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With the emerging of blockchain technology, new technical solutions are available for secure storage and trusted computing in the data traceability. However, there are a number of problems with blockchain-based traceability systems. Firstly, querying the historical data of the blockchain is not efficient, becoming a critical performance bottleneck in traceability systems. Secondly, most of blockchain-based traceability systems are not well designed in terms of data privacy and access control. To address the above issues, we propose an efficient and secure blockchain-based traceability system. Specifically, we design a Merkle tree independent index structure that aims to support efficient traceability queries. In addition, we deeply integrate the system with cloud computing technology, and utilize searchable encryption and attribute-based encryption to achieve secure data storage and fine-grained access control. Finally, we simulate and evaluate our system in Hyperledger Fabric. The simulation results demonstrate that the proposed system has better execution efficiency. [ABSTRACT FROM AUTHOR]

Ce, Yb co-doped YAlO films were prepared by pulse laser deposition. X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence spectra were used to characterize their structural and luminescent properties. Near-infrared quantum cutting from the films was observed via a cooperative energy transfer from Ce to Yb ions. The high quantum efficiency of the films implies that Ce,Yb co-doped YAlO films have potential application by tuning the solar spectrum to enhance the efficiency of silicon solar cells. [ABSTRACT FROM AUTHOR]

CaNbO:Sm films were prepared on quartz glass and α-AlO(001) substrates by pulsed laser deposition. The structural, morphological, and optical properties of the CaNbO:Sm films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), emission-scan electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL) measurements. The results show that the structure and properties of CaNbO:Sm films were dependent on substrates. The CaNbO:Sm films on AlO(0001) substrate have better crystallinity. The full-width at half-maximum (FWHM) of (131) peak are 0.45 and 0.32 for the CaNbO:Sm film on glass and AlO(001), respectively. The crystallite size of CaNbO:Sm films grown on glass and AlO(001) was about 8.22 and 9.98 nm, respectively. The oxidation state of the Sm element on the films was Sm state. The photoluminescence (PL) spectra were measured at room temperature, the CaNbO:Sm films on AlO(001) substrate have a better PL intensity, the identified emission bands were by the intra 4f transitions of Sm from the excited level to the lower levels at 567 nm for G→H transition, at 609 nm for G→H transition, and at 657 nm for G→H transition. [ABSTRACT FROM AUTHOR]

As photocatalysts exhibit selectivity toward various pollutants, it is necessary to develop different and novel photocatalysts. In this work, a novel photocatalyst-nitrogen-doped simonkolleite Zn5(OH)8Cl2·H2O (DSM) is prepared through a new facile method: calcinating the mixture of zinc hydroxide, urea, and guanidine hydrochloride at 575 °C for 1 h in a furnace with an air atmosphere. The as-prepared sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectra, UV-visble near-infrared diffuse reflection spectra (UV-Vis-NIR DRS), Brunauer-Emmett-Teller (BET) method, Ramen spectra and Zeta potential measurement, photocatalytic properties, as well as active species trapping experiments. XRD and XPS show the as-prepared powder is nitrogen-doped simonkolleite Zn5(OH)8Cl2H2O (DSM) with a small ZnCl2 fraction. SEM investigation indicates that the as-prepared powder possesses a flower-like layered shape. The UV-Vis-NIR exhibits that after doping, the DSM possesses strong light absorption in the ranges of 300-500 and 1400-2500 nm, a direct electronic transition with a band gap energy of 2.469 eV. PL measurement reveals a strong photoluminescence and an up-conversion from lower to higher-energy visible light in as-prepared samples. Zeta potential investigations show that during photocatalysis, the charges on as-prepared photocatalyst are positive. The photocatalytic experiments show a good dark adsorption, a high photodegradation (99.4% at 60 min), a high pseudo-first-order constant (k) of 0.0261 min−1. Meanwhile, the active species trapping experiments suggest that hole (h+) is the dominant active species during photocatalysis. It is concluded that the doping favors in enhancing vis-light-photocatalysis. This work makes a significant contribution to the literature. [ABSTRACT FROM AUTHOR]

In photocatalyst design, the rapid recombination of photo-generated electron-hole pairs in the bulk or on the surface of semiconductors is a major limiting factor in achieving high photocatalytic efficiency, which is a key scientific issue. Surface modification is used to change the surface properties of photocatalyst related to dark adsorption and photocatalytic efficiency. In this work, micro-sized CuO powder was surface modified by in situ-growing heterojunctions CuO/Cu2O and CuO/Cu2O/Cu when simply calcinating a mixture of CuO and urea, in which urea acted as a reducing agent. The phases, microstructure, composition, photogenerated carrier lifetime, dark adsorption rate, photodegradation rate, and surface charges of the as-modified powder were investigated. The surface modification was found to change the negative surface charge of micro-sized CuO to a positive one, resulting in enhanced dark adsorption (nearly twice that of pristine CuO). Furthermore, the surface modification prolonged the photogenerated carrier lifetime, which in turn enhanced the photocatalytic efficiency. Overall, this work implies that the electric properties of surface charges and carrier lifetime can be altered by constructing an appropriate heterojunction on the surface of the photocatalyst. [ABSTRACT FROM AUTHOR]