Self-Assembled Regenerated Cellulose Spacer Film in Thin Film and Generator-Collector Electrodes Anne Vuorema,* a, b Mika Sillanpää, a Marianna Vehviläinen, c Taina Kamppuri, c Pertti Nousiainen, c Wim Thielemans , d, e Frank Marken* b a Laboratory of Green Chemistry, Faculty of Technology, Lappeenranta University of Technology, Sammonkatu 12, FI-50130Mikkeli, Finland b Department of Chemistry, University of Bath, Bath BA27AY, UK c Department of Materials Science, Tampere University of Technology, P.O. Box 589, 33101 Tampere, Finland d School of Chemistry, University of Nottingham, Nottingham NG72RD, UK e Process & Environmental Research Division, Faculty of Engineering, University of Nottingham, Nottingham NG72RD, UK *e-mail: anne.vuorema@lut.fi; f.marken@bath.ac.uk Received: March 27, 2013 Accepted: April 26, 2013 Published online: June 10, 2013 Abstract Reconstituted cellulose spontaneously self-assembles at surfaces from an alkaline cellulose solution (ca. 1 wt%, pH 14, prepared with an enzymatic method from wood pulp) into porous films with approximately 300 nm thickness per layer, for example onto immersed tin-doped indium oxide (ITO) electrodes. Sequential multi-layer deposition allows control over the thickness of the assembled films. The hydrophilic properties of the cellulose film electrodes are utilised here (i) as dip-probe with capillary force picking up sample solution and (ii) as flow-through generator- collector probe, for example for future application in in situ chromatographic separation in end-column detection with nano-molar sensitivity. Keywords: Regenerated nano-cellulose, Double layer, Hydrophilicity, Electrochemistry, Voltammetry, Assembly, ITO, Junction, End-column sensor DOI: 10.1002/elan.201300141 1 Introduction Cellulose as a sustainable raw material with an estimated annual biomass production of approximately 1.5  10 12 tons [1] has many applications in traditional analytical chemistry and is the most common natural polymer [2]. Derivatives of cellulose have found a wide range of appli- cations in coatings, pharmaceuticals, foods, and in textiles. These applications take advantage of biocompatibility and its fibrous nature, which allows it to be spun into long fibres and networks. For applications in analytical science, there are benefits from inherent chirality for im- mobilization of proteins [3] and for enantiomer analysis [4]. Cellulose fibrils have also been investigated exten- sively to reinforce polymer composites and to prepare porous materials [5–7]. Natural cellulose has a complex nanoarchitecture, which can be disassembled down to its nanosized crystal- line components [6,8,9]. These rod-like nanoparticles can then be re-assembled into stable nano-cellulose films, 3D- porous materials or used as reinforcement of composite films [6,9–11]. Cellulose films electrodeposited from col- loidal solution have been used to modify and protect elec- trode surfaces [12]. Cellulose nanowhisker films have also been deposited by electrostatic layer-by-layer self-assem- bly with appropriate binders for sensor applications [13,14] by codeposition with electronically conducting polymers to form supercapacitor materials [15] and by drop-casting followed by drying [11]. Nano-cellulose has been used as a precursor for pyrolysed carbon, for exam- ple in nanocarbon-surface modified electrodes [13]. A recent review was published on the use of cellulose nano- whiskers in electrochemical applications [16]. In this report spontaneously self-assembled porous cel- lulose films on tin-doped indium oxide (ITO) electrodes are introduced. Upon immersion, the cellulose films de- posit freely in the form of layers directly from an alkaline cellulose solution prepared from wood pulp [17]. Cellu- lose is a polysaccharide which is made up of monomeric d-glucopyranose units [18]. The linear cellulose chains crosslink with each other by multiple hydrogen bonds using some of the available hydroxyl groups and Van der Waals interactions between planes of hydrogen bonded cellulose chains consistently along the molecule length. The free hydroxyl groups on the cellulose surface can in- teract with water molecules to result in hydration and give the film a hydrophilic nature [19]. The ability of the cellulose to absorb water into amorphous parts of the structure is well-known and has been exploited for exam- ple in paper-making [20], stabilisation of moisture sensi- Electroanalysis 2013, 25, No. 7, 1773 – 1779 # 2013 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim 1773 Full Paper