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Metal Sulfide Photocatalysis: Visible-Light-Induced Organic Transformations
摘要： Transition-metal sulfides belong to an important subgroup of semiconductor photocatalysts that could promote a variety of valuable redox reactions under mild conditions. One notable merit of metal sulfides is their relatively smaller bandgaps than metal oxides, which in turn make sure that many of them can directly utilize visible light. Historically, the deployment of metal sulfides for visible-light-induced organic transformations took place shortly after the genesis of the research field of heterogeneous photocatalysis. In this review, we primarily focus on recent state-of-the-art advancements of metal sulfide photocatalysis aimed at visible-light-induced selective organic transformations. Interests in this specific branch of photocatalysis have been rekindled due to the new methods for materials synthesis; the pursuit of new mechanisms; or the integration of metal sulfides with metal oxides, metal nanoparticles or other emerging materials. Thus we categorize them into four sections according to the different strategies in developing novel or more efficient organic processes. Binary and ternary metal sulfides, usually associated with new materials synthesis and mechanistic insights, can be used directly for visible-light-induced organic transformations. This is the basis of other further developments and will be introduced firstly. Next, the cooperation between metal sulfides and metal oxides or metal nanoparticles can be conducive to many photocatalytic systems. These developments will be discussed in the next two ensuing sections. Furthermore, the integration of metal sulfides with recent developed emerging materials such as metal-organic frameworks (MOFs), graphene and graphitic carbon nitride (g-C3N4) would be discussed in another section to highlight the importance of merging metal sulfides with these materials. We attempt to keep an impartial panorama of these four distinctive sections even though the phases of development are quite different among sections, leaving plenty of room for the future expansion of this burgeoning area.
关键词： Metal Sulfide,Selective Oxidation,Photocatalysis,Visible Light,Selective Reduction
更新于2025-09-23 15:23:52
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Design and characterization of the double-layered defected ground structure transmission line with less radiation loss
摘要： A double-layered DGS transmission line is proposed with a smaller DGS size and less radiation loss. Changing the air boundary to a dielectric boundary reduces the effective electric length at the DGS aperture area. An equivalent circuit model is introduced to analyze the DGS transmission line and the resonator circuit designs. Due to the increase in the effective dielectric constant, the proposed structure can be realized with less sensitivity to metallic environments. From the experimental results, the proposed double-layered DGS can achieve a reduction of 90.1% in size and insensitivity at up to 5 mm of separation from the DGS aperture to the metallic plate.
关键词： equivalent circuit models,effective dielectric constants,radiation loss,size reduction,defected ground structures
更新于2025-09-23 15:23:52
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Survey of Object-Based Data Reduction Techniques in Observational Astronomy
摘要： Dealing with astronomical observations represents one of the most challenging areas of big data analytics. Besides huge variety of data types, dynamics related to continuous data flow from multiple sources, handling enormous volumes of data is essential. This paper provides an overview of methods aimed at reducing both the number of features/attributes as well as data instances. It concentrates on data mining approaches not related to instruments and observation tools instead working on processed object-based data. The main goal of this article is to describe existing datasets on which algorithms are frequently tested, to characterize and classify available data reduction algorithms and identify promising solutions capable of addressing present and future challenges in astronomy.
关键词： feature extraction,astronomy,dimensionality reduction,big data,data condensation
更新于2025-09-23 15:23:52
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Expansion of the Supply of Solar Energy and Cost Cutting of Housing Programs for Low-Income and Middle Class Families
摘要： The purpose of this article to reconcile two public policy objectives: to provide housing for low-income families (through the expansion of the Minha Casa, Minha Vida (My Home, My Life) Program) with reduction of costs, and to expand the supply of renewable (solar) energy to dilute the harmful effects on the environment of the excessive use of energy from hydroelectric and thermal sources. The idea is not new, as similar programs already exist in Germany that invests heavily in solar power. What is encouraging is the amplitude of solar power generation that can be achieved in Brazil. Solar energy accounts for 40% of the global energy mix as opposed to Brazil’s share of 0.01%, showing enormous potential for expansion, as we are blessed with considerable year-round solar energy, unlike countries with very unstable weather conditions. We show that the cost to install solar panels and batteries for a low-income three-member family with the sale of surplus energy to a power distribution concessionaire represents an approximate increase of R$ 48,000 on the total amount that they already pay for their home loan. However, these families will actually pay around 40% of the funding, as the balance is deducted from the surplus value generated by the photovoltaic system. The total generation of solar energy would reach 164TWh with this program — today it is 11MWh —, climbing steeply from a 0.01% share in the composition of the mix to over 31% of the national power generation. This proposal also provides an increase in the disposable income of families participating in housing programs and reduces the subsidy for housing programs.
