Synthesis and applications of a  colorimetric sensor based on polyethyleneimine doped graphene quantum dots nanoparticles directed to cations

B. Boyacioglu1, H. Ünver2, M. Yıldız3, Neslihan Demir4, Nuray Yıldırım5, Ayhan Elmalı6
1Vocational School of Health Services, Ankara University, TR-06290 Kecioren-Ankara, Turkey
E-mail: email.of. corresponding_bboyacioglu@ankara.edu.tr
2Department of Physics, Faculty of Sciences, University of Ankara, TR-06100 Besevler-Ankara, Turkey
3Department of Chemistry, Faculty of Sciences and Arts, Çanakkale Onsekiz Mart University, TR-17100 Çanakkale, Turkey
4Department of Biology, Faculty of Arts and Sciences, Çanakkale Onsekiz Mart University, 17100 Çanakkale, Turkey
5Vocational School of Health Services, Çanakkale Onsekiz Mart University, 17100 Çanakkale, Turkey
6Department of Physics Engineering, Faculty of Engineering, Ankara University, TR-06100, Beşevler , Turkey

Graphene quantum dots (GQDs) have received enormous attention because of their unique chemical, electronic and optical properties. They also show good biocompatibility, excellent water solubility and stable photoluminescence [1,2]. N-doped GQDs were prepared by hydrothermal reaction using citric acid (CA) and an N-containing base such as polyethyleneimine [3]. 
The nanoparticles (GQDs) exhibited highly selective recognition for Fe2+, Co2+, Cu2+, Zn2+ and Fe3+ among a wide range of metal ions tested in water. In the presence of these cations, the sensor underwent a dramatic color change from Brown, green to yellow, while the presence of other metal cations such as Mn2+, Ni2+, Cr3+, Cd2+, Hg2+ and Pb2+ illustrated no effect on the colour. Moreover, the antimicrobial activities of nanoparticles were tested for its minimum inhibitory concentration (MIC), and the interactions with DNA was investigated using UV-Visible spectroscopy and gel electrophoresis. 
 
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