The Influence of the Nature of the Polymer Incorporating the Same A3B Multifunctional Porphyrin on the Optical or Electrical Capacity to Recognize Procaine.

The multifunctionality of an A3B mixed-substituted porphyrin, namely 5-(4-carboxyphenyl)-10,15,20-tris(4-methylphenyl)porphyrin (5-COOH-3MPP), was proven due to its capacity to detect procaine by different methods, depending on the polymer matrix in which it is incorporated. The hybrid nanomaterial containing k-carrageenan and AuNPs (5-COOH-3MPP-k-carrageenan-AuNPs) was able to optically detect procaine in the concentration range from 5.76 × 10-6 M to 2.75 × 10-7 M, with a limit of detection (LOD) of 1.33 × 10-7 M. This method for the detection of procaine gave complementary results to the potentiometric one, which uses 5-COOH-3MPP as an electroactive material incorporated in a polyvinylchloride (PVC) membrane plasticized with o-NPOE. The detected concentration range by this ion-selective membrane electrode is wider (enlarged in the field of higher concentrations from 10-2 to 10-6 M), linearly dependent with a 53.88 mV/decade slope, possesses a detection limit of 7 × 10-7 M, a response time of 60 s, and has a certified stability for a working period of six weeks.

Nanomaterials Based on Collaboration with Multiple Partners: Zn3Nb2O8 Doped with Eu3+ and/or Amino Substituted Porphyrin Incorporated in Silica Matrices for the Discoloration of Methyl Red.

Designing appropriate materials destined for the removal of dyes from waste waters represents a great challenge for achieving a sustainable society. Three partnerships were set up to obtain novel adsorbents with tailored optoelectronic properties using silica matrices, Zn3Nb2O8 oxide doped with Eu3+, and a symmetrical amino-substituted porphyrin. The pseudo-binary oxide with the formula Zn3Nb2O8 was obtained by the solid-state method. The doping of Zn3Nb2O8 with Eu3+ ions was intended in order to amplify the optical properties of the mixed oxide that are highly influenced by the coordination environment of Eu3+ ions, as confirmed by density functional theory (DFT) calculations. The first proposed silica material, based solely on tetraethyl orthosilicate (TEOS) with high specific surface areas of 518-726 m2/g, offered better performance as an adsorbent than the second one, which also contained 3-aminopropyltrimethoxysilane (APTMOS). The contribution of amino-substituted porphyrin incorporated into silica matrices resides both in providing anchoring groups for the methyl red dye and in increasing the optical properties of the whole nanomaterial. Two different types of methyl red adsorption mechanisms can be reported: one based on surface absorbance and one based on the dye entering the pores of the adsorbents due to their open groove shape network.

Polymeric Carbon Nitrides for Photoelectrochemical Applications: Ring Opening-Induced Degradation.

Active and stable materials that utilize solar radiation for promoting different reactions are critical for emerging technologies. Two of the most common polymeric carbon nitrides were prepared by the thermal polycondensation of melamine. The scope of this work is to investigate possible structural degradation before and after photoelectrochemical testing. The materials were characterized using synchrotron radiation and lab-based techniques, and subsequently degraded photoelectrochemically, followed by post-mortem analysis. Post-mortem investigations reveal: (1) carbon atoms bonded to three nitrogen atoms change into carbon atoms bonded to two nitrogen atoms and (2) the presence of methylene terminals in post-mortem materials. The study concludes that polymeric carbon nitrides are susceptible to photoelectrochemical degradation via ring opening.

The pH Influence on the Water-Splitting Electrocatalytic Activity of Graphite Electrodes Modified with Symmetrically Substituted Metalloporphyrins.

Hydrogen, considered to be an alternative fuel to traditional fossil fuels, can be generated by splitting water molecules into hydrogen and oxygen via the use of electrical energy, in a process whose efficiency depends directly on the employed catalytic material. The current study takes part in the relentless search for suitable and low-cost catalysts relevant to the water-splitting field by investigating the electrocatalytic properties of the O2 and H2 evolution reactions (OER and HER) of two metalloporphyrins: Zn(II) 5,10,15,20-tetrakis(4-pyridyl)-porphyrin and Co(II) 5,10,15,20-tetrakis(3-hydroxyphenyl)-porphyrin. The TEM/STEM characterisation of the porphyrin samples obtained using different organic solvents revealed several types of self-assembled aggregates. The HER and OER experiments performed on porphyrin-modified graphite electrodes in media with different pH values revealed the most electrocatalytically active specimens. For the OER, this specimen was the electrode manufactured with one layer of Co-porphyrin applied from dimethylsulfoxide, exhibiting an overpotential of 0.51 V at i = 10 mA/cm2 and a Tafel slope of 0.27 V/dec. For the HER, it was the sample obtained by drop casting one layer of Zn-porphyrin from N,N-dimethylformamide that displayed a HER overpotential of 0.52 V at i = -10 mA/cm2 and a Tafel slope of 0.15 V/dec.

