Preparation of silver nanoparticles with controlled particle size

Silver colloids show different colors due to light absorption and scattering in the visible region based on plasmon resonance. The resonance wavelength depends on particle size and shape. Here we report chemical reduction methods for preparation of silver nanoparticles exhibiting multicolor in aqueous solutions. Depending on chemical conditions the obtained nanoparticles are different regarding size and morphology.In order to investigate the relationship between size, stability and color of silver colloids we obtained silver nanoparticles in aqueous solutions using different reducing agents. The effect of polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA) on stabilization of obtained silver colloids was investigated. We have also studied the effect of silver precursor and its concentration on the formation of stable silver colloids.UV-VIS spectrum for silver colloids contains a strong plasmon band near 410 nm, which confirms silver ions reduction to Ag° in the aqueous phase. The formation of metal silver was also confirmed by powder X-ray diffraction (XRD) analysis. The diameter size of silver nanoparticles was in the range from 5 nm to 100 nm     

Atmospheric Pressure Plasma Discharge for Polysiloxane Thin Films Deposition and Comparison with Low Pressure Process

An atmospheric pressure dielectric barrier plasma discharge has been used to study a thin film deposition process. The DBD device is enclosed in a vacuum chamber and one of the electrodes is a rotating cylinder. Thus, this device is able to simulate continuous processing in arbitrary deposition condition of pressure and atmosphere composition. A deposition process of thin organosilicon films has been studied reproducing a nitrogen atmosphere with small admixtures of hexamethyldisiloxane (HMDSO) vapours. The plasma discharge has been characterized with optical emission spectroscopy and voltage-current measurements. Thin films chemical composition and morphology have been characterized with FTIR spectroscopy, atomic force microscopy (AFM) and contact angle measurements. A strong dependency of deposit character from the HMDSO concentration has been found and then compared with the same dependency of a typical low pressure plasma enhanced chemical vapour deposition process.     

Generation of nanoparticles with adjustable size and controlled stoichiometry: recent advances

We present a bottom-up fabrication route based on the sputtering gas aggregation source that allows the generation of nanoparticles with controllable and tunable chemical composition while keeping the control of the cluster size. We demonstrate that the chemical composition of the particles can be monitored by the individual adjustment of the working parameters of the magnetrons inserted in a gas aggregation zone. Such control of the parameters leads to a fine control of the ion density of each target material and hence to the control of the chemical composition of the nanoparticles. In particular, we show through X-ray photoemission, atomic force microscopy, and high-resolution transmission electron microscopy that it is possible to generate bimetallic (AgAu) and trimetallic (AgAuPd) alloy nanoparticles with well-defined and tunable stoichiometries from three targets of pure Ag, Au, and Pd. The proposed route for the generation of nanoparticles opens new possibilities for the fabrication of nanoparticles using a physical method that, for some applications, could be complementary to the chemical methods.     

Preparation and characterization of the antibacterial Cu nanoparticle formed on the surface of SiO2 nanoparticles

Cu deposition on the surface of spherical SiO2 nanoparticles was studied to achieve the hybrid structure of Cu-SiO2 nanocomposite. SiO2 nanoparticles served as seeds for continuous Cu metal deposition. The chemical structure and morphology were studied with X-ray photoelectron spectroscopy (XPS), scanning electron microscope energy dispersive X-ray (SEM-EDX), and a transmission electron microscope (TEM). The antibacterial properties of the Cu-SiO2 nanocomposite were examined with disk diffusion assays. The homogeneously formed Cu nanoparticles on the surface of SiO2 nanoparticles without aggregation of Cu nanoparticles showed excellent antibacterial ability.     

