Concentration Of HAuCl4 Research Articles

Biocompatible Gold Nanoparticle Arrays Photodeposited on Periodically Proton Exchanged Lithium Niobate.

Photodeposition of silver nanoparticles onto chemically patterned lithium niobate having alternating lithium niobate and proton exchanged regions has been previously investigated. Here, the spatially defined photodeposition of gold nanoparticles onto periodically proton exchanged lithium niobate is demonstrated. It is shown that the location where the gold nanoparticles form can be tailored by altering the concentration of HAuCl4. This enables the possibility to sequentially deposit gold and silver in different locations to create bimetallic arrays. The cytocompatibility of photodeposited gold, silver, and bimetallic ferroelectric templates to osteoblast-like cells is also investigated. Gold samples provide significantly greater cell biocompatibility than silver samples. These results highlight a potential route for using photodeposited gold on lithium niobate as a template for applications in cellular biosensing.

Xanthan gum stabilized PEGylated gold nanoparticles for improved delivery of curcumin in cancer

In recent years, gold nanoparticles (AuNPs) have received immense interest in various biomedical applications including drug delivery, photothermal ablation of cancer and imaging agent for cancer diagnosis. However, the synthesis of AuNPs poses challenges due to the poor reproducibility and stability of the colloidal system. In the present work, we developed a one step, facile procedure for the synthesis of AuNPs from hydrogen tetrachloroaurate (III) hydrate (HAuCl4. 3H2O) by using ascorbic acid and xanthan gum (XG) as reducing agent and stabilizer, respectively. The effect of concentrations of HAuCl4, 3H2O, ascorbic acid and methoxy polyethylene glycol-thiol (mPEG800-SH) were optimized and it was observed that stable AuNPs were formed at concentrations of 0.25 mM, 50 μM and 1 mM for HAuCl4.3H2O, ascorbic acid, and mPEG800-SH, respectively. The XG stabilized, deep red wine colored AuNPs (XG-AuNPs) were obtained by drop-wise addition of aqueous solution of ascorbic acid (50 mM) and XG (1.5 mg ml−1). Synthesized XG-AuNPs showed λmax at 540 nm and a mean hydrodynamic diameter of 80 ± 3 nm. PEGylation was performed with mPEG800-SH to obtain PEGylated XG-AuNPs (PX-AuNPs) and confirmed by Ellman’s assay. No significant shift observed in λmax and hydrodynamic diameter between XG-AuNPs and PX-AuNPs. Colloidal stability of PX-AuNPs was studied in normal saline, buffers within a pH range of 1.2–7.4, DMEM complete medium and in normal storage condition at 4 ˚C. Further, water soluble curcumin was prepared using PVP-K30 as solid dispersion and loaded on to PX-AuNPs (CPX-AuNPs), and evaluated for cellular uptake and cytotoxicity in Murine melanoma (B16F10) cells. Time and concentration dependent studies using CPX-AuNPs showed efficient uptake and decreased cell viability compared to free curcumin.

Instant synthesis of gold nanoparticles at room temperature and SERS applications

Nowadays, gold nanoparticles (AuNps) can be used in a variety of applications, thus efficient methods to produce them are necessary. Several methods have been proposed in this area, but NPs production time is one limitation of these approaches. In this study, we propose a high competitive method to synthesize gold colloidal nanoparticles, instantaneously, using no-toxic reducing agents. These substances allow the instantaneous synthesis at room temperature, even without magnetic stirrers, ovens or ultrasonic baths. Optic analysis showed two absorption bands, associated with surface Plasmon as function of HAuCl4 concentration. The nanoparticles synthesized have a 10–20 nm size, seen by the transmission electron microscopy (TEM). Therefore, it was possible to obtain several geometric patterns of AuNps, and the synthesis was performed reducing significantly processing time. Additionally, Mie and Fuchs theories were used to predict the location of the absorption bands linked to the plasmon surface in gold nanoparticles. The Surface Enhanced Raman Spectroscopy (SERS) effect was analyzed considering natural zeolite (Chabazite) as analyte, in order to determinate its possible application in soil analysis.

