This article shows the differentiation between water adsorbed outside of a single-walled carbon nanotube (CNT) and that confined inside. This distinction is made possible by tracking the electronic transport of a CNT-based field effect transistor constructed with an individual nanotube and exposed to controlled environments. The presence of water shifts the electrical neutrality point, indicating charge transfer between the nanotube and its environment. We identify three types of water molecules: (i) chemically adsorbed on the SiO2 surface, forming silanol groups, (ii) physically adsorbed outside the nanotube, and (iii) confined inside. The first type is eliminated only by high-temperature treatment under vacuum, while the latter two desorb at room temperature under moderate or high vacuum, i.e. 10-3 mbar. We observe that water confinement inside the nanotube is fast and thermodynamically favorable, with no qualitative influence from the metallicity of the nanotube.

In this article, we show that it is possible to differentiate between water adsorbed on the outside of a single-walled carbon nanotube and that confined inside. To this aim, we measured the electronic transport of a carbon nanotube based field effect transistor (CNTFET) constructed with an isolated single carbon nanotube subjected to controlled environments. More precisely, this distinction is made possible by observing the evolution of the transfer characteristic as a function of the electric field imposed by the gate voltage. It appears that the presence of water results in a displacement of the electrical neutrality point, corresponding to a charge transfer between the nanotube and its environment. Using this approach, we demonstrate the existence of 3 types of water molecules: (i) chemically adsorbed on the SiO2 surface of the substrate, i.e., forming silanol groups; (ii) physically adsorbed outside next to the nanotube; and (iii) confined inside the nanotube. The first one can only be eliminated by high temperature treatment under vacuum, the second one desorbs in a moderate vacuum at room temperature, while the confined water can be removed at room temperature at higher vacuum, i.e. 10^-3 mbar. We also observe that both water adsorption outside and water confinement inside the nanotube are spontaneous and rather fast, i.e. less than 1 minute in our experimental conditions, while removing the water adsorbed outside and confined inside takes much longer, i.e. 40-60 minutes, thus indicating that water confinement is thermodynamically favorable. It is also shown that the metallicity of the nanotube has no qualitative influence on its interaction with water. Our results experimentally prove the stronger affinity of water for the inner surface of CNT than for the outer one.

In this article, we conduct comparative studies on the optical properties of metallic carbon nanotubes. First, we compare the complex dielectric constant predicted by an analytical model, the linear surface conductivity model, with ab initio calculations based on density functional theory. We highlight the similarities and differences between these two models, with the major discrepancy being the significantly different behavior of the plasma frequency with respect to the carbon nanotube diameter. In the second step, we compare the predictions of these models with experimental measurements of the dielectric function. We demonstrate that the screened plasma frequency serves as a reliable quantifier for distinguishing between the two models. In conclusion, we find that the ab initio calculations more accurately describe the optical properties of metallic carbon nanotubes compared with the commonly used linear surface conductivity model.

Polarized fluorescence emission of nanoscale emitters has been extensively studied for applications such as bioimaging, displays, and optical communication. Extending the polarization properties in large assemblies of compact emitters is, however, challenging because of self-aggregation processes, which can induce depolarization effects, quenching, and cancellations of molecular dipoles. Here we use α-sexithiophene (6T) molecules confined inside boron nitride nanotubes (6T@BNNTs) to induce fluorescence anisotropy in a transparent host. The experiments first indicate that individual 6T@BNNTs exhibit a high polarization extinction ratio, up to 700, at room temperature. Using aberration-corrected HRTEM, we show that the fluorescence anisotropy is consistent with a general alignment of encapsulated 6T molecules along the nanotube axis. The molecular alignment is weakly influenced by the nanotube diameter, a phenomenon ascribed to stronger molecule-to-sidewall interactions compared to intermolecular interactions. By stretching a flexible thin film made of transparent polymers mixed with 6T@BNNTs, we induce a macroscopic fluorescence anisotropy within the film. This work demonstrates that the dyes@BNNT system can be used as an easy-to-handle platform to induce fluorescence anisotropy in photonic materials.

