Luminescence Nanothermometry: Investigating Thermal Memory in UiO-66-NH2 Nanocrystals.

Metal-organic frameworks (MOFs), a diverse and rapidly expanding class of crystalline materials, present many opportunities for various applications. Within this class, the amino-functionalized Zr-MOF, namely, UiO-66-NH2, stands out due to its distinctive chemical and physical properties. In this study, we report on the new unique property where UiO-66-NH2 nanocrystals exhibited enhanced fluorescence upon heating, which was persistently maintained postcooling. To unravel the mechanism, the changes in the fluorescence signal were monitored by steady-state fluorescence spectroscopy, lifetime measurements, and a fluorescence microscope, which revealed that upon heating, multiple mechanisms could be contributing to the observed enhancement; the MOFs can undergo disaggregation, resulting in a fluorescent enhancement of the colloidally stable MOF nanocrystals and/or surface-induced phenomena that result in further fluorescence enhancement. This observed temperature-dependent photophysical behavior has substantial applications. It not only provides pathways for innovations in thermally modulated photonic applications but also underscores the need for a better understanding of the interactions between MOF crystals and their environments.

Synchronous fluorescence detection of nitrite in meat products based on dual-emitting dye@MOF and its portable hydrogel test kit.

A novel ratiometric fluorescent nanoprobe (Rh6G@UIO-66-NH2) was fabricated for efficient nitrite (NO2-) detection in the present study. When NO2- was introduced, it interacted with the amino groups on the surface of Rh6G@UIO-66-NH2, forming diazonium salts that led to the quenching of blue fluorescence. With this strategy, a good linear relationship between NO2- concentration and the fluorescent intensity ratio of the nanoprobe in the range of 1-100 µM was established, with a detection limit of 0.021 µM. This dual-readout nanosensor was applied to analyze the concentration of NO2- in real meat samples, achieving satisfactory recovery rates of 94.72-104.52%, highlighting the practical potential of this method. Furthermore, a portable Gel/Rh6G@UIO-66-NH2 hydrogel test kit was constructed for on-spot dual-mode detection of NO2-. This kit allows for convenient colorimetric analysis and fluorometric detection when used in conjunction with a smartphone. All the photos taken with the portable kit was converted into digital information using ImageJ software. It provides colorimetric and fluorescent visual detection of NO2- over a range of 0.1-1.5 mM, achieving a direct quantitative tool for NO2- identification. This methodology presents a promising strategy for NO2- detection and expands the application prospects for on-spot monitoring of food safety assessment.

A universal design of turn-on fluorescent aptasensor based on luminescent MOFs: Application for the detection of bisphenol A in water, milk and chicken samples.

A universal design of turn-on fluorescent aptasensor based on aptamer functionalized gold nanoparticles (AuNPs) and luminescent metal-organic frameworks (LMOFs) complex (AuNPs-Apt/NH2-MIL-125(Ti)) was realized for bisphenol A (BPA) detection. LMOF NH2-MIL-125(Ti) was prepared using facial hydrothermal method. BPA aptamer functionalized AuNPs were prepared and adsorbed on the surface of NH2-MIL-125(Ti) to obtain platform of the fluorescent aptasensor. The fabrication process, sensing performance and applicability of the proposed aptasensor were characterized and investigated carefully. Linear detection range of the constructed aptasensor was from 1 × 10-9 mol L-1 to 1 × 10-4 mol L-1 with good selectivity, repeatability, stability and reproducibility under optimal experimental conditions. Meanwhile, the fluorescent aptasensor was successfully utilized for BPA detection in real samples with the recoveries of 95.80%-103.12%. The proposed aptasensor based on AuNPs-Apt/NH2-MIL-125(Ti) holds significant potential for BPA detection in environmental and food samples, promoting the construction and application of LMOFs-based aptasensor.

Förster resonance energy transfer-based molecularly imprinted polymer /amine-functionalized metal-organic framework nanocomposite for trace level detection of 4-nitrophenol.

Herein, luminescent metal-organic framework (LMOF) is modified with molecularly imprinted polymer (MIP) and employed as an efficient and cost-effective nanoprobe for the determination of 4-nitrophenol (4-NP). Amine-UiO-66 support with unique luminescence property is chosen for creating the template of 4-NP using MIP to construct a highly selective LMOF-based sensor (amine-UiO-66/MIP nanocomposite). The imprinted sites formed at the surface of LMOF significantly enhance the selectivity of the probe for 4-NP over its analogs. 4-NP can effectively quench the fluorescent intensity of the optical sensor via the Förster resonance energy transfer (FRET) mechanism. Amine-UiO-66/MIP sensor provided the linear range of 0.05-50 µM and low limit of detection of 0.009 µM for sensing of 4-NP. The application of probe for the fluorometric analysis of real samples, including drinking and environmental water, provided satisfactory recovery results with low relative standard deviation (RSD).

