Kinetic insight on the long-range exclusion of dissolved substances by interfacial interactions of water and hydrophilic surface

• The long-range exclusion of dissolved substances with small molecular weights near hydrophilic surface has been verified. • Surface hydrophilicity and solution concentration determine not only EZ occurrence, but also its size at equilibrium. • The proposed UV/Vis spectrophotometric method is applicable for the EZ characterization in optical transparent solutions. Exclusion-zone (EZ) phenomenon generally refers to a long-range exclusion of particles at the interface between a hydrophilic surface and a bulk aqueous solution. Although the rejection of dissolved substances such as dyes and ions has previously been reported, it is still disputable till now due to the limitation of the optical microscopic observation. The controversy on the solute exclusion not only leads to significant divergence on our understanding of the EZ formation mechanisms, but also constrains the application of EZ phenomenon in physical, chemical, biological, and environmental processes. Therefore, here we propose a UV/Vis spectrophotometric method to clarify the occurrence of solute exclusion in the presence of hydrophilic surface. The consistence of the microscopic and UV/Vis spectrophotometric results in both particles and solutes proves that the UV/Vis spectrophotometric method is suitable for the quantitative characterization of the EZ formation process. Through this spectrophotometric method, we found the exclusion of particles and solutes with different exclusion behavior near hydrophilic surface. We expect this work will provide a different insight in understanding the underlying mechanisms for EZ formation and the long-range interactions between water and hydrophilic surface, as well as the possible application of this exclusion phenomenon in relevant fields.