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  • Enhanced photochemical activity and ultrafast photocarrier dynamics in sustainable synthetic melanin nanoparticle-based donor–acceptor inkjet-printed molecular junctions
Title: Enhanced photochemical activity and ultrafast photocarrier dynamics in sustainable synthetic melanin nanoparticle-based donor–acceptor inkjet-printed molecular junctions
Melanin is a stable, widely light-absorbing, photoactive, and biocompatible material viable for energy con- version, photocatalysis, and bioelectronic applications. To achieve multifunctional nanostructures, we synthesized melanin nanoparticles of uniform size and controlled chemical composition (dopamelanin and eumelanin) and used them with titanium dioxide to fabricate donor–acceptor bilayers. Their size enhances the surface-to-volume ratio important for any surface-mediated functionality, such as photo- catalysis, sensing, and drug loading and release, while controlling their chemical composition enables to control the film’s functionality and reproducibility. Inkjet printing uniquely allowed us to control the de- posited amount of materials with minimum ink waste suitable for reproducible materials deposition. We studied the photochemical characteristics of the donor–acceptor melanin–TiO2 nanostructured films via photocatalytic degradation of methylene blue dye under selective UV-NIR and Vis-NIR irradiation con- ditions. Under both irradiation conditions, they exhibited photocatalytic characteristics superior to pure melanin and, under UV-NIR irradiation, superior to TiO2 alone; TiO2 is photoactive only under UV irradiation. The enhanced photocatalytic characteristics of the melanin–TiO2 nanostructured bilayer films, particularly when excited by visible light, point to charge separation at the melanin–TiO2 interface as a possible mechanism. We performed ultrafast laser spectroscopy to investigate the photochemical charac- teristics of pure melanin and the melanin–TiO2 constructs and found that their time-resolved photo- excited spectral patterns differ. We performed singular value decomposition analysis to quantitatively deconvolute and compare the dynamics of photochemical processes for melanin and melanin–TiO2 heterostructures. This observation supports electronic interactions, namely, interfacial charge separation at the melanin and TiO2 interface. The excited-state relaxation in melanin–TiO2 increases markedly from 5 ps to 400 ps. The results are remarkable for the future intriguing application of melanin-based con- structs for bioelectronics and energy conversion.  more » « less
Award ID(s):
2239539
PAR ID:
10479208
Author(s) / Creator(s):
; ; ; ; ; ;
Editor(s):
Cinzia Casiragi
Publisher / Repository:
Nanoscale
Date Published:
Journal Name:
Nanoscale
Volume:
15
Issue:
35
ISSN:
2040-3364
Page Range / eLocation ID:
14346 to 14364
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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