关键词： reduction of subsidies for affordable housing,solar energy,renewable energy
更新于2025-09-23 15:23:52
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Growth and Self-Assembly of Silicon–Silicon Carbide Nanoparticles into Hybrid Worm-Like Nanostructures at the Silicon Wafer Surface
摘要： This work describes the growth of silicon–silicon carbide nanoparticles (Si–SiC) and their self-assembly into worm-like 1D hybrid nanostructures at the interface of graphene oxide/silicon wafer (GO/Si) under Ar atmosphere at 1000 °C. Depending on GO film thickness, spread silicon nanoparticles apparently develop on GO layers, or GO-embedded Si–SiC nanoparticles self-assembled into some-micrometers-long worm-like nanowires. It was found that the nanoarrays show that carbon–silicon-based nanowires (CSNW) are standing on the Si wafer. It was assumed that Si nanoparticles originated from melted Si at the Si wafer surface and GO-induced nucleation. Additionally, a mechanism for the formation of CSNW is proposed.
关键词： nanoparticles,thermal reduction,silicon carbide,graphene oxide,self-assembly,silicon,nanowires
更新于2025-09-23 15:23:52
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On-site identification of psychoactive drugs by portable Raman spectroscopy during drug-checking service in electronic music events
摘要： Introduction and Aims. Hundreds of new psychoactive substances (NPS) have burst into the marketplace, making both the scientific community and people who use drugs lacking of adequate information about their diffusion and effects. In this scenario, drug-checking services have been recently proposed to assist harm reduction policies and provide a global description of the circulating drugs. Design and Methods. The results obtained by a portable Raman spectroscopy device on 472 alleged drugs within the first formal implementation of drug checking in Italy, are reported. The testing was made through a plastic bag held by the applicant and containing the alleged drug. The substance identification was executed by comparison with a spectral library. Results. Illicit substances were detected in 304 samples. Findings included MDMA (106 samples), ketamine (87 samples), cocaine (51 samples), amphetamine (47 samples), methamphetamine (two samples), heroin (two samples) and NPS (nine samples). Two samples were identified as precursors of psychoactive substances. Identification of a non-controlled substance occurred in 38 samples. Output of inconclusive result was recorded from 128 samples tested on-site, from which the applicant allowed us to collect a small portion in 68 cases, for a delayed laboratory analysis by GC–MS or LC–MS/MS. Discussion and Conclusions. Drug checking by Raman spectroscopy proved effective to identify psychoactive drugs including NPS and track the drug distribution in various recreational settings. The field testing activity revealed the presence of several NPS in the nightlife scenario, often in replacement of traditional illicit drugs, thus posing a high overdose risk and a life-threatening situation.
关键词： drug checking,harm reduction,Raman,NPS
更新于2025-09-23 15:23:52
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Radar cross section reduction metasurfaces based on phase gradient and chessboard structure
摘要： In this article, wideband radar cross section (RCS) reduction metasurface is proposed. The unit of the metasurface is consisted of a noncentral symmetry hexagon patch with 2 semi-circular slots at the symmetric corners. As a result, the unit has an anisotropic response for x- and y-polarized wave. The reflection phase is varied with the radius of slots. The range of phase variation is extended by rotation of the unit with 90°. According to the generalized Snell’s Law, 4 different phase gradient supercells with dual polarization characteristics and different gradient directions are obtained. To improve the RCS reduction, chessboard structure is used. By combining these 2 technological approaches, a wideband, polarization insensitive RCS reduction is designed, which can reflect the electromagnetic wave uniformly. Both numerical and measured results show that it enables to realize a 10 dB RCS reduction in a wideband from 8.5 to 13 GHz.
