Gold Salts Research Articles

Fabrication and In-Situ Thermal Reduction of Gold Nanofibers

One-dimensional gold nanofibers are good candidates for next generation nanoelectronic devices. Here, gold nanofibers were synthesized via electrospinning with subsequent in-situ thermal reduction. The thermal behavior of the precursor nanofibers was investigated by thermogravimetric/differential thermal analysis and fourier transform infrared. The polymer parts are decomposed and removed step by step, meanwhile, gold salt is decomposed and in-situ reduced to form gold nanoparticles in air without any reducing agent or gas due to its strong oxidation ability. The effects of gold content, polymers type (PVP, PVA, PAN), calcination atmospheres (Air, H2, H2/Ar) and temperatures (200 °C to 500 °C) on the morphology and structures of gold nanofibers were characterized by XRD, SEM, and TEM. The results shows that PVP is the optimal polymer with the gold content of 6:1 (PVP:Au) to fabricate the continuous gold nanofibers with good morphology and structures. The final gold nanofibers with average diameter of 60 nm and several hundred micrometers long, were fabricated after calcined at 500 °C in air for 2 hours. It was composed of gold nanoparticles that ranged from 5 to 30 nm.

Comparative Study on Antibacterial Activity of Metal Ions, Monometallic and Alloy Noble Metal Nanoparticles Against Nosocomial Pathogens

Unbeatable widespread antimicrobial resistance in nosocomial pathogens is a major public health concern in hospitals. In the present study, aqueous stem extract of C. tagal (CTSE) is used as a bioreducing agent for synthesis of various monometallic and alloy nanoparticles. Nanoparticle formation was dependent on time, temperature, and metal salts’ concentration. UV-Visible spectroscopy demonstrated peaks at 444 and 556 nm for silver and gold nanoparticles, respectively, while both alloy Ag–Au nanoparticles exhibited peaks at 535 nm. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy results revealed shape, size, and involvement of functional groups in formation of stable nanoparticles. Further, minimum inhibitory concentration (MIC) of two metal ions, four monometallic nanoparticles, and two alloy noble metal nanoparticles was evaluated against nosocomial pathogens. Silver nanoparticles synthesized from AgNO3 and Ag2SO4 exhibited cytotoxicity against all tested microorganisms. Alloy (Ag–Au) nanoparticles from salts of silver nitrate and gold were more effective than alloy nanoparticles prepared from salts of silver sulfate and gold. However, gold and copper nanoparticles were effective only against Staphylococcus aureus and Escherichia coli respectively. Ionic silver was more cytotoxic as compared to copper ions and monometallic and alloy nanoparticles. This is the first report on comparative antimicrobial activity of metal ions and various nanoparticles synthesized from CTSE against nosocomial pathogens from the intensive care unit (ICU) and burn wound intensive care unit (BWICU).

Gold nanoparticle aptamer assay for the determination of histamine in foodstuffs.

Thedevelopment of a gold nanoparticle aptamer assay is persuedfor rapid and sensitive determination of histamine in foodstuffs, which could be deployed for on-site use. The assay isbased on a histamine-specific aptamer and gold nanoparticles and the salt-induced aggregation of the particles in the presence of histamine indicated by the color change from red to blue. Gold nanoparticle size, salt type, and concentration as well as aptamer concentration were optimized, and using optimum conditions, a limit of detection of 8nM (~ 0.05mg/kg) was obtained. Finally, the aptamer AuNP assay was applied to the determination of histamine in quality control fish samples. The histamine levels of these samples had previously been determined using HPLC and commercial ELISA kits by numerous independent laboratories and a good correlation was obtained. The developed AuNP assay is rapid, sensitive, and reproducible. Graphical abstract.

Efficient synthesis of amino acids capped gold nanoparticles from easily reducible aryldiazonium tetrachloroaurate(III) salts for cellular uptake study.

