Institute of Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius, Lithuania.
Molecules. 2021 Mar 25;26(7):1848. doi: 10.3390/molecules26071848.
In the present work, Cr-substituted MgAlCr layered double hydroxides (LDHs) were synthesised through the phase conversion of sol-gel-derived mixed-metal oxides in an aqueous medium. The chromium substitution level in the range of 1 to 25 mol% was investigated. It was demonstrated that all synthesised specimens were single-phase LDHs. The results of elemental analysis confirmed that the suggested synthetic sol-gel chemistry approach is suitable for the preparation of LDHs with a highly controllable chemical composition. The surface microstructure of sol-gel-derived MgAlCr LDHs does not depend on the chromium substitution level. The formation of plate-like agglomerated particles, which consist of hexagonally shaped nanocrystallites varying in size from approximately 200 to 300 nm, was observed. Optical properties of the synthesised MgAlCr LDHs were investigated by means of photoluminescence. All Cr-containing powders exhibited characteristic emission in the red region of the visible spectrum. The strongest emission was observed for the sample doped with 5 mol% Cr ions. However, the emission intensity of samples doped with 1-10 mol% Cr ions was relatively similar. A further increase in the Cr ion concentration to 25 mol% resulted in severe concentration quenching.
在本工作中，通过在水介质中对溶胶-凝胶衍生的混合金属氧化物进行相转化，合成了 Cr 取代的 MgAlCr 层状双氢氧化物（LDHs）。研究了 Cr 取代水平在 1 至 25 摩尔%的范围内。结果表明，所有合成的样品均为单相 LDHs。元素分析的结果证实，所提出的合成溶胶-凝胶化学方法适用于具有高度可控化学组成的 LDHs 的制备。溶胶-凝胶衍生的 MgAlCr LDHs 的表面微观结构不依赖于 Cr 取代水平。观察到由尺寸约为 200 至 300nm 的六方形状纳米晶组成的板状团聚颗粒的形成。通过光致发光研究了合成的 MgAlCr LDHs 的光学性质。所有含 Cr 的粉末在可见光谱的红色区域均表现出特征发射。对于掺杂 5 摩尔%Cr 离子的样品，观察到最强的发射。然而，掺杂 1-10 摩尔%Cr 离子的样品的发射强度相对相似。进一步将 Cr 离子浓度增加到 25 摩尔%会导致严重的浓度猝灭。
