An Overview of the Recent Progress in the Synthesis and Applications of Carbon Nanotubes

Recent Advances in Carbon Nanotube Utilization in Perovskite Solar Cells: A Review

Due to their exceptional optoelectronic properties, halide perovskites have emerged as prominent materials for the light-absorbing layer in various optoelectronic devices. However, to increase device performance for wider adoption, it is essential to find innovative solutions. One promising solution is incorporating carbon nanotubes (CNTs), which have shown remarkable versatility and efficacy. In these devices, CNTs serve multiple functions, including providing conducting substrates and electrodes and improving charge extraction and transport. The next iteration of photovoltaic devices, metal halide perovskite solar cells (PSCs), holds immense promise. Despite significant progress, achieving optimal efficiency, stability, and affordability simultaneously remains a challenge, and overcoming these obstacles requires the development of novel materials known as CNTs, which, owing to their remarkable electrical, optical, and mechanical properties, have garnered considerable attention as potential materials for highly efficient PSCs. Incorporating CNTs into perovskite solar cells offers versatility, enabling improvements in device performance and longevity while catering to diverse applications. This article provides an in-depth exploration of recent advancements in carbon nanotube technology and its integration into perovskite solar cells, serving as transparent conductive electrodes, charge transporters, interlayers, hole-transporting materials, and back electrodes. Additionally, we highlighted key challenges and offered insights for future enhancements in perovskite solar cells leveraging CNTs.

Oro-Respiratory Dysbiosis and Its Modulatory Effect on Lung Mucosal Toxicity during Exposure or Co-Exposure to Carbon Nanotubes and Cigarette Smoke

The oro-respiratory microbiome is impacted by inhalable exposures such as smoking and has been associated with respiratory health conditions. However, the effect of emerging toxicants, particularly engineered nanoparticles, alone or in co-exposure with smoking, is poorly understood. Here, we investigated the impact of sub-chronic exposure to carbon nanotube (CNT) particles, cigarette smoke extract (CSE), and their combination. The oral, nasal, and lung microbiomes were characterized using 16S rRNA-based metagenomics. The exposures caused the following shifts in lung microbiota: CNT led to a change from Proteobacteria and Bacteroidetes to Firmicutes and Tenericutes; CSE caused a shift from Proteobacteria to Bacteroidetes; and co-exposure (CNT+CSE) had a mixed effect, maintaining higher numbers of Bacteroidetes (due to the CNT effect) and Tenericutes (due to the CSE effect) compared to the control group. Oral microbiome analysis revealed an abundance of the following genera: Acinetobacter (CNT), Staphylococcus, Aggregatibacter, Allobaculum, and Streptococcus (CSE), and Alkalibacterium (CNT+CSE). These proinflammatory microbial shifts correlated with changes in the relative expression of lung mucosal homeostasis/defense proteins, viz., aquaporin 1 (AQP-1), surfactant protein A (SP-A), mucin 5b (MUC5B), and IgA. Microbiota depletion reversed these perturbations, albeit to a varying extent, confirming the modulatory role of oro-respiratory dysbiosis in lung mucosal toxicity. This is the first demonstration of specific oro-respiratory microbiome constituents as potential modifiers of toxicant effects in exposed lungs.

Estrogen contributes to sex differences in M2a macrophages during multi-walled carbon nanotube-induced respiratory inflammation

Lung diseases characterized by type 2 inflammation are reported to occur with a female bias in prevalence/severity in both humans and mice. This includes previous work examining multi-walled carbon nanotube (MWCNT)-induced eosinophilic inflammation, in which a more exaggerated M2a phenotype was observed in female alveolar macrophages (AMs) compared to males. The mechanisms responsible for this sex difference in AM phenotype are still unclear, but estrogen receptor (ER) signaling is a likely contributor. Accordingly, male AMs downregulated ERα expression after MWCNT exposure while female AMs did not. Thus, ER antagonist Fulvestrant was administered prior to MWCNT instillation. In females, Fulvestrant significantly attenuated MWCNT-induced M2a gene expression and eosinophilia without affecting IL-33. In males, Fulvestrant did not affect eosinophil recruitment but reduced IL-33 and M2a genes compared to controls. Regulation of cholesterol efflux and oxysterol synthesis is a potential mechanism through which estrogen promotes the M2a phenotype. Levels of oxysterols 25-OHC and 7α,25-OHC were higher in the airways of MWCNT-exposed males compared to MWCNT-females, which corresponds with the lower IL-1β production and greater macrophage recruitment previously observed in males. Sex-based changes in cholesterol efflux transporters Abca1 and Abcg1 were also observed after MWCNT exposure with or without Fulvestrant. In vitro culture with estrogen decreased cellular cholesterol and increased the M2a response in female AMs, but did not affect cholesterol content in male AMs and reduced M2a polarization. These results reveal the modulation of (oxy)sterols as a potential mechanism through which estrogen signaling may regulate AM phenotype resulting in sex differences in downstream respiratory inflammation.

