Synthesis Of Size-controlled Gold Nanoparticles Research Articles

Size-controlled synthesis of gold nanoparticles and related molecular imaging contrast for computed tomography

Size-controlled synthesis of gold nanoparticles and related molecular imaging contrast for computed tomography

Gold nanoparticles with natural polymer synthesized by plasma–liquid interactions: Size-control, characterization and colorimetric detection of melamine based on the size effect of gold nanoparticles

This work reports the synthesis of size-controlled gold nanoparticles as AuNP colloids in aqueous solutions with capping natural polymer matrices – the sodium salt of carboxymethyl cellulose, using a liquid-phase plasma process. The effects of the solution plasma process discharge time, concentrations of gold(III) chloride trihydrate precursor (0.06–2.5 mmol/L) and correlations of the precursor/CMC ratios on the characteristics on the synthesized Au NPs, including size distribution and optical absorption properties, were investigated. The average size (20–90 nm) and form (spherical, hexagonal and triangular) of the AuNPs can be change depending on the initial concentration of Au3+ and the ratios of precursor/CMC on the process synthesis. Gold nanoparticles were used to study a straightforward colorimetric detection of melamine. Melamine caused the AuNPs to agglomerate in aqueous solution, changing their visible color from red to blue. The prepared AuNPs can be used for the detection of melamine with a low LOD and an extremely wide linear range (0.005–0.21 μM.).

Size-Controlled Synthesis of Gold Nanoparticles Tethering Antimicrobial Peptides with Potent Broad-Spectrum Antimicrobial and Antibiofilm Activities.

New antimicrobials are urgently needed to combat the rising global health concern of antibiotic resistance. Antimicrobial peptides (AMPs) are one of the leading candidates as new antimicrobials since they target bacterial membranes and are therefore less prone to bacterial resistance. However, poor enzymatic stability, high production costs, and toxicity are drawbacks that limit their clinical use. Conjugation of AMPs to gold nanoparticles (NPs) may help to improve enzymatic stability and, thus, their overall antimicrobial efficiency. We did a one-pot synthesis of size-controlled (10 nm) gold NPs selectively conjugated to lipopeptides and determined their antibacterial activity. The conjugates exhibited potent (0.13-1.25 μM) antimicrobial activity against clinical isolates, including Gram-positive methicillin-resistant Staphylococcus aureus (S. aureus) ATCC33593, Gram-negative Escherichia coli (E. coli) CTX-M-14, multidrug-resistant Pseudomonas aeruginosa LESB58 and Acinetobacter baumannii ATCC19606, and showed promising activity (90% inhibition of initial biofilms and 80% reduction of preformed biofilms) against S. aureus and E. coli DH5α biofilms at low micromolar concentrations. The conjugates were stable in rat serum and not toxic to representative mammalian cell lines in vitro (≤64 μM) and in vivo (≤100 μM).

Size-controlled synthesis of gold nanoparticles by ultrafine bubbles and pulsed ultrasound

Size-controlled gold nanoparticles (AuNPs) were synthesized by ultrasonic irradiation of HAuCl4 aqueous solutions with the aid of ultrafine bubbles (UFBs) in the absence of any capping and reducing agents. Upon addition of air-UFBs, the mean diameter of the spherical AuNPs decreased. This result was attributed to the sonochemical reduction of gold ions in aqueous solution being accelerated by the UFBs. Moreover, the AuNPs were stable in a solution containing UFBs because AuNPs electrostatically adsorbed onto UFBs, whose lifetime in water was very long. Compared with the mean diameter of AuNPs synthesized with argon-, nitrogen- and oxygen-UFBs, that of AuNPs synthesized with air-UFBs was smaller. Pulsed ultrasound delivered with the same time-averaged power as continuous-wave irradiation further decreased the mean diameter of the AuNPs. Size-controlled synthesis of AuNPs without the use of a capping or reducing agent was successful through optimization of the number air-UFBs and the pulsed ultrasound conditions.

