Extracellular biosynthesis of silver nanoparticles using the fungus Fusarium semitectum

Development of environmental friendly procedures for the synthesis of metal nanoparticles through biological processes is evolving into an important branch of nanobiotechnology. In this paper, we report on the use of fungus “Fusarium semitectum” for the extracellular synthesis of silver nanoparticles from silver nitrate solution (i.e. through the reduction of Ag⁺ to Ag⁰). Highly stable and crystalline silver nanoparticles are produced in solution by treating the filtrate of the fungus F. semitectum with the aqueous silver nitrate solution. The formations of nanoparticles are understood from the UV-vis and X-ray diffraction studies. Transmission electron microscopy of the silver particles indicated that they ranged in size from 10 to 60 nm and are mostly spherical in shape. Interestingly the colloidal suspensions of silver nanoparticles are stable for many weeks. Possible medicinal applications of these silver nanoparticles are envisaged.     

A facile synthesis of ordered ultralong silver nanobelts

Large-scale ordered ultralong silver nanobelts, which built a beautiful chrysanthemum-like structure, are prepared on the interface between dibutyl sebacate (DBS) and silver nitrate solution by a chemical electro-deposition technique. The influences of chemical circumvent of interface, concentration of silver nitrate solution and applied voltage on the formation of silver nanobelts are investigated. It is shown that the silver nanobelts possess a perfect single crystal structure and well-defined nanobelt-like morphology with a length of 5 mm, width 80-150 nm, and thickness 20 nm, respectively. The growth mechanism of the nanobelts is discussed. Furthermore, UV-vis spectra of the silver nanobelts show similar surface plasmon resonance properties to silver nanowires.     

Spontaneous formation of silver nanoparticles on polymeric supports

Silver nanoparticles with a size range of 2-4 nm were prepared on polyethylene glycol-coupled 2-chlorotrityl resins without using any reducing agents. In contrast to the polyol process, silver nanoparticles were simply reduced in the tetrahydrofuran/chloroform system on the resin without using any alcohols, and the resulting silver nanoparticles exhibited a uniform size distribution. The polyethylene glycol spacer on the resin played an important role in obtaining silver nanoparticles, probably acting as a polydentate-chelating agent for the silver ions.     

Selected-control synthesis of hierarchical nickel structures

Nickel with urchinlike and sisallike structures has been successfully fabricated by a facile hydrothermal method. Investigations have revealed that the addition of surfactants and the presence of hydrazine hydrate and glycine are essential for the morphologies development. Furthermore, the magnetic properties of the samples with different morphologies have been studied, and the possible formation process is also discussed.     

Antibacterial effects of biosynthesized silver nanoparticles using aqueous leaf extract of Rosmarinus officinalis L.

In this study, we demonstrate a green approach for the synthesis of silver nanoparticles (AgNPs) using aqueous leaf extract of Rosmarinus officinalis under ambient conditions. The uniqueness of this method lies in its rapid synthesis within 15 min. The synthesized AgNPs were characterized using UV–vis, FTIR, XRD, FE-SEM coupled with EDX, TEM and AFM. The synthesized particles were found to be 14.20–42.42 nm with face centered cubic geometry. The functional group of flavonoids and terpenoids was largely identified by FTIR which was found to be responsible for the synthesis and stabilization of the AgNPs. Further, antibacterial efficacy of the biologically synthesized AgNPs was investigated by the standard method against Pseudomonas aeruginosa and Staphylococcus aureus. The results showed that the aqueous leaf extract mediated synthesized AgNPs is an excellent antibacterial agent against clinical pathogens.     

A facile and novel way for the synthesis of nearly monodisperse silver nanoparticles

A facile and novel way was reported for the preparation of nearly monodisperse silver nanoparticles with controlled hydrophilic or hydrophobic surface, using trioctylphosphine as the surfactant and stabilizer. The synthesized nanoparticles were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and UV-vis spectroscopy. The monodisperse silver nanoparticles showed a strong surface plasmon resonance band at 402 nm from the UV-vis spectrum.     

