Designing and preparing highly sensitive and accurate fluorescent chemosensors for monitoring tetracycline antibiotics remains a challenge. Herein, a fluorescent chemosensor based on lanthanide metal-organic frameworks (Ln-MOFs) is proposed to realize high-precision monitoring by adjusting the ratio of lanthanide ions. LnMOFs with good aqueous stability were prepared by a solvothermal method using Eu3+, Tb3+ and the ligand 4,4 ',4 ''-s-triazine-2,4,6-triyltribenzoic acid (H3TATB) in DMF/NMP/H2O. The Ln-MOFs could recognize oxytetracycline (OTC) and doxycycline (DOX), and the detection limits of OTC and DOX were as low as 8.6 and 4.8 nM, respectively. In particular, Eu(1.4 mu M)-Tb-MOF sensors were used for visual detection of OTC and DOX in combination with smartphones with detection lines as low as 9.8 nM and 14.2 nM, respectively. Meanwhile, Eu-MOF, Tb-MOF and Eu(1.4 mu M)-Tb-MOF can be used for latent fingerprint (LFP) visualization, demonstrating their potential applications in the field of criminal case investigation. The developed probes were successfully applied to determining OTC and DOX in milk, beef and pork with recoveries ranging from 92.0 % to 109.63 % and relative standard deviations (RSDs) ranging from 1.83 % to 4.56 %. Eu(1.4 mu M)-Tb-MOF is believed to utilize its lanthanide metal ion coordination and photoinduced electron transfer (PET) mechanism to achieve highly selective and accurate OTC and DOX detection, which is supported by experimental and density functional theory (DFT) calculations.

The development of fluorescent probes for the recognition of HSO4− is important for social security and human health. In this work, Zn-MOF ([(Zn2+)(L+)2(H2O)2]∙6(H2O) ∙2(FDCA2−)) materials were synthesized using Zn2+ as the metal center and 1,3,5-triimidazolylbenzene (L) and 2,5-furan dicarboxylic acid (FDCA) as the bi-conjugate. The characterization was carried out by single crystal X-ray diffraction, powder X-ray diffraction (PXRD), thermogravimetric analysis (TG), Zeta potential, and scanning electron microscopy (SEM). The fluorescence sensing experiments showed that Zn-MOF can be used as a fluorescent probe, which produces an obvious fluorescence burst in a short time, and has a good selectivity for the detection of HSO4−, with a low limit of detection (LOD) as low as 0.18 μM, and a good immunity to interference. The recognition mechanism of Zn-MOF was explored by electron transfer analysis methods and density functional theory (DFT) calculations, which indicated that the fluorescence burst mechanism was hydrogen bond formation.

A simple and rapidly responsive novel chemosensor SN (4-(((2-hydroxynaphthalen-1-yl)methylene)amino)-N-(pyrimidine-2-yl)benzenesulfonamide) was designed and synthesized using 2-hydroxy-1-naphthaldehyde as a fluorescent group and its structure was characterized by H-1 NMR, C-13 NMR and HRMS. Upon addition of only Al3+ in a mixed solvent system (DMSO/H2O, V/V = 9:1), significant changes in UV-visible and fluorescence spectra were observed. At the same time, the solution exhibited noticeable color changes (from yellow to colorless) and fluorescence responses (from no fluorescence to blue fluorescence). The fluorescence chemosensor SN demonstrated excellent selectivity and sensitivity towards Al3+ with detection limits (LOD) of 1.174 x 10(-8) M. Therefore, the SN chemosensor enables rapid and efficient detection of trace amounts of Al3+ in both environmental and biological settings through colorimetric and dual-channel fluorescence responses. Furthermore, under the same conditions, the in-situ generated [SN + Al3+] system was used for relay detection of Fe3+ without the need for further optimization, purification, or separation steps. The experimental results showed that the addition of Fe3+ led to fluorescence quenching, eliminating interference from Al3+ during Fe3+ detection, and the detection limit was 1.85x10(-8) M. In addition, the binding and sensing mechanism of chemosensor SN to Al3+ and [SN + Al3+] to Fe(3+)were described in detail by H-1 NMR titration experiment, HRMS, density functional theory (DFT) calculation and time-dependent density functional theory (TD-DFT).

