Rf 5301 spectrometer

Fluorescence spectroscopy was carried out in a DMSO/H₂O ∼ HEPES buffer (80/20, v/v; pH 7.23) solution on a Shimadzu RF-5301 spectrometer. Any changes in the fluorescence spectra of the synthesized compound were recorded upon the addition of perchlorate salts while keeping the ligand concentration constant (2.0 × 10⁻⁵ M) in all experiments. The perchlorate salts of the ions (Fe³⁺, Hg²⁺, Ca²⁺, Cu²⁺, Co²⁺, Ni²⁺, Cd²⁺, Pb²⁺, Zn²⁺, Cr³⁺, and Mg²⁺) were used for the fluorescence experiments.
For ¹H NMR titrations, the solution of L and Zn²⁺ were prepared in DMSO-d_6. Aliquots of the solutions were mixed directly in the NMR tubes d₆-DMSO.

2,2’-OEtBP4 was synthesized according to our previously reported method [47 (link)]. P and B were purchased from Shanghai Aladdin Bio-Chem Technology Co.,LTD. ¹H NMR and ¹³C NMR spectra were recorded on a Bruker AV500 instrument. The fluorescence emission spectra were determined with a SHIMADZU RF5301 spectrometer. Deuterated phosphate buffer solutions (20 mM) of pD 7.4 for ¹H NMR experiments were prepared by mixing K₂DPO₄ deuterium oxide solution (20 mM) and KD₂PO₄ deuterium oxide solution (20 mM) according to the calculated volume ratios. The pH/pD values of the buffer solutions were verified on a pH-meter calibrated with two standard buffer solutions.

Transmission electron microscopy (TEM) images were obtained with a JEM2100F high-resolution transmission electron microscope (JEOL, Tokyo, Japan) at an acceleration voltage of 200 kV. All measurements of fluorescence were performed under a 360 nm excitation wavelength. All samples were decanted in a standard 1 cm pathway spectrophotometric cuvette. The fluorescence signal corresponded the maximum emission of GQDs well at 466 nm. Records were obtained on a Shimadzu RF-5301 spectrometer (Shimadzu, Kyoto, Japan). Optical measurements were done in aqueous solutions at room temperature.