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Cluster-like network structures of single-walled carbon nanotubes (SWNTs) were synthesized by chemical grafting poly 2-hydroxyethyl methacrylate (polyHEMA) to the sidewalls of SWNTs. Acid chloride-functionalized tubes were coupled with commercially available HEMA monomer, which was in turn polymerized using a radical initiator. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to identify the surface changes on the nanocomposites. Microscopic observations of the nanotube complexes by field emission scanning electron microscopy (FE-SEM) show that the tubes were dispersed and formed cluster-like network, branched structures with less bundling, thus, strongly suggesting a firm coating of the polymer on nanotube walls. The coating was further confirmed by transmission electron microscopy. The thermal properties of the nanotube complex as studied by thermal gravimetric analysis (TGA) revealed that coating enhanced stability of the complex, when compared to that of bulk polyHEMA and pristine SWNTs. The nanotube complexes showed excellent suspension stability when dispersed in organic solvent.

Carbon atoms can connect with themselves and with other atoms (both electronegative and electropositive elements) in various ways. Thanks to these abilities, the diversity of carbon compounds is increasing day by day. This growth was even faster after the discovery of carbon nanoallotropes, i.e. carbon nanotubes, fullerenes, and graphene. At present, these carbon nanoallotropes are widely studied, and new hybrid structures have been synthesized based on these nanoallotropes. Hybrid structures formed by the covalent bond of fullerenes to the outside carbon nanotubes are called carbon nanobuds (CNBs). Development of synthesis methods, computational calculations, and the study of CNB properties was much faster than other hybrid structures. However, only fewer articles on CNBs have been published in recent years. CNBs show a synergistic effect and have the unique properties of the carbon nanoallotropes from which they formed. This review discusses CNBs and reports the recent research on CNBs, mostly after 2016.

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The symmetry of single-wall carbon and inorganic tubes is reviewed. For the carbon nanotubes it is used to get the full set of quantum numbers, in the efficient precision (combined density functional and tight-binding methods) calculation of electronic bands and their complete assignation, to obtain the selection rules for optical transitions and the momenta matrix elements for the Bloch eigen-states. The optical characteristics are thoroughly found, and discussed.

A comprehensive ab-initio investigation of the stability, structural, electronic, optical and Raman-active properties has been performed for the small diameter armchair carbon nanotubes. A number of new features not discussed earlier are observed in the present study. The binding energies (BEs) for the ultrathin nanotubes with respect to the graphine sheet are negative and the magnitude of the negative BE decreases with the diameter of the tube approaching zero for the graphine sheet. The separation between the two van Hove singularities (vHs) around the Fermi level increases with the diameter of the tube. The main absorption arises from the transitions between the states at nonzero values of k_z lying in the range 0.38–0.50. There is a large variation in the magnitude of the optical matrix-element with the wave vector. The energy range of the strong optical absorption increases with the diameter of the tube. The presently predicted absorption and the RBM frequencies are in good agreement with the available experimental data. The variation of the radial breathing mode (RBM) frequency with diameter "d" of a tube obeys a relation which is very close to an experimentally determined relation obtained for a number of wide semiconducting nanotubes possessing a wide range of chiral angles.

Soft chemical routes are employed effectively for the synthesis of nanocrystals of semiconductor materials. Several methods have been developed for the synthesis of multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) and specially noteworthy are the precursor route and nebulized spray pyrolysis for the synthesis of MWNTs and junction nanotubes. Nanotubes of inorganic layered materials are obtained by ingenious chemical methods. Nanowires of inorganic materials can be synthesized not only by high-temperature methods such as the carbon-assisted route but also by soft chemical routes.