Photoluminescence of single-walled carbon nanotubes is monitored at the individual scale by molecule encapsulation into their hollow core. Depending on the electronic character (electron donor or acceptor) of the confined molecule, enhancement or quenching of the photoluminescence intensity is demonstrated. This behavior is assigned to a charge transfer, evidenced by the shift of the Raman G-band, and a correlated Fermi level shift shown by photoemission experiments. Our experimental results are supported by DFT calculations. A consistent picture of the physical interactions taking place in the hybrid systems and their effects on the optical and electronic properties is given. Our results indicate that the electron affinity or ionization potential of the encapsulated molecules and the diameter of the nanotube are relevant parameters to tune the light emission properties of the hybrid systems at the nanoscale.

The title paper [Spectrochim. Acta A 213 (2019): 391-396] reports an improvement of the "Poor Man's Kramers-Kronig analysis" and of the "Kramers-Kronig constrained variational analysis" thanks to an ad hoc modification of some analytical formulas existing in the literature. This ad hoc modification is not based on mathematical grounds. In this comment we show that no ad hoc modification is required but a correction of the analytical formula used by the authors of the title paper [Spectrochim. Acta A 213 (2019): 391-396]. (c) 2021 Elsevier B.V. All rights reserved.

The one-dimensional structure of single-walled carbon nanotubes (NT) display optical absorption and near-infrared emission (thanks to van Hove singularities). Chromophore encapsulation into host single-walled carbon nanotubes allows to create hybrid nano-systems with tunable opto-electronic properties. Up to now, we have been confining different kinds of chromophores,1-4 absorbing from the blue/ green (400/500 nm) range (tetracyanoquinodimethane (TNCQ), quaterthiophene derivatives (4T) and tetramethyl-paraphenylenediamine (TMPD)) to the red (700 nm) range (phthalocyanine (MPc)). In addition then can be either electron donor (4T, TMPD) or acceptor (TNCQ). In this study, we investigate, at both the macroscopic and the individual scales, the electronic and the optical properties of our hybrid systems by means of Raman and photoluminescence spectroscopies. Photoluminescence experiments clearly demonstrate changes on the emission properties after encapsulation. The intensities can be increased or reduced depending on the nature of the confined chromophores (electron donor or acceptor) and on the NT diameter. From Raman measurements, a significant charge transfer from the confined dye to the nanotube is evidenced. The main relevant parameters that govern the charge transfer are the nanotube diameter and the nature of the chromophores (electron donor or acceptor). Therefore, Raman and photoluminescence experiments strongly suggest charge transfer between the confined molecules and the nanotubes, leading to a Fermi level shift which governs the radiative de-excitation efficiency. References [1] L. Alvarez et al, J. Phys. Chem. C, 119, (2015), pp. 5203−5210 [2] Y. Almadori et al, J. Phys. Chem. C; 118, (2014), pp. 19462−19468 [3] A. Belhboub et al, J. Phys. Chem. C; 120, (2016), pp. 28802−28807 [4] Y. Almadori et al, Carbon 149, (2019), pp. 772-780

The polarized fluorescence emission of organic fluorophores has been extensively studied in photonics and is increasingly exploited in single molecule scale bio-imaging. Expanding the polarization properties of compact molecular assemblies is, however, extremely challenging due to depolarization and quenching effects associated with the self-aggregation of molecules into the sub-nanometer scale. Here we demonstrate that Boron Nitride Nanotubes (BNNTs) can act as a 1D host-template for the alignment of encapsulated a-sexithiophene (6T) inside BNNTs, leading to an optically active 6T@BNNT nanohybrid. We show that the fluorescence from the nanohybrid is strongly polarized with extinction ratios as high as 700 at room temperature. A statistical analysis of the 6T orientation inside BNNTs with inner diameter up to 1.5 nm shows that at least 80% of the encapsulated 6Ts exhibit a maximum deviation angle of less than 10{\deg} with respect to the BNNT axis. Despite a competition between molecule-molecule and molecule-BNNT adsorption in larger BNNTs, our results also show that more than 80% of the molecules display a preferential orientation along the BNNT axis with a deviation angle below 45{\deg}.

