Control of size and yield of pure-silica-zeolite MFI nanocrystals by addition of methylene blue to the synthesis solution

We investigate the effect of adding methylene blue to the pure-silica-zeolite (PSZ) MFI precursor solution on the size and yield of the MFI nanocrystals using a two-stage synthesis method. A low methylene blue concentration (i.e., 10−6 mol/L) can significantly enhance the yield of nanocrystals and keep the nanocrystal size small. When methylene blue is added to the system, a yield of over 54% for 50 nm nanocrystals can be obtained, while 60 nm crystals have a yield of 72%. Methylene blue is believed to enhance the nucleation process and inhibit crystal growth during the low-temperature nucleation stage.