We report on a number of new effects of self-organization at nanoscale, leading to creation of new functional nanomaterials, including carbon and carbon–metal nanotoroids and nanodiscs and self-assembling of magnetic nanoparticles into helices and chains. We also extensively used a new approach of biopattern nanoengineering to create DNA-based complexes with metal or CdSe/ZnS core-shell nanorods (22 × 4.5 nm) which possess strong linearly polarized photoluminescence due to unidirectional orientation of nanorods along DNA filaments. Optical, electrical, and topological (geometrical) properties of such complexes were investigated. This work is a result of a coherent effort (since 1980s) of a consortium of Russian research groups in Nano-technology (INTC: Interdisciplinary Nanotechnology Consortium) aimed at creating molecular electronic devices based on individual and collective properties of specially designed and fabricated nanoclusters.

We demonstrate Co, Fe, and Ni encapsulated polyaniline (PAni) nanotubes using a three-step anodization and electrodeposition process. The electrodeposition process is used to create the tubes, as well as the wires, in a highly reliable manner. The metal-filled PAni structures embedded inside nanoporous alumina templates are fabricated in the form of an array. The magnetic properties of these structures are investigated as a function of temperature. These results are compared with the magnetic properties of nanowires embedded inside nanoporous alumina templates.

This work presents template synthesis of ordered arrays of nickel, cobalt and nickel hexacyanoferrates (NiHCF) with several distinct morphologies such as dots, rods, and tubes. Anodic alumina oxide (AAO) with preferred pore diameters and thickness was fabricated by electrochemical anodization of aluminum used as template. Ni and Co nanostructures inside AAO template were prepared by electrodeposition using galvanostatic method. NiHCF nanostructures were prepared by electrochemical oxidation of Ni using cyclic voltametry (CV) in the presence of hexacyanoferrate ions. The morphology, chemical, and functional properties of prepared nanostructures were investigated by scanning electron microscopy (SEM), energy-dispersive X-ray microscopy (EDAX), and electrochemical methods. The electrocatalytic properties of NiHCF nanorod arrays electrode and their potential for the detection of hydrogen peroxide and biosensing application were demonstrated.

Ultralong zinc oxide nanotubes have been synthesized on glass substrate by a simple chemical bath deposition. The nanotubes are hexagonal with the core diameter about ~200 nm. The length of the nanotubes was about 10 μm. No specific alignment of the nanotubes on the glass substrate was observed. The morphology of the nanostructures depends highly on the concentration of zinc acetate solution, duration of mechanical stirring, and temperature during synthesis. Depending upon these experimental conditions nanorods and nanotubes were observed. The material was structurally characterized using grazing incidence X-ray diffraction, showing hexagonal unit cell structure. Transmission electron microscopy results revealed that the walls of the nanotubes are hexagonal. Room temperature photoluminescence spectrum shows a strong violet emission at ~420 nm from the ZnO nanotubes due to transition between zinc interstitial and zinc vacancy level. These results will be very useful in optoelectronic and nanophotonic device applications.

Carbonaceous nanotubes with a calculated specific heat of 710J K${}^{-1}$ Kg${}^{-1}$, and an outer diameter of 58nm, made by a micro-thermal reaction, using polypyrrole nanotubes precursor is presented here. Three degradation stages from the thermal curves are identified. We observe a decomposition temperature at 371${}^{\circ }$C that relates to the presence of amorphous carbon on samples for the first time in this material. Also, it is identified that gradual decomposition of the fragments provides a different kind of residue percentage in the range 48–32% that is related to stirring speed used in each synthesis. It is worthy to note that electron transmission microscope images of carbonaceous nanotubes present defects as well, wherein we identify chloride and nitrogen as doped agents. Finally, results of nanotubes using Infrared, Raman spectrometry analysis, scanning electron microscopy and electron diffraction are presented here.

Inorganic fullerene-like (IF) nanoparticles of MoS₂ were synthesized using gas-phase reaction starting from MoCl₅ and H₂S. The IF-MoS₂ nanoparticles are spherical and in some cases faceted with diameters in general ranging between 20 and 80 nm. The IF-MoS₂ nanoparticles have large hollow cores, filled in some cases with amorphous material. Various parameters have been investigated to understand the growth and formation of the IF-MoS₂ nanoparticles. The parameters that have been studied include flow rates of the various carrier gases, temperature at which the reaction was carried out, time of the reaction and heating of the precursor material. The best set of conditions wherein maximum yields of the IF-MoS₂ nanoparticles are obtained have been identified. Additionally, annealing the as-obtained samples or heating them in a mixture of H₂ along with H₂S improves the crystallinity and reduces the amorphous material filling in the core. Apart from the fullerene-like nanoparticles under certain experimental conditions nanotubes of MoS₂ have also been obtained nonetheless in small yields.

