Surfactant monolayers:

  We are exploring both fundamental and applied aspects of surfactant monolayers, with an emphasis on controlling phase-separation of mutually immiscible surfactants to control surface patterning.  A recent emphasis has been developing a fundamental understanding of thermodynamic and chemical factors that control phase-separation in mixtures of hydrogenated and perfluorinated surfactants.  While this work is primarily of a fundamental nature, potential applications include the development of lung surfactant formulations and patterning of photoactive materials.

  We have recently begun investigating the application of novel gemini surfactants for agricultural applications, including the controlled delivery of inorganic ions and small molecules.

AFM image of phase-separated arachidic acid-perfluorotetradecanoic acid monolayer
(10 mm x 10 mm). From: Qaqish et al. Langmuir, 2007

Noncoherent photon upconversion:

  Noncoherent photon upconversion (NCPU) is a photophysical process in which two low-energy photons can be combined to yield one higher energy photon or excited state.  This process has the potential to improve incident photon to electron conversion efficiencies in photovoltaic devices (solar cells).

  We are exploring NCPU that occurs through photoexcited triplet-triplet annihilation processes in organic molecules.  Goals include understanding and ultimately improving the efficiency of the NCPU process through control of molecular aggregation states.  This work is part of a national and international collaborative effort aimed at improving photovoltaic conversion efficiencies.

Jablonoski diagram illustrating the spectroscopic principle of TTA-based NCPU.

Energy transfer using single-molecule fluorescence spectroscopy:

  The use of high-sensitivity imaging tools has given researchers the ability to measure fluorescence emission from individual molecules.  We use single-molecule fluorescence spectroscopy as a useful complementary tool for probing the spectroscopy and photophysics of energy transfer processes; measuring properties of individual molecules can provide insight into photophysical processes that is not easily accessible through ensemble measurements alone.  We have used these approaches in a number of systems in which intra- and in some cases, intermolecular energy transfer is important and regulates the observed spectroscopic output of molecules.

Single-molecule fluorescence trajectory from labeled Au nanoparticle.  From:

Lu et al. JPC-C, 2008

Matthew F. Paige, Department of Chemistry, University of Saskatchewan, Email:  matthew.paige@usask.ca