Shape Of Nanospheres Research Articles

Ag/CeO2 nanospheres: Efficient catalysts for formaldehyde oxidation

Ag/CeO2 nanosphere catalysts, prepared by a one-step hydrothermal method, were used to eliminate the indoor formaldehyde (HCHO) pollution. The activity test results showed that Ag/CeO2 nanosphere catalysts exhibited much higher catalytic activity than normal Ag/CeO2 particles prepared by conventional impregnation method. Ag/CeO2 nanosphere catalysts could reach complete HCHO oxidation above 110°C under relatively high space velocity. The specific reaction rate per second and per unit of surface area of Ag/CeO2 nanosphere catalysts were almost 3.6 times higher than normal Ag/CeO2 particle catalysts at 110°C. The prepared catalysts were also characterized by various methods. HRTEM, BET, and XRD results showed that Ag/CeO2 products were nanosphere shapes with average sizes around 80–100nm, and were comprised of many small particles with a crystallite size of 2–5nm. Cerium and silver were well distributed throughout the individual Ag/CeO2 nanosphere crystal. According to the results in XPS, H2-TPR, O2-TPD, and Raman spectra, surface chemisorbed oxygen easily formed on the Ag/CeO2 nanosphere catalysts. The synergetic interaction might exist between Ag and CeO2 nanosphere, and the presence of silver could facilitate surface chemisorbed oxygen activation, which mainly contributed to the HCHO oxidation. Based on In-situ DRIFTS results, formate species (HCOO−) were found to be the key intermediates and be activated on the surface active oxygen of Ag/CeO2 nanosphere catalysts in the catalytic oxidation process of HCHO, which would be further oxidized into the final product water and carbon dioxides.

Modifying aluminum–water reaction to generate nano-sized aluminum hydroxide particles beside hydrogen

Al–water reaction is used to produce nanoparticles of aluminum hydroxide. Ball-milling of aluminum powder in water was examined for promoting this reaction. Scanning electron microscopy and X-ray diffraction assisted by Rietveld refinement were used to study the by-products of the reaction. Results showed that the activated Al powder completely reacted with water at room temperature. Hydrogen, gibbsite and bayerite were formed at the end of the reaction. A mechanism is proposed to explain how wet milling of Al powder can promote the reaction. The morphology of the by-products changed with the milling time. Notably the samples milled for 7 and 12 h had the shapes of nanospheres, nanospindles and nanorods. The calcination process made in conventional furnace and microwave oven changed the morphology of the produced alumina phases.

Improvement of the structural, morphology, and optical properties of TiO2 for solar treatment of industrial wastewater

Hydrothermal preparation of pure anatase TiO2 with hybrid nano and micro-morphologies directly from titania sol under acidic condition in the absence of any additives or templates has rarely been reported. The present work has found that the post-hydrothermal treatment at 200 °C for different times (6, 12, 24, and 36 h) of titania sol under an acidic environment affected strongly on the structural, morphology, and optical properties of TiO2. A single-crystalline anatase phase with high surface area was obtained. The TEM results showed that shape of TiO2 nanoparticles could be manipulated by post-hydrothermal treatment. The increasing of hydrothermal time (pH 2.5) significantly altered the morphology of TiO2 from pure aggregated nanospherical shape (6 h) into branched micro-flowers as a major shape in addition to nanorod, nanocube, and nanosphere shapes (24 h). Shape-controlled TiO2 nanoparticles showed a red shift in UV–Vis light reflectance spectra as compared to TiO2 nanoparticles obtained without any hydrothermal treatment. The photoluminescence measurements confirm that hydrothermal treatment significantly decrease the electron–hole recombination chance in the obtained TiO2. The fluorescent probe method was used for evaluation of the photo-oxidative activity of different TiO2 nanomaterials. The highly active TiO2 nanoparticle (hydrothermally treated for 24 h) was applied for industrial wastewater treatment using solar radiation as a renewable energy source.

Preparation and properties of polydimethylsiloxane‐mica composites

AbstractThis is a comparison study of the effects of various colloids on polydimethylsiloxane (PDMS) nanocomposites. Mica of layered structure and silica of nanospherical shape were both used with different content. Silane coupling agent was used for surface modification of mica to improve its dispersion. Wide X‐ray diffraction patterns showed no intercalation during the incorporation of mica into PDMS matrix. Rheological characterization of the PDMS composites before curing showed that viscosities of PDMS‐mica composites were much lower than that of PDMS composites with silica, particularly at low shear rates. Scanning electron microscope (SEM) suggested the existence of mica lamellar structure with high aspect ratio within the PDMS matrix. After vulcanization at room temperature, PDMS‐mica composites could obtain mechanical properties close to that of PDMS composites with silica at same filler content. The cooperative effects of mica with silica showed that same mechanical properties of PDMS composites could be obtained at much lower viscosity, cost, and processing insecurity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Effect of multiwall carbon nanotube and au nanoparticle on the structure–property relationship of poly(N‐isopropyl acrylamide)

