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The developments concerning new hybrids based on porphyrin derivatives and colloids destined for the detection of ascorbic acid (AA) in the relevant range for medical investigations are presented. Mn(III) tetratolylporphyrin chloride (MnTTPCl), spherical gold colloid (n-Au), and their hybrid (MnTTPCl/n-Au) were chosen to be comparatively investigated by ultravioletevisible spectroscopy in the presence of AA. The hybrid material (MnTTPCl/n-Au) has the best capacity to detect concentrations of AA in the range of 2.6 Â 10 À6 e4.38 Â 10 À5 M. Modified glassy carbon (GC) electrodes were obtained by thin film deposition of MnTTPCl, n-Au alone, and in successive mixed thin films, comparing their response during the electrochemical oxidation of AA. The electrocatalytic effect of the MnTTPCl on the AA oxidation is justified both by the increase in the peak current density and by the shift toward more negative potentials (0.024 V). The GC/MnTTPCl electrode has the best electrocatalytic effect for the AA oxidation and is promising for sensor applications.

Abstract:The present report deals with the tailoring, preparation and characterization of novel nanomaterials sensitive to CO2 for use in detection of this gas during space habitation missions. A new nanostructured material based on mixed substituted asymmetrical A3B porphyrin: 5-(4-pyridyl)-10,15,20-tris(3,4-dimethoxyphenyl)-porphyrin (PyTDMeOPP) was synthesized and characterized by 1 H-NMR, FT-IR, UV-vis, fluorescence, MS, HPLC and AFM. Introducing one pyridyl substituent in the 5-meso-position of porphyrin macrocycle confers some degree of hydrophilicity, which may cause self-assembly properties and a better response to increased acidity. The influence of pH and nature of the OPEN ACCESSMolecules 2014, 19 21240 solvent upon H and J aggregates of the porphyrin are discussed. Porphyrin aggregation at the air-THF interface gave a triangular type morphology, randomly distributed but uniformly oriented. When deposition was made by multiple drop-casting operations, a network of triangles of uniform size was created and a porous structure was obtained, being reorganized finally in rings. When the deposition was made from CHCl3, ring structures ranging in internal diameter from 300 nm to 1 µm, but with the same width of the corona circular of approx. 200 nm were obtained. This porphyrin-based material, capable of generating ring aggregates in both THF and CHCl3, has been proven to be sensitive to CO2 detection. The dependence between the intensity of porphyrin UV-vis absorption and the concentration of CO2 has a good correlation of 98.4%.

This study reports the incorporation of an A 3 B mixed functionalized porphyrin, namely 5-(4-pyridyl)-10,15,20-tris(4-phenoxyphenyl)porphyrin (PyTPOPP), into polyvinylpyrrolidone (PVP), a biocompatible polymer, with the purpose of preparing water-soluble polymer-dye (PVP-PyTPOPP) hybrids. The hybrids were obtained in two variants, differing by molar ratios, and their molecular characteristics and aggregation in dilute aqueous solutions were investigated using static and dynamic light scattering and analytical ultracentrifugation methods. The hybrids were characterized using 1 H NMR, UV-visible and Fourier transform infrared spectroscopies, atomic force microscopy (AFM) and transmission electron microscopy (TEM). A study of the influence of acidic media on the electronic spectra was carried out, evidencing the similar behaviour of the hybrids and the bare porphyrin. The interaction between CO 2 and the PVP-PyTPOPP hybrids was studied using UV-visible spectroscopy and a continuous hypochromic response of the Soret band in direct relationship with increased CO 2 concentration was noticed. Based on the UV-visible spectral differences between the PVP-PyTPOPP hybrids in acidic media and during CO 2 exposure, we can presume that the mechanism of CO 2 detection is not based on pH changes of the solution but on chemisorption phenomena which modify the surface properties as confirmed by TEM and AFM. These porphyrin-PVP hybrid nanomaterials offer the possibility for achieving optical and colorimetric sensors for monitoring CO 2 and are also promising for biomedical applications.

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