featuring exceptional electronic, mechanical, and surface properties, have emerged as frontrunners in advanced sensing technologies. However, to achieve widespread industrial adoption, advancements in the fabrication and integration of large-area graphene devices are essential. Critical parameters such as enhanced sensitivity, scalable production methods, economic viability, integration capabilities, and consistent uniformity must be meticulously addressed. In this work, we demonstrate that our ultra-clean, chemical wet transfer protocol of large-area graphene enables a scalable, smooth integration of graphene into an established assay platform for transporter protein drug discovery. Furthermore, we demonstrate sensitive detection of electrolytic buffers, varying pH, bovine serum albumin (BSA) and single-stranded DNA (ssDNA) adsorption, using our large-area graphene solution-gated field-effect transistor (SGFET) sensors, thereby proving their robust and reliable performance. The sensors’ biocompatibility and ion sensitivity, down to the picomolar range, substantiate their suitability for the investigation of electroactive transport in ion channels and membrane transporters.

Deep Learning-Based Kinetic Analysis in Paper-Based Analytical Cartridges Integrated with Field-Effect Transistors.

This study explores the fusion of a field-effect transistor (FET), a paper-based analytical cartridge, and the computational power of deep learning (DL) for quantitative biosensing via kinetic analyses. The FET sensors address the low sensitivity challenge observed in paper analytical devices, enabling electrical measurements with kinetic data. The paper-based cartridge eliminates the need for surface chemistry required in FET sensors, ensuring economical operation (cost < $0.15/test). The DL analysis mitigates chronic challenges of FET biosensors such as sample matrix interference, by leveraging kinetic data from target-specific bioreactions. In our proof-of-concept demonstration, our DL-based analyses showcased a coefficient of variation of <6.46% and a decent concentration measurement correlation with an r2 value of >0.976 for cholesterol testing when blindly compared to results obtained from a CLIA-certified clinical laboratory. These integrated technologies have the potential to advance FET-based biosensors, potentially transforming point-of-care diagnostics and at-home testing through enhanced accessibility, ease-of-use, and accuracy.

Enhanced Detection of Klebsiella Pneumoniae Using Electric-Double-Layer FET Sensor: Rapid, Temperature-Boosted Probe-Target Binding Analysis

Klebsiella pneumoniae demonstrates versatility in its pathogenicity, leading to diverse infections in humans such as pneumonia, urinary tract infections, bacteremia, wound infections, meningitis, endocarditis, and sepsis. The severity of these infections is contingent upon the patient's immune status, the site of infection, and the existence of underlying medical comorbidities. A sputum or urine culture, on the other hand, typically takes between 24 and 72 hours to produce results. Over recent years, various innovative methodologies have emerged, including optical and electrochemical techniques and molecular detection via PCR. Despite the diversity of available techniques, concerns persist regarding their sensitivity and specificity. Moreover, fluorescence-based methodologies and Surface Plasmon Resonance (SPR)-based sensors have been explored for bacterial detection. However, these existing methods have drawbacks such as elevated costs, prolonged turnaround times, the need for sophisticated instrumentation, and a demand for skilled personnel. Field-effect transistor (FET) sensors have garnered considerable scientific attention since their inception due to their remarkable sensitivity, facile signal readout, and the capability for label-free assays. The aim of this research is to detect the detect Klebsiella pneumoniae bacteria in blood serum by double electric layer (EDL) extended-gate field-effect transistor (FET) sensor. In this study, a preliminary investigation employed a single-step surface functionalization approach to immobilize receptor probes, specifically single-stranded DNA (ssDNA). This strategy aimed to enable the rapid detection of complementary DNA (cDNA) across varying concentrations, leveraging differential gate voltages to modulate the sensitivity of this analytical platform. The designed probes were successfully immobilized onto a disposable chip housing a pair of gold electrodes. A handheld reader, integrating enhancement-mode N-channel MOSFETs, established connectivity with a laptop via a USB port to facilitate the measurement of sensor signals. By applying pulsed gate voltage to the input electrode, which modulates the channel conductivity which behaves as a function of the charge distribution within the EDL structure, consequently influencing the drain current of the MOSFET. The immobilized probe, positioned on the gate electrode, underwent testing using varying concentrations of cDNA introduced into TE buffer. Detection of probe-target binding occurred through fluorescence alterations and electrically by assessing changes in drain current. In order to improve the response time, we elevated the temperature near the Tm enhances sensitivity and binding rates, in shorter time period of 1 minutes. Figure 1

