Green Synthesis of Carbon Dots and Their Application as Photocatalyst in Dye Degradation Studies
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RESEARCH ARTICLE-CHEMISTRY
Green Synthesis of Carbon Dots and Their Application as Photocatalyst in Dye Degradation Studies Maria Zaib1
· Ammama Akhtar1 · Faseeha Maqsood1 · Tayyaba Shahzadi1
Received: 27 March 2020 / Accepted: 19 August 2020 © King Fahd University of Petroleum & Minerals 2020
Abstract This paper presents work on green synthesis of the carbon dots from leaves of Elettaria cardamomum (E.C) using simple ultrasonication technique. In X-ray diffraction analysis, peak at 2θ value of 22.9° confirmed the amorphous nature of synthesized carbon dots. Furthermore, Raman investigations of the synthesized carbon dots illustrated D and G band at 1365 cm−1 and 1575 cm−1 , respectively, showing graphitic structure of carbon dots. Similarly, Fourier transform infrared spectrum of carbon dots confirmed the presence of different functional groups such as C=O, C=C, OH, C–OH at absorption peaks values of 1715 cm−1 , 1634 cm−1 , 3257 cm−1 and 1027 cm−1 , respectively. Photoluminescence spectral analysis of carbon dots confirms photoluminescent nature by exhibiting two emission peaks at 520 nm and 850 nm, respectively. UV–visible spectrophotometric investigations confirmed the presence of carbon dots showing two absorption peaks at 220 nm and 272 nm. After confirmation and characterization, the synthesized carbon dots were utilized for studying visible light-induced degradation of congo red and methylene blue dyes. This further investigation showed that the maximum degradation of congo red dye was observed in acidic media at pH 4 with a dye concentration of 5 ppm in a time interval of 50 min. For methylene blue dye, optimum degradation was observed in alkaline medium at a pH value of 8 with 5 ppm dye concentration in a time interval of 55 min. Keywords Carbon dots · Green synthesis · Dye degradation · Methylene blue dye · Congo red dye
1 Introduction Carbon dots (CDs) are considered as the new member of carbon-based material class, with tolerable proportion of hydrogen, oxygen and mostly sp2 hybridized carbon atoms in nature. They have a size up to or lesser than 10 nm. Their low-cost and easy preparation approaches are resulting in their countless applications [1, 2]. The comparison of carbon dots with the metal-based quantum dots (QDs) revealed that carbon dots have preferable properties over the metal-based quantum dots due to their aqueous soluble nature, easy functionalization, chemical inactivity, less perniciousness, suitable biocompatibility and fluorescence features [3]. On the other hand, QDs yet show controlled applications in many fields. These are costly materials and showed toxicity issues especially in biomedi-
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Maria Zaib [email protected]
cal applications. Contrary to quantum dots the carbon dots can now be mostly synthesized by using low-cost natural materials and one step methodologies especially applying green synthesis techniques. Therefore, they are becoming alternative of quantum dots in different application in order to decrease the use of heavy metals [4]. However, the conventio
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