Search Results (34)

The article investigates the role of carbon nanomaterials (CNMs), surface-oxidized carbon nanotubes (CNTs) and few-layer graphene fragments (FGFs), as well as FGFs hetero-doped with N and P atoms, as anticorrosive additives in industrial paints based on polyvinyl chloride. All CNMs were characterized by thermogravimetry, transmission electron microscopy, low-temperature nitrogen adsorption, and X-ray photoelectron spectroscopy. Corrosion resistance was determined using electrochemical tests and impedance spectroscopy. The surface and internal 3D structure of steel and coated steel were visualized using laser confocal microscopy and computed tomography. Coatings containing polyvinyl chloride with 0.05 wt% oxidized CNTs or FGFs show the highest electrochemical resistance and the best anticorrosive properties. The corrosion rate for coatings containing CNMs decreases by an average of 5–7 times compared to uncoated steel. It is shown that the improvement in anticorrosive characteristics is determined by the texture parameters and the composition of CNMs. The pores in CNMs act as a reservoir for the electrolyte and increase the corrosion rate. Oxygen-containing surface groups prevent corrosion by increasing the resistance of the materials. Full article

Silica aerogels are ideal candidates for gas adsorption due to their exceptional porosity and high specific surface area; however, the inherent mechanical fragility of their skeletal framework significantly compromises their operational stability in engineering applications. While the incorporation of carbon nanomaterials effectively enhances the mechanical robustness of aerogels, the specific microscopic mechanisms by which filler microstructure and surface chemistry dictate gas adsorption behavior remain insufficiently understood. In this study, we employed all-atom molecular dynamics (MD) simulations to develop a model of silicon-based porous composites synergistically doped with carbon nanotubes (CNTs) and graphene. The adsorption and diffusion characteristics of nitrogen (N₂) were systematically investigated across a CNT doping concentration range of 5% to 20%, and the influence of surface hydrophilicity/hydrophobicity on adsorption performance was quantitatively analyzed by modulating potential energy parameters. Our results demonstrate that the introduction of CNTs reconfigures the porous architecture, leading to an approximately 18.25% increase in the normalized specific surface area, which subsequently drives a 15% enhancement in the overall adsorption capacity of the composite. Nevertheless, analysis reveals that the weight-specific adsorption efficiency of the CNT component itself exhibits a declining trend as the doping concentration increases. This phenomenon is primarily attributed to the convex curvature of the CNTs, which restricts the effective contact area and weakens the adsorption potential, alongside the steric hindrance effects arising from local filler agglomeration at higher concentrations. Furthermore, surface chemical properties exert a significant regulatory influence on adsorption; a strongly hydrophilic modified surface (λ = 1.5) achieved an adsorption capacity approximately 98% higher than the baseline condition—an improvement that exceeds the gains provided by purely physical volume expansion. This research elucidates the synergistic mechanism between physical architecture and surface chemical modification in the adsorption process, suggesting that while the physical architecture determines the abundance of potential adsorption sites, the surface chemistry governs the actual efficiency of site utilization. These findings provide critical theoretical insights for the future design of composite aerogel materials that balance structural stability with superior adsorption performance. Full article

Cobalt-based oxides are promising candidates for supercapacitor electrodes, but their practical application is often hindered by poor electrical conductivity, limited ion diffusion, and insufficient cycling stability. Herein, we present a novel strategy to improve the electrochemical performance of Co₃O₄ by growing grape-like Co₃O₄ clusters on a nitrogen-doped carbon framework consisting of nitrogen-doped graphene oxide (NGO) and nitrogen-doped carbon nanotubes (NCNTs) through a controlled hydrothermal process. The nitrogen functionalities in the carbon matrix not only facilitate strong interactions between the NGO and NCNTs but also provide abundant nucleation sites for the growth of Co₃O₄ spinel nanoparticles (30–50 nm). This unique structure promotes an efficient electron conduction and ion transport network, which significantly improves the electrochemical performance of the Co₃O₄ electrode. The Co₃O₄@NGO/NCNT ternary nanocomposite, containing 39% Co₃O₄ and featuring a high specific surface area of 162 m² g⁻¹, delivers a specific capacitance of 269 F g⁻¹ at 1 A g⁻¹ and maintains 82% of its capacitance when the current density increases to 10 A g⁻¹. Notably, the nanocomposite demonstrates outstanding cycling stability, with negligible capacitance decay after 2000 charge–discharge cycles at a current density of 5 A g⁻¹, underscoring its excellent electrochemical robustness. This Co₃O₄@NGO/NCNT nanocomposite represents a promising and efficient material for high-performance supercapacitor electrodes. Full article

