Research On Novel Non-aggregation Colorimetric Sensors Based On Gold Nanorods

Gold nanorods (AuNRs) are rod-shaped gold nanoparticles with unique optical properties in visible and near infrared region, corresponding to their width and length known as the transverse (TSPR) and longitudinal plasmon bands (LSPR) on the spectrum. The SPR varies according to the physical properties such as aspect ratio, shape, size, and the environment medium. Mesnwhile, the AuNRs solution also presents different color. This provides the ideal platform for the building and development of new colorimetric sensor.Seed-mediated growth method was used for preparing uniform gold nanorods (AuNRs) in this paper firstly. Then AuNRs were dispersed in polyvinyl alcohol (PVA) solution. With glutaraldehyde as crosslinking agent, AuNRs-PVA composite hydrogels responsive to the bivalent mercury (Hg2+) ions was prepared. Hg2+ in the solution was reduced to Hg0 in the presence of nontoxic ascorbic acid (AA). Then Hg0 combined with AuNRs in the PVA membrane forming gold amalgamation, which caused the aspect ratio of AuNRs to decrease, and the color of the hydrogel also changed significantly. The sensor was good for Hg2+ responsiveness and selectivity. Besides There was a good linear relationship with R2= 0.997 over the range 0-3.0 ?M, and the total procedure taked less than 5 min. Through the immobilization of AuNRs, the stability problem was overcomed in complex environment. The optical sensor has the advantages of method simple and high stability. And it can be used for the detection of trace mercury ion in water.Formaldehyde is a kind of strong excitant chemical, it has serious threat to human health. There are strong affinity between mercury and AuNRs. Hg2+ was introduced as auxiliary reagent, and Hg2+ was reduced to Hg0 by formaldehyde in alkaline environment. By testing the LSPR gold nanorods and the color change of the solution, a novel non-aggregation colorimetric sensor based on gold nanorods was developed. This method has good potential for the actual on the determination of formaldehyde content in water samples as it is high selectivity and sensitivity. And it is a kind of of formaldehyde detection method with strong practicability and application prospect.Because of the existence of surfactant layer, AuNRs prepared by seed-mediated growth method has positively charged in aqueous solution. In this paper, with amphoteric polyelectrolytes gelatin as stabilizer, gelatin coated AuNRs (Gelatin AuNRs) was prepared with electrostatic interaction of gelatin and AuNRs. Zeta potential, transmission electron microscopy (SEM) and UV-Vis spectra analysis indicated that the existence of the gelatin layer markedly enhanced the salt tolerance of AuNRs, and the faults that gold nanorods were prone to aggregation and sedimentation in high concentration of electrolyte solution was overcomed. At the same time, the response of Gelatin-AuNRs to Hg2+ was markedly different from pure AuNRs. The solution color change was bright, and the testing results for Hg2+ with absorption spectrum were more accurate. The mechanism of this phenomenon was discussed in this paper.