Preparation and usage of nanomaterials in biomedicine

Nanotechnology is one of the most promising and decisive technologies in the world. Nanomaterials, as the primary research aspect of nanotechnology, are quite different from macroscopic materials because of their unique optical, electrical, magnetic, thermal properties, and more robust mechanical properties, which make them play an essential role in the field of materials science, biomedical field, aerospace field, and environmental energy. Different preparation methods for nanomaterials have various physical and chemical properties and are widely used in different areas. In this review, we focused on the preparation methods, including chemical, physical, and biological methods due to the properties of nanomaterials. We mainly clarified the characteristics, advantages, and disadvantages of different preparation methods. Then, we focused on the applications of nanomaterials in biomedicine, including biological detection, tumor diagnosis, and disease treatment, which provide a development trend and promising prospects for nanomaterials.

Overview of Engineering Carbon Nanomaterials Such As Carbon Nanotubes (CNTs), Carbon Nanofibers (CNFs), Graphene and Nanodiamonds and Other Carbon Allotropes inside Porous Anodic Alumina (PAA) Templates

The fabrication and design of carbon-based hierarchical structures with tailored nano-architectures have attracted the enormous attention of the materials science community due to their exceptional chemical and physical properties. The collective control of nano-objects, in terms of their dimensionality, orientation and size, is of paramount importance to expand the implementation of carbon nanomaterials across a large variety of applications. In this context, porous anodic alumina (PAA) has become an attractive template where the pore morphologies can be straightforwardly modulated. The synthesis of diverse carbon nanomaterials can be performed using PAA templates, such as carbon nanotubes (CNTs), carbon nanofibers (CNFs), and nanodiamonds, or can act as support for other carbon allotropes such as graphene and other carbon nanoforms. However, the successful growth of carbon nanomaterials within ordered PAA templates typically requires a series of stages involving the template fabrication, nanostructure growth and finally an etching or electrode metallization steps, which all encounter different challenges towards a nanodevice fabrication. The present review article describes the advantages and challenges associated with the fabrication of carbon materials in PAA based materials and aims to give a renewed momentum to this topic within the materials science community by providing an exhaustive overview of the current synthesis approaches and the most relevant applications based on PAA/Carbon nanostructures materials. Finally, the perspective and opportunities in the field are presented.

Anti-Infective and Toxicity Properties of Carbon Based Materials: Graphene and Functionalized Carbon Nanotubes

Recently, antimicrobial activities of various carbon-based nanomaterials against specific pathogens have become one of the most significant research interests in this field. Carbon nanotubes (CNTs) are promising multidisciplinary nanostructures in biomedicine, drug delivery, genetic engineering, biosensors, and artificial implants. However, the biomedical administration of CNTs is dependent on their solubility, toxicity, and biocompatibility, as well as novel drug-delivery applications through optimization of the drug's loading capacity, cellular absorption, and continuous release within the target cell. The usage of CNTs and Graphene materials as antimicrobial agents and nanocarriers for antibiotics delivery would possibly improve their bioavailability and facilitate better anti-infective therapy. However, it is worth mentioning that CNTs' antimicrobial activity and toxicity are highly dependent on their preparation and synthesis method. Various types of research have confirmed that diameter, length, residual catalyst, metal content, surface coating, electronic structure, and dispersibility would affect CNTs' toxicity toward bacteria and human cells. In this review article, a general study was performed on the antimicrobial properties of carbon-based nanomaterials, as well as their toxicity and applications in confronting different microorganisms. This study could be useful for researchers who are looking for new and effective drug delivery methods in the field of microbial resistance.

Characterization of Carbon Nanostructures by Photoelectron Spectroscopies

Recently, the scientific community experienced two revolutionary events. The first was the synthesis of single-layer graphene, which boosted research in many different areas. The second was the advent of quantum technologies with the promise to become pervasive in several aspects of everyday life. In this respect, diamonds and nanodiamonds are among the most promising materials to develop quantum devices. Graphene and nanodiamonds can be coupled with other carbon nanostructures to enhance specific properties or be properly functionalized to tune their quantum response. This contribution briefly explores photoelectron spectroscopies and, in particular, X-ray photoelectron spectroscopy (XPS) and then turns to the present applications of this technique for characterizing carbon nanomaterials. XPS is a qualitative and quantitative chemical analysis technique. It is surface-sensitive due to its limited sampling depth, which confines the analysis only to the outer few top-layers of the material surface. This enables researchers to understand the surface composition of the sample and how the chemistry influences its interaction with the environment. Although the chemical analysis remains the main information provided by XPS, modern instruments couple this information with spatial resolution and mapping or with the possibility to analyze the material in operando conditions at nearly atmospheric pressures. Examples of the application of photoelectron spectroscopies to the characterization of carbon nanostructures will be reviewed to present the potentialities of these techniques.

A Methodical Review on Carbon-Based Nanomaterials in Energy-Related Applications

Carbon nanomaterials are endowed with novel and magnificent optical, electrical, chemical, mechanical, and thermal properties, with a promising prospect in different advanced applications such as electronics, batteries, capacitors, wastewater treatment, membranes, heterogeneous catalysis, and medical sciences. However, macroscopic synthesis of carbon materials for industrial use has been a great challenge. Furthermore, structural nonhomogeneity and indefinite fabrication have hindered vigorous and consistent implementation of these materials in extensive technologies. Nevertheless, they offer exotic physics, and as a result, they have continued to attract great interest from the scientific community in an effort aimed to optimize their properties through innovative synthesis techniques, ensuring macroscopic production and discovering new applications. Hence, this study endeavours to provide a conscious review of these materials via the comprehensive discussion of the various allotropes of carbon (fullerenes, carbon nanotubes, and graphene), synthesis techniques (arc discharge, laser ablation, and chemical vapor deposition), and their applications in energy-related fields (batteries, capacitors, photocells, hydrogen storage, sensors, etc.) and their impending prospects.

