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.

The development of electronic nose systems is an important but rather challenging task nowadays. Organic field-effect transistors provide a powerful platform that is promising for electronic nose creation. In this work the sensory properties of a recently synthesized series of siloxane dimers of benzothieno[3,2-b][1]benzothiophene (BTBT) with different terminal alkyl groups (D2-Und-BTBT-Alkyl) as well as the possible mechanism of their sensitivity were investigated in detail. It was found that in spite of very similar chemical structure the dimers demonstrated dissimilar sensitivity and selectivity to various analytes-H2S, NH3, SO2, NO2, and several volatile organic compounds. The proposed mechanism of the patterns observed depends on both the correlations between the HOMO/LUMO energy levels of the dimer and the analyte and the dimer layer morphology/molecular packing. PCA analysis allowed us to choose the best four OFETs based on different siloxane dimers without any receptor layer for separation of the analytes and determining their concentrations on a 2D plot. These findings demonstrate that a rather small difference in the chemical structure of the organic semiconducting materials used for the OFET fabrication makes it possible to apply them as an array for the electronic nose creation.

Synthesis and characterization of a series of novel graft copolymers based on siloxane backbones containing 50%, 20%, and 10% of laterally attached π-conjugated [1]benzothieno[3,2-b][1]benzothiophene (BTBT) units are presented. The copolymers were synthesized via hydrosilylation reaction of linear poly(methylhydrosiloxanes) of varying functionality with alkenyl-functionalized 2-octyl-7-(undec-10-en-1-yl)-BTBT. Comprehensive investigations by DSC, TGA, and synchrotron SAXS/WAXS revealed that at room temperature all the copolymers synthesized form crystalline phases with layered structures, where both the phase-transition temperatures and the layer thickness strongly depend on the grafting density. As the grafting density decreases, the fraction of crystallizable side chains is reduced, leading to an increase in the amorphous component. Their semiconductor properties were preliminarily elucidated in organic field-effect transistors fabricated via spin-coating, which showed the hole mobilities in the range of 1.6 × 10-4 to 2 × 10-2 cm2V-1s-1 depending on the grafting density of BTBT units to the polysiloxane main chain. These are the first graft copolymers containing BTBT side chains possessing semiconductor properties comparable to those of π-conjugated linear copolymers. These findings establish grafted polysiloxanes as a promising platform for developing solution-processable, high-performance organic semiconductors.

Despite significant advances in the development of organic semiconductors (OSCs) for organic field-effect transistors (OFETs), there is still a great demand for materials with high charge carrier mobility and long-term stability to enable the wide application of OFETs. An effective method to combine the high charge carrier mobility of small-molecule OSCs with the stability of polymers is to use their blends. In this work, a siloxane copolymer P50 containing 50% of methylsiloxane units grafted with undecyl-[1]benzothieno[3,2-b][1]benzothiophene-octyl (C11-BTBT-C8) side groups was mixed with a small-molecule OSC 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) to facilitate their cocrystallization. The formation of cocrystalline lamellas of P50/C8-BTBT was confirmed by differential scanning calorimetry and X-ray scattering data, which allowed us to suggest a model of BTBT units packing in P50/C8-BTBT cocrystals. The OFETs using these blends demonstrated significantly improved long-term stability with the charge carrier mobility up to 0.45 cm2 V-1 s-1, which is similar to the mobility of pure C8-BTBT devices obtained under the same conditions.

Novel donor-acceptor arylsilane molecules, Si(PP-DCV)4 and Si(PT-DCV)4, featuring three-dimensional starshaped geometries, were synthesized and investigated in comparison to model compounds. These compounds, comprising a tetraphenylsilane core linked to terminal phenyldicyanovinyl groups through phenylene or thienyl It-spacers, exhibit a range of promising physicochemical properties, including high thermal stability (up to 490 degrees C), deep-lying HOMO energy levels (up to -6.4 eV), ambipolar charge carrier mobility, efficient light absorption, and high crystallinity. A comprehensive experimental and theoretical investigation, in comparison to model compounds, revealed the nonordinal optical properties of these compounds, elucidating the nature of electronic transitions and fluorescence efficiency. Substitution of the phenylene spacer with a thiophene spacer led to significant changes, including a red shift in the absorption spectrum, an increased extinction coefficient, lower HOMO energy levels, enhanced crystallinity, and improved ambipolar charge carrier mobility in films. Additionally, the polar and amphiphilic nature of these donor-acceptor molecules enabled the formation of stable nanoparticles (50-110 nm) in aqueous solutions without surfactants. These findings highlight the potential of these materials for applications in optoelectronic and biological applications.