Developing Field Effect Transistor Sensors Based on DNA Probes to Detect Staphylococcus Lugdunensis Bacteria

The goal of this research is to work with an Electrical Double Layer (EDL)-gated Field Effect Transistor (FET) to detect the bacteria Staphylococcus lugdunensis, which can cause a variety of illnesses, including infections of the skin and soft tissues. In rare cases, Staphylococcus lugdunensis can be successfully identified using the combination of a positive catalase test, a negative tube coagulase test, a positive PYR test, and a positive ornithine decarboxylase test. We are employing an Electrical DoubleLayer (EDL)-gated Field Effect Transistor (FET) to speed up the procedure because this test is time consuming and requires a highly competent individual to perform. An ssDNA probe was developed, and effectively immobilized on a gold surface electrode sensor with a square surface, and due to hybridization with the cDNA at different concentrations, electrical signals were generated in the form of current.Our sensor was fabricated using photolithography where the gold electrode surface having 500 μm x 500 μm gate sensing area consisting of each individually addressable sensor arranged in a 1 x 8 array which is the extent gate was expose for immobilization purpose. The sensor was then subjectedto O2 plasma & HCl solution for surface cleaning and fluorescence image of baregold were taken Figure1(b).The Single-Stranded DNA comprising of fluorescent dye (FAM) at 3’ and thiol modifier at 5’ was drop-casted on the gold surface and was incubated for 24 hours at 24°C. After, it went through a washing process in order to remove the unbound ssDNA and fluorescence images were taken. We observed that intensity was higher than that of baregold which indicates that our probe has successfully immobilized on the gold surface Figure 1(b).Figure 1(a) represents the device that we designed. The system works with N-Channel Enhancement-Mode DMOS FET (VN10LP) in which a continuous drain voltage (3.5 V) was applied and the drain current which is the signal, were measured at two distinct gate bias voltage (2V and 3V). cDNA having quencher (BHQ1) at 5’ was diluted in different concentration namely 1fM, 10fM, 100fM and 1000fM. These cDNA with different concentrations were drop-casted on our sensor with Tris-EDTA (TE) buffer as the baseline and starting with lower concentration to higher concentration every after 12 seconds periodically where we record the change in signal as shown in Figure 1(c).After the electrical measurement, fluorescence image was taken and we can observe that it quenched which indicates that the cDNA and the immobilized ssDNA has successfully hybridized which give the signal change. Figure 1: (a) Surface Immobilization Principal Display in Extended Gate EDL BioFETs. (b)Fluorescence value comparison. (c) Plot showing the change in drain current over time for aptamersensors exposed to various cDNA concentrations. Figure 1

The alcohol lock built on carbon-based field-effect transistor sensor with Pd/ZnO floating gate structure used for drunk driving surveillance

The ignition interlock device, an onboard alcohol detection system for supervising cases of driving under the influence (DUI), is crucial for ensuring traffic safety. As a key component of this system, ethanol sensor faces challenges like integration difficulties and poor anti-humidity property, limiting its potential applications. Herein, from the perspective of miniaturization and integration, a carbon-based field effect transistor (FET) gas sensor with a floating-gate (FG) structure is proposed for fast ethanol detection in exhaled breath. The proposed sensing FG structure enables the traditional FET to acquire the perceptibility toward target gas, and the FET with excellent amplification ability further enhances the gas-sensing response. The detection range of the sensor is 0–600 ppm, with a response deviation of merely 11 % toward 50 ppm ethanol within a humidity range of 10 %-90 % relative humidity (RH). Additionally, benefited from the good consistency of the semiconductor technology, relative standard deviation (RSD) of the responses from different batches is 2.1 %, confirming its potential for mass production. The tiny size (1.5 mm×1.5 mm) of the sensor and the compatible fabrication process with MEMS process are conducive to the on-chip integration. This work provides a boost to the process of advancing the research and development of automotive alcohol locks, and facilitate their popularization.

