Design of a dual-mode ratiometric fluorescent probe via MOF-on-MOF strategy for Al (III) and pH detection.

BACKGROUND: The construction of ratiometric fluorescent MOF sensors with integrated self-calibration and dual-channel detection can efficiently overcome the deficiencies of single-signal sensing. In this regard, the rational design of structurally functionalized MOFs is paramount for enhancing their performance in ratiometric fluorescent sensors. Lately, the concept of MOF-on-MOF design has garnered notable interest as a potential strategy for regulating the structural parameters of MOFs by integrating two or more distinct MOF types. Great efforts have been dedicated to exploring new MOF-on-MOF hybrids and developing their applications in diverse fields. Even so, these materials are still in the stage of advancement in the sensing field. RESULTS: Herein, a Zr-based metal-organic framework anchored on a rare-earth metal-organic framework (UiO-66(OH)2@Y-TCPP) was prepared for the ratiometric fluorescence detection toward Al (III) and pH. In this probe, the UiO-66(OH)2 featured hydroxyl active sites for Al (III), leading to a significant enhancement in fluorescence intensity upon the addition of Al (III), while the signal emitted by the red-emitting Y-TCPP, serving as the reference, remained constant. UiO-66(OH)2@Y-TCPP exhibited excellent selectivity for Al (III) sensing with a wider linear range of 0.1-1000 µM, and a lower detection limit of 0.06 µM. This probe has also been utilized for the quantitative determination of Al (III) in hydrotalcite chewable tablets with satisfactory results. In addition, the probe realized ratiometric pH sensing in the range of 7-13 using UiO-66(OH)2 as an interior reference. The paper-based probe strip was developed for visual pH sensing. By installing color recognition and processing software on a smartphone, real-time and convenient pH sensing could be achieved. SIGNIFICANCE: This is the first ratiometric fluorescent sensor for Al (III) and pH detection based on a MOF-on-MOF composite probe, which yields two different response modes. The detection results of Al (III) in hydrotalcite chewable tables and smartphone imaging for pH test paper demonstrate the practicability of the probe. This work opens up a new outlook on constructing a multi-functional application platform with substantial potential for employment in environmental and biological analysis tasks.

Undescribed matrine-type alkaloids from Sophora alopecuroides with anti-inflammatory activity.

A phytochemical investigation on the alkaloid fractions of Sophora alopecuroides L. led to the production of 11 undescribed matrine-type alkaloids, sophaloseedlines I-S (1-11), 12 known analogs (12-23), and an unexpected artificial matrine-derived Al(III) complex (24). The corresponding structures were elucidated by the interpretation of spectroscopic analyses, quantum chemical calculation, and six instances (1-4, 18, and 24), verified by X-ray crystallography. The biological activities screening demonstrated that none of the isolates exhibited cytotoxicity against four human cancer cell lines (HepG2, A549, THP-1, and MCF-7) and respiratory syncytial virus (RSV) at 50 µM, while moderate anti-inflammatory activity with IC50 value from 15.6 to 47.8 µM was observed. The key structure-activity relationships of those matrine-type alkaloids for anti-inflammatory effects have been summarized. In addition, the most potent 7-epi-sophoramine (19) and aluminum sophaloseedline T (24) could effectively inhibit the release of pro-inflammatory factors (TNF-α, IL-6, and IL-1ß), as well as the expression of iNOS and COX-2 proteins.

Designing of efficient two-armed colorimetric and fluorescent indole appended organosilicon sensors for the detection of Al(III) ions: Implication as paper-based sensor.

Metal ions have significant roles in diagnosis, industry, human health, and the environment. To design and develop new lucid molecular receptors for the selective detection of metal ions is important for environmental and medical applications. In the present work, two-armed indole appended Schiff bases conjoined with 1,2,3-Triazole bis-organosilane and bis-organosilatrane skelton sensors for naked eye colorimetric and fluorescent detection sensors for Al(III) are developed. The introduction of Al(III) in sensor 4 and 5 show red shift in UV-visible spectra, changes in fluorescence spectra and immediate color change from colorless to dark yellow. Furthermore, the pH and time response studies were explored for both sensors 4 & 5. The sensors 4 and 5 exhibited significantly low detection limit (LOD) in nano-molar range 1.41 × 10-9 M and 0.17 × 10-9 M respectively from emission titration. The LOD form absorption titration was found to be 0.6 × 10-7 M for sensor 4 and 0.22 × 10-7 M for sensor 5. In addition, the sensing model is developed as paper based sensor for its practical applicability. The theoretical calculations were performed on Gaussian 03 program by relaxing the structures using Density functional theory.

