Single-step synthesis of germanium nanowires encapsulated within multi-walled carbon nanotubes

We report the single-step synthesis of Ge nanowires encapsulated within multi-walled carbon nanotubes (MWCNTs) from a phenyltrimethylgermane (C₆H₅Ge(CH₃)₃) precursor, using a simple chemical vapor deposition (CVD) method. The MWCNT/germanium nanowires were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) measurements. TEM analysis reveals that the nanowires consist of well crystallized Ge cores which are completely encapsulated by the sheath-like MWCNTs, the latter corresponding to a layer thickness of 5-10 nm. SEM images, corresponding to various stages of nanowire growth, indicate that MWCNT growth occurs at Ge nanoparticles and that the growing MWCNTs carry Ge as nanowires away from the nanoparticles. By optimizing the CVD parameters, nanowires can be produced with uniform length and diameter in the range 6-10 μm and 200-300 nm, respectively.     

水热合成法制备高长径比的银纳米线

以季铵盐型阳离子Gemini表面活性剂[C16H33(CH3)2N+(CH2)3N+(CH3)2C16H33]×2Br-(16-3-16)为结构导向剂和稳定剂,以六次甲基四胺为还原剂,用水热合成法由硝酸银制备了直径约30 nm、长约50 mm的银纳米线. 用X射线衍射(XRD)、紫外-可见吸收光谱和透射电子显微镜(TEM)等手段对制备产物的表征结果表明,所得银纳米线具有面心立方结构,并且是沿着{111}晶面生长的. 银纳米线的长度与反应时间有关,而直径则变化不大. 反应温度对产物的形貌有较大影响,在100和120℃下得到的是纳米线,而在150℃下得到的多为不规则的纳米颗粒.     

银纳米线的光吸收性能研究

结合晶种法和光化学还原法成功制备出银纳米线,其直径在50nm左右,长度为4～5μm。采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、紫外-可见光谱(UV-vis)、红外光谱(FT-IR)对产物的结构进行了表征,并对银纳米线的光吸收性能及生长机理进行了初步探讨。结果表明,所制得的银纳米线具有面心立方结构,沿着(111)晶面生长;紫外-可见光谱显示在350nm和416nm处存在吸收峰。     

Optical properties of group-I-doped ZnO nanowires

Undoped and group-I elements doped ZnO nanowires were synthesized using a thermal evaporation method. Field emission scanning electron microscopy (FESEM) results showed that, the undoped ZnO nanowires were ultra-long with uniform diameters. On the other hand, the length of the doped ZnO nanowires was in the range of some hundred of nanometers. X-ray diffraction (XRD) patterns clearly indicated hexagonal structures for all of the products. X-ray photoelectron spectroscopy (XPS) studies confirmed the oxidation states of Li, Na, K, in the ZnO lattice. An asymmetric O 1s peak indicated the presence of oxygen in an oxide layer. The effect of doping on the optical band-gap and crystalline quality was also investigated using photoluminescence (PL), UV–vis, and Raman spectrometers. The Raman spectra of the products indicated a strong E₂ (high) peak. The PL spectra exhibited a strong peak in the ultraviolet (UV) region of the electromagnetic spectrum for all of the ZnO nanowires. The UV peak of the doped ZnO nanowires was red-shifted compared to the undoped ZnO nanowires. In addition, the UV–vis spectra of the samples showed similar results compared to the PL results.     

Ag nanowires and its application as electrode materials in electrochemical capacitor

Silver nanowires were synthesized on a large scale by using anodic aluminum oxide (AAO) film as templates and serving ethylene glycol as reductant. Their morphological and structural characterizations were characterized with field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and selected area electron diffraction (SAED). The electrochemical properties of silver nanowires as electrode materials for electrochemical capacitors were investigated by cyclic voltammetry (CV) and galvanostatic charge/discharge technique in 6 M KOH aqueous electrolyte. The Ag₂O/Ag coaxial nanowires were formed by the incomplete electrochemical oxidation during the charge step. The maximum specific capacitance of 987 F g^?1 was obtained at a charge–discharge current density of 5 mA cm^?2.     

Structural and thermal studies of silver nanoparticles and electrical transport study of their thin films

This work reports the preparation and characterization of silver nanoparticles synthesized through wet chemical solution method and of silver films deposited by dip-coating method. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and energy dispersive spectroscopy (EDX) have been used to characterize the prepared silver nanoparticles and thin film. The morphology and crystal structure of silver nanoparticles have been determined by FESEM, HRTEM, and FETEM. The average grain size of silver nanoparticles is found to be 17.5 nm. The peaks in XRD pattern are in good agreement with that of face-centered-cubic form of metallic silver. TGA/DTA results confirmed the weight loss and the exothermic reaction due to desorption of chemisorbed water. The temperature dependence of resistivity of silver thin film, determined in the temperature range of 100-300 K, exhibit semiconducting behavior of the sample. The sample shows the activated variable range hopping in the localized states near the Fermi level.     

