Diazo-reaction-based SERS substrates for detection of nitrite in saliva

Nitrite is a biomarker to diagnosis oral disease such as nasopharynx cancer, and obstructive lipoprotein. As an important biomarker of human oral disease, determination of nitrite ions is a demand task. Herein, we demonstrate a novel and pragmatic approach based on surface enhanced Raman scattering (SERS) spectroscopy to detect the concentration of nitrite. Firstly, we functionalize the cleaned glasses by (3-aminopropyl) trimethoxysilane for self-assembling Au nanoparticles and then modify the resultant Au array with urea for synthesizing SERS substrate. On the basis of specific diazo reaction between nitrite and urea in acidic media, resulting that intensity of urea SERS band at 1003 cm(-1) suppress, a good linear relationship ranging from 20 to 120 mu M is obtained. This specific SERS substrate can be used to detect nitrite in human saliva without pretreatment process, exhibiting its advantages of rapidness, sensitivity and selectivity.