Cellulose as an Inert Scaffold in Plasmon-Assisted Photoregeneration of Cofactor Molecules

Plasmonic nanoparticles exhibit excellent light-harvesting properties in the visible spectral range, which makes them a convenient material for the conversion of light into useful chemical fuel. However, the need for using surface ligands to ensure colloidal stability of nanoparticles inhibits their photochemical performance due to the insulating molecular shell hindering the carrier transport. We show that cellulose fibers, abundant in chemical functional groups, can serve as a robust substrate for the immobilization of gold nanorods, thus also providing a facile way to remove the surfactant molecules. The resulting functional composite was implemented in a bioinspired photocatalytic process involving dehydrogenation of sodium formate and simultaneous photoregeneration of cofactor molecules (NADH, nicotinamide adenine dinucleotide) using visible light as an energy source. By systematic screening of experimental parameters, we compare photocatalytic and thermocatalytic properties of the composite and evaluate the role of palladium cocatalyst.M.G. acknowledges funding from the Spanish MINECO (grant MAT2013-49375-EXP) and the BBVA Foundation "Primera convocatoria de ayudas fundacion BBVA a investigadores, innovadores y creadores culturales". N.T.-S. acknowledges the support from the BioTechNan (NCBiR) program of interdisciplinary PhD studies at Wroclaw University of Science and Technology as well as the support from the Photonics and Bionanotechnology Association (PhoBiA). The work was also financed by a statutory activity subsidy from the Polish Ministry of Science and Higher Education for the Faculty of Chemistry of Wroclaw University of Science and Technology. S.V. D. and V. P. acknowledge the support by the Spanish Ministry of Science, Innovation, and Universities (project BIO2017-88030-R), Maria de Maeztu Units of Excellence Program from the Spanish State Research Agency grant no. MDM-2017-0720

Gold Nanorods Grant an ON-OFF Control over the Kinetics of the Z-E Isomerization of Azobenzene-Based Photoswitch via Thermoplasmonic Effect

Proper formulation of systems containing plasmonic and photochromic units, such as gold nanoparticles and azobenzene derivatives, yields materials and interfaces with synergic functionalities. Moreover, gold nanoparticles are known to accelerate the Z-E isomerization of azobenzene molecules in the dark. However, very little is known about the light-driven, plasmon-assisted Z-E isomerization of azobenzene compounds. Additionally, most of the azobenzene-gold hybrids are prepared with nanoparticles of small, isotropic shapes and azobenzene ligands covalently linked to the surface of nanostructures. Herein, a formulation of a novel system combining azobenzene derivative, gold nanorods, and cellulose nanofibers is proposed. The system\u27s structural integrity relies on electrostatic interactions among components instead of covalent linkage. Cellulose, a robust scaffold, maintains the material\u27s functionality in water and enables monitoring of the material\u27s plasmonic-photochromic properties upon irradiation and at elevated temperatures without gold nanorods\u27 aggregation. Experimental evidence supported by statistical analysis suggests that the optical properties of plasmonic nanometal enable indirect control over the Z-E isomerization of the photochromic component with near-infrared irradiation by triggering the thermoplasmonic effect. The proposed hybrid material\u27s dual plasmonic-photochromic functionality, versatility, and ease of processing render a convenient starting point for further advanced azobenzene-related research and 3D printing of macroscopic light-responsive structures