Particle Size Of Gold Nanoparticles Research Articles

Raman enhancement effects of gold nanoparticles with different particle sizes on clenbuterol and ractopamine

Clenbuterol and ractopamine can be used to improve carcass leanness in swine, but their residues in pork also pose health risks. This study used surface-enhanced Raman scatter (SERS) technology to establish MLR and PLSR prediction models for clenbuterol and ractopamine, respectively, to achieve rapid detection and identification of ractopamine (RAC) and clenbuterol hydrochloride (CL) residues. In this report, the detection of clenbuterol and ractopamine was carried out using three gold colloids with different particle sizes as enhanced substrates. It was found that the larger particle size of gold nanoparticles was, the better enhancement effect was, which indicated that gold nanoparticles with larger particle sizes were more conducive to the adsorption of RAC and CL. Then, the SERS spectra of 0.1–10 µg/mL clenbuterol and ractopamine solution were collected by using NaCl aqueous solution of 1 mol/L as aggregating compound and gold colloid A as enhanced substrate. Automatic Whittaker Filter (AWF) was used for preprocessing to reduce fluorescence background contained in the original Raman spectra collected. Finally, models were established between SERS intensity at each characteristic peak and the concentration of clenbuterol and ractopamine, respectively. The results show that the PLSR model for clenbuterol using six peaks was stable. The correlation coefficient R2 and the root mean square error of correction set were 0.99 and 0.025 µg/mL, respectively. The correlation coefficient R2 and the root mean square error of prediction set were 0.99 and 0.026 µg/mL, respectively. The MLR model for ractopamine using six peaks had a higher correlation coefficient and a lower root mean square error (RMSEC) than other models. The correlation coefficient R2 and the root mean square error of correction set were 0.99 and 0.043 µg/mL, respectively. The correlation coefficient R2 and the root mean square error of prediction set were 0.99 and 0.05 µg/mL, respectively. The detection limit (LOD) value of this method for the detection of clenbuterol and ractopamine was 18 ng/mL and 24 ng/mL, respectively. This study is helpful for further development of a simple SERS detection method of clenbuterol and ractopamine based on gold colloid.

Ultrafine gold nanoparticles dispersed in conjugated microporous polymers with sulfhydryl functional groups to improve the reducing activity of 4-nitrophenol

Achieving the preparation of uniformly loaded ultrafine metal nanoparticles catalysts is a key problem in the field of catalysis. In this study, ultrafine gold nanoparticle catalysts were prepared by using conjugated microporous polymers (CMPs) modified with sulfhydryl group to support gold. High-resolution transmission electron microscopy (HR-TEM) at Au@TBD-S-SH showed that the average particle size of gold nanoparticles (Au NPs) was 3.4 nm. The higher catalytic activity was shown by comparing the normalized reaction rate constants (Knor = 117) from the work of other investigators. Moreover, the catalysts maintained their activity after ten cycles. Meanwhile, Au NPs increased in size probably on account of adsorption products and slight agglomeration. These studies demonstrated that functionalized CMPs loaded with noble metals can efficiently remove phenolic compounds from wastewater.

Gold Nanoparticle-Optimized Computed Tomography Imaging Combined with Transcranial Magnetic Stimulation on Rehabilitation Training of Children with Cerebral Palsy

Traditional computed tomography (CT) contrast agents, such as iodine-containing small molecules (omnipaque), have limitations in some applications. The development of nanotechnology has made it possible to develop CT contrast agents based on this technology. In this study, a large number of surface functional groups of the fifth-generation polyamide-amine dendrimer (P5-NH2) were applied to functionally modify polyethylene glycol (PEG), targeting molecules, or drugs, which were used as the carrier of CT contrast agents. With the help of sodium borohydride (NaBH4), there was a rapid reduction. The fluorescein thiocyanate (FT) and PEG modified with lactobionic acid (PEG-LA) weres connected before gold coating to obtain gold nanoparticles coated with targeted dendrimer (Au(P5-LA)DENPs). In the experiment, the gold nanoparticles were characterized, and the liver cancer nude mouse model was established, so as to analyze the CT imaging performance of the material. Besides, the above was applied in the motor function of children with cerebral palsy, and the improvement effect of CT imaging combined with transcranial magnetic stimulation based on the preparation of nanomaterials on the movement function of children was analyzed and demonstrated with the help of graph theory. The results showed that the average particle size of gold nanoparticles was 1.88 nm. Within the range of 5 °C–50 °C and pH = 4–7, the physical properties of the aqueous solution of this material were stable. What’s more, the cell activity still exceeded 80% when the material concentration reached 2000 nm. The nude mouse model of liver cancer indicated that the CT imaging based on this material enhanced the image contrast effect of the tumor part, and the material had no obvious toxic and side effects. CT imaging based on the preparation of nanomaterials can promote transcranial magnetic stimulation to accelerate the efficiency of brain movement, accelerate the global and local information exchange and integration speed of brain network, thereby improving the movement function of children.