Liquid multisensors are in high demand due to their wide range of applications. Recent advances in electronics allow an integration of several individual devices for target and control measurements on one chip. We studied aptamer-modified electrolyte-gated field-effect transistors (EGOFETs) as basic sensor elements for single-chip multitarget detection. We used an aptamer with a pH-dependent conformational switch as a model recognition element allowing application of the EGOFET as a single element for detecting three targets of different nature. The fabricated EGOFET device has been shown to be sensitive to the conformation of the aptamer. The sensor is sensitive to the pH changes in the range of pH 6-8 due to the H+-dependent assembly of an i-motif DNA structure. Under the i-motif-unfavorable conditions (pH ≥ 7.3), the unfolded cytosine loop forms a complex with Ag+ ions providing a new conformation. Finally, under the i-motif-favorable conditions (pH < 7.3), the folded i-motif binds to influenza A virus. The EGOFET signals for these three analytes lie in different ranges allowing their clear discrimination. Applicability of the designed device under biologically relevant conditions was proved for biological fluids such as saliva and plasma with a viral load typical for patients with influenza. The proof-of-concept for single-chip multitarget detection based on EGOFETs with one recognition element is implemented for the first time. This example of the model recognition element with combined properties integrated into the EGOFET paves the way to managing the properties of the EGOFET-based biosensors and, in the future, to developing single-chip multisensors on the EGOFET platform.

While fluorene-containing materials are widely used in organic optoelectronics as bright emitters and hole semiconductors, their diazafluorene analogues have been poorly explored, though their nitrogen atoms could result in electron transport and bring sensory abilities. Here, we report the synthesis, characterization, and detailed study of a series of 4,5-diazafluorene-derivatives with different donor/acceptor substituents and organic semiconductors based on these molecules. The crystal structures of all the materials were solved by X-ray diffraction, indicating the presence of extensive π-stacking and anisotropic charge-transfer pathways. The materials were applied as active layers in single-crystal and thin-film organic field-effect transistors (OFETs) demonstrating air-stable electron transport with charge-carrier mobility up to 0.02 cm2/(V s) for (2,7-diphenyl-4,5-diazafluorene-9-ylidene)malononitrile (P-DAF-CN). Moreover, P-DAF-CN thin-film OFETs were employed as gas sensors demonstrating a sensor response toward sub-ppm concentrations of hydrogen sulfide. 4,5-Diazafluorene-based materials are shown to be promising organic semiconductors on the way to high-performance air-stable n-channel OFETs and electronic nose applications.

The work describes one of the stages of development of flexible polymer gas sensors based on organic field-effect transistors (OFETs) and is devoted to revealing the dependencies of the electrical and sensory properties of these devices on the characteristics of the polymer dielectric layer of the OFETs. The influence of the material of the dielectric layer, as well as the conditions of its application to the polymer substrate were investigated. It was shown that the surface morphology and the properties of the semiconductor layer, which was formed on top of the polymer dielectric by thermal evaporation in vacuo, strongly depend on the value of the surface energy of the dielectric used, while the roughness of its layer has no considerable effect on the morphology. The highest electrical characteristics were demonstrated by the OFETs based on the dielectric with the highest value of surface energy, that is, polymethyl methacrylate. At the same time, regardless of the dielectric used, all the sensor devices demonstrate a high sensitivity towards nitrogen dioxide, which has values that are comparable to those characterizing the sensitivity of similar devices fabricated on silicon substrates using the studied dielectrics as interface layers, as well as an ability towards recovery of the starting properties in pure air that is higher compared to that of silicon samples, which is very promising for the commercial application of the developed polymer gas sensors.

