A novel technique including two steps for modulus prediction in polymer halloysite nanotube composites.

A two-step methodology has been developed utilizing the models of Paul and Takayanagi to determine the modulus of polymer halloysite nanotube (HNT) products. Initially, HNTs and the adjacent interphase are considered as pseudoparticles, and their modulus is evaluated using the Paul model. Subsequently, the modulus of a nanocomposite, consisting of a polymer medium and pseudoparticles, is predicted by Takayanagi equation. The impacts of various factors on the modulus of the products are analyzed, and the results from the two-step method are compared with experimental data from different samples. It has been observed that the modulus of samples progressively increases with an increase in interphase depth. Also, a higher interphase modulus contributes to an enhanced modulus of samples. Nevertheless, excessively high interphase moduli (Ei > 60 GPa) result in only a marginal improvement in the modulus of nanocomposites. Additionally, narrower HNTs are advantageous for producing stronger samples, though the modulus of the nanocomposites slightly diminishes at very high HNT radii (R > 55 nm). The outputs of two-step method agree with the experimental moduli of various HNT-filled systems.

Halloysite functionalized with dendritic moiety containing vitamin B1 hydrochloride as a bio-based catalyst for the synthesis of 5-hydroxymthylfurfural.

Using halloysite clay and vitamin B1 hydrochloride, a novel acidic halloysite-dendrimer catalytic composite has been developed for conversion of fructose to 5-hydroxymthylfurfural. To grow the dendritic moiety on halloysite, it was first functionalized and then reacted with melamine, epichlorohydrin and vitamin B1 hydrochloride respectively. Then, the resulting composite was treated with ZnCl2 to furnish Lewis acid sites. Use of vitamin B1 as the cationic moiety of ionic liquid obviated use of toxic chemicals and resulted in more environmentally friendly composite. Similarly, dendritic moiety of generation 2 was also grafted on halloysite and the activity of both catalysts for conversion of fructose to 5-hydroxymthylfurfural was investigated to disclose the role of dendrimer generation. For the best catalytic composite, the reaction variables were optimized via RSM and it was revealed that use of 0.035 g catalyst per 0.1 g fructose at 95 °C furnished HMF in 96% yield in 105 min. Turnover numbers (TONs) and frequencies (TOFs) were estimated to be 10,130 and 5788 h-1, respectively. Kinetic studies also underlined that Ea was 22.85 kJ/mol. The thermodynamic parameters of Δ H ≠ , Δ S ≠ and Δ G ≠ , were calculated to be 23 kJ/mol, - 129.2 J/mol and 72.14 kJ/mol, respectively. Notably, the catalyst exhibited good recyclability and hot filtration approved heterogeneous nature of catalysis.

Modification of polymethylmethacrylate bone cement with halloysite clay nanotubes.

BACKGROUND: Polymethylmethacrylate (PMMA) bone cement is used in orthopedics and dentistry to get primary fixation to bone but doesn't provide a mechanically and biologically stable bone interface. Therefore, there was a great demand to improve the properties of the PMMA bone cement to reduce its clinical usage limitations and enhance its success rate. Recent studies demonstrated that the addition of halloysite nanotubes (HNTs) to a polymeric-based material can improve its mechanical and thermal characteristics. OBJECTIVES: The purpose of the study is to assess the compressive strength, flexural strength, maximum temperature, and setting time of traditional PMMA bone cements that have been manually blended with 7 wt% HNT fillers. METHODS: PMMA powder and monomer liquid were combined to create the control group, the reinforced group was made by mixing the PMMA powder with 7 wt% HNT fillers before liquid mixing. Chemical characterization of the HNT fillers was employed by X-ray fluorescence (XRF). The morphological examination of the cements was done using a scanning electron microscope (SEM). Analytical measurements were made for the compressive strength, flexural strength, maximum temperature, and setting time. Utilizing independent sample t-tests, the data was statistically assessed to compare mean values (p < 0.05). RESULTS: The findings demonstrated that the novel reinforced PMMA-based bone cement with 7 wt% HNT fillers showed higher mean compressive strength values (93 MPa) and higher flexural strength (72 MPa). and lower maximum temperature values (34.8 °C) than the conventional PMMA bone cement control group, which was (76 MPa), (51 MPa), and (40 °C), respectively (P < 0.05). While there was no significant difference in the setting time between the control and the modified groups. CONCLUSION: The novel PMMA-based bone cement with the addition of 7 wt% HNTs can effectively be used in orthopedic and dental applications, as they have the potential to enhance the compressive and flexural strength and reduce the maximum temperatures.

