Facile Synthesis Bi2Te3 Based Nanocomposites: Strategies for Enhancing Charge Carrier Separation to Improve Photocatalytic Activity

Varying structure Bi2Te3-based nanocomposite powders including pure Bi2Te3, Bi2Te3/Bi core−shell, and Bi2Te3/AgBiTe2 heterostructure were synthesized by hydrothermal synthesis using Bi2S3 as the template and hydrazine as the reductant. Successful realization of Bi2Te3-based nanostructures were concluded from XRD, FESEM, and TEM. In this work, the improvement in the performance of the rhodamine B (RhB) decomposition efficiency under visible light was discussed. The Bi2Te3/AgBiTe2 heterostructures revealed propitious photocatalytic performance ca. 90% after 60 min. The performance was over Bi2Te3/Bi core-shell nanostructures (ca. 40%) and more, exceeding pure Bi2Te3 (ca. 5%). The reason could be scrutinized in terms of the heterojunction structure, improving the interfacial contact between Bi2Te3 and AgBiTe2 and enabling retardation in the recombination rate of the photogenerated charge carriers. A credible mechanism of the charge transfer process in the Bi2Te3/AgBiTe2 heterostructures for the decomposition of an aqueous solution of RhB was also explicated. In addition, this work also investigated the stability and recyclability of a Bi2Te3/AgBiTe2 heterojunction nanostructure photocatalyst. In addition, this paper anticipates that the results possess broad potential in the photocatalysis field for the design of a visible light functional and reusable heterojunction nanostructure photocatalyst.

Efficiency Analysis of OLAP-data Hypercube Decomposition for Exponential Computational Complexity Methods

The paper studies problems of reduction (decomposition) of OLAP-hypercube multidimensional data models. When decomposing large hyper-cubes of multidimensional data into sub-cube components the goal is to increase the computational performance of analytical OLAP systems, which is related to decreasing computational complexity of reduction methods for solving OLAP-data analysis problems with respect to the computational complexity of non-reduction methods, applied to data directly all over the hypercube. The paper formalizes the concepts of reduction and non-reduction methods and gives a definition of the upper bound for the change in the computational complexity of reduction methods in the decomposition of the problem of analyzing multidimensional OLAP-data in comparison with non-reduction methods in the class of exponential degree of computational complexity.The exact values of the upper bound for changing computational complexity are obtained for the hypercube decomposition into two sub-cubes on sets consisting of an even and an odd number of sub-cube structures, and its main properties are given, which are used to determine the decomposition efficiency. A formula for the efficiency of decomposition into two sub-cube structures for reduction of OLAP data analysis problems is obtained, and it is shown that with an increase in the dimension “n” of the lattice specifying the number of sub-cubes in the hypercube data structure, the efficiency of such a decomposition obeys an exponential law with an exponent “n/2”, regardless of the parity “n”. The examples show the possibility to use the values (found) of the upper bound for the change in computational complexity to establish the effectiveness criteria for reduction methods and the expediency of decomposition in specific cases.The paper results can be used in processing and analysis of information arrays of hypercube structures of analytical OLAP systems belonging to the Big-Data or super-large computer systems of multidimensional data.

Enhanced Catalytic Activities of TiO2 Nanotube Arrays Co-Sensitized with Pt/CdS/ZnS via Electrodeposition and Successive Ionic Layer Adsorption and Reaction (SILAR) Method Approach

In this work, we have synthesized a nanocomposite ZnS/CdS/Pt/TiO2 nanotube arrays (denoted ZCP-NTAs). Firstly, TiO2 nanotube array (NTAs) material was fabricated by the anodic method of a titanium plate in an electrolyte solution containing 0.35 M NaHSO4 and 0.24 M NaF and incubated in the air at 500 ºC for 2 hours. After that, pulsed electrodeposition technology was used to decorate platinum nanoparticles (denoted as Pt NPs) onto the surface of TiO2 nanotubes to form P-NTAs photoelectrodes. Then, the SILAR method is used to deposition CdS quantum dots (symbolized as CdS QDs) on the surface of P-NTAs to form CP-NTAs material. Finally, by the SILAR method, a ZnS passive layer that protects against optical corrosion and inhibits recombination of e−/h+ pairs was coated onto the CP-NTAs to form ZCP-NTAs material. As-prepared ZCP-NTAs photocatalytic material has good absorbability of light in the visible region with light absorption wavelength up to 608 nm, photon conversion efficiency up to 5.32% under light intensity AM1.5G, and decomposition efficiency of 10 mg L−1 methyl orange (MO) in 120 minutes reached 91.50%. This material promises to bring high application ability in the photocatalytic field applied for environmental treatment and other applications.

