Synthesis Of Monodisperse Gold Nanoparticles Research Articles

Eco-benign synthesis of nano‑gold chitosan-bacterial cellulose in spent ground coffee kombucha consortium: Characterization, microbiome community, and biological performance

Biomaterials that are mediocre for cell adhesion have been a concern for medical purposes. In this study, we fabricated nano‑gold chitosan-bacterial cellulose (CBC-Au) via a facile in-situ method using spent ground coffee (SGC) in a kombucha consortium. The eco-benign synthesis of monodispersed gold nanoparticles (Au NPs) in modified bacterial cellulose (BC) was successfully achieved in the presence of chitosan (CHI) and a symbiotic culture of bacteria and yeast (SCOBY). The dominant microbiome community in SGC kombucha were Lactobacillaceae and Saccharomycetes. Chitosan–bacterial cellulose (CBC) and CBC-Au affected the microfibril networks in the nano cellulose structures and decreased the porosity. The modified BC maintained its crystallinity up to 80 % after incorporating CHI and Au NPs. Depth profiling using X-ray photoelectron spectroscopy (XPS) indicated that the Au NPs were distributed in the deeper layers of the scaffolds and a limited amount on the surface of the scaffold. Aspergillus niger fungal strains validated the biodegradability of each scaffold as a decomposer. Bacteriostatically CBC-Au showed better antimicrobial activity than BC, in line with the adhesion of NIH-3T3 fibroblast cells and red blood cells (RBCs), which displayed good biocompatibility performance, indicating its potential use as a medical scaffold.

Sustainable synthesis of monodispersed gold nanoparticles from Phoenix dactylifera L. and in vivo anti-diabetic activity on Alloxan induced mice

In the present study, gold nanoparticles biogenically synthesized from Date palm seeds (Phoenix dactylifera L.) were investigated for its anti-diabetic properties. About thirty-two albino mice were selected and 7 days of acclimatization were studied then they were randomly divided into 4 groups (I-IV) of 8 rats each. These groups were intraperitoneally injected with 100 mg/Kg body weight of Alloxan monohydrate. The groups were labeled as a diabetic group, control group, diabetic group treated with standard drug Glibenclamide (100 mg/Kg body weight), and diabetic group treated with AuNPs (100 mg/Kg body weight). This treatment was performed for 28 days via oral administration. The results showed a significant decline in the concentration of their blood glucose level after 28 days of continuous administration of AuNPs. Additionally, AuNPs significantly recovered the damage done to pancreatic, renal, and hepatic tissues in Alloxan induced mice. Hence, AuNPs formed through Phoenix dactylifera L. has appreciable anti-diabetic outcome in preclinical settings.

Analyzing the critical mixing time for the liquid-phase reduction synthesis of monodisperse gold nanoparticles using glass microfluidics

Analyzing the critical mixing time for the liquid-phase reduction synthesis of monodisperse gold nanoparticles using glass microfluidics

Photochemically prepared monodisperse gold nanoparticles as doxorubicin carrier and its cytotoxicity on leukemia cancer cells

In this study, a new thioxanthone derivative called 3,3′-disulfanediylbis(1-hydroxy-9H-thioxanthen-9-one) was utilized in situ for the photochemical synthesis of monodisperse gold nanoparticles, and simple characterization was achieved by formation of a typical surface plasmon resonance band of gold nanoparticles at 535 nm accompanied by a nice pink color. Dynamic light scattering method was employed for determination of the size of the in situ-prepared gold nanoparticles and, with good polydispersity value at around 30 nm, it was in good agreement with the surface plasmon resonance band. After successful preparation of gold nanoparticles, a well-known cancer drug, doxorubicin, at different amounts was loaded onto prepared gold nanoparticles. The adsorbed and released doxorubicin amount onto the gold nanoparticles was calculated by a fluorescence spectrophotometer using a calibration curve. Doxorubicin-loaded gold nanoparticles were examined using a MTT assay for both HL-60 and K562 leukemia cancer cells and HUVEC cells, and 5 µL doxorubicin-loaded gold nanoparticles significantly reduced cell viability. In normal HUVEC cells, 5 µL doxorubicin-loaded gold nanoparticles were found less cytotoxic compared to doxorubicin alone. The data obtained in this study showed that gold nanoparticles loaded with 5 µL doxorubicin are much more effective than doxorubicin used alone in cancer treatment.

The highly sensitive determination of serotonin by using gold nanoparticles (Au NPs) with a localized surface plasmon resonance (LSPR) absorption wavelength in the visible region.

