Synthesis of novel C-doped g-C3N4 nanosheets coupled with CdIn2S4 for enhanced photocatalytic hydrogen evolution.

Photocatalytic hydrogen generation from water splitting has become a favorable route for the utilization of solar energy. An effective strategy, the combination of C-doping with nanocomposite semiconductors, is presented in this work. C-doped g-C3N4 (CCN) was prepared by supramolecular self-assembly and subsequently a number of CdIn2S4/CCN composite photocatalysts were designed and fabricated though in situ decoration of CdIn2S4 crystals on the surface of CCN nanosheets via a hydrothermal method. This unique architecture was able to efficiently promote the transfer and separation of photon-generated charges, enhance light absorption, and significantly increase photocatalytic H2 production. Detailed characterization was performed to analyze the crystal structure, morphology, elementary composition, optical properties and catalytic mechanism. The CdIn2S4/CCN nanocomposites with optimal CdIn2S4 content exhibited a maximum H2 production rate of 2985 µmol h-1 g-1, almost 15 times more than that obtained using pure g-C3N4 (205 µmol h-1 g-1). In addition, the hybrid photocatalysts display good recycling stability under visible-light irradiation. This research may provide promising information for the preparation of more efficient multifunctional hybrid photocatalysts with excellent stability in fine chemical engineering.

Electrochemiluminescent biosensor with DNA link for selective detection of human IgG based on steric hindrance.

A highly selective DNA-based electrochemiluminescence (ECL) based biosensor is described for the detection of human IgG. It is exploiting the effect of steric hindrance that affects the strength of the ECL signal in the presence of IgG. Digoxin-linked signaling DNA was specifically bound to IgG, and this causes steric hindrance which limits the ability of DNA to hybridize with capturing DNA attached to a gold electrode. Europium (II) doped CdSe quantum dots were covalently linked to the DNA in order to generate the ECL signal. Using this steric hindrance hybridization method, the ECL signal of the biosensor were proportional to the concentration of IgG with a wide linear range and a 14 pM detection limit. Conceivably, the method can be expanded to the detection of a wide range of proteins for which homologous recognition elements are available.

Chitosan/silver nanocomposites for colorimetric detection of glucose molecules.

This study was about the simple method for the rapid colorimetric and visual detection of glucose molecules in water medium. Silver nanoparticles were spread on the chitosan surface (CS/Ag NCs) and it was characterized by UV-visible spectroscopy, fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The CS/Ag NCs displayed a strong surface plasmon resonance band at 429 nm which disappears in the addition of accelerative concentrations of glucose molecules and it was attended by color alteration from yellow to colorless. The interaction of glucose molecules on the CS/Ag NCs was displayed through TEM technique. Glucose molecules was detected not only by naked eyes (from yellow to purple grey) but also by UV-vis spectrophotometer in the concentration range between 0 and 100 µM, with limit detection of 5 µM and a good linear relationship of R2 value = 0.99. The proposed paper was used for the application of the detection of glucose molecules in water sample with adequate outcome. This CS/Ag NCs was very simple and low cost system without using any other enzymatic catalyst and organic chromogenic agents for glucose molecules detection.

Biologically synthesized copper oxide nanoparticles enhanced intracellular damage in ciprofloxacin resistant ESBL producing bacteria.

