Abstract
Nanocomposite engineering of biosensors, biomaterials, and flexible electronics demand a highly tunable synthesis of precursor materials to achieve enhanced or desired properties. However, this process remains limited due to the need for proper synthesis-property strategies. Herein, we report on the ability to synthesize chitosan-gold nanocomposite thin films (CS/AuNP) with tunable properties by chemically reducing HAuCl4 in chitosan solutions and different HAuCl4/sodium citrate molar relationships. The structure, electrical, and relaxation properties of nanocomposites have been investigated as a function of HAuCl4/sodium citrate molar relation. It was shown that gold particle size, conductivity, Vogel temperature (glass transition), and water content strongly depend upon HAuCl4/sodium citrate relationships. Two relaxation processes have been observed in nanocomposites; the α-relaxation process, related to a glass transition in wet CS/AuNP films, and the σ-relaxation related to the local diffusion process of ions in a disordered system. The ability to fine-tune both α- and σ-relaxations may be exploited in the proper design of functional materials for biosensors, biomaterials, and flexible electronics applications.
Highlights
The band at 2880 cm−1 is associated with a symmetric stretching of the methyl group, the band present at 1640 cm−1 belongs at C=O
Antisymmetric, from citrate moiety, the band at 1550 cm−1 is assigned to the antisymmetric deformation of NH3 +
CS/AuNP thin films have been synthesized by chemical reduction of HAuCl4 in the presence of sodium citrate (SC) and chitosan solutions
Summary
Metal nanoparticles exhibit unique optical, electrical, mechanical, and biomedical properties In this regard, the number of publications related to polymer-metal nanocomposites has recently increased [1–15]; various studies report on the use of such nanocomposites in biomedicine, biosensors for protein recognition, and flexible electronics. The number of publications related to polymer-metal nanocomposites has recently increased [1–15]; various studies report on the use of such nanocomposites in biomedicine, biosensors for protein recognition, and flexible electronics Most of these reports rely on the proper chemical synthesis of Au nanoparticles; the challenge to fine-tune the structure, size, and functionality is still at large. Interesting chemical reduction methods to produce functional metal nanoparticles have been discussed in the literature; in this regard, Ag [17], Au/Ag [18], Pt/Pd [19], and biofunctionalized Au nanoparticles [20] These studies reveal the importance of proper synthesis methods for biosensor applications
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