Tryptophan (Trp) and tryptamine (Tryp), critical biomarkers in mood regulation, immune function, and metabolic homeostasis, are increasingly recognized for their roles in both oral and systemic pathologies, including neurodegenerative disorders, cancers, and inflammatory conditions. Their rapid, sensitive detection in biofluids such as saliva—a non-invasive, real-time diagnostic medium—offers transformative potential for early disease identification and personalized health monitoring. This review synthesizes advancements in electrochemical sensor technologies tailored for Trp and Tryp quantification, emphasizing their clinical relevance in diagnosing conditions like oral squamous cell carcinoma (OSCC), Alzheimer’s disease (AD), and breast cancer, where dysregulated Trp metabolism reflects immune dysfunction or tumor progression. Electrochemical platforms have overcome the limitations of conventional techniques (e.g., enzyme-linked immunosorbent assays (ELISA) and mass spectrometry) by integrating innovative nanomaterials and smart engineering strategies. Carbon-based architectures, such as graphene (Gr) and carbon nanotubes (CNTs) functionalized with metal nanoparticles (Ni and Co) or nitrogen dopants, amplify electron transfer kinetics and catalytic activity, achieving sub-nanomolar detection limits. Synergies between doping and advanced functionalization—via aptamers (Apt), molecularly imprinted polymers (MIPs), or metal-oxide hybrids—impart exceptional selectivity, enabling the precise discrimination of Trp and Tryp in complex matrices like saliva. Mechanistically, redox reactions at the indole ring are optimized through tailored electrode interfaces, which enhance reaction kinetics and stability over repeated cycles. Translational strides include 3D-printed microfluidics and wearable sensors for continuous intraoral health surveillance, demonstrating clinical utility in detecting elevated Trp levels in OSCC and breast cancer. These platforms align with point-of-care (POC) needs through rapid response times, minimal fouling, and compatibility with scalable fabrication. However, challenges persist in standardizing saliva collection, mitigating matrix interference, and validating biomarkers across diverse populations. Emerging solutions, such as AI-driven analytics and antifouling coatings, coupled with interdisciplinary efforts to refine device integration and manufacturing, are critical to bridging these gaps. By harmonizing material innovation with clinical insights, electrochemical sensors promise to revolutionize precision medicine, offering cost-effective, real-time diagnostics for both localized oral pathologies and systemic diseases. As the field advances, addressing stability and scalability barriers will unlock the full potential of these technologies, transforming them into indispensable tools for early intervention and tailored therapeutic monitoring in global healthcare. Full article

A supercapacitor’s energy storage capability is greatly dependent on electrode materials. Layered double hydroxides (LDHs) were extensively studied as battery-type electrodes because of their 2D structure and quick intercalation/deintercalation of electrolyte ions. However, the energy storage capability for pristine LDHs is limited by their large aggregation tendency and poor electrical conductivity. Herein, a novel NiCoMn-LDH/SWCNTs (single-walled carbon nanotubes) composite electrode material, with ultrathin NiCoMn-LDH nanosheets dispersedly grown among the highly conductive networks of SWCNTs, was prepared via a facile zeolitic imidazolate framework-67 (ZIF-67)-derived in situ etching and deposition procedure. The NiCoMn-LDH/SWCNTs electrode demonstrates a specific capacitance as large as 1704.3 F g⁻¹ at 1 A g⁻¹, which is ascribed to its exposure of more active sites than NiCoMn-LDH. Moreover, the assembled NiCoMn-LDH/SWCNTs//BGA (boron-doped graphene aerogel) hybrid supercapacitor exhibits a superior capacitance of 167.9 F g⁻¹ at 1.0 A g⁻¹, an excellent energy density of 45.7 Wh kg⁻¹ with a power density of 700 W kg⁻¹, and an outstanding cyclic stability with 82.3% incipient capacitance maintained when subjected to 5000 charge and discharge cycles at the current density of 10 A g⁻¹, suggesting the significant potential of NiCoMn-LDH/SWCNTs as the electrode material applicable in supercapacitors. Full article

