Fabrication and optical properties of single-crystalline beta barium borate nanorods

Single-crystalline beta barium borate (β-BaB2O4, β-BBO) nanorods with a diameter of 10–20 nm and a length up to several micrometers have been fabricated by a cetyltrimethyl ammonium bromide assisted hydrothermal method and subsequent annealing in air at 700 °C. Structure and composition characterizations were performed by X-ray powder diffraction, Fourier transform infrared spectra, Raman spectra and X-ray photoelectron spectra. The results indicate that β-BBO nanorods have an orthorhombic structure with space group of C3v−R3C. Linear and nonlinear optical properties of β-BBO nanorods were examined by the absorption spectra, photoluminescence spectra and the powders second-harmonic generation measurement. The optical characterizations indicate that β-BBO nanorods are transparent from ultraviolet to the mid-infrared regions and exhibit a strong ultraviolet emission band at 382 nm. Compared with that of urea, higher second-harmonic generation conversion efficiency of β-BBO nanorods was measured. The possible growth process of β-BBO nanorods was also discussed briefly.