Abstract
In this work we report the preparation and characterization of free-standing keratin-based films containing Au/Ag nanorods. The effect of nanorods surface chemistry on the optical and mechanical properties of keratin composite films is fully investigated. Colloid nanorods confer to the keratin films interesting color effects due to plasmonic absorptions of the metal nanostructures. The presence of metal NRs induces also substantial change in the protein fluorescence emission. In particular, the relative contribution of the ordered-protein aggregates emission is enhanced by the presence of cysteine and thus strictly related to the surface chemistry of nanorods. The presence of more packed supramolecular structures in the films containing metal nanorods (in particular cysteine modified ones) is confirmed by ATR measurements. In addition, the films containing nanorods show a higher Young's modulus compared to keratin alone and again the effect is more pronounced for cysteine modified nanorods. Collectively, the reported results indicate the optical and mechanical properties of keratin composites films are related to a common property and can be tuned simultaneously, paving the way to the optimization and improvement of their performances and enhancing the exploitation of keratin composites in highly technological optoelectronic applications.
Highlights
The preparation of innovative and multifunctional bionanocomposite free-standing films starting from natural polymers and nanosized metals represents an attractive challenge for several applications including packaging, catalysis, optics, biomedicine, tissue engineering, drug delivery, and electronics (Ruiz-Hitzky et al, 2010)
transmission electron microscope (TEM) images recorded on Au@AgNRs sample, shows rod-like structures with a homogeneous contrast, suggesting that silver is deposited on the gold nanostructures forming an uniform layer without significantly alter the dimension and the morphology of the rod (Figures 1b, 2)
Nanorods samples present extinction spectra characterized by two main bands, generated by the transversal, and longitudinal surface plasmonic resonance (SPR), due to the resonant oscillations of the conductive electrons of the material induced by the incident radiation
Summary
The preparation of innovative and multifunctional bionanocomposite free-standing films starting from natural polymers and nanosized metals represents an attractive challenge for several applications including packaging, catalysis, optics, biomedicine, tissue engineering, drug delivery, and electronics (Ruiz-Hitzky et al, 2010). Keratin is one of the most abundant renewable and non-food proteins, being the principal component of hair, wool, feather, horns and nails of mammals, reptiles, and birds. This protein can be Keratin-Au/Ag Nanorods Based Films extracted from readily available and low-cost wastes, such as raw wool not suitable for spinning, feathers from butchery, and by-products of the wool textile industry (Aluigi et al, 2007). Keratin films have been investigated as innovative natural support material for a new generation of sustainable and greener electronic and optoelectronic devices (Natali et al, 2019; Posati et al, 2019)
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