This investigation reports on the efficacy of a photoelectrocatalysis (PEC) system enhanced by a nitrogen-doped TiO₂ nanocrystal-modified TiO₂ nanotube array (N-TiO₂ NCs/TNTAs) anode paired with a graphene oxide/activated carbon (GO/AC) photocathode for diclofenac removal from effluent. The FE-SEM and EDX analyses validated the elemental composition of the anode—27.56% C, 30.81% N, 6.03% O, and 26.49% Ti. The XRD results confirmed the anatase phase and nitrogen integration, essential for photocatalytic activity enhancement. Quantum chemical simulations provided a comprehensive understanding of the red-shifted absorption bands in N-TiO₂, and UV-vis DRS demonstrated a red-shift in absorption to the visible spectrum, indicating improved light utilization. The PEC configuration achieved a photocurrent density of 9.8 mA/dm², significantly higher than the unmodified and solely nitrogen-doped counterparts at 4.8 mA/dm² and 6.1 mA/dm², respectively. Notably, this system reduced diclofenac concentrations by 58% within 75 min, outperforming standard photocatalytic setups. These findings underscore the potential of N-TiO₂ NCs/TNTAs-AC-GO/PTFE composite material for advanced environmental photoelectrocatalytic applications. Full article

Thermal analysis is widely employed for the characterization of nanomaterials. It encompasses a variety of techniques that allow the evaluation of the physicochemical properties of a material by monitoring its response under controlled temperature. In the case of carbon nanomaterials, such as carbon nanotubes and graphene derivatives, thermogravimetric analysis (TGA) is particularly useful to determine the quality and stability of the sample, the presence of impurities and the degree of functionalization or doping after post-synthesis treatments. Furthermore, TGA is widely used to evaluate the thermal stability against oxidation by air, which can be, for instance, enhanced by the purification of the material and by nitrogen doping, finding application in areas where a retarded combustion of the material is required. Herein, we have evaluated key parameters that play a role in the data obtained from TGA, namely, gas flow rate, sample weight and temperature rate, used during the analysis. We found out that the heating rate played the major role in the process of combustion in the presence of air, inducing an increase in the temperature at which the oxidation of CNTs starts to occur, up to ca. 100 °C (from 1 °C min⁻¹ to 50 °C min⁻¹). The same trend was observed for all the evaluated systems, namely N-doped CNTs, graphene produced by mechanical exfoliation and N-doped reduced graphene samples. Other aspects, like the presence of impurities or structural defects in the evaluated samples, were analyzed by TGA, highlighting the versatility and usefulness of the technique to provide information of structural aspects and properties of carbon materials. Finally, a set of TGA parameters are recommended for the analysis of carbon nanomaterials to obtain reliable data. Full article

The substitutional doping of nitrogen is an efficient way to modulate the electronic properties of graphene and carbon nanotubes (CNTs). Therefore, it could enhance their physical and chemical properties as well as offer potential applications. This paper provides an overview of the experimental and theoretical investigations regarding nitrogen-doped graphene and CNTs. The formation of various nitrogen defects in nitrogen-doped graphene and CNTs, which are identified by several observations, is reviewed. The electronic properties and transport characteristics for nitrogen-doped graphene and CNTs are also reviewed for the development of high-performance electronic device applications. Full article

