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151.
本文开发了基于纳米金修饰的碳纤维超微电极(CFME)用于儿茶素的定量检测。通过使用柠檬酸三钠还原氯金酸制得纳米金粒子(AuNPs),采用恒电位电沉积法将纳米金修饰在CFME表面。在pH 2.00的Tris-HCl缓冲溶液中,采用差分脉冲法和循环伏安法考察了修饰前后电极对儿茶素的电催化性能。结果表明,纳米金修饰电极对儿茶素具有明显的电催化效果。在优化实验条件下,纳米金修饰的碳纤维超微电极(AuNPs/CFME)与儿茶素浓度在1.00×10-3~10.0μmol/L范围内呈良好的线性关系,且AuNPs/CFME的电化学性能非常稳定,具有良好的重现性。该方法操作简单,准确性高,可用于对儿茶素进行定量检测。 相似文献
152.
将生物质转化为高附加值化学品以替代传统化石能源衍生的碳资源不可再生能源已经引起了人们的广泛关注. 本工作制备了内部中空的ZnS@CdS/Ni纳米管催化剂用于光催化氧化5-羟甲基糠醛(HMF). 通过X射线光电子能谱表征了催化剂内部存在ZnS缺陷态使得ZnS能带带隙降低. 光照条件下, 光生空穴能够从CdS迁移至ZnS缺陷态, 抑制了ZnS@CdS内部的载流子复合, 提高了光催化性能. 中空的纳米管表面负载Ni催化剂可以参与质子还原产氢的反应, 而ZnS@CdS内部产生的空穴可以催化氧化HMF选择性生成2,5-呋喃二甲醛(DFF). 光反应1 h后, HMF的转化率达到36%, 产物DFF选择性为99%, 并且催化剂可以重复利用三次而不降低催化效果. 相似文献
153.
Hanling Bao Yabei Wu Yuhang Jiang Prof. Dr. Hao Zhang Prof. Dr. Zhiyong Wang 《化学:亚洲杂志》2021,16(1):80-86
Modulation of the reactivity of metallofullerenes is critical for production of metallofullerene derivatives with desired properties and functionalities. In this study, we investigate the effects of reduction and oxidation on the reactivity and regioselectivity in Diels–Alder reaction of metallofullerene La@C82 by means of density functional theory calculations. Because of the enhanced electron-deficiency characteristic upon oxidation, the oxidized metallofullerene exhibits higher thermodynamic and kinetic reactivity as compared with neutral La@C82. The regioselectivity in the reaction of La@C82 with cylcopentadiene is remarkably changed after oxidation of the metallofullerene, which is explained in terms of the changes in the geometrical structure and the electronic structure of the metallofullerene. Quantitative analysis based on the activation-strain model demonstrates that the low activation energy barrier for the reaction of the cation La@C82+ with cyclopentadiene originates from small strain energy and large interaction energy between the reactants. Energy decomposition analysis on the transition states of the reactions reveals that the exchange-repulsion interaction energy is one of the critical factors that determine the kinetic reactivity of the metallofullerene. This study not only provides new theoretical insights on how to modulate the reactivity of metallofullerenes, but also offers guideline for future experimental synthesis of new metallofullerene derivatives. 相似文献
154.
Chen Cao Shu-Jin Bao Dr. Xiao-Yan Tang Ze-Ming Xu Chun-Yan Ni Prof. Dr. Jian-Ping Lang 《化学:亚洲杂志》2021,16(18):2674-2680
Reactions of (NH4)2WS4 with CuCN, CuCN/1,2-bis(4-pyridyl)propane (bppa) or [Cu(MeCN)4]PF6/bppa under different reaction conditions afforded a set of two- or three-dimensional W/Cu/S cluster-based coordination polymers including {[Et4N]2[WS4Cu4(μ-CN)2(μ-I)2]}n ( 1 ), [WS4Cu4(μ-CN)2(bppa)2]n ( 2 ) and {[WS4Cu4(bppa)4](PF6)2}n ( 3 ), respectively. Compound 2 can be readily formed from reaction of 1 with bppa under solvothermal conditions. Compounds 1 and 2 feature two-dimensional networks with a “sql” topology, while 3 possesses a two-fold interpenetrated three-dimensional net with a rare “reo” topology. Compounds 1 – 3 in DMF exhibited different third-order nonlinear optical responses, and they all showed a reverse saturable absorption while 2 held a strong self-focusing effect. 相似文献
155.
