Direct electrochemistry and electrocatalysis of cytochrome <Emphasis Type="Italic">c</Emphasis> based on dandelion-like Bi<Subscript>2</Subscript>S<Subscript>3</Subscript> nanoflowers

The direct electrochemistry and electrocatalysis of cytochrome c (Cyt c) based on dandelion-like bismuth sulfide (d-Bi₂S₃) nanoflowers have been developed. The morphologies and composition of the d-Bi₂S₃ were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). Then, the electrochemical behaviors of Cyt c immobilized within the d-Bi₂S₃/chitosan film and its electrocatalytic ability toward hydrogen peroxide (H₂O₂) reduction were investigated by cyclic voltammetry. The electron transfer rate constant was estimated to be 13.1 s^?1, suggesting that a fast direct electron transfer was realized. The prepared Cyt c/d-Bi₂S₃/chitosan nanobiocomposite-modified electrode possessed excellent electrocatalytic ability toward H₂O₂ reduction that showed linearity in the range from 0.5 μM to 1.56 mM with a correlation coefficient of 0.9993. The detection limit was 0.2 μM on signal-to-noise ratio of 3. In addition, the d-Bi₂S₃ nanoflowers may be also applied to direct electron transfer of other redox proteins.     

Aptamer based lysozyme assay using fluorescent CuInS<Subscript>2</Subscript> quantum dots and graphene oxide,and its application to inhibitor screening

We report on a widely applicable approach for protein detection by using triple-helix DNA mediated CuInS₂ quantum dot (QD) and graphene oxide (GO) nanocomposite. The CuInS₂ QDs were coated with mercaptopropionic acid and then covalently linked to a hairpin aptamer against lysozyme (HLA). Single-stranded DNA (triple helix-forming oligonucleotide; THFO) readily absorbs on the surface of GO via π-stacking interaction, and this results in the formation of THFO-GO. If HLA-CuInS₂ QDs are added to the THFO-GO system, the fluorescence of HLA-CuInS₂ QDs (at excitation/emission wavelengths of 590/665 nm) is quenched. Lysozyme has a higher affinity for HLA than THFO. Therefore, in the presence of lysozyme, it will bind to the HLA-CuInS₂ QD and displace the THFO-GO. This results in the restoration of fluorescence that is related to the concentration of lysozyme. The fluorescence of the QDs is turned on. The calibration plot is linear in the 0.01 to 1.8 ng·mL￣¹ concentration range, with a 3 pg·mL￣¹ detection limit (at a signal-to-noise ratio of 3). The method was also applied to study the inhibition of lysozyme by Ivy _Ec . In our perception, this method has a wide scope in that it may become applicable to any protein for which an appropriate aptamer is available.

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Graphical abstract A novel convenient and universal fluorescence nanoprobe for sensitive and selective detection of lysozyme and inhibitor screening was established using triple-helix DNA mediated CuInS₂ QDs and GO nanocomposites

     

Direct synthesis of indium nanoparticles and their application to prepare CuInS<Subscript>2</Subscript> thin films and solar cells

This paper reports a simple hot-injection method to prepare monodisperse indium nanoparticles which are applied as indium sources to prepare CuInS₂ thin films and solar cells. Indium nanoparticles with particle sizes of about 10 nm or even smaller are synthesized and are influenced by the stabilizing agent, reaction temperature and solvent, which can be elucidated by a burst nucleation and growth mechanism. Moreover, the inks from the indium nanoparticles are used to prepare compact and well crystallized CuInS₂ (CIS) films which are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and I–V measurement. Finally, the CIS solar cells are fabricated on the basis of the CIS films, and their efficiency is about 2.08%, which can be further improved by decreasing series resistance.     

Solvent‐free Synthesis of Hexagonal Iron Sulfide Nanoflowers

Employing green and economic solvent‐free synthesis route, hexagonal iron sulfide (Fe₇S₈) nanoflowers were successfully synthesized for the first time. In the experiment, ferric hexadecylxanthate was used as the precursor, and hexagonal iron sulfide (Fe₇S₈) nanoflowers were obtained by thermal decomposition of the precursor at 260°C without any additional solvent or inert gas protection. The as‐prepared iron sulfide nanoflowers were characterized by means of X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The characterization results indicated that the nanoflowers had uniform size distribution with an average size of about 160 nm. The proposed strategy provides a possible general route for the synthesis of other metal chalcogenide nanostructures.     

