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A distance-related spectral descriptor is a graphical index with defining structure built on eigenvalues of chemical matrices relying on distances in graphs. This paper explores the predictive ability of both existing and new distance-related spectral descriptors for estimating thermodynamic characteristics of polycyclic hydrocarbons (PHs). As a standard choice, the entropy and heat capacity are selected to represent thermodynamic properties. Furthermore, 30 initial members of PHs are considered as test molecules for this study. Three new molecular matrices have been proposed and our research demonstrates that distance-spectral graphical indices built by these novel matrices surpass in efficiency relative to famous distance-spectral indices. First, a novel computational method is put forwarded to evaluate distance-spectral indices of molecular graphs. The proposed methodology is utilized to compute both pre-existing and novel distance-related spectral descriptors, with an aim to assess their predictive efficacy using experimental data pertaining to two selected thermodynamic properties. Subsequently, we identify the five most promising distance-related spectral descriptors, comprising the degree-distance and Harary energies, the recently introduced second geometric-arithmetic energy along with its associated Estrada invariant, and 2 atom-bond connectivity (ABC) Estrada index. Notably, the 2 ABC Estrada index and Harary energy demonstrate correlation coefficients exceeding 0.95, while certain conventional spectral indices including the distance energy as well as its associated Estrada index, display comparatively lower performance levels. Moreover, we illustrate the practical implications of our findings on specific classes of one-hexagonal nanocones and carbon polyhex nanotubes. These outcomes hold potential for enhancing the theoretical determination of certain thermodynamic attributes of these nanostructures, offering improved accuracy and minimal margin of error. [ABSTRACT FROM AUTHOR]

To achieve a higher energy density for the supercapacitor without degrading cycle stability, functionalization of biomass based-AC with oxygen-containing groups was applied. Nanostructured carbon materials were produced from barley straw biomass waste using the activation-functionalization by FeCl3 and urea via the pyrolysis method in a tubular reactor at 900 °C. The electrode made up of carbon BCF-U in the three-electrode cell in aqueous KOH electrolyte showed high-specific capacitance of 515 F g–1 at current density of 2 A g−1 and in aqueous Na2SO4 electrolyte the capacitance of 379 F g−1 at 3 A g−1. The BCF-U electrode showed cycling stability, retaining more than 99% capacitance after 5000 cycles in 1 M Na2SO4 electrolyte. The fabricated symmetric supercapacitor device with carbon BCF-U showed a high-energy density of 10.7 Wh kg–1 and a power density of 720 W kg−1 in aqueous 6 M KOH. Different characterizations were carried out to show that the functional group and morphological features of the activated carbon were closely related to the superior capacitive performance by enhancing diffusion of electrolyte ions. The analysis proved the formation of graphitic nature with mixed micro- and mesoporous textures in addition to carbon nanotube, carbon nano rod, and graphene. These unique features make synthetic activated and functionalized samples possess good adsorption capacity for electrical double layer capacitors. The results demonstrate that nanostructured carbon materials derived from a low-cost biomass waste can serve as an economical carbon feedstock for production of high-performance electrode material for supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract Nanotubes showed merits including high structural strength-to-weight ratio. However, tubes are less favored regarding stiffness and strength. Nano-I-beams are proposed for improved nano-mechanics. Computationally, the study proposes novel molecular designs of I-beam-like shaped structures. A conformation analysis, molecular dynamics and first principles-based optimization are presented. The study proposes options based on the configuration of the molecular nano-I-beam structure providing less number of planes of symmetry and hence more stability than nanotube-like structures. These designs feature a unique geometrical differentiator of having the walls of the out-of-plane hexagonal motif-based molecular nano-I-beam (C60H46) inclined with different inclination angles enabling promising properties. The stability of the proposed nano-I-beam is proved on par with the corresponding nanotube-like structure. First principles-based evidence is provided on the comparable polarizability and the comparable ability to store energy of the supercell of the crystalline slab nano-I-beam in comparison with the corresponding nanotube. A proposed hybrid octa-hexagonal-cubic molecular nano-I-beam (C24H12) remedies the nano-buckling observed in the alike square-octagonal nanostructure. The molecular nano-I-beam exhibits intrinsic switchability that enables the nano-I-beam to be a topological semiconductor/insulator. The results show promising electronic and elastic properties of the proposed nano-I-beams that suit several applications such as their use in capacitors, transistors, insulators, batteries, quantization-based nano-devices, solid lubricant additive to grease, toughening fibers of nanocomposites, hydrophobic films, emissions adsorbents, catalytic sensors, PAH materials for space, and sustainable energy. The molecular nano-I-beam provides the base of the corresponding 2-D crystalline slab nano-I-beams.

