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A combined cyclic voltammetry (CV) and grazing angle attenuated total reflectance (GA-ATR) IR study on the interchain interaction driven reorganization of self-assembled monolayers (SAMs) in an electric field was presented. The study focused on an N-(2-hydroxyethyl)-3-mercaptopropanamide (NMPA) SAM endowed with interchain hydrogen bonding, strongly affected by an external electric field interacting with the dipole moment associated with the hydrogen bonding. Conversely, a 1-hexanethiol SAM was characterized by interchain hydrophobic interaction not affected by the applied field. These features were demonstrated by means of reiterated CV experiments involving an electroactive negatively charged probe, namely Fe(CN)64−, and a Au-SAM serving as a working electrode. The diffusional/interpenetration and kinetics parameters provided the apparent electron transfer rate constant (k0) values. For the NMPA, the interchain rearrangement kinetics was that of an ion-permeable layer that reached, in the electric field, a steady-state configuration after about 50 minutes. The 1-hexanethiol chains’ reorganization exhibited more complex kinetics involving a first phase (ca. 50 minutes) of an ion-permeable phase followed by a sharp decrease in the anodic peak current related to the tightening of the structure, likely due to the interchain hydrophobic interaction, hindering ion diffusion. The change in the SAM structure upon cycling in the electric field was confirmed by the GA-ATR measurements.

Several three-terminal organic bioelectronic structures have been proposed so far to address the needs for a variety of biosensing applications. The most popular ones utilized organic field-effect transistors operated in an electrolyte, to detect both proteins and genomic analytes. They are endowed with selectivity by immobilizing a layer of bio-recognition elements. These features along with the foreseen low-cost for their production, make them very appealing for point-of-care biomedical applications. However, organic bioelectronic transistors do not always exhibit a performance level beyond state-of-the-art electrochemical sensors, which have been dominating the field for decades. This review offers a perspective view based on a systematic comparison between the potentiometric and amperometric electrochemical sensors and their organic bioelectronic transistor counterparts. The key-relevant aspects of the sensing mechanisms are reviewed for both, and when the mathematical analytical expression is actually available, the amplification factors are reported as the ratio between the response of a rationally designed transistor (or amplifying circuit) and that of a homologous electrochemical sensor. The functional dependence of the bioelectronic sensor responses on the concentration of the species to be detected enabling their correct analytical quantification, is also addressed.

Organic bioelectronic sensors based on an electrolyte gated field-effect transistor are gaining momentum due to their extraordinary high-performance level that enables label-free selective single-molecule detection of both genomic and protein biomarkers with a millimeter-wide electrolyte-gated field-effect transistor (EGOFET) device. The organic semiconductor channel material used so far is a spin-coated regio-regular poly(3-hexylthiophene) (P3HT). Of paramount importance is to design an EGOFET sensor that is stable and cost-effective. To address the latter feature, an ink-jet printed regio-regular P3HT film is here investigated as the channel material. Moreover, the EGOFET device structure is intended to comprise a coplanar lateral gate electrode that enables mechanical and electrical stability. Overall, the structure is compatible with large area processing so it can be fabricated at low-costs and can be operated continuously for eight days. Additionally, systematic optical and Raman characterization of the P3HT film proves that the printing process results in a film with a low energetic disorder (better π–π stacking in the crystalline regions) that likely enables stable operation. However, the higher quality crystalline regions (as compared to a spin-coated film) are dispersed in a more significant fraction of the amorphous disordered material with a larger amount of trap states. The higher crystalline order is ascribed to the higher boiling point and slower evaporation of the ortho-dichlorobenzene solvent used in the printing process. Overall, the present study provides a systematic insight into the structure–property correlations, essential to design a well-functioning and cost-effective EGOFET for high-performance electronic biosensing. It also provides one of the few investigations comparing the features characterizing a spin-coated and an ink-jet printed P3HT film.