Synthesis and antibacterial activity of Ag/CeO<Subscript>2</Subscript> hybrid architectures

Flower-like ceria (CeO₂) architectures consisting of well aligned nanosheets were first synthesized by a glycol solvothermal method. The size of CeO₂ architectures is about 5?μm in width and 10?μm in length, with the nanosheets thickness below 100?nm. Subsequently, the adsorbed Ag ions on the surface of CeO₂ were in situ reduced to form Ag nanoparticles (NPs), leading to the fabrication of Ag/CeO₂ hybrid architectures (HAs). The formed Ag NPs with sizes of 20–40?nm were uniformly loaded on the surface of the CeO₂ sheets. The antibacterial properties of Ag/CeO₂ HAs against Gram-negative E. coli and Gram-positive S. aureus were evaluated by minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and a filter paper inhibition zone method. The results demonstrated that Ag/CeO₂ HAs displayed excellent antibacterial activity toward S. aureus and E. coli, which were attributed to the synergistic antibacterial effect between Ag NPs and CeO₂ in HAs_. Here, CeO₂ nanoflowers as a new substrate could restrict Ag NPs aggregations and improve their antibacterial activities. Therefore, the resulted Ag/CeO₂ HAs would be considered as a promising antibacterial agent.

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Effect of Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> addition on structure and magnetic properties of Ni<Subscript>0.5</Subscript>Zn<Subscript>0.5</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanofibers

Ni_0.5Zn_0.5Fe₂O₄ nanofibers with addition of 0–5 wt% Bi₂O₃ were synthesized by calcination of the electrospun polyvinylpyrrolidone/inorganic composite nanofibers at the temperature below the melting point of Bi₂O₃. The effects of Bi₂O₃ addition on the phase structure, morphology and magnetic properties of the nanofibers were investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, selected area electron diffraction and vibrating sample magnetometer. It is found that the nanofiber diameter, crystallite size and magnetic parameters can be effectively tuned by simply adjusting the amount of Bi₂O₃ addition. The average diameter of Ni_0.5Zn_0.5Fe₂O₄ nanofibers doped with different contents of Bi₂O₃ ranges from 40 to 63 nm and gradually decreases with increasing Bi₂O₃ content. The addition of Bi₂O₃ does not induce the phase change and all the samples are a single-phase spinel structure. The amorphous Bi₂O₃ tends to concentrate on the nanoparticle surface and/or grain boundary and can retard the particles motion as well as the grain growth, resulting in a considerable reduction in grain size compared to the pristine sample. The specific saturation magnetization and coercivity of the nanofibers gradually decrease with the increase of Bi₂O₃ amount. Such behaviors are explained on the basis of chemical composition, surface effect, domain structure and crystal anisotropy.     

Electrochemical performance of novel Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> glass-ceramic nanocomposites as electrodes for energy storage devices

The novel Li₃V₂(PO₄)₃ glass-ceramic nanocomposites were synthesized and investigated as electrodes for energy storage devices. They were fabricated by heat treatment (HT) of 37.5Li₂O–25V₂O₅–37.5P₂O₅?mol% glass at 450 °C for different times in the air. XRD, SEM, and electrochemical methods were used to study the effect of HT time on the nanostructure and electrochemical performance for Li₃V₂(PO₄)₃ glass-ceramic nanocomposites electrodes. XRD patterns showed forming Li₃V₂(PO₄)₃ NASICON type with monoclinic structure. The crystalline sizes were found to be in the range of 32–56 nm. SEM morphologies exhibited non-uniform grains and changed with variation of HT time. The electrochemical performance of Li₃V₂(PO₄)₃ glass-ceramic nanocomposites was investigated by using galvanostatic charge/discharge methods, cyclic voltammetry, and electrochemical impedance spectroscopy in 1 M H₂SO₄ aqueous electrolyte. The glass-ceramic nanocomposites annealed for 4 h, which had a lower crystalline size, exhibited the best electrochemical performance with a specific capacity of 116.4 F g^?1 at 0.5 A g^?1. Small crystalline size supported the lithium ion mobility in the electrode by decreasing the ion diffusion pathway. Therefore, the Li₃V₂(PO₄)₃ glass-ceramic nanocomposites can be promising candidates for large-scale industrial applications in high-performance energy storage devices.     

