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Research on electrolyte-gated and organic electrochemical transistor (OECT) architectures is motivated by the prospect of a highly biocompatible interface capable of amplifying bioelectronic signals at the site of detection. Despite many demonstrations in these directions, a quantitative model for OECTs as impedance biosensors is still lacking. We overcome this issue by introducing a model experiment where we simulate the detection of a single cell by the impedance sensing of a dielectric microparticle. The highly reproducible experiment allows us to study the impact of transistor geometry and operation conditions on device sensitivity. With the data we rationalize a mathematical model that provides clear guidelines for the optimization of OECTs as single cell sensors, and we verify the quantitative predictions in an in-vitro experiment. In the optimized geometry, the OECT-based impedance sensor allows to record single cell adhesion and detachment transients, showing a maximum gain of 20.2±0.9 dB with respect to a single electrode-based impedance sensor.

Inkjet printing is a promising technology providing cost-effective method for processing various materials on deformable substrates. In this work, linear and serpentine inkjet printed interconnects on two different substrates were fabricated and electromechanically characterized. A particular attention was given to the optimization of the process parameters; high quality can be achieved only printing slowly in vertical direction and optimizing the drop spacing to the specific pattern. The electromechanical results showed that the geometrical layout and printing direction strongly affect the printing quality and the electromechanical response; serpentine shapes should be preferred to straight interconnects as better gauge factors are obtained.

The ability to control the energy levels in semiconductors is compelling for optoelectronic applications. In this study, we managed to tune the work function (WF) of halide perovskite semiconductors using self-assembled monolayers of small molecules to induce stable dipoles at the surface. The direction and intensity of the surface dipoles rely on specific molecule-to-surface interactions. Electron acceptor or donor molecules result in the positive or negative WF shifts up to several hundreds of meV. Our approach provides a versatile tool to control the WF of halide perovskite and adjust the energy level alignment at the interface with charge transport materials in perovskite-based optoelectronics. The impact on perovskite solar cells is reported and discussed in detail with the support of modelling. publishedVersion

The development of portable and wearable sensors is of high importance in several fields such as point-of-care medical applications and environmental monitoring. Here we design, synthesize and exploit a new composite material based on Ag/AgCl nanoparticles and PEDOT:PSS (poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate)) to fabricate a novel kind of sensor inspired by the organic electrochemical transistor (OECT). We are able to integrate an Ag/AgCl gate electrode into the semiconducting polymer in the form of NPs. As a consequence, our sensor combines an intrinsically amplified response with a simple two terminal electrical connection. Electrostatic Force Microscopy and Electrochemical Impedance Spectroscopy demonstrate the electronic coupling between the electrochemically active nanoparticles and the ionic charge gated semiconducting polymer, allowing to explain the sensor amplified transduction. The analytical signal is the current that flows in the composite polymer and its variation is directly proportional to the logarithm of Cl− concentration in the range 10−4 to 1 M, with a limit of detection of 0.5 10−4 M. Moreover, the device exhibits a shorter response time than the one of a conventional OECT endowed with an Ag/AgCl gate electrode. The sensor was used for in-situ detection of salinity in water and a textile device was obtained by depositing the composite material directly onto a cotton yarn for real-time sweat monitoring.

The application of organic electronic materials for the detection of ionizing radiations is very appealing thanks to their mechanical flexibility, low-cost and simple processing in comparison to their inorganic counterpart. In this work we investigate the direct X-ray photoconversion process in organic thin film photoconductors. The devices are realized by drop casting solution-processed bis-(triisopropylsilylethynyl)pentacene (TIPS-pentacene) onto flexible plastic substrates patterned with metal electrodes; they exhibit a strong sensitivity to X-rays despite the low X-ray photon absorption typical of low-Z organic materials. We propose a model, based on the accumulation of photogenerated charges and photoconductive gain, able to describe the magnitude as well as the dynamics of the X-ray-induced photocurrent. This finding allows us to fabricate and test a flexible 2 × 2 pixelated X-ray detector operating at 0.2 V, with gain and sensitivity up to 4.7 × 104 and 77,000 nC mGy−1 cm−3, respectively., Organic electronics show advantages in easy processing, mechanical flexibility and low costs compared to their inorganic counterparts, yet there are not many proofs for the sake of X-ray detection. Here, Basiricò et al. build a flexible X-ray detector operated at sub-1 V using pentacene-based thin films.