GeP3 monolayer as a promising 2D sensing materials in detecting SO2, H2S, SOF2 and SO2F2

The detection of SF6 decomposition components using gas-sensitive sensors is significantly important for characterizing internal insulation failures and assessing the operational status of SF6 gas-insulated equipment. In this paper, the adsorption properties of GeP3 monolayers for SO2, H2S, SOF2 and SO2F2 gases were investigated based on density functional theory. Four gas adsorption systems were constructed, and the adsorption mechanisms and sensing characteristics of GeP3 monolayers on target gases were investigated by calculating parameters such as adsorption energy, charge transfer, density of states, and recovery time, along with their potential application as resistive gas sensors and field-effect transistor sensors. It is demonstrated that GeP3 monolayers were suitable for the detection of SO2, H2S, SOF2 and SO2F2 gases, all of which exhibited good chemisorption with adsorption energies of −1.36 eV, −0.78 eV, −1.82 eV and −2.91 eV, respectively. The adsorption of SO2 and H2S is found to cause a significant change in the conductivity of the GeP3 monolayers, and desorption is achieved at the optimal operating temperature in only 54.428 s and 10.686 s, respectively. Also the adsorption of SOF2 and SO2F2 can make the work function of the GeP3 monolayers significantly larger. Consequently, the GeP3 monolayers have the potential to be used as a resistive gas sensor for SO2 and H2S gases, or as a field effect transistor sensor for SOF2 and SO2F2 gases. This study provides theoretical guidance for the development of GeP3-based sensors for monitoring the insulation status and operational conditions of SF6 gas-insulated equipment.

Molecularly imprinted polymer-based extended-gate field-effect transistor chemosensors for selective determination of antiepileptic drug.

Ultrathin molecularly imprinted polymer (MIP) films were deposited on the surfaces of ZnO nanorods (ZNRs) and nanosheets (ZNSs) by electropolymerization to afford extended-gate field-effect transistor sensors for detecting phenytoin (PHT) in plasma. Molecular imprinting efficiency was optimized by controlling the contents of functional monomers and the template in the precursor solution. PHT sensing was performed in plasma solutions with various concentrations by monitoring the drain current as a function of drain voltage under an applied gate voltage of 1.5V. The reliability and reproducibility of the fabricated sensors were evaluated through a solution treatment process for complete PHT removal and PHT adsorption-removal cycling, while selectivity was examined by analyzing responses to chemicals with structures analogous to that of PHT. Compared withthe ZNS/extracted-MIP sensor and sensors with non-imprinted polymer (NIP) films, the ZNR/extracted-MIP sensor showed superior responses to PHT-containing plasma due to selective PHT adsorption, achieving an imprinting factor of 4.23, detection limit of 12.9ng/mL, quantitation limit of 53.0ng/mL, and selectivity coefficients of 3-4 (against tramadol) and ~ 5 (against diphenhydramine). Therefore, we believe that the MIP-based ZNR sensing platform is promising for the practical detection of PHT and other drugs and evaluation of their proper dosages.

Exploring Pore Formation and Gas Sensing Kinetics Using Conjugated Polymer-Small Molecule Blends.

Controlling miscibility between mixture components helps induce spontaneous phase separation into distinct domain sizes, thereby resulting in porous conjugated polymer (CP) films with different pore sizes after selective removal of auxiliary components. The miscibility of the CP mixture can be tailored by blending auxiliary model components designed by reflecting the difference in solubility parameters with the CP. The pore size increases as the difference in solubility parameters between the matrix CP and auxiliary component increases. Electrical properties are not critically damaged even after forming pores in the CP; however, excessive pore formation enables pores to spread to the vicinity of the dielectric layer of CP-based field-effect transistors (FETs), leading to partial loss of the carrier-transporting active channel in the FET. The porous structure is advantageous for not only increasing detection sensitivity but also improving the detection speed when porous CP films are applied to FET-based gas sensors for NO2 detection. The quantitative analysis of the response-recovery trend of the FET sensor using the Langmuir isotherm suggests that the response speed can be improved by more than 2.5 times with a 50-fold increase in NO2 sensitivity compared with pristine CP, which has no pores.

