Can We Optimize Arc Discharge and Laser Ablation for Well-Controlled Carbon Nanotube Synthesis?

Synthesis mechanism from graphene quantum dots to carbon nanotubes by ion-sputtering assisted chemical vapor deposition

We present the first work of the synthesis mechanism from graphene quantum dots (GQDs) to carbon nanotubes (CNTs) by an ion-sputtering assisted chemical vapor deposition. During the annealing process, a Pt thin film deposited by the ion-sputtering was dewetted and agglomerated to form many nanometer-sized particles, leading to Pt nanoparticles (PtNPs) that can act as catalysts for creating carbon allotropes. The shape of the allotropes can be effectively tailored from GQDs to CNTs by controlling three key parameters such as the dose of catalytic ions (D), amounts of carbon source (S), and thermal energy (T). In our work, it was clearly proved that the growth control from GQDs to CNTs has a comparably proportional relationship with D and S, but has a reverse proportional relationship with T. Furthermore, high-purity GQDs without any other by-products and the CNTs with the cap of PtNPs were generated. Their shapes were appropriately controlled, respectively, based on the established synthesis mechanism.

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.

Carbon Nanomaterial Fluorescent Probes and Their Biological Applications

Fluorescent carbon nanomaterials have broadly useful chemical and photophysical attributes that are conducive to applications in biology. In this review, we focus on materials whose photophysics allow for the use of these materials in biomedical and environmental applications, with emphasis on imaging, biosensing, and cargo delivery. The review focuses primarily on graphitic carbon nanomaterials including graphene and its derivatives, carbon nanotubes, as well as carbon dots and carbon nanohoops. Recent advances in and future prospects of these fields are discussed at depth, and where appropriate, references to reviews pertaining to older literature are provided.

Carbon Dots and Their Polymeric Nanocomposites: Insight into Their Synthesis, Photoluminescence Mechanisms, and Recent Trends in Sensing Applications

Carbon dots (CDs), a novel class of carbon-based nanoparticles, have received a lot of interest recently due to their exceptional mechanical, chemical, and fluorescent properties, as well as their excellent photostability and biocompatibility. CDs' emission properties have already found a variety of potential applications, in which bioimaging and sensing are major highlights. It is widely acknowledged that CDs' fluorescence and surface conditions are closely linked. However, due to the structural complexity of CDs, the specific underlying process of their fluorescence is uncertain and yet to be explained. Because of their low toxicity, robust and wide optical absorption, high chemical stability, rapid transfer characteristics, and ease of modification, CDs have been recognized as promising carbon nanomaterials for a variety of sensing applications. Thus, following such outstanding properties of CDs, they have been mixed and imprinted onto different polymeric components to achieve a highly efficient nanocomposite with improved functional groups and properties. Here, in this review, various approaches and techniques for the preparation of polymer/CDs nanocomposites have been elaborated along with the individual characteristics of CDs. CDs/polymer nanocomposites recently have been highly demanded for sensor applications. The insights from this review are detailed sensor applications of polymer/CDs nanocomposites especially for detection of different chemical and biological analytes such as metal ions, small organic molecules, and several contaminants.

Carbon-Based Nanostructures as Emerging Materials for Gene Delivery Applications

Gene therapeutics are promising for treating diseases at the genetic level, with some already validated for clinical use. Recently, nanostructures have emerged for the targeted delivery of genetic material. Nanomaterials, exhibiting advantageous properties such as a high surface-to-volume ratio, biocompatibility, facile functionalization, substantial loading capacity, and tunable physicochemical characteristics, are recognized as non-viral vectors in gene therapy applications. Despite progress, current non-viral vectors exhibit notably low gene delivery efficiency. Progress in nanotechnology is essential to overcome extracellular and intracellular barriers in gene delivery. Specific nanostructures such as carbon nanotubes (CNTs), carbon quantum dots (CQDs), nanodiamonds (NDs), and similar carbon-based structures can accommodate diverse genetic materials such as plasmid DNA (pDNA), messenger RNA (mRNA), small interference RNA (siRNA), micro RNA (miRNA), and antisense oligonucleotides (AONs). To address challenges such as high toxicity and low transfection efficiency, advancements in the features of carbon-based nanostructures (CBNs) are imperative. This overview delves into three types of CBNs employed as vectors in drug/gene delivery systems, encompassing their synthesis methods, properties, and biomedical applications. Ultimately, we present insights into the opportunities and challenges within the captivating realm of gene delivery using CBNs.

