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Ceramic-based absorbing composite is irreplaceable in high-temperature conditions. This work has fabricated a novel biomass–derived porous SiCnw/SiC composite for structure–function integrated electromagnetic wave (EMW) absorption through selective laser sintering (SLS) 3D printing and carbothermal reduction. SLS processed the biomass-derived wood precursor with unique porous microstructures. The structure–function properties were controlled by changing the SiO carbothermal reduction temperatures, which facilitated the growth of SiC nanowires for effective EMW absorption. The 3D printed porous SiCnw/SiC composite shows efficient EMW absorption abilities with a minimum reflection loss of −49.01 dB and an effective absorption bandwidth of 5.1 GHz. The bulk density and flexural strength of porous SiCnw/SiC composite are respectively 0.73 ± 0.001 g/cm3 and 6.21 ± 0.66 MPa. Despite a high open porosity of 75.58 ± 0.31%, the porous SiCnw/SiC composite demonstrates excellent thermal conductivities of 3.21∼4.99 W/(m·K) and superior fire-resistant ability. The 3D printed SiCnw/SiC composite integrates structure and functions, indicating wide applications in specific harsh environments. [ABSTRACT FROM AUTHOR]

A surface enhanced Raman spectroscopy (SERS) substrate with high sensitivity for the rapid determination of pesticide residues was developed by combining silver nanoparticles (AgNPs) and a fibrous swab. The SERS substrate was prepared simply by forming a SERS-active area on the section of fibrous swab and centrifuge tube with a soak-absorb approach. Rhodamine 6 G (R6G), a common SERS probe molecule, was used for performance characterization of the prepared SERS substrate that was shown to have high sensitivity, good stability and good reproducibility. Due to its good flexibility, the prepared SERS substrate was used to wipe contaminated surfaces for residue extraction. High sensitivity for detecting trace-level pesticides was verified for thiram. The limits of detection (LODs) for thiram on apple, grape and eggplant epidermis were calculated to be as low as 0.5313, 0.5768, and 0.5495 ng·cm−2, respectively, nearly 2 orders of magnitude below the maximum residue limit (MRL) for pesticide in food issued by the National Food Safety Standard of China. In addition, there was a linear relationship between the SERS intensity and the concentration of thiram in these three samples, indicating the good potential of this substrate for quantitative SERS analysis. [ABSTRACT FROM AUTHOR]

Holographic gratings in nematic liquid crystals doped with Disperse Red 1 (DR1) were investigated using a linearly polarised He–Ne laser. Although the electric transitions of the samples were almost off-resonant, the diffraction of the transient holographic grating was found to exhibit a sinusoidal feature with changing the polarisation of recording beams, and the diffraction intensities and response time of the gratings were strongly dependent on DR1 concentration. The results revealed that the diffraction of holographic grating depends on the rate of trans–cis isomerisation of DR1 molecules. Moreover, the temperature dependence of diffraction indicated that the grating formation mechanism was attributed to photoinduced reorientation of photoisomerisation effect. [ABSTRACT FROM AUTHOR]

The nonlinear optical properties of p-aminoazobenzene (PAAB), methyl orange (MO) and p-dimethylamino benzene arsenic acid (PDBAA) were investigated by a single beam Z-scan technique, respectively. Their solution samples all exhibited large nonlinear refractive indices under the excitation of a 633 nm laser. Among the three azo dyes, PDBAA showed the largest value of nonlinear refractive index. Moreover, the process of nonlinear refraction induced by the laser thermal effect was also analyzed in this paper. [ABSTRACT FROM AUTHOR]