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141.
《Journal of Saudi Chemical Society》2021,25(12):101390
Currently, highly luminescent colloidal upconversion nanoparticles (UCNPs) have expanded an increasing interest of researchers because of their facilitating lability in the biomedical/clinical field. In this study, NaYF4:Yb,Er UCNPs are prepared by eco-friendly metal complexation-based thermal decomposition method at a lower temperature in aqueous media. The phase structure, crystallinity, phase purity, morphology, colloidal dispersibility, surface structure, surface charge, and optical and luminescent properties were evaluated carefully by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive x-ray analysis (EDX), Thermogravimetric analysis (TGA), zeta potential, Fourier transform infrared (FTIR), UV/visible and photoluminescent spectroscopic techniques. XRD pattern shows a pure single-phase cubic structure with an average grain size of 30–35 nm. TEM and SEM micrographs exhibited irregularly shaped spherical morphologies, porous surface structures highly aggregated UCNPs with the narrow-size distribution. Positive zeta potential has shown value signifying high absorption in the visible region which indicates particle's good colloidal stability in aqueous media. Under NIR-laser light excitation, the UCNPs emit strong UC emission transitions in the visible region. A broad infrared absorption peak of hydroxyl groups (–OH) in FTIR spectrum and mass loss at a lower temperature in TGA verified the surface functionality of UCNPs, with high colloidal stability, and excellent biocompatibility in aqueous media. In terms of their surface characteristics and high luminescent properties, the NaYF4:Yb,Er UCNPs could be interestingly applied in tagging of biomolecules, drug delivery, proteins labeling, and therapeutic and thermostats applications. 相似文献
142.
使用大规模自旋极化密度泛函理论计算研究了表面修饰和尺寸对金刚石纳米线(DNs)中氮空位(NV)色心的几何结构、 电子结构、 磁性和稳定性的影响. 理论上设计了几种不同的DNs, 这些DNs具有不同的表面修饰(干净、 氢化和氟化), 并且直径达数百个原子. 实验结果证明, 中性(NV0)和带1个负电荷(NV-)的NV色心的电子结构不受半导体表面修饰和DNs直径大小的影响, 但NV色心的稳定性对这两个因素具有不同的响应. 此外, 研究中还发现, 由于DNs中存在圆柱形表面电偶极子层, 对DNs中掺杂的NV-色心的稳定性, 表面改性诱导了不依赖尺寸的长程效应. 特别地, 对于n型氟化金刚石表面, 掺杂在DN中的NV-色心可以稳定存在, 而对于p型氢化表面, NV0则相对更稳定. 因此, 表面修饰为控制金刚石纳米线中的NV色心的电子结构和稳定性提供了一种精确有效的调控方法. 相似文献
143.
E. Marin F. Boschetto M. Zanocco W. Zhu T. Adachi N. Kanamura T. Yamamoto B.J. McEntire E.N. Jones C. Powell J. Hendry R.M. Bock B.S. Bal G. Pezzotti 《Materials Today Chemistry》2021
Most structural bioceramics are comprised of metallic oxides such as alumina and zirconia. They are generally considered to be completely bioinert, but a non-oxide ceramic, silicon nitride, achieves equivalent levels of mechanical reliability while being bioactive. Silicon nitride can not only stimulate cellular proliferation but it is also antipathogenic with demonstrated efficacy against Gram-positive and Gram-negative bacteria, fungi, and viruses. In this work, three physical vapor deposition coatings with different Si:N ratios (silicon-rich, stoichiometric, and nitrogen-rich) were deposited on mirror-polished silica glass substrates. The coatings were characterized by spectroscopic and microscopic techniques and tested in vitro against E. coli and KUSA-A1 mesenchymal cells. Results showed that nitrogen-enriched SixNy has a strong antibacterial effect against E. coli and contributes to cellular proliferation while silicon-enriched SixNy stimulates the production of bone tissue, with higher indexes for mineralization and quality. These results suggest that SixNy's biological properties can be optimized for specific applications by carefully tuning its surface chemistry. 相似文献
144.
