Preparation and optical properties of ZnO@PPEGMA nanoparticles

The poly(poly(ethylene glycol) methyl ether monomethacrylate) (PPEGMA) grafted zinc oxide (ZnO) nanoparticles were successfully prepared via the surface-initiated atom transfer radical polymerizations (ATRP) from the surfaces functionalized ZnO nanoparticles. The 2-bromoisobutyrate (BIB) was immobilized onto the surface of the ZnO nanoparticles through the reaction between 2-bromoisobutyryl bromide (BIBB) and the hydroxyl groups on nanoparticles, serving as the initiator to induce the ATRP of poly(ethylene glycol) monomethacrylate (PEGMA). Well-defined polymer chains were grown from the surfaces to yield hybrid nanoparticles comprised of ZnO cores and PPEGMA polymer shells having multifunctional end groups. The structure and morphology of the nanoparticles were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The optical properties of the nanoparticles were investigated by UV-vis absorption spectroscopy and photoluminescence spectroscopy (PL). The results showed that the dispersion and near-band edge (NBE) emission of ZnO nanoparticles could be improved by the grafted PPEGMA polymer segments.     

Synthesis of gelatin-capped gold nanoparticles with variable gelatin concentration

Gelatin-stabilized gold nanoparticles (AuNPs-gelatin) with controlled particle size were synthesized with simple variation of concentration of gelatin by reducing in situ tetrachloroauric acid with sodium citrate. The nanoparticles showed excellent colloidal stability. Transmission electron microscopy (TEM) revealed the formation of well-dispersed gold nanoparticles (AuNPs) with different sizes. The methodology produces particles 10–15 nm in size depending on the concentration of gelatin used. The measured AuNPs are 10, 11, 12, 13, 14, and 15 nm for AuNPs-gelatin 1, 0.5, 0.25, 0.1 and 0.05%, and pure AuNPs, respectively. The AuNPs-gelatin exhibit size-dependent localized surface plasmon resonance behavior as measured by UV–visible spectroscopy. UV–vis spectroscopy and TEM results suggest that higher concentration of gelatin favor smaller particle size and vice versa. FTIR spectroscopy analysis of AuNPs-gelatin revealed the amino bands and carboxyl peak of gelatin. The crystalline nature of AuNPs was investigated by X-ray diffraction.     

Preparation and application of polymer-grafted magnetic nanoparticles for lipase immobilization

Functionalized superparamagnetic particles were prepared by graft polymerization of glycidyl methacrylate and methacryloxyethyl trimethyl ammonium chloride onto the surface of modified-Fe₃O₄ nanoparticles. The resultant particles were characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The results indicate that the polymer chains had been effectively grafted onto the surface of Fe₃O₄ nanoparticles. The functionalized particles remained dispersive and superparamagnetic. Lipase was immobilized on the magnetic particles under mild conditions by electrostatic adsorption and covalent binding with the activity recovery up to 70.4%. The immobilized lipase had better thermal stability compared to free lipase.     

Effective surface modification by stimuli-responsive polymers onto the magnetite nanoparticles by layer-by-layer method

Effective surface modification of poly(N-isopropylacrylamide)-based temperature-responsive polymers onto the magnetite nanoparticles was investigated. To achieve this purpose, layer-by-layer method was applied. This technique is based on sequential chemical reactions between the temperature-responsive polymers with carboxyl groups and other another polymers with amino groups. After the polyion complex formation, carbodiimide chemistry was used to cross-link both the functional polymers. As a result, we could confirm the successful preparation using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and the dispersion measurement of the modified magnetite nanoparticles. The thickness was tunable be the number of the layer-by layer reaction. As expected, the magnetite nanoparticles show the very sensitive temperature-responsive behavior.     

Layer by layer growth of silver chloride nanoparticle within the pore channels of SBA-15/SO3H mesoporous silica (AgClNP/SBA-15/SO3K): Synthesis,characterization and antibacterial properties

The growth of silver chloride nanoparticles within the pore channels of functionalized SBA-15 mesoporous was achieved by sequential dipping steps in alternating bath of potassium chloride and silver nitrate under ultrasound irradiation at pH=9. The effects of sequential dipping steps in growth of the AgCl nanoparticles have been studied. The growth and formation of AgCl nanoparticles inside the sulfonated SBA-15 were characterized by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Antibacterial activity of the synthesized materials was investigated against Escherichia coli (E.coli) using the conventional diffusion-disc method. The materials showed high antibacterial activity.     

