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.

Determination of food freshness, which is the most ancient role of the human sense of smell, is still a challenge for compact and inexpensive electronic nose devices. Fast, sensitive, and reusable sensors are long-awaited in the food industry to replace slow, labor-intensive, and expensive bacteriological methods. In this work, we present microbiological verification of a novel approach to food quality monitoring and spoilage detection using an electronic nose based on organic field-effect transistors (OFETs) and its application for distinguishing products. The compact device presented is able to detect spoilage-related gases as early as at the 4 × 10⁴ CFU g^-1 bacteria count level, which is 2 orders of magnitude below the safe consumption threshold. Cross-selective sensor array based on OFETs with metalloporphyrin receptors were made on a single substrate using solution processing leading to a low production cost. Moreover, machine learning methods applied to the sensor array response allowed us to compare spoilage profiles and separate them by the type of food: pork, chicken, fish, or milk. The approach presented can be used to monitor food spoilage and distinguish different products with an affordable and portable device.

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.

An efficient synthetic method for the preparation of self-assembling conjugated organic materials with a silazane anchor group based on direct hydrosilylation reaction is reported. A novel organic semiconductor molecule, NH(Si-Und-BTBT-Hex)₂, consisting of a polar silazane anchor group linked through undecylenic (Und) aliphatic spacers to conjugated blocks based on benzothieno[3,2-b][1]benzothiophene (BTBT) and solubilizing hexyl (Hex) end groups, was synthesized. Its self-organization on the air-water interface and solid substrates into ultrathin layers obtained by the Langmuir–Schaefer or Langmuir–Blodgett methods was investigated. Monolayer organic field-effect transistors manufactured from NH(Si-Und-BTBT-Hex)₂ showed operation in the p-type mode.