All-natural aerogel of nanoclay/cellulose nanofibers with hierarchical porous structure for rapid hemostasis.

Developing an effective and user-friendly hemostatic agent is highly desired in the treatment of hemorrhage. Inspired by the natural nanostructure and abundant hydroxyl groups of cellulose and clay minerals, we designed an aerogel (HNTs/TOCNs) composed of halloysite nanotubes (HNTs) and TEMPO-oxidized cellulose nanofibers (TOCNs) with a hierarchical porous structure for the treatment of bleeding, using a simple and environmentally friendly self-assembly method. TOCNs formed a three-dimensional porous scaffold with excellent water-holding capacity. The incorporation of HNTs enhanced the hemostatic efficiency and mechanical properties of the 3D framework. The large interlayer spaces and wide channels within the HNTs/TOCNs aerogel provided rapid passage for blood, facilitating blood concentration and offering ample room for interactions between the HNTs/TOCNs aerogel and platelets, erythrocytes, and coagulation factors, thereby promoting hemostasis. Benefiting from the natural hemostatic properties and well-designed structure, the HNTs/TOCNs aerogel displayed excellent hemostatic performance both in vitro and in vivo. Notably, the hemostatic time of HNTs/TOCNs-2 was only 74 ± 8 s, which is approximately 50 % shorter than the blank control (151 ± 20 s) in liver femoral artery injury model. This design of an HNTs/TOCNs aerogel presents a unique opportunity to enhance hemostatic efficacy by synergizing the advantages of natural materials.

Development of alginate film filled with halloysite-carbon dots for active food packaging.

The development of functional bionanocomposites for active food packaging is of current interest to replace non-biodegradable plastic coatings. In the present work, we report the synthesis of an alginate-based nanocomposite filled with modified halloysite nanotubes (HNTs) to develop coatings with improved barrier properties for food packaging. Firstly, HNTs were chemically modified by the introduction of carbon dots units (CDs) onto their external surface (HNTs-CDs) obtaining a nanomaterial where CDs are uniformly present onto the tubes as verified by morphological investigations, with good UV absorption and antioxidant properties. Afterwards, these were dispersed in the alginate matrix to obtain the alginate/HNTs-CDs nanocomposite (Alg/HNTs-CDs) whose morphology was imaged by AFM measurements. The UV and water barrier properties (in terms of moisture content and water vapor permeability) were investigated, and the antioxidant properties were evaluated as well. To confer some antimicrobial properties to the final nanocomposite, the synthetized filler was loaded with a natural extract (E) from M. cisplatensis. Finally, the extract kinetic release both from the filler and from the nanocomposite was studied in a medium mimicking a food simulant and preliminary studies on the effect of Alg/HNTs-CDs/E on coated and uncoated fruits, specifically apples and bananas were also carried out.

Hydrothermal synthesized kaolin group lamellar/spongy aluminosilicates for enhanced lead vapor capture.

