Organic Field-effect Transistors Sensors Research Articles

Highly stable organic polymer field-effect transistor sensor for selective detection in the marine environment

In recent decades, the susceptibility to degradation in both ambient and aqueous environments has prevented organic electronics from gaining rapid traction for sensing applications. Here we report an organic field-effect transistor sensor that overcomes this barrier using a solution-processable isoindigo-based polymer semiconductor. More importantly, these organic field-effect transistor sensors are stable in both freshwater and seawater environments over extended periods of time. The organic field-effect transistor sensors are further capable of selectively sensing heavy-metal ions in seawater. This discovery has potential for inexpensive, ink-jet printed, and large-scale environmental monitoring devices that can be deployed in areas once thought of as beyond the scope of organic materials.

Large sensitivity enhancement in semiconducting organic field effect transistor sensors through incorporation of ultra-fine platinum nanoparticles

We report remarkable improvement in sensitivity of pentacene-based field effect transistor devices towards trace nitro-aromatic explosive vapors through the incorporation of high density, sub-2 nm platinum nanoparticles (NPs) within these structures. Exploiting the unique electronic properties of these NPs, we have demonstrated a detection limit of 56.6 parts per billion of 2,4-dinitrotoluene (DNT) vapor while control samples without any embedded NPs showed no observable sensitivity to DNT vapor. We attribute this remarkable enhancement in sensitivity to the ability of these NPs to function as discrete nodes, participating in the charge transfer with adsorbed nitro-aromatic molecules.

An analytical model for bio-electronic organic field-effect transistor sensors

A model for the electrical characteristics of Functional-Bio-Interlayer Organic Field-Effect Transistors (FBI-OFETs) electronic sensors is here proposed. Specifically, the output current-voltage characteristics of a streptavidin (SA) embedding FBI-OFET are modeled by means of the analytical equations of an enhancement mode p-channel OFET modified according to an ad hoc designed equivalent circuit that is also independently simulated with pspice. An excellent agreement between the model and the experimental current-voltage output characteristics has been found upon exposure to 5 nM of biotin. A good agreement is also found with the SA OFET parameters graphically extracted from the device transfer I-V curves.

Investigation of Protein Detection Parameters Using Nanofunctionalized Organic Field-Effect Transistors

Biodetection using organic field-effect transistors (OFETs) is gaining increasing interest for applications as diverse as food security, environmental monitoring, and medical diagnostics. However, there still lacks a comprehensive, empirical study on the fundamental limits of OFET sensors. In this paper, we present a thorough study of the various parameters affecting biosensing using an OFET decorated with gold nanoparticle (AuNP) binding sites. These parameters include the spacing between receptors, pH of the buffer, and ionic strength of the buffer. To this end, we employed the thrombin protein and its corresponding DNA binding aptamer to form our model detection system. We demonstrate a detection limit of 100 pM for this protein with high selectivity over other proteases in situ. We describe herein a feasible approach for protein detection with OFETs and a thorough investigation of parameters governing biodetection events using OFETs. Our obtained results should provide important guidelines to tailor the sensor's dynamic range to suit other desired OFET-based biodetection applications.

Gas Dielectric Transistor of CuPc Single Crystalline Nanowire for SO2 Detection Down to Sub‐ppm Levels at Room Temperature

Sulfur dioxide (SO 2 ) is one of the most dangerous air pollutants that impair environment and human health. SO 2 in air is released during the burning of fossil fuels and plays one major role in the formation of acid rain. The repeated exposure to low levels of SO 2 can cause permanent pulmonary impairment for humans. [ 1 ] The long and short-term exposure limits for SO 2 gas are 2 and 5 ppm, respectively, [ 1 , 2 ] and the U. S. Environmental Control Agency has set the acceptable limit for SO 2 in ambient air at a level of 0.5 ppm. [ 3 ] It is of great importance to measure low concentration of SO 2 in air accurately and fast for human health protection and air-quality monitoring. Semiconductor resistor sensors are, for more than 30 years, one of the most common used gas sensors to detect toxic and fl ammable gases such as NO 2 , H 2 S, CO, NH 3 , and H 2 because of their distinguished merits such as low cost, long lasting, high sensitivity, and good reliability, etc. [ 4 ] Organic fi eld-effect transistor (OFET) is another alternative semiconductor sensing technology with advantages over resistors, and has attracted much attention only recently. [ 5 ] The sensitivity can be dramatically enhanced by changing the source-drain current ( I SD ) of OFET when operating the sensors in the sub-threshold regime, as a result of the current modulation by the extra gate electrode. [ 6 ] Another advantage of OFET sensors is that the sensing response can be enhanced by integrating them in oscillator and adaptive amplifi er circuits. [ 7 ] These advantages combined with low cost and light weight of organic semiconductors ensure that OFET sensors have attracted much attention for the detection of a wide range of gases. [ 8 ]

