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71.
Amphiphilic and hydrophilic oligomers were synthesized and coated on fused silica capillaries using a sol-gel technique. Sol-gel-coated capillaries were evaluated for the solid-phase microextraction and preconcentration of a wide variety of non-polar and polar analytes. Both types of coatings were stable under high temperature (up to 280 degrees C). The extraction efficiency of the sol-gel coatings was evaluated for the extraction of both non-polar and polar analytes, including organochlorine pesticides, triazine herbicides, estrogens and alkylphenols (APs) and bisphenol-A (BPA). Compared with commercially available solid-phase microextraction (SPME) adsorbents such as poly(dimethylsiloxane)divenylbenzene and polyacrylate, the new materials showed comparable selectivity and sensitivity towards both non-polar and polar analytes. The new coatings gave good linearity and detection limits. For example with triazines, a detection limit of <0.005 microl l(-1), precision from 5.0 to 11.0% (n = 6) and linearity of the calibration plots (0.5 to 50 microl l(-1)) were obtained. The sol-gel coated SPME capillaries were used for the determination of triazine herbicides in reservoir water samples collected in Singapore. 相似文献
72.
Metal‐Doped Nitrogenated Carbon as an Efficient Catalyst for Direct CO2 Electroreduction to CO and Hydrocarbons 下载免费PDF全文
Dr. Ana Sofia Varela Dr. Nastaran Ranjbar Sahraie Julian Steinberg Wen Ju Dr. Hyung‐Suk Oh Prof. Dr. Peter Strasser 《Angewandte Chemie (International ed. in English)》2015,54(37):10758-10762
This study explores the kinetics, mechanism, and active sites of the CO2 electroreduction reaction (CO2RR) to syngas and hydrocarbons on a class of functionalized solid carbon‐based catalysts. Commercial carbon blacks were functionalized with nitrogen and Fe and/or Mn ions using pyrolysis and acid leaching. The resulting solid powder catalysts were found to be active and highly CO selective electrocatalysts in the electroreduction of CO2 to CO/H2 mixtures outperforming a low‐area polycrystalline gold benchmark. Unspecific with respect to the nature of the metal, CO production is believed to occur on nitrogen functionalities in competition with hydrogen evolution. Evidence is provided that sufficiently strong interaction between CO and the metal enables the protonation of CO and the formation of hydrocarbons. Our results highlight a promising new class of low‐cost, abundant electrocatalysts for synthetic fuel production from CO2. 相似文献
73.
A Family of Molecular Sieves Containing Framework‐Bound Organic Structure‐Directing Agents 下载免费PDF全文
Jun Kyu Lee Dr. Jiho Shin Nak Ho Ahn Alessandro Turrina Dr. Min Bum Park Dr. Youngchul Byun Prof. Sung June Cho Prof. Paul A. Wright Prof. Suk Bong Hong 《Angewandte Chemie (International ed. in English)》2015,54(38):11097-11101
Organic structure‐directing agents (OSDAs), such as quaternary ammonium cations and amines, used in the synthesis of zeolites and related crystalline microporous oxides usually end up entrapped inside the void spaces of the crystallized inorganic host lattice. But none of them is known to form direct chemical bonds to the framework of these industrially important catalysts and adsorbents. We demonstrate that ECR‐40, currently regarded as a typical silicoaluminophosphate molecular sieve, constitutes instead a new family of inorganic‐organic hybrid networks in which the OSDAs are covalently bonded to the inorganic framework. ECR‐40 crystallization begins with the formation of an Al–OSDA complex in the liquid phase in which the Al is octahedrally coordinated. This unit is incorporated in the crystallizing ECR‐40. Subsequent removal of framework‐bound OSDAs generates Al‐O‐Al linkages in a fully tetrahedrally coordinated framework. 相似文献
74.
