Search Results (503)

In recent years, energy storage devices have had a lower energy density for supercapacitor devices. Fortunately, certain drawbacks limit the liquid-based battery-type aqueous zinc-ion hybrid capacitor electrodes. For this reason, zinc–manganese (Zn-Mn)-based zinc-ion hybrid supercapacitors (ZIHSCs) have been designed using a manganese-dioxide-functionalized carbon nanotube (MnO₂–f-MWCNT) battery-type cathode in a semi-solid gel–free-standing film electrolyte. Herein, as-prepared MnO₂–MWCNTs are synthesized and assembled for nanostructured cathode composite materials by a facile hydrothermal technique. In this work, MnO₂ nanorods with f-MWCNTs are applied to the electrode, resulting in a semi-solid-state gel film electrolyte realized by assembling the Zn-Mn hybrid capacitor. The materials’ physical–chemical conformation and their unique characteristics, crystalline structures, and different morphologies are studied through XRD, FE-SEM, FE-TEM, and XPS analysis. In this work, the design of major-source MnO₂-based materials for positive and battery-type zinc metal anode approaches, along with the electrochemical properties of MnO₂–MWCNT//Zn hybrid charge storage mechanisms, are evaluated. The coin-cell-type ZIHSC investigation of cyclic voltammetric (CV) curves and lower constant current charge/discharge (GCD) and electrochemical impedance (EIS) methods is also carried out. In addition, the maximum specific capacitance values, 339.98 mAh/g and 203.52 mAh/g, were observed for MnO₂–MWCNT//Zn and MnO₂//Zn at 0.2 mA/g, respectively. Finally, the higher cycling stability of MnO₂−f-MWCNT of a 94.15% capacity retention after 15,000 cycles was evaluated and compared to MnO₂//Zn of 73.05% retention in ZIHSC device applications. The assessment of electrochemical MnO₂ cathode-based Zn-Mn ZIHSC performance is applicable for future aqueous electrical energy storage devices. Full article

Ti6Al7Nb biomedical alloy is difficult to machine because its low thermal conductivity and high chemical reactivity promote heat accumulation, high cutting loads, and poor surface quality. This study evaluated the side milling performance of Ti6Al7Nb under dry machining, vortex tube cooling, and MWCNT-assisted nanoparticle minimum quantity lubrication (NMQL) to identify a more sustainable and effective machining strategy. Experiments were conducted using two cutting speeds and three feed rates, and machinability was assessed in terms of cutting temperature, resultant cutting force, surface roughness, Tol wear and tool life, chip morphology, and multi-criteria ranking. Compared with dry machining, vortex tube cooling provided the strongest thermal control, reducing cutting temperature by 25–36% compared with dry conditions, owing to the cold air stream generated by the Ranque–Hilsch effect. MWCNT-NMQL produced the greatest reductions in cutting force and surface roughness, with improvements of 7–28% and 10–20%, respectively, compared with dry conditions, due to improved lubrication, reduced adhesion, possible tribofilm formation, rolling/sliding effects of MWCNTs, and enhanced heat transfer. Chip morphology observations confirmed that both assisted environments improved chip formation compared with dry machining. The overall ranking identified vortex tube cooling at Vc = 30 m/min and f = 0.08 mm/rev as the best overall condition, while NMQL was more favorable for force reduction and surface finish improvement. The findings of this study provide practical guidance for the selection of sustainable and effective cutting strategies in the precision machining of biomedical titanium alloys. Full article