The development of improved methods for the synthesis of monodisperse gold nanoparticles (Au NPs) is of high priority because they can be used as substrates for surface-enhanced Raman scattering (SERS) applications relating to biological lipids. Herein, Au NPs have been successfully synthesized via a seed-mediated growth method. The LSPR peak is controlled via adjusting the gold nanoseed component, and different fabrication methods were studied to establish the effect of sonication time on NP size. The simple, facile, and room-temperature method is based on a conventional ultrasonic bath, which leads to ultrasonic energy effects on the size and morphology of the Au NPs. This research offers new opportunities for the production of highly monodispersed spherical Au NPs without the use of a magnetic stirrer method, as evidenced by ultraviolet-visible reflectance spectra and scanning electron microscopy (SEM) analysis. SEM images indicate that the spherical Au NP colloidal particles are stable and reliable, which paves the way for their use as a nanostructured biosensor platform that can be exploited for multiple applications, for example, in materials science, sensing, catalysis, medicine, food safety, biomedicine, etc. The highest enhancement factor that could be achieved in terms of the SERS enhancement activity of these Au NP arrays was determined using 10−9 M serotonin (5-hydroxytryptamine, 5-HT) as the Raman probe molecules.

Continuous flow synthesis of monodisperse gold nanoparticles by liquid‐phase reduction method on glass microfluidic device

Monodisperse gold nanoparticles (GNPs) in aqueous dispersion were synthesised using a low-cost glass microfluidic device with a Y-shaped microchannel. The effects of channel width and flow rate on the size distribution of the synthesised GNPs were investigated. An aqueous solution of tetrachloroauric (III) acid (source of Au ions), and a mixture of an aqueous solution of sodium citrate acid (reducing agent) and tannic acid (protective agent), were injected into a microchannel in the microfluidic device by using a syringe pump. The absorption spectra at low flow rates showed sharper peaks in comparison with those at high flow rates. At the channel width of 260 μm, the full width at half maximum of the absorption peak was 79.2 nm for 0.05 ml/min and 92.9 nm for 0.06 ml/min. From transmission electron microscopy images, the GNPs synthesised using a channel width of 260 μm and flow rate of 0.05 ml/min were found to have a mean diameter of 11.5 nm and coefficient of variation of 0.09. These results confirmed that the combination of a low-flow rate and a small channel width is essential to obtain monodisperse GNPs.

A helpful method for controlled synthesis of monodisperse gold nanoparticles through response surface modeling

The interest in applying gold nanoparticles is principally based on their monodispersity. Therefore, the synthesis of monodisperse gold nanocrystals has a key role in designing nanomaterials for their specific application. However, it can represent a cutting edge for many laboratories, mainly because it requires a variety of complex techniques for properly characterizing metal nanoparticles with expensive and rugged equipment. Herein, we propose an approach to synthesize nanoparticles with controlled monodispersity that can be adjusted through the factorial experimental plan 32 using response surface modeling (RSM). The particles were characterized on the basis of visual observation, UV–visible spectroscopy, transmission electron microscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS) and statistics. Our findings illustrate how factorial design is important to providing accurate projections of nanoparticle production using sodium citrate and borohydride as reducers. The proposed method leverages facile and inexpensive routes to synthesize monodisperse gold nanocrystals without the assistance of time-consuming image-based characterization tools.

Rapid synthesis for monodispersed gold nanoparticles in kaempferol and anti-leishmanial efficacy against wild and drug resistant strains

Synthesis of monodispersed gold nanoparticles using kaempferol and antileishmanial activity with high macrophage uptake capacity.

A step ahead towards the green synthesis of monodisperse gold nanoparticles: the use of crude glycerol as a greener and low-cost reducing agent

Crude glycerol obtained directly from transesterification reaction was employed as a low-cost and greener reducing agent to prepare monodisperse AuNPs (∼8 nm).

Synthesis of monodisperse gold nanoparticles via electrospray-assisted chemical reduction method in cyclohexane

Abstract We present a fast and versatile method of monodisperse gold nanoparticles (AuNPs) synthesis, directly in non-polar solvent at room temperature, by electrospray-assisted chemical reduction method. The electrospray technique was used to spray a dispersed aerosol of gold precursor [gold (III) chloride hydrate] into the reaction bath containing reducing agent (octadecylaminomethanol) and non-polar solvent (cyclohexane). To find the best homogeneity in the size and low polydispersity of synthesized AuNPs, two methods of reagent incorporation into the reaction bath were compared: incorporation by continuous stream flow using a capillary, and by continuous fine droplet flow using electrospray technique. The obtained AuNPs were characterized by UV–vis spectroscopy, dynamic light scattering (DLS) and scanning transmission electron microscopy (STEM). Results confirmed the formation of AuNPs in both cases and showed that the size of NPs synthesized via chemical reduction method in non-polar solvent depends on the method of reagents incorporation. The continuous incorporation of precursor resulted in polydisperse colloid with NPs size of about: 4.4 ± 0.6 nm and 10.9 ± 1.4 nm, whereas incorporation of fine droplets to the reaction bath resulted in a highly monodisperse colloid with the NPs size of about 5.7 ± 0.5 nm.

