Solvent effect on the absorption and emission spectra of carbon dots: evaluation of ground and excited state dipole moment

Parisa Mohammad-Jafarieh,Rahman Salamat-Ahangari,Abolfazl Akbarzadeh,Kazem Jamshidi-Ghaleh,Mohammad Pourhassan-Moghaddam

doi:10.1186/s13065-021-00779-6

Parisa Mohammad-Jafarieh, Rahman Salamat-Ahangari + Show 3 more

Open Access

https://doi.org/10.1186/s13065-021-00779-6

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Abstract

BackgroundCarbon dots (C-dots) are photoluminescent nanoparticles with less than 10 nm in size. Today, many studies are performed to exploit the photoluminescence (PL) property of carbon dots, and our focus in this study is to estimate the dipole moment of carbon dots. For reaching our aims, C-dots were synthesized and dissolved in the different solvents.ResultsCarbon dots with intense photoluminescence properties have been synthesized by a one-step hydrothermal method from a carbon bio-source. In this research, we report on the effect of aprotic solvents on absorption and fluorescence spectra and dipole moments of C-dots dispersed in a range of many aprotic solvents with various polarity and dielectric constant at room temperature. The change in the value of dipole moment was estimated by using the Stokes shifts. The difference between the dipole moment of the excited state and the ground state was shown using an extended form of Lippert equations by Kawski and co-workers.ConclusionsThe values found for μg = 1.077 D, and μe = 3.157 D, as well as the change in the dipole moments. The results showed that the dipole moment of the excited state is more than the ground state, indicating a high density and redistribution of electrons in the excited state. Finally, the quantum yield of C-dots in the eclectic aprotic solvents was communicated and discussed.

Highlights

Carbon-based nanomaterials such as carbon nanotubes, fullerene and graphene have poor solubility in water and lack strong fluorescence in the visible area, limiting their applications [1]
The UV–vis absorption spectra of the Carbon dots (C-dots) were observed in the UV region with maximum absorption at 237–256 nm and a tail extending into the visible range (Fig. 1)
One possible reason for the PL behaviour is the presence of different particle sizes of C-dots; and the different distribution of C-dots surface energy traps, the nature of the surface, and the presence of numerous functional groups on the surface of the C-dots may result in a series of emissive traps between π and π* of C–C. [37]

Summary

Introduction

Carbon-based nanomaterials such as carbon nanotubes, fullerene and graphene have poor solubility in water and lack strong fluorescence in the visible area, limiting their applications [1]. C-dots are heavily fluorescent, non-blinking, water soluble, chemically stable and can be synthesized Owing to their physicochemical properties, C-dots can take part in the chemiluminescence reaction as oxidants, Mohammad‐Jafarieh et al BMC Chemistry (2021) 15:53 emitting species, energy acceptors of chemical reaction energy or even as catalyst involving in different chemiluminescence systems [14, 15]. No single theory can be used for a quantitative explanation of the effects of the environment on fluorescence Explanation of these effects depends on polarity considerations and on the structure of the C-dots and the types of chemical interactions it can experience with other near molecules. C-dots were synthesized and dissolved in the different solvents

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