The effect of ultraviolet, visible and near-infrared irradiation on the yield and morphology of single crystalline C₆₀ fullerene nanowhiskers (FNWs) and nanotubes (FNTs) was investigated in an effort to produce large-scale quantities of FNWs and FNTs. These fullerene nanomaterials were synthesized by the liquid–liquid interfacial precipitation method using pyridine and isopropyl alcohol (IPA) as solvents. The C₆₀–pyridine solution was illuminated using different wavelengths for 24 h at ambient pressure and temperature before addition of IPA. High yields (30–38 mg/L) were obtained upon irradiation using wavelengths in the ultraviolet region in accordance with the increased photoabsorption signal of solid C₆₀ and C₆₀ dissolved in pyridine acquired by a UV-VIS-NIR spectrophotometer. However, elevated yields (21–27 mg/L) were also obtained in the 600–800 nm regions, where C₆₀ absorption is particularly weak. Such an enhanced yield of FNTs and FNWs is probably related to the reported rise in transient absorption of the triplet excited state of C₆₀ in the 740 nm region formed by the decay of the photoexcited singlet C₆₀ through intersystem crossing. The formation of photopolymerized fullerene nanofibers was also observed by Raman spectroscopy, it is attributed to ultraviolet and visible light irradiation. SEM and TEM observations suggest that preparation of FNWs and FNTs by irradiation using different wavelengths of light does not produce apparent morphological transformations on the surface of these fullerene materials.

Fe-decorated fullerene nanowhiskers were prepared by using the liquid–liquid interfacial precipitation method. The prepared nanowhiskers were characterized using scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), X-ray diffraction (XRD) and Raman spectroscopy. Formation of both tubular and nontubular nanowhiskers was observed with fine dispersion of Fe ions. The XRD and Raman-spectroscopic studies showed the fcc crystalline nature and polymerization of the nanowhiskers, respectively. The results were compared with Ce- and Ni-incorporated fullerene nanowhiskers.

Ultra-thin (10–100 nm) conformal coatings of poly(ethyl 2-cyanoacrylate) and poly(p-xylylene) have been synthesized via vapor deposition in the confined nanochannels of anodized alumina membranes. Poly(ethyl 2-cyanoacrylate) nanotubes and coaxial poly(ethyl 2-cyanoacrylate)/poly(p-xylylene) nanotubes with precisely-controlled wall thickness were obtained after the removal of the inorganic anodized alumina membrane. Platinum nanoparticles have also been deposited in the coaxial nanotubes via supercritical carbon dioxide.

Time-dependent wet-processing of HiPCo nanotubes in ~ 0.5 M phosphoric acid and its effect on the structural, transport, infrared light absorption and photoconduction characteristics have been studied. Nanotubes were treated for nominal time intervals of 1, 2 and 3 h. The treatment is found to be a two-step process that initially results in the removal/partial replacement of most pre-existing C-O, O–H and CH_x groups with phosphorous oxy and carbonyl groups. According to T-dependent current–voltage measurements, the differential conductance, G of nanotube network varies with temperature as ~ T^a, with a exhibiting a slight increase as a result of the treatment, attributed to a slight increase in disorder and not doping effects. The nanotubes processed for three hours also show an order of magnitude improvement in photoconduction response time compared to that of untreated tubes, with growth/decay characteristic time constants approaching a sub-second range.