Developing high-temperature-resistant adsorbents with superior porous properties is crucial for safely disposing of heavy metal-containing solid waste via pyrolysis. We synthesized aluminosilicates hydrothermally and observed that acidic conditions, especially HCl (pH=2.6), favored sponge-like mineral (NC2.6) formation with a specific surface area of 500.31 m²/g and pore volume of 0.986 cm³ /g, while alkaline conditions (pH=12.0) promoted spherical particle growth. NC2.6 exhibited higher adsorption capacity compared to kaolinite and halloysite in the PbCl2 vapor adsorption, reaching a maximum of 137.68 mg/g at 700 â„ƒ (75.91 % stable). We examined the effect of CO2 and H2O on adsorption efficiency and explored the mechanisms using DFT and GCMC simulations. From GCMC results, CO2 negatively impacted PbCl2 adsorption due to competitive adsorption, while H2O increased adsorption content (144.24 mg/g at 700 â„ƒ) by converting PbCl2 into oxides. DFT revealed the presence of CO2 enhanced the adsorption stability of PbCl2 via the formation of covalent bonds between O in CO2 and Pb, and active O on the aluminosilicate surface. H2O increased PbCl2 adsorption energy, as O in H2O occupied an active Al that originally formed a covalent bond with Cl, while the H formed a weak hydrogen bond with this Cl.

Halloysite-based inorganic-organic hybrid coatings for durable flame retardant, hydrophobic and antibacterial properties of cotton fabrics.

Developing durable protective cotton fabrics (CF) against potential environmental dangers such as fire hazards and bacterial growth remains an imperative but tough challenge. In this study, flame retardant, antibacterial and hydrophobic CF were successfully prepared via two-step coating. The inner coating entailed polyelectrolyte complexes consisting of polyethyleneimine and ammonium polyphosphate with the goal of enhancing the flame retardancy of CF. Halloysite nanotubes (HNTs), a kind of tubular silicate mineral, were creatively modified and introduced to multifunctional coatings to improve flame retardant and antibacterial properties of CF. N-halamine modified HNTs (HNTs-EA-Cl) and polydimethylsiloxane were applied as the outer coating to endow CF with antibacterial and hydrophobic properties and further improve the flame retardancy of CF. After halloysite-based inorganic-organic hybrid coatings, the limiting oxygen index of the treated samples (PAHP-CF) was over 28 %, and the release of heat and smoke was significantly inhibited. PAHP-CF could inactivate 100 % E. coli and S. aureus within 2 h. More importantly, PAHP-CF showed excellent hydrophobicity with a water contact angle of 148° and exhibited great prevention of bacterial adhesion. PAHP-CF exhibited excellent washing durability undergoing 5 washing cycles. This study promotes the development of multifunctional coatings and offers a new way to manufacture multifunctional cotton fabrics.

Mechanical and Shape Memory Properties of Additively Manufactured Polyurethane (PU)/Halloysite Nanotube (HNT) Nanocomposites.

This paper investigates the impact of halloysite nanotube (HNT) content on mechanical and shape memory properties of additively manufactured polyurethane (PU)/HNT nanocomposites. The inclusion of 8 wt% HNTs increases their tensile strength by 30.4% when compared with that of virgin PU at 44.75 MPa. Furthermore, consistently significant increases in tensile modulus, compressive strength and modulus, as well as specific energy absorption are also manifested by 47.2%, 34.0%, 125% and 72.7% relative to neat PU at 2.29 GPa, 3.88 MPa, 0.28 GPa and 0.44 kJ/kg respectively. However, increasing HNT content reduces lateral strain due to the restricted mobility of polymeric chains, leading to a decrease in negative Poisson's ratio (NPR). As such, shape recovery ratio and time of PU/HNT nanocomposites are reduced by 9 and 45% with the inclusion of 10 wt% HNTs despite an increasing shape fixity ratio up to 12% relative to those of neat PU.

The Effect of Silanized Halloysite Nanotubes on the Structure of Polyethylene-Based Composite.

Chemical modification of the surface of halloysite nanotubes (HNT) by alkalization (with sodium hydroxide (NaOH)) and grafting with silanes (bis(trimethylsilyl)amine (HMDS)) was carried out. The efficiency of the alkalization and grafting process was evaluated by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and the nitrogen adsorption method were used. XRD and FTIR analysis confirmed the formation of bonds of trimethylsilyl groups to the HNT surface which changed the nature of the surface from hydrophilic to hydrophobic. In addition, it was noted that grafting with silanes decreases by 7.2% the specific surface area of the halloysite compared to the alkalized material. High-density polyethylene (HDPE) composites with halloysite (HNT), alkalized halloysite (alk-HNT), and HMDS-modified halloysite (m-HNT) were processed in the molten state in a Brabender mixer chamber. On SEM/EDS micrographs of HDPE composites with silanized HNT, a change in surface characteristics from smooth to ductile was observed. Higher melting point values based on differential scanning calorimetry (DSC) analysis of HDPE composites with 5%wt silanized halloysite in comparison with HNT and alk-HNT of, respectively, 2.2% and 1.4% were found, which indicates a slight beneficial influence of the filler on the quality of ordering of the crystalline phase of the matrix.