A nanoengineered surface acoustic wave device for analysis of mercury in gas phase

We show that the nickel (Ni)-gold (Au) alloy nanostructures can be directly grown on the electrodes of a surface acoustic wave (SAW) device and can be utilized to detect toxic metal (i.e. elemental mercury (Hg0) in this case), without the requirement of the device having delay line sorption layer and thereby removing the necessity for any additional lithography steps to be undertaken. A set of SAW devices with Ni (100nm thick) electrodes were fabricated using photo-lithography and wet etching processes where each device contained 180 finger pairs in their input and output transducers with 18μm width and spacing (i.e. resonance frequency of ∼42.7MHz). Au nanostructures were then deposited on the Ni surface through galvanic replacement (GR) reaction by utilizing different HAuCl4 concentrations (i.e. 0.5mM/1mM) and reaction times (i.e. 10/20/30min). The results indicated that higher Au concentration can be utilized for acquiring smaller size of Ni-Au alloy nanostructures while the number of Au nanostructures can be increased by the control of the reaction time. It was found that the SAW device with 20min GR reaction time in 1mM HAuCl4 (1mM—20min GR SAW) solution allowed the optimum growth conditions for Ni-Au alloy nanostructures on the electrode surface for Hg0 vapor sensing. Hg0 vapor testing experiments showed that a limit of detection (LoD) of 1.3ppbv toward Hg0 vapor can be achieved with the developed 1mM—20min GR SAW device tested at 35°C. This optimum reaction conditions allowed for ∼100% and ∼200% higher response magnitudes than the 0.5mM—20min and 1mM—10min GR SAW counterparts, respectively when exposed toward low Hg0 vapor concentrations (<400ppbv). Further analysis showed that the effect of interfering gas species such as ammonia, acetaldehyde, ethyl mercaptan and humidity on the sensor’s selectivity toward Hg0 vapor can be reduced by choosing an optimum temperature of 85°C and an optimum Hg0 vapor exposure time of 6min. Overall analysis indicated that, the developed SAW based sensor holds great prospect in chemical sensing applications.

Memory properties of Au nanoparticles prepared by tuning HAuCl4 concentration using low-temperature hydrothermal reaction

An organic memory device with embedded gold nanoparticles (AuNPs) as charge storage elements and polymethylsilsesquioxane (PMSSQ) as organic dielectric layer was fabricated in this work. The AuNPs were prepared using sacrificial hydrothermal reaction on Al template, and the effect of HAuCl4 on size of AuNPs was studied. Field-emission scanning electron microscopy confirmed the increase of particle size with the increase in HAuCl4 concentration. X-ray diffraction analysis confirmed the formation of AuNPs with face-centered cubic (FCC) structure. The electrical properties of the memory system were investigated using a semiconductor characterization system. Current–voltage analysis confirmed the nonvolatile electrical bistability behavior and charge transport mechanism. Capacitance–voltage measurement indicated a memory behavior with flatband voltage shift because the AuNPs trapped and stored charges in the device. The optimal memory properties of AuNPs embedded in PMSSQ were obtained for FCC-structured AuNPs grown in 0.010M HAuCl4, with a mixture of 82±5nm (area density, 1.3×1012m−2) and 42±7nm (area density, 2.7×1012m−2) grain sizes that produced the lowest switch ON voltage of 2.2V and highest flatband voltage of 2.6V.

One-pot synthesis of size-tunable hollow gold nanoshells via APTES-in-water suspension

Abstract A one-pot synthetic strategy was developed for fabrication of hollow gold nanoshells by direct reduction of HAuCl4 in 3-aminopropyltriethoxysilane (APTES)-in-water suspension. Diameters of the APTES droplets which may act as templates for the hollow gold nanoshells could be readily tuned by changing the concentration of HAuCl4 used in the reactions. This flexibility facilitated the tailoring of the sizes of the gold naoshells in the range of 37–96 nm and their corresponding surface plasmon resonance (SPR) in the visible and near infrared region of 657–957 nm. The as-prepared hollow gold nanoshells showed high photothermal conversion efficiency (up to 45%) and excellent stability under laser irradiation.

Study on Green Synthesis of Gold Nanoparticles and Their Potential Applications as Catalysts

Gold being the most biocompatible metal nanoparticle has become an important biosynthesized drug to be studied in recent field of bioscience. The fungus Aspergillus fischeri has been isolated from fruit crop and thus exploited for the synthesis process. Synthesized GNPs were characterized by UV–visible spectroscopy showed absorption spectra in the range of 530–550 nm at different concentrations of HAuCl4. At the optimum reaction concentration of 1 mM HAuCl4, absorption peak was obtained at 543 nm. The GNPs have been further characterized by X-ray diffraction, FTIR, DLS and TEM analysis. The DLS graph showed that the particles were monodispersed. The TEM image showed the formation of spherical shaped GNPs in the range of 50 nm which was in accordance of the particle size analysis by DLS. The potential applications of the gold nanoparticles are yet to be explored and thus, we have conducted a time dependent comparative catalytic activity for methylene blue degradation of chemically synthesized and biosynthesized GNPs which showed biosynthesized ones are better catalysts than chemical ones.