The oxygen reduction reaction (ORR) is a key cathodic reaction in energy-converting systems, such as fuel cells (FCs). Thus, it is of utmost importance to develop cost-effective and efficient electrocatalysts (ECs) without noble metals to substitute the Pt-based ones. This study focuses on polyoxometalate (POM)-based ECs for ORR applications. A Wells–Dawson POM salt K₇ [P₂W₁₇(FeOH₂)O₆₁].·20H₂O was immobilised onto graphene flakes and multiwalled carbon nanotubes doped with nitrogen, denominated as P₂W₁₇Fe@GF_N8 and P₂W₁₇Fe@MWCNT_N8. The successful preparation of the composites was proved with various characterisation techniques, including FTIR, XPS and SEM. Both materials showed good ORR performance in an alkaline medium with similar potential onset values of ~0.84 V vs. RHE and diffusion-limiting current densities of −3.9 and −3.3 mA cm⁻² for P₂W₁₇Fe@MWCNT_N8 and P₂W₁₇Fe@GF_N8, respectively. Furthermore, both composites presented low Tafel slopes (48–58 mV dec⁻¹). Chronoamperometric tests revealed that the as-prepared nanocomposites rendered a significant improvement achieving between 90 and 94% of current retention in tolerance to methanol in comparison with Pt/C, and moderate to good long-term electrochemical stability with current retentions comprised between 68 and 88%. This work reinforces the use of POMs as important electroactive species for the preparation of alternative ORR electrocatalysts, exhibiting good activity, stability and selectivity towards the ORR in the presence of methanol. Full article

Graphene aerogels (GAs) possess a remarkable capability to absorb electromagnetic waves (EMWs) due to their favorable dielectric characteristics and unique porous structure. Nevertheless, the introduction of nitrogen atoms into graphene aerogels can result in improved impedance matching. In recent years, nitrogen-doped graphene aerogels (NGAs) have emerged as promising materials, particularly when combined with magnetic metals, magnetic oxides, carbon nanotubes, and polymers, forming innovative composite systems with excellent multi-functional and broadband absorption properties. This paper provides a comprehensive summary of the synthesis methods and the EMW absorption mechanism of NGAs, along with an overview of the absorption properties of nitrogen-doped graphene-based aerogels. Furthermore, this study sheds light on the potential challenges that NGAs may encounter. By highlighting the substantial contribution of NGAs in the field of EMW absorption, this study aims to facilitate the innovative development of NGAs toward achieving broadband absorption, lightweight characteristics, and multifunctionality. Full article

Diuron (DU) abuse in weed removal and shipping pollution prevention always leads to pesticide residues and poses a risk to human health. In the current research, an innovative electrochemical sensor for DU detection was created using a glassy carbon electrode (GCE) that had been modified with chitosan-encapsulated multi-walled carbon nanotubes (MWCNTs-CS) combined with nitrogen-doped graphene quantum dots (NGQDs). The NGQDs were prepared by high-temperature pyrolysis, and the MWCNTs-CS@NGQDs composite was further prepared by ultrasonic assembly. TEM, UV-Vis, and zeta potential tests were performed to investigate the morphology and properties of MWCNTs-CS@NGQDs. CV and EIS measurements revealed that the assembly of MWCNTs and CS improved the electron transfer ability and effective active area of MWCNTs. Moreover, the introduction of NGQDs further enhanced the detection sensitivity of the designed sensor. The MWCNTs-CS@NGQDs/GCE electrochemical sensor exhibited a wide linear range (0.08~12 μg mL⁻¹), a low limit of detection (0.04 μg mL⁻¹), and high sensitivity (31.62 μA (μg mL⁻¹)⁻¹ cm⁻²) for DU detection. Furthermore, the sensor demonstrated good anti-interference performance, reproducibility, and stability. This approach has been effectively employed to determine DU in actual samples, with recovery ranges of 99.4~104% in river water and 90.0~94.6% in soil. The developed electrochemical sensor is a useful tool to detect DU, which is expected to provide a convenient and easy analytical technique for the determination of various bioactive species. Full article

