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Size tunable and structure tailored core-shell-shell nanospheres containing silica cores, gold nanoparticle shells, and controlled thicknesses of smooth, corrugated, or porous silica shells over the gold nanoparticles have been synthesized. The synthesis involved the deposition of gold nanoparticles on silica cores, followed by sol-gel processing of tetraethoxysilane (TEOS) or sodium silicate to form dense or porous silica shells, respectively, over the gold nanoparticles. The structures and sizes of the resulting core-shell-shell nanospheres were found to heavily depend on the sizes of the core nanoparticles, the relative population of the gold nanoparticles on each core, and the concentration of TEOS. While a higher TEOS concentration resulted in thicker and more uniform silica shells around individual larger silica cores (approximately > or =250 nm in diameter), the same TEOS concentration resulted in aggregated and twin core-shell-shell nanostructures for smaller silica cores (approximately < or =110 nm in diameter). The thinner silica shells were synthesized by using a lower TEOS concentration. By using sodium silicate (Ung et al. J. Phys. Chem. B 1999, 103, 6770), the porous silica shells were synthesized. Controlled chemical etching of the core-shell-shell nanoparticles with an aqueous KCN solution resulted in corrugated silica shells around the gold nanoparticles or corrugated silica nanospheres with few or no gold nanoparticles. This has allowed synthesis of new types of core-shell-shell nanoparticles with tailored corrugated shells. The nanoporous silica shells provided accessible structures to the embedded metal nanoparticles as observed from the electrochemical response of the gold nanoparticles. 相似文献
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Coupling Mo2C with Nitrogen‐Rich Nanocarbon Leads to Efficient Hydrogen‐Evolution Electrocatalytic Sites 下载免费PDF全文
Yipu Liu Prof. Guangtao Yu Prof. Guo‐Dong Li Yuanhui Sun Prof. Tewodros Asefa Prof. Wei Chen Prof. Xiaoxin Zou 《Angewandte Chemie (International ed. in English)》2015,54(37):10752-10757
In our efforts to obtain electrocatalysts with improved activity for water splitting, meticulous design and synthesis of the active sites of the electrocatalysts and deciphering how exactly they catalyze the reaction are vitally necessary. Herein, we report a one‐step facile synthesis of a novel precious‐metal‐free hydrogen‐evolution nanoelectrocatalyst, dubbed Mo2C@NC that is composed of ultrasmall molybdenum carbide (Mo2C) nanoparticles embedded within nitrogen‐rich carbon (NC) nanolayers. The Mo2C@NC hybrid nanoelectrocatalyst shows remarkable catalytic activity, has great durability, and gives about 100 % Faradaic yield toward the hydrogen‐evolution reaction (HER) over a wide pH range (pH 0–14). Theoretical calculations show that the Mo2C and N dopants in the material synergistically co‐activate adjacent C atoms on the carbon nanolayers, creating superactive nonmetallic catalytic sites for HER that are more active than those in the constituents. 相似文献
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Dr. Tao Zhang Dr. Jingxiang Low Prof. Jiaguo Yu Dr. Alexei M. Tyryshkin Dr. Eliška Mikmeková Prof. Tewodros Asefa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(35):15110-15117
A mesoporous TiO2−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 TiO2−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. 相似文献
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Jima Wegene Demisie Dada Tewodros Kassa Palanisamy Thanikaivelan 《Journal of Thermal Analysis and Calorimetry》2019,135(6):3289-3295
Journal of Thermal Analysis and Calorimetry - Traditionally garment leathers are used in cold environment to protect the humans from chill weather. This is because leather garments have low heat... 相似文献
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Tewodros Birhanu Aychiluhim 《合成通讯》2014,44(10):1422-1429
A one-pot, multicomponent reaction of 3-(2-bromo acetyl)coumarins, 4-amino-5-hydrazino-4H-[1,2,4]triazole-3-thiol, and different derivatives of ethyl 2-(2-(aryl)hydrazono)-3-oxobutanoates provide an efficient and direct method for the synthesis of 4-(arylydrazono)-3-methyl-1-(6-(coumarin-3-yl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazin-3-yl)-1H-pyrazol-5(4H)-ones (4a–h). A similar methodology was also developed for the synthesis of pyrazolyl-triazolothiadiazines (9a–f) using acetyl acetone, 4-amino-5-hydrazino-4H-[1,2,4]triazole-3-thiol, and different derivatives of phenacylbromide. The resulting products were characterized by analytical and spectral data. 相似文献
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AYCHILUHIM Tewodros Birhanu VEDULA Rajeswar Rao 《高等学校化学研究》2014,30(4):601-604
A series of 3-[(4-phenyl-thiazol-2-yl)-hydrazono]-1,3-dihydro-indole-2-one(4a-4g) and 3-{[4-(2-oxo2H-chromen-3-yl)-thiazol-2-yl]-hydrazono}-1,3-dihydro-indol-2-one(6a-6d) has been prepared in a one-step procedure from condensation reaction of isatin(1),thiosemicarbazide(2) and bromoacetophenones(3)/or 3-(2-bromoacetyl)coumarins(4).The method provides a simple and efficient route to prepare the compounds in good yields and in a short experimental time as compared to its stepwise procedure. 相似文献