Ultra-wide-dynamic-range gas sensing by optical pathlength multiplexed absorption spectroscopy

Laser absorption spectroscopy(LAS) has become the most widely used laser spectroscopic technique for gas detection due to its capability of accurate quantification and straightforward operation. However, since resolving weak absorption and averting over-absorption are always mutually exclusive, the dynamic range of the LAS-based gas sensor is limited and insufficient for many applications in fundamental study and industry. To overcome the limitation on the dynamic range, this article reports optical pathlength(OPL) multiplexed absorption spectroscopy using a gas cell having multiple internal reflections. It organically fuses together the transmission and reflection operation modes: the former directly uses the entire OPL of the gas cell, while the latter interrogates different internal short OPLs by optical interferometry, yielding >100-fold OPL variation. The achieved dynamic range is more than 6 orders of magnitude that surpasses other LAS techniques by 2–3 orders of magnitude. The proposed method promotes a novel way for the development of large-dynamic-range spectroscopic gas sensors for fundamental studies and industrial applications.

Rapid Detection of Sildenafil Drugs in Liquid Nutraceuticals Based on Surface-Enhanced Raman Spectroscopy Technology

In this study, surface-enhanced Raman Spectroscopy （SERS） technology was used to rapidly detect illegally added sildenafil drugs. A detailed attribution analysis by density functional theory （DFT） was used to guide specific experiments. The Raman signals were obtained from a silver colloid （Ag col） substrate, and they increased in the presence of the mineral salt, potassium iodide （KI）. These methods detected sildenafil in aqueous solutions as low as 1 μg/mL with high signal uniformity （RSD=3.77%）. Prior to this study, traditional Raman techniques detected substances in solid samples only. Here, Raman technology detected low contents of sildenaful drugs in liquid nutraceuticals. Therefore, SERS technology has great potential for on-site and real-time detection of illegal drugs in water and in liquid nutraceuticals.

A Review of WBG and Si Devices Hybrid Applications

In recent years,next-generation power semiconductor devices,represented by silicon carbide(SiC)and gallium nitride(GaN),have gradually emerged.Because wide-bandgap(WBG)devices have better electrical characteristics than those of silicon(Si)based devices,they have attracted increased attention both from academic researchers and industrial engineers.Employing WBG devices will further improve the efficiency and power density of power converters.However,the current price of WBG devices remains extremely high.Thus,some researches have focused on the hybrid utilization of WBG devices and Si-based devices to achieve a tradeoff between the performance and cost.To summarize the current research on WBG/Si hybrid applications,the issues mentioned above with representative research approaches,results,and characteristics,are systematically reviewed.Finally,the current research on WBG/Si hybrid applications and their future trends are discussed.

Gas sensing with 7-decade dynamic range by laser vector spectroscopy combining absorption and dispersion

Laser absorption spectroscopy(LAS) has been widely used for unambiguous detection and accurate quantification of gas species in a diverse range of fields. However, up-to-date LAS-based gas sensors still face challenges in applications where gas concentrations change in a wide range, since it is extremely difficult to balance spectral analysis strategies for different optical thicknesses. Here we present laser vector spectroscopy that combines absorption spectroscopy with dispersion spectroscopy, simultaneously taking advantage of the former's high sensitivity in the low-concentration region and the latter's high linearity in the high-concentration region. In the proof-of-concept demonstration of acetylene measurement, it achieves a linear dynamic range of 6 × 10^(7)(R^(2)> 0.9999), which surpasses all other state-of-the-art LAS techniques by more than an order of magnitude,with the capability of highly accurate quantification retained. The proposed laser spectroscopic method paves a novel way of developing large-dynamic-range gas sensors for environmental, medical, and industrial applications.