Silicon And Nafion Nanowires: Syntheses And Applications In Nanopower Sources

The goal of nanotechnology is to build nanosystems that are most intelligent, multifunctional, supersmall, extremely sensitive, and low power consumption. When the size of the nanosystem is small for applications such as in-vivo implanted biomedical sensors and environmental monitoring, a nano-power source is required for continuous, independent and mobile operation of the nanosystem.An extrusion method, using anodic aluminium oxide membranes as templates, has been developed to fabricate Nafion nanowire arrays. Surface decoration of the templates plays an important role in the synthesis of the Nafion nanowire arrays. Electrospinning is also used to prepare"long"Nafion nanowires, the as-prepared nanowires can reach centimeters.In addition, the proton conductivity of an individual Nafion nanowire ranging from 500nm to 16.6μm in diameter has been measured, respectively. The diameter dependent proton conductivity is increasing dramatically with the decreasing diameters as the diameter is smaller than 2.5μm, following a power law.We present a novel design of nano-fuel cell based on Nafion nanowires. One nano-fuel cell has been successfully accomplished on an individual Nafion nanowire in our experiment. The high performance nano fuel cell is easy to fabricate and reproducible. The best performance of our nano-fuel cell can be obtained: open circuit voltage 430mV, maximum current density and power density about 4.33μA/μm2 and 0.44μW/μm2, respectively, which is enhanced by orders of magnitude compared with the traditional fuel cell.We also report the nano biofuel cell (NBFC) based on a single Nafion nanowire for converting chemical energy from biofluid such as glucose/blood into electricity. The NBFC uses glucose oxidase as catalyst to dissociate glucose and produce and separate protons and electrons at the anode side. The glucose is supplied by biofluid, and the NW serves as the proton conductor. The NBFC has been integrated with a nanowire based pH, glucose or photon sensor for performing self-powered sensing. By combining lithography and metal-assisted etching, we successfully fabricated large scale both silicon nanowire arrays and single crystal core/shell Si/SiGe heterojunction arrays. The morphology, microstructure, and properties of these nanostructures were also systematically investigated. Inspiring by the excellent anti-reflection property of large-area core/shell Si/SiGe heterojunction arrays over a wide spectral bandwidth between 1200~300 nm, we design and manufacture a new type of solar cell.Our nanofuel cells, nano biofuel cells and nano solar cells provide a new approach for self-powered nanotechnology that harvests electricity from the environment for applications such as implantable biomedical devices, wireless sensors, and even portable electronics that are important for biological sciences, environmental monitoring, defense technology and even personal electronics.