The one-dimensional structure of single-walled carbon nanotubes renders these materials ideal for optoelectronic applications as they can transport electrons or holes with quasi-ballistic features and as they display optical absorption and near-infrared emission (thanks to van Hove singularities). Nevertheless, functionalities can to be added to nanotube to both improve and control the physical properties. To this aim, chromophore encapsulation into host single-walled carbon nanotubes allows to create hybrid nano-systems with tunable opto-electronic properties. Up to now, we have been confining different kinds of molecules,1-4 either absorbing in the blue/green range, being electron donor (quaterthiophene derivatives (4T) and tetramethyl-paraphenylenediamine (TMPD)) or electron acceptor (tetracyanoquinodimethane (TCNQ)), or absorbing in the red visible range (phthalocyanine (MPc)). In this study, we investigate, at both the macroscopic and the individual scales, the electronic and the optical properties of our hybrid systems by means of Raman and photoluminescence spectroscopies. From Raman measurements, a significant charge transfer from the confined dye to the nanotube is evidenced. Experiments also suggest a photo-activated electron transfer for small diameter (~9 Å) semiconducting and metallic tubes. The main relevant parameters that govern the charge transfer are the nanotube diameter and the electronic properties of both the nanotube (metallic or semiconducting) and the chromophores (electron donor or acceptor). Photoluminescence experiments clearly demonstrate changes on the emission properties after encapsulation. The intensities can be increased or reduced depending on the nature of the confined chromophores (electron donor or acceptor). These behaviors are consistent with a charge transfer. Therefore, Raman and photoluminescence experiments strongly suggest charge transfer between the confined molecules and the nanotubes, leading to a Fermi level shift which governs the radiative de-excitation efficiency and the electron-phonon coupling. References [1] L. Alvarez et al, J. Phys. Chem. C, 119, (2015), pp. 5203−5210 [2] Y. Almadori et al, J. Phys. Chem. C; 118, (2014), pp. 19462−19468 [3] A. Belhboub et al, J. Phys. Chem. C; 120, (2016), pp. 28802−28807 [4] Y. Almadori et al, Carbon 149, (2019), pp. 772-780

Dye confinement into carbon nanotube significantly affects the electronic charge density distribution of the final hybrid system. Using the electron-phonon coupling sensitivity of the Raman G-band, we quantify experimentally how charge transfer from thiophene oligomers to single walled carbon nanotube is modulated by the diameter of the nano-container and its metallic or semiconducting character. This charge transfer is shown to restore the electron-phonon coupling into defected metallic nanotubes. For sub-nanometer diameter tube, an electron transfer optically activated is observed when the excitation energy matches the HOMO-LUMO transition of the confined oligothiophene. This electron doping accounts for an important enhancement of the photoluminescence intensity up to a factor of nearly six for optimal confinement configuration. This electron transfer shifts the Fermi level, acting on the photoluminescence efficiency. Therefore, thiophene oligomer encapsulation allows modulating the electronic structure and then the optical properties of the hybrid system.

We study the intrinsic optical spectroscopy (UV-vis-NIR absorption, Raman and photoluminescence) signatures of single wall carbon nanotubes (SWNT) dispersed in degassed water without additives, so called ‘‘eau de nanotubes” (EdN). They are found to be very close to those of SWNT dispersed in aqueous suspensions stabilized with surfactants. Absorption peaks appear to be even slightly better resolved for EdN, suggesting sharper excitonic resonances, which is also supported by the Raman data. On the other hand, the photoluminescence signal is significantly weaker. These signatures suggest that SWNT are dispersed as individuals in degassed water, in a similar way single layer graphene was recently shown to be readily dispersable in degassed water [1-3]. References [1]G. Bepete et al, Nat. Chem. 2016, DOI 10.1038/NCHEM2669 [2]G. Bepete et al, J. Phys. Chem. C 2016, 120 (49), 28204–28214. [3]G. Bepte et al, Phys. Stat. Solidi 2016, 10 (12), 895-899.

