Conductive nanomaterials with the set of valuable characteristics are one of the most opportune materials used in advanced applications nowadays. In this thesis, I present new nanomaterials which, in my opinion, possibly will contribute to the solution of two rather important problems faced by modern society, i.e. high energy consumption and costs for medical care due to ageing population.
In connection with the first problem, the effectiveness of energy storage devices such as supercapacitors, to a big extent, depends on carbon nanomaterials used for accumulation of electrostatic charges. At the moment, the production of carbon materials mostly relies on unsustainable fossil fuels as precursors. I describe the fabrication of freestanding functional carbon nanofibrous (CNF) materials derived from cellulose, the most abundant renewable resource, via consecutive steps of cellulose acetate electrospinning, subsequent deacetylation to cellulose, and carbonization. I report the technologically simple and environmentally friendly method of CNF synthesis from cellulose that improves carbon yield from 13% to 20% and significantly reduces the regeneration step. The obtained CNF sheets are mechanically stable, have hydrophobic surface and consist of nitrogen-doped randomly oriented nanofibrous network.
Moreover, I demonstrate the prospect of effective using of several modified types of CNF-based materials as electrodes in supercapacitors. Incorporation of highly conductive carbon nanotubes (DWCNTs, MWCNTs and cvd CNTs) and reduced graphene oxide (rGO) into CNF frameworks improves electrical conductivity and increases the surface area of the produced composite materials, which leads to high specific capacitance values (up to 241 F/g), cyclic stability, and power density of these materials. Despite their slightly lower specific surface area in comparison with pristine CNFs, nitrogen-doped CNF materials (4-5.6 at.% of nitrogen) had about 2.5 times higher specific capacitance due the positive effect of pseudocapacitance. These results suggest that cellulose is a suitable precursor for the synthesis of sustainable and efficient carbonaceous electrodes for supercapacitors. Functionalization methods used in this study proved to be helpful in enhancing the electrochemical performance of carbonized cellulose materials.
In connection with the second problem, biocompatible and electrically conductive nanostructures are viewed as very prospective scaffolds in tissue engineering (TE) field. TE approach can help to cure neurodegenerative diseases of elderly population via development of healthy replacement neural tissues or in vitro models for drug testing. Cellulose-derived biomaterials are assessed as scaffolds for the growth of neural tissue. These scaffold materials are characterized with excellent biocompatibility, nanosized topography and electrical conductivity to support adhesion, growth and differentiation of SH-SY5Y neuroblastoma cells. Possibility of using inks from nanofibrillated cellulose for 3D printing allows even more effective assembly of designed conductive patterns for cell guidance. The results show prolific cell attachment, proliferation and differentiation of neural cells along the guidelines.
In overall, the positive implementation of the cellulose-derived nanofibrous materials in the above mentioned applications suggest that the synthesis of sustainable and efficient materials based on renewable resources is a very prospective approach. Such materials should play a major role in our future effort to satisfy the increasing demand on functional high-tech products.
Keywords: cellulose, nanofibrillated cellulose, electrospinning, carbon nanofibers, carbon composites, 3D printing, energy storage, neural tissue engineering
Plats: MC2, Kemivägen 9, Kollektorn