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Climate change results in increased attention to factors determining the dynamics of biogeochemical processes in the active layer of biosphere (seasonally thawing/freezing soils) at the boundary with permafrost. There are geological, geomorphic, and weather conditions associated with atmospheric precipitation, which determine the differences in the segregation and the thawing depth of permafrost in various regions. The research area is the Bureya River Basin with discontinuous permafrost within unique landscape units: Mari. They are formed in swampy and poorly drained areas where the active soil layer is in contact with permafrost, and they exert a direct impact on the quality of surface waters. The results of the study include data on the chemical composition of water in tributaries of different orders; spectral characteristics of soluble organic matter (OM) in water extracts (WEs) of soils from different horizons of the active layer; and the assessment of the activity of microbial complexes in relation to humic substances (HSs), depending on the permafrost depth. The heterogeneity of landscapes is an important factor, influencing the transport of OM into watercourses. Microbial complexes of the active layer involved in the transformation of HSs play a decisive role in changing the composition of soluble OM. It is experimentally shown that temperature affects the qualitative composition of metabolism products of HSs, including the ratio of aliphatic and aromatic fragments to chromophoric groups responsible for the color of natural waters. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (rGO) has attracted interest in its potential application in large area photodetectors owing to its ease of manufacture and wideband optical absorbance. Here, we report that thin rGO films produced via vacuum filtration of GO followed by reduction by immersion in L-ascorbic acid are capable of sensing light through a bolometric mechanism. The photoresponse of these rGO thin films can be further enhanced by dropcasting graphene quantum dots (GQDs) on the rGO surface. These GQDs were observed to increase the opacity of the rGO film and hence its absorptivity of light, thereby enabling a significant increase in the photoresponse of the device. [ABSTRACT FROM AUTHOR]

It is attractive to control the properties of macro objects and films by employing simple nanolayer composites, as in the case of nanoarchitectured Layer-by-Layer (LbL) coating. In this paper, we use chitosan as a surface-based pH buffer to protect adsorbed supramolecular fibres from pH-mediated disassembly. Protons are generated on a titania surface under illumination at 405 nm leading to an appreciable pH change on the surface. We find that supramolecular polymers that are highly sensitive to pH change will not disassemble after irradiation if a nanolayer of chitosan is present. We propose that chitosan can be used as an efficient pH-responsive protective layer for pH sensitive soft materials. [ABSTRACT FROM AUTHOR]

Ultrasonically induced shock waves stimulate intensive interparticle collisions in suspensions and create large local temperature gradients in AlNi particles. These trigger phase transformations at the surface rather than in the particle interior. We show that ultrasonic processing is an effective approach for developing the desired compositional gradients in nm-thick interfacial regions of metal alloys and formation of effective catalysts toward the hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

This work describes the encapsulation of hydrogen storage materials from organic solvents. Due to complex formation the shell provides stability and selective permeability. Specifically, sodium borohydride particles were encapsulated within polymer films by the layer-by-layer self-assembly of oppositely charged polyelectrolytes (polyethyleneimine and poly(acrylonitrile-co-butadiene-co-acrylic acid)). The polymer nanofilm fabrication was performed using dichloromethane as a working media. IR spectroscopy was applied to investigate the chemical interaction between the polyelectrolytes. The multilayer film preparation was verified by Z-potential measurements, scanning electron microscopy, and confocal laser microscopy. The stability of sodium borohydride protected with a polyelectrolyte shell was increased compared to that of the pure material under ambient conditions.

Two types of microcontainers were prepared by using the adsorption of polyamide on the surface of micrometer-sized inorganic porous calcium carbonate microparticles followed by thermal conversion of the polyamide layers into polyimide coatings. The effect of the preparation conditions on the structure and morphology of the microcontainers was studied by transmission electron microscopy and scanning electron microscopy. The smoothest and defect-free coatings were prepared using polyethylenimine as the supporting polymer. The thickness of the polyamide/polyimide shells was estimated by atomic force microscopy and scanning electron microscopy between 50 and 150 nm depending on the quantity of the layers. The water-soluble antibiotic, doxorubicin hydrochloride, was used as a model compound to demonstrate the efficiency of the microcontainers for encapsulation. The resistance of the novel microcontainers to solvent treatment was visualized by the confocal scanning fluorescence microscopy. It was demonstrated that the combination of the high thermal and chemical resistance of polyamide/polyimide shell and the sorption capacity of the CaCO3 is very useful for development of highly protective microcontainers and thermal detectors for smart fabrics.