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171.
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贵金属纳米粒子作为增强基底已经广泛应用于表面增强拉曼光谱(SERS)研究,传统的贵金属纳米基底在制备方法、增强能力、准确性等方面仍有待改进和提高。采用一种简易、高效的方法制备出了一种具有膜状结构的新型金纳米增强基底:以聚乙烯吡咯烷酮(PVP)作保护剂和粘结剂,通过化学还原法制备金纳米基底。实验考察了还原剂种类、反应温度、体系pH和柠檬酸钠浓度对反应的影响,制备出增强效果最佳的新型膜状金纳米基底。利用罗丹明B作为探针分子,考察基底的SERS特征,其增强因子可达6.5×105。利用扫描电镜(SEM)对纳米粒子的结构进行了表征,结果表明其具有膜状结构,且比表面积大,利于分子的吸附。相比于传统的贵金属纳米基底,该实验所制备的新型膜状金纳米基底增强效果更佳、灵敏度和准确度更高,具有很大的应用前景。 相似文献
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Variable temperature diffuse reflectance infrared spectroscopy is used to monitor the dehydration of sodium Linde type A zeolite (NaA). Between ambient temperature and 423 K, water desorbs from NaA α-cages. At 423 K, remaining NaA water molecules are primarily confined to β-cages. Variable temperature infrared difference spectra band shape and intensity trends reflect the influence of water-Na+ interactions and hydrogen bonding on α-cage water desorption mechanisms. Difference spectrum variations suggest that water loss is accompanied by rearrangement of the remaining NaA water molecules to establish new interactions and minimize potential energies. Water molecules that do not interact with Na+ form multiple water-water hydrogen bonds and attain near bulk water configurations. These waters desorb at the lowest temperatures. Most α-cage waters are involved in Na+ interactions. These water molecules participate in hydrogen bonding with neighboring water molecules, but opportunities diminish with increased dehydration, resulting in systematic temperature-dependent vibrational spectrum changes. 相似文献
175.
NaA, NaX and NaZSM-5 zeolites were prepared by using silica extracted from rice hull ash as a raw material, and they were investigated for CO2 adsorption performance as an adsorbent in order to solve the problem of suppressing the global warming. Three zeolites were synthesized by hydrothermal methods with seed technology, and a series of characterization methods, including XRD, FTIR, nitrogen adsorption-desorption and SEM, were used to demonstrate their advantages compared to traditional hydrothermal methods. The maximum equilibrium adsorption capacity of NaA-RS, NaX-RS and NaZSM-5-RS was 1.46, 3.12 and 2.20 mmol/g at 0 °C and 101.3 kPa, respectively. The CO2 and N2 adsorption isotherms recorded at different temperatures were perfectly fitted by the Dual-site Langmuir model. The CO2/N2 selectivity and Henry's law constants were calculated to demonstrate that the samples have a stronger affinity for CO2, especially at low pressures. The isosteric heat of CO2 and N2 adsorption of the three zeolites was calculated, which was indicated that they were in an excellent potential for adsorption and separation of CO2 in industrial flue gas. 相似文献
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Pengyao Sun Dr. Chong Liu Haiyong Wang Yuhe Liao Prof. Xuning Li Prof. Qiying Liu Prof. Bert F. Sels Prof. Chenguang Wang 《Angewandte Chemie (International ed. in English)》2023,62(6):e202215737
Via hydrothermal synthesis of Sn-Al gels, mild dealumination and ion exchange, a bimetallic Sn-Ni-Beta catalyst was prepared which can convert glucose to methyl lactate (MLA) and methyl vinyl glycolate (MVG) in methanol at yields of 71.2 % and 10.2 %, respectively. Results from solid-state magic-angle spinning nuclear magnetic resonance, X-ray photoelectron spectroscopy, transmission electron microscopy, spectroscopic analysis, probe-temperature-programmed desorption, and density functional theory calculations conclusively reveal that the openness of the Sn sites, such as by the formation of [(SiO)3−Sn−OH] entities, is governed by an adjacent metal cation such as Ni2+, Co2+, and Mn2+. This relies on the low structure-defective pore channel, provided by the current synthesis scheme, and the specific silica hydroxyl anchor point is associated with the incorporation of Sn for additional and precise metal ion localization. The presence of metal cations significantly improved the catalytic performance of Sn-Ni-Beta for glucose isomerization and conversion to MLA of sugar compared with Sn-Beta. 相似文献
178.
NaY zeolite functionalized by sulfamic acid/Cu(OAc)_2[NaY/SA/Cu(Ⅱ)] was synthesized and used as a new,efficient and recyclable catalyst for preparation of formamides. This novel organic-inorganic hybrid catalyst was characterized by several techniques such as FT-IR, XRD, SEM, EDX and TG analysis.Chemoselectivity, easy procedure, excellent yields, very short reaction times, solvent-free and mild reaction conditions are some benefits of this new protocol. 相似文献
179.
对Y型沸石原粉及几种不同脱铝样品进行了几种不同NMR方法的测量,确定了不同处理过程的脱铝机制和骨架内外铝状态的变化,29Si MAS NMR谱给出了骨架Si、Al分布的信息,反映了不同方法处理样品其脱铝机制的差异,据此可以控制Y沸石脱铝过程获得更高的硅铝比,27Al MAS NMR谱、二维章动NMR及1H-27Al CP/MAS NMR测量表明:水热处理的Y沸石中存在4种不同的铝状态。综合29Si和27Al MAS NMR观测,可相当程度地推断Y型沸石分子筛脱铝改性所发生的内部过程。 相似文献
180.