Synthesis of Carbon Dots with Carbogenic π-Conjugated Domains for Full-Band UV Shielding

Abstract

Our skin and materials are constantly exposed to detrimental ultraviolet light (UV) rays from the sun. It is essential to protect our health and the life of materials by intercepting this detrimental high-energy radiation with UV absorbers. Carbon dots (CDs) with low toxicity and low cost have brought a choice for UV absorbers. However, high-efficiency absorption CDs that can achieve absorption in the full ultraviolet region have rarely been reported. Herein, we synthesized a full-band carbon dot ultraviolet absorber by expanding the CD π-conjugation domain. In addition, by encapsulating CDs in a polyurethane (PU) matrix, the absorptivity of the 5 wt % CDs@PU film in the ultraviolet region was 100%, and the transmittance reached 90% in the visible region, successfully protecting the two dyes from photodegradation. The UV shielding efficiency slightly decreased under the accelerated aging experiment of 288 h. Moreover, to remove the ultraviolet light in the light-emitting diode (LED), we applied a layer of the CD film to the surface of the LED lamp, and the results indicated that the UV light was successfully blocked by the CD film without affecting the LED luminescence performance. This study offers a valid method to evolve high-efficiency, nontoxic antiaging materials and healthy lighting devices.

Highly fluorescent nitrogen-doped carbon dots with large Stokes shifts

“…The strong absorption peak at about 270 nm corresponds to the p p* transitions from the aromatic CQC bonds in the graphitic core of CDs. [49][50][51] Both CDs display a prominent absorption band between 300 and 400 nm, associated with the np* transitions through the non-bonding orbitals at the edge of the sp 2 -hybridized core. These edge states originated from the boundary between the sp 2 -and sp 3 -hybridized carbons, where the surface functional groups connect to the sp 2 -carbon lattice.…”

Oil-Soluble Ultraviolet-Absorbing Carbon Dots Dispersed in Polyethylene Films as Antiaging Materials

“…Among these properties, the absorption of UV for CDs is a newly developed process in recent years. Our research group has also carried out many studies on the UV absorption properties of CDs and applied them in the fields of UV shielding, − sunscreen, healthy light source lamps, and so on. Hu et al synthesized full-band UV-absorbent water-soluble (NH,OH)-functionalized silicon quantum dots, investigated its stability, and compared their stability and UV absorptivity with commercial water-soluble UV absorbents .…”