TY - JOUR
T1 - Exploring the Emissive States of Heteroatom-Doped Graphene Quantum Dots
AU - Yang, Guancao
AU - Wu, Chuanli
AU - Luo, Xiaojun
AU - Liu, Xiaoyan
AU - Gao, Yuan
AU - Wu, Ping
AU - Cai, Chenxin
AU - Scott Saavedra, S.
N1 - Funding Information:
This work is supported by the NSFC (21335004, 21405083, and 21675088) and Priority Academic Program Development of Jiangsu Higher Education Institutions.
Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/3/22
Y1 - 2018/3/22
N2 - The photoluminescence (PL) emission states of heteroatom-doped graphene quantum dots (GQDs) remain unknown, particularly the assignment of the low-energy excitation band (more than 330 nm). To address these issues, this work synthesized three different types of GQDs: undoped GQDs (UGQDs), nitrogen-doped GQDs (NGQDs), and boron-doped GQDs (BGQDs), with similar sizes, chemical compositions (types and compositions of surface functional groups), and defects using a constant potential electrolysis method. The PL emissive states in these GQDs and the effects of the dopant heteroatom on the PL were revealed based on the combination of spectroscopic methods and theoretical calculations. The results indicated that the GQDs exhibit multiemissive centers for the PL emission mechanism. An excitation-independent PL emission band (band I) results from a high-energy transition originating from the quantum confinement of the carbon core (carbon π-π∗ transitions in sp2 domain), and an excitation-dependent PL emission band (band II) originates from a low-energy edge band transition, which is attributed to radiative recombination associated with both the n-π∗ transition of N/O/B-containing groups and the π-π∗ charge transfer between the carbon core and the edge of the GQDs. Moreover, the PL emission maxima (both bands I and II) for NGQDs and BGQDs show a blue shift and a red shift, respectively, relative to UGQDs because of the doping that led to the alteration in the electronic structure and the distribution of molecular orbitals in the GQDs. These results clarify previous inconsistencies regarding the PL emission mechanism and the electronic properties of GQDs and can thus provide a foundation for the application of doped GQDs in electronics, photonics, and biology.
AB - The photoluminescence (PL) emission states of heteroatom-doped graphene quantum dots (GQDs) remain unknown, particularly the assignment of the low-energy excitation band (more than 330 nm). To address these issues, this work synthesized three different types of GQDs: undoped GQDs (UGQDs), nitrogen-doped GQDs (NGQDs), and boron-doped GQDs (BGQDs), with similar sizes, chemical compositions (types and compositions of surface functional groups), and defects using a constant potential electrolysis method. The PL emissive states in these GQDs and the effects of the dopant heteroatom on the PL were revealed based on the combination of spectroscopic methods and theoretical calculations. The results indicated that the GQDs exhibit multiemissive centers for the PL emission mechanism. An excitation-independent PL emission band (band I) results from a high-energy transition originating from the quantum confinement of the carbon core (carbon π-π∗ transitions in sp2 domain), and an excitation-dependent PL emission band (band II) originates from a low-energy edge band transition, which is attributed to radiative recombination associated with both the n-π∗ transition of N/O/B-containing groups and the π-π∗ charge transfer between the carbon core and the edge of the GQDs. Moreover, the PL emission maxima (both bands I and II) for NGQDs and BGQDs show a blue shift and a red shift, respectively, relative to UGQDs because of the doping that led to the alteration in the electronic structure and the distribution of molecular orbitals in the GQDs. These results clarify previous inconsistencies regarding the PL emission mechanism and the electronic properties of GQDs and can thus provide a foundation for the application of doped GQDs in electronics, photonics, and biology.
UR - http://www.scopus.com/inward/record.url?scp=85044381087&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85044381087&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.8b01385
DO - 10.1021/acs.jpcc.8b01385
M3 - Article
AN - SCOPUS:85044381087
SN - 1932-7447
VL - 122
SP - 6483
EP - 6492
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 11
ER -