Size‐controlled gold nanoparticles inside polyacrylamide microgels

ABSTRACTGold nanoparticles (AuNPs) of different sizes were synthesized into a crosslinked network of polyacrylamide (PAAm) microgels. PAAm was prepared by means of semicontinuous inverse heterophase polymerization under monomer‐starving conditions with a z‐average particle size of 384 ± 18 nm. AuNPs with controlled size were obtained by a reduction reaction of Au+3 to Au0 from a gold(III) chloride trihydrate (HAuCl4) solution inside microgel the crosslinked network (AuNP‐PAAm). The reduction reaction was verified for 2 h by ultraviolet–visible spectroscopy (UV–vis). AuNP–PAAm exhibited a particle size between 288 ± 12 and 230 ± 15 nm at HAuCl4 concentrations of 0.4 and 1.3 mM, respectively. The AuNP–PAAms were observed by transmission electron microscopy, and their sizes were determined to be 19 ± 2 nm (1.3 mM) and 17 ± 2 nm (1.1 mM). With UV–vis spectroscopy, we detected the formation of AuNPs at a wavelength of 552 nm, and with X‐ray diffraction analysis, we proved that the crystal arrangement was face‐centered cubic. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43560.

Procedure Optimization for Increasing Biosynthesis Rate of Gold Nanoparticles by Aspergillus flavus Supernatant

Biosynthesis of gold nanoparticles was investigated using Aspergillus flavus and the procedure was optimized for maximum production. The color changing from whitish-yellow to purple along with the maximum absorbance at 540 nm in UV-vis spectrum approved the production of gold nanoparticles preliminarily. The XRD spectrum of nanoparticles showed 2θ values corresponding to the gold nanocrystals. TEM micrographs demonstrated the extracellular formation of spherical gold nanoparticles. The optimization process revealed that the maximum rate of gold nanoparticles production achieved after 6 h at 28°C, 2.5 mM HAuCl4 concentration, and pH 6 with different shapes in the size range of 30–50 nm.

One-step synthesis of hollow porous gold nanoparticles with tunable particle size for the reduction of 4-nitrophenol

Hollow porous gold nanoparticles (HPGNPs) were synthesized via a one-step solution phase method at ambient temperature. The particle size, ranging from 80nm to 350nm, was easily controlled by changing the concentration of HAuCl4. The morphology and the structure of the as-prepared HPGNPs were investigated by SEM, TEM, HRTEM and XPS. Langmuir isotherm analysis yielded values of 8973m2/g for the outer surface area and 58724m2/g for the inner surface area for the 80nm HPGNPs. Due to a special hollow porous nanostructure, the HPGNPs exhibited superior catalytic activity and stability for the reduction of 4-nitrophenol (4-NP). No significant inactivation of the 80nm HPGNPs was observed, even after recycling for six cycles or storing for more than 1 month. Due to these excellent properties, it is expected that HPGNPs can be used in such applications as water pollutant removal and environmental remediation.

UV-light aided photoelectrochemical synthesis of Au/TiO2 NTs for photoelectrocatalytic degradation of HPAM

TiO2 NTs loaded with Au nanoparticles were fabricated as an electrode for enhanced photoelectrocatalytic activity toward HPAM degradation. (a) and (b) depicted the degradation rate under different systems and different concentrations of HAuCl4.

Electrodeposition of Gold Films from a Glycerol Solution on Carbon Paste Electrode and the Effect of Chemical and Electrochemical Parameters of Electrodeposition on the Electrode Performance in Potassium Ferrocyanide Solution

The gold electrodeposition process from a glycerol solution on a carbon paste electrode (CPE) was investigated by voltammetry and the morphologies of the electrodeposits were analyzed by scanning electron microscopy (SEM). Voltammetric study indicated that AuCl4− was reduced to Au0 and the process was mixed controlled (mass transport and electron transfer), preceded probably by AuCl4− decomplexation. Glycerol affected the kinetic of gold electrodeposition in function of the AuCl4− concentration. SEM images indicated that the gold electrodeposit covered totally some of the graphite flake by a homogeneous morphology, regardless of the electrodeposition condition. Moreover, using a full factorial planning it was verified that the deposition charge and potential affected the modified CPE performance in a potassium ferrocyanide solution, while HAuCl4 and glycerol concentrations affected only by interactions with the other factors.

