We have increased organic field-effect transistor (OFET) NH3 response using tris-(pentafluorophenyl)borane (TPFB) as receptor. OFETs with this additive detect concentrations of 450 ppb v/v, with a limit of detection of 350 ppb, the highest sensitivity yet from semiconductor films; in comparison, when triphenylmethane (TPM) and triphenylborane (TFB) were used as an additive, no obvious improvement of sensitivity was observed. These OFETs also show considerable selectivity with respect to common organic vapors, and stability to storage. Furthermore, excellent memory of exposure was achieved by keeping the exposed devices in a sealed container stored at −30°C, the first such capability demonstrated with OFETs.

An investigation of how systematic variation of peptide sequence influences the nanoscale and bulk properties of 1D-nanostructure forming peptide–π–peptide hydrogelators is reported herein.

Printable and flexible electronics attract sustained attention for their low cost, easy scale up, and potential application in wearable and implantable sensors. However, they are susceptible to scratching, rupture, or other damage from bending or stretching due to their “soft” nature compared to their rigid counterparts (Si-based electronics), leading to loss of functionality. Self-healing capability is highly desirable for these “soft” electronic devices. Here, a versatile self-healing polymer blend dielectric is developed with no added salts and it is integrated into organic field transistors (OFETs) as a gate insulator material. This polymer blend exhibits an unusually high thin film capacitance (1400 nF cm −2 at 120 nm thickness and 20–100 Hz). Furthermore, it shows pronounced electrical and mechanical self-healing behavior, can serve as the gate dielectric for organic semiconductors, and can even induce healing of the conductivity of a layer coated above it together with the process of healing itself. Based on these attractive properties, we developed a self-healable, low-voltage operable, printed, and flexible OFET for the first time, showing promise for vapor sensing as well as conventional OFET applications.

π-Conjugated peptide materials are attractive for bioelectronics due to their unique photophysical characteristics, biofunctional interfaces, and processability under aqueous conditions. In order to be relevant for electrical applications, these types of materials must be able to support the passage of current and the transmission of applied voltages. Presented herein is an investigation of both the current and voltage transmission activities of one-dimensional π-conjugated peptide nanostructures. Observations of the nanostructures as both semiconducting and gate layers in organic field-effect transistors (OFETs) were made, and the effect of systematic changes in amino acid composition on the semiconducting/conducting functionality of the nanostructures was investigated. These molecular variations directly impacted the hole mobility values observed for the nanomaterial active layers over 3 orders of magnitude (∼0.02 to 5 × 10(-5) cm(2) V(-1) s(-1)) when the nanostructures had quaterthiophene cores and the assembled peptide materials spanned source and drain electrodes. Peptides without the quaterthiophene core were used as controls and did not show field-effect currents, verifying that the transport properties of the nanostructures rely on the semiconducting behavior of the π-electron core and not just ionic rearrangements. We also showed that the nanomaterials could act as gate electrodes and assessed the effect of varying the gate dielectric layer thickness in devices where the conventional organic semiconductor pentacene spanned the source and drain electrodes in a top-contact OFET, showing an optimum performance with 35-40 nm dielectric thickness. This study shows that these peptides that self-assemble in aqueous environments can be used successfully to transmit electronic signals over biologically relevant distances.

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Electronic biosensing is a leading technology for determining concentrations of biomolecules. In some cases, the presence of an analyte molecule induces a measured change in current flow, while in other cases, a new potential difference is established. In the particular case of a field effect biosensor, the potential difference is monitored as a change in conductance elsewhere in the device, such as across a film of an underlying semiconductor. Often, the mechanisms that lead to these responses are not specifically determined. Because improved understanding of these mechanisms will lead to improved performance, it is important to highlight those studies where various mechanistic possibilities are investigated. This review explores a range of possible mechanistic contributions to field-effect biosensor signals. First, we define the field-effect biosensor and the chemical interactions that lead to the field effect, followed by a section on theoretical and mechanistic background. We then discuss materials used in field-effect biosensors and approaches to improving signals from field-effect biosensors. We specifically cover the biomolecule interactions that produce local electric fields, structures and processes at interfaces between bioanalyte solutions and electronic materials, semiconductors used in biochemical sensors, dielectric layers used in top-gated sensors, and mechanisms for converting the surface voltage change to higher signal/noise outputs in circuits.

Ethylene sensing is a highly challenging problem for the horticulture industry because of the limited physiochemical reactivity of ethylene. Ethylene plays a very important role in the fruit life cycle and has a significant role in determining the shelf life of fruits. Limited ethylene monitoring capability results in huge losses to the horticulture industry as fruits may spoil before they reach the consumer, or they may not ripen properly. Herein we present a poly(3-hexylthiophene-2,5-diyl) (P3HT)-based organic field effect transistor as a sensing platform for ethylene with sensitivity of 25 ppm V/V. To achieve this response, we used N-(tert-Butoxy-carbonyloxy)-phthalimide and palladium particles as additives to the P3HT film. N-(tert-Butoxy-carbonyloxy)-phthalimide is used to increase the porosity of the P3HT, thereby increasing the overall sensor surface area, whereas the palladium (<1 μm diameter) particles are used as receptors for ethylene molecules in order to further enhance the sensitivity of the sensor platform. Both modifications give statistically significant sensitivity increases over pure P3HT. The sensor response is reversible and is also highly selective for ethylene compared to common solvent vapors.