OPAA template-directed synthesis and optical properties of metal nanocrystals

Ag and Cu nanocrystals (NCs) were assembled into ordered porous anodic alumina (OPAA) by a single-potential-step chronoamperometry technique. The composition, morphology, microstructure, and optical property were analyzed by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and optical absorption spectroscopy. The results indicate that metallic NCs/OPAA composite possesses a significant surface plasmon resonance absorption. For continuous electrodeposition, metallic nanowires are smooth and uniform with face-centered cubic (fcc) single-crystalline structure; however, for interval electrodeposition, the nanowires are bamboo-like or pearl-chain-like with fcc polycrystalline structure. The length of the nanoparticle nanowires or the single-crystalline nanowires can be controlled well by adjusting the experimental cycle times or the continuous depositing time. The transverse dipole resonance of metallic NCs enhances and displays a blue shift with increasing electrodeposition time or experimental cycle times, which is consistent with Zong''s results but contradictory to Duan''s results. The formation mechanisms of the nanoparticle nanowires and the single-crystalline nanowires were discussed in detail.     

Synthesis,Characterisation and DFT Studies of Stigmasterol Mediated Silver Nanoparticles and Their Anticancer Activity

The present investigation reports the facile, reproducible and eco-friendly biological synthesis of nano silver using Ficus Hispida leaf extract (FHLE) as a reductant. The properties of the synthesized silver nanoparticles (Ag-NP’s) is characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy (TEM), UV–visible spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction studies. The synthesized Ag-NPs are found to have spherical shape with average particle size in the range of 50–100 nm. The XRD studies and selected area electron diffraction pattern of TEM images confirm the face cantered cubic structure of biosynthesised silver nanoparticles. The DFT studies reveal that the stigmasterol present in FHLE is responsible for leaf extract to behave as a reducing agent for reduction of Ag⁺ ions into Ag⁰. The antitumor studies against DLA cell lines of the biosynthesized Ag-NPs is found to have 100% inhibition with concentration of 200 µg/ml of Ag-NP’s.     

Electrochemical synthesis of silver oxide nanowires,microplatelets and application as SERS substrate precursors

We describe the electrochemical synthesis of silver oxide nanowires and nanowire bundles, filled platelets and hollow microplatelets in either basic or acidic N,N-dimethylformamide solution. We propose that these nanostructures are formed at the electrode surface via two competing reactions namely, silver dissolution off the electrode in the presence of NH₃ or HF during the anodization of silver, and silver oxide precipitation. Results show that the precipitated silver oxide nanoparticles aggregate into nanowires as well as into filled and hollow microscale platelets, depending upon the nuclei concentration and the anodization current density. X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) and Raman scattering spectroscopy show that the nanowires and microplatelets are mainly composed of Ag₂O. Nanowire bundles are used as substrates for surface-enhanced Raman scattering (SERS) where single molecule detection is achieved and evidenced using a bianalyte Raman technique.     

Size controlled synthesis of well-distributed nano-silver on hydroxyapatite using alkanolamine compounds

A well-distributed nano-silver hydroxyapatite composite has been successfully prepared by a one-pot synthesis method. Hydroxyapatite was separately synthesized by a sol-gel method, then impregnated with silver nanoparticles with the mediation of Uncaria gambir Roxb. leaf extract in the presence of three kinds of alkanolamine compound; monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA) as capping agents. The effect of different capping agents on the properties of the silver nanoparticles and the nano-silver hydroxyapatite composite were studied. UV–visible spectrophotometer analysis exhibited absorbance peaks at 402–439 nm which specifically corresponds to spherical silver nanoparticles. Higher optical absorbance was observed in TEA-capped silver nanoparticles, than in DEA and MEA-capped ones. X-ray diffraction (XRD) analysis showed a highly crystalline hexagonal structure for hydroxyapatite and no detected metallic silver. However, the presence of 1.65% silver was confirmed by energy dispersive x-ray (EDX) spectroscopy analysis. Transmission electron microscopy (TEM) analysis revealed spherical silver nanoparticles with a size range of 2–62 nm (smallest mean diameter of 2 nm) adhered to the hydroxyapatite surface. The TEA capped impregnated silver nanoparticles were the smallest, corresponding to the best capping performance, followed by those capped by DEA and MEA. Small-sized nanoparticles on hydroxyapatite are beneficial for highly antibacterial bone implants.     