Size-controlled synthesis of monodispersed silver nanoparticles capped by long-chain alkyl carboxylates from silver carboxylate and tertiary amine

Monodispersed silver nanoparticles capped by long-chain alkyl carboxylates were prepared by the reaction of silver carboxylate with tertiary amine at 80 degrees C for 2 h. This approach is a unique, size-controlled synthetic method for the large-scale preparation of silver nanoparticles. Long-chain alkyl carboxylate derived from a precursor acts as a stabilizer to avoid the aggregation of silver nanoparticles and to control particle size. In addition, amine plays an important role both as a reagent to form a thermally unstable, amine-coordinated intermediate, bis(amine)silver(I) carboxylate, and as a mild reducing agent for the intermediate to produce nanoparticles at a low temperature. The silver core and carboxylate-capping ligand of silver nanoparticles were characterized by various techniques such as transmission electron microscopy, optical absorption spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, gas chromatograph mass spectroscopy, and thermogravimetric and differential thermal analysis. The diameter of the nanoparticles can be strongly influenced by the alkyl chain length and the structure of the carboxylate. The average diameters of the silver nanoparticles were controlled to less than 5 nm in the case of silver carboxylate with a single alkyl chain length of 13 or 17 carbon atoms. On the contrary, the average diameters of silver nanoparticles became large and polydisperse in the case of silver carboxylate with a chain length of 7 carbon atoms or a branched chain. In comparing triethylamine with trioctylamine, there was no obvious effect to regulate the size distribution of the nanoparticles because they could not function as a capping ligand of the nanoparticles due to their weak coordination to silver. In addition, the heat treatment of silver nanoparticles in solution rather than in the solid state was effective for the growth of particles while maintaining narrow size distributions.     

Mechanism of growth of colloidal silver nanoparticles stabilized by polyvinyl pyrrolidone in gamma-irradiated silver nitrate solution

Silver nanoparticles were prepared by using polyvinyl pyrrolidone (PVP) as a stabilizer and gamma-irradiation. Transmission electron microscopy (TEM) results showed that both the amount and the molecular weight of PVP in the irradiated solution considerably affect the average size of the silver nanoparticles. The average size of the silver nanoparticles decreases with increasing the amount of PVP in the solution, but increases with increasing its molecular weight. Further, TEM showed that the silver nanoparticles become disassembled into smaller nanoparticles after dilution with distilled water and sonication. Since the processes of dilution and sonication are not expected to result in chemical reactions or to split the silver nanoparticles, we conclude that each silver nanoparticle prepared by [Formula: see text] -irradiation consists of several smaller nanoparticles surrounded by PVP. Thus, based on these observations, we propose a three-step mechanism for the growth of the silver nanoparticles under the conditions considered here. In the first step, the silver ions interact with PVP, then in the second step the silver ions that are exposed to gamma-irradiation are reduced to silver atoms; nearby silver atoms then aggregate at close range. These aggregates are the primary nanoparticles. Finally, these primary nanoparticles coalesce with other nearby primary nanoparticles or interact with PVP to form larger aggregates which are the secondary (final) nanoparticles.     

Microwave-Assisted Coating of PMMA beads by silver nanoparticles

Microwave (MW) irradiation was found to be a new technique for coating silver nanoparticles with an average size of approximately 31 nm onto the surface of poly(methyl methacrylate) PMMA beads (3 mm diameter). The microwave polyol reduction was carried out under an argon atmosphere. Silver nanoparticles were obtained by the MW irradiation of a solution mixture containing silver nitrate (or silver acetate), poly(ethylene glycol), ethanol, water, and 24 wt % aqueous ammonia for 5 min in the presence of PMMA beads, yielding a PMMA-nanosilver composite. By controlling the atmosphere and reaction conditions, we could achieve the deposition of silver nanoparticles onto the surface of poly(methyl methacrylate) and vary the amount of the silver anchored to the surface. The resulting silver-deposited PMMA samples were characterized using X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray analysis, high-resolution scanning electron microscopy, X-ray photoelectron spectroscopy, and volumetric titration with potassium thiocyanate (KSCN) according to the Folgard method.     

