Article

Charge transfer in steam purified arc discharge single walled carbon nanotubes filled with lutetium halides

April 2020
Physical Chemistry Chemical Physics 22(18)

DOI:10.1039/D0CP01408G

Authors:

Magdalena Kierkowicz

Elzbieta Pach

Materials Science Institute of Barcelona

Denisa Darvasiova

Slovak University of Technology in Bratislava

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In the present work, the effect of doping on electronic properties in bulk purified and filled arc-discharge single-walled carbon nanotubes samples is studied for the first time by in situ Raman spectroelectrochemical method. A major challenge to turn the potential of SWCNTs into customer applications is to reduce or eliminate their contaminants by means of purification techniques. Besides, the endohedral functionalization of SWCNTs with organic and inorganic materials (i.e. metal halides) allows the development of tailored functional hybrids. Here, we report the purification and endohedral functionalization of SWCNTs with doping affecting the SWCNTs. Steam-purified SWCNTs have been filled with selected lutetium(III) halides, LuCl3, LuBr3, LuI3, and sealed using high-temperature treatment, yielding closed-ended SWCNTs with the filling material confined in the inner cavity. The purified SWCNTs were studied using TGA, EDX, STEM and Raman spectroscopy. The lutetium(III) halide-filled SWCNTs (LuX3@SWCNTs) were characterized using STEM, EDX, Raman spectroscopy and in situ Raman spectroelectrochemistry. It was found that there is a charge transfer between the SWCNTs and the encapsulated LuX3 (X = Cl, Br, I). The obtained data testify to the acceptor doping effect of lutetium(III) halides incorporated into the SWCNT channels, which is accompanied by the charge transfer from nanotube walls to the introduced substances.

Phemenology of Filling, Investigation of Growth Kinetics and Electronic Properties for Applications of Filled Single-Walled Carbon Nanotubes

Article

Full-text available

Jan 2023

This review discusses the phemenology of filling, the investigation of kinetics, and the electronic properties for applications of filled single-walled carbon nanotubes (SWCNTs), and summarizes five main achievements that were obtained in processing the spectroscopic data of SWCNTs filled with metal halogenide, metal chalcogenide, metal and metallocenes. First, the methods of processing kinetic data were developed to reveal precise trends in growth rates and activation energies of the growth of SWCNTs. Second, the metal-dependence of kinetics was revealed. Third, metallicity-sorted (metallic and semiconducting) SWCNTs were filled with a range of substances and the electronic properties were investigated. Fourth, new approaches to processing the data of spectroscopic investigations of filled SWCNTs were developed, which allowed more reliable and precise analysis of the experimental results. Fifth, the correlation between the physical and chemical properties of encapsulated substances and the electronic properties of SWCNTs were elucidated. These points are highlighted in the review.

Metal and Metal Halogenide-Filled Single-Walled Carbon Nanotubes: Kinetics, Electronic Properties, Engineering the Fermi Level

Article

Full-text available

Dec 2022

Here, we present a review of the major achievements in kinetics, electronic properties, and engineering in the Fermi level of single-walled carbon nanotubes (SWCNTs). Firstly, the kinetics of metal-filled SWCNTs were revealed with precision over several minutes. Secondly, the growth rates of nanotubes were calculated. Thirdly, the activation energies of nanotubes were measured. Fourthly, the methods of the quantitative analysis of the doping level were developed. Indeed, only qualitative analysis has been previously performed. The quantitative analysis allowed us to obtain quantitative data on charge transfer. Fifthly, the correlation between the physical properties, chemical properties, electronic properties of SWCNTs was elucidated.

Spectroscopy of Filled Single-Walled Carbon Nanotubes

Article

Full-text available

Dec 2022

Many envisaged applications, such as nanoelectronics, photovoltaics, thermoelectric power generation, light-emission devices, energy storage and biomedicine, necessitate single-walled carbon nanotube (SWCNT) samples with specific uniform electronic properties. The precise investigation of the electronic properties of filled SWCNTs on a qualitative and quantitative level is conducted by optical absorption spectroscopy, Raman spectroscopy, photoemission spectroscopy and X-ray absorption spectroscopy. This review is dedicated to the description of the spectroscopic methods for the analysis of the electronic properties of filled SWCNTs. The basic principle and main features of SWCNTs as well as signatures of doping-induced modifications of the spectra of filled SWCNTs are discussed.

Filled Carbon Nanotubes: Promising Material for Applications

Article

Full-text available

Sep 2023

Marianna V. Kharlamova

Carbon nanotubes (CNTs) were first filled with a number of metals starting in 1993 [...]