Dr. Liang Bao Qinyu Bao Dr. Huaiwei Zhang Prof. Dr. Yongjun Yuan 《Chemphyschem》2021,22(21):2168-2171
A feasible tuning method for oxygen vacancies was realized by annealing under 3 atm H2 with (001)-exposed TiO2 nanosheets. The colored TiO2 sample exhibits an excellent N2 photo-fixation rate owing to the abundant oxygen vacancies (OVs) thus demonstrating that annealing with high pressure H2 is exceedingly efficient for tuning surface OVs. 相似文献
156.
Grant Korensky Xinye Chen Mengdi Bao Abbi Miller Blanca Lapizco-Encinas Myeongkee Park Ke Du 《Electrophoresis》2021,42(1-2):95-102
A planar, transparent, and adaptable nanosieve device is developed for efficient microalgae/bacteria separation. In the proposed method, a sacrificial layer is applied with dual photolithography patterning to achieve a 1D channel with a very low aspect ratio (1:10 000). A microalgae/bacteria mixture is then introduced into the deformable PDMS nanochannel. The hydrodynamic deformation of the nanochannel is regulated to allow the bacteria cells to pass through while leaving the microalgae cells trapped in the device. At a flow rate of 4 μL/min, the supernatant collected from the device is indistinguishable from a control solution, indicating that nearly all the microalgae cells are trapped in the device. Additionally, this device is capable of single cell auto-fluorescence tracking. These microalgae cells demonstrate minimal photobleaching over 250 s laser exposure and could be used to monitor hazardous compounds in the sample with a continuous flow. This method will be valuable to purify microalgae samples containing contaminations and study single-cell heterogeneity. 相似文献
157.
Dayang Yu Guoliang Mao Huaixun Cai Shuhua Wang Jiandang Liu Pengju Pan Yongzhong Bao 《Journal of polymer science. Part A, Polymer chemistry》2021,59(9):754-763
2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole-co-tetrafluoroethylene (PDD-TFE) copolymer is a good candidate to prepare gas separation membranes with excellent permeability due to its free volume characteristics. However, the influence of PDD-TFE copolymer structure on its free volume characteristics is less studied. In this paper, PDD-TFE copolymers with different compositions and molecular weights were synthesized, and their free volume characteristics were analyzed by positron annihilation lifetime spectroscopy and a molecular dynamics simulation. It indicated that the molar fraction of PDD in copolymers had a significant effect on free volume characteristics, while the molecular weight of copolymers exerted a slight influence on free volume when the molecular weight exceeded a critical region (intrinsic viscosity [η] > 68 ml g−1). PDD-TFE copolymers with greater PDD molar fractions (i.e., 72% and 84%) showed bimodal distributions in positron lifetime and free volume size distributions, while PDD-TFE copolymers with lower PDD molar fractions (i.e., 27% and 35%) exhibited a single peak. The long-lifetime parameter τ3 was assigned to micro-cavities formed by [-(TFE)y-PDD-] segments and τ4 was attributed to micro-cavities formed by [-(PDD)x-TFE-] segments. The cis and trans transitions of PDD led to a local multilayer spiral structure with a 2.6–4.3 Å layer spacing, which would also increase the free volume of copolymers. 相似文献
158.
采用“一锅法”制备了四氧化三铁/半胱氨酸(Fe3O4/Cys)磁性纳米微球,随后对Fe3O4/Cys进行亚氨基二乙酸(IDA)修饰得到Fe3O4/Cys/IDA磁性双功能化纳米微球。研究发现Fe3O4/Cys中的L-Cys是通过—SH基团接枝到Fe3O4表面的,随后IDA分子中的羧基与Fe3O4/Cys中的—NH2形成酰胺键,最终形成多支链多羧基的Fe3O4/Cys/IDA磁性纳米修复剂。基于修复剂表面短支链-长支链交替的多羧基结构,实现了羧基基团的高密度接枝。同时,Fe3O4/Cys/IDA磁性纳米微球对Pb2+、Cd2+、Cu2+、Co2+、Ni2+、Zn2+为专性吸附,而对Hg2+属于非专性吸附,且吸附重金属后得到的钝化产物均表现了良好的稳定性。另外,Fe3O4/Cys/IDA对重金属离子的吸附符合Langmuir模型,属于单层均相吸附,其吸附过程符合准二级动力学模型,最大吸附量为49.05 mg·g-1。 相似文献
159.
160.