Chemically modified flubendazole carbon electrochemical sensor for aluminum determination in food stuff, Multivitamin syrup and real water samples supported by DFT calculations, IR and morphological tools.

Aluminum is a key component in nearly nourishment stuffs and medications. It is also found in treated drinking water in the form of reactive species, and aluminum salts are commonly utilized as flocculants in water treatment. Meanwhile, it was not thought to be a dangerous metal for people, but research showed a possible link with Alzheimer's disease, breast cancer, autism, and aluminum. Controlling the amount of aluminum in food processing, agriculture, and drinking water is crucial, thus newly synthesized Al(III) ion selective electrode based on innocuous reagent, flubendazole drug, has been developed. The electrode displayed Nernstian slopes of 20.11 0.47 mV decade-1 at 25 ± 1 °C, covering a wide concentration range of Al(III) from 1 × 10-7 to 1 × 10-1 mol L-1. The response mechanism is studied using IR, computational calculations, morphological tools. The developed sensor has been utilized to accurately measure Al(III) ions in genuine water samples, multivitamin syrup, and food stuff.

Synthesis of Fluorophore Based Functional Material for Selective Detection of Al3+ Ion in Water and Decoding the AIEE Property of Its Hydrosol.

A designed aggregation-induced emission enhancement (AIEE) active fluorescence probe 2,3-Bis-[(2-hydroxy-napthalen-1-ylmethylene)-amino]-but-2-enedinitrile (L) was synthesized via one step condensation method. The probe shows swift sensitivity and selectivity toward Al3+over other relevant metal ions and also exhibits significant AIEE phenomena in methanol/water mixture. Significant enhancement of fluorescence intensity is triggered via chelation-enhanced fluorescence through complex (Al3+-L) formation. A 2:1 metal to ligand ratio is observed from Job's plot based on UV - Vis absorption titration and detection limit (LOD) is found as low as 31.14 nM. Moreover, 1H NMR titrations and fluorescence reversibility by adding Al3+ and EDTA sequentially had been performed to establish the binding site of sensor complex (Al3+-L). Time-resolved photoluminescence, dynamic light scattering, optical microscopy, and on-site visualization studies have been performed to understand the AIEE mechanism of L in different volume percentage of water and methanol mixture. An INHIBIT molecular logic gate has been constructed utilizing the fluorescence behavior of the probe, L in presence of Al3+ and strong chelating ligand EDTA.

Sensitive ratiometric sensor for Al(III) detection in water samples using luminescence or eye-vision.

A facile, quick, and sensitive ratiometric luminescence sensor is designed for detection aluminum ions in water samples using luminescence or eye-vision. This approach relies on the emission change of the europium(III) complex with 3-(2-naphthoyl)-1,1,1,-trifluoro acetone (3-NTA) after interaction with various concentration of aluminum ions. The addition of aluminum ions suppressed the Eu(III) emission at 615 nm under 333 nm excitation, while simultaneously enhancing the ligand emission at 480 nm. Optimum detection was obtained in methanol. The quantification of aluminum ions using ratiometric method was determined by plotting the luminescence ratio (F480nm/F615nm) versus aluminum ions concentration. The calibration plot was obtained within the range 0.1-100 µM with LOD = 0.27 µM. Additionally, the concentration of aluminum ions can be estimated semi-quantitatively by visually observing the luminescence colour change of the probe from red to light green and then to dark green after being excited by a UV lamp with 365 nm. As far as we are aware, this is the first luminescent lanthanide complex-based ratiometric probe for the detection of aluminum ions. The probe showed remarkable aluminum ions selectivity relative to that of other metal ions. The suggested sensor was used effectively to identify aluminum ions in water samples with good results.

N-doped carbon nanomaterials as fluorescent pH and metal ion sensors for imaging.

