Influence of fluoride on f-f transitions of Eu in LiEuM2O8 (M=Mo, W)

The influence of fluoride on the luminescence of LiEuM₂O₈ (M=Mo, W) was studied. LiEuMo₂O₈ and LiEuW₂O₈ formed the whole range of solid solutions, which emitted intense red luminescence under the excitations by 395, 465 and 535 nm wavelengths. When doped with fluoride, the materials also formed solid solutions and the luminescent intensity was remarkably enhanced. The phosphor with optimized compositions in this system would be a promising red component for solid-state lighting devices based on GaN light-emitting diodes.     

A simple and general method for the synthesis of multicomponent Na2V6O16.3H2O single-crystal nanobelts

Multicomponent Na2V6O16.3H2O (barnesite) single-crystalline nanobelts were synthesized by a direct reaction-crystallization growth of bulk V2O5 and NaF powders under hydrothermal treatment without using any templates or catalysts. This new strategy could be extended to prepare other one-dimensional multicomponent nanomaterials including ammonium, alkali-metal or alkali-earth metal vanadium oxide bronzes and other transition metal oxyfluorides. This is an efficient and mild solution method with clear advantages over the traditional high-temperature approach for the large-scale production of 1D multicomponent nanomaterials. The applicability of this approach toward the preparation of other inorganic systems, such as tungstates and molybdates, will be explored.     

Characterization of mesoporous nanocrystalline TiO2 photocatalysts synthesized via a sol-solvothermal process at a low temperature

Nanocrystalline TiO₂ samples with mesoporous structure were prepared via a solvothermal treatment of surfactant-stabilized TiO₂ sols. The samples were obtained from media of different acidities including nitric acid, deionized water, and ammonia (denoted as HT-1, HT-2 and HT-3, respectively). These samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂-sorption (BET surface area), micro-Raman spectroscopy, infrared absorption spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the samples were tested by the self-photosensitized degradation of an azo dye, Mordant Yellow 10 (MY), in aqueous solution under visible light irradiation. The results reveal that all three samples have high surface area and are pure anatase phase. The sample prepared in nitric acid medium possesses the most ideal mesoporous structure and also exhibits a blue shift in the Raman spectrum. All three samples show much higher photocatalytic activity than the commercial P-25. The activity order of the three samples is HT-1>HT-2>HT-3.     

The Effect of SiO2 Addition on the Grain Size and Photocatalytic Activity of TiO2 Thin Films

The uniform transparent TiO₂/SiO₂ nanometer composite thin films were prepared via sol-gel method on the soda lime glass substrates, and were characterized by X-ray photoelectron spectroscopy (XPS), FTIR spectroscopy, UV-VIS spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and BET surface areas. It was found that the addition of SiO₂ to TiO₂ thin films could suppress the grain growth of TiO₂ crystal and increase the hydroxyl content of the surface of TiO₂ films. The photocatalytic activity of the as-prepared TiO₂/SiO₂ composite thin films increases for SiO₂ content of less than 5 mol%.     

A Renal‐Clearable Duplex Optical Reporter for Real‐Time Imaging of Contrast‐Induced Acute Kidney Injury

Despite its high morbidity and mortality, contrast‐induced acute kidney injury (CIAKI) remains a diagnostic dilemma because it relies on in vitro detection of insensitive late‐stage blood and urinary biomarkers. We report the synthesis of an activatable duplex reporter (ADR) for real‐time in vivo imaging of CIAKI. ADR is equipped with chemiluminescence and near‐infrared fluorescence (NIRF) signaling channels that can be activated by oxidative stress (superoxide anion, O₂^.?) and lysosomal damage (N‐acetyl‐β‐d ‐glucosaminidase, NAG), respectively. By virtue of its high renal clearance efficiency (80 % injected doses after 24 h injection), ADR detects sequential upregulation of O₂^.? and NAG in the kidneys of living mice prior to a significant decrease in glomerular filtration rate (GFR) and tissue damage in the course of CIAKI. ADR outperforms the typical clinical assays and detects CIAKI at least 8 h (NIRF) and up to 16 h (chemiluminescence) earlier.     