The Role of Y<Subscript>2</Subscript>O<Subscript>3</Subscript> and MgO Additives on the Photoluminescence Properties of Si<Subscript>3</Subscript>N<Subscript>4</Subscript> Nanoparticles

The current research addressed synthesizing and studying photoluminescence studies of β-Si₃N₄ nanoparticles. The effect of MgO and Y₂O₃ as the typical additives on photoluminescence behaviour was evaluated. The β-Si₃N₄ with MgO and Y₂O₃ additive specimens were fabricated by a solid state technique (ball-milled method). The as-prepared products were characterized by X-ray diffraction technique, transmission electron microscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and Raman analysis. The results showed that after ball-milled process, hexagonal β-Si₃N₄ with MgO or Y₂O₃ as the additives with the size distribution of 45–50 nm was obtained. The optical properties of the as-synthesized product were also investigated by photoluminescence and diffuse reflection spectroscopy. The obtained results confirmed that employing MgO as an additive, in comparison to the Y₂O₃, could enhance emission properties in the synthesized silicon nitride nanoparticles. The obtained results also showed that MgO–Si₃N₄ pair acted as FRET system to enhance the emission intensity of β-Si₃N₄ nanoparticles.     

Biodegradable nanoprobe based on MnO<Subscript>2</Subscript> nanoflowers and graphene quantum dots for near infrared fluorescence imaging of glutathione in living cells

Near infrared (NIR) emitting semiconductor quantum dots can be excellent fluorescent nanoprobes, but the poor biodegradability and potential toxicity limits their application. The authors describe a fluorescent system composed of graphene quantum dots (GQDs) as NIR emitters, and novel MnO₂ nanoflowers as the fluorescence quenchers. The system is shown to be an activatable and biodegradable fluorescent nanoprobe for the “turn-on” detection of intracellular glutathione (GSH). The MnO₂-GQDs nanoprobe is obtained by adsorbing GQDs onto the surface of MnO₂ nanoflowers through electrostatic interaction. This results in the quenching of the NIR fluorescence of the GQDs. In the presence of GSH, the MnO₂-GQDs nanoprobe is degraded and releases Mn²⁺ and free GQDs, respectively. This gives rise to increased fluorescence. The nanoprobe displays high sensitivity to GSH and with a 2.8 μM detection limit. It integrates the advantages of NIR fluorescence and biodegradability, selectivity, biocompatibility and membrane permeability. All this makes it a promising fluorescent nanoprobe for GSH and for cellular imaging of GSH as shown here for the case of MCF-7 cancer cells.

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Graphical abstract A biodegradable NIR fluorescence nanoprobe (MnO₂-GQDs) for the “turn-on” detection of GSH in living cell was established, with the NIR GQD as the fluorescence reporter and the MnO₂ nanoflower as the fluorescence quencher.

     

CuInS2量子点敏化太阳能电池中尺寸依赖的电子注入和光电性质

研究了CuInS₂（CIS）量子点敏化太阳能电池（QDSSCs）的电子注入和器件性能与粒子尺寸之间的依赖关系. 首先合成了不同尺寸的CuInS₂量子点（QDs）,制备了CuInS₂量子点敏化的TiO₂薄膜,并组装了量子点敏化太阳能电池. 通过循环伏安法确定了CuInS₂量子点的能级位置. 采用时间分辨荧光光谱分析测量了CuInS₂量子点到TiO₂薄膜的电子转移速率和效率. 结果发现,随着粒子尺寸从4.0 nm减小到2.5 nm,电子注入速率略微增加而电子注入效率减小,同时量子点敏化太阳能电池的开路电压基本不变,而光电转换效率、短路电流和填充因子（FF）均减小. 上述研究结果表明量子点敏化太阳能电池性能的优化可以通过改变量子点的尺寸来实现.     

Enhancing the Performance of Dye‐Sensitized Solar Cells with a Gold‐Nanoflowers Box

To improve the electron collection, electron lifetime, and light‐harvesting efficiency of dye‐sensitized solar cells simultaneously, Au nanoflowers were prepared and used to cover the entire TiO₂ film. Deposition of Au nanoflowers around the TiO₂ film formed a light‐scattering “box” that covered the entire TiO₂ film. Compared with a light‐scattering layer that only covers the top surface of TiO₂, the Au‐nanoflowers box exhibited better light‐harvesting efficiency due to omnidirectional light scattering, faster electron transport (attributed to the formation of electron channels between the metallic Au nanoflowers and the electron‐collection electrode), and slower charge recombination. As a consequence, the short‐circuit photocurrent and open‐circuit photovoltage were both enhanced significantly, which improved the power conversion efficiency from 8.12 to 10.91 % (34 %) when an Au‐nanoflowers box was wrapped around the photoanode.     

