Deep Fluorescence Solvatochromic Study of Nitrogen Doped Carbon Dots: Polar Sensitive Nanoprobe application

Document Type : Original Article

Authors

1 Department of Organic Colorant, Institute for Color Science and Technology, , P. O. Box: 167654-654, Tehran, Iran

2 Department of Organic Colorant, Institute for Color Science and Technology, Tehran, Iran

3 Department of Surface Coating and Corrosion, Institute for Color Science and Technology, Tehran, Iran

Abstract

In this research, we synthesized nitrogen-doped carbon dots using three isomers of phenylenediamine (o-PDA, m-PDA, and p-PDA). The carbon dots produced contain nitrogen, carboxyl, and hydroxyl groups that interact with the environment and exhibit a change in emission based on the surroundings. Our team conducted an in-depth analysis of the fluorescence emissions exhibited by carbon dots. The study involved examining the behavior of these particles in solvents with varying degrees of polarity, ranging from weakly polar CHCl3 to strongly polar protic water and a binary mixture of H2O-Acetone. The results of the study provide valuable insights that could contribute to advancing our understanding of carbon dots properties. Interestingly, with increasing the water content of organic solvents, the carbon dots changed their fluorescence color from blue to green. We utilized the Lippert-Mataga plot to exhibit a direct correlation between polarity and carbon dots emission wavelength, which demonstrated a positive linear trend as the polarity was increased. The slope for the three isomers was ∆µ=38959, 42115, 2346.5 for O-CD, M-CD and P-CD, respectively. Our results confirm that the polarity of CDs in ground state is less than exited state (μg < μex). We also analyzed the optical properties of M-CD and found a linear response to the polarity and water content of the organic solvent, which suggests the possibility of M-CD as a humidity sensor for detecting water in organic solvents.

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