水分子在均三嗪基g-C3N4上的吸附

气体分子与光催化剂之间的相互作用对于光催化反应的触发非常重要.对于TiO2,ZnO和WO3等传统金属氧化物光催化剂上的水分解反应而言,已有许多报道研究了水分子在它们表面的吸附行为.结果表明,水分子与催化剂表面的原子形成了O-H…O氢键.石墨相氮化碳(g-C3N4)是一种具有可见光响应且化学性质稳定的光催化剂,对其进行修饰以增强其分解水产氢性能的研究非常多.本文通过密度泛函理论计算,全面研究了水分子在均三嗪(s-triazine)基g-C3N4上的吸附情况.首先构建了一系列初始吸附模型,考察了各种吸附位和水分子的朝向.通过比较分析计算得到的吸附能,确定了一种最优的吸附构型,即水分子以竖直的朝向吸附于褶皱的单层g-C3N4表面.水分子中的一个极性O-H键与g-C3N4中一个二配位富电子的氮原子结合形成了分子间的O-H…N氢键.其中,H原子与N原子的间距为1.92?,O-H键的键长由0.976?增至0.994?.进一步通过计算Mulliken电荷,态密度和静电势曲线分析了该吸附体系的电子性质.结果发现在分子间氢键的桥接作用下,g-C3N4上的电子转移至水分子,由此导致g-C3N4的费米能级降低,功函数由4.21 eV增至5.30 eV.在该吸附模型的基础上,考查了不同的吸附距离.当水分子与g-C3N4的间距设为1至4?时,几何优化后总是能得到相同的吸附构型,吸附能和氢键长度也十分相近.随后,通过改变吸附基底g-C3N4的大小和形状,验证了这种吸附构型具有很强的重复性.将2′2单层g-C3N4吸附基底替换为2′2多层g-C3N4(2至5层),3′3和4′4单层g-C3N4,以及具有不同管径的单壁g-C3N4纳米管后,水分子的吸附能随着体系原子数的增多而增大,但吸附模型的几何结构和电子性质基本不变,包括O-H…N氢键的形成和键长,以及电子转移和增大的功函数.另外还研究了非金属元素(P,O,S,Se,F,Cl和Br)掺杂对吸附能的影响.构建模型时,杂质原子以取代二配位氮原子的方式进行掺杂,水分子放置于杂质原子上方.结果显示,引入杂质原子后水分子的吸附能增大,在理论上从吸附的角度解释了元素掺杂增强g-C3N4分解水活性.总之,本文揭示了一种在分子间氢键的作用下,具有高取向性的水分子吸附的g-C3N4构型,这有助于g-C3N4基光催化剂上水分解过程的理解和优化设计.     

可见光铋系光催化剂的研究进展

当前工业发展导致了严重的能源和环境危机,光催化为这一难题提供了有效的解决方案.然而在实际应用中,传统氧化物光催化剂宽的带隙限制了它的可见光吸收,于是窄带隙光催化剂成为了研究的热点.其中铋系光催化剂以其高的可见光光催化活性引起了人们的广泛关注.因此本文介绍了铋系光催化剂的种类、制备、形貌、复合、性能等方面的研究现状,并展望了含铋可见光催化剂发展前景.     

Designing a 0D/2D S‐Scheme Heterojunction over Polymeric Carbon Nitride for Visible‐Light Photocatalytic Inactivation of Bacteria

Constructing heterojunctions between two semiconductors with matched band structure is an effective strategy to acquire high‐efficiency photocatalysts. The S‐scheme heterojunction system has shown great potential in facilitating separation and transfer of photogenerated carriers, as well as acquiring strong photoredox ability. Herein, a 0D/2D S‐Scheme heterojunction material involving CeO₂ quantum dots and polymeric carbon nitride (CeO₂/PCN) is designed and constructed by in situ wet chemistry with subsequent heat treatment. This S‐scheme heterojunction material shows high‐efficiency photocatalytic sterilization rate (88.1 %) towards Staphylococcus aureus (S. aureus) under visible‐light irradiation (λ≥420 nm), which is 2.7 and 8.2 times that of pure CeO₂ (32.2 %) and PCN (10.7 %), respectively. Strong evidence of S‐scheme charge transfer path is verified by theoretical calculations, in situ irradiated X‐ray photoelectron spectroscopy, and electron paramagnetic resonance.     

A Blinking Mesoporous TiO2−x Composed of Nanosized Anatase with Unusually Long‐Lived Trapped Charge Carriers

A mesoporous TiO_2?x material comprised of small, crystalline, vacancy‐rich anatase nanoparticles (NPs) shows unique optical, thermal, and electronic properties. It is synthesized using polymer‐derived mesoporous carbon (PDMC) as a template. The PDMC pores serve as physical barriers during the condensation and pyrolysis of a titania precursor, preventing the titania NPs from growing beyond 10 nm in size. Unlike most titania nanomaterials, during pyrolysis the NPs undergo no transition from the anatase to rutile phase and they become catalytically active reduced TiO_2?x. When exposed to a slow electron beam, the NPs exhibit a charge/discharge behavior, lighting up and fading away for an average period of 15 s for an extended period of time. The NPs also show a 50 nm red‐shift in their UV/Vis absorption and long‐lived charge carriers (electrons and holes) at room temperature in the dark, even long after UV irradiation. The NPs as photocatalysts show a good activity for CO₂ reduction.     

Preparation and photocatalytic behavior of MoS2 and WS2 nanocluster sensitized TiO2

A new approach has been developed for the fabrication of visible light photocatalysts. Nanoclusters of MoS2 and WS2 are coupled to TiO2 by an in situ photoreduction deposition method taking advantage of the reducing power of the photogenerated electrons from TiO2 particles. The photocatalytic degradation of methylene blue and 4-chlorophenol in aqueous suspension has been employed to evaluate the visible light photocatalytic activity of the powders. The blue shift in the absorption onset confirms the size quantization of MS2 nanoclusters, which act as effective and stable sensitizers, making it possible to utilize visible light in photocatalysis. Quantum size effects alter the energy levels of the conduction and valence band edges in the coupled semiconductor systems, which favors the interparticle electron transfer. In addition, the coupled systems are believed to act in a cooperative manner by increasing the degree of charge carrier separation, which effectively reduces recombination.