Electronic and Mechanical Properties of Endohedral Composites of Carbon Nanotubes with Potassium Iodide: DFT Study

Article

Full-text available

May 2023
J STRUCT CHEM+

Structure, longitudinal elasticity, and electronic properties of endohedral assembled composites of single-walled carbon nanotubes and a one-dimensional crystal KI - KI@CNT - are studied by the density functional theory method. It is established that electronic properties of defect-free composites KI@CNT are predetermined by the electronic properties of the parent nanotube. The introduction of K or I vacancies stimulates the charge transfer between the encapsulate and the nanotube, accompanied by increasing concentration of electron or hole charge carriers in the nanotube. Young′s moduli of KI@CNT are 20-50% lower than those of parent nanotubes, irrespective of their chirality type and presence of atomic vacancies in the KI encapsulate. These results approve the preservation of high strength of carbon nanotubes within their composites with halides and provide a helpful guideline for applications of nanotubes as delivery agents, nanoreactors, etc.

Kinetics, Electronic Properties of Filled Carbon Nanotubes Investigated with Spectroscopy for Applications

Article

Full-text available

Dec 2022

Marianna V. Kharlamova

The paper is dedicated to the discussion of kinetics of growth, and electronic properties of filled carbon nanotubes investigated by spectroscopy for applications. The paper starts with discussion of growth of carbon nanotubes inside metallocene-filled carbon nanotubes. Nickelocene, cobaltocene are considered for growth of carbon nanotubes. Then, the investigations of filled carbon nanotubes by four spectroscopic techniques are discussed. Among them are Raman spectroscopy, near edge X-ray absorption fine-structure spectroscopy, photoemission spectroscopy, optical absorption spectroscopy. It is discussed that metal halogenides, metal chalcogenides, metals laed to changes in electronic structure of nanotubes with n- or p-doping. The filling of carbon nanotubes with different organic and inorganic substances results in many promising applications. This review adds significant contribution to understanding of the kinetics and electronic properties of filled SWCNTs with considering new results of recent investigations. Challenges in various fields are analyzed and summarized, which shows the author’s viewpoint of progress in the spectroscopy of filled SWCNTs. This is a valuable step toward applications of filled SWCNTs and transfer of existing ideas from lab to industrial scale.

Electrochemistry of Carbon Materials: Progress in Raman Spectroscopy, Optical Absorption Spectroscopy, and Applications

Article

Full-text available

Feb 2023

This paper is dedicated to the discussion of applications of carbon material in electrochemistry. The paper starts with a general discussion on electrochemical doping. Then, investigations by spectroelectrochemistry are discussed. The Raman spectroscopy experiments in different electrolyte solutions are considered. This includes aqueous solutions and acetonitrile and ionic fluids. The investigation of carbon nanotubes on different substrates is considered. The optical absorption experiments in different electrolyte solutions and substrate materials are discussed. The chemical functionalization of carbon nanotubes is considered. Finally, the application of carbon materials and chemically functionalized carbon nanotubes in batteries, supercapacitors, sensors, and nanoelectronic devices is presented.

Neutron Activated 153 Sm Sealed in Carbon Nanocapsules for In Vivo Imaging and Tumor Radiotherapy

Article

Full-text available

Nov 2019

Radiation therapy along with chemotherapy and surgery remain the main cancer treatments. Radiotherapy can be applied to patients externally (external beam radiotherapy) or internally (brachytherapy and radioisotope therapy). Previously, nanoencapsulation of radioactive crystals within carbon nanotubes, followed by end-closing, resulted in the formation of nanocapsules that allowed ultrasensitive imaging in healthy mice. Herein we report on the preparation of nanocapsules initially sealing ‘cold’ isotopically enriched samarium (¹⁵²Sm), which can then be activated on demand to their ‘hot’ radioactive form (¹⁵³Sm) by neutron irradiation. The use of ‘cold’ isotopes avoids the need for radioactive facilities during the preparation of the nanocapsules, reduces radiation exposure to personnel, prevents the generation of nuclear waste and evades the time constraints imposed by the decay of radionuclides. A very high specific radioactivity is achieved by neutron irradiation (up to 11.37 GBq/mg), making the ‘hot’ nanocapsules useful not only for in vivo imaging but also therapeutically effective against lung cancer metastases after intravenous injection. The high in vivo stability of the radioactive payload, selective toxicity to cancerous tissues and the elegant preparation method offer a paradigm for application of nanomaterials in radiotherapy.

Enter the Tubes: Carbon Nanotube Endohedral Catalysis

Article

Full-text available

Feb 2019

The unique morphological characteristics of carbon nanotubes (CNTs) present the intriguing opportunity of exploiting the inner cavity for carrying out chemical reactions. Such reactions are catalysed either by the individual tubes that function both as catalysts and nanoreactors or by additional catalytic species that are confined within the channel. Such confinement creates what is called “confinement effect”, which can result in different catalytic features affecting activity, stability and selectivity. The review highlights the recent major advancements of catalysis conducted within the CNTs, starting from the synthesis of the catalytic composite, and discussing the most notable catalytic processes that have been reported in the last decade.

