White light tunable emissions from ZnS: Eu3+ nanophosphors over 330–465nm excitation range for white LED applications

摘要

(ZnS: Eu3+ -CMC) nanophosphors of cubic (zinc blende) structure were synthesized using audprecipitation technique with doping concentrations of Eu3+ ions 1 mol% and 5 mol%. The crystaludsizes were 2.56 nmand 2.91 nmrespectively. Annealing at 300 °Cin a sulfur-rich atmosphere alteredudthe crystal size to 4.35 nmand 3.65 nmrespectively and the band gap from 4.2 eV to 3.76 eV andud3.81 eV respectively. The as-synthesized samples gave pure orange-red emission when excited atudwavelengths of 394 nmand 465 nm. After thermal annealing of the samples, a broad emission band inudthe blue-green region assigned to defect related states emerged or were enhanced. Also enhanced wereudthe emission lines of Eu3+ ions in the orange-red region. A combination of these two transitions gaveudwhite light of different shades (recorded on the CIE 1931 chromaticity diagram) from cool whiteudthrough day-light to warm white light, depending on Eu3+ concentration and the excitationudwavelengths (UV-330 to blue 465 nm), thus showing great potential of these nano-phosphors in theudgeneration of high quality white light.