Construction of size-controllable gold nanoparticles immobilized on polysaccharide nanotubes by in situ one-pot synthesis

A green method for in situ one-pot synthesis of size-controlled gold nanoparticles (AuNPs) was provided in this work. In our findings, a β-1,3-D-glucan, AF1, extracted from black fungus was used as a support of AuNPs. The AuNPs were dispersed in the AF1 aqueous solution without additional reducing and stabilizing or dispersing agents. The infrared spectrum (FT-IR), thermogravimetry (TG), X-ray photoelectron spectra (XPS) and atomic force microscope (AFM) results indicated that the AuNPs synthesized by AF1 were immobilized on the AF1 nanotubes with controllable shape and size of 5–45nm. The hydroxyl groups on AF1 nanotubes not only acted as reducing agents but also were able to stabilize AuNPs by the strong interaction between the surface Au atoms of AuNPs and oxygen atoms of AF1 nanotubes. The AuNPs exhibited a good catalytic activity for the rapid reduction from 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by excess borohydride, further confirming the dispersion of AuNPs in water.

Size-controlled synthesis of gold nanoparticles by a novel atmospheric pressure glow discharge system with a metallic pin electrode and a flowing liquid electrode

A direct current atmospheric pressure glow discharge operated between a pin-type solid metallic electrode and the surface of a flowing solution, positively or negatively charged and serving as the flowing liquid anode or cathode, was used for synthesizing gold nanoparticles.

A Green and Simple Route for the Controlled-Size Synthesis of Gold Nanoparticles Using Preyssler Heteropolyacid

The authors describe a facile procedure for size-controlled synthesis of gold nanoparticles based on the reduction of Au3+ (HAuCl4) using Preyssler heteropolyacid (H14[NaP5W30O110]) under UV irradiation. Preyssler plays the role of green reducing agent and also efficient stabilizer. This method allows the synthesis of uniform hexagonal nanoparticles with an average size that is tunable between 1.35 and 86.7 nm by varying the gold ion concentration, molar ratio of gold ion to Preyssler, and Propan-2-ol amount. The authors found that there is a critical ratio for [Au3+]/[Preyssler] in which two opposing trends in the size of nanoparticles would happened.

Controlled synthesis of gold nanoparticles by fluorescent light irradiation

A novel photochemical synthesis of size-controlled gold nanoparticles wasreliably accomplished via both a direct reduction and a seeded-growth methodat room temperature under the irradiation of fluorescent light. These methodsutilized the intensity of fluorescent light that closely resembles daily sunlight (∼100 mW cm − 2). This effectively allowed for the formation of gold nanoparticles with tunable sizes simplyby controlling the concentration of trisodium citrate and gold chloride. The broad bandfluorescent light was found to be an efficient source for inducing the formation of goldnanoparticles at ambient conditions. The size distribution and absorption property of theresulting nanoparticles were thoroughly characterized by scanning/transmission electronmicroscopy, dynamic light scattering, UV–visible spectroscopy and powder x-raydiffraction. This photochemical synthesis demonstrates, for the first time, the reliablepreparation of gold nanoparticles at room temperature upon irradiation with fluorescentlight.

Polyphenol-grafted collagen fiber as reductant and stabilizer for one-step synthesis of size-controlled gold nanoparticles and their catalytic application to 4-nitrophenol reduction

A facile method for one-step synthesis of size-controlled gold nanoparticles (AuNPs) supported on collagen fiber (CF) at room temperature was proposed. Epigallocatechin-3-gallate (EGCG), a typical plant polyphenol, was grafted onto CF surface to serve as reducing/stabilizing agent, so that the AuNPs were generated on CF surface without introduction of extra chemical reagents or physical treatments. The prepared AuNPs were fully characterized, and the results showed that the dispersed AuNPs were successfully produced and the mean particle size of AuNPs could be effectively controlled in range of 18 to 5 nm simply by varying the grafting degree of EGCG on CF surface. These stabilized AuNPs were found to be active heterogeneous catalysts for the reduction of 4-nitrophenol to 4-aminophenol in aqueous phase. The catalytic behaviors of AuNPs depended on the particle size and the grafting degree of EGCG. A distinct advantage of these catalysts is that they can be easily recovered and reused at least twenty times, because of the high stability of the AuNPs supported by EGCG-grafted CF.

One-step, size-controlled synthesis of gold nanoparticles at room temperature using plant tannin

Bayberry tannin (BT), a natural plant polyphenol, was used for one-step synthesis of gold nanoparticles (AuNPs) in aqueous solution at room temperature. During the synthetic process, BT simultaneously serves as a reducing agent and stabilizing agent, while no additional reagent (surfactant, template, and capping agent) or treatment (heat and photo-irradiation) is needed. The particle diameter and size distribution of BT-stabilized AuNPs (BT-AuNPs) can be facilely controlled by varying the concentration of BT, and the particle size of BT-AuNPs is as small as 1.8 ± 0.3 nm when the BT concentration was 800 mg L−1. Furthermore, this green approach for the auto-reduction synthesis of AuNPs can be completed in several minutes and exhibits high reproducibility, which shows great potential for practical applications.