Size-dependent optical and electrochemical properties of gold nanoparticles to L-cysteine

A series of gold nanoparticles were synthesized by stepwise growth method under the condition of citrate as a reducing agent and stabilizer. The optical properties with the maximum absorption wavelength (λmax) and electrochemical properties of the oxidation potential (Ep) dependence on the particle size were analyzed. The method of calculating the particle size from the UV-visible spectrum and the electrochemical oxidation peak was deduced, following the theoretical prediction trend and consistent with previous observations. Furthermore, we investigated the application performance based on the electrochemical catalytic activity and the aggregation of the spherical gold nanoparticles using L-cysteine as a target. The results indicated that the optical and electrochemical properties of the gold nanoparticles to L-cysteine were closely related to the particle size of gold nanoparticles. With the increased size of the nanoparticles, the full width at half maximum in the UV-visible absorption spectrum increased and the electrochemical oxidation potential was positively shifted.

Flower-like gold nanoparticles labeled and silver deposition rapid vertical flow technology for highly sensitive detection of Brucella antibodies.

To prevent the transmission of brucellosis, rapid vertical flow technology (RVFT) was developed to detect brucellosis antibodies. To improve the sensitivity of the technique, lipopolysaccharides (LPS) were purified and used to detect brucellosis antibodies. To improve the sensitivity of serum antibody detection, a single multifunctional buffer was established in whole blood and other biological samples, and the advantages of the lateral flow immunoassay were retained. Flower-like gold nanoparticles were applied to RVFT for the first time. In this study, silver ions were catalyzed by flower-like gold nanoparticles into metal silver deposited on the surface of gold nanoparticles for the first time, which not only increased the particle size of gold nanoparticles, but also showed a more distinguishable black color on the test zone, further improving the sensitivity of RVFT. Standard Brucella-positive serum (containing Brucella antibody at 4000 IU mL-1) could be detected in this system even for a dilution factor of 2 × 10-3. The detection limit was 2 IU mL-1. RVFT can effectively avoid the false negative phenomenon in lateral flow immunoassay. RVFT is simple to operate, with a short reaction time, 2-3 minutes visible to the naked eye, without any equipment. Because it is very important to control the brucellosis epidemic, this approach has great application prospects in basic medical units and for veterinarians.

Gold Catalysts Synthesized Using a Modified Incipient Wetness Impregnation Method for Propylene Epoxidation

AbstractPropylene epoxidation in the presence of oxygen and hydrogen were measured for a series of Au/TS‐1 catalysts prepared by a modified incipient wetness impregnation (mIWI) method. This method enables precise control of the Au : Ti ratio in the Au/TS‐1 catalysts. The optimized Au/TS‐1 catalyst exhibited 12 % propylene conversion, 87 % PO selectivity, and 25 % hydrogen efficiency. The particle size of gold nanoparticles prepared by the modified IWI was between 2 and 3 nm, as demonstrated by XRD patterns, STEM images, and X‐ray absorption spectroscopy at the Au L3 edge. XPS spectra showed that the surface species on the catalysts were similar. UV‐Vis spectra suggested that in the modified IWI method, the chlorine ligands in Au(Cl)4− were replaced by hydroxyl groups, which contributes to form small gold nanoparticles. Kinetic studies showed that the active sites of Au(mIWI)/TS‐1 are similar to the Au(DP)/TS‐1 prepared by deposition precipitation.

