Kocsis K, Niedermaier M, Schwab T, Kasparek V, Berger T, Diwald O
Department of Chemistry and Physics of Materials, University of Salzburg, Jakob-Haringer-Strasse 2a, A-5020 Salzburg.
Central European Institute of Technology, Brno University of Technology, Purkynova 123, Brno 612 00, Czech Republic.
ChemPhotoChem. 2018 Nov;2:994-1001. doi: 10.1002/cptc.201800104.
Adsorption of organic molecules at ZnO nanoparticle surfaces enables the transfer of energy or charge across resulting organic-inorganic interfaces and, consequently, determines the optoelectronic performance of ZnO based hybrids. We investigated on aqueous colloidal ZnO dispersions adsorption-induced changes with photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopy. Citrate and acetate ion adsorption increases or decreases radiative exciton annihilation at hν = 3.3 eV and at room temperature, respectively. Searching for a correspondence between PL emission and the yield of trapped charge carriers originating from exciton separation - using photon energies of hν = 4.6 eV and fluxes of = 10 cm s for excitation - we found that there is a negligible fraction of paramagnetic products that originate from exciton separation. Upon polychromatic excitation with significantly higher photon fluxes (Ṅ = 10 cm·s), ZnO specific shallow defects trap unpaired electrons in citrate and acetate functionalized samples. The adsorption dependent PL intensity changes and the excitation parameter dependent yield of separated charges (EPR) in colloidal ZnO nanoparticles underline that the distribution over the different exciton annihilation channels sensitively depends on interface composition and the intensity of the photoexcitation light.
有机分子在氧化锌纳米颗粒表面的吸附能够使能量或电荷在形成的有机-无机界面间转移，因此决定了基于氧化锌的杂化材料的光电性能。我们通过光致发光（PL）和电子顺磁共振（EPR）光谱研究了水相胶体氧化锌分散体中吸附引起的变化。柠檬酸根离子和醋酸根离子的吸附分别在室温下hν = 3.3 eV时增加或减少辐射激子湮灭。利用hν = 4.6 eV的光子能量和 = 10 cm s的通量进行激发，寻找PL发射与激子分离产生的俘获电荷载流子产率之间的对应关系，我们发现源自激子分离的顺磁产物比例可忽略不计。在用显著更高的光子通量（Ṅ = 10 cm·s）进行多色激发时，氧化锌特定的浅缺陷会在柠檬酸根和醋酸根功能化的样品中俘获未配对电子。胶体氧化锌纳米颗粒中吸附依赖的PL强度变化和激发参数依赖的分离电荷产率（EPR）强调，不同激子湮灭通道的分布敏感地取决于界面组成和光激发光的强度。