The integration of enzyme-loaded polymeric matrices with carbon-based nanomaterials and metallic nanoparticles into wearable multisensing patches, coupled with miniaturized portable detection devices, enables real-time, highly sensitive, and simultaneous monitoring of key clinical biomarkers (e.g., glucose, lactate, and H₂O₂) in clinical and point-of-care applications. Multiplex biosensors were fabricated by modifying screen-printed carbon paste electrodes (SPEs) with different composite nanomaterials based on carbon nanomaterials such as multi-walled carbon nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs), or fullerenol (FL), the redox mediator Prussian Blue, and platinum nanoparticles (PtNPs). Chitosan and sol–gel polymer matrices were used to immobilize the enzymes glucose oxidase (GOx) and lactate oxidase (LOx), thus ensuring not only increased sensitivity and operational stability, but also high specificity for biomarker detection (glucose and lactate). Among the nanomaterials used for the development of multiplex biosensors, the SWCNT-PtNP composite was highlighted by electrochemical studies as having a significantly superior electrocatalytic activity toward the reduction of H₂O₂. This reaction occurs at a low applied potential of only −0.2 V vs. Ag/AgCl, achieving a specific sensitivity of 224.6 mA·M⁻¹·cm⁻², over a concentration range of 0.07 to 28.26 mM, and a detection limit of 3.2 μM. When functionalized with enzymes, SWCNT-PtNP-based biosensors exhibit improved conductivity, allowing the detection of glucose and lactate at a potential of −0.05 V vs. Ag/AgCl. The specific sensitivities obtained are 20.25 mA·M⁻¹·cm⁻² for glucose and 94.76 mA·M⁻¹·cm⁻² for lactate, and the corresponding detection limits are 23.6 μM and 5.0 μM, respectively. Finally, a wearable patch integrating the multiplex (bio)sensor with a portable potentiostat enabled simultaneous, sensitive, and selective detection of glucose, lactate, and H₂O₂ in sweat samples. Full article

It is essential to design electrode structures which simultaneously ensure mechanical strength and facilitate rapid sodium-ion transport to enable practical and large-scale sodium-ion battery (SIB) applications. In this study, we report a novel anode material featuring a cross-linked architecture composed of MoS₂ reinforced internally by catalytically derived CoS₂@C-supported carbon nanotubes (CNTs), and externally by commercial multi-walled carbon nanotubes (MWCNTs). This dual-reinforced configuration effectively prevents MoS₂ layer aggregation, enhances structural integrity, and establishes continuous conductive frameworks for efficient electron transmission. Additionally, it offers ample ion-diffusion pathways and mechanical resilience to buffer volume changes during cycling. Density functional theory (DFT) simulations reveal that the modified MoS₂ structure exhibits a significantly reduced sodium-ion diffusion barrier, contributing to enhanced charge-discharge kinetics. The CoS₂@C/CNTs@MoS₂@MWCNTs electrode achieves remarkable cycling stability, retaining 395 mA h g⁻¹ at 1 A g⁻¹ for 2000 cycles. In situ X-ray diffraction (XRD) along with kinetic analyses confirm a pseudocapacitance-dominated storage mechanism. Furthermore, full coin-type cells assembled with Na₃V₂(PO₄)₃ cathodes demonstrate excellent cycling performance, demonstrating the practical potential of this design strategy for advanced SIBs. Full article

The removal of phenol from contaminated effluents presents an industrial challenge owing to its toxicity at trace concentrations. Multi-walled carbon nanotubes (MWCNTs) have been studied as adsorbents for this purpose, given their high adsorption capacity and ease of separation. This work presents a theoretical phenomenological and numerical analysis of mass transport coupled to phenol adsorption on MWCNTs (external diameter $d_{ext}=50$ nm), parameterized using published experimental equilibrium data acquired under neutral pH conditions at 298 K. The mathematical model incorporates an effective pore diffusivity ($D_e=3.213\times {10}^{-10}$ m²/s) derived from pore structure parameters and describes three distinct scenarios: (1) pure physical adsorption via a modified Fick’s Second Law; (2) coupled diffusion–reaction with 0.5-order kinetics, herein treated as an empirical kinetic ansatz with phenomenological divergence from lumped empirical models (PFO/PSO); and (3) a parametric and sensitivity analysis on particle size (1–100 nm) and inlet concentration (1–5 mg/L). Numerical solutions confirm a Thiele modulus $\varphi \ll 1$ across the tested range, indicating a kinetically controlled regime with effectiveness factor $\eta \approx 1.0$, and validate the theoretical scaling $\varphi \propto C_s^{-0.25}$. During effluent polishing operations (reduction from 5 to 1 mg/L), the relative diffusive resistance increases by 49.5%, suggesting proportional increases in contact time or adsorbent dosage are required. A one-at-a-time (OAT) sensitivity analysis on $D_e$, $\kappa$, and $k_{obs}$ confirms that the kinetically controlled regime is preserved across plausible parameter ranges. The nanoscale architecture of MWCNTs reduces theoretical intraparticle diffusional resistance by several orders of magnitude relative to macroscopic granular adsorbents. We emphasize that these conclusions describe theoretical mass-transport advantages; experimental and pilot-scale validation under realistic, multi-component wastewater conditions remains an essential step before industrial deployment. Full article