Visible-light photocatalytic degradation of methylene blue with laser-induced Ag/ZnO nanoparticles

The preparation of Ag doped ZnO nanoparticles conducted through the method of laser-induction is presented in this work. The Ag/ZnO nanoparticles attained from various weight percentages of added AgNO₃ relative to ZnO were applied under visible-light irradiation for evaluating the heterogeneous photocatalytic degradations of methylene blue (MB) solutions. It was shown that the catalytic behavior of Ag/ZnO nanoparticles in the visible-light range is notably improved through the Ag deposition onto ZnO nanoparticles by the method of laser-induction with a maximum effectiveness of 92% degradation. The properties of the nanoparticles were characterized by the employments of UV-vis spectroscopy (UV-vis), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and selected-area electron diffraction (SAED).     

Biological Production of Gold Nanoparticles at Different Temperatures: Efficiency Assessment

The study aims to compare different approaches and efficacies during the biological production of nanoparticles (NPs). Gold nanoparticles (AuNPs) are produced by Fusarium oxysporum at two different temperatures. One flask is incubated at 37 °C (“Common”) and the other is directly heated for 5 min at 80 °C (“Heat-treated”). Obtained AuNPs are analyzed and compared by spectrophotometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), dynamic light scattering (DLS), and Fourier transform infrared spectroscopy (FTIR). Graphite furnace atomic absorption spectroscopy (GF-AAS) is used to determine the particle concentration after the AuNPs production. The AuNPs prepared by both (the Common and the Heat-treated) methods exhibit maximum absorption peaks at 541 and 528 nm, respectively, and have round shapes and sizes of less than 50 nm. Their zeta potential is about −28 mV. GF-AAS shows that the efficiency of AuNP production in Common- and Heat-treated samples is equal, between 65% and 68%. Since the Heat-treated sample shows a better size distribution, the use of higher temperature and shorter time period is preferable for the bioproduction of AuNPs. It seems that shortening the time for the production of AuNPs prevents the formation of larger NPs.     

Pulsed spark-discharge assisted synthesis of colloidal gold nanoparticles in ethanol

A green method, using pulsed spark-discharge (PSD) to synthesize gold nanoparticles (AuNPs) in ethanol, is studied in this article. Unlike conventional methods for metal nanoparticles synthesis, the PSD method does not require the addition of chemical surfactants and stabilizers. The size of PSD–AuNPs is examined by transmission electron microscopy, with a range 5–50 nm. The chemical compounds, crystal structure, and surface plasmon resonance of PSD–AuNPs are studied using energy dispersive X-ray spectroscopy, X-ray diffraction, and UV–Visible spectroscopy, respectively. Zeta potential analysis shows that a negative charge (−40 mV) on the surface of the PSD–AuNPs may be contributing to the stability of the suspension. During the gold electrodes discharge in the ethanol, under an intensive electric field and thermal energy, bulk metallic gold and ethanol may produce AuNPs and varieties of chemical derivatives, which are also studied by GC/MS and FTIR to investigate the suspension mechanism. The analysis results show that there is an oxidation reaction of ethanol occurring during the PSD process to produce ethanol derivatives, such as acetaldehyde, acetic acid, and ethyl acetate, which may modify the surface of AuNPs by coordination of oxygen atoms. However, only acetic acid can form a negative charge by the deprotonation of the carboxylic group of surface in ethanol, resulting in the creation of a repulsion force between the particles to form the stable colloid system. The experimental results indicate that PSD is an alternative green process to synthesize gold nanoparticles suspension in ethanol. Moreover, with a gold rod consumption rate of 15 mg/L, concentrations of gold nanoparticles ~9 ppm have been observed; therefore, the net production rate is around 60%.     

