For this study, Cu-In-S nanocrystals were developed as a low toxic fluorescent. The stoichiometric CuInS(2) nanocrystals were synthesized facilely by heating a solution of metal complexes and dodecanethiol. The fluorescence would be originated from the crystal defect. We intentionally introduced the crystal defect in nanocrystal with the prospect that the fluorescence intensity would be increased. The defect structure of products was analyzed using Raman spectroscopy and other techniques. The nanocrystals have many defects without phase separation as observed in the bulk material. Consequently, the fluorescence quantum yield achieved approximately 5%. Moreover, the fluorescence quantum yield was increased up to 15% by the ZnS coating.

The structure-selective precise synthesis of carbon nanotubes (CNTs) has been long sought in materials science. The aromatic molecules corresponding to segment structures of CNTs, i.e. carbon nanobelts (CNBs), have been of interest as templates for CNT growth. Although two of three types, armchair and chiral CNBs, have been synthesized recently, zigzag CNBs remain elusive. Herein we report the synthesis and isolation of a zigzag CNB. The synthesis involves an iterative Diels-Alder reaction sequence followed by reductive aromatization of oxygen-bridged moieties. As predicted by theoretical calculations, this CNB was isolated as a stable compound. The structure of the zigzag CNB was fully characterized by X-ray crystallography, and its wide energy gap with blue fluorescence properties were revealed by photophysical measurement. With synthetic strategies towards all three types of CNBs in hand, the road to the precise synthesis of CNTs can now proceed to the next stage. File list (3) download file view on ChemRxiv CheungZigzag_.pdf (9.75 MiB) download file view on ChemRxiv SI_CheungZigzag_.pdf (4.72 MiB) download file view on ChemRxiv cheung.cif (1.23 MiB)

Atomic-scale defects/disorded states induced by sulfur sublimation are responsible for reduced lattice thermal conductivity of thermoelectric colusite.

Technologies for the creation of topological carbon nanostructures have greatly advanced synthetic organic chemistry and materials science. Although simple molecular nanocarbons with a belt topology have been constructed, analogous carbon nanobelts with a twist—more specifically, Möbius carbon nanobelts (MCNBs)—have not yet been synthesized owing to their high intrinsic strain. Here we report the synthesis, isolation and characterization of a MCNB. Calculations of strain energies suggest that large MCNBs are synthetically accessible. Designing a macrocyclic precursor with an odd number of repeat units led to a successful synthetic route via Z-selective Wittig reactions and nickel-mediated intramolecular homocoupling reactions, which yielded (25,25)MCNB over 14 steps. NMR spectroscopy and theoretical calculations reveal that the twist moiety of the Möbius band moves quickly around the MCNB molecule in solution. The topological chirality that originates from the Möbius structure was confirmed experimentally using chiral HPLC separation and circular dichroism spectroscopy.

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Selectivity is an important parameter of resistive-type gas sensors that use metal oxides. In this study, a highly selective toluene sensor is prepared using highly dispersed gold-nanoparticle-loaded zinc oxide nanoparticles (Au-ZnO NPs). Au-ZnO NPs are synthesized by coprecipitation and calcination at 400 °C with Au loadings of 0.15, 0.5, and 1.5 mol %. The Au NPs on ZnO are about 2-4 nm in size, and exist in a metallic state. Porous gas-sensing layers are fabricated by screen printing. The responses of the sensor to 200 ppm hydrogen, 200 ppm carbon monoxide, 100 ppm ethanol, 100 ppm acetaldehyde, 100 ppm acetone, and 100 ppm toluene are evaluated at 377 °C in a dry atmosphere. The sensor response of 0.15 mol % Au-ZnO NPs to toluene is about 92, whereas its sensor responses to other combustible gases are less than 7. Such selective toluene detection is probably caused by the utilization efficiency of the gas-sensing layer. Gas diffusivity into the sensing layer of Au-ZnO NPs is lowered by the catalytic oxidation of combustible gases during their diffusion through the layer. The present approach is an effective way to improve the selectivity of resistive-type gas sensors.

The paper presents new relative measurements of the viscosity of argon, neon, and krypton and of the binary mixtures Ar–Ne and Ar–Kr, all at atmospheric pressure, in the nominal temperature range 25–700°C, and with a precision of ± 0.1%. The oscillating-disk method was employed. The experimental data were used to calculate the binary diffusion coefficient for the mixtures, and the thermal conductivity of the pure gases as well as the mixtures. The data for the pure gases can be correlated separately with the aid of a suitable potential of the 6-n family, and optimum values of the parameters σ, ε, and n are given for each of them. The same data can be correlated equally well with the aid of a universal, empirical expression for the collision integral with two individual parameters, s and p, being adequate to describe each gas separately. The conventional combination rules as well as those proposed by Kalelkar and Kestin [J. Chem. Phys. 52, 4268 (1970)] have been tested, and it was found that the latter represent the results as well as the expression for mixture viscosity in terms of the viscosity of the pure components and the coefficient of binary diffusion. Wassiljewa coefficients have been evaluated for the representation of the viscosity and the thermal conductivity of the mixtures.