Probing nanoscale electrical properties of organic semiconducting materials at the interface with an electrolyte solution under externally applied voltages is key in the field of organic bioelectronics. It is demonstrated that the conductivity and interfacial capacitance of the active channel of an electrolyte‐gated organic field‐effect transistor (EGOFET) under operation can be probed at the nanoscale using scanning dielectric microscopy in force detection mode in liquid environment.
Local electrostatic force versus gate voltage transfer characteristics are obtained on the device and correlated with the global current–voltage transfer characteristics of the EGOFET. Nanoscale maps of the conductivity of the semiconducting channel show the dependence of the channel conductivity on the gate voltage and its variation along the channel due to the space charge limited conduction. The maps reveal very small electrical heterogeneities, which correspond to local interfacial capacitance variations due to an ultrathin non‐uniform insulating layer resulting from a phase separation in the organic semiconducting blend. Present results offer insights into the transduction mechanism at the organic semiconductor/electrolyte interfaces at scales down to ≈100 nm, which can bring substantial optimization of organic electronic devices for bioelectronic applications such as electrical recording on excitable cells or label‐free biosensing.
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Nanoscale Mapping of the Conductivity and Interfacial Capacitance of an Electrolyte‐Gated Organic Field‐Effect Transistor under Operation
Adrica Kyndiah, Martí Checa, Francesca Leonardi, Ruben Millan‐Solsona, Martina Di Muzio, Shubham Tanwar, Laura Fumagalli, Marta Mas‐Torrent, Gabriel Gomila
Since the inception of the atomic force microscope (AFM), dynamic methods (dynamic atomic force microscopy) have been very fruitful by establishing methods to quantify dissipative and conservative forces in the nanoscale and by providing a means to apply gentle forces to the samples with high resolution. Here, we discuss developments that cover over a decade of our work on energy dissipation, phase contrast, and the extraction of relevant material properties from observables.
Nickel(II) bis(dithiolene) complexes can provide crystalline conducting materials either in their monoanionic or neutral forms. Here we show that the use of chiral dithiolene ligands with one or two stereogenic centres, together with variation of the counter-ion in the anionic complexes, represents a powerful strategy to modulate the conducting properties of such molecular materials.The chiral ligands 5-methyl-5,6-dihydro-1,4-dithiin-2,3-dithiolate (me-dddt) and 5,6-dimethyl-5,6-dihydro-1,4-dithiin-2,3-dithiolate (dm-dddt) have been generated from the thione precursors 1 and 2 which have been structurally and chiroptically characterized.
The functionalization of single-walled carbon nanotubes (SWCNTs) with luminescent sp3 defects has greatly improved their performance in applications such as quantum light sources and bioimaging. Here, we report the covalent functionalization of purified semiconducting SWCNTs with stable organic radicals (perchlorotriphenylmethyl, PTM) carrying a net spin.
The spin–spin interactions between unpaired electrons in organic (poly)radicals, especially nitroxides, are largely investigated and are of crucial importance for their applications in areas such as organic magnetism, molecular charge transfer, or multiple spin labeling in structural biology. Recently, 2,2,6,6-tetramethylpiperidinyloxyl and polymers functionalized with nitroxides have been described as successful redox mediators in several electrochemical applications; however, the study of spin–spin interaction effect in such an area is absent.
Metallacarboranes with the shape of the Greek letter θ, such as [Co(C2B9H11)2]−, were tested, for the first time, as efficient photoredox catalysts in the oxidation of aromatic and aliphatic alcohols in water. Their efficiency is linked to their high solubility in water, their high oxidizing power (Co4+/3+), and their absence of fluorescence on excitation, among others.