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Circulating microRNAs (miRNAs) play a pivotal role in the occurrence and development of acute myocardial infarction (AMI), and precise detection of them holds significant clinical implications. The development of luminol-based luminophores in the field of electrochemiluminescence (ECL) for miRNA detection has been significant, while their effectiveness is hindered by the instability of co-reactant hydrogen peroxide (H2O2). In this work, an iron single-atom catalyst (Fe-PNC) was employed for catalyzing the luminol-O2 ECL system to achieve ultra-sensitive detection of myocardial miRNA. Target miRNA triggers a hybridization chain reaction (HCR), resulting in the generation of a DNA product featuring multiple sticky ends that facilitate the attachment of Fe-PNC probes to the electrode surface. The Fe-PNC catalyst exhibits high promise and efficiency for the oxygen reduction reaction (ORR) in electrochemical energy conversion systems. The resulting ECL biosensor allowed ultrasensitive detection of myocardial miRNA with a low detection limit of 0.42 fM and a wide linear range from 1 fM to 1.0 nM. Additionally, it demonstrates exceptional performance when evaluated using serum samples collected from patients with AMI. This work expands the application of single-atom catalysis in ECL sensing and introduces novel perspectives for utilizing ECL in disease diagnosis. [ABSTRACT FROM AUTHOR]

Humic acid–based carbon dots (HACDs) have excellent properties and are widely used in environmental detection, bioimaging, and optoelectronic materials. Herein, we investigated the structure–activity relationship between the morphology and optical properties of HACDs, and reported on a novel strategy for metronidazole (MNZ) and ornidazole (ONZ) sensing in multiple real samples. It was found that the average particle size decreased from 3.28 to 2.44 nm, optimal emission wavelength was blue-shifted from 500 to 440 nm, and the quantum yield (QY) improved from 5 to 23% with the temperature increasing from 110 to 400 °C. Under the oxidation of hydrogen peroxide (H2O2) and potassium permanganate (KMnO4), the UV–vis spectra of HACD aqueous solution showed time-dependent behavior, and the fluorescence emission of HACDs achieved spectrally tunable multi-color luminescence in the temporal dimension. The surface of HACDs contained a large number of hydroxyl (–OH) and carboxyl (–COOH) fluorophores, resulting in excellent pH sensing. Meanwhile, the synthesized HACDs revealed sensitive response to MNZ and ONZ with the limit of detection (LOD) of 60 nM and 50 nM in aqueous solutions, which had also been successfully applied in various actual samples such as lake water, honey, eggs, and milk with satisfactory results because of the inner filter effect (IFE). Our research is advantageous to enhance the potential applications of HACDs in advanced analytical systems. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) are a new type of porous crystal materials that have been widely used in various fields. Owing to their adjustable porous structure, MOF photocatalysts with high catalytic activity have become a research hotspot. In this study, NH2-MIL-125/CoSx samples were investigated as a novel visible light-responsive catalyst for the removal of organic dye. The NH2-MIL-125/CoSx-20 composites showed the best photodegradation efficiency, where photodegradation of the rhodamine B reached 95.4% in 45 min. CoSx was able to effectively extend the wavelength absorption range of NH2-MIL-125 and effectively separate the photogenerated electrons and holes and that could lead to the improved photocatalytic performance of the composites. The reactive superoxide radical (·O2−) was identified as the main active species using reactive species capture experiments, and a reasonable photocatalytic mechanism was proposed. This paper is intended to guide the development of organic–inorganic hybrid materials for environmental remediation. [ABSTRACT FROM AUTHOR]

Anisotropic noble-metal structures are attracting increasing attention because of interesting size- and shape-dependent properties and have emerging applications in the fields of optics and catalysis. However, it remains a significant challenge to overcome chemical contributions and acquire molecular insight into the relationship between Raman enhancement and photocatalytic activity. This study gives visualized experimental evidence of the anisotropic spatial distribution of Raman signals and photocatalytic activity at the level of single nanometer-thin Au microtriangles and microhexagons. Theoretical simulations indicate an anisotropic spatial distribution and sharpness-dependent strength of the electric-field enhancement. Analysis by using statistical surface-enhanced Raman scattering (SERS) supports this view, that is, Raman enhancement is on the order of corner>edge>face for a single microplate, but SERS measurements at different depths of focus also imply a concentration-dependent feature of SERS signals, especially at the corners and edges. Similarly, the SERS signals of product molecules in plasmonic photocatalysis also exhibit asymmetrical strengths at different corners of the same microplate. However, by examining the variations in the relative intensities of the SERS peaks, the difference in the photocatalytic activities at the corners, edges, and faces has been successfully calculated and is highly consistent with electric-field simulations, thus indicating that an increased number of molecules adsorbed at specific sites does not necessarily lead to a higher conversion ratio in noble-metal photocatalysis. Our strategy weakens the assumed impact of plasmonic local heating and, to a certain extent, excludes the influence of concentration effects and chemical contributions in noble-metal photocatalysis, thus clearly profiling plasmon-related characteristics. This study also promises a new research direction to understand the enhancement mechanism of SERS-active structures., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Surface-enhanced resonance Raman scattering (SERRS) is not realized for most molecules of interest. Here, we developed a new SERRS platform for the fast and sensitive detection of 2,4,6-trinitrotoluene (TNT), a molecule with low Raman cross section. A cationic surfactant, cetylpyridinium chloride (CPC) was modified on the surface of silver sols (CP-capped Ag). CPC not only acts as the surface-seeking species to trap sulfite-sulfonated TNT, but also undergoes complexation with it, resulting in the presence of two charge-transfer bands at 467 and 530 nm, respectively. This chromophore absorbs the visible light that matches with the incident laser and plasmon resonance of Ag sols by the use of a 532.06 nm laser, and offered large resonance Raman enhancement. This SERRS platform evidenced a fast and accurate detection of TNT with a detection limit of 5×10(-11) M under a low laser power (200 μW) and a short integration time (3 s). The CP-capped Ag also provides remarkable sensitivity and reliable repeatability. This study provides a facile and reliable method for TNT detection and a viable idea for the SERS detection of various non-resonant molecules., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)