The development of smart nanomaterials has attracted great attention in several fields like nanoscience, materials science,engineering and nanotechnology due to their unique response to external stimuli. Many of them are based on polymers thatcan exhibit great shape-changes when submitted to environmental modifications. Poly(N-isopropylacrylamide), PNIPAM, is sucha thermo-responsive polymer. It is water soluble at room temperature, forming gels by cross-linking but undergoes a reversiblecoil-to-globule volume phase transition (VPT) at a lower critical solution temperature (LCST) close to 32 °C due to thedehydration and subsequent collapse of its chains into compact globules.
Hybrid nanocomposite microgels associating PNIPAM and gold nanoparticles (GNP) have been designed in order to takeadvantage of the outstanding plasmonic and photo-thermal properties of GNP to promote the volume phase transition of themicrogels through an efficient photo-thermal conversion. With their strong diameter-dependent optical absorption in the nearinfrared (NIR) and their large surface area favoring photo-thermal transfer, semiconducting SWNT (s-SWNT) are goodcandidates for photo-thermal conversion in the NIR and may therefore be used to prepare multi-responsive hybrid microgels(Figure 1). However, to the best of our knowledge, no thorough studies of such nanomaterials have been reported so far.
Here we report the preparation of smart SWNT/PNIPAM nanocomposites through non-covalent functionalization techniques.These SWNT/PNIPAM hybrid microgels are stable in water and show a VPT, which can be promoted either by direct heating orby excitation of the resonant absorption of s-SWNT in the near infrared. Furthermore, the photoluminescence (PL) signal of s-SWNT is modulated at the phase transition and therefore, the PL signal can be used to monitor the VPT. This is illustrated inFigure 2, showing coupled Raman/PL measurements below and above the LCST, where a redshift of the PL bands is observedwhen crossing the LCST while the Raman signatures remain essentially the same.

Temperature is one of the basic parameters often required to characterize a system. A great demand has arisen for localmeasurements, especially in liquids or complex biological environments. Various approaches have been proposed to study thetemperature at the nano-scale level. Some of them are based on the spectroscopic properties of carbon nanotubes (CNT) usedas sensors.
Raman spectroscopy is indeed a powerful technique to identify single-walled carbon nanotubes (SWNT) and to study theirstructure, defects and electronic properties through the measurement of specific Raman signatures (RBM, D, G and 2D bands).On the other hand, individual SWNT or small bundles emit light in the near infrared and the photoluminescence (PL) spectra isvery sensitive to the quality of the dispersion and the dielectric environment of the nanotubes. In particular, when SWNT aredispersed in aqueous solutions, the PL energies are sensitive to the nature of the surfactants or polymers, to theirconcentration, and to the way they adsorb on/wrap around the nanotubes.
In this work we show that the PL/Raman spectra of SWNT dispersed with sodium dodecyl sulfate (SDS) is very sensitive to thetemperature (figure 1) in a large range of SDS concentrations. We discuss the influence of the chiral angle of the SWNT onthese PL changes, and the origin of the changes in terms of SDS reorganization at the surface of the nanotubes. Similarchanges are obtained with increasing laser power (figure 2), showing the local heating of the nanotubes. These results pavethe way for the development of SWNT-based nano-thermometers.

Downsizing electronic and electric equipment requires the optimization of electric field distributions in order to avoid localized dielectric breakdown (also called partial discharges). This paper presents a novel dielectric composite material aimed at grading electrical local surface stress. This functional material has a conductivity which increases by several orders with the applied electric field giving the ability to distribute the field by itself. It is prepared for the first time by dispersing graphite nanoplatelets in a polymer and may be used as a resistive or capacitive field grading material in electronic and electrical applications. Mechanisms at the origin of the nonlinear behavior are discussed.

Pesticide sensing is an important object of study due to its increasing use worldwide. Herein, we report a SERS study of 4-nitrophenol (PNP), which is product of neutralization processes of various pesticides such as Paraoxon, and can be used as a target molecule for monitoring. PNP is also widely used in the chemical industry and due to its high toxicity is considered a concerning pollutant. The sensing was carried out with a reduced graphene oxide nanocomposite functionalized with cysteamine and Ag nanoparticles (rGOSHAg), and compared with raw reduced graphene oxide and a commercial SERS substrates (SERStrate (TM)). A mechanistic evaluation was also carried out, focused in the degradation of PNP caused by the different exciting laser lines, evidencing the PNP dimerization in substrates containing Ag NPs (under 532 nm laser), which has important outcomes for sensing purposes. The nanocomposite rGOSHAg presented the highest sensitivity towards PNP, detecting concentrations as low as 10(-6) mol L-1 and with a high potential for field applications and real-time measurements of molecules commonly present in pesticides and industrial contaminants.

PNIPAm microgels synthesized via free radical polymerization (FRP) are often considered as neutral colloids in aqueous media, although it is well known, since the pioneering works of Pelton and coworkers, that the vanishing electrophoretic mobility characterizing swollen microgels largely increases above the lower critical solution temperature (LCST) of PNIPAm, at which microgels partially collapse. The presence of an electric charge has been attributed to the ionic initiators that are employed when FRP is performed in water and that stay anchored to microgel particles. Combining dynamic light scattering (DLS), electrophoresis, transmission electron microscopy (TEM) and atomic force microscopy (AFM) experiments, we show that collapsed ionic PNIPAm microgels undergo large mobility reversal and reentrant condensation when they are co-suspended with oppositely charged polyelectrolytes (PE) or nanoparticles (NP), while their stability remains unaffected by PE or NP addition at lower temperatures, where microgels are swollen and their charge density is low. Our results highlight a somehow double-faced electrostatic behavior of PNIPAm microgels due to their tunable charge density: they behave as quasi-neutral colloids at temperature below LCST, while they strongly interact with oppositely charged species when they are in their collapsed state. The very similar phenomenology encountered when microgels are surrounded by polylysine chains and silica nanoparticles points to the general character of this twofold behavior of PNIPAm-based colloids in water.

When a microparticle is trapped at a fluid interface, particle's electrical charge and weight combine to deform the interface. Such deformation is expected to affect the particle diffusion via hydrodynamics boundary conditions. Using available models of particle-induced electrostatic deformation of the interface and particle dynamics at the interface, we are able to analytically predict particle diffusion coefficient values in a large range of particle's contact angle and size. This might offer a solid background of numerical values to compare with for future experimental studies in the field of particle diffusion at a fluid interface.