The strong and controllable chemical sensitivity of organic semiconductors (OSCs) and the amplification capability of transistors in circuits make use of OSC-based field-effect transistors compelling for chemical sensors. Analytes detected and assayed range from few-atom gas-phase molecules that may have adverse health and security implications to biomacromolecules (proteins, nucleic acids) that may be markers for physiological processes and medical conditions. This review highlights recent progress in organic field-effect transistor (OFET) chemical sensors, emphasizing advances from the past 5 years and including aspects of OSC morphology and the role of adjacent dielectrics. Design elements of the OSCs and various formats for the devices are illustrated and evaluated. Challenges associated with the present state of the art and future opportunities are also discussed.

Chemical and Biomolecule Sensing with Organic Field-Effect Transistors

ConspectusThe rise of organic bioelectronics efficiently bridges the gap between semiconductor devices and biological systems, leading to flexible, lightweight, and low-cost organic bioelectronic devices suitable for health or body signal monitoring. The introduction of organic semiconductors in the devices can soften the boundaries between microelectronic systems and dynamically active cells and tissues. Therefore, organic bioelectronics has attracted much attention recently due to the unique properties and promising applications. Organic thin film transistors (OTFTs), owing to their inherent capability of amplifying received signals, have emerged as one of the state-of-the-art biosensing platforms. The advantages of organic semiconductors in terms of synthetic freedom, low temperature solution processing, biocompatibility, and mechanical flexibility render OTFTs ideal transducers for wearable electronics, e-skin, and implantable devices.How to realize highly sensitive, selective, rapid, and efficient si...

Functionalized Organic Thin Film Transistors for Biosensing

The inherent specificity and electrochemical reversibility of enzymes poise them as the biorecognition element of choice for a wide range of metabolites. To use enzymes efficiently in biosensors, the redox centers of the protein should have good electrical communication with the transducing electrode, which requires either the use of mediators or tedious biofunctionalization approaches. We report an all-polymer micrometer-scale transistor platform for the detection of lactate, a significant metabolite in cellular metabolic pathways associated with critical health care conditions. The device embodies a new concept in metabolite sensing where we take advantage of the ion-to-electron transducing qualities of an electron-transporting (n-type) organic semiconductor and the inherent amplification properties of an ion-to-electron converting device, the organic electrochemical transistor. The n-type polymer incorporates hydrophilic side chains to enhance ion transport/injection, as well as to facilitate enzyme conjugation. The material is capable of accepting electrons of the enzymatic reaction and acts as a series of redox centers capable of switching between the neutral and reduced state. The result is a fast, selective, and sensitive metabolite sensor. The advantage of this device compared to traditional amperometric sensors is the amplification of the input signal endowed by the electrochemical transistor circuit and the design simplicity obviating the need for a reference electrode. The combination of redox enzymes and electron-transporting polymers will open up an avenue not only for the field of biosensors but also for the development of enzyme-based electrocatalytic energy generation/storage devices.

Direct metabolite detection with an n-type accumulation mode organic electrochemical transistor.

Recent challenges in biomedical diagnostics show that the development of rapid affinity sensors is very important issue. Therefore, in this review we are aiming to outline the most important directions of affinity sensors where polymer-based semiconducting materials are applied. Progress in formation and development of such materials is overviewed and discussed. Some applicability aspects of conducting polymers in the design of affinity sensors are presented. The main attention is focused on bioanalytical application of conducting polymers such as polypyrrole, polyaniline, polythiophene and poly(3,4-ethylenedioxythiophene) ortho-phenylenediamine. In addition, some other polymers and inorganic materials that are suitable for molecular imprinting technology are also overviewed. Polymerization techniques, which are the most suitable for the development of composite structures suitable for affinity sensors are presented. Analytical signal transduction methods applied in affinity sensors based on polymer-based semiconducting materials are discussed. In this review the most attention is focused on the development and application of molecularly imprinted polymer-based structures, which can replace antibodies, receptors, and many others expensive affinity reagents. The applicability of electrochromic polymers in affinity sensor design is envisaged. Sufficient biocompatibility of some conducting polymers enables to apply them as “stealth coatings” in the future implantable affinity-sensors. Some new perspectives and trends in analytical application of polymer-based semiconducting materials are highlighted.

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Advances in molecularly imprinted polymers based affinity sensors (review)

Highly selective and sensitive sensor based on an organic electrochemical transistor for the detection of ascorbic acid.

Chirality detection of amino acid enantiomers by organic electrochemical transistor.

We report the development of gallic acid sensors using organic electrochemical transistors (OECTs) based on poly(3,4-ethylenedioxythiophene): poly(styrene sulfonic acid) (PEDOT:PSS) for the first time. The device performance was optimized by functionalizing the gate electrodes of the OECTs with nanocomposites of poly(diallyldimethylammonium chloride) (PDDA) and multiple carbon nanomaterials. The detection limit of the optimized OECT sensor was identified to be as low as 10 nM of GA. We also demonstrated that the optimized OECT sensor worked with a high recovery for rapid and accurate assessment of total phenol content of practical tea samples. Since the OECT is based on the oxidation-reduction reaction at the gate electrode of target analytes, we believe our low-cost and easy-fabricating OECT-based sensor offers a promising platform for the development of disposable and portable sensors with high sensitivity for a wide range of practical samples.

Highly sensitive detection of gallic acid based on organic electrochemical transistors with poly(diallyldimethylammonium chloride) and carbon nanomaterials nanocomposites functionalized gate electrodes

Selective recognition of Histidine enantiomers using novel molecularly imprinted organic transistor sensor

Copper is an essential element in the environment and the human body, but at the same time, exposure to high concentrations of Cu2+ ions will potentially lead to acute toxicity and various neurodegenerative diseases. Thus, it is of great significance for the development of highly sensitive and selective strategies for the detection of Cu2+ ions. Here, we report a highly efficient poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) based organic electrochemical transistor (OECT) sensor, for real-time Cu2+ ions detection. The detection limit of the OECT device is as low as 100 nM, far beyond the sensitivity required for practical uses. The detection mechanism may base on the chemical reactivity of Cu2+ ions oxiding the PEDOT:PSS in solution both in absence and presence of the base potential. The OECT devices also exhibit excellent selective response to Cu2+ ions rather than other metal ions. Finally, we also demonstrate the determination of Cu2+ ions in tap water with the OECT Cu2+ sensor. Considering the high sensitivity and selectivity, as well as the real-time and low cost features of our Cu2+ OECT sensor, it is ideal for portable and disposable applications for environment monitoring and public health.

Lijun Zhang

Papers

Highly selective and sensitive sensor based on an organic electrochemical transistor for the detection of ascorbic acid.

Chirality detection of amino acid enantiomers by organic electrochemical transistor.

Highly sensitive detection of gallic acid based on organic electrochemical transistors with poly(diallyldimethylammonium chloride) and carbon nanomaterials nanocomposites functionalized gate electrodes

Selective recognition of Histidine enantiomers using novel molecularly imprinted organic transistor sensor

Real-time detection of Cu(II) with PEDOT:PSS based organic electrochemical transistors