Abstract The present work reports the synthesis of multi-wall carbon nanotubes (MWCNTs) over graphite nanosheets by an easy and simple approach without using any external catalyst. Simply, yellow corn seeds were thermally annealed in a hydrogen atmosphere at 1050 °C for 3 h without any pretreatments. Notably, the growth of MWCNTs was observed to preferentially occur on the outer surface of the corn shell. This uncomplicated approach not only emphasizes the feasibility of synthesizing carbon nanomaterials using agricultural by-products but also underscores the potential applications of these synthesized materials in various fields. Samples were examined through a comprehensive analysis employing various techniques, including scanning electron microscopy (SEM), Raman spectroscopy, FTIR, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). The findings unveiled the formation of rolled graphene accompanied by the presence of vertical multi-wall carbon nanotubes (MWCNTs) positioned over stacked graphene sheets. This detailed characterization provides insights into the structural features and arrangement of the synthesized materials, paving the way for a deeper understanding of their potential applications. The pyrolysis temperature is a crucial factor in the morphological characteristics of the synthesized carbon nanostructures. While graphene cage-like structures were obtained at 800 °C, small carbon nanotubes were grafted to larger ones and formed three-dimensional hierarchical morphologies when the annealing temperature increased to 900 °C. The growth mechanism of the carbon nanotubes was explained based on the jet self-extrusion of the generated gases through the inherent pores of the corn seeds. The current technique employed in manufacturing MWCNTs shows significant promise as a green synthesis method for producing catalyst-free MWCNTs suitable for industrial applications including sensors and energy storage materials.

The present work reports the synthesis of multi-wall carbon nanotubes (MWCNTs) over graphite nanosheets by an easy and simple approach without using any external catalyst. Simply, yellow corn seeds were thermally annealed in a hydrogen atmosphere at 1050 °C for 3 h without any pretreatments. Notably, the growth of MWCNTs was observed to preferentially occur on the outer surface of the corn shell. This uncomplicated approach not only emphasizes the feasibility of synthesizing carbon nanomaterials using agricultural by-products but also underscores the potential applications of these synthesized materials in various fields. Samples were examined through a comprehensive analysis employing various techniques, including scanning electron microscopy (SEM), Raman spectroscopy, FTIR, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). The findings unveiled the formation of rolled graphene accompanied by the presence of vertical multi-wall carbon nanotubes (MWCNTs) positioned over stacked graphene sheets. This detailed characterization provides insights into the structural features and arrangement of the synthesized materials, paving the way for a deeper understanding of their potential applications. The pyrolysis temperature is a crucial factor in the morphological characteristics of the synthesized carbon nanostructures. While graphene cage-like structures were obtained at 800 °C, small carbon nanotubes were grafted to larger ones and formed three-dimensional hierarchical morphologies when the annealing temperature increased to 900 °C. The growth mechanism of the carbon nanotubes was explained based on the jet self-extrusion of the generated gases through the inherent pores of the corn seeds. The current technique employed in manufacturing MWCNTs shows significant promise as a green synthesis method for producing catalyst-free MWCNTs suitable for industrial applications including sensors and energy storage materials. [ABSTRACT FROM AUTHOR]

Thermoelectric materials have been widely recognized as a simple approach to harness green energy by converting thermal gradients into electrical energy. However, the intricate interplay between electrical conductivity, Seebeck coefficient, and thermal conductivity in thermoelectric materials presents a challenge to improving their efficiency. Traditional experimental methods and calculation methods have troublesome steps and long cycles for predicting new thermoelectric materials. In this work we present materials informatics-based approach, where statistical and machine learning models like correlation matrix, multiple linear regression, principal component analysis and artificial neural network were employed to find the relationship between features and thermoelectric performance. Furthermore, artificial neural network was used to analyze the roles of several compositional and microstructural features along with temperature on electrical conductivity, thermal conductivity, Seebeck coefficient and thermoelectric figure of merit (ZT) for PANI and quasi 0D carbon-based composites. [ABSTRACT FROM AUTHOR]