New types of core–shell nanoparticles are reported: Pb@GaS fullerene-like and nanotubular structures, achieved via the continuously high reactor temperatures and ultra-hot strong-gradient annealing environments created by highly concentrated sunlight. Structural and chemical characterizations suggest a formation mechanism where vaporized Pb condenses into nanoparticles that are stabilized as they become covered by molten GaS, the ensuing crystallization of which creates the outer layers. Hollow-core GaS fullerene-like nanoparticles and nanotubes were also observed among the products, demonstrating that a single solar procedure can generate a variety of core–shell and hollow nanostructures. The proposed formation mechanisms can account for their relative abundance and the characterization data.

Pure and Eu-doped (1.0, 3.0, 5.0wt.%) $\alpha$-Fe₂O₃ (PFO and EFO) nanotubes and nanowires have been successfully synthesized through the combination of electrospinning and calcination techniques. The structures, morphologies and chemical compositions of the as-obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric and differential scanning calorimetry (TG-DSC) and energy dispersive spectrum (EDS), respectively. To demonstrate the superior gas sensing performance of the doped nanotubes, a contrastive gas sensing study between PFO (EFO) nanotubes and nanowires was performed. It turned out that Eu doping could magnify the impact of morphology on gas sensitivity. Specifically, at the optimum operating temperature of 240${}^{\circ }$C, the response value of PFO nanotubes to 100ppm acetone is slightly higher than that of nanowires (3.59/2.20). EFO (3.0wt.%) nanotubes have a response of 84.05, which is almost 2.7 times as high as that of nanowires (31.54). Moreover, they possess more rapid response/recovery time (11s and 36s, respectively) than nanowires (17s and 40s, respectively). The lowest detection limit for acetone is 0.1ppm and its response is 2.15. In addition, both of EFO nanotubes and nanowires sensors have a good linearity (0.1–500ppm) and favorable selectivity in acetone detection.

Carbon nanotubes (CNTs) have properties that promise an exciting role in nervous tissue repair. CNTs are strong, extremely light weight, biocompatible and electrically conductive. A relatively novel form of CNT material, multiple strands of CNTs spun into thread, accentuates the linear geometry of CNTs while retaining electrical conductivity. We propose that CNT thread, which is strong, pliable and readily manipulated, has the potential to support longitudinal growth of nerves after injury, in nervous system prostheses. Towards understanding how CNT materials support nervous tissue regeneration, we examined the in vitro interactions between CNT materials and neural stem cell-containing neurospheres, prepared from newborn mouse cortices. Intact neurospheres attached to pieces of as-grown arrays of CNTs, CNT "ribbon" material pulled from the arrays, and CNT thread. Stem cells differentiated into both neurons and glia under these conditions. Processes and cells aligned with the longitudinal axis of the CNT materials, both with and without coatings. For comparisons, dissociated neurosphere cells were plated on CNT thread, polypropylene surgical suture thread and commercial carbon fibers. Initial cell attachment (within seconds) and attachment at 24 h was greater on CNT thread than on the other fiber types. Stem cells on CNT threads differentiated into neurons and astrocytes over several days, on all fibers. The presence of serum greatly aided the health and spreading of both neurons and astrocytes. These findings demonstrate that CNT materials, in particular the thread form, are viable preparations for neural cell attachment, outgrowth and differentiation.

Nanotubes (NT) composed of the electrically active polymer poly (3,4-ethylenedioxythiophene) (PEDOT) have been used for photothermal ablation of both gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria. Since infrared absorption of PEDOT is dominated by bipolarons strongly coupled to phonons, we hypothesize that nonradiative decay of these states leads to heat generation. Photothermal death of bacteria by PEDOT NT was compared to single-wall carbon nanotubes (SWNT). Complete eradication of bacterial colonies incubated with 100 ug/ml of either PEDOT NT or SWNT occurred with a single exposure to 1064 nm light (3.8 W/cm²) for 60 s. PEDOT NT were also shown to elicit a mild antibacterial response upon incubation with bacteria and no infrared exposure. PEDOT NT have the same capacity for photothermal ablation of bacteria as compared to SWNT; therefore, they represent an exciting new class of polymer based nanoparticles for medically-relevant photothermal therapies.