Green synthesis of zinc oxide nanoparticles by aloe barbadensis miller leaf extract: Structure and optical properties

Biological methods for nanoparticle synthesis using microorganisms, enzymes, and plants or plant extracts have been suggested as possible ecofriendly alternatives to chemical and physical methods. In this paper, we report on the synthesis of nanostructured zinc oxide particles by both chemical and biological method. Highly stable and spherical zinc oxide nanoparticles are produced by using zinc nitrate and Aloe vera leaf extract. Greater than 95% conversion to nanoparticles has been achieved with aloe leaf broth concentration greater than 25%. Structural, morphological and optical properties of the synthesized nanoparticles have been characterized by using UV-Vis spectrophotometer, FTIR, Photoluminescence, SEM, TEM and XRD analysis. SEM and TEM analysis shows that the zinc oxide nanoparticles prepared were poly dispersed and the average size ranged from 25 to 40 nm. The particles obtained have been found to be predominantly spherical and the particle size could be controlled by varying the concentrations of leaf broth solution.     

Phospholipid-assisted synthesis of size-controlled gold nanoparticles

Morphology and size control of gold nanoparticles (AuNPs) by phospholipids (PLs) has been reported. It was found that gold entities could form nanostructures with different sizes controlled by PLs in an aqueous solution. During the preparation of 1.5 nm gold seeds, AuNPs were obtained from the reduction of gold complex by sodium borohydride and capped by citrate for stabilization. With the different ratios between seed solution and growth solution, which was composed by gold complex and PLs, gold seeds grew into larger nanoparticles step by step until enough large size up to 30 nm. The main discovery of this work is that common biomolecules, such as PLs can be used to control nanoparticle size. This conclusion has been confirmed by transmission electron micrographs, particle size analysis, and UV-vis spectra.     

Microwave-hydrothermal synthesis of perovskite bismuth ferrite nanoparticles

Hydrothermal microwave method (HTMW) was used to synthesize crystalline bismuth ferrite (BiFeO₃) nanoparticles (BFO) in the temperature of 180 °C with times ranging from 5 min to 1 h. BFO nanoparticles were characterized by means of X-ray analyses, FT-IR, Raman spectroscopy, TG-DTA and FE-SEM. X-ray diffraction results indicated that longer soaking time was benefit to refraining the formation of any impurity phases and growing BFO crystallites into almost single-phase perovskites. Typical FT-IR spectra for BFO nanoparticles presented well defined bands, indicating a substantial short-range order in the system. TG-DTA analyses confirmed the presence of lattice OH⁻ groups, commonly found in materials obtained by HTMW process. Compared with the conventional solid-state reaction process, submicron BFO crystallites with better homogeneity could be produced at the temperature as low as 180 °C. These results show that the HTMW synthesis route is rapid, cost effective, and could be used as an alternative to obtain BFO nanoparticles in the temperature of 180 °C for 1 h.     

Shape controlled synthesis of Cu2O and its catalytic application to synthesize amorphous carbon nanofibers

Octahedral Cu₂O particles and Cu₂O nanowires were synthesized by a simple solution-phase route using N₂H₄·H₂O as reducing agent at room temperature. Amorphous carbon nanofibers were synthesized using octahedral Cu₂O particles and an acetylene gas source at atmospheric pressure. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric (TG) analysis. SEM and TEM images indicated that most of the obtained octahedral Cu₂O particles had an edge length of 400-700 nm. The obtained nanowires had uniform diameters of about 15 nm, and the length of the nanowires ranged from 5 to 10 μm. The XRD result revealed the amorphous feature of the nanofibers. IR spectrum revealed that the nanofibers consist of -CH, -CH_2, -CC- and -CH₃ groups. The concentrations of N₂H₄·H₂O and NaOH played important roles in controlling the geometric shape of the Cu₂O.     

Dendrigraft polymer-based synthesis of silver nanoparticles showing bright blue fluorescence

A novel method is reported here for the synthesis of optically clear and stable colloidal solutions of silver nanoparticles. According to size they show different colours depending upon their plasmonic absorption frequencies. The materials have been synthesized at room temperature by chemical reduction of silver ions (silver nitrate) coordinated with dendrigraft polymer, polyethyleneimine (PEI) using formaldehyde in aqueous medium. UV-vis absorption and transmission electron microscopy (TEM) studies show single-band absorption with peak maximum at 354 nm for ∼3 nm sized particles, whereas a side band at ∼400 nm was observed when the particle size increased to ∼20 nm. Highly narrow particle size distribution was observed in case of samples having ∼3 nm size silver particles and also the process of reduction could be completed within minutes. More interestingly, the 3-nm sized particles showed strong blue (474 nm) fluorescence under UV excitation. Thin films of all synthesized samples were prepared on silica substrate by fine spray coating technique.     