Mitigating microplastic pollution: A critical review on the effects, remediation, and utilization strategies of microplastics

Microplastics are found ubiquitous in the natural environment and are an increasing source of worry for global health. Rapid industrialization and inappropriate plastic waste management in our daily lives have resulted in an increase in the amount of microplastics in the ecosystem. Microplastics that are <150 μm in size could be easily ingested by living beings and cause considerable toxicity. Microplastics can aggregate in living organisms and cause acute, chronic, carcinogenic, developmental, and genotoxic damage. As a result, a sustainable approach to reducing, reusing, and recycling plastic waste is required to manage microplastic pollution in the environment. However, there is still a significant lack of effective methods for managing these pollutants. As a result, the purpose of this review is to convey information on microplastic toxicity and management practices that may aid in the reduction of microplastic pollution. This review further insights on how plastic trash could be converted as value-added products, reducing the load of accumulating plastic wastes in the environment, and leading to a beneficial endeavor for humanity.

Recent progresses, challenges, and opportunities of carbon-based materials applied in heavy metal polluted soil remediation

The application of carbon-based materials (CBMs) for heavy metal polluted soil remediation has gained growing interest due to their versatile properties and excellent remediation performance. Although the progresses on applications of CBMs in removing heavy metal from aqueous solution and their corresponding mechanisms were well known, comprehensive review on applications of CBMs in heavy metal polluted soil remediation were less identified. Therefore, this review provided insights into advanced progresses on utilization of typical CBMs including biochar, activated carbon, graphene, graphene oxide, carbon nanotubes, and carbon black for heavy metal polluted soil remediation. The mechanisms of CBM remediation of heavy metals in soil were summarized, mainly including physical adsorption, precipitation, complexation, electrostatic interaction, and cationic-π coordination. The key factors affecting the remediation effect include soil pH, organic matter, minerals, microorganisms, coexisting ions, moisture, and material size. Disadvantages of CBMs were also included, such as: potential health risks, high cost, and difficulty in achieving co-passivation of anions and cations. This work will contribute to our understanding of current research advances, challenges, and opportunities for CBMs remediation of heavy metal-contaminated soils.

Myocardial Cell Preservation from Potential Cardiotoxic Drugs: The Role of Nanotechnologies

Cardiotoxic therapies, whether chemotherapeutic or antibiotic, represent a burden for patients who may need to interrupt life-saving treatment because of serious complications. Cardiotoxicity is a broad term, spanning from forms of heart failure induction, particularly left ventricular systolic dysfunction, to induction of arrhythmias. Nanotechnologies emerged decades ago. They offer the possibility to modify the profiles of potentially toxic drugs and to abolish off-target side effects thanks to more favorable pharmacokinetics and dynamics. This relatively modern science encompasses nanocarriers (e.g., liposomes, niosomes, and dendrimers) and other delivery systems applicable to real-life clinical settings. We here review selected applications of nanotechnology to the fields of pharmacology and cardio-oncology. Heart tissue-sparing co-administration of nanocarriers bound to chemotherapeutics (such as anthracyclines and platinum agents) are discussed based on recent studies. Nanotechnology applications supporting the administration of potentially cardiotoxic oncological target therapies, antibiotics (especially macrolides and fluoroquinolones), or neuroactive agents are also summarized. The future of nanotechnologies includes studies to improve therapeutic safety and to encompass a broader range of pharmacological agents. The field merits investments and research, as testified by its exponential growth.

