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Solution‐processed organic and hybrid semiconductor materials have great potential for ionizing radiation direct detection, as they combine high sensitivity, low‐power consumption, and flexibility. There is, however, an open challenge related to the stability in ambient/operational conditions of this class of devices. In this work, an air‐stable, solution‐processed and flexible X‐ray detector is reported, based on the integration of hybrid perovskite and organic thin films used as active layer and functional interlayers, respectively. The diode architecture and the engineering of the interface between the hybrid perovskite and the organic hole transporting material (solvent‐modified poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate) is the key to achieve enhanced detector's air stability and performance. The unencapsulated flexible device, measured in air and in passive operation (0 V), shows a limit‐of‐detection of 0.37 ± 0.04 µGy s−1 and a sensitivity as high as 5.2 µC Gy−1 cm−2, which is retained within 25% after 42 days exposure to ambient conditions. [ABSTRACT FROM AUTHOR]

The patterning of composites with carbon-based additives of nanometer or micrometer size was studied by the precise modification of material surfaces using laser technology. Initially, the composites are electrical insulators, but we can make them conductive by selective patterning; this process allows us to create conductive tracks within seconds, with a sheet resistance that can be adjusted over a wide range, from 108 Ω/sq down to 2.5 Ω/sq. The additives used include graphene nanoplatelets, graphene oxide nanosheets, and aramid fibers. By conducting microscopic and spectroscopic characterizations before and after laser treatment, we can distinguish between two different processes that lead to electrical conduction: (a) localized increase in the concentration of conductive additives or (b) localized reduction and pyrolysis of insulating additives. To demonstrate the versatility and usefulness of this technique in different fields of application, such as automotive, we fabricate three different devices on polyurethane: a heater, a proximity sensor, and an amperometric sensor for detecting biological analytes. [ABSTRACT FROM AUTHOR]

A four-step methodology for the valorization of polysaccharide-based materials into bifunctional heterogeneous catalysts, active in the conversion of CO2 and epoxides into cyclic carbonates, is presented. The synthesis protocol consists of (i) pyrolysis of the starting material to produce biochar; (ii) oxidation to increase the number of –OH and –COOH functionalities; (iii) anchoring of (3-aminopropyl)triethoxysilane (APTES) on the surface of the oxidized biochar; (iv) quaternarization of the amine groups into alkylammonium iodide salts. The versatility of the method was demonstrated by applying the same protocol to six different polysaccharidic materials and wastes: six catalysts with no appreciable differences in terms of chemical composition and catalytic activity were obtained. The bifunctionality given by –OH and ammonium iodide groups was confirmed by several analyses performed on the catalysts. An extensive characterization (elemental analysis composition, FTIR, Raman, SEM, XPS and porosimetry) was done on all the functionalized biochars for every synthetic step. The catalysts were widely investigated in their activity for the conversion of CO2 and epoxides into cyclic carbonates, demonstrating to be effective under mild conditions (3 bar of CO2; 70 °C; 7 h). TONs and TOFs were calculated for each catalyst and condition. Yields up to 96%, with >99% selectivity, were obtained for terminal epoxides. The recyclability of the bifunctional heterogeneous catalysts was also confirmed over five cycles. [ABSTRACT FROM AUTHOR]

The quality and the performance of hybrid perovskite (HP)'s films strongly depend on the complete conversion into MAPbI3 of a spin-coated solution of methylammonium iodide (MAI) and PbI2. Highly crystalline PbI2 on a substrate limits such a conversion and, consequently, the HP's solar cell performances. We investigate for the first time the use of short-chain organic acids as additives in a non-complexing solvent like γ-butyrolactone (GBL), that can retard retard the crystallization of PbI2. Based on XRD analyses of the spin coated films, the acetic acid is the most effective additive in retarding the PbI2 crystallization, making Pb2+ available for a subsequent reaction with MAI. These results open a new experimental path for fabricating perovskite films by single or sequential step methods involving acid additives. [ABSTRACT FROM AUTHOR]

Investigations are made by means of temperature-dependent vibrational spectroscopy, the properties of neutral single crystal of C(sub 60) intercalated with biphenyl. The Raman data depict phase transitions in 2P-C(sub 60) in several ways.

Aqueous suspensions of composite nanoparticles of poly(3‐hexylthiophene) (P3HT) and [6,6]‐phenyl C61 butyric acid methyl ester (PCBM) are fabricated by miniemulsion method using three different ionic surfactants. The aim is to study how the length and conformation of the surfactants alkyl chains affect the properties of the nanoparticles. While the morphology and dimensions of the nanoparticles are similar, UV–vis spectroscopy evidences that the internal aggregation and ordering of the P3HT chains varies within the three nanoparticle formulations. The surfactant with branched alkyl chains promote the highest degree of ordering of P3HT chains in the nanoparticles (leading to increased conjugation length). In contrast, the lowest ordering is found for the nanoparticles with the surfactant having the shortest linear alkyl chain. The optical/structural properties of nanoparticles are partially retained in the films. Besides, the surfactant with branched alkyl chains favors the strongest coalescence of nanoparticles in the thin film, promoting a further ordering of the polymeric chains in the most external shell of the nanoparticles as evidenced by steady‐state and time‐resolved UV–vis spectroscopy and confocal fluorescence microscopy. These findings might guide the engineering of new surfactants for composite nanoparticles for optoelectronic applications. [ABSTRACT FROM AUTHOR]

A new approach to the analysis of the internal phonons of tris(quinolin-8-olato) aluminum(III) is presented, which enlightens the role played by the ligands in determining the vibrational properties of the organometallic compound and evidences the importance of the contributions arising from the coupling terms among the three quinolinato fragments. An accurate exam of the normal modes of the meridianal isomer evidences the role of the interactions among the fragments in the vibrational dynamics of the ground state. Due to the special attention paid to the quinolinato fragments, a preliminary investigation on the vibrational properties of 8-hydroxyquinoline, taken as a model fragment, was also performed. The vibrational properties of the polymorph species β of the organometallic molecule were obtained refining the calculated frequencies, the dipole moment derivative matrix, and the polarizability derivative tensor derived by the hybrid density functional B3LYP/6-31G* comparing with the frequencies and intensities recorded by the infrared and the Raman spectroscopies performed on a polycrystalline sample. One thus obtains the most accurate intramolecular force constants up to date for the meridianal isomer in a crystalline phase. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]