Study of Aggregation of Gold Nanoparticles in Chitosan

In this work it is reported the synthesis of gold nanoparticles supported in situ in chitosan by solvated metal atom dispersion technique in order to study the inclusion of Au nanoparticles in the biopolymer matrix. To study their aggregation along time and compare with the synthesis of Au/2-propanol colloid by chemical liquid deposition technique. Studies of Au nanoparticles aggregation along time, supported nanoparticles and colloidal nanoparticles morphology were also carried out. The characterization of Au nanoparticles was performed by transmission electron microscopy, field-emission and scanning electron microscopy, infrared spectroscopy, X-ray diffraction, light scattering and ultraviolet–visible spectroscopy. Metal colloid showed fractal agglomeration type and delay time after the synthesis, the agglomeration size increased to flocculate. Au nanoparticles supported in chitosan showed the same shape as colloids and fractal aggregation was mostly distributed on the matrix.     

Preparation of Silver Nanoparticles through Alcohol Reduction with Organoalkoxysilanes

Silver nanoparticles of narrow size distribution were prepared through the chemical reduction in an alcohol solution with several organoalkoxysilanes. In this system, organoalkoxysilanes served as a stabilizer, protecting silver nanoparticles from aggregation. The changes in size and morphology of colloidal silver nanoparticles were investigated with the addition of organoalkoxysilanes such as 3-aminopropyltriethoxysilane (APS), methyltriethoxysilane (MTS), phenyltrimethoxysilane (PTS), vinyltriethoxysilane (VTS), and 3-glycidoxypropyltrimethoxysilane (GPS) as stabilizers. The organic functional groups of organoalkoxysilanes interact with silver ions and clusters, which stabilize silver nanoparticles in the system. The silver nanoparticles obtained were characterized with transmission electron microscopy (TEM), UV-vis spectroscopy, etc.     

聚合物存在下纳米银复合材料的制备与表征

以聚丙烯腈聚乙二醇嵌段共聚物PAN-b-PEG-b-PAN为稳定剂, 在超声辐照下成功地制备了分散性较好、尺寸均匀的纳米银颗粒. 用X射线衍射(XRD)、红外光谱(FTIR)、透射电镜(TEM)、紫外-可见吸收光谱(UV-Vis)和热分析(TGA)等对制备的纳米银复合材料进行了表征. 红外结果表明超声辐照并没有破坏聚合物的链结构. 聚合物的引入, 对纳米银颗粒起到了很好的分散保护作用. 用低浓度的硝酸银溶液, 得到粒径较小的纳米银颗粒; 随着硝酸银浓度增大, 纳米银颗粒粒径也增大. 而聚合物的浓度增大时, 所得银纳米颗粒粒径减小. 对银纳米颗粒的形成机理进行了讨论.     

A novel approach to prepare silver chloride nanoparticles grown on the surface of PAN nanofibre via electrospinning combined with gas–solid reaction

Well-defined silver chloride nanoparticles grown on the surface of PAN nanofibre were synthesized by electrospinning technology combined with gas–solid reaction. This method can avoid the possibility of the waste of raw material as well as enhance the usage rate of AgNO₃. The PAN nanofibre can be recycled easily. X-ray powder diffraction (XRD) shows the presence of crystal AgCl, X-ray photoelectron spectroscopy (XPS) confirm that there are chemical bonds and interaction between the surface modified PAN nanofibre and Ag ions. This will be propitious to prevent nanoparticles from aggregation. Field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) gave the direct evidence that AgCl nanoparticles have been dispersed on the surface of PAN nanofibre homogeneously.     

