Rediscovering mechanochemistry: new opportunities in the synthesis of nanocomposites by High Energy Ball Milling

1. IntroductionHigh Energy Ball Milling (HEBM) is a top-down synthesis approach developed in the 70s as an industrial process to produce alloys and composites[1]. Recently, it has shown to be versatile and succesfully also for... [ view full abstract ]

1. Introduction

High Energy Ball Milling (HEBM) is a top-down synthesis approach developed in the 70s as an industrial process to produce alloys and composites^[1]. Recently, it has shown to be versatile and succesfully also for the production of several novel materials by chemical transformations that are accessible with difficulty or not at all in solution. Moreover, HEBM has the advantage to avoid the use of solvents demonstrating to be a green, energy efficient, inexpensive, fast and easy to scale-up synthesis method.

This work presents an assortment of novel nanocomposites (NCs) for biomedical applications prepared by HEBM synthesis approach at University of Cagliari: Superparamagnetic Magnetite-Silica NCs (Fe₃O₄/SiO₂); Caffeine-Silica NCs (CAF/SiO₂); Natural Extract-Silica NCs (NE/SiO₂)^[2-4].

2. Methods

Fe₃O₄/SiO₂. In a typical synthesis Fe2O3 and Si mixture was sealed in a stainless steel vial with steel balls. Ball milling experiments were performed in a vibratory mill apparatus.

CAF/SiO₂ and NE/SiO₂. A mixture of anhydrous caffeine or a natural extract (Vitis Vinifera and Centella Asiatica) with fumed SiO₂ was milled in an agate vial together with agate balls using a planetary mill.

The effect of milling was monitored by X-Ray Powder Diffraction, Infrared Spectroscopy, Transmission and Scanning Electron Microscopy performed on small portions of the powder samples at different milling time.

3. Results and discussions

Fe₃O₄/SiO₂. The milling process produced NCs with an average size ranging from 100 to 200nm, where Fe₃O₄ nanoparticles (4-6nm size) are homogeneously dispersed into the amorphous SiO₂ matrix.

CAF/SiO₂. After milling process, caffeine was nanosized and embedded in the SiO₂ matrix in core-shell and multilayered structures. The inclusion of the caffeine in the SiO₂ matrix reduced drug molecule diffusion through the matrix and then the drug release.

NE/SiO₂. NCs with high antioxidant activity were obtained by the milling process, showing an enhanced agglomeration increasing the milling time and the NE amount.

References

[1] Kong et al., Progress in Materials Science 2008, 53, 207-322.

[2] Scano et al., Materials Research Express (Volume 4) 2017.

[3] Pilloni et al., International Journal of Pharmaceutics 2010, 401, 103-112.

[4] Pilloni et al., Pharmaceutical Development and Technology 2013,18(3), 626-33