S and N double-doped high surface area biomass-derived carbons were obtained from marine biomass-derived ι-carrageenan. Adding carbon nanoparticles (CNPs), namely graphene oxide (GO) or carbon nanotubes (CNTs), in the early stage of the synthesis leads to a modified porous texture and surface chemistry. The porous textures were characterized by N₂ (−196.15 °C) and CO₂ (0 °C) isotherms. The best GO- and CNT-added carbons had an apparent surface area of 1780 m²/g and 1170 m²/g, respectively, compared to 1070 m²/g for the CNP-free matrix. Analysis of the Raman spectra revealed that CNT was more efficient in introducing new defects than GO. Based on XPS, the carbon samples contain 2–4.5 at% nitrogen and 1.1 at% sulfur. The Dubinin–Radushkevich (DR) and Henry models were used to assess the strength of the interactions between various gases and the surface. The N₂/H₂ and CO₂/CH₄ selectivities were estimated with ideal adsorbed solution theory (IAST). While the CNPs, particularly GO, had a remarkable influence on the porous texture and affected the surface chemistry, their influence on the separation selectivity of these gases was more modest. Full article

A FeNx-C-based catalyst is considered one of the most promising candidates for the highest oxygen reduction reaction (ORR) activities among nonprecious metal-based electrocatalysts. In this work, a unique catalyst of nitrogen-doped twisted macroscopic graphene tubes decorated with Fe-Nx and bamboo-like carbon nanotubes (CNT) was prepared by using twisted iron wire as a template and cyanamide as a carbon source. The microstructure and physicochemical natures of the samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopic (XPS), X-ray diffraction (XRD), and nitrogen adsorption/desorption measurements. Torsion can promote the dislocation of the iron wire lattice, and activate the surface Fe atoms, thus leading to the growth of bamboo-like carbon nanotubes and forming iron nitride. The product has a graphene-like macroscopic tube structure and exhibits excellent ORR activity. Such excellent ORR performance may be ascribed to the synergistic effect, including high ORR catalytic sites caused by the dislocation of the iron wire lattice, nitrogen heteroatoms doping, favorable reactant transport channels provided by macroscopic tube structure, and fast electron transfer rate induced by 3D continuous networks. Full article

The rareness and weak durability of Pt-based electrocatalysts for oxygen reduction reactions (ORRs) have hindered the large-scale application of fuel cells. Here, we developed an efficient metal-free catalyst consisting of N, S co-doped graphene nanoribbons (N, S-GNR-2s) for ORRs. GNRs were firstly synthesized via the chemical unzipping of carbon nanotubes, and then N, S co-doping was conducted using urea as the primary and sulfourea as the secondary heteroatom sources. The successful incorporation of nitrogen and sulfur was confirmed by elemental mapping analysis as well as X-ray photoelectron spectroscopy. Electrochemical testing revealed that N, S-GNR-2s exhibited an E_onset of 0.89 V, E_1/2 of 0.79 V and an average electron transfer number of 3.72, as well as good stability and methanol tolerance. As a result, N, S-GNR-2s displayed better ORR property than either N-GNRs or N, S-GNRs, the control samples prepared with only a primary heteroatom source, strongly clarifying the significance of secondary-heteroatom-doping on enhancing the catalytic activity of carbon-based nanomaterials. Full article

Solid-contact ion-selective electrodes (SC-ISEs) exhibit great potential in the detection of routine and portable ions which rely on solid-contact (SC) materials for the transduction of ions to electron signals. Carbon-based materials are state-of-the-art SC transducers due to their high electrical double-layer (EDL) capacitance and hydrophobicity. However, researchers have long searched for ways to enhance the interfacial capacitance in order to improve the potential stability. Herein, three representative carbon-based SC materials including nitrogen-doped mesoporous carbon (NMC), reduced graphene oxide (RGO), and carbon nanotubes (CNT) were compared. The results disclose that the NMC has the highest EDL capacitance owing to its mesopore structure and N-doping while maintaining high hydrophobicity so that no obvious water-layer effect was observed. The Ca²⁺-SC-ISEs based on the SC of NMC exhibited high potential stability compared with RGO and CNT. This work offers a guideline for the development of carbon-material-based SC-ISEs through mesoporous and N-doping engineering to improve the interfacial capacitance. The developed NMC-based solid-contact Ca²⁺-SC-ISE exhibited a Nernstian slope of 26.3 ± 3.1 mV dec⁻¹ ranging from 10 μM to 0.1 M with a detection limit of 3.2 μM. Finally, a practical application using NMC-based SC-ISEs was demonstrated through Ca²⁺ ion analysis in mineral water and soil leaching solutions. Full article