Adsorption of NO,NH<Subscript>3</Subscript> and H<Subscript>2</Subscript>O on V<Subscript>2</Subscript>O<Subscript>5</Subscript>/TiO<Subscript>2</Subscript> catalysts

The adsorption of small molecules NO, NH₃ and H₂O on V₂O₅/TiO₂ catalysts is studied with the semiempirical SCF MO method MSINDO as pre-stage for the selective catalytic reduction of NO. The mixed catalyst is represented by hydrogen-terminated cluster models. The local arrangement of the cluster atoms is in accordance with available experimental information. Partial relaxation of cluster atoms near the adsorption sites is taken into account. Calculated adsorption energies are compared with experimental literature data. Rapid convergence of computed properties with cluster size is observed. A possible reaction mechanism for the catalytic reduction of NO with NH₃ and O₂ is outlined.     

Anodic composite deposition of RuO2·xH2O–TiO2 for electrochemical supercapacitors

This communication demonstrates the first work on anodic composite deposition of oxide nanocomposites. Rutile TiO₂ nanoflowers with an average petal size of ca. 10 nm in diameter and 100 nm in length were synthesized from a TiCl₃ solution purged with air at 25 °C for 12 days prior to the composite deposition. Hydrous ruthenium oxide (RuO₂·xH₂O) and TiO₂ nanoflowers were composite-deposited onto Ti substrates for supercapacitors. In comparing with RuO₂·xH₂O deposits, RuO₂·xH₂O–TiO₂ nanocomposites with a highly porous nature exhibit the weakly mass-dependent specific capacitance and high-power capacitive characteristics.     

Shape and size controlled synthesis of CuInS<Subscript>2</Subscript> particles in polyalcohol system used as “printable ink” for thin films

Chalcopyrite semiconductor CuInS₂ (CIS) particles are synthesized using a simple method and low-cost solvent. Two kinds of agents are used to adjust and control the sizes and shapes of the particles. The phases, morphologies and grown processes of the products are studied. The results show that the sizes and shapes of the CIS particles can be adjusted and controlled. Furthermore, CIS thin films are fabricated using these two kinds of particles. The thin films appear different morphologies and qualities via different kinds of particles, indicating the importance of controlling the shape and size of the precursor particles.     

Gold catalysts supported on ZnO/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> for low-temperature CO oxidation

Gold catalysts with loadings ranging from 0.5 to 7.0 wt% on a ZnO/Al₂O₃ support were prepared by the deposition–precipitation method (Au/ZnO/Al₂O₃) with ammonium bicarbonate as the precipitation agent and were evaluated for performance in CO oxidation. These catalysts were characterized by inductively coupled plasma-atom emission spectrometry, temperature programmed reduction, and scanning transmission electron microscopy. The catalytic activity for CO oxidation was measured using a flow reactor under atmospheric pressure. Catalytic activity was found to be strongly dependent on the reduction property of oxygen adsorbed on the gold surface, which related to gold particle size. Higher catalytic activity was found when the gold particles had an average diameter of 3–5 nm; in this range, gold catalysts were more active than the Pt/ZnO/Al₂O₃ catalyst in CO oxidation. Au/ZnO/Al₂O₃ catalyst with small amount of ZnO is more active than Au/Al₂O₃ catalyst due to higher dispersion of gold particles.     

Relationship between the microstructure,structure and magnetic properties in Ni<Subscript>3</Subscript>(XO<Subscript>4</Subscript>)<Subscript>2 </Subscript>orthophosphate and orthovanadate obtained by two different preparation methods

Powders of composition Ni₃(XO₄)₂ with X = P and V were synthesized by both the ceramic conventional and the Pechini-type in situ polymerizable complex (IPC) method. The Pechini-type IPC technique produces these materials as single phases at reduced temperatures (750–810 °C) as opposed to the conventional solid-state reaction methods in which processing temperatures higher than 800 °C are usually required to obtain a single-phase of these materials. Reflections peaks of the samples obtained in both cases can be indexed well with the standard patterns for Ni₃(PO₄)₂ and Ni₃(VO₄)₂ compounds. The lattice parameters of these materials were calculated by the Rietveld refinement method from X-ray diffraction data (XRD). The average crystal size as well as the crystallinity and morphology of the powder samples were characterized by scanning electron microscopy (SEM). The results show a clearly minor particle size by using the Pechini-IPC method than the ceramic one. Moreover, the magnetic behaviour was studied on powered samples by using magnetic susceptibility data.     

