Biopolymer-metal composites

Optical devices are today based mainly on glass or synthetic polymers, which hinders their use in biological interfaces owing to the lack of biocompatibility and biodegradability. This is why synthetic plastics are progressively being replaced by their bioplastic counterparts, thus bringing new challenges associated with processability, environmental sustainability, and large-scale fabrication of successful products. Natural polymers or biopolymers are fascinating self-assembled block polymer structures of nearly unlimited and inexpensive renewable resources, now finding applications in various fields, including optics. The ability to control the assembly and conformation of natural polymers into optical quality solutions and films brings the opportunity to revisit their application usually restricted to packaging and medical area. Of particular importance is to combine these polymers with metallic nanoparticles whose tunable localized surface plasmon resonance can be exploited in engineering composite materials with enhanced optical properties. The combined advantages also make them an ideal integration platform to foster biodegradable, bioresorbable, environmentally friendly, and sustainable electronic and optoelectronic devices. This chapter provides comprehensive coverage of advances and trends of how natural polymers and natural polymer-metallic nanoparticle composites have been explored for developing optical devices such as colorimetric sensors, transparent electrodes, optical waveguides, and light amplification devices. Examples will be given of optical composites made of chitin and chitosan, bacterial cellulose, silk fibroin, and DNA, with special emphasis on the challenges and ongoing efforts to fabricate useful devices.