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A series of nonionic amphiphiles derived from polyglycerol dendrons were studied for their ability to solubilize and isolate single-walled carbon nanotubes. The amphiphiles possessed differently sized polar head groups, hydrophobic tail units, and various aromatic and non-aromatic groups between the head and tail groups. Absorbance analysis revealed that amphiphiles with anchor groups derived from pyrene were far inferior to those that possessed simple linear aliphatic tail groups. Absorbance and near-infrared fluorescence analyses revealed a weak dependence on the dendron size of the head group, but a strong positive trend in suspended nanotube density and fluorescence intensity for amphiphiles with longer tail units. Variations in the moieties linking the head and tail groups led to a range of effects on the suspensions, with linkers imparting flexibility and a bent shape that gave improved performance overall. This was illustrated most dramatically by a pair of benzamide-containing amphiphiles, the para isomer of which showed evidence in the fluorescence data of increased nanotube aggregate formation when compared with the meta isomer. In addition, statistical AFM was used to illustrate more directly the microscopic differences between amphiphiles that were effective at nanotube bundle disruption and those that were not.

We use three alkyl-polyglycerol derivatives to suspend singlewalled carbon nanotubes. The molecules differ by the aromatic moieties between the alkyl tail and the polyglycerol head. The suspended nanotubes are analysed by photoluminescence spectroscopy. We observe a dependence of the luminescence intensity and hence nanotube abundance on the aromatic moieties. Interestingly, the strength of interaction depends on the nanotube families.

Aqueous dispersions of carbon nanotubes (CNTs) were obtained by noncovalent adsorption of an azobenzene derivative carrying polyglycerol dendric structures. UV/Vis absorption spectra and photoluminescence maps were recorded to confirm successful nanotube debundling and suspension. Comparison to dispersion of nanotubes using sodium dodecyl sulfate (SDS) revealed shifts of the nanotube E22 excitation peaks from 28 to 67 meV as well as shifts from 21 to 37 meV of the E11 emission peaks.

Tin–titanium solid solutions at increasing Ti molar fraction, x = 0.1, 0.3, 0.5, 0.7 and 0.9, were prepared by symplectic gel co-precipitation (SGC) method from stoichiometric hydroalcoholic solutions of Ti and Sn metalalkoxides. Structural, spectroscopic and electrical analyses were performed and the results have been correlated. The peaks of the XRD patterns change from the positions of SnO 2 cassiterite to those of TiO 2 rutile, when increasing the Ti content in the solid solution. Photoluminescence (PL), FT-IR and UV–vis-NIR characterizations are in agreement with the formation of solid solutions: PL peak falls either in the visible or IR region, depending on the Ti content in the solid solution; FT-IR spectra reveal a progressive upward shift of the high-frequency absorption edge of the skeletal vibration modes from the value of SnO 2 to one of TiO 2 on increasing the Ti content; UV–vis-NIR spectra reveal a progressive downward shift of the VB–CB absorption edge on increasing Ti content. The changes induced by CO interaction at increasing temperature in the FT-IR and UV–vis-NIR spectra revealed a different behaviour of the materials following the Ti content: for the lowest Ti molar fraction ( x = 0.1) as well as for SnO 2 the reduction gives rise to mono-ionized oxygen vacancies, for the other solid solution the loss of reticular oxygen gives rise to doubly ionized oxygen vacancies and to Ti 3+ ions. From the electrical-conductance point of view, two groups of films can be identified: pure SnO 2 and the solid solution with x = 0.1, and all the other solutions including pure titania, in agreement with the results of FT-IR investigations. The best response to carbon monoxide was achieved by the solutions with x = 0.3 and x = 0.5. Opposite to electrical properties, exhibiting good responses to reducing gases, these agents did not appreciably modify the PL yield of the solid solutions. Conversely, PL emissions were sensitive to NO 2 , particularly for Ti 0.5 Sn 0.5 O 2 .

Here we present our results on the optimization of a nanometallic-carbon nanotubes plasmonic hybridization process to enhance the photoluminescence quantum yield of single walled carbon nanotubes. Swelling the micelles containing the hybrids through an organic solvent improves the matching between the hybrids constituents; the optimized hybrids exhibit enhancement of the emitted photoluminescence without affecting the physical mechanisms involved in the exciton-plasmon coupling process.

We report the properties of perylene-nanotube complexes that form efficient energy transfer systems. Most perylene-derivatives yield similar ratios between transfer and direct luminescence (0.66 ± 0.04). The photoluminescence spectra of the free compounds and the transfer complex are similar indicating that perylene and nanotubes act as separate systems. A further increase in interaction yields 40% higher transfer rates and luminescence excitation spectra that indicate a change in stacking of the perylene on the nanotube wall. All measurements are consistent with a transfer mechanism based on a dipole-dipole interaction at a distance much smaller than the Förster radius.

Aiming to enhance the luminescence yield of carbon nanotubes, we introduce a new class of hybrid nanoplasmonic colloidal systems (π-hybrids). Nanotubes dispersed in gold nanorod colloidal suspensions yield hybrid structures exhibiting enhanced luminescence up to a factor of 20. The novelty of the proposed enhancement mechanism relies on including metal proximity effects in addition to its localized surface plasmons. This simple, robust and flexible technique enhances the luminescence of nanotubes with chiralities whose enhancement has never reported before, for example the (8,4) tube.