A charge-balanced aqueous hybrid supercapacitor was constructed by coupling Co-modified MnWO₄ nanorods with H₂O₂-treated carbon nanotubes (OH-CNTs) in 1 M KOH. The samples were designated by the nominal Co/(Mn + Co) precursor molar fraction; ICP-OES measured bulk Co fractions of 0.09 ± 0.01, 0.47 ± 0.03, and 0.75 ± 0.04 mol% for the nominal 0.1, 0.5, and 0.8 mol% samples, respectively. Rietveld refinement confirmed retention of the monoclinic P2/c MnWO₄ phase with only small composition-dependent lattice changes. At an active-material loading of 2.00 ± 0.05 mg cm⁻², the optimized nominal 0.5 mol% sample delivered 429.5 ± 11.0 C g⁻¹ (119.3 ± 3.1 mAh g⁻¹) at 1 A g⁻¹ and retained 280.5 ± 8.5 C g⁻¹ (77.9 ± 2.4 mAh g⁻¹) at 15 A g⁻¹. Because the positive electrode exhibits battery-type behavior, specific charge and specific capacity are used as the primary performance descriptors. Over −0.9–0 V vs. SCE, pristine CNT and OH-CNT electrodes delivered of 189.0 ± 7.2 and 246.6 ± 8.1 C g⁻¹, corresponding to electrode-level apparent specific capacitances of 215 ± 8 and 280 ± 9 F g⁻¹ at 1 A g⁻¹ after correction for the measured IR drop. These values apply to the stated 90:5:5 CNT (or OH-CNT)/acetylene-black/PVDF formulation and CNT-active-mass normalization and should not be interpreted as intrinsic capacitances of isolated commercial MWCNT powders. Charge matching based on the measured gave m⁺/m⁻ = 0.574; integration at the actual device loadings yielded q⁺ = 0.861 ± 0.015 C and q⁻ = 0.854 ± 0.015 C (q⁺/q⁻ = 1.008). The device operated over 0–1.6 V and delivered 97.9 ± 3.1 F g⁻¹ at 0.51 A g⁻¹, corresponding to 34.8 Wh kg⁻¹ at 408 W kg⁻¹ when normalized to the combined active mass of both electrodes. Three independently assembled devices retained 96.0 ± 0.7% of the initial capacitance and showed a coulombic efficiency of 98.8 ± 0.1% at the 10,000th cycle at 5.13 A g⁻¹. Device metrics are normalized to the combined active mass of both electrodes and exclude current collectors, separator, electrolyte, and packaging. Full article

Multiwalled carbon nanotubes (MWCNTs) and nanoalumina (nano-Al₂O₃) have each been studied separately in asphalt binders, but whether their combined thermal gain translates into microwave-induced healing at the mixture scale remains unestablished. This study aimed to evaluate, through a multiscale approach, their combined incorporation into a polymeric asphalt binder modified with 4% styrene-butadiene-styrene (SBS), focusing on mechanical performance and microwave-induced healing. Binders with 0 to 6% hybrid nanomaterial (50:50) were characterized structurally, chemically, rheologically, and thermally, and mixtures were evaluated for rutting, four-point bending fatigue, and microwave heating and healing. A content of 2.3% was selected from rheological and thermal criteria. At this content, the mixture heating rate rose from 0.18 to 0.41 °C/s (127.8%) and rut depth decreased by 22.1%. The nanomodified binder reduced the top-to-bottom Jnr_3.2 gradient from over 250% to 56–59%, indicating improved storage compatibility rather than complete stability. Fatigue life at 250 μm/m decreased by 53.7%. Despite this, healing increased by 9.6% in dynamic modulus recovery and 61.9% in fatigue healing index. Overall, hybrid nanomodification improved resistance to permanent deformation and microwave-induced healing, clarifying their combined effect, although the fatigue penalty requires further investigation. Full article