Towards monitoring of critical illness via the detection of histones with extended gate field-effect transistor sensors

Extracellular histone proteins in the blood indicate a heightened risk of morbidity after trauma or in major illnesses such as sepsis. We present the development of an aptasensor for histone detection with an extended gate field-effect transistor (EGFET) configuration, which benefits from low power consumption, rapid response, and compatibility with miniaturized gold electrodes. Histones have a high isoelectric point and charge density, which cause them to physically adsorb to non-specific elements of the sensor that have available electrostatic charges. To combat this, the sensing surface is formed with a thiol-modified, high-affinity and histone-specific RNA aptamer sequence and by co-immobilizing with poly(ethylene glycol) methyl ether thiol (PEG) as a blocking agent. Surface plasmon resonance (SPR) is used to analyze aptamer and PEG immobilization strategies, confirm histone binding, and calculate kinetic binding constants. Through comparison of different blocking agents and time-dependent preparation, the ideal equilibrium dissociation constant (KD) is estimated to be below 200 pM, which is the upper range of extracellular histone concentrations in critically ill patients with high mortality. The EGFET sensitivity of the optimized aptasensor is 6.65 mV/decade concentration change for histone H4 with a physiologically relevant 5 pM limit of detection. Selectivity tests with 100 nM bovine serum albumin (BSA) demonstrate a signal response that is 13-fold smaller than for histones. This EGFET aptasensor platform is suitable for future point-of-care monitoring of histone levels in critically ill patients, thus permitting the early detection of increased risk and the need for more aggressive interventional measures to prevent mortality.

Supramolecular methods: utilising ChemFETs to evaluate aqueous anion affinity of hydrophobic receptors

ABSTRACT The host–guest interaction and affinity of hydrophobic receptors towards aqueous anions can be evaluated by incorporating a receptor into a polymeric membrane and applying these membranes to FET-based sensing devices. A series of anions screened using these ChemFET (chemically sensitive field effect transistor) sensors based on different receptors can also provide a Hofmeister-like ordering of anions based on their respective detection limits. Although the general trends of selectivity coefficients often follow the Hofmeister Series, the specific anion affinity profiles are generally unique to each receptor and provide insight into receptor selectivity. In this methodspaper, we provide a detailed example of how our lab uses ChemFETs to evaluate host–guest interactions of hydrophobic host receptors with aqueous anions, and a detailed procedure for fabricating ChemFET sensor devices is presented along with selected case studies for readers interested in applying related ion recognition strategies in sensors of this type.

Enhancing Electrochemical Sensing through Molecular Engineering of Reduced Graphene Oxide-Solution Interfaces and Remote Floating-Gate FET Analysis.

Two-dimensional nanomaterials such as reduced graphene oxide (rGO) have captured significant attention in the realm of field-effect transistor (FET) sensors due to their inherent high sensitivity and cost-effective manufacturing. Despite their attraction, a comprehensive understanding of rGO-solution interfaces (specifically, electrochemical interfacial properties influenced by linker molecules and surface chemistry) remains challenging, given the limited capability of analytical tools to directly measure intricate solution interface properties. In this study, we introduce an analytical tool designed to directly measure the surface charge density of the rGO-solution interface leveraging the remote floating-gate FET (RFGFET) platform. Our methodology involves characterizing the electrochemical properties of rGO, which are influenced by adhesion layers between SiO2 and rGO, such as (3-aminopropyl)trimethoxysilane (APTMS) and hexamethyldisilazane (HMDS). The hydrophilic nature of APTMS facilitates the acceptance of oxygen-rich rGO, resulting in a noteworthy pH sensitivity of 56.8 mV/pH at the rGO-solution interface. Conversely, hydrophobic HMDS significantly suppresses the pH sensitivity from the rGO-solution interface, attributed to the graphitic carbon-rich surface of rGO. Consequently, the carbon-rich surface facilitates a denser arrangement of 1-pyrenebutyric acid N-hydroxysuccinimide ester linkers for functionalizing capturing probes on rGO, resulting in an enhanced sensitivity of lead ions by 32% in our proof-of-concept test.