In this work, we address the phenomenon of charge transport in DNA using a simple, but chemically specific, approach that is intimately related to the Su-Schrieffer-Heeger (SSH) model. The emerging potential energy surface for hole transport is analyzed using Marcus' theory of charge transfer. Our results are fully compatible with the conjecture of charge transfer in DNA via two competing mechanisms, and the computations provide the corresponding charge-transfer rates both in the short-range superexchange and in the long-range hopping regime as the output of a single atomistic theory. Finally, the model allows the computation of the transport properties of systems containing modified bases and of more complex arrangements of base pairs as an additional element of verification.

Made available in DSpace on 2018-12-11T17:30:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-06-01 Water-gated organic transistors have been successfully exploited as potentiometric transducers in a variety of sensing applications. The device response does not depend exclusively on the intrinsic properties of the active materials, as the substrate and the device interfaces play a central role. It is therefore important to fine-tune the choice of materials and layout in order to optimize the final device performance. Here, polyethylene naphthalate (PEN) has been chosen as the reference substrate to fabricate and test flexible transistors as bioelectronic transducers in liquid. PEN is a biocompatible substrate that fulfills the requirements for both bio-applications and micro-fabrication technology. Three different semiconducting or conducting polymer thin films employing pentacene, poly(3-hexylthiophene) or poly(3, 4-ethylenedioxythiophene):poly(styrenesulfonate) were compared in terms of transconductance, potentiometric sensitivity and response time. The different results allow us to identify material properties crucial for the optimization of organic transistor-based transducers operating in water. Dipartimento di Scienze della Vita Università di Modena and Reggio Emilia (UNIMORE), Via Campi 103 Programa de Pós-graduação em Ciência e Tecnologia de Materiais (POSMAT) Universidade Estadual Paulista (UNESP) Istituto per Lo Studio Dei Materiali Nanostrutturati (ISMN) Consiglio Nazionale Delle Ricerche (CNR), Via Gobetti n.101 Departamento de Física Química e Matemática (DFQM) Universidade Federal de São Carlos (UFSCar) ST Microelectronics Analog and MEMS Group (AMG), Str. Primosole 50 ST Microelectronics Analog and MEMS Group (AMG), Via Remo de Feo 1 Faculdade de Ciências e Tecnologia (FCT) Universidade Estadual Paulista (UNESP) Laboratório Nacional de Nanotecnologia (LNNano) Centro Nacional de Pesquisa em Energia e Materiais (CNPEM) Institut de Ciéncia de Materials de Barcelona (ICMAB) Consejo Superior de Investigaciones Cientifica (CSIC) University of Cambridge Electrical Engineering Division, 9 JJ Thomson Avenue Programa de Pós-graduação em Ciência e Tecnologia de Materiais (POSMAT) Universidade Estadual Paulista (UNESP) Faculdade de Ciências e Tecnologia (FCT) Universidade Estadual Paulista (UNESP)

This paper explores the utility of data mining and machine learning algorithms for the induction of mutagenicity structure-activity relationships (SARs) from noncongeneric data sets. We compare (i) a newly developed algorithm (MOLFEA) for the generation of descriptors (molecular fragments) for noncongeneric compounds with traditional SAR approaches (molecular properties) and (ii) different machine learning algorithms for the induction of SARs from these descriptors. In addition we investigate the optimal parameter settings for these programs and give an exemplary interpretation of the derived models. The predictive accuracies of models using MOLFEA derived descriptors is similar to10- 15 %age points higher than those using molecular properties alone. Using both types of descriptors together does not improve the derived models. From the applied machine learning techniques the rule learner PART and support vector machines gave the best results, although the differences between the learning algorithms are only marginal. We were able to achieve predictive accuracies up to 78% for 10-fold cross-validation. The resulting models are relatively easy to interpret and usable for predictive as well as for explanatory purposes. ispartof: Journal of chemical information and computer sciences vol:44 issue:4 pages:1402-1411 ispartof: location:United States status: published

In this work, we approach the problem of charge transfer in deoxyribonucleic acid (DNA) from a theoretical and numerical perspective. We focus on a DNA geometry characteristic of the eukaryotic genome and study transport along a superhelix that contains 292 nucleobases. The electronic structure is described within the Su-Schrieffer-Heeger model in an atomistic parameterization, which has been extended by a nonretarded reaction field to take dielectric polarization effects into account. The emerging potential energy surface is analyzed using the Marcus theory of electron transfer. The computed reaction coefficients are compared to their counterparts originating from idealized geometries and to experimental findings. This comparison and the palindromic nature of the DNA sequence used here permit the assessment of fluctuations in the local orientation of the bases and their impact upon transport properties.