Size-controlled Synthesis of Gold Nanoparticles by Thermolysis of a Gold(I)-Sulfide Complex in the Presence of Alkylamines

A size-controlled synthesis of gold nanoparticles has been developed by the thermolysis of AuCl(SMe2) in the presence of alkylamines at 120 °C. In the procedure, the key intermediate was [Au(NH2R)2]Cl, detected by electrospray ionization (ESI) mass spectrometry. This thermally unstable intermediate was reduced by alkylamines under mild conditions to produce alkylamine-capped gold nanoparticles. The average diameters of the gold nanoparticles could be regulated in a range from 4.3 to 6.1 nm by applying primary alkylamines with alkyl chains of different lengths. Larger gold nanoparticles with diameters from 10 to 22 nm were prepared by a combination of alkylamines and alkylcarboxylic acids with various lengths of the alkyl chains. The gold nanoparticles were characterized by transmission electron microscopy (TEM), UV/Vis absorption spectroscopy, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), gas chromatography/mass spectroscopy (GC/MS), and thermogravimetric and differencial thermal analyses (TG/DTA)

Size-controlled synthesis of gold nanoparticles using a micro-mixing system

A new microfluidic reaction chip capable of mixing, transporting and controlling reactions has been developed for the size-tunable synthesis of gold nanoparticles. This chip allows for an accelerated and efficient approach for the synthesis of gold nanoparticles. The microfluidic reaction chip is made by computer-numerically controlled machining and PDMS casting processes, which integrate a micro-mixer, a normally closed valve and a micro-pump onto a single chip. The micro-mixer is capable of generating a vortex-type flow field, which achieves a mixing efficiency as high as 95% within 1 s. Successful synthesis of dispersed gold nanoparticles has been demonstrated within an 83% shorter period of time (13 min), as compared to traditional methods (around 2 h). By using different volumes of reagents, the dispersed gold nanoparticles are found to have average diameters of 19, 28, 37 and 58 nm. The optical absorption spectra indicate that these synthesized nanoparticles have different surface plasmon resonance peaks, which are 521, 525, 530 and 537 nm, respectively. The development of this microfluidic reaction system holds promise for the synthesis of functional nanoparticles for further biomedical applications.

Spacer-Mediated Synthesis of Size-Controlled Gold Nanoparticles Using Geminis as Ligands

We report a new methodology for the size-controlled aqueous synthesis of gold nanoparticles using geminis with different spacers as ligands. Geminis possess a unique structure in which two hydrophobic chains and two polar headgroups are combined via a spacer. We herein demonstrate that the spacer can be used as a tool to control particle size when geminis are used as ligands for gold nanoparticles. Varying the spacer length of geminis yields facile control over the size and size distribution of nanoparticles. For the 18-s-18-capped gold nanoparticles, FTIR and TGA experiments indicate that the geminis form bilayers on the surface of gold nanoparticles, which serve as templates that control the formation of nanoparticles. The smallest particles are obtained with a moderate spacer length (s = 8) because in that case the gemini bilayers interdigitate to the fullest degree to reach the maximum chain-chain interaction, thus yielding the most compact coating on the surface of gold nanoparticles. This work provides a new approach to the size control of nanoparticles.

Application of Stimuli-Responsive Nanogels for High-Performance Nanoreactor and Nanoreservoir of Gold Nanoparticles

Size-controlled synthesis of gold nanoparticles (AuNPs) was successfully achieved through the autoreduction of HAuCl4 using stimuli-responsive PEGylated nanogels, composed of cross-linked polyamine core and tethered PEG chains. Transmission electron microscopy images revealed that the synthesized AuNPs located only in the polyamine gel core of the nanogels. Number of the AuNPs per nanogel decreased with the increase in the N/Au (number of amino groups / number of Au atoms) ratio. Mean diameter of the AuNPs prepared at 60 C was almost constant (~ 8 nm) regardless of the N/Au ratio, whereas that prepared at 25 C was not controllable. Worth noticing that the mean diameter of the AuNPs prepared at N/Au = 1 decreased with the increase in temperature. We found that the degree of protonation of core-polyamine is far different between 25 C and 60 °C. This result indicates that shrinking and hydrophobic polyamine gel core at 60 C may play an important role for the stabilization and size-controlled synthesis of AuNPs. Therefore, stimuli -responsive PEGylated nanogels act as both nanoreactor and nanoreservoir for AuNPs.

