Halloysite Nanotubes Research Articles

Improvement of Mechanical and Acoustic Characteristics of Halloysite Nanotube-Reinforced Polyurethane Elastomer Composites and Their Applications

Polyurethane incorporated with nanofillers such as carbon nanotubes, basalt fibers, and clay nanoparticles has presented remarkable potential for improving the performance of the polymeric composites. In this study, the halloysite nanofiller-reinforced polyurethane elastomer composites were prepared via the semi-prepolymer method. The impact of different halloysites (halloysite nanotubes and halloysite nanoplates) in polyurethane composites was investigated. Scanning electron microscopy, X-ray diffraction, infrared spectroscopy, electronic universal tensile testing, and acoustic impedance tube testing were employed to characterize the morphology, composition, phase separation, mechanical properties, and sound insulation of the samples. The composite fabricated with 0.5 wt% of halloysite nanotubes introduced during quasi-prepolymer preparation exhibited the highest tensile strength (22.92 ± 0.84 MPa) and elongation at break (576.67 ± 17.99%) among all the prepared samples. Also, the incorporation of 2 wt% halloysite nanotubes into the polyurethane matrix resulted in the most significant overall improvements, particularly in terms of tensile strength (~44%), elongation at break (~40%), and sound insulation (~25%) within the low-frequency range of 50 to 1600 Hz. The attainment of these impressive mechanical and acoustic characteristics could be attributed to the unique lumen structure of the halloysite nanotubes, good dispersion of the halloysites in the polyurethane, and the interfacial bonding between the matrix and halloysite fillers.

Decoration of Pt–Ni Alloy on Molten Salt Etched Halloysite Nanotubes for Enhanced Catalytic Reduction of 4-Nitrophenol

Decoration of Pt–Ni Alloy on Molten Salt Etched Halloysite Nanotubes for Enhanced Catalytic Reduction of 4-Nitrophenol

Unveiling the Potential of Halloysite Nanotubes: Insights into Their Synthesis, Properties, and Applications in Nanocomposites

AbstractHalloysite nanotubes (HNTs) have attracted considerable attention due to their unique properties and wide range of applications. This review explores HNT‐based nanocomposites, focusing on their preparation methods and improvements in mechanical, thermal, and barrier properties. Various synthesis techniques, including solution mixing, melt compounding, in situ polymerization, and surface modification, are discussed, along with their benefits and limitations. The role of HNT characteristics such as aspect ratio, dispersion, and surface chemistry in enhancing nanocomposite properties is examined. HNTs significantly boost mechanical properties, including tensile strength, Young’s modulus, and toughness, due to their reinforcement effects. Improved dispersion and interfacial adhesion between HNTs and the polymer matrix enhance these properties. HNTs also act as thermal barriers, improving heat resistance and dimensional stability, while enhancing barrier properties against gases and moisture. These synergistic effects allow for the customization of nanocomposites for specific applications in packaging, automotive, electronics, and biomedical fields. Future research should focus on optimizing synthesis methods and processing techniques to further improve HNT‐based nanocomposites’ performance. This review provides a comprehensive overview of HNT‐based nanocomposites, offering valuable insights for advancing nanomaterials science and engineering.

Multi-channeled halloysite nanotube-blended polybenzimidazole separators for enhancing lithium-ion battery performance

The microscopic transport mode of lithium ions in the separator is crucial for solving the problem of irregular lithium dendrite growth, thereby enhancing the safety of battery operation, and it also has a positive impact on the electrochemical performance of the battery. Furthermore, the heat resistance of the separator is an important indicator for measuring the performance of the separator and the safety of battery usage. In this work, we have introduced sulfonated and lithiated halloysite nanotubes into a high-temperature-resistant OPBI matrix through an easily implementable NIPS, resulting in a high-temperature-resistant separator with multiple lithium-ion micro-transport morphologies. Lithium ions can shuttle through the halloysite nanotube pores, negatively charged sulfonate groups on the surface, and larger finger-like pores formed by NIPS within the separator, creating a high and uniform lithium-ion flux that prevents excessive localized ion flow leading to the aggressive growth of lithium dendrites. According to the characterization data, this separator exhibits relatively satisfactory performance, such as an ionic conductivity of 1.82 mS cm−1, a porosity of 82 %, an electrolyte uptake of 397 %, and no significant physical shrinkage at 200 °C. Additionally, the cells assembled using the OPBI@sHNT-Li20 separator delivers higher discharge capacity (164.92 mAh·g−1), more stable cycle, superior rate performance. So the OPBI@sHNT-Li separator is expected to play an active role in improving the safety and electrochemical performance of lithium-ion batteries.