Nitrogen dioxide sensors are important for environmental monitoring, and OFETs‐based devices feature high sensitivity, low production cost and power consumption. While transient pulsed saturation measurements are the most common approach to measure the sensor response, here we systematically compare it with the periodic transfer curves measurement method in both linear and saturation regimes for C8‐BTBT OFETs sensitive to NO 2 . We show that the sensitivity strongly depends on the measurement routine, governed by competition for deep trap sites between the electrically injected holes and NO 2 ‐induced doping. The transfer curves method reveals that mobility change dominates in the saturation regime, while threshold voltage shift dominates in the linear regime, confirming deep traps role as key sensing receptor sites. Pulsed measurements, especially in the linear regime, yielded the highest sensitivity (218 ± 18%/ppm) by combining low charge density with low duty cycle kinetics to maximize the initial deep trap availability. DFT calculations support preferential hole transfer from NO 2 to the trap states. Altogether confirming that minimizing trap filling by injected charge (i.e., lower current density operation) enhances OFET sensitivity. This dependence on the measurement routine persists even for OFETs containing metalloporphyrin receptor layers. These findings provide guidelines for optimizing OFET sensor design and operation.

Developing organic photothermal agents that are highly stable and have tunable electronic properties is important for advancing low-invasive cancer therapy. In this study, we present the synthesis and evaluation of three conjugated photothermal agents inspired by non-fullerene Y-series acceptors: the small molecule BTPT-OD, as well as two of its polymer derivatives with regular (r-BTPT) and irregular (ir-BTPT) structures. All of the compounds absorb light effectively in the red and near-infrared spectral ranges, with absorption maxima from 734 to 746 nm, and form stable nanoparticles (NPs) via nanoprecipitation, ranging in size from 13 to 39 nm. NPs exhibited negative surface charges, with ζ-potentials of −12.9, −15.5, and −17.9 mV for BTPT-OD, r-BTPT, and ir-BTPT NPs, respectively. Irradiation at a wavelength of 730 nm revealed that r-BTPT and ir-BTPT polymer NPs exhibited a 22- to 40-fold greater phototoxicity against A-549, Sk-Br-3, and MCF-7 human carcinoma cells than the non-polymeric analogue BTPT-OD. The measured photothermal conversion efficiencies ranged from 24 to 27 ± 5%. At the same time, the intracellular ROS generation quantified by the 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) assay was low, allowing us to propose heat-mediated photothermal therapy as a more significant cell death predictor than ROS-mediated photodynamic therapy. This work is one of the first to compare small and polymeric non-fullerene acceptor materials for phototherapy purposes, demonstrating the advantages of using polymers.

Organic semiconductor materials are interesting due to their application in various organic electronics devices. [1]benzothieno[3,2-b][1]benzothiophene (BTBT) is a widely used building block for the creation of such materials. In this work, three novel solution-processable regioisomeric derivatives of BTBT—2,7-bis(3-octylthiophene-2-yl)BTBT (1), 2,7-bis(4-octylthiophene-2-yl)BTBT (2), and 2,7-bis(5-octylthiophene-2-yl)BTBT (3)—were synthesized and investigated. Their optoelectronic properties were characterized experimentally by ultraviolet–visible and fluorescence spectroscopy, time-resolved fluorimetry, and cyclic voltammetry and studied theoretically by Time-Dependent Density Functional Theory calculations. Their thermal properties were investigated by a thermogravimetric analysis, differential scanning calorimetry, polarizing optical microscopy, and in situ small-/wide-angle X-ray scattering measurements. It was shown that the introduction of alkyl substituents at different positions (3, 4, or 5) of thiophene moieties attached to a BTBT fragment significantly influences the optoelectronic properties, thermal stability, and phase behavior of the materials. Thin films of each compound were obtained by drop-casting, spin-coating and doctor blade techniques and used as active layers for organic field-effect transistors. All the OFETs exhibited p-channel characteristics under ambient conditions, while compound 3 showed the best electrical performance with a charge carrier mobility up to 1.1 cm2·V−1s−1 and current on/off ratio above 107.

