Oxidise your sample at high temperature (700-900° C) and dissolve Metal Oxides in 20% H2SO4

Dear Nasrin, thank you for asking this interesting technical question. I'm afraid that dissolving both molybdenum disulfide and nickel nitrate in the same solvent is not possible. Nickel sulfate is quite soluble in water, so that's no problem. In contrast, molybdenum disulfide (MoS2) is insoluble in water (as you have already observed in your hydrothermal synthesis), dilute acids and organic solvents. Nanoparticles of MoS2 can only be dispersed in solvents, but not dissolved. You can of course "dissolve" MoS2 in concentrated sulfuric acid or aqua regia, but this "dissolution" is accompanied by decomposition. This means that as soon as molybdenum disulfide dissolves, it's gone!

Good luck with your work and best wishes!

Frank T. Edelmann Thank you so much for your complete answer. Did you mean we can disperse MoS2 in organic solvent?

Dear Nasrin, yes, there are reports showing that MoS2 can be dispersed in organic solvents. For example, please have a look at the following useful research articles:

A generic solvent exchange method to disperse MoS2 in organic solvents to ease the solution process

https://pubs.rsc.org/en/content/articlelanding/2014/cc/c4cc00425f#!divAbstract

Characterization of 2D MoS2 and WS2 Dispersed in Organic Solvents for Composite Applications

https://www.cambridge.org/core/journals/mrs-advances/article/abs/characterization-of-2d-mos2-and-ws2-dispersed-in-organic-solvents-for-composite-applications/98FED139252535C330CD40464450ABF4

Controlling the metal to semiconductor transition of MoS2 and WS2 in solution

https://www.osti.gov/pages/servlets/purl/1235256

Fortunately the third article is freely available as public full text (see attached pdf file). It reports the dispersion of chemically exfoliated molybdenum disulfide sheets in organic solvents with high boiling points.

Frank T. Edelmann Thank you so much