Observation of Surface/Defect States of SnO₂ Nanowires on Different Substrates from X-ray Excited Optical Luminescence

SnO₂ nanowires (NWs) have been successfully synthesized on two different substrates (stainless steel (SS) and copper) via a facile hydrothermal process. SnO₂ NWs with varying degrees of crystallinity are obtained on different substrates. The growth mechanisms are also deducted by observing the morphology revolution at various reaction times. Furthermore, the electronic structures and optical properties have been investigated by X-ray absorption near edge structure (XANES) and X-ray excited optical luminescence (XEOL) measurements. The yellow-green luminescence from SnO₂ NWs is originated from the intrinsic surface states. Compared with SnO₂ NWs on copper, a near infrared (NIR) luminescence is observed for SnO₂ NWs on SS, which resulted from poor crystallinity and an abundance of defect/surface states