Nanocrystalline hydroxyapatite powders by a chitosan–polymer complex solution route: Synthesis and characterization

Nanocrystalline hydroxyapatite (HAp) powders were successfully synthesized by a simple method using chitosan–polymer complex solution. To obtain HAp nanopowders, the prepared precursor was calcined in air at 400–800 °C for 2 h. The phase composition of the calcined samples was studied by X-ray diffraction (XRD) technique. The XRD results confirmed the formation of HAp phase with a small trace of monotite phase. With increasing calcination temperature, the crystallinity of the HAp increased, showing the hexagonal structure of HAp with the lattice parameter a in a range of 0.94030–0.94308 nm and c of 0.68817–0.68948 nm. The particle sizes of the powder were found to be 55.02–73.36 nm as evaluated by the XRD line broadening method. The chemical composition of the calcined powders was characterized by FTIR spectroscopy. The peaks of the phosphate carbonate and hydroxyl vibration modes were observed in the FTIR spectra for all the calcined powders. TEM investigation revealed that the prepared HAP samples consisted of rod-like nanoparticles having the particle size in the range of 100–300 nm. The corresponding selected-area electron diffraction (SAED) analysis further confirmed the formation of hexagonal structure of HAp.     

Thermal plasma synthesis of nanotitania and its characterization

Titanium dioxide (TiO₂) nanoparticles were prepared by the thermal plasma synthesis; which give a highly crystalline product. Their morphological studies are carried out by using techniques like SEM, EDAX, TEM and SEAD. Crystal size was calculated by XRD using Scherrer equation; which is observed at two current amperes; at 80 A size ranges between 25 and 30 nm and at 120 A size ranges between 30 and 42 nm. Composition analysis was done by TEM–EDAX, FTIR and Fast Fourier Transform techniques. The FTIR peaks clearly show that synthesized TiO₂ nanoparticles are in anatase phase; this phase is generally preferred because of its high photocatalytic activity, since it has a more negative conduction band edge potential (higher potential energy of photogenerated electrons), high specific area, nontoxic, photochemically stable and relatively in expensive.     

Synthesis of gold nanoparticles by microemulsion assisted photoreduction method

A new, clean, cost-effective and rapid method for the synthesis of stable spherical gold nanoparticles (AuNPs) is developed. This novel technique combines microemulsion as one of soft-nanotechnology techniques of wet chemistry, with photo-physics of UV-radiation in a unique versatile method to design and obtain controlled nanostructures for multifunctional materials. Based on a phase diagram in ternary water/Brij 30/n-heptane system pristine, and thiol functionalized, gold nanoparticles were obtained by a microemulsion assisted photoreduction technique, allowing increased flexibility during the synthesis and selection of materials. The spherical nanoparticles obtained by this route show a homogeneous size distribution, with an average diameter of 11 nm, for pristine gold nanoparticles and of 12 nm, for functionalized species. The evolution of the system at the nanoscale has been studied using, in tandem, UV-VIS and DLS measurements. The structure, size and shape of the final nanoparticles obtained have been evaluated by adequate instrumental techniques: FTIR, XRD and TEM image analysis. Kinetic studies have also been performed in order to follow the evolution of nanospecies during irradiation procedure.     

Synthesis of Co3O4 nanostructures using a solvothermal approach

The controlled synthesis of Co₃O₄ nanostructures with morphologies of micro-spheres, nanobelts, and nanoplates was successfully achieved by a simple solvothermal method. Various comparison experiments showed that several experimental parameters, such as the reaction temperature and the concentration of NH₃·H₂O, play important roles in the morphological control of Co₃O₄ nanostructures. A lower temperature and a lower concentration of NH₃·H₂O favor spherical products with a diameter of 1–1.5 μm, whereas a higher temperature and a higher concentration of NH₃·H₂O generally lead to the formation of nanobelts with a width of 20–150 nm. In addition, Co₃O₄ hexagonal nanoplates with an edge length of about 200–300 nm are also obtained by adding surfactant CTAB. A rational mechanism is proposed for the selective formation of various morphologies. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and field-emission scanning electron microscope (FE-SEM) were used to characterize the products.     

