Nitrogen-Doped Titanium Dioxide Mixed with Calcium Peroxide and Methylcellulose for Dental Bleaching under Visible Light Activation

The available tooth whitening products in the market contain high concentrations of hydrogen peroxide (H₂O₂) as an active ingredient. Therefore, in order to curb the high H₂O₂ concentration and instability of liquid H₂O₂, this study evaluated the efficacy and cytotoxicity of the bleaching gel composed of 10% calcium peroxide (CaO₂) and visible-light-activating nitrogen-doped titanium dioxide (N-TiO₂) with methyl cellulose as a thickener. Extracted bovine teeth were discolored using coffee and black tea stain solution and were divided into two groups (n = 6). Bleaching was performed thrice on each tooth specimen in both the groups, with one minute of visible light irradiation during each bleaching time. The CIELAB L*a*b* values were measured pre- and post-bleaching. The N-TiO₂ calcinated at 350 °C demonstrated a shift towards the visible light region by narrowing the band gap energy from 3.23 eV to 2.85 eV. The brightness (ΔL) and color difference (ΔE) increased as bleaching progressed each time in both the groups. ANOVA results showed that the number of bleaching significantly affected ΔE (p < 0.05). The formulated bleaching gel exhibits good biocompatibility and non-toxicity upon exposure to 3T3 cells. Our findings showed that CaO₂-based bleaching gel at neutral pH could be a stable, safe, and effective substitute for tooth whitening products currently available in the market.     

具有可见光催化活性的TiO2系光催化剂研究进展

由于受激发波长的限制，TiO2只能利用太阳能中不足5％的紫外光。本文较为详细NTiO2可见光催化剂的制备、性能及应用进行了综述。研究表明，通过金属及非金属离子掺杂改性、离子注入以及染料光敏化等方法可以将TiO2光催化反应红移到可见光区域进行。     

Selectivity of Silicon Carbide/Stainless Steel Solid-State Reactions and Discontinuous Decomposition of Silicon Carbide

Solid-state reactions of SiC with a multicomponent system, stainless steel, have been studied at 1125°C. Four-layered reaction products consisting of modulated carbon precipitation zone, random carbon precipitation zone, four-phase mixture zone, and grain-boundary precipitation zone were formed in the reaction zone. The carbon precipitates were embedded in a matrix of complex metal silicides. In addition, extensive interfacial melting was noted. Carbon atom was found to diffuse faster than Si and selectively reacted with Cr to form Cr carbide(s) along the grain boundaries of stainless steel. No Fe carbides or Ni carbides were ever detected. Among the consituents existing in stainless steel, Ni atoms have the highest affinity for Si. An uphill diffusion of Ni toward the SiC reaction front was observed. While the diffusion of Cr and Fe toward SiC followed a downhill concentration gradient, very small amounts of Cr reached the SiC interface. The selective reactions of Si and C with Ni, Fe, and Cr are discussed on the basis of Gibbs free energy of formation of various compounds. The diffusion kinetics of C and Si atoms in selected metal/SiC reactions are discussed on the basis of their chemical affinities for respective metals. The modulation of carbon precipitation is correlated with previous results from Ni/SiC, Ni₃Al/SiC, Fe/SiC, Co/SiC, and Pt/SiC, reactions. A general model describing discontinuous decomposition of SiC is proposed to explain the origin of carbon modulation.     

Kinetics of Solid-State Reactions in Heterogeneous Catalysis from Time-Resolved X-Ray Absorption Spectroscopy

The potentials of X-ray absorption spectroscopy (XAS) (quantitative phase composition and average valence together with a short-range order structure analysis) combined with a time-resolution in the second range make time-resolved (TR-) XAS a powerful tool for investigating the reactivity of solids in catalysis and solid-state chemistry. General aspects of TR-XAS investigations are discussed (i.e., instrumentation, data analysis). In addition, some experiments illustrate how the kinetics of solid-state reactions in heterogeneous catalysis can be elucidated from TR-XAS studies.     

钒酸盐掺杂二氧化钛可见光响应的复合光催化剂的研究进展

开发可见光响应和高效稳定的二氧化钛基复合光催化剂是当前的研究热点之一.本文介绍了高活性、高稳定性的窄带隙半导体材料钒酸盐掺杂二氧化钛复合光催化剂的研究进展,重点讨论了钒酸盐掺杂二氧化钛的光催化机理,列举了国内外所取得的成果.     

Calibration and Intercomparison of Filter-Based Measurements of Visible Light Absorption by Aerosols

Data on light absorption by atmospheric particles are scarce relative to the need for global characterization. Most of the existing data come from methods that measure the change in light transmission through a filter on which particles are collected. We present a calibration of a recently developed filter-based instrument for continuous measurement of light absorption (model PSAP, Radiance Research, Seattle, WA) that has been incorporated in several measurement programs. This calibration uses a reference absorption determined as the difference between light extinction and light scattering by unaltered (suspended) particles. In addition, we perform the same calibration for two other common filter-based methods: an Integrating Plate and the Hybrid Integrating Plate System. For each method, we assess the responses to both particulate light scattering and particulate light absorption. We find that each of the instruments exhibits a significant response to nonabsorbing aerosols and overestimates absorption at 550 nm by suspended particles by about 20-30%. We also present correction factors for the use of the PSAP.     