Rapid Synthesis of Size-controlled Gold Nanoparticles by Complex Intramolecular Photoreduction

Abstract A rapid synthesis of size-controlled gold nanoparticles was proposed. The method is based on the sensitive intramolecular photoreduction reaction of Fe (III)-EDTA complex in chloroacetic acid-sodium acetate buffer solution, where Fe(II)-EDTA complex generated by photo-promotion acts as a reductant of AuCl − 4 ions. Gold nanoparticles formed were stabilized by EDTA ligand or other protective agents added. As a result, well-dispersed gold nanoparticles with an average diameter range of 6.7 to 50.9 nm were obtained. According to the characterizations by the UV spectrum and TEM, the intramolecular charge transfer of the excited states of complex Fe(III)-EDTA and the mechanism of forming gold nanoparticles were discussed in detail.

Phospholipid-assisted synthesis of size-controlled gold nanoparticles

Morphology and size control of gold nanoparticles (AuNPs) by phospholipids (PLs) has been reported. It was found that gold entities could form nanostructures with different sizes controlled by PLs in an aqueous solution. During the preparation of 1.5 nm gold seeds, AuNPs were obtained from the reduction of gold complex by sodium borohydride and capped by citrate for stabilization. With the different ratios between seed solution and growth solution, which was composed by gold complex and PLs, gold seeds grew into larger nanoparticles step by step until enough large size up to 30 nm. The main discovery of this work is that common biomolecules, such as PLs can be used to control nanoparticle size. This conclusion has been confirmed by transmission electron micrographs, particle size analysis, and UV–vis spectra.

Pyrene-Assisted Synthesis of Size-Controlled Gold Nanoparticles in Sodium Dodecyl Sulfate Micelles

Gold nanoparticles prepared by chemical reduction in sodium dodecyl sulfate (SDS) solution are size-controlled with the addition of pyrene. Micellar electrokinetic capillary chromatography (MEKC) is applied to the system to examine the size and polydispersity of gold nanoparticles and to show that pyrene has the extraordinary effect in decreasing the size and narrowing the dispersity of gold nanoparticles. The MEKC electropherograms further suggest that pyrene could be oxidized by the aqueous Au(III) complexes first. All the reduced Au complexes were then solubilized in the pyrene-SDS micelles. The growth of gold nanoparticles beyond the embryonic stage was subsequently inhibited by the encapsulating SDS and electrophilic pyrene.

Size-Controlled Synthesis of Gold Nanoparticles from Bulk Gold Substrates by Sonoelectrochemical Methods

Size-controlled gold nanoparticles, ranging from 2 to 15 nm in diameter, were first prepared from gold substrates in 0.1 N HCl aqueous solutions without the addition of any stabilizers by sonoelectrochemical methods. First, an Au substrate was cycled in a deoxygenated aqueous solution containing 0.1 N HCl from −0.28 to +1.22 V vs Ag/AgCl at 500 mV/s with 100 scans. The durations at the cathodic and anodic vertexes are 10 and 5 s, respectively. After this process, Au- and Cl-containing complexes were left in the solution. The Au working electrode was then immediately replaced by a Pt electrode, and cathodic overpotentials of 0.2, 0.4, and 0.6 V from the open circuit potential (OCP) of ca. 0.82 V vs Ag/AgCl were applied under sonification to synthesize Au nanoparticles. The prepared nanoparticles increase in size from 2 to 15 nm with the increase of the cathodic overpotential applied from 0.2 to 0.6 V. Furthermore, the ratio of Au nanoparticles to Au-containing nanocomplexes in solutions can be controlled by adjusting the sonoelectrochemical reduction time.

Size-Controlled Synthesis of Gold Nanoparticles via High-Temperature Reduction

Size and dispersity control of metallic nanoparticles is of fundamental necessity for their useful chemical implementation. A single-step synthesis of Au nanoparticles 4−15 nm in diameter and with low polydispersity is presented. Amine-induced reduction of a Au(I) precursor in the presence of coordinating ligands leads to nucleation of small particles which ripen to form larger particles. The rate of particle growth and subsequent aggregation is strongly dependent on the relative concentrations of protecting ligands and is monitored by both transmission electron microscopy and UV−visible absorption spectroscopy.