Graphene-based field effect transistor in two-dimensional paper networks

We demonstrate the fabrication of a graphene-based field effect transistor (GFET) incorporated in a two-dimensional paper network format (2DPNs). Paper serves as both a gate dielectric and an easy-to-fabricate vessel for holding the solution with the target molecules in question. The choice of paper enables a simpler alternative approach to the construction of a GFET device. The fabricated device is shown to behave similarly to a solution-gated GFET device with electron and hole mobilities of ∼1256 cm² V⁻¹ s⁻¹ and ∼2298 cm² V⁻¹ s⁻¹ respectively and a Dirac point around ∼1 V. When using solutions of ssDNA and glucose it was found that the added molecules induce negative electrolytic gating effects shifting the conductance minimum to the right, concurrent with increasing carrier concentrations which results to an observed increase in current response correlated to the concentration of the solution used.     

Glucose-sensitive field effect transistor using totally synthetic compounds

A field effect transistor (FET)-based glucose sensor was fabricated. As a totally synthetic and thus stable glucose-sensing moiety, 3-acrylamidophenylboronic acid was chemically introduced onto the FET gate surface in the form of a thin copolymer gel layer. Excellent transistor characteristics were confirmed even after the surface modification, ensuring validity of the modification procedure herein developed. Glucose-induced changes in the FET’s electric characteristics were obtained in quantitative as well as reversible manners. It was also demonstrated that the prepared FET is able to continuously perceive the change in the glucose concentration in the milieu. The detected signals were attributed to the faction change of the gate-introduced phenyborate anions, also presumably involving other parameter changes such as permittivity and conductivity. The use of the fabricated FET could further be extended to the construction of stable, readily minutualizable, and label-free carbohydrate molecule-sensing systems.     

场效应管药物传感器

将场效应管与药物敏感膜结合,以硅钨酸或四苯硼钠未转型的定域体试剂为电活性物质的药物传感器.该传感器制作简单,线性范围宽于或检测下限低于文献值.并对器件的影响因素进行了详尽的讨论.     

A novel Urushi matrix chloride ion-selective field effect transistor

A durable chloride ion-selective field effect transistor (ISFET) is proposed with Urushi as the membrane matrix. The chloride ion-sensing material is a quaternary ammonium chloride: trioctylmethylammonium chloride (TOMA-Cl) or tridodecylmethylammonium chloride (TDMA-Cl). The optimum composition of the Urushi membrane was found by use of Urushi ion-selective electrodes. The mixture with the most favourable composition was coated on the gate region of the FET device. The Urushi ISFET with TDMA-Cl proved to be superior to that with TOMA-Cl, in sensitivity, linearity and selectivity. The Urushi ISFET with TDMA-Cl showed a linear response of about -51 mV per decade change of chloride ion activity in the range 10(-4)-1M. The Urushi ISFET showed excellent stability and durability for over two months, because of strong adhesion of the membrane to the Si(3)N(4) gate.     

A microsensor for adenosine-5′-triphosphate pH-sensitive field effect transistors

The sensor for adenosine-5′-triphosphate (ATP) is based on H⁺-ATPase immobilized via a polyvinylbutyral resin on a pH-sensitive field effect transistor. A linear relationship was obtained between the initial rate of change of the differential gate output voltage and the logarithm of the ATP concentration over the range 0.2–1.0 mM ATP. The optimum pH was 9.0 at 40°C but pH 7.0 was preferred for routine measurements. Only slight responses were obtained for 1 mM glucose, creatinine or urea. The ATP-sensing system exhibited a response to 1 mM ATP for at least 18 days.     

Incorporating TCNQ into thiophene-fused heptacene for n-channel field effect transistor

Incorporation of electron-deficient tetracyanoquinodimethane (TCNQ) into electron-rich thiophene-fused heptacene was successfully achieved for the purpose of stabilizing longer acenes and generating new n-type organic semiconductors. The heptacene-TCNQ derivative 1 was found to have good stability and an expected electron transporting property. Electron mobility up to 0.01 cm(2) V(-1) s(-1) has been obtained for this novel material in solution processed organic field effect transistors.     