Hydrogen bubble dynamic template synthesis of porous gold for nonenzymatic electrochemical detection of glucose

Gold (Au) films with open interconnected macroporous walls and nanoparticles have been successfully sculptured using the hydrogen bubble dynamic template synthesis followed by a galvanic replacement reaction. Copper (Cu) films with open interconnected macroporous walls and nanoparticles were synthesized using the electrochemically generated hydrogen bubbles as a dynamic template. Then through a galvanic replacement reaction between the porous Cu sacrificial templates and KAu(CN)₂ in solution, the porous Cu films were converted to porous Au films with the similar morphologies. Additional electrochemical dealloying process was introduced to remove the remaining Cu from the porous Au films. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Energy-dispersive X-ray (EDX), X-ray diffraction (XRD) and electrochemical methods were adopted to characterize the porous Au films. The resulted porous Au films show excellent catalytic activity toward the electrooxidation of glucose. A nonenzymatic glucose sensor based on those Au film electrodes shows a linear range from 2 to 10 mM with a sensitivity of 11.8 μA cm⁻² mM⁻¹, and a detection limit of 5 μM.     

Preparation of hexagonal nanoporous nickel hydroxide film and its application for electrochemical capacitor

Nanoporous nickel hydroxide film has been successfully electrodeposited on titanium substrate from nickel nitrate dissolved in the aqueous domains of the hexagonal lyotropic liquid crystalline phase of Brij 56. Low-angle X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM) studies show that the film has a regular nanostructure consisting of a hexagonal array of cylindrical pores with a repeat center-to-center spacing of about 7 nm. Preliminary electrochemical studies are carried out using cyclic voltammetry (CV) and chronopotentiometry technology. A maximum specific capacitance of 578 F g⁻¹ could be achieved for the nanoporous Ni(OH)₂ film electrode, suggesting its potential application in electrochemical capacitors.     

Carbosilane dendrons as stabilizing agents for the formation of gold nanoparticles

The synthesis and characterization of two new carbosilane dendrons functionalized in the focal point with a single thiol group is described. These molecules were used as stabilizing agents for the formation of gold nanoparticles. These materials were obtained by the reduction of hydrogen tetrachloroaurate phase-transferred into toluene in the presence of the carbosilane dendrons. The gold nanoparticle-cored dendrons (NCDs) were characterized by TEM, XPS, AFM, IR, UV, and NMR techniques. Average particle diameter ranged from 2.5 to 2.6 nm with narrow size distribution and remarkable stability; in particular, the elimination of the protecting shells to give naked gold, after NCDs deposition on a support, is more difficult using carbosilane dendrons than in the case of conventional dodecanethiol-protected gold nanoparticles.     

Biosynthesis of Au nanoparticles using olive leaf extract: 1st Nano Updates

The biological synthesis of gold nanoparticles (AuNPs) of various shapes (triangle, hexagonal, and spherical) using hot water olive leaf extracts as reducing agent is reported. The size and the shape of Au nanoparticles are modulated by varying the ratio of metal salt and extract in the reaction medium. Only 20 min were required for the conversion into gold nanoparticles at room temperature, suggesting a reaction rate higher or comparable to those of nanoparticles synthesis by chemical methods. The variation of the pH of the reaction medium gives AuNPs nanoparticles of different shapes. The nanoparticles obtained are characterized by UV–Vis spectroscopy, photoluminescence, transmission electron microscopy (TEM), X-ray diffraction (XRD), FTIR spectroscopy and thermogravimetric analysis. The TEM images showed that a mixture of shapes (triangular, hexagonal and spherical) structures was formed at lower leaf broth concentration and high pH, while smaller spherical shapes were obtained at higher leaf broth concentration and low pH.     

Synthesis of ZnS nanoparticles from pyridine adducts of zinc(II) dithiocarbamates

Zn(thqdtc)₂, Zn(thqdtc)₂(py) and Zn(thiqdtc)₂(py) (where thqdtc = 1,2,3,4-tetrahydroquinolinecarbodithioate, thiqdtc = 1,2,3,4-tetrahydroisoquinolinecarbodithioate and py = pyridine) have been used as single source precursors for the synthesis of ZnS nanoparticles. The formation of ZnS nanoparticles was achieved by thermal decomposition of the complex under heating in presence of triethylenetetraamine. Transmission electron microscopy, energy dispersive X-ray analysis (EDAX) and powder X-ray diffraction studies were carried out to study the structure and morphology of the nanoparticles. The optical properties of the ZnS nanoparticles were studied by UV–visible and fluorescence emission spectral studies. UV–visible absorption spectral studies indicate a blue shift in the absorption maxima due to the quantum size effect. A single crystal X-ray analysis was carried out for a precursor [Zn(thqdtc)₂].     

