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We report a mid-infrared quartz-enhanced photoacoustic sensor for highly sensitive nitrous oxide (N2O) detection using a 4.56 µm quantum cascade laser (QCL) with a butterfly package type. This new type of QCL features a compact size (30 mm × 12.7 mm × 13 mm), low threshold current (< 120 mA) at room temperature, and relatively high emission power (> 100 mW), which are suitable for portable trace gas sensor development. In this work, the QCL beam is directly coupled to the QEPAS detection module by using only one focusing lens. By measuring N2O mixtures with different concentrations (120 ppb to 3.16 ppm), the developed sensor shows a good linearity (R-square value of 0.999) and a minimum detection limit of below 1 ppb. The sensor has been successfully deployed for ambient air measurement, demonstrating the applicability and promising potential of using this QCL with butterfly package for various gas sensing applications. [ABSTRACT FROM AUTHOR]

Rice hull biochar modified by ZnS nanocrystals (RBZ) was developed as an efficient absorbent for the removal of Cu(II) in aqueous solution. Response surface methodology (RSM) was applied for modeling and optimizing the performance of RBZ. The maximum adsorption capacity of RBZ toward Cu(II) through the Langmuir model fitting was 248.98 mg g−1, which was four times larger than that of rice hull biochar (RB). The adsorption kinetics of Cu(II) and XPS analysis revealed that the chemisorption process played the leading role when using RBZ. Through competition ions study, Pb(II), Cd(II), or Ca(II) can slightly reduce the adsorption of Cu(II). According to the Box Behnken design method, the analysis of variance results showed that the pH and adsorbent dosage had significant effects on the predicted responses of adsorption capacity and removal efficiency. When using the optimum conditions, pH 6, temperature 27 °C, and dosage 0.20 mg mL−1 for removing Cu(II) in solution, the maximum adsorption capacity and relatively higher removal efficiency could be obtained through the 3D response surface plots. The results demonstrated that RSM is feasible to achieve optimal conditions for adsorption capacity and removal efficiency simultaneously toward heavy metals from aqueous medium, and the interaction between them when using the biochar/ZnS composite. [ABSTRACT FROM AUTHOR]

The effects of distributed Raman amplification (DRA) on temporal characteristics of an optical soliton that are numerically investigated by using the split-step Fourier method are compared with the experimental data measured by employing the second-harmonic generation frequency-resolved optical gating analyzer. It is found that the numerical results are consistent with the experimental data. DRA that can compensate the fiber loss does not change the temporal wave form of the soliton. The soliton width performs a various oscillation with propagation distance when considering the fiber loss and different Raman gain. Compensation of the fiber loss increases with the increase of the Raman pumping power. [ABSTRACT FROM AUTHOR]