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121.
The signatures of nanosolvation on the one‐ and two‐dimensional (1D and 2D) IR spectra of a proton‐transfer mode in a hydrogen‐bonded complex dissolved in polar solvent molecule nanoclusters of varying size are elucidated by using mixed quantum–classical molecular dynamics simulations. For this particular system, increasing the number of solvent molecules successively from N=7 to N=9 initiates the transition of the system from a cluster state to a bulk‐like state. Both the 1D and 2D IR spectra reflect this transition through pronounced changes in their peak intensities and numbers, but the time‐resolved 2D IR spectra also manifest spectral features that uniquely identify the onset of the cluster‐to‐bulk transition. In particular, it is observed that in the 1D IR spectra, the relative intensities of the peaks change such that the number of peaks decreases from three to two as the size of the cluster increases from N=7 to N=9. In the 2D IR spectra, off‐diagonal peaks are observed in the N=7 and N=8 cases at zero waiting time, but not in the N=9 case. It is known that there are no off‐diagonal peaks in the 2D IR spectrum of the bulk version of this system at zero waiting time, so the disappearance of these peaks is a unique signature of the onset of bulk‐like behavior. Through an examination of the trajectories of various properties of the complex and solvent, it is possible to relate the emergence of these off‐diagonal peaks to an interplay between the vibrations of the complex and the solvent polarization dynamics. 相似文献
122.
Prof. Katherine A. Willets 《Chemphyschem》2013,14(14):3186-3195
Surface‐enhanced Raman scattering (SERS) is quickly growing as an analytical technique, because it offers both molecular specificity and excellent sensitivity. For select substrates, SERS can even be observed from single molecules, which is the ultimate limit of detection. This review describes recent developments in the field of single‐molecule SERS (SM‐SERS) with a focus on new tools for characterizing SM‐SERS‐active substrates and how they interact with single molecules on their surface. In particular, techniques that combine optical spectroscopy and microscopy with electron microscopy are described, including correlated optical and transmission electron microscopy, correlated super‐resolution imaging and scanning electron microscopy, and correlated optical microscopy and electron energy loss spectroscopy. 相似文献
123.
锂硫电池的商用化受到硫和多硫化锂低的电导率、多硫化锂在有机电解液中的溶解、放电过程中硫的体积膨胀等因素的制约。我们通过自模板法制备了具有石墨化孔壁结构的介孔碳纳米纤维(MCNF),并利用这种结构将硫和多硫化锂封装在碳骨架内。具有石墨化孔壁结构的一维MCNF能够在循环中为硫和多硫化锂提供良好的导电网络。MCNF中小的介孔能够抑制长链多硫化锂的扩散。另外,MCNF大的孔容能够负载比较多的硫,并且能够为硫的放电膨胀提供足够的纳米空间。本工作制备的MCNF-硫纳米复合材料在0.8A·g-1的电流密度下,经过100次循环后仍有820mAh·g-1的比容量。 相似文献
124.
Dr. Shengliang Hu Ruixue Tian Lingling Wu Qing Zhao Prof. Jinlong Yang Prof. Jun Liu Shirui Cao 《化学:亚洲杂志》2013,8(5):1035-1041
Carbon quantum dots (CQDs) were synthesized by heating various carbon sources in HNO3 solution at reflux, and the effects of HNO3 concentration on the size of the CQDs were investigated. Furthermore, the oxygen‐containing surface groups of as‐prepared CQDs were selectively reduced by NaBH4, leading to new surface states. The experimental results show that the sizes of CQDs can be tuned by HNO3 concentration and then influence their photoluminescent behaviors; the photoluminescent properties are related to both the size and surface state of the CQDs, but the photocatalytic activities are determined by surface states alone. The different oxygen‐containing groups on the surface of the CQDs can induce different degrees of the band bending upward, which determine the separation and combination of the electron–hole pairs. The high upward band bending, which is induced by C?O and COOH groups, facilitates separation of the electron–hole pairs and then enhances high photocatalytic activity. In contrast, the low upward band bending induced by C? OH groups hardly prevents the electron–hole pairs from surface recombination and then exhibits strong photoluminescence. Therefore, both the photocatalytic activities and optical properties of CQDs can be tuned by their surface states. 相似文献
125.
Dr. Xuecheng Chen Dr. Krzysztof Kierzek Karolina Wenelska Krzystof Cendrowski Jiang Gong Dr. Xin Wen Prof. Tao Tang Prof. Paul K. Chu Prof. Ewa Mijowska 《化学:亚洲杂志》2013,8(11):2627-2633
Core–shell‐structured mesoporous silica spheres were prepared by using n‐octadecyltrimethoxysilane (C18TMS) as the surfactant. Hollow mesoporous carbon spheres with controllable diameters were fabricated from core–shell‐structured mesoporous silica sphere templates by chemical vapor deposition (CVD). By controlling the thickness of the silica shell, hollow carbon spheres (HCSs) with different diameters can be obtained. The use of ethylene as the carbon precursor in the CVD process produces the materials in a single step without the need to remove the surfactant. The mechanism of formation and the role played by the surfactant, C18TMS, are investigated. The materials have large potential in double‐layer supercapacitors, and their electrochemical properties were determined. HCSs with thicker mesoporous shells possess a larger surface area, which in turn increases their electrochemical capacitance. The samples prepared at a lower temperature also exhibit increased capacitance as a result of the Brunauer–Emmett–Teller (BET) area and larger pore size. 相似文献
126.
