Excuse me, How can I synthesis WSe2 by hydrothermal method without using DMF as a solvent? As I read, some use N2H4 to dissolve (or solube) Se powder into Se-2; some use both N2H4 and NaBH4; some use only NaBH4; which is the best?. I tried to dissolve Se, Se vanished initial color but after 1-2 hours, its black color appeared again and precipitated, is that reversible reaction? And how can I reduce Na2WO4.2H2O to ion W+4; is that okay with NaBH4 as a reductant. Because W+4 is unstable, and after a short period, it returns W+6 or precipitates. Please let me know how can I maximize my procedure or replace my precursors. Thank you very much!