Functionalization of Au Nanoparticles on ZnO Nanorods through Low-Temperature Synthesis

Hybrid nanomaterials exhibit multi-functionalities, which is synergy or enhanced physical and optical properties over their single components with promising potentials for various applications in dye-sensitized solar cell and photocatalytic materials. In this present research, the Au nanoparticles were prepared at HAuCl4 concentration of 0.5 mM on ZnO nanorod templates and silicon wafer substrate by hydrothermal reaction process. The prepared samples were investigated the crystal structure, chemical composition and morphologies by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and field-emission scanning electron microscopy (FESEM), respectively. The XRD results shown that ZnO was preferred orientation along the c-axis (002). The FE-SEM images indicated to the difference of size-Au NPs decorated on ZnO nanorods and silicon wafer. The relationship between the surface area and the size of Au NPs of the prepared samples was investigated and possible growing mechanism of Au NPs on ZnO nanorods templates will be discussed.

Facile Growth of Multi-twined Au Nanostructures

We describe a facile growth of chain-like Au nanostructures and their spontaneous transformation to multi-twined nanostructure using a mild reducing agent bisphenol A (BPA). The growth Au nanostructures involves the chemical reduction of HAuCl4 by BPA in the presence of cetyltrimethylammonium bromide (CTAB) as capping agent in alkaline condition without any seeds. Wire and chain-like Au nano-network structures with diameter in the range of 4 to 9 nm are obtained in the initial stage of the reaction. These chain-like nanostructures undergo spontaneous transformation into multi-twined nanostructures within 24 h. These nanocrystalline multi-twined structures have an average size of 80-90 nm. X-ray and selected area electron diffraction measurements reveal that the Au nanoparticles have (111), (200), (220) and (311) planes of a face centered cubic structure. High resolution transmission electron microscopic measurement shows that the nanostructures are mainly composed of (111) lattice plane with twin boundaries. The concentration of HAuCl4, BPA and CTAB has pronounced effect in the growth of nanostructures. The multi-twined nanostructures are highly stable at room temperature over a period of one month and can be used for catalytic applications. Growth of chain-like Au nanoaggregates and the spontaneous transformation to multitwined Au nanostructure are described.

Amphiphilic β‐cyclodextrin‐based star‐like block copolymer unimolecular micelles for facile in situ preparation of gold nanoparticles

ABSTRACTMultifunctional polymer unimolecular micelles, which are used as templates to fabricate stable gold nanoparticles (GNPs) in one‐step without external reductant, have been designed and prepared. Amphiphilic 21‐arm star‐like block copolymers β‐cyclodextrin‐{poly(lactide)‐poly(2‐(dimethylamino) ethyl methacrylate)‐poly[oligo(2‐ethyl‐2‐oxazoline)methacrylate]}21 [β‐CD‐(PLA‐PDMAEMA‐PEtOxMA)21] and the precursors are synthesized by the combination of ring‐opening polymerization (ROP) and activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). The tertiary amine groups of PDMAEMA block reduce the counterion to zerovalent gold in situ, and these gold atoms combine mutually to form final GNPs. GNPs with relatively small size and narrow size distribution can be obtained in longer DMAEMA block copolymer, larger molar ratio of DMAEMA to HAuCl4 and smaller absolute concentrations of both polymer and HAuCl4. These results showed that the unimolecular micelles can be used as templates for preparing and stabilizing GNPs in situ without any external reducing agents and organic solvents, suggesting that the nanocomposite systems are latent nanocarriers for further biomedical application. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 186–196

Surface plasmon resonance in ZnO nanorod arrays caused by gold nanoparticles for solar cell application

AbstractIn this paper, we study the growth of gold nanoparticles (Au‐NPs) onto ZnO nanorod arrays (ZnO‐NRAs) and the surface plasmon resonance effect caused by them. ZnO‐NRAs were deposited by the chemical spray pyrolysis method. Au‐NPs were obtained by spin‐coating of HAuCl4 in ethanol solution over the nanorod samples. According to XRD, the average size of Au‐NPs on ZnO‐NRAs increases from 27 nm to 72 nm by increasing the HAuCl4 concentration in solution from 0.01 to 0.1 mol/L. There are no visible changes in ZnO‐NRAs morphology using the solutions with 0.0004‐0.03 mol/L, partial dissolution of nanorods occurs when using HAuCl4 solution with the concentration of 0.05 mol/L or higher. ZnO‐NRAs covered with Au‐NPs show the red shift of the surface plasmon resonance band from 545 to 555 nm with increasing the HAuCl4 solution concentration from 0.002 to 0.05 mol/L. (© 2015 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