N-doped carbon-coated halloysite nanotubes as cathode materials for high-performance lithium-sulfur batteries

The practical application and development of lithium-sulfur batteries (LSBs) remains a serious issue as a consequence of the shuttle effect of lithium polysulfides (LiPSs). Halloysite (HNT), a clay mineral with a unique hollow tubular structure, is a potential carrier for sulfur. In this work, we employed a strategic approach to modify both inner and outer surfaces of HNT. We synthesized N-doped carbon-coated thin-wall hollow nanotube HNT composites (A5HNT@NC), which were subsequently utilized as sulfur carriers in the cathode of LSBs. This method alleviates the shuttle effect of LiPSs and controls the volume expansion of sulfur during charge-discharge. Acid heat treatment reduced Al-O octahedron in HNT, expanding the inner diameter to enhance the loading of sulfur. A5HNT@NC, prepared through phase inversion and high-temperature pyrolysis, effectively enhanced the electrical conductivity of thin-walled HNT, facilitating Li+ and electron transfer. Meanwhile, the structure of A5HNT@NC effectively adapted volume expansion of sulfur, realized high sulfur loading, and provided abundant active sites for anchoring of LiPSs. Moreover, the incorporation of N elements on carbon layer enhanced the ability to catalyze and adsorb LiPSs. Consequently, A5HNT@NC/S cathode exhibited high cycle stability and specific capacity. At 0.2 C, it retained high capacity of 619.7 mAh g−1 after 100 cycles, achieving 84.67 % capacity retention. At a higher current density of 0.5 C, A5HNT@NC/S cathode also retained specific capacity of 515.0 mAh g−1 after 300 cycles. This work can expand the application of HNT for energy storage, provide inspiring insights into the design of novel sulfur carrier materials for LSBs.

Optimization of nanofiller compositions for enhancing thermo-mechanical properties of epoxy-based composites through the application of response surface methodology with central composite design

An epoxy based composite of modified halloysite nanotubes (A) and modified fly ash (B) with improved thermo mechanical and morphological properties has been successfully fabricated. The primary objective of this study is to analyze the factors (composition of A and B) that significantly affect the properties of nanocomposites and to find out the best optimize values of these factors using Response Surface Methodology (RSM) with Central Composite Design(CCD). The enhancement of 80 percent in the tensile strength, nearly 240 percent of flexural strength, and nearly 166 percent in impact strength has been achieved at the optimal composition of A and B. The scanning electron microscopy (SEM) analysis in the present study highlight the importance of achieving proper dispersion and interaction with the polymer matrix in order to address issues like HNT aggregation. The efficient dispersion of A (3 wt%) and B (6 wt%) in the polymer is confirmed by SEM studies. In addition the TGA graph shows good thermal stability at 340 °C.

Ion-Engineered Clay Nanozyme via Tumor Microenvironment Remodeling for Enhanced Tumor Therapy.

