Boosting the Optical Absorption of Melanin-like Polymers

As a typical type of melanin-inspired materials, polydopamine (PDA) has been widely used in photothermal conversion and energy harvesting applications due to its broad spectral absorption feature, but its limited absorption in the visible light region severely hinders further utilization. Although enhancing the visible light absorption and photothermal performance of PDA is urgent, it is quite difficult to achieve this goal via structural tailoring strategies because of the complicated and disordered structure within PDA. To address this issue, we reported a facile approach involving nitrogen-containing heterocycles toward the design of two new kinds of PDA nanomaterials. The introduction of nitrogen-containing heterocycles greatly reduced the lowest unoccupied molecular orbital of the molecular segments and then promoted electron delocalization in the local area. We verified the changes of energy bandgap and exciton decay of nitrogen-containing heterocycle-doped PDA through spectral analysis, density functional theory calculation, and electrostatic potential distribution on the molecular surface. Therefore, these heterocycle-doped PDAs exhibited improved visible light absorption and photothermal performances, which can be used in solar power generation applications. This work provides new opportunities for the rational design and structural tailoring of bioinspired photothermal materials.