New pyridinium-functionalized metalloporphyrins MEtPpBr4 (M = Zn2+, Co2+, Ni2+, Cu2+; EtPp = 5, 10, 15, 20-tetra(4-(3-(N-ethyl-4-pyridyl)pyrazolyl)phenyl)porphyrin) were synthesized as bifunctional catalysts for the cycloaddition reactions of epoxides and CO2. The effects of catalyst loading, CO2 pressure, reaction temperature and time on catalytic activity were investigated. ZnEtPpBr4 ( 1 ) and CoEtPpBr4 ( 2 ) exhibited efficient activities in the cycloaddition reactions of various epoxides with CO2 as at 120 °C under 2 MPa of CO2 pressure without solvent. Most of corresponding cyclic carbonates could be obtained in almost quantitative yields and > 99.9% selectivity with molar ratio of epoxide/catalyst 2222 after 8 hr of reaction. 相似文献
黄芩素可通过电子转移效应猝灭聚乙烯亚胺(PEI)包覆的锰(Mn)掺杂硫化锌(Zn S)量子点(PEIMn/Zn S QDs)的室温磷光。基于上述原理,建立了一种简单、快速测定黄芩素含量的室温磷光检测方法,PEI-Mn/Zn S QDs以水相共沉淀法获得。结果表明:当pH=8.0,反应时间为10 min时,量子点的磷光猝灭程度与黄芩素浓度呈良好的线性关系,线性范围为0.07~0.60 mg·L~(-1),方法检出限为0.039 mg·L~(-1),相关系数(r)为0.997,相对标准偏差为4.1%,实际样品的检测回收率为96.0%~100.7%。所建立的方法可有效避免常见离子和氨基酸等的干扰,适用于黄芩饮片及血清中黄芩素含量的快速测定,有望应用于医药行业中黄芩素含量的测定分析,也为其他药物基于量子点电子转移机制的检测提供了技术依据。 相似文献
A study is presented on the binding kinetics and mechanism of the adsorption of dsDNA on citrate-capped gold nanoparticles (AuNPs). Methods include fluorescence titration, isothermal calorimetry (ITC) titration, dynamic light scattering and gel electrophoresis. It is found that the fluorescence of probe DNA (labeled with Rhodamine Green and measured at excitation/emission peaks of 498/531 nm) is quenched by addition of AuNPs. The Stern-Volmer quenching constant (Ksv) is 1.67?×?10^9 L·mol?1 at 308 K and drops with increasing temperature. The quenching mechanism is mainly static. The results of both fluorescence titrations and ITC show negative values for ΔH and ΔS values. This shows ion-induced dipole-dipole interaction to be the main attractive forces between dsDNA and AuNPs, while electrostatic interactions result in repulsion. The repulsive forces lead to a lower affinity between dsDNA and AuNPs (compared to single-strand DNA). It is also found that dsDNA can prevent the aggregation of AuNPs which is accompanied by a color change from red into blue. The visual detection limit with bare eyes for dsDNA1 is 36 pM. Based on these findings, a colorimetric method was developed to detect the proto-oncogene of serine/threonine-protein kinase B-Raf V600E point mutation in HT29, Ec109, A549, Huh-7 and SW480 cell lines.
Graphical abstract Schematic of the salt-induced aggregation of uncapped gold nanoparticles (AuNPs) which leads to a color change from red to blue. If the AuNPs are coated with dsDNA, aggregation is suppressed.
The traditional treatment has inevitable drawbacks of nonspecific lymph targeting, poor therapeutic efficiency and residual metastatic for advanced cancer patients with lymph node metastases. To overcome these shortcomings, we prepare a nano-carrier drug delivery system. Photosensitizer hematoporphyrin monomethyl ether (HMME)-loaded poly (n-butylcyanoacrylate) nanoparticles (PBCA-NPs) was prepared successfully. The particle size was approximately 160 nm, the envelopment rate was 87.9%, and the drug loading rate was about 13.4%. The drug release study in vitro showed that the cumulative release rates of HMME-PBCA-NPs group was much less than free HMME group. The drug distribution in different tissues showed that the peak-reach time was 3 h in free HMME group and 6 h in nanoparticles group. All of these results confirmed the slow release characteristic of nanoparticles. In lymph node tissues, the HMME concentrations in HMME-PBCA-NPs group were much higher than those of the free HMME group at any time points we tested, in which the maximum difference concentration of HMME appeared at 6 h (1.2884?±?0.04695 vs. 0.0438?±?0.00558 µg/mg) after drug delivery. The mesenteric lymph nodes of rabbits were enlarged obviously in the NP group than in free HMME group at 6 h after drug delivery. All of these results confirmed the slow release characteristic and the lymphatic targeting characteristic of nanoparticles. In summary, we developed a lymphatic targeting nanoparticles drug delivery system successfully, which showed perfect lymph targeting and has the potential to be a new therapy strategy for advanced cancer patients with lymph node metastasis. 相似文献
The solvent‐free selective oxidation of alcohols to aldehydes with molecular oxygen is highly attractive yet challenging. Interfacial sites between a metal and an oxide support are crucial in determining the activity and selectivity of such heterogeneous catalysts. Herein, we demonstrate that the use of supported single‐atom catalysts (SACs) leads to high activity and selectivity in this reaction. The significantly increased number of interfacial sites, resulting from the presence of individually dispersed metal atoms on the support, renders SACs one or two orders of magnitude more active than the corresponding nanoparticle (NP) catalysts. Lattice oxygen atoms activated at interfacial sites were found to be more selective than O2 activated on metal NPs in oxidizing the alcohol substrate. This work demonstrates for the first time that the number of interfacial sites is maximized in SACs, providing a new avenue for improving catalytic performance by developing appropriate SACs for alcohol oxidation and other reactions occurring at metal–support interfacial sites. 相似文献