Solvent-bar microextraction (SBME) based on two-phase (water-to-organic) extraction was for the first time used as the sample pretreatment method for the non-aqueous capillary electrophoresis (NACE) of herbicides of environmental concern. Due to the compatibility of the extractant organic solvent and the NACE separation system, the extract could be introduced directly to the CE system after SBME. Through investigations of the effect of sample pH, extraction time, agitation speed and salt addition on extraction efficiency, the most suitable extraction conditions were determined: sample solution at a pH of 1, without added salt, and stirring at 700 revolutions per minute for 30 min. SBME as applied here was also compared with single-drop microextraction and hollow fiber-protected liquid-phase microextraction. SBME showed the highest extraction efficiency. In addition, field-amplified sample injection with pre-introduced organic solvent plug removal using the electroosmotic flow as a pump (FAEP) was used to enhance the sensitivity further in NACE. Based on studies of the effect of different organic solvents, different lengths of the organic plugs and different volumes of sample injection on stacking efficiency under the most suitable separation conditions, methanol was found to be the most efficient solvent for on-line preconcentration. Combined with SBME, FAEP-NACE achieved limits of detection of between 0.08 ng/mL and 0.14 ng/mL for the studied analytes. This preconcentration approach for NACE was demonstrated to be amenable to aqueous environmental samples by applying it to spiked river water. 相似文献
75.
Jin Young Park Hong Chae Jung G. Seeta Rama Raju Byung Kee Moon Jung Hyun Jeong Jung Hwan Kim 《Solid State Sciences》2010,12(5):719-724
A series of Eu3+ ions co-doped (Gd0.9Y0.1)3Al5O12:Bi3+, Tb3+ (GYAG) phosphors have been synthesized by means of solvothermal reaction method. The XRD pattern of GYAG phosphor sintered at 1500 °C confirms their garnet phase. The luminescence properties of these phosphors have been explored by analyzing their excitation and emission spectra along with their decay curves. The excitation spectra of the GYAG:Bi3+, Tb3+, Eu3+ phosphors consists of broad bands in the shorter wavelength region due to 4f8 → 4f75d1 transition of Tb3+ ions overlapped with 6s2 → 6s16p1 (1S0 → 3P1) transition of Bi3+ ions and the charge transfer band of Eu3+–O2?. The present phosphors exhibit green and red colors due to 5D4 → 7F5 transition of Tb3+ ions and 5D0 → 7F1 transition of Eu3+ ions, respectively. The emission was shifted from green to red color by co-doping with Eu3+ ions, which indicate that the energy transfer probability from Tb3+ to Eu3+ ions are dependent strongly on the concentration of Eu3+ ions. 相似文献
76.
Chiral molecular squares 1-12 based on [M(dppe)](2+) metallocorners (M = Pd or Pt, and dppe = bis(diphenylphosphino)ethane) and new angular bipyridine bridging ligands derived from the 1,1'-binaphthyl framework were readily assembled and characterized by a variety of techniques including infrared, UV-vis, circular dichroism (CD), and NMR spectroscopy, and ESI mass spectrometry. All these chiral metallocycles are highly luminescent in solution at room temperature with quantum efficiency of 0.06-0.63. Interestingly, when equal molar enantiopure molecular squares of opposite handedness were mixed in solution, a new meso dimeric metallocycle with C(2) symmetry formed. This result indicates the lability of the M-pyridyl bonds in these metallocycles, which may hinder their applications in many enantioselective processes. 相似文献
77.
