Carbon Quantum Dots from Coconut Husk: Green Synthesis and Evaluation of Antioxidant and Cytotoxic Activity L A Avinash Chunduri, Aditya Kurdekar, Sandeep Patnaik, Vishnu Dev B, Tanu Mimani Rattan, Venkataramaniah Kamisetti* Department of Physics, Sri Sathya Sai Institute of Higher Learning, Prasanthi Nilayam, A.P., India.
Objectives •
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Photoluminescence Spectroscopy
Green synthesis of Carbon Quantum Dots (CQDs) by a single hydrothermal carbonization from coconut husk To study their structural and optical properties of these CQDs To evaluate their antioxidant and cytotoxic activity
Experiment • • • •
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Carbon dots are prepared from coconut fiber by hydrothermal treatment in a single step. In a typical synthesis 2 gm. of coconut fiber powder was added to 100 ml of Millipore water. This mixture was transferred into a 100 ml Teflon lined autoclave and heated at 200ºC for 3 hours. The fluorescent carbon dots were separated through centrifugation at 15000 rpm and resulting solution was lyophilized to obtain solid CQDs. The CDs were dispersed in distilled water at a conc. of 0.5 mg/ml and used for all the characterizations.
a) Photoluminescence excitation and emission spectra of carbon quantum dots in aqueous solutions. b) Emission spectra of CQDs various excitation wave lengths
Tranmission Electron Microscopy
a) Fluorescence spectra of CQDs with variation in pH b) Fluorescence intensity variation with pH (pH sensor)
FTIR and UV-vis Spectroscopy a) HRTEM image of CQDs synthesized from coconut husk b) size distribution histogram obtained from the TEM image c) Lattice fringes and d) Electron diffraction pattern of CQDs
XRD and Raman Spectroscopy
- OH
G band
- OH D band
- COOH
a) XRD pattern and b) Raman spectrum of CQDs from coconut husk
DPPH assay
a) FTIR spectrum and 3b) UV-vis spectrum of carbon quantum dots and inset with photographs under b) white light (brown color) and UV lamp 365 nm (blue color)
Conclusions
Hemolysis assay •
Water soluble, surface passivated and stable Fluorescent CQDs were successfully synthesised by one step hydrothermal carbonisation from coconut husk.
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TEM, XRD data confirmed the crystalline nature of CQDs and Raman spectra confirmed formation of low
EC50 =60µg/mL
dimensional carbon nanostructures. •
The pH sensitive emission can be explored for pH sensor applications
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The antioxidant and non cytotoxic properties of these CQDs can exploited for bio imaging and drug delivery
DPPH - free radical scavenging assay of CQDs
% of cell hemolysis for various CQDs concentrations
applications.
Acknowledgements
Authors thank Bhagawan sri Sathya Sai Baba for his constant inspiration. Avinash is grateful to UGC for sponsoring UGC BSR fellowship for his research.