Development and characterization of negative air ion emitting mica- and sericite-based antimicrobial pearlescent pigments

In modern era, people are spending their time indoors around 90%. Therefore, in terms of public health, increasing indoor air quality is of great importance. In this study, it was aimed to develop pearlescent pigments that emit negative air ions in order to increase indoor air quality, and the potential of such pigments for use in composite wall paint was evaluated. For this purpose, low refractive index muscovite mica and sericite clay minerals, which were shown to emit negative ions, were combined with high refractive index TiO2. The use of two different clay minerals, different proportions of SnO2 dopant, and calcination process application were selected as experimental parameters and the effect of these parameters on the anatase-rutile phase transformation of TiO2 in the pigments was investigated. Increasing the rutile TiO2 ratio in the synthesized pigments were resulted in a better pearlescent effect and lower photocatalytic activity. In order to increase the negative air ion emitting effect of these pigments with the desired pearlescent pigment properties, these samples were also combined with extract of the Chlorophytum comosum, which also is known to emit negative air ions. As a result of the negative ion emission measurements, it was found that the samples were continued to emit negative ions without a time-dependent decrease even when not combined with the extract of C. comosum. In addition, it was showed that the prepared samples have antibacterial effect against Escherichia coli, which is abundant in indoor environments, especially in health centers such as hospitals and dispensaries, and antifungal effect against Aspergillus niger, which is known as black mold, growing on moist walls.