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Various pre-modified and post-modified cyclodextrin-calixarene hyper-reticulated co-polymers were synthesized, fully characterized by different techniques (FT-IR, 13C{1H} CP-MAS and LGFS solid-state NMR, thermogravimetry, porosimetry), and tested to assess their absorption abilities as nanosponges. The construction of the polymer network was accomplished exploiting the well-known CuAAC reaction between two different heptakis-6-azido-β-cyclodextrins and two different propargyloxy-calix[4]arenes. Post-modification was aimed to achieve the presence of ionizable (acidic or basic) groups on the polymer framework. Sequestration tests towards two model pollutant molecules surprisingly showed that both pristine and post-modified materials actually possess the abilities to act as pH-tunable nanosponges.

Halloysite (HNT) is a promising natural nanosized tubular clay mineral that has many important uses in different industrial fields. It is naturally occurring, biocompatible, and available in thousands of tons at low cost. As a consequence of a hollow cavity, HNT is mainly used as nanocontainer for the controlled release of several chemicals. Chemical modification of both surfaces (inner lumen and outer surface) is a strategy to tune the nanotube's properties. Specifically, chemical modification of HNT surfaces generates a nanoarchitecture with targeted affinity through outer surface functionalization and drug transport ability from functionalization of the nanotube lumen. The primary focus of this review is the research of modified halloysite nanotubes and their applications in biological and medical fields.

The thermal responsive behavior of adsorbed layers of diblock copolymers of poly(N-isopropylacrylamide) (PNIPAAM) and poly((3-acrylamidopropyl)trimethylammonium chloride) (PAMPTMA(+)) with γ-cyclodextrin (γ-CD) at the solid/liquid interface has been investigated using three in situ techniques: null ellipsometry, quartz–crystal microbalance with dissipation monitoring, and neutron reflectometry. The measurements provided information about the adsorbed amounts, the layer thickness, hydration and viscoelastic properties, and the interfacial structure and composition. The copolymers adsorb to silica with the cationic PAMPTMA(+) blocks sitting as anchors in a flat conformation and the PNIPAAM chains extending into the solution. The copolymer system alone exhibits reversible collapse above the lower critical solution temperature of PNIPAAM. The addition of γ-CD to pre-adsorbed copolymer layers results in a highly extended conformation as well as some loss of copolymer from the surface, which we discuss in terms of the formation of surface-invoked lateral steric repulsion of formed inclusion complexes. © 2017, The Author(s).

Extensive usage of long-lasting petroleum based plastics for short-lived application such as packaging has raised concerns regarding their role in environmental pollution. In this research, we have developed active, healable, and safely dissolvable alginate-pectin based biocomposites that have potential applications in food packaging. The morphological study revealed the rough surface of these biocomposite films. Tensile properties indicated that the fabricated samples have mechanical properties in the range of commercially available packaging films while possessing excellent healing efficiency. Biocomposite films exhibited higher hydrophobicity properties compared to neat alginate films. Thermal analysis indicated that crosslinked biocomposite samples possess higher thermal stability in temperatures below 120 &deg, C, while antibacterial analysis against E. coli and S. aureus revealed the antibacterial properties of the prepared samples against different bacteria. The fabricated biodegradable multi-functional biocomposite films possess various imperative properties, making them ideal for utilization as packaging material.

Many chemicals used nowadays for the preservation of cultural heritage pose a risk to both human health and the environment. Thus, it is desirable to find new and eco-friendly biocides that can replace the synthetic ones. In this regard, plant essential oils represent effective alternatives to synthetic substances for the preservation of historical monuments. Thymbra capitata (syn. Thymus capitatus) is a medicinal and aromatic plant growing in the Mediterranean area and endowed with important pharmacological properties related to its essential oil. Among them, the antimicrobial ones make the T. capitata essential oil an ideal candidate for industrial applications, for instance, as biocide for the inhibition and elimination of biological patinas of cyanobacteria and green algae on historical monuments. In the present work, we studied the chemical composition of the essential oil from T. capitata growing in Malta by gas chromatography-mass spectrometry (GC/MS). The major volatile component is the phenolic monoterpene carvacrol (73.2%), which is capable of damaging the cytoplasmic membrane and to interfere both in the growth curve and in the invasive capacity, though the contribution of minor components &gamma, terpinene and p-cymene cannot be disregarded. For the oil application on the stone surface, Pickering emulsions systems were prepared with an essential oil/water 1:3 mass ratio stabilized with kaolinite at 4 mass% in the presence of Laponite&reg, this allowed to limit the fast volatility of the oil and guaranteed a better application and an easier removal from the artefacts attacked by biodeteriogens both indoor and outdoor. This formulation caused the elimination of biodeteriogens from treated surfaces without residuals or films on artworks surface, and the effect was retained up to four months.

The filling of halloysite nanotubes with active compounds solubilized in aqueous solvent was investigated theoretically and experimentally. Based on Knudsen thermogravimetric data, we demonstrated the water confinement within the cavity of halloysite. This process is crucial to properly describe the driving mechanism of halloysite loading. In addition, Knudsen thermogravimetric experiments were conducted on kaolinite nanoplates as well as on halloysite nanotubes modified with an anionic surfactant (sodium dodecanoate) in order to explore the influence of both the nanoparticle morphology and the hydrophobic/hydrophilic character of the lumen on the confinement phenomenon. The analysis of the desorption isotherms allowed us to determine the water adsorption properties of the investigated nanoclays. The pore sizes of the nanotubes’ lumen was determined by combining the vapor pressure of the confined water with the nanoparticles wettability, which was studied through contact angle measurements. The thermodynamic description of the water confinement inside the lumen was correlated to the influence of the vacuum pumping in the experimental loading of halloysite. Metoprolol tartrate, salicylic acid and malonic acid were selected as anionic guest molecules for the experimental filling of the positively charged halloysite lumen. According to the filling mechanism induced by the water confinement, the vacuum operation and the reduced pressure enhanced the loading of halloysite nanotubes for all the investigated bioactive compounds. This work represents a further and crucial step for the development of halloysite based nanocarriers being that the filling mechanism of the nanotube's cavity from aqueous dispersions was described according to the water confinement process.

