Charge-based molecular separation using conical nanopores in SiO2 membranes

Membrane-based charge selective separation is emerging as an excellent platform for separating biomolecules and nanoparticles. For efficient charge-selective molecular separation, thin membranes with a well-defined surface charge and a narrow pore size distribution are desirable. This work demonstrates the application of uniform conical nanopores in a SiO2 membrane as a cutting-edge charge-based molecular separation platform. The conical nanopores were fabricated using the ion-track etching technique. The native negative surface charge of the SiO2 membrane can be altered to a positive charge by attaching an aminosilane moiety. Our separation experiments demonstrate excellent separation efficiencies of molecules based on their charges. Negatively charged nanopore membranes transport positive molecules up to 48 times more efficiently than negative molecules. In contrast, positively charged membranes transport negative molecules approximately 15 times more efficiently than positive ones. Furthermore, these membranes demonstrate effective charge-based molecular separation capabilities, successfully isolating specific molecule types from mixed solutions.