Silver nanopopcorns decorated on flexible membrane for SERS detection of nitrofurazone.

The synthesis of three-dimensional silver nanopopcorns (Ag NPCs) onto a flexible polycarbonate membrane (PCM) for the detection of nitrofurazone (NFZ) on the fish surface by surface-enhanced Raman spectroscopy (SERS) is presented. The proposed flexible Ag-NPCs/PCM SERS substrate exhibits significant Raman signal intensity enhancement with the measured enhancement factor of 2.36 × 106. This is primarily attributed to the hotspots created on Ag NPCs, including numerous nanoscale protrusions and internal crevices distributed across the surface of Ag NPCs. The detection of NFZ by this flexible SERS substrate demonstrates a low limit of detection (LOD) of 3.7 × 10-9 M and uniform and reproducible Raman signal intensities with a relative standard deviation below 8.34%. It also exhibits excellent stability, retaining 70% of its efficacy even after 10 days of storage. Notably, the practical detection of NFZ in tap water, honey water, and fish surfaces achieves LOD values of 1.35 × 10-8 M, 5.76 × 10-7 M, and 3.61 × 10-8 M, respectively,  which highlights its effectiveness across different sample types. The developed Ag-NPCs/PCM SERS substrate presents promising potential for sensitive SERS detection of toxic substances in real-world samples.

A Spin-Frustrated Azide- and Alkoxide-Bridged Heterobimetallic Mixed-Valence MnIIMnIII2NiII4 Disc with S = 17/2 or 19/2.

Seven-membered homometallic FeIII7, MnIII3MnII4 coordination clusters were previously reported to be spin-frustrated molecular discs. Herein, a mixed bimetallic and mixed-valence dicationic [MnIIMnIII2NiII4(N3)4(hmp)10](NO3)2 (12+(NO3)2) was isolated in pure form without scrambling of Ni/Mn ions. It was structurally characterized by single-crystal X-ray single-crystal diffraction. The presence of MnII ions at the center of the disc has been confirmed by EPR measurements. The magnetic studies suggest that complex 12+(NO3)2 possesses spin frustration with spin ground states S = 17/2 and 19/2, which has been studied and supported by DFT calculation. The purity of 12+(NO3)2 was confirmed by powder XRD measurements, and the ratio of Ni:Mn = 4:3 was further determined by SEM-EDX analysis.

Synthesis, oligomerization and catalytic studies of a redox-active Ni4-cubane: a detailed mechanistic investigation.

A robust tetrameric nickel complex [Ni4((Oal -)2L-Me)4(s)4] (3) (s = solvent) with cubane-like Ni4O4 core topology was isolated as a light greenish-orange crystalline solid in excellent yield. The mechanism of formation of 3 involving the two chloride-containing precursors [Ni4((Oal -)2L-Me)4(s)4]·2MeOH (1) and [Ni4((O-)2L-Me)3((Oal -)(OH)L-Me)Cl] (2) was studied by ESI mass spectrometry and confirmed by the solid state isolation and single-crystal X-ray diffraction. The challenging ligand fields containing mono/di-anionic O2N donating atoms and/or chloride ions stabilized the pentacoordinate Ni(ii) ions in 1-2 upon controlling the experimental conditions. Complexes 1-3 have been characterized by NMR, UV-Vis and mass spectrometric analysis. Complex 3 was found to be redox active by cyclic voltammetry (CV) studies. Theoretical calculations were carried out to shed light on the effects of ligand fields on the stability of complexes 1-3. Complex 3 was found to be a potential catalyst for the diastereoselective cyclopropanation of heteroarenes with good to excellent yields. The ESI mass spectrometric analysis revealed the existence of solution dynamics and oligomerization of 3 in solution. Mechanistic investigation of the catalytic cycle revealed that complex 3 and its various oligomers bind to the diazoester employed, followed by dissociative insertion of the respective carbene moieties to the C2-C3 double bond of the involved aromatic heterocycle, leading to the diastereoselective cyclopropanation.