The exponential growth in plastic consumption results in unwanted accumulation on the streets of most cities due to inadequate plastic disposal, landfills overloading, and pollution of the soil, atmosphere, and oceans. This work aims to investigate the use of PET (polyethylene terephthalate) waste to produce solid acid catalysts. The catalysts were synthesized via chemical activation with ZnCl2 or K2CO3, followed by carbonization in an inert atmosphere and sulfonation. Catalytic tests were carried out on the esterification reaction of oleic acid and methanol. The best result was obtained using zinc chloride as an activating agent, functionalized at 80 °C for 2 h. Carbonaceous materials were obtained with SBET, Vt, Vmic, and Vmes of 272 m2 g-1, 0.36 cm3 g-1, 0.14 cm3 g-1, and 0.22 cm3 g-1, respectively. An 88% conversion to methyl oleate was observed. The synthesis of a heterogeneous acid catalyst is a sustainable and promising alternative for reusing PET waste.
When a common power supply is shared by analog and digital circuits on a high-frequency mixed-signal board, noise generated by high-speed digital circuits propagates through the power delivery network (PDN) and degrades the performance of sensitive analog blocks. This work investigates power integrity enhancement using diamond-based via-loaded square power island (SPI) metamaterial structures over the frequency range of 0–20 GHz. The integration of diamond as a dielectric material, owing to its low loss tangent, high thermal conductivity, and stable permittivity, significantly improves high-frequency noise suppression and thermal performance. The proposed structure achieves a peak suppression of approximately −72 dB at 14 GHz and maintains suppression better than −30 dB across the 8–20 GHz frequency band. The results are validated through full-wave electromagnetic simulations, demonstrating the effectiveness of the proposed design in enhancing power integrity and reliability in high-frequency mixed-signal PDNs.
Controlling nitrogen functionalities in graphene are crucial for high-performance supercapacitors. In this study, we report the scalable synthesis of nitrogen-doped reduced graphene oxide (N-rGO) via a hydrothermal process using readily available inorganic precursors in an aqueous phase, enabling controlled manipulation of nitrogen functionalities. The optimized N-rGO (GO:aqueous NH3 = 1:6) exhibits a areal capacitance of 0.4 F cm−2 at a scan rate of 5 mV s−1. In a symmetric two-electrode system, N-rGO delivers a high specific capacitance of 532 F g−1, along with an energy density of 41 Wh kg−1 and a power density of 375 W kg−1 at 0.5 A g−1, with a capacitance retention of ∼78% after 10,000 cycles at 1.96 V. These performance metrics are attributed to an optimal defect concentration combined with a high proportion of amino and pyrrolic nitrogen functionalities. Quantum capacitance calculations reveal an enhanced electronic density of states near the Fermi level, thereby improving charge storage performance.
Carbon-based materials are pivotal in next generation energy technologies due to their tunable electronic properties, porosity, and chemical stability. Structural variations from 0D to 3D; graphene, carbon nanotubes, carbon aerogels, and biomass derived activated carbons; enable multifunctional roles as conductive scaffolds, catalysts, adsorbents, and enzyme supports. In biofuel production, they enhance biomass pretreatment, fermentation, and biodiesel synthesis, achieving up to 95% biodiesel yields and 30%–50% faster fermentation. In thermochemical processes, porous carbons improve hydrocarbon cracking, deoxygenation, and tar conversion, boosting selectivity by 20%–40% and reducing byproducts by 25%. For CO2 valorization, carbon nanomaterials enable selective conversion with Faradaic efficiencies >80% and CO2-to-methanol rates up to 0.5 mmol g-1 h-1. In solar and hydrogen technologies, they enhance charge transport, stability, and catalysis, delivering photocurrents of 15–25 mA cm-2, solar-to-hydrogen efficiencies of 12%–18%, and 40% higher H2 yields in biomass gasification. Heteroatom doping and surface functionalization allow precise control over activity and selectivity. Despite scalability and integration challenges, AI-guided design, waste derived carbons, and hybrid architectures promise sustainable, high performance solutions. This review underscores carbon’s role in bridging fundamental science and industrial applications, driving the transition toward a sustainable energy future.
