Novel wet chemical and hydrothermal synthesis of hBN nanodots and luminescent BCN

Hexagonal Boron Nitride (hBN) is a wide band gap insulator (Ebandgap~ 6eV) with highly interesting properties such as non-toxicity, high thermal and chemical stability and flexibility. Due to its super-flat surface as a 2D Van der Waals material and the mentioned properties it is an extremely desired material for electronic industry and green energy production. Based on that easy production synthesis routes at low-cost of hBN nanostructures are from great interest and are in the focus of our work.

Here, we show two simple, non toxic and green synthesis routes to obtain synthesize hBN. Firstly, a wet chemical route is employed to obtain a precursor which can be thermally treated to obtain hBN. Additionally, hydrothermal synthesis is employed to yield hBN quantum nanodots at relatively low temperatures. Boric acid and melamine and urea respectively, are used as educts for both synthesis routes as well as water as solvent. Compared to other toxic and expensive approaches these synthesis routes guarantee a low-toxic, low-cost and environmentally harmless route for synthesising hBN. Further, the easy availability of high amounts of the educts underline the great advantages of this approach. It was found for the wet chemical approach of the precursor synthesis that a poly condensation occurs between urea and boric acid and melamine and boric acid. This yields a polymeric compound is thermally treated to yield either hBN or luminescent BCN.Further, it is found that the amount of carbon in the final product can be varied in either the precursor synthesis and the thermal annealing. For the hydrothermal synthesis luminescent hBN nanodots can be obtained.

This work implicates facile and inexpensive synthesis route for both bulk hBN and nanoscopic hBN