In-situ preparation of size-tunable gold nanoparticles in porous resorcinol–formaldehyde resin

Abstract In this work, porous resorcinol–formaldehyde resin (RF) particles were used as support for in-situ preparation of Au nanoparticles (NPs) by directly immersing the RF into the solution of tetrachloroauric acid (HAuCl4). The Au NPs can be deposited on the RF particle surface or inside the RF particles by simply mediating pH of the reaction solutions. It was revealed that the phenolic hydroxyl groups contained in the RF support can act as both ligand and reductant to promote the formation of the Au NPs. Size of the Au NPs deposited inside the RF particles was tunable in the range of 3.7–14.0 nm by changing the concentration of HAuCl4. The Au NPs loaded in RF with optimal size were identified to show balanced activity and stability in catalyzing the reduction of 4-nitroaniline by NaBH4.

L-Arginine-assisted electrochemical fabrication of hierarchical gold dendrites with improved electrocatalytic activity

Shape and size control of gold (Au) nanocrystals plays important roles in their catalytic and optical properties. Hierarchical Au nanodendrites were directly electrodeposited on a glassy carbon electrode (GCE) using l-arginine as a growth-directing agent, while there is no seed, template, or surfactant involved. It was found that the experimental conditions such as the applied potentials, concentrations of HAuCl4 and l-arginine, and deposition time were essential to the final morphology of the Au deposits. The as-synthesized Au nanocrystals displayed enhanced electrocatalytic activity and improved stability for ethylene glycol (EG) oxidation in acidic media as compared to Au nanoparticles.

Aspect ratio control of Au nanorods via covariation of the total amount of HAuCl4 and ascorbic acid

Controlling the aspect ratio (AR) of gold nanorods (GNRs) via covariation of the total concentrations of HAuCl4 ([HAuCl4]) and ascorbic acid ([AA]) has been studied. Characteristics of GNRs were examined by transmission electron microscopy (TEM) and ultraviolet–visible (UV–vis) absorption spectrophotometry. TEM results showed that single crystalline GNRs grew along an elongated growth direction of [100]. TEM results also revealed that the quantity of plate shaped and nearly spherical nanoparticles increased as the total amount of [HAuCl4] and [AA] decreased. The AR value measured from TEM images decreased from 4.74 to 2.41 as the total amount of [HAuCl4] and [AA] was increased from 0.305 to 2.44mM. The UV–vis absorption spectra of all samples showed that the wavelength of transverse surface plasmon resonance (TSPR) peak appeared at around 530nm for all samples. The wavelength of longitudinal surface plasmon resonance (LSPR) peak increased from 640 to 894nm as the total amount of [HAuCl4] and [AA] decreased from 2.44 to 0.305mM. The wavelength of LSPR peak shows a red-shifted effect except when the total amount of [HAuCl4] and [AA] was 0.122mM.

Synthesis of Au Nanoparticles by Thermal, Sonochemical and Electrochemical Methods: Optimization and Characterization

The present study concentrates on the synthesis of Au nanoparticles (AuNPs) using aqueous solution of Polyvinylpyrrolidone (PVP) and tetrachloroaurate by different methods as thermal, sonochemical and electrochemical reduction. The PVP has been used as a reducing agent and acts as a stabilizer for Au nano particles that obtained as principal product. In all synthesis procedures, the active radicals resulted from degradation of PVP caused to reduce the Au ions in the solution. A design of experiment (DOE) techniques, the response surface methodology (RSM) and Taguchi method have been used to optimize the selected experimental parameters. As the size of produced nano particles depends on the reaction conditions, we studied the effect of some factors such as the concentration of HAuCl4, the molecular weight of PVP and the time interval for the sonoechemical synthesis of nano particles by the RSM. In electrochemical synthesis, the Taguchi method has been used to optimize the three parameters, interval time of synthesis, applied current density and concentration of HAuCl4. Characterization of AuNPs was carried out by Transition electron microscopy (TEM), UV-Vis spectroscopy, and particle size analyser. The average size of synthesized nanoparticles in optimum condition, estimated by the particle size analyser, were about 130 nm, 26 nm and 91 nm in thermal, sonochemical and electrochemical methods, respectively.