Environmental impacts of wastewater from textile and dyestuff industries are of growing concern due to limited freshwater availability and inadequate treatment facilities. Carbon nanotubes (CNTs) offer excellent adsorption potential because of their outstanding mechanical and chemical properties, however; their application in textile effluent treatment has not been widely studied. Moreover, laboratory-based studies are often costly and limited to a few variables, making it challenging to reveal the underlying relationships among several physicochemical parameters and CNT treatments. Multivariate statistical analysis (MVSA) offers an effective approach to overcome this challenge. To the best of our knowledge, no studies have integrated laboratory analysis of nanotube-based textile effluent treatment with an MVSA approach. This study aims to evaluate the physicochemical characterization of textile effluent, treat effluent with CNT, and explore the relationship between physicochemical parameters and CNT by integrating laboratory experiments with MVSA. For this purpose, single-walled CNT (SWCNT) and multi-walled CNT (MWCNT) were applied in batch mode adsorption experiments using various dosages and adsorption times. Scanning electron microscopy and Fourier transform infrared spectroscopy (FTIR), along with physicochemical analyses, were conducted to characterize the effluent and adsorption processes. The FTIR spectrum indicated that the absorption peaks of C=C, C=O, and the acidic f -OH group on CNTs enhance wettability and hydrophilic character, thereby increasing adsorption capacity. Experimental results demonstrated significant reductions in electrical conductivity (EC), total dissolved solids (TDS), turbidity, total organic carbon (TOC), and chemical oxygen demand (COD). CNT dosages of 1 to 5 g/100 mL and adsorption times of 2 to 5 h achieved removal efficiencies ranging from approximately 20% to 90% for SWCNT and MWCNT. MVSA indicated that MWCNT was more strongly associated with ionic and physical parameters (turbidity, TDS, EC, and pH), whereas SWCNT was more strongly related to organic load indicators, particularly COD and TOC. Overall, this study highlights the potential of CNT coupled with the MVSA technique as an effective and sustainable approach for textile wastewater treatment and offers valuable insights for researchers working in this field. Full article

Cement slurry is a staple grouting agent, yet its properties can weaken when exposed to heat. Studying grouting materials for use in high-temperature tunnels is therefore a matter of considerable importance. To enhance the applicability of cement-based slurry in high-temperature tunnels, multi-walled carbon nanotubes (MWCNTs), polycarboxylate ether superplasticizer (PCE), and hydroxypropyl methylcellulose (HPMC) were added to improve their performance at elevated temperatures. Various experimental methods were employed to investigate the properties of the modified slurry at different temperatures, including flowability, setting time, compressive strength, and dynamic water retention ratio. Additionally, X-ray diffraction (XRD), thermogravimetric analysis (TG), and scanning electron microscopy (SEM) were used to study the effects of temperature on hardened slurry. Experimental results indicate that the optimal MWCNTs content is 0.32%. At this content, the compressive strength of the hardened slurry after 28 days of curing at 80 °C increases by approximately 20%, reaching 26.4 MPa. PCE improves the fluidity of the slurry, while HPMC enhances its water dynamic water retention ratio. The optimal proportion was found to be 0.3% PCE and 0.2% HPMC. At this ratio, the fluidity of the slurry increased by about 8%, reaching approximately 17.7 cm; the dynamic water retention ratios of 0.8 m/s and 1.0 m/s improved by approximately 22% and 38%, respectively, achieving 35.8% and 18.1%. Furthermore, multi-walled carbon nanotubes significantly enhance the compressive strength of the hardened slurry primarily by suppressing the formation of ettringite during the later stages of hydration, as well as by providing nucleation sites, encapsulating hydration products, and bridging hydration product clusters within the microstructure. This investigation lays a theoretical groundwork for formulating and choosing grouting materials suited to high-temperature tunnel environments. Full article

