scholarly journals Facile Synthesis of Nanoporous Amorphous Silica on Silicon Substrate

2020 ◽  
Vol 2020 ◽  
pp. 1-6
Author(s):  
Luo Hui ◽  
Huang Yongquan ◽  
Wu Lili ◽  
Ge Yanming ◽  
Huang Kaichen ◽  
...  
Keyword(s):  
Amorphous Silica ◽  
Large Scale ◽  
Room Temperature ◽  
Thermal Evaporation ◽  
Metal Particles ◽  
Nanoporous Structure ◽  
Facile Synthesis ◽  
Ultraviolet Emission ◽  
Key Factor ◽  
Nanoporous Structures

Large-scale nanoporous amorphous silica nanostructure is fabricated via a simply etched approach and effective thermal evaporation process. The nanoporous amorphous silica was synthesized by a general and scalable process via etching by metal particles on the silica sheets. In this study, we elucidated how a nanoporous structure was performed and the addition of indium is the key factor that determined the formation of the nanoporous structures. The morphology and the sizes of the porous structure could be tunable by the sizes and the shape of the metal. We discovered a promising optical property in the as-synthesized nanostructures, which have a photoluminescence in an intensive ultraviolet emission as well as a broad visible emission at room temperature.

The Formation of Ordered Nanoporous Structure with Controlled Micelle Size

2002 ◽  
Vol 733 ◽  
Author(s):  
Jeongho Chang ◽  
Yongsoon Shin ◽  
Li-Qiong Wang ◽  
Gregory J. Exarhos
Keyword(s):  
Room Temperature ◽  
Nanoporous Structure ◽  
Nanoporous Silica ◽  
Wall Structure ◽  
Pore Shape ◽  
Preparation Time ◽  
Micelle Size ◽  
Nmr Techniques ◽  
Chain Lengths ◽  
Nanoporous Structures

AbstractSelected MPEG-b-PDLLA block copolymers have been synthesized with systematic variation of the chain lengths of the resident hydrophilic and hydrophobic blocks. The size and shape of the micelles that spontaneously form in solution are then controlled by the characteristics of the copolymer template. Formation of nanoporous silica at room temperature with short-preparation time is demonstrated and silica-containing materials evolve with uniform pore shape and wall structure. The formation mechanism of these nanoporous structures obtained by controlling the micelle size has been confirmed using both liquid and solid state 13C and 29Si NMR techniques.

scholarly journals Gas Phase Growth of Wurtzite ZnS Nanobelts on a Large Scale

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
Jing Wang ◽  
Yang Jiao ◽  
Yang Liu ◽  
Zhenglin Zhang ◽  
Fengyu Qu ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Large Scale ◽  
Room Temperature ◽  
Thermal Evaporation ◽  
Deep Level ◽  
Green Emission ◽  
X Ray Diffraction ◽  
Phase Growth ◽  
X Ray ◽  
Transmission Electron

We showed large-scale synthesis of ZnS nanobelts by simply thermal evaporation of ZnS powder in the presence of Au catalysts at 1020°C. Scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD) analyses demonstrated that the as-obtained ZnS nanobelts possess hexagonal wurtzite structures. The nanobelts have lengths ranging from tens to hundreds of micrometers, thicknesses of tens of nanometers, and widths ranging from hundreds of nanometers to the order of micrometers. The growth process was proposed on the basis of known vapor-liquid-solid (VLS) mechanism. Room temperature photoluminescence measurements showed that the as-synthesized ZnS nanostructures had a strong green emission bands at a wavelength of 427 nm, which can be attributed to deep-level emissions induced by defects or impurities.

scholarly journals STRONG PHOTOLUMINESCENCE EMISSION AT ROOM TEMPERATURE OF ZnS MICROWIRES AND MICROBELTS GROWN BY THERMAL DEPOSITION

2017 ◽  
Vol 33 (3) ◽  
Author(s):  
Nghia Nguyen Van
Keyword(s):  
Room Temperature ◽  
High Efficiency ◽  
Thermal Evaporation ◽  
Optical Transition ◽  
Free Exciton ◽  
Great Promise ◽  
Ultraviolet Emission ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Ar Gas

In this work, we report on the controlled synthesis of ZnS microstructures with high purity on Au-coated silicon substrates by thermal evaporation of ZnS powder in Ar gas ambient at atmospheric pressure. The growth mechanism is confirmed as a typical vapor–liquid–solid process. The prepared ZnS microstructures have wurtzite (hexagonal) structures. The catalytically grown ZnS microstructures, including microwires and microbelts, are tens of micrometers in length. EDS shows that the oxygen composition in the microstructures is trivial. The photoluminescence spectrum reveals strong ultraviolet emission and no other emission at room temperature also demonstrates that the ZnS microstructures are of high crystalline perfection. Optical transition from free exciton A, free exciton B are observed and analyzed through power-dependent at 10 K and temperature-dependent photoluminescence spectroscopy measurements performed from 10 to 300 K. Our results indicate that ZnS microstructures grown by thermal evaporation, suggesting a great promise for high-efficiency light-emitting devices and lasers in the UV region.

