Semiconductor quantum dots (QDs) represent a remarkable class of nanostructures, characterized by size-dependent optical and electronic properties, making them prime candidates for high-performance hybrid optoelectronic devices in energy conversion applications. Among the various QD materials, zinc selenide (ZnSe) stands out as a leading contender for next-generation QD-based technologies. However, the impact of surface characteristics and defect states on the electronic properties of ZnSe QDs remains inadequately understood. In this talk, I will present how the combined UV-Vis and X-ray spectroscopy techniques can be utilized to probe and characterize defect states in ZnSe QDs.