Chongqing University of Technology

With the development of industrialization and urbanization, as the main air pollutants, the concentration detection of nitric oxide (NO) and ammonia (NH₃) are very important for environmental management and air quality assessment. Ultraviolet differential optical absorption spectroscopy (UV-DOAS) plays an important role in the field of gas detection with many advantages. However, in the face of mixed gas detection scenarios with overlapping absorption spectra, the detection accuracy still faces challenges. Therefore, a parallel dual output spectral separation model based on multi-dimensional feature fusion is proposed. According to the absorption spectrum features of NO and NH₃ in the model, the corresponding feature extraction branch is designed to realize the synchronous separation of the differential optical density (DOD) of the two gases. Secondly, the polynomial curve concentration inversion model is established, and the relationship between DOD and single-component gas concentration is constructed. Finally, the gas concentration is determined according to the DOD after separation. Based on the data of 200-230 nm band collected by UV-DOAS system, the experiment shows that the uncertainty of NO and NH₃ are 1.71 % and 1.28 %, respectively, and the detection limits are 0.087 ppm·m and 0.05 ppm·m, respectively. This study is expected to be widely applied in the field of multi-component gas detection, contributing to public health and environmental protection.

Bloodstream infections have high morbidity and mortality rates. Currently, the gold standard for diagnosing bloodstream infections involves re-culturing bacteria from positive culture bottles for mass spectrometry and drug resistance analysis. However, this process incurs a delay of at least a day, which can lead to a 7.6 % increase in the hourly mortality rate. Therefore, accelerating the identification of bacterial species and determining drug resistance is critical. Here, we present a new high-throughput Dean flow fractionation (DFF^HT) spiral chip to efficiently sort pathogenic bacteria from positive blood culture bottles, achieving an efficiency >80 %. Pathogens enriched in DFF^HT devices are directly identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), followed by the determination of drug-resistance by aptamer fluorescence, thereby eliminating the need for plate recultivation. Three high probability drug-resistant bacteria (carbapenem-resistant Acinetobacter baumannii [CRAB], carbapenem-resistant Pseudomonas aeruginosa [CRPA], and methicillin-resistant Staphylococcus aureus [MRSA]) were successfully identified directly from positive blood culture bottles. This combination of DFF^HT microfluidic bacterial isolation and aptamer-based detection of drug resistance can be completed within 1 h with a 2 mL sample from a positive blood bottle, which is helpful for doctors choosing the right antibiotic in time to treat the patient effectively.

A novel fiber-optic ammonia Mach-Zehnder interferometer (MZI) with an asymmetric-sensing structure was developed and experimentally validated. The sensor was fabricated through successive fusion splicing of single-mode fiber (SMF), coreless fiber (NCF), SMF, thin-core fiber (TCF), and SMF, thereby forming an SMF-NCF-SMF-TCF-SMF interferometric structure. Experimental and simulation results demonstrated that the sensor exhibited a linear response within the refractive index range of 1.3320-1.3636. Using the layer-by-layer (LbL) self-assembly technique, ultrathin two-dimensional (2D) self-assembled tetrakis(4-carboxyphenyl) zinc porphyrin (SA-ZnTCPP) and zinc acetate (Zn(OAc)₂) nanoporous films were deposited onto the fiber sensing region. The structural, morphological, and compositional properties of the nanomaterials and films were analyzed via Fourier-transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). NH₃ adsorption by the thin film modifies the sensor's effective refractive index, enabling gas detection. Experimental results revealed that the interference intensity of the monitoring peak increased proportionally with NH₃ concentration. Within the 0-600 ppb range, the sensor demonstrated high sensitivity (7.12 dB/ppm) and linearity, achieving a detection limit of 2 ppm with response-recovery times of 40 s and 50 s, respectively. The sensor demonstrates notable advantages, including high sensitivity, excellent selectivity, straightforward design, and ultra-low detection limits, indicating strong potential for toxic NH₃ monitoring in chemical engineering and industrial applications.