Synthesis of Ni nanoparticles and their characterizations

Ni nanoparticles were synthesized by solution reduction process successfully. The influence of parameters on the size of Ni nanoparticles was studied and the referential process parameters were obtained. The morphology and structure of the synthesized Ni nanoparticles were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), QELS data and infrared spectroscopy (IR). The result shows that Ni nanoparticles are of high purity and the average size of Ni nanoparticles was found to be 13 ± 2 nm.     

Au-assisted visible laser MALDI

The excitation of UV-absorbing MALDI matrixes with visible laser (532 nm wavelength) and the desorption/ionization of biomolecules were performed by coating the analytes doped matrix with Au thin film (5–10 nm) using ion sputtering deposition. The Au film was first ablated with the laser of higher fluence, resulting in a crater/hole about the size of the laser beam spot on the target. After a few initial laser shots, analytes and matrix related ions were observed from the crater even at lower laser fluence. Electron microscopy inspection on the laser ablated region revealed the formation of nanoparticles with sizes ranging from <10 to 50 nm. Compared with the infra-red laser (1064 nm) excitation, the visible laser produced much higher abundance of matrix radical ions, and less heating effect as measured by the thermometer molecules. The results suggest the photo-excitation and photo-ionization of matrix molecules by the visible laser, possibly assisted by the gold nanoparticles and nanostructures left on the ablated crater.     

Influences of surfactant (PVA) concentration and pH on the preparation of copper nanoparticles by electron beam irradiation

Electron beam irradiation method was successfully applied to the preparation of Cu nanoparticles in aqueous solution under room temperature and ambient pressure using polyvinyl alcohol (PVA) as the surfactant. The influences of the pH on the products were studied by X-ray diffraction (XRD), and those of the surfactant PVA concentration on the particle size and agglomeration by ultraviolet–visible spectrophotometry (UV–vis) and laser scattering particle size distribution analysis (LSPSDA). The products were characterized by XRD and transmission electron microscopy (TEM). The results showed that the grain size of Cu nanoparticles, within a certain range, can decrease with increasing PVA concentration. Pure Cu nanoparticles with the grain size distribution of 5–50 nm were prepared when the pH was adjusted between 5.0 and 9.0, and the PVA concentration was 2.20 g/100 mL.     

Uniform In2S3 octahedron-built microspheres: Bioinspired synthesis and optical properties

Uniform In₂S₃ octahedron-built microspheres were synthesized by using a mild hydrothermal treatment in the presence of L-glutamic acid at 180 °C. The microsphere with an average size of 5 μm was composed of interconnected octahedrons with diameters in the range from 100 to 150 nm. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS). The synthesis of various hollow and solid sphere structures and flower structures was achieved using different amino acids. This is the first report on synthesizing In₂S₃ nanostructures using different amino acids to modulate the morphology of the final products. Primary photoluminescence studies on the prepared In₂S₃ microspheres show promising results.     

Green synthesis of plant-stabilized Au nanoparticles for the treatment of gastric carcinoma

In this study, gold nanoparticles (AuNPs) were green synthesized using plant extract. The obtained nanoparticles (Au NPs) were characterized by advanced physical and chemical techniques like TEM, FTIR, UV–vis, SEM, XRD and EDX. SEM image displayed the quasi-spherical shaped nanoparticles of mean diameter 20–50 nm. All the particles were of uniform shape and texture. From the XRD pattern, four distinct diffraction peaks at 38.2°, 44.2°, 64.7° and 77.4° are indexed as (1 1 1), (2 0 0), (2 2 0) and (3 1 1) planes of fcc metallic gold. The in vitro cytotoxic and anti-gastric carcinoma effects of biologically synthesized Au NPs against cancer cell lines were assessed. The IC₅₀ of the Au NPs were 192, 149, 76 and 85 µg/mL against NCI-N87, MKN45, GC1401 and GC1436 gastric cancer cell lines. The anti-gastric carcinoma properties of the Au NPs could significantly remove the cancer cell lines in a time and concentration-dependent manner. So, the findings of the recent research show that biologically synthesized Au NPs might be used to cure cancer.     

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.     