Going the Distance

2020 ◽  
Author(s):  
Ron Harris
Keyword(s):  
Large Scale ◽  
Western Europe ◽  
Family Firms ◽  
Global Trade ◽  
Long Distance ◽  
Business Corporation ◽  
Modern Economy ◽  
Key Factor ◽  
Silk Route ◽  
Passive Investors

Before the seventeenth century, trade across Eurasia was mostly conducted in short segments along the Silk Route and Indian Ocean. Business was organized in family firms, merchant networks, and state-owned enterprises, and dominated by Chinese, Indian, and Arabic traders. However, around 1600 the first two joint-stock corporations, the English and Dutch East India Companies, were established. This book tells the story of overland and maritime trade without Europeans, of European Cape Route trade without corporations, and of how new, large-scale, and impersonal organizations arose in Europe to control long-distance trade for more than three centuries. It shows that by 1700, the scene and methods for global trade had dramatically changed: Dutch and English merchants shepherded goods directly from China and India to northwestern Europe. To understand this transformation, the book compares the organizational forms used in four major regions: China, India, the Middle East, and Western Europe. The English and Dutch were the last to leap into Eurasian trade, and they innovated in order to compete. They raised capital from passive investors through impersonal stock markets and their joint-stock corporations deployed more capital, ships, and agents to deliver goods from their origins to consumers. The book explores the history behind a cornerstone of the modern economy, and how this organizational revolution contributed to the formation of global trade and the creation of the business corporation as a key factor in Europe's economic rise.

In-situ construction of direct Z-scheme AgBr/α-Ag2WO4 heterojunction with promoted spatial charge migration and photocatalytic performance

2021 ◽  
Author(s):  
Xiao-Ya Zhai ◽  
Yifan Zhao ◽  
Guo-Ying Zhang ◽  
Bing-Yu Wang ◽  
Qi-Yun Mao
Keyword(s):  
Anion Exchange ◽  
Large Scale ◽  
Room Temperature ◽  
Photocatalytic Performance ◽  
Charge Migration ◽  
Time Saving ◽  
Spatial Charge ◽  
Construction Strategy ◽  
Large Scale Synthesis

In the work, a direct Z-scheme AgBr/α-Ag2WO4 heterojunction was prepared by in-situ anion exchange at room temperature. The construction strategy is energy- and time-saving for large scale synthesis. The α-Ag2WO4...

scholarly journals Trace element catalyses mineral replacement reactions and facilitates ore formation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yanlu Xing ◽  
Joël Brugger ◽  
Barbara Etschmann ◽  
Andrew G. Tomkins ◽  
Andrew J. Frierdich ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Trace Elements ◽  
Fluid Flow ◽  
Large Scale ◽  
Metal Accumulation ◽  
Nucleation And Growth ◽  
Reaction Interface ◽  
Ore Formation ◽  
Key Factor ◽  
Mineral Replacement

AbstractReaction-induced porosity is a key factor enabling protracted fluid-rock interactions in the Earth’s crust, promoting large-scale mineralogical changes during diagenesis, metamorphism, and ore formation. Here, we show experimentally that the presence of trace amounts of dissolved cerium increases the porosity of hematite (Fe2O3) formed via fluid-induced, redox-independent replacement of magnetite (Fe3O4), thereby increasing the efficiency of coupled magnetite replacement, fluid flow, and element mass transfer. Cerium acts as a catalyst affecting the nucleation and growth of hematite by modifying the Fe2+(aq)/Fe3+(aq) ratio at the reaction interface. Our results demonstrate that trace elements can enhance fluid-mediated mineral replacement reactions, ultimately controlling the kinetics, texture, and composition of fluid-mineral systems. Applied to some of the world’s most valuable orebodies, these results provide new insights into how early formation of extensive magnetite alteration may have preconditioned these ore systems for later enhanced metal accumulation, contributing to their sizes and metal endowment.

Notizen:Phosphorescence Decay in Thallium-Doped Ammonium Chloride

1978 ◽  
Vol 33 (10) ◽  
pp. 1241-1242 ◽  
Author(s):  
S. Chaudhari ◽  
T. R. Joshi ◽  
R. V. Joshi
Keyword(s):  
Aqueous Solution ◽  
Ammonium Chloride ◽  
Mechanical Treatment ◽  
Room Temperature ◽  
Host Lattice ◽  
Luminescence Decay ◽  
Decay Rates ◽  
Negative Ion ◽  
Ultraviolet Emission ◽  
Near Ultraviolet

Abstract The phosphorescence decay rates of thallium-doped ammonium chloride (NH4Cl:Tl) phosphors, prepared by crystallization from aqueous solution, have been studied at room temperature for near-ultraviolet emission. The effects of impurity concentration as well as thermal and/or mechanical treatment on the decay rates have been examined. Phosphorescence centres consisting of a Tl+ion and a nearby negative ion vacancy are suggested to be responsible for the observed luminescence decay. The changes in the decay characteristics after pretreatments are explained on the basis of the location of the centres in normal and distorted regions of the host lattice.

Room Temperature Solvent-Free Synthesis of Monodisperse Magnetite Nanocrystals

2006 ◽  
Vol 6 (3) ◽  
pp. 852-856 ◽  
Author(s):  
X. R. Ye ◽  
C. Daraio ◽  
C. Wang ◽  
J. B. Talbot ◽  
S. Jin
Keyword(s):  
Oleic Acid ◽  
Solid State ◽  
Large Scale ◽  
Room Temperature ◽  
Solvent Free ◽  
Two Dimensional ◽  
New Process ◽  
High Boiling Point ◽  
Magnetite Nanocrystals ◽  
Solvent Free Synthesis

We have successfully demonstrated a facile, solvent-free synthesis of highly crystalline and monodisperse Fe3O4 nanocrystallites at ambient temperature avoiding any heating. Solid state reaction of inorganic Fe(II) and Fe(III) salts with NaOH was found to produce highly crystalline Fe3O4 nanoparticles. The reaction, if carried out in the presence of surfactant such as oleic acid–oleylamine adduct, generated monodisperse Fe3O4 nanocrystals extractable directly from the reaction mixture. The extracted nanoparticles were capable of forming self-assembled, two-dimensional and uniform periodic array. The new process utilizes inexpensive and nontoxic starting materials, and does not require a use of high boiling point and toxic solvents, thus is amenable to an environmentally desirable, large-scale synthesis of nanocrystals.

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