Size-controllable synthesis of spherical ZnO nanoparticles: Size- and concentration-dependent resonant light scattering

A new and simple direct precipitation method assisted with ultrasonic agitation was proposed for the preparation of spherical ZnO nanoparticles. The size of the ZnO nanoparticles, 10 nm to 85 nm, was tuned through controlling the calcination temperature and changing the ratio of the reactants. The resonant light scattering (RLS) of the ZnO nanoparticles dispersed/suspended in aqueous solution of Triton X-100 was studied under room temperature. It was found that the ZnO nanoparticles of different size or concentration all have a characteristic RLS peak at 387 nm. Under optimal conditions, the RLS intensity was proportional to the ZnO concentration in the range of 7.3 × 10^?8–1 × 10^?4 mol L^?1, while the cubic root of the RLS intensity was found to be proportional to the size of ZnO nanoparticles. Further, the quantitative relationship of the size of the ZnO nanoparticles versus the calcination temperature was derived, and this could be used to forecast/control the nano-size in the nano-ZnO preparation.     

Ultra-sensitive cholesterol biosensor based on low-temperature grown ZnO nanoparticles

A high-sensitive cholesterol amperometric biosensor based on the immobilization of cholesterol oxidase (ChOx) onto the ZnO nanoparticles has been fabricated which shows a very high and reproducible sensitivity of 23.7 μA mM^?1 cm^?2, detection limit (based on S/N ratio) 0.37 ± 0.02 nM, response time less than 5 s, linear range from 1.0 to 500.0 nM and correlation coefficient of R = 0.9975. A relatively low value of enzyme’s kinetic parameter (Michaelis–Menten constant) ～4.7 mM has been obtained which indicates the enhanced enzymatic affinity of ChOx to Cholesterol. To the best of our knowledge, this is the first report in which such a very high-sensitivity and low detection limit has been achieved for the cholesterol biosensor by using ZnO nanostructures modified electrodes.     

Electrodeposition of monodispersed metal nanoparticles in a nafion film: Towards highly active nanocatalysts

We have explored a new and facile method for the fabrication of metal nanoparticles on the electrode surface. The approach for fabricating metal nanoparticles was carried out by two steps consisting of ion-exchange in nafion film coated on the electrode and subsequent reduction of metal ions to metallic nanoparticles by electrochemical method. The results of characterization by TEM show that metal nanoparticles were nearly monodispersed in the whole nafion film. The average diameters of Cu, Co and Ni nanoparticles were statistically measured to be 5.1 nm ± 0.2 nm, 4.6 nm ± 0.2 nm and 4.7 nm ± 0.2 nm, respectively. The amount of metal nanoparticles can be readily controlled by the amount of nafion coated on the electrode. By performing the H₂O₂ reduction at the obtained Cu nanoparticles, the high electrocatalytic activity of metal nanoparticles fabricated has been confirmed.     

Fabrication of metallic nanoparticles by electrochemical discharges

A method for the fabrication of metallic nanoparticles in large quantities by electrochemical discharges is presented. In an aqueous electrolyte, large current density (∼1 A/mm² at ∼20 V) leads to the formation of a ‘gas film’ around the electrode through which discharges occur. When metal ions are additionally present in the electrolyte and when the applied potential is cathodic, metal nanoparticles (typically 10–150 nm) are produced. The nanoparticles are formed in the solution and the gas film prevents them from depositing on the electrode. To control the size of the particles a method based on ‘rotating electrode’ is developed. Rotating the cathode rotates the fluid around it, which provides centrifugal force to the particles to move away from the electrode where they cannot grow. This method has been successfully used for fabrication of nanoparticles from several metal salts.     