Controlled synthesis,characterization and thermal properties of Mg<Subscript>2</Subscript>B<Subscript>2</Subscript>O<Subscript>5</Subscript>

Optimum conditions for synthesizing monoclinic and triclinic Mg₂B₂O₅ compounds by high-temperature solid-state reactions were investigated. Mixtures composed of boric acid and magnesium oxide at MgO:B₂O₃ mole ratios of 1:0.25, 1:0.5 and 1:1.5 were heated for 1 hour at temperatures between 600–1050°C and the formed phases were identified by XRD analysis. Monoclinic Mg₂B₂O₅ was formed by heating at 850°C for 4 hours together with minimum amounts of triclinic Mg₂B₂O₅, while triclinic Mg₂B₂O₅ was formed as a single phase at 1050°C for the same reaction time. The products obtained at optimum conditions were subjected to a series of tests to determine their chemical compositions, particle size distributions, surface area values, IR spectra and TG/DTA patterns.      

In situ synthesis of plate-like Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles in porous cellulose films with obvious magnetic anisotropy

Nanocomposite cellulose films with obvious magnetic anisotropy have been prepared by in situ synthesis of plate-like Fe₂O₃ nanoparticles in the cellulose matrix. The influence of the concentrations of FeCl₂ and FeCl₃ solutions on the morphology and particle size of the synthesized Fe₂O₃ nanoparticles as well as on the properties of the composite films has been investigated. The Fe₂O₃ nanoparticles synthesized in the cellulose matrix was γ-Fe₂O₃, and its morphology was plate-like with size about 48 nm and thickness about 9 nm, which was totally different from those reported works. The concentration of FeCl₂ and FeCl₃ solution has little influence on the particle size and morphology of the Fe₂O₃ nanoparticles, while the content of Fe₂O₃ nanoparticles increased with the increase of the concentration of the precursor solution, indicating that porous structured cellulose matrix could modulate the growth of inorganic nanoparticles. The unique morphology of the Fe₂O₃ nanoparticles endowed the composite films with obvious magnetic anisotropy, which would expand the applications of the cellulose based nanomaterials.     

Glass formation in the CaO-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-B<Subscript>2</Subscript>O<Subscript>3</Subscript> and SrO-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-B<Subscript>2</Subscript>O<Subscript>3</Subscript> systems

A physicochemical study of glasses based on the MO-Bi₂O₃-B₂O₃ and SrO-Bi₂O₃-B₂O₃ systems was performed. Glass formation regions were found. The structural and optical properties, as well as the thermal behavior of the glasses, were studied.     

Synthesis of Na<Subscript>2</Subscript>Ti<Subscript>3</Subscript>O<Subscript>7</Subscript> nanoparticles by sonochemical method for solid state electrolyte applications

Na₂Ti₃O₇ ceramic materials have been widely used in sodium-ion battery applications with relative good results; however, there are still several studies that might be carried out in the improvement of the Na₂Ti₃O₇ properties and the overall batteries’ performance. In this direction, we used sonochemical method following a thermal treatment in order to synthetized pure phase Na₂Ti₃O₇ nanopowders. X-ray diffraction characterization revealed that Na₂Ti₃O₇ is the primary phase in nanopowders and ceramic sample; although, a high level of amorphization was observed in the sonicated nanopowder without heat treatment process. Nanopowder-prepared ceramic sample showed a crystallite size of 50 nm after sintering at 900 °C for 1 h. The specific surface area, pore volume, and pore size were obtained from the B.E.T. measurements, being 51 m² g^?1, 0.07 cm³ g^?1, and 55 Å, respectively. The capacitance values of the nanopowder-prepared ceramic sample were in the order of microfarad. The total energy of the system was used to determine relaxation time of the sample (τ ₀ = 31 ms).