A tool box to ascertain the nature of doping and photoresponse in single-walled carbon nanotubes

Article

Full-text available

Jan 2019

The effect of doping on electronic properties in bulk single-walled carbon nanotubes (SWCNT) samples is studied for the first time by a new in situ Raman spectroelectrochemical method, and further verified by DFT calculations and photoresponse. We use p-/n- doped SWCNTs prepared by diazonium reactions as a versatile chemical strategy to control the SWCNT behavior. The measured and calculated data testify an acceptor effect of 4-aminobenzenesulfonic acid (p-doping), and a donor effect (n-doping) in the case of benzylalcohol. In addition, pristine and covalently functionalized SWCNTs were used for the preparation of photoactive film electrodes. The photocathodic current in the photoelectrochemical cell is consistently modulated by the doping group. These results validate the in situ Raman spectroelectrochemistry as a unique tool box for predicting the electronic properties of functionalized SWCNTs in the form of thin films and their operational functionality in thin film devices for future optoelectronic applications.

Epoxidation of Carbon Nanocapsules: Decoration of Single-Walled Carbon Nanotubes Filled with Metal Halides

Article

Full-text available

Feb 2018

Methyl(trifluoromethyl)dioxirane (TFDO) can be used for the oxyfunctionalization of SWCNTs filled with NaI and LuCl₃ under mild conditions. The chosen metal halides are of interest for theranostics, both for imaging and therapy when in their radioactive form. The applied functionalization methodology does not require metal catalyst, preserves the integrity of the nanotubes during treatment, avoiding the release of the filling material. In this way, epoxidation can be considered as an efficient methodology for the functionalization of carbon nanocapsules, where the traditional harsh oxidation conditions by acids are not applicable.

Design of antibody-functionalized carbon nanotubes filled with radioactivable metals towards a targeted anticancer therapy

Article

Full-text available

Dec 2015
Nanoscale

In the present work we have devised the synthesis of a novel promising carbon nanotube carrier for the targeted delivery of radioactivity, through a combination of endohedral and exohedral functionalization. Steam-purified single-walled carbon nanotubes (SWCNTs) have been initially filled with radioactive analogues (i.e. metal halides) and sealed by high temperature treatment, affording closed-ended CNTs with the filling material confined in the inner cavity. The external functionalization of these filled CNTs was then achieved by nitrene cycloaddition and followed by the derivatization with a monoclonal antibody (Cetuximab) targeting the epidermal growth factor receptor (EGFR), overexpressed by several cancer cells. The targeting efficiency of the so-obtained conjugate was evaluated by immunostaining with a secondary antibody and by incubation of the CNTs with EGFR positive cells (U87-EGFR+), followed by flow cytometry, confocal microscopy or elemental analyses. We demonstrated that our filled and functionalized CNTs can internalize more efficiently in EGFR positive cancer cells.

Raman modes of metallic carbon nanotubes

Article

Full-text available

Dec 1998

The anomalous resonant behavior of the tangential Raman modes of carbon nanotubes has been studied in the critical region of laser energies 1.7-2.2 eV. The special enhancement of the Raman modes is explained by a model that takes into account the transition between the singularities in the one-dimensional density of electronic states for the metallic nanotubes and the distribution of diameters in the sample. The results agree with direct measurements of the electronic density of states for the metallic nanotubes and establish their association with the specially enhanced high frequency, first-order Raman modes. @S0163-1829~98!50848-X# Resonant Raman spectroscopy is a very useful tool for the characterization of the one-dimensional ~1D! properties of carbon nanotubes. It has been used to study multiwall nano- tubes ~MWNT!,1 single-wall nanotubes ~SWNT!,2-5 and was recently examined theoretically.6 We show here evidence that special tangential phonon modes of metallic carbon nanotubes are enhanced in a narrow range of laser energies between 1.7 and 2.2 eV by electronic transitions between the first singularities in the 1D electronic density of states ~DOS! in the valence and conduction bands v 1!c 1 . This result establishes the association of the specially enhanced high- frequency, tangential modes with the metallic carbon nano- tubes.

Raman Scattering in Carbon Nanotubes

Chapter

Full-text available

Proceedings of SPIE

The vibrational properties of single-walled carbon nanotubes reflect the electron and phonon confinement as well as the cylindrical geometry of the tubes. Raman scattering is one of the prime techniques for studying the fundamental properties of carbon tubes and nanotube characterization. The most important phonon for sample characterization is the radial-breathing mode, an in-phase radial movement of all carbon atoms. In combination with resonant excitation it can be used to determine the nanotube microscopic structure. Metallic and semiconducting tubes can be distinguished from the high-energy Raman spectra. The high-energy phonons are remarkable because of their strong electron–phonon coupling, which leads to phonon anomalies in metallic tubes. Acommon characteristic of the Raman spectra in nanotubes and graphite is the appearance of Raman peaks that correspond to phonons from inside the Brillouin zone, the defect-induced modes. In this Chapter we first introduce the vibrational, electronic, and optical properties of carbon tubes and explain important concepts such as the nanotubes’ family behavior. We then discuss the Raman-active phonons of carbon tubes. Besides the vibrational frequencies and symmetries Raman spectroscopy also allows optical (excitonic) transitions, electron–phonon coupling and phase transitions in single-walled carbon nanotubes to be studied.

