Photo‐Induced Hydrogel Formation Based on g‐C₃N₄ Nanosheets with Self‐Cross‐Linked 3D Framework for UV Protection Application

Abstract

Composite hydrogels of graphitic carbon nitride nanosheets (CNNS) and polyacrylamide (PAM) with superior UV absorption and visible transparence capabilities are reported. CNNS is employed not only as a photocatalytic initiator to trigger the polymerization of acrylamide, but also as a cross‐linker to 3D connected PAM chains via hydrogen bonds. The obtained CNNS/PAM hydrogels are highly moldable for preparing various forms, and have good mechanical properties, self‐healing ability, and photo‐stability. Furthermore, the composite hydrogels have a wide spectral range for UV absorption compared to conventional UV protective materials. Besides the complete screening of UVB (280–315 nm) in sun radiation, the CNNS/PAM hydrogel film can also filter >95% UVA radiation (315–400 nm) by regulating the coating thickness, meanwhile retaining a high visible transmittance. Therefore, the CNNS/PAM hydrogels have potential applications for shielding UV radiation. Additionally, this strategy provides a common and facile route to fabricate functional composite hydrogels via photo‐induced polymerization.

Graphitic carbon nitride and polymers: a mutual combination for advanced properties

“…Dong and coworkers obtained acrylamide-based hydrogels for ''light filtering'' applications. 199 AAm was utilized as monomer in a visible light induced polymerization. Due to the hydrogen bonding interactions between g-C 3 N 4 and PAAm in the hydrogel self-healing was observed after cutting the hydrogel.…”

Functionalized Graphitic Carbon Nitrides for Environmental and Sensing Applications

“…A solution for this was proposed by Dong and coworkers, who designed a composite hydrogel using alkali‐exfoliated CNNSs as a crosslinking agent, initiator, and reinforcer in PAM. [ 126 ] They proposed a simple hydrogel fabrication method using photoinduced polymerization. The photoactive CNNS initiated polymerization of acrylamide monomers, and a 3D network was formed due to hydrogen bonds.…”

“…[125] As shown in Figure 10a, photocatalysis by semiconductors involves the generation of charges under light, which in turn reacts with O 2 or H 2 O to form free radicals. [126] While g-C 3 N 4 itself does not form hydroxyl radicals, it reduces oxygen to superoxide radicals, and the polymerization is initiated (Figure 10b). Using bulky g-C 3 N 4 might not form stable hydrogel with polyacrylamide (PAM) as the chains have weak interaction within them.…”

“…Reproduced with permission. [126] Copyright 2019, Wiley-VCH GmbH. g-C 3 N 4 /TiO 2 -NT nanocomposite.…”

Photoinduced post-modification of graphitic carbon nitride-embedded hydrogels: synthesis of 'hydrophobic hydrogels' and pore substructuring

“…Integration of g-CN into hydrogels has been popularized in the last four years, where g-CN nanosheets can be implemented into hydrogels through embedding [ 36 ] or covalent binding [ 37 – 38 ] for the target application such as reinforced hydrogels [ 39 ] and hydrogels for photoredox-based applications [ 40 – 41 ].…”