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首页> 外文期刊>RSC Advances >Mechanism of photoluminescence enhancement and quenching in Nd2O3 nanoparticles-ferroelectric liquid crystal nanocomposites
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Mechanism of photoluminescence enhancement and quenching in Nd2O3 nanoparticles-ferroelectric liquid crystal nanocomposites

机译：Nd2O3纳米颗粒-铁电液晶纳米复合材料中光致发光增强和猝灭的机理

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The mechanism of photoluminescence enhancement and quenching in np-Nd2O3: FLC nanocomposites has been explored in the current study by UV-Vis and photoluminescence (PL) spectroscopy techniques. UV-Vis absorption spectra of Nd2O3 NPs in the 200-800 nm range shows two absorptions at 248 nm and 292 nm whereas pure FLC gives a broad absorption in the 265 nm to 348 nm region. PL emission intensity of np-Nd2O3: FLC composites recorded at 248 nm excitation wavelength where Nd2O3 NPs show intense emission, increases with gradually increasing the concentration of NPs up to 8 mu l. This enhancement in PL intensity without blue/red shifting the FLC's emission band was attributed to the up-conversion of doped Nd3+ ions and transfer of excitation energy to liquid crystal molecules. When excited with 248 nm, the Nd3+ ground state I-4(9/2) absorption excites electrons to a higher excited state (2)G(5/2). The excited Nd3+ ions in (2)G(5/2) level relax non-radiatively to the metastable H-2(11/2) state and then re-excites to an unstable (4)G(11/2) level. The electrons populated in (4)G(11/2) release energy either radiatively to different defect energy levels in the visible region or transfers this excitation energy to liquid crystal molecules which resulted into the enhancement in PL emission intensity. On the other hand, emission spectra at 303, 323, 333, 343 nm excitation wavelengths exhibit quenching of all emission bands in np-Nd2O3: FLC composites due to the stress induced structural disordering by the Nd2O3 NPs in the FLC matrix and creation of non-radiative channels in the system.
机译：在当前的研究中，已通过UV-Vis和光致发光（PL）光谱技术探索了np-Nd2O3：FLC纳米复合材料中光致发光增强和猝灭的机理。 Nd2O3 NP在200-800 nm范围内的UV-Vis吸收光谱在248 nm和292 nm处显示两次吸收，而纯FLC在265 nm至348 nm范围内显示宽吸收。 np-Nd2O3：FLC复合材料在248 nm激发波长下记录的PL发射强度，其中Nd2O3 NPs表现出强发射，随着NPs浓度的增加逐渐增加，直至8μl。 PL强度的这种提高而蓝光/红光不会移动FLC的发射带，这归因于掺杂Nd3 +离子的上转换和激发能转移到液晶分子上。当以248 nm激发时，Nd3 +基态I-4（9/2）吸收将电子激发到更高的激发态（2）G（5/2）。在（2）G（5/2）能级中激发的Nd3 +离子以非辐射方式松弛到亚稳态H-2（11/2）状态，然后再激发到不稳定的（4）G（11/2）能级。 （4）G（11/2）中的电子释放能量到可见光区域的不同缺陷能级，或将激发能转移到液晶分子，从而导致PL发射强度的提高。另一方面，在303、323、333、343 nm激发波长处的发射光谱显示出np-Nd2O3：FLC复合材料中所有发射带的猝灭，这是由于FLC基质中Nd2O3 NP引起的应力诱导的结构无序和非发光的产生。 -系统中的辐射通道。

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