Polyethylene glycol-functionalized single-walled carbon nanotubes (SWCNT-PEG) have been studied for many biomedical applications because of their unique physicochemical properties. Due to their reduced size and high stability in physiological media, SWCNT-PEG are candidates for crossing the blood–brain barrier (BBB), with potential use in treating central nervous system diseases that are currently unresponsive to pharmacological interventions because of the tightly regulated permeability of the BBB. In this study, we investigated the biodistribution of intravenously delivered SWCNT-PEG using Raman spectroscopy, as well as possible toxicological outcomes using morphological, histological, biochemical, and behavioral analyses. SWCNT-PEG were identified in the brain cortex, blood, spleen, and liver of rats. Biochemical and histological analyses did not reveal toxic effects in rats 24 h after SWCNT-PEG injection. Additionally, no behavioral impairments were observed in treated animals subjected to the Morris water maze task. Our preliminary experimental results clearly indicate that SWCNT-PEG were able to cross biological membranes and reach the rat brain cortex parenchyma (but not other brain structures) after systemic administration without the presence of acute toxic effects. The biodistribution of SWCNT-PEG in a specific region of the brain tissue encourages further studies regarding the application of SWCNTs in neuroscience.
Graphene oxide (GO) has attracted significant attention from the scientific community due to its mechanical, optical, electrical, and chemical properties. This review outlines synthetic methods for GO functionalization, including those involving covalent and noncovalent bonds with organic molecules. In a novel contribution to this field, particular emphasis is placed on functionalization via epoxy ring opening, a poorly studied and understood topic. We first provide an overview of the basic structure and properties of graphene oxide. We then explore the various methods employed to functionalize graphene oxide, noting the complexity of these reactions, which sometimes occur in a non-specific manner. However, there are some strategies for targeted functionalization. Furthermore, we present a critical analysis of the covalent functionalization through epoxy groups, demonstrating important aspects to be considered when choosing the reaction medium. An alkaline environment seems to favor this reaction, and there is no consensus regarding the advantages and disadvantages of using basic pH in functionalization reactions. We also demonstrate some challenges involving the characterization and confirmation of the functionalization, mainly in the basal plane, and we show advances in characterization techniques that can be explored in future studies. Finally, some current challenges and future research directions are presented to contribute to the advancement of the field.
The omnipresence of emerging contaminants in the aquatic environment is indisputable. These contaminants include chemical substances not removed in traditional water and sewage treatment processes. To ensure the quality of water and healthy aquatic ecosystems, new treatment technologies and materials are essential to effectively control the presence of these contaminants in the aquatic environment. More than that, it is important to know how molecules interact with these new materials. A low-cost alternative currently available is adsorption. Despite this method being widely studied, describing the interaction mechanisms between the materials and the analytes is not usual, limiting the obtainment of more efficient materials. Thus, the objective of this work was to understand, in a theoretical-experimental way, the forms of interaction in the adsorption of the drug paracetamol, widely used worldwide, in materials based on graphene with different chemical and structural properties. For this, kinetic and isothermal experimental studies were carried out using four materials that contemplated different dimensions, pore sizes, and oxidation degrees. In theoretical studies, density functional theory (DFT) simulations were performed to cover quantum details, revealing how paracetamol interacts with different graphene structures. According to theoretical studies, binding energies, binding distances, and charge transfer between oxidized graphene and paracetamol drug are compatible with physical adsorption, strongly dependent on the type and number of functional groups on the graphene surface. These results agree with the experimental data where the highest adsorptions were observed precisely for materials containing a higher proportion of functional groups and where these groups are more available (more porous), with adsorptive capacities reaching 235.7 mg/g. Our findings contribute to scientific knowledge about using graphene structures as an adsorbent material, providing a solid basis for future studies and developing more efficient and advanced water treatment technologies.
Single crystal diamond (SCD) is the most promising future semiconductor. However, it has not been able to make much inroad into the microelectronics industry due to its major disadvantage of the wafer size. Among a few contender technologies, epitaxial lateral outgrowth (ELO) using microwave plasma-assisted chemical vapor deposition (MPACVD) has shown early promise toward lateral area gain during epitaxial growth. While promising, significant wafer area enhancement remains challenging. This study explores the growth dynamics of SCD in a constrained system—a pocket holder—whose effect is twofold: linear dimension and area enhancement and polycrystalline diamond (PCD) edge rim suppression. A series of pocket-type holder designs were introduced that demonstrated that the depth and substrate-to-wall distance are the major means for optimizing and enhancing lateral outgrowth while still suppressing the PCD rim. When taken together with reactor modeling, the pocket effect on the extent of ELO could be understood as directly manipulating and perturbing methyl radical flux near the growing diamond surface, thereby directly manipulating gas-to-solid phase transformation kinetics. Because it was further discovered that simple box-like pockets limit the ELO process to an exponential-decay scenario, a new generation of angled pockets was proposed that allowed boosting ELO to its fullest extent where a constant rate, linear, outgrowth was found. Our results indicate that ELO by MPACVD could become an industrial means of producing SCD at scale.