We have prepared new biohybrid materials based on halloysite nanotubes and natural polymers (alginate and chitosan) for the controlled and sustained release of bioactive species. A functional nanoarchitecture has been designed allowing us to generate a layered tablet with a chitosan/halloysite nanocomposite film sandwiched between two alginate layers. The assembly of the raw components and the final structure of the hybrid tablet have been highlighted by the morphological and wettability properties of the prepared materials. Since the biohybrid has been designed as a smart carrier, halloysite nanotubes have been first loaded with a model drug (sodium diclofenac). The effect of the tablet thickness on the drug release kinetics has been investigated, confirming that the delivery capacity can be controlled by modifying the alginate amounts of the external layers. A simulation of the typical pH conditions along the human gastro-intestinal path has been carried out. Strong acidic conditions (pH = 3, typical in the stomach) prevent the drug release. In contrast, the drug was released at pH = 5.7 and 7.8, which simulate the duodenum/ileum and colon paths, respectively. These results demonstrate that the proposed nanoarchitecture is suitable as a functional material with tunable delivery capacity.

The work aim is focused on two different aspects: first, the investigation of the effect of extended ultra-sound-assisted treatment (us) of carbonaceous nanoparticles, such as carbon nanotubes (CNTs) and carbon black (CB), on their radical scavenging activity, and second, the investigation of the oxidative resistance of polymer-based nanocomposites, containing us-treated CNTs and CB. Particularly, the CNTs and CB have been subjected to us sonication for different time intervals and the performed analysis reveals that both kinds of nanoparticles show decreased average hydrodynamic diameters and large content of surface defects. Really, the increased content of CNTs and CB defects, achieved during the sonication time, leads to an increased reactivity toward 1,1-diphenyl-2-pycryl (DPPH) radicals and an enhanced anti-oxidant activity toward macro-radicals, coming from the photo-degradation of the host polymer matrix. The studies of photo-oxidative behavior of the nanocomposites, based on Ultra High Molecular Weight (UHMWPE), reveal that the us treatment of the nanoparticles has a benefic effect on the oxidative resistance of the nanocomposites, especially at long exposure times. Overall, the ultra-sound-assisted treatment can be considered twofold powerful tool: (i) for disruption of the nanoparticles aggregations, and (ii) for capitalization of surface defects, amplifying and tuning in a controlled way the radical scavenging activity of the carbonaceous nanoparticles.

Alterations in the normal gastrointestinal microbial community caused by unhealthy diet, environmental factors, and antibiotic overuse may severely affect human health and well-being. Novel antimicrobial drug formulations targeting pathogenic microflora while not affecting or even supporting symbiotic microflora are urgently needed. Here we report fabrication of a novel antimicrobial nanocontainer based on halloysite nanotubes loaded with curcumin and protected with a dextrin outer layer (HNTs+Curc/DX) and its effective use to suppress the overgrowth of pathogenic bacteria in Caenorhabditis elegans nematodes. Nanocontainers have been obtained using vacuum-facilitated loading of hydrophobic curcumin into halloysite lumens. We have applied UV-vis and infrared spectroscopy, thermogravimetry and microscopy to characterize the HNTs+Curc/DX nanocontainers. In experiments in vitro we found that HNTs+Curc/DX effectively suppressed the growth of Serratia marcescens cells, whereas Escherichia coli bacteria were not affected. We applied HNTs+Curc/DX nanocontainers to alleviate the S. marcescens infection in C. elegans nematodes in vivo. The nematodes ingest HNTs+Curc/DX at 4-6 ng per worm, which results in improvement of the nematodes' fertility and life expectancy. Remarkably, treatment of S. marcescens-infected nematodes with HNTs+Curc/DX nanocontainers completely restored the longevity, demonstrating the enhanced bioavailability of hydrophobic curcumin. We believe that our results reported here open new avenues for fabrication of effective antimicrobial nanoformulations based on hydrophobic drugs and clay nanotubes.

Hypothesis Polydopamine (PDA) is widely used as hydrophilic coating for several applications. However, most of the methods studied to improve or manipulate PDA properties are multistep and time-consuming, and there is a need for versatile strategies aimed at controlling and modifying the properties of PDA. Experiments PDA-halloysite nanocomposites were produced under different oxidation conditions in alkaline and acidic media and were characterized by UV–visible and attenuated total refraction- Fourier Transform Infrared spectroscopies, thermogravimetric analysis, porosimetry, scanning electron microscopy, X-ray diffraction and contact angle measurements against the reference PDA polymer. Findings Inclusion of the inorganic halloysite nanofiller in the PDA component was found to affect the thermal properties of the nanocomposite as well as its structure, depending on the experimental conditions. The ability of the nanocomposites to adsorb organic dyes as possible membrane coatings for environmental remediation was also investigated by different models, suggesting promising applications as adsorbents for the treatment of wastewaters.

We investigated the adsorption process of quercetin onto several inorganic fillers, such as kaolinite, calcium carbonate and alumina. Firstly, we performed equilibrium adsorption studies in order to determine the quercetin/filler adsorption isotherms, which were successfully fitted through the Langmuir model. Based on the adsorption data analysis, we estimated the maximum adsorption capacity of each filler as well as the Langmuir constant, which is related to the affinity between quercetin and the surfaces of the inorganic particles. Then, we prepared hybrids formed by fillers saturated with quercetin. The obtained composites were characterized by thermogravimetric analysis with the aim of determining the loading efficiency as well as the effect of the adsorption process on the quercetin thermal stability. According to the Langmuir isotherms, alumina revealed the most efficient support for quercetin adsorption. Finally, we observed that the interactions with the fillers’ surfaces induce a reduction in the quercetin degradation temperature.