Controlling the morphology and composition of one-dimensional (1D) and two-dimensional (2D) assemblies of matter is essential to design and create nanostructures with exceptional material properties, for applications ranging from nanoelectronics to nanomedicine. Within this latter, a great interest is placed on assembling magnetoplasmonic nanostructures to enable multimodal biosensing and bioimaging for early diagnosis and prognosis of diseases. To date, the synthesis of such complex nanostructures is mostly relying on wet chemistry and templates. Herein, we employed a templateless physical method to generate FeAg-based anisotropic nanostructures, using a modified cluster source. Under tuned experimental conditions, we demonstrated the successful magnetic-assisted assembly of Fe nanoclusters (Fe NCs), to form stable and permanent branched Fe nanorods (Fe NRs), core@shell Fe@Ag-NRs, Fe nanosheets (Fe NSs), and Fe/Ag-NSs. This assembly is driven by the need to reduce their magnetic interaction energy on one hand and their overall surface energy on the other hand. When NCs and NRs are magnetically brought into intimate contact, they undergo a coalescence process, through the interfacial diffusion of the surface atoms, resulting in the formation of 1D and 2D nanostructures. For Fe@Ag NRs, the advantage conferred by the Ag shell is to protect Fe NRs from oxidation and prevent them from aggregation at the same time. The observed contrast reversal in Scanning Electron Microscopy (SEM) images of Fe NRs and Fe NSs is discussed. 相似文献
145.
熔融碳酸盐燃料电池阳极材料表面改性 总被引:1,自引:0,他引:1
选择铌作为合金化元素,通过氟化物熔盐电化学表面合金化的方法对熔融碳酸盐燃料电池阳极材料镍进行表面改性,改性后的阳极材料的耐蚀性能与电催化性能均得到明显的改善。 相似文献
146.
MoO3—SiO2表面复合物金属催化剂载体的制备与表征 总被引:4,自引:0,他引:4
采用MoOCl4的盐酸溶液负载于SiO2的表面反应法,制备了负载型和键联型两种MoO3-SiO2(MoSO)表面复合物载体。利用红外光谱法研究了MoSO的表面构造及其化学吸附性能;并利用TPR技术考察了该表面复合物载体对负载金属Pd,Cu氧化物还原过程的影响。 相似文献
147.
The physicochemical surface characteristics and interfacial behavior of two strains of Brevibacterium linens (BL-MGE and BL-9174), that may enhance cheese flavor, were assessed. Cell surface hydrophobicity was determined by measuring the contact angle of a variety of polar and non-polar wetting agents on lawns of the bacterial cells. The contact angles obtained were used to calculate the cell surface free energy components γLW, γAB, γ+ and γ−. The Lifshitz van der Waals component and the Lewis acid-base component were approximately 35 mJ m−2 and 22 mJ m−2, respectively, for both strains. Under conditions of physiological pH and low ionic strength, neither strain exhibited affinity for an octyl ligand in hydrophobic interaction chromatography. This occurred despite a favorable free energy of interfacial interaction which was attributable almost entirely to favorable acid-base interactions between cells and octyl-sepharose. The nature of surface functional groups was evaluated using X-ray photoelectron spectroscopy. Excluding H, the mean percentage of atomic fraction for C, O, N and P for BL-MGE was 57.7, 37.8, 3.9 and 0.6%, respectively and 61.0, 31.8, 7.0 and 0.2%, respectively for BL-9174. 相似文献
148.
149.
Guo Zhang Xu Jian Hua Dong Kun Yuan Qiu 《Journal of polymer science. Part A, Polymer chemistry》1997,35(4):643-650
Several N-phenyl maleimides with different p-substituents have been synthesized from the maleic anhydride and relevant aromatic amine. In the presence of N,N-dimethyl-4-toluidine (DMT), the N-substituted phenyl maleimide (4-XPhMIs) could be polymerized under UV irradiation. It was observed that a new absorption appeared on the UV-Vis spectrum of the mixture solution of 4-XPhMI and DMT, which reveals the formation of charge-transfer complex in the ground state. It was found that the fluorescence of DMT was quenched by 4-XPhMI and the quenching constant of 4-XPhMI, obtained from the Stern–Volmer plot, increases with the electron-deficiency of ethylene double bond of 4-XPhMI. The dynamic quenching of the fluorescence of DMT by 4-XPhMI suggests the formation of exciplex in excited state between DMT and 4-XPhMI. The radicals formed in the systems have been detected by spin-trapping techniques and electron paramagnetic resonance (EPR) spectrometer. Based on all of these results, it has been proposed that the initiation process of the polymerization involves the formation of exciplex and the initial radicals were produced by proton-transfer in the exciplex from DMT to 4-XPhMI. © 1997 John Wiley & Sons, Inc. 相似文献
150.
Surface forces in wetting films 总被引:4,自引:0,他引:4
Churaev NV 《Advances in colloid and interface science》2003,103(3):197-218
A short review of various components of surface forces acting in a non-symmetrical system such as wetting films is presented here. Experimental results are compared with modified DLVO theory, which includes, besides dispersion and electrostatic, structural (solvation) forces caused by a change in liquid structure in conditions of confined geometry. The peculiarities of disjoining pressure isotherms and conditions of the film stability of non-polar and polar simple liquids, as well as of aqueous solutions of electrolytes and surfactants, are systematically considered from a historical perspective. 相似文献