Morphological, Thermal, and Mechanical Properties of Nanocomposites Based on Bio-Polyamide and Feather Keratin-Halloysite Nanohybrid.

One solution to comply with the strict regulations of the European Commission and reduce the environmental footprint of composites is the use of composite materials based on bio-polymers and fillers from natural resources. The aim of our work was to obtain and analyze the properties of bio-polymer nanocomposites based on bio-PA (PA) and feather keratin-halloysite nanohybrid. Keratin (KC) was mixed with halloysite (H) as such or with the treated surface under dynamic conditions, resulting in two nanohybrids: KCHM and KCHE. The homogenization of PA with the two nanohybrids was conducted using the extrusion processing process. Two types of nanocomposites, PA-KCHM and PA-KCHE, with 5 wt.% KC and 1 wt.% H were obtained. The properties were analyzed using SEM, XRD, FTIR, RAMAN, TGA, DSC, tensile/impact tests, DMA, and nanomechanical tests. The best results were obtained for PA-KCHE due to the stronger interaction between the components and the uniform dispersion of the nanohybrid in the PA matrix. Improvements in the modulus of elasticity and of the surface hardness by approx. 75% and 30%, respectively, and the resistance to scratch were obtained. These results are promising and constitute a possible alternative to synthetic polymer composites for the automotive industry.

The Horizons of Medical Mineralogy: Structure-Bioactivity Relationship and Biomedical Applications of Halloysite Nanoclay.

Medical mineralogy explores the interactions between natural minerals and living organisms such as cells, tissues, and organs and develops therapeutic and diagnostic applications in drug delivery, medical devices, and healthcare materials. Many minerals (especially clays) have been recognized for pharmacological activities and therapeutic potential. Halloysite clay (Chinese medicine name: Chishizhi), manifested as one-dimensional aluminum silicate nanotubes (halloysite nanotubes, HNTs), has gained applications in hemostasis, wound repair, gastrointestinal diseases, tissue engineering, detection and sensing, cosmetics, and daily chemicals formulations. Various biomedical applications of HNTs are derived from hollow tubular structures, high mechanical strength, good biocompatibility, bioactivity, and unique surface characteristics. This natural nanomaterial is safe, abundantly available, and may be processed with environmentally safe green chemistry methods. This review describes the structure and physicochemical properties of HNTs relative to bioactivity. We discuss surface area, porosity and surface defects, hydrophilicity, heterogeneity and charge of external and internal surfaces, as well as biosafety. The paper provides comprehensive guidance for the development of this tubule nanoclay and its advanced biomedical applications for clinical diagnosis and therapy.

Anti-tumor therapy through high ROS performance induced by Ag nanoenzyme from boron cluster with halloysite clay nanotubes.

The conventional silver nanoparticles (Ag NPs) are characterized with high loading rate and stacking phenomenon, leading to shedding caused biotoxicity and low catalytic efficiency. This seriously hinders their application in biomedicine. Here, we modified the highly dispersible Ag NPs and Ag single-atoms (SAs) synthesis by combining the halloysite clay nanotubes (HNTs) and dodecahydro-dodecaborate (closo-[B12H12]2-) to increase the biocompatible properties and decrease the loading rate. This novel Ag single-atom nanoenzyme alongside Ag NPs nanoenzyme avoid the elevated-temperature calcination while maintaining the exceptionally high-level efficiency of Ag utilization via the reducibility and coordination stabilization of closo-[B12H12]2- and HNTs. With theoretical calculation and electron paramagnetic resonance, we confirmed that both Ag SAzymes and Ag NPs in HNT@B12H12@Ag nanoenzyme are capable decompose the H2O2 into hydroxyl radical (·OH). For the application, we investigated the catalytic activity in the tumor cells and antitumor effects of HNT@B12H12@Ag nanoenzyme both in vitro and in vivo, and confirmed that it effectively suppressed melanoma growth through ·OH generation, with limited biotoxicity. This study provides a novel Ag nanoenzyme synthesis approach to increase the possibility of its clinical application.