关键词： chessboard structure,metasurface,phase gradient,RCS reduction,phase variation
更新于2025-09-23 15:23:52
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A novel Z-scheme Ag3VO4/BiVO4 heterojunction photocatalyst: Study on the excellent photocatalytic performance and photocatalytic mechanism
摘要： A novel three-dimensional microspheres mediator-free Z-scheme Ag3VO4/BiVO4 heterojunction photocatalyst was successfully obtained for the first time. The photocatalytic performance of the as-prepared photocatalyst was systematically examined via the photocatalytic reduction of Cr6+ and oxidation of Bisphenol S under visible-light irradiation. Among these samples, 0.24-Ag3VO4/BiVO4 exhibits the highest photocatalytic performances, the photocatalytic reduction and oxidation efficiency of 74.9 and 94.8 %, respectively, can be achieved. The enhanced photocatalytic performance is attributed to the build-in electric field assisted charge transfer between the Ag3VO4 and BiVO4, and the increasing lifetime of the charge carrier confirmed by the results of time-resolved fluorescence spectra and photoelectrochemical measures. Moreover, based on the results of free radical scavenging activity test, and EPR experiments, it has been verified that the Ag3VO4/BiVO4 heterostructures follow a typical Z-scheme charge transfer mechanism rather than conventional type-II heterojunction charge transfer mechanism. Furthermore, the theoretical understanding of the underlying mechanism was also supported, while the energy band structure, and Fermi level were systematically calculated using the density functional theory approach. The results show that a built-in electric field directed from Ag3VO4 to BiVO4 surface was established as an equalized Fermi level was reached, which benefits the separation of photogenerated charge carriers in the way of a Z-scheme charge transfer mechanism. The strategy to form the three-dimensional microspheres Z-scheme heterojunction photocatalyst may offer new insight into the Z-scheme charge transfer mechanism for applications in the field of solar energy conversion.
关键词： Bismuth Vanadate,Z-scheme heterojunction photocatalyst,photocatalytic reduction and oxidation.
更新于2025-09-23 15:23:52
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Photocatalysis as an advanced reduction process (ARP): the reduction of 4-nitrophenol using titania nanotubes-ferrite nanocomposites
摘要： TiO2 photocatalysis is an advanced process, employed worldwide for the oxidation of organic compounds, that leads to significant technological applications in the fields of health and environment. The use of the photocatalytic approach in reduction reactions seems very promising and can open new horizons for green chemistry synthesis. For this purpose, titanium dioxide nanotubes (TNTs) were developed in autoclave conditions using TiO2 P25 as a precursor material. Based on these nanotubular substrates, TiO2/CoFe2O4 (TCF) nanocomposites were further obtained by wet impregnation method. The materials were thoroughly characterized and their structural, textural, vibrational, optoelectronic and magnetic properties were determined. The composite materials combine absorbance in the visible optical range and high BET surface area values (~100 m2/g), showing extremely high yield in the photocatalytic reduction of 4-nitrophenol (4-NP), exceeding 94% within short illumination time (only 35 min). The developed nanocomposites were successfully reused in consecutive photocatalytic experiments and were easily removed from the reaction medium using magnets. Both remarkable recycling ability and high-performance stability in the photocatalytic reduction of nitrophenol were observed, thus justifying the significant economic potential and industrial perspectives for this advanced reduction process.
关键词： Cobalt ferrite,4-nitrophenol reduction.,Nanocomposite photocatalyst,TiO2 nanotubes
更新于2025-09-23 15:23:52
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Hydrogen reduction characteristics of WO3 based on density functional theory
摘要： The ?rst principle theory in DFT (Density Function Theory) was applied to study the hydrogen adsorption on O-terminated and WO-terminated surface of WO3 (0 0 1). The exploration of the two terminated surfaces structure and hydrogen adsorption characteristics was conducted from the micro-structure point of view. The result indicates that energy of O-terminated surface with enriched oxygen is higher than the WO-terminated surface with less oxygen. The chemical adsorption occurs when the distance between hydrogen molecules and surface atom ranged from 0.6 ? to 0.8 ?, while the physical adsorption occurs when the distance was bigger than 0.8 ?. The energy of hydrogen adsorption on O-terminated surface is lower than energy of hydrogen adsorption on WO-terminated surface, the chemical adsorption of hydrogen is easier to happen compare to physical adsorption. The energy of hydrogen adsorption on O1c on O-terminated surface is lower than energy of hydrogen adsorption on O2c on the same surface. The adsorption of hydrogen not only changes the structure of surfaces of WO3 and cause the conducting electrons jumping into valence band and energy declining but also make a part of electrons in orbit 2p of O to jump into orbit 5p of W.
关键词： Hydrogen adsorption,First principle,Density of states,Reduction,WO3
更新于2025-09-23 15:23:52