Recently, intensive efforts are dedicated to convert and store the solar energy in a single device. Herein, dye-synthesized solar cell technology is combined with lithium-ion materials to investigate light-assisted battery charging. In particular we report the direct photo-oxidation of lithium iron phosphate nanocrystals in the presence of a dye as a hybrid photo-cathode in a two-electrode system, with lithium metal as anode and lithium hexafluorophosphate in carbonate-based electrolyte; a configuration corresponding to lithium ion battery charging. Dye-sensitization generates electron–hole pairs with the holes aiding the delithiation of lithium iron phosphate at the cathode and electrons utilized in the formation of a solid electrolyte interface at the anode via oxygen reduction. Lithium iron phosphate acts effectively as a reversible redox agent for the regeneration of the dye. Our findings provide possibilities in advancing the design principles for photo-rechargeable lithium ion batteries.

No abstract

A versatile method to fabricate self-supported aerogels of nanoparticle (NP) building blocks is presented. This approach is based on freezing colloidal NPs and subsequent freeze drying. This means that the colloidal NPs are directly transferred into dry aerogel-like monolithic superstructures without previous lyogelation as would be the case for conventional aerogel and cryogel fabrication methods. The assembly process, based on a physical concept, is highly versatile: cryogelation is applicable for noble metal, metal oxide, and semiconductor NPs, and no impact of the surface chemistry or NP shape on the resulting morphology is observed. Under optimized conditions the shape and volume of the liquid equal those of the resulting aerogels. Also, we show that thin and homogeneous films of the material can be obtained. Furthermore, the physical properties of the aerogels are discussed.

No abstract

No abstract

In this work we applied colloidal preparation methods to synthesize AuCu nanocrystals (NCs) in the ordered tetragonal phase with an atomic composition close to 50:50. We deposited the NCs on a support (Al 2 O 3 ), studied their transformations upon different redox treatments, and evaluated their catalytic activity in the CO oxidation reaction. The combined analyses by energy dispersive X-ray spectroscopy (EDX)-scanning transmission electron microscopy (STEM), selected area electron diffraction (SAED), and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) highlighted a phase segregation between gold and copper upon the high-temperature (350 °C) oxidizing treatment. While gold remained localized in the NCs, copper was finely dispersed on the support, likely in the form of oxide clusters. AuCu alloyed NCs, this time in the form of solid solution, face-centered cubic phase, were then restored upon a reducing treatment at the same temperature, and their catalytic activity was significantly enhanced in comparison to that of the oxidized system. The composition of the NCs and consequently the CO oxidation reaction rate were also affected by the CO/O 2 reacting atmosphere: regardless of the pretreatment, the same catalytic activity was approached over time on stream at temperatures as low as 100 °C. Consistently, the same situation was observed on the catalyst surface as probed by EDX-STEM, SAED, and DRIFTS. All of these transformations were found to be fully reversible.

Electrospun spiropyran-embedded nanofibers for fast photocontrollable and reversible optochemosensing of acidic vapors.

The combination of two or more metals, forming alloys, core−shells, or other complex heterometallic nanostructures, has substantially spanned the available options to finely tune electronic and structural properties, opening a myriad of opportunities that has yet to be fully explored in different fields. In catalysis, the rational exploitation and design of bimetallic and trimetallic catalysts has just started. Several major aspects such as stability, phase segregation, and alloy− dealloy mechanisms have yet to be deeply understood and correlated with intrinsic factors such as nanoparticle size, composition, and structure and with extrinsic factors, or external agents, such as temperature, reaction gases, and support. Here, by combining model catalysts based on AuCu nanoparticles supported on silica or alumina with in situ characterization techniques under redox pretreatments and CO oxidation reaction, we demonstrate the crucial role of the support with regard to determining the stable active phase of bimetallic supported catalysts. This strategy, associated with theoretical studies, could lead to the rational design of unique active sites.