Modified Halloysite as an Adsorbent for the Removal of Cu(II) Ions and Reactive Red 120 Dye from Aqueous Solutions.

The adsorption of copper ions and Reactive Red 120 azo dye (RR-120) as models of water pollutants on unmodified halloysite (H-NM), as well as halloysites modified with sulfuric acid (H-SA) and (3-aminopropyl)triethoxysilane (H-APTES), was investigated. The results showed that adsorption of both the adsorbates was pH-dependent and increased with the increase in halloysite dosage. The adsorption kinetics were evaluated and the results demonstrated that the adsorption followed the pseudo-second-order model. The adsorption isotherms of Cu(II) ions and RR-120 dye on the halloysites were described satisfactorily by the Langmuir model. The maximum adsorption capacities for the Cu(II) ions were 0.169, 0.236, and 0.507 mmol/g, respectively, for H-NM, H-SA, and H-APTES indicating that the NH2-functionalization rather than the surface area of the adsorbents was responsible for the enhanced adsorption. The adsorption capacities for RR-120 dye were found to be 9.64 µmol/g for H-NM, 75.76 µmol/g for H-SA, and 29.33 µmol/g for H-APTES. The results demonstrated that APTES-functionalization and sulfuric acid activation are promising modifications, and both modified halloysites have good application potential for heavy metals as well as for azo dye removal.

Construction of hyperbranched imprinted nanomaterials for selective adsorption of cadmium (II).

A hyperbranched ion-imprinted polymer (IIP) material containing multiple selective adsorption sites was synthesized using halloysite nanotubes, methyl acrylate, and ethylenediamine in the presence of a template ion [i.e. Cd (II) heavy metal]. The successful preparation of the Cd-IIP composition was confirmed by FT-IR, XRD, TEM, TGA, and elemental analysis. The polymers exhibited good adsorption of Cd (II) with a maximum adsorption capacity of 64.37 mg·g-1. The imprinting factor (α) for Cd (II) was 2.62 and the selection factor (ß) was 1.78, indicating a specific adsorption of Cd (II) ion. The selection coefficients of Cd-IIP for Cd (II)/Pb (II), Cd (II)/Cu (II), Cd (II)/Ni (II), Cd (II)/Cr (III), and Cd (II)/Na (I) also indicated an excellent selectivity of the hyperbranched polymers for Cd (II) in the presence of competitive ions. The removal efficiency remained more than 75% after five cycles of desorption/adsorption. We envision that the HNTs based Cd-IIP has promising applications in the removal of Cd (II) from wastewater.

Development of Halloysite Nanotube-Infused Thermoset Soybean Bio-Resin for Advanced Medical Packaging.

The development of eco-friendly, mechanically stable, and biocompatible materials for medical packaging has gained significant attention in recent years. Halloysite nanotubes (HNTs) have emerged as a promising nanomaterial due to their unique tubular structure, high aspect ratio, and biocompatibility. We aim to develop a novel soybean oil-based thermoset bio-resin incorporating HNTs and to characterize its physical and functional properties for medical packaging. Soybean oil was epoxidized using an eco-friendly method and used as a precursor for preparing the thermoset resin (ESOR). Different amounts of HNTs (0.25, 0.50, and 1.0 wt.%) were used to prepare the ESOR/HNTs blends. Various characteristics such as transparency, tensile strength, thermal resistance, and water absorption were investigated. While incorporating HNTs improved the tensile strength and thermal properties of the ESOR, it noticeably reduced its transparency at the 1.0 wt.% level. Therefore, HNTs were modified using sodium hydroxide and (3-Aminopropyl) triethoxysilane (APTES) and ESOR/HNTs blends were made using 1.0 wt.% of modified HNTs. It was shown that modifying HNTs using NaOH improved the transparency and mechanical properties of prepared blends compared to those with the same amount of unmodified HNTs. However, modifying using (3-Aminopropyl) triethoxysilane (APTES) decreased the transparency but improved the water absorption of prepared resins. This study provides valuable insights into the design of HNT-based ESOR blends as a sustainable material for medical packaging, contributing to the advancement of eco-friendly packaging solutions in the healthcare industry.

