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731.
D. C. Perdian Sangwon Cha Jisun Oh Donald S. Sakaguchi Edward S. Yeung Young Jin Lee 《Rapid communications in mass spectrometry : RCM》2010,24(8):1147-1154
Mass spectrometric imaging has been utilized to localize individual astrocytes and to obtain cholesterol populations at the single‐cell level in laser desorption ionization (LDI) with colloidal silver. The silver ion adduct of membrane‐bound cholesterol was monitored to detect individual cells. Good correlation between mass spectrometric and optical images at different cell densities indicates the ability to perform single‐cell studies of cholesterol abundance. The feasibility of quantification is confirmed by the agreement between the LDI‐MS ion signals and the results from a traditional enzymatic fluorometric assay. We propose that this approach could be an effective tool to study chemical populations at the cellular level. Published in 2010 by John Wiley & Sons, Ltd. 相似文献
732.
733.
An unusual aggregation phenomenon that involves positively charged poly(L-lysine) (PLL) and negatively charged gold nanoparticles (Au NPs) is reported. Discrete, submicrometer-sized spherical aggregates are found to form immediately upon combining a PLL solution with gold sol (diameter approximately 14 nm). These PLL-Au NP assemblies grow in size with time, according to light scattering experiments, which indicates a dynamic flocculation process. Water-filled, silica hollow microspheres (outer diameter approximately microns) are obtained upon the addition of negatively charged SiO2 NPs (diameter approximately 13 nm) to a suspension of the PLL-Au NP assemblies, around which the SiO2 NPs form a shell. Structural analysis through confocal microscopy indicates the PLL (tagged with a fluorescent dye) is located in the interior of the hollow sphere, and mostly within the silica shell wall. The hollow spheres are theorized to form through flocculation, in which the charge-driven aggregation of Au NPs by PLL provides the critical first step in the two-step synthesis process ("flocculation assembly"). The SiO2 shell can be removed and re-formed by decreasing and increasing the suspension pH about the point-of-zero charge of SiO2, respectively. 相似文献
734.
Starting with the tricyclic core 2b, annulation to form the 13-membered western ring of sarain A has been achieved to afford the macrocycle 30a by initial construction of the sterically congested quaternary center at C-3, followed by elaboration of the C-3 side-chain and ring-closing olefin metathesis. Also included is a parallel conversion of tricycle 2c to macrocycle 30b containing a functionalized side-chain at N-1 suitable for attachment of the eastern macrocyclic ring. 相似文献
735.
Hamid Ilbeygi In Young Kim Min Gyu Kim Wangsoo Cha Paskalis Sahaya Murphin Kumar Dae‐Hwan Park Ajayan Vinu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(32):10965-10970
Heteropoly acids (HPAs) are unique materials with interesting properties, including high acidity and proton conductivity. However, their low specific surface area and high solubility in polar solvents make them unattractive for catalytic or energy applications. This obstacle can be overcome by creating nanoporosity within the HPA. We synthesized mesoporous phosphotungstic acid (mPTA) with a spherical morphology through the self‐assembly of phosphotungstic acid (PTA) with a polymeric surfactant as stabilized by KCl and hydrothermal treatment. The mPTA nanostructures had a surface area of 93 m2 g?1 and a pore size of 4 nm. Their high thermal stability (ca. 450 °C) and lack of solubility in ethylene carbonate/diethyl carbonate (EC/DEC) electrolyte are beneficial for lithium‐ion batteries (LIBs). Optimized mPTA showed a reversible capacity of 872 mAh g?1 at 0.1 A g?1 even after 100 cycles for LIBs, as attributed to a super‐reduced state of HPA and the storage of Li ions within the mesochannels of mPTA. 相似文献
736.
The direct synthesis of nanostructured electrode materials on three‐dimensional substrates is important for their practical application in electrochemical cells without requiring the use of organic additives or binders. In this study, we present a simple two‐step process to synthesize a stable core–shell structured cobalt sulfide/cobalt aluminum hydroxide nanosheet (LDH‐S) for pseudocapacitor electrode application. The cobalt aluminum layered double hydroxide (CoAl‐LDH) nanoplates were synthesized in basic aqueous solution with a kinetically‐controlled thickness. Owing to the facile diffusion of electrolytes through the nanoplates, thin CoAl‐LDH nanoplates have higher specific capacitance values than thick nanoplates. The as‐grown CoAl‐LDH nanoplates were transformed into core–shell structured LDH‐S nanosheets by a surface modification process in Na2S aqueous solution. The chemically robust cobalt sulfide (CoS) shell increased the electrochemical stability compared to the sulfide‐free CoAl‐LDH electrodes. The LDH‐S electrodes exhibited high electrochemical performance in terms of specific capacitance and rate capability with a galvanostatic discharge of 1503 F g?1 at a current density of 2 A g?1 and a specific capacitance of 91 % at 50 A g?1. 相似文献
737.