Biomimetic synthesis of gold nanoparticles (GNPs) is critical in biomedical applications. Gold bioconjugates were fabricated by capping the water-dispersible gold-carbon nanoparticles with tyrosine, tryptophan and cysteine amino acids. Incubation of the water-soluble and easily reducible aryldiazonium gold(III) salt [HOOC-4-C6H4N≡N]AuCl4 with amino acids at room temperature formed a purple color over a few minutes with tryptophan and tyrosine and over two hours with cysteine. Rarely that cysteine is capable of reducing gold(III) precursors; however, a cysteine capped gold bioconjugate was synthesized and characterized in this study. Capping GNPs with amino acids was confirmed by high resolution transmission electron microscopy (TEM) and agarose gel electrophoresis. Depending on the amino acid, synthesized particles size was 27.2 ± 5.4nm, 14.6 ± 7.7nm and 8.6 ± 2.6nm for tyrosine, tryptophan and cysteine, respectively. The amino acids capped GNPs showed negligible cytotoxicity to human dermal normal fibroblast cell lines. The highly water dispersible bioconjugates were studied for in vitro cellular uptake by HeLa cancer cells using confocal laser scan microscopy (CLSM) after being labelled with FITC (GNPs-COOH-FITC) and the nuclei were counter stained with DAPI fluorescent dyes. The biomimetic route for the synthesis of the amino acids reduced gold-carbon nanoparticles will benefit the applications in biomedical devices and biosensors.

The Generation and Study of a Gold‐Based Chemobrionic Plant‐Like Structure

AbstractThe generation of chemical gardens based on tetrachloroauric acid and silicate is presented. The structures were studied with SEM, XRD and micro‐Raman spectroscopy and a new mechanism that participates in their development was revealed. Specifically, the structures were decorated with metallic Au that is derived during the process of plant‐like growth. Probably, the instability of gold salts and hydroxides on silica templates accounts for their reduction to metallic Au.

Surface state-regulated redox carbon nanodots for plasmonic morphology-dependent ratiometric sensing

Controlled-synthesis of carbon nanodots (CNDs) with tunable properties has always been challenging. Here, novel CNDs (blue-emitting CNDs (b-CNDs) and green-emitting CNDs (g-CNDs)) with tunable redox abilities and emission are synthesized via one-pot hydrothermal method. The redox ability of CNDs is regulated by surface state tailoring. The abundant reductive groups on the surfaces endow the b-CNDs appealing reducibility, whereas g-CNDs with fewer surface functional groups are deficient in reducibility. Using HAuCl4 indicator, the distinct reducibility of CNDs is visually identified. Gold salts are reduced to Au nanobelts under reduction and stabilization of b-CNDs, causing plasmons-induced color changes, whereas g-CNDs have no reduction effect on Au3+. The size-evolution process of Au nano-species can guide not only plasmonic absorbance alteration but also fluorescence (FL) and second-order scattering (SOS) changes. Therefore, based on the plasmonic morphology-induced SOS increasement and the Förster resonance energy transfer-induced FL switch off, the b-CNDs contribute to a ratiometric sensor coupled with FL and SOS for Au3+ detection. The ratiometric strategy displays a better sensitivity and selectivity and a broader linear range than single-signal SOS or FL method. The regulation of redox CNDs and ratiometric assay of Au3+ provide a new prospect for the preparation and application of versatile CNDs.

The Bio-fabrication of Gold Nanoparticles (AuNPs) by Green Method and Study of its Electrochemical Applications

This study reports a green method for the synthesis of gold nanoparticles (AuNPs) using the aqueous extract of Salix aegyptiaca extract. The effects of gold salt concentration, extract concentration and extract quantity were investigated on nanoparticles synthesis. Novel methods of ideally synthesizing AuNPs are thus thought that are formed at ambient temperatures, neutral pH, low costs and environmentally friendly fashion. AuNPs were characterized with different techniques such as UV–vis spectroscopy, FT-IR spectroscopy, X-ray diffraction, and TEM. FT-IR spectroscopy revealed that gold nanoparticles were functionalized with biomolecules that have primary carbonyl group, -OH groups and other stabilizing functional groups. TEM experiments showed that these nanoparticles are formed with various shapes and X-ray diffraction pattern showed high purity and face centered cubic structure of AuNPs. For electrochemical properties of AuNPs, a modified glassy carbon electrode using AuNPs (AuNPs/GCE) was investigated. The results show that electronic transmission rate between the modified electrode and [Fe (CN)6]3-/4- increased.