On-site SNP discrimination of Monkeypox viral DNA at room temperature using dCas9-enhanced extended-gate field-effect transistor

During the COVID-19 pandemic, there was heightened concern about the sudden spread of viral diseases. As the threat of coronavirus transmission began to diminish, a subsequent outbreak caused by monkeypox virus (MPXV) emerged in Europe and North America. Notably, MPXV infection tends to be transmitted through sexual contact, increasing the difficulty of tracing the infection route through passive testing. As a result, there is a pressing need for cost-effective, precise, and rapid on-site screening techniques to detect MPXV. Recently, the CRISPR system, known as a genome editing tool, has been used as a rapid on-site diagnostic tool for detecting nucleic acids mostly through the use of Cas12a and Cas13a. Intriguingly, deficient Cas9 (dCas9) can recognize specific double-stranded DNA (dsDNA) sequences and bind to complementary DNA sequences. Here, we devised an innovative digital field-diagnosis platform that can be readily employed in clinical settings. This platform combines an ultrasensitive field-effect transistor (FET) with the dCas9 system, enabling quantitative analysis of biomarkers. Our dCas9-EG-FET can directly detect viral dsDNA without any amplification or pretreatment. When the dCas9 of our dCas9-EG-FET system recognizes the specific target viral DNA, the EG-FET system provides voltage differences by using FET features that measure the ion concentration on the surface of the FET sensor. Furthermore, it takes only 20 min to detect MPXV DNA using our dCas9-EG-FET system at room temperature (RT), and this system can be used to effectively distinguish single-point mutations with high sensitivity. Our findings suggest that the use of a CRISPRCas-based biosensor could lead to an effective strategy for screening for infectious diseases.

Machine Learning Discrimination and Ultrasensitive Detection of Fentanyl Using Gold Nanoparticle-Decorated Carbon Nanotube-Based Field-Effect Transistor Sensors.

The opioid overdose crisis is a global health challenge. Fentanyl, an exceedingly potent synthetic opioid, has emerged as a leading contributor to the surge in opioid-related overdose deaths. The surge in overdose fatalities, particularly due to illicitly manufactured fentanyl and its contamination of street drugs, emphasizes the urgency for drug-testing technologies that can quickly and accurately identify fentanyl from other drugs and quantify trace amounts of fentanyl. In this paper, gold nanoparticle (AuNP)-decorated single-walled carbon nanotube (SWCNT)-based field-effect transistors (FETs) are utilized for machine learning-assisted identification of fentanyl from codeine, hydrocodone, and morphine. The unique sensing performance of fentanyl led to use machine learning approaches for accurate identification of fentanyl. Employing linear discriminant analysis (LDA) with a leave-one-out cross-validation approach, a validation accuracy of 91.2% is achieved. Meanwhile, density functional theory (DFT) calculations reveal the factors that contributed to the enhanced sensitivity of the Au-SWCNT FET sensor toward fentanyl as well as the underlying sensing mechanism. Finally, fentanyl antibodies are introduced to the Au-SWCNT FET sensor as specific receptors, expanding the linear range of the sensor in the lower concentration range, and enabling ultrasensitive detection of fentanyl with a limit of detection at 10.8fgmL-1.

A Host Receptor Nanodisc-Based Biosensor Platform for the Detection of a Specific Virus and Its Variants.

The host receptor is a key element in the initial stage of the virus entry into the host. The use of this host receptor is valuable as a sensing element for selectively and sensitively detecting specific viruses. Also, viruses tend to escape neutralizing antibodies through viral mutation but still utilize the cell entry process using the same host receptors, so it would be a powerful detection tool even for the mutant viruses. The angiotensin-converting enzyme 2 (ACE2) receptor, which is the representative host receptor, performs an essential function in facilitating viral penetration by interacting with the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein. In this study, we introduce a novel approach, where we fabricated a carbon nanotube field-effect transistor (CNT-FET) sensor and combined it with ACE2 receptor-embedded nanodisc (ND). ACE2 was produced using an E. coli expression system, purified, and integrated into the ND platform. ACE2 NDs showed robust functionality through interactions with a pseudotyped virus (PV) containing the spike protein, enabling sensitive detection of both SARS-CoV-2 and its genetic variations at 102 PFU/mL. The ACE ND-based sensor exhibited excellent selectivity by accurately differentiating SARS-CoV-2 wild-type and variants (Omicron, Delta) from other viruses (ZIKA and MERS-CoV). As a result of comparative analysis, ACE2 ND showed approximately 49% superior long-term functionality up to the second week compared to that of soluble ACE2. These findings highlight the high selectivity and sensitivity of host receptor-based sensors for detecting viral variants and provide a promising tool to prevent the spread of unknown viruses.

