In this work, a green and economical strategy to prepare silanized carbon dots (Si-CDs) based on Ficus virens leaves was carried out. The prepared difunctional Si-CDs showed high water-solubility and favorable photostability. The morphology and surface functional groups were analyzed by TEM, FT-IR, and XPS. Si-CDs had amorphous nature with no crystal lattice and the average diameter of 1.95 nm. Some functional groups like nitrogen groups, oxygen groups, and silicon groups were discovered. Attributing to the small size of Si-CDs, positive charges, and the generation of singlet oxygen and hydrogen radicals, Si-CDs possessed effective antibacterial activity. The minimum inhibitory concentration of Si-CDs against Escherichia coli and Staphylococcus aureus was 0.078 mg/mL. Moreover, Si-CDs exhibited selective and sensitive fluorescence quenching response to Fe³⁺ through static quenching process. The limit of detection was 0.84 μmol/L in the liner range of 5–50 μmol/L. Analysis of real samples led to 99.8–102.0% recoveries and <1% relative standard deviation. Consequently, this work discovered a new, green, economical silanized carbon dot with the potential application as a potent antibacterial agent and an effective fluorescent sensor of iron ion.