A model for the formation of gold nanoparticles in the citrate synthesis method

This paper presents a new model for predicting the evolution of the particle size of gold nanoparticles (GNPs) in the citrate synthesis method. In this method, the precursor is an acid solution of tetrachloroauric acid, while the reducing agent is a base solution of sodium citrate. The acid-base properties of the solutions influence how the size of the particles evolves during the synthesis. In the literature, various mechanistic theories have been proposed to explain this evolution. Turkevich et al. (1951), who pioneered this synthesis method, suggested the “organizer theory”. This mechanistic description of the synthesis was modelled by Kumar et al. (2007), but recently Agunloye et al. (2017) showed that in several cases this model performed poorly, since it does not account for the acid-base properties of the reactants. In this work, we present a kinetic model based on the synthesis seed-mediated mechanistic description proposed by Wuithschick et al. (2015). In this description, the precursor concurrently reduces into gold atoms and hydroxylates into a passive form. The gold atoms then aggregate into seed particles, which finally react with the passive form of the precursor in a growth step. We validated the model using experimental data from the literature obtained for conditions in which the seed-mediated mechanism is valid. The predicted GNP final sizes closely agree with those obtained experimentally.

Influence of ligands property and particle size of gold nanoparticles on the protein adsorption and corresponding targeting ability

Nanoparticulated vesicles were widely used for carriers of drugs and imaging probes. To improve the targeting delivery efficiency of these vesicles, ligands were often functionalized onto their surfaces. However, the interaction between vesicles and plasma proteins may cover the ligands and hinder the targeting delivery. It is important to address the potential influence of ligands modification on plasma protein adsorption and the following targeting delivery. In this study, two common used ligands were chosen as the model: transferrin and RGD peptide. Gold nanoparticles were utilized as model particles. Sodium dodecyl sulfate polyacrylamide gel electrophoresis data demonstrated that higher PEG modification and smaller particle size could reduce the plasma protein adsorption, while ligand modification could increase. The cellular uptake results showed that the targeting ability of smaller ligand RGD peptide would be more easily influenced by the proteins corona.

Effect of Particle Size of Gold Nanoparticles on Matrix Metalloprotease Inhibition, Cytotoxicity and Genotoxicity

Effect of Particle Size of Gold Nanoparticles on Matrix Metalloprotease Inhibition, Cytotoxicity and Genotoxicity

Size controlled synthesis of gold nanostructures using ketones and their catalytic activity towards reduction of p-nitrophenol

This work reports a rapid, facile, surfactant free and size controlled microwave assisted synthesis of colloidal gold nanostructures in aqueous medium. The growth of gold nanostructures was taking place using auric chloride with different ketones. The various ketones such as cyclohexanone, 2,4-pentanedione, 2,5-hexanedione, 1,4-cyclohexanedione, 1,3-cyclopentanedione, cyclopentanone, 2,3-butanedione and 2-butanone were used for the synthesis of gold nanostructures. Ketone plays a crucial role in synthesis and it act as a reducing, stabilizing as well as structure directing agent. The nanoparticle size and their rates of formation were found to be dependent on the enol content (keto-enol equilibrium constant) and water solubility of the ketones. The size of the gold nanoparticles was tunable in the range of 20–80nm and 200–500nm for the nanoplates with the specific selection of ketone. The phase structure, elemental composition, morphology and surface plasmon resonance (SPR) properties of the synthesized gold nanostructures were studied using XRD, EDS, FEG-SEM and UV–Visible spectroscopy respectively. Furthermore, the catalytic activity and recyclability of gold nanoparticles for the reduction of p-nitrophenol to p-aminophenol in the presence of sodium borohydride was evaluated using UV–Visible spectroscopy at room temperature. Interestingly, the catalytic activity was found to be depended on the particle size of gold nanoparticles.