Effect of ultra-fast mixing in a microchannel due to a soft wall on the room temperature synthesis of gold nanoparticles

The room-temperature synthesis of mono-dispersed gold nanoparticles, by the reduction of chlorauric acid (HAuCl4) with tannic acid as the reducing and stabilizing agent, is carried out in a microchannel. The microchannel is fabricated with one soft wall, so that there is a spontaneous transition to turbulence, and thereby enhanced mixing, when the flow Reynolds number increases beyond a critical value. The objective of the study is to examine whether the nanoparticle size and polydispersity can be modified by enhancing the mixing in the microchannel device. The flow rates are varied in order to study nanoparticle formation both in laminar flow and in the chaotic flow after transition, and the molar ratio of the chlorauric acid to tannic acid is also varied to study the effect of molar ratio on nanoparticle size. The formation of gold nanoparticles is examined by UV-visual spectroscopy and the size distribution is determined using scanning electron microscopy. The synthesized nanoparticles size decreases from ≥6 nm to ≤4 nm when the molar ratio of chlorauric acid to tannic acid is increased from 1 to 20. It is found that there is no systematic variation of nanoparticle size with flow velocity, and the nanoparticle size is not altered when the flow changes from laminar to turbulent. However, the standard deviation of the size distribution decreases by about 30% after transition, indicating that the enhanced mixing results in uniformity of particle size.

Urease immobilized fluorescent gold nanoparticles for urea sensing.

We report a surfactant-free synthesis of monodispersed gold nanoparticles (AuNPs) with average size of 15 nm. An approach for visual and fluorescent sensing of urea in aqueous solution based on shift in surface plasmon band (SPB) maxima as well as quench in fluorescence intensity. To enable the urea detection, we functionalized the thiol-capped gold nanoparticles with urease, the enzyme specific to urea using carbodiimide chemistry. The visible color changed of the gold colloidal solution from red to blue (or purple); this was evident from quenching in absorbance and fluorescence intensity, is the principle applied here for the sensing of urea. The solution turns blue when the urea concentration exceeds 8 mg/dL which reveals visual lower detection limit. The lower detection limits governed by the fluorescence quenching were found 5 mg/dL (R(2) = 0.99) which is highly sensitive and selective compared to shift in SPB maxima. The approach depicted here seems to be important in clinical diagnosis.

Synthesis of Monodisperse Au Nanoparticles Using Co Nanoparticles as a Sacrificial Template

Abstract In this letter, we demonstrate the facile synthesis of monodisperse gold nanoparticles by aging an oleylamine–H[AuCl4] toluene solution in the presence of cobalt nanoparticles as a sacrificial template. The precursor of Au is a key factor for the formation of Au nanoparticles. The ratio between Co nanoparticles and H[AuCl4] also affects the morphology and monodispersity of nanoparticles.

Spontaneous ultra fast synthesis of gold nanoparticles using Punica granatum for cancer targeted drug delivery

Rapid synthesis of mono-dispersed gold nanoparticles through economically feasible green chemistry approach is highly desirable. In this study, we have developed a method to synthesize mono-dispersed gold nanoparticles (PAuNPs) by mixing gold solution with fruit peel extract of Punica granutum without using any surfactant or external energy. In this method, physiologically stable, biocompatible PAuNPs were formed within 60s. Casein, being a biocompatible polymer, is used to couple the prepared PAuNPs for functionalization of folic acid, which is highly expressed in cancer cells. These functionalized PAuNPs could be used for targeted drug delivery for cancer with enhanced therapeutic efficacy and minimal side effects. PAuNPs were characterized by UV, IR, TEM, Particle size analyzer and zeta potential measurement. In vitro stability of the PAuNPs was also analyzed. Hemocompatibility of PAuNPs was evaluated in human blood samples and found that the particles were hemocompatible. The toxicity of the PAuNPs, 5-Fu and 5Fu@PAuNPs was analyzed in zebrafish embryos. The in vitro cytotoxicity of free 5-Fu, 5Fu@PAuNPs-Fa was investigated against MCF-7 cells (breast cancer) and observed that the amount of 5-Fu required to achieve 50% of growth of inhibition (Ic50) was much lower when compared to free 5-Fu.