The admixture of PEDOT:PSS with Graphene Oxide (GO) in precise proportions achieves a substantial reduction in electrical resistivity, thereby augmenting its suitability as an electrode in organic devices. This study explores the electrical and morphological attributes of commercial PEDOT:PSS and chemically synthesized aqueous PEDOT ink when both are combined with GO. The investigation extends to the application of these conductive inks as active layers in flexible methanol sensing devices. Notably, a resistivity minimum is observed in the case of GO:PEDOT:PSS 78%, while the highest response to methanol is attained with GO:PEDOT:PSS 68%. To establish a theoretical underpinning for these findings, and to understand the interaction between gas/vapors with nanostructured materials, a model rooted in Kirchhoff’s Circuit approach is developed, with the aim of elucidating the factors behind the resistivity minimum and response maximum at distinct specific mass ratios between PEDOT and GO. Calculating the equivalent resistivity and response of the systems, the positions of minimum and maximum points are in agreement with the experimental data. Furthermore, the influence of PSS in the samples is examined, unveiling diverse interaction mechanisms between methanol molecules and the active layer, resulting in varying signals during the exposure to alcoholic vapor. The theoretical model is subsequently applied to these systems, demonstrating qualitative and quantitative agreement with the experimental results.
The recently synthesized 30° twisted bilayer graphene (30°-TBG) systems are unique quasicrystal systems possessing dodecagonal symmetry with graphene’s relativistic properties. We employ a real-space numerical atomistic framework that respects both the dodecagonal rotational symmetry and the massless Dirac nature of the electrons to describe the local density of states of the system. The approach we employ is very efficiency for systems with very large unit cells and does not rely on periodic boundary conditions. These features allow us to address a broad class of multilayer two-dimensional crystal with incommensurate configurations, particularly TBGs. Our results reveal that the 30°-TBG electronic spectrum consist of extended states together with a set of localized wave functions. The localized states exhibit fractal patterns consistent with the quasicrystal tiling.
Recent studies have shown the wide array of biomedical applications for nanomaterials such as single-walled carbon nanotubes (SWCNTs) and zinc oxide nanowires (ZnO NWs). SWCNTs are non-cytotoxic and have a varying range of mechanical, physical, and electrical properties useful to biomedical research. ZnO NWs are biocompatible, antibacterial, and exhibit piezoelectric properties that could stimulate cell growth. While recent research has been conducted using these nanomaterials independently, our study is focused on testing cell behaviors when seeded on SWCNTs, ZnO NWs and their heterostructure assemblies. ZnO NWs/SWCNTs heterostructures prepared via chemical vapor deposition (CVD) have not been used in biomedical applications to date. Here, we describe fabrication and characterization of the two nanomaterials independently and in a heterostructure formation. The NIH 3T3 fibroblast cells and U87 glioblastoma cells were seeded on all samples, including SiO2/Si control/reference samples, and the cell growth was studied via fluorescence microscopy and scanning electron microscopy. The focus of this study was to evaluate cell spreading, filopodia extensions, and cell viability on these nanomaterial assemblies. Results indicated that cells were able to extend filopodia on all nanostructures, however cell spreading was more pronounced on SWCNTs, and cell viability was compromised on the ZnO NWs and the ZnO NWs/SWCNTs heterostructures. In addition, soluble compounds from the nanomaterials were tested to determine their cytotoxicity towards both NIH 3T3 and U87 cells. Results indicated a significant decrease in filopodia length, cell spreading, and cell viability when cells were exposed to ZnO NWs-conditioned cell media. These findings on cellular behavior involving SWCNTs, ZnO NWs, and ZnO NWs/SWCNTs heterostructure provide valuable information on the suitability of SWCNTs and ZnO NWs for future uses in biomedical applications.