Current Understanding of Water Properties inside Carbon Nanotubes

Confined water inside carbon nanotubes (CNTs) has attracted a lot of attention in recent years, amassing as a result a very large number of dedicated studies, both theoretical and experimental. This exceptional scientific interest can be understood in terms of the exotic properties of nanoconfined water, as well as the vast array of possible applications of CNTs in a wide range of fields stretching from geology to medicine and biology. This review presents an overreaching narrative of the properties of water in CNTs, based mostly on results from systematic nuclear magnetic resonance (NMR) and molecular dynamics (MD) studies, which together allow the untangling and explanation of many seemingly contradictory results present in the literature. Further, we identify still-debatable issues and open problems, as well as avenues for future studies, both theoretical and experimental.

Carbon nanotubes in biomedical applications: current status, promises, and challenges

In the past decade, there has been phenomenal progress in the field of nanomaterials, especially in the area of carbon nanotubes (CNTs). In this review, we have elucidated a contemporary synopsis of properties, synthesis, functionalization, toxicity, and several potential biomedical applications of CNTs. Researchers have reported remarkable mechanical, electronic, and physical properties of CNTs which makes their applications so versatile. Functionalization of CNTs has been valuable in modifying their properties, expanding their applications, and reducing their toxicity. In recent years, the use of CNTs in biomedical applications has grown exponentially as they are utilized in the field of drug delivery, tissue engineering, biosensors, bioimaging, and cancer treatment. CNTs can increase the lifespan of drugs in humans and facilitate their delivery directly to the targeted cells; they are also highly efficient biocompatible biosensors and bioimaging agents. CNTs have also shown great results in detecting the SARS COVID-19 virus and in the field of cancer treatment and tissue engineering which is substantially required looking at the present conditions. The concerns about CNTs include cytotoxicity faced in in vivo biomedical applications and its high manufacturing cost are discussed in the review.

What is an artificial muscle? A comparison of soft actuators to biological muscles

Interest in emulating the properties of biological muscles that allow for fast adaptability and control in unstructured environments has motivated researchers to develop new soft actuators, often referred to as 'artificial muscles'. The field of soft robotics is evolving rapidly as new soft actuator designs are published every year. In parallel, recent studies have also provided new insights for understanding biological muscles as 'active' materials whose tunable properties allow them to adapt rapidly to external perturbations. This work presents a comparative study of biological muscles and soft actuators, focusing on those properties that make biological muscles highly adaptable systems. In doing so, we briefly review the latest soft actuation technologies, their actuation mechanisms, and advantages and disadvantages from an operational perspective. Next, we review the latest advances in understanding biological muscles. This presents insight into muscle architecture, the actuation mechanism, and modeling, but more importantly, it provides an understanding of the properties that contribute to adaptability and control. Finally, we conduct a comparative study of biological muscles and soft actuators. Here, we present the accomplishments of each soft actuation technology, the remaining challenges, and future directions. Additionally, this comparative study contributes to providing further insight on soft robotic terms, such as biomimetic actuators, artificial muscles, and conceptualizing a higher level of performance actuator named artificial supermuscle. In conclusion, while soft actuators often have performance metrics such as specific power, efficiency, response time, and others similar to those in muscles, significant challenges remain when finding suitable substitutes for biological muscles, in terms of other factors such as control strategies, onboard energy integration, and thermoregulation.

Cytocompatibility of carboxylated multi-wall carbon nanotubes in stem cells from human exfoliated deciduous teeth

Carboxylated multi-wall carbon nanotube (MWCNT-COOH) presents unique properties due to nanoscale dimensions and permits a broad range of applications in different fields, such as bone tissue engineering and regenerative medicine. However, the cytocompatibility of MWCNT-COOH with human stem cells is poorly understood. Thus, studies elucidating how MWCNT-COOH affects human stem cell viability are essential to a safer application of nanotechnologies. Using stem cells from the human exfoliated deciduous teeth model, we have evaluated the effects of MWCNT-COOH on cell viability, oxidative cell stress, and DNA integrity. Results demonstrated that despite the decreased metabolism of mitochondria, MWCNT-COOH had no toxicity against stem cells. Cells maintained viability after MWCNT-COOH exposure. MWCNT-COOH did not alter the superoxide dismutase activity and did not cause genotoxic effects. The present findings are relevant to the potential application of MWCNT-COOH in the tissue engineering and regenerative medicine fields.