In this study, nanostructures palladium was synthesized using an ultrasonic wave which is innovative, expeditious, and ecologically benign protocol. In the procedure, ultrasonic probe with 150 W was applied to an aqueous solution of Na2PdCl4 containing sodium citrate for 1 h at room temperature. The as‐prepared palladium nanoparticles were characterized through deployment of XRD, TEM, EDX, and UV‐Vis techniques. Moreover, the study extends to take the benefits from palladium nanoparticles to produce a novel carbon‐based composite using graphene oxide (Pd‐GO) which was characterized by XRD, TEM, EDX, and UV‐Vis. The organic‐inorganic nanohybrid (Pd‐GO) was then applied in a systematic investigation aimed at assessing its ability to enhance the hydrogen storage properties of GO as nano‐palladium was incorporated at a ratio of 1 Pd: 100 GO, yielding a significant enhancement (48%) in the storage capabilities of pure GO. [ABSTRACT FROM AUTHOR]

A simple, low-cost, and environmentally benign process for synthesizing nanostructured NiO/NiAl2O4 on multiple kinds of carbon nanostructures (CNS) is presented. This method develops polylactic acid (PLA) based waste plastic materials for the producing CNS. These composites (NiO@NiAl2O4/CNS) were examined as potential electrodes in supercapacitors (SC) as they exhibit good charge/discharge reversibility and provide adequate specific capacitance values with a maximum being 1984 F/g at 0.5 A g-1. It is noteworthy that the cycling stability of this sample at 10 A g-1 maintained 101.7% of its initial capacity even after 5000 GCD cycles. An asymmetric supercapacitor (ASC) was built and analyzed, with NiO@NiAl2O4/CNS serving as the cathode and activated carbon serving as the anode of the device. The concluded device has an energy density of 58 Wh kg-1 with a power density of 986 W kg-1 and a SCs of 216.5 F/g. The results showed that the materials mentioned are a great option to use as electrode materials in applications involving the storage of energy. [ABSTRACT FROM AUTHOR]

Titanium is the most used material for implant production. To increase its biocompatibility, continuous research on new coatings has been performed by the scientific community. The aim of the present paper is to prepare new coatings on the surfaces of the pure Ti Grade 2 and the Ti6Al4V alloy. Three types of coatings were achieved by applying anodization and chemical vapor deposition (CVD) methods: TiO2 nanotubes (TNTs) were formed by anodization, carbon nanotubes (CNTs) were obtained through a metal-catalyst-free CVD process, and a bilayer coating (TiO2 nanotubes/carbon nanostructures) was prepared via successive anodization and CVD processes. The morphology and structure of the newly developed coatings were characterized using SEM, EDX, AFM, XRD, and Raman spectroscopy. It was found that after anodization, the morphology of the TiO2 layer on pure Ti consisted of a "sponge-like" structure, nanotubes, and nano-rods, while the TNTs layer on the Ti alloy comprised mainly nanotubes. The bilayer coatings on both materials demonstrated different morphologies: the pure Ti metal was covered by a layer of nanotubular and nano-rod TiO2 structures, followed by a dense carbon layer decorated with carbon nanoflakes, and on the Ti alloy, first, a TNTs layer was formed, and then carbon nano-rods were deposited using the CVD method. [ABSTRACT FROM AUTHOR]

In this work, using X-ray diffractometry and optical microscopy, studies of epoxy-based composites containing a small amount of nanostructures (nanotubes and graphene oxide) were carried out. The test substance was used to glue two aluminum plates together, and then they were stretched in different directions until rupture. Using X-ray diffractometry, it was found that the introduction of an impurity does not lead to the formation of crystalline inclusions in the adhesive layer. For samples with an admixture of graphene oxide, the formation of graphene oxide conglomerates with a linear size of the order of 10 μm is observed. [ABSTRACT FROM AUTHOR]

Nano-PCMs, which contain nanostructured materials, can enhance the low thermal conductivity of phase change materials (PCMs). It is crucial to predict the precise thermal conductivity of nano-PCM to assess the heat transfer during phase change procedures such as melting and solidification. In this study, artificial neural network (ANN) and response surface method (RSM) were used to develop a model for predicting the thermal conductivity of carbon-based nano-enhanced phase change materials (NEPCMs) using 482 experimental samples collected from various datasets. The carbon-based nano-particles were SWCNTs, MWCNTs, graphite, graphene, and (CNFs). Six input parameters were considered with varying temperature, mass fractions, sizes, thermal conductivities of PCMs and nano-particles, and the phase of PCM. The ANN was designed using a multi-layered feed-forward structure and Levenberg–Marquardt back-propagation algorithm with one hidden layer consisting of eight neurons. The transfer function was varied to achieve optimal performance. It was revealed that the predictive capacity of the ANN model is greater than that of the RSM model based on their corresponding the coefficient of determination (R2) and root mean square error (RMSE) values. The developed ANN achieved a R2 value of 0.99, while the RSM method model achieved an R2 value of 0.79.

