Demonstration of a Magic Reaction: Accelerating DNA Functionalization of Gold Nanoparticles by Freezing

DNA-functionalized gold nanoparticles (DNA-AuNPs) have become a popular science theme since their invention in 1990s. They impact our daily lives by playing key roles in rapidly identifying and quantifying important analytes, and are a well-suited chemistry course content for beginners of chemical research. While the salt-aging method represents the most commonly used for preparation of DNA-AuNPs, it is unfortunate that it necessitates elaborative operation and long-time (1–2 days) reaction. Introduction of a simple yet efficient functionalization approach to students may inspire their interest in DNA-AuNPs, giving a good start to their research careers. We carried out an investigation into fast (2 h) preparation of DNA-AuNPs by freezing, and demonstrate the applicability of the resultant DNA-AuNPs in colorimetric Hg2+ detection. Although students initially suspected a slower reaction in the frozen mixture, each student could smoothly accomplish the preparation of DNA-AuNPs eventually using the freezing method, with a large number of DNA functionalized per AuNP. Theoretical calculation of DNA number per AuNP and the detection application further convinced the students of the success in DNA functionalization of the AuNPs, providing a valuable research experience for the students. Given the robustness of the magic method for preparation of DNA-AuNPs, we have presented an exceptional example that improves students' view of the chemical reaction, and inspires their creative thinking and interest in nanoprobes.