Monia Demelas

Ultralow Voltage, OTFT‐Based Sensor for Label‐Free DNA Detection

An organic ultralow voltage field effect transistor for DNA hybridization detection is presented. The transduction mechanism is based on a field-effect modulation due to the electrical charge of the oligonucleotides, so label-free detection can be performed. The device shows a sub-nanometer detection limit and unprecedented selectivity with respect to single nucleotide polymorphism.

A deeper insight into the operation regime of all-polymeric electrochemical transistors

All-Organic Electrochemical Transistors (OECTs) realized by employing Poly(3,4-EthyleneDiOxyThiophene) doped with Poly(Styrene Sulfonate) as conductive polymer show a dependence of their behavior on the gate to channel area ratio. This peculiarity has been investigated and the working mechanism has been explained in view of the behavior of the ionic component of the device. In particular, taking into account the current theory of OECT behavior, we have focused our attention on the role of the gate, trying to clarify if these devices may be considered as working in Faradaic or capacitive regime.

Dopamine amperometric detection at a ferrocene clicked PEDOT:PSS coated electrode

Chemically modified electrodes are widely employed in electroanalytical chemistry and an important goal is to strongly anchor redox mediators on the electrode surface. In this work, indium tin oxide (ITO) electrodes have been coated with PEDOT:PSS that has been ferrocene-functionalized, by a two-step procedure consisting of the electrodeposition of PEDOT-N3 followed by copper-catalyzed azide-alkyne cycloaddition of ethynylferrocene. The coated electrodes have been characterized by XPS, showing successful ferrocene immobilization, by AFM, and by cyclic voltammetry (CV), which is dominated by the stable and highly reversible response of ferrocene. The electrocatalytical performance of the device is assessed by analyzing 3,4-dihydroxyphenyl ethylamine, also commonly known as dopamine (DA). The sensor presents a linear range between 0.01 and 0.9 mM, a mean sensitivity of 196 mA M-1 cm-2 and a limit of detection (LoD) of 1 µM.

Preparation and characterisation of transparent and flexible PEDOT:PSS/PANI electrodes by ink-jet printing and electropolymerisation

Novel flexible PEDOT:PSS/PANI bilayered thin-film electrodes were successfully prepared by ink-jet printing of PEDOT:PSS on a PEN substrate and subsequent electrochemical polymerisation of PANI. Scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to systematically investigate the structure, morphology and electrochemical behaviour of the electrodes. The PEDOT:PSS/PANI bilayer nanofilms have been tested as pH sensors. As a comparison, either PEDOT:PSS or PANI electrodes have been tested for pH measurements. The results show that the sensitivity of the PEDOT:PSS/PANI bilayer film is higher than that of PEDOT:PSS and PANI electrodes, indicating a synergistic effect of the two polymers. A reversible near-Nerstian behaviour of the open circuit voltage with pH was found, with a slope of 58.9 mV pH−1 unit in a wide range of pH values from 2 to 14.

Chemical Sensors using Organic Thin-Film Transistors (OTFTs)

The ability of organic semiconductors to be electrically conductive while maintaining the structural and mechanical properties of organic materials may be successfully exploited to realize sensing systems for different physicochemical parameters in applications ranging from wearable electronics to robotic interfaces. This chapter focuses on chemosensors (in both gas/vapour and liquid environments) that may be employed to create large-area, flexible platforms for multimodal sensing.

DNA hybridization detection based on an Organic charge modulated Field Effect Transistor

We present a novel sensor based on an Organic Field Effect Transistor (OFET) for DNA detection. The measure does not need any labeling step and the readout signal is an electric current. The devices working mechanism does not depend on the materials used for its fabrication. Successful experiments proved the feasibility of the approach.