Changes in Optical Properties upon Dye–Clay Interaction: Experimental Evaluation and Applications

Abstract

The development of hybrid materials with unique optical properties has been a challenge for the creation of high-performance composites. The improved photophysical and photochemical properties observed when fluorophores interact with clay minerals, as well as the accessibility and easy handling of such natural materials, make these nanocomposites attractive for designing novel optical hybrid materials. Here, we present a method of promoting this interaction by conjugating dyes with chitosan. The fluorescent properties of conjugated dye–montmorillonite (MMT) hybrids were similar to those of free dye–MMT hybrids. Moreover, we analyzed the relationship between the changes in optical properties of the dye interacting with clay and its structure and defined the physical and chemical mechanisms that take place upon dye–MMT interactions leading to the optical changes. Conjugation to chitosan additionally ensures stable adsorption on clay nanoplatelets due to the strong electrostatic interaction between chitosan and clay. This work thus provides a method to facilitate the design of solid-state hybrid nanomaterials relevant for potential applications in bioimaging, sensing and optical purposes.

Metal-Modified Montmorillonite as Plasmonic Microstructure for Direct Protein Detection

“…In this study, the effect of combining metallic structures and MMT is particularly evident considering the low enhancement observed with the MMT. As observed in our previous work [9], the fluorescent enhancement achieved using MMT is related to the amount of clay employed as well as to the concentration of the dye. In this work, we used a low concentration of MMT (0.1 wt%) and pico-and nano-molar concentrations of FITC.…”

“…The changes in the optical properties of dyes upon interaction with MMT are well documented in other papers. The fluorescent enhancement observed with MMT has been mainly associated with the restriction of intermolecular rotation (RIR) and aggregation-induced emission (AIE) phenomenon which can occur after dye-particle interaction [9]. However, the mechanism of signal harvesting varies depending on the optical and physical properties of the molecules studied as we discussed in our previous work.…”

“…However, the mechanism of signal harvesting varies depending on the optical and physical properties of the molecules studied as we discussed in our previous work. Taking advantage of the remarkable fluorescent enhancement achieved after dye-MMT interaction, we recently proposed the use of clay-organic hybrids for the development of fluorescence-based platforms for sensing biological compounds [9].…”

Adsorption of Dye Molecules and Its Potential for the Development of Photoactive Hybrid Materials Based on Layered Silicates

“…Very common and effective methods include the functionalization with adsorbed cationic surfactants or polyelectrolytes. In this way, it is possible to achieve the adsorption of even anionic or neutral chromophores. − Using the modification of silicates with oppositely charged polyelectrolyte or surfactant molecules, it is possible to tune the surface charge of silicates . In addition to the regulation of their charge, hydrophilic vs hydrophobic properties of the silicate surfaces can also be controlled by the adsorption of surfactants. , …”

“…This well-known solvatochromic dye has been considered as a nonluminescent zwitterionic substance with negatively charged phenolate and positively charged pyridinium groups in its aqueous solution. As it was already mentioned earlier, in order to have systems applicable for neutral dyes, it is necessary to modify the surface of the silicate particles through the adsorption of polyelectrolytes , or surfactants . These types of surface functionalization of the silicate substrate can help to achieve such desired properties as the controlled charge density and topography of the surface.…”