Tuning surface charge property by floating gate field effect transistor

Tuning surface charge property by a floating gate field effect transistor (FGFET) is proposed and analyzed for the first time. The FGFET has an additional floating gate electrode embedded inside the dielectric channel wall and is superior to the conventional FET to tune the surface charge property of a dielectric material in contact with an aqueous solution.     

Conductivity and field effect transistor of La2@C80 metallofullerene

We first demonstrate a field-effect-transistor operation of dimetallofullerene La2@C80 with the icosahedral cage symmetry. The thin-film device showed an n-type behavior with a mobility of 1.1 x 10-4 cm2/V s at room temperature under high vacuum. Taking the nature of LUMO into account, the n-type behavior indicates an occurrence of carrier conduction through encapsulated La ions. The low mobility, suggesting an intermolecular hopping mechanism, is ascribed to the intrinsic and extrinsic reasons, which are discussed in the text.     

Amphiphilic perylenetretracarboxyl diimide dimer and its application in field effect transistor

A novel perylene diimide (PDI) derivative with typical amphiphilic character, 2, was designed and prepared. The spectroscopic studies on this compound in solution revealed the face-to-face dimeric configuration and effective pi-pi interaction between the two perylene rings. This amphiphilic PDI derivative was fabricated into highly ordered films by Langmuir-Blodgett (LB) technique and fabricated into an organic field effect transistor (OFET), which shows carrier mobility around 0.05 cm(2) V(-1) s(-1) and current modulation of 10(3). This OFET performance is much better than that of monomeric PDI 1 and can be attributed to the unique face-to-face structure of 2, which promotes the interactions between neighboring PDI ring in LB film as indicated by the pi-A isotherms and UV-vis absorption.     

Micro-enzyme field effect transistor sensor using direct covalent bonding of urease

Enzyme field effect transistors (ENFETs), which have been previously proposed for the detection of urea, consist of a pH ion-sensitive FET with urease enzyme immobilized in a polymeric membrane. A new means of preparing the enzymatic sensing layer is proposed in which urease is directly covalently bonded onto the silica insulator. The sensitivity, lifetime and response time of the ENFETs obtained are fairly good.     

A microsensor for urea based on an ion-selective field effect transistor

The pH response of a pH-sensitive field-effect transistor (FET) is not affected by a ca. 1-μm thick membrane formed from λ-aminopropyltriethoxysilane and glutaraldehyde over the gate insular by a vapor deposition method. The response between pH 5.5 and 8.5 is ca. 61 mV pH^?1 at 37°C in 5 mM Tris-HCl buffer. When urease is immobilized on the membrane, the sensor gives a linear relationship between the initial rate of the output gate voltage change and the logarithmic value of urea concentration between 16.7 and 167 mM. Determination of urea is possible within 30 s. The optimum pH is 6.0–6.5, at 37°C. The system can be used for 20 days with only slight loss of enzymatic activity.     

A miniaturized urea sensor based on the integration of both ammonium based urea enzyme field effect transistor and a reference field effect transistor in a single chip

A urea biosensor prepared by covalent binding of urease directly to the surface of an ammonium-sensitive field effect transistor (FET) is described. Nonactin incorporated in carboxylated polyvinyl chloride was used to obtain the sensitive membrane of the ammonium-sensitive FET. The grafting of urease on the polyvinylchloride-COOH membrane surface was performed through carbodiimide coupling. The activity of the immobilized enzyme was spectrometrically controlled through the time-dependent disappearance of the absorbance of NADH at 340 nm. An apparent activity of 50% was found, compared with free enzyme. The sensitivity of the urea enzyme FET is 50 mV/pUrea working in a differential mode of 2 muM to 1 mM, this sensitivity being constant during 15 days. Finally, in order to test the potentialities of the urea biosensor for the environmental applications, the detection of heavy metal ions such as Cu(II) and Hg(II) in solution was performed by measuring the remaining activity of the inhibited enzyme.     