Characterization of thin InP anodic oxide layers: Correlation of morphological investigations with chemical and electrical properties

Depending on the applied electrochemical parameters, various oxide films can be grown onto InP in aqueous media. In this work, two oxide layers have been grown in borate buffer solution at pH = 9 by applying a low (0.2 mA cm⁻²) or a high (30 mA cm⁻²) current density, but a similar coulometric charge. Capacitance–voltage measurements performed before and after the anodic processes have been made to investigate the electrical properties of new interfaces, while X-ray photoelectron spectroscopy (XPS) analysis and atomic force microscopy (AFM) observations were used to access to the chemical and topographic aspects of the two oxidized surfaces. It is demonstrated that AFM observations coupled with electrochemical and XPS measurements is a good probe for the study of thin oxide on InP. A correlation between the anodization parameters and the resulting electrical and morphological aspects of the anodic layers is clearly evidenced.     

Formation of a gold superlattice on an S-layer with square lattice symmetry

This work describes a new strategy in which a crystalline bacterial cell surface layer (S-layer) composed of a monolayer of a single protein species was used as periodic nanometric template in the nucleation of ordered arrays of gold nanoparticles. A square superlattice of uniform 4 to 5 nm sized gold particles with 12.8 nm repeat distance was fabricated by exposing the S-layer lattice of Bacillus sphaericus CCM2177, in which thiol groups had been introduced before, to a tetrachloroauric(III) acid solution. Transmission electron microscopical studies showed that the gold nanoparticles were formed in the pore region during electron irradiation of an initially grainy gold coating covering the whole S-layer lattice. The shape of the gold particles resembled the morphology of the pore region of the square S-layer lattice. By electron diffraction and energy dispersive X-ray analysis the crystallites were identified as gold (Au(0)). Electron diffraction patterns revealed that the gold nanoparticles were crystalline but in the long range order not crystallographically aligned. It is postulated that S-layers will allow the fabrication of a wide range of inorganic nanocrystal superlattice arrays.     

Nanostructured electropolymerized film of 5-amino-2-mercapto-1,3,4-thiadiazole on glassy carbon electrode for the selective determination of l-cysteine

We report the electropolymerization of 5-amino-2-mercapto-1,3,4-thiadiazole (AMT) in 0.1 M H₂SO₄ on glassy carbon electrode (GCE) and utilization of the resulting polymer film for the selective determination of l-cysteine (CY) at physiological pH for the first time. The electropolymerized film was characterized by cyclic voltammetry (CV), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). AFM image shows a homogeneous film containing spherical structure with a thickness of ～25 nm for p-AMT deposited by 15 cycles. The binding energies at 163.5, 400.2 and 398.8 eV in the XPS corroborate that the p-AMT was linked by S–S, HN–NH and NN groups. The p-AMT film successfully separates the voltammetric signals of CY and ascorbic acid (AA) with a potential difference of 480 mV which is higher than the previous reports.     

Modification of a glassy carbon surface with amine-terminated dendrimers and its application to electrocatalytic hydrazine oxidation

Amine-terminated polyamidoamine (PAMAM) dendrimers were immobilized on glassy carbon electrodes (GCEs) via electrochemical oxidation of the terminal amine groups of dendrimers. The electrochemical immobilization of dendrimers was confirmed by cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS). The immobilized dendrimer films were robust and behaved as charge-selective electrochemical gates for oppositely charged redox molecules. The immobilization approach was applied to assemble Au dendrimer-encapsulated nanoparticles (Au DENs, dia. 1.5 ± 0.3 nm) on GCEs, and the resulting Au DEN films showed electrocatalytic activity to hydrazine oxidation.     

Surfactant assisted hydrothermal synthesis of SnO nanoparticles with enhanced photocatalytic activity

SnO nanoparticles have been successfully synthesized in the presence of Triton-X 100 (TX-100) surfactant via hydrothermal method for the first time, and the photocatalytic activity under UV and visible light irradiation for the degradation of Methylene Blue (MB) and Rhodamine B (RdB) organic textile dyes was investigated. The structural, morphological and chemical characterizations were investigated by using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR), UV–vis. diffuse reflectance spectroscopy (UV–vis DRS) and photoluminescence (PL) analysis. The results reveal that the addition of surfactant, TX-100, in the precursor solutions leads to reduction in crystallite size with significant changes in morphological structure of SnO nanoparticles. The synthesized SnO nanoparticles show excellent photocatalytic activity under UV or visible light irradiation. MB and RdB dyes degraded completely under UV irradiation after 90 and 150 min, respectively. Also, MB and RdB dyes degraded only 150 min later under visible light illumination with a little amount of photocatalyst (0.8 g/L). Hence, this work explores the facile route to synthesizing efficient SnO nanoparticles for degrading organic compound under both UV and visible light irradiations.