An X-ray diffractometer
[Ultima IV Rigaku, USA, 18 kW with the rotating anode source Cu Kα1 line (λ = 1.54 Å)] was used to identify
the crystal structure of CDs. Raman spectra [MRS-320 Raman Instrument
system (Horiba Ltd, Japan)] identified the molecular interaction of
CDs at an excitation wavelength of 532 nm. A Fourier transform infrared
spectrophotometer [model IR Tracer-100 (Shimadzu, Japan)] was used
to analyze the functional groups of CDs with the wavenumber ranging
from 4000 to 400 cm–1 using the potassium bromide
(KBr) pellet technique. A X-ray photoelectron spectrometer [Escalab
250Xi spectrometer with an Al Kα radiation (hυ = 1486.6
eV)] determined the composition of CDs. A spectrofluorometer (FluoroMax-4)
and a UV–vis spectrophotometer (Shimadzu UV-1800) were used
to measure fluorescence and absorbance spectra, respectively. The
PL of the HA CDs was measured comparatively by referring to rhodamine
6G [R6G, QY (95%)]; the % QY of HA CDs was determined by the following
equation where I, A, and η are the integral PL intensity,
UV absorbance and the
optical density, and solvent reflective index, respectively.
[Ultima IV Rigaku, USA, 18 kW with the rotating anode source Cu Kα1 line (λ = 1.54 Å)] was used to identify
the crystal structure of CDs. Raman spectra [MRS-320 Raman Instrument
system (Horiba Ltd, Japan)] identified the molecular interaction of
CDs at an excitation wavelength of 532 nm. A Fourier transform infrared
spectrophotometer [model IR Tracer-100 (Shimadzu, Japan)] was used
to analyze the functional groups of CDs with the wavenumber ranging
from 4000 to 400 cm–1 using the potassium bromide
(KBr) pellet technique. A X-ray photoelectron spectrometer [Escalab
250Xi spectrometer with an Al Kα radiation (hυ = 1486.6
eV)] determined the composition of CDs. A spectrofluorometer (FluoroMax-4)
and a UV–vis spectrophotometer (Shimadzu UV-1800) were used
to measure fluorescence and absorbance spectra, respectively. The
PL of the HA CDs was measured comparatively by referring to rhodamine
6G [R6G, QY (95%)]; the % QY of HA CDs was determined by the following
equation where I, A, and η are the integral PL intensity,
UV absorbance and the
optical density, and solvent reflective index, respectively.