Size-controlled synthesis of monodispersed gold nanoparticles via carbon monoxide gas reduction.

An in depth analysis of gold nanoparticle (AuNP) synthesis and size tuning, utilizing carbon monoxide (CO) gas as a reducing agent, is presented for the first time. The sizes of the AuNPs are tunable from ~4 to 100 nm by altering the concentration of HAuCl4 and inlet CO gas-injection flow rate. It is also found that speciation of aqueous HAuCl4, prior to reduction, influences the size, morphology, and properties of AuNPs when reduced with CO gas. Ensemble extinction spectra and TEM images provide clear evidence that CO reduction offers a high level of monodispersity with standard deviations as low as 3%. Upon synthesis, no excess reducing agent remains in solution eliminating the need for purification. The time necessary to synthesize AuNPs, using CO, is less than 2 min.

Synthesis of monodisperse gold nanoparticles in ionic liquid by applying room temperature plasma

Sub-atmospheric dielectric barrier discharge (SADBD) plasma was used for the reduction of gold trichloride to synthesize gold nanoparticles. By introducing poly vinyl pyrrolidone (PVP) as a capping agent, the nanoparticle size has been controlled to be ~ 1.7 nm in average with a narrow size distribution. These nanoparticles show enhanced activity and stability for electro-oxidation of methanol.

Heat-Induced Formation of Monodisperse Gold Nanoparticles in Different Conditions

We investigate the preparation of nearly monodisperse gold nanoparticles by heat treatment in different conditions. The effects of various solvents, heating temperature, and heating time length on the monodispersity of gold nanoparticles were studied systematically and a general route to generate gold nanoparticles with uniform size was determined. The first step was to prepare gold nanoparticles with less than 3 nm and the following operation was to heat the gold nanoparticles in the present of thiolated solvents where monodispersed gold nanoparticles could be obtained easily. Our approach has enriched synthesis of monodisperse gold nanoparticles, and may provide some valuable experimental data about how the heating process affects the size evolution of gold nanoparticles.

Flow-focused synthesis of monodisperse gold nanoparticles using ionic liquids on a microfluidic platform

A microfluidic device was used in tandem with an imidazolium-based ionic liquid to fabricate monodisperse gold nanoparticles (4.38 ± 0.53 nm) with excellent control over size and morphology.

Size-controlled synthesis of monodispersed gold nanoparticles stabilized bypolyelectrolyte-functionalized ionic liquid

The size-controlled synthesis of monodispersed gold nanoparticles (AuNPs) stabilizedby polyelectrolyte-functionalized ionic liquid (PFIL) is described. The resultingAuNPs’ size, with a narrow distribution, can be tuned by the concentration ofHAuCl4.Such PFIL-stabilized AuNPs (PFIL-AuNPs) showed a high stability in water at room temperaturefor at least one month; they were also quite stable in solutions of pH 7–13 and high concentrationof NaCl. In addition, the PFIL-AuNPs exhibited obvious electrocatalytical activity towardβ-nicotinamide adenine dinucleotide (NADH for short, a cofactor in enzymatic reactions ofNAD+/NADH−-dependent dehydrogenases) oxidation, suggesting a potential application forbioelectroanalysis.

Design of Polymeric Stabilizers for Size-Controlled Synthesis of Monodisperse Gold Nanoparticles in Water

A new methodology is described for the one-step aqueous preparation of highly monodisperse gold nanoparticles with diameters below 5 nm using thioether- and thiol-functionalized polymer ligands. The particle size and size distribution was controlled by subtle variation of the polymer structure. It was shown that poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) were the most effective stabilizing polymers in the group studied and that relatively low molar mass ligands (approximately 2500 g/mol) gave rise to the narrowest particle size distributions. Particle uniformity and colloidal stability to changes in ionic strength and pH were strongly affected by the hydrophobicity of the ligand end group. "Multidentate" thiol-terminated ligands were produced by employing dithiols and tetrathiols as chain-transfer agents, and these ligands gave rise to particles with unprecedented control over particle size and enhanced colloidal stability. It was found throughout that dynamic light scattering (DLS) is a very useful corroboratory technique for characterization of these gold nanoparticles in addition to optical spectroscopy and TEM.