Raman spectroscopic study on boron-doped silicon nanoparticles

Raman analyses were performed on thin films prepared from B-doped Si nanoparticles with an average diameter of 15 nm using the spin-coating method. The resulting spectrum exhibited a broad band with a peak near 520 cm⁻¹. The band was decomposed into three bands corresponding to the crystalline, grain boundary (GB), and amorphous regions by the least-squares band-fitting method based on the three Voigt bands. The fractions of the crystalline, GB, and amorphous regions were 37%, 35%, and 28%, respectively. A spherical particle exhibited an ordered crystalline core surrounded by a disordered shell in a transmission electron microscope (TEM) image. The crystalline fraction of the 15-nm B-doped Si nanoparticle film was much lower than that of the 19-nm P-doped Si nanoparticle film. This result suggested that the B-doping mechanism was different from that of P-doping. The temperature of the sample was estimated from the ratio of the peak intensities of anti-Stokes to Stokes Raman bands (I^AS/I^S) observed near 520 cm⁻¹. The temperature of the B-doped Si nanoparticle film upon irradiation at a power density of 4.6 kW/cm² was 298 °C, whereas the temperature of the P-doped Si nanoparticle film was 92 °C. The B-doped Si nanoparticle films were capable of producing light-induced heat.     

Anodic electrochemiluminescence of CdSe nanoparticles coreacted with tertiary amine and halide induced quenching effect

The novel anodic electrochemiluminescence (ECL) behaviors of the CdSe nanoparticles coreacted with tertiary amine were observed. The ECL intensity peak located near +1.2 V, accompanied with a shoulder above +1.5 V. The ECL emission peak estimated at about 580 nm was almost identical with that of the photoluminescence (PL), indicating the passivation of the surfaces of the nanoparticles. The dependence of the ECL on system pH and the concentration of the coreactants were also discussed. The halide ions could quench ECL, with the effective order I^? > Br^? > Cl^?. Based on these results the possible ECL processes were proposed.     

Polyol-mediated synthesis of ultrafine tin oxide nanoparticles for reversible Li-ion storage

A simple, cheap and versatile, polyol-mediated fabrication method has been extended to the synthesis of tin oxide nanoparticles on a large scale. Ultrafine SnO₂ nanoparticles with crystallite sizes of less than 5 nm were realized by refluxing SnCl₂ · 2H₂O in ethylene glycol at 195 °C for 4 h under vigorous stirring in air. The as-prepared SnO₂ nanoparticles exhibited enhanced Li-ion storage capability and cyclability, demonstrating a specific capacity of 400 mAh g⁻¹ beyond 100 cycles.     

Electrochemical sensing of hydroxylamine by gold nanoparticles on single-walled carbon nanotube films

The arrays of gold nanoparticles (AuNPs) were fabricated on flexible and transparent single-walled carbon nanotube (SWCNT) films using the electrochemical deposition method, and the patterned nanotubes were then used as electrodes for hydroxylamine detection. The sizes and densities of the AuNPs could easily be controlled by varying the amount of charge deposited, and the gold-deposited area showed a homogeneous distribution on the exposed SWCNT film surface. X-ray diffraction analysis of the AuNPs shows a face-centered cubic structure that is dominated by the lowest energy {111} facets. The oxidation of the hydroxylamine on the AuNP-deposited SWCNT films depended strongly on the solution pH, and the maximum catalytic current was observed at a pH of 9.0. A linear electrical response was observed for concentrations ranging from 0.016 to 0.210 mM, and the detection limit and the sensitivity were 0.72 μM and 165.90 μAmM^?1 cm^?2, respectively. Moreover, the amperometric response in hydroxylamine showed a stable response for a long time (300 s), during which time it retained 94% of its initial value. In the long-term storage stability test, the current response to hydroxylamine decreased slightly, with only 17% leakage after 30 days.     

Synthesis and characterization of ZnO nanoparticles by thermal decomposition of a curcumin zinc complex

ZnO nanoparticles were generated by thermal decomposition of a binuclear zinc (II) curcumin complex as single source precursor. Thermal behavior of the precursor showed a considerable weight loss at about 374 °C by an exothermic reaction with a maximum weight loss rate of 14%/min. Complete decomposition of precursor was observed within 49 min with a heating rate of 10 °C/min. Synthesized nanoparticles have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and selected area electron diffraction microscopy. Results revealed monodispersed hexagonal zincite structure with an average size of 117 ± 4 nm.     