Electrolyte-gated organic field-effect transistors are electronic devices that are being actively developing as a platform for ultra-sensitive biosensors. The organic semiconductor shelf-life stability is important for the practical application of EGOFETs. Therefore, we aimed to develop the organic semiconductor that combines high electrical performance with stability of thin film morphology and electrical characteristics. Two OSC materials were investigated: commercially available C8-BTBT and siloxane dimer BTBT, D2-Und-BTBT-Hex, both characterized by high transconductance and ON/OFF ratio after EGOFET fabrication. Shelf-life was evaluated by keeping the devices under ambient conditions and periodical measuring transfer characteristics in water. C8-BTBT devices demonstrated a sharp decline of ON/OFF ratio within three weeks, which was associated with the thin film reorganization from metastable surface induced 2D crystals to thermodynamically stable 3D crystals leading to appearance of defects in the thin film and subsequent separation into individual crystals. D2-Und-BTBT-Hex had much more stable morphology due to intrinsic properties of the dimer molecules: the presence of a bulky but flexible disiloxane group linking two BTBT moieties together, which leads to a higher molar weight and less crystallization enthalpy. Both these factors stabilize the surface phase thus increasing stability of the thin films of the dimer. It was shown that the devices using D2-Und-BTBT-Hex as a semiconductor layer can be stored at shelf without any additional precautions for at least 4 months.

In this work an approach for the fabrication of a fully printed polymer device applicable as a capacitive gas sensor is presented. The fabrication techniques and optimal conditions for the sequential screen printing of additive polymer layers (electrodes, interface layers, and dielectric) of a printed polymer device (capacitor) was selected and optimized. The necessary adhesion of the printed functional layers to each other and to the substrate surface was ensured via the modification of the substrate surface/dielectric surface with oligomerized 3-aminopropyltriethoxysilane from solution followed by thermal annealing. The fabricated sensors demonstrated a reversible response to ammonia in a wide range of concentrations from 0 to 24 ppm, with a detection limit of 1.5 ppm in dry air. They did not lose their functionality in humid air up to a relative humidity of at least 40

The optimal composition of PEDOT:PSS-based ink for inkjet printing of the semiconductor layer for liquid sensors is determined. It was proposed to modify silicon substrates with (3-aminopropyl)triethoxysilane to improve the adhesion of the printed semiconductor layer. This made it possible to fabricate organic electrochemical transistors that demonstrated stable operation under reusable conditions in physiological solutions with high ionic strength without significant loss of performance.

A correlation between the sensing and electrical properties of monolayer OFETs based on novel organosilicon derivatives of BTBT with different lengths of terminal alkyl groups was revealed.

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.

Electrolyte-gated organic field-effect transistors (EGOFETs) is a popular platform for numerous sensing and biosensing applications in aqueous media. In this work, the variation of electrical characteristics of EGOFETs based on small-molecule organic semiconductor C8-BTBT and polystyrene blend in water solutions at different pH values was investigated. A positive shift of the threshold voltage with near-Nernstian pH sensitivity was demonstrated in the pH range from 4.9 to 2.8, while no measurable pH dependence in the range from 4.9 to 8.6 pH was registered. These results indicate chemical doping of the molecules of organic semiconductors by protons from the electrolyte in the acidic region. In order to check the applicability of the EGOFETs in a flow mode, a flow chamber was designed and assembled. The preliminary results obtained in the flow mode measurements showed a fast response to pH variation.

Determination of food freshness is the most ancient role of the sense of smell while still being a challenge for compact electronic nose devices. Fast, sensitive and reusable sensors are long-awaited in the food industry to replace long and expensive bacteriological methods. In this work, we present some new results on the emerging application of electronic noses based on Organic Filed-Effect Transistor to the problems of food spoilage detection and its quality estimation.

Printed polymer field-effect transistors are promising devices for manufacturing highly sensitive gas and liquid sensors based on them. However, their practical application as sensors imposes special requirements on structured substrates for the deposition of active semiconductor and receptor layers. A simple approach to the production of a structured polymer substrate using exclusively additive methods for manufacturing from it a printed polymer field-effect transistor suitable for the use as a gas/liquid sensor is presented.