超声引发无皂乳液聚合制备纳米银/PAAEM复合材料及其表征

在不使用气体保护及乳化剂的条件下,超声辐射引发无皂乳液聚合双原位合成纳米银/聚乙酰乙酸基甲基丙烯酸乙酯(PAAEM)复合材料。并通过XRD、FTIR、TEM、HRTEM、XPS和TG等分析方法对其进行表征。结果表明:纳米银粒子具有面心立方结构和球形或近球形形貌,且较均匀地分散在聚合物基体中;纳米银粒子与基体之间的相互作用是纳米银与基体中乙酰乙酸基的羰基氧原子配位所产生的;而且纳米银粒子对基体PAAEM的热学性能有很大影响。     

单分散性银纳米粒子的可控制备

以卤化银或氧化银作为前驱体,室温下以水为溶剂,在较高溶液浓度下,利用化学还原法制备了单分散性银纳米粒子,并通过改变前驱体的种类,实现了粒径可控制备。采取扫描电子显微镜（SEM）、紫外-可见光谱仪（UV-Vis）、X射线-粉末衍射仪（XRD）、X射线-光电子能谱仪（XPS）等对所制备的银纳米粒子的形貌及成分进行了表征。结果显示,所制备的银纳米粒子具有较高的单分散性,粒径在40~150 nm之间,具有面心立方多晶结构。该方法制备的银纳米粒子可用于喷墨打印RFID天线。     

Phytochemical fabrication and characterization of silver nanoparticles by using Pepper leaf broth

The Pepper leaves extract acts as a reducing and capping agent in the formation of silver nanoparticles. A UV–Vis spectrum of the aqueous medium containing silver nanoparticles demonstrated a peak at 458 nm corresponding to the plasmon absorbance of rapidly synthesized silver nanoparticles that was characterized by UV–Vis spectrophotometer. The morphology and size of the benign silver nanoparticles were carried out by the transmission electron microscope (TEM) and field emission scanning electron microscope (FE-SEM). The sizes of the synthesized silver nanoparticles were found to be in the range of 5–60 nm. The structural characteristics of biomolecules hosted silver nanoparticles were studied by X-ray diffraction. The chemical composition of elements present in the solution was determined by energy dispersive spectrum. The FTIR analysis of the nanoparticles indicated the presence of proteins, which may be acting as capping agents around the nanoparticles. This study reports that synthesis is useful to avoid toxic chemicals with adverse effects in medical applications rather than physical and chemical methods.     

Variable-energy positron annihilation study of subnanopores in SiOCH-based PECVD films

Subnanoporosity was introduced into SiOCH-based thin films by mixing tetraethyl orthosilicate with hexamethyldisiloxane (HMDSO) in the plasma enhanced chemical vapor deposition process, and was evaluated by the variable-energy positron annihilation lifetime technique. It was found that with increasing the HMDSO fraction both porosity and pore size were enhanced, as evidenced by the decreased refractive index and increased ortho-positronium lifetime. The lifetimes from 2.0 to 6.8 ns suggested the tunable pore volumes within a range of 0.1–0.7 nm³.     

Fungal based synthesis of silver nanoparticles—An effect of temperature on the size of particles

A simple and effective approach to aqueous based biosynthesis of silver nanoparticles was demonstrated and the effect of temperature on controlling size of silver nanoparticles was studied. The morphology and uniformity of silver nanoparticles were investigated by UV–Vis spectroscopy, X-ray diffraction and HrTEM. The functional group of protein molecule was identified using FTIR. Increase in reaction temperature leads to decrease in size of silver nanoparticles and increase in monodispersity.     

Ag/Au Alloy LSPR Engineering by Co‐deposition of RF‐Sputtering and RF‐PECVD

Silver‐Gold alloy/diamond like carbon (Ag‐Au/DLC) nanocomposite films were prepared by co‐deposition of RF‐sputtering and RF‐PECVD on glass substrates by using acetylene gas and silver‐gold target. The deposition process was carried out at room temperature in one minute with the variable parameters of initial pressures and RF powers. X‐ray diffraction analysis demonstrated the formation of Ag/Au alloy nanoparticles with a face‐centered cubic (FCC) structure. Localized surface plasmon and optical properties of Ag‐Au alloy nanoparticles were studied by UV‐visible spectrophotometry which showed that increasing RF power and initial pressure cause a redshift in all samples. Moreover, the effect of RF power and initial pressure on the size and shape of nanoparticles were studied by 2D Atomic force microscopy images. Energy dispersive X‐ray spectroscopy revealed the formation of Ag‐Au/DLC nanoparticles and the percentages of C, Ag, Au and O in all samples. The applied method for Ag/Au alloy preparation is the one step and low‐cost method which makes the samples ready for sensing application.     