Preparation of conducting silver paste with Ag nanoparticles prepared by e-beam irradiation

Conducting silver paste was prepared by using Ag nanoparticles which were synthesized by e-beam irradiation method (from KAERI); its conductivity was comparatively determined with Ag nanoparticles which were prepared by thermolysis method (commercial). The silver nanoparticles with the diameter of approximately 150 nm size prepared by e-beam irradiation were mixed with glass frit and sintered for 1 h at 500 °C. It is presumably concluded that the wt% of silver nanoparticle, size distribution and homogenous dispersibility of Ag nanoparticles in the pastes are the critical factors for the high conductivity of the paste. Among the various wt% of silver nanoparticle in the conducting silver pastes, silver paste with 90 wt% of silver nanoparticle has the highest conductivity as 1.6×10⁴ S cm^?1. This conductivity value is 1.6 times higher than the Ag pastes which were prepared with silver nanoparticles obtained by thermolysis method.     

Chemical bath deposition of CdS quantum dots on vertically aligned ZnO nanorods for quantum dots-sensitized solar cells

Formation of CdS quantum dots (Q dots) on the vertically aligned ZnO nanorods electrode was carried out by chemical bath deposition. The diameter and thickness of ZnO nanorods are ～100–150 nm and ～1.6 μm, respectively, and CdS Q dots on ZnO nanorods have a diameter of smaller than 15 nm. In application of the Q dots-sensitized solar cells, composite film exhibited a power conversion efficiency of 0.54% under air mass 1.5 condition (80 mW/cm²), and incident-photon-to-current conversion efficiency showed 18.6%.     

Mesoporous Fe2O3 nanoparticles as high performance anode materials for lithium-ion batteries

This work introduces an effective, inexpensive, and large-scale production approach to the synthesis of Fe₂O₃ nanoparticles with a favorable configuration that 5 nm iron oxide domains in diameter assembled into a mesoporous network. The phase structure, morphology, and pore nature were characterized systematically. When used as anode materials for lithium-ion batteries, the mesoporous Fe₂O₃ nanoparticles exhibit excellent cycling performance (1009 mA h g^− 1 at 100 mA g^− 1 up to 230 cycles) and rate capability (reversible charging capacity of 420 mA h g^− 1 at 1000 mA g^− 1 during 230 cycles). This research suggests that the mesoporous Fe₂O₃ nanoparticles could be suitable as a high rate performance anode material for lithium-ion batteries.     

Nanorods of transition metal oxalates: A versatile route to the oxide nanoparticles

A versatile route has been explored for the synthesis of nanorods of transition metal (Cu, Ni, Mn, Zn, Co and Fe) oxalates using reverse micelles. Transmission electron microscopy shows that the as-prepared nanorods of nickel and copper oxalates have diameter of 250 nm and 130 nm while the length is of the order of 2.5 μm and 480 nm, respectively. The aspect ratio of the nanorods of copper oxalate could be modified by changing the solvent. The average dimensions of manganese, zinc and cobalt oxalate nanorods were 100 μm, 120 μm and 300 nm, respectively, in diameter and 2.5 μm, 600 nm and 6.5 μm, respectively, in length. The aspect ratio of the cobalt oxalate nanorods could be modified by controlling the temperature.The nanorods of metal (Cu, Ni, Mn, Zn, Co and Fe) oxalates were found to be suitable precursors to obtain a variety of transition metal oxide nanoparticles. Our studies show that the grain size of CuO nanoparticles is highly dependent on the nature of non-polar solvent used to initially synthesize the oxalate rods. All the commonly known manganese oxides could be obtained as pure phases from the single manganese oxalate precursor by decomposing in different atmospheres (air, vacuum or nitrogen). The ZnO nanoparticles obtained from zinc oxalate rods are ～55 nm in diameter. Oxides with different morphology, Fe₃O₄ nanoparticles faceted (cuboidal) and Fe₂O₃ nanoparticles (spherical) could be obtained.     