[EN] Based on the unique ability of defibrillated sepiolite (SEP) to form stable and homogeneous colloidal dispersions of diverse types of nanoparticles in aqueous media under ultrasonication, multicomponent conductive nanoarchitectured materials integrating halloysite nanotubes (HNTs), graphene nanoplatelets (GNPs) and chitosan (CHI) have been developed. The resulting nanohybrid suspensions could be easily formed into films or foams, where each individual component plays a critical role in the biocomposite: HNTs act as nanocontainers for bioactive species, GNPs provide electrical conductivity (enhanced by doping with MWCNTs) and, the CHI polymer matrix introduces mechanical and membrane properties that are of key significance for the development of electrochemical devices. The resulting characteristics allow for a possible application of these active elements as integrated multicomponent materials for advanced electrochemical devices such as biosensors and enzymatic biofuel cells. This strategy can be regarded as an >a la carte> menu, where the selection of the nanocomponents exhibiting different properties will determine a functional set of predetermined utility with SEP maintaining stable colloidal dispersions of different nanoparticles and polymers in water., The authors thank the MINECO (project MAT2015-71117-R) for financial support. GLD and LL acknowledge the University of Palermo for the “UOB21 Borse di studio finalizzate alla ricerca” grants. BW thanks the MINECO for an IJCI contract (IJCI-2015-23886). The authors also thank Dr. M. Darder, Dr. M. L. Ferrer, and Dr. N. López-Salas for fruitful discussions on bioelectrocatalysis.

The objective of this study was simultaneous extraction and encapsulation of cornelian cherry active principles. As an encapsulating agent, β-cyclodextrin (β-CD) was used to enhance the ultrasound-assisted extraction of cornelian cherry polyphenols and iridoids. Lyophilized cornelian cherry fruit was extracted by four different solvents: pure water, 50% aqueous ethanol (conventional system), 1.5% β-CD water solution and 1.5% β-CD aqueous ethanol solution. The highest enhancement of the extraction efficiency was observed for flavonoids and anthocyanins, especially for cyaniding 3-galactoside and pelargonidin 3-galactoside. Water-ethanolic extract was used to form inclusion complexes between β-CD and cornelian cherry bioactives in the solid form. The encapsulation efficiency of cornelian cherry polyphenols in β-CD was 65.62%. Due to the polyphenol encapsulation within β-CD, the extract showed better solubility in water, higher antioxidant power (for 40.61%), and the release of anthocyanins from the dried powder was prolonged for 50% in the first 2 h making it suitable for diverse applications in food and pharmaceutical industries.

We report on the restoration of a XVII century’s predella reliquary, which is a part of a larger setup that includes a wall reliquary and a wooden crucified Christ, both belonging to the church of “Madre Maria SS. Assunta”, in Polizzi Generosa, Sicily, Italy. The historical/artistic and paleographic research was flanked successfully by the scientific objective characterization of the materials. The scientific approach was relevant in the definition of the steps for the restoration of the artefact. The optical microscopy was used for the identification of the wood species. Electron microscopy and elemental mapping by energy-dispersive X-ray (EDX) was successful in the identification of the layered structure for the gilded surface. The hyperspectral imaging method was successfully employed for an objective chemical mapping of the surface composition. We proved that the scientific approach is necessary for a critical and objective evaluation of the conservation state and it is a necessary step toward awareness of the historical, liturgical, spiritual and artistic value. In the second part of this work, we briefly describe the conservation protocol and the use of a weak nanocomposite glue. In particular, a sustainable approach was considered and therefore mixtures of a biopolymer from natural resources, such as funori from algae, and naturally occurring halloysite nanotubes were considered. Tensile tests provided the best composition for this green nanocomposite glue.

The synthesis, liquid crystal and conductivity properties of a series of 27 salts based on the 5-(4-(alkyloxy)phenyl)-1,2,4-triazol-4-ium cation bearing a perfluoroalkyl chain with triflate, tetrafluoroborate and bistriflimide anion are reported. The cations are regarded as triphilic on account of their three distinct regions – hydrocarbon, fluorocarbon and ionic. The mesophases were characterised by a combination of polarised optical microscopy, calorimetry and small-angle scattering experiments using both X-rays and neutrons, while thermal stability was probed using thermogravimetric analysis. The liquid crystal properties are found to be dependent on the anion and the length of the perfluorocarbon chain, which effects combine to determine aspects of the self-organisation in the mesophases. A strong dependence of conductivity on the anion is seen, which is in turn related to its charge density.

Cornelian cherry fruit extract rich in anthocyanins and iridoids was encapsulated in the halloysite nanotubes in order to obtain a stable nanoscale system for better delivery and prolonged release of bioactive constituents. The cyclic vacuum technique was used for halloysite nanotubes-cornelian cherry composite preparation and the loading of 8.5 wt% was achieved. Pure cornelian cherry extract exhibited antiproliferative effect on HT-29, MCF7, and MRC-5 cells, pristine halloysite nanotubes affected the growth of MCF7 cells, while halloysite nanotubes-cornelian cherry composites demonstrated proliferative activity in all tested cells. The sustained release of anthocyanins was achieved by this encapsulation strategy. Additional implementation of halloysite nanotubes-cornelian cherry into yogurt prolonged the release of iridoid molecules. Obtained results indicate that halloysite nanoclay is a suitable nanocarrier for cornelian cherry constituents that can be utilized in food and pharmaceutical industries.

This work represents a contribution to the design, preparation, and characterization of nanocomposite materials based on biocompatible components. The effects of composition, filler geometry, and polymer charge were highlighted, and their role on the final properties of the nanocomposites was revealed. We combined some biopolymers (methylcellulose, alginate, chitosan) with two nanoclays (kaolinite sheets and halloysite nanotubes) to prepare nanocomposites by means of the casting method from water. The thermal stability, the surface wettability, and the mechanical properties of the obtained films were studied. SEM micrographs highlighted the surface morphology of the biocomposite materials. X-ray data allowed us to correlate the mesoscopic structure to the properties of these nanocomposites.

The structures of pristine halloysite nanotubes (HNTs) and ones functionalized by anionic surfactants (sodium dodecanoate and sodium dodecyl sulfate) were investigated by small angle neutron scattering (SANS). These experiments evidenced the structural organization of the surfactants adsorbed onto the HNT cavity and the importance of the surfactant headgroup. Contrast matching experiments were employed in order to mask the dominant scattering effect of the clay hollow nanotubes and to focus on the surfactant organization within the lumen. Further investigation on the mesoscopic structure of the investigated materials was carried out by electric birefringence (EBR), which allowed study of the rotational mobility of both pristine and functionalized HNTs. The gained structural insights were used to deduce some relevant properties of the hybrids, such as their surfactant loading, charge, and solubilization ability toward hydrophobic compounds. For the latter, the HNT lumen hydrophobization was straightforwardly demonstrated by both fluorescence spectroscopy and fluorescence correlation spectroscopy (FCS) using Nile Red as fluorescent probe. This paper correlates the structural properties of the hybrid material with micellar properties based on HNT and anionic surfactants, showing that for the dodecanoate a much more pronounced aggregation tendency within the HNT cavity prevails compared to the dodecyl sulfate. The attained knowledge is crucial for designing innovative sustainable nanostructures that are based on ecofriendly halloysite and anionic surfactants that can be used for the solubilization and delivery of hydrophobic compounds from such hybrid materials.

