Fabrication of Multi-functionalized Gold Nanoparticles and the Application to Electrochemical Detection of Nitrite

This paper reports the fabrication of multi-functionalized gold nanoparticles (MFAuNPs) and the application to electrochemical detection of nitrite. While gold nanoparticles are modified with thiolated oligonucleotides as usual, they are also immobilized with 5- [1, 2]dithiolan-3-yl-pentanoic acid [2-(naphthalene-1-ylamino)-ethyl]amide (DPAN). Therefore, the oligonucleotides molecules can enhance the solubility of the MFAuNPs and absorb hexaammineruthenium(III) chloride ([Ru(NH3)6]3+) as electrochemical species on the one hand, with the help of nitrite ions, DPAN immobilized on MFAuNPs will react with 4-(2-aminoethyl)benzenamine which has been previously modified on the surface of a gold electrode on the other hand, thus an electrochemical method for nitrite detection is also proposed. Although the maximum contaminant level (MCL) defined by the Environmental Protection Agency (EPA) for nitrite in drinking water is as low as 1 ppm (21.7 μM), which is difficult to make detections by the current techniques, the proposed method in this work can give very satisfactory results.