Organic thin film transistor (OTFT) sensors are capable of fast, sensitive and reliable detection of
a variety of analytes. They have been successfully tested towards many chemical and biological
"odor" molecules showing high selectivity, and displaying the additional advantage of being
compatible with plastic technologies. Their versatility is based on the possibility to control the
device properties, from molecular design up to device architecture. Here phenylene-thiophene
based organic semiconductors functionalized with ad hoc chosen side groups are used as active
layers in sensing OTFTs. These materials, indeed, combine the detection capability of organic
molecules (particularly in the case of bio-substituted systems) with the electronic properties of
the conjugated backbone. A new OTFT structure including Langmuir-Schäfer layer by layer
organic thin films is here proposed to perform chemical detection of organic vapors, including
vapor phase chiral molecules such as citronellol vapors, with a detection limit in the ppm range.
Thermally evaporated α6T based OTFT sensors are used as well to be employed as standard
system in order to compare sensors performances.
A poly(phenyleneethynylene) polymer bearing amino acid pendant groups is used as enantioselective active layer in solid-state sensing devices. The chiral analyte in the present study is menthol in both the natural (-) and synthetic (+) enantiomers. The polymer bearing amino acid chiral sites is demonstrated to interact more favorably with the natural menthol than the synthetic one in a quartz crystal microbalance revealing system. Promising perspectives are seen for the use of such polymers in chiral discriminating, chemically sensitive resistors or even transistors.
Sensitivity is a key issue in designing high performance organic based chemical and biological sensors. Several strategies have been adopted in the past to improve this important figure of merit. In this paper, a pentacene based organic thin film transistor is operated as an alcohol sensor and it is demonstrated that the sensitivity is enhanced when the device works in the accumulation mode.
Organic Thin Film Transistors (OTFTs) have been fabricated, in a standard bottom gate configuration, with Langmuir-Schafer (LS) or cast thin films of regioregular poly[1,4-(2,5-dioctyloxyphenylene)-2,5-thiophene], synthesized via an organometallic protocol, as active layers. The transistors electrical characterization has evidenced that LS based devices exhibit better performance level than cast film ones. Appealing perspectives for newly substituted conjugated polymers in OTFT sensing devices are discussed.
Organic thin-film transistors have seen a dramatic improvement of their performance in the last decade. They have been also proposed as gas sensors. This paper deals with the interesting new aspects that polycrystalline based conducting polymer transistors present when operated as chemical sensors. Such devices are capable to deliver multi-parameter responses that are also extremely repeatable and fast at room temperature. Interesting are also the perspectives for their use as chemically selective devices in array type sensing systems.