This paper proposes to apply a newly developed Non-Dispersive Infrared Spectroscopy (NDIR) gas sensing system composed of pyroelectric infrared detectors to monitor the thermal runaway (TR) process of lithium-ion batteries in real time and achieve an early warning system for the battery TR process. The new Electrical Vehicle Safety—Global Technical Regulation (EVS-GTR) requires that a warning be provided to passengers at least five minutes before a serious incident. The experimental results indicate that carbon dioxide and methane gas were detected during the overcharge test of the automotive battery, and the target gas was detected 25 s in advance before the battery TR when the battery vent was closed. In order to further explore the battery TR mechanism, an experiment was carried out using the battery sample with the battery vent opened. The target gas was detected about 580 s before the battery temperature reached the common alarm temperature (60 °C) of the battery management system (BMS). In this study, the beneficial effects of NDIR gas sensors in the field of thermal runaway warnings for automotive batteries were demonstrated and showed great application prospects and commercial value.

Increasing concerns about air quality due to fossil fuel combustion, especially nitrogen oxides (NO_x) from marine and diesel engines, necessitate advanced monitoring systems due to the significant health and environmental impacts of nitrogen dioxide (NO₂). In this study, a gas detection system based on the principle of the non-dispersive infrared (NDIR) technique is proposed. Firstly, the pyroelectric detector was developed by employing an ultra-thin LiTaO₃ (LT) layer as the sensitive element, integrated with nanoscale carbon material prepared by wafer-level graphics technology as the infrared absorption layer. Then, the sensor was hermetically sealed using inert gas through energy storage welding technology, exhibiting a high detectivity (D*) value of 4.19 × 10⁸ cm·√Hz/W. Subsequently, a NO₂ gas sensor was engineered based on the NDIR principle employing a Micro Electro Mechanical System (MEMS) infrared (IR) emitter, featuring a light path chamber length of 1.5 m, along with integrated signal processing and software calibration algorithms. This gas sensor was capable of detecting NO₂ concentrations within the range of 0–500 ppm. Initial tests indicated that the gas sensor exhibited a full-scale relative error of less than 0.46%, a limit of 2.8 ppm, a linearity of −1.09%, a repeatability of 0.47% at a concentration of 500 ppm, and a stability of 2% at a concentration of 500 ppm. The developed gas sensor demonstrated significant potential for application in areas such as industrial monitoring and analytical instrumentation.

High sensitivity and reproducibility are highly desirable to a SERS sensor in diverse detection applications. Moreover, it is a great challenge to determine how to promote the target molecules to be more concentrated on the hotspots of the SERS substrate by engineering a surface with switching interfacial wettability. Along these lines, wafer-scale uniformly hydrophobic silicon nanorods arrays (SiNRs) decorated with Au nanoparticles were designed as the SERS substrate. Typically, the SERS substrate was fabricated by enforcing the polystyrene (PS) sphere self-assembly, as well as the plasma etching and the magnetron sputtering techniques. Consequently, the SERS substrate was treated by soaking within a n-dodecyl mercaptan (NDM) solution at different times in order to obtain adjustable wettabilities. By leveraging the electromagnetic enhancement resulted from the Au nanostructures and enrichment effect induced by the hydrophobicity, the SERS substrate is endowed with efficient SERS capabilities. During the detection of malachite green (MG), an ultralow relative standard deviation (RSD) 4.04–6.14% is achieved and the characteristic signal of 1172 cm⁻¹ can be detected as low as 1 ng/mL. The proposed SiNRs’ structure presents outstanding SERS activity with sensitivity and reproducibility rendering thus an ideal candidate for potential application in analytical detection fields.

Surface-enhanced Raman spectroscopy (SERS) substrates with high sensitivity and reproducibility are highly desirable for high precision and even molecular-level detection applications. Here, large-scale uniformly hybrid nanoparticle-enhanced Raman spectroscopy (NERS) substrates with high reproducibility and controllability were developed. Using oxygen plasma treatment, large-area and uniformly rough polystyrene sphere (URPS) arrays in conjunction with 20 nm Au films (AuURPS) were fabricated for SERS substrates. Au nanoparticles and clusters covered the surface of the URPS arrays, and this increased the Raman signal. In the detection of malachite green (MG), the fabricated NERS substrates have high reproducibility and sensitivity. The enhancement factor (EF) of Au nanoparticles and clusters was simulated by finite-difference time-domain (FDTD) simulations and the EF was more than 10⁴. The measured EF of our developed substrate was more than 10⁸ with a relative standard deviation as low as 6.64%–13.84% over 15 points on the substrate. The minimum limit for the MG molecules reached 50 ng/mL. Moreover, the Raman signal had a good linear relationship with the logarithmic concentration of MG, as it ranged from 50 ng/mL to 5 μg/mL. The NERS substrates proposed in this work may serve as a promising detection scheme in chemical and biological fields.

In this work, a surface-enhanced Raman scattering (SERS)-active substrate is prepared simply by flame deposition of candle soot and sputtering of a metal layer. On surface of the SERS substrate covered with carbon-metal composite nanoparticles (CNPs), superhydrophobicity is observed. Subsequently, by rolling a droplet on such a SERS substrate, CNPs can be collected and enriched into the droplet, thus a SERS-active droplet is formed, which shows 26.5 times higher SERS signals than the SERS substrate. Such a highly SERS-active droplet can either be directly adopted for SERS detections with much less focusing requirements, or be transferred to any other substrates or targets for further detections. Consequently, an extremely simple, flexible and highly sensitive SERS detection technique applicable in a wide range is demonstrated.