PtRu electrocatalysts on carbon nanotubes treated by phenylphosphonic acid for electrooxidation of methanol

Phenylphosphonic acid (PPA)-assisted one-pot method for preparation of PtRu nanoparticles with high dispersion and stabilization on carbon nanotubes (CNTs) is reported. Based on the π–π stacking between phenylphosphonic acid and CNTs, abundant phosphonate groups were uniformly introduced on CNTs' surface, which significantly not only improve the solubility and dispersibility of CNTs in polar solvents but also enhance the dispersion of PtRu nanoparticles on CNTs' surface. The obtained PtRu/PPA-CNT electrocatalysts are characterized by transmission electron microscopy, infrared spectroscopy, thermal gravimetric analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray powder diffraction. The results reveal that CNTs were successfully functionalized by PPA, and PtRu nanoparticles were uniformly dispersed on PPA-CNT surface with average particle diameter of 2.5 nm. Electrochemical studies certified that PtRu/PPA-CNT electrocatalysts have much higher electrocatalytic activity and stability for methanol oxidation in comparison with PtRu nanoparticles supported on the pristine CNTs because of their highly electrochemical surface area at 612.7 cm² mg^?1.     

Preparation, characterization and surface morphology of novel optically active poly(ester-amide)/functionalized ZnO bionanocomposites via ultrasonication assisted process

Novel bionanocompoites (BNCs) were prepared using zinc oxide (ZnO) nanoparticles which functionalized by γ-methacryloxypropyltrimethoxysilane (KH570) as a coupling agent. Poly(ester-amide) (PEA) based on tyrosine natural amino acid was synthesized and used as a polymer matrix. PEA/ZnO BNCs were characterized by fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). All the results confirmed that the surface of ZnO particle has sufficient compatibility with PEA through the link of the coupling agent between ZnO and polymer and also proved that the presence of ZnO nanoparticles appeared to be dispersed in nanosize in polymer composite matrix. In addition, thermogravimetric analysis (TGA) data indicated an enhancement of thermal stability of new BNC materials compared with the pure polymer.     

Sonochemical fabrication of gold nanoparticles–boron nitride sheets nanocomposites for enzymeless hydrogen peroxide detection

A simple sonochemical route was developed for the preparation of gold nanoparticles/boron nitride sheets (AuNPs/BNS) nanocomposites without using reducing or stabilizing agents. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and UV–vis absorption spectra were used to characterize the structure and morphology of the nanocomposites. The experimental results showed that AuNPs with approximately 20 nm were uniformly attached onto the BNS surface. It was found that the AuNPs/BNS nanocomposites exhibited good catalytic activity for the reduction of H₂O₂. The modified electrochemical sensor showed a linear range from 0.04 to 50 mM with a detection limit of 8.3 μM at a signal-to-noise ratio of 3. The findings provide a low-cost approach to the production of stable aqueous dispersions of nanoparticles/BNS nanocomposites.     

Raman spectroscopy of combinatory anticancer drug release from gold nanoparticles inside a single leukemia cell

Combinatory anticancer drug release from gold nanoparticles (AuNPs) in K562 human myeloid leukemia cells was performed using Raman spectroscopy. We fabricated the anticancer drug of imatinib as a BCR‐ABL tyrosine kinase inhibitor on AuNP surfaces along with a transferrin (Tf)‐targeting moiety to treat the leukemia cells. DNA topoisomerase I inhibitor topotecan was also assembled to monitor its fluorescence onto AuNPs. The linker group of 4‐carboxylic benzoic acid was used to conjugate to targeting the Tf protein. Our Raman data indicated that the drug molecules were not detached in the cell culture media but released after treatment with glutathione (2 mM). Intracellular distribution and release of the anticancer drug–AuNP conjugates in K562 cells were examined by both fluorescence microscopy and dark‐field microscopy with surface‐enhanced Raman scattering. Copyright © 2013 John Wiley & Sons, Ltd.     