Hybrid material based on halloysite nanotubes (HNTs) and sodium perfluorooctanoate (NaPF8) was used as a consolidant for paper treatment. The consolidation efficiency was determined by thermogravimetry as well as by paper grammage determination. Morphological analysis of the treated paper was performed by means of scanning electron microscopy while the effect of modified HNTs on the thermal behaviour of the cellulose fibres was investigated by differential scanning calorimetry which determined the combustion enthalpy of the paper.Water contact angle measurements were performed to study the paper wettability. The physico-chemical properties investigated (mesoscopic structure, thermal stability and wettability) of the treated paper were correlated successfully with the consolidation loading and, consequently, to the affinity between the fluorinated modified HNTs and the fibrous cellulose structure. This study proposes a new green protocol for paper consolidation based on natural tubular nanoparticles with a flame retardant effect.

Hybrid materials based on halloysite nanotubes (HNT) and cucurbit[8]uril (CB[8]) were prepared with the aim to obtain efficient nanosponges towards hydrocarbons both in liquid and vapor phases. The loading on both HNT surfaces and the hybrid morphology were evidenced by FTIR spectroscopy, thermogravimetric analysis and scanning electron microscopy. In order to highlight the interactions in the hybrid 13C {1H} CP-MAS NMR experiments were performed. The aqueous colloidal stability of HNT/CB[8] was highlighted through ζ potential and dynamic light scattering measurements. The HNT/CB[8] composite was employed as nanosponge to capture aromatic oils in aqueous phase as evidenced by fluorescence emission spectra of pyrene. These results were correlated with the adsorption capacity of the hybrid toward toluene in vapor phase. This paper provides an efficient way to prepare a biocompatible hybrid material that could be used as a potential multi-pockets nano-container for decontamination of polluted water and/or air.

A thermo-responsive polymer such as poly(N-isopropylacrylamide) (PNIPAAM) was covalently grafted on the external surface of halloysite nanotubes (HNTs) by means of microwave irradiation. This nanomaterial was used as a support and stabilizer for palladium nanoparticles. The obtained HNT–PNIPAAM/PdNPs was characterized by means of TGA, SEM, EDS and TEM analyses. The palladium content of the catalyst was estimated to be 0.4 wt%. The stability of the catalytic material at different temperatures (below and above the PNIPAAM lower critical solution temperature) was tested in the Suzuki reaction under microwave irradiation. In addition, TEM analysis after five consecutive runs was performed. The catalyst showed a good catalytic activity toward the Suzuki cross-coupling reaction between phenylboronic acid and several aryl halides in aqueous media under microwave irradiation and low palladium loading (0.016 mol%, 8 mg of Pd). Turnover numbers (TONs) and frequencies (TOFs) up to 6250 and 37 500 h1, respectively, were reached. The catalyst was easily separated from the reaction mixture by centrifugation and reused for five consecutive cycles with a small drop in its catalytic activity.

Mixed cyclodextrin–calixarene nanosponges were used to prepare some composites with the well known polyphenolic bioactive compounds quercetin and silibinin. The composites were characterized by means of different techniques (UV-vis, FT-IR, microcalorimetry, thermogravimetry), in order to assess their loading and thermal stability. The kinetics of release of the bioactive molecules into aqueous solution were studied at two different pH values (1.0, 6.4), which mimic typical physiological conditions. Finally the possible antiproliferative effects in vitro were assayed towards three triple negative breast cancer cell lines (SUM 149, SUM 159 and MDA-MB-23). Our results point out the role assumed by the triazole linkers, present in the nanosponge network, in affecting both the adsorption abilities of the materials towards the bioactive molecules, and the antiproliferative activity of the composites. This work puts forward an efficient strategy to prepare nanosponge based nanocarriers with three different cavities that could encapsulate two or more drug molecules with different physico-chemical properties.

Environmental friendly halloysite-dicationic triazolium salts (second generation) obtained by subsequent click reactions of a diyne derivative in the presence of 2-azidopropyl-modified halloysite nanotubes, were used as supports for palladium catalyst. Thanks to the high triazolium loading (25%) these materials were able to support higher amount of the metal than that on the monocationic derivative (first generation). Such materials were characterized by thermogravimetric analysis, FT-IR spectroscopy and SEM investigations. The new catalytic system was employed in the ligand free Suzuki cross-coupling under microwave irradiation. A set of solvent, time and% loading of palladium was screened. The palladium catalyst displayed good activity allowing the synthesis of several biphenyl in high yields working with only 0.1 mol% of palladium loading at 120 °C in water, for an irradiation time of 10 min. The second generation catalyst, also, showed good recyclability without any loss in activity and negligible palladium leaching that are significant improvements over the first generation triazolium catalyst.

Electrolyte additions are used to control the functionality of a nanostructured oxide. Dopant ions affect the size and shape of deposit crystallites and modify the host structure. Such ions can be incorporated into the deposit or form a separate oxide phase. The manganese dioxide family of polymorphs with ion-molecular sieve properties represents the additional possibilities of “template” effects of dopant ions on the phase composition, heterovalent substitution in the cationic sublattice, changes in morphology and alteration of nanocrystallite size during electrocrystallisation. The effects of electrolyte doping in electrodeposited, non-stoichiometric manganese dioxide (NH4+, Li+ and Co2+), chromium oxide-based films (Co2+, Li+) were investigated. The structural characteristics and morphology were studied for all the obtained nanocomposites and deposits were evaluated as highly crystalline cathode materials cathodes, having high cyclability, in Li batteries. The improved functionality of the electrodeposited nanomaterials was correlated to structural changes. Hollandite and pyrolusite electrodeposition pathways were proposed, based on symmetry principles of phase transitions.

