Electron transparent gold platelets

Engelbrecht, J.A.A.; Snyman, H. C.

doi:10.1007/bf03214625

Cited by 7 publications

(4 citation statements)

References 12 publications

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“…analogously to the glycyl- l -tyrosine sample, none of the nuclei could be found using the microscope, and in contrast to both other samples, the particle surfaces are extremely rough. The shapes also hint at platelike morphologies, which are indicative of repressed growth, , during the depositional stage. This suggests that the growth process involves nucleation and subsequent coagulation, followed by limited depositional growth.…”

Section: Resultsmentioning

confidence: 85%

Gold Nanoparticle Formation during Bromoaurate Reduction by Amino Acids

et al. 2005

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The synthesis and characterization of water-soluble dispersions of gold nanoparticles by the reduction of a potassium tetrabromoaurate precursor solution using the amino acids L-tyrosine, glycyl-L-tyrosine, and L-arginine using alkaline synthesis conditions are reported. The particle sizes determined by small-angle X-ray scattering (SAXS) and high-resolution transmission electron microscopy (HRTEM) measurements are found to be inversely proportional to the rate of particle formation, which was determined by time-resolved UV-visible spectrophotometry measurements, and vary very slowly at intermediate gold concentrations and rapidly at the extremes. Dispersions produced with a mixture of the two amino acids glycyl-L-tyrosine and L-tyrosine showed particle sizes and particle size distributions which were directly proportional to the ratio of the two L-amino acids, thus offering the possibility for control over the properties of the gold nanoparticle dispersions.

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Section: Resultsmentioning

confidence: 85%

Gold Nanoparticle Formation during Bromoaurate Reduction by Amino Acids

et al. 2005

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“…Consequently, we obtain a much higher population of spherical nanoparticles in comparison with triangular ones when the temperature of the reaction system is high (Figure F). The formation of the gold nanotriangles is a kinetically driven process and is a result of aggregation and rearrangement of smaller size particles, which act as a nuclei for further growth into anisotropic, triangular structures . We believe that the low rate of reduction of metal ions at lower temperatures might possibly facilitate the oriented growth of nuclei and thus should promote the formation of anisotropic nanoparticles .…”

Section: Resultsmentioning

confidence: 98%

Role of Halide Ions and Temperature on the Morphology of Biologically Synthesized Gold Nanotriangles

et al. 2005

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In this paper, we demonstrate the effect of halide ions on the formation of biogenically prepared gold nanotriangles using the leaf extract of lemongrass (Cymbopogon flexuosus) plant. We have also studied the effect of halide ions on the morphology of biogenic nanotriangles. It has been shown that iodide ions have a greater propensity to transform flat gold nanotriangles into circular disk-like structures as compared to other halide ions. The study also suggests that the presence of Cl- ions during the synthesis promotes the growth of nanotriangles, whereas the presence of I- ions distorts the nanotriangle morphology and induces the formation of aggregated spherical nanoparticles. The change in the morphology of gold nanotriangles has been explained in terms of the ability of the halide ions to stabilize or inhibit the formation of (111) faces to form [111] oriented gold nanotriangles. Last, we have also shown that the temperature is an important parameter for controlling the aspect ratio and the relative amounts of gold nanotriangles and spherical particles. The results show that, by varying the temperature of reaction condition, the shape, size, and optical properties of anisotropic nanoparticles can be fine-tuned.

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“…54 Increasing the reaction temperature during the reduction of gold ions (AuCl 4 À ) using cefaclor leads to an increase in the rate of reduction of the gold ions, which promotes an enhanced nucleation rate with the formation of a large population of nuclei. [61][62][63] Gold ions are further reduced on the surface of gold nuclei, thus promoting the formation of spherical gold nanoparticles of smaller sizes, which are subsequently capped and stabilized by cefaclor (Scheme 1). 59 Within another possible threestep growth mechanism, gold nuclei (2 nm) first form bigger particles (4 nm) through coalescence 64 or Oswald ripening.…”

Section: Resultsmentioning

confidence: 99%

Antibiotic mediated synthesis of gold nanoparticles with potent antimicrobial activity and their application in antimicrobial coatings

2010

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We report a one-pot synthesis of spherical gold nanoparticles (52-22 nm) and their capping with cefaclor, a second-generation antibiotic, without use of other chemicals. The differently sized gold nanoparticles were fabricated by controlling the rate of reduction of gold ions in aqueous solution by varying the reaction temperature (20-70 C). The primary amine group of cefaclor acted as both the reducing and capping agent for the synthesis of gold nanoparticles leaving the b-lactam ring of cefaclor available for activity against microbes. Antimicrobial testing showed that cefaclor reduced gold nanoparticles have potent antimicrobial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria as compared to cefaclor or gold nanoparticles alone. The minimum inhibition concentrations (MICs) of cefaclor reduced gold nanoparticles were 10 mg mL À1and 100 mg mL À1 for S. aureus and E. coli respectively. The cefaclor reduced gold nanoparticles were further coated onto poly(ethyleneimine) (PEI) modified glass surfaces to obtain antimicrobial coatings suitable for biomedical applications and were tested against E. coli as an exemplar of activity. The antimicrobial coatings were very robust under adverse conditions (pH 3 and 10), inhibited the growth of E. coli on their surfaces, and could be used many times with retained activity. Results from a combined spectroscopic (FTIR) and microscopic study (AFM) suggest that the action of these novel particles is through the combined action of cefaclor inhibiting the synthesis of the peptidoglycan layer and gold nanoparticles generating ''holes'' in bacterial cell walls thereby increasing the permeability of the cell wall, resulting in the leakage of cell contents and eventually cell death.

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Electron transparent gold platelets

Cited by 7 publications

References 12 publications

Gold Nanoparticle Formation during Bromoaurate Reduction by Amino Acids

Gold Nanoparticle Formation during Bromoaurate Reduction by Amino Acids

Role of Halide Ions and Temperature on the Morphology of Biologically Synthesized Gold Nanotriangles

Antibiotic mediated synthesis of gold nanoparticles with potent antimicrobial activity and their application in antimicrobial coatings

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