Xiaoyun Hu

Hydrophobic graphene nanosheets decorated by monodispersed superparamagnetic Fe3O4 nanocrystals as synergistic electromagnetic wave absorbers

The comprehension of the interactions between the building blocks in hybrids can give us an insight into the design and application of highly efficient electromagnetic wave absorption materials. Herein, we report a facile in situ thermal decomposition route for the fabrication of superparamagnetic Fe3O4 nanocrystals anchored on hydrophobic graphene nanosheets as synergistic electromagnetic wave absorbers. The microstructures and interactions of the Fe3O4–graphene hybrids are systematically investigated, and the results suggest that the Fe3O4 nanocrystals are uniformly decorated and chemically bonded on the surface of graphene nanosheets without obvious conglomeration or large vacancies. The Fe3O4–graphene hybrids show hydrophobic and superparamagnetic characteristics. Combing the benefits of superparamagnetic Fe3O4 nanocrystals and electrically conducting graphene, the Fe3O4–graphene hybrids show a maximum reflection loss (RL) of −40 dB at 6.8 GHz with a matching thickness of 4.5 mm, and the effective absorption bandwidth (RL < −10 dB) is 4.6–18 GHz with an absorber thickness of only 2–5 mm. However, due to the lack of dielectric loss, only a weak RL of −5 dB is obtained in bare Fe3O4 nanocrystals. The remarkably enhanced electromagnetic wave absorption properties of the Fe3O4–graphene hybrids are owing to effective impedance matching and synergistic interaction. Moreover, compared with other reported graphene-based electromagnetic wave absorption materials, the hydrophobic Fe3O4–graphene hybrids prepared in this work are considered to be more stable and suitable to be applied in some particular environmental conditions, such as rain.

In situ growing Bi2MoO6 on g-C3N4 nanosheets with enhanced photocatalytic hydrogen evolution and disinfection of bacteria under visible light irradiation

Bi2MoO6/g-C3N4 heterojunctions were fabricated by an in situ solvothermal method using g-C3N4 nanosheets. The photocatalytic activities of as-prepared samples were evaluated by hydrogen evolution from water splitting and disinfection of bacteria under visible light irradiation. The results indicate that exfoliating bulk g-C3N4 to g-C3N4 nanosheets greatly enlarges the specific surface area and shortens the diffusion distance for photogenerated charges, which could not only promote the photocatalytic performance but also benefit the sufficient interaction with Bi2MoO6. Furthermore, intimate contact of Bi2MoO6 (BM) and g-C3N4 nanosheets (CNNs) in the BM/CNNs composites facilitates the transfer and separation of photogenetrated electron-hole pairs. 20%-BM/CNNs heterojunction exhibits the optimal photocatalytic hydrogen evolution as well as photocatalytic disinfection of bacteria. Furthermore, h+ was demonstrated as the dominant reactive species which could make the bacteria cells inactivated in the photocatalytic disinfection process. This study extends new chance of g-C3N4-based photocatalysts to the growing demand of clean new energy and drinking water.

Synergistic Effect of N and Ni 2 + on Nanotitania in Photocatalytic Reduction of CO 2

Nitrogen and nickel codoped nanotitania ( N - Ni / TiO 2 ) photocatalysts for producing methanol by photocatalytic reduction of CO 2 were prepared by an improved sol-gol method. The catalysts were characterized by XRD, HRTEM, DES, FTIR, TG-DSC, and UV-Vis, respectively. The experimental results indicated that nano- N - Ni / TiO 2 had better properties than the pure nanotitania ( TiO 2 ), N doped titania ( N / TiO 2 ), and Ni 2 + doped titania ( Ni / TiO 2 ), considering their performance of photoresponse and photocatalytic reduction of CO 2 . The methanol yield could reach 482.0μmol/g-cat under optimal conditions. Additionally, the synergetic effect of N and Ni 2 + on nano- TiO 2 in photocatalytic reduction of CO 2 was explained, and the mechanism of photocatalytic reduction CO 2 on N - Ni / TiO 2 catalyst was proposed.

