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Dissolved gas analysis (DGA) is an effective method for diagnosing potential faults in oil-immersed power transformers. Metal oxide semiconductor (MOS) gas sensors exhibit excellent performance. However, high operating temperatures can accelerate device aging, thereby reducing the reliability of online monitoring. In this study, hierarchical porous pure ZnO and WO₃/NiO-ZnO heterojunction nanocomposites were synthesized via a facile hydrothermal method. The acetylene sensing characteristics of pure ZnO and heterojunction sensors were investigated in the absence and presence of UV irradiation. The results indicated that the NiO-ZnO sensor exhibited superior gas sensitivity compared to pure ZnO and WO₃-ZnO sensors. For the NiO-ZnO sensor, the optimal operating temperature under UV irradiation decreased to as low as 60 °C. Additionally, the performance decay of the sensor over 60 days of accelerated aging was documented. Notably, the long-term stability of sensors was significantly improved under UV irradiation. The enhanced properties were possibly attributed to the synergistic effect between photoelectrons excited by UV light and heterojunctions. Photo-activated free electrons could promote the adsorption of oxygen, leading to the formation of photoinduced oxygen ions.

Exosomes have emerged as a powerful biomarker for early cancer diagnosis, however, accurately detecting cancer-derived exosomes in biofluids remains a crucial challenge. In this study, we present a novel label-free electrochemical biosensor utilizing titanium dioxide nanotube array films (TiO₂NTAs) for the sensitive detection of exosomes in complex biological samples. This innovative biosensor takes advantage of the excellent electrochemical properties of TiO₂NTAs and their specific interactions with the phosphate groups of exosomes. The transport of ions and electrons within the exosome-captured TiO₂ nanotubes is hindered, leading to a significant alteration in the electrochemical response signal and enabling highly sensitive detection of exosomes. Consequently, the biosensor demonstrates a wide linear detection range from 5 × 10¹ to 1 × 10⁷ particles/μL with a limit of detection of 12.7 particles/μL and 12.6 particles/μL for the exosomes derived from hepatocellular carcinoma and colon cancer cells, respectively. Furthermore, the TiO₂NTAs biosensor can successfully distinguish the signal of extracellular vesicles in real human serum samples between 20 hepatocellular carcinoma, 20 colon cancer and 20 healthy persons (p < 0.0001). This method had a promising potential in biochemical analysis and clinical cancer diagnosis.

The excessive use of pesticides is an urgent issue facing environmental sustainability and human health. In this study, a uniform dispersion size, good fluorescence performance and mesoporous structure of a ratiometric fluorescent probe were constructed for nicosulfuron detection. A solvent-free in situ solid-phase synthesis method was used to encapsulate biomass carbon dots within mesoporous silica (CDs@mSiO₂), followed by the modification of l-cysteine-modified manganese-doped zinc sulfide quantum dots (ZnS:Mn QDs), to construct a ratiometric fluorescent probe for highly sensitive and selective detection of nicosulfuron. This design effectively prevents the aggregation of CDs and reduces interference between the two fluorescent signals. Nicosulfuron detection had a low detection limit of 0.082 μM. Density functional theory calculations were carried out to uncover the specific interactions between nicosulfuron and ZnS:Mn QDs. The process of fluorescence quenching is ascribed to photoinduced electron transfer. This work offers a special strategy to produce a ratiometric fluorescent probe and illustrate the mechanism, which is crucial for sensing and environmental engineering.

Respiratory syncytial virus (RSV) is a major cause of acute respiratory tract infections in infants and elderly individuals, leading to hospitalisation and potentially fatal outcomes, posing a serious threat to global health and economy. This study proposes a smartphone-based mobile digital pressure sensor (smartphone-MDPS) for the quantitative detection of the RSV fusion protein (RSV-F) in clinical nasopharyngeal samples. The smartphone-MDPS utilized two monoclonal antibodies (mAbs) specific to the F protein, of which mAb1 was conjugated with Au@PtNPs (Au@PtNPs-mAb1) as the detection antibody and mAb2 was coupled with magnetic beads (MB-mAb2) as a coating antibody to establish a novel sandwich immunoassay. During the immune reaction, the substrate H₂O₂ was catalyzed to release O₂ gas by the Au@PtNPs nanozyme within the Au@PtNPs-mAb1-RSV-F-mAb2-MB immunocomplexes. The pressure intensity of O₂ was measured using a mobile digital pressure sensor and transmitted wirelessly to a smartphone application for analysis. The programming codes for the sensor module and Android app were developed considering the performance requirements of the smartphone-MDPS. With a quantitation range of 0.09-1.953 ng/mL, the system had a limit of quantitation (LOQ) of 0.09 ng/mL and a limit of detection (LOD) of 0.03 ng/mL. When nasopharyngeal samples from 27 patients with RSV infection and 46 healthy individuals were tested, the smartphone-MDPS and enzyme-linked immunosorbent assays (ELISA) exhibited 100 % positivity and specificity as well as a strong correlation coefficient (R² = 0.991) for quantitative measurements between these two assays. In conclusion, the smartphone-MDPS has high portability, affordability, efficiency, sensitivity, and specificity, making it a promising immunoassay for quantitative point-of-care testing of RSV infection.

