Synthesis and Characterization of Halloysite-Cyclodextrin Nanosponges for Enhanced Dyes Adsorption

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

A synergic nanoantioxidant based on covalently modified halloysite-trolox nanotubes with intra-lumen loaded quercetin

We describe the preparation and properties of the first example of a synergic nanoantioxidant, obtained by different functionalizations of the external surface and the inner lumen of halloysite nanotubes (HNTs). Trolox, a mimic of natural α-tocopherol, was selectively grafted on the HNT external surface; while quercetin, a natural polyphenolic antioxidant, was loaded into the inner lumen to afford a bi-functional nanoantioxidant, HNT-Trolox/Que, which was investigated for its reactivity with transient peroxyl radicals and a persistent 1,1-diphenyl-2-picrylhydrazyl (DPPH•) radical in comparison with the corresponding mono-functional analogues HNT-Trolox and HNT/Que. Both HNT-Trolox and HNT/Que showed good antioxidant performance in the inhibited autoxidation of organic substrates; however HNT-Trolox/Que protection by reaction with peroxyl radicals was 35% higher in acetonitrile and 65% in chlorobenzene, as compared to the expected performance based on the sum of contributions of NHT-Trolox and NHT/Que. Similar enhancement was observed also in the trapping of DPPH• radicals. Synergism between the distinct antioxidant functions was based on the rapid reaction of externally exposed Trolox (rate constant with peroxyl radicals was 1.1 × 106 M-1 s-1 and 9 × 104 M-1 s-1 respectively in chlorobenzene and acetonitrile, at 30 °C), followed by its regeneration by quercetin released from the HNT lumen. The advantages of this novel nanoantioxidant are discussed

Materiali ibridi a base di nanotubi di allosite per la rimozione d’inquinanti

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

Analysis of substituent effects in the reactions of some2-L-3-nitro-5-X-thiophenes with aniline in benzene. A new interpretation ofthe`element effect`

The kinetic constants for the title reactions have been measured in benzene, at 25 \ub0C, at various aniline concentrations. In spite of the low kB/k0 ratios, the reactions are inferred to be genuinely base-catalyzed. The susceptibility constants estimated for the various steps of the reaction mechanism(s) have allowed to make clear the limits of the so-called "element effect" criterion