Fig. 3

Release of SeNPs from SeNPs-C/C. a Photos taken when SeNPs were mixed with HCl or NaOH solution of pH 2.0, 2.5, 3.0, 3.5, 7.2 and 10.0. Photos were taken at 1 h after the mixing. After standing for another 1 h, the solutions were photoed again. b TEM image of SeNPs obtained at 8 h after mixing SeNPs-C/C with pH 2.5 HCl solution. TEM images of SeNPs taken at c 30 min or d 4 h after adding SeNPs-C/C to HCl solution (pH 2.5)