UiO-66-NDC (1,4-naphthalenedicarboxilic acid) as a novel fluorescent probe for the selective detection of Fe3+

Colorimetric detection of Fe2+ and Cr2O72- in environmental water samples based on dual-emitting RhB-embedded Zr-MOFs

Three dye-loaded tunable dual-emission colorimetric fluorescent probes RhB@UiO-66-Ph (R@U-P) were prepared by in-situ encapsulation method under solvothermal conditions. The resonance energy transfer between UiO-66-Ph and RhB made the dual emission of R@U-P easily tunable with the embedded dye content changing. The R@U-P composites achieved emission from purple light to red light, and served as probes to realize comparative detection of Fe3+, Fe2+ and Cr2O72- in water through colorimetric or quenching detection mode. Mechanism study indicates that the resonance energy transfer or electron transfer interactions between R@U-P composites and inorganic ions resulted in the relative changes of the two emission peaks and realized the selective detection of analytes. The preparation and application of R@U-P probes provide a promising strategy for the in-situ encapsulation dye to obtain two dual-emission composites for the comparative detection of Fe3+, Fe2+ and Cr2O72- in water samples.

3D rhombohedral microcrystals metal-organic frameworks for electrochemical and fluorescence sensing of tetracycline

Zirconium-based metal-organic frameworks (MOF) exhibiting 3D rhombohedral microcrystals were synthesized by the solvothermal method. The structure, morphology, composition, and optical properties of the synthesized MOF were carried out using different spectroscopic, microscopic, and diffraction techniques. Synthesized MOF was rhombohedral in shape and the cage structure of these crystalline molecules was the active binding site of the analyte, tetracycline (TET). The electronic property and size of the cages are chosen such that a specific interaction with TET was observed. Sensing of the analyte was demonstrated by both the electrochemical and fluorescent techniques. The MOF had significant luminescent properties and exhibited excellent electro-catalytic activity due to embedded zirconium metal ions. An electrochemical and fluorescence sensor was fabricated towards TET where TET binds via hydrogen bond to MOF, and causes fluorescence quenching due to the transfer of electrons. Both approaches exhibited high selectivity and good stability in the presence of interfering molecules such as antibiotics, biomolecules, and ions; and showed excellent reliability in tap water and wastewater sample analysis.

Advanced experimental techniques for the sensitive detection of a toxic bisphenol A using UiO-66-NDC/GO-based electrochemical sensor

In the present study, a simple and sensitive method for detecting bisphenol A (BPA) in various environments, including groundwater, was described using a widespread electrochemical method. BPA is well-known for its endocrine-disrupting properties, which may cause potential toxicological effects oon the nervous, reproductive, and immune systems. A novel metal-organic framework (UiO-66-NDC/GO) was synthesized, and its existence was confirmed by several characterization techniques like FTIR, UV-visible, XRD, SEM-EDX, Raman spectroscopy, and TGA. Due to the excellent electrocatalytic nature, UiO-66-NDC/GO was chosen as the sensor material and integrated on the surface of the bare carbon paste electrode (BCPE). The UiO-66-NDC/GO modified carbon paste electrode (MCPE) was engaged for the detection of BPA using techniques like cyclic Voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The applied sensor exhibited an astonishing outcome for BPA detection with high sensitivity and selectivity. The lower detection limit (LLOD) of 0.025 μM was achieved at the modified sensor with a linear concentration range of 10-70 μM. Moreover, the practical applicability of the sensor was tested on tap water, drinking water, and fresh liquid milk, giving an excellent recovery of BPA in the range of 94.8-99.3 (v.%). The proposed method could be employed for electrochemical device or a solid state device fabrication for the onsite monitoring of BPA.

A systematic study of arsenic adsorption and removal from aqueous environments using novel graphene oxide functionalized UiO-66-NDC nanocomposites

This study investigates the removal of As(V) from aqueous media using water stable UiO-66-NDC/GO prepared via the solvothermal procedure. The synthesized material was analyzed by Raman spectroscopy, UV-visible, X-ray powder diffraction (XRD), Transmission electron microscopy (TEM), Fourier Transform Infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) support its applicability as a super-adsorbent for the adsorption of As(V) ions from aqueous solutions. The effect of various parameters, including initial ion concentration, temperature, adsorbent dose, and pH on the adsorption of As(V) was studied to recognize the optimum adsorption conditions. The qmax obtained for this study using Langmuir isotherms was found at 147.06 mg/g at room temperature. Thermodynamic parameters ΔH°, ΔG°, and ΔS° were also calculated and negative values of ΔG° represent that the As(V) adsorption process occurred exothermically and spontaneously. Meanwhile, theoretical density functional simulation findings are accommodated to support these experimental results. It is observed that the dynamic nature of graphene oxide and the UiO-66 NDC nanocomposite system becomes superior for adsorption studies due to delocalized surface states. UiO-66-NDC/GO also showed high reusability for up four regeneration performances using 0.01 M HCl as a regenerant.

Facile and Green Synthesis of Starfruit-Like ZIF-L, and Its Optimization Study

Due to its excellent characteristics, zeolitic imidazole framework-L (ZIF-L) is widely used in various applications, such as drug delivery, wastewater treatments and energy storage. In the synthesis of ZIF-L, the molar ratio of ligand to metal, the reaction time and the temperature are essential parameters to produce excellent ZIF-L. In this work, ZIF-L was synthesized using a facile and green synthesis method. It was statistically investigated and optimized to obtain the best operating conditions. The optimization was carried out toward the amount of adsorbed crystal violet (CV) dye (q) as the response in the statistics. The optimal ZIF-L was obtained using a molar ratio of ligand to metal of 8.2220 for 97 min at 29 °C, where the q value of the CV adsorption onto this optimal ZIF-L reached 823.02 mg/g. The obtained ZIF-L was characterized using SEM, XRD, FTIR and TGA analyses to ensure its excellent characteristics.

Effects of ligand functionalization on the band gaps and luminescent properties of a Zr12 oxo-cluster based metal–organic framework

Herein, effective optical band gap engineering of a robust Zr₁₂ oxo-based hcp UiO-66 has been realized through linker functionalization.