Concentration dependent debundling and single tube dispersions of pristine multiwalled carbon nanotubes functionalized with double tail phospholipids

Multiwalled carbon nanotubes (MWNTs) exist as aggregates of highly entangled tubes due to large aspect ratios and strong Van der Waals interactions among them in their native states. In order to render them suitable for any application, MWNTs need to be separated and dispersed uniformly in a solvent preferably as individual tubes. In the present work, it is demonstrated that a double tail lipid such as 1, 2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) is capable of dispersing MWNTs in ethanol. Ultra-stable suspensions were obtained by optimizing two key parameters: DPPE to MWNT weight ratio (ε) and MWNT concentration (c). Stability of the suspensions increased with the increasingεvalue up to an optimum point (ε= 1.8) and then decreased drastically beyond that. CNT dispersions withε= 1.8 were extremely stable (with a Zeta potential of 108.26 ± 2.15 mV) and could be retained in suspended form up to 3 months. Effect of MWNT concentration on disaggregation was very significant and stable suspensions could be formed for MWNT concentrations only below 0.14 mg ml^-1. Above this concentration, no stable dispersions could be obtained even withε= 1.8. Compression isotherms of Langmuir monolayers of the DPPE functionalized MWNTs spread at the air water interface were highly repeatable, suggesting that the MWNTs in dispersion were present as separate tubes coated with phospholipids. SEM micrographs of the Langmuir-Blodgett (LB) films, deposited at high surface pressures on silicon wafers, show that MWNTs remain as single nanotubes with no signs of reaggregation. TEM micrographs of MWNT suspensions indicated random adsorption of DPPE on MWNTs. Our work makes it possible to explore potential applications of LB films of MWNTs (stabilized by DPPE) in the development of conducting thin films for sensor applications or as supports to immobilize catalysts for heterogenous reactions.

Ultrafast Interface Charge Separation in Carbon Nanodot-Nanotube Hybrids

Carbon dots are an emerging family of zero-dimensional nanocarbons behaving as tunable light harvesters and photoactivated charge donors. Coupling them to carbon nanotubes, which are well-known electron acceptors with excellent charge transport capabilities, is very promising for several applications. Here, we first devised a route to achieve the stable electrostatic binding of carbon dots to multi- or single-walled carbon nanotubes, as confirmed by several experimental observations. The photoluminescence of carbon dots is strongly quenched when they contact either semiconductive or conductive nanotubes, indicating a strong electronic coupling to both. Theoretical simulations predict a favorable energy level alignment within these complexes, suggesting a photoinduced electron transfer from dots to nanotubes, which is a process of high functional interest. Femtosecond transient absorption confirms indeed an ultrafast (<100 fs) electron transfer independent of nanotubes being conductive or semiconductive in nature, followed by a much slower back electron transfer (≈60 ps) from the nanotube to the carbon dots. The high degree of charge separation and delocalization achieved in these nanohybrids entails significant photocatalytic properties, as we demonstrate by the reduction of silver ions in solution. The results are very promising in view of using these "all-carbon" nanohybrids as efficient light harvesters for applications in artificial photocatalysis and photosynthesis.

Low Toxicological Impact of Commercial Pristine Multi-Walled Carbon Nanotubes on the Yeast Saccharomyces cerevisiae

Carbon nanotubes (CNTs) have attracted the attention of academy and industry due to their potential applications, being currently produced and commercialized at a mass scale, but their possible impact on different biological systems remains unclear. In the present work, an assessment to understand the toxicity of commercial pristine multi-walled carbon nanotubes (MWCNTs) on the unicellular fungal model Saccharomyces cerevisiae is presented. Firstly, the nanomaterial was physico-chemically characterized, to obtain insights concerning its morphological features and elemental composition. Afterwards, a toxicology assessment was carried out, where it could be observed that cell proliferation was negatively affected only in the presence of 800 mg L^-1 for 24 h, while oxidative stress was induced at a lower concentration (160 mg L^-1) after a short exposure period (2 h). Finally, to identify possible toxicity pathways induced by the selected MWCNTs, the transcriptome of S. cerevisiae exposed to 160 and 800 mg L^-1, for two hours, was studied. In contrast to a previous study, reporting massive transcriptional changes when yeast cells were exposed to graphene nanoplatelets in the same exposure conditions, only a small number of genes (130) showed significant transcriptional changes in the presence of MWCNTs, in the higher concentration tested (800 mg L^-1), and most of them were found to be downregulated, indicating a limited biological response of the yeast cells exposed to the selected pristine commercial CNTs.

On detour index of cycloparaphenylene and polyphenylene molecular structures

Cycloparaphenylene is a particle that comprises a few benzene rings associated with covalent bonds in the para positions to frame a ring-like structure. Similarly, poly (para-phenylenes) are macromolecules that include benzenoid compounds straightforwardly joined to each other by C-C bonds. Because of their remarkable architectural highlights, these structures have fascinated attention from numerous vantage focuses. Descriptors are among the most fundamental segments of prescient quantitative structure-activity and property relationship (QSAR/QSPR) demonstrating examination. They encode chemical data of particles as quantitative numbers, which are utilized to create a mathematical correlation. The nature of a predictive model relies upon great demonstrating insights, yet additionally on the extraction of compound highlights. To a great extent, Molecular topology has exhibited its adequacy in portraying sub-atomic structures and anticipating their properties. It follows a two-dimensional methodology, just thinking about the interior plan, including molecules. Explicit subsets speak the design of every atom of topological descriptors. When all around picked, these descriptors give a unique method of describing an atomic system that can represent the most significant highlights of the molecular structure. Detour index is one such topological descriptor with much application in chemistry, especially in QSAR/QSPR studies. This article presents an exact analytical expression for the detour index of cycloparaphenylene and poly (para-phenylene).

