Spectroscopic investigation of the electronic and excited state properties of para-substituted tetraphenyl porphyrins and their electrochemically generated ions

Multispectroscopic Investigations of the Binding Interaction between Polyethylene Microplastics and Human Hemoglobin

In this investigation, different multispectroscopic analytical techniques have been used to explore the interaction between polyethylene microplastics (PE-MPs) and human hemoglobin (HHb), an oxygen carrier in the human blood circulatory system. Ultraviolet-visible absorption studies have demonstrated that HHb molecules may interact with PE-MPs, and thermal melting studies have indicated that PE-MPs have a stabilizing effect on HHb. Further circular dichroism and Fourier transform infrared spectroscopic studies have revealed the distinct changes in HHb's secondary structures caused by the formation of the HHb-PE-MP binding complex. These findings imply that PE-MPs could enter the blood circulation system of humans and may be hazardous to humans. This work explains the potential binding interaction of microplastics at the molecular level and offers insight into the intermolecular interaction between PE-MPs and HHb.

One A3B Porphyrin Structure—Three Successful Applications

Porphyrins are versatile structures capable of acting in multiple ways. A mixed substituted A₃B porphyrin, 5-(3-hydroxy-phenyl)-10,15,20-tris-(3-methoxy-phenyl)-porphyrin and its Pt(II) complex, were synthesised and fully characterised by ¹H- and ¹³C-NMR, TLC, UV-Vis, FT-IR, fluorescence, AFM, TEM and SEM with EDX microscopy, both in organic solvents and in acidic mediums. The pure compounds were used, firstly, as sensitive materials for sensitive and selective optical and fluorescence detection of hydroquinone with the best results in the range 0.039–6.71 µM and a detection limit of 0.013 µM and, secondly, as corrosion inhibitors for carbon–steel (OL) in an acid medium giving a best performance of 88% in the case of coverings with Pt-porphyrin. Finally, the electrocatalytic activity for the hydrogen and oxygen evolution reactions (HER and OER) of the free-base and Pt-metalated A₃B porphyrins was evaluated in strong alkaline and acidic electrolyte solutions. The best results were obtained for the electrode modified with the metalated porphyrin, drop-casted on a graphite substrate from an N,N-dimethylformamide solution. In the strong acidic medium, the electrode displayed an HER overpotential of 108 mV, at i = −10 mA/cm² and a Tafel slope value of 205 mV/dec.