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91.
以TiCl4为原料,采用水解沉淀法,并在空气气氛下于不同温度煅烧2h,制备得到纳米TiO2。采用XRD、TEM及UV-Vis对样品进行表征。在卤钨灯照射下,研究了不同煅烧温度、不同pH值以及H2O2的加入等因素对TiO2光催化降解次甲基蓝的影响。结果表明:以水解沉淀法制备的纳米TiO2,随煅烧温度的提高,在600℃开始向金红石相转变,1000℃时全部转变为金红石相,并且TiO2粒子长大,吸收带边向长波方向移动。锐钛矿相与金红石相共存的纳米TiO2比纯锐钛矿相和金红石相有更优异的光催化活性,在卤钨灯下照射90min,对次甲基蓝的降解率达到97%。 相似文献
92.
A novel and general strategy to fabricate monodisperse hollow supraparticles (SPs) via selective chemical oxidation is developed. Core‐shell SPs made of semiconductor nanocrystals (NCs) are first obtained by an in situ assembly method. Subsequently, the cores can be selectively removed by preferential oxidation with dilute H2O2, resulting in formation of monodisperse hollow SPs. The structural parameters of the products, such as size, shell thickness, and composition, are tailored easily. The hollow structures achieved from CdSe/CdS core‐shell SPs possess high fluorescence quantum yields and a large Stokes shift, the latter is remarkably different from that of conventional organic dyes and quantum dots. In addition to simple hollow structures, rattle‐type nanostructures composed of semiconductor SPs or noble metal‐semiconductor hybrids are also prepared, exemplifying the versatility of the proposed strategy. 相似文献
93.
This paper investigates the morphology changes that occur with the oxidation of a ti-tanium silicide—polysilicon system. These
changes were studied as a function of poly-silicon doping and silicide formation parameters. Emphasis was placed on transmission
electron microscopy studies of the samples by planar and cross sectional techniques. Various surface analysis methods have
also been used to characterize the films. This study helps to define the possible use and shortcomings of a self aligned titanium
silicide insulator. The results show that varying quality insulators result, dependent largely on the initial conditions of
the titanium silicide. After oxidation the Auger and TEM anal-ysis show that in all cases some form of silicon dioxide was
created, but typically a considerable amount of titanium oxide was also present. For instance, it was apparent that more titanium
oxide formed on the samples RTA’ed for 1 min at 700° C than the 5 min at 800° C and considerably more on the arsenic doped
sample than the boron doped. The silicide also had morphology changes as the result of the oxidation. There was a phase change
from the C49 to C54 phase for the 1 min at 700° C samples as would be expected at the time and temperature of the oxidation.
There also was a sig-nificant amount of agglomeration and epitaxial growth observed. Further work is re-quired to completely
characterize these phenomena. 相似文献
94.
本文研究了有无氧化硅保护层时Al0.85Ga0.15As层的高温湿法氧化。实验结果表明:氧化硅层对Al0.85Ga0.15As层的高温侧向湿法氧化速率基本无影响;被氧化区域SEM图像的衬度和有氧化硅保护层样品As拉曼峰的缺乏归因于被氧化区域中不存在氧化反应产物As,这有利于提高氧化层的热稳定性;有SiO2保护层样品的发光强度比无SiO2保护层样品的发光强度强的多,且具有SiO2保护层样品的发光峰位和半高全宽与氧化前的样品基本一致,而无SiO2保护层样品的发光峰位红移,半高宽展宽,这是由于氧化硅层阻止了GaAs盖层的氧化。 相似文献
95.
Rui Tang Shujie Zhou Caixia Li Ran Chen Luyuan Zhang Zhiwei Zhang Longwei Yin 《Advanced functional materials》2020,30(19)
MXene materials have attracted increasing attention in electrochemical energy‐storage applications while MXene also becomes photo‐active at the quantum dot scale, making it an alternative for solar‐energy‐conversion devices. A Janus‐structured cobalt‐nanoparticle‐coupled Ti3C2 MXene quantum dot (Co‐MQD) Schottky catalyst with tunable cobalt‐loading content serving as a photoelectrochemical water oxidation photoanode is demonstrated. The introduction of cobalt triggers concomitant surface‐plasmon effects and acts as a water oxidation center, enabling visible‐light harvesting capability and improving surface reaction kinetics. Most importantly, due to the rectifying effects of Co‐MQD Schottky junctions, photogenerated carrier separation/injection efficiency can be fundamentally facilitated. Specifically, Co‐MQD‐48 exhibits both superior photoelectrocatalysis (2.99 mA cm?2 at 1.23 V vs RHE) and charge migration performance (87.56%), which corresponds to 194% and 236% improvement compared with MQD. Furthermore, excellent photostability can be achieved with less than 6.6% loss for 10 h cycling reaction. This fills in gaps in MXene material research in photoelectrocatalysis and allows for the extension of MXene into optical‐related fields. 相似文献
96.
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99.
Zhongliang Huang Longlong Fan Feigang Zhao Bin Chen Kaiji Xu Shu‐Feng Zhou Jinli Zhang Qingbiao Li Dan Hua Guowu Zhan 《Advanced functional materials》2019,29(42)
Hybrid metal oxides with multilayered structures exhibit unique physical and chemical properties, particularly important to heterogeneous catalysis. However, regulations of morphology, spatial location, and shell numbers of the hybrid metal oxides still remain a challenge. Herein, binary Co3O4/ZnO nanocages with multilayered structures (up to eight layers) are prepared via chemical transformation from diverse Matryoshka‐type zeolitic imidazolate frameworks (ZIFs) via a straightforward and scalable calcination method. More importantly, the obtained ZIF‐derived metal oxides (ZDMOs) with versatile layer numbers exhibit remarkable catalytic activity for both gas‐phase CO oxidation and CO2 hydrogenation reactions, which are directly related to the sophisticated shell numbers (i.e., Co3O4‐terminated layers or ZnO‐terminated layers). Particularly, in situ reflectance infrared Fourier transform spectroscopy (DRIFTS) results indicate that the promotional effects of the multilayered structures indeed exist in CO2 hydrogenation, wherein the key reaction intermediates are quite different for five‐layer and six‐layer ZDMOs. For instance, *HCOO is the predominant intermediate over the six‐layer ZDMO; on the contrary, *H3CO is the crucial species over the five‐layer ZDMO. The ZnO/Co3O4 interface should be the active sites for CO2 hydrogenation to *HCOO and *H3CO species, which are ultimately converted to the products (CH4 or methanol). Accordingly, the work here provides a convenient way to facilely engineer multilayered Co3O4/ZnO nanocomposites with precisely controlled shell numbers for heterogeneous catalysis applications. 相似文献
100.