CdO nanoparticles, c-MWCNT nanoparticles and CdO nanoparticles/c-MWCNT nanocomposite fibres: in vitro assessment of anti-proliferative and apoptotic studies in HeLa cancer cell line

A simple ultrasonic assisted chemical technique was used to synthesise cadmium oxide (CdO) nanoparticles (NPs) and CdO NPs/c-Multiwalled carbon nanotube (c-MWCNT) nanocomposite fibres.To confirm the physio-chemico properties and to analyse surface morphology of the obtained nanomaterials X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM) were performed. To evaluate the anti-cancer property of CdO NPs, c-MWCNT NPs and CdO NPs/c-MWCNT nanocomposite fibres, an anti-proliferative assay test (Methylthiazolyl diphenyl- tetrazolium bromide - MTT assay) were performed on HeLa cells which further estimated IC50 value (Least concentration of sample in which nearly 50% of cells remain alive) under in-vitro conditions. On comparison, CdONPs/c-MWCNT based system was found to be superior by achieving 52.3% cell viability with its minimal IC50 value of 31.2 μg/ml. Lastly, the CdO NPs based system was taken up for an apoptotic study using DNA fragmentation assay for estimating its ability to cleave the DNA of the HeLa cells into internucleosomal fragments using the agarose gel electrophoresis method. In conclusion, based on our observations, CdO NPs/c-MWCNT hybrid based system can be further used for the development of efficient drug delivery and therapeutic systems.

An Overview of Antimicrobial Properties of Carbon Nanotubes-Based Nanocomposites

The development of carbon-based nanomaterials has extensively facilitated new discoveries in various fields. Carbon nanotube-based nanocomposites (CNT-based nanocomposites) have lately recognized as promising biomaterials for a wide range of biomedical applications due to their unique electronic, mechanical, and biological properties. Nanocomposite materials such as silver nanoparticles (AgNPs), polymers, biomolecules, enzymes, and peptides have been reported in many studies, possess a broad range of antibacterial activity when incorporated with carbon nanotubes (CNTs). It is crucial to understand the mechanism which governs the antimicrobial activity of these CNT-based nanocomposite materials, including the decoupling individual and synergistic effects on the cells. In this review, the interaction behavior between microorganisms and different types of CNT-based nanocomposites is summarized to understand the respective antimicrobial performance in different conditions. Besides, the current development stage of CNT-based nanocomposite materials, the technical challenges faced, and the exceptional prospect of implementing potential antimicrobial CNT-based nanocomposite materials are also discussed.

Nanotechnology-based antiviral therapeutics

The host immune system is highly compromised in case of viral infections and relapses are very common. The capacity of the virus to destroy the host cell by liberating its own DNA or RNA and replicating inside the host cell poses challenges in the development of antiviral therapeutics. In recent years, many new technologies have been explored for diagnosis, prevention, and treatment of viral infections. Nanotechnology has emerged as one of the most promising technologies on account of its ability to deal with viral diseases in an effective manner, addressing the limitations of traditional antiviral medicines. It has not only helped us to overcome problems related to solubility and toxicity of drugs, but also imparted unique properties to drugs, which in turn has increased their potency and selectivity toward viral cells against the host cells. The initial part of the paper focuses on some important proteins of influenza, Ebola, HIV, herpes, Zika, dengue, and corona virus and those of the host cells important for their entry and replication into the host cells. This is followed by different types of nanomaterials which have served as delivery vehicles for the antiviral drugs. It includes various lipid-based, polymer-based, lipid-polymer hybrid-based, carbon-based, inorganic metal-based, surface-modified, and stimuli-sensitive nanomaterials and their application in antiviral therapeutics. The authors also highlight newer promising treatment approaches like nanotraps, nanorobots, nanobubbles, nanofibers, nanodiamonds, nanovaccines, and mathematical modeling for the future. The paper has been updated with the recent developments in nanotechnology-based approaches in view of the ongoing pandemic of COVID-19.Graphical abstract.

Recent advances in the extraction of triazine herbicides from water samples

Pesticides are excessively used in agriculture to improve the quality of crops by eliminating the negative effects of pests. Among the different groups of pesticides, triazine pesticides are a group of compounds that contain a substituted C₃ H₃ N₃ heterocyclic ring, and they are widely used. Triazine pesticides can be dangerous for humans as well as for the aquatic environment because of their high toxicity and endocrine disrupting effect. However, the concentration of these chemical compounds in water samples is low. Moreover, other compounds that may exist in the water samples can interfere with the determination of triazine pesticides. As a result, it is important to develop sample preparation methods that provide preconcentration of the target analyte and sufficient clean-up of the samples. Recently, a wide variety of novel microextraction and miniaturized extraction techniques (e.g., solid-phase microextraction and liquid-phase microextraction, stir bar sorptive extraction, fabric phase sorptive extraction, dispersive solid-phase extraction, and magnetic solid-phase extraction) have been developed. In this review, we aim to discuss the recent advances regarding the extraction of triazine pesticides from environmental water samples. Emphasis will be given to novel sample preparation methods and novel sorbents developed for sorbent-based extraction techniques.

