Gongwu Song

Fluorescence spectroscopic studies on the interaction of Gemini surfactant 14-6-14 with bovine serum albumin.

The interaction of the cationic Gemini surfactant hexamethylene-1,3-bis (tetradecyldimethylammonium bromide) (14-6-14) with bovine serum albumin (BSA) has been investigated by fluorescence quenching spectra and three-dimensional (3D) fluorescence spectra. The Stern-Volmer quenching constants K(SV) and the corresponding thermodynamic parameters ΔH, ΔG and ΔS have been estimated by the fluorescence quenching method. The results indicated that hydrophobic forces were the predominant intermolecular forces between BSA and the surfactant. Competitive experiments and the number of binding sites calculation show that 14-6-14 can be inserted in site-II (in subdomain IIIA) of BSA. The effect of 14-6-14 on the conformation of BSA was evaluated by synchronous fluorescence spectroscopy and 3D fluorescence spectral methods. The results show that the conformation of BSA was changed dramatically in the presence of 14-6-14, by binding to the Trp and Try residues of BSA. The investigation provides interaction between BSA and 14-6-14 as a model for molecular design and industrial research.

A graphene oxide–rhodamine 6G nanocomposite as turn-on fluorescence probe for selective detection of DNA

An electrostatic nanocomposite from Rhodamine 6G (R6G) and GO for the cost-effective, label-free, facile, sensitive and selective detection of DNA was constructed. Upon the interaction between positively charged dye and negatively charged GO, the charge-transfer complex R6GGO formed and significantly fluorescence quenching was observed. Due to the high electrostatic and non-covalent interactions between R6G and DNA, in the present of DNA, the interaction between R6G and GO was disturbed, which will turn on the fluorescence of R6G. The key advance of this R6GGO biosensor platform is attributed to the high quenching and absorbing capabilities of GO, which make it an effective candidate for DNA detection.

Brightly near-infrared to blue emission tunable silver-carbon dot nanohybrid for sensing of ascorbic acid and construction of logic gate

Recently, carbon dots (CDs) have drawn extensive attention owing to their unique properties. While more and more research had been focusing on the exploration of CDs as fluorescence sensors, the blue or green fluorescence emission of CDs restricts further applications of CDs, particularly in the biology-relevant fields due to the commonly blue auto-fluorescence of biological matrix. Therefore, the preparation of CDs with strong emission at long wavelengths is highly desirable. For these situations, a facile, straightforward and extra-reductant needless method was established to fabricate silver-carbon dot nanohybrid with enhanced near-infrared fluorescence through metal-enhanced fluorescence (MEF). We applied the Ag-CD nanohybrid as a probe to detect antioxidants such as ascorbic acid in near-infrared window, and the probe possesses a linear range of 0.2-60μM. More importantly, this sensor could not only function in aqueous solution, but also display well selective response in intricate biological fluids. In addition, an IMPLICATION logic gate was constructed based on the unique characteristics of Ag-CD nanohybrid which presages more opportunities for application in single and multiple biological sensing.

Glutathione-protected silver nanoclusters for sensing trace-level Hg2+ in a wide pH range

An effective fluorescence method for the selective and rapid determination of trace-level Hg2+ in a wide pH range had been proposed based on the glutathione-protected Ag nanoclusters (NCs). Factors affecting the fluorescence intensity of GSH–Ag NCs were investigated. We found that the fluorescence intensity of Ag NCs remained high and stable under pH from 4 to 10, which benefits the monitoring of Hg2+ under different pH conditions in real samples. The fluorescence quenching mechanism is also discussed. The fluorescence of Ag NCs could be quenched in the presence of Hg2+ with a detection limit as low as 1 nM. Good linear correlations were obtained over the concentration range from 0 to 2.5 μM under different pH values (pH = 7, pH = 4 and pH = 9). In addition, this method was successfully applied to the determination of Hg2+ in real samples.

Efficient degradation of methylene blue by magnetically separable Fe3O4/chitosan/TiO2 nanocomposites

AbstractIn this work, a facile and low-cost method for fabrication of the Fe3O4/chitosan/TiO2 nanocomposites with good adsorptive, photocatalytic, regenerated, and magnetic properties was demonstrated. The synthesized nanocomposites had potential applications for adsorption and degradation of organic pollutants in wastewater. Under the optimal condition, degradation rate of methyl blue by the Fe3O4/chitosan/TiO2 nanocomposites was 93%. The renewable photocatalytic activity of the nanocomposites was also investigated. After multi-run experiments, the reused Fe3O4/chitosan/TiO2 nanocomposites still kept high photocatalytic performance. Thus, Fe3O4/chitosan/TiO2 nanocomposites could serve as convenient, effective, and recyclable photocatalysts.