Metal oxide nanomaterials tailored at the nanoscale are opening new avenues for advanced electroanalytical sensing devices with enhanced properties, including improved electrocatalytic activity. In this work, a novel Mn₂Mo₃O₈/MnO-MWCNT nanocomposite was employed to modify a screen-printed carbon electrode, enabling the fabrication of an amperometric sensor for H₂O₂ operating at relatively low applied potential due to the catalytic activity of the nanocomposite. Further functionalization of this nanostructured surface with glucose oxidase allowed the construction of an electrochemical glucose biosensor, where the Mn₂Mo₃O₈/MnO-MWCNT material acted as an efficient electrocatalyst for hydrogen peroxide detection. The H₂O₂ sensor exhibited a linear response from 0.06 mM to 3.00 mM, with a sensitivity of (2.22 ± 0.02) µA mM⁻¹ and a detection limit of 22 µM. The glucose biosensor showed a linear response in the range from 0.10 mM to 18.9 mM glucose, with a sensitivity of (0.345 ± 0.005) µA mM⁻¹, and a detection limit of 29 µM. The biosensor displayed excellent selectivity and high stability and was successfully applied to the determination of glucose in lactose-free skimmed milk. Full article

The use of hydrolytic enzymes is one of the most promising methods for combating bacterial biofilms. However, the use of native enzymes is limited by the rapid loss of activity under unfavorable conditions. Immobilization of enzymes on carbon nanoparticles enhances their stability, allows for biocatalyst reuse, and creates a synergistic effect due to the intrinsic antimicrobial properties of the nanomaterials. The aim of this investigation was to create and comparatively analyze conjugates of acid and alkaline proteases with carboxylated multiwalled carbon nanotubes (MWCNTs-COOH) and to assess their effect on the formation and destruction of E. coli VKM B-3858D biofilms. The immobilization efficiency and kinetics of enzyme adsorption on the support were quantified by determining the protein concentration using the Bradford assay. The morphology and dispersion of the resulting conjugates were analyzed using atomic force microscopy (AFM). Protease activity was determined by a modified Anson method using the Folin–Ciocalteu reagent. Biofilm biomass was determined using crystal violet staining. The binding efficiency of the acid protease to MWCNTs-COOH was shown to reach 93%, which is significantly higher than that of the alkaline protease. The highest degree of immobilization was observed at a protein concentration of 117–338 μg/mL (10–20 mg/mL of the enzyme preparations). The interaction of the acid protease with the carbon nanoparticles increased dispersion, reducing the size of aggregates from ~1 μm to ~68 nm. As a result, acid protease conjugates with MWCNTs-COOH significantly reduced the biofilm biomass compared to both the enzyme-free control and the native enzyme. Alkaline protease, unlike the acid protease, destroys mature biofilms, and immobilization on MWCNTs-COOH enhances this ability. Native alkaline protease and acid protease conjugates with MWCNTs-COOH are effective in combating the biofilm formation of Gram-negative bacteria, while alkaline protease conjugates are suitable for disrupting mature biofilms. Full article

Demographic growth and the global environmental crisis have intensified the need to reconcile energy generation with the protection of terrestrial ecosystems. Traditional organic waste management systems are inefficient in handling high pollutant loads, leading to uncontrolled methane emissions and degradation of soil and water. In response to this challenge, the present study aimed to conduct a critical review of how Microbial Fuel Cells (MFCs) valorize biomass to align climate action (SDG 13) with the protection of terrestrial life (SDG 15). Through a bibliometric analysis of the Scopus database (2010–2026), supported by tools such as Bibliometrix, 460 documents were examined, complemented by a systematic literature review addressing biomass types, microbial interactions, and electrode modifications. The main findings indicate that MFC research is currently in an exponential growth phase (R² = 0.99954), with Environmental Sciences (23%) and Chemical Engineering (15%) as the predominant fields. Industrial and plant residues exhibit the highest bioelectric potential, while mixed microbial consortia—particularly fungal–bacterial synergies—outperform pure cultures in degradative efficiency and energy generation, reaching up to 1760 mW/m² with Geobacter sulfurreducens bioaugmentation. Electrode modification with nanomaterials such as NiO or MWCNTs substantially enhances charge transfer. Standardization of measurement protocols, ecological impact assessment of nanomaterials, and evaluation of the economic–environmental feasibility of MFC-integrated biorefineries are recommended to ensure scalability and effective contributions to SDGs 13 and 15. Full article

