Most solar-energy conversion applications are based on trapping and transferring photoinduced electrons on oxide semiconductor nanoparticles, such as titanium dioxide, and broad UV-vis absorption (400~800 nm) and monotonic IR absorption (1100~3000 cm⁻¹) signals have long been considered signatures of the electron-trapping state on titanium dioxide nanoparticles. Here we show that, under proton-free conditions and using iodide ions in acetonitrile as the hole scavenger, the intrinsic electron-trapping feature of titanium dioxide nanoparticles does not exhibit the characteristic UV-vis absorption and infrared absorption signatures. Further electron spin resonance studies identify the proton-free electron-trapping state as the lattice octahedral Ti_6c³⁺ species, differing from the traditional proton-participating surface tetrahedral Ti_4c³⁺ species. Synchronized radiation ultraviolet photoelectron spectroscopy results also show that the internal electron-trapping state without protons has a larger Ti_3d binding energy (1.8 eV) than the blue electron-trapping state (1.3 eV) that forms when protons participate and thus shows different electron transfer abilities.

大多数太阳能转换应用是基于在氧化物半导体纳米颗粒（例如二氧化钛）上捕获和转移光生电子，并且宽的UV-vis吸收（400〜800 nm）和单调IR吸收（1100〜3000 cm ^-1）信号具有长期以来，人们一直认为二氧化钛纳米粒子具有电子俘获态的特征。在这里，我们表明，在无质子的条件下，并使用乙腈中的碘离子作为空穴清除剂，二氧化钛纳米粒子的固有电子俘获特征没有表现出特征的UV-vis吸收和红外吸收特征。进一步的电子自旋共振研究确定无质子的电子俘获态为晶格八面体Ti _6c ³⁺与传统的质子参与表面四面体Ti _4c ³⁺物种不同。同步辐射紫外光电子能谱结果还表明，没有质子的内部电子俘获态具有比质子参与时形成的蓝色电子俘获态（1.3 eV）更大的Ti _3d结合能（1.8 eV），从而表现出不同的电子转移能力。