The DNA templated self-assembly of gold nanoparticles clustered in different configurations (nn = 2–∞) was investigated in the colorimetric detection of ToLCNDV DNA using a gold nanoparticle conjugated bifunctional oligonucleotide probe.
A novel way to synthesize gold nanoparticles (AuNPs) using naturally occurring bile salts, namely, sodium cholate (NaC) and sodium deoxy cholate (NaDC), as reducing and capping agents at room temperature has been reported. Variations of NaC concentration provided good control over the size and shape of the AuNPs, allowing us to tune the color of NPs from green to red. While the hydroxyl group of bile salt reduced the Au3+ ions, the carboxylate group binds strongly to the surface of the NPs. The optical properties, size, and shape of the NPs were analyzed using UV–visible spectroscopy and transmission electron microscopy (TEM). The interaction of NaC on the AuNP surface was studied using cyclic voltammetry, FT-IR, and thermogravimetric analysis (TGA). The combination of steady-state and time-resolved quenching studies using fluorescent probes confirmed the hydrophobic interaction between NaC micelles and AuNPs. The color change properties associated with the aggregation of NPs were used for the colorimetric detection of plant-associated Gemini viruses using degenerate probes. The assay was completed within 20 min, and ≥600 pmol of the target DNA could be detected by UV–visible spectroscopy.
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.
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