Positional Isomeric Symmetric Dipodal Receptors Dangled with Rotatable Binding Scaffolds: Fluorescent Sensing of Silver Ions and Sequential Detection of l-Histidine and Their Multifarious Applications.

Three simple dipodal artificial acyclic symmetric receptors, SDO, SDM, and SDP, driven by positional isomerism based on xylelene scaffolds were designed, synthesized, and characterized by 1H NMR, 13C NMR, and mass spectroscopy techniques. Probes SDO, SDM, and SDP demonstrated selective detection of Ag+ metal ions and amino acid l-histidine in a DMSO-H2O solution (1:1 v/v, HEPES 50 mM, pH = 7.4). The detection of Ag+ metal ions occurred in three ways: (i) inhibition of the photoinduced electron-transfer (PET) process, (ii) blueshifted fluorescence enhancement via the intramolecular charge-transfer (ICT) process, and (iii) restricted rotation of the dangling benzylic scaffold following coordination with a Ag+ metal ion. Job's plot analysis and quantum yields confirm the binding of probes to Ag+ in 1:1, 1:2, and 1:2 ratios with LODs and LOQs found to be 1.3 µM and 3.19 × 10-7 M, 6.40 × 10-7 and 2.44 × 10 -6 M, and 9.76 × 10-7 and 21.01 × 10-7 M, respectively. 1H NMR titration, HRMS, ESI-TOF, IR analysis, and theoretical DFT investigations were also used to establish the binding stoichiometry. Furthermore, the probes were utilized for the detection of Ag+ ions in water samples, food samples, soil analysis, and bacterial imaging in Escherichia coli cells and a molecular logic gate was constructed.

Magnetic solid-phase extraction based on nano-zeolite imidazolate framework-8-functionalized magnetic graphene oxide for the quantification of residual fungicides in water, honey and fruit juices.

In this work, zeolite imidazolate framework-8 (ZIF-8) functionalized magnetic graphene oxide (Fe3O4@APTES-GO/ZIF-8) was successfully synthesized and used as a novel adsorbent in magnetic solid-phase extraction (MSPE) for the determination of four triazole fungicides in water, honey and fruit juices. The main parameters such as extraction time, amount of adsorbent, the pH value of the sample, ionic strength, and desorption solvent which could affect the experiment results were optimization. Under the optimum condition, the obtained linearity of this method ranged from 1 to 1000 µg L-1 for all analytes, with correlation coefficients (R2) ≥ 0.9914. Limit of detections (LODs) and limit of qualifications (LOQs) of four triazole fungicides were ranged from 0.014 to 0.109 µg L-1 and from 0.047 to 0.365 µg L-1, respectively. Based on comparison with outcomes from other studies, Fe3O4@APTES-GO/ZIF-8-MSPE could provide high performance and achieve satisfied results for the analysis of trace triazole fungicides in complicated matrices.