Room Temperature Surfactant-Free Syntheses of Gold Nanoparticles in Alkaline Mixtures of Water and Alcohols: A Model System to Introduce Nanotechnology and Green Chemistry to Future Chemists and Engineers

Gold nanoparticles (AuNPs) are textbook model systems to introduce "Nanomaterials" and "Nanotechnology" to students and laypersons. AuNPs are also suitable materials to raise awareness about the "Green Chemistry" principles. The unique optical and catalytic properties of nanosized gold make it ideal to timely develop hands-on experiments for nanomaterial synthesis requiring only few chemicals and simple equipment, such as a UV-vis spectrophotometer. While the Turkevich-Frens synthesis has been a preferred model system to date due to its simplicity, it still requires access to specific equipment and chemicals, e.g., to heat up the solution at relatively high temperature of ca. 100 °C. Various room temperature syntheses have been reported but suffer from relatively poor size control and/or the need for relatively harmful chemicals such as NaBH[subscript 4]. In contrast, room temperature and surfactant-free syntheses that only require HAuCl[subscript 4], water, an alcohol, such as ethanol, ethylene glycol, or glycerol, and a base at relatively low concentration (<10 mM) are presented and their benefits to develop hands-on experiments are highlighted. The concepts that these simple syntheses can convey cover topics as broad as "Nanotechnology," planning experimental screening of multiple variables, collaborative and open data science, or "Green Chemistry."