research

1. A.P. Sunitha1 *, Praveen P.2, K. Sandeep3, K . J. Saji2,4,5
1 Dept. of Physics, Govt. Victoria College, Palakkad, Kerala-678001, India
2 International School of Photonics, Cochin University of Science and Technology, Kochi-682022, India
3Dept. of Chemistry, Govt. Victoria College, Palakkad, Kerala-678001, India
4Centre of Excellence in Advanced Materials, Cochin University of Science and Technology, Kochi, 682022, India
5Inter-University Centre for Nanomaterials and Devices, Cochin University of Science and Technology, Kochi, 682022, India, * Corresponding Author: sunivictoria82@gmail.com
Upconverting Carbon Quantum Dots for Photovoltaic Applications
Abstract
•40 ml each of lemon and onion extract was filtered out and subjected to
microwave treatment at 200 0 C for 35 min.
•The resultant solution was centrifuged at 8000 rpm for 10 min. The clear
brown colored solution was filtered out from the bulk remnant.
In the present work, the synthesis, characterization and application of CQDs through green route have been discussed. The carbon quantum dots are
characterized by dynamic light scattering, transmission electron microscopy, absorption spectroscopy, photoluminescence spectroscopy and found blue
luminescent emission. The size was observed to be less than 10 nm. The sample can be modified and applied to bioimaging.
•Growth of carbon quantum dots (QDs) from natural extracts
•Study of optical transitions in absorbance spectra of carbon QD solution
•Study Photon upconversion and downconversion photoluminescence
•Study of life time of excited states
Experimental:Objectives:
Estimation of the size of carbon QDs by DLS and TEM Photoluminescence decay with PH variation
Photon upconversion, downconversion photoluminescence and time resolved PL of carbon quantum dots
Carbon quantum dots properties Absorption spectra of carbon QDs
 CQDs were produced by cost effective solution method
 transition corresponding to QDs were observed in absorption spectra
 Size of the QDs were estimated by DLS in range less than 10 nm
 Photon upconversion PL emission peaking at 438 nm and downconversion PL emission peaking around 438 nm
 Life time of excited state as estimated by time resolved PL is 3.88 ns on three exponential fit
Conclusions
Acknowledgement:
KJS thank Cochin University of Science and Technology for financial
support under SMNRI scheme.
Future Prospects:
•Development CQD based solar cells
• Development bioimaging devices
Carbon quantum dots
Upconversion PL Downconversion PL
400 500 600
300
450
600
Intensity(a.u)
Wavelength, nm
Excitation 695 nm
400 500 600
2500
5000
7500
10000
Intensity(a.u.)
Wavelength, nm
Excitation 335 nm
400 500
2500
5000
7500
basic
neutral
Intensity(a.u.)
Wavelength, nm
acidic
 Luminescent Carbon quantum
dots can be applied for
developing bioimaging devices
Upconverting carbon quantum
dots are smart materials for
energy harvesting, when
incorporated in solar cells for
exploring the IR window.