金ナノ粒子ネットワーク膜の形成と光学的・電気的特性に及ぼす自己集積化条件の影響

Gold nanoparticles were grown under various sodium citrate concentration and self-assembled gold nanoparticle films were formed on a glass substrate under various conditions to examine the effect of sodium citrate concentration on the particle size of gold nanoparticles and the effect of processing time and processing temperature on the optical properties and electrical resistivity of the self-assembled gold nanoparticle film. As a result, it was found that the ratio of tetrachloroauric (III) acid to sodium citrate is preferably 1:3 was appropriate to obtain fine gold nanoparticles. The self-assembled gold nanoparticle films showed a network structure formed by nano-wires for all assembled conditions. However the thickness or the assembled state of the gold nano-wires was sensitive to the processing temperature whereas the processing time hardly affected the properties of the nano-wires. In particular, higher processing temperature led to a break in the nano-wires and then the optical properties and electrical resistivity was degraded.

Thermal Stability of Gold Catalyst Supported on Mesoporous Titania Nanofibers

By deposition-precipitation with urea method, gold was loaded on mesoporous TiO 2 whisker, which was prepared from a potassium titanate whisker precursor through solid phase sintering process. The morphology and structure of these as-prepared catalysts were characterized by N 2 adsorption-desorption, X-ray diffraction, and transmission electron microscopy. The reduction of 4-nitrophenol to 4-aminophenol by NaBH 4 was evaluated as a probe reaction. After calcination at high temperature, the activity of the catalysts supported on mesoporous TiO 2 nanofiber was well maintained, and the particle size of gold nanoparticles was hardly changed. This might be attributed to the peculiar crystallographic structure and mesoporous nanoarchitecture of the mesoporous TiO 2 whisker. 以二钛酸钾晶须为前驱体, 通过固相烧结工艺制备了介孔 TiO 2 晶须, 然后使用沉积沉淀法将 Au 纳米颗粒担载于其上, 并采用低温 N 2 吸附-脱附 X 射线衍射及透射电镜等技术对催化剂的形貌和结构进行了表征, 以 NaBH 4 还原对硝基苯酚 (PNP) 为探针反应, 评价了催化剂的活性及稳定性. 结果表明, 500 丰C 热处理前后, 介孔 TiO 2 负载的 Au 纳米颗粒的平均粒径变化不大, 且催化 PNP 还原活性得到了很好的保持. 这主要与介孔 TiO 2 晶须独特的双晶构型及介孔结构有关. The unique crystallographic structure and mesoporous architecture of the TiO 2 whisker ensure the excellent sinter-resistant properties of gold nanoparticles. Consequently, the activity of the catalyst supported on the mb-TiO 2 is well maintained after high temperature calcination.

Crystal-Face-Selective Supporting of Gold Nanoparticles on Layered Double Hydroxide as Efficient Catalyst for Epoxidation of Styrene

Au catalysts with layered double hydroxide (LDH) as support were fabricated and the crystal faces feature of LDH platelets was revealed to have a crucial effect on the location and particle size of gold nanoparticles (AuNPs). A preferential deposition of AuNPs with a narrow size distribution was formed on the lateral {101̅0} faces of LDH platelets. Catalytic property evaluation of the resulting Au/LDH samples showed that the conversion of styrene with tert-butyl hydroperoxide (TBHP) to styrene oxide (SO) occurred on the AuNPs with particle size of 2−3 nm, mainly deposited on the lateral faces of LDH support.

Flow field-flow fractionation: a versatile approach for size characterization of α-tocopherol-induced enlargement of gold nanoparticles

Flow field-flow fractionation (FlFFF) was used for size characterization of gold nanoparticles. The measured particle sizes obtained from FlFFF for the commercial 10 nm gold nanoparticle standard and the gold nanoparticles synthesized in the laboratory were in good agreement with those measured by transmission electron microscopy (TEM). Further, the capability of alpha-tocopherol to induce enlargement of gold nanoparticles by catalysis of the reduction of AuCl(4)(-) by citrate was observed by monitoring the changes in particle size of gold nanoparticles using FlFFF. The effects of alpha-tocopherol and incubation time on enlargement of the gold nanoparticles were examined. Higher concentrations of alpha-tocopherol resulted in larger nanoparticles. At fixed alpha-tocopherol concentration, larger nanoparticles were formed at longer incubation times.

