Design and Optical Properties of Thermoswitchable Hybrid Plasmonic Nanostructures
Prof. Nordin Félidj
Laboratoire ITODYS, Université Paris Diderot, CNRS UMR 7086, 75013 Paris, France
17:00 - 18:00 Tuesday 09 December 2014 KFU HS 5.01 The combination of an inorganic nanomaterial with soft matter can give access to an interesting class of hybrid structures yielding new properties. For example the stimuli-responsive character of the soft component can drastically modify the electrical, magnetic, optical or catalytic properties of the inorganic component. If the hybrid system is made of gold or silver nanostructures coated with stimuli-responsive polymer, the plasmonic properties of this system can be dynamically and reversibly modified or switched provided that an external stimulus (pH, temperature, electrical conductivity…) modifies the physical or chemical properties of the polymer.
In this presentation, we will focus on the design and study of a novel type of hybrid system consisting of lithographic gold nanorods (GNR) coated with a thermosensitive polymer based on poly(N-isopropylacrylamide) (pNIPAM) - GNR@pNIPAM. The atom transfer radical polymerization method is used to graft the thermosensitive polymer, and control its thickness. The change of thickness of polymer brushes grafted on the gold nanorods arrays is measured using atomic force microscopy (AFM) in water as a function of temperature (from 25 to 42 oC). The temperature-dependent optical properties (i.e. the localized surface plasmon resonance, or LSPR) of this hybrid system are also monitored. The LSPR variations result from local refractive index changes due to a phase transition from a hydrophilic state (swollen regime) to a hydrophobic state (collapsed regime) of the polymer chains. Besides their use as an efficient optical reporter of the polymer state in a controlled and reversible manner (with LSPR shifts up to 30 nm), the GNR@pNIPAM structures appear to be of primary importance for applications spanning from surface enhanced spectroscopies to nanoscale adhesion and environmental sensing.
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