Characterization of Adsorption Behavior of Sucrose Monolaurate on Gold Substrate Using the Quartz Crystal Microbalance (QCM). Issue 4 (4th May 2016) - Kwek, Jin W.
Abstract: One class of biodegradable surfactants, sucrose fatty acid esters (SEs), has attracted wide interest in the food and cosmetic industries due to their excellent biocompatibility, biodegradability and lower pH‐ and temperature‐sensitivity. The objective of this study was to evaluate the adsorption behavior of pure sucrose monolaurate (SML) at the solid–liquid interface as a function of concentration, 0.02–0.5 % w/w, and medium pH, as these can be the pre‐determinants of their performance. The quartz crystal microbalance (QCM), an effective and versatile surface adsorption tool with customizable surfaces, was used for the first time in real‐time characterization of the adsorption behavior. Adsorption was fast, between 1 and 3 min, with a typical one‐step monolayer adsorption mechanism occurring at most concentrations and medium pH used, thus justifying the application of the Sauerbrey equation to determine the deposited mass. The adsorption isotherm was likely Langmuirian and the SML deposition on gold was significantly higher, at and beyond 0.1 % w/w, in de‐ionised water (pH 6.9) than in aqueous buffer (physiological pH 5.5) due to the interaction of water molecules with the adsorbed layer. The results from this work highlight the importance of media for studying the adsorption behaviors of SEs and serve as a reference for future investigations on different functionalized surfaces.