Guoqing Jiang

Studies on the interaction of salvianolic acid B with human hemoglobin by multi-spectroscopic techniques.

The interaction between salvianolic acid B (Sal B) and human hemoglobin (HHb) under physiological conditions was investigated by UV-vis absorption, fluorescence, synchronous fluorescence and circular dichroism spectroscopic techniques. The experimental results indicate that the quenching mechanism of fluorescence of HHb by Sal B is a static quenching procedure, the binding reaction is spontaneous, and the hydrophobic interactions play a major role in binding of Sal B to HHb. Based on Försters theory of non-radiative energy transfer, the binding distance between Sal B and the inner tryptophan residues of HHb was determined to be 2.64 nm. The synchronous fluorescence experiment revealed that Sal B can not lead to the microenvironmental changes around the Tyr and Trp residues of HHb, and the binding site of Sal B on HHb is located at α(1)β(2) interface of HHb. Furthermore, the CD spectroscopy indicated the secondary structure of HHb is not changed in the presence of Sal B.

Detection of dopamine on a mercapto-terminated hexanuclear Fe(III) cluster modified gold electrode

In this study, a novel mercapto-terminated hexanuclear iron(III) cluster [Fe6O2(OH)2(O2CC6H4SCH3)10(hep)2]·CH3CN·CH2Cl2 [hep=2-(2-hydroxyethyl) pyridine] (Fe6) modified Au electrode was fabricated, having highly sensitive dopamine (DA) detection capabilities. In such Fe6 molecules, 10 thiomethyl groups are located at the periphery of the cluster, which enable the Fe6 molecules to self-assemble onto the surface of Au electrodes through the formation of Au-S bonds. The as-prepared Fe6-modified Au electrode (Au/Fe6) exhibits excellent electrocatalytic activity for the oxidation of dopamine (DA) in PBS with a diffusion coefficient of 3.12×10(-5) cm(2)/s. Using the square wave voltammetry (SWV) technique, the calibration curve for DA determination was obtained in the range of 0.2 to 30 μM, and the detection limit for DA was ~0.07 μM. Furthermore, the modified electrode can accurately separate the DA signal from the interfering effect of uric acid (UA), thus providing simultaneous detection of DA and UA in their binary mixtures. This electrode can be reliably used to assay DA in its real drug composition.

Binding of dihydromyricetin to human hemoglobin: Fluorescence and circular dichroism studies

The binding reaction between dihydromyricetin (DMY) and human hemoglobin (HHb) was investigated systematically with various spectroscopic methods including fluorescence quenching technique, ultraviolet (UV)-vis absorption, synchronous fluorescence, circular dichroism (CD) spectroscopy. The experimental results showed that DMY effectively quenched the intrinsic fluorescence of HHb via static quenching. DMY binds to HHb with a stoichiometry that varies from 0.972:1 to 0.906:1 as the temperature increases from 296 to 304 K. The DMY-HHb binding constants were determined to be K(296)=2.79 × 10(4) and K(304)=1.18 × 10(4) Lmol(-1). The reaction is characterized by negative enthalpy (ΔH=-80.46 kJ mol(-1)) and negative entropy (ΔS=-186.72 kJ mol(-1)), indicating that the predominant forces in the DMY-HHb complex are van der Waals and hydrogen bonding forces. Based on the Försters theory of non-radiative energy transfer, the binding distance between DMY and the inner tryptophan residues of HHb was determined to be 3.15 nm. Furthermore, the CD spectroscopy indicated the secondary structure of HHb is not changed in the presence of DMY.

Yolk–shell ZnWO4 microspheres: one-pot synthesis, characterization and photocatalytic properties

Novel yolk–shell ZnWO4 microspheres have been fabricated via a one-pot hydrothermal process in the presence of L-aspartic acid (L-Asp). The as-obtained products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption–desorption experimentation and UV-vis absorption spectroscopy. The effects of the reaction conditions on the morphology and crystallinity of the products were studied, as well as the amount of L-Asp, reaction time and reaction temperature. As the chelating agent and shape modifier, L-Asp plays a key role in the crystal growth of the yolk–shell ZnWO4 microspheres. A possible formation mechanism for the yolk–shell microspheres is proposed. The photocatalytic properties of the yolk–shell ZnWO4 microspheres were investigated by the decomposition of Rhodamine B (RhB) and methylene blue (MB) under UV light irradiation and the results show that they have excellent photocatalytic activities. Furthermore, the obtained yolk–shell ZnWO4 microspheres are chemically stable and the efficiency remained almost the same after being recycled five times, suggesting that the yolk–shell ZnWO4 microspheres are promising photocatalysts for practical applications.