Luminescent binuclear Zinc(II) organic framework as bifunctional water-stable chemosensor for efficient detection of antibiotics and Cr(VI) anions in water.

To achieve the ultrastable LMOFs with predominant luminescent sensing performances, the aromatic π-electron mixed ligands strategy was introduced, and the ternary LMOF of {[Zn2(HDDB)(bib)1.5]·3H2O}n (1), was fabricated based on 3,5-di(2',4'-dicarboxylphenyl)benozoic acid (H5DDB) and the N-donor of meta-bis(imidazol-1-yl)benzene (bib) under mixed solvothermal condition. LMOF 1 features the first reported 3D 3,4,4-c {62.83.10}{62.8}2{63.82.10}2 framework with 21.2 % porosity as well as high thermal and chemical stability. Further luminescent sensing showed that LMOF 1 as a bifunctional chemosensor possessing predominant detectability for sensitive detect the hexavalent chromates and nitroimidazoles/nitrofurans antibiotics in water through strong luminescent quenching effects, with excellent reusability as well as trace detection limits. Moreover, luminescent quenching mechanisms were further investigated from electron transfer and energy transfer viewpoints.

Ultrasensitive, rapid and selective sensing of hazardous fluoride ion in aqueous solution using a zirconium porphyrinic luminescent metal-organic framework.

The development of a rapid and sensitive method for the detection of fluoride ion (F-) in aqueous systems is of great significance for human health and environmental monitoring. In this study, a zirconium porphyrinic luminescent metal-organic framework (LMOF), PCN-222, was employed as a novel fluorescent probe for the ultrasensitive, rapid and selective detection of F- in water. The PCN-222 probe was prepared by a facile solvothermal method. It exhibited good fluorescence stability and was highly stable in water. The fluorescence emission of PCN-222 could be effectively and selectively quenched by F- due to the strong coordination affinity of F- to the zirconium clusters in PCN-222. The proposed fluorescence method for F- detection based on PCN-222 probe afforded a linear response range of 1-20 µmol/L and a very low detection limit (0.048-0.065 µmol/L) in reference to many reported F- fluorescent probes. Moreover, a rapid response time (<10 s) was obtained due to the open and uniform pore structure of PCN-222 that allowed the fast diffusion of F- to interact with the zirconium recognition sites. Finally, the PCN-222 probe was successfully applied for the fluorescence detection of F- in real water samples. These results highlight the great application potential of LMOF in the sensing fields.

Recent advances in process engineering and upcoming applications of metal-organic frameworks.

Progress in metal-organic frameworks (MOFs) has advanced from fundamental chemistry to engineering processes and applications, resulting in new industrial opportunities. The unique features of MOFs, such as their permanent porosity, high surface area, and structural flexibility, continue to draw industrial interest outside the traditional MOF field, both to solve existing challenges and to create new businesses. In this context, diverse research has been directed toward commercializing MOFs, but such studies have been performed according to a variety of individual goals. Therefore, there have been limited opportunities to share the challenges, goals, and findings with most of the MOF field. In this review, we examine the issues and demands for MOF commercialization and investigate recent advances in MOF process engineering and applications. Specifically, we discuss the criteria for MOF commercialization from the views of stability, producibility, regulations, and production cost. This review covers progress in the mass production and formation of MOFs along with future applications that are not currently well known but have high potential for new areas of MOF commercialization.

An aptamer based fluorometric assay for amyloid-ß oligomers using a metal-organic framework of type Ru@MIL-101(Al) and enzyme-assisted recycling.

Amyloid-beta (Aß) oligomers causing neuron damage are regarded as potential therapeutic targets and diagnostic markers for Alzheimer's disease (AD). A homogeneous turn-on fluorometric aptasensor is described for Aß oligomers. It is highly selective and non-invasive and based on (a) the use of a luminescent metal-organic framework carrying aptamer-modified AuNPs (L-MOF/Apt-Au) as tracking agent, and (b) enzyme-assisted target recycling signal amplification. The tracking agent does not emit fluoresce by fluorescence resonance energy transfer (FRET) between the luminescent MOF as donor and Apt-Au as the acceptor under the excitation wavelength of 466 nm. When Aß oligomers are added to the tracking agent solution, the Apt-Au on tracking agent can preferentially bind with Aß oligomers and then be released. This turns the "off" signal of the luminescent MOF tracer to the "on" state. The enzyme (Rec Jf exonuclease) added into the supernatant further improves sensitivity due to enzyme-assisted target-recycling signal amplification. The assay has an excellent linear response to Aß oligomers from 1.0 pM to 10 nM, with a detection limit of 0.3 pM. This homogeneous turn-on fluorometric method is expected to have potential and applications in clinical diagnosis. Graphical abstractSchematic representation of fluorometric assay for amyloid-ß oligomers based on luminescence metal-organic framework nanocomposites as tracking agent with exonuclease-assisted target recycling.