Evaluation of the skin sensitizing potential of gold nanoparticles and the impact of established dermal sensitivity on the pulmonary immune response to various forms of gold

Abstract Gold compounds are associated with diverse immune effects, including allergy. Whether gold nanoparticles (AuNP) cause similar effects remains unknown. To address this, three in vivo studies were performed. AuNP (29nm)dermal sensitization potential was assessed via Local Lymph Node Assay (LLNA) along with soluble gold salts (AuCl3) and larger particles (Au, 942nm). AuCl3 caused lymph node (LN) expansion (SI 10.9), whereas Au and AuNP did not, indicating minimal potential for dermal sensitization. Next, pulmonary immune effects of AuNP (10μg, 30μg, 90μg) were assessed 1d, 4d, 8d post-aspiration. AuNP had no effect on lung injury or inflammation, but did increase LN CD4+ T- and B-cells by 4d. Finally, mice were dermally sensitized to AuCl3 (d1-3), then aspirated 1× (d10),2× (d10, 14), or 3× (d10, 14, 18) with Au or AuNP in doses normalized for mass or surface area (SA), to assess impact of existing contact sensitivity on lung immune responses. In dermally sensitized groups, increased BAL lymphocytes were seen after two and three aspirations, which correlated to the administered SA. The highest AuNP dose caused the greatest increase in total BAL lymphocytes, as well as increased number, proportion, and activation of BAL/LN CD8+ T-cells. Comparatively, the lower SA-based doses of Au/AuNP resulted in elevated numbers of BAL T-cells(predominantly CD4+ phenotype), exposure-dependent increases in serum IgE, and selective expansion/activation of LN CD4+ T- and B-cells, suggestive of a Th2-polarized state. Overall, these findings suggest that AuNP are not likely to cause allergic sensitization; however, established contact sensitivity to gold may be associated with increased immune reactivity to AuNP following respiratory exposure.

Diazonium Gold Salts as Novel Surface Modifiers: What Have We Learned So Far?

The challenges of diazonium salts stabilization have been overcome by their isolation as metal salts such as tetrachloroaurate(III). The cleavage of molecular nitrogen from diazonium salts even at very low potential or on reducing surfaces by fine tuning the substituents on the phenyl ring expanded their applications as surface modifiers in forensic science, nanomedicine engineering, catalysis and energy. The robustness of the metal–carbon bonding produced from diazonium salts reduction has already opened an era for further applications. The integration of experimental and calculations in this field catalyzed its speedy progress. This review provides a narrative of the progress in this chemistry with stress on our recent contribution, identifies potential applications, and highlights the needs in this emerging field. For these reasons, we hope that this review paper serves as motivation for others to enter this developing field of surface modification originating from diazonium salts.

Effect of pH on the conformation of bovine serume albumin - gold bioconjugates

Biodegradable, biocompatible nanoparticles with tuneable fluorescence - due to their great potential in biology, medicine and sensor development - are widely studied nowadays. Recently it was shown that the complex red emitting spectroscopic feature of Bovine Serum Albumin - gold (BSAAu) bioconjugates can be related to the versatility of conformational changes of the BSA protein. In our study, we performed a comprehensive study on the structural changes of the host BSA molecules by infrared spectroscopy (FTIR) and small-angle X-ray scattering (SAXS). Both methods revealed that the BSA structure is not reversible after a neutral - alkali - neutral pH cycle and this behaviour is more pronounced in the presence of the gold salt (HAuCl4). The changes in the monitored secondary structural elements of BSA-(HAuCl4) system, with the fitted molecular shapes indicate that all steps in the synthesis route influence both the fine and the global structures of BSA and result in a complex structural prehistory dependent hindering of the total structural reversibility. A robust connection exists between the structural/conformational changes and the fluorescence behaviours.

Bio responsive self-assembly of Au-miRNAs for targeted cancer theranostics.

BackgroundMicroRNA (miRNA) therapeutics are a promising approach to cancer treatment. However, this method faces considerable challenges to achieve tissue-specific, efficient, and safe delivery of miRNAs in vivo.MethodsHerein, we developed a miRNA delivery system based on the in situ self-assembly of Au-miRNA nanocomplexes (Au-miRNA NCs). Within the cancer microenvironment, we constructed in situ self-assembled Au-miRNA NCs by coincubating gold salt and tumor suppressor mimics, such as let-7a, miRNA-34a, and miRNA-200a.FindingsThe in vitro experiments demonstrated that characteristic in situ self-assembled Au-miRNA NCs were present in cancer cells and can be taken up to inhibit the proliferation of cancer cells effectively. Most importantly, as proven in subcutaneous tumor treatment models, Au-miRNA NCs were especially useful for accurate target imaging and tumor suppression, with significantly enhanced antitumor effects for combination therapy.InterpretationThese observations highlight that a new strategy for the in situ biosynthesis of Au-let-7a NCs, Au-miR-34a NCs, and Au-miR-200a NCs is feasible, and this may assist in the delivery of more miRNA to tumor cells for cancer treatment. This work opens up new opportunities for the development of miRNA tumor therapy strategies.FundingNational Natural Science Foundation of China (91753106); Primary Research & Development Plan of Jiangsu Province (BE2019716); National Key Research and Development Program of China (2017YFA0205300).

