1：Experimental Design and Method Selection:

The study involved synthesizing N-GQD by hydrothermal treatment, optimizing nitrogen doping for ROS generation, conjugating APTES for charge-reversal, and evaluating drug delivery and PDT efficacy using various spectroscopic and imaging techniques.

2：Sample Selection and Data Sources:

Breast cancer cell line MDA-MB-231 was used, sourced from ATCC. Reagents were purchased from Sigma-Aldrich, Thermo Fisher Scientific, Alfa Aesar, Bio-Rad, MP Biomedicals, and MYM Biological Technology.

3：List of Experimental Equipment and Materials:

Equipment included SpectraMax M5 Microplate Reader, JEOL JEM2100F TEM, InnoRam-785S Raman system, Nano ZS Zetasizer, PerkinElmer Victor 3 plate reader, Zeiss Axiovert S100 and Axio Observer Z1 microscopes, Elmasonic sonicator. Materials included citric acid, dicyandiamide, DCFDA, DOX, APTES, DMSO, DHE, AgNO3, NaOH, Triton X-100, HH, dialysis membrane.

4：Experimental Procedures and Operational Workflow:

Steps included synthesis of GQD and N-GQD, DOX loading, APTES conjugation, in vitro drug release studies, MTT assays for cytotoxicity, ROS measurement using DCFDA and DHE, fluorescence imaging for intracellular and nuclear accumulation.

5：Data Analysis Methods:

Data were analyzed using UV-Vis and fluorescence spectroscopy, Raman spectroscopy, zeta potential measurements, MTT assay for cell viability, and image analysis with ZEN software.