Operationally Stable Ultrathin Organic Field Effect Transistors Based on Siloxane Dimers of Benzothieno[3,2‐b][1]Benzothiophene Suitable for Ethanethiol Detection

Abstract

Ultrathin organic field effect transistors (OFETs) demonstrate great potential as highly sensitive gas sensors since its electrical performance strongly depends on the environment. However, fabrication of high performance OFETs with reliable operational stability for continuous measurements by fast, rather simple, and inexpensive technique is still a challenge. Herein, electrical and sensing properties of ultrathin OFETs based on siloxane dimers of benzothieno[3,2‐b][1]benzothiophene (BTBT) with different aliphatic spacer lengths fabricated by Langmuir–Blodgett, Langmuir–Schaefer (LS) or spin‐coating techniques are studied, compared and optimized. Investigation of the influence of interface dielectric layer on electrical performance and operational stability of the devices allowed obtaining uniform low‐defect ultrathin semiconducting layers responsible for improved electrical performance. Field‐effect mobility up to 0.47 cm2 V−1 s−1 is achieved for the devices based on the dimer with undecylenic spacer between the BTBT core and disiloxane central fragment fabricated by LS method on the top of poly(methyl methacrylate) interface layer. Promising operational stability lead to advanced sensory properties demonstrated by sensing of ethanethiol with the limit of detection of 30 ppb in the humid air, which is a record value for portable sensing technologies.

Luminescent High‐Mobility 2D Organic Semiconductor Single Crystals

“…[27] In fact, 2D OFETs fabricated from BTBT-based polycrystalline (Langmuir) films showed the much lower shelf-life stability. [28] And finally, alkyl chains in 2D crystals can work as a hydrophobic and encapsulation layer protecting from atmospheric water and oxygen.…”

Biorecognition Layer Based On Biotin-Containing [1]Benzothieno[3,2-b][1]benzothiophene Derivative for Biosensing by Electrolyte-Gated Organic Field-Effect Transistors

“…D2-Hept-BTBT-Hex is highly stable under normal conditions (20–25 °C, in air) and does not undergo hydrolysis or doping in water . It can be easily transformed from the extended conformation into the closed one during the layer compression by Langmuir through barriers due to flexible heptylenic spacers and especially a disiloxane unit, which is able to form hydrogen bonds with water molecules as opposite to the fully hydrophobic terminal hexyl group of the dimer molecule. , Figure a shows a typical Langmuir isotherm of the blend of D2-Hept-BTBT-Hex and BTBT – biotin and Brewster angle microscopy (BAM) images of the water surface under different barrier pressures obtained for a 30% BTBT – biotin mixture. The Langmuir isotherm of the blend contains three easily distinguished regions: the first one correlates with the formation of separate non-interacting monolayer islands of the biotin-containing and disiloxane molecules in their extended conformations undergoing spontaneous gradual transformation into the closed conformation (area per molecule of ca.…”

“…The capacitance and the morphology of the active layer, after bioreceptor coating, changes and influences in such way that the electrical properties of the device decrease but not significantly (Figure a). Due to the fact that the siloxane dimer is a semiconductor, and there are several publications on its OFET properties, ,,,, the BTBT – biotin -based bioreceptor layer does not act as a dielectric. At the same time, the device with only the BTBT – biotin -based bioreceptor layer and without an active OSC layer shows low electrical properties with currents in the nA region and low stability as it is a monolayer, which is not suitable for the OET sensor application (Figure S13).…”

“…Synthesis of the OSC necessary for the formation of the active layer of the device2,7-dioctyl-benzothieno­[3,2- b ]­[1]­benzothiophenewas performed as described elsewhere . Synthesis of the OSC required for the formation of the framework of the bioreceptor layer, which was an organosilicon derivative of dialkyl-benzothienobenzothiophene ( D2-Hept-BTBT-Hex , BTBT dimer )1,3-bis­{11-(7-heptyl­[1]­benzothieno­[3,2- b ]­[1] benzothio-2-yl)­hexyl}-1,1,3,3-tetramethyldisiloxanewas performed as described elsewhere. , Organic solvents (toluene and dimethylsulfoxide) were purchased from Acros Organics. PS, M w = 280 000, was purchased from Sigma-Aldrich and used as received.…”

“…The biorecognition layer is based on a novel derivative of the BTBT-containing biotin fragment in the molecular structure ( BTBT – biotin ), which provides a universal anchor for bioanalytes. It can be fabricated by the Langmuir–Schaefer technique from the blend of BTBT – biotin with a siloxane dimer of BTBT ( D2-Hept-BTBT-Hex ) on the top of a usual OSC C 8 -BTBT-C 8 . In order to provide the desired biorecognition properties, the fabricated biotin-containing layer can be further modified.…”