From Avocado Seed Waste to Green Synthesis Laser-Induced Graphene: A Rapid, Direct, Low Cost and Flame-Retardant-Free Route

Laser-induced graphene (LIG) offers a rapid and versatile route for converting carbon-rich precursors into conductive graphitic materials. However, the direct conversion of lignocellulosic biomass remains challenging because of its heterogeneous composition and thermal degradation behavior. In this work, Fuerte avocado seed ( Persea americana Mill.) waste was investigated as a lignocellulosic precursor for the direct synthesis of LIG using CO₂ laser irradiation without flame retardants or chemical pretreatment. The influence of laser power, scanning speed, number of irradiation passes, inter-irradiation time, processing atmosphere, irradiation area, and precursor particle size was systematically evaluated. Raman spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy revealed that the structural and chemical characteristics of the resulting carbon material strongly depend on the applied processing conditions. Larger irradiation areas and the T-80 precursor fraction produced lower defect densities, while an argon atmosphere reduced the I D /I G ratio compared with processing in air. Based on the combined evaluation of defect density and structural integrity, LIG was subsequently produced using the T-80 precursor fraction, a single irradiation pass, 8.8 W laser power, 50 mm s⁻¹ scanning speed, and an irradiation area of 56.4 mm². The resulting material exhibited a porous morphology, an I D /I G ratio of 0.16 ± 0.07, an I 2D /I G ratio of 0.48 ± 0.07, and a sheet resistance of 25.31 ± 2.44 Ω sq⁻¹. These results demonstrate the feasibility of directly converting avocado seed waste into conductive graphitic structures and provide a processing framework for the flame-retardant-free conversion of lignocellulosic biomass into LIG.