Herein we describe the facile synthesis of new N-doped carbon nanoparticles (CNPs) obtained from 1,10-phenanthroline by the solvothermal method. Characterization of CNPs were carried out with transmission electron microscope (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectra (FTIR), UV-vis absorption spectra, and luminescence spectra. CNPs were pH sensitive and exploited as fluorescent chemosensors and imaging agents for Al(III) and Zn(II) ions in real-life samples. Remarkably, we show that CNPs can be used for the detection of Al(III) and Zn(II) ions in water samples. Accordingly, the results indicate that CNPs are highly effective in detecting Zn(II) content of cosmetic creams. We also demonstrated that the CNPs could be used for in vitro imaging of Al(III) and Zn(II) in Human Larynx Squamous Cell Carcinoma (Hep-2). Finally, Al(III) imaging in Angelica Officinalis root tissue was also achieved successfully. The CNPs are promising as luminescent multianalyte (pH, Al(III) and Zn(II)) sensors.

Fate of Cr(VI) during aging of ferrihydrite-humic acid co-precipitates: Comparative studies of structurally incorporated Al(III) and Mn(II).

Ferrihydrite-humic acid co-precipitates have impacts on the adsorption and reduction of Cr(VI) in the natural environment. Besides, ferrihydrite-humic acid co-precipitates usually coexist with foreign metal cations like Al(III) and Mn(II), which may change the properties of ferrihydrite and affect the fate of Cr(VI). In this work, structurally incorporated Al(III) or Mn(II) in ferrihydrite-humic acid co-precipitates with Cr(VI) (Fh-HA-Cr-Al or Fh-HA-Cr-Mn) were prepared, and the behavior and phase transformation of co-precipitates were explored via the characterization analyses of samples during aging for 10 days. This study showed that partial adsorbed Cr(VI) was reduced to Cr(III) in the presence of humic acid, thereby reducing the toxicity of Cr(VI). Interestingly, two different results occurred because of the incorporation of Al(III) and Mn(II). Al(III) hindered the transformation of ferrihydrite and changed the aging products by inhibiting the dissolution of ferrihydrite, which decreased Cr to incorporate iron minerals. By contrast, doping of Mn(II) accelerated the phase transformation of co-precipitates, and was more conducive to the encapsulation and fixation of Cr. The results of this study can facilitate the understanding of the effects of Al(III) and Mn(II) on Cr(VI) fixation during the aging of Fh-HA-Cr.

A Review on Coordination Properties of Al(III) and Fe(III) toward Natural Antioxidant Molecules: Experimental and Theoretical Insights.

This review focuses on the ability of some natural antioxidant molecules (i.e., hydroxycinnamic acids, coumarin-3-carboxylic acid, quercetin, luteolin and curcumin) to form Al(III)- and Fe(III)-complexes with the aim of evaluating the coordination properties from a combined experimental and theoretical point of view. Despite the contributions of previous studies on the chemical properties and biological activity of these metal complexes involving such natural antioxidants, further detailed relationships between the structure and properties are still required. In this context, the investigation on the coordination properties of Al(III) and Fe(III) toward these natural antioxidant molecules might deserve high interest to design water soluble molecule-based metal carriers that can improve the metal's intake and/or its removal in living organisms.

Deciphering the transformation mechanism of substituted polycyclic aromatic hydrocarbons on Al(III)-montmorillonite: An experimental and density functional theory study.

The researches on transformation of polycyclic aromatic hydrocarbons (PAHs) on clay minerals modified by metal ions have received increasing attention. However, the transformation of PAHs with electron-withdrawing or electron-donating substitutional groups on clay minerals is not well understood currently. In this study, the degradation of anthracene (ANT) with different substituents (including -CH3, -CHO, -Br, -OMe, and -NO2) on Al(III)-montmorillonite (MMT) was investigated in the dark. The results showed that aromatic compounds were degraded with the rate constants (kobs) of 0.004-0.141 d-1. Moreover, ANT with electron-donating substituents (e.g., -CH3, -OMe) had a higher transformation rate than that with electron-withdrawing substituents (e.g., -Br, -NO2). The reactive oxygen species (ROS) quenching experiments indicated that ROS played a significant role in the transformation of ANT and ANT derivatives. Density functional theory (DFT) calculations revealed that the reactivity of single substituted PAHs was highly correlated with their ionization potential (IP), the energy of highest occupied molecular orbital (EHOMO), the energy of lowest unoccupied molecular orbital (ELUMO), and electronegativity (ζ), while independent of hardness (η). This study provides novel insights into predicting the reactivity of PAHs derivatives, and lays a fundamental basis for better understanding the fate of substituted PAHs in soils.