Microchimica Acta最新文献

Cytosine-rich and poly(adenine)-tailed tetrahedral DNA framework (TDF) is designed as template (A₈-TDF) for anchoring silver nanoclusters (AgNCs) and igniting the dual-color fluorescence of AgNCs. The resultant DNA-AgNCs simultaneously emits red and green fluorescence, and the quantum yield of red fluorescence is as high as 44.8%. The red fluorescence can be selectively quenched by Hg²⁺ within 2 min due to the redox reaction between Hg²⁺ and Ag⁰ as well as the subsequent Ag amalgamation. Meanwhile, the green fluorescence is enhanced. Thus a ratiometric fluorescence sensor is constructed for rapid and visual Hg²⁺ detection based on the synchronous change of two fluorescence signals. In addition, the resultant AgNCs probe also provides ratiometric colorimetric sensing of Hg²⁺ and simultaneously shows a visible color change from pink to yellow along with increasing content of Hg²⁺. The detection limits of ratiometric fluorescence and colorimetric modes are 0.24 nM and 1.32 nM, respectively. The method has been applied to the determination of Hg²⁺ in water samples, and recoveries ranged between 94.1 and 108.7%. This study not only provides a new guideline to modulate the fluorescence emission of AgNCs by scientifically designing terminal DNA sequence but also provides a facile and efficient single-probe and dual-mode ratiometric sensing platform for the routine determination and field monitoring of Hg²⁺.

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A polyethyleneimine (PEI)-assisted simple and efficient one-pot hydrothermal reduction method is reported to prepare high-quality gold nanodendrites (AuNDs) on a carbon nanotube (CNT) sheet. We observed that the prepared AuNDs have a well-defined backbone-multiple branching structure. With the systematical investigation of the growth mechanism, it was found that the bromide (Br⁻) ion concentration has an essential effect on the formation of AuNDs. By evaluating the growth conditions of AuNDs, it was demonstrated that PEI attached on the surface of CNT sheet plays multiple crucial roles as a reducing agent, stabilizer, and structure director in the formation of AuNDs. The prepared CNT-AuNDs hybrid was employed as a flexible surface-enhanced Raman scattering (SERS) substrate to detect the analyte Congo red (CR). Due to the unique structure of AuNDs, such as 3-D branches, rough surface, and sharp edges, the analyte can be detected efficiently down to a concentration as low as 1 × 10⁻⁸ M with an enhancement factor as high as 5.6 × 10⁷.

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Rapid and accurate detection of Escherichia coli (E. coli) is critical for maintaining water quality, and protecting aquatic ecosystems and public health. This research focuses on the development of a Förster resonance energy transfer (FRET)–based “turn-on” fluorescent nanosensor for real time, sensitive detection of E. coli. Copper nanoclusters–encapsulated metal organic frameworks (CuNCs@ZIF-8) were sythesized as a fluorescent donor with excellent luminescence properties. Further, MnO₂ nanospheres were synthesized as a receptor with good adsorption and quenching abilities. This novel nanoconjugate (CuNCs@ZIF-8@ MnO₂) was employed for the construction of a sensitive, accurate, and rapid sensing platform against E. coli in water on the basis of p-benzoquinone/hydroquinone (p-BQ/HQ) redox pair formation. Fluorescence is quenched by energy transfer when MnO₂ nanospheres are added to CuNCs@ZIF-8. Upon contact with E. coli, NADH-quinone reductase converts p-BQ to HQ, which reduces MnO₂ to Mn²⁺, releasing the nanospheres and restoring fluorescence in the composite. Based on this FRET ON–OFF-ON fluorescent probe, E. coli can be detected across a broad concentration range (5 × 10¹ to 5 × 10⁵ CFU/mL), with a detection limit as low as 8 CFU/mL within 50 min. The sensor’s practicality was verified through the investigation of E. coli in real water samples, with recoveries in the range 94.3 to 106.5%. This approach offers an efficient method for on-site detection and quantification of E. coli in both environment and food safety domains.

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For the first time a novel fluorescent La@ZrMOF nanomaterial was synthesized for the convenient and visual detection of ethephon (ETH) based on the ligand–metal charge transfer process. The fluorescence signal gradually enhanced as the concentration of ETH increased, accompanied by a change in the color from colorless to blue. The assay can be completed within 75 min with a detection limit of 0.03 mg/L. A paper-based approach for the rapid and visual determination of ETH has also been devised, enabling the efficient used in a variety of actual products, with apples, pears, and tomatoes as examples. It proved to be simple, easy to use, and sensitive, and has the potential for further uses of ETH detection.

