C11347 11

The detailed morphology, size distribution, absorption, composition ratio, and PL for QDs were characterized by a transmission electron microscope (TEM) with an acceleration voltage of 200 kV, UV visible spectroscopy, X-ray diffraction (XRD), energy-dispersive x-ray spectroscopy (EDX) line-scan profile, and photo-luminescence spectroscopy using a HeCd laser source with a 325 nm wavelength. FWHM and absolute PL quantum yield were measured by QE-2100 (Otsuka electronics), and those were cross-checked with photo-luminescence spectroscopy using organic dyes (Rhodamine 6 G, QY = 95% in ethanol). For quantum yield measurements in photo-luminescence spectroscopy, optical density (i.e. 0.05 absorbance) was adjusted to 0.005 wt% in excitation of 325 nm. In addition, the quantum yield for QDs were confirmed by measuring time-resolve PL decay curves (Hamamatsu C11347-11 using 365-nm LED source and 1 MHz).

The photoluminescence absolute quantum yield (QY) of the prepared g-C₃N₄QDs was measured using an absolute PL quantum yield spectrometer with an integrating sphere (C11347-11, Hamamatsu, Japan) under excitation with a 150 W xenon light source at 325 nm. The test principle and method were referred to ref. 30 and 31 (link). The absolute fluorescence quantum yield = the number of emitted photons/the number of absorbed photons.^{30 (link)}

Bromophenol red (BR), bromophenol blue (BPB) and tetrabromophenol blue (TBPB) were purchased from Shanghai Macklin Biochemical Co., Ltd. Polyvinyl alcohol (PVA, alcoholysis degree 87%) was purchased from Shanghai Aladdin Bio-Chem Technology Co., Ltd. All solvents were purchased commercially and used without further purification. The UV-Vis absorption spectra were obtained on a Cary 60 (Agilent Technologies) spectrophotometer. Fluorescence, phosphorescence and the lifetime of delayed emission spectra were recorded on an Agilent Cary Eclipse spectrophotometer. Phosphorescence mode; delay time = 0.1 ms; gate time = 2.0 ms. Photoluminescence spectra were recorded on the HORIBA FluoroMax-4 spectrometer. Absolute PL quantum yields were determined with a spectrometer C11347-11 (Hamamatsu, Japan).