We demonstrated citrate-capped gold nanoparticles assisted characterization of amine functionalized polystyrene plate and glass slide surfaces through AuNPs staining method. The effect of AuNPs concentration on the characterization of amine modified surfaces was also studied with different concentration of AuNPs (ratios 1.0-0.0). 3-Aminopropylyl triethoxy silane has been used as amine group source for the surface modification. The interactions of AuNPs on modified and unmodified surfaces were investigated using atomic force microscopy and the dispersibility, and the aggregation of AuNPs was analyzed using UV-visible spectrophotometer. Water contact angle measurement and X-ray photoelectron spectroscopy (XPS) were used to further confirmation of amine modified surfaces. The aggregation of AuNPs in modified multiwell plate leads to the color change from red to purple and they are found to be adsorped on the modified surfaces. Aggregation and adsorption of AuNPs on the modified surfaces through the electrostatic interactions and the hydrogen bonds were revealed by XPS analysis. Remarkable results were found even in the very low concentration of AuNPs (ratio 0.2). This AuNPs staining method is simple, cost-effective, less time consuming, and required very low concentration of AuNPs. These results can be read out through the naked eye without the help of sophisticated equipments.
Purification of begomovirus from infected ash gourd leaf samples using anti-ACMV antibody-conjugated magnetic nanoparticles (Ab-MNPs) and their characterization.
AuNPs phytosynthesized using the aqueous leaves extract of Rosa indica-wichuriana hybrid Francois guillot showed a welldefined surface plasmon band centered at around 520 nm which is the characteristic of gold nanoparticles. HRTEM micrograph showed that the size of the AuNPs were in the range of 5-13 nm. The AuNPs were functionalized using glutathione via the thiol group from the cysteine moiety to develop highly responsive GSH-AuNPs probe for precise colorimetric detection of Cd 2+ . The functionalization was confirmed by FT-IR. Atomic absorption spectroscopy was used to quantify the heavy metals present in the two water samples collected from the water bodies in Ranipet, a suburb town and industrial hub of Vellore city in the state of Tamil Nadu in southern India. The colorimetric selectivity of the GSH-AuNPs probe to the quantified metal ions Mg 2+ , Ca 2+ ,Ba 2+ , Ni 2+ , Mn 2+ , Cu 2+ , Hg 2+ , Co 2+ , Cd 2+ , Cr 3+ , Fe 2+ was ascertained by UV-Vis spectroscopy. The observations demonstrate that only Cd 2+ stimulated the GSH-AuNPs solution to turn purple from ruby red and a substantial shift in the SP band to longer wavelength of 594 nm owing to GSH-AuNPs aggregation. The minimum and maximum detection limit of Cd 2+ by GSH-AuNPs probe was inferred to be 30 nM-70 nM (3 ×10 −8 M and 7×10 −8 M) respectively. The feasibility of employing the probe practically in the environment to detect Cd 2+ was demonstrated using two water samples. The aggregation-based change in color from ruby red to purple resulted in less than 10 min. This result could be considered a straight forward and instantaneous detection of Cd 2+ devoid of any interference from other metal ions those were present in the water samples.
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