Green synthesis of silane-assisted fluorescent carbon dots based on sanding dusts and its application in flame-retardant and anti-leaching wood materials

Novel silane-assisted flame-retardant carbon dots (FR-CDs) were synthesized via the hydrothermal carbonization strategy using recycled wood sanding dusts, tris(hydroxymethyl) phosphine oxide (THPO), phosphoric acid (PA), and amino-silane as precursors. The highly transparent FR-CDs suspension appears pale yellow color under daylight and exhibits a strong fluorescence response to light excitations, which helps to keep the original color of the wood and also has broad application prospects for monitoring the leaching behavior of FR-wood. The as-prepared FR-CDs can be applied in FR-wood materials using the facile dipping process owing to their tiny nanoparticles, uniform dispersion, and numerous nitrogen–phosphorus groups. In the flame test, the FR-CDs treated wood composites emitted little smoke initially and maintained primary carbon layer that did not catch fire for over 180 s. The flame-retardancy of the FR-wood materials was confirmed by the thermo-analysis, limiting oxygen index, exposure to a high heat flux (50 kW/cm2), and the propane blowtorch tests (∼600 °C). Moreover, the formation mechanism of the silane-assisted FR-CDs during hydrothermal process and the FR-wood materials with dipping method was proposed. This study provides a facile and efficient strategy for developing highly transparent and cheap flame retardants for the wood materials, which could expand the application of the wood sanding dusts and the silane-assisted carbon-based nanomaterials in the design of anti-leaching flame-retardant materials.