Exploring the Gelation Mechanisms and Cytocompatibility of Gold (III)-Mediated Regenerated and Thiolated Silk Fibroin Hydrogels.

Accelerating the gelation of silk fibroin (SF) solution from several days or weeks to minutes or few hours is critical for several applications (e.g., cell encapsulation, bio-ink for 3D printing, and injectable controlled release). In this study, the rapid gelation of SF induced by a gold salt (Au3+) as well as the cytocompatibility of Au3+-mediated SF hydrogels are reported. The gelation behaviors and mechanisms of regenerated SF and thiolated SF (tSF) were compared. Hydrogels can be obtained immediately after mixing or within three days depending on the types of silk proteins used and amount of Au3+. Au3+-mediated SF and tSF hydrogels showed different color appearances. The color of Au-SF hydrogels was purple-red, whereas the Au-tSF hydrogels maintained their initial solution color, indicating different gelation mechanisms. The reduction of Au3+ by amino groups and further reduction to Au by tyrosine present in SF, resulting in a dityrosine bonding and Au nanoparticles (NPs) production, are proposed as underlying mechanisms of Au-SF gel formation. Thiol groups of the tSF reduced Au3+ to Au+ and formed a disulfide bond, before a formation of Au+-S bonds. Protons generated during the reactions between Au3+ and SF or tSF led to a decrease of the local pH, which affected the chain aggregation of the SF, and induced the conformational transition of SF protein to beta sheet. The cytocompatibility of the Au-SF and tSF hydrogels was demonstrated by culturing with a L929 cell line, indicating that the developed hydrogels can be promising 3D matrices for different biomedical applications.

New trends of nanofluids to combat Staphylococcus aureus in clinical isolates

Methicillin-resistant Staphylococcus aureus (MRSA), multi-drug-resistant (MDR) Staphylococcus aureus and sensitive Staphylococcus aureus were selected for this study to check the antibacterial effects of gold nanoparticles and drug-conjugated gold nanoparticles to overcome the emerging drug resistance. Culture and purification of selected bacterial isolates, drug profiling, minimum inhibitory concentration, preparation of gold salt solution, preparation of drug-conjugated gold nanoparticles and susceptibility pattern by well diffusion assay and disk diffusion method is performed to evaluate the results. MRSA (sample MBH-2), sensitive strain (sample MBH-3) and MDR strain (sample MBH-1) showed different patterns of susceptibility. We analyzed that the drug-conjugated nanoparticles showed remarkable antibacterial activity against all three strains of S. aureus. The best bactericidal activity was observed at 100 µL gold nanoparticles concentration for all three strains. The minimal inhibitory concentration was 47, 53 and 51 mM for MRSA, MDR and sensitive S.aureus, respectively, which further approves that drug-conjugated AuNPs are more effective than the drug alone nanoparticles are smaller in size and great antimicrobial activity in our study we have seen remarkable antimicrobial activity of drug-conjugated gold nanoparticles against staphylococcus aureus shown in well diffusion assay and disk diffusion assay, we also analyzed minimum inhibitory concentration of drug-conjugated gold nanoparticles. Its recommended that future use of drug-conjugated gold nanoparticles should be used to overcome the developing drug resistance in health care facilities, because nanoparticles have very smaller size and large surface area thus it can carry large amount of drug on their targets.

Comparative study on stability, antioxidant and catalytic activities of bio-stabilized colloidal gold nanoparticles using microalgae and cyanobacteria

Vast applications of gold nanoparticles (AuNPs) in biomedical, catalytic and electronic fields has raise some concerns on the safety of AuNPs used, especially towards human and the environment. Together with the challenge to control the morphology and to produce stable AuNPs, more research has been designed to provide a simple and safer method of synthesis. Bio-stabilized colloidal AuNPs were synthesized using only gold salt, water and natural ingredients from two different groups: microalgae (chlorella) and cyanobacteria (spirulina). The stabilizers contain phytochemicals which are able to reduce and stabilize the AuNPs solution, and further provide antioxidant and catalytic properties. The biosynthesized colloidal AuNPs were characterized with UV–vis, XRD, Raman spectroscopy, and HRTEM. The antioxidant activity was determined using DPPH and hydroxyl assays. The catalytic activity was studied via 4-nitrophenol reduction. Spirulina-stabilized colloidal AuNPs showed prominent potential with average particle diameter of 14.14 nm with spherical shape. The sample also possessed higher DPPH and hydroxyl scavenging activity of 60.08 % and 58.89 % respectively and catalyzed the reduction of 4-nitrophenol faster than chlorella-stabilized colloidal AuNPs. The performance of bio-stabilized colloidal AuNPs in this study provide a promising hope of fully using natural ingredients instead of hazardous chemicals to produce safe AuNPs for its wide application.

