Preparation of ultrafine silver powder using ascorbic acid as reducing agent and its application in MLCI

The preparation of ultrafine silver powder with chemical reduction method was investigated. Ascorbic acid was employed as reducing agent. Reaction of AgNO₃ with ascorbic acid gives polyhedron monodispersed ultrafine silver powder. Effect of reaction temperature on particles was studied. The average congeris sizes (D₅₀) reduces linearly from 3.1 μm to 1.0 μm as the reaction temperature increases from 20 °C to 60 °C. The silver powder having excellent dispersibility and different size was prepared through different pH value or different dosage surfactant. The TG/DTA of silver was discussed with thermal analyzer. As-prepared silver powder was applied in ferrite multi-layer chip inductor (MLCI). The silver end termination has high adhesion strength, excellent solderability and solder leaching resistance behavior.     

Preparation of fine copper powder using ascorbic acid as reducing agent and its application in MLCC

The preparation of ultrafine copper powder with chemical reduction method was investigated. Ascorbic acid was employed as reducing agent. Reaction of CuSO₄·5H₂O with ascorbic acid at 70 °C gives polyhedron monodispersed ultrafine copper powder. The copper powder having excellent dispersibility was prepared when the pH value was controlled at 6 with aqueous ammonia. Influences of reaction temperature on the efficiency of copper powders were also studied. TG/DTG/DTA of copper powder was discussed with thermal analyzer. As-prepared copper powder was applied in BME-MLCC. The micro-structures of end termination and interface were discussed with SEM and polarized light microscope. The copper end termination has high adhesion force, excellent solderibility behavior and resistance behavior to soldering.     

Synthesis and agglomeration of gold nanoparticles in reverse micelles

Reverse micelles prepared in the system water, sodium bis-(2-ethylhexyl) sulfoccinate (AOT), and isooctane were investigated as a templating system for the production of gold nanoparticles from Au(III) and the reducing agent sulfite. A core-shell Mie model was used to describe the optical properties of gold nanoparticles in the reverse micelles. Dynamic light scattering of gold colloids in aqueous media and in reverse micelle solution indicated agglomeration of micelles containing particles. This was verified theoretically with an analysis of the total interaction energy between pairs of particles as a function of particle size. The analysis indicated that particles larger than about 8?nm in diameter should reversibly flocculate. Transmission electron microscopy measurements of gold nanoparticles produced in our reverse micelles showed diameters of 8-10?nm. Evidence of cluster formation was also observed. Time-correlated UV-vis absorption measurements showed a red shift for the peak wavelength. This was interpreted as the result of multiple scattering and plasmon interaction between particles due to agglomeration of micelles with particles larger than 8?nm.     

Preparation of gold nanoparticles in an aqueous medium using 2-mercaptosuccinic acid as both reduction and capping agent

Monolayer protected gold nanoparticles with diameters above 10 nm were prepared by a simple, one step reaction in water. 2-mercaptosuccinic acid (MSA) was used both as reduction agent for hydrogen tetrachloroaurate (HAuCl4) and as stabilizing agent for the gold nanoparticles. Size distribution and surface chemistry were investigated by UV-Vis spectroscopy, scanning electron microscopy and Fourier Transform Infrared Spectroscopy. Particle size can be controlled by adjusting the molar portions of the reactants. The resulting particles are efficiently stabilized against aggregation when MSA is used in a concentration of 40% and above. Below a minimum MSA concentration a long-term particle growth is observed.     

Preparation and characterization of reduced graphene oxide using ascorbic acid and sodium citrate as binary reductant

In this article, we successfully prepared transparent and gauze-like reduced graphene oxide (RGO) film with the thickness of only 1.32 nm using modified Hummers method and binary reductant consisting of ascorbic acid and sodium citrate. SEM, TEM, AFM, XRD, UV-Vis, and FTIR results all convincingly demonstrated that the reduction of graphite oxide using binary reductant is a feasible method to prepare RGO. In addition, the results also revealed that extending the oxidation time and increasing the ultrasonic oscillation reasonably might improve the oxidation degree of the graphite oxide, the ratio of the D-band Raman intensity to that of the G band (I_D/I_G) reached up to 1.244 in the as-obtained graphite oxide. Moreover, sodium citrate not only increased the reducibility of binary reduction system but also improved the dispersion of graphite oxide. Furthermore, reasonable annealing treatment could reduce the defects of RGO. It is a potential route to prepare RGO films and increase practical applications in large-scale production of graphene.     