Copper oxide nanoparticles (CuO NPs) were synthesized biologically using leaf extract of Camilla japonica. The typical UV-visible spectral peak of CuO NPs was observed at a wavelength of ∼290 nm, which confirmed their successful synthesis. From scanning electron microscope (SEM) and transmission electron microscope (TEM) analyses, the synthesized CuO NPs were found to possess spherical shape. Energy dispersive X-ray analyzer (EDX) results revealed that the CuO NPs are almost pure with atomic percentages of 50.92 for Cu and 49.08 for O. Fourier transform infrared (FTIR) confirmed the presence of an absorption peak located at a wavenumber position of ∼480 cm-1 typical for highly pure CuO NPs. TEM images displayed that the particles are relatively uniform in size ∼15-25 nm. The P. aeruginosa and K. pneumonia showed complete resistance against Hexa 077 antibiotic discs. The result of ≤22 ceftazidime and ≤27 cefotaxime confirmed that both the uropathogens were ESBL producers. The ≥8 mm of the MIC stripe further confirmed that both the uropathogens were ESBL producers. Furthermore, the antibacterial activity of CuO NPs against selected ESBL producing P. aeruginosa and K. pneumoniae at minimum inhibition concentration (MIC) of 100 µg/mL. The decreased cell viability and damaged membrane construction of both the uropathogens were observed by confocal laser scanning microscope (CLSM) using AO/EB stains at desired MIC dose. The morphological damage of the bacterial cells was demonstrated by SEM analysis. Hence, based on the above in vitro findings, the results suggested that the CuO NPs are efficient antibacterial compounds against ESBL producing bacteria, and that the plant leaf mediated CuO NPs can be considered as novel and promising material to act against various infectious bacteria.

Synthesis of ultrathin WSe2 nanosheets and their high-performance catalysis for conversion of amines to imines.

Tungsten diselenide (WSe2) is the material with the lowest thermal conductivity in the world. Most physical methods are used for the synthesis of tungsten diselenide. Here, a simple colloidal method is reported for the synthesis of WSe2 nanosheets. The composition, valence, size, morphology and properties of the samples were characterized and measured. Results showed that the obtained WSe2 nanosheets with a thickness of 0.7 nm had strong blue fluorescence. Significantly, the synthesized WSe2 nanosheets exhibited excellent catalytic activity for the aerobic coupling of amines to imines, with 100% yield under visible light irradiation and air atmosphere. As a photocatalyst, it exhibited excellent recyclability, and maintained a high yield after 5 cycles. It was found that this reaction could also happen in the presence of natural light by slightly extending the reaction time. Moreover, H2O was used as a solvent in the catalytic process, avoiding expensive and toxic organic solvents. This work provides an efficient, economical and sustainable process for the synthesis of imines and shows the great potential of WSe2 nanosheets as photocatalysts for organic synthesis.

Enhanced photoelectrochemical DNA sensor based on TiO2/Au hybrid structure.

A novel enhanced photoelectrochemical DNA sensor, based on a TiO2/Au hybrid electrode structure, was developed to detect target DNA. The sensor was developed by successively modifying fluorine-tin oxide (FTO) electrodes with TiO2 nanoparticles, gold (Au) nanoparticles, hairpin DNA (DNA1), and CdSe-COOH quantum dots (QDs), which acted as signal amplification factors. In the absence of target DNA, the incubated DNA1 hairpin and the CdSe-COOH QDs were in close contact with the TiO2/Au electrode surface, leading to an enhanced photocurrent intensity due to the sensitization effect. After incubation of the modified electrode with the target DNA, the hairpin DNA changed into a double helix structure, and the CdSe QDs moved away from the TiO2/Au electrode surface, leading to a decreased sensitization effect and photoelectrochemical signal intensity. This novel DNA sensor exhibited stable, sensitive and reproducible detection of DNA from 0.1 µM to 10 fM, with a lower detection limit of 3 fM. It provided good specificity, reproducibility, stability and is a promising strategy for the detection of a variety of other DNA targets, for early clinical diagnosis of various diseases.

A label-free photoelectrochemical biosensor for urokinase-type plasminogen activator detection based on a g-C3N4/CdS nanocomposite.

