Colloidal AgNPs Research Articles

An Evaluation of Acute Toxicity of Colloidal Silver Nanoparticles

Tests for acute oral toxicity, eye irritation, corrosion and dermal toxicity of colloidal silver nanoparticles (AgNPs) were conducted in laboratory animals following OECD guidelines. Oral administration of AgNPs at a limited dose of 5,000 mg/kg produced neither mortality nor acute toxic signs throughout the observation period. Percentage of body weight gain of the mice showed no significant difference between control and treatment groups. In the hematological analysis, there was no significant difference between mice treated with AgNPs and controls. Blood chemistry analysis also showed no differences in any of the parameter examined. There was neither any gross lesion nor histopathological change observed in various organs. The results indicated that the LD(50) of colloidal AgNPs is greater than 5,000 mg/kg body weight. In acute eye irritation and corrosion study, no mortality and toxic signs were observed when various doses of colloidal AgNPs were instilled in guinea pig eyes during 72 hr observation period. However, the instillation of AgNPs at 5,000 ppm produced transient eye irritation during early 24 hr observation time. No any gross abnormality was noted in the skins of the guinea pigs exposed to various doses of colloidal AgNPs. In addition, no significant AgNPs exposure relating to dermal tissue changes was observed microscopically. In summary, these findings of all toxicity tests in this study suggest that colloidal AgNPs could be relatively safe when administered to oral, eye and skin of the animal models for short periods of time.

Antibody@Silica Coated Iron Oxide Nanoparticles: Synthesis, Capture of E.coli and Sers Titration of Biomolecules with Antibacterial Silver Colloid

Silica coated iron oxide (SiO 2 /Fe 3 O 4 + γ- Fe 2 O 3 ) nanoparticles (SIO-NPs; 75±10 nm in diameter) were prepared by encapsulation of iron oxide NPs with silica using sol-gel method and characterized through spectroscopy methods. The SIO NPs were chemically activated by cyanogens bromide and then functionalized with Escherichia coli ( E. coli ) antibodies. These immuno-magnetic (IM NPs) were used to capture and concentrate E. coli from ~ 180 cfu/ mL suspension. The identification of bacteria was performed by plating on nutrient agar, fluorescent microscopy and scanning electron microscopy. Surface enhanced Raman spectroscopy (SERS) was used to identify different biomolecules of bacterial cell upon the interaction of colloidal silver nanoparticle (Ag NPs 6±4 nm) at different period of time. In our previous report we demonstrated the antibacterial property of colloidal Ag NPs. Therefore, current approach, using IM, and Ag NPs and SERS, provide detailed molecular identification of E. coli as Ag NPs interact over the time. This method would be applicable for food safety, environment protection, biological threat material, antibacterial and other routine E. coli identification projects.

Synthesis and antimicrobial effects of colloidal silver nanoparticles in chitosan by γ-irradiation

Radiation-induced synthesis of colloidal silver nanoparticles (Ag-NPs) using chitosan (CTS) as a stabiliser and free radical scavenger is feasible and satisfiable to green method. The conversion dose (Ag+ into Ag0) was determined by UV-Vis spectroscopy and Ag-NPs size was characterised by transmission electron microscopy. The average diameter of Ag-NPs was smaller than 10 nm with narrow size distribution and the colloidal Ag-NPs have good stability for a long time of storage. The effect of several parameters, such as pH, Ag+ and CTS concentration and molecular weight of CTS on Ag-NPs size was also investigated. Ag-NPs of ∼7 nm exhibited highly antimicrobial effect. The inhibitory efficiency of Ag-NPs for Staphylococcus aureus was more than 99.9% at 5 ppm and the effective dose (ED50) of inhibition for Corticium salmonicolor was of 27.2 ppm.

The effect of concentration on the thermo-optical properties of colloidal silver nanoparticles

The thermo-optical properties of colloidal silver nanoparticles (AgNPs) are investigated under a low power laser irradiation at 532 nm. Colloidal AgNPs are synthesized by nanosecond pulsed laser ablation of a pure silver plate in distilled water. The morphology and size of the AgNPs are determined by transmission electron microscopy. Closed Z-scan measurements reveal that nonlocal thermo-optic process is responsible for the nonlinear refractive index of colloid containing different concentrations of silver nanoparticles. The Z-scan behavior of the nanoparticle samples has been investigated based on a nonlocal thermo-optic process and it is shown that the aberrant thermal lens model is in excellent agreement with the experimental results. Z-scan measurement fits have allowed the values of nonlinear refractive index ( n 2) and thermo-optic coefficients ( dn/ dt) to be determined at different concentrations of silver nanoparticles. Large enhancement factors were measured for values of n 2 and dn/ dt of the colloids at higher silver nanoparticle volume fraction. Our results suggest that nonlocal thermal nonlinear processes will play an important role in the development of photonic applications involving metal nanoparticle colloids.

Thermo-optic nonlinear response of silver nanoparticle colloids under a low power laser irradiation at 532 nm

The thermo-optical properties of silver nanoparticles (AgNPs) in the water are investigated under irradiation of a continuous wave (CW) laser at 532 nm. Thermal conductivity of the AgNP colloids is estimated using the Maxwell model. The closed Z-scan measurements reveal thermal contribution for the nonlinear refractive index of the AgNPs. The Z-scan behavior is investigated based on nonlocal thermo-optic process. It is shown that the aberrant thermal lens model is in excellent agreement with the Z-scan experimental results of the sample. A fit allows extracting the values of nonlinear refractive index and thermo-optic coefficient to be −1.0 × 10−8 cm2/W and −0.99 × 10−4 W/mK, respectively. Our results suggest that thermal nonlinear effects play an important role in the development of photonic application involving metal nanoparticle colloids and in the investigation of nonlocal nonlinear processes.

Imaging 3-aminopropyltriethoxysilane self-assembled monolayers on nanostructured titania and tin (IV) oxide nanowires using colloidal silver nanoparticles

Self-assembled monolayers (SAM) of 3-aminopropyltriethoxysilane (APTES) were grown on nanostructured titania (NST) and tin oxide nanowires (SnO 2 NW) and the functionalized metal oxide surfaces were decorated with borohydride-reduced silver nanoparticles (AgNPs) and imaged. Comparative studies with the mono- and di-ethoxysilanes were also carried out. The nanoparticle-modified silane films are found to be greatly stabilized against oxidation. Because colloidal AgNP bind preferentially to the amino functionality of the silane molecules, they serve as an assay for the surface’s utility towards species that bind to that group. The particle density also reflects the relative number of natively bound APTES in the SAM.

One-step synthesis of silver nanoparticles by sonication or heating using amphiphilic block copolymer as templates

Block copolymer-supported Ag Nps (nanoparticles) have either a “cherry”-like or “raspberry”-like morphology [Antonietti, et al., Adv. Mater. 7 (1995) 1000–1005] depending on the amount of silver nitrate loading and the external conditions. Sonication favors silver nitrate and polyethyleneimine diffusion; the nucleation sites are well distributed in the micellar cores, so it is easy to form the cherry-like Ag NP colloids. However, when the amount of silver nitrate is decreased, it is heating that induces the formation of raspberry-like Ag NP colloids. The Ag NP colloids were investigated by transmission electron microscopy to demonstrate the nanosize dimensions and the location of the Ag NPs in the micelles. X-ray diffraction was employed to determine the crystal structure of the Ag NPs. UV–vis spectroscopy was employed for further qualitative characterization of the optical properties of Ag NPs.