Carbon Nanomaterials: Synthesis, Functionalization and Sensing Applications

Recent advances in nanomaterial design and synthesis has resulted in robust sensing systems that display superior analytical performance. The use of nanomaterials within sensors has accelerated new routes and opportunities for the detection of analytes or target molecules. Among others, carbon-based sensors have reported biocompatibility, better sensitivity, better selectivity and lower limits of detection to reveal a wide range of organic and inorganic molecules. Carbon nanomaterials are among the most extensively studied materials because of their unique properties spanning from the high specific surface area, high carrier mobility, high electrical conductivity, flexibility, and optical transparency fostering their use in sensing applications. In this paper, a comprehensive review has been made to cover recent developments in the field of carbon-based nanomaterials for sensing applications. The review describes nanomaterials like fullerenes, carbon onions, carbon quantum dots, nanodiamonds, carbon nanotubes, and graphene. Synthesis of these nanostructures has been discussed along with their functionalization methods. The recent application of all these nanomaterials in sensing applications has been highlighted for the principal applicative field and the future prospects and possibilities have been outlined.

Tailoring Carbon Nanotubes to Enhance their Efficiency as Electron Shuttle on the Biological Removal of Acid Orange 10 Under Anaerobic Conditions

Anaerobic treatments have been described for the biodegradation of pollutants. However, the reactions proceed slowly due to the recalcitrant nature of these compounds. Carbon nanomaterials (CNM) intermediate in, and favor, the electron transfer, accelerating the anaerobic reduction of pollutants, which act as final electron acceptors. In the present work, different carbon nanotubes (CNT) with modified surface chemistry, namely CNT oxidized with HNO₃ (CNT_HNO₃) and CNT doped with nitrogen in a ball milling process (CNT_N_MB) were prepared using commercial CNT as a starting material. The new CNM were tested as redox mediators (RM), 0.1 g L^-1, in the biological reduction of the azo dye, Acid Orange 10 (AO10), with an anaerobic granular sludge, over 48 h of reaction. Methane production was also assessed to verify the microorganism's activity and the CNM's effect on the methanogenic activity. An improvement in the biological removal of AO10 occurred with all CNM (above 90%), when compared with the control without CNM (only 32.4 ± 0.3%). The best results were obtained with CNT_N_MB, which achieved 98.2 ± 0.1% biological AO10 removal, and an 11-fold reduction rate increase. In order to confer magnetic properties to the CNM, tailored CNT were impregnated with 2% of iron-samples: CNT@2%Fe, CNT@2%Fe_N_MB, and CNT@2%Fe_HNO₃. The better performance of the CNT doped with nitrogen was confirmed with CNT@2%Fe_N_MB, and the magnetic character facilitated its recovery after treatment, and did not affect its good catalytic properties. No dye removal was observed in the abiotic assays, so the removal was not due to adsorption on the CNM. Furthermore, the microorganism's viability was maintained during the assay and methane production was not affected by the presence of the CNM. Despite the toxic character of the aromatic amines formed, detoxification was observed after the biological process with thermally treated CNT.

An in-silico layer-by-layer adsorption study of the interaction between Rebaudioside A and the T1R2 human sweet taste receptor: modelling and biosensing perspectives

The human sweet taste receptor (T1R2) monomer-a member of the G-protein coupled receptor family that detects a wide variety of chemically and structurally diverse sweet tasting molecules, is known to pose a significant threat to human health. Protein that lack crystal structure is a challenge in structure-based protein design. This study focused on the interaction of the T1R2 monomer with rebaudioside A (Reb-A), a steviol glycoside with potential use as a natural sweetener using in-silico and biosensing methods. Herein, homology modelling, docking studies, and molecular dynamics simulations were applied to elucidate the interaction between Reb-A and the T1R2 monomer. In addition, the electrochemical sensing of the immobilised T1R2-Reb-A complex with zinc oxide nanoparticles (ZnONPs) and graphene oxide (GO) were assessed by testing the performance of multiwalled carbon nanotube (MWCNT) as an adsorbent experimentally. Results indicate a strong interaction between Reb-A and the T1R2 receptor, revealing the stabilizing interaction of the amino acids with the Reb-A by hydrogen bonds with the hydroxyl groups of the glucose moieties, along with a significant amount of hydrophobic interactions. Moreover, the presence of the MWCNT as an anchor confirms the adsorption strength of the T1R2-Reb-A complex onto the GO nanocomposite and supported with electrochemical measurements. Overall, this study could serve as a cornerstone in the development of electrochemical immunosensor for the detection of Reb-A, with applications in the food industry.

Recent Achievements in Polymer Bio-Based Flocculants for Water Treatment

Polymer flocculants are used to promote solid-liquid separation processes in potable water and wastewater treatment. Recently, bio-based flocculants have received a lot of attention due to their superior advantages over conventional synthetic polymers or inorganic agents. Among natural polymers, polysaccharides show many benefits such as biodegradability, non-toxicity, ability to undergo different chemical modifications, and wide accessibility from renewable sources. The following article provides an overview of bio-based flocculants and their potential application in water treatment, which may be an indication to look for safer alternatives compared to synthetic polymers. Based on the recent literature, a new approach in searching for biopolymer flocculants sources, flocculation mechanisms, test methods, and factors affecting this process are presented. Particular attention is paid to flocculants based on starch, cellulose, chitosan, and their derivatives because they are low-cost and ecological materials, accepted in industrial practice. New trends in water treatment technology, including biosynthetic polymers, nanobioflocculants, and stimulant-responsive flocculants are also considered.

