Effectiveness and Compatibility of Nanoparticle Based Multifunctional Coatings on Natural and Man-Made Stones

Martina Zuena,Maria Antonietta Ricci,Armida Sodo,Ludovica Ruggiero,Giancarlo Della Ventura,Edoardo Bemporad

doi:10.3390/coatings11040480

Abstract

The interaction of microorganisms with stone materials leads to biodeterioration processes, which may cause aesthetic damages and the loss of durability and strength of the substrates. Innovative solutions against this process are represented by nanotechnologies. In our previous works, 2-mercaptobenzothiazole was successfully encapsulated within two silica-based nanodevices: nanocapsules and mesoporous nanoparticles. Such loaded nanodevices have been dispersed in TEOS based coatings, characterized as far as their chemical–physical properties and in vitro biocide efficacy. Here, we adopt a multi-technic approach, to assess the coatings efficacy and compatibility with four types of stones of cultural heritage interest, namely, mortar, brick, travertine, and Carrara marble. In particular, we determine the protective function of the coatings, based on water transport properties (reduction up to a factor 10 of the water absorption for brick and mortar, without significantly influencing water vapor transmission rate), morphology of the surface (absence of coating cracks and color changes), and TiO2 photocatalytic activity. Consequently, these coatings can be considered suitable for application on stone artifacts, without interfering with their artistic appearance.

Highlights

Both natural and man-made stone materials, used in the field of cultural heritage, undergo a weathering process of deterioration when exposed to outdoor conditions
The effectiveness of the coatings in preventing water penetration and reducing water transport was evaluated by static contact angle, water absorption through capillarity, and water vapor permeability measurements
We reported the chemico-physical characterization of novel multifunctional nanoparticle coatings suitable for application on stone materials of cultural heritage interest

Summary

Introduction

Both natural and man-made stone materials, used in the field of cultural heritage, undergo a weathering process of deterioration when exposed to outdoor conditions. Biocides are usually toxic and can be subject to environmental stresses, due to temperature excursion, UV radiation, and rains, leading to a reduced efficacy [7,8,9,10]. These interventions need frequent re-applications (every 6 months-one year), implying relevant costs for private and public sectors [6]; requiring the search for an innovative approach. Encapsulation of biocides into nanocontainers dispersed in a coating formulation can be a good strategy for managing the release of the biocide compounds, reducing, at the same time, their environmental degradation and toxic effects [11,12,13,14]

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Results

Conclusion