Surfactants are needed to create stable suspensions of carbon nanotubes. Increasingly, these surfactants are given additional functionalities, resulting in bigger and more complex molecules with several subunits. We investigate the effect of assembly of these subunits for a class of perylene- based functional surfactants. The subunits that all surfactants are based on are a perylene core, hydrophilic polyglycerol dendrons, and alkyl chains of different orientations and lengths. The assembly of these subunits affects both the molecules' performance as a surfactant and the efficiency of the energy-transfer complexes formed by the nanotube and surfactant through a π–π stacking mechanism. This results in a best practice guide for designing functional surfactants with π–π stacking cores, and affords more general insights that are applicable to non π–π stacking systems as well.

The non-covalent functionalization of carbon nanotubes with spiropyran molecules, serving as optically addressable dipole switches, is reported. Two kinds of pyrene–spiropyran-based dyads with spacers of different lengths resulting in different switch–tube distances were investigated. While both surfactants were able to form stable carbon nanotube suspensions, the different distances between the switch and the tube affected both of the components’ optical properties. In the case of the shorter spacer, the nanotubes’ luminescence as well as the merocyanine absorption band were red- shifted and furthermore, the rate of the merocyanine → spiropyran thermal back isomerization was decreased.

A functional surfactant designed to solubilize and individualize nanotubes efficiently in aqueous media and to form energy transfer complexes with the carbon nanotubes through π–π stacking is presented. Upon excitation of the adsorbed perylene unit an emission from the nanotubes is observed that indicates a successful excitation transfer. The efficiency of the indirect excitation via the adsorbant is of the same order of magnitude as the direct excitation of the nanotubes. Under optimized preparation conditions the pH independent perylene-imido-diester compound isolates and solubilizes carbon nanotubes in biocompatible aqueous environments without additional surfactants. The resulting solutions are stable over many months.

Single-walled carbon nanotubes (SWCNTs) are functionalized with a spiropyran derivative, which is attached non-covalently to the SWCNT’s sidewall via a pyrene anchor group. Using this non-covalent functionalization strategy, individual SWCNTs can be stabilized in solution without the need for additional surfactants. Bright luminescence confi rms the presence of individual tubes in the thus-prepared samples. In these samples, the majority of pyrene-spiropyran molecules are attached to the walls of the SWCNTs. Upon complex formation with the SWCNT, the switching moiety retains its ability to switch, i.e., to undergo reversible transformations between the closed spiropyran and the opened merocyanine form, and is stable over many cycles of operation.

Stimulus responsive surfactants based on dendritic glycerol azobenzene conjugates were used to solubilize and debundle single-walled carbon nanotubes in aqueous media. Their debundling property as well as their reaggregation behavior upon irradiation with light was examined and light triggered reversible bundling and precipitation are shown.

Carbon nanotubes (CNTs) were solubilized using akyl/polyglycerol amphiphiles. Similar cosurfactants, bearing different aromatic moieties between head and tail, were added to these samples. The interaction strength between these amphiphiles and CNTs changes depending on the inserted aromatic moieties. The insertion of a phenyl ring allows the amphiphile to replace the starting one indicating a higher interaction strength, while the insertion of a triazol pentagon does not, suggesting that the interaction strength is lower. The replacement was monitored via PLE mapping.

The crystallization of silicon rich hydrogenated amorphous silicon carbon films prepared by Plasma Enhanced Chemical Vapor Deposition technique has been induced by excimer laser annealing as well as thermal annealing. The excimer laser energy density (Ed) and the annealing temperature were varied from 123 to 242 mJ/cm2 and from 250 to 1200 °C respectively. The effects of the two crystallization processes on the structural properties and bonding configurations of the films have been studied. The main results are that for the laser annealed samples, cubic SiC crystallites are formed for Ed ≥ 188 mJ/cm2, while for the thermal annealed samples, micro-crystallites SiC and polycrystalline hexagonal SiC are observed for the annealing temperature of 800 and 1200 °C respectively. The crystallinity degree has been found to improve with the increase in the laser energy density as well as with the increase in the annealing temperature.

We present a joint theory-experiment study investigating the excitonic absorption of spiropyran-functionalized carbon nanotubes. The functionalization is promising for engineering switches on a molecular level, since spiropyrans can be reversibly switched between two different conformations, inducing a distinguishable and measurable change of optical transition energies in the substrate nanotube. Here, we address the question of whether an optical read-out of such a molecular switch is possible. Combining density matrix and density functional theory, we first calculate the excitonic absorption of pristine and functionalized nanotubes. Depending on the switching state of the attached molecule, we observe a red-shift of transition energies by about 15 meV due to the coupling of excitons with the molecular dipole moment. Then we perform experiments measuring the absorption spectrum of functionalized carbon nanotubes for both conformations of the spiropyran molecule. We find good qualitative agreement between the theoretically predicted and experimentally measured red-shift, confirming the possibility for an optical read-out of the nanotube-based molecular switch.