In this work, we present all-oxide p-n junction core-shell nanowires (NWs) as fast and stable self-powered photodetectors. Hydrothermally grown n-type ZnO NWs were conformal covered by different thicknesses (up to 420 nm) of p-type copper oxide layers through metalorganic chemical vapor deposition (MOCVD).The ZnO NWs exhibit a single crystalline Wurtzite structure, preferentially grown along the [002] direction, and energy gap Eg=3.24 eV. Depending on the deposition temperature, the copper oxide shell exhibits either a crystalline cubic structure of pure Cu2O phase (MOCVD at 250 C) or a cubic structure of Cu2O with the presence of CuO phase impurities (MOCVD at 300 C), with energy gap of 2.48 eV.The electrical measurements indicate the formation of a p-n junction after the deposition of the copper oxide layer. The core-shell photodetectors present a photoresponsivity at 0V bias voltage up to 7.7 µA/W and time response ≤0.09 s, the fastest ever reported for oxide photodetectors in the visible range, and among the fastest including photodetectors with response limited to the UV region. The bare ZnO NWs have slow photoresponsivity, without recovery after the end of photo-stimulation. The fast time response for the core-shell structures is due to the presence of the p-n junctions, which enables fast exciton separation and charge extraction. Additionally, the suitable electronic structure of the ZnO-Cu2O heterojunction enables self-powering of the device at 0V bias voltage. These results represent a significant advancement in the development of low-cost, high efficiency and self-powered photodetectors, highlighting the need of fine tuning the morphology, composition and electronic properties of p-n junctions to maximize device performances.

The coexistence of a conjugated organic macrocyclic structure and a transition metal center provides MPor with numerous properties that fostered their use in catalysis, [2,3] theranostic, [4] and nonlinear optic. [5] Another application area of MPor is chemosensing, [6] in which interactions with a chemical analyte modifies the physical properties of MPor film that can be transduced into a measurable signal. Based on the nature of signal transductions, MPorbased optical, acoustic, magnetic, and electrical chemosensors have been developed [7] to detect myriad of species such as redox gases, [8] volatile organic compounds, [9] and inorganic biochemical species. [10] Particularly, MPor chemosensors based on electrical transductions such as chemiresistors, ChemFet, and conductometric sensors have drawn interests exploiting the semiconducting nature of MPor, which can be effectively tuned by adding substituents to its macrocyclic periphery or ligands at the metal center. Song et al. reported a chemiresistor based on highly ordered nanotubes of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin zinc(II) to selectively detect NO 2 at sub-ppm concentration. [11] Elsewhere, self-assembled monolayers of MPor films in ChemFet configuration were used to detect organic vapors and redox gases, exhibiting the strong influence of metal atom on sensors responses. [12,13] However, most of the MPor are poor conducting materials owing to low π-conjugation, limiting the sensors performances. To overcome this limitation, different approaches have been adopted such as forming a composite with more conducting materials like carbon nanotubes, [14,15] conductive polymers, [16,17] or metal oxides. [18,19] An alternative solution to the MPor low conductivity can be the formation of highly conjugated porphyrin polymers to extend the molecular π-system. However, the synthesis of conjugated porphyrin polymers requires significant synthetic efforts. In 2001, Tsuda and Osuka provided a new route toward the easy synthesis of directly fused metalloporphyrins, known as porphyrin tapes (Scheme 1). [20] Porphyrin tapes possess a series of outstanding properties such as electronic transitions in the IR region, [20] increased catalytic activity, [21] two-photon absorption, [22] and low conductance attenuation factors. [23,24] The synthesis of porphyrin tapes relies on the Modulating the interfacial charge alignments by molecular engineering in an organic heterojunction device is a smart strategy to improve its conductivity, which can be exploited in high-performance gas-sensor development. Herein, the fabrication of new organic heterojunction devices based on porphyrin tapes and phthalocyanines and their potentiality in ammonia sensing at different relative humidity (rh) are investigated. The devices are built using dry approach relying on oxidative chemical vapor deposition for simultaneous synthesis, doping, and deposition of the porphyrin tape layer and physical vapor deposition of phthalocyanine layer. The association of the porphyrin tapes with copper ph...