Surface modification of ceria nanoparticles and their chemical mechanical polishing behavior on glass substrate

To improve their chemical mechanical polishing (CMP) performance, ceria nanoparticles were surface modified with γ-aminopropyltriethoxysilane (APS) through silanization reaction with their surface hydroxyl group. The compositions, structures and dispersibility of the modified ceria particles were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), laser particle size analyzer, zeta potential measurement and stability test, respectively. The results indicated that APS had been successfully grafted onto the surface of ceria nanoparticles, which led to the modified ceria nanoparticles with better dispersibility and stability than unmodified ceria particles in aqueous fluids. Then, CMP performance of the modified ceria nanoparticles on glass substrate was investigated. Experimental results showed that the modified ceria particles exhibited lower material removal rate (MRR) but much better surface quality than unmodified ceria particles, which may be explained by the hardness reduction of ceria particles, the enhancement of lubrication of the particles and substrate surfaces, and the elimination of the agglomeration among the ceria particles.     

Controlled surface functionalization of silica-coated magnetic nanoparticles with terminal amino and carboxyl groups

General and versatile methods for the functionalization of superparamagnetic, silica-coated, maghemite nanoparticles by surface amino and/or carboxyl groups have been established. The nanoparticles were synthesized using co-precipitation from aqueous solutions and coated with a thin layer of silica using the hydrolysis and condensation of tetraethoxysilane (TEOS). For the amino functionalization, 3-(2-aminoethylamino)propylmethyldimethoxysilane (APMS) was grafted onto the nanoparticle surfaces in their aqueous suspensions. The grafting process was followed by measurements of the ζ-potential and a determination of the concentration of the surface amino groups with conductometric titrations. The surface concentration of the amino groups could be varied by increasing the amount of APMS in the grafting process up to approximately 2.3 –NH₂ groups per nm². The carboxyl functionalization was obtained in two ways: (i) by a ring-opening linker elongation reaction of the surface amines at the functionalized nanoparticles with succinic anhydride (SA) in non-aqueous medium, and (ii) by reacting the APMS and SA first, followed by grafting of the carboxyl-terminated reagent onto the nanoparticle surfaces. Using the first method, the SA only reacted with the terminal primary amino groups (–NH₂) of the surface-grafted APMS molecules. Infra-red spectroscopy (ATR FTIR) and mass spectrometry (HRMS) showed that the second method enables the bonding of up to two SA molecules per one APMS molecule, since the SA reacted with both the primary (–NH₂) and secondary amino (–NH–) groups of the APMS molecule. When using both methods, the ratio between the surface amino and carboxyl groups can be controlled.     

Green synthesis and characterization of gold nanoparticles using extract of anti-tumor potent Crocus sativus

In the present study, we have explored anti-tumor potent Crocus sativus (saffron) as a reducing agent for one pot size controlled green synthesis of gold nanoparticles (AuNps) at ambient conditions. The nanoparticles were characterized using UV–vis, scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and FTIR analysis. The prepared AuNPs showed surface Plasmon resonance centered at 549 nm with average particle size of 15±5 nm. Stable, spherical and triangular crystalline AuNPs with well-defined dimensions were synthesized using anti-tumor potent Crocus sativus (saffron). Crystalline nature of the nanoparticles is confirmed from the HR-TEM, SAED and SEM images, and XRD patterns. From the FTIR spectra it is found that the biomolecules are responsible for capping in gold nanoparticles.     

Selfassembly of gold nanoparticles onto the surface of multiwall carbon nanotubes functionalized with mercaptobenzene moieties

We have developed a new and effective method to robustly self-assemble gold nanoparticles onto the surface of multiwall carbon nanotubes (MWNTs) functionalized with mercaptobenzene moieties. Fourier transform infrared and electron diffraction spectroscopy were used to verify whether or not the mercaptobenzene moieties have been attached to the π-conjugated body of MWNTs. Transmission electron microscope images give direct evidences for the success of selfassembly of gold nanoparticles onto the functionalized MWNTs.     