Star-Shaped Fe3-xO4-Au Core-Shell Nanoparticles: From Synthesis to SERS Application.

In this work, the preparation of magneto-plasmonic granular nanostructures and their evaluation as efficient substrates for magnetically assisted surface enhanced Raman spectroscopy (SERS) sensing are discussed. These nanostructures consist of star-shaped gold Au shell grown on iron oxide Fe3-xO4 multicores. They were prepared by seed-mediated growth of anisotropic, in shape gold nanosatellites attached to the surface of polyol-made iron oxide polycrystals. In practice, the 180 nm-sized spherical iron oxide particles were functionalized by (3-aminopropyl) triethoxysilane (APTES) to become positively charged and to interact, in solution, with negatively charged 2 nm-sized Au single crystals, leading to nanohybrids. These hybrids acted subsequently as nucleation platforms for the growth of a branched gold shell, when they were contacted to a fresh HAuCl4 gold salt aqueous solution, in the presence of hydroquinone, a reducing agent, for an optimized nominal weight ratio between both the starting hybrids and the gold salt. As expected, the resulting nanocomposites exhibit a high saturation magnetization at room temperature and a rough enough plasmonic surface, making them easily attracted by a lab. magnet, while exhibiting a great number of SERS hot spots. Preliminary SERS detection assays were successfully performed on diluted aqueous thiram solution (10−8 M), using these engineered substrates, highlighting their capability to be used as chemical trace sensors.

Optical and magnetic properties of iron-enriched Fe/FexOy@Au magnetoplasmonic nanostructures

Synthesis and utilization of nanostructures exhibiting both magnetic and plasmonic characteristics have been considered significantly important. In this research, 12-nm iron nanoparticles were first synthesized by the electric arc discharge procedure. Gold nanoparticles were then synthesized via the chemical reduction of gold salt which were used to cover magnetic nanoparticles uniformly. X-ray powder diffraction, scanning and transmission electron microscopies, and UV–Vis spectroscopy were implemented to determine available phases, particles sizes, the morphology of nanoparticles and optical characteristics. Surface plasmon resonance behavior appeared at $$\lambda =548$$ nm for iron-based@gold nanoparticles. Vibrating sample magnetometry of iron nanoparticles and iron-based@gold nanoparticles show a superparamagnetic behavior at room temperature and resulted in saturation magnetization values of 80.5 emu/g and 25.7 emu/g, respectively. The results of the facile synthesis will be beneficial for a range of applications in biomedicine including magnetic resonance imaging contrast enhancement as well as magnetic and optical photothermal therapies.

In situ derivatization of Au nanoclusters via aurophilic interactions of a triphenylphosphine gold(i) salt with neurotransmitters and their rapid MALDI-TOF-MS detection in mice brain tissue extracts.

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) has attracted much attention for the detection of small molecules such as neurotransmitters due to its softness, high sensitivity, extensive compatibility and diverse mass analyzers. However, it has been really a difficult challenge to develop a highly specific organic compound as a matrix for the rapid, sensitive and selective detection of neurotransmitters. Herein, we report tris(triphenylphosphine)gold oxonium tetrafluoroborate ([Ph3PAu]3O+BF4-) for the first time as an efficient matrix for the rapid and simultaneous MALDI-MS detection of neurotransmitters. [Ph3PAu]3O+BF4- facilitates the in situ derivatization of gold nanoclusters (Au NCLs) during the interaction with neurotransmitters, which increases their ionization energy by absorbing more ultra-violet (UV) radiation during MALDI-TOF-MS detection. The results show that this [Ph3PAu]3O+BF4- matrix can exhibit a 10-fold faster response time compared to previously reported pyrylium matrices. In addition, [Ph3PAu]3O+BF4- can also provide the simultaneous derivatization of various neurotransmitters, including dopamine (DA), noradrenaline (NAd), serotonin (5-HT), γ-aminobutyric acid (GABA), histamine (H) and tyramine (TY), in mice brain tissue extracts, which can be detected in the MALDI-TOF-MS spectra.

Heterobimetallic propargyl gold complexes with π-bound copper or silver with enhanced anticancer activity.

