1：Experimental Design and Method Selection:

The study employed a one-pot solvothermal process to synthesize boron-doped carbon dots (B–CDs) using polythiophene-3-boronic acid (PTB) as both carbon and boron source. The rationale was to create a metal-free bimodal probe for fluorescence and MR imaging. Methods included oxidative polymerization for PTB synthesis, solvothermal carbonization for B–CDs preparation, and various characterization techniques.

2：Sample Selection and Data Sources:

Samples included B–CDs, boron-free CDs (prepared from polythiophene without boron), PTB, thiophene-3-boronic acid (TB), boric acid, and boric acid-glucose complex. Biological samples included HeLa cells and nude mice for in vitro and in vivo imaging.

3：List of Experimental Equipment and Materials:

Equipment: Tecnai G2 F20 transmission electron microscope (TEM), Agilent Carry 100 UV-vis spectrophotometer, FL-4600 fluorescence spectrometer (Hitachi, Japan), Thermo ESCALAB 250XI XPS, Bruker Vector 22 FT-IR spectrophotometer, confocal laser fluorescence microscopy (TCS SP5, Leica, Germany), Edinburgh FS920P fluorescence spectrometer,

4：2 T MR imaging system (Huantong, Shanghai, China), small animal in vivo imaging system (NightOWL LB983, Berthold Technologies GmbH & Co. KG, Germany). Materials:

Ferric chloride (FeCl3) from Energy Chemical Co., China; chloroform, methanol, ethanol from Tianjin Fengchuan Chemical reagent technologies, China; thiophene-3-boronic acid (TB) from J&K Scientific, China; ultrathin carbon film based copper TEM substrate from Zhongjingkeyi Technology Co., Ltd., China.

5：Experimental Procedures and Operational Workflow:

Synthesis of PTB via oxidative polymerization using FeCl3 catalyst in CHCl3. Preparation of B–CDs by solvothermal treatment of PTB in ethanol at 170°C for 12 h. Characterization using TEM, UV-vis, fluorescence spectroscopy, XPS, FT-IR. Cell viability test via MTT assay on HeLa cells. In vitro imaging using confocal microscopy. In vivo imaging on nude mice for fluorescence and MR signals.

6：Preparation of B–CDs by solvothermal treatment of PTB in ethanol at 170°C for 12 h. Characterization using TEM, UV-vis, fluorescence spectroscopy, XPS, FT-IR. Cell viability test via MTT assay on HeLa cells. In vitro imaging using confocal microscopy. In vivo imaging on nude mice for fluorescence and MR signals. Data Analysis Methods:

5. Data Analysis Methods: Data analysis included size distribution from TEM images, quantum yield calculation using integrating sphere, relaxivity calculation from MR signals, and statistical analysis for cell viability (mean ± standard deviation).