The new 2D transitions metal dichalcogenide (TMDs) as MoS2 represents ideal material for multiple purposes. MoS2 is promising for electronic transistor and fundamentals phenomena such as superconductivity or valleytronic. It is a rich platform for optoelectronic; excitonic effects have high binding energy, strain engineering can induce a high tunability of the band gap itself. Moreover, MoS2 transit between different crystalline phase (2H-1T) making this material interesting for memristive devices and energy storage. Nanomechanical systems have been at the heart of recent physic discoveries of importance, from the detection of cosmic gravitational waves to the sensitivity record for detection of mass or force. It is a recent and almost universal probe of condensed matters issues and quantum mechanics. Since 2007, the emergence of suspended atomically thin materials, with the largest geometrical aspect ratio which can be obtained, brought new insight in nanomechanical resonators with very low mass and spring constant, high elongation resistance, high frequency-tuning and especially strong mechanical non-linearities. A high potential release in MoS2 for nanomechanics. It opens new experimental perspectives by measuring unique intrinsic properties when transduced into the mechanical motion. We propose to focus on unexpected electrical behaviors measured in our samples 1,2 : a strong photodoping under illumination and a hysteretic loop in the I-V curve corresponding to a memristive effect. We use the sensitivity of our mechanical MoS2 membrane as a non-conventional probe to explore deeply these intriguing behaviors and we have seen a strong effect of softening due to the non-linear charge of the devices. 1. Chaste, J. et al. Intrinsic Properties of Suspended MoS2 on SiO2/Si Pillar Arrays for Nanomechanics and Optics. ACS Nano (2018). doi:10.1021/acsnano.7b07689 2. Chaste, J. et al. Nanostructures in suspended monoand bilayer epitaxial graphene. Carbon 125, 162–167 (2017). Figure 1 We explore these topics within unique sample geometry of a suspended single layer membrane of the MoS2 embedded in a nano-opto-electromechanical system (NOEMS) graph-and-co18 Conference Room Monday October 15th, 2018 16:00/16:20 (20min) 5 sciencesconf.org:graph-and-co18:222836 Chemistry: Synthesis and growth

The main hurdle preventing the widespread use of single-walled carbon nanotubes remains the lack of methods with which to produce formulations of pristine, unshortened, unfunctionalized, individualized single-walled carbon nanotubes, thus preserving their extraordinary properties. In particular, sonication leads to shortening, which is detrimental to percolation properties (electrical, thermal, mechanical, etc.). Using reductive dissolution and transfer into degassed water, open-ended, water-filled nanotubes can be dispersed as individualized nanotubes in water-dimethyl sulfoxide mixtures, avoiding the use of sonication and surfactant. Closed nanotubes, however, aggregate immediately upon contact with water. Photoluminescence and absorption spectroscopy both point out a very high degree of individualization while retaining lengths of several microns. The resulting transparent conducting films are 1 order of magnitude more conductive than surfactant-based blanks at equal transmittance.

We show that the properties of thin conductive inkjet printed lines of single-walled carbon nanotubes (SWCNT) can be greatly tuned, using only a few deposition parameters. The morphology, anisotropy and electrical resistivity of single-stroke printed lines are studied as a function of ink concentration and drop density. An original method based on coupled profilometry-Raman measurements is developed to determine the height, mass, orientational order and density profiles of SWCNT across the printed lines with a micrometric lateral resolution. Height profiles can be tuned from 'rail tracks' (twin parallel lines) to layers of homogeneous thickness by controlling nanotube concentration and drop density. In all samples, the nanotubes are strongly oriented parallel to the line axis at the edges of the lines, and the orientational order decreases continuously towards the center of the lines. The resistivity of 'rail tracks' is significantly larger than that of homogeneous deposits, likely because of large amounts of electrical dead-ends.