Several propargyl functionalised substrates with different heteroatoms (N, O or S) have been used for the preparation of propargyl gold(i) phosphine complexes. The complexes were prepared in high yields either by reaction of the substrate with [Au(acac)PPh3] or by reaction of [AuCl(PPh3)] with potassium hydroxide and the substrate in methanol. Several of the complexes have been characterised by X-ray diffraction showing the presence of secondary bonds such as π-stacking and aurophilic interactions. The reaction of the propargyl gold(i) phosphine complexes with [Cu(NO3)(PPh3)2] or [Ag(OTf)(PPh3)2] afforded heterobimetallic complexes with π-coordination of {Cu(PPh3)2} or {Ag(PPh3)2} to the alkyne bond. When the substituent of the propargyl unit contained more strongly coordinating pyridine moieties, [(PyCH2)2NCH2C[triple bond, length as m-dash]CAuPPh3], coordination of the heterometal to the pyridine units occurred, displacing the phosphine groups and giving rise to a dimeric structure. The antiproliferative activity of the complexes against cisplatin resistant lung cancer cell line A549 was determined by MTT assay. The mononuclear gold complexes showed excellent activities with IC50 values < 14 μM. Coordination of copper of silver to the alkynyl fragment resulted in a significant increase in activity suggesting a synergistic effect between the two metal centres.

The role of pre-nucleation clusters in the crystallization of gold nanoparticles.

The syntheses of metal nanoparticles by reduction in apolar solvents in the presence of long chain surfactants have proven to be extremely effective in the control of the particle size and shape. Nevertheless, the elucidation of the nucleation/growth mechanism is not straightforward because of the multiple roles played by surfactants. The nucleation stage, in particular, is very difficult to describe precisely and requires in situ and time-resolved techniques. Here, relying on in situ small angle X-ray scattering (SAXS), X-ray absorption spectroscopy (XAS) and high-energy X-ray diffraction (HE-XRD), we propose that ultra-small gold particles prepared by reduction of gold chloride in a solution of oleylamine (OY) in hexane with triisopropylsilane do not follow a classical nucleation process but result from pre-nucleation clusters (PNCs). These PNCs contain Au(iii) and Au(i) precursors; they are almost stable in size during the induction stage, as shown by SAXS, prior to undergoing a very fast shrinkage during the nucleation stage. The gold speciation as a function of time deduced from the XAS spectra has been analyzed through multi-step reaction pathways comprising both highly reactive species, involved in the nucleation and growth stages, and poorly reactive species acting as a reservoir for the reactive species. The duration of the induction period is related to the reactivity of the gold precursors, which is tuned by the coordination of OY to the gold complexes, while the nucleation stage was found to depend on the size and reactivity of the PNCs. The role of the PNCs in determining the final particle size and structure is also discussed in relation to previous studies. The multiple roles of OY, as the solubilizing agent of the gold salt, the ligand of the gold complexes determining both the size of the PNCs and the reactivity of the gold precursors, and finally the capping agent of the final gold particles as oleylammonium chloride, have been clearly established. This work opens new perspectives to synthesize metal NPs via metal-organic PNCs and to define new synthesis routes for nanoparticles that may present structure and morphologies different from those obtained by the classical nucleation routes.

The Effect of Gold Salt Concentration in the Production of Gold Nanospheres

The optical, electrical and chemical properties of the gold nanospheres synthesized by different gold concentrations in deionized water through a simple chemical reduction method (Turkevich method) were studied. They were dependent on the variation of the gold salt concentration. The peaks of the surface Plasmon resonance (SPR) absorption band and their wavelengths were detected by a UV-visible spectrophotometer. The diameters of the spherical gold nanoparticles were measured theoretically using UV-visible absorption spectrum analysis of the synthesized gold nanoparticles in colloidal form by calculating the ratio of the absorbance at the surface Plasmon resonance (SPR) peak to the absorbance at the lowest peak closed to SPR peak. The values of the gold nanoparticles diameters were (23 nm) and decreased to (13 nm) as the function of molarity changed in the range (0.1 - 0.3 mM). They were compared with the results of the transmission electron microscopy (TEM), which was about (15 - 20 nm) measured by the reference images of Sigma-Aldrich values. The conductivity measurements showed increasing the conductivity with molarity increased. The total dissolved solids (TDS) exhibited increase by linear relation with molarity increasing. The pH-value of the gold nanoparticles solutions varied with the molarity and recorded a bowing value of pH-value at (0.2 mM).