Preparation and catalytic behavior of hollow Ag/carbon nanofibers

A novel carbon nanofiber containing silver nanoparticles (NPs) with hollow structure was fabricated via co-electrospinning and in situ reduction. The hollow structure avoided the waste of silver NPs embedded in the nanofibers while ensuring high specific surface area. The formation of silver NPs was confirmed by Field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The catalytic behavior of the nanofibers obtained to the reduction of methylene blue with NaBH₄ was tracked by UV–visible spectroscopy. The results showed that carbon nanofibers containing silver NPs with hollow structure possessed significant catalytic properties.     

Electrochemical synthesis of CdS nanowires by underpotential deposition in anodic alumina membrane templates

Cadmium sulfide (CdS) nanowires were electrosynthesized within the pores of the anodic alumina membranes (AAM) using underpotential deposition (UPD) through an electrochemical co-deposition at room temperature (25 °C). The nanowire arrays were grown from an aqueous solution of CdSO₄, ethylenediaminetetraacetic acid (EDTA), and Na₂S at pH 4.0. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis absorption spectroscopy, and energy dispersive spectroscopy (EDS) were employed to characterize the nanowires. These nanowires have uniform diameters of approximately 90 nm, and their lengths are up to 7 μm. XRD analysis reveals that the electrosynthesized nanowires deposited at −500 mV (vs. Ag/AgCl) have a preferential orientation along (1 1 0) direction for hexagonal crystal. Electrochemical and EDS results of the deposits confirm that the atomic ratio of Cd to S is very close to 1:1 stoichiometry. UV-vis absorption measurement shows a blue-shifted absorption at 488 nm because of the quantum confinement at low dimensions.     

Synthesis of SiC nanowires via catalyst-free pyrolysis of silicon-containing carbon materials derived from a hybrid precursor

SiC nanowires were successfully synthesized without catalyst by pyrolysis of silicon-containing pitch-derived carbon materials in a closed graphite crucible. These silicon-containing carbon materials were obtained by homogenization and co-carbonization of a hybrid precursor consisting of the toluene soluble fraction of coal tar pitch with polycarbosilane (PCS). The composition, morphology and structure of the nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The influence of pyrolysis temperature on the growth of the nanowires was investigated by Fourier transform infrared spectroscopy (FTIR) and thermo-gravimetry coupled with mass spectroscopy (TG-MS) analysis. The results indicate that the growth of the SiC nanowires starts at around 1200 °C. As the pyrolysis temperature increases to 1300–1500 °C, a large quantity of nanowires are formed on the top surface of the pitch-derived carbon substrate. In addition, increasing the pyrolysis temperature leads to an increase in the average diameter and a change in the typical morphology produced. The synthesized SiC nanowires have single-crystalline structure and are grown along the [111] direction with numerous stacking faults and twins. The vapor-solid (VS) mechanism may be responsible for the growth process of the SiC nanowires.     

Radiation synthesis and characterization of poly(vinyl alcohol)/poly(N-vinyl-2-pyrrolidone) based hydrogels containing silver nanoparticles

A series of PVA/PVP based hydrogels at different compositions were prepared by gamma irradiation. The gel fraction degree of swelling were investigated. Highly stable and uniformly distributed silver nanoparticles have been obtained onto hydrogel networks. The morphology and structure of (PVA/PVP) hydrogel and dispersion of the silver nanoparticles in the polymeric matrix were examined by scanning electron microscopy (SEM) and infrared spectroscopy (FT-IR), respectively. The formation of silver nanoparticles has been confirmed by ultraviolet visible (UV–vis) spectroscopy. A strong characteristic absorption peak was found to be around 420 nm for the silver nanoparticles in the hydrogel nanocomposite. The X-ray diffraction pattern confirmed the formation of silver nanoparticles with average particle size of 12 nm. The diameter distribution of silver nanoparticles was determined by dynamic light scattering DLS. Transmission electron microscope (TEM) showed almost spherical and uniform distribution of silver nanoparticles through the hydrogel network and the mean size of silver nanoparticles ranging is 23 nm. The good swelling properties and antibacterial of PVA/PVP-Ag hydrogel suggest that it can be a good candidate as wound dressing.     

A Novel Way for Synthesizing Phosphorus-Doped Zno Nanowires

We developed a novel approach to synthesize phosphorus (P)-doped ZnO nanowires by directly decomposing zinc phosphate powder. The samples were demonstrated to be P-doped ZnO nanowires by using scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction spectra, X-ray photoelectron spectroscopy, energy dispersive spectrum, Raman spectra and photoluminescence measurements. The chemical state of P was investigated by electron energy loss spectroscopy (EELS) analyses in individual ZnO nanowires. P was found to substitute at oxygen sites (P_O), with the presence of anti-site P on Zn sites (P_Zn). P-doped ZnO nanowires were high resistance and the related P-doping mechanism was discussed by combining EELS results with electrical measurements, structure characterization and photoluminescence measurements. Our method provides an efficient way of synthesizing P-doped ZnO nanowires and the results help to understand the P-doping mechanism.     

