Highly sensitive determination of iron (III) ion based on phenanthroline probe: Surface-enhanced Raman spectroscopy methods

Luminescent Guests Encapsulated in Metal-Organic Frameworks for Portable Fluorescence Sensor and Visual Detection Applications: A Review

Metal-organic frameworks (MOFs) have excellent applicability in several fields and have significant structural advantages, due to their open pore structure, high porosity, large specific surface area, and easily modifiable and functionalized porous surface. In addition, a variety of luminescent guest (LG) species can be encapsulated in the pores of MOFs, giving MOFs a broader luminescent capability. The applications of a variety of LG@MOF sensors, constructed by doping MOFs with LGs such as lanthanide ions, carbon quantum dots, luminescent complexes, organic dyes, and metal nanoclusters, for fluorescence detection of various target analyses such as ions, biomarkers, pesticides, and preservatives are systematically introduced in this review. The development of these sensors for portable visual fluorescence sensing applications is then covered. Finally, the challenges that these sectors currently face, as well as the potential for future growth, are briefly discussed.

4-(1H-Imidazo[4,5-f][1,10]phenanthrolin-2-yl)benzaldehyde as a probe in pure solvents: Solvatochromism, electric dipole moment and pH influence

The spectral properties of 4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)benzaldehyde (1) in eleven organic solvents of different polarity have been studied. In order to determine the contributions of specific and non-specific interactions between the considered compound and the solvents, the solvatochromic Lippert-Mataga, McRae, Bakhshiev methods have been applied. The compound demonstrates positive solvatochromism. The dipole moment of the excited state of 1 obtained using the Reichardt method is equal to 10.56/7.08 D for trans- and cis-conformers, respectively, and agrees well with the theoretically calculated value. The influence of the polarizability of 1 on changes in the dipole moments has been analyzed using the Bilot-Kawski method. The multiple linear regression analysis in the framework of the Kamlet-Abboud-Taft and Catalán models has highlighted that the main properties which determine the Stokes shift of 1 are the acidity and dipolarity of the solvent. The variation of pH by additions of acid or base to solution 1 leads to significant changes in absorption and fluorescence spectra, therefore, 1 can be of interest as a solvatochromic probe, being sensitive to acidic/base properties of the environment. It has also been found out that the anion form of 1 is present in the DMSO solution. An addition of N,N-dimethylcyclohexylamine intensifies the dissociation of the considered compound in the DMSO solution and suppresses the fluorescence at a large amine excess.

A Water-Stable Zn-MOF Used as Multiresponsive Luminescent Probe for Sensing Fe3+/Cu2+, Trinitrophenol and Colchicine in Aqueous Medium

A water-stable Zn-MOF was constructed based on H₂PBA and 1, 10-phenanthroline under solvothermal conditions. The compound exhibited a 3D (2,3,8)-connected (4³)₂(4⁶.6⁶.8¹⁵.12)(8) topology framework. The crystal structure and phase purity of the compound was verified by single crystal X-ray diffraction. Subsequently, some studies on the morphology, structure, and luminescent properties were carried out. The results showed that this compound could be used as a versatile chemosensor for Fe³⁺/Cu²⁺, trinitrophenol and colchicine via a luminescence quenching effect in an aqueous medium.

A Multifunctional 3D Supermolecular Co Coordination Polymer With Potential for CO2 Adsorption, Antibacterial Activity, and Selective Sensing of Fe3+/Cr3+ Ions and TNP

A 3D supermolecular structure [Co₃(L)₂ (2,2′-bipy)₂](DMF)₃(H₂O)₃ 1) (H₃L = 4,4′,4″-nitrilotribenzoic acid) has been constructed based on H₃L, and 2,2′-bipy ligands under solvothermal conditions. Compound 1 can be described as a (3, 6)-connected kgd topology with a Schläfli symbol (4³)₂(4⁶.6⁶.8³) formed by [Co₃(CO₂)₆] secondary building units. The adsorption properties of the activated sample 1a has been studied; the result shows that 1a has a high adsorption ability: the CO₂ uptakes were 74 cm³·g⁻¹ at 273 K, 50 cm³·g⁻¹ at 298 K, the isosteric heat of adsorption (Q_st) is 25.5 kJ mol⁻¹ at zero loading, and the N₂ adsorption at 77 K, 1 bar is 307 cm³ g⁻¹. Magnetic measurements showed the existence of an antiferromagnetic exchange interaction in compound 1, besides compound 1 exhibits effective luminescent performance for Fe³⁺/Cr³⁺ and TNP.

Synthesis and Characterization of an Antioxidative Galactomannan⁻Iron(III) Complex from Sesbania Seed

Galactomannan, a water-soluble polymer in the cell wall of leguminous plants, has been proven to possess anticancer and antioxidative activity. In this work, galactomannan with different molecular weights (GM-40 and GM-65) was obtained from Sesbania seeds and synthesized into galactomannan–iron(III) complexes, which are termed as GM-40-Fe and GM-65-Fe, respectively. These galactomannan–iron(III) complexes are intended to function as organic iron supplements to treat iron deficiency with the added benefit of antioxidative activity. The prepared galactomannan–iron(III) complexes were characterized for chemical composition, morphology, antioxidant capacity, and bioavailability in vitro. The results showed that galactomannan–iron(III) complexes could be produced with iron contents as high as 65.4 mg/g. Antioxidant assays indicated that both GM-40-Fe and GM-65-Fe exhibited antioxidant activities for scavenging radicals in vitro. The iron release/bioavailability assays showed that the iron was easily released into artificial gastric and intestinal juices, resulting in iron release rates of 88–94% over 300 min. These results suggest that galactomannan–iron(III) complexes synthesized from Sesbania seed polysaccharides are capable of being administered as organic iron supplements to patients with iron deficiency.

Carrier Density-Dependent Localized Surface Plasmon Resonance and Charge Transfer Observed by Controllable Semiconductor Content

We discuss how the controllable carrier influences the localized surface plasmon resonance (LSPR) and charge transfer (CT) in the same system based on ultraviolet-visible and surface-enhanced Raman scattering (SERS) measurements. The LSPR can be easily tuned from 580 to 743 nm by changing the sputtering power of Cu₂S in the Ag and Cu₂S composite substrate. During this process, surprisingly, we find that the LSPR is proportional to the sputtering power of Cu₂S. This observation indicates that LSPR can be accurately adjusted by changing the content of the semiconductor, or even the carrier density. Moreover, we characterize the carrier density through the detection of the Hall effect to analyze the Raman shift caused by CT and obtain the relationships between them. These fundamental discussions provide a guideline for tunable LSPR and the investigation of CT.