The innovative ligand H2L, featuring a benzimidazole structure substituted with 8-hydroxyquinoline and equipped with N,O donor sites, underwent successful synthesis and meticulous characterization. Notably, this ligand was exclusively synthesized through catalysis under protonated conditions, accompanied by an in-depth exploration of the catalytic mechanism. Employing single-crystal X-ray diffraction, we acquired and authenticated four distinct asymmetric double-decker sandwich mononuclear transition metal complexes: [Cu(HL)2]·2H2O, [Co(HL)2]·CH3OH, [Ni(HL)2] and [Zn(HL)2]·CH2Cl2. Among these, complex 1 revealed an intriguing five-coordinate Cu(II) center adopting a distorted square pyramidal geometry, whereas the central metal ions in complexes 2–4 exhibited a six-coordinate configuration, characterized by a distorted octahedral geometry. Noteworthy is the observation that the dihedral angles within the crystal structures of complexes 2–4 approached approximately 90° to a significant extent. To delve deeper into the electronic properties and transitions, meticulous DFT and TD-DFT calculations were performed on both the ligand H2L and complexes 1–4. Furthermore, a comprehensive investigation into the luminescence properties of both H2L and its complexes was conducted, revealing a pronounced luminescence quenching effect in the complexes compared to the ligand. Through thorough analysis utilizing Hirshfeld surface examination and IRI analysis, various weak intermolecular interactions within the system were elucidated.

The development of convenient and intelligent visualization of rapid pesticide detection methods is key to ensuring food quality and safety. This paper presents a smartphone-based ratiometric fluorescence sensor for smart field visualization and detection of diquat (DQ). Three-dimensional Zn-MOFs are prepared by the solvothermal method using the rigid ligand 4,4 ',4 ''-s-triazine-2,4,6-triyltribenzoic acid (H(3)TATB), the flexible ligand 1,4-bis((1H-imidazol-1-yl)methyl)benzene (bimb), and the transition metal (Zn2+), which shows good structural and thermal stability. Zn-MOF is a three-dimensional framework crystallizing in a triclinic crystal system in the P & imacr; space group. Then, RhB@Zn-MOF is obtained by introducing rhodamine B (RhB) into the Zn-MOF framework using the same method. Internal Filter Effect (IFE) quenches red fluorescence and Fluorescence Resonance Energy Transfer (FRET) enhances blue fluorescence, enabling high sensitivity and visual detection of DQ. The sensor has a low detection limit of 10.50 nM and is linear over the 0-70.00 mu M concentration range. Compared to Zn-MOF (detection limit of 16.90 nM), the introduction of RhB significantly improved the precision and sensitivity of DQ detection. The combination of a smartphone and RGB analysis enables fast and accurate quantitative analysis of DQ in tap water and apple samples. The sensor platform has the advantages of convenience, intelligent real-time detection, etc. It has a wide prospect of practical application and consolidates a solid foundation for food safety control.

Diquat (DQ) is a typical bipyridine herbicide widely used to control weeds in fields and orchards. The severe toxicity of diquat poses a serious threat to the environment and human health. Metal-organic frameworks (MOFs) have received widespread attention due to their unique physical and chemical properties and applications in the detection of toxic and harmful substances. In this work, a two-dimensional (2D) Tb(III) functionalized MOF Tb (III)@ 1 ( 1 = [Cd(HTATB)(bimb)] n & sdot;H 2 O (Cd-MOF), H 3 TATB = 4,4 ' ,4 '' -triazine-2,4,6-tribenzoicacid, bimb = 1,4bis((1H-imidazol-1-yl)methyl)benzene) has been prepared and characterized. Tb(III)@ 1 has excellent optical properties and high water and chemical stability. After the Tb(III) is fixed by the uncoordinated -COO- in the 1 framework, Tb(III)@ 1 emits the typical green fluorescence of the lanthanide ion Tb(III) through the "antenna effect ". It is worth noting that Tb(III)@ 1 can be used as a dual emission fluorescence chemical sensor for the ratio fluorescence detection of pesticide DQ, exhibiting a relatively low detection limit of 0.06 nM and a wide detection range of 0 -50 nM. After the addition of DQ, a rapid color change of Tb(III)@ 1 fluorescence from green to blue was observed due to the combined effects of IFE, FRET and dynamic quenching. Therefore, a simple test paper box has been designed for direct on-site determination of pesticide DQ. In addition, the developed sensor has been successfully applied to the detection of DQ in real samples (fruits a Yin-Xia Sun and Bo-Tao Ji contributed equally to this work and should be considered co-first authors.nd vegetables) with satisfactory results. The results indicate that the probe developed in this study has broad application prospects in both real sample detection and actual on-site testing.

