Ultrasensitive Nitrite Detection via Colorimetry/Raman Spectroscopy using Ag Nanoparticles: A Novel Experiment in Postgraduate Classroom Teaching

The integration of knowledge from various chemical subdisciplines into postgraduate education is helpful for developing students’ versatile problem-solving skills. This study demonstrates a practical experiment designed for postgraduates that successfully merges concepts and techniques from inorganic, analytical, and food chemistry. In this experiment, students first synthesized silver nanoparticles using the classical sol–gel method (inorganic chemistry). They then employed UV–vis absorption and Raman spectroscopy (analytical chemistry) to detect nitrite via its diazo reaction with toluidine blue, which yields a clear visual color change and a quantifiable decrease in signal intensities. Finally, we apply this method to analyze nitrite levels in real food samples (food chemistry). This integrated approach provides students with hands-on experience in nanomaterial synthesis, spectroscopic detection, and food safety analysis, effectively bridging the gap among different fields of chemistry.