Au/TiO 2 catalysts prepared by photo-deposition method for selective CO oxidation in H 2 stream

A series of Au/TiO 2 catalysts were prepared by photo-deposition (PD) method. Various preparation parameters, such as pH value, power of UV light and irradiation time on the characteristics of the catalysts were investigated. The catalysts were characterized by inductively-coupled plasma-mass spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The preferential oxidation of CO in H 2 stream (PROX) on these catalysts was carried out in a fixed-bed micro reactor with a feed of CO: O 2: H 2: He = 1: 1: 49: 49 (volume ratios) and a space velocity of 30,000 ml/g h. Limited amount of O 2 was used to investigate the selectivity of O 2 reacting with CO or H 2. Au/TiO 2 catalysts prepared by PD method showed narrow particle size distribution of gold particles within few nanometers and were found to be ∼1.5 nm. The particle size of gold nanoparticles deposited on the support depends on irradiation time, UV light source and pH value of preparation. The electronic structure of Au was a function of particle size. The smaller the Au particle size was, the higher the concentration of Au cation was. Using weak power of UV light, appropriate irradiation time and suitable pH value, very fine gold particles on the support could be obtained even in the powder form. The samples prepared with PD method did not need heat treatment to reduce Au cation, UV irradiation could reduce it. Therefore it is easier to have smaller particle size. Au/TiO 2 catalysts prepared by PD method were very active and selective in PROX reaction. In long time test, the catalysts were stable at 80 °C for more than 60 h.

Uncertainty estimation of nanoparticle size distribution from a finite number of data obtained by microscopic analysis

Various techniques are used to measure the mean particle size (PS) and the particle size distribution (PSD) and relevant uncertainties of the measured mean PS and PSD can be obtained by using statistical treatments. Among those techniques, microscopic analysis methods provide the possibility to observe individual particles, allowing detailed information about the PS. However, there is no existing method to estimate the uncertainty of the PSD from a finite number of data obtained by microscopic measurement. We found that it is possible to adopt the method of deducing the standard deviation of the sample standard deviation to estimate the PSD uncertainty from the result of a microscopic analysis when the sample data follow a normal or log-normal distribution. The recommended minimum number of data for the application of developed statistical methods was deduced by simulation with population data sets of pseudorandom numbers. It was found that the PS of gold nanoparticles (NPs) synthesized by the conventional reduction method in aqueous solution followed a log-normal distribution, indicating that this method is applicable to estimate the PSD uncertainty of synthetic Au NPs from the measured PS data obtained by microscopic methods.

Effect of polyvinyl alcohol molecular weight and UV-photoactivation on the size of gold nanoparticle

Abstract The preparation and optical properties of gold nanoparticles prepared by the UV-photoactivation technique at two wavelengths (365 and 254 nm) at different irradiation times were studied. Polyvinyl alcohol two molecular weights ( M w =125,000 and 6000) was used as a radical surfactant stabilizer. The structure and optical properties were investigated by transmission electron microscopy (TEM) and ultraviolet–visible (UV–VIS) spectroscopy. The configuration of particles is rather spherical and exhibits narrow size distribution with mean diameter depending on the power of irradiation and the molecular weight of the surfactant stabilizer for all samples. The maximum bands appearing in the range (528–546 nm) are related to surface plasmon resonance (SPR). Red shift with broadening of (SPR) bands has been observed depending not only on UV-photoactivation but also on the molecular weight of the surfactant stabilizer. The absorption band at 308 nm could be attributed the electron transfer between the surfactant stabilizer and NaBH 4 through the gold particles. This study presents a simple method for synthesis and control of the particle size of gold nanoparticles.

Antioxidant-potentiality of gold–chitosan nanocomposites

Gold nanoparticles were prepared in the presence of chitosan via reduction of HAuCl 4 with sodium borohydride. The average particle size of gold nanoparticles was significantly affected with the concentration of chitosan added and was ranged between 6 and 16 nm. The gold–chitosan nanocomposites are formed by adsorbing chitosan molecules on the gold nanoparticles. The catalytic activity of gold–chitosan nanocomposites upon elimination of hydroxyl radicals formed in an H 2O 2/FeSO 4 system was examined using a spin-trapping method. The catalytic activity increased with the concentration of chitosan added and showed a maximum and then decreased with a further concentration of chitosan added, although a strict correlation between the average diameter of gold and the catalytic activity was not found. In addition, the activity of gold–chitosan was 80 times higher than that of ascorbic acid, which is well known as an antioxidant.