Herein, we established a novel ultrasensitive photoelectrochemical biosensor for detecting urokinase-type plasminogen activator (u-PA), based on a g-C3N4/CdS nanocomposite. The prepared nanocomposite was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible absorption spectroscopy, and Fourier transform infrared spectroscopy, thus indicating that the nanocomposite was prepared successfully. In the typical process, the prepared nanocomposite was deposited on the surface of a bare FTO electrode. After being air-dried, the g-C3N4/CdS nanocomposite modified electrode was successively incubated with antibody against urokinase-type plasminogen activator and the blocking agent BSA to produce a photoelectrochemical biosensor for u-PA. In the presence of target u-PA antigen, the photocurrent response of the prepared biosensor electrode decreased significantly. The proposed novel photoelectrochemical biosensor exhibited good sensitivity, specificity, and reproducibility for u-PA detection, and a low detection limit of 33 fg mL-1, ranging from 1 µg mL-1-0.1 pg mL-1. The proposed strategy should provide a promising method for detection of other biomarkers.

Biologically synthesized zinc oxide nanoparticles as nanoantibiotics against ESBLs producing gram negative bacteria.

The accelerative outgrowth of extended spectrum ß-lactamases (ESBLs) producing Escherichia coli (E. coli) and Proteus mirabilis (P. mirabilis) was mainly due to incessant relentless influence of antibiotics thereby increasing incidence and death rate which was obvious from the survey of ESBLs producing bacteria related health problem. In the present paper, we synthesized and characterized zinc oxide nanoparticles (ZnO NPs) employing using Camellia japonica leaf extract, bactericidal action of these NPs against extended spectrum ß lactamases (ESBLs) positive E. coli and P. mirabilis clinical strains owing the minimal inhibitory concentration (MIC) percentage 83, 81% at 100 µg/mL concentration and minimum bactericidal concentration (MBC) final inhibiting concentration at 150 µg/mL. Moreover, confocal laser scanning microscopy (CLSM) and scanning electron microscope (SEM) results evident for loss of viability, cell shrinkage, disarrangement of cell membrane, and cell wall lysis activity of ZnO NPs against ESBLs positive E. coli BDUMS3 (KY617770) and P. mirabilis BDUMS1 (KY617768) strains. From the results, it was observed that the biologically synthesized ZnO NPs has stronger antibacterial effect against ESBLs producing bacterial strains. Nevertheless, current date there is no reports of antibacterial activity of metal oxide (ZnO) NPs against ESBL producing gram negative bacteria. Consequently, this finding is the first report in this respect and it shows band gap energy and ROS accumulation to damage the cell wall and inhibit the growth of ESBL producing gram negative strains.

Highly sensitive electrochemical biosensor for streptavidin detection based on CdSe quantum dots.

An electrochemical biosensor was developed based on a steric hindrance hybridization assay to allow the highly sensitive detection of streptavidin. In the steric hindrance hybridization assay, the signaling strand DNA (sig-DNA) was labeled at the 3' end with CdSe quantum dots (QDs) and at the 5' end with biotin, and capturing strand DNA (the complementary strand of sig-DNA) was labeled at the 5' end with thiol. The steric hindrance effect generated by streptavidin which was bound with the signaling DNA strand. The streptavidin limited the ability of the sig-DNA to hybridize with the cap-DNA, which were linked on the surface of a gold electrode. Therefore, the concentration of streptavidin was detected indirectly based on the concentration of CdSe QDs on the electrode surface. The concentration of CdSe QDs on the electrode surface was detected by differential pulse anodic stripping voltammetry. Under optimal conditions, the streptavidin detection range using the as-prepared biosensor was 1.96pg/mL to 1.96µg/mL and the detection limit was 0.65pg/mL. The experimental results showed that the electrochemical biosensor could detect streptavidin rapidly and accurately.

Colloidal Synthesis and Thermoelectric Properties of CuFeSe2 Nanocrystals.