A graphitic-C3N4-hybridized Ag3PO4 tetrahedron with reactive {111} facets to enhance the visible-light photocatalytic activity

A graphitic-C3N4-hybridized Ag3PO4 tetrahedron with reactive {111} facets was prepared though a facile solvent evaporation method and applied for the photocatalytic degradation of methyl blue (MB) in aqueous solution and removal of NO at the indoor air level under visible light irradiation (>400 nm). In addition to the superior photocatalytic performance of the highly reactive {111} facets of tetrahedral Ag3PO4, the hybridization with g-C3N4 was confirmed to further improve the photocatalytic activity, and the content of g-C3N4 had a great influence on the photocatalytic activity. The photocatalytic activity enhancement of g-C3N4/Ag3PO4 {111} hybrid photocatalysts could be ascribed to the efficient separation of electron–hole pairs through a Z-scheme system composed of Ag3PO4, Ag and g-C3N4, in which Ag particles acted as the charge separation center. Furthermore, h+ and O2˙− played the major roles in the photocatalysis process. This work suggested that the synthesized g-C3N4/Ag3PO4 {111} hybrid would be a promising visible light driven photocatalytic material for environmental remediation.

Studies on the binding of rhaponticin with human serum albumin by molecular spectroscopy, modeling and equilibrium dialysis

Rhaponticin (RHA) possesses a variety of pharmacological activities including potent antitumor, antitumor-promoting, antithrombotic, antioxidant and vasorelaxant effects. In the solvation effect, RHA exhibited bathochromic shift in emission spectra with the increasing solvent polarity. The binding between RHA and HSA was investigated by molecular spectroscopy combining with modeling and equilibrium dialysis. Fluorescence data showed that the quenching of HSA by RHA was result of forming the complex of RHA-HSA. According to Stern-Volmer equation, the binding parameters between RHA and HSA were determined. The enthalpy change (ΔH) and entropy change (ΔS) were calculated to be -2.75kJmol(-1) and 1.58Jmol(-1)K(-1), indicating that the hydrogen bonds and hydrophobic interactions played a dominant role in the binding. The conformational investigation revealed the α-helical structure was decreased and the polypeptides of HSA were slightly folded upon the addition of RHA. The effect of common ions on the binding between RHA and HSA was also investigated. Furthermore, the result of warfarin displacement site indicated that RHA could bind to the site I of HSA, which was in agreement with the molecular modeling. When excitation wavelength was set at 260 or 355nm, RHA exhibited a fluorescence peak at 390nm, based on which, a simple and rapid fluorimetric method was developed and validated to determine RHA in the equilibrium dialysis. Calibration curves of RHA were linear over the concentration range of 1.1-15.0μM with the detection limits of 0.03μM. Examination of protein binding ability showed that RHA with 8.0μM concentrations in HSA achieved the percent of bound 82.3±2.5%.

Solvent effect on the absorption and fluorescence of ergone: Determination of ground and excited state dipole moments

The effect of solvents on the absorption and emission spectra of ergone has been studied in various solvents at 298 K. The bathochromic shift was observed in absorption and fluorescence spectra with the increase of solvents polarity, which implied that transition involved was π→π*. And the normalized transition energy value E(T)(N) showed some scattering when plotted versus Δν. The ground state and excited state dipole moments were calculated by quantum-mechanical second-order perturbation method as a function of the dielectric constant (ε) and refractive index (n). The result was found to be 1.435 D and 2.520 D in ground state and excited state respectively. And also, the density functional calculations were used to obtain the ground state and excited state dipole moments for it has proven to be suitable for calculating electronic excitation energy. And the result is consistent with the experimental.