Metal ions show tremendous promise for tumor therapy due to their critical roles in many important catalytic circulations and immune processes. However, the valence state variability and systemic side-effects of metal ions cause ineffective ion enrichment in tumor cells, which limit their further application. Here, a Mn3+ ion delivery system (Mn-HNT) is constructed based on halloysite nanotubes (HNT) via an ion-engineered strategy. Due to the stabilizing effect of HNT on Mn3+ ions, Mn-HNT not only maintained the valence state of Mn3+ ions, but also presented strong catalase (CAT)- and glutathione oxidase (GSHOx)-like catalytic activity to catalyze O2 generation and GSH consumption to relieve the inhibition of tumor microenvironment on photodynamic therapy (PDT). After further coordination with the photosensitizer porphyrin (TCPP), obtained TCPP-Mn-HNT not only inherited the catalytic properties of Mn-HNT to produce oxygen and consume GSH, but acted as photosensitizer for ROS accumulation to effectively destroy tumor cells. Moreover, TCPP-Mn-HNT can promote the maturation of dendritic cells (≈2.8 times), and present the tumor antigen triggered by PDT to T cells to strengthen high-efficient tumor therapy. The study provides new opportunities for designing metal ion delivery system with versatile biofunctions and offers a paradigm of synergistic metal-ion-mediated tumor therapy.

Tensile modulus of polymer halloysite nanotubes nanocomposites assuming stress transferring through an imperfect interphase

In this work, Hui-Shia model is developed to reveal the efficiency of a deficient interphase on the tensile modulus of polymer halloysite nanotube (HNT) nanocomposites. “Lc” as essential HNT length providing full stress transferring is defined and effective HNT size, effective HNT concentration, and efficiency of stress transferring (Q) are expressed by “Lc”. Furthermore, the influences of all terms on the “Q” and nanocomposite’s modulus are clarified, and also the calculations of the model are linked to the tested data of some nanocomposites. Original Hui-Shia model overpredicts the moduli, but the innovative model’s predictions appropriately fit the measured data. Lc = 200 nm maximizes the sample’s modulus to 2.6 GPa, but the modulus reduces to 2.11 GPa at Lc = 700 nm. Therefore, there is a reverse relation between the sample’s modulus and “Lc”. Q = 0.5 produces the system’s modulus of 2.1 GPa, while the modulus of 2.35 GPa is achieved at Q = 1 providing a direct relation between the nanocomposite’s modulus and “Q”. Generally, narrow and big HNTs, along with a low “Lc”, enhance the “Q”, because a lower “Lc”, reveals a tougher interphase improving the stress transferring.

Physiochemical and In-Vitro Bioactivity Characterization of Polyvinyl Alcohol / Halloysite Nanotube / Collagen (PVA/HNT/Col) using Freeze-Thawing Method and Spin Coated Technique for Wound Healing Applications

Hydrogels are still relevant instruments that can support and improve the dynamic biological process of wound healing. This paper modified hydrogel film by combining polyvinyl alcohol (PVA), halloysite nanotube (HNT), and collagen using simple freeze-thawing and spin-coating techniques. The modification aims to improve the physiochemical and in-vitro bioactivity of the PVA/HNT hydrogel films via the inclusion of different concentrations of collagen. 0.092 mm PVA/HNT/Col3 hydrogel film was suggested to have excellent morphological properties with 94.11 % porosity. It also has good tensile properties with excellent hydrophilicity performance at 38.40o contact angle and 83.528% swelling capacity compared to other modified films. In-vitro bioactivity suggested that the PVA/HNT/Col3 are safe and non-toxic toward host tissue and can promote healing at 93.12% wound closure after 24 hours of treatment. Hence, this material displays huge potential as a wound healing matrix template.

Synergistic effects of graphene nanoparticles on the thermomechanical properties of PEEK-HNTs nanocomposites

In our previous study, we selected a 3% concentration (PH3) from various prepared PEEK-HNTs nanocomposites. Poly (ether ether ketone) (PEEK) is characterized by non-perfluorinated aromatic compounds with 1,4-disubstituted phenyl groups linked by carbonyl (––CO––) and ether (––O––) groups, offering exceptional thermal stability, mechanical strength, tribological properties, and chemical resistance at high temperatures. Halloysite nanotubes (HNTs) are known for their non-toxic, environmentally friendly, cost-effective properties, with tunable release and rapid adsorption rates. In this study, we prepared graphene nanoparticle (GNP) composites at three different concentrations while maintaining constant PH3 levels. The composites underwent comprehensive characterization using FTIR, TGA, DSC, SEM, and DMA techniques. Thermomechanical properties were evaluated using a universal testing machine. Results demonstrate significant enhancements in hardness, impact strength, elongation at break, tensile modulus, and flexural modulus, with the highest performance observed in the GNP-loaded 0.3% (PHG3) concentration. The synergistic effects of GNP fillers in PH3 are attributed to enhanced interfacial adhesion and favorable interactions with the polymer matrix.

