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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.

Thiolated self-assembled monolayers (SAMs) are typically used to anchor on a gold surface biomolecules serving as recognition elements for biosensor applications. Here, the design and synthesis of N-(2-hydroxyethyl)-3-mercaptopropanamide (NMPA) in biotinylated mixed SAMs is proposed as an alternative strategy with respect to on-site multistep functionalization of SAMs prepared from solutions of commercially available thiols. In this study, the mixed SAM deposited from a 10:1 solution of 3-mercaptopropionic acid (3MPA) and 11-mercaptoundecanoic acid (11MUA) is compared to that resulting from a 10:1 solution of NMPA:11MUA. To this end, surface plasmon resonance (SPR) and attenuated total reflectance infrared (ATR-IR) experiments have been carried out on both mixed SAMs after biotinylation. The study demonstrated how the fine tuning of the SAM features impacts directly on both the biofunctionalization steps, i.e., the biotin anchoring, and the biorecognition properties evaluated upon exposure to streptavidin analyte. Higher affinity for the target analyte with reduced nonspecific binding and lower detection limit has been demonstrated when NMPA is chosen as the more abundant starting thiol. Molecular dynamics simulations complemented the experimental findings providing a molecular rationale behind the performance of the biotinylated mixed SAMs. The present study confirms the importance of the functionalization design for the development of a highly performing biosensor.

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.

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.

Diketopyrrolopyrroles (DPPs) have recently attracted much interest as very bright and photostable red‐emitting molecules. However, their tendency to form nonfluorescent aggregates in water through the aggregation‐caused quenching (ACQ) effect is a major issue that limits their application under the microscope. Herein, two DPP molecules have been incorporated into the membrane of highly stable and water‐soluble quatsomes (QS; nanovesicles composed of surfactants and sterols), which allow their nanostructuration in water and, at the same time, limits the ACQ effect. The obtained fluorescent organic nanoparticles showed superior structural homogeneity, along with long‐term colloidal and optical stability. A thorough one‐ (1P) and two‐photon (2P) fluorescence characterization revealed the promising photophysical features of these fluorescent nanovesicles, which showed a high 1P and 2P brightness. Finally, the fluorescent QSs were used for the in vitro bioimaging of Saos‐2 osteosarcoma cell lines; this demonstrates their potential as nanomaterials for bioimaging applications., This work was financially supported by the DGI, Spain (Grant MOTHER; MAT2016‐80826‐R); AGAUR, Generalitat de Catalunya (Grant 2017 SGR 918); and the Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine (CIBER‐BBN). Part of the characterization work has been performed by the ICTS “NANBIOSIS”, at the Biomaterial Processing and Nanostructuring Unit #6 of the CIBER in Bioengineering, Biomaterials & Nanomedicine (CIBER‐BBN). D.B. and A.A. acknowledge the European Commission (EC) FP7‐PEOPLE‐2013‐Initial Training Networks (ITN) “NANO2FUN” project no. 607721 for their predoctoral contracts. This work was also supported by the Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR; Progetto PRIN 2012 prot. 2012A4Z2RY and Project PON02_00563_3316357 (PON MAAT)). Financial support from the Fonds National Suisse de la Recherche Scientifique (no. 200020‐165890) and the University of Geneva is also acknowledged.

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.

Souto, Manuel et al., There is a growing interest in the development of single-component molecular conductors based on neutral organic radicals that are mainly formed by delocalized planar radicals, such as phenalenyl or thiazolyl radicals. However, there are no examples of systems based on nonplanar and spin-localized C-centered radicals exhibiting electrical conductivity due to their large Coulomb energy (U) repulsion and narrow electronic bandwidth (W) that give rise to a Mott insulator behavior. Here we present a new type of nonplanar neutral radical conductor attained by linking a tetrathiafulvalene (TTF) donor unit to a neutral polychlorotriphenylmethyl radical (PTM) with the important feature that the TTF unit enhances the overlap between the radical molecules as a consequence of short intermolecular S···S interactions. This system becomes semiconducting upon the application of high pressure thanks to increased electronic bandwidth and charge reorganization opening the way to develop a new family of neutral radical conductors., This work was supported by the EU ITN iSwitch 642196 DGI grant (BeWell; CTQ2013-40480-R), the Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine (CIBER-BBN), and the Generalitat de Catalunya (grant 2014- SGR-17). This work has also been supported by MINECO through the projects CSD2007-00045, CTQ2012- 38599-C02- 02 and CTQ2013-48252-P. 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). M.S. is grateful to Spanish Ministerio de Educación, Cultura y Deporte for a FPU grant and he is enrolled in the Material Science Ph.D. program of UAB. D.B. is grateful to the EC ITN Nano2fun grant no607721. M.P.A. is grateful to the Spanish Ministerio de Educación, Cultura y Deporte for an FPU grant. M.P.A. and V.G.B. thank the project CTQ2015-67755-C2-1-R. H.O. Jeschke, M. Tomic and R. Valenti thank the Deutsche Forschungsgemeinschaft (DFG) for funding through grant SFB/TRR49 and Steve Winter for useful discussions. We thank Carlos Goḿ ez-Garcıá (Univ. Valencia) for SQUID measurements as well as Xavier Fontrodona (Univ. Girona) for X-ray diffraction measurements and Mercedes Taravillo (UCM) for the support provided during the high pressure Raman measurements.

1,2,3-Triazole rings bearing hydrophobic aliphatic or hydrophilic oligoether chains were easily introduced at the two ends of the conjugated skeleton of bisthiophene–diketopyrrolopyrrole (TDPP) derivatives by simple click cycloaddition reactions. The combination of side chains with different structures and polarities on the triazole rings with the side chains on the N-atoms of the lactam groups of the TDPP moiety enabled the solubility and the solid-state spectroscopic properties of the resulting conjugated molecules to be tuned. Formation of nanostructured aggregates and dependence of their spectroscopic behavior on the substitution pattern were investigated., This work was financially supported by the Ministero dell'Istruzi-one, dell'Università e della Ricerca (MIUR) [Progetto PRIN 2012prot. 2012A4Z2RY”, “Project PON02_00563_3316357 (PONMAAT), and Project PON03PE_00004_1 (PON MAIND)]. Thiswork was also supported by the Dirección General de Investiga-ción y Gestión del Plan Nacional de I+D+i (DGI) of the Ministeriode Ciencia y Tecnología (Spain) (Grant BE-WELL CTQ2013-40480-R), Agència de Gestió d'Ajuts Universitaris i de Recerca(AGAUR), Generalitat de Catalunya (Grant 2014-SGR-17), and theNetworking Research Center on Bioengineering, Biomaterials,and Nanomedicine (CIBER-BBN). D. B. and A. A. acknowledgethe European Commission (EC) FP7-PEOPLE-2013-Initial Train-ing Networks (ITN) (NANO2FUN Project No. 607721) for theirpredoctoral contracts.

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.