Carbon nanotube field effect transistor biosensor for the detection of toxins in seawater

Disposable field effect transistors (FET) biosensors (bio-FET) based on carbon nanotubes were fabricated for detection of domoic acid (DA), which belongs to the group of biotoxins associated with the amnesic shellfish poisoning. The analytical results obtained with the bio-FET were compared with those obtained with a traditional methodology (enzyme-linked immunosorbent assay) in order to validate the bio-FET for DA detection. Standard solutions of DA with concentrations between 10 and 500 ng L^?1 were tested in order to construct the calibration curve, where five bio-FET were used for reproducibility estimation and two analytical measurements were performed for each bio-FET for repeatability estimation. Ten spiked artificial seawater samples were used to validate the bio-FET. The obtained reproducibility (0.52–1.43%), repeatability (0.57–1.27%), limit of detection (10 ng L^?1) and recovery range (92.3–100.3%) reveal an adequate analytical performance of the bio-FET for the detection of DA in environmental samples such as seawater samples.     

A novel enzyme biosensor for steroidal glycoalkaloids detection based on pH-sensitive field effect transistors.

For the design of a biosensor sensitive to steroidal glycoalkaloids, pH-Sensitive Field Effect Transistors as transducers and immobilised butyrylcholinesterase as a biorecognition element have been used. The total potato glycoalcaloids can be measured by this biosensor in the concentration range 0.5-100 microM with detection limits of 0.5 microM for alpha-chaconine and of 2.0 microM for alpha-solanine and solanidine, respectively. The responses of the developed biosensors were reproducible with a relative standard deviation of about 1.5% and 5% for intra- and inter-sensor responses (both cases, n=10, for an alkaloid concentration of 5 microM), respectively. Moreover, due to the reversibility of the enzyme inhibition, the same sensor chip with immobilised butyrylcholinesterase can be used several times (for at least 100 measurements) after a simple washing by a buffer solution and can be stored at 4 degrees C for at least 3 months without any significant loss of the enzymatic activity.     

Hydroquinone monosulfonate-doped polypyrrole electrodeposited on very low cost commercial junction field effect transistors as a novel ion sensitive field effect transistor pH sensor

In this study, for the first time, we introduce a simple and low cost pH sensor based on a commercial junction field effect transistor. The transistor was mechanically treated, isolated and used as an ion sensitive field effect transistor for pH detection, after electrodeposition of the sensing membrane on its surface. Polypyrrole, as a suitable sensing membrane, was electrodeposited on the copper metal gate of transistor from a solution containing pyrrole monomer, hydroquinone monosulfonate as a proper ligand and sodium salicylate for avoiding the substrate oxidation, under a two-step deposition conditions. The prepared sensor showed a near-Nernstian response of 52.3 mV pH^?1 over a linear pH range of 2.75–12.20, an ultra low hysteresis of 0.56 mV, a very low drift of 0.14 mV h^?1 and a low response time of less than 8 s.     

Immobilization of glucose oxidase on ZnO nanorods decorated electrolyte-gated field effect transistor for glucose detection

In this paper, we report on growth of ZnO nanorods on the surface of gold interdigital electrodes and its implementation as a conductive n-type channel for the fabrication of a liquid-gated field effect transistor. Glucose oxidase was immobilized on the surface of the ZnO nanorods and the fabricated device was used as a four-electrode glucose biosensor. The resistance of the conductive channel was affected by addition of glucose. The applied bias voltage to the gate in the fabricated device affects the channel resistance in the same manner as the increase of enzymatic products during the glucose oxidation. Large effective area, good conductivity, and biocompatibility properties of ZnO nanorods are the key features in this highly sensitive and stable biosensor. Our measurements showed that the threshold voltage of transistor was about 0.75 V. The current increased in the presence of the glucose and exhibited a dynamic linear range with the logarithm of glucose concentration in the range between 0.01 and 5 mM. The detection limit was about 3.8 μM.     