Jianxiang Wu Xiang Liu Yaming Hao Shaoyan Wang Ran Wang Wei Du Shuangshuang Cha Xian-Yin Ma Xuejing Yang Ming Gong 《Angewandte Chemie (International ed. in English)》2023,62(9):e202216083
The electro-reforming of glycerol is an emerging technology of simultaneous hydrogen production and biomass valorization. However, its complex reaction network and limited catalyst tunability restrict the precise steering toward high selectivity. Herein, we incorporated the chelating phenanthrolines into the bulk nickel hydroxide and tuned the electronic properties by installing functional groups, yielding tunable selectivity toward formate (max 92.7 %) and oxalate (max 45.3 %) with almost linear correlation with the Hammett parameters. Further combinatory study of intermediate analysis and various spectroscopic techniques revealed the electronic effect of tailoring the valence band that balances between C−C cleavage and oxidation through the key glycolaldehyde intermediate. A two-electrode electro-reforming setup using the 5-nitro-1,10-phenanthroline-nickel hydroxide catalyst was further established to convert crude glycerol into pure H2 and isolable sodium oxalate with high efficiency. 相似文献
738.
Xiahui Zhang Panpan Dong Seunghyo Noh Xianghui Zhang Younghwan Cha Su Ha Ji-Hoon Jang Min-Kyu Song 《Angewandte Chemie (International ed. in English)》2023,62(4):e202212942
The LiOH-based cathode chemistry has demonstrated potential for high-energy Li−O2 batteries. However, the understanding of such complex chemistry remains incomplete. Herein, we use the combined experimental methods with ab initio calculations to study LiOH chemistry. We provide a unified reaction mechanism for LiOH formation during discharge via net 4 e− oxygen reduction, in which Li2O2 acts as intermediate in low water-content electrolyte but LiHO2 as intermediate in high water-content electrolyte. Besides, LiOH decomposes via 1 e− oxidation during charge, generating surface-reactive hydroxyl species that degrade organic electrolytes and generate protons. These protons lead to early removal of LiOH, followed by a new high-potential charge plateau (1 e− water oxidation). At following cycles, these accumulated protons lead to a new high-potential discharge plateau, corresponding to water formation. Our findings shed light on understanding of 4 e− cathode chemistries in metal–air batteries. 相似文献
739.
Seong-Keuck Cha 《Journal of Polymer Science.Polymer Physics》1997,35(1):165-172
Pyrrole, thiophene, and a mixture of the two monomers were electrochemically polymerized to investigate polymerization rates and the morphology change of the polymer matrix, and to improve the aging and cyclic voltammetric behaviors of the polymers. Thiophene was polymerized on a smooth surface of Pt electrode by two steps. The first step was controlled by electron transfer at the electrical double layer and the other by diffusion of the monomer reacting on the immobilized layer consisting of the precoated thiophene polymer. The electropolymerization rate of the second step was 1.85 × 10−4 cm3 mol−1 s−1, which is faster by 8.63 × 102 times than the first step. Some supporting electrolytes such as KPF6, LiClO4, TBAP, and TBABF4 were employed in the polymerization reaction to see the effects of dopant anions on the polymerization rate, and KPF6 was the fastest one at 2.41 × 10−6 cm s−1. However, owing to its sensitivity to oxygen, LiClO4 was used for the polymerization that is fairly stable in air and the same rate as KPF6. For the competitive polymerization reaction of the two monomers the rate of thiophene was found to be about 11 times slower than that of thiophene alone. When the starting concentration of the thiophene monomer was higher than pyrrole by five times, its portion in the composite polymer was found to be only 8–10%. However, this level gave desirable results in terms of redox properties and aging. The resistance against aging was explained by the morphology change, which came from great shrinking of its porosity. © 1997 John Wiley & Sons, Inc. 相似文献
740.
Excited states and autoionization states of the erbium atom were investigated by the use of multicolor resonance ionization mass spectrometry. Among the observed first excited states, a level [4f12(3H6)6s6p(3P1)] located 17,348 cm−1from the ground state is regarded as the most efficient state for excitation within the wavelength range investigated (560–600 nm), while a level located 17,080 cm−1from this first excited state (E= 34,458 cm−1) is identified as the best second excited state for the optimal photoionization scheme. Many ionization schemes adopting an autoionization state are also investigated, and the most efficient scheme is identified as 4f126s2(3H6) → 4f12(3H6)6s6p(3P10), 17,348 cm−1→ 34,458 cm−1→ continuum state, which corresponds to the two-color (ω1+ ω2+ ω1,2) scheme. Various concentrations of standard solutions for erbium are determined and the minimum amount detectable by two-color three-photon ionization was determined to be 20 pg. 相似文献