Effect of functionalized halloysite nanotubes on fire resistance and water tolerance of intumescent fire-retardant coatings for steel structures

To improve the comprehensive performance of intumescent fire-retardant coatings, the functionalized halloysite nanotubes (HNTs-D, HNTs@Fe3O4, and HNTs-D@Fe3O4) were synthesized as synergistic flame retardants and incorporated into intumescent fire-retardant coatings (IFRC) for steel structures, demonstrating significant flame retardant properties. Among these modified halloysite nanosheets, HNTs-D@Fe3O4 showed the best flame retardancy and water resistance. Adding the optimal addition amount (3 wt%) of HNTs-D@Fe3O4 can increase the residual weight of coating from 28.10 % to 38.40 % and reduce the backside temperature of the coated steel plate from 288 °C to 177 °C, indicating that HNTs-D@Fe3O4 can effectively improve the thermal stability and insulation performances of intumescent fire-retardant coatings. Cone calorimetric analysis showed HNTs-D@Fe3O4 can effectively suppress the heat and smoke release of the intumescent fire-retardant coatings. Compared with the unmodified coating sample, the total heat release (THR) and total smoke release (TSR) of the HNTs-D@Fe3O4-containing coating sample were reduced by 66.04 % and 11.36 %. HNTs-D@Fe3O4 facilitates the formation of dense char layers confirmed by the micro morphology characterization. Further mechanism analysis shows that HNTs-D@Fe3O4 has obvious catalytic carbonization effect and is helpful to construct the dense expanded char layer with higher graphitization degree. The uniformly dispersed HNTs-D@Fe3O4 improved the water resistance of intumescent fire-retardant coatings, which is mainly due to the hydrophobicity and barrier effect, thus effectively preventing the loss of water-soluble components.

In-plane electrical conductivity of PEDOT:PSS/Halloysite composite thin films

PEDOT:PSS has found numerous applications in the field of advanced materials, especially in the development of organic electronics. Embedding nanoparticles into the polymer matrix has emerged as an effective strategy to modify the properties of PEDOT:PSS and develop advanced functional composites. Over the past decade, Halloysite nanotubes (HNT) have garnered significant interest and utility as nanofillers and/or templates due to their unique physical-chemical properties, small size, relatively low cost, and large availability. Interestingly, pairing PEDOT:PSS with non-conductive HNT has been demonstrated to enhance the charge transport properties of the composite film. Our discoveries show how the HNT can act as scaffolding for PEDOT:PSS by improving the local ordering of PEDOT chains and enabling the formation of conductive pathways. Consequently, the mechanism responsible for the observed changes in conductivity and the correlation between PEDOT:PSS and insulating nanofillers (HNT) could be different to that previously proposed. Hence, in this work it was observed that PEDOT:PSS/HNT composite films exhibited a non-linear conductivity dependence as a function of the HNT loading. From thermogravimetric analysis, infrared and UV-Vis-NIR spectroscopies, as well as impedance spectroscopy, a more complex interaction between the polymer chains and the nanotubes is revealed. Our study includes the modification of the interaction between the PEDOT chains and the nanofillers by using the secondary doping effect and functionalization of the nanotubes, which confirms our findings. These results represent a significant progress toward a deeper understanding of the emergence of a conductive polymer network on the nanofiller surface, leading to improvements in the electrical conductivity in the composite material.