The anomalous dispersion of the disorder-induced and the second-order Raman Bands in Carbon Nanotubes

Article

Full-text available

Jun 2000
BRAZ J PHYS

In this work we have studied the dispersion of the disorder-induced (D) and the second-order (G') Raman bands in single wall carbon nanotubes using several laser excitation energies (E laser) in the range 1.5-3.0 eV. An anomalous step-like behavior was observed in the E laser dependence of the G'-band frequency. This result is interpreted as a manifestation of the one-dimensional (1D) behavior of the phonon spectrum in carbon nanotubes.

Chirality Distribution and Transition Energies of Carbon Nanotubes

Article

Full-text available

Nov 2004

From resonant Raman scattering on isolated nanotubes we obtained the optical transition energies, the radial breathing mode frequency, and the Raman intensity of both metallic and semiconducting tubes. We unambiguously assigned the chiral index (n(1),n(2)) of approximately 50 nanotubes based solely on a third-neighbor tight-binding Kataura plot and find omega(RBM)=(214.4+/-2) cm(-1) nm/d+(18.7+/-2) cm(-1). In contrast to luminescence experiments we observe all chiralities including zigzag tubes. The Raman intensities have a systematic chiral-angle dependence confirming recent ab initio calculations.

Raman Spectroscopy in Graphene Related Systems

Book

Jan 2011

Vibrational Spectrocopic Studies of Organic Molecules After Encapsulation Inside Single-Walled Carbon Nanotubes

Article

Oct 2019
J NANOSCI NANOTECHNO

7,7,8,8-tetracyano-p-quinodimethane (TCNQ), tetrathiafulvalene (TTF), and dodecanethiol (DoSH) were encapsulated inside single-walled carbon nanotubes (SWNTs), (TCNQ@SWNT, TTF@SWNT, and DoSH@SWNT). We measured the Fourier transform infra-red (FTIR) spectra and X-ray diffraction (XRD) patterns to confirm the encapsulation of organic molecules. Slight shifts of the FTIR peaks and the disappearance of an XRD peak at ~6°, corresponding to the SWNT (10) reflection, were observed. From the measurements of the current-voltage curves, it was revealed that the current of TTF@ SWNT and DoSH@SWNT decreased, and the current of TCNQ@SWNT increased compared with that of pristine SWNTs.

Fermi level shift in carbon nanotubes by dye confinement

Article

Apr 2019
CARBON

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.

Structure of inorganic nanocrystals confined within carbon nanotubes

Article

Apr 2019
INORG CHIM ACTA

There are many examples in which the cavities of carbon nanotubes have been filled with a variety of compounds. Unprecedented structures compared to those of the same material in the bulk are observed, such as low dimensional crystals. Such encapsulated materials can have unusual properties that differ from those of the bulk material. The scope of this review is to give a brief approach to the different nanostructures formed after encapsulation of inorganic compounds within the inner cavities of carbon nanotubes. The confined materials can take the form of one-dimensional nanowires, nanoclusters or even inorganic nanotubes. This review is part of the special issue of the journal dedicated to Prof. Malcolm L.H. Green, and special emphasis is thus given to the work performed by the group of Prof. Green.

Films of filled single-wall carbon nanotubes as a new material for high-performance air-sustainable transparent conductive electrodes operating in a wide spectral range

Article

Mar 2019

In this paper we show the advantages of transparent high conductive films based on filled single-wall carbon nanotubes. The nanotubes with internal channels filled with acceptor molecules (copper chloride or iodine) form networks demonstrating significantly improved characteristics. Due to the charge transfer between the nanotubes and filler, the doped-nanotube films exhibit the electrical sheet resistance drop by an order of magnitude together with a noticeable rise of films transparency in the visible and near-infrared spectral range. The thermoelectric power measurements show a significant improvement of air-stability of nanotube network in course of the filling procedure. For the nanotube films with the initial transparency of 87% at 514 nm and the electrical sheet resistance of 862 Ohm/sq we observed the improvement of transparency up to 91% and the decrease of sheet resistance down to 98 Ohm/sq. The combinations of nanotube synthesis technique and molecules for encapsulation have been optimized for applications in optoelectronics.

Comparative study of shortening and cutting strategies of single-walled and multi-walled carbon nanotubes assessed by scanning electron microscopy

Article

Jun 2018

Short carbon nanotubes (CNTs) are desired for a variety of applications. As a consequence, several strategies have been reported to cut and shorten the length of as-produced CNTs via chemical and physical routes. The efficiency of a given strategy largely depends on the physico-chemical characteristics of the CNTs employed. In order to be able to directly compare the advantages and disadvantages of commonly used protocols, a single batch of chemical vapor deposition single-walled CNTs (SWCNTs) and a batch of multi-walled CNTs (MWCNTs) were subjected to four cutting/shortening strategies, namely acid cutting, piranha treatment, steam shortening and ball milling. The length distribution was assessed by means of scanning electron microscopy. Sample purity and CNT wall structure were determined by Raman spectroscopy, thermogravimetric analysis and magnetic measurements. Within the employed experimental conditions, piranha treatment turned out to be the most efficient to achieve short SWCNTs with a narrow length distribution in a good yield, whereas a mixture of sulfuric/nitric acid was preferred in the case of MWCNTs. A subsequent short steam treatment allowed to remove functional groups present in the samples, leading to median length distributions of 266 nm and 225 nm for SWCNTs and MWCNTs respectively after the combined protocols.

