Monolayer organic field effect transistors (OFETs) provide opportunity for ultrahigh sensitivity gas sensor applications due to a strong dependence of OFET key parameters on the environment. However, an impressive combination of both high sensitivity and instantaneous response of such gas sensors can be achieved only on low-defect dense monolayers with high electrical performance. Herein, we investigated monolayer thin film formation of recently developed benzothieno[3,2-b][1]benzothiophene (BTBT) organosilicon dimer D2-Und-BTBT-Hex by Langmuir–Blodgett, Langmuir–Schaefer and spin-coating methods. For all these techniques, the conditions of uniform low-defect monolayer formation were found. These monolayers were used for preparation of OFET devices, which demonstrated excellent electrical performance with a hole mobility up to 7 × 10⁻² cm² V⁻¹ s⁻¹, a threshold voltage around 0 V and an on–off ratio of 10⁵ as well as long-term stability of half-year storage under ambient conditions. Preliminary investigations demonstrated that the monolayer OFETs give an instantaneous response to ammonia at low concentrations (down to 400 ppb). These findings show a great potential of BTBT-based OFETs for large-area sensing device application.

Elaboration of biosensors on the base of organic transistors with embedded biomolecules which can operate in an aqueous environment is of paramount importance. Electrolyte-gated organic field-effect transistors demonstrate high sensitivity in detection of various analytes. In this paper, we demonstrated the possibility of quantitative fast specific determination of virus particles by an aptasensor based on EGOFET. The sensitivity and selectivity of the devices were examined with the influenza A virus as well as with control bioliquids like influenza B, Newcastle disease viruses or allantoic fluid with different dilutions. The influence of the semiconducting layer thickness on EGOFETs sensory properties is discussed. The fabrication of a multi-flow cell that simultaneously registers the responses from several devices on the same substrate and the creation of a multi-sensor flow device are reported. The responses of the elaborated bioelectronic platform to the influenza A virus obtained with application of the portable multi-flow mode are well correlated with the responses obtained in the laboratory stationary mode.

The synthesis and systematic investigation of organosilicon derivatives of benzothieno[3,2-b][1]benzothiophene (BTBT) with different lengths of terminal alkyl groups (from C2 to C13), or without them, capable of self-assembly at the water–air interface are described. All novel compounds were obtained with high yields and purity, which was proved by ¹H, ¹³C and ²⁹Si-NMR spectroscopy, gel permeation chromatography and elemental analysis. The study of their phase behavior by differential scanning calorimetry and polarizing optical microscopy showed that all the compounds are crystalline at room temperature. However, at elevated temperatures those with terminal alkyl substituents form enantiotropic smectic A or C mesophases, while the compound without terminal alkyl groups forms a monotropic nematic mesophase. The increase of the alkyl chain length from C2 to C8 leads to higher temperatures of both phase transitions: from the crystal to the disordered smectic mesophase and to the isotropic melt. X-ray diffraction measurements confirm the presence of disordered SmA and SmC phases and the ordered SmE or SmK phase, and suggest models of their packing depending on the terminal alkyl chain length. The investigation of the electrical properties of monolayer OFETs based on these compounds and their sensing responses to NO₂ revealed the dependence of charge carrier mobility values and sensitivity parameters mainly on the surface morphology of organic semiconductors. A comparison of the semiconducting and sensing properties of different compounds investigated revealed a weak correlation between these parameters, while the best characteristics were observed for the OFETs based on the siloxane dimer of BTBT with C8 terminal groups.