分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Excessive uptake of NO2− is detrimental to human health, but the currently available methods used to sensitively detect this ion in the environment are cumbersome and expensive. In this study, we developed an improved NO2− detection system based on a redox etching strategy of CTAB-stabilized Ag–Au core– shell nanoparticles (Ag@AuNPs). The detection mechanism was verified by UV-Vis spectroscopy, TEM and XPS. The detection system produces a color change from purple to colorless in response to an increase of NO2− concentration. The selectivity of detection of NO2−, both with the unaided eye and by measure- ment of UV-Vis spectra, is excellent in relation to other ions, including Cu2+, Co2+, Ni2+, Cr3+, Al3+, Pb2+, Cd2+, Ca2+, Ba2+, Zn2+, Mn2+, Mg2+, Fe3+, Hg2+, Ag+, K+, F−, PO43−, C2O42−, SO32−, CO32−, SO42−, NO3− and CH3–COO− (Ac−). The limit of detection (LOD) for NO2− is 1.0 μM by eye and 0.1 μM by UV-Vis spec- troscopy. The LOD by eye is lower than the lowest previously reported value (4.0 μM). There is a good linear relationship between A/A0 and the concentration of NO2− from 1.0 to 20.0 μM NO2−, which permits a quantitative assay. The applicability of our detection system was also verified by analysis of NO2− in tap water and lake water. The results demonstrate that our Ag@AuNP-based detection system can be used for the rapid colorimetric detection of NO2− in complex environmental samples, with excellent selectivity and high sensitivity.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Phenylboronic acid and folate grafted chitosan hydrochloride (FHCSPBA) was synthesized and confirmed by FTIR and 1H NMR. Glucose and pH dually responsive micelles were obtained through self-assembly of the amphiphilic polymers. The prepared FHCSPBA micelles displayed good biocompatibility and sustained drug release of the model drug doxorubicin hydrochloride (DOX). The cumulative drug release from the polymeric micelles showed obvious pH and glucose dependence and was accelerated by slightly decreasing the medium pH or increasing the glucose concentration. In vitro antitumor efficiency was evaluated by incubating the DOX loaded micelles with 4T1 breast cancer cells, and the results showed that folate-targeted micelles had higher antitumor activity than the non-targeted ones. Cellular uptake demonstrated by confocal microscopy indicated that free DOX was internalized in the nuclei of 4T1 cells, while the DOX loaded micelles were internalized in the cytoplasm. The cellular uptake of the micelles was enhanced by folate, with stronger fluorescence intensity in the cytoplasm, due to active FR-mediated endocytosis. These folate-conjugated glucose and pH dually responsive micelles may be a potential antitumor drug delivery system for cancer chemotherapy.