New Fire-Retardant Open-Cell Composite Polyurethane Foams Based on Triphenyl Phosphate and Natural Nanoscale Additives.

Despite the mechanical and physical properties of polyurethane foams (PUF), their application is still hindered by high inflammability. The elaboration of effective, low-cost, and environmentally friendly fire retardants remains a pressing issue that must be addressed. This work aims to show the feasibility of the successful application of natural nanomaterials, such as halloysite nanotubes and nanocellulose, as promising additives to the commercial halogen-free, fire-retardant triphenyl phosphate (TPP) to enhance the flame retardance of open-cell polyurethane foams. The nanocomposite foams were synthesized by in situ polymerization. Investigation of the mechanical properties of the nanocomposite PUF revealed that the nanoscale additives led to a notable decrease in the foam's compressibility. The obtained results of the flammability tests clearly indicate that there is a prominent synergetic effect between the fire-retardant and the natural nanoscale additives. The nanocomposite foams containing a mixture of TPP (10 and 20 parts per hundred polyol by weight) and either 10 wt.% of nanocellulose or 20 wt.% of halloysite demonstrated the lowest burning rate without dripping and were rated as HB materials according to UL 94 classification.

Effects of multi-walled carbon nanotubes and halloysite nanotubes on plasma lipid profiles and autophagic lipolysis pathways in mouse aortas and hearts.

Multi-walled carbon nanotubes (MWCNTs) and halloysite nanotubes (HNTs) are widely used tubular-structured nanomaterials (NMs), but their cardiovascular effects are not clear. This study compared the effects of MWCNTs and HNTs on lipid profiles in mouse plasma and gene expression profiles in aortas and hearts. Mice were intravenously injected with 50 µg NMs, once a day, for 5 days. Then, the plasma was collected for lipidomics analysis, and aortas and hearts were collected for RNA-sequencing analysis. While MWCNTs or HNTs did not induce obvious pathological changes in aortas or hearts, the lipid profiles in mouse plasma were altered. Further analysis revealed that MWCNTs more effectively upregulated sphingolipids and sterol lipids, whereas HNTs more effectively upregulated glycerophospholipids and fatty acyls. Consistently, RNA-sequencing data indicated that MWCNTs and HNTs altered signaling pathways related with lipid synthesis and metabolism, as well as those related with endoplasmic reticulum, lysosomes and autophagy, more significantly in aortas than in hearts. We further verified the changes of proteins involved in autophagic lipolysis, that MWCNTs were more effectively to suppress the autophagic biomarker LC3, whereas HNTs were more effectively to affect lipid metabolism proteins. These results may provide novel understanding about the influences of MWCNTs and HNTs on lipid profiles and lipid signaling pathways in cardiovascular systems. Importantly, previous studies considered HNTs as biocompatible materials, but the results from this study suggested that both MWCNTs and HNTs were capable to affect lipid profiles and autophagic lipolysis pathways in cardiovascular systems, although their exact influences were different.

Halloysite nanotubes enhanced polyimide/oxidized-lignin nanofiber separators for long-cycling lithium metal batteries.