Thin films composed of irregular micro-block arrays of closely packed CdS nanoparticles for enhanced photoelectrochemical performance

CdS is a very important semiconductor, and various micro-/nano-structured forms of CdS have been fabricated with the aim of improving its photoelectrochemical performance. We report here for the first time the preparation of a CdS film consisting of irregular micro-block arrays of closely packed CdS nanoparticles. It performs outstandingly well as a photoanode because it possesses the advantages of both arrays and nanoparticles. This CdS film is prepared simply by a combination of reaction and assembly at the gas/liquid interface (RAG/L) with successive ionic layer adsorption and reaction (SILAR), requiring no templates or expensive equipment. In this approach, the nanopores in the film of loosely aggregated CdS nanoparticles produced by RAG/L are filled by CdS nanoparticles via SILAR, forming a compact CdS film. Network micro-cracks form in the compact CdS film due to calcination caused by differential thermal expansion compared with the substrate, and these cut the CdS film into irregular micro-block arrays. This micro-/nano-structure in the prepared CdS film improves its capacity for visible light absorption, facilitates the generation/separation of excited charges, and enhances mass transfer. In an alkaline solution of methanol, the prepared CdS film exhibits the highest saturation photocurrent density (6.5 mA cm^− 2) ever reported on CdS-based photoanodes under visible light illumination.     

Honey mediated green synthesis of silver nanoparticles

The paper reports the pH controlled synthesis of silver nanoparticles using honey as reducing and stabilizing agents. By adjusting the pH of the aqueous solution containing metal ions and honey, nanoparticles of various size could be obtained at room temperature. The nanoparticles were characterized by UV–visible, high-resolution TEM, XRD and FTIR measurements. The colloid obtained at a pH of 8.5 is found to consist of monodispersed and nearly spherical silver nanoparticles of size ～4 nm which is a significant advancement in biosynthesis. The high crystallinity with fcc phase is evidenced by clear lattice fringes in the high-resolution TEM image and peaks in the XRD pattern corresponding to (1 1 1), (2 0 0), (2 2 0), (3 1 1) and (2 2 2) planes. FTIR spectrum indicates that the nanoparticles are bound to protein through the carboxylate ion group.     

High contrast ratio and fast switching polymeric electrochromic films based on water-dispersible polyaniline-poly(4-styrenesulfonate) nanoparticles

We prepared polyaniline-poly(4-styrenesulfonate) nanoparticles (PANI/PSS-NPs) by chemical oxidation polymerization in aqueous solution. We investigated the potential of the PANI/PSS-NPs to be used as an anode electrode for electrochromic devices and the effect of Li⁺ insertion (or deinsertion) kinetics and diffusion of Li⁺. A uniform electrochromic layer of PANI/PSS-NPs with a size of ca. 28 nm could be obtained by a solution process, specifically spin coating. The PANI/PSS-NPs film has a high Li⁺ diffusion coefficient (～7.7 × 10^?9 cm² s^?1) and low charge transfer resistance (～99 Ω), which result in its having a fast electrochromic response time (coloring time <1.7 s, bleaching time <2.4 s), and high coloration efficiency (>108 cm² C^?1).     

Extraction and preconcentration of trace levels of cobalt using functionalized magnetic nanoparticles in a sequential injection lab-on-valve system with detection by electrothermal atomic absorption spectrometry

A new approach to performing extraction and preconcentration employing functionalized magnetic nanoparticles for the determination of trace metals is presented. Alumina-coated iron oxide nanoparticles were synthesized and used as the solid support. The nanoparticles were functionalized with sodium dodecyl sulfate and used as adsorbents for solid phase extraction of the analyte. Extraction, elution, and detection procedures were performed sequentially in the sequential injection lab-on-valve (SI-LOV) system followed by electrothermal atomic absorption spectrometry (ETAAS). Mixtures of hydrophobic analytes were successfully extracted from solution using the synthesized magnetic adsorbents. The potential use of the established scheme was demonstrated by taking cobalt as a model analyte. Under the optimal conditions, the calibration curve showed an excellent linearity in the concentration range of 0.01–5 μg L^?1, and the relative standard deviation was 2.8% at the 0.5 μg L^?1 level (n = 11). The limit of detection was 6 ng L^?1 with a sampling frequency of 18 h^?1. The present method has been successfully applied to cobalt determination in water samples and two certified reference materials.     

