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

Abstract

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.