Engineering plants with carbon nanotubes: a sustainable agriculture approach

Sustainable agriculture is an important conception to meet the growing food demand of the global population. The increased need for adequate and safe food, as well as the ongoing ecological destruction associated with conventional agriculture practices are key global challenges. Nanomaterials are being developed in the agriculture sector to improve the growth and protection of crops. Among the various engineered nanomaterials, carbon nanotubes (CNTs) are one of the most promising carbon-based nanomaterials owing to their attractive physiochemical properties such as small size, high surface area, and superior mechanical and thermal strength, offering better opportunities for agriculture sector applications. This review provides basic information about CNTs, including their history; classification; and electrical, thermal, and mechanical properties, with a focus on their applications in the agriculture field. Furthermore, the mechanisms of the uptake and translocation of CNTs in plants and their defense mechanisms against environmental stresses are discussed. Finally, the major shortcomings, threats, and challenges of CNTs are assessed to provide a broad and clear view of the potential and future directions for CNT-based agriculture applications to achieve the goal of sustainability.

Carbon-Based Materials for Oxidative Desulfurization and Denitrogenation of Fuels: A Review

Sulfur (S) and nitrogen (N) are elements naturally found in petroleum-based fuels. S- and N-based compounds in liquid fuels are associated with a series of health and environmental issues. Thus, legislation has become stricter worldwide regarding their content and related emissions. Traditional treatment systems (namely hydrodesulfurization and hydrodenitrogenation) fail to achieve the desired levels of S and N contents in fuels without compromising combustion parameters. Thus, oxidative treatments (oxidative desulfurization–ODS, and oxidative denitrogenation-ODN) are emerging as alternatives to producing ultra-low-sulfur and nitrogen fuels. This paper presents a thorough review of ODS and ODN processes applying carbon-based materials, either in hybrid forms or as catalysts on their own. Focus is brought to the role of the carbonaceous structure in oxidative treatments. Furthermore, a special section related to the use of amphiphilic carbon-based catalysts, which have some advantages related to a closer interaction with the oily and aqueous phases, is discussed.

Advances and Perspectives in the Use of Carbon Nanotubes in Vaccine Development

Advances in nanobiotechnology have allowed the utilization of nanotechnology through nanovaccines. Nanovaccines are powerful tools for enhancing the immunogenicity of a specific antigen and exhibit advantages over other adjuvant approaches, with features such as expanded stability, prolonged release, decreased immunotoxicity, and immunogenic selectivity. We introduce recent advances in carbon nanotubes (CNTs) to induce either a carrier effect as a nanoplatform or an immunostimulatory effect. Several studies of CNT-based nanovaccines revealed that due to the ability of CNTs to carry immunogenic molecules, they can act as nonclassical vaccines, a quality not possessed by vaccines with traditional formulations. Therefore, adapting and modifying the physicochemical properties of CNTs for use in vaccines may additionally enhance their efficacy in inducing a T cell-based immune response. Accordingly, the purpose of this study is to renew and awaken interest in and knowledge of the safe use of CNTs as adjuvants and carriers in vaccines.

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.

Carbon Nanomaterials for Electro-Active Structures: A Review

The use of electrically conductive materials to impart electrical properties to substrates for cell attachment proliferation and differentiation represents an important strategy in the field of tissue engineering. This paper discusses the concept of electro-active structures and their roles in tissue engineering, accelerating cell proliferation and differentiation, consequently leading to tissue regeneration. The most relevant carbon-based materials used to produce electro-active structures are presented, and their main advantages and limitations are discussed in detail. Particular emphasis is put on the electrically conductive property, material synthesis and their applications on tissue engineering. Different technologies, allowing the fabrication of two-dimensional and three-dimensional structures in a controlled way, are also presented. Finally, challenges for future research are highlighted. This review shows that electrical stimulation plays an important role in modulating the growth of different types of cells. As highlighted, carbon nanomaterials, especially graphene and carbon nanotubes, have great potential for fabricating electro-active structures due to their exceptional electrical and surface properties, opening new routes for more efficient tissue engineering approaches.

