Fabrication of a flexible porous polypyrrole film with a 3D micro-nanostructure and its electrochemical properties.

Flexible energy storage systems have become attractive alternatives for applications in wearable energy storage and sensor devices. This study reports a simple electro-polymerization method for the fabrication of PPy films coated on PPy nanotubes (PPy NTs), which are binding-free, self-standing, and could be used as a flexible electrode for supercapacitors. With optimized kinetics for ion transportation, the mass specific capacitance of the flexible porous PPy films can be elevated to 1.36 F cm-2 at a charging/discharging rate of 2 mA cm-2 (0.45 A g-1). The mass specific capacitance of the flexible porous PPy films reaches 6.5 times as large as that of compact PPy films at a scan rate of 20 mV s-1. Furthermore, due to the large free space for volume change, the capacitance fading of the flexible porous PPy films is less than 3% after 10 000 cycles. This novel design provides an efficient method to synthesize high-performance, flexible and low-cost materials used in supercapacitors.

Unzipping the cuticle of the human hair shaft to obtain micron/nano keratin filaments.

An attempt has been made to obtain intact individual keratin filaments of various levels from micron cortical, micron macrofibril to nano intermediate filament and polypeptide alpha-helix from the human hair shaft. The feasibility of this initiative has been largely demonstrated by finding that there is a longitudinal seam/zipper on the cuticle of the human hair shaft, which can be unzipped by certain solvents such as performic acid and urea, allowing one to use an anatomical approach to separate intact individual micron/nano filaments. Micron cortical and macrofibril filaments have been obtained. It is also found that the cortical filaments are twisted together to form a yarn, giving rise to the strength for the hair shaft; and that individual cortical filaments are often 2-2 paired in a similar structure to the double helix.

Depression of the melting temperature by moisture for alpha-form crystallites in human hair keratin.

DSC thermal analysis has been carried out for human hair samples with various moisture contents to investigate the melting temperature depression behavior of alpha-form crystallites in human hair. This is achieved by adopting a novel technique using silicon oil as the thermal medium, which permits hair samples to retain a range of moisture contents in between completely dry and fully saturated. The results show that the melting temperature of the alpha-form crystallites in human hair varies with moisture content from 205 degrees C for dry hair to 155 degrees C for the hair sample with moisture content of 23%. These experimental results are particularly useful for clarification of the conceptual ambiguities associated with the molecular properties of alpha-helices and alpha-form crystallites. Furthermore, the Flory-Huggins theory was employed to determine the water-helix interaction parameter (chi = 4.5) and the alpha-form crystallinity of human hair (22%), a figure consistent with that obtained by the XRD method (21%).