In this work, we have developed a novel strategy to prepare hybrid nanostructures with controlled release properties towards khellin by exploiting the electrostatic interactions between chitosan and halloysite nanotubes (HNT). Firstly, khellin was loaded into the HNT lumen by the vacuum-assisted procedure. The drug confinement within the halloysite cavity has been proved by water contact angle experiments on the HNT/khellin tablets. Therefore, the loaded nanotubes were coated with chitosan as a consequence of the attractions between the cationic biopolymer and the halloysite outer surface, which is negatively charged in a wide pH range. The effect of the ionic strength of the aqueous medium on the coating efficiency of the clay nanotubes was investigated. The surface charge properties of HNT/khellin and chitosan/HNT/khellin nanomaterials were determined by &zeta, potential experiments, while their morphology was explored through Scanning Electron Microscopy (SEM). Water contact angle experiments were conducted to explore the influence of the chitosan coating on the hydrophilic/hydrophobic character of halloysite external surface. Thermogravimetry (TG) experiments were conducted to study the thermal behavior of the composite nanomaterials. The amounts of loaded khellin and coated chitosan in the hybrid nanostructures were estimated by a quantitative analysis of the TG curves. The release kinetics of khellin were studied in aqueous solvents at different pH conditions (acidic, neutral and basic) and the obtained data were analyzed by the Korsmeyer&ndash, Peppas model. The release properties were interpreted on the basis of the TG and &zeta, potential results. In conclusion, this study demonstrates that halloysite nanotubes wrapped by chitosan layers can be effective as drug delivery systems.

Functionalization of halloysite nanotubes surface by using organosilanes is sensitive to the reaction conditions. Halloysite nanotubes (HNTs) were modified using (3-Mercaptopropyl) trimethoxy silane (MPTMS). The experiments were performed under different reaction conditions including, various solvents [Toluene, Tetrahydrofuran (THF), Ethanol, n-Hexane, 1,4 Dioxane and Acetonitrile], water content in the reaction media, volume of solvent, number of moles of silane and catalysts (triethyl amine, ammonia solution and tetra-ethoxy titanium). The elemental analysis, FT-IR analysis were used to identify the samples, which attained the highest percent of functionalization. SEM image and thermogravimetric analysis were provided for the pristine halloysite nanotubes and the modified halloysite nanotubes samples. This work provides a systematic investigation of the reaction conditions highlighting the best protocol to perform such a modification that represents a relevant strategy to control the surface properties of halloysite nanotubes as well as the optimization of the first step toward further modifications of this nano clay.

The aim of this study is the design and preparation of Mater-Bi/halloysite nanocomposite materials that could be employed as bioplastics alternative to the petroleum derived products. The biocomposite materials at variable halloysite content (from 0 to 30 wt%) were prepared by using the solvent casting method. We investigated the mechanical behaviour and the thermal properties of the prepared nanocomposites in order to estimate their suitability as biocompatible packaging materials. The thermo-mechanical characteristics were correlated to the nanocomposites' morphologies, which were studied by Scanning Electron Microscopy (SEM). As a general result, the physico-chemical performances of Mater-Bi were improved by the presence of small amounts of nanotubes, which evidenced a homogenous distribution in the polymer matrix. The strongest enhancements of the thermal stability and tensile properties were achieved for Mater-Bi/halloysite 10 wt%. A further addition of nanotubes determined the worsening of both thermal stability and mechanical behaviour. The attained knowledge represents the starting step for the development of packaging films composed by Mater-Bi and halloysite nanotubes.

Halloysite nanotubes were functionalized with stimuli-responsive macromolecules to generate smart nanohybrids. Poly(N-isopropylacrylamide)-co-methacrylic acid (PNIPAAM-co-MA) was selectively adsorbed into halloysite lumen by exploiting electrostatic interactions. Amine-terminated PNIPAAM polymer was also investigated that selectively interacts with the outer surface of the nanotubes. The adsorption site has a profound effect on the thermodynamic behavior and therefore temperature responsive features of the hybrid material. The drug release kinetics was investigated by using diclofenac as a non-steroidal anti-inflammatory drug model. The release kinetics depends on the nanoarchitecture of the PNIPAAM/halloysite based material. In particular, diclofenac release was slowed down above the LCST for PNIPAAM-co-MA/halloysite. Opposite trends occurred for halloysite functionalized with PNIPAAM at the outer surface. This work represents a further step toward the opportunity to extend and control the delivery conditions of active species, which represent a key point in technological applications. © 2018 IOP Publishing Ltd.

The aim of this work is the investigation of the effect of ultrasound treatment on the structural characteristics of carbon nanotubes (CNTs) and the consequent influence that the shortening induced by sonication exerts on the morphology, rheological behaviour and thermo-oxidative resistance of ultra-high molecular weight polyethylene (UHMWPE)-based nanocomposites. First, CNTs have been subjected to sonication for different time intervals and the performed spectroscopic and morphological analyses reveal that a dramatic decrease of the CNT's original length occurs with increased sonication time. The reduction of the initial length of CNTs strongly affects the nanocomposite rheological behaviour, which progressively changes from solid-like to liquid-like as the CNT sonication time increases. The study of the thermo-oxidative behaviour of the investigated nanocomposites reveals that the CNT sonication has a detrimental effect on the thermo-oxidative stability of nanocomposites, especially for long exposure times. The worsening of the thermo-oxidative resistance of sonicated CNT-containing nanocomposites could be attributed to the lower thermal conductivity of low-aspect-ratio CNTs, which causes the increase of the local temperature at the polymer/nanofillers interphase, with the consequent acceleration of the degradative phenomena.

Hypothesis: Oral insulin administration is not actually effective due to insulin rapid degradation, inactivation and digestion by proteolytic enzymes which results in low bioavailability. Moreover insulin is poorly permeable and lack of lipophilicity. These limits can be overcome by the loading of protein in some nanostructured carrier such as halloysite nanotubes (HNTs). Experiments: Herein we propose an easy strategy to obtain HNT hybrid materials for the delivery of insulin. We report a detailed description on the thermal behavior and stability of insulin loaded and released from the HNTs hybrid by the combination of several techniques. Findings: Release experiments of insulin from the HNTs revealed the efficacy of the nanocarrier. Circular Dichroism data evidenced that the released insulin exhibits its native-like secondary structure confirming the suitability of HNT/insulin as delivery system for at least three months. The loaded nanotubes were filled into chitosan matrix with the aim to prepare bionanocomposite films that can be used for transdermal delivery. This work puts forward an efficient strategy to prepare halloysite based nanocarriers containing insulin that could be employed in several biomedical applications. The detailed description of the prepared HNT/insulin hybrid represents a fundamental point for designing advanced delivery systems. © 2018 Elsevier Inc.

