Charge-Based Molecular Separation Using Conical Nanopores in SiO ₂ Membranes

Membrane-based charge-selective separation is emerging as an excellent platform for the separation of 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. However, existing membrane technologies often struggle to achieve such a high performance. This work demonstrates the use of uniform conical nanopores in SiO 2 membranes as a charge-based molecular separation platform. The conical nanopores were fabricated by using the ion-track etching technique. The native negative surface charge of the SiO 2 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 charge. Negatively charged nanopore membranes transport positively charged molecules up to 36 times more efficiently than negatively charged molecules. In contrast, positively charged membranes transport negatively charged molecules approximately 20 times more efficiently than positively charged ones. Furthermore, these membranes demonstrate effective charge-based molecular separation capabilities, successfully isolating oppositely charged molecules from mixed solutions.