Chiroptical properties of two chiral atropisomers of propeller‐like trityl‐based radical derivatives have been analyzed. A new absolute configuration (AC) assignment has been made, according to the combination of experimental and theoretical data. In this sense, their ACs have been determined through the comparison of the Cotton effects recorded by electronic circular dichroism (ECD) with the theoretical ECD of the open shell structures obtained by TD‐DFT calculations. Finally, their circularly polarized luminescence (CPL) responses have been addressed. Remarkably, this is the first description of organic free radicals as intrinsic CPL emitters. Opposite signed CPL has been detected for each pair of conformers, with acceptable luminescent dissymmetry factors (|glum|≈0.5–0.8×10−3) considering their pure organic nature. In fact, highly efficient chiral emissions have been demonstrated, according to the comparison of |glum| with their respective absorption anisotropy factors (|gabs|). This pioneering study lays the foundations for the optimization of new magnetically active organic chiral emitters.

Electrolyte-gated graphene field-effect transistors are here proposed for biosensing applications. To this end, a label-free immunosensor based on this technology is employed for the sensitive and selective detection of IgG. Differently from the typical approach based on the bioreceptor immobilization onto a graphene layer, in this work sensitivity in the lower femtomolar range can be reached thanks to the formation of a closely packed layer of anti-IgG receptors anchored to the gold gate electrode.

Correction for ‘Printed, cost-effective and stable poly(3-hexylthiophene) electrolyte-gated field-effect transistors’ by Davide Blasi et al., J. Mater. Chem. C, 2020, DOI: 10.1039/d0tc03342a.

In this work, the luminescence properties of new materials based on open-shell molecular systems are studied. In particular, we prepared polymeric films and organic nanoparticles (ONPs) doped with triphenylmethyl radical molecules. ONPs exhibit a uniform size distribution, spherical morphology and high colloidal stability. The emission spectrum of low-doped ONP suspensions and low-doped films is very similar to the emission spectrum of TTM in solution, while the luminescence lifetime and the luminescence quantum yield (LQY) are highly increased. Increasing the radical doping leads to a progressive decrease of the LQY and the appearance of a new broad excimeric band at longer wavelengths, both for ONPs and films. Thus, not only the luminescence properties were improved, but also the formation of excimers from stable and persistent supramolecular radical-pairs was observed for the first time. The good stability and luminescence properties with emission in the red-NIR region (650–800 nm), together with the open-shell nature of the emitter, make these free-radical excimer-forming materials promising candidates for optoelectronic and bioimaging applications., The research leading to these results received funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7/2007–2013 under a REA grant agreement no. 607721 (ITN Nano2Fun). A DGI grant (BeWell; CTQ2013-40480-R and Dynamo MAT2013-50036-EXP), the Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine (CIBER-BBN), the Generalitat de Catalunya (grant 2014-SGR-17) are also acknowledged. ICMAB acknowledges support from the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2015-0496). This work has been developed inside the Materials Science PhD programs of Universitat Autonoma de Barcelona and of University of Parma.

Self-assembled monolayers (SAMs) of N-(2-hydroxyethyl)-3-mercaptopropanamide (NMPA) were synthesized directly on the surface of electron-beam evaporated Au films, starting from 3-mercaptopropionic acid (3MPA) via ethyl-3-(3-dimethylamino-propyl)carbodiimide/N-hydroxysulfosuccinimide sodium salt (EDC/NHSS) coupling with ethanolamine hydrochloride. The influence on the reaction yield of the acidity of EDC/NHSS solutions (pH = 5.6 or 4.8) was assessed by exploiting the high surface sensitivity of infrared attenuated total reflection spectroscopy. The light-matter interaction was modeled in the framework of a matrix formalism considering the complete multi-layer sample structure. A comparison between the relative intensity of the main absorption bands, associated with amide I and carbonyl stretching of carboxylic acid or amide II vibrations, with a calibration curve obtained from the measurement of mixed 3MPA/NMPA SAMs, show that the more acid solution is 16% more efficient. This is mostly due to the higher protonation of the 3MPA.