Fig xA Spectrophotometric titration of a
Nowadays white-light-emitting diodes (White LEDS) are considered as a promising new light emitting source for solid state lightening applications, for their advantages as a high luminescent efficiency, long lifetimes, low CTEP (RO4956371) consumption and environmental friendly characteristics , , ,  and . The development of White LEDs was first realized by combining a blue LED and a yellow phosphor (Y, Ga)3(Al, Ga)5O12:Ce3+. The other approaches consisting of assembling red, green and blue LEDs in one device or by combining a near UV LED chip (370–410) with red, green and blue phosphors were also used for white LEDs. However, such LEDs have lower efficiency, short lifetime, instability and poor color rendering index. These drawbacks can be overcome by using a UV chip with primary emission of 370–410 nm instead of blue LED ,  and . That is, the UV chip is used as excitation light. Therefore, the near UV chip with excitable phosphors is another attractive combination for white light generation. Recently, white LEDs fabricated using near ultraviolet LED or ultraviolet (UV) LED with single host emission color-tunable phosphor have been investigated to improve the color-rendering index and to tune the correlated color temperature by systematically tuning the relative dopant content to sensitizer and activator. A single-phase white light phosphor is produced by co-doping sensitizer and activator into the same host matrix, using the principle of energy transfer from sensitizer to activator. For instance, Ba1.3Ca0.7SiO4:Eu2+–Mn2+, BaMgP2O7:Eu2+–Mn2+ and Ca9A(PO4)7:Eu2+, Mn2+ (A = Y, La, Gd) ,  and  are reported to be the white emitter phosphors. Very recently, white light emitting Lu6O5F8:20% Yb3+, 1% Er3+ (Tm3+) nanoparticles co-doped with Li+ have been reported . As a continuation of the approach towards the development of white LEDs we attempt to synthesize the Pb2+ co-doped YVO4:5Dy3+ phosphors in the present work. The transition metal Pb2+ has 6s2 configuration and Pb2+ is a more active metal so 6s electron can be easily excited to harvest the near-UV light or transfer to the empty d-orbital of V5+.