A novel green protocol for the deacidifying consolidation of waterlogged archaeological woods through aqueous dispersions of polyethylene glycol (PEG) 1500 and halloysite nanotubes containing calcium hydroxide has been designed. First, we prepared functionalized halloysite nanotubes filled with Ca(OH)2 in their lumen. The controlled and sustained release of Ca(OH)2 from the halloysite lumen extended its neutralization action over time, allowing the development of a long-term deacidification of the wood samples. A preliminary thermomechanical characterization of clay/polymer nanocomposites allows us to determine the experimental conditions to maximize the consolidation efficiency of the wood samples. The penetration of the halloysite-Ca(OH)2/PEG composite within the wooden pores conferred the robustness of the archaeological woods based on the clay/polymer composition of the consolidant mixture. Compared to the archeological woods treated with pure PEG 1500, the addition of modified nanotubes in the consolidant induced a remarkable improvement in the mechanical performance in terms of flexural strength and rigidity. The pH measurements of the treated woods showed that the halloysite-Ca(OH)2 are effective alkaline fillers. Accordingly, the modified nanotubes provided a long-term protection for lignin present in the woods that are exposed to artificial aging under acidic atmosphere. The attained knowledge shows that an easy and green protocol for the long-term preservation of wooden artworks can be achieved by the combination of PEG polymers and alkaline tubular nanostructures obtained through the confinement of Ca(OH)2 within the halloysite cavity. © 2018 American Chemical Society.

The structure of halloysite nanotubes (Hal) from different mines was investigated by Small-Angle Neutron Scattering (SANS) and Electric Birefringence (EBR) experiments. The analysis of the SANS curves allowed us to correlate the sizes and polydispersity and the specific surfaces (obtained by a Porod analysis of the SANS data) of the nanotubes with their specific geological setting. Contrast matching measurements were performed on patch Hal (from Western Australia) in order to determine their experimental scattering length density for a more precise analysis. Further characterization of the mesoscopic structure of Hal was carried out by Electric Birefringence (EBR), which allowed to study the rotational mobility of Hal. From the obtained rotational diffusion coefficients of the different Hal we deduced their length via the Broersma theory, which compares well to TEM data. The analysis of both SANS and EBR data provided a bulk average information on the Hal structure in water, which, for instance, documented the markedly higher degree of well-definedness of the PT-Hal and the thinner tube walls present here. The attained systematic structural knowledge represents a step forward for the robust structural description of halloysites selected from four geological deposits and shows that Hal of different origin differ very markedly with respect to their mesoscopic structure. © 2017 Elsevier B.V.

Halloysite nanotubes were used to incorporate anionic surfactant micelles and an organic solvent to generate a cleaning system to be applied in Cultural Heritage restoration. The targeted adsorption is driven by electrostatic interactions based on the nanotubes peculiar charge separation. Namely anionic species are driven to the positively charged inner surface while being prevented from interacting with the halloysite outer surface that possesses a positive charge density. The hybrid organic/inorganic emulsion was characterized by dynamic light scattering. Analysis of the autocorrelation function allowed us to define the presence of surfactant aggregates inside/outside the nanotube lumen as a function of the nanotube/surfactant ratio in an aqueous mixture. The application of this prepared emulsion for the controlled cleaning of a marble artifact is demonstrated. To this purpose, a membrane of nanofibrous polyacrylonitrile was prepared by electrospinning and was applied between the work of art and the cleaning agent to avoid the release of residues on the marble surface. This work represents a further step toward the opportunity to extend the use of emulsions for cleaning protocols for stone-based artifacts or in technological applications where surfactant separation is required by a simple centrifugation/sedimentation method. © 2018 by the authors.

Halloysite is natural tubular clay suitable as a component of biocompatible nanosystems with specific functionalities. The selective modification of halloysite inner/outer surfaces can be achieved by exploiting supramolecular and covalent interactions resulting in controlled colloidal stability adjusted to the solvent polarity. The functionalized halloysite nanotubes can be employed as reinforcing filler for polymers as well as carriers for the sustained release of active molecules, such as antioxidants, flame-retardants, corrosion inhibitors, biocides and drugs. The tubular morphology makes halloysite a perspective template for core-shell metal supports for mesoporous catalysts. The catalysts can be incorporated with selective and unselective metal binding on the nanotubes' outer surface or in the inner lumens. Micropatterns of self-assembled nanotubes have been realized by the droplet casting method. The selective modification of halloysite has been exploited to increase the nanotubes' ordering in the produced patterns. Pickering emulsions, induced by the self-assembly of halloysite nanotubes on oil-water interface, can be used for petroleum spill bioremediation and catalysis. © 2018 Elsevier Ltd

We report a differential scanning calorimetry study to investigate the effect of cyclodextrins (CD) on the crystallinity of a copolymer. Tetronics was selected as copolymer with star-like shape formed by four polyethylene oxide flanked by four polypropylene oxide blocks linked to ethylenediamine central group. The use of CD with different cavity size was exploited for a block selective inclusion. A model for supramolecular association was considered for a quantitative description of the enthalpy data. The polymer chain incorporation into the CD cavity generates a loss of crystallinity. The stoichiometry of the CD/copolymer aggregates can be tuned by changing the CD cavity size. The investigated systems represent interesting necklace-like supramolecular structures with tunable crystallinity. © 2018 Akadémiai Kiadó, Budapest, Hungary

Within the conservation of artworks materials, this chapter describes innovative strategies based on clay nanoparticles that are promising for protective coating, surface cleaning, and consolidation. We present the preparation of polymer/montmorillonite nanocomposites, which are revealed as efficient protective coatings for highly porous stones, marbles, and bread-made artifacts. Anticorrosive films for metal substrates have been obtained by polymer filling with laponite and halloysite nanotubes (HNTs) containing corrosion inhibitors into their lumen. The dispersion of hydrophobically modified HNTs into chitosan matrix drives to fabricate biofilms with surface cleaning capacity. Rust stains have been removed from marble samples by using laponite/cellulose fibers. Regarding the preservation of lignocellulosic artworks, composite systems based on sustainable polymers (cellulose ethers and beeswax) and HNTs have been successfully employed as consolidants of archaeological woods. Encapsulation of Ca(OH)2 into an HNT cavity has been explored for paper deacidification. In conclusion, we have summarized the nanoclay-based protocols used in conservation issues. © 2019 Copyright

