Determination of dimethylsulfide and dimethylselenide in human urine by portable gas chromatography–photoionization detection with headspace sampling

A simple and sensitive method for the determination of dimethylsulfide (DMS) and dimethylselenide (DMSe) employing a gas chromatograph–photoionization detector with headspace sampling (HS-GC-PID) was developed. Parameters affecting the HS-GC-PID sensitivity including matrix effect, heating temperature, extraction time and carrier gas flow-rate were optimized. The matrix effect was required for standard addition calibration method for quantification purposes. The method has been validated when rectilinear relationship was between the concentrations of analytes and peak area in the range of 0.2–50 ng mL^{− 1} for DMSe and 0.5–100 ng mL^{− 1} for DMS, the correlation coefficients were from 0.995–0.998, and the limits of detection for DMS and DMSe were 25 pg mL^{− 1} and 48 pg mL^{− 1}, respectively. The proposed method was further applied to quantification of DMS and DMSe in urine samples.     

Catalytic ignition and autothermal combustion of JP-8 and its surrogates over a Pt/γ-Al2O3 catalyst

With the aim of utilizing JP-8 fuel for small scale portable power generation systems, catalytic combustion of JP-8 is studied. The surface ignition, extinction and autothermal combustion of JP-8, of a six-component surrogate fuel mixture, and the individual components of the surrogate fuel over a Pt/γ-Al₂O₃ catalyst are experimentally investigated in a packed bed flow reactor. The surrogate mixture exhibits similar ignition–extinction behavior and autothermal temperatures compared to JP-8 suggesting the possibility of using this surrogate mixture for detailed kinetics of catalytic combustion of JP-8. It is shown that JP-8 ignites at low temperatures in the presence of catalyst. Upon ignition, catalytic combustion of JP-8 and the surrogate mixture is self-sustained and robust combustion is observed under fuel lean as well as fuel rich conditions. It is shown that the ignition temperature of the hydrocarbon fuels increases with increasing equivalence ratio. Extinction is observed under fuel lean conditions, whereas sustained combustion was also observed for fuel rich conditions. The effect of dilution in the air flow on the catalytic ignition and autothermal temperatures of the fuel mixture is also investigated by adding helium to the air stream while keeping the flow rate and the equivalence ratio constant. The autothermal temperature decreases linearly as the amount of dilution in the flow is increased, whereas the ignition temperature shows no dependence on the dilution level under the range of our conditions, showing that ignition is dependent only on the type and relative concentration of the active species.     

Recoverable Flexible Perovskite Solar Cells for Next-Generation Portable Power Sources

Flexible perovskite solar cells (FPSCs) with excellent recoverability show a wide range of potential applications in portable power sources. The recoverability of FPSCs requires outstanding bendability of each functional layer, including the flexible substrates, electrodes, perovskite light absorbers, and charge transport materials. This review highlights the recent progress and practical applications of high-recoverability FPSCs, and illustrates the routes toward improvement of the recoverability and environmental stability through the choice of flexible substrates and the preparation of high-quality perovskite films, as well as the optimization of charge-selective contacts. In addition, we explore the intrinsic properties of each functional layer from the physical perspective and analyze how to select suitable functional layers. Additionally, some effective strategies are summarized, including material modification engineering of selective contacts, additives and interface engineering of interlayers, which can release mechanical stress and increase the power-conversion efficiency (PCE) and recoverability of the FPSCs. The challenges of making high-performance FPSCs with long-term stability and high recoverability are discussed. Finally, future applications and perspectives for FPSCs are discussed, aiming to promote more extensive commercialization processes for lightweight and durable FPSCs.