A novel core-shell upconversion nanoparticles@zirconium-based metal organic framework fluorescent nanoprobe for efficient continuous detection of trace methylene blue and ferrous ions

A dual-optical sensor for mancozeb by UCNP@PVP@MnO2 nanozyme

In this work, a fluorescence/colorimetric dual-mode detection method based on MnO₂ nanoflower-decorated upconversion nanoparticles: NaYF₄:Yb/Er@polyvinylpyrrolidone@MnO₂ (UCNP@PVP@MnO₂) was proposed to detect the presence of mancozeb (MB). In this detection system, the MnO₂ nanoflowers in the nanocomplex of UCNP@PVP@MnO₂ would quench the fluorescence of the UCNP. With the addition of H₂O₂ and 3,3',5,5'-tetramethylbenzidine (TMB), the reaction between MnO₂ and H₂O₂ resulted in the dissolution of MnO₂ and the dissolution of the MnO₂ layer contributed to the fluorescence recovery of UCNP. Simultaneously, MnO₂ oxidized the colorless TMB to a blue product oxidized 3,3',5,5'-tetramethylbenzidine (oxTMB). The blue solution was able to quench the recovered fluorescence of UCNP due to the fluorescence inter filter effect (IFE) between the UCNP and blue oxTMB. Finally, with the addition of MB, the oxTMB was reduced to TMB by MB and the color of the solution became lighter while the fluorescence intensity of the solution increased. The detection method had a good linear range of 5-120 μM and 0.5-60 μM for fluorescence and colorimetric detection, respectively, and the limits of detection (LOD) were 2.34 and 0.245 μM, respectively.

Turn-on fluorescence ferrous ions detection based on MnO2 nanosheets modified upconverion nanoparticles

A turn on upconversion fluorescence probe based on the combination of ~32 nm NaYF₄: Yb/Tm nanoparticles and MnO₂ nanosheets has been established for rapid, sensitive detection of Fe²⁺ ions levels in aqueous solutions and serum. X-ray diffraction (XRD), transmission electron microscopy (TEM), absorption and emission spectra have been used to characterize the crystal structure, morphology and optical properties of the samples. MnO₂ nanosheets on the surface of UCNPs act as a fluorescence quencher, resulting in the quenching of the blue fluorescence (with excitation/emission maximum of 980/476 nm) via fluorescence resonance energy transfer from upconversion nanoparticles to MnO₂ nanosheets. With the adding of Fe²⁺, upconversion fluorescence of the nanocomposites recovers due to the reduction of MnO₂ to Mn²⁺. Because of the low background of the probe offered by upconversion fluorescence, this probe can be used for detecting Fe²⁺ in aqueous solutions in the range of 0.1-22 μM with detection limit of 0.113 μM. The developed method has also been applied to detect 10 μM Fe²⁺ ions in serum with recoveries ranging from 97.6 to 105.3% for the five serum samples. Significantly, the probe shows fast response and stable signal, which is beneficial for long-time dynamic sensing. Thus, the proposed strategy holds great potential for disease diagnosis and treatment.

A facile visualized solid-phase detection of virus-specific nucleic acid sequences through an upconversion activated linear luminescence recovery process

Based on the LRET between UCNPs and AuNPs, a solid-phase biosensor was developed for detection of virus-specific nucleic acid sequences by the naked eye, and is expected to become a fast, facile, efficient and reliable POCT platform.

A Review of Off-On Fluorescent Nanoprobes: Mechanisms, Properties, and Applications

With the development of nanomaterials, fluorescent nanoprobes have attracted enormous attention in the fields of chemical sensing, optical materials, and biological detection. In this paper, the advantages of "off-on" fluorescent nanoprobes in disease detection, such as high sensitivity and short response time, are attentively highlighted. The characteristics, sensing mechanisms, and classifications of disease-related target substances, along with applications of these nanoprobes in cancer diagnosis and therapy are summarized systematically. In addition, the prospects of "off-on" fluorescent nanoprobe in disease detection are predicted. In this review, we presented information from all the papers published in the last 5 years discussing "off-on" fluorescent nanoprobes. This review was written in the hopes of being useful to researchers who are interested in further developing fluorescent nanoprobes. The characteristics of these nanoprobes are explained systematically, and data references and supports for biological analysis, clinical drug improvement, and disease detection have been provided appropriately.

Upconversion luminescent nanomaterials: A promising new platform for food safety analysis

Foodborne diseases have become a significant threat to public health worldwide. Development of analytical techniques that enable fast and accurate detection of foodborne pathogens is significant for food science and safety research. Assays based on lanthanide (Ln) ion-doped upconversion nanoparticles (UCNPs) show up as a cutting edge platform in biomedical fields because of the superior physicochemical features of UCNPs, including negligible autofluorescence, large signal-to-noise ratio, minimum photodamage to biological samples, high penetration depth, and attractive optical and chemical features. In recent decades, this novel and promising technology has been gradually introduced to food safety research. Herein, we have reviewed the recent progress of Ln³⁺-doped UCNPs in food safety research with emphasis on the following aspects: 1) the upconversion mechanism and detection principles; 2) the history of UCNPs development in analytical chemistry; 3) the in-depth state-of-the-art synthesis strategies, including synthesis protocols for UCNPs, luminescence, structure, morphology, and surface engineering; 4) applications of UCNPs in foodborne pathogens detection, including mycotoxins, heavy metal ions, pesticide residue, antibiotics, estrogen residue, and pathogenic bacteria; and 5) the challenging and future perspectives of using UCNPs in food safety research. Considering the diversity and complexity of the foodborne harmful substances, developing novel detections and quantification techniques and the rigorous investigations about the effect of the harmful substances on human health should be accelerated.