Polyhydroxybutyrate/poly(ε‐caprolactone)‐based electrospun membranes loaded with amoxicillin‐potassium clavulanate halloysite nanotubes for biomedical applications

AbstractBiopolymers exhibit distinct properties for biomedical applications. Different biopolymer classes are utilized for various applications, for example antibacterial properties, drug delivery, tissue engineering, tissue scaffolds etc. In the present investigation, a nano‐bioengineering approach was followed to prepare polyhydroxybutyrate and polycaprolactone polymer‐based drug‐loaded halloysite nanotube electrospun membranes for biomedical applications. Functionalized halloysite nanotubes ((3‐aminopropyl)triethoxysilane acid treated halloysite nanotubes) at different weight percentages (1, 3, 5 and 7 wt%) were loaded with a broad‐spectrum antibiotic amoxicillin trihydrate‐potassium clavulanate, incorporated into the electrospun membranes, and characterized by different techniques such as XRD, FTIR, SEM, TEM and TGA. Different physical and mechanical properties were evaluated, such as porosity, water uptake, water vapor transmission rate, wettability and tensile properties. The developed membranes exhibited good in vitro biological properties, for example antibacterial, effective cell migration and less toxicity, as confirmed by disk diffusion, MTT (3‐(4,5‐dimethylthiazolyl‐2)‐2,5‐diphenyltetrazolium bromide) and cell scratch assays. A sustained drug release profile was observed from all the developed membranes. Overall results on the characterization of the developed membranes confirm the suitability of their use for different biomedical applications and as a wound dressing application. © 2024 Society of Chemical Industry.

Development of efficient CO2 adsorbents: Synthesis and performance evaluation of dopamine-modified halloysite nanotubes loaded with ZIF-8

Carbon capture, utilization, and storage (CCUS) is a crucial technology for achieving carbon reduction targets. The key to CCUS technology lies in developing and designing efficient and low-cost CO2 capture materials. Metal-organic frameworks (MOFs) have emerged as promising CO2 adsorbents in the field of carbon capture. However, high agglomeration of nanoparticles and high cost have severely hindered the application of MOF-based solid adsorbents. This study employs an in-situ growth method to prepare a novel “corncob-shaped” PHNT@ZIF-8 composite material. During the reaction process, surface modification of halloysite nanotubes (HNT) enhances the interaction between HNT and ZIF-8. The resulting PHNT@ZIF-8 exhibits an enhanced CO2 adsorption capacity of 1.48 mmol/g. Notably, the functionalized PHNT@ZIF-8 as CO2 adsorbents demonstrated significant adsorption properties: a high specific surface area of 409.74 m2/g, good selectivity in simulated flue gas composition of 15%/85% (CO2/N2) (39.1), excellent thermal stability, and superior regenerability. Moreover, PHNT@ZIF-8 adsorbs CO2 primarily through van der Waals forces, which involve low energy and are easily reversible. After eight adsorption–desorption cycles, CO2 capacity retention rate remains as high as 93% (1.37 mmol/g). This work enriches the repertoire of solid CO2 composite adsorbents, providing a novel pathway for enhancing CO2 adsorption performance.

Dispersion of halloysite nanotube/lipase nanohybrids as nanofillers into polyvinyl alcohol-sodium alginate cryogel: Characterization and bio-catalytic activity analysis

The purpose of this study is to formulate and characterize the cryogels containing halloysite nanotube (HNT)/lipase nanohybrid (NH-cryogel) in comparison to pure cryogels as well as cryogels containing lipase (lipase-cryogel). The cryogels were synthesized using polyvinyl alcohol (PVA) and sodium alginate (SA). The products are tested to explore the influence of the HNT/lipase nanohybride (NH) as nanofillers on the cryogel properties using methods such as swelling degree, water uptake measurement, TGA, XRD, FESEM and FTIR. Additionally, the effects of cryogels on the stability and biocatalytic activities of lipase and NH, were studied and compared to the free lipase to evaluate their potential applications as enzyme carriers. The addition of nanofillers into the cryogel improved is thermal stability. The results implied that NH-cryogel had better enzyme activity than lipase-cryogel and free lipase at different temperatures and pH values. The NH-cryogel residual activity was 85.5 % after ten cycles of reuse while lipase-cryogel showed lower residual activity (60.3 %). Furthermore, the NH-cryogel retained 81.1 % of its residual activity while this was 51.0 % for lipase-cryogel after thirty days of storage. Therefore, the presented results in this study provide a pathway to show that produced nano-composite cryogels could be useful substances for food and pharmaceutical industries applications.