A novel Zn–TiO2/C@SiO2 nanoporous material on rice husk for photocatalytic applications under visible light

AbstractA series of self-nitrogen-doped and Zn-doped TiO2/C@SiO2 (ZTRH) nanoporous composites with high surface area and excellent biological hierarchical porous structure have been synthesized by sol–gel method at different temperatures. The porous SiO2 and activated carbon from the decomposition of rice husk (RH) were regarded as the template and porous catalytic carrier. The structure, crystallinity, morphology, and other physical–chemical properties of the samples were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transforminfrared spectroscopy, N2 adsorption–desorption isotherms, and UV–vis diffuse reflectance spectroscopy. The feasibility of ZTRH nanoporous composites for decomposing pollutants was evaluated by rhodamine B under visible light irradiation. Compared with the traditional photocatalytic materials, ZTRH nanoporous materials not only performed high efficiency in pollutants degradation, but also exhibited good adsorption prop...

Hydrothermal synthesis of easy-recycled tobermorite/SiO2/Fe3O4 composites for efficient treatment of phosphorus in wastewater

AbstractIn this work, tobermorite/SiO2/Fe3O4 composites were designed and synthesized by hydrothermal method for the treatment of phosphorus in wastewater. The composites were characterized by scanning electron microscopy and X-ray diffraction. The removal efficiency of phosphorus on the tobermorite/SiO2/Fe3O4 composites was carried out and investigated under various conditions, such as contact time, sorbent content, and pH. After the multi-run experiments, the phosphorous elimination of the tobermorite/SiO2/Fe3O4 composites was declined slightly comparing with the first-run experiments. Compared with the conventional crystallization methods, tobermorite/SiO2/Fe3O4 composites not only gave high efficiency to remove phosphorus from wastewater without any complicated pretreatment, but also provided excellent magnetic properties for separating the phosphorus from water, which made it easy recycled. Moreover, tobermorite/SiO2/Fe3O4 composites had excellent P-elimination properties even in the strong acidic or...

Investigation on the analytical application of cationic Gemini surfactant 12-4-12 and its interaction with DNA.

The quantitative determination of nucleic acids is of great importance in fundamental research and clinical diagnosis. In this work, the interaction between DNA and cationic Gemini surfactant 12-4-12, which changes the conformation of DNA, was investigated by UV-vis absorption, FT-IR spectra and steady-state fluorescence techniques. A hydrophobic pyrene probe was used to investigate the microenvironment change and calculate the critical micelle concentration (CMC) of Gemini surfactant 12-4-12 (0.69 mmol/L), which is close to the value obtained from the conductivity method (0.79 mmol/L). A new detection assay for DNA is proposed with Gemini surfactant 12-4-12, using the resonance light-scattering (RLS) technique. The formation of DNA-12-4-12 complex resulted in enhanced RLS signals at 368 nm, which is proportional to DNA concentration in the range 0.304-5.32 mg/L, with a detection limit of 35 µg/L. Most coexisting substances do not interfere in the detection and four synthetic samples were analyzed satisfactorily.

Spectral study of interaction between poly [acrylamide-(2-methyl acryloxyethyl) dimethyl buthylammonium bromide] and nucleic acids.

A polycation, poly[acrylamide-(2-methylacryloxyethyl) dimethyl buthylammonium bromide] [P (AM-DMB)], was synthesized. The interaction between P (AM-DMB) and DNA was studied by spectral methods. Resonance light scattering spectra, FTIR-spectra and UV-spectra were used to study the mechanisms of the interaction. The results indicate that the conformation of the DNA alters during the interaction because the microenvironment of DNA changes. The binding constant K between P (AM-DMB) and DNA is 8.0 × 10(3)  L mol(-1) .

Amino-functionalized silica-encapsulated Mn/ZnS quantum dots for the room-temperature phosphorescence determination of graphene oxide in environmental water samples

We developed a simple and sensitive room-temperature phosphorescence (RTP) method for the determination of graphene oxide (GO) in environmental water samples using amino-functionalized silica-encapsulated Mn/ZnS quantum dots (Mn/ZnS@SiO2-NH2) as a phosphorescent probe. The maximum phosphorescence excitation and emission wavelengths of the synthesized Mn/ZnS@SiO2-NH2 nanoparticles were 320 nm and 595 nm. The RTP intensity of the Mn/ZnS@SiO2-NH2 nanoparticles could be quenched in the presence of GO with a detection limit as low as 1.0 mg L−1. Good linear correlations were obtained over the concentration range from 0 to 10.0 mg L−1 with a correlation coefficient of 0.9987, and 10.0 to 25.0 mg L−1 with a correlation coefficient of 0.9979. The phosphorescence quenching mechanism was also discussed. This method was successfully applied to the determination of GO in environmental water samples which allows more opportunities for its application in biological and environmental systems.