Graphene quantum dots (GQDs), fascinating semiconductors with stable photoluminescence (PL), have important potential applications in the fields of biology, medicine, and new semiconductor devices. However, it is still challenging to overcome the weak PL intensity. Here, we report a strategy for selective resonance enhancement of GQD fluorescence using gold nanoparticles (AuNPs) as plasmas. Interestingly, the addition of low concentration AuNP makes AuNP/GQDs exhibit significant fluorescence enhancement of 2.67 times in the visible range. The addition of high concentration AuNP leads to the formation of an excitation peak at 421 nm and selectively enhances certain radiation modes. We concluded that the main reason for the selective enhancement of PL intensity in high concentration AuNP is the transfer of generous hot electrons at high energy states from AuNP to GQD and relaxation to the ground state. The electron resonance of low concentration AuNP transfers to GQD and relaxes to lower energy levels, exhibiting an overall enhancement of PL intensity. We apply it for detection of the heavy metal ion Cr³⁺, and verify that it has a correlation coefficient of 97.36%. We believe AuNP/GQDs can be considered excellent candidates for heavy metal detection and high fluorescence bio-imaging.

Bioaerosol, a significant constituent of the atmosphere, exhibits excellent broadband extinction performance and has attracted increasing attentions in the fields of atmospheric science, environmental science and electromagnetic field, et al. Relative humidity of the atmosphere has obvious diurnal and seasonal variation characteristics, and the frequent variation of relative humidity has a significant impact on bioaerosol in the atmosphere. However, the influence of relative humidity on broadband extinction performance of bioaerosol is unclear. Herein, we present the humidity growth model of bioaerosol. And the variation law of broadband extinction performance of bioaerosol in different humidity conditions was obtained by simulation. The simulation results and experimental data from an aerosol chamber experiment show that as the relative humidity values above 70%, the broadband extinction performance of bioaerosol will be increased with humidity. As the relative humidity increases from 70% to 90%, the extinction performance of AN0913 spores increase about 30% in visible and mid-infrared bands, about 20% in ultraviolet and far-infrared bands. And the extinction performance of AO0907 spores increase about 23% in the all four bands.

Artificially prepared microbial spores have excellent electromagnetic attenuation properties due to their special composition and structure. At present, studies on the optical properties of microbial spores have mainly focused on those with a single band or a single germplasm, which has limitations and cannot reveal the optical properties comprehensively. In this paper, 3 kinds of laboratory-prepared microbial spores were selected for compounding, and the spectral reflectivities of single-germplasm biospores and compound biospores were measured in the wavebands of 0.25–2.4 and 3–15 μm. The complex refractive indices (CRIs) were calculated in combination with the Kramers–Kronig (K-K) algorithm. Relying on the smoke box broadband test system, the transmittance of single-germplasm bioaerosols and compound bioaerosols from the ultraviolet (UV) band to the far-infrared (FIR) band was measured, and the mass extinction coefficients were calculated. The results indicate that the trend of the complex refractive indices of the compound spores is consistent with that of the single-germplasm spores with a larger particle size. For the single-germplasm bioaerosols, the lowest transmittance values were 2.21, 5.70 and 6.27% in the visible (VIS), near-infrared (NIR) and middle-infrared (FIR) bands, and the mass extinction coefficients reached 1.15, 0.87 and 0.84 m²/g, respectively. When AO and BB spores were compounded at 4:1, the extinction performance of the bioaerosols somewhat improved in all wavebands. These results can help to comprehensively analyze the optical properties of bioaerosols and provide ideas for the development of new extinction materials.

A multilayer structure of microbial cells can result in multiple attenuations of electromagnetic waves, making the biological particles have a strong extinction ability. However, the influence of various morphologies on infrared band optical extinction performance of biomaterials is unclear. The combination of shape, dimension, and structure parameters is proposed to evaluate and enhance the optical extinction properties of artificial bioparticles. Combined with the preliminary work of our research group, four artificial biological particles were selected to simulate and calculate their extinction performance with different parameters theoretically based on the discrete-dipole approximation method. The results show the extinction properties of bioparticles with different shapes and dimensions in the 3.0 to 5.0 μm and 8.0 to 14.0 μm wavebands. It was found that the chain-shaped particles with more constituent spheres and a bending angle of 60 deg as well as the ellipsoid-shaped particles with an axis ratio of 1:2 exhibit better extinction properties in the above two bands. Among them, the regulation of extinction efficiency can reach ∼13.92 % and 18.16%.

The prediction of infrared extinction performance is one of the indispensable factors for the research of smoke screen. So far, it is still short of an accurate numerical simulation for the infrared extinction performance after releasing smoke screen. We present a method for calculating the infrared extinction performance of smoke screen. The standard k − ε turbulence model and the concentration equation of smoke screen are combined to carry out numerical simulation research on the sedimentation and diffusion process of smoke screen in the field. The shape and mass concentration distribution of smoke screen are studied under different wind speeds and ground roughness. Lambert–Beer’s law is combined to calculate the infrared extinction area of the smoke screen under different conditions, and the influence law on the smoke screen extinction performance is analyzed under different conditions. The validity of the numerical simulation results is verified by the field test. It is a useful method for guiding the design of field experiments. This work is widely used in the evaluation of extinction performance and provided more information for use by decision makers.