Shikuo Li

Green synthesis of silver nanoparticles using Capsicum annuum L. extract

Silver nanoparticles (NPs) were rapidly synthesized by treating silver ions with a Capsicum annuum L. extract. The reaction process was simple and convenient to handle, and was monitored using ultraviolet-visible spectroscopy (UV-vis). The effect of Capsicum annuum L. proteins on the formation of silver NPs was investigated using X-ray photoemission spectroscopy (XPS), electrochemical measurements, Fourier-transform infrared spectroscopy (FTIR) and differential spectrum techniques. The morphology and crystalline phase of the NPs were determined from transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD) spectra. The results indicated that the proteins, which have amine groups, played a reducing and controlling role during the formation of silver NPs in the solutions, and that the secondary structure of the proteins changed after reaction with silver ions. The crystalline phase of the NPs changed from polycrystalline to single crystalline and increased in size with increasing reaction time. A recognition–reduction–limited nucleation and growth model was suggested to explain the possible formation mechanism of silver NPs in Capsicum annuum L. extract.

Self‐Assembled 3D Flowerlike Hierarchical Fe3O4@Bi2O3 Core–Shell Architectures and Their Enhanced Photocatalytic Activity under Visible Light

Three-dimensional (3D) flowerlike hierarchical Fe(3)O(4)@Bi(2)O(3) core-shell architectures were synthesized by a simple and direct solvothermal route without any linker shell. The results indicated that the size of the 3D flowerlike hierarchical microspheres was about 420 nm and the shell was composed of several nanosheets with a thickness of 4-10 nm and a width of 100-140 nm. The saturation magnetization of the superparamagnetic composite microspheres was about 41 emu g(-1) at room temperature. Moreover, the Fe(3)O(4)@Bi(2)O(3) composite microspheres showed much higher (7-10 times) photocatalytic activity than commercial Bi(2)O(3) particles under visible-light irradiation. The possible formation mechanism was proposed for Ostwald ripening and the self-assembled process. This novel composite material may have potential applications in water treatment, degradation of dye pollutants, and environmental cleaning, for example.

Magnetic Fe3O4@C@Cu2O composites with bean-like core/shell nanostructures: Synthesis, properties and application in recyclable photocatalytic degradation of dye pollutants

Magnetic Fe3O4@C@Cu2O composites with a bean-like core/shell nanostructure have been successfully synthesized by a self-assembly approach. The synthetic route is feasible, low-cost and green. The size of the as-prepared magnetic composites is about 420 nm and the shells are composed of several nanoparticles in the range of 5∼10 nm. Interestingly, the carbonaceous layer with bound hydrophilic groups inherited from the starting materials acted as both the linker and the stabilizer between Fe3O4 and Cu2O. The Fe3O4@C@Cu2O composites exhibit ferromagnetic behaviour, and good dispersibility in aqueous solution. Importantly, the bean-like core/shell composites show universal and powerful visible-light-photocatalytic activity for the degradation of Rhodamine-B (RhB), methyl orange (MO), and alizarin red (AR) relative to commercial Cu2O and Degussa P-25 powders. These novel magnetic composites may find applications in dye water treatment, degradation of organic pollutants and environmental cleaning etc.

In Situ Growth of Matchlike ZnO/Au Plasmonic Heterostructure for Enhanced Photoelectrochemical Water Splitting

In this paper, we report a novel matchlike zinc oxide (ZnO)/gold (Au) heterostructure with plasmonic-enhanced photoelectrochemical (PEC) activity for solar hydrogen production. The matchlike heterostructure with Au nanoparticles coated on the tip of ZnO nanorods is in situ grown on a zinc (Zn) substrate by using a facile hydrothermal and photoreduction combined approach. This unique heterostructure exhibits plasmonic-enhanced light absorption, efficient charge separation and transportation properties with tunable Au contents. The photocurrent density of the matchlike ZnO/Au heterostructure reaches 9.11 mA/cm(2) at an applied potential of 1.0 V (vs Ag/AgCl) with an Au/Zn atomic ratio of 0.039, which is much higher than that of the pristine ZnO nanorod array (0.33 mA/cm(2)). Moreover, the solar-to-hydrogen conversion efficiency of this special heterostructure can reach 0.48%, 16 times higher than that of the pristine ZnO nanorod array (0.03%). What is more, the efficiency could be further improved by optimizing the Au content of the heterostructure. The formation mechanism of such a unique heterostructure is proposed to explain the plasmonic-enhanced PEC performance. This study might contribute to the rational design of the visible-light-responsive plasmonic semiconductor/metal heterostructure photoanode to harvest the solar spectrum.

Assembly of dandelion-like Au/PANI nanocomposites and their application as SERS nanosensors.

The monodisperse, uniform dandelion-like Au/polyaniline (PANI) composite nanospheres were synthesized by a simple one-step process without any additives or templates. The nanospheres are really composed of many short nanorods and the average diameter of whole nanospheres is about 180 nm. The morphology of Au/PANI composites could be controlled by adjusting the molar ratio of HAuCl(4) to aniline. The prepared nanocomposite is developed as a wonderful sensor for the detection of Hg(2+) ions, which is based upon the Raman intensity response of PANI to Hg(2+) ions. Results from the morphology-dependent sensitivity investigations show that the dandelion-like nanospheres have an ultra sensitive response (as low as 10(-11)M) compared with other morphologies. The nanosensor also exhibits good reproducibility and greater selectivity for Hg(2+) ions than the other heavy metal ions. And the mechanism was proposed. The proposed nanosensors can be applied for highly sensitive and selective chemical analysis in a variety of environmental detection.