Adenosine 5'-triphosphate (ATP) plays a pivotal role as an essential intermediate in energy metabolism, influencing nearly all biological metabolic processes. Cancer cells predominantly rely on glycolysis for ATP production, differing significantly from normal cells. Real-time in situ monitoring and rapid response to intracellular ATP levels offers more valuable insights into cancer cell physiology. Herein, we report a novel ratiometric luminescent probe, Ru-Rho, comprised of a ruthenium(II)-based complex and rhodamine 6G (Rho 6G) with excellent water solubility and photostability. Notably, Ru-Rho selectively responds to ATP at acidic conditions, matching the need of monitoring ATP under the acidic intracellular environment of cancer cells. Moreover, the fast ratiometric detection and imaging of ATP under single wavelength excitation improve the detection accuracy. Ru-Rho has been effectively utilized not only for ratio imaging ATP in cells and zebrafish, but also for assessing the efficacy of glycolysis-inhibiting anticancer drugs in intracellular levels, which accelerates the screening process for anticancer drugs and supports the development of new therapeutic agents. The design strategy based on transition metal ruthenium(II) complexes opens a new pathway for constructing ATP luminescent probes, allowing for better adaptation to complex detection requirements.

The current surface-enhanced Raman scattering (SERS) substrates typically feature a single energy level, posing challenges in coordinating electromagnetic enhancement (EM) and chemical enhancement (CM), thereby limiting the sensitive detection of numerous crucial target molecules. In this study, novel aggregated nanorings (a-NRs) hybridizing Ag, Au and AgCl are constructed as SERS substrates. On one hand, the obtained a-NRs exhibit robust localized surface plasmon resonance absorption, whose wavelength can be tuned to match three commonly used laser wavelengths (532, 633 and 785 nm) to gain strong EM effect. On the other hand, these materials possess the Fermi levels of Au nanoparticles and Au/Ag alloy, in addition to the valence band and conduction band of AgCl. The abundant energy levels of the obtained a-NRs facilitate increased charge transfer opportunities for molecules, leading to a strong CM effect. Therefore, the obtained a-NRs show ultra-high SERS sensitivity towards numerous molecules. Moreover, the unique chemical composition makes the obtained a-NRs have good long-term stability in terms of SERS activity. Besides providing high-performance SERS substrates, the valuable experience for coordinating EM and CM to construct highly active SERS substrate demonstrated in this work are expected to significantly advance the application of SERS.

Epinephrine (Ep) is an important neurotransmitter, which plays an important role in the nervous system and glycogen metabolism of living organisms. Hence, a novel NCQDs/FeCoFe-PBA composite with FeCoFe-Prussian blue analogues (PBA) as the core and nitrogen-doped carbon quantum dots (NCQDs) as the shell was constructed by a one-pot hydrothermal method, and it was used for the efficient detection of Ep. As a good electroactive material, NCQDs in the composite not only improved the weak conductivity of FeCoFe-PBA, but also limited the self-aggregation of FeCoFe-PBA, and formed a uniform shell on FeCoFe-PBA. The heterogeneous structure formed between the core and shell layer resulting in NCQDs/FeCoFe-PBA nanocomposites with more active sites, electron transport channels and a larger effective surface area. Further, under optimal conditions, the electrochemical method was used to evaluate the NCQDs/FeCoFe-PBA sensor, and the results revealed that the sensor had exceptional sensing performance for Ep, with an excellent linear range from 0.01 to 306.7 μM and a low detection limit of 0.002 μM. Simultaneously, the practicality, repeatability, and stability tests yielded positive results, confirming the feasibility of practical development and application of NCQDs/FeCoFe-PBA.