Copper-based chalcogenides that contain abundant, low-cost and environmentally-friendly elements, are excellent materials for numerous energy conversion applications, such as photocatalysis, photovoltaics, photoelectricity and thermoelectrics (TE). Here, we present a high-yield and upscalable colloidal synthesis route for the production of monodisperse ternary I-III-VI2 chalcogenides nanocrystals (NCs), particularly stannite CuFeSe2, with uniform shape and narrow size distributions by using selenium powder as the anion precursor and CuCl2·2H2O and FeCl3 as the cationic precursors. The composition, the state of valence, size and morphology of the CuFeSe2 materials were examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM), respectively. Furthermore, the TE properties characterization of these dense nanomaterials compacted from monodisperse CuFeSe2 NCs by hot press at 623 K were preliminarily studied after ligand removal by means of hydrazine and hexane solution. The TE performances of the sintered CuFeSe2 pellets were characterized in the temperature range from room temperature to 653 K. Finally, the dimensionless TE figure of merit (ZT) of this Earth-abundant and intrinsic p-type CuFeSe2 NCs is significantly increased to 0.22 at 653 K in this work, which is demonstrated to show a promising TE materialand makes it a possible p-type candidate for medium-temperature TE applications.

Photoelectrochemical immunoassay for human interleukin 6 based on the use of perovskite-type LaFeO3 nanoparticles on fluorine-doped tin oxide glass.

A film of perovskite-type LaFeO3 nanoparticles (NPs) was deposited on fluorine-doped tin oxide (FTO) conducting glass via dipping-lifting and calcination. Scanning electron microscopy shows that the NPs are evenly distributed on the surface of the glass. The modified glass was further coated with antibody against human interleukin 6 (IL-6) to result in a photoelectrochemical immunosensor for IL-6. The well-established photoelectrochemical immunoassay has a linear current response in the range of 0.1 pg·mL-1 to 0.1 µg·mL-1 and a detection limit as low as 33 fg·mL-1. Graphical abstract Schematic of a novel photoelectochemical immunoassay for the measurement of IL-6 based on perovskite-type LaFeO3 nanoparticles. The immunoassay had a higher sensitivity and may also be applied to other bioanalysis and environment monitoring.

Synthesis of TiO2-loaded Co0.85Se thin films with heterostructure and their enhanced catalytic activity for p-nitrophenol reduction and hydrazine hydrate decomposition.

P-nitrophenol (4-NP) and hydrazine hydrate are considered to be highly toxic pollutants in wastewater, and it is of great importance to remove them. Herein, TiO2-loaded Co0.85Se thin films with heterostructure were successfully synthesized by a hydrothermal route. The as-synthesized samples were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, transmission electron microscopy and selective-area electron diffraction. The results demonstrate that TiO2 nanoparticles with a size of about 10 nm are easily loaded on the surface of graphene-like Co0.85Se nanofilms, and the NH3 · H2O plays an important role in the generation and crystallization of TiO2 nanoparticles. Brunauer-Emmett-Teller measurement shows that the obtained nanocomposites have a larger specific surface area (199.3 m(2) g(-1)) than that of Co0.85Se nanofilms (55.17 m(2) g(-1)) and TiO2 nanoparticles (19.49 m(2) g(-1)). The catalytic tests indicate Co0.85Se-TiO2 nanofilms have the highest activity for 4-NP reduction and hydrazine hydrate decomposition within 10 min and 8 min, respectively, compared with the corresponding precursor Co0.85Se nanofilms and TiO2 nanoparticles. The enhanced catalytic performance can be attributed to the larger specific surface area and higher rate of interfacial charge transfer in the heterojunction than that of the single components. In addition, recycling tests show that the as-synthesized sample presents stable conversion efficiency for 4-NP reduction.

Multifunctional Co(0.85)Se-Fe(3)O(4) nanocomposites: controlled synthesis and their enhanced performances for efficient hydrogenation of p-nitrophenol and adsorbents.