Green Synthesis and Characterization of Silver Nanoparticles Using Ferocactus echidne Extract as a Reducing Agent

The green synthesis of silver nanoparticles using an aqueous extract of Ferocactus echidne(a member of the cactus family) as a reducing agent is reported. It is simple, efficient, rapid, and ecologically friendly compared to chemical-mediated methods. Ferocactus echidne is a plant of high medicinal value and rich in polyphenolic antioxidants. The extraction is simple and the product rapidly reduces silver ions without involvement of any external chemical agent. The reduction of silver nanoparticles was characterized by ultraviolet-visible spectrometry as a function of time and concentration. The results show that Ferocactus echidne reduces silver ions within 6 h depending upon the concentration. Further increases in reaction time may result in a blue shift, indicating an increase in particle size, whereas concentration had a minor effect on the particle size. The structure of synthesized nanoparticles was investigated by infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. The infrared spectra indicated the association of organic materials with silver nanoparticles to serve as capping agents. Scanning electron micrographs showed that synthesized silver nanoparticles were nearly uniform and elliptical in shape with diameters of 20 to 60 nm. X-ray diffraction confirmed the formation of silver nanoparticles with an approximate 20 nm particle size calculated using the Debye-Scherer equation. Biological tests revealed that the silver nanoparticles were active against gram positive and negative bacteria( Escherichia coli and Staphylococcus aureus) and fungi (Candida albicans), indicating their broad spectrum antibiotic and antifungal abilities.     

Immobilization of silver nanoparticles obtained by electric discharge method on a track membrane surface

Composite poly(ethylene terephthalate) track membranes containing immobilized silver nanoparticles with the aim of using them for surface-enhanced Raman scattering spectroscopy have been obtained and studied. A dispersion of negatively charged silver nanoparticles has been synthesizes by the method of pulsed electrical discharge between silver electrodes immersed in distilled water. To ensure the electrostatic deposition of nanoparticles onto the track membrane surface, it has been modified with polyethyleneimine. The composition and morphology of the surface of the obtained composite membranes have been studied by X-ray photoelectron spectroscopy and scanning electron microscopy. Aggregation of nanoparticles on the surface has been analyzed. The coefficient of Raman-scattering enhancement has been determined by the example of rhodamine 6G molecules adsorbed on a membrane with immobilized silver nanoparticles.     

Constitution and Properties of Nanocomposites Prepared by Thermal Decomposition of Silver Salts Sorbed by Polyacrylate Matrix

Constitution and dispersity of the products of thermal decomposition of silver nitrate ammonia complex sorbed by polyacrylate matrix are studied by the methods of small- and wide-angle X-ray scattering, optical, photoelectron and Auger-electron spectroscopies. It is shown that, at temperatures of 140–150°C, the complete decomposition of the complex occurs with the formation of nanoparticles and charged silver clusters in polymer bulk. No initial or intermediate products were observed. The average size of obtained nanoparticles is equal to 5 nm. The particles with the size less than 5 nm are amorphous according to X-ray data. The stabilization of nanoparticles occurs due to the adsorption of acrylic copolymer (presumably, via oxygen atoms) on their surfaces. Upon long-term storage in air, the self-diffusion of silver particles and clusters takes place from the surface to composite bulk caused by the detachment of oxygen-containing groups occurring at the metal–polymer interface.