The presence of environmental contaminants is a major problem today. In this context, it is necessary to develop new sustainable materials to be used to remediate these contaminants. In this work, the serpentinite rock was impregnated with cobalt, 5%, 10% and 20% and used as a support for the synthesis of carbon nanostructures by CVD (chemical vapour deposition) process, at 900°C. This temperature was chosen due to the high thermal stability of the carbon source. The materials were characterized by X-ray diffraction, Raman spectroscopy, thermal analysis, scanning and transmission microscopy. As expect the main phases formed were forsterite, Mg 2 SiO 4 , graphitic carbon and metallic cobalt. All the synthesis showed the formation of carbon structures as multiwalled carbon nanostructures over cobalt cores. The carbon structures showed good thermal stability, between 470 and 600°C. The higher the cobalt content, the higher the yield of the carbon structures synthesis, i.e. 14%, 23% and 37% for Serp5, Serp10 and Serp20, respectively. The produced materials were used to removal of the environmental contaminant sulfentrazone. After CVD process, the removal of sulfentrazone increase to 17.3%, 18.4% and 25.2% for Serp5, Serp10 and Serp20, respectively, showing an increase in sulfentrazone removal with the increase in carbon content. In addition, the percentage of sulfentrazone removal by Serp20 was greater at acidic pH values, decreasing from 41.7% to 12.7% with an increase from 2 to 10 in pH. The removal capacity obtained experimentally at a sulfentrazone concentration of 50 mg L −1 was equal to 14.9 mg g −1 . According to literature and data obtained in this work, it was observed that the removal of contaminants from the aqueous medium occurred through two mechanisms: reduction of the organic compound by Co nanoparticles and adsorption carried out by carbon nanostructures.
Rubber (elastomer) based polymer nanocomposites have attracted wide range of attention from industries and other fields due to its exceptionally good mechanical, thermal and electrical properties. One of the promising candidates of this category is CNT filled rubber nanocomposites. This review throws light on the historical trajectory of development of CNT filled rubber nanocomposites. Various fabrication methods, detailed explanation of reinforcement mechanism in CNT/rubber nanocomposites and the relationship between the structure and properties are reviewed. The next part of the review discusses about the morphological and interface characteristics. An attempt to investigate the versatile mechanical, thermal, and electrical properties also included in the review. The final part of the review includes the applications of CNT filled rubber nanocomposites. Major applications in fields like electronics, sustainable biomedical and EMI shielding are discussed in detail. The review also focuses on the key challenges that arises while incorporating CNTs into rubber matrices.
Introduction: Insertion of N atoms at a nanoscale subsurface depth in single-crystal diamond (SCD) may enable new generations of quantum electronics devices. In this sense, it is critical to understand the interaction between implanted N atoms and C atoms in the diamond lattice. Methods: The investigation of the interaction of N atoms with SCD at the atomic scale using X-ray photoelectron spectroscopy (XPS) analysis involves in situ bombardment of the SCD surface with relatively low-energy (5,000 eV) N2 ions. In situ XPS analyses of SCD and highly oriented pyrolytic graphite (HOPG) before and after N-atom implantation are compared with published XPS analyses of C-N materials (e.g., g-CN, N in poly/single-crystal diamond). Results: The analyses revealed three N 1s peaks at 398–399 eV (N1), 399–400.5 eV (N2), and 401–403 eV (N3), with the N1 and N2 peaks assigned to C-N bonds and an N3 peak inaccurately assigned, in prior publications, to N-bonded contaminants (e.g., O, NH). In situ cleaning of the SCD and HOPG surfaces prior to N-atom implantation was performed to eliminate all atmospheric contaminants. This cleaning process revealed that the N3 peak is associated with N-C-bonded atoms and not the C-O/NH linkage, as previously suggested. Ex situ high resolution transmission electron microscopy (HRTEM) studies of N-implanted SCD show a defect-structured subsurface region. Discussion: An important side effect of the relatively low-energy N implantation in SCD is the formation of a 5–8 nm electrically conductive surface layer, an effect that may open the pathways for future research in diamond-based micro- and nano-electronics.