Filling Single-Walled Carbon Nanotubes with Lutetium Chloride: A Sustainable Production of Nanocapsules Free of Non-Encapsulated Material

Article

Jan 2017

Filled carbon nanotubes are of interest for a wide variety of applications ranging from sensors to magnetoelectronic devices and going through the development of smart contrast and therapeutic agents in the biomedical field. In general, regardless of the method employed, bulk filling of carbon nanotubes results in the presence of a large amount of external non-encapsulated material. Therefore further processing is needed to achieve a sample in which the selected payload is present only in the inner cavities of the nanotubes. Here, we report on a straightforward approach that allows the removal of non-encapsulated compounds in a time efficient and environmentally friendly manner, using water as a ‘green’ solvent, whilst minimizing the residual waste. The results presented herein pave the way towards the production of large amounts of high-quality closed-ended filled nanotubes, also referred to as carbon nanocapsules, readily utilizable in the foreseen applications.

Electronic properties of single-walled carbon nanotubes filled with manganese halogenides

Article

Aug 2016

Marianna V. Kharlamova

In this work, single-walled carbon nanotubes (SWCNTs) were filled with manganese chloride and manganese bromide by a capillary filling method. The electronic properties of the filled SWCNTs were investigated by Raman spectroscopy and X-ray photoelectron spectroscopy. It was found that the encapsulated manganese halogenides led to hole doping of the SWCNTs due to the charge transfer from the nanotubes to the encapsulated compounds. The embedded MnCl2 had stronger doping effect on the SWCNTs than MnBr2.

Effect of Steam‐Treatment Time on the Length and Structure of Single‐Walled and Double‐Walled Carbon Nanotubes

Article

Dec 2015

A major challenge to turn the potential of carbon nanotubes (CNTs) into customer applications is to reduce or eliminate their toxicity. Taking into account health and safety concerns, intensified research efforts have been conducted to improve the biocompatibility of CNTs, including the development of new shortening and purification strategies. Ideally, the methods used for improving the biocompatibility of CNTs should not alter the electronic properties of CNTs. Herein, we report on the shortening of a sample containing single-walled and double-walled CNTs using steam and obtain new insights in the properties of the steam-treated CNTs. The present study shows that short CNTs (median length ca. 200 nm) can be obtained under the reported conditions. Raman analysis reveals that wider and outer nanotubes undergo more significant changes than the narrower and inner ones, especially after a prolonged steam treatment.

Multipurpose Nature of Rapid Covalent Functionalization on Carbon Nanotubes

Article

Nov 2015
CHEM-EUR J

In the vast field of functionalization routes to carbon nanoforms, the fulfillment of such critical requirements as quick and nonharsh methods, good dispersibility, introduction of reactive groups, short reaction time, and low cost can be quite challenging. Traditional thermally induced diazonium chemistry on single-walled carbon nanotubes (SWCNTs) is revisited by using commercial anilines and providing useful insight into the versatility of this approach. Functionalized SWCNTs with multiple controllable features, such as degree (and ratio) of coverage, orthogonalization, doping, and high water dispersibility, are obtained by introducing benzenesulfonic acid and benzylamine moieties. The scenario opens up an avenue to address relevant applications in which most functionalization methods could not be applied in a straightforward way.

Tailoring the electronic properties of single-walled carbon nanotubes via filling with nickel acetylacetonate

Article

Oct 2015
PHYS STATUS SOLIDI B

Although chemical functionalization of single-walled carbon nanotubes was extensively studied, in many cases detailed information about the influence of the nanotube metallicity and diameter is missing. Here, we present an X-ray photoemission and absorption spectroscopy study of endohedrally functionalized carbon nanotubes with different diameters, where Ni(II)acetylacetonate molecules are reacted to tailor the nanotubes’ electronic properties. The filling factor is found to be dependent on the SWCNT base material used. We trace the reaction process of the filling material at several annealing steps and reveal their dependence on annealing temperature, which allows doping of nanotubes to be controlled.

Advances in tailoring the electronic properties of single-walled carbon nanotubes

Article

Apr 2016

Marianna V. Kharlamova

Considerable progress has been made in the last several years in the fields of investigation and understanding of the influence of encapsulated substances on the electronic properties of single-walled carbon nanotubes (SWCNTs). Relevant data on the modified electronic properties of filled SWCNTs were obtained. The possibility of achieving both acceptor and donor doping and precise changes of the SWCNT doping level by the filling of channels and transformation of incorporated substances was demonstrated. This article presents a comprehensive review of the current status of the research on the electronic properties of filled SWCNTs. The review begins with a brief description of basic aspects of the band theory of solids and peculiarities of the band structure and electronic properties of SWCNTs. The next part of the review is dedicated to a systematization and description of different methods for modification of the SWCNT electronic properties. Then, the review introduces filling methods of SWCNT inner channels. The main part of the review is dedicated to an analysis, systematization and generalization of the up-to-date reported results on experimental and theoretical investigations of the electronic properties of filled SWCNTs and nanostructures obtained as result of chemical reactions inside the SWCNT channels. Finally, the possible applications of filled nanotubes are highlighted.