A sensitive hydrazine hydrate sensor based on a mercaptomethyl-terminated trinuclear Ni(II) complex modified gold electrode

In this study, a novel mercapto-terminated trinuclear Ni(II) complex (Ni3) was synthesized and used as an electrocatalyst for the detection of hydrazine hydrate in real water samples. The as-prepared Ni3 molecule possesses six thiomethyl groups at its periphery and these SCH3 groups can react with Au electrodes to immobilize the Ni3 molecules on their surface through the formation of a self-assembled monolayer. The Ni3-modified Au electrode (Ni3/Au) demonstrates excellent electrocatalytic activity for the oxidation of hydrazine hydrate through a significant decrease in overpotential. The chronoamperometry study shows a diffusion coefficient (D) of 5.82 × 10−5 cm2 s−1 and a catalytic rate constant of 8.57 × 103 M−1 s−1. Using the square wave voltammetry (SWV) technique, this Ni3/Au electrode based hydrazine hydrate sensor exhibits a high sensitivity in quantitative analysis, and its detection limit could be as low as ∼0.07 μM with linearity ranging from 0.2 to 50 μM. In addition, due its good reproducibility, anti-interference performance, and long-term stability, the proposed sensor is capable of detecting trace levels of hydrazine hydrate in real water samples.

Probing the Interaction of Anti-Cancer Agent Dihydromyricetin with Human Serum Albumin: A typical Method Study

The interaction between dihydromyricetin (DMY) with human serum albumin (HSA) under the physiological conditions was investigated by fluorescence spectroscopy, circular dichroism (CD) spectra and UV-visible absorption spectroscopy. In the mechanism discussion it was proved that the fluorescence quenching of HSA by DMY is a result of the formation of DMY-HSA complex. Binding parameters calculated showed that DMY bind to HSA with the binding affinities of the order 105∼106 L�mol-1. The enthalpy change (ΔH) and entropy change (ΔS) were calculated to be -28.76 kJ�mol-1 and 18.21 J�mol-1�K-1, respectively, which implied that the hydrophobic and hydrogen bonds interactions play predominant roles in the binding process. The binding site of DMY on HSA may be located in hydrophobic cavity of subdomain IIA by the analysis data of fluorescence and synchronous fluorescence spectra. The specific binding distance r (3.37 nm) between donor (Trp-214) and acceptor (DMY) was obtained according to Forster non-radiative resonance energy transfer theory. CD spectral result demonstrates that DMY does not affect the secondary structure of HSA and can maintain protein stabilization. In addition, the effect of some common metal ions (e.g. Zn2+, Cu2+, Co2+, Ni2+, Fe3+) on the binding constant between DMY and HSA was examined.

LaF3 and LaF3:Ln3+ (Ln = Eu, Tb) hierarchical microstructures: synthesis, characterization and photoluminescence

Without any templates or surfactants, large-scale 3D persimmon-shaped hierarchical LaF3 and LaF3:Ln3+ (Ln = Eu, Tb) have been synthesized via a simple hydrothermal route using organic tetrafluroborate complexes N(C4H9)4BF4 as the fluoride source. The phase and morphology of the products have been characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The SEM and TEM results indicate the 3D persimmon-shaped hierarchical microstructures are constructed by numerous nanodisks with mean thickness of 50 nm. It is found that several factors, including the fluoride sources, molar ratio of reagents and the reaction time, play crucial roles in the formation of the multilayer stacked structures. Detailed studies indicate that the layer-by-layer self-assembly of nanodisks is responsible for the formation of 3D hierarchical structures. The possible mechanism of the crystal growth and assembled procedure are also proposed. Furthermore, the photoluminescent properties of LaF3:Ln3+ (Ln = Eu, Tb) are studied, which exhibit orange-red (Eu3+:5D0–7F1,2,3,4) and green (Tb3+, 5D4–7F3,4,5,6) emission, respectively.

