Synthesis and Characterization of Nanomaterial Based on Halloysite and Hectorite Clay Minerals Covalently Bridged.

Marina Massaro,Carmelo Giuseppe Colletti,Fátima García-Villén,Cesar Viseras Iborra,Serena Riela,Giuseppe Lazzara,Giuseppe Cavallaro

doi:10.3390/nano11020506

Abstract

Halloysite is an aluminosilicate clay with a predominantly hollow tubular structure (HNTs) able to act as a nanocontainer for the encapsulation of several chemicals. However, HNTs possess low affinity for metal ions in their pristine form and they need to be modified for improving their adsorption capabilities. Therefore, to overcome this issue herein we report a straightforward approach for the covalent modification of the external surface of halloysite nanotubes with hectorite clay. Compared to halloysite, hectorite possesses a lamellar structure with higher cation exchange capacity. The covalent linkage between the two clays was verified by several techniques (FTIR spectroscopy, 13C CP-MAS NMR, TGA, ζ−potential, DLS, and XRD measurements) and the morphology was imaged by TEM investigations. As proof of concept the adsorption ability of the obtained nanomaterial in comparison to pristine clays was proved using ciprofloxacin and silver ions chosen as models for their different chemical characteristics.

Highlights

Clay minerals are natural phyllosilicates which present peculiar morphologies that are a challenge for chemical manipulation
The covalent linkage between the two clays was verified by several techniques (FTIR spectroscopy, 13 C CP-MAS NMR, thermogravimetric analysis (TGA), ζ−potential, DLS and XRD measurements) and the morphology was imaged by Transmission electron microscopy (TEM)
By means of this synthetic pathway we obtain the best conditions to minimize repulsive interactions that occur between halloysite and hectorite external surfaces

Summary

Introduction

Clay minerals are natural phyllosilicates which present peculiar morphologies that are a challenge for chemical manipulation. Their combination at the microor nanometric scale plays an important role as scaffold for the development of appealing artificial nanocomposites for several applications ranging from industry to biomedical engineering. Halloysite is an aluminosilicate with a predominantly hollow tubular structure (HNTs) [1]. It is dioctahedral 1:1 clay mineral present in the soil, belonging to the kaolin group. Halloysite possesses different charged surfaces: positive in the inner lumen, where mostly of aluminum hydroxide groups are present; negative on the external surface, which consists in silicon dioxide. Several approaches have been exploited but few of them envisage the possibility to delivery simultaneously two or more active ingredients

Methods

Results

Conclusion