Luminescent and cytotoxicity properties of h-BN nanowalls obtained by PECVD at low temperature

The hexagonal boron nitride nanowalls (BNNWs) with different structures were obtained by plasma enhanced chemical vapor deposition (PECVD) from gas mixtures of borazine B₃N₃H₆ or trimethylamine borane (C₂H₅)₃N∙BH₃ (TEAB). The chemical composition and structure of the nanowalls were characterized by EDS, XPS, GIXRD and HRTEM. Morphology and geometrical parameters of h-BN nanowalls can be well-controlled by synthesis temperature, initial gas composition and deposition time. h-BN nanowalls obtaining from borazine composed from chaotically oriented h-BN nanocrystallites less 10 nm in size. When used TEAB as a precursor, we obtained vertically aligned h-BN nanosheets with two morphology types. The first type- maze-like nanowalls – was grown at 400 - 600°C. On the other hand, we observed the formation of free standing nanowalls at 700°C. The BNNWs thermal stability in oxidative (air) and inert (argon) atmospheres was studied. The annealing caused the sample surface oxidation with the replacement of nitrogen atoms by oxygen in the hexagonal h-BN structure, which led to destruction of the layered structure and formation of h-BNO nanowalls. Strong UV light emission with a broad band ranging from 300 to 500 nm at room temperature was detected. Changes in composition, morphology, structure and luminescent properties of the samples before and after annealing in different atmospheres are reported. The BNNWs were stable at the temperatures up to 1100 °C and improved their luminescence properties after annealing. (author)