Experimental and theoretical studies on the electronic properties of praseodymium chloride-filled single-walled carbon nanotubes

Article

Aug 2015

Praseodymium chloride (PrCl3) was encapsulated into channels of 1.4 nm diameter single-walled carbon nanotubes (SWCNTs) by a capillary filling method. The high-resolution transmission electron microscopy data demonstrated a high filling factor of the nanotubes and the formation of one-dimensional (1D) PrCl3 nanocrystals. The optical absorption, Raman spectroscopy, and X-ray photoelectron spectroscopy data testified to the filling-induced lowering of the Fermi level of the nanotubes as a result of the electron transfer from the SWCNTs to the embedded PrCl3. The density functional theory modeling showed the absence of local chemical interactions between the nanotubes and the 1D crystals. It was found that the incorporated PrCl3 has stronger influence on the electronic properties of metallic nanotubes than semiconducting SWCNTs.

Rare-earth metal halogenide encapsulation-induced modifications in Raman spectra of single-walled carbon nanotubes

Article

Jan 2015

Marianna V. Kharlamova

In the present work, a detailed Raman spectroscopy investigation on the single-walled carbon nanotubes (SWCNTs) filled with praseodymium chloride, terbium chloride and thulium chloride was performed. The salts were incorporated inside the SWCNTs by a capillary filling method using melts, and the high-resolution transmission electron microscopy data proved the high filling degree of the nanotube channels. A thorough analysis of the radial breathing mode and G-band of the Raman spectra of the pristine and filled SWCNTs showed that the encapsulated salts cause acceptor doping of the host nanotubes, and the doping efficiency depends on the compound. The incorporated thulium chloride has the strongest doping effect on the SWCNTs, whereas praseodymium chloride has the weakest effect. It was found that the encapsulated salts modify more significantly the electronic structure of metallic nanotubes than semiconducting SWCNTs.

Raman Intensities of Totally Symmetrical Modes of Homogeneously Deformed Single-Walled Carbon Nanotubes

Article

Sep 2014

Raman excitation profiles for 55 homogeneously deformed single- walled carbon nanotubes with diameters from 0.7 to 1.2 nm are calculated and systematically analyzed. Torsion and uniaxial strain produce a number of interesting observable effects, important in designing electromechanical devices. The deformations shift phonon energies. The torsion alone causes mixing of high energy modes, while the uniaxial compression generates interchange of their vibrating directions. It is found that electronic transition energies depend almost linearly on deformation; for some tubes, they cover the entire visible spectrum, making them perfectly tunable light absorbers. On the other hand, this shift causes a number of interference effects. The type of interference and its influence on the excitation profiles is completely determined by electron−phonon coupling matrix elements. Collapse of Raman intensity in resonant scattering experiments is explained either by destructive interference or by moving away from the resonant window. Finally, the deformation causes increase of the lower high energy mode resonant intensity, which should further produce the appreciable change in the G mode profil

Charge transfer in single-walled carbon nanotubes filled with cadmium halogenides

Article

Dec 2013

In this work the internal channels of the single-walled carbon nanotubes (SWCNTs) were filled with cadmium chloride, cadmium bromide, and cadmium iodide by a capillary method using melts of these salts. The influence of incorporated chemical compounds on the electronic properties of the carbon nanotubes was investigated by optical absorption spectroscopy, Raman spectroscopy, near edge X-ray absorption fine structure spectroscopy, and X-ray photoelectron spectroscopy. It was found that there is the chemical bonding between carbon atoms of nanotube walls and metal atoms of encapsulated CdX2 nanocrystals. The obtained data testify acceptor doping effect of cadmium halogenides incorporated into the SWCNT channels, which is accompanied by the charge transfer from nanotube walls to introduced substances.

Interaction between single walled carbon nanotube and 1D crystal in CuX@SWCNT (X = Cl, Br, I) nanostructures

Article

Sep 2012
CARBON

The influence of doping on the Raman intensity of the D band in single walled carbon nanotubes

Article

Mar 2010
CARBON

The D band in the Raman spectra of single walled carbon nanotubes is considered as an indicator of defects in carbon nanotubes. However, its dependence on charge-transfer doping is generally ignored, despite the studied samples are often naturally doped. We studied the intensity of the D band, the ratio of the intensities of the D band and TG band (ID/ITG) and the ratio of the intensities of the D and G′ band (ID/IG′) in the Raman spectra of the single walled carbon nanotubes in dependence on a doping level. We tested two laser excitation energies viz 2.41 and 1.92eV, which are in resonance with semiconducting and metallic tubes, respectively in our sample. It is shown that the D band intensity is significantly attenuated in doped carbon nanotubes sample for both semiconducting and metallic tubes. The ID/ITG ratio is weakly dependent on doping for semiconducting tubes but for metallic tubes the ID/ITG ratio exhibits strong dependence on doping. The ID/IG′ ratio is suggested for evaluation of the defects in carbon nanotubes samples since it is less sensitive to doping both for semiconducting and metallic tubes. Nevertheless, for highly doped samples even the ID/IG′ ratio exhibits significant dependence on doping level.

