Dynamic perspective on the function of thermoresponsive nanopores from in situ AFM and ATR-IR investigations.
This article describes the morphological and chemical characterization of stimuli-responsive functionalized silicon surfaces provided in parallel by atomic force spectroscopy (AFM) and Fourier transform infrared spectroscopy (FT-IR) enhanced by the single-beam sample reference attenuated total reflection method (SBSR-ATR). The stimuli-responsive behavior of the surfaces was obtained by grafting-to in melt carboxyl-terminated poly-N-isopropylacryl amides (PNIPAAM) with different degree of polymerization (DP) on epoxide-functionalized silicon substrates. The unprecedented real time and in situ physicochemical insight into the temperature-triggered response of the densely packed superficial brushes allowed for the selection of a PNIPAAM with a specific DP as a suitable polymer for the fabrication of silicon membranes exhibiting switchable nanopores. The fabrication process combines the manufacture of nanoporous silicon surfaces and their subsequent chemical functionalization by the grafting-to in melt of the selected polymer. Then, relevant information was obtained in what concerns the chemical modifications behind the topographical changes that drive the functioning of PNIPAAM-based hybrid nanovalves as well as the timescale on which the opening and closing of the nanopores occur.
Popa
Ana Maria
AM
Centre Suisse d'Electronique et de Microtechnique SA, Rue Jaquet Droz 1, CH-2000 Neuchâtel, Switzerland. ana-maria.popa@empa.ch
Angeloni
Silvia
S
Bürgi
Thomas
T
Hubbell
Jeffrey A
JA
Heinzelmann
Harry
H
Pugin
Raphaël
R
D018625:Microscopy, Atomic Force / Q000379:methods*; D058608:Nanopores; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013499:Surface Properties