Mangnus Mark J J, Benning Vincent R M, Baumgartner Bettina, Prins P Tim, van Swieten Thomas P, Dekker Ayla J H, van Blaaderen Alfons, Weckhuysen Bert M, Meijerink Andries, Rabouw Freddy T
Inorganic Chemistry and Catalysis group, Debye Institute for Nanomaterials Science and Institute for Sustainable and Circular Chemistry, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands.
Soft Condensed Matter group, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 1, 3584 CC Utrecht, The Netherlands.
Nanoscale. 2023 Oct 26;15(41):16601-16611. doi: 10.1039/d3nr02997b.
The photoluminescence (PL) of lanthanide-doped nanocrystals can be quenched by energy transfer to vibrations of molecules located within a few nanometers from the dopants. Such short-range electronic-to-vibrational energy transfer (EVET) is often undesired as it reduces the photoluminescence efficiency. On the other hand, EVET may be exploited to extract information about molecular vibrations in the local environment of the nanocrystals. Here, we investigate the influence of solvent and gas environments on the PL properties of NaYF:Er,Yb upconversion nanocrystals. We relate changes in the PL spectrum and excited-state lifetimes in different solvents and their deuterated analogues to quenching of specific lanthanide levels by EVET to molecular vibrations. Similar but weaker changes are induced when we expose a film of nanocrystals to a gas environment with different amounts of HO or DO vapor. Quenching of green- and red-emitting levels of Er can be explained in terms of EVET-mediated quenching that involves molecular vibrations with energies resonant with the gap between the energy levels of the lanthanide. Quenching of the near-infrared-emitting level is more complex and may involve EVET to combination-vibrations or defect-mediated quenching. EVET-mediated quenching holds promise as a mechanism to probe the local chemical environment-both for nanocrystals dispersed in a liquid and for nanocrystals exposed to gaseous molecules that adsorb onto the nanocrystal surface.
镧系元素掺杂的纳米晶体的光致发光（PL）可通过能量转移至距离掺杂剂几纳米内的分子振动而猝灭。这种短程电子 - 振动能量转移（EVET）通常是不理想的，因为它会降低光致发光效率。另一方面，EVET可用于提取有关纳米晶体局部环境中分子振动的信息。在这里，我们研究了溶剂和气体环境对NaYF:Er,Yb上转换纳米晶体PL性质的影响。我们将不同溶剂及其氘代类似物中PL光谱和激发态寿命的变化与通过EVET至分子振动对特定镧系元素能级的猝灭联系起来。当我们将纳米晶体薄膜暴露于含有不同量HO或DO蒸汽的气体环境中时，会诱导出类似但较弱的变化。Er的绿色和红色发射能级的猝灭可以用EVET介导的猝灭来解释，该猝灭涉及与镧系元素能级之间的间隙共振的能量的分子振动。近红外发射能级的猝灭更为复杂，可能涉及到EVET至组合振动或缺陷介导的猝灭。EVET介导的猝灭有望成为一种探测局部化学环境的机制——无论是对于分散在液体中的纳米晶体，还是对于暴露于吸附在纳米晶体表面的气态分子的纳米晶体。