Green and facile microwave-assisted synthesis of TiO2/graphene nanocomposite and their photocatalytic activity for methylene blue degradation

TiO2 (P25)/graphene nanocomposite photocatalyst have been successfully synthesized with P25 and different ratios of graphene oxide through a green and facile one-step microwave-assisted method. Graphene oxide was restored to graphene sheets and P25 was coated on it simultaneously during the reaction. The method offers easy access to the semiconductor/graphene nanocomposites with a uniform coating and strong interactions between semiconductor and the underlying graphene sheets. The prepared P25/graphene nanocrystals hybrid has superior photocatalytic activity in the degradation of methylene blue, showing an impressive photocatalytic enhancement over P25. The improved photocatalytic activities may be attributed to increased adsorptivity of dyes, extended light absorption range, and efficient charge separation properties of a two-dimensional graphene network.

Hydrothermal synthesis of Graphene-TiO2 nanowire with an enhanced photocatalytic activity

The hydrothermal method was used to synthesize TiO2 nanowire (NW) and then fabricate graphene-TiO2 nanowire nanocomposite (GNW). Graphene oxide (GO) was prepared via improved Hummers’method. GO reduction to graphene and hybridization between NW and graphene by forming chemical bonding. The as-prepared composites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM), and ultraviolet visible (UV-Vis) diffuse reflectance spectra. The photocatalytic activity was evaluated by the photodegradation of methylene blue (MB). The prepared GNW nanocomposite has superior photocatalytic activity in the degradation test, showing an impressive photocatalytic enhancement over NW. At the same time, in comparison with Graphene-TiO2 nanoparticle (NP) nanocomposite (GNP), GNW have a better activity which because NW have more uniform dispersion on graphene with less agglomeration.

Incorporation of lanthanide (Eu3+) ions in ZnS semiconductor quantum dots with a trapped-dopant model and their photoluminescence spectroscopy study

Doping quantum dots (QDs) with lanthanide (Ln) ions is promising to modify the optical properties of QDs, but incorporating Ln(3+) ions into QD hosts remains a challenge. In this work, we adopt the trapped-dopant model for fabricating Eu-doped ZnS QDs via direct wet chemical synthesis. Sharp Eu dopant photoluminescence (PL) was observed in the PL spectra of the as-prepared Eu-doped ZnS QDs and the bands at ~590, ~618 and ~695 nm were assigned to transitions from (5)D0 to (7)F1, (7)F2 and (7)F4, respectively. Quenching of the ZnS bandgap PL and enhancement of the Eu dopant PL were observed with increasing Eu(3+) doping concentration, and also, the excitation spectra for Eu emission (618 nm) were similar to the typical excitonic features of the ZnS host. These spectroscopic results, as well as the XRD and EDS data, demonstrated that Eu(3+) ions were incorporated in the ZnS host rather than just on the surface, and the Eu dopant PL was derived from energy transfer from the QD host to Eu(3+) rather than direct excitation of Eu(3+). By surface passivation, the sharp Eu emission was well-separated from the ZnS bandgap emission, which led to a good signal-to-noise ratio for more sensitive detection.

Folate-functionalized nanoparticles for controlled ergosta-4,6,8(14),22-tetraen-3-one delivery.

To improve the therapeutic effect of ergosta-4,6,8(14),22-tetraen-3-one (ergone), a folate-decorated ergone-bovine serum albumin nanoparticles (abbreviated FA-ergone-BSANPs) was prepared. The properties were extensively studied by Zetasizer Nano Particle Size Analyzer and TEM, which indicated the prepared nanoparticles were spherical in shape and uniform in size with a zeta potential of -23.8 mV. The drug-loading capacity also has been determined with drug loading content of 2.73% and encapsulation efficiency of 61.8%. In vitro release studies proved the much slow drug release from the nanoparticles during circulating in the blood stream and the increase of drug release at the target sites. The FA-ergone-BSANPs showed enhanced cellular uptake, increased targeting capacity, and increased cytotoxicity against KB cells over-expressing folate receptor (FR), which indicated that its potent cell-killing activity is specific for cells that express the FR. In vivo experiment also confirmed that FA-ergone-BSANPs represent a FR-targeted chemotherapeutic that can produce potent activity against FR-positive tumors. In conclusion, this report has a great significance in pharmacology and clinical medicine as well as methodology. Further detailed dose-optimization studies will be required for better understanding in vivo pharmacokinetic and bio-distribution behaviors.