多孔阳极氧化铝模板组装Fe纳米线及其表征

Fe nanowire arrays are prepared by electrodeposition in porous anodic aluminum oxide template from a composite electrolyte solution. These nanowires have an uniform diameter of approximate 25 nm and a length in excess of 2.5μm.The micrographs and crystal structures of Fe nanowlres are studied by transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and X-ray diffraction(XRD). It is found that each nanowire is essentially a single crystal and has a different orientation in each array. Hysteresis loops of Fe nanowire array show that its easy magnetization direction is perpendicular to the sample plane.     

Influence of Mn-doping on the photocatalytic and solar cell efficiency of CuO nanowires

Pristine copper oxide (CuO) and manganese (Mn) doped CuO nanostructures with different ratios were synthesized via wet chemical method. As-prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-rays (EDX), UV–Visible and emission spectroscopy. Further, the doped nanowires were employed in the hybrid solar cells in combination with P3HT and gave better current densities than their corresponding undoped counterparts. The photoactivity of synthesized materials was evaluated by the photocatalytic oxidation of Rhodamine B (RhB). The results showed that the 2% Mn doped CuO photocatalyst is highly photoactive than other corresponding undoped and doped CuO nanowires. The increase in solar cell efficiency and photocatalytic activity of the doped CuO nanowires is solely due to the improvement in the charge separation efficiency in the 2% Mn doped CuO nanowires.     

Characterization of SnO2 nanowires synthesized from SnO by carbothermal reduction process

In this paper, single-crystalline SnO₂ nanowires have been successfully prepared by a carbothermal reduction process employing SnO as the starting material and CuO as the catalyst. Their morphologies, purity and sizes of the products were characterized by transmission electron microscopy (TEM), selected area electron diffraction, X-ray diffraction, field emission scanning electron microscopy (FESEM) and Raman spectroscopy, respectively. The FESEM images reveal wire-like and rod-shaped nanowires of about 100–800 μm in length and 30–200 nm in the transverse dimensions. The three observed Raman peaks at 474, 634 and 774 cm⁻¹ indicate the typical rutile phase of the SnO₂ which is in agreement with the X-ray diffraction results. The influence of some reaction parameters, including the temperature and the reaction duration, on the forming, morphology and particle size of SnO₂ crystallize is discussed.     

Hollow mesoporous silica spheres supported Ag and Ag–Au catalyzed reduction of 4-nitrobenzo-15-crown

Hollow mesoporous silica (HMS) spheres of size within the range 120–220 nm have been prepared using propanol–water solvent as template and cetyltrimethylammonium bromide (CTAB) as stabilizer. HMS supported silver and silver–gold catalysts were prepared by impregnating metal nanoparticles on HMS and were characterized by ultraviolet–visible spectroscopy (UV–vis), dynamic light scattering (DLS), optical microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), inductive coupled plasma optical emission spectroscopy (ICP-OES) and N₂ adsorption–desorption. The reduction of 4-nitrobenzo-15-crown (4-NB-15-C) was compared using HMS supported silver and silver–gold nanocatalysts varying experimental parameters. Bimetallic Ag–Au/HMS nanocatalysts was found to be more active than monometallic Ag/HMS nanocatalyst.     

Nanostructure silver-doped zinc oxide films coating on glass prepared by sol–gel and photochemical deposition process: Application for removal of mercaptan

Silver-doped zinc oxide (SDZO) films have been grown on glass substrate by a novel combination of sol–gel and photochemical deposition processes (SGPD). The effect of sintering on structural, electrical and optical properties was investigated. The films were characterized by UV–vis absorption spectroscopy (UV–vis), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The result of X-ray photoelectron spectroscopy (XPS) revealed that the binding energy of Ag 3d_5/2 for SDZO shifts remarkably to the lower binding energy compared to the pure metallic Ag due to the interaction between silver and zinc oxide. The XRD spectra of the SDZO films indicate that silver was incorporated in the hexagonal crystal structure of zinc oxide. SEM micrographs show the uniform distribution of spherical grains of about 73 nm grain size for the pure zinc oxide thin films. The results indicated that silver doping photochemical deposition was a feasible method to tune the optical properties of zinc oxide nanostructures. SDZO films coated on glass were applied for the photodegradation of mercaptan in water. SDZO films were applied for degradation of mercaptobenzoxazole which reduced the mercaptan concentration to more than 98%.