The high energy density and robust cycle properties of lithium-ion batteries contribute to their extensive range of applications. Polyolefin separators are often used for the purpose of storing electrolytes, hence ensuring the efficient internal ion transport. Nevertheless, the electrochemical performance of lithium-ion batteries is constrained by its limited interaction with electrolytes and poor capacity for cation transport. This work presents the preparation of a new bio-based nanofiber separator by combining oxidized lignin (OL) and halloysite nanotubes (HNTs) with polyimide (PI) using an electrospinning technique. Analysis was conducted to examine and compare the structure, morphology, thermal characteristics, and EIS of the separator with those of commercially available polypropylene separator (PP). The results indicate that the PI@OL and PI-OL@ 10 % HNTs separators exhibit higher lithium ion transference number and ionic conductivity. Moreover, the use of HNTs successfully impeded the proliferation of lithium dendrites, hence exerting a beneficial impact on both the cycle performance and multiplier performance of the battery. Consequently, after undergoing 300 iterations, the battery capacity of LiFePO4|PI-OL@ 10 % HNTs|Li stays at 92.1 %, surpassing that of PP (86.8 %) and PI@OL (89.6 %). These findings indicate that this new bio-based battery separator (PI-OL@HNTs) has the great potential to serve as a substitute for the commonly used PP separator in lithium metal batteries.

Spherical Assembly of Halloysite Clay Nanotubes as a General Reservoir of Hydrophobic Pesticides for pH-Responsive Management of Pests and Weeds.

The development of smart systems for pesticidal delivery presents a significant advancement in enhancing the utilization efficiency of pesticides and mitigating environmental risks. Here an acid-responsive pesticidal delivery system using microspheres formed by the self-assembly of halloysite clay nanotubes (HNTs) is proposed. Insecticide avermectin (AVM) and herbicide prometryn (PMT) are used as two models of hydrophobic pesticide and encapsulated within the porous microspheres, followed by a coating of tannic acid/iron (TA/FeIII) complex films to generate two controlled-release pesticides, named as HCEAT and HCEPT, resulting in the loading capacity of AVM and PMT being 113.3 and 120.3 mg g-1, respectively. Both HCEAT and HCEPT exhibit responsiveness to weak acid, achieving 24 h-release ratios of 85.8% and 80.5% at a pH of 5.5. The experiment and simulation results indicate that the coordination interaction between EDTA2- and Ca2+ facilitates the spherical aggregation of HNTs. Furthermore, these novel pesticide formulations demonstrate better resistance against ultraviolet (UV) irradiation, higher foliar affinity, and less leaching effect, with negligible impact of the carrier material on plants and terrestrial organisms. This work presents a promising approach toward the development of efficient and eco-friendly pesticide formulations, greatly contributing to the sustainable advancement of agriculture.

Comparison of Synthetic Pathways for Obtaining Fluorescent Nanomaterials Based on Halloysite and Carbon Dots for Potential Biological Sensing.

Recently, fluorescent sensors have gained considerable attention due to their high sensitivity, low cost and noninvasiveness. Among the different materials that can be used for this purpose, carbon dots (CDs) represent valuable candidates for applications in sensing. These, indeed, are easily synthesized, show high quantum yield and are highly biocompatible. However, it was pointed out that the photoluminescence properties of these nanomaterials are strictly dependent on the synthetic and purification methods adopted. The presence of halloysite nanotubes (HNTs), a natural, low cost and biocompatible clay mineral, has been found to be efficient in obtaining small and highly monodispersed CDs without long and tedious purification techniques. Herein, we report the comparison of synthetic pathways for obtaining halloysite-N-doped CDs (HNTs-NCDs) that could be used in biological sensing. One was based on the synthesis of N-doped CDs by a bottom-up approach on HNTs' surface by a MW pyrolysis process; the other one was based on the post-modification of pristine N-doped CDs with halloysite derivatives. The evaluation of the best synthetic route was performed by different physico-chemical techniques. It was found that the bottom-up approach led to the formation of N-doped CDs with different functional groups onto the HNTs' surface. This evidence was also translated in the different fluorescence quantum yields and the existence of several functional groups in the obtained materials was investigated by potentiometric titrations. Furthermore, the ability of the synthesized nanomaterials as sensors for Fe3+ ions detection was assessed by spectroscopic measurements, and the cellular uptake was verified by confocal/fluorescence microscopies as well.