A naked-eye colorimetric and fluorescent response dual-channel Schiff base chemosensor (L1) with simple structure and excellent performance was synthesized by the ammoniacal aldehyde condensation reaction of 6-amino coumarin with 4-methoxy salicylaldehyde. The chemical sensor L1 showed high sensitivity and selec-tivity to HSO4- that caused obvious colorimetric (from yellow to colorless) and fluorescent (from no fluorescence to orange fluorescence) response in mixed solvents (EtOH/H2O, v/v = 9:1). And the binding constants (Ka) and limit of detection (LOD) for HSO4 -were 6.4 x 103 M-1 and 4.63 x 10-7 M, respectively. The 1H NMR and HR-MS studies confirmed that the sensing mechanism for L1 was attributed to C--N hydrolysis cleavage promoted by HSO4-. L1-loaded test strips could be employed for detecting HSO4- under daylight and 365 nm UV light without resorting to any expensive instrumentation. In addition, it was also applied to the detection of trace HSO4 -in simulated water samples, including drinking water, and tap water. It was worth mentioning that L1 has been successfully used to recognition of HSO4 -in the Zebrafish organism, indicating that the practical application of sensor L1 in the field of biology and environment provided the possibility.

A multifunctional probe Cd-MOF was successfully prepared by hydrothermal reaction using Cd2+ as a node, 1,3,5-triimidazoly benzene (L) and ligands D(+)-camphoric acid (D-H(2)cam) as linkers. It was characterized by single crystal X-ray diffraction (XRD), powder X-ray diffraction (PXRD), chromaticity coordinates (CIE), and thermogravimetric analysis (TGA). The study of fluorescence properties revealed that the fluorescence of Cd-MOF at 325 nm was significantly quenched in the presence of HSO4- or acidic amino acids (glutamate (Glu) or aspartic acid (Asp)) because of the formation of hydrogen bonds between analyte and Cd-MOF. Interestingly, the in-situ generated [Cd-MOF-Glu/Asp] system could be used for relay recognition of basic amino acids arginine (Arg) and lysine (Lys). Fluorescence could be 'turned on' under the same experimental conditions. This could be attributed to the destruction of the hydrogen bond between Cd-MOF and acidic amino acids. The sensing process possessed outstanding sensitivity and selectivity, rapid time responsiveness, and recyclability in aqueous solution. Finally, the sensing mechanisms of Cd-MOF and [Cd-MOF-Glu/Asp] systems were investigated by PXRD, UV spectroscopy, and DFT theoretical calculations.

A novel colorimetric-fluorescent dual-mode chemosensor (JT5) based on rhodamine B has been produced for monitoring Sn4+ in the DMSO/H2O (4:1, v/v) medium. It has high sensitivity, a low detection limit, a short response time (1 s) and high stability, and can still be maintained after two weeks with the red dual fluorescence/ colorimetric response. Enhancement of red fluorescence (591 nm) and red colorimetric (567 nm) response of JT5 by Sn4+ addition. The electrostatic potential of the sensor JT5 molecule was simulated to speculate on the sensing mechanism, and the IR, mass spectrometry and 1H NMR titration were utilized to further demonstrate that JT5 was coordinated to Sn4+ with a 1:1 type, the rhodamine spironolactam ring of JT5 opens up to form a penta-membered ring with Sn4+, meanwhile, its system may have chelation enhanced fluorescence (CHEF) effect. In addition, theoretical calculations were carried out to give the energy gaps of JT5 and [JT5 + Sn4+] as well as to simulate the electronic properties of the maximal absorption peaks. Notably, the sensor JT5 was successfully applied to monitoring Sn4+ in zebrafish, and the JT5-loaded filter paper provided a solid-state platform for detecting Sn4+ by both naked eye and fluorescent methods. In summary, this work contributes to monitoring Sn4+ in organisms and solid-state materials and promotes understanding of Sn4+ functions in biological systems, environments, and solid-state materials.