An aqueous star-like copolymer solution was titrated with perfluoro carboxylic acids at various compositions to prepare a polymeric surfactant composed of fluorinated nano-domains. The copolymer is X-shaped where each arm contains ethylene oxide and propylene oxide repetitive units linked to a central ethylenediamine group. The aggregation behavior of the hybrid macromolecule was studied from the physico-chemical point of view by changing parameters like temperature and composition. The solubilization of perfluorinated and hydrogenated alcohols in mixed self-assembled structure revealed that a selectivity toward the fluorinated moiety can be done. The self-assembled structures are promising for applications where the coexistence of nano-domains with dual lipophobic and hydrophobic character is required. Therefore, they are tools to incorporate selectively hydrogenated and fluorinated oils sparingly soluble in water.

The grafting of poly(N-isopropylacrylamide) (PNIPAAM) onto the halloysite external surface is proposed in order to obtain a novel thermoresponsive drug carrier for curcumin delivery. The new nanomaterial is characterized by means of FT-IR spectroscopy, thermogravimetric analysis, and SEM investigations. A high density of polymer chain was achieved at the nanoparticle surface. The PNIPAAM dehydration phenomenon was observed in water above 32 °C that is nearly coincident with the lower critical solution temperature for the polymer. The colloidal stability as well as the wettability of the obtained nanomaterial may be triggered by temperature stimuli. In vitro tests simulating the gastro-intestinal transit demonstrated that the proposed delivery system allows a targeted release of curcumin, preventing its degradation in an acidic medium. We synthesized a new hybrid nanoparticle that is very promising for several applications due to the copresence of a biocompatible region, to the temperature response, and to the hollow cavity, which can load active species.

Halloysite nanotubes (HNTs) are clay minerals with a hollow nanotubular structure. There is growing interest in these nanomaterials, due to their biocompatibility, potential applications and availability. The surface chemistry of HNTs is versatile for the targeted chemical modification of the inner lumen and outer surface. Functionalized halloysite constitutes a valuable support for metal nanoparticles, promoting catalytic applications with tunable properties. The peculiar tubular shape of HNTs favors the dispersion and surface availability of the supported metal nanoparticles that are active in the catalytic path. Moreover, the presence of an empty lumen opens new perspectives for the production of nanoarchitectures with synergistic catalytic effects, due to the increase in local concentrations and confinement. The main focus of this review is the research on modified halloysite nanotubes for the preparation of valuable supports for metal nanoparticles and their applications in catalytic processes.

Studies on the adsorption of biopolymers onto halloysite nanotubes (HNTs) in water were conducted. Three polymers with different charges-anionic (pectin), neutral (hydroxypropyl cellulose), and cationic (chitosan)-were chosen. The thermodynamic parameters for the adsorption of polymers onto the HNT surface were determined by isothermal titration calorimetry (ITC). The experimental data were interpreted based on a Langmuir adsorption model. The standard variations in free energy, enthalpy, and entropy of the process were obtained and discussed. Turbidimetry was used to evaluate the stability of functionalized nanoparticles in water. The ζ-potential clarified the surface charge properties of functionalized nanotubes upon polymer adsorption. The interaction of modified nanotubes with polymers led to the formation of a colloidal system with tunable stability and surface properties, which offers different perspectives on new applications of these dispersions, such as carriers for substances to be released in response to external stimuli. © 2017 American Chemical Society.

Novel composite bioplastics were successfully prepared by filling pectin matrix with treated coffee grounds. The amount of coffee dispersed into the pectin was changed within a wide filler range. The morphology of the pectin/coffee hybrid films was studied by microscopic techniques in order to investigate their mesoscopic structure as well as the sizes distribution of the particles dispersed into the matrix. The micrographs showed that the coffee grounds are uniformly dispersed within the polymeric matrix. The morphological characteristics of the biocomposite films were correlated to their properties, such as wettability, water uptake, thermal behavior and mechanical performances. Dynamic mechanical test were conducted as a function of the humidity conditions. As a general result, a worsening of the mechanical performances was induced by the addition of the coffee grounds into the pectin. An additional UV curing treatment was conducted on the pectin/coffee films with the aim to improve their tensile and viscoelastic features. The cured films showed promising and tunable properties that are dependent on both the filler content and the UV irradiation. In particular, the presence of single coffee particles into the pectin matrix renders the UV curing treatment effective in the enhancement of the elasticity as well as the traction resistance, whereas the cured composite films containing coffee clusters showed only more elastic characteristics. With this study, we fabricated pectin/coffee bioplastics with controlled behavior appealing for specific application within the food packaging. © 2017 Elsevier Ltd

A promising strategy to immobilize a natural stabilizer in polymeric films is presented. Par-Ticularly, nevadensin (N, a natural basil flavonoid) molecules have been encapsulated in Pluronic F-127 micelles [F127, a triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)] and the obtained nanoparticles have been introduced in poly(ethylene glycol), PEG [otherwise known as poly(ethylene oxide), PEO]. In order to verify the effectiveness of the micelles as anti-oxidant carriers, PEG-based films have been subjected to artificial weathering. The encapsulation of anti-oxidant molecules allows the enhancement of N solubility in PEG, leading to advanced materials with enhanced photo-oxidative stability.

Inorganic-organic nanosponge hybrids based on halloysite clay and organic cyclodextrin derivatives (HNT-CDs) were developed by means of microwave irradiations in solvent-free conditions. The HNT-CDs nanomaterials characterized by FT-IR, TGA, BET, TEM, SEM, DLS, and zeta-potential have showed a hyper-reticulated network which possesses both HNT and cyclodextrin peculiarities. The new HNT-CDs nanosponge hybrids were employed as nanoadsorbents, first choosing Rhodamine B as the dye model, and furthermore for the removal of some cationic and anionic dyes, under different pH values (1.0, 4.54, and 7.4). The collected results showed that the pH solution as well as the electrostatic interactions affect the adsorption process. Factors controlling the adsorption process were discussed. The experimental adsorption equilibrium and kinetic data were best described by the Freundlich isotherm model. Excellent adsorption efficiency for cationic dyes were observed with respect to anionic ones. The results suggest that HNT-CDs nanosponge hybrids are a good nanoadsorbent for selective adsorption of cationic dyes with respect to the anionic ones from aqueous solutions.

