分类: 材料科学 >> 纳米科学和纳米技术 提交时间: 2017-03-30
摘要: Ozone treatment is a common way to functionalize commercial multi-walled carbon nanotubes (CNTs) with various oxygen functionalities like carboxyl, phenol and lactone groups, in order to enhance their textural properties and chemical activity. In order to
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.
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: Among the heavy metal ions, copper(II) can cause eye and liver damage at high uptake. The existence of copper ions (Cu2+) even with an ultralow concentration of less than 0.1 μg g−1 can be toxic to living organisms. Thus, it is highly desirable to develop efficient adsorbents to remove Cu2+ from aqueous solu- tions. In this work, without any surface functionalization or pretreatment, a water-stable zeolitic imidazo- late framework (ZIF-8) synthesized at room temperature is directly used as a highly efficient adsorbent for removal of copper ions from aqueous solutions. To experimentally unveil the adsorption mechanism of Cu2+ by using ZIF-8, we explore various effects from a series of important factors, such as pH value, contact time, temperature and initial Cu2+ concentration. As a result, ZIF-8 nanocrystals demonstrate an unexpected high adsorption capacity of Cu2+ and high removal efficiency for both high and low concen- trations of Cu2+ from water. Moreover, ZIF-8 nanocrystals possess fast kinetics for removing Cu2+ with the adsorption time of less than 30 min. In addition, the pH of the solution ranging from 3 to 6 shows little effect on the adsorption of Cu2+ by ZIF-8. The adsorption mechanism is proposed for the first time and systematically verified by various characterization techniques, such as TEM, FTIR, XPS, XRD and SEM.