Octahedral crystals of Fe(III)-based Mil-101 and amino-functionalized Mil-101 are directly grown on Si(100) using easy solution routes under mild conditions. Images from microscopy analyses show that samples consist of a layer of isolated octahedral crystals in which the [111]direction develops vertically with respect to the Si(100) substrate. Structural and chemical characterizations indicate that crystals consist of Mil-101(Fe) with the following stoichiometry: Fe 3 (O)Cl-(DMF) 2 (Terepht) 3 (DMF = dimethylformamide and Terepht = terephthalate or aminoterephthalate). Both Si-grown Mil-101(Fe) and NH 2 -Mil-101(Fe) layers are capable of adsorbing two aromatic gases with different polarities, toluene and nitrobenzene. Their characteristic thermal desorption profiles depend on the aminofunctionalization of the terephthalate ligand as well as on the mutual interactions between the two guests when adsorbed from a mixture. It is also shown that, by adapting suitable experimental conditions, Mil-101(Fe) layers are capable of separating a toluene/nitrobenzene gas mixture through selective thermal desorption. A model based on the evaluation of the involved host−guest interactions through the density functional theory (DFT) approach is proposed to explain the observed selective desorption and to account for the key parameters involved in the desorption process of aromatic vapors.

The low efficiency of water electrolysis mostly arises from the thermodynamic uphill oxygen evolution reaction. The efficiency can be greatly improved by rationally designing low-cost and efficient oxygen evolution anode materials. Herein, we report the synthesis of Ni–P alloys adopting a facile electroless plating method under mild conditions on nickel substrates. The relationship between the Ni–P properties and catalytic activity allowed us to define the best conditions for the electroless synthesis of highperformance Ni–P catalysts. Indeed, the electrochemical investigations indicated an increased catalytic response by reducing the thickness and Ni/P ratio in the alloy. Furthermore, the Ni–P catalysts with optimized size and composition deposited on Ni foam exposed more active sites for the oxygen evolution reaction, yielding a current density of 10 mA cm−2 at an overpotential as low as 335 mV, exhibiting charge transfer resistances of only a few ohms and a remarkable turnover frequency (TOF) value of 0.62 s−1 at 350 mV. The present study provides an advancement in the control of the electroless synthetic approach for the design and large-scale application of high-performance metal phosphide catalysts for electrochemical water splitting.

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Chemical approaches, either through vapor or solution routes, are applied to the preparation of tri-doped CaF2-based films for upconversion applications.

Nanocomposites obtained by the decoration of graphene-based materials with silver nanoparticles (AgNPs) have received increasing attention owing to their antimicrobial activity. However, the complex synthetic methods for their preparation have limited practical applications. This study aims to synthesize novel NanoHybrid Systems based on graphene, polymer, and AgNPs (namely, NanoHy-GPS) through an easy microwave irradiation approach free of reductants and surfactants. The polymer plays a crucial role, as it assures the coating layer/substrate compatibility making the platform easily adaptable for a specific substrate. AgNPs’ loading (from 5% to 87%) can be tuned by the amount of Silver salt used during the microwave-assisted reaction, obtaining spherical AgNPs with average sizes of 5–12 nm homogeneously distributed on a polymer-graphene nanosystem. Interestingly, microwave irradiation partially restored the graphene sp2 network without damage of ester bonds. The structure, morphology, and chemical composition of NanoHy-GPS and its subunits were characterized by means of UV-vis spectroscopy, thermal analysis, differential light scattering (DLS), Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray analysis (EDX), Atomic Force Microscopy (AFM), and High-Resolution Transmission Electron Microscopy (HRTEM) techniques. A preliminary qualitative empirical assay against the typical bacterial load on common hand-contacted surfaces has been performed to assess the antibacterial properties of NanoHy-GPS, evidencing a significative reduction of bacterial colonies spreading.

Abstract