Analysis of optical properties of bio-smoke materials in the 0.25-14 μm band

At present, research into optical properties of bio-smoke materials mostly concentrates on single band or single germplasm. Herein, we measured the spectral reflectance of three eukaryotic bio-smoke materials and three prokaryotic bio-smoke materials in the waveband from 0.25 μm to 14 μm. Based on the Kramers-Kroning algorithm, the complex refractive index m(λ) was calculated and the Fourier-transform infrared (FTIR) spectra of materials were analyzed. The results show that n(λ) of bio-smoke materials varies between 1.1-2, and n(λ) values in the visible light to near-infrared wavebands are significantly larger than those in other wavebands. The k(λ) of bio-smoke materials varies between 0-0.4. At 6-6.5 μm, k(λ) of prokaryotic materials is 3 times that of eukaryotic materials, which is caused by C=O stretching vibration of amide I and C-N stretching vibration of amide Ⅱ in proteins. At 2.5-3 μm and 9.75 μm, k(λ) values of eukaryotic bio-smoke materials are nearly 2 times that of prokaryotic ones. The absorption peak at 2.5-3 μm is mainly triggered by C-H stretching vibration in lipid and O-H stretching vibration in bound water. The absorption peak at 9.75 μm is mainly caused by symmetric stretching vibration of PO₂^- in nucleic acids.