Micro-patterns of Au@SiO2 core-shell nanoparticles formed by electrostatic interactions

In this paper, silica-coated Au nanoparticles (Au@SiO₂) were prepared by the technique of vortex mixing. Subsequently, these monodisperse Au@SiO₂ nanoparticles were functionalized by the silane reagents 3-aminopropyltriethoxysilane (APS) and 3-mercaptopropyltriethoxysilane (MPTS) respectively. Then, these NH₂-terminated and SO₃²⁻-terminated Au@SiO₂ nanoparticles were respectively assembled onto the substrates, which have been patterned with different self-assembly monolayers (SAMs), to form close-packed two-dimensional Au@SiO₂ nanoparticle arrays by electrostatic interactions. The morphologies and the optical properties of Au@SiO₂ nanoparticles with different silica-shell thicknesses were characterized by TEM and UV-vis. The compositions and zeta potentials of the functionalized Au@SiO₂ nanoparticles were examined by X-ray photoelectron spectroscopy (XPS) and dynamic light scattering (DLS). The morphologies of the patterns formed on different templates were characterized by atomic force microscopy (AFM).     

A facile method to prepare monodispersed ZnO–Ag core-shell microspheres

Monodispersed and core-shell structured ZnO–Ag microspheres were realized by coating the Ag nanoparticles onto the surface of ZnO microspheres via a novel solution method. The obtained materials were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible (UV–Vis) absorption measurement. It was shown that face-center-cubic Ag nanoparticles with the mean size of 20 nm were successfully grown on the surface of ZnO microspheres. The absorption band of ZnO–Ag core-shell microspheres showed a large redshift comparing to pure Ag nanoparticles, indicating the strong interfacial interaction between ZnO and Ag. The effects of Ag coating thickness on the structure, morphology and optical absorption of ZnO–Ag core-shell microspheres were investigated. The discussion on the growth process of ZnO–Ag core-shell microspheres revealed the important role of Sn²⁺. This approach was simple, mild and readily scaled up, affording a simple method for the synthesis of size-tunable inorganic-metal core-shell nanostructures.     

Synthesis of gold nanoparticles by <Emphasis Type="Italic">Cacumen Platycladi</Emphasis> leaf extract and its simulated solution: toward the plant-mediated biosynthetic mechanism

In this study, biogenic fabrication of gold nanoparticles (AuNPs), respectively, by Cacumen Platycladi leaf extract and the simulation of its active components were thoroughly investigated. The simulated solution was prepared based on components measurement and Fourier-transform infrared spectroscopy analysis of Cacumen Platycladi leaf extract before and after reaction. Several analytic methods such as UV–Vis spectrophotometry, X-ray diffraction, transmission electron microscopy, and thermogravimetric study were adopted to characterize the AuNPs. The results showed that flavonoid and reducing sugar were the main reductive and protective components in the extract vital in the biosynthesis of the AuNPs. In addition, pH of the reaction solution was proved to be the most significant factor upon the synthesis process. The bioreduction mechanism of chloroaurate ions and the formation mechanism of AuNPs were also discussed. To the best of our knowledge, this is the first report on plausible elucidation of the biosynthetic mechanism through comparative study between a plant extract and its simulated solution.     

Synthesis of platinum and platinum–ruthenium-modified diamond nanoparticles

With the aim of developing dimensionally stable-supported catalysts for direct methanol fuel cell application, Pt and Pt–Ru catalyst nanoparticles were deposited onto undoped and boron-doped diamond nanoparticles (BDDNPs) through a chemical reduction route using sodium borohydride as a reducing agent. As-received commercial diamond nanoparticles (DNPs) were purified by refluxing in aqueous nitric acid solution. Prompt gamma neutron activation analysis and transmission electron microscopy (TEM) techniques were employed to characterize the as-received and purified DNPs. The purified diamond nanoparticulates, as well as the supported Pt and Pt–Ru catalyst systems, were subjected to various physicochemical characterizations, such as scanning electron microscopy, energy dispersive analysis, TEM, X-ray diffraction, inductively coupled plasma-mass spectrometry, X-ray photoelectron spectroscopy, and infrared spectroscopy. Physicochemical characterization showed that the sizes of Pt and Pt–Ru particles were only a few nanometers (2–5 nm), and they were homogeneously dispersed on the diamond surface (5–10 nm). The chemical reduction method offers a simple route to prepare the well-dispersed Pt and Pt–Ru catalyst nanoparticulates on undoped and BDDNPs for their possible employment as an advanced electrode material in direct methanol fuel cells.