AbstractTemperature‐sensitive poly(N‐isopropyl acrylamide) (PNIPAAm) was synthesized both in the presence and absence of nanomaterials like allyl mercaptan decorated gold nanoparticle and allyalcohol‐conjugated multiwall carbon nanotube. The influence of the nanomaterials on the structure–property relationship of PNIPAAm was analyzed and critically compared to the pristine PNIPAAm. During the in situ polymerization, the nanosphere shape of Au nanoparticle was converted into Au nanorod shape, which was confirmed through UV–vis spectroscopy. The glass transition temperature (Tg) of polymer/nanocomposites was greater than that of the pristine polymer. Thermogravimetric analysis declared that the polymer/nanocomposites exhibited higher thermal stability than the homopolymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Magnetic-plasmonic nanoparticles for the life sciences: calculated optical properties of hybrid structures

Magnetic-plasmonic nanoparticles, combining magnetic and plasmonic components, are promising structures for use in life sciences. Optical properties of core-shell magnetite-gold nanostructures, such as the wavelength of the plasmon resonance, the extinction cross-section, and the ratio of scattering to absorption at the plasmon wavelength are critical parameters in the search for the most suitable particles for envisioned applications. Using Mie theory and the discrete dipole approximation (DDA), optical spectra as a function of composition, size, and shape of core-shell nanospheres and nanorods were calculated. Calculations were done using simulated aqueous media, used throughout the life sciences. Our results indicate that in the advantageous near-infrared region (NIR), although magnetic-plasmonic nanospheres produced by available chemical methods lack the desirable tunability of optical characteristics, magnetic-plasmonic nanorods can achieve the desired optical properties at chemically attainable dimensions. The presented results can aid in the selection of suitable magnetic-plasmonic structures for applications in life sciences. From the Clinical EditorIn this basic science study, magnetic-plasmonic nanoparticles are studied for future applications in life sciences. Optical properties of core-shell magnetite-gold nanostructures, such as the wavelength of the plasmon resonance, the extinction cross-section, and the ratio of scattering to absorption at the plasmon wavelength are critical parameters in the search for the most suitable particles for proposed future applications.

Solvothermal synthesis of uniform bismuth nanospheres using poly(N-vinyl-2-pyrrolidone) as a reducing agent.

Uniform bismuth nanospheres were successfully prepared from bismuth nitrate in the presence of poly(N-vinyl-2-pyrrolidone) (PVP) by solvothermal process. The product was characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and energy-dispersive X-ray. PVP plays a critical role both as a reducing agent and a capping agent in the formation of bismuth nanospheres. Shape and size of bismuth nanospheres could be tuned by changing the employed PVP/bismuth salt ratio. It was also found the solvent had an effect on the morphologies of bismuth nanomaterials. The possible formation and growth mechanism of bismuth nanospheres were also discussed and proposed to explain the reduction step.

A Convenient Solvothermal Synthesis Route to Metal Phosphides with a Shape of Hollow Nanospheres

InP hollow nanospheres with an average size of 550 nm and shell thickness of about 110 nm were solvothermally synthesized in EA (ethanolamine)-H2O binary solution at 190 degrees C for 36 h. The shells of InP hollow nanospheres were composed of small nanoparticles. The similar route has been extended to prepare Cd3P2, Cu3P and Sn4P3 hollow nanospheres in 150-190 degrees C for 24-36 h.

Low temperature preparation and characterization of nanospherical anatase TiO 2 and its photocatalytic activity on Congo red degradation under sunlight

Nanospherical titanium oxide with anatase structure was obtained at low temperature and normal pressure using a simple method of preparation. The dilute titanium (III) chloride solution was stirred at room temperature for several hours, and then ammonium hydroxide with hydrogen peroxide was added. A yellow gel TiO 2· xH 2O was obtained with nanodot shape and amorphous structure. Heated at 300 °C, it crystallized to pure anatase structure with nanospherical shape. The anatase particles prepared show good adsorption and photodegradation of Congo red solution under the sunlight. Materials were characterized by powder X-ray diffraction, thermal analysis, transmission electron microscope and UV spectroscopy.

