Effects of the Surface Charge Density of Clay Minerals on Surface-Fixation Induced Emission of Acridinium Derivatives

Yuma Yoshida; Tetsuya Shimada; Tamao Ishida; Shinsuke Takagi

doi:10.1021/acsomega.1c03157

Effects of the Surface Charge Density of Clay Minerals on Surface-Fixation Induced Emission of Acridinium Derivatives

ACS Omega. 2021 Aug 13;6(33):21702-21708. doi: 10.1021/acsomega.1c03157. eCollection 2021 Aug 24.

Authors

Yuma Yoshida¹, Tetsuya Shimada¹, Tamao Ishida^{1

2

3}, Shinsuke Takagi^{1

3}

Affiliations

¹ Department of Applied Chemistry for Environment, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji-shi, Tokyo 192-0397, Japan.
² Research Center for Gold Chemistry, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachiohji-shi, Tokyo 192-0397, Japan.
³ Research Center for Hydrogen Energy-based Society (ReHES), Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachiohji-shi, Tokyo 192-0397, Japan.

Abstract

Surface-fixation induced emission is a fluorescence enhancement phenomenon, which is expressed when dye molecules satisfy a specific adsorption condition on the anionic clay surface. The photophysical behaviors of two types of cationic acridinium derivatives [10-methylacridinium perchlorate (Acr⁺) and 10-methyl-9-phenylacridinium perchlorate (PhAcr⁺)] on the synthetic saponites with different anionic charge densities were investigated. Under the suitable conditions, the fluorescence quantum yield (Φ_f) of PhAcr⁺ was enhanced 22.3 times by the complex formation with saponite compared to that in water without saponite. As the inter-negative charge distance of saponite increased from 1.04 to 1.54 nm, the Φ_f of PhAcr⁺ increased 1.25 times. In addition, the increase in the negative charge distance caused the increase in the integral value of the extinction coefficient and the radiative deactivation rate constant (k _f) and the decrease in the nonradiative deactivation rate constant. It should be noted that the 2.3 times increase in k _f is the highest among the reported values for the effect of clay. From these results, it was concluded that the photophysical properties of dyes can be modulated by changing the charge density of clay minerals.