The innovative ligand H2L, featuring a benzimidazole structure substituted with 8-hydroxyquinoline and equipped with N,O donor sites, underwent successful synthesis and meticulous characterization. Notably, this ligand was exclusively synthesized through catalysis under protonated conditions, accompanied by an in-depth exploration of the catalytic mechanism. Employing single-crystal X-ray diffraction, we acquired and authenticated four distinct asymmetric double-decker sandwich mononuclear transition metal complexes: [Cu(HL)2]& sdot; 2H2O, [Co(HL)2]& sdot;CH3OH, [Ni(HL)2] and [Zn(HL)2]& sdot;CH2Cl2. Among these, complex 1 revealed an intriguing fivecoordinate Cu(II) center adopting a distorted square pyramidal geometry, whereas the central metal ions in complexes 2-4 exhibited a six-coordinate configuration, characterized by a distorted octahedral geometry. Noteworthy is the observation that the dihedral angles within the crystal structures of complexes 2-4 approached approximately 90 degrees to a significant extent. To delve deeper into the electronic properties and transitions, meticulous DFT and TD-DFT calculations were performed on both the ligand H2L and complexes 1-4. Furthermore, a comprehensive investigation into the luminescence properties of both H2L and its complexes was conducted, revealing a pronounced luminescence quenching effect in the complexes compared to the ligand. Through thorough analysis utilizing Hirshfeld surface examination and IRI analysis, various weak intermolecular interactions within the system were elucidated.

A simple, fast responsive fluorescent chemical sensor for 3-aldehyde-4-hydroxyphenylpropylpyran-2-keto4-hydroxybenzoyl (JT) was designed and synthesized, which was characterized by 1 H NMR and MS. The fluorescent chemical sensor JT showed outstanding selectivity and high sensitivity for identifying Al 3 + and the limit of detection (LOD) was 9.76 x 10 -8 M in EtOH/H 2 O (9:1, v/v) system. Furthermore, the in situ generated [JT + Al 3 + ] system was used for the relay detection of Fe 3 + without separation and purification, and the experimental results showed a new fluorescence quenching signal under the same conditions and the LOD to Fe 3 + was 5.21 x 10 -7 M. In addition, density functional theory (DFT) calculations were carried out to obtain optimized structures and orbital energy for the chemical sensor JT, [JT + Al 3 + ] and [JT + Fe 3 + ] complexes. Moreover, the test strips experiments were given for rapid detection of Al 3 + and continuous monitoring of Fe 3 + . Ultimately, it is worth mentioning that we have successfully achieved the recognition of Al 3 + and relay identification Fe 3 + by the sensor using zebrafish as a biological carrier, which indicate the sensor own excellent practical application prospect. (c) 2023 Elsevier B.V. All rights reserved.

A multifunctional fluorescent sensor Zn-MOF was successfully prepared by hydrothermal reaction, Zn2+ as node, 1,3,5-tris(1-imidazolyl)-benzene (L) and chiral ligands D(+)-camphoric acid (D-H2cam) as linkers. It had been characterized by single crystal X-ray diffraction (XRD), powder X-ray diffraction (PXRD), circular dichroism (CD), chromaticity coordinates (CIE) and thermogravimetric analysis (TGA). The study of fluorescence properties revealed that the multifunctional fluorescent sensor Zn-MOF exhibited high selectivity and sensitivity to detect HSO4− or glutamate (Glu) / aspartic (Asp) by “Turn Off” the emission. Furthermore, the in situ generated [Zn-MOF + Glu/Asp] system was used for the relay detection of arginine (Arg) / lysine (Lys) without separation and purification and exhibited a new fluorescence “Turn On” signal under the same conditions. In addition, the sensing process possessed out-standing cost-saving, rapid responsiveness as well as recyclability in aqueous solution.

A highly selective Schiff-type fluorescent probe (SY) with aggregation-induced emission (AIE) characteristics was synthesized based on salicylaldehyde derivatives. With increasing water content, it exhibits good sensitivity and interference resistance for the detection of Cu2+ in mixed solvents (DMSO/H2O, v/v = 3:2), and uses a fluorescence burst mechanism to rapidly analyze Cu2+ ions in aqueous media with a detection limit as low as 3.98 x 10(-8) M, which is well below the permissible standard for Cu2+ (similar to 20 mu M) in drinking water (WHO). Importantly, the probe has been successfully applied to the determination of Cu2+ in real water samples with good reversibility and recoveries ranging from 99.3% to 106.6% in tap water, and can also be used for the detection of Cu2+ ions under 365 nm UV light. In addition, the coordination pattern of the probe with Cu2+ was evaluated by mass spectrometry and working curves, and the stoichiometry of the probe and Cu2+ ions was determined to be 2:1. In addition, density functional theory (DFT) was performed to help understand the electronic nature of SY and Cu2+ complexation and chelation induced quenching mechanism.

