Fast luminescence from rare-earth-codoped BaSiF6 nanowires with high aspect ratios

Inorganic materials with short radiative decay time are highly desirable for fast optical sensors. This paper reports fast photoluminescence (PL) from a series of barium hexafluorosilicate (BaSiF6) superlong nanowires with high aspect ratios, codoped with Ce3+/Tb3+/Eu3+ ions, with a subnanosecond decay time. Solvothermally synthesized BaSiF6 nanowires exhibit a uniform morphology, with an average diameter less than 40 nm and aspect ratios of over several hundreds, grown in the c-axis direction with {110} surfaces. The PL emission from the codoped BaSiF6 nanowires, when excited by a 254 nm source, is dependent on Tb3+ concentration, and the energy transfer from Ce3+ to Tb3+ and to Eu3+ ions allows efficient emissions in the visible spectra when excited by a near UV source. Annealing BaSiF6 nanowires at 600 °C in a vacuum produced barium fluoride (BaF2) nanowires composed of nanocrystals. Both BaSiF6 and BaF2 nanowires exhibit fast emissions in the visible spectra, with enhanced intensities compared with their codoped microparticle counterparts. The decay time of codoped BaSiF6 nanowires is found to be shorter than that of codoped BaF2 nanowires. The energy transfer is also observed in their cathodoluminescence spectra with high-energy irradiation.