Construction of MoS2 field effect transistor sensor array for the detection of bladder cancer biomarkers

Bladder cancer is one of the commonest malignant tumors of urinary system with high recurrence. However, currently developed bladder cancer urine diagnosis methods are hindered by the low detection sensitivity and accuracy. Herein, a molybdenum disulfide(MoS_2) nanosheets-based field effect transistor(FET) sensor array was constructed for simultaneous detection of multiple bladder cancer biomarkers in human urine. With the excellent electronic property of MoS_2 and the high specific identification capability of recognition molecules, the proposed biosensor array could simultaneously detect nuclear matrix protein 22(NMP22) and cytokeratin 8(CK8) with a wide linear range of 10~(-6)–10~(-1) pg mL~(-1) and an ultra-low detection limit of 0.027 and 0.019 aM, respectively. Furthermore, this highly sensitive and specific MoS_2 FET sensor array could be used to identify bladder cancer biomarkers from human urine samples. This designed high-performance biosensor array shows great potential in the future diagnosis of bladder cancer.     

Fabrication of ozone gas sensor based on FeOOH/single walled carbon nanotube-modified field effect transistor

A novel ozone (O₃) sensor is fabricated using commercial metal oxide field effect transistor (MOSFET), modified with single-walled carbon nanotubes (SWCNTs). In this study, integrated circuit (IC: BS250) was selected as the selective probe for O₃ detection. For this purpose, a plastic cover on the surface of the drain was drilled to bare the drain surface, followed by its modification with nitrogen and sulfur-functionalized SWCNTs by chemical vapor deposition (CVD) process. The CVD-synthesized SWCNTs were then electrodeposited with FeOOH nanostructures. According to the figures of merit, the fabricated sensor gave a linear output from 20 to 450 parts per billion (ppb). Detection limit was also 4.1?ppb. Relative standard deviation (RSD) for seven replicate analyses was 3.61%. Based on 90% of maximum response (t₉₀), the response time was ～1.5?min. Calibration sensitivity was measured to 1.3?mV/ppb. No interference was observed, when introducing at least 500 folds of interferences of gaseous species such as H₂O, HCl, H₂S, O₂, H₂, CO, CO₂, NO₂, SO₂, Cl₂, C₂H₂, CH₄ and volatile organic compounds (VOCs) to 250?ppb of O₃ solution. Reliability of the sensor was also evaluated via determination of O₃ in different air samples.     

Development of an ion-sensitive field effect transistor based on PVC membrane technology with improved long-term stability

An NH -ISFET sensor based on PVC membrane technology with improved long-term stability has been developed. As a new approach, the plasticizer (tetra-n-undecyl) 3,3′,4,4′ -benzhydroltetracarboxylate (ETH2112) was used in membrane preparation. Its lipophilic nature provides a restricted diffusion of the membrane components to the external solution and improves membrane adhesion to the gate area of the ISFET. The good performance of this plasticizer was confirmed by comparison with usual plasticizers applied in standard ISE technology. Moreover, the durability and stability of the sensor were enhanced by the application of a graphite-epoxy layer as an internal reference between the gate area and the PVC membrane. This composite layer permits the reduction of the optical sensitivity and improves the adherence of the PVC membrane to the ISFET surface. Furthermore, this composite layer acts as a plug, preventing the entrance of water upon the encapsulant-chip interface, thus protecting electrical connections from moisture. As a result, an NH -ISFET with a long-term stability of three months and a sensitivity of −58.7 ± 2.3 mV decade⁻¹ in a linear range of 10⁻⁵ −0.1 mol dm⁻³ has been developed. The application of this sensor to a continuous-flow system has confirmed the feasibility of the technological approach proposed.