Preparation of Silica Nanospheres: Effect of Silicon Alkoxide and Alcohol on Silica Nanospheres

Special attention has recently been paid to methods for controlling the nanospheres' size and distribution, because they exhibit peculiar and desirable properties in the wafer polishing process. Monodisperse silica nanospheres were first synthesized by Stober et al. using the sol-gel method, which induces high purity in the resulting particles. Bogush and Zukoski reported the influence of reaction parameters such as ammonia and water contents on the particles' size and distribution. They observed that, for a particular concentration of tetraethylorthosilicate (TEOS) with ethanol as solvent, particle size reaches a maximum and then decreases as both ammonia and water concentrations are increased. Similar behavior was observed for all the TEOS concentrations studied, and the maximum particle size moved to higher ammonia and water concentrations as the TEOS concentration was increased. The maximum monodisperse size achievable by this process was found to be 800 nm. While narrow size distributions were achievable by this process, the solid content of the resulting dispersion was less than 2 wt.%. Attempts to increase solid content by simply increasing the initial TEOS concentration for a particular concentration of ammonia and water resulted in larger particle sizes and broader size distributions. Recently, silica nanospheres have been considered effective candidates for chemical-mechanical polishing materials, so several investigators have reported ways to control particle size by using reactor type and varying the concentrations of ammonia, water, and alcohol solvent. Kim et al. found that the effect of the parameters on the particle size of silica nanospheres was increased in the following order: reaction temperature, [H2O/TEOS] ratio, concentration of ammonia, and feed rate of reactant. They also examined the influence of reaction method (such as semi-batch reaction and batch reaction) on particle size and distribution. A relatively slow rate of hydrolysis of the TEOS occurred during the semibatch process, which resulted in larger silica particles and a narrower size distribution. Even though several studies detail how various controlling factors affect the size and distribution of silica nanospheres, there are no systematic reports about the effect of silicon alkoxides and solvent types on nanosphere formation. In this study, we have synthesized silica nanospheres using four different silicon alkoxides (tetramethylorthosilicate (TMOS), tetraethylorthosilicate (TEOS) tetrapropylorthosilicate (TPOS), tetrambutylorthosilicate (TBOS)) and solvents (methanol (MeOH), ethanol (EtOH), propanol (PrOH), butanol (BuOH)) and characterized the nanospheres’ sizes and shapes by FESEM. This experiment used two types of solutions: a solution “A” of silicon alkoxide in alcohol solvent and a solution “B” of ammonium hydroxide and water in alcohol. “B” was added to “A” and stirred for 3 h at room temperature. The resulting powders were obtained by centrifugation and dried at 80 °C for 12 h. The particle shape and size in this study were determined by a field emission scanning electron microscope (FE-SEM, JEOL JSM-6700F). Table 1 summarizes the effects of using various silicon alkoxides (TMOS, TEOS, TPOS, and TBOS) on nanosphere shapes and sizes; images are shown in Figure 1. The silica nanoparticles were synthesized using 0.5 M silicon alkoxide, 6 M H2O, 0.7 M NH4OH, and 10 mL propanol at room temperature. The particles had round shapes, except those prepared by TMOS, which had irregular shapes and a broad size distribution. TMOS was thus shown to be an inadequate precursor for synthesis of silica nanospheres. Nanoparticles produced by other alkoxides, whose sizes range from 260 mm to 380 nm, exhibit round shapes and a narrow size distribution. The maximum mean particle size of 380 nm was observed when using TEOS (Figure 1(b)). As the length of the carbon chain increased from TEOS to TBOS, the particle sizes gradually decreased. This phenomenon might be explained by steric effect of silicon alkoxide on hydrolytic stability. Aelion et al. reported hydrolysis rate quickly reduced as increasing carbon chain of the silicon alkoxide. The effects of various alcohols as solvents on silica particle size and distribution are shown in Figure 2. TPOS

Nonliposomal Approach—A Study of Preparation of Egg Albumin Nanospheres Containing Amphotericin-B

The stability of liposomes after introduction into the body is presently being discussed and needs thorough understanding. Hence, as a nonliposomal approach, egg albumin nanospheres were prepared by the pH-coacervation method, and a preliminary study was carried out of the influence of process variables on the size and shape of nanospheres by changing the pH of the albumin solution, concentration of albumin solution, and volume of cross-linking agent. The batch prepared with an albumin medium of pH 9, 2% concentration, and 100 μl of 4% glutaraldehyde-ethanol solution was found to have a spherical uniform shape with an average size of 497.6 nm. The ideal batch was loaded with the systemic antifungal drug amphotericin-B. Drug-loaded nanospheres were evaluated to study their in vitro release. They were found to exhibit a biphasic pattern with a cumulative percentage release of 97.7%.