Traditional UV absorbers encounter challenges stemming
from incomplete
UV absorption and potential toxicity concerns. Carbon dots are a promising
ecofriendly UV absorber. However, they still interfere with visible
light transmission and have limited UV absorption efficiency. Furthermore,
research on the stability of UV-absorbing carbon dots is limited.
This study synthesized carbon dots (CDs) using citric acid (CA) and
ethylenediamine (EDA) as precursors. The amide group is the cause
of the ability of CDs to absorb UVA (long-wave ultraviolet light).
To broaden the absorption region, o-phenylenediamine
(o-PD) was employed as a modifier to synthesize efficient
three-component full-band UV absorption carbon dots (NCDs). The introduction
of o-PD constructed a large conjugated domain on
the surface of NCDs, which enhances the absorption capacity of NCDs
for UVB through π–π* transitions without affecting
visible light. Furthermore, the salt resistance, acid–alkali
resistance, thermal stability, and light-bleaching resistance of NCDs
were investigated. These properties are linked to the hydrophilicity,
structural stability, and electronic transition activity of NCDs.
Additionally, NCDs were used in combination with polyurethane (PU)
to design light-colored sunglasses that provide excellent UV protection
and light-bleaching resistance. This work is significant for utilizing
the electronic transition characteristics of conjugated structures
to expand the UV absorption range of carbon dots.