Structural, Thermal, and Release Properties of Hybrid Materials Based on Layered Zinc Hydroxide and Caffeic Acid.

Christhy V Ruiz,Oscar Giraldo,María E Becerra

doi:10.3390/nano10010163

Christhy V Ruiz, Oscar Giraldo + Show 1 more

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https://doi.org/10.3390/nano10010163

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Journal: Nanomaterials	Publication Date: Jan 17, 2020
Citations: 7	License type: CC BY 4.0

Affiliation: Universidad Nacional de Colombia

Abstract

Caffeic acid (CA) molecules were immobilized in a layered inorganic host matrix based on zinc hydroxide structures with different starting interlayer anions, nitrate, and acetate. The chemical composition, structure, thermal stability, morphology, and surface of the host matrices and hybrid compounds were analyzed by X-ray diffraction (XRD), themogravimetric/differencial thermal analysis (TG/DTA), Fourier transform infrarred spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Additionally, the surface charge of the materials was investigated using zeta potential at pH ~7. The results show an influence of the surface charge on the chemical, interaction, and structure of the resulting hybrid materials as a function of the starting layered structures. An expansion of the basal spacing to 10.20 Å for zinc hydroxide nitrate (ZHN), and a shrinkage to 10.37 Å for zinc hydroxide acetate (ZHA). These results suggest that the CA lies with a tilt angle in the interlayer region of the inorganic host matrix. The immobilization of CA is favored in ZHN, with respect to ZHA, because a single-layered phase was identified. A higher thermal stability at 65 °C was observed for ZHN-CA than for ZHA-CA. The evaluation of the release behavior showed a higher percentage of CA released from ZHN than ZHA, and the release mechanism was described by the Elovich model. The hybrid materials show potential characteristics for use as bioactive delivery systems.

Highlights

Layered inorganic materials, such as layered double hydroxides (LDH) and zinc hydroxy salts (ZHS), are characterized by retaining different chemical species compatible in the interlayer region due to the charge of their layers, thereby achieving the charge balance of the layered structure
The chemical composition, structure, thermal stability, morphology, and surface of the host matrices and hybrid compounds were analyzed by X-ray diffraction (XRD), themogravimetric/differencial thermal analysis (TG/DTA), Fourier transform infrarred spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS)
The evaluation of the release behavior showed a higher percentage of Caffeic acid (CA) released from zinc hydroxide nitrate (ZHN) than zinc hydroxide acetate (ZHA), and the release mechanism was described by the Elovich model

Summary

Introduction

Layered inorganic materials, such as layered double hydroxides (LDH) and zinc hydroxy salts (ZHS), are characterized by retaining different chemical species compatible in the interlayer region due to the charge of their layers, thereby achieving the charge balance of the layered structure. This possibility enables the creation of a wide variety of hybrid materials with new applications and functionalities [1]. With regard to layered double hydroxides (LDH), a wide range of molecules such as complex ions, vitamins, organic acids, genes, and drugs, amongst others, were extensively investigated [3,4,5,6,7]. In terms of ZHS, there is still much to be explored about immobilization studies of functional molecules, such as antioxidants, dyes, and drugs [8,9]

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