Au/Ag芯-壳复合结构纳米颗粒的制备和表征

利用二步液相还原法制备了 Au/Ag 芯 壳复合结构的纳米颗粒。用 TEM对反应液中金离子和银离子的摩尔比分别为1∶2和1∶1时所制备的 Au/Ag芯 壳复合结构的纳米颗粒的尺寸和形貌进行了表征。其紫外 可见吸收光谱具有 2 个可区分的吸收带,与纯金和纯银纳米颗粒的光学吸收特性对比后认为:随着反应液中银离子摩尔份数的增加,等离子体共振吸收峰始终位于 410nm附近的吸收带为银纳米颗粒的等离子体吸收带;另一个将随之产生蓝移的吸收带为Au/Ag芯 壳复合结构纳米颗粒的等离子体吸收带,蓝移是由于银壳厚度的增加而引起的。     

Highly selective colorimetric detection of hydrochloric acid using unlabeled gold nanoparticles and an oxidizing agent

We report a colorimetric system for the detection of HCl in aqueous environments using unlabeled gold nanoparticle (AuNP) probes. This nonaggregation-based detection system relies on the ability of chloro species to cause rapid leaching of AuNPs in an aqueous dispersion containing a strong oxidizing agent, such as HNO(3) or H(2)O(2). The leaching process leads to remarkable damping of the surface plasmon resonance peak of the AuNP dispersion. This method works only with AuNPs of a particular size (～30 nm diameter). It is highly selective for HCl over several common mineral acids, salts, and anions. This simple and cost-effective sensing system provides rapid and simple detection of HCl at concentrations as low as 500 ppm (far below the hazard limit) in natural water systems.     

Formation of monetite nanoparticles and nanofibers in reverse micelles

Reverse micelles solution of water and cyclohexane containing either cetyltrimethylammonium bromide (CTAB) or polyoxyethylene-8-dodecyl ether (C₁₂E₈) surfactants and n-pentanol as co-surfactant have been used as organized reaction microenvironments for monetite (dicalcium phosphate anhydrous, DCPA) precipitation. Well-crystallized monetite nanoparticles with various morphologies such as spheres, nanofibers and bundles of nanowires were obtained in CTAB reverse micelles solution. The molar ratio of water and surfactant (W _o) and the molar ratio of co-surfactant and surfactant (P _o) have great influence on the structure and morphology of the final products. A generalized mechanism for the growth of monetite in reverse micelles is proposed, in which the interaction between the surfactant molecules and PO₄³⁻ ions leads to the formation of a surfactant/CaHPO₄ complex. It is because of this central complex that the further fusion with reactant ions containing reverse micelles will occur only in one direction. Changing the content of water and co-surfactant has great influence on the morphology of reverse micelles and on the interaction between the surfactant/CaHPO₄ complex leading to a fine tuning of the morphology of products. By contrast, lacking of this interaction in the C₁₂E₈ system only tablet amorphous calcium phosphate can be formed.     

A study on gold nanoparticle synthesis using oleylamine as both reducing agent and protecting ligand

The growth kinetics and mechanism of a gold nanoparticle synthesis using water as a single phase solvent and oleylamine as both reducing agent and monolayer protection agent were studied. FT-IR and 1H NMR spectroscopic analysis revealed a conversion of oleylamine ligands to oleylamides when gold(III) was reduced to gold(I) and gold atoms. During the reaction, it was found by UV-Vis absorption spectroscopy and transmission electron microscopic study that oleylamine ligands formed large complex aggregates with gold salt instantly upon mixing these two agents together. At an elevated temperature of 80 degrees C, the complex decomposed first into very small particles and then the small particles recombined together into larger and thermally stable particles with an average core size around 9-10 nm. The oleylamide ligands formed a protecting monolayer around the nanoparticles through a hydrogen bonding network between the amide groups. The recombination of small particles into larger ones was found to follow a logistic model, as confirmed by a nonlinear regression fitting of the UV-Vis absorption data of the reaction solution with the mathematical model.     

Preparation and characterization of CdSe nanoparticles in the presence of Triocytlphosphine as solvent and capping agent

Triocytlphosphine (TOP)-capped CdSe nanoparticles (NPs) have been successfully prepared by the one-pot solution growth method at 240 °C under argon atmosphere. In particular, The TOP used in this process as the single coordinating solvent is favorable for probing capping mechanism of CdSe NPs surface. The growth process and characterization of CdSe NPs were determined by photoluminescence (PL) spectroscopy, X-ray diffraction (XRD), Transmission electron microscopy (TEM), Ultraviolet-visible (UV-Vis) spectroscopy and Fourier transform infrared spectroscopy (FTIR). Results demonstrated the TOP-capped CdSe NPs to be well dispersed and uniform in shape and the diameter of the particle was confined within 8 nm. PL measurement showed the near band-edge luminescence of the final product.     

A single-step synthesis of gold nanochains using an amino acid as a capping agent and characterization of their optical properties

We demonstrated a simple single-step synthesis of gold nanochains by reducing aqueous chloroaurate ions (AuCl(4)(-)) with sodiumborohydride (NaBH(4)) in the presence of an amino acid (glutamic acid and histidine) as a stabilizer. The structure and optical properties of gold nanochains and nanowires were characterized by transmission electron microscopy, UV-visible spectroscopy, infrared spectroscopy and femtosecond z-scan measurements. The results suggested that the gold nanochains and nanowires were formed via the nanospheres fusing into one another by an oriented attachment mechanism through dipole-dipole interactions. The z-scan measurements on Au nanowires showed a transition from saturable absorption to reverse saturable absorption as the pump intensity increased.     

