Structural and morphology of silver-crosslinked chitosan thin films for SPR sensor

Abstract

Purpose – This purpose of this study is to investigate the structural and morphology of hybrid silver-crosslinked chitosan thin films potentially for surface plasmon resonance (SPR) sensor application. Silver, silver-chitosan and silver-crosslinked chitosan (annealed) thin films also were prepared as controls for this study. Design/methodology/approach – Silver was firstly coated on top of the glass substrate by magnetron sputtering method. Different chitosan solutions (with and without glutaraldehyde) were coated on top of the substrate by spin coating method. Annealing treatment was carried out for one of silver-crosslink chitosan sample. The structural and morphology of all the thin films were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The SPR curves also were measured by the SPR sensor with air and deionised (DI) water as analytes. Findings – The structure of silver-crosslinked chitosan thin film presented a monoclinic structure with high crystallinity of 131.71 nm at the prominent peak by XRD analysis. The FESEM and AFM analyses revealed the morphology to be rough in surface attributed to enhanced contact with analytes in SPR measurement compared to other thin films. Research limitations/implications – In the present study, the glutaraldehyde used to crosslink the thin film increased hydrophobicity and allows for more binding capacity. Originality/value – The proposed silver-crosslinked chitosan thin film may prove beneficial for biosensing such as in environmental applications by SPR sensor.