Ultrathin membrane for separating nanoparticles, protein

A joint research team from Saudi Arabia, Qatar and China has synthesized free-standing, nanoporous, ultrathin silica membranes that can separate particles at the nanometre scale — membranes with the potential to make a wide variety of filter devices¹. 

Using a reaction system that contains oil and water, the scientists prepared the thin membranes on a silicon wafer. The membranes themselves have average thickness of 50 nm with vertically aligned nanochannels whose size can be tuned.

“This work paves a promising way to develop new membrane devices with well-defined pore diameters for highly efficient separation at the macroscale,” says co-corresponding author Wei Li from the Fudan University, China. The team also included researchers from the Qatar University, Qatar, and King Saud University, Saudi Arabia.  

Nanofilters made of the silica membranes showed excellent size-selective separation power for gold nanoparticles mixtures, ovalbumin and cytchrome c proteins. 

The small gold nanoparticles (5 nm) and cytochrome c molecules could pass freely through the silica membranes while large gold nanoparticles (15 nm) and ovalbumin were almost completely blocked. 

Sophisticated imaging techniques show that the membranes are continuous and smooth without any cracking. Besides silicon wafer, they can be transferred onto various substrates such as glass and indium-tin-oxide-coated glass.

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