Visual detection of Hg2+ based on Hg(2+)-xanthine complex preventing aggregation of gold nanoparticles.

Xanthine, which can specifically bind with mercury ion (Hg2+) to form xanthine-Hg(2+)-xanthine complex, was used as Hg2+ binding molecule in this paper. In the absence of Hg2+, imide group of xanthine easily adsorbs onto the surface of gold nanoparticles (AuNPs) and induces aggregation of AuNPs, resulting in a blue color. In the presence of Hg2+, however, the selective binding of xanthine with Hg2+ prevents the AuNPs against xanthine induced aggregation, resulting in a visible color change from blue to red depend on the concentration of Hg2+.

Sensitive and selective detection of mercury (II) based on the aggregation of gold nanoparticles stabilized by riboflavin.

Gold nanoparticles (AuNPs) can be stabilized by riboflavin against tris buffer-induced aggregation. However, in the presence of mercury (II) (Hg2+), riboflavin can be released from the AuNPs surface and the riboflavin-Hg2+ complex formed, leading to the aggregation of AuNPs in tris buffer. The aggregation extent depends on the concentration of Hg2+.

Highly Selective Hg (II) Ion Detection Based on Linear Blue-Shift of the Maximum Absorption Wavelength of Silver Nanoparticles.

A new method of detecting Hg (II) ion with silver nanoparticles (AgNPs) is developed in this contribution. When Hg (II) ions were added into AgNPs solution, the solution displayed rapid color change and blue shift of the maximum absorption wavelength (Δλ), which was in proportion to the Hg (II) ion concentration over the range of 2.0 × 10(-7)-6.

Colorimetric assay of melamine based on the aggregation of gold nanoparticles.

Under certain acidic condition, thioglycolic-acid-modified gold nanoparticles (Au-NPs) can react with melamine, resulting in the aggregation of Au-NPs through electrostatic interactions between -COO(-) groups on the surface of Au-NPs and -NH3+ groups of melamine. The aggregation extent depends on the concentration of melamine, which can be validated by SEM imaging and UV-vis spectra. During the aggregation procedure, color change can be observed.

Sensitive and selective detection of copper ions based on the aggregation of chitosan-stablized silver nanoparticles.

In this contribution, we present a simple and sensitive method for detecting Cu2+ based on the Cu(2+)-induced aggregation of silver nanoparticle (AgNPs) capped with chitosan. Chitosan could be adsorbed on the surface of AgNPs, and keep AgNPs against aggregation. However, in the presence of Cu2+, AgNPs aggregate again, the absorption decreases, and the color changes from yellow to colorless, which is due to the coordination of Cu2+ and chitosan.

Immunoassay by detecting enhanced resonance light scattering signals of immunocomplex using a common spectrofluorometer.

A sensitive, highly specific immunoassay method has been developed by measuring the enhanced resonance light scattering (RLS) signals of immunoreactions with simultaneously scanning both the excitation and the emission monochromators of a common spectrofluorometer. For a given content of antibody (Ab), the RLS signals of an immunoreaction follow Gaussian distribution with antigen (Ag) concentration. The central position of the Gaussian curve represents the concentration of given Ab, and the half bandwidth has proved to be a characteristic constant of a given Ab-Ag immunoreaction.