A solvothermal post‐treatment method was developed to synthesize Fe3O4@mesosilica core–shell nanospheres (CSNs) with a well‐preserved morphology, mesoporous structure, and tunable large pore diameters (2.5–17.6 nm) for the first time. N,N‐Dimethylhexadecylamine (DMHA), which was generated in situ during the heat‐treatment process, was mainly responsible for this pore‐size enlargement, as characterized by NMR spectroscopy. This pore‐size expansion can be strengthened with the aid of hexamethyldisilazane (HMDS), whilst the nature of the surface of the Fe3O4@mesosilica CSNs can be easily modified with trimethylsilyl groups during the pore‐size‐expansion process. The hydrophobicity of the Fe3O4@mesosilica CSNs increased for the enlarged mesopores and the adsorption capacity of these CSNs for benzene (up to 1.5 g g?1) is the highest ever reported for Fe3O4@mesosilica CSNs. The resultant Fe3O4@mesosilica CSNs (pore size: 10 nm) showed a 3.6‐times higher adsorption capacity of lysozyme than those without the pore expansion (pore size: 2.5 nm), thus making them a good candidate for loading large molecules. 相似文献
127.
128.
Yi‐Chin Chen Sheng‐Cih Huang Dr. Yu‐Kuo Wang Dr. Yuan‐Ting Liu Prof. Dr. Tung‐Kung Wu Prof. Dr. Teng‐Ming Chen 《化学:亚洲杂志》2013,8(11):2652-2659
In this study, surface‐functionalized, branched polyethylenimine (BPEI)‐modified YVO4:Bi3+,Eu3+ nanocrystals (NCs) were successfully synthesized by a simple, rapid, solvent‐free hydrothermal method. The BPEI‐coated YVO4:Bi3+,Eu3+ NCs with high crystallinity show broad‐band excitation in the λ=250 to 400 nm near‐ultraviolet (NUV) region and exhibit a sharp‐line emission band centered at λ=619 nm under excitation at λ=350 nm. The surface amino groups contributed by the capping agent, BPEI, not only improve the dispersibility and water/buffer stability of the BPEI‐coated YVO4:Bi3+,Eu3+ NCs, but also provide a capability for specifically targeted biomolecule conjugation. Folic acid (FA) and epidermal growth factor (EGF) were further attached to the BPEI‐coated YVO4:Bi3+,Eu3+ NCs and exhibited effective positioning of fluorescent NCs toward the targeted folate receptor overexpressed in HeLa cells or EGFR overexpressed in A431 cells with low cytotoxicity. These results demonstrate that the ligand‐functionalized, BPEI‐coated YVO4:Bi3+, Eu3+ NCs show great potential as a new‐generation biological luminescent bioprobe for bioimaging applications. Moreover, the unique luminescence properties of BPEI‐coated YVO4:Bi3+,Eu3+ NCs show potential to combine with a UVA photosensitizing drug to produce both detective and therapeutic effects for human skin cancer therapy. 相似文献
129.
Celecoxib belongs to a new NSAID family specifically inhibiting cyclooxygenase‐2 (COX‐2). The present formulations require high dosage since the transmembrane transport fluctuates and is very difficult to control. We solubilized celecoxib in micelles of nonionic microemulsions and hydrophilic surfactant. The supersaturated solubilized drug was precipitated from the nano‐droplets to form a new solid structure with improved dissolution properties. The selected microemulsion systems loaded with celecoxib were characterized by SAXS, SD‐NMR, viscosity, and electrical conductivity techniques. Precipitation was conducted from W/O as well as from O/W U‐type microemulsions. The crystals obtained by the precipitation were characterized by x‐ray powder scattering, differential scanning calorimetry, FTIR measurements, and microscopic scans. 相似文献
130.
Mohammad Mahdi Doroodmand Shirin Nasresfahani Mohammad Hossein Sheikhi 《International journal of environmental analytical chemistry》2013,93(9):946-958
A novel ozone (O3) sensor is fabricated using commercial metal oxide field effect transistor (MOSFET), modified with single-walled carbon nanotubes (SWCNTs). In this study, integrated circuit (IC: BS250) was selected as the selective probe for O3 detection. For this purpose, a plastic cover on the surface of the drain was drilled to bare the drain surface, followed by its modification with nitrogen and sulfur-functionalized SWCNTs by chemical vapor deposition (CVD) process. The CVD-synthesized SWCNTs were then electrodeposited with FeOOH nanostructures. According to the figures of merit, the fabricated sensor gave a linear output from 20 to 450 parts per billion (ppb). Detection limit was also 4.1?ppb. Relative standard deviation (RSD) for seven replicate analyses was 3.61%. Based on 90% of maximum response (t90), the response time was ~1.5?min. Calibration sensitivity was measured to 1.3?mV/ppb. No interference was observed, when introducing at least 500 folds of interferences of gaseous species such as H2O, HCl, H2S, O2, H2, CO, CO2, NO2, SO2, Cl2, C2H2, CH4 and volatile organic compounds (VOCs) to 250?ppb of O3 solution. Reliability of the sensor was also evaluated via determination of O3 in different air samples. 相似文献