Objective In the development of environment-friendly wood preservatives, its tracer function is of great significance to the evaluation of wood preservative effect. A new type of wood preservative based on boron doping Ginkgo biloba leaves carbon quantum dots (B-CQDs) was prepared, aiming to make full use of the antifungal properties of Ginkgo biloba leaves, the flame retardant properties of borax and the fluorescent tracer function of carbon quantum dots. B-CQDs will enrich the environment-friendly wood preservative system, and broaden the antifungal properties and fluorescent tracer applications of carbon quantum dots.

Method The wood preservative of B-CQDs were one-step hydrothermal synthesized by green biomass Ginkgo biloba leaves as carbon source and borax as boron dopant. The optimum preparation process was investigated by single factor experiment. It was characterized by fluorescence spectrum, UV-visible spectrum, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The antifungal effects with different mass fractions of B-CQDs were evaluated by antifungal zone test with white rot fungi Trametes versicolor and brown rot fungi Gloeophyllum trabeum as the tested fungi.

Result Taking the fluorescence intensity as the test index, the optimum preparation conditions of B-CQDs were hydrothermal reaction time 3.0 h, hydrothermal reaction temperature 180 ℃, dosage of ginkgo biloba 0.5 g, and mass ratio of Ginkgo biloba leaves to borax 5∶1. B-CQDs were semispherical with better dispersion. The average particle size was 2.41 nm. B-CQDs wood preservatives had excitation wavelength dependence and fluorescence stability, emitting bright blue fluorescence under ultraviolet light at 365 nm. The elements composition and functional group information analyzed by FTIR and XPS were consistent, which indicated that boron elements were successfully incorporated into carbon quantum dots. The results of antifungal zone test of wood rot fungi showed that with the increase of the mass fraction of B-CQDs, the control effect against the two kinds of wood rot fungi had gradually improved. Among them, the antifungal effect of B-CQDs wood preservatives were better than non-doped carbon quantum dots wood preservatives. When the mass fraction of B-CQDs increased to 0.80%, the diameter of the antifungal zone of the two groups reached the maximum, which were 54.15 and 63.59 mm, respectively.

Conclusion The preparation of B-CQDs wood preservative is studied successfully. It has photoluminescence characteristics and fluorescent tracer function. The preservative has good antifungal effect on two kinds of common wood rot fungi (Trametes versicolor and Gloeophyllum trabeum). It has the potential to be used as the environment-friendly wood preservative with the function of fluorescent tracer.