Antibacterial and enhanced stability of carbon dot based on L-arginine modified by HPMC

Carbon dots tend to aggregate into clusters during lyophilisation, and the obtained powder is highly hygroscopic and not easy to store. This study introduces a simple way to solve it. Hydroxypropyl methyl cellulose(HPMC)was selected to enhance the stability of carbon dot powder after freeze-dried. Firstly, an interesting carbon dot had been prepared from L-arginine via hydrothermal method, which showed certain antibacterial properties towards E. coli and S.aureus. Secondly, mixing carbon dots aqueous solution with HPMC according to mass ration and stirred evenly. Put the mixture into freeze drying oven until dried, and got the powder, which was tested by XPS and IR. The results demonstrated that the content of surface element in carbon dots powder has changed and owned the characteristics of HPMC. The developed carbon dot powder exhibited similar antibacterial and optical properties to those solutions and emitted significant blue fluorescence when irradiated by an ultraviolet lamp. Importantly, the solid carbon dot powder has high stability under ambient temperatures. It is stable in storage for up to one year and is no longer hygroscopic. However, the common carbon dot aqueous solution without HPMC after freeze-drying is extremely hygroscopic at room temperature and not easy to store.