Hybrid structures are needed to fully exploit the great advantages of Si photonics and severalt approaches have been addressed where Si devices are bonded to different materials and nanostructures. Here we study the use of semiconductor carbon nanotubes for emission in the 1300 nm wavelength range to functionalize Si photonic structures in view of optoelectronic applications. The Si microrings are fully characterized by near field forward resonant scattering with 100 nm resolution. We show that both TE and TM modes can be addressed on the top of the microrings in a vectorial imaging of the in-plane polarization components. We coupled the Si microresonators with selected carbon nanotubes for high photoluminescence emission. Coupling nanotubes with the evanescent tails in air of the electric field localized in the photonic modes of the microresonators is demonstrated by sharp resonances overimposed to the nanotube emission bands. By mapping the Si and the nanotube emission we demonstrate that strong enhancement of the nanotube photoluminescence can be achieved both in the photonic modes of microdisks and slot microrings, whenever the spatial overlap between nanoemitters and photonic modes is fulfilled.

Les nanotubes de carbone monofeuillets (SWNT) presentent des proprietes physiques originales dues a leur composition –ils sont constitues uniquement d’atomes de carbone– et a leur faible dimensionnalite. En ce qui concerne leurs proprietes optiques, les SWNT semi-conducteurs emettent de la lumiere dans le proche infrarouge –on parle de photoluminescence ou de fluorescence– a des longueurs d’onde qui dependent de leur structure et de leur environnement dielectrique. Cet article traitera des phenomenes physiques a l’origine de la photoluminescence des SWNT, et en particulier leurs proprietes excitoniques, l’influence de la structure et de l’environnement sur le spectre de photoluminescence, ainsi que les perspectives d’applications en photonique.

Semiconducting carbon nanotubes are an emerging material for photonics. We report on the enhancement of semiconducting carbon nanotubes photoluminescence with silicon microring resonators. Polyfluorene extracted semiconducting carbon nanotubes, deposited on such resonators, display sharp emission peaks superposed to nanotube emission, which is attributed to the interaction with the cavity modes of the microring resonators. Ring resonators with radii of 5 and 10 mu m were used, to demonstrate the tuning of the spectral distance between two successive emission resonances. Quality factors ranged between 3000 and 4000 in emission. These are among the highest values reported so far for carbon nanotubes coupled with optical microcavity on the silicon platform, highlighting the bright perspectives for carbon nanotube photonics. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)

Silicon photonics has emerged as a very promising technology platform for the implementation of high-performance, low-cost, ultra-compact circuits that can monolithically cointegrate electronic, opto-electronic and optic functionalities. However, Si neither has efficient light emission or detection in the telecom wavelength range, nor exhibits efficient electro-optic Pockels effect, hindering the implementation of integrated active devices like sources, detectors, or modulators. Current approaches relay on different materials to provide active functionalities in Si photonics, resulting in highly complex integration schemes that compromise cost-effectiveness. Semiconducting single-wall carbon nanotubes (SWNTs) are capable of emitting and detecting near-infrared light at room temperature and exhibit intrinsically fast electro-optic effects. They have also proven promising uses in micro-electronic devices, making them an ideal material to provide active functionalities in the Si photonic platform. In this work, we propose and experimentally validate the possible use of slot photonic waveguides to improve interaction between SWNTs and Si waveguide modes. Fabricated Si slot micro-ring shown an experimental ~ 60% photo-luminescence improvement compared to previous demonstration based on Si strip waveguide resonators. These results prove the potential of Si slot waveguides for the implementation of efficient SWNT-based Si photonic devices.

This paper reports on recent results on the integration of carbon nanotubes on the silicon photonic platform. Light coupling from carbon nanotubes in a fully integrated silicon resonator will be presented.