Abstract
The development of smart nanomaterials has attracted great attention in several fields like nanoscience and nanotechnology due to their unique response to external stimuli. Many of them are based on polymers that can exhibit a shape-changes when submitted to environmental modifications. Poly(N-isopropylacrylamide), PNIPAM, is a thermo-responsive polymer. Linear chains are water soluble at room temperature but undergo a reversible coil-to-globule transition at a lower critical solution temperature (LCST) close to 32°C due to the dehydration and subsequent collapse of its chains into compact globules. [1] This phenomenon results in a volume phase transition (VPT) in PNIPAM based crosslinked microgels and can be used to promote original thermal effects.Hybrid nanocomposite microgels associating PNIPAM and gold nanoparticles (GNP) have thus been designed in order to take advantage of the outstanding plasmonic and photo-thermal properties of GNP to promote the VPT of the microgels through an efficient photo-thermal conversion. [2] With their strong diameter-dependent optical absorption in the near infrared (NIR) and their large surface area favoring photo-thermal transfer, semiconducting single-walled carbon nanotubes (s-SWNT) are also good candidates for photo-thermal conversion in the NIR (Figure 1a). However, to the best of our knowledge, no thorough studies of nanomaterials based on both SWNT and PNIPAM have been reported so far.Here we describe the preparation of SWNT/PNIPAM hybrid microgels through a non-covalent functionalization technique. These nanoparticles are stable in water and show a VPT, which can be promoted either by direct heating or by excitation of the resonant absorption of s-SWNT in the NIR (Figure 1b-c). The photoluminescence (PL) signal can be used to monitor the VPT by a redshift observed when crossing the LCST, while the Raman signatures remain essentially the same.