L’allosite (HNT) è un interessante materiale argilloso allumino-silicato naturale, non tossico e biocompatibile, con la caratteristica forma tubolare cava dotata di parziale carica positiva interna e negativa esterna.Combinando le peculiarità di un composto organico con le proprietà di un materiale inorganico, è possibile ottenere sistemi ibridi organici–inorganici con interessanti proprietà e vasti campi di applicazione. Sono un esempio delle “nanospugne” capaci di adsorbire efficacemente potenziali inquinanti. In questo contesto sono stati preparati, dei materiali ibridi “spugna” costituiti da unità ciclodestriniche e allosite e ancora un sistema ibrido HNT-Cucurbit[8]uril. Il primo possiede una struttura altamente ramificata e mostra interessanti capacità di assorbimento di coloranti organici con proprietà modulabili in funzione di pH e temperatura, il secondo è stato dimostrato possedere una spiccata attività di adsorbimento di toluene e pirene.

Diimidazolium and dipyrrolidinium organic salts were tested for their ability to gel both organic solvents and ionic liquids. Organic salts containing 1-(1-imidazolylmethyl)-3,5-di-(3'-octylimidazolylmethyl)-benzene and 1-(N-pyrrolidylmethyl)-3,5-di-(N,N-octylpyrrolidylmethyl)-benzene cations were used. In addition to the simple bromide anion, also dianions having a naphthalene core such as 1,5- and 2,6-naphthalenedisulfonate and 2,6-naphthalenedicarboxylate were taken into account. Gelation tests demonstrated that organic salts used were able to harden ionic liquids. The materials obtained were investigated for their thermal stability and also for electric conductivity properties using micro-DSC and dielectric spectroscopy. Furthermore, the opacity of some gel phases was monitored using UV-vis measurements. To obtain information about the gelation mechanism, gel phase formation was studied as a function of time by means of resonance light scattering investigation. Finally, the ability of materials to respond to external stimuli such as magnetic stirring or ultrasound irradiation was also analyzed. Data collected show that different relationships exist among the gelator and the ionic liquid structure, determining the properties of materials and their possible applications.

We investigated the filling process of cellulose-based paper with natural clay nanotubes and their mixtures with hydroxypropyl cellulose (HPC) that is commonly used as glue and consolidant for degraded paper. A comprehensive characterization of the materials was carried out through morphology, wettability, thermal degradation, and tensile properties. The treatment with halloysite nanotubes generated a decrease of the paper mechanical performance and did not alter the thermal properties. The co-presence of HPC and nanoparticles generated a more uniform nanotubes distribution in the paper fibrous structure and a significant enhancement of both the mechanical properties and the surface hydrophobicity with respect to the HPC treatment. This work proposes the use of halloysite/HPC mixture in a new protocol for paper consolidation and represents a starting point to develop, with a biocompatible approach, smart composite material in which the nanotube cavity is filled with active species for paper protection or active response to external stimuli. © 2014 Akadémiai Kiadó, Budapest, Hungary.

Hyper-reticulated co-polymers jointly formed by cyclodextrin and calixarene units, which can be considered as a new class of nanosponges, were easily obtained by means of a click chemistry approach. In particular, we succeeded in preparing our materials by exploiting the copper-catalyzed 1,3-dipolar cycloaddition (CuAAC) reaction between heptakis-(6-deoxy)-(6-azido)-beta-cyclodextrin and (5,11,17,23-tetra-tert-butyl)-(25,26,27,28-tetra-propargyloxy)-calix-[4]-arene, mixed in different proportions. These materials were fully characterized by means of combined FT-IR, thermogravimetric, C-13 {H-1} CP-MAS NMR and nitrogen adsorption/desorption techniques. In particular, C-13 {H-1} CP-MAS spectra allowed us to perform a quantitative analysis of the co-polymers obtained. Tests on their possible sequestering abilities towards some organic molecules, in particular nitroarenes and commercial dyes chosen as suitable pollutants or drug models, were successfully carried out. Results obtained point out that absorption abilities seem affected by polymer composition and porosity as well.

The use of nanocomposites based on biopolymers and nanoparticles for controlled drug release is an attractive notion. We used halloysite nanotubes that were promising candidates for the loading and release of active molecules due to their hollow cavity. Gel beads based on chitosan with uniformly dispersed halloysite nanotubes were obtained by a dropping method. Alginate was used to generate a coating layer over the hybrid gel beads. This proposed procedure succeeded in controlling the morphology at the mesoscale and it had a relevant effect on the release profile of the model drug from the nanotube cavity.

We prepared hybrid halloysite nanotubes (HNT/sodium alkanoates) in which the inner cavity of the nanoclay was selectively modified. Physicochemical studies evidenced the interactions between HNT and sodium alkanoates, ruled out clay exfoliation, quantified the amount of the loaded substance, and showed an increase of the total net negative charge, allowing us to obtain rather stable aqueous nanoclay dispersions. These dispersions were exploited as inorganic micelles to capture hydrocarbon and aromatic oils in the vapor and liquid states and were revealed to be nonfoaming but very efficient in encapsulating oils. Here, we have fabricated biocompatibile and low-cost inorganic micelles that can be exploited for industrial applications on a large scale.

Nanocomposites of poly(ethylene) glycol (PEG) 20000 filled with clay nanotubes (HNTs) were prepared. The thermal properties obtained from thermogravimetry and differential scanning calorimetry were correlated to the morphology imaged by scanning electron microscopy. Low amounts of HNTs generate compact structure while large amounts of HNTs create craters and voids. The decrease of polymer degradation temperature in the presence of large amount of nanoclay (ca. 80 wt%) is a consequence of the morphology at the mesoscale range. The thermal opposite effect observed in the HNTs low regime (up to ca. 20 wt%) is due to the gas entrapment into the nanoparticles lumen. The quantitative analysis of the PEG 20000 enthalpy of melting in the presence of HNTs allowed us to characterize the polymer adsorption onto the nanoclay surface.