Xing Ma Yun Zhao Prof. Kee Woei Ng Prof. Yanli Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(46):15593-15603
A hollow mesoporous silica nanoparticle (HMSNP) based drug/siRNA co‐delivery system was designed and fabricated, aiming at overcoming multidrug resistance (MDR) in cancer cells for targeted cancer therapy. The as‐prepared HMSNPs have perpendicular nanochannels connecting to the internal hollow cores, thereby facilitating drug loading and release. The extra volume of the hollow core enhances the drug loading capacity by two folds as compared with conventional mesoporous silica nanoparticles (MSNPs). Folic acid conjugated polyethyleneimine (PEI‐FA) was coated on the HMSNP surfaces under neutral conditions through electrostatic interactions between the partially charged amino groups of PEI‐FA and the phosphate groups on the HMSNP surfaces, blocking the mesopores and preventing the loaded drugs from leakage. Folic acid acts as the targeting ligand that enables the co‐delivery system to selectively bind with and enter into the target cancer cells. PEI‐FA‐coated HMSNPs show enhanced siRNA binding capability on account of electrostatic interactions between the amino groups of PEI‐FA and siRNA, as compared with that of MSNPs. The electrostatic interactions provide the feasibility of pH‐controlled release. In vitro pH‐responsive drug/siRNA co‐delivery experiments were conducted on HeLa cell lines with high folic acid receptor expression and MCF‐7 cell lines with low folic acid receptor expression for comparison, showing effective target delivery to the HeLa cells through folic acid receptor meditated cellular endocytosis. The pH‐responsive intracellular drug/siRNA release greatly minimizes the prerelease and possible side effects of the delivery system. By simultaneously delivering both doxorubicin (Dox) and siRNA against the Bcl‐2 protein into the HeLa cells, the expression of the anti‐apoptotic protein Bcl‐2 was successfully suppressed, leading to an enhanced therapeutic efficacy. Thus, the present multifunctional nanoparticles show promising potentials for controlled and targeted drug and gene co‐delivery in cancer treatment. 相似文献
78.
Wang X Yu JC Yip HY Wu L Wong PK Lai SY 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(10):2997-3004
A novel metal/semiconductor nanocomposite with catalytic and photocatalytic functions has been prepared. The new material consists of highly dispersed platinum (Pt) nanoparticles embedded in a cubic mesoporous nanocrystalline anatase (meso-nc-TiO2) thin film. The porous thin film possesses a narrow pore-size distribution and a large surface area. The diameter of the Pt cluster can be controlled to below 5 nm, and the high dispersion of these clusters gives rise to catalytic activity for the oxidation of carbon monoxide, an important reaction for automobile exhaust treatment. This novel ordered mesoporous Pt/TiO2 nanoarchitecture is also a promising photochemical material, as demonstrated by the photo-driven killing of Micrococcus lylae cells on the film. 相似文献
79.
Jang JS Ham DJ Ramasamy E Lee J Lee JS 《Chemical communications (Cambridge, England)》2010,46(45):8600-8602
Mesoporous tungsten carbides displayed an excellent solar conversion efficiency (7.01%) as a counter electrode for dye sensitized solar cells under 100 mW cm(-2), AM 1.5G illumination, which corresponded to ca. 85% of the efficiency of the conventional platinum electrode. 相似文献
80.
Soo Chool Lee Min Sun Cho Suk Yong Jung Chong Kul Ryu Jae Chang Kim 《Adsorption》2014,20(2-3):331-339
A range of potassium-based alumina sorbents were fabricated by impregnation of alumina with K2CO3 to examine the effects of the structural and textural properties of alumina on the CO2 sorption and regeneration properties. Alumina materials, which were used as supports, were prepared by calcining alumina at various temperatures (300, 600, 950, and 1,200 °C). The CO2 sorption and regeneration properties of these sorbents were examined during multiple tests in a fixed-bed reactor in the presence of 1 vol% CO2 and 9 vol% H2O. The regeneration capacities of the potassium-based alumina sorbents increased with increasing calcination temperature of alumina. The formation of KHCO3 increased with increasing calcination temperature during CO2 sorption, whereas the formation of KAl(CO3)(OH)2, which is an inactive material, decreased. These results is due to the fact that the structure of alumina by the calcination temperature is related directly to the formation of the by-product [KAl(CO3)(OH)2]. The structure of alumina plays an important role in enhancing the regeneration capacity of the potassium-based alumina sorbent. Based on these results, a new potassium-based sorbent using δ-Al2O3 as a support was developed for post-combustion CO2 capture. This sorbent maintained a high CO2 capture capacity of 88 mg CO2/g sorbent after two cycles. In particular, it showed a faster sorption rate than the other potassium-based alumina sorbents examined. 相似文献