Single crystal growth of Mn2N using an In-Na flux

Hexagonal platelet and pyramidal single crystals of Mn₂N were prepared by using an In-Na flux at 700 °C and 5 MPa of N₂ pressure. The crystal structure (space group P6₃/mmc) with lattice parameters a=2.8185(6) Å and c=4.5371(12) Å was confirmed by X-ray single-crystal diffraction. Nitrogen atoms statistically occupy a half of the octahedral interstitial sites in a hexagonal closest packing arrangement of Mn atoms.     

Microwave-assisted synthesis of ceria nanoparticles

Nanocrystalline ceria (CeO₂) particles have been successfully prepared by microwave-assisted heating technique from an aqueous solution containing ammonium Ce(IV) nitrate and sodium hydroxide. Further thermal treatment of the as-prepared powder at 500 °C resulted in the formation of the well-crystallized CeO₂ nanoparticles with an average crystal size of about 8 nm, varying with the heating temperature. The as-prepared powder and the CeO₂ nanoparticles were examined using X-ray diffraction (XRD) and transmission electron microscope (TEM) techniques. It was found that the morphologies of the synthesized powder show from rod-like for the as-prepared sample to sphere-like for the heat-treated nanoparticles. Mechanism of CeO₂ nanocrystallite growth during annealing is primarily investigated.     

In situ etching WO3 nanoplates: Hydrothermal synthesis, photoluminescence and gas sensor properties

A novel hydrothermal process using p-nitrobenzoic acid as structure-directing agent has been employed to synthesize plate-shaped WO₃ nanostructures containing holes. The p-nitrobenzoic acid plays a critical role in the synthesis of such novel WO₃ nanoplates. The morphology, structure and optical property of the WO₃ nanoplates have been characterized by transmission electron microcopy (TEM), scanning electron microcopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL). The lateral size of the nanoplates is 500-1000 nm, and the thickness is about 80 nm. The formation mechanism of WO₃ nanoplates is discussed briefly. The gas sensitivity of WO₃ nanoplates was studied to ethanol and acetone at different operation temperatures and concentrations. Furthermore, the WO₃ nanoplate-based gas sensor exhibits high sensitivity for ethanol and acetone as well as quick response and recovery time at low temperature.     

On the existence of PbBi3PO8: Its synthesis and crystal structure

The title compound crystallizes in the tetragonal system, a = 11.733(2) Å, c = 15.587(3) Å, I4 mm, Z = 10. Data were collected at the Argonne National Laboratory synchrotron source at λ = 0.15359 Å. Least squares refinement on F² converged to R1 = 0.039. The oxygen coordination polyhedra around Bi and Pb display the distortions typical of 6s² lone-pair atoms. One Bi is disordered. BiO bonds vary from 2.08(2) to 2.96(1) Å. One Pb is in cubic coordination to oxygen and the second Pb is bonded to six oxygen atoms that form a rectangular pyramid and a seventh oxygen is off one of the rectangular faces of the pyramid. PbO bonds vary from 2.303(6) to 2.804(17) Å. Of the two crystallographically independent P one is in a single tetrahedral coordination while the second is at the center of two disordered tetrahedra. Units of OM₄ tetrahedra, M = Bi/Pb, articulate into a three-dimensional framework by corner and edge sharing that is strengthened by corner sharing with PO₄ moieties.     

Solvothermal synthesis of copper sulfide semiconductor micro/nanostructures

Covellite copper sulfide (CuS) micro/nanometer crystals in the shape of hierarchical doughnut-shaped, superstructured spheric-shaped and flowerlike architectures congregated from those nanoplates with the thickness of 20-100 nm have been prepared by a solvothermal method. The as-obtained CuS products were characterized by means of scanning electron microscopy (SEM), X-ray diffractometry (XRD) and energy-dispersive X-ray spectroscopy (EDS). A systematic investigation has been carried out to understand the factors influencing the evolution of CuS particle morphology which found to be predominant by solvent, surfactant, sulfur resource and copper salt. The possible formation mechanism for the nanostructure formation was also discussed. These CuS products show potential applications in solar cell, photothermal conversion and chemical sensor.     