Electrochemical sensing provides an alternative approach for the trace detection of bioactive substances in fruits. However, the complex matrix in fruit tissues, the coexistence of multiple active components, and the varied pH environments limit the sensing performance and accurate quantitative detection of conventional electrochemical sensors. Herein, a dual-mode electrochemical sensor based on a Co₃O₄@N-MWCNTs modified glassy carbon electrode was developed for the sequential detection of quercetin, rutin, and glucose in fruits under acidic and alkaline conditions. The as-prepared electrode exhibited improved charge transfer efficiency and favorable electrocatalytic activity toward the three target analytes. Under optimal conditions, the sensor displayed wide linear ranges of 0.5~70 μM for quercetin and 0.5~5 μM for rutin in acidic environment, with low detection limits of 0.124 μM and 0.045 μM, respectively. In alkaline environment, the detection limit for glucose was determined to be 8.86 μM. Moreover, four combined machine learning models with feature selection algorithms were established, among which the CARS-RFE+RFR model achieved the best prediction accuracy and robustness for multicomponent quantification. Furthermore, the proposed sensing system was applied to the rapid determination of quercetin, rutin, and glucose in real litchi samples, with recoveries ranging from 98.4% to 105.4%. This study provides a feasible electrochemical strategy for multicomponent detection in complex plant matrices, showing good applicability for rapid on-site analysis in agricultural and food-related applications. Full article

Effective regulation of the adsorption strength of oxygen reduction reaction (ORR) intermediates on active sites is the key to enhancing their catalytic performance. This study proposes an axial coordination modulation strategy by successfully anchoring the dioxin-linked FePcF₁₆-based covalent organic frameworks (COFs) onto amino-functionalized multi-walled carbon nanotubes (NH₂-MWCNTs), constructing a FePcF₁₆-COF/NH₂-MWCNT hybrid catalyst. Experimental results demonstrate that the catalyst exhibits outstanding ORR activity (E_1/2 = 0.901 V; J_L = 5.133 mA cm⁻²), outperforming commercial 20% Pt/C and most reported Fe-based non-precious metal catalysts. Furthermore, the robust dioxin-linked COF skeleton endows the catalyst with excellent electrochemical stability. A zinc–air battery using this catalyst as the cathode also demonstrates superior power density and cycling performance. This work provides a new strategy for designing highly efficient ORR catalysts through axial coordination environment engineering. Full article

Polysulfone (PSF) nanofiltration membranes incorporating oxidized multi-walled carbon nanotubes (o–MWCNTs) and terbium oxide (Tb₂O₃) nanoparticles were fabricated via the non-solvent-induced phase inversion technique. The effect of Tb₂O₃ loading (0, 1, 3, and 5% w/w) on membrane morphology, hydrophilicity, water permeability, dye rejection, and antibiofouling performance was systematically investigated. Membrane structure was characterized by FTIR spectroscopy, SEM, EDX, XRD, and water contact angle measurements. The results confirmed the successful incorporation of Tb₂O₃ within the membrane matrix, and morphological analysis revealed a relatively dense membrane structure without macrovoid formation. Filtration experiments conducted in a dead-end cell under pressures of 1–4 bar demonstrated a maximum water flux of 53 L m⁻² h⁻¹, with dye rejection exceeding 99.9% for both methylene blue (MB) and Congo red (CR) at 4 bar. Antibiofouling performance, evaluated by colony-forming unit analysis, revealed bacterial growth reductions of 59% against Gram-negative Escherichia coli and 89% against Gram-positive Candida albicans, attributed to the dark-active generation of reactive oxygen species by Tb₂O₃, eliminating the need for UV irradiation. These results demonstrate that the synergistic integration of o–MWCNTs and Tb₂O₃ effectively addresses the permeability-selectivity trade-off and mitigates biofouling limitations associated with pristine PSF membranes, thereby offering a promising multifunctional platform for sustainable industrial wastewater treatment. Full article