Hydrogen is a promising energy source for resolving the world's energy demands without releasing pollution, but storing hydrogen poses a significant challenge. Carbon materials such as activated carbon (AC), carbon nanotubes (CNT), carbon nanofibers (CNF), carbon nano-onions (CNOs) and graphene are potential substrate materials for hydrogen storage through physisorption/chemisorption due to their large surface areas and the ability to bind hydrogen. We investigate the hydrogen storage capacity of CNOs synthesized through thermal chemical vapour deposition using acetylene in this paper. SEM and XRD analysis revealed that the CNOs are spherical and comprised 18 shells at 850 °C and 7 shells at 1000 °C. However, the CNO interlayer thickness increased from 3.42 to 3.58 A0, which has a significant impact on the physisorption process. Functionalized CNOs were studied for their hydrogen storage capacities at 77 K and 1.5 atm, demonstrated a hydrogen storage capacity of 18.2%. The BET measurements revealed that the CNOs samples have a surface area of 642 m2/gm and FTIR showed a significant increase in –OH and –CH bond vibrations. Desorption studies of hydrogen reveal primarily two stages. The removal of hydrogen from CNO requires a first-stage activation energy of 6 kJ/mol and a second-stage activation energy of 127 kJ/mol, confirming the presence of both physiosorbed and chemisorbed hydrogen. This study found that hydrogen storage capacity of CNOs is extremely promising, and has a potential for mobile applications. • The hydrogen storage capacity of synthesized CNOs was determined. • The functional groups are determined using FTIR analysis. • The number of shells, carbon atoms, interlayer thickness are calculated by XRD. • The hydrogen desorption kinetics are investigated using Coat's-Redfern's method. [ABSTRACT FROM AUTHOR]

Carbon-based nanostructures have been firmly established as highly scalable and versatile platforms, which have found extensive applications in several fields of multifunctional nanocomposites, energy storage, environment protection, and electronics device. Pickering emulsion template method is one of the efficient strategies for assembling metastable carbon nanomaterials into stable macroarchitectures. Here, the combination of graphene oxide (GO) and carbon nanotubes (CNTs) was chemically and continuously treated with 2-ethyl-4-methylimidazole (EMI) to acquire tunable wettability. The hybridization of CNTs and reduction of GO can make the as-synthesized carbon nanohybrids be capable of stabilizing oil-in-water (O/W) and water-in-oil (W/O) Pickering emulsions, respectively. The major shift in the type of Pickering emulsion is conveniently implemented through the catalytic reduction of GO by EMI. The sp2-hybridized carbon networks self-assembled with CNTs and reduced graphene oxide (RGO) are intentionally located at the biphasic liquid interface of different types of Pickering emulsions, which can endow the architecture elaborated from Pickering emulsion strategy with multiple functionalities. [ABSTRACT FROM AUTHOR]

Carbon-based solid lubricants are excellent options to reduce friction and wear, especially with the carbon capability to adopt different allotropes forms. On the macroscale, these materials are sheared on the contact along with debris and contaminants to form tribolayers that govern the tribosystem performance. Using a recently developed advanced Raman analysis on the tribolayers, it was possible to quantify the contact-induced defects in the crystalline structure of a wide range of allotropes of carbon-based solid lubricants, from graphite and carbide-derived carbon particles to multi-layer graphene and carbon nanotubes. In addition, these materials were tested under various dry sliding conditions, with different geometries, topographies, and solid-lubricant application strategies. Regardless of the initial tribosystem conditions and allotrope level of atomic ordering, there is a remarkable trend of increasing the point and line defects density until a specific saturation limit in the same order of magnitude for all the materials tested. [ABSTRACT FROM AUTHOR]

Carbon nanostructures such as carbon nanotubes, graphene, and its multi‐layer derivatives exhiibit temperature‐dependent electrical conductivity. They can form percolated networks inside polymers, which render electrical conductivity to nanocomposites. Upon the formation of a percolated network, thermal energy applied to the material drives structural changes of the network, which manifest as changes in electrical conductivity. This principle is used to develop smart materials with self‐sensing temperature capabilities. This critical review covers past and present research on the electrical response to temperature (thermoresistivity) of carbon nanostructures and their polymeric nanocomposites. It covers few‐ and multi‐layer graphene, carbon nanotubes, carbon‐nanostructured arrays and fibers (yarns). The mechanisms driving the thermoresistive response of individual nanostructures, their arrays, and of their polymeric nanocomposites are addressed. The role of the nanostructured filler on the thermoresistivity of polymer nanocomposites depends on its morphology and concentration. For low filler concentrations, thermal expansion of the polymer may dominate over the inherent thermoresistivity of the filler. For high filler concentrations, or for densely packed arrays of carbon nanostructures, the inherent (quantum) thermoresistive response of the nanostructures becomes dominant. The review addresses recent progress in the field, highlights current issues, synthesizes published data, and provides outlooks and insights into future directions. [ABSTRACT FROM AUTHOR]