Chirality-selective Raman scattering of the D mode in carbon nanotubes

Article

Sep 2001

We show that D-mode Raman scattering in single-walled carbon nanotubes is due to a double-resonant Raman process. The unusual shift of the D-mode frequency with excitation energy is even expected for a single nanotube. The magnitude of the shift and the D-mode frequency depend strongly on the tube’s diameter and chirality. Only tubes with (n1-n2)/3n integer contribute to the D-mode spectrum because of the particular electronic structure of carbon nanotubes.

Raman Spectroscopy of Carbon Nanotubes in 1997 and 2007†

Article

Oct 2007

Over the last 10 years, carbon nanotubes have offered a unique system for the study of Raman spectra in one-dimensional systems, and at the same time Raman spectroscopy has provided a widely used and powerful tool for the characterization of single walled carbon nanotubes (SWNTs). The 10 year history of Raman scattering in SWNTs is reviewed here and future prospects for the field are discussed.

Electronic properties of Ag- and CrO3-filled single-wall carbon nanotubes

Article

Apr 2005
CHEM PHYS LETT

The structural and electronic charge distributions of single-wall carbon nanotubes (SWNTs) chemically modified with Ag and CrO3 were investigated by ab initio methods. Using first-principles spin-polarized calculations, we studied the structural and electronic behavior of Ag atoms and CrO3 molecules interacting with an (8, 0) semiconducting SWNT. We have found that the Ag atom behaves as an electron donor and the CrO3 as an electron acceptor in the presence of the SWNT. Resonance Raman experiments performed on Ag and CrO3-adsorbed SWNTs confirm the donor and acceptor behavior, respectively.

Electrochemistry of Carbon Nanotubes

Chapter

Dec 2007
TOP APPL PHYS

The electrochemistry of carbon nanotubes is reviewed with the aim of summarizing what we can learn using these techniques, and what are the potential applications of nanotubes as electrode materials. Electrochemical charging changes the electronic structure. Consequently, electrochemistry and in-situ spectroelectrochemistry provide versatile tools for the investigation of fundamental effects related to the electronic structure of carbon nanotubes. This approach is compatible with chemical doping, but the electrochemical charging of nanotubes allows for precise control of the doping conditions. Salient (spectro)electrochemical data accumulated during the last ten years on SWNTs, DWNTs and fullerene peapods are here reviewed.

Resonance Raman spectroscopy of the radial breathing modes in carbon nanotubes

Article

Mar 2010
PHYSICA E

In the last decade, many theoretical and experimental achievements have been made in the photophysics of single wall carbon nanotubes (SWNTs). Such accomplishments allowed us to gain a deep understanding of the photophysics behind the transition energy (Eii) and the radial breathing mode frequency (ωRBM) dependence on nanotube chirality (n, m). This work is devoted to assemble and discuss what has been done on the research of the SWNT electronic and vibrational properties, based on the radial breathing mode (RBM) resonance Raman spectroscopy. Attention is directed to the understanding of how a change in the environment changes the correlation between (Eii,ωRBM) and (n, m). From the analysis of several data in the literature, we derive a simple routine for the (Eii,ωRBM)→(n,m) assignment.

Raman spectroscopy on isolated single wall carbon nanotubes* 1

Article

Dec 2002
CARBON

A review is presented on the resonance Raman spectra from one isolated single wall carbon nanotube. The reasons why it is possible to observe the spectrum from only one nanotube are given and the important structural information that is provided by single nanotube spectroscopy is discussed. Emphasis is given to the new physics revealed by the various phonon features found in the single nanotube spectra and their connection to spectra observed for single wall nanotube bundles. The implications of this work on single wall carbon nanotube research generally are also indicated.

Spectroelectrochemistry of Carbon Nanotubes

Article

Jan 2011
CHEMPHYSCHEM

This Minireview is a critical survey of results accumulated during the last decade on the characterization of carbon nanotubes using a combination of electrochemical and spectroscopic methods. The article updates earlier reviews on the topic with special emphasis to recent progress in the field.