Ti3C2Tx MXene-functionalized Hydroxyapatite/Halloysite nanotube filled poly– (lactic acid) coatings on magnesium: In vitro and antibacterial applications

Magnesium (Mg) stands out in temporary biomaterial applications due to its biocompatibility, biodegradability, and low Young's modulus. However, controlling its corrosion through next-generation polymer-based functional coatings is crucial due to the rapid degradation behavior of Mg. In this study, the function of 2D lamellar Ti3C2Tx (MXene) in Hydroxyapatite (HA) and Halloysite nanotube (HNT) hybrid coatings in biodegradable poly– (lactic acid) (PLA) was investigated. The morphological and structural characterizations of the coatings on Mg were revealed through HRTEM, XPS, SEM-EDX, XRD, FTIR, and contact angle analyses/tests. Electrochemical in vitro corrosion tests (OCP, PDS, and EIS-Nyquist) were conducted for evaluate corrosion resistance under simulated body fluid (SBF) conditions. The bioactivity of the coatings in SBF have been revealed in accordance with the ISO 23,317 standard. Finally, antibacterial disk diffusion tests were conducted to investigate the functional effect of MXene in coatings. It has been determined that the presence of MXene in the coating increased not only surface wettability (131°, 85°, 77°, and 74° for uncoated, pH, PHH, and PHH/MXene coatings, respectively) but also increased corrosion resistance (1857.850, 42.357, 1.593, and 0.085 × 10–6, A/cm2 for uncoated, pH, PHH, and PHH/MXene coatings, respectively). It has been proven that the in vitro bioactivity of PLA-HA coatings is further enhanced by adding HNT and MXene, along with SEM morphologies after SBF. Finally, 2D lamellar MXene-filled coating exhibits antibacterial behavior against both E. coli and S. aureus bacteria.

Tannic acid-loaded halloysite clay grafted with silver nanoparticles improved the mechanical, antimicrobial, and degradation properties of linear low-density polyethylene films

Synthetic polymers used for food packaging contribute to plastic pollution due to poor degradability. While they prevent the entry of microorganisms, they may not protect against spoilage microorganisms in the packed food. Nanofillers have been used to improve such properties, but end-of-life degradation remains an issue, making plastic a persistent pollutant. Here, we tested a nanocomposite (Nc) of tannic acid-loaded halloysite nanotubes grafted with silver nanoparticles as a reinforcement to enhance the mechanical, antimicrobial, and degradation properties of Linear low-density polyethylene (LLDPE) films. LLDPE films incorporated with Nc significantly improved tensile strength (TS), elongation at break (EB), and oxygen permeability rate. Nc incorporated (at 5%-and 10%) LLDPE films exhibited a 1.89–2.85 log10 reduction in multi-drug resistant Staphylococcus aureus 1158c in chicken fillets. Both film types demonstrated silver migration below the European Food Safety Authority-mandated acceptable limit. Nc/LLDPE films disintegrated faster when exposed to incandescent light for 6 h, evidenced by significant reduction of weight, TS, and EB. Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy suggested oxidative degradation and breakdown of the polymer. Conclusively, Nc improved the functional properties and degradation rate of LLDPE films when exposed to light, showing potential for enhancing the sustainability of synthetic polymers.