Physical characterization of a novel wireless DRX Plus 3543C using both a carbon nano tube (CNT) mobile x-ray system and a traditional x-ray system

This work aims to characterize the novel DRX Plus 3543C detector in terms of detective quantum efficiency (DQE) using both a mobile x-ray system called Carestream DRX Revolution Nano and a traditional x-ray system (Carestream DRX Evolution). We used the commercial system DRX Revolution Nano, equipped with a new x-ray source based on CNT technology and field emission (FE) as the electron emitter (cathode). An innovative aspect of this device is its intrinsic selection of the focal spot size. We tested the system using three IEC-specified beam qualities (RQA3, 5 and 7) in terms of modulation transfer function (MTF), normalized noise power spectra (NNPS) and DQE as defined in the IEC 62220-1-1:2015. We compared the results obtained using DRX Revolution Nano and DRX Evolution with correlation and with Bland-Altman plots to study their agreement. RQA3 MTF is slightly lower than the RQA5 and 7 curves between 0.5 and 2.5 cycles mm^-1. We measured MTF values of about 0.6 at 1 lp mm^-1 and about 0.28 lp mm^-1 at 2 lp mm^-1. The NNPS curves show a decreasing trend with the energy regarding the DRX Revolution Nano. On the other hand, the DRX Evolution NNPS curve at RQA3 is greater than the one at RQA5, but the one at RQA5 is less than the one at RQA7. The DQE(0) ranged between about 0.82 (DRX Evolution at RQA3) and 0.54 (DRX Evolution at RQA7). As expected, the squared Pearson's correlation coefficients between the two x-ray tubes were always in an optimal agreement, and Bland-Altman plots confirmed a substantial equivalence between the two physical characterizations of the wireless detector. In conclusion, we can show that the dynamic focal selection of the system equipped with CNT does not play a substantial role in image quality compared to a traditional system in terms of physical characterisation of the detector in our measurement conditions.

From Bio to Nano: A Review of Sustainable Methods of Synthesis of Carbon Nanotubes

This review summarizes the up-to-date techniques devised to synthesize carbon nanotubes (CNTs) from liquid or solid precursors of sustainable nature. The possibility to replace petroleum-based feeds for renewable resources such as essential oils or plant shoots is critically examined. The analysis shows that the complex nature of such resources requires the optimization of the reaction conditions to obtain products of desired microstructure and chemical composition. However, appropriate tuning of the process parameters enables the synthesis of even high-purity single-walled CNTs with a spectrum of demonstrated high-performance applications at low cost. The sheer number of successful studies completed on this front so far and described herein validate that the development of techniques for the manufacture of such products of high-added value from common precursors is not only possible but, most importantly, promising.

A Review of Applications Using Mixed Materials of Cellulose, Nanocellulose and Carbon Nanotubes

Carbon nanotubes (CNTs) have been extensively studied as one of the most interesting nanomaterials for over 25 years because they exhibit excellent mechanical, electrical, thermal, optical, and electrical properties. In the past decade, the number of publications and patents on cellulose and nanocellulose (NC) increased tenfold. Research on NC with excellent mechanical properties, flexibility, and transparency is accelerating due to the growing environmental problems surrounding us such as CO2 emissions, the accumulation of large amounts of plastic, and the depletion of energy resources such as oil. Research on mixed materials of cellulose, NC, and CNTs has been expanding because these materials exhibit various characteristics that can be controlled by varying the combination of cellulose, NC to CNTs while also being biodegradable and recyclable. An understanding of these mixed materials is required because these characteristics are diverse and are expected to solve various environmental problems. Thus far, many review papers on cellulose, NC or CNTs have been published. Although guidance for the suitable application of these mixed materials is necessary, there are few reviews summarizing them. Therefore, this review introduces the application and feature on mixed materials of cellulose, NC and CNTs.

Electrodeposition of Sn and Sn Composites with Carbon Materials Using Choline Chloride-Based Ionic Liquids

Nano carbons, such as graphene and carbon nanotubes, show very interesting electrochemical properties and are becoming a focus of interest in many areas, including electrodeposition of carbon–metal composites for battery application. The aim of this study was to incorporate carbon materials (namely oxidized multi-walled carbon nanotubes (ox-MWCNT), pristine multi-walled carbon nanotubes (P-MWCNT), and reduced graphene oxide (rGO)) into a metallic tin matrix. Formation of the carbon–tin composite materials was achieved by electrodeposition from a choline chloride-based ionic solvent. The different structures and treatments of the carbon materials will create metallic composites with different characteristics. The electrochemical characterization of Sn and Sn composites was performed using chronoamperometry, potentiometry, electrochemical impedance, and cyclic voltammetry. The initial growth stages of Sn and Sn composites were characterized by a glassy-carbon (GC) electrode surface. Nucleation studies were carried out, and the effect of the carbon materials was characterized using the Scharifker and Hills (SH) and Scharifker and Mostany (SM) models. Through a non-linear fitting method, it was shown that the nucleation of Sn and Sn composites on a GC surface occurred through a 3D instantaneous process with growth controlled by diffusion. According to Raman and XRD analysis, carbon materials were successfully incorporated at the Sn matrix. AFM and SEM images showed that the carbon incorporation influences the coverage of the surface as well as the size and shape of the agglomerate. From the analysis of the corrosion tests, it is possible to say that Sn-composite films exhibit a comparable or slightly better corrosion performance as compared to pure Sn films.