Direct electron transfer of cytochrome c and its biosensor based on gold nanoparticles/room temperature ionic liquid/carbon nanotubes composite film

A robust and effective composite film based on gold nanoparticles (GNPs)/room temperature ionic liquid (RTIL)/multi-wall carbon nanotubes (MWNTs) modified glassy carbon (GC) electrode was prepared by a layer-by-layer self-assembly technique. Cytochrome c (Cyt c) was successfully immobilized on the RTIL-nanohybrid film modified GC electrode by electrostatic adsorption. Direct electrochemistry and electrocatalysis of Cyt c were investigated. The results suggested that Cyt c could be tightly adsorbed on the modified electrode. A pair of well-defined quasi-reversible redox peaks of Cyt c was obtained in 0.10 M, pH 7.0 phosphate buffer solution (PBS). RTIL-nanohybrid film showed an obvious promotion for the direct electron transfer between Cyt c and the underlying electrode. The immobilized Cyt c exhibited an excellent electrocatalytic activity towards the reduction of H₂O₂. The catalysis currents increased linearly to the H₂O₂ concentration in a wide range of 5.0 × 10⁻⁵– 1.15 × 10⁻³ M. Based on the multilayer film, the third-generation biosensor could be constructed for the determination of H₂O₂.     

Ultrasensitive determination of serum albumin using resonance light scattering based on ZnS-polyacrylic acid nanoparticles

ZnS-polyacrylic acid (ZnS-PAA) was prepared by an in situ polymerization method using nano-ZnS as core in the presence of acrylic acid (AA), and ZnS-PAA nanoparticles was characterized by ultraviolet spectrometry (UV) and transmission electron microscopy (TEM). Based on the significant increase of the resonance light scattering (RLS) intensity with the interaction between nanoparticles and serum albumin, RLS method was developed for the sensitive determination of serum albumin (BSA and HSA). Under optimum conditions, the change of the intensity (ΔI) of the RLS spectra at λ = 392 nm was linearly proportional to the concentration of BSA and HSA. The linear range was 1–100 ng mL^?1 for HSA and 1–120 ng mL^?1 for BSA, and the limit of detection (LOD) was 0.4 ng mL^?1 for HSA and 0.5 ng mL^?1 for BSA. This method proved to be very sensitive, rapid, simple and tolerant of most interfering substances.     

Spectrofluorimetric determination of fexofenadine hydrochloride in pharmaceutical preparation using silver nanoparticles

A novel sensitive fluorimetric method was investigated for the assay of fexofenadine hydrochloride (FEX) using silver nanoparticles (NPs) as a fluorescence probe. The NPs, which were prepared by chemical reduction of silver nitrate with sodium borohydride (reducing agent) in aqueous solution (without organic stabilizers) were water soluble, stable and had narrow emission band. The addition of drug to NPs solution caused considerable quenching of the emission band of silver NPs, which was likely due to the complexation of the drug to silver NPs. Under the optimum conditions, the quenched fluorescence (FL) intensity was linear with the concentration of FEX in the range of 1 × 10^?7 to 2.5 × 10^?5 mol L^?1 (0.9985) with a detection limit of 1.2 × 10^?8 mol L^?1. The quenching mechanism of the studied drug on the emission band of silver NPs was explained by Stern–Volmer law. The developed method was applied to FEX determination in a pharmaceutical formulation (allegra tablets) and biological fluids (human serum and urine).