Improving broadband absorption of carbon dot conjugated melanin via pre-doping strategy as interfacial photothermal evaporator

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-11, Vol.500, p.156705, Article 156705
• Main Authors: Kan, Guoyu, Li, Yukong, Chang, Qing, Deng, Xiaoyong, Xie, Yijun
• Format: Article
• Language: English
• Subjects: Carbon quantum dots; Photothermal conversion; Polydopamine; Pre-doping; Solar-driven seawater desalination
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.156705

[Display omitted] •CQDs are covalently bonded to MPDA through pre-doping strategy.•CQD doping reduces the bandgap of MPDA by fostering donor–acceptor pairs.•The evaporation rate of MPDA-8 reaches 2.10 kg m−2 h−1 under one sun irradiation.•MPDA-8 exhibits excellent outdoor durability, salt resistance, and hydrophilicity. Photothermal seawater desalination harnesses solar energy to induce heat and expediates seawater evaporation and purification. The desalination efficacy heavily relies on the light absorption capability and microstructure of the solar evaporator. Polydopamine (PDA) represents a typical synthetic melanin with broad spectral absorption characteristics. However, its absorption capacity within the near-infrared (NIR) region is limited, leading to inadequate photothermal conversion efficiency. To overcome this challenge, we adopt a straightforward approach involving the pre-doping of N,S-doped carbon quantum dots (N,S-CQDs) with dopamine through covalent interaction to fabricate CQDs-loaded mesoporous polydopamine (MPDA-8). This strategy effectively reduces the band gap of PDA by fostering additional donor–acceptor pairs and π-stacking structures, thereby broadening the absorption capacity across the UV–Vis-NIR spectrum through nonradiative transitions. The MPDA-8 coated Balsa wood and cellulose evaporator achieved high evaporation rates of 1.82 kg m−2 h−1 and 2.10 kg m−2 h−1, respectively, overcoming the limit of 2D interfacial evaporator. The small pores and fiber channels within the wood, coupled with the hydrophilicity of MPDA-8, facilitates efficient water transportation and reduces evaporation enthalpy. Outdoor evaporation experiments conducted under sunlight corroborated the practical viability of this material. This study introduces a new perspective for advancing synthetic melanins in photothermal applications through the nanoparticle pre-doping strategy.