Two unexpected tetranuclear supramolecular boxes, [Zn-4(L')(4)(CH3OH)(2)]center dot 2CH(3)OH (1) and [Co-4(L)(2)(L')(2)(CH3OH)(2)]center dot acetone (2), with M-4(mu(3)-O)(2)(mu(2)-O)(4) core were obtained through reacting coumarin Schiff base H2L (H2L = 4-hydroxy-3-((2-hydroxyphenyl-imino)-methyl)-2hchrome-2-one) with Zn(OAc)(2)center dot 4H(2)O and Co(OAc)(2)center dot 4H(2)O, respectively. Interestingly, the original ligand (H2L) has changed into a new structure (H2L') in the process of forming single crystals. The structures of 1 and 2 were characterized by X-ray single crystal diffraction. 1 and 2 are tetranuclear structures including four metal centers (Zn(II) or Co(II)), four completely deprotonated ligands (four new (L')(2-) in 1, two original (L)(2-) and two new (L')(2-) in 2), two coordinated methanol molecules and several crystalline solvent molecules. Significantly, due to the action of Zn(II) and Co(II), the original Schiff base H2L completely changed from coumarin skeleton to quinoline skeleton to form a new ligand (H2L') in 1, while in 2 half of the ligands H2L involved in coordination changed to H2L' configuration, the other half maintained the original structure. In 1, Zn1 ions are six-coordinate octahedral configuration and Zn2 are five-coordinate distorted square-pyramidal configuration with tau = 0.38. In 2, Co1 are six-coordinate octahedral configuration and Co2 are five-coordinate triangular bipyramidal configuration with tau = 0.66.

The reaction mechanisms for acetylene cyclotrimerization using TiO2 and Ti catalysts were studied by the density functional theory (DFT) method. Interestingly, the reaction catalysed by TiO2 occurs on the potential energy surface (PES) with a singlet state. For the same reaction catalysed by Ti, spin-orbit coupling (SOC) calculations were performed to discuss spin inversion between the triplet and singlet PESs. The chance that an electron hops in the vicinity of the minimum-energy crossing point (MECP) was verified regarding the Landau-Zener model. The possibilities of single (P1ISC) and double (P2ISC) at MECP1 (SOC = 253.38 cm(-1)) are about 0.35 and 0.46, respectively. The energetic span model developed by Kozuch was applied in the above reactions. The turnover frequency (TOF)-determining transition state (TDTS) and TOF-determining intermediate (TDI) were verified. The TOF value indicates that Ti is a more active catalyst compared with TiO2 in C2H2 cyclotrimerization.

With high activity of IL electron system, acetylene can produce cyclic trimerization (Cyclotrimerization) under certain conditions to generate benzene. The reaction mechanism for acetylene cyclotrimerization catalyzed by PdCl2 together with CuCl2 has been investigated using the density functional theory (DM calculations at the B3LYP/6-31+G(d,p) level. The computational results suggested that one acetylene molecule combined with metal center of PdCl2 to yield intermediate 1M1, and then the second acetylene molecule participates into react with metal center of PdCl2 which leads to intermediate IM2. The intermediate IM2 continued to react with the third acetylene molecule to get the final product benzene via three possible paths (I, II and III). According to the energy profiles, path III is the most favorable one with lower energy barrier and is kinetically available. The addition of copper chloride plays an important role in improving the reaction rate and regioselectivity and reducing the possibility of dimerization and polymerization reactions. The results could provide valuable insights into these types of interactions and related ones. (C) 2017 Elsevier B.V. All rights reserved.

Graphene-based nanocomposites are emerging as a new class of materials that hold promise for many applications due to their unique nanostructure and particular properties. In this paper, a novel graphene sheets/Ag2S composite was synthesized through a facile solvothermal method and its electrochemical performance was carried on a modified glassy carbon electrode (GCE) in a three-electrode electrochemical cell. The microstructure and morphology of the composites were characterized by X-ray diffraction and field emission scanning electron microscope. The results revealed that β-Ag2S nanoparticles (NPs) with an average size of ca. 53nm were uniformly deposited on the surface of graphene sheets (Gs). The composite materials showed better electrochemical performance than the pure individual components and can be employed as supercapacitor materials.