In situ optical microspectroscopy of the growth and oxidation of silver nanoparticles in silica thin films on soda-lime glass

An in situ optical microspectroscopy investigation of the growth and oxidation of silver nanoparticles (NPs) embedded in SiO₂ thin films deposited on soda-lime glass has been conducted in real time during thermal processing in air. Variation of Ag NP size is followed by fitting of surface plasmon resonance (SPR) with spectra calculated by Mie theory, and analysed concurrently with the time evolution of SPR peak intensity. The NP transformations appeared to be temperature and time dependent. Silver NPs were indicated to grow at relatively high temperatures (e.g. 600 °C) due to Ostwald ripening, followed by a plateau and a gradual decrease in size resulting in SPR vanishing due to oxidation. The three phases were well separated in time. Oxidation appeared dominant at lower temperatures (e.g. 400 °C) as indicated by a continuous decrease in Ag particle size. The product of Ag NP oxidation was revealed by photoluminescence spectroscopy as single Ag⁺ ions. Furthermore, the data indicated that: (i) Ag⁺ ions are formed during heat treatment under an Ag/Ag⁺ redox equilibrium; (ii) the ions diffuse from the SiO₂ matrix towards the soda-lime substrate where they stabilize; and (iii) the continuous removal of these ions from the matrix is necessary in order for the equilibrium to be displaced towards oxidation.     

Preparation, structure and luminescent properties of a new potassium yttrium borate K3Y3(BO3)4

A new yttrium borate compound K₃Y₃(BO₃)₄ has been obtained in the K₂O-Y₂O₃-B₂O₃ ternary system. Its structure, determined from single crystal X-ray diffraction data, shows that it belongs to space group P2₁/c with unit cell dimensions of a = 10.4667(16) Å, b = 17.361(3) Å, c = 13.781(2) Å and β = 110.548(8)°. The structure consists sheets of [Y₈B₈O₂₄]_∞ linked by out of sheet BO₃ groups and Y ions to form a three-dimensional framework. The luminescent properties of Eu³⁺ and Tb³⁺ doped K₃Y₃(BO₃)₄ materials have also been studied.     

Structural,electronic properties and charge density distribution of the LiNaB4O7: Theory and experiment

The title compound was synthesized by employing high-temperature solution reaction methods at 840 °C. Single-crystal XRD analysis showed that it crystallizes in the orthorhombic noncentrosymmetric space group Fdd2, with unit cell parameters a = 13.326(3) Å, b = 14.072(3) Å, c = 10.238(2) Å, Z = 16, and V = 1919.9(7) Å³. It has two independent and interpenetrating 3D frameworks consisting of [B₄O₉]⁶⁻ groups bridged by O atoms, with intersecting channels occupied by Na⁺ and Li⁺ cations. The IR spectrum further confirmed the presence of both BO₃ and BO₄ groups. UV–vis diffuse reflectance spectrum showed a band gap of about 3.88 eV. Solid-state fluorescence spectrum exhibited the maximum emission peak at around 337.8 nm. Furthermore we have performed theoretical calculations by employing the state-of-the-art all-electron full potential linearized augmented plane wave (FP-LAPW) method to solve the Kohn Sham equations. We have optimized the atomic positions taken from our XRD data by minimizing the forces. The optimized atomic positions are used to calculate the electronic band structure, the atomic site-decomposed density of states, electron charge density and the chemical bonding features. The calculated electronic band structure and densities of states suggested that this single crystal possesses a wide energy band gap of about 2.80 eV using the local density approximation, 2.91 eV by generalized gradient approximation, 3.21 eV for the Engel–Vosko generalized gradient approximation and 3.81 eV using modified Becke–Johnson potential (mBJ). This compares well with our experimentally measured energy band gap of 3.88 eV. From our calculated electron charge density distribution, we obtain an image of the electron clouds that surround the molecules in the average unit cell of the crystal. The chemical bonding features were analyzed and the substantial covalent interactions were observed between O and O, B and O, Li and O as well as Na and O atoms.     

Size-controlled synthesis of alumina nanoparticles from aluminum alkoxides

Aluminum oxide nanoparticles were prepared by the hydrolysis of aluminum oxide alkoxides followed by calcinations, in the presence of surface stabilizing agents, such as Na(AOT) molecules. The size of alumina precursors (bohemite) was 20-30 nm, yielding aluminum oxide particles with an average size of 80 nm after calcinations at 1200 °C. The shape of the α-alumina nanoparticles was mainly spherical and the high temperature inhibited the formation of the hexagonal crystals. The introduction of Na(AOT) during the appropriate processing step, had the effect of controlling the size of the particles, the degree of aggregation and the particles shapes.