Ammonia gas sensor based on pentacene organic field-effect transistor

Abstract Ammonia (NH3) sensors based on bottom contact organic field-effect transistors (OFETs) were created using pentacene as an active layer and polymerthylmethacrylate (PMMA) as an insulator. The OFET sensors exhibited a change in the electric characteristic such as the threshold voltage, the saturation current, and the field-effect charge carrier mobility when the sensors were exposed to different NH3 concentrations. Meanwhile, the favorable and rapid NH3 response characteristics of the OFET sensors were observed from the change in the drain-source current as a function of time, when the sensors were exposed to various cycles of exposure/evacuation of different NH3 concentrations ranging from 10 to 100 ppm. Moreover, the environmental stability of the OFET sensors to constantly detect the NH3 gas in air was studied by storing the sensors in air for 30 days.

OFET Sensors with Poly 3-hexylthiophene and Pentacene as Channel Materials for Ionizing Radiation

ABSTRACTPentacene and poly 3-hexylthiophene (P3HT) are the most promising p-type organic semiconducting materials for fabrication of organic field effect transistors (OFETs). OFETs with aforesaid organic semiconducting materials have been demonstrated as total dose detectors for ionizing radiation, wherein the changes in the electrical characteristic parameters, such as, increase in the OFF current, increase in the ON current, change in the current ratio, shift in the threshold voltage, change in the subthreshold swing, etc., were used as a measure of ionizing radiation dose. Upon exposure to ionizing radiation P3HT based OFET sensor has shown an OFF current sensitivity of 4.4 nA/Gy while pentacene based OFET sensor has shown an OFF current sensitivity of 26.7 nA/Gy for a total of 50 Gy dose of ionizing radiation. Change in the conductivity of the thin-films of pentacene and P3HT were observed and compared using electrostatic force microscopy (EFM) imaging before and after exposure to ionizing radiation. Effects of ionizing radiation on the energy band structures of the organic semiconducting materials, pentacene and P3HT, have been studied using UV-visible spectroscopy. Moreover, analysis of UV-visible spectra of the thin-films suggested the generation of energy states in larger quantity in case of pentacene thin-film as compared to P3HT thin-film upon exposure to the same dose of ionizing radiation. These results confirm the higher sensitivity observed in pentacene OFET sensor as compared to P3HT OFET sensor in terms of the change in electrical parameters.

ChemInform Abstract: Molecular and Supramolecular Architectures of Organic Semiconductors for Field‐Effect Transistor Devices and Sensors: A Synthetic Chemical Perspective

AbstractReview: 268 refs.

Ionizing Radiation Total Dose Detectors Using Oligomer Organic Semiconductor Material and Devices

ABSTRACTOrganic semiconducting oligomer – Pentacene, as a material and organic electronic devices based on it, are proposed here as total dose detectors for ionizing radiation. Pentacene, when exposed to ionizing radiation of γ – rays using Cobalt – 60 (60Co) radiation source, shows increase in the conductivity of the material which can be used as a sensing phenomenon for determining the dose of ionizing radiation. The change in material property was also verified using UV-visible (UV-VIS) spectrum for pentacene thin-films with rising absorption peaks at the oxidized positions in the wavelength. A pentacene resistor can be used as a detector, as the change in the conductivity of the pentacene film can be easily quantified by measuring the change in resistance of the pentacene resistor after different total radiation dose exposures. The experiments resulted in a sensitivity of 340 kΩ/Gy for a total 100 Gy radiation dose for the pentacene resistor. Furthermore, employing this simple electrical measurement technique for determining the dose of ionizing radiation and to improve the sensitivity of the sensor by transistor action, a pentacene based organic field effect transistor (OFET) was exposed to ionizing radiation. Change in OFF current (IOFF) of the OFET sensor with W/L = 19350 μm/100 μm, suggests a sensitivity of 21 nA/Gy for 100 Gy dose. Also, changes in various other parameters like threshold voltage, subthreshold swing, field effect mobility, number of interface states etc. can be extracted from the electrical characterizations which prove their usefulness as a detector for ionizing radiation.

Low-Operating-Voltage Operation and Improvement in Sensitivity With Passivated OFET Sensors for Determining Total Dose Radiation

Using high-k material in a gate dielectric stack, low-operating-voltage organic semiconducting material sensors for determining total dose radiation are proposed. To improve the stability of organic semiconducting layer in the atmospheric conditions, a thin silicon nitride layer deposited by hot-wire CVD process was used as a passivation layer. Furthermore, in order to achieve higher sensitivity, a parallel connection of organic field-effect transistors (OFETs) is explored in this letter. These sensors are exposed to ionizing radiation using a cobalt-60 radiation source for different total dose values. A three-times improvement in sensitivity was observed in the off current with a three-OFET array.