Temperature-sensitive gold-nanotube array membranes modified with poly( N -isopropylacrylamide)

A kind of temperature-sensitive nanotube array membrane was developed by modifying gold-nanotube array membranes with poly(N-isopropylacrylamide) (PNIPAm). The permeation ability of the membranes at different temperatures was investigated using sodium fluorescein and quantum dots as probes. The results showed that the pore diameter of nanotube was changed due to the reversible response of PNIPAm-modified membranes to temperature, and then the permeation ability of the membranes was changed. The permeation of fluorescence probes was slow and even almost blocked at 25°C (below the lower critical solution temperature, LCST), since PNIPAm formed expanded structures and decreased the pore size. While at 40°C (above the LCST), the permeation was increased, since PNIPAm became compact structures and the pore diameter was increased. Furthermore, the permeation ability of the temperature-sensitive nanotube array membranes could be adjusted reversibly and it is possible to use the membranes in nanofluidic devices, nanogates, etc. Supported by the National Key Basic Research Program of China (Grant No. 2002CB513110), Key Technologies Research and Development Program of China (Grant Nos. 2003BA310A16 and 2005EP090026), Key Project of International Technologies Collaboration Program of China (Grant No. 2003DF000039), and National Natural Science Foundation of China (Grant Nos. 90606003, 20475015 and 20620120107)