Abstract
The enhancement of red emission of YVO4:Eu3+ nanocrystals by Li+ codoping has been achieved. The effect of Li+ codoping on the crystalline properties and the luminescence of Eu3+ has been thoroughly studied. An increase of the unit cell volume and crystallinity of the nanocrystals is observed as the concentration of Li+ codoping increases. The lattice expansion could be related to occupation of the interstitial sites by the Li+ ions. The nanocrystals appear to be assemblies of rodlike nanostructures along with cube-shaped rough nanostructures of uniform size. The optimum concentration of Li+ codoping for luminescence enhancement is found to be 5 at. % at which Eu3+ emission is increased by about 2.5 times. The fall in Eu3+ emission after codoping of Li+ (7-15 at. %) is observed. Is it the increased crystallinity (i.e., the size) or the lattice expansion that poses a limit to luminescence enhancement? Annealing at 500 and 850 °C increased the luminescence emission by threefold and fivefold, respectively. The samples are readily dispersible in deionized water and incorporated easily in the flexible polymer film made of polyvinylidene fluoride. The dispersion-in-water shows bright red luminescence as low as 50 μg/mL. The emission intensity of the dispersion decreases linearly with concentration with a slope almost equal to unity. The dispersion and the flexible film do not show luminescence degradation under the influence of oxidizing H2O2 medium. The oxidant-resistant nature with enhanced luminescence could serve as a suitable red emitter for lighting and display applications.