Enhanced saturable absorption in the laser-treated free-standing carbon nanotube films

We demonstrate an increase of optical transmittance and saturable absorption of laser-treated free-standing single-walled carbon nanotube (SWNT) films. The combined acid and low-power non-destructive laser treatment ensures an enhancement of linear transmittance across the visible range and double-digit increase of the saturable absorption of femtosecond laser radiation at 795 nm. The saturable absorption coefficient and the ratio of saturable to non-saturable losses increase by 26% and 35%, correspondingly, while the saturation intensity decreases by 20% because of the treatment. Our analysis indicates that with the performed treatment one can significantly improve the nonlinear optical properties of free-standing SWNT-based ultrafast saturable absorbers.

Circumferential confinement consequence on the magnetic properties of a punctured nanotube in the presence of an axial electric field

In this paper, we present magnetic properties of a finite graphene sheet with a triangle punctured vacancy, and its counterpart single-wall carbon nanotube as a rolled-up graphene sheet in the framework of the Hubbard model in the presence of an axial electric field, in order to form a comparison study between these two graphene samples. We have noticed that the tight-binding part of the Hamiltonian consists of two types of zero-energy states in the case of the graphene sheet, the strict zero-energy states, and the quasi zero-energy states. The first type takes part in a ferromagnetic coupling between the triangle edges and one edge of the rectangle graphene sheet, while the latter one has an antiferromagnetic alignment with the opposite edge of the rectangle graphene sheet. Involving the Coulomb interaction through Hubbard term, we have observed that the slope of the cluster edge states in nanotube is higher than the graphene sheet. Additionally, spin-depolarization happens in single-wall nanotube sooner than the graphene sheet by slightly increasing an axial electric field. Also, the graphene sheet is more robust than the single wall nanotube at low electric fields.

Carbon nanotube dielectrophoresis: Theory and applications

Carbon nanotubes (CNTs) are one of the most extensively studied nanomaterials in the 21st century. Since their discovery in 1991, many studies have been reported advancing our knowledge in terms of their structure, properties, synthesis, and applications. CNTs exhibit unique electrothermal and conductive properties which, combined with their mechanical strength, have led to tremendous attention of CNTs as a nanoscale material in the past two decades. To introduce the various types of CNTs, we first provide basic information on their structure followed by some intriguing properties and a brief overview of synthesis methods. Although impressive advances have been demonstrated with CNTs, critical applications require purification, positioning, and separation to yield desired properties and functional elements. Here, we review a versatile technique to manipulate CNTs based on their dielectric properties, namely dielectrophoresis (DEP). A detailed discussion on the DEP aspects of CNTs including the theory and various technical microfluidic realizations is provided. Various advancements in DEP-based manipulations of single-walled and multiwalled CNTs are also discussed with special emphasis on applications involving separation, purification, sensing, and nanofabrication.

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.

Applications of Carbon Nanotubes in Bone Tissue Regeneration and Engineering: Superiority, Concerns, Current Advancements, and Prospects

With advances in bone tissue regeneration and engineering technology, various biomaterials as artificial bone substitutes have been widely developed and innovated for the treatment of bone defects or diseases. However, there are no available natural and synthetic biomaterials replicating the natural bone structure and properties under physiological conditions. The characteristic properties of carbon nanotubes (CNTs) make them an ideal candidate for developing innovative biomimetic materials in the bone biomedical field. Indeed, CNT-based materials and their composites possess the promising potential to revolutionize the design and integration of bone scaffolds or implants, as well as drug therapeutic systems. This review summarizes the unique physicochemical and biomedical properties of CNTs as structural biomaterials and reinforcing agents for bone repair as well as provides coverage of recent concerns and advancements in CNT-based materials and composites for bone tissue regeneration and engineering. Moreover, this review discusses the research progress in the design and development of novel CNT-based delivery systems in the field of bone tissue engineering.

