2 research outputs found
Two-Dimensional Nitrogen-Enriched Carbon Nanosheets with Surface-Enhanced Raman Scattering
We
have fabricated two-dimensional nitrogen-enriched carbon nanosheets
(2D-NECNs) through the pyrolysis of cross-linked polyÂ(4-vinylpyridine)
homopolymers as a platform for detecting physically absorbed dye molecules
using Raman-scattering spectra. Upon pyrolysis, a polymeric layer
consisting of pyridinic rings was converted into a carbonized nanosheet
enriched with pyridinic nitrogen (N<sub>6</sub>), pyrrolic nitrogen
(N<sub>5</sub>), graphitic nitrogen (GN), and nitrogen oxide (NO)
groups, the fractions of which were finely controlled through pyrolysis
at temperatures selected in the range of 430–550 °C. The
effects of temperature on the formation of nitrogen- and carbon-containing
species in 2D-NECN were examined by XPS, which showed that N<sub>6</sub> and N<sub>5</sub> were the dominant species over GN and NO at 430
°C. Increasing the temperature of pyrolysis produced carbonized
nanosheets containing more GN and NO generated at the expense of pyridinic
groups. Using rhodamine 6G (R6G) and crystal violet (CV) molecules
as probes for Raman measurements, we found that the Raman enhancement
on 2D-NECN is due to a chemical mechanism (CM) and that the observed
enhancement of the Raman intensity of molecules adsorbed on 2D-NECN
hence shows a clear dependence on the nitrogen configuration of the
four types. Among the nitrogen species, GN dominates the large enhancement.
The chemical Raman enhancement is ascribed to the ability of GN to
improve the π-conjugated domains and narrow the energy gap in
2D-NECN