可见光响应的二氧化钛复合材料抗菌活性及机理研究

研究不同纳米二氧化钛复合材料抗菌活性和抑菌率,选择更为有效的纳米二氧化钛复合抗菌材料。通过牛津杯法确定材料的抗菌活性,振荡摇瓶法测定抑菌率,通过扫描电镜探索抗菌机理。复合材料(纳米Ti O2、氧化石墨烯、硫化镉三种材料复合而成)对大肠杆菌抑菌率可达80.5%,对金黄色葡萄球菌抑菌率可达87.5%;氧化石墨烯能够提高二氧化钛可见光的抗菌活性和抑菌率;抗菌材料作用后的细菌表面凹凸不平,胞容物流出,菌体萎缩死亡。     

加氢改性二氧化钛的可见光光催化性能研究

针对二氧化钛的禁带宽度大、太阳能利用率低的问题,对合成的纳米二氧化钛部分加氢还原改性,制备了可见光响应二氧化钛光催化材料。水热法合成了锐钛矿相的二氧化钛纳米粒子,用高压低温加氢还原和常压高温加氢还原两种方法进行改性,用X射线粉末衍射仪、扫描电子显微镜表征其结构和形貌,用固体紫外漫反射光谱研究其光响应范围,以罗丹明B的可见光降解反应为探针反应,初步研究其光催化性能,结果表明常压高温加氢处理后的锐钛矿二氧化钛纳米粒子具有更好的可见光光催化性能。     

Meso-C@TiO2 @Ag复合光催化剂的制备及其可见光催化性能

采用混合溶剂法,通过改变钛酸四丁酯(TBOT)的量合成一系列不同比例的RF@TiO2核-壳结构,于氮气气氛600℃下煅烧得到meso-C@TiO2,进一步对所得产物表面进行贵金属沉积最终得到meso-C@TiO2@Ag复合光催化剂.通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、全自动比表面积及微孔物理吸附仪(BET)等对样品的成份、形貌和结构进行了表征.结果表明,成功制备了meso-C@TiO2@Ag三元介孔复合光催化材料,并且比表面积达到173.9 m2/g.在可见光照射下,以降解亚甲基蓝为模型,探讨了TBOT用量以及Ag负载量对产物光催化性能的影响.研究发现,当加入TBOT的量为0.3mL、AgNO3的投入量为10wt％时,所制备的meso-C@TiO2@Ag对亚甲基蓝的降解效果最佳,40 min内降解率接近100％,性能明显优于市售的纳米二氧化钛P25.     

非金属掺杂对TiO2可见光吸收影响的研究现状

TiO2在光催化领域有广阔的应用前景,但大的禁带宽度限制其不能有效利用太阳能,当前研究的重点是开发能有效利用太阳光的光催化剂.许多研究通过表面改性和掺杂过渡金属离子扩大光谱响应吸收范围和提高光催化活性,概述了近年来关于TiO2改性的工艺、机理及优缺点,重点总结了非金属元素掺杂的研究,并对今后的研究作了展望.     

光稳定剂复配对核壳WPC抗紫外老化性能的影响

为探索经济、环保且效果更好的木塑复合材料(WPC)表面耐老化处理方法,采用共挤技术,以不同复配方式将纳米白炭黑、HALS–L944及UV327添加于核壳型WPC壳层。对试样进行紫外光加速老化试验,并对其弯曲性能、表面颜色及化学成分结构进行了测试表征与方差分析。研究结果表明,当壳层加入1%纳米白炭黑与1%UV327复配时效果最好,紫外老化2 500 h后,较之空白样,WPC的弯曲强度保留率提高了14.7%,弹性模量保留率提高了17.4%,保护效果最好,具有一定的协同作用;表面颜色变化较为缓慢,色差下降了44.9%,优于单独添加光稳定剂效果;O/C值增长幅度为9.1%,氧化的碳/未氧化的碳比值增加了11.8%,表面氧化程度最低。说明纳米白炭黑与UV327具有一定的协同作用,能够更好地提高核壳WPC的抗紫外老化性能,降低其光氧化降解程度。     

碳化硅—二硼化钛系多层陶瓷复合材料的制取与性能

介绍了制取多层陶瓷用的材料和方法 ,讨论了一些因素对材料性能的影响 ,并给出了几种复合材料的组成     

AgBr/TiO_2复合催化剂:双注法制备及其可见光催化性能

以TiO2为载体,采用双注法合成了AgBr/TiO2复合光催化剂.利用X射线衍射仪(XRD)、紫外可见分光光度计(UV-Vis)和扫描电子显微镜(SEM)对AgBr/TiO2的结构、光吸收、形貌进行了表征.研究了AgBr/TiO2在可见光下对甲基橙和丁基罗丹明B的光催化活性.结果表明,与TiO2相比,AgBr/TiO2的光吸收范围拓展到400—600nm波段,并且随着AgBr负载量的增加,AgBr/TiO2的可见光吸收强度增强;当AgBr与TiO2的摩尔比为0.25时,AgBr/TiO2具有最大催化活性;在相同条件下,AgBr/TiO2对丁基罗丹明B的降解效果优于甲基橙.     