Synthesis of carbon nanotubes using biochar as precursor material under microwave irradiation

Biochar is a carbon-rich porous material obtained by the thermochemical treatment of biomass. Biochar presents a suitable composition as precursor material for carbon nanotubes (CNTs) growth, and can be used as a sustainable alternative in the valorization of biomass. In this study, the synthesis of CNTs using biochar as biological precursor material is presented. CNTs were synthesized using a mixture of biochar and ferrocene including microwave assisted heating. Biochar samples used in the synthesis of CNTs were obtained from agroindustrial waste such as wheat straw, oat hulls, rapeseed cake and hazelnut hulls pyrolyzed at 400 °C and 600 °C. Synthesized CNTs were examined by dynamic light scattering, UV-VIS spectroscopy, Raman spectroscopy and transmission electron microscopy. The results indicate that the physicochemical properties of CNTs were influenced by pyrolysis temperature of biomass. Biochars obtained at 600 °C produced higher CNTs concentration and smaller hydrodynamic diameter. Moreover, CNTs synthesized from biochar of hazelnut hulls and wheat straw show a higher degree of wall graphitization, suggesting superior CNT quality. The results of this study show the feasible production of CNTs using biochar as precursor material.

Chemical Vapour Deposition of MWCNT on Silica Coated Fe3O4 and Use of Response Surface Methodology for Optimizing the Extraction of Organophosphorus Pesticides from Water

Multiwalled carbon nanotube (MWCNT) was fixed onto the surface of a magnetic silica (Fe₃O₄@SiO₂) substrate via chemical vapour deposition (CVD). Acetylene gas was used as the carbon source and cobalt oxide as the catalyst. The chemical and physical characteristics of the materials were investigated by transmission electron microscopy (TEM), Raman spectroscopy (RS), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and nitrogen adsorption/desorption isotherm. The synthesized Fe₃O₄@SiO₂-MWCNT nanocomposite was used as a magnetic solid phase extraction (MSPE) adsorbent for the preconcentration of organophosphorus pesticides (OPPs), specifically, azinphos methyl, chlorpyrifos, parathion, and malathion. The factors influencing the extraction efficiency such as pH, contact time, and adsorbent dosage were investigated and optimized by response surface methodology (RSM) and desirability function. Linear response was obtained in the concentration range of 10–200 μg/L for the analytes with determination coefficients ranging between 0.9955 and 0.9977. The limits of detection (LODs) and quantification (LOQs) were in the range of 0.004-0.150 μg/L and 0.013-0.499 μg/L, respectively. Fe₃O₄@SiO₂-MWCNT was applied in the extraction and subsequent determination of OPPs in water samples from Vaal River and Vaal Dam with recoveries ranging from 84.0 to 101.4% (RSDs = 3.8–9.6%, n = 3) in Vaal River and 86.2 to 93.8% (RSDs = 2.9–10.4%, n = 3) in Vaal Dam. The obtained results showed that the newly synthesized Fe₃O₄@SiO₂-MWCNT nanocomposite can be an efficient adsorbent with good potential for the preconcentration and extraction of selected OPPs from aqueous media.

Optimization of the Synthesis of Superhydrophobic Carbon Nanomaterials by Chemical Vapor Deposition

Demand is increasing for superhydrophobic materials in many applications, such as membrane distillation, separation and special coating technologies. In this study, we report a chemical vapor deposition (CVD) process to fabricate superhydrophobic carbon nanomaterials (CNM) on nickel (Ni)-doped powder activated carbon (PAC). The reaction temperature, reaction time and H₂/C₂H₂ gas ratio were optimized to achieve the optimum contact angle (CA) and carbon yield (CY). For the highest CY (380%) and CA (177°), the optimal reaction temperatures were 702 °C and 687 °C, respectively. However, both the reaction time (40 min) and gas ratio (1.0) were found to have similar effects on CY and CA. Based on the Field emission scanning electron microscopy and transmission electron microscopy images, the CNM could be categorized into two main groups: a) carbon spheres (CS) free carbon nanofibers (CNFs) and b) CS mixed with CNFs, which were formed at 650 and 750 °C, respectively. Raman spectroscopy and thermogravimetric analysis also support this finding. The hydrophobicity of the CNM, expressed by the CA, follows the trend of CS-mixed CNFs (CA: 177°) > CS-free CNFs (CA: 167°) > PAC/Ni (CA: 65°). This paves the way for future applications of synthesized CNM to fabricate water-repellent industrial-grade technologies.