Short Wavelength Light Absorption and Conversion Films Containing Carbon Nanodots for Light Damage Prevention

The carbon nanodots (CNDs) can absorb short wavelength light and enable excited electrons to achieve light conversion to long wavelength emission by radiative transition, while accompanying the non-radiative transition of excited electrons, in order to block the short wavelength light. The CNDs were prepared from chitosan as the carbon source, and then mixed with polyvinyl alcohol (PVA) to prepare CNDs-based optical blocking films (CND-OBFs) containing different proportions of CNDs. Images were clearly visible through CND-OBFs under both close and long-distance observation, demonstrating good transparency. The CND-OBFs were shown to block both UV light from sunlight and harmful blue light from computers, mobile phones and white light-emitting diodes. The CND-OBFs can thus be used to effectively block short wavelength light. Samples of wood were covered with different CND-OBFs and the wood surfaces were then irradiated with UV light (340 nm, 80 W). The results show that different CND-OBFs block short wavelength light to different extents; CND-OBF containing 15.7 % CNDs can completely block short wavelength light through absorption and conversion, protecting the wood samples from discoloration. This work provides a new research approach in which CNDs are used to protect wood by blocking short wavelength light.