Ningombam Goutam Singh, David Thiyam Singh, Singh Nongmaithem Rajmuhon
Department of Chemistry, Manipur University, Imphal 795003, Manipur, India.
Department of Chemistry, National Institute of Technology, Takyel 795004, Manipur, India.
ACS Omega. 2019 Aug 15;4(9):13762-13771. doi: 10.1021/acsomega.9b01265. eCollection 2019 Aug 27.
The enhancement of red emission of YVO:Eu nanocrystals by Li codoping has been achieved. The effect of Li codoping on the crystalline properties and the luminescence of Eu 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 Eu emission is increased by about 2.5 times. The fall in Eu 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 HO medium. The oxidant-resistant nature with enhanced luminescence could serve as a suitable red emitter for lighting and display applications.
通过共掺杂锂实现了YVO:Eu纳米晶体红色发射的增强。对共掺杂锂对晶体性质和Eu发光的影响进行了深入研究。随着共掺杂锂浓度的增加，观察到纳米晶体的晶胞体积和结晶度增大。晶格膨胀可能与锂离子占据间隙位置有关。纳米晶体似乎是由棒状纳米结构与尺寸均匀的立方体形粗糙纳米结构组成的聚集体。发现共掺杂锂增强发光的最佳浓度为5原子%，此时Eu发射增强约2.5倍。观察到共掺杂锂（7 - 15原子%）后Eu发射下降。是结晶度（即尺寸）的增加还是晶格膨胀对发光增强构成了限制？在500和850℃退火分别使发光增强了三倍和五倍。样品易于分散在去离子水中，并易于掺入由聚偏二氟乙烯制成的柔性聚合物薄膜中。在去离子水中的分散体在低至50μg/mL时显示出明亮的红色发光。分散体的发射强度随浓度呈线性下降，斜率几乎等于1。分散体和柔性薄膜在氧化性HO介质的影响下不显示发光降解。具有增强发光的抗氧化性质可作为照明和显示应用的合适红色发光体。