Dopamine hydrochloride and L-arginine Co-functionalized halloysite nanotubes for modification of polyethersulfone ultrafiltration membrane with improved separation performance

In recent years, a range of high-performance ultrafiltration membranes have been developed, but maintaining high retention without sacrificing high throughput remains a serious challenge. In this paper, functionalized halloysite nanotubes is constructed by copolymerization and by a one-step reaction of L-arginine and dopamine hydrochloride using halloysite nanotubes as carriers. Subsequently, modified polyethersulfone membranes are prepared by blending them as additives through non-solvent-induced phase transition separation. As the synthesized nanofillers is rich in functional groups, negative electronegativity, and unique structures, the study focuses on adding nanofillers’ effect on the membrane structure and physicochemical properties. The addition of appropriate nanofillers enhances the membrane surface wettability and negative electronegativity, and the enlarged internal pores and the dense layer that remains flat and homogeneous effectively promote the flux of small molecules, the retention of large molecules, and the cyclic stability of the membrane. The prepared polyethersulfone membranes demonstrate exceptional cycle stability, high separation efficiency (almost 100 % for Congo red), and significantly improved permeation performance (initial permeate flux up to 316.5 L m-2h−1). The results demonstrate the high potential of the modified prepared polyethersulfone membranes for pertinent environmental separation processes.

Effect of Hybrid Nanofillers on the Mechanical Characteristics of Polymethyl Methacrylate Denture Base Composite

The research study focused on enhancing the mechanical characteristics of polymethyl methacrylate (PMMA) denture bases. PMMA is commonly used in dentistry due to its easy fabrication, cost-effectiveness, and favourable physical properties. However, its limitations include low wear resistance, hardness, and mechanical strength, making it less suitable for long-term dental applications. To address these limitations, the study employed a combination of hybrid nano-fillers, specifically HNTs (halloysite nanotubes) and MWCNTs (multi-walled carbon nanotubes), at varying loading levels to improve the mechanical characteristics of the PMMA composite. These nano-fillers underwent treatment by using a coupling agent to enhance their compatibility with PMMA. Key findings of the research include that introducing HNTs/MWCNTs into the PMMA matrix led to a substantial increase in flexural strength, with a significant improvement of 109.1 MPa compared to unfilled PMMA. This indicates that the composite material became more resistant to bending or deformation. There was a substantial rise in flexural modulus values, suggesting improved stiffness in the nanocomposite compared to unfilled PMMA. In addition, the tensile strength of the PMMA composite increased by 64.4 MPa with the addition of the hybrid nano-fillers, indicating enhanced resistance to stretching or pulling forces. The study found that the improvement in flexural and tensile strength was dependent on the concentration of MWCNTs. Increasing the MWCNT concentration up to 0.75 wt.% led to improved mechanical properties, but further increases resulted in a reduction in PMMA properties. Although there was a modest improvement in Vickers hardness (approximately 18.93 kg/mm<sup>2</sup>), the addition of HNTs/MWCNTs as hybrid nano-fillers effectively enhanced the properties of the PMMA nanocomposite. The study concludes that incorporating hybrid nano-fillers into PMMA could contribute to the longevity and durability of dental composites, addressing some of the material's inherent limitations. The specific combination and concentration of nano-fillers played a crucial role in determining the mechanical properties of the resulting nanocomposite.

Halloysite Nanotube Modified (CuO@HNTs-SO3H) Novel Heterogeneous Catalyst for One-Pot Synthesis of Tetrahydrobenzo[ɑ]Xanthen-11-One

In this study, CuO@HNTs-SO3H was investigated as a novel eco-friendly heterogeneous solid acid catalyst prepared by straightforward co-precipitation method. Thus, the cost-effective CuO NPs was used to modify halloysite nanotubes initially, which were subsequently further functionalized with sulfonic acid. The prepared catalyst was analyzed by means of FT-IR, XRD, EDX, SEM and TGA methods. Its catalytic activity is investigated in the solvent-free one-pot condensation of various aromatic aldehydes, dimedone, and β-naphthol to produce tetrahydrobenzo[a]xanthen-11-one derivatives. A few benefits of the discovered method are its simple process, quick reaction time, high yields (96%), affordable cost, and the catalyst ability to be reused without losing its activity.