Evaluation of photocatalytic activities in decomposition of methylene blue in aqueous solution of Mn-ZIF-8 and Mn@Zn

In the present study, manganese modified zeolitic imidazolate framework-8 (Mn-ZIF-8) and zinc-manganese bimetallic oxides (denoted as Mn@Zn), which was formed by Mn-ZIF-8 heat treatment, had been prepared and applied as photocatalysts to decompose methylene blue (MB) under UV radiation. The influence of manganese content on the structure of ZIF-8, as well as the temperature and heat treatment time of Mn-ZIF-8 material to produce Mn@Zn with high photocatalytic activity was investigated. Results showed that all Mn-ZIF-8 samples have photocatalytic activity, but the MB decomposition efficiency of Mn-ZIF-8 samples were lower than pure ZIF-8. The suitable condition for heat treatment of Mn-ZIF-8 to produce Mn@Zn with high photocatalytic activity was at 500 ºC for 5 hours. However, the MB decomposition efficiency of this sample only reached 22% after 180 minutes of UV radiation.

The Effect of Catalyst Calcination Temperature on Catalytic Decomposition of HFC-134a over γ-Al2O3

This paper explores the thermal and catalytic pyrolysis of HFC-134a over γ-Al2O3 calcined at temperatures of 550 °C (A550), 650 °C (A650), 750 °C (A750), and 850 °C (A850). The physicochemical properties of catalysts were studied through thermogravimetric analysis (TGA), Brunauer–Emmett–Teller equation for nitrogen physisorption analysis (BET), X-ray diffraction (XRD), and temperature-programmed desorption of ammonia (NH3-TPD). The non-catalytic pyrolysis of HFC-134a showed less than 15% decomposition of HFC-134a. Catalysts increased the decomposition as A650 revealed the highest decomposition efficiency by decomposing more than 95% HFC-134a for 8 h followed by A750, A850, and A550. The larger surface area and pore volume paired with a low amount of strong acidic sites were considered as the main contributors to the comparatively longer catalytic activity of A650.

Analysis of the Relationships between Tourism Efficiency and Transport Accessibility—A Case Study in Hubei Province, China

There is a close relationship between tourism efficiency and transport accessibility, but there is little research on the topic. This paper takes 17 administrative units in Hubei Province as the research object, evaluates their tourism efficiency from 2011 to 2017 and transportation accessibility in 2011 and 2017, and explores the temporal and spatial correlation between the two. The results showed that, from 2011 to 2017, tourism efficiency of Hubei province was high and steadily improving, space non-equilibrium gradually decreased, and differences shrank. In 2011 and 2017, the province had a good tourism transport accessibility, and the spatial distribution pattern was high in the east and low in the west. At the same time, tourism transport continued to improve, and spatial imbalance declined. In 2011 and 2017, the coupling and coordination of tourism efficiency and its decomposition efficiency and transport accessibility in Hubei Province were both good, indicative of the development of a tourism economy and the improvement of tourism transport facilities in all regions of the province. There is also a poor spatial matching of tourism efficiency and its decomposition efficiency with transport accessibility during the study period. This study suggested that the tourism efficiency and transport accessibility increased in Hubie province, but the coupling and spatial match remain not very good. Therefore, each region should improve the spatial match and coupling degree of tourism efficiency and transport accessibility, and enhance the sustainability of tourism development.

Efficient Visible Active Ternary Bi2MoO6-rGO-TiO2 Composite Material for Photodecomposition of Ofloxacin

The ternary Bi2MoO6-reduced graphene oxide (rGO)-TiO2 catalyst were synthesized using a simple hydrothermal method. The improvement of the photocatalytic decomposition efficiency of Bi2MoO6-rGO-TiO2 composite is 92.3% than the pure and binary photocatalyst. The effects of operational parameters like catalyst ratio, the different catalyst, different ratio rGO and different pH, have been analyzed. As prepared ternary photocatalyst is low Photoluminescence and high photocurrent density responsible, it exhibited that photon-induced electron and hole-recombination were suppressed and also charged separation is effective. The present study shows the rGO is an excellent electron transfer performance and enhanced the photocatalytic reaction stability.

AIE Active Polyelectrolyte Based Photosensitizers: The Effects of Structure on Antibiotic-Resistant Bacterial Sensing and Killing, and Pollutant Decomposition

A facile and effective multifunctional platform with high bacteria detection sensitivity, good antibacterial activity, and excellent dye decomposition efficiency holds great promise for wastewater treatment. To explore design rationality and...

Catalytic removal of methylene blue with different stoichiometric ratios of ZnCuS nanoparticles

Photocatalytic decomposition of methylene blue (BM) solution by Cu-doped ZnS nanoparticles in the presence of UV light has been studied. The effect of the molar ratio of Cu ions affecting the rate of degradation reaction has been investigated. Photocatalytic reactivity of ZnS:Cu nanoparticles could be tailored by the proper amount of Cu ions. The maximum decolorizing efficiency (85%) of 5 ppm MB was obtained by 30 mgL−1 nanoparticles containing 2 wt% Cu, which was ascribed to the most effective surface area of these particles. However, at more than 2 wt% Cu doping concentration, nanoparticles aggregated due to their high surface energy, and the decomposition efficiency was decreased.