posted on 2017-08-23, 00:00authored bySayan Bayan, Anupam Midya, Narendar Gogurla, Achintya Singha, Samit K. Ray
We
report on the tuning of luminescence response of few layered graphitic
carbon nitride (g-C3N4) nanosheets by reducing
the functional groups though chemical reduction. The nanosheets of
g-C3N4 have been obtained from its bulk counterpart
through liquid phase exfoliation, while the attached functional groups
have been removed through sodium borohydride treatment. X-ray photoelectron
and micro Raman studies indicate the improved aromatization through
the removal of the functional groups, while structural defect formation
has been realized at higher reduction levels. It has been found that
the increase in sp2 C–N cluster size as a result
of improved aromatization leads to the enhanced absorption through
π → π* transition. Consequently, the luminescence
response has been found to increase at the lower reduction level.
On the other hand, near-ultraviolet emission and suppressed visible
emission has been witnessed at higher reduction levels. The improvement
in near-ultraviolet emission originates from the modified density
of states which favors the transitions involving δ* and N lone
pair states. Better understanding of the reduction mechanism can lead
to the fabrication of prototype flexible light emitting devices that
can emit light in the ultraviolet as well as the visible region of
the spectrum.