The infiltration of pesticides into agricultural soils has emerged as a critical concern, posing substantial threats to the agriculture industry due to soil and water contamination. The detection of these contaminants is critical towards implementing effective environmental remediation strategies and achieving ecosystem sustainability. Electrochemical sensor technology has been demonstrated to be highly promising for this application. Graphene and its derivatives and composites are widely used as modifying materials in these sensors to enhance their analytical performance. This short review discusses recent progress in the application of graphene-based electrochemical sensors in three-electrode and field-effect transistor configurations for the detection of pesticides posing significant risks to the agricultural sector. It highlights the growing significance of graphene-based sensors in mitigating pesticide-related environmental challenges and underscores their role in ensuring the health and diversity of agricultural ecosystems.
The wound healing process is accompanied by changes in pH values. Monitoring this physicochemical parameter can indicate the effectiveness of the applied treatment and act as early identification of wound infection. This study focuses on the development of a fluorescent film-based polyvinyl alcohol (PVA) and carbon dots (CDs) derived from lemon bagasse (CD-L) and ortho -phenylenediamine (CD-oPD) named to act as antioxidants and potential ratiometric fluorescent pH sensors, in wound applications. The I 460 /I 550 intensity ratio, as a function of pH value for the dual-system CDs prepared from the mixture of CD-L and CD-oPD, named CD-L/oPD, was investigated. The fit corresponded to a sigmoidal function in the pH range of 5–10, with a relationship having a r 2 = 0.992. The variation in the values of the I 460 /I 550 ratio allows for the visualization of the color change from yellowish-green to green with increasing pH. Through a simulated ex vivo pig skin model, it was possible to note that the films prepared from mixed of the CD-L and CD-oPD carbon dots incorporated in a matrix PVA named CD-L/oPD-F was more efficient at visually discriminating color in relation to changes in pH than the films prepared from both individual CD-L (CD-L-F) and CD-oPD (CD-oPD-F) carbon dots. CD-L and CD-oPD demonstrated antioxidant capacity against reactive oxygen species (ROS). The IC 50 values for CD-L and CD-oPD were 56.7 and 39.5 μg mL −1 in the DPPH ● inhibition assay, and 25.1 and 63.4 μg mL −1 in the HOCl scavenging one, respectively. MTT viability assays using human non-tumoral skin fibroblast (HFF-1) cell showed a cell survival rate of over 80% for both CDs up to a concentration of 1,000 μg mL −1 . Finally, the developed films can act in a bifunctional way, by monitoring healing through pH changes and by acting as an antioxidant agent in the treatment of wounds.
Fractal systems are now considered alternative routes for engineering physical properties on the nanoscale. In particular, stable annular quantum corrals have been demonstrated in distinct synthesis procedures and can provide interesting localized and resonant states. We here present a theoretical description of effective fractal lattices, mainly composed of annular Koch geometries based on carbon atoms, and of more complex organic molecules described by triangular Sierpinski geometries. A single band tight-binding approach is considered to derive electronic and transport properties. Fractal molecular linear chains composed of fractal Koch quantum corrals are proposed, and their electronic transport is discussed based on the complexity of the neighboring hopping. The spatial charge distributions at different energies highlight the contribution of the composing metallic and carbons atoms in the quantum corral features, serving as a guide to new functionalization applications based on the symmetry and fractal peculiarities of the proposed nanostructured lattices.
Carbon-based nanomaterials have drawn significant interest as desirable nanomaterials and composites for the adsorptive removal of various classes of pollutants from water owing to their versatile physicochemical properties. The underlying sorption mechanisms serve as the bedrock for the development of carbonaceous adsorbents for various target pollutants. Microwave-assisted synthesis can be regarded as a recent and well-advanced technique for the development of carbon-based nanomaterials, and the use of biobased materials/wastes/residues conforms with the concept of green and sustainable chemistry. For advancements in carbon-based functional nanomaterials and their industrial/field applications, it is essential to fully comprehend the sorption performance and the selective/non-selective interaction processes between the contaminants and sorbents. In this regard, research on the development of carbon-based nanomaterials for the adsorption of chemical contaminants, both organic and inorganic, in water has made considerable strides as discussed in this review. However, there are still several fundamental hurdles associated with microwave-assisted chemical synthesis and commercial/industrial scale-up applications in nano-remediation. The challenges, benefits, and prospects for further research and development of carbon-based nanomaterials/nanocomposites for the purification of water are also discussed.