A new kind of multifunctional Co0.85 Se-Fe3 O4 nanocomposites is synthesized by loading Fe3 O4 nanoparticles (NPs) with a size of about 5 nm on the surface of Co0.85 Se nanosheets under hydrothermal conditions without using any surfactant or structure-directing agents. The Co0.85 Se-Fe3 O4 nanocomposite exhibits remarkable catalytic performance for hydrogenation of p-nitrophenol (4-NP) at room temperature and good adsorption behavior for methylene blue trihydrate in water. This nanocomposite also shows a high specific surface area and magnetic separation capability for recyclable utilization. The enhanced performances both in catalysis and adsorption are better than either individual component of Co0.85 Se nanosheets or Fe3 O4 nanoparticles, demonstrating the possibility for designing new multifunctional nanocomposites with improved performances for catalysis, adsorbents, and other applications.

Fabrication of GO/PANi/CdSe nanocomposites for sensitive electrochemiluminescence biosensor.

A novel graphene oxide sheets/polyaniline/CdSe quantum dots (GO/PANi/CdSe) nanocomposites were successfully synthesized and used for the sensitive electrochemiluminescence (ECL) biosensing. The GO/PANi/CdSe nanocomposites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), ultraviolet-visible (UV-vis) absorption spectroscopy, photoluminescence (PL) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Finally, the nanocomposites were employed to construct the biosensor via layer-by-layer assembly for the ECL detection of Cytochrome C (Cyt C). The whole process was characterized by cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS). Experimental parameters such as the ratio of GO/PANi, the K(2)S(4)O(8) concentration and the pH value of electrolyte solution were studied to investigate the effect on the ECL intensity. Under the optimized conditions, the ECL intensity decreased linearly with the Cyt C concentrations in the range from 5.0×10(-8) to 1.0×10(-4) M with detection limit of 2.0×10(-8) M. Besides, the as-proposed biosensor exhibits high specificity, good reproducibility, and stability, and may be applied in more bioanalytical systems.

Direct electrochemistry and electrocatalytic behavior of hemoglobin entrapped in Ag@C nanocables/gold nanoparticles nanocomposites film.

Direct electrochemistry of hemoglobin (Hb) was successfully fabricated by immobilizing Hb on the nanocomposites containing of Ag@C nanocables and Au nanoparticles (AuNPs) modified glassy carbon electrode (GCE). The immobilized Hb retained its biological activity and shown high catalytic activities to the reduction of H2O2 by circular dicroism (CD) spectrum, fourier transform infrared (FT-IR) spectrum and cyclic voltammetry (CV). Experimental conditions such as scan rate and pH Value were studied and optimized. The results indicated that the resulting biosensor are linear to the concentrations of H2O2 in the ranges of 6.67 x 10(-7)-2.40 x 10(5) M, and the detection limit is 2.02 x 10(-7) M. The electrochemical biosensor has also high stability and good reproducibility.

A novel enzymatic hydrogen peroxide biosensor based on Ag/C nanocables.

A novel enzymatic hydrogen peroxide sensor was successfully fabricated based on the nanocomposites containing of Ag/C nanocables and gold nanoparticles (AuNPs). Ag/C nanocables have been synthesized by a hydrothermal method and then AuNPs were assembled on the surface of Ag/C nanocables. The nanocomposites were confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS). The above nanocomposites have satisfactory chemical stability and excellent biocompatibility. Cyclic voltammetry (CV) was used to evaluate the electrochemical performance of the Ag/C/Au nanocomposites at glassy carbon electrode (GCE). The results indicated that the Ag/C/Au nanocomposites exhibited excellent electrocatalytic activity to the reduction of H(2)O(2). It offered a linear range of 6.7×10(-9) to 8.0×10(-6) M, with a detection limit of 2.2×10(-9) M. The apparent Michaelis-Menten constant of the biosensor was 51.7×10(-6) M. These results indicated that Ag/C/Au nanocomposites have potential for constructing of a variety of electrochemical biosensors.

Ultralong silver trimolybdate nanowires: synthesis, phase transformation, stability, and their photocatalytic, optical, and electrical properties.

