• Dynamic Perspective on the Function of Thermoresponsive Nanopores from in Situ AFM and ATR-IR Investigations
    A.M. Popa, S. Angeloni, T. Bürgi, J.A. Hubbell, H. Heinzelmann and R. Pugin
    Langmuir, 26 (19) (2010), p15356-15365
    DOI:10.1021/la102611k | unige:14783 | Abstract | Article HTML | Article PDF
 
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.
  
  • Probing Chiral Nanoparticles and Surfaces by Infrared Spectroscopy
    C. Gautier, M. Bieri, I. Dolamic, S. Angeloni, J. Boudon and T. Bürgi
    Chimia, 60 (11) (2006), p777-782
    DOI:10.2533/chimia.2006.777 | unige:14749
Chiral metal surfaces and nanoparticles have the potential to be used for the selective production, the resolution and the detection of enantiomers of a chiral compound, which renders them highly attractive in view of the tremendous consequences of homochirality on earth. Their capability to distinguish between enantiomers of a chemical compound relies on their structure and the ability to form intermolecular interactions. However, molecular-level understanding of the interactions that are at the origin of enantiodiscrimination is lagging behind due to the lack of powerful experimental techniques that are able to spot these interactions selectively with high sensitivity. In this article two techniques based on infrared spectroscopy are presented that are able to selectively target the chiral properties of nanoparticles and interfaces. These are the combination of attenuated total reflection infrared (ATR-IR) with modulation excitation spectroscopy (MES) to probe enantiodiscriminating interactions at chiral solid-liquid interfaces and vibrational circular dichroism (VCD), which is used to probe the structure of chirally modified metal nanoparticles.

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