Electrochemical techniques are used to investigate a variety of novel and natural cellulose materials. Novel cellulose architectures are formed using electrodeposition of cellulose microfibrils (from spruce tree) and by the layer-by-layer deposition or solvent casting of cellulose nanofibrils (from sisal). Pure cellulose (with a crystal structure of cellulose-I) constitutes the majority of all architectures, however additional properties were incorporated via the addition of polymers (polydiallyldimethylammonium chloride, chitosan), nanoparticles (TiO2) or binding molecules (boronic acid dendrimer). Cotton fabric, a natural form of cellulose, was also investigated via the physical attachment to the electrode surface of graphite flake modified cotton samples using a course lycra membrane. All samples are characterised using a combination of scanning electron microscopy, atomic force microscopy and small and wide angle x-ray scattering.
The absorption, diffusion and detection of charged species in cellulose materials is studied using voltammetry under aqueous conditions. Firstly, architectures are probed using charged metal species like Fe(CN)63-/4- and Ru(NH3)3+/2+ in order to construct a model of diffusion and absorption. Later, target analytes such as environmental molecules (triclosan, sodium dodecylsulfate) and physiological type molecules (alizarin red S) are detected within a typical range of 10-6 – 10-3 M. Approximations of Fick’s Laws are used to calculate membrane diffusion co-efficients. Langmuir type binding is assumed and the binding of species in the cellulose architectures is quantified.
The reactivity of molecules in cellulose matrices is studied. Methyl viologen (MV2+/+) is shown to form aggregates in when partitioned in a cellulose environment. Methemoglobin undergoes a novel demetallation when in a charged nanocellulose-TiO2 matrix. The reactivity of a well-known catalase model system, the dinuclear manganese metal complex [Mn(IV)2(μ-O)3L2](PF6)2 (with L = 1,4,7-trimethyl-1,4,7-triazacyclononane), is shown to be affected by the presence of a cellulose matrix.
|Date of Award||1 Sept 2008|
|Sponsors||Unilever Research and Development UK|
|Supervisor||Frank Marken (Supervisor)|