N和Al共掺杂TiO2粉体的固相合成及可见光降解性能

采用固相反应法合成了N与Al共掺杂TiO2(N-Al-TiO2)粉体材料,利用XRD,UV-Vis,N2吸附及XPS等对其进行了物相织构表征,并研究了可见光辐照下催化剂对中性红的降解性能.结果表明,N和Al均进入TiO2晶格或晶格间隙,材料表面不仅存在替位取代形成的N-Ti-O与Ti-O-Al键,且存在间隙掺杂形成的T...     

纳米Cu-Zn复合氧化物自组装合成及可见光催化性能

采用阴阳离子表面活性剂复合囊泡相为软模板,自组装合成了Cu-Zn复合氧化物纳米材料,分析了自组装过程。研究了铜的掺杂量对纳米材料的形貌、晶型、能级变化以及电子结构的影响,评价了不同铜掺杂量的ZnO-CuO样品光催化性能。结果表明,随着铜掺杂量的增加,样品ZnO-CuO中ZnO的X射线衍射(XRD)特征峰强度逐渐降低;形貌由多面体晶粒转向片层结构;铜的引入使ZnO的发光能级发生变化,并随着铜离子的量增加,光生载流子浓度变小。可见光催化结果显示,样品ZnO-CuO光催化性能随掺杂铜离子量的增加先增加后减弱。在金属离子Cu2+和Zn2+物质的量之比为5:95时光催化效果为最佳。     

Ag@AgCl-TiO2-粉煤灰微珠复合光催化剂的制备及其可见光光催化性能

采用离子交换法在粉煤灰微珠(FMS)表面沉积Ag@AgCl纳米颗粒,制备Ag@AgCl-FMS复合基底,采用水解-沉淀工艺,以TiCl4为钛源在复合基底表面再包覆纳米TiO2薄膜,经500℃煅烧2 h后得到Ag@AgCl- FMS-TiO2复合光催化剂. 对材料微观形貌、晶体结构、可见光光催化性能进行了表征与测试. 结果表明,复合基底表面包覆的TiO2薄膜均匀完整. 500℃煅烧后的物相为90%锐钛矿型TiO2和10%金红石型TiO2. 复合催化剂料在Ag@AgCl等离子共振效应的作用下,表现出明显的可见光响应,经可见光照射80 min后对甲基橙的降解率达99%,5次重复使用对甲基橙的降解率保持在85%.     

CeO_2-CdS/埃洛石纳米管的制备及可见光催化性能

采用微波辐射法制备埃洛石纳米管(HNTs)负载CeO_2-CdS复合材料CeO_2-CdS/HNTs。用X射线衍射、透射电子显微镜、紫外-可见漫反射光谱、Fourier变换红外光谱等对CeO_2-CdS/HNTs样品结构和形貌进行表征,考察了可见光下降解亚甲基蓝的光催化活性,讨论了CeO_2/CdS摩尔比对光催化剂活性的影响。结果表明:纳米颗粒CeO_2、CdS以紧密结合的形式牢固的负载在HNTs表面,二者具有协同催化作用。当CeO_2/CdS摩尔比为3:7时,80 min内亚甲基蓝的降解率可达95%。     

一步富氧煅烧法制备长可见光吸收的WO3及其水氧化性能

三氧化钨(WO3)仅对460 nm以下波长的太阳光有响应,大大限制了其对太阳光的利用率.因此,如何拓宽WO3的光谱响应范围是当前的研究重点.本文以仲钨酸铵[(NH4)10H2W12O42·xH2O]为前驱体,通过一步富氧煅烧法制备了具有宽光谱可见光响应能力的N2插入的纳米WO3(N2-WO3).通过XRD、SEM、ED...     

Preparation of g-C3N4/MoS2 Composite Material and Its Visible Light Catalytic Performance

The g-C₃N₄ nanosheet was prepared by calcination method, the MoS₂ nanosheet was prepared by hydrothermal method. The g-C₃N₄/MoS₂ composites were prepared by ultrasonic composite in anhydrous ethanol. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible spectroscopy, and photoluminescence techniques were used to characterize the materials. The photocatalytic degradation of Rhodamine B (Rh B) by g-C₃N₄/MoS₂ composites with different mass ratios was investigated under visible light. The results show that a small amount of MoS₂ combined with g-C₃N₄ can significantly improve photocatalytic activity. The g-C₃N₄/MoS₂ composite with a mass ratio of 1:8 has the highest photocatalytic activity, and the degradation rate of Rh B increases from 50 to 99.6%. The main reason is that MoS₂ and g-C₃N₄ have a matching band structure. The separation rate of photogenerated electron–hole pairs is enhanced. So the g-C₃N₄/MoS₂ composite can improve the photocatalytic activity. Through the active material capture experiment, it is found that the main active material in the photocatalytic reaction process is holes, followed by superoxide radicals.