Making new materials to control heat transfer has always been of interest. Carbon-based nanomaterials are promising for heat transfer due to their excellent thermal properties. Coiled carbon nanotubes (CCNTs) are among artificial carbon nanostructures due to their special mechanical properties, including high stretchability and good thermal properties are often used in many applications such as making nanodevices or advanced nanocomposites. In this research, using the molecular dynamics simulation technique and non-equilibrium molecular dynamics method, the effect of hydrogen functionalization with hydrogenation percentages of 5, 15, and 30% on the thermal properties of spring nanotubes has been investigated. The results show that the thermal conductivity of CCNTs is strongly affected by functionalization. So that by functionalizing them by 5%, their thermal conductivity coefficient decreases by 50%. Also, unlike other carbon nanostructures, the thermal conductivity of CCNTs does not decrease with the increase in the degree of functionalization, so the coefficient of thermal conductivity of 30% hydrogenated CCNTs is higher than the hydrogenated samples with lower percentages

Electrically conductive elastomer composites (CECs) with segregated networks of conductive nanofillers show high potential in stretchable strain sensors due to balanced mechanical and electrical properties, yet the sensitivity at low strain is generally insufficient for practical application. Herein, we report an easy and effective way to improve the resistive response to low strain for CECs with segregated network structure via adding stiff alumina into carbon nanostructures (CNS). The CEC containing 0.7 ​wt% CNS and 5 ​wt% Al2O3 almost sustains the same elasticity (elongation at break of ∼900%) and conductivity (0.8 ​S/m) as the control, while the piezoresistive sensitivity is significantly improved. Thermoplastic polyurethane (TPU) composites with a segregated network of hybrid nanofillers (CNS and Al2O3) show much higher strain sensitivity (Gauge factor, GF ​= ​566) at low strain (45% strain) due to a local stress concentration effect, this sensitivity is superior to that of TPU/CNS composites (GF ​= ​11). Such a local stress concentration effect depends on alumina content and its distribution at the TPU particle interface. In addition, CECs with hybrid fillers show better reproducibility in cyclic piezoresistive behavior testing than the control. This work offers an easy method for fabricating CECs with a segregated filler network offering stretchable strain sensors with a high strain sensitivity.

Abstract Carbon-based solid lubricants are excellent options to reduce friction and wear, especially with the carbon capability to adopt different allotropes forms. On the macroscale, these materials are sheared on the contact along with debris and contaminants to form tribolayers that govern the tribosystem performance. Using a recently developed advanced Raman analysis on the tribolayers, it was possible to quantify the contact-induced defects in the crystalline structure of a wide range of allotropes of carbon-based solid lubricants, from graphite and carbide-derived carbon particles to multi-layer graphene and carbon nanotubes. In addition, these materials were tested under various dry sliding conditions, with different geometries, topographies, and solid-lubricant application strategies. Regardless of the initial tribosystem conditions and allotrope level of atomic ordering, there is a remarkable trend of increasing the point and line defects density until a specific saturation limit in the same order of magnitude for all the materials tested.

The weakening of the manmade load on the environment has become a global goal of humanity. The accumulation of toxic substances in effl uents can increase the acceleration of pollution of the planet’s watersheds, resulting in biota pollution. To solve this problem, it is necessary to create photocatalysts that cause self-excitation under the ignition of light. Also, important parameters of photocatalysts are simple synthesis and low cost. This article demonstrates a one-step approach to the synthesis of carbon nanostructures (CNS) with photocatalytic activity. For this purpose, the “green chemistry ” method is used – hydrothermal treatment of various polysaccharides (sodium dextran sulfate (SDS), starch, pectin), which opens up the possibility of recycling products. A comprehensive study of the properties of the synthesized CNS has been carried out. To study the optical properties of CNS, absorption and luminescence spectroscopy, and IR spectroscopy, have been used. The CNS obtained have been successfully used in the processes of photocatalytic destruction of a model of the organic dye tartrazine, which is widely used in the fi ber and textile industries. The eff ect of lyophilization on the photocatalytic properties of СNS has been studied, and cytotoxicity has been evaluated.