Novel structure CuI/PANI nanocomposites with bifunctions: superhydrophobicity and photocatalytic activity

CuI/polyaniline (PANI) nanocomposites with novel structure were successfully synthesized using CuSO4 as the oxidant for aniline in the presence of KI. The morphology of the composites can be controlled by adjusting the reaction conditions. Remarkably, the nanocomposite films display excellent superhydrophobicity without further modification by low-free energy materials. The static contact angle (CA) for water on the surface of the resulting nanocomposites is over 160°. The special wettability is attributed to the novel structure of the CuI/PANI nanocomposites with high roughness. Moreover, for the first time, the photocatalytic property of the as-synthesized CuI/PANI nanocomposites has been studied, showing that they display excellent photocatalytic activity for the degradation of rhodamine B (RhB) under visible light irradiation. It is attributed to a synergic effect between PANI and CuI. According to the experimental results, a photocatalytic mechanism is proposed. The developed nanocomposites could have potential applications in superhydrophobic coatings, decontamination corrosion prevention, radiation proofing and so on.

Self-healable hydrogel on tumor cell as drug delivery system for localized and effective therapy

A self-healable chitosan(CS)/polyvinyl alcohol (PVA) hydrogel as an injectable drug carrier was first prepared in situ on tumor cells for effective and localized therapy. PVA molecules have a synergistic effect on the formation and maintenance of 3D network conformation of hydrogel. The hydrogel shows good biocompatibility and could be easily and rapidly formed. When loaded with fluorouracil (5-FU), the hydrogel possessed good drug retention ability at pH 7.4, which can prevent the loss of drug to normal cells and reduce the side effect. As well, the hydrogel shows continuous and controllable drug release, with the final cumulative releasing amount of 84.8% at pH 5.0. Therefore, the hydrogel not only could maintain a higher 5-FU concentration around tumor cells to enhance the antitumor effect, but also can achieve pH sensitive controllable drug release at the lesion site. Meantime, the attractive self-healing ability of the CS/PVA hydrogel is first revealed in this study, which contributes to the regeneration of its integral network from the broken fragments. The CS/PVA hydrogel may hold promise for better applications in anti-tumor therapy.

Novel TiO2/PEGDA Hybrid Hydrogel Prepared in Situ on Tumor Cells for Effective Photodynamic Therapy

A novel inorganic/organic hybrid hydrogel system containing titanium dioxide (TiO2)/poly(ethylene glycol) double acrylates (PEGDA) was prepared by in situ photopolymerization on tumor cells for photodynamic therapy (PDT). TiO2 nanorods with diameter of ∼5 nm and length of ∼25 nm in this system presented dual functions, as effective photosensitizers for PDT and initiators for causing the in situ formation of hydrogel, under near-infrared (NIR) irradiation. The hybrid hydrogel retained the TiO2 around tumor cell to form a drug-loaded hydrogel shell. This resulted in a high concentration of singlet oxygen ((1)O2) under NIR irradiation, which induced apoptosis of tumor cell. Also, the hydrogel could reduce the side effects by preventing TiO2 from migrating to normal tissue. Furthermore, the TiO2 nanorods in this hydrogel shell were photochemically recyclable and could be reused in regular treatment. The outcomes of this study provide a new way to exploit multifunction of inorganic semiconductor nanomaterials for a variety of biomedical applications.

One-step synthesis of silver nanoparticles in self-assembled multilayered films based on a Keggin structure compound

Ag nanoparticles (NPs) formed in situ by the photochemical reduction of phosphotungstic acid (H3PW12O40, PTA) under UV-irradiation in polyelectrolyte multilayer nanoreactors composed of poly(ethyleneimine)–silver ions (PEI–Ag+) and PTA fabricated on solid substrates by alternating adsorption, wherein the PTA plays the role of a UV-switchable reducing agent and an assembly reagent. Transmission electron microscopy (TEM) images show the formation of sphere-like silver NPs with sizes smaller than 12 nm in the multilayer films. Atomic force microscopy (AFM) and field emission scanning microscopy (FESEM) imply a film with a rough surface. The UV-vis characteristic absorbances of PTA and Ag NPs increase almost linearly with the number of bilayers, suggesting that the deposition process was regular and highly reproducible from layer to layer. X-Ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) confirm the incorporation of PEI–Ag and PTA into the films. The multilayer films also exhibit good electrocatalytic activity for the oxidation of uric acid, which may be used in electrochemical biosensors.

Controlled synthesis, growth mechanism and optical properties of FeWO4 hierarchical microstructures

Monoclinic ferrous tungstate (FeWO4) microcrystals with hierarchical nano/microstructures have been selectively synthesized via a facile hydrothermal process in the presence of ethylenediamine tetraacetic acid disodium salt (Na2EDTA) and hexamethylenetetramine (HMT). HMT played triple roles as the reducing agent, alkaline source, and crystal growth modifier, while Na2EDTA served as the chelating reagent and structure-directing agent. The appropriate conditions for synthesis of multilayer flower-like FeWO4 were 200 °C and 8 h with the concentrations of Na2EDTA and HMT at 0.03 mol L−1 and 0.025 mol L−1, respectively. The morphology of FeWO4 showed dramatic changes from a bulky amorphous crystal to multilayer hexangular microcrystals with increasing Na2EDTA concentration, while increasing HMT concentration would transform the hexagonal structure to a sixfold symmetry architecture and the aspect ratio of symmetry axis decreased gradually. Ostwald ripening and the self-assembled process was proposed for the possible formation mechanism. The photoluminescence (PL) intensity of the multilayer FeWO4 microcrystals was higher than that of other FeWO4 structures. Magnetic measurement of hexangular FeWO4 microcrystals showed a small ferromagnetic ordering at low temperature. Furthermore, this work may open novel routes to the chelating reagent-assisted synthesis of hierarchical architectures with various morphologies.