Functionalization of Carbon Nanomaterials for Biomedical Applications

Over the past decade, carbon nanostructures (CNSs) have been widely used in a variety of biomedical applications. Examples are the use of CNSs for drug and protein delivery or in tools to locally dispense nucleic acids to fight tumor affections. CNSs were successfully utilized in diagnostics and in noninvasive and highly sensitive imaging devices thanks to their optical properties in the near infrared region. However, biomedical applications require a complete biocompatibility to avoid adverse reactions of the immune system and CNSs potentials for biodegradability. Water is one of the main constituents of the living matter. Unfortunately, one of the disadvantages of CNSs is their poor solubility. Surface functionalization of CNSs is commonly utilized as an efficient solution to both tune the surface wettability of CNSs and impart biocompatible properties. Grafting functional groups onto the CNSs surface consists in bonding the desired chemical species on the carbon nanoparticles via wet or dry processes leading to the formation of a stable interaction. This latter may be of different nature as the van Der Waals, the electrostatic or the covalent, the π-π interaction, the hydrogen bond etc. depending on the process and on the functional molecule at play. Grafting is utilized for multiple purposes including bonding mimetic agents such as polyethylene glycol, drug/protein adsorption, attaching nanostructures to increase the CNSs opacity to selected wavelengths or provide magnetic properties. This makes the CNSs a very versatile tool for a broad selection of applications as medicinal biochips, new high-performance platforms for magnetic resonance (MR), photothermal therapy, molecular imaging, tissue engineering, and neuroscience. The scope of this work is to highlight up-to-date using of the functionalized carbon materials such as graphene, carbon fibers, carbon nanotubes, fullerene and nanodiamonds in biomedical applications.

Recent Progress in Carbon-Based Buffer Layers for Polymer Solar Cells

Carbon-based materials are promising candidates as charge transport layers in various optoelectronic devices and have been applied to enhance the performance and stability of such devices. In this paper, we provide an overview of the most contemporary strategies that use carbon-based materials including graphene, graphene oxide, carbon nanotubes, carbon quantum dots, and graphitic carbon nitride as buffer layers in polymer solar cells (PSCs). The crucial parameters that regulate the performance of carbon-based buffer layers are highlighted and discussed in detail. Furthermore, the performances of recently developed carbon-based materials as hole and electron transport layers in PSCs compared with those of commercially available hole/electron transport layers are evaluated. Finally, we elaborate on the remaining challenges and future directions for the development of carbon-based buffer layers to achieve high-efficiency and high-stability PSCs.

Mechanism of Catalytic CNTs Growth in 400–650 °C Range: Explaining Volcano Shape Arrhenius Plot and Catalytic Synergism Using both Pt (or Pd) and Ni, Co or Fe

The Arrhenius plot of catalytic carbon formation from olefins on Ni, Co, and Fe has a volcano shape in the range 400–550 °C with reaction orders 0 (at lower T: Below ~500 °C) and one (at higher T: Above ~500 °C) at each side of the maximum rate. The reaction follows a catalytic route with surface decomposition of the gas (olefin) on the catalyst nanoparticle, followed by the bulk diffusion of carbon atoms and carbon nanotube growth on the opposite side. At the higher temperature region (500–550 °C), the initial surface reaction step controls the rate and the reaction order is one, both in olefins and hydrogen (H). This confirms that H is essential for the surface reaction to occur. This is very valuable information to get faster CNT growth rate at relatively low temperatures. The apparent activation energy observed must correspond with the surface reaction Ea corrected for the temperature dependence of the two molecules involved (olefin and H). Adding a noble metal (Pt, Pd) to the carbon formation catalyst is frequently found to increase the reaction rate further. This effect has been described as an H spillover since 1964. However, there is evidence that the bulk diffusion of H atoms prevails and does not “spillover” the surface diffusion. Diffusion of H atoms through the solids involved is easy, and the H atoms remain single (“independent”) until emerging on a surface.

The Advances in Biomedical Applications of Carbon Nanotubes

Unique chemical, physical, and biological features of carbon nanotubes make them an ideal candidate for myriad applications in industry and biomedicine. Carbon nanotubes have excellent electrical and thermal conductivity, high biocompatibility, flexibility, resistance to corrosion, nano-size, and a high surface area, which can be tailored and functionalized on demand. This review discusses the progress and main fields of bio-medical applications of carbon nanotubes based on recently-published reports. It encompasses the synthesis of carbon nanotubes and their application for bio-sensing, cancer treatment, hyperthermia induction, antibacterial therapy, and tissue engineering. Other areas of carbon nanotube applications were out of the scope of this review. Special attention has been paid to the problem of the toxicity of carbon nanotubes.