350 d digital camera

The fluorescence spectra were obtained on a PerkinElmer LS-55 luminescence spectrometer. Mass spectra were recorded on a Thermo Proteome X-LTQ MS. ¹H-NMR spectrum was acquired on a Brucker Avance 400 MHz, using CDCl₃ as solvent and tetramethylsilane (TMS) as internal standard. Fluorescence photos were taken under a UV lamp, with a Canon 350D digital camera.

Citric acid, polyethylenimine (M = 600), ethanol and all metal salts were supplied by Sinopharm Chemical Reagent Company, Ltd. (Shanghai, China). P-phenylenediamine (p-PDA) was purchased from Sigma-Aldrich. All chemicals were used as received without further purification unless otherwise specified. Ultrapure water (18.2 MΩ cm) was produced with a Millipore water purification system.
Fluorescence measurement was recorded on a Perkin-Elmer LS-55 luminescence spectrometer (Liantriant, UK). The structures and morphologies of CDs were examined using a JEOL 2010 transmission electron microscope. The UV-visible absorption spectra were obtained with a Shimadzu UV-2550 spectrometer. Infrared spectra of infrared spectra of the dried CDs etc. dispersed in KBr pellets were recorded on a Thermo-Fisher Nicolet iS10 FT-IR spectrometer. Fluorescent photos were taken under AGL-9406 portable UV lamp (254 nm) by a Canon 350 D digital camera.

p-Phenylenediamine (p-PDA) and (3-aminopropyl)trimethoxysilane (APTMS) were purchased from Aldrich. Sodium citrate, NaOH, H₂SO₄, ethanol and all the metal salts were supplied by Sinopharm Chemical Reagent Company, Ltd (Shanghai, China). All chemicals were used as received without further purification unless otherwise specified. Ultrapure water (18.2 MΩ cm) was prepared with a Millipore water purification system.
The structure and morphology were examined using a JEOL 2010 transmission electron microscope. Fluorescence spectra were recorded with a Cary Eclipse fluorescent spectrophotometer. The UV–visible absorption spectra were obtained with a Shimadzu UV-2550 spectrometer. Fourier transform infrared (FT-IR) spectra were obtained with a Thermo Fisher Nicolet iS10 FT-IR spectrometer. X-ray photoelectron spectroscopy (XPS) measurements were carried out with a Thermo ESCALAB 250 high performance electron spectrometer with Al Kα (1486.6 eV) radiation. Fluorescent photos were taken under an AGL-9406 portable UV lamp (365 nm) by a Canon 350 D digital camera.