Ultralong orthorhombic silver trimolybdate nanowires (NWs) can be synthesized by a simple hydrothermal process without using any structure directing agent. Their phase transformation and stability to thermal and modeling sunlight from a Xe lamp have been systematically studied. Well-dispersed Ag nanoparticles can in situ form on the backbone of the nanowires by photoirradiation, and their photocatalytic and optical properties have been investigated. The investigations on photocatalytic, photoluminescent, and surface-enhanced Raman scattering (SERS) of the as-synthesized nanowires indicate that these nanowires loaded with Ag nanoparticles by photoirradiation can be a new kind of photocatalytic and luminescent material and potentially can be used as an efficient SERS substrate. The electrical conductivity of an individual nanowire exhibits almost nonlinear and symmetric current/voltage (I/V) characteristics for bias voltages in the range of -5 to 5 V. Ohmic mechanism, Schottky, and the Poole-Frenkel emission play an important part, respectively, in low, medium, and high electrical fields.

Superlong beta-AgVO3 nanoribbons: high-yield synthesis by a pyridine-assisted solution approach, their stability, electrical and electrochemical properties.

Monoclinic beta-silver vanadate (beta-AgVO(3)) nanoribbons with widths of 300-600 nm, thicknesses of ca. 40 nm, and lengths of 200-300 microm can be easily synthesized in high yield directly from a hydrothermal reaction between V(2)O(5) and AgNO(3) in a solution containing a small amount of pyridine. The results demonstrated that the formation of single-crystal AgVO(3) nanoribbons is strongly dependent on the reaction temperature, especially, the presence of pyridine and its dosage. A possible growth mechanism of single-crystal AgVO(3) nanoribbons has been proposed. Exposure of the nanoribbons to electron beam will easily result in the formation of Ag nanoparticles embedded in situ on the backbone of the nanoribbons, making the nanoribbons potentially useful as efficient catalyst support. The electrical conductivity of an individual single-crystal beta-AgVO(3) nanoribbon exhibits nonlinear and symmetric current/voltage (I-V) characteristics for bias voltages in the range of -6 to 6 V.

Cellulose acetate-directed growth of bamboo-raft-like single-crystalline selenium superstructures: high-yield synthesis, characterization, and formation mechanism.

High-yield synthesis of bamboo-raft-like single-crystalline selenium superstructures has been realized for the first time via a facile solvothermal approach by reducing SeO2 with ethylene alcohol in the presence of cellulose acetate. The formation of a raftlike superstructure with various forms is strongly dependent on the temperature, amount of cellulose acetate, reaction time, and even preheating treatment. The suitable amount of cellulose acetate is essential for the formation of elegant and uniform raft Se. The morphology, microstructure, optical properties, and chemical compositions of bamboo-raft-like selenium were characterized using various techniques (X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution (HR) TEM, X-ray photoelectron spectroscopy, UV-vis spectroscopy, FTIR spectroscopy, and Raman spectroscopy). A possible growth mechanism has been proposed. Such special superstructures could provide a useful precursor for potential applications.

Crystallization and shape evolution of single crystalline selenium nanorods at liquid-liquid interface: from monodisperse amorphous Se nanospheres toward Se nanorods.

The reduction of selenious acid solution with hydrazine hydrate in the presence of poly(vinylpyrrolidone) (PVP) can produce a stable dispersion of uniform and amorphous selenium particles capped with PVP with a size of 100 nm. Further addition of a solvent with low polarity such as n-butyl alcohol into this aqueous solution and mild stirring result in the transportation of amorphous selenium particles onto a liquid-liquid interface between water and n-butyl alcohol. Subsequent crystallization and shape evolution on this interface occurred and finally resulted in the formation of single crystalline selenium nanorods. The results demonstrated that the enrichment of nanoparticles with amphiphilic property at a liquid-liquid interface between a polar solvent and another solvent of low polarity can result in crystallization and phase transformation for the formation of nanostructures.