Electrochemical Charging of Individual Single-Walled Carbon Nanotubes

Article

Aug 2009
ACS NANO

The influence of the electrode potential on the electronic structure of individual single-walled carbon nanotubes is studied using Raman spectroscopy. By analyzing the radial breathing mode intensity versus electrode potential profiles in the Raman spectra at many different laser excitation energies, we show that the charging of individual carbon nanotubes causes a broadening of the resonant Raman profiles (resonance window). This effect is observed for both a semiconducting and a metallic tube. The broadening of the resonance Raman profiles already begins at potentials where the first electronic states of a particular tube are filled or depleted. The important consequence of this effect is a striking difference between the Raman intensity versus potential profiles of metallic and semiconducting tubes. While for a metallic tube the intensity of the Raman signal is attenuated at potentials which deviate slightly from 0 V, for a semiconducting tube, the Raman intensity is significantly attenuated only after the electrode potential reaches the first van Hove singularity. Furthermore, for the metallic tube, a strong asymmetry is found in the bleaching of the Raman signal with respect to positive and negative potentials, which results from the different energy bandwidth for the pi* band and the pi band.

Competition between the Spring Force Constant and the Phonon Energy Renormalization in Electrochemically Doped Semiconducting Single-Walled Carbon Nanotubes

Article

Oct 2008

A detailed analysis of the in situ Raman spectroelectrochemical behavior of individual semiconducting single-walled carbon nanotubes (SWCNTs) is presented. Special attention has been paid to the development of the tangential (TG) mode frequency, which shifts when the externally applied potential Ve is shifted away from Ve=0. The magnitude and direction (upshift or downshift) of the tangential mode band has been found to be dependent on the diameter of the semiconducting tubes. For negative charging, the small-diameter tubes exhibit a downshift while the large-diameter tubes exhibit an upshift. This behavior is explained by a competition between two effects which cause opposite shifts in the TG mode frequency during negative charging: a phonon renormalization effect and a C-C bond weakening during the charging process. Positive charging always causes an upshift of the TG mode frequency. However, the magnitude of the upshift is dependent on the tube diameter.

Steam Purification for the Removal of Graphitic Shells Coating Catalytic Particles and the Shortening of Single-Walled Carbon Nanotubes

Article

Sep 2008
SMALL

Purification and shortening of single-walled carbon nanotubes (SWNTs) is carried out by treatment with steam. During the steam purification the graphitic shells coating the catalytic metal particles are removed. Consequently, the exposed catalytic particles can be easily dissolved by treatment with hydrochloric acid. No damage to the carbon nanotube tubular structure is observed, even after prolonged treatment with steam. Samples are characterized by HRTEM, TGA, magnetic measurements, Raman spectroscopy, AFM, and XPS.

Stable and controlled amphoteric doping by encapsulation of organic molecules inside carbon nanotubes

Article

Nov 2003

Single-walled carbon nanotubes (SWNTs) have strong potential for molecular electronics, owing to their unique structural and electronic properties. However, various outstanding issues still need to be resolved before SWNT-based devices can be made. In particular, large-scale, air-stable and controlled doping is highly desirable. Here we present a method for integrating organic molecules into SWNTs that promises to push the performance limit of these materials for molecular electronics. Reaction of SWNTs with molecules having large electron affinity and small ionization energy achieved p- and n-type doping, respectively. Optical characterization revealed that charge transfer between SWNTs and molecules starts at certain critical energies. X-ray diffraction experiments revealed that molecules are predominantly encapsulated inside SWNTs, resulting in an improved stability in air. The simplicity of the synthetic process offers a viable route for the large-scale production of SWNTs with controlled doping states.

Purification and Opening of Carbon Nanotubes Using Steam

Article

Dec 2006

Purification and opening of carbon nanotubes has been carried out by treatment of as-made single-wall carbon nanotubes (SWNTs) with pure steam at 1 atm pressure. Treated samples have been characterized by high-resolution transmission electron microscopy and IR and Raman spectroscopy. Comparison between the steam purification and the standard nitric acid purification treatment shows that steam is less aggressive toward damage to the tubular nanotube wall structure and forms fewer functional groups.

Development of the Tangential Mode in the Raman Spectra of SWCNT Bundles during Electrochemical Charging

Article

May 2008

The detailed analysis of the in situ Raman spectroelectrochemical behavior of single walled carbon nanotube (SWCNT) bundles is presented. The Raman modes of metallic SWCNTs exhibit striking changes even before the potential of the first van Hove singularity is achieved. Special attention has been paid to the development of the tangential (TG) mode broadening, which subsequently vanishes if the potential is shifted away from V = 0. The tangential mode band has been fitted by four components. During the electrochemical doping, three components of the tangential mode follow the predictions of a theoretical model for the LO modes of metallic tubes based on the Kohn anomaly. On the other hand, the behavior of the fourth component is consistent with a model based on electron-plasmon coupling. The TO mode of metallic tubes has been identified only at a doping level corresponding to 1.0 V or above. Our results also indicate an asymmetry in the behavior of the TG mode for positive electrode potentials relative to negative ones.

Jan 2018
1465-1472

S Sandoval
M Kierkowicz
E Pach
B Ballesteros
G Tobias

S. Sandoval, M. Kierkowicz, E. Pach, B. Ballesteros, G. Tobias. MethodsX 5 (2018) 1465-1472

Charge transfer in steam purified arc discharge single walled carbon nanotubes filled with lutetium halides

Abstract

No full-text available

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