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A SiO₂@Au@Polyaniline (SiO₂@Au@PAN) system has been successfully fabricated leveraging the synergistic effects of gold nanoparticles (AuNPs) to realize enhanced photothermal performance. The SiO₂@Au@PAN exhibited strong near-infrared (NIR) absorbance, excellent photothermal conversion efficiency, good dispersibility, and outstanding photostability. The SiO₂ nanospheres as the template provided numerous binding sites for coating of AuNPs. Subsequently, aniline was grafted onto SiO₂ to form PAN, which further facilitated the growth of AuNPs. The high efficiency of electron transfer from PAN to AuNPs was utilized to enhance the photothermal performance, resulting in a photothermal conversion efficiency of 41.47%. Additionally, the effects of SiO₂ with different sizes on the anchoring of AuNPs and the impact of aniline with varying concentrations on the morphology and photothermal properties of the materials were investigated. Finally, we verified the photothermal therapeutic (PTT) effect of SiO₂@Au@PAN at cellular level, with results demonstrating effective destruction of cancer cells. This work may provide an approach for establishing a multi-component PTT platform based on the synergistic effects of AuNPs, holding significant potential for biomedical and biochemistry applications.

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A composite nanomaterial of Prussian blue@gold nanoparticles (PB@Au) with catalytic and photothermal properties was proposed, which combined with anti-matrix interference aptamers to achieve robust specificity and sensitivity in the detection of Salmonella typhimurium (S. typhimurium). The detection probe, PB@Au-Aptamer (PB@Au-Apt), was designed to exhibit high specificity for the target and catalyze the signal generation to produce a color change, thereby enabling rapid detection. Additionally, the excellent photothermal performance of the PB@Au catalytic system was utilized for multimodal sensitive detection in the multimodal nanoenzyme-linked aptamer assay. Moreover, the utilization of both catalytic and photothermal dual-mode detection was mutually verified to enhance detection accuracy. Under optimal conditions, the detection of S. typhimurium in a sample can be completed in 2 h. The developed assay exhibited exceptional specificity in detecting S. typhimurium, with an impressive detection limit down to 23 CFU·mL⁻¹. Furthermore, the assay exhibited excellent repeatability and stability. Real sample analyses have proven the high reliability and practicality of this assay, highlighting its significant potential for applications in food safety testing.

A smartphone-integrated colorimetric sensor is introduced for the rapid detection of phenolic compounds, including 8-hydroquinone (HQ), p-nitrophenol (NP), and catechol (CC). This sensor relies on the peroxidase-mimicking activity of aspartate-based metal–organic frameworks (MOFs) such as Cu-Asp, Ce-Asp, and Cu/Ce-Asp. These MOFs facilitate the oxidation of a colorless substrate, 3,3′,5,5′-tetramethylbenzidine (TMB), by reactive oxygen species (ROS) derived from hydrogen peroxide (H₂O₂), resulting in the formation of blue-colored oxidized TMB (ox-TMB). Among the synthesized MOFs, Cu/Ce-Asp nanorods had the highest activity, probably due to the synergistic effect of aspartate and copper coordination, as well as their large surface area, which allows for improved electron transport. Consequently, Cu/Ce-Asp nanorods were utilized for the detection of phenolic compounds under optimized conditions. In the presence of phenolic compounds, the interaction between TMB and H₂O₂ is inhibited, resulting in various colorimetric responses. This method accurately determined HQ, NP, and CC in a linear range of up to 5 μM, with detection limits of 0.30 μM, 0.76 μM, and 0.50 μM, respectively. To facilitate real-time and portable analysis, smartphone technology was integrated for color detection, eliminating the need for expensive and bulky laboratory-based optical instruments. In addition, the sensor was effectively employed for real water sample analysis, yielding satisfactory recovery outcomes. The proposed sensor offers a rapid, user-friendly, and portable method for detecting phenolic compounds, even at low concentrations. This study not only advances the application of MOF-based nanozymes in environmental monitoring but also expands their potential use in other fields.

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Traditional surface-enhanced Raman scattering (SERS) substrates seeking uniformity and reproducibility of the Raman signal often assume and require that hot spots remain consistently stable during Raman testing. Recently, the non-uniform accumulation in SERS sample pre-concentration strategies have inspired the direct use of self-healing noble metal aerogels (NMAs), as the sample pretreatment presented in this work, and uncovered more diverse Raman information of substances during the dynamic process of laser irradiation. Rare characteristic peaks such as 820 cm⁻¹ for R6G within a specific concentration range were observed, and potential processes including R6G dimerization and desorption were analyzed. These results provide insights into how to obtain more Raman information of diverse molecule forms under conventional conditions to distinguish the aggregation state, which turn the blinking of signals at low concentration or single molecule level into useful information.

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A novel dual-mode detection method for microRNA-21 was developed. Photoluminescent (PL) and multiphonon resonant Raman scattering (MRRS) techniques were combined by using ZnTe nanoparticles as signal probes for reliable detection. The catalytic hairpin assembly (CHA) strategy was integrated with superparamagnetic Fe₃O₄ nanoparticle clusters (NCs) to enhance sensitivity. A remarkable detection sensitivity was achieved, with an ultralow limit of detection (LOD) of 310 aM for PL and 460 aM for MRRS. A wide detection range spanning from 500 aM to 100 nM for PL and 500 aM to 10 nM for MRRS was demonstrated, showcasing the versatility and efficacy of the method. Comparing to current methods and our previous work, both sensitivity and detection range showed significant advancements. The consistency between the detection results of PL and MRRS modes highlights the reliability and robustness of our method, offering compelling internal validation. This work not only opens new avenues for achieving sensitive and accurate detection of miRNAs, but also shows significant promise for advancing diagnostic applications in disease management.

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