Sensitized room-temperature luminescence in reverse micelles using lanthanide counterions as acceptors

The analytical usefulness of sensitized room-temperature luminescence in reverse micelles using lanthanide counterions is examined. The technique is based on the unique luminescent properties of tripositive lanthanide metal ions as counterions for the surfactant and the molecular organization produced by reverse micelles. After excitation, the analyte molecule transfers its triplet-state energy to an acceptor molecule (lanthanide), which subsequently emits luminescence. Two surfactants with different lanthanide counterions have been synthesized and characterized by spectroscopic and mass spectrometric techniques. When compared to the lanthanide salt, the sensitized luminescence of the lanthanide surfactant is substantially enhanced. The exact locations of the analyte and the counterion in the micellar system are discussed. The efficiencies of energy transfer for the two surfactants are compared.     

Preparation and characterization of ceria nanoparticles using crystalline hydrate cerium propionate as precursor

Ceria nanoparticles were synthesized simply by pyrolysis method using hydrate cerium propionate as precursor. The effect of pyrolysis temperature on the physical properties of ceria was investigated. It was found that the large crystals of precursor cracked to many nano-sized ceria particles on heating, and the medium particle sizes D₅₀ determined by laser scattering (LS) method decreased firstly and then increased with minimum value around 460 nm at calcination temperature of 1000 °C. SEM observations showed that the average particle size of synthesized ceria powders ranged from 20 to 50 nm.     

Preparation of SiO2/(PMMA/Fe3O4) nanoparticles using linolenic acid as crosslink agent for nucleic acid detection using chemiluminescent method

Usually, magnetic nanoparticles (MNPs) are prepared based on the famous St?ber process in which divinylbenzene (DVA) is often used as a crosslink agent to synthesize SiO2/(PMMA/Fe3O4) nanoparticles. Compared with DVA, linolenic acid (LNA) is innoxious and can polymerize more easily for it has three unsaturated double bonds. In this paper, LNA was used as a new crosslink agent instead of DVA to synthesize the SiO2/(PMMA/Fe3O4) nanoparticles. The results showed that the core-shell structure could be observed obviously. The sizes of nanoparticles with core-shell structure range from 200 to 500 nm. The DNA probes which was immobilized on the surface of MNPs were used to capture the biotin modified complementary sequence of the probe, and the formed complexes were bonded with streptavidin-modified alkaline phosphatase (SA-AP). Finally the chemiluminescent signals were detected by adding 3-(2'-spiroadamantane)-4-methoxy-4-(3"-phosphoryloxy) phenyl-1, 2-dioxetane (AMPPD) which was the substrate reagent of AP. The specificity and sensitivity of this approach were investigated in this paper.     

Preparation of antibody-conjugated gold nanoparticles

We here describe a method for the simple synthesis of gold nanoparticles (~ 10 nm in diameter) conjugated with antibody to E. coli O157:H7. Gold nanoparticles with pendant carboxylic acid and alcohol functional groups were synthesized and characterized using transmission electron microscopy (TEM) and infrared spectroscopy. These nanoparticles were then reacted with anti-E. coli O157:H7, using EDC coupling chemistry, and the product was characterized with X-ray photoelectron spectroscopy. Furthermore, binding of the antibody-gold conjugates to E. coli O157:H7 was demonstrated using transmission electron microscopy.     

Biogenic gold nanoparticles as fotillas to fire berberine hydrochloride using folic acid as molecular road map

Use of biologically modified gold nanoparticles (GNPs) as molecular vehicle to ferry potential anti-cancer drug berberine hydrochloride (BHC) using folic acid (FA) as targeting molecule is reported in this work. A tropical fruit peel, Trapa bispinosa is used to fabricate highly monodispersed GNPs, passivated with essential functional groups which were used as linkers to attach FA and BHC via amide linkage. Flocculation Parameter (FP) of biologically synthesized GNPs was calculated under different salt concentrations which were found to be very ideal under a physiological condition. Various statistical models were used to find drug release profile out of which Higuchi was found to be the most ideal. GNP–FA–BHC complexes were found to be active against folic acid expressing HeLa cells.     

Preparation of carboxyl-coated polystyrene nanoparticles using oleic acid

Novel carboxyl group-decorated crosslinked polystyrene nanoparticles were prepared via the soapless emulsion polymerisation of styrene and divinyl benzene with oleic acid as functional comonomer. The existence of the surface carboxyl group was verified by zeta potential analysis. Particle sizes of the functional nanoparticles prepared with the proposed method were found to be in the range of 60-100-nm by transmission electron microscopy and dynamic light scattering analyses. Functionalised nanoparticles are proposed as carriers for biomolecules or drugs.