Search results for " Halloysite"
showing 10 items of 36 documents
Gold nanoparticles stabilized by modified halloysite nanotubes for catalytic applications
2019
A highly sustainable prototype of a flow system based on gold nanoparticles (4.2 nm) supported on thiol-functionalized halloysite nanotubes (HNTs) was developed for catalytic applications. The catalytic performances were evaluated using the reduction of 4-nitrophenol to 4-aminophenol as a model system. Under the best experimental conditions (0.0001 mol%, 1.97 × 10−8 mg of Au nanoparticles), an impressive apparent turnover frequency value up to 2 204 530 h−1 was achieved and the halloysite-based catalyst showed full recyclability even after ten cycles. The high catalytic activity confirms the importance of the use of HNTs as support for Au nanoparticles that can exert a synergistic effect bo…
Halloysite nanotubes as support for metal-based catalysts
2017
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 prod…
Clay-based drug-delivery systems: what does the future hold?
2017
Clays for drug delivery have been used from ancient time due to the large availability of clay minerals and their unprecedented properties. The empirical use of nanoclays from the past is converted in a stimulating scientific task aimed at building up nanoarchitectonic vehicles for drug delivery in a targeted and stimuli-responsive fashion. Here the historical aspects are discussed; next the modern examples of applications of different clay-based materials are discussed. A special focus is given to halloysite clay nanotubes, which are an emerging and very promising nanomaterial for drug-delivery purposes due to its special morphology and unique chemical properties. Advantages and limitatio…
Synthesis and Characterization of Halloysite-Cyclodextrin Nanosponges for Enhanced Dyes Adsorption
2017
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 a…
Halloysite Nanotubes: Controlled Access and Release by Smart Gates
2017
© 2017 by the authors. Licensee MDPI, Basel, Switzerland. Hollow halloysite nanotubes have been used as nanocontainers for loading and for the triggered release of calcium hydroxide for paper preservation. A strategy for placing end-stoppers into the tubular nanocontainer is proposed and the sustained release from the cavity is reported. The incorporation of Ca(OH) 2 into the nanotube lumen, as demonstrated using transmission electron microscopy (TEM) imaging and Energy Dispersive X-ray (EDX) mapping, retards the carbonatation, delaying the reaction with CO 2 gas. This effect can be further controlled by placing the end-stoppers. The obtained material is tested for paper deacidification. We…
Keratin/alginate hybrid hydrogels filled with halloysite clay nanotubes for protective treatment of human hair
2022
Keratin/alginate hydrogels filled with halloysite nanotubes (HNTs) have been tested for the protective coating of human hair. Preliminary studies have been conducted on the aqueous colloidal systems and the corresponding hydrogels obtained by using Ca2+ ions as crosslinkers. Firstly, we have investigated the colloidal properties of keratin/alginate/HNTs dispersions to explore the specific interactions occurring between the biomacromolecules and the nanotubes. Then, the rheological properties of the hydrogels have been studied highlighting that the keratin/alginate interactions and the subsequent addition of HNTs facilitate the biopolymer crosslinking. Finally, human hair samples have been t…
Ecotoxicity of halloysite nanotube–supported palladium nanoparticles in Raphanus sativus L
2015
Halloysite nanotubes (HNTs) are natural nanomaterials that are biocompatible and available in large amounts at low prices. They are emerging nanomaterials with appealing properties for applications like support for metal nanoparticles (NPs). The potential environmental impacts of NPs can be understood in terms of phytotoxicity. Current research has been focusing on HNT applications in cell or animal models, while their use in plants is limited so their ecotoxicological impact is poorly documented. To date there are no studies on the phytotoxic effects of functionalized halloysites (functionalized-HNTs). To develop a quantitative risk assessment model for predicting the potential impact of H…
Palladium nanoparticles immobilized on halloysite nanotubes covered by a multilayer network for catalytic applications
2018
The synthesis of pure fine chemicals for industrial purposes is one of the most attractive challenges of chemical research. The use of catalytic pathways mediated by palladium nanoparticles (PdNPs) for C-C bond formation is a useful way to obtain these kinds of compounds. To achieve this objective, the PdNPs can be efficiently loaded on a functionalized natural nanostructured support such as halloysite nanotubes (HNTs). Hybrid materials based on thiol functionalized halloysite nanotubes and highly cross-linked imidazolium salts were successfully developed and used for the stabilization of PdNPs. The HNT/Pd hybrids were thoroughly characterized from a physico-chemical point of view and teste…
Halloysite nanotubes as sustainable nanofiller for paper consolidation and protection
2014
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 hydroph…
Effect of Morphology and Size of Halloysite Nanotubes on Functional Pectin Bionanocomposites for Food Packaging Applications
2017
Pectin bionanocomposite films filled with various concentrations of two different types of halloysite nanotubes were prepared and characterized in this study as potential films for food packaging applications. The two types of halloysite nanotubes were long and thin (patch) (200-30 000 nm length) and short and stubby (Matauri Bay) (50-3000 nm length) with different morphological, physical, and dispersibility properties. Both matrix (pectin) and reinforcer (halloysite nanotubes) used in this study are considered as biocompatible, natural, and low-cost materials. Various characterization tests including Fourier transform infrared spectroscopy, field emission scanning electron microscopy, rele…