Single particle - inductively coupled plasma - mass spectrometry (SP-ICP-MS) is a powerful technique for characterization of the elemental and isotopic composition of individual particles. In this work, the capabilities of the newest generation of MC-ICP-MS with acquisition rates down to 50 ms were evaluated for single particle analysis, with a focus on isotopic precision achievable on a single-particle level. Nd (NdVO₄) nanoparticles (∼120 nm in diameter) were used as case study and were first characterized in terms of mass (respective size) and particle number concentration by SP-ICP-TOF-MS and then by SP-MC-ICP-MS for isotopic precision. For the isotopic ratio measurements, the MC-ICP-MS performance was compared to the ICP-TOF-MS and it was found that the isotope ratio precision was increased (R² between 0.98 and 0.99) compared to ICP-TOF-MS (R² between 0.88 and 0.97). The accuracy attained on a single particle level, was compared to bulk digestion followed by MC-ICP-MS analysis, and the SP-MC-ICP-MS technique was able to determine the particle population average to be <4 %, percent relative differences for the ¹⁴²Nd/¹⁴⁴Nd, ¹⁴³Nd/¹⁴⁴Nd, ¹⁴⁵Nd/¹⁴⁴Nd, ¹⁴⁶Nd/¹⁴⁴Nd, and ¹⁴⁸Nd/¹⁴⁴Nd ratios The detection limit for the SP-MC-ICP-MS approach was also assessed. When utilizing an all Faraday-cup based detection scheme the determined LOD for the measurements was 0.2 fg for Nd, per particle. Based on these results, the newest generation of MC-ICP-MS has demonstrated its utility for performing SP measurement, particularly when high precision isotopic determination is warranted.

MicroRNAs (miRNAs) serve as potential biomarkers for many diseases such as cancer, neurodegenerative diseases and cardiovascular conditions. The portable and accurate detection of miRNA is of great significance for the early diagnosis, treatment optimization and prognostic evaluation of diseases. Herein, a photothermal/visual dual-mode assay for let-7a is developed utilizing oxidized 3, 3', 5, 5' - tetramethylbenzidine (oxTMB) as signal reporter. Let-7a efficiently initiates two cascade amplification processes of catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR) on the magnetic microspheres. It is worth noting that the hairpin DNA employed for HCR is labeled with horseradish peroxidase (HRP). Consequently, a substantial accumulation of HRP occurs on the magnetic microspheres and further catalyzes the oxidation of TMB by H₂O₂ to oxTMB. The blue color of oxTMB enables its detection through visual sensing, while the photothermal conversion characteristic of oxTMB allows for its detection through photothermal sensing. The concentration of miRNA is positively correlated with the enrichment of HRP on magnetic microspheres, which in turn affects the production of oxTMB. Therefore, the photothermal and visual dual-mode assay for let-7a can be indirectly realized by the detection of oxTMB. The dual signals are cross-validated to effectively reduce false positives. Precise miRNA quantification is achieved using a household thermometer, which is conducive to the popularization of this proposed strategy. Moreover, by adjusting the hairpin DNA sequences utilized for CHA and HCR, the dual-mode assay platform has a potential to serve as a universal approach for other biomarkers.

The challenge of increasing food production while maintaining environmental sustainability can be addressed by using biofertilizers such as Azospirillum, which can enhance plant growth and colonize more than 100 plant species. The success of this biotechnology depends on the amount of plant growth-promoting bacteria associated with the plant during crop development. However, monitoring bacterial population dynamics after inoculation requires time-consuming, laborious, and costly procedures. To address these issues, this study describes an effective electrochemical DNA biosensor to detect Azospirillum brasilense. The biosensor comprises a glassy carbon electrode modified with a nanocomposite based on carbon nanotubes and gold nanoparticles capped with 3-n-propylpyridinium chloride silsesquioxane, followed by the immobilization of a thiolated probe oligonucleotide that binds specifically to the A. brasilense genome (AZO_genome). The nanocomposite was characterized utilizing spectroscopic and morphological methods. Its presence on the biosensor's surface enhanced electrochemical responses due to its excellent electrocatalytic properties, as observed during electrochemical impedance spectroscopy and cyclic voltammetry experiments. The biosensor enabled the detection of AZO_genome after the hybridization event, which alters the electrochemical response of the electrode and was rapidly detected by square wave voltammetry. The detection range of the bacterial genome was 1.17 pmol L^-1 to 146.8 pmol L^-1, with LOD and LOQ of 0.261 and 0.322 pmol L^-1, respectively, and sensitivity of -15.560 μA/log [AZO_genome] (pmol L^-1). The biosensor showed good selectivity and reproducibility, with a coefficient of variation of -5.69 %, in addition to satisfactory sensitivity and stability for up to seven weeks. These promising analytical features allowed the quantification of A. brasilense in low concentrations in soil metagenomic DNA samples.