Comparative Study of Field-Effect Transistors Based on Graphene Oxide and CVD Graphene in Highly Sensitive NT-proBNP Aptasensors.

Graphene-based materials are actively being investigated as sensing elements for the detection of different analytes. Both graphene grown by chemical vapor deposition (CVD) and graphene oxide (GO) produced by the modified Hummers' method are actively used in the development of biosensors. The production costs of CVD graphene- and GO-based sensors are similar; however, the question remains regarding the most efficient graphene-based material for the construction of point-of-care diagnostic devices. To this end, in this work, we compare CVD graphene aptasensors with the aptasensors based on reduced GO (rGO) for their capabilities in the detection of NT-proBNP, which serves as the gold standard biomarker for heart failure. Both types of aptasensors were developed using commercial gold interdigitated electrodes (IDEs) with either CVD graphene or GO formed on top as a channel of liquid-gated field-effect transistor (FET), yielding GFET and rGO-FET sensors, respectively. The functional properties of the two types of aptasensors were compared. Both demonstrate good dynamic range from 10 fg/mL to 100 pg/mL. The limit of detection for NT-proBNP in artificial saliva was 100 fg/mL and 1 pg/mL for rGO-FET- and GFET-based aptasensors, respectively. While CVD GFET demonstrates less variations in parameters, higher sensitivity was demonstrated by the rGO-FET due to its higher roughness and larger bandgap. The demonstrated low cost and scalability of technology for both types of graphene-based aptasensors may be applicable for the development of different graphene-based biosensors for rapid, stable, on-site, and highly sensitive detection of diverse biochemical markers.

Lead ions detection using CVD-grown ReS2-FET with the facilitation of a passivation layer

Field-effect transistor (FET)-based heavy-metal detection is garnering attention due to its heightened sensitivity, affordability, convenient fabrication, and portability. Flower-like rhenium disulfide (ReS2) offers potential for high-performance FET sensors, but direct exposure of channel materials to the ionic solution without a passivation layer results in multiple signals arising from the ionic transmission, doping impact, and gating effect. Introducing a passivation layer to the channel surface enhances sensor sensitivity without compromising device performance, ensuring conductance changes are primarily due to the gating effect. Here, a large surface area of Chemical Vapor Deposition (CVD)-grown vertically aligned ReS2 is employed in the FET-based sensor, and the utilization of the HfO2 layer is to isolate analytes from the elements of the conducting channel. For real-time lead monitoring in a water environment, it exhibits strong electrical stability, an impressive LoD (≈2 nM), a rapid response time (≈1.1 sec), and notable selectivity. Additionally, sensing operations are characterized by developing a unique amplifier circuit by integrating the fabricated sensor, contributing to advancements in sensor integration to detect hazardous metals in industrial electronics. These results underscore the potential for enhancing the performance of ion-sensitive FETs through structural optimization and improvements to the fundamental sensor mechanism.

High-Performance Ni3(HHTP)2 Film-Based Flexible Field-Effect Transistor Gas Sensors.

Conductive metal-organic frameworks (MOFs) have received increasing attention in recent years and present high application potential as sensing elements in electronic sensors. In this study, flexible field-effect transistor (FET) sensors based on conductive MOF, i.e., Ni3(HHTP)2, have been constructed. This Ni3(HHTP)2 sensor has high sensitivity (detection limit of 56 ppb) as well as superior selectivity for NO2 detection at room temperature, which is demonstrated by accurate gas detection in a mixed gas atmosphere. Moreover, by employing six flexible substrates, i.e., polyimide (PI), tape (PET), facemask, paper cup, tablecloth, and take-out bag (textile), we successfully demonstrate the universality of the flexible sensor construction with conductive MOF as sensing film on various substrates. This study of conductive MOF-based flexible electronic sensors offers a new opportunity for a wide range of sensing applications with wearable and portable electronic devices.