A new Co-nitroimidazolate–dicarboxylate pillared-layer network with various types of channels and ultra-large cages for gas uptake

A novel porous coordination polymer based on a Co-nitroimidazolate–dicarboxylate pillared-layer network, namely, [Co7(bdc)6(nIm)2(H2O)6]·3H2O·3DMF, (1, H2bdc = 1,4-benzenedicarboxylic acid, nIm = 2-nitroimidazole), has been synthesized by a solvothermal reaction. The microporous layers of 1 consisted of two kinds of SBUs, six-connected Co3(O2CR)6 and three-connected [Co2(O2CR)3]+, forming unprecedented Co3-Co2-bdc-based layers with three types of diamonded grids in the bc plane. The layers are further linked by bidentate-bridging nIm ligands as pillars into a 3-D metal–organic framework with two kinds of rectangular channels parallel to the c axis. It is worth mentioning that compound 1 also exhibits uniquely polyhedral cages with a maximum diagonal dimension of up to 31.019 A, which has fallen in the scope of mesoporous (2–50 nm). To systematically evaluate the channels and special cages, the adsorption ability of 1 was measured by N2, H2 and CO2 sorption experiments. Topological analysis indicates that compound 1 adopts a new topological structure with a point symbol of {412·614·82}{46}2. Moreover, thermal gravimetric analysis (TGA) of as-synthesized 1 reveals a stability range up to 311 °C.

Synthesis, structure and characterization of Fe6 molecular clusters with peripheral sulfur atom-capped silver nanoparticles

There are rare reports of high-nuclear transition metal clusters with thiol groups in their periphery. In this work, a novel cluster, [Fe6O2(OH)2(O2CC6H4SCH3)10(hep)2]·CH3CN·CH2Cl2 (Fe6) has been constructed by coordinating an octahedral Fe(III) ion with 4-mercaptobenzoate and hepH (hepH = 2-(2-hydroxyethyl) pyridine). The functionalized thiomethyl groups around the periphery of the Fe6 cluster may provide binding sites for the surfaces of some specific materials, such as noble metals. Therefore, silver nanoparticle coated Fe6 (Ag@Fe6) complexes have been prepared by spontaneous self-assembly reactions. Transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) images show that the Fe6 cluster layer is formed on the surface of the silver nanoparticles and the diameter of the Fe6 cluster is about 2 nm. In addition, powder X-ray diffraction (XRD), UV-vis spectroscopy, surface enhanced Raman spectroscopy (SERS), and cyclic voltammetry of the Fe6 and Ag@Fe6 complexes were also investigated.

3D hierarchical ZnOHF nanostructures: synthesis, characterization and photocatalytic properties

3D hierarchical ZnOHF nanoflowers with mean diameter of 200 nm have been synthesized via a simple template-free hydrothermal route by using (NH4)2SiF6 as the fluoride source. The crystalline phase and morphologies of the as-prepared products have been characterized by XRD, SEM and TEM. The XRD results show that the products are well-crystallized orthorhombic phase of ZnOHF. The SEM and TEM results indicate that the ZnOHF nanoflowers are assembled by numerous nanoflakes with mean thickness of 20 nm. Some factors influencing the morphologies of the ZnOHF nanostructures have been systematically investigated, such as the reaction time, temperature and fluoride source. A growth mechanism is proposed on the basis of a series of time-dependent morphological evolution results. The hierarchical ZnOHF nanoflowers exhibit a high specific surface area up to 97.1919 m2 g−1 with a pore size of 50.098 nm. The as-obtained ZnOHF can be transformed into ZnO nanoflowers by calcination in air at 600 °C. The photocatalytic properties of ZnOHF have been studied by the decomposition of methyl orange (MO) under UV light irradiation. The results indicate that the flower-like ZnO nanostructures are chemically stable, and the efficiency remained almost the same after five times recycling.