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.

Efficient Decrease in Corrosion of Steel in 0.1 M HCl Medium Realized by a Coating with Thin Layers of MnTa2O6 and Porphyrins Using Suitable Laser-Type Approaches.

The purpose of this research is to meet current technical and ecological challenges by developing novel steel coating systems specifically designed for mechanical equipment used in aggressive acid conditions. Homogeneous sandwich-type layered films on the surface of steel electrodes were realized using a pseudo-binary oxide, MnTa2O6, and two different substituted porphyrin derivatives, namely: 5-(4-carboxy-phenyl)-10,15,20-tris (4-methyl-phenyl)-porphyrin and 5-(4-methyl-benzoate)-10,15,20-tris (4-methyl-phenyl)-porphyrin, which are novel investigated compound pairs. Two suitable laser strategies, pulsed laser deposition (PLD) and matrix-assisted pulsed laser evaporation (MAPLE), were applied in order to prevent porphyrin decomposition and to create smooth layers with low porosity that are extremely adherent to the surface of steel. The electrochemical measurements of corrosion-resistant coating performance revealed that in all cases in which the steel electrodes were protected, a significant value of corrosion inhibition efficiency was found, ranging from 65.6 to 83.7%, depending on the nature of the porphyrin and its position in the sandwich layer. The highest value (83.7%) was obtained for the MAPLE/PLD laser deposition of 5-(4-carboxy-phenyl)-10,15,20-tris (4-methyl-phenyl)-porphyrin/MnTa2O6(h), meaning that the inhibitors adsorbed and blocked the access of the acid to the active sites of the steel electrodes.

Beyond Nitrogen in the Oxygen Reduction Reaction on Nitrogen-Doped Carbons: A NEXAFS Investigation.

Polymer electrolyte membrane fuel cells require cheap and active electrocatalysts to drive the oxygen reduction reaction. Nitrogen-doped carbons have been extensively studied regarding their oxygen reduction reaction. The work at hand looks beyond the nitrogen chemistry and brings to light the role of oxygen. Nitrogen-doped nanocarbons were obtained by a radio-frequency plasma route at 0, 100, 250, and 350 W. The lateral size of the graphitic domain, determined from Raman spectroscopy, showed that the nitrogen plasma treatment decreased the crystallite size. Synchrotron radiation photoelectron spectroscopy showed a similar nitrogen chemistry, albeit the nitrogen concentration increased with the plasma power. Lateral crystallite size and several nitrogen moieties were plotted against the onset potential determined from oxygen reduction reaction curves. There was no correlation between the electrochemical activity and the sample structure, as determine from Raman and synchrotron radiation photoelectron spectroscopy. Near-edge X-ray absorption fine structure (NEXAFS) was performed to unravel the carbon and nitrogen local structure. A difference analysis of the NEXAFS spectra showed that the oxygen surrounding the pyridinic nitrogen was critical in achieving high onset potentials. The work shows that there were more factors at play, other than carbon organization and nitrogen chemistry.

Hybrid Silica Materials Applied for Fuchsine B Color Removal from Wastewaters.

Hybrid materials, with applications in fuchsine B color removal from wastewaters, were obtained by in situ incorporation of platinum nanoparticles and/or Pt-porphyrin derivatives into silica matrices. The inorganic silica matrices were synthesized by the sol-gel method, conducted in acid-base catalysis in two steps and further characterized by Nitrogen porosimetry, Small Angle Neutron Scattering (SANS), Scanning electron microscopy, Atomic force microscopy and UV-vis spectroscopy. All of the investigated silica hybrid materials were 100% efficient in removing fuchsine B if concentrations were lower than 1 × 10-5 M. For higher concentrations, the silica matrices containing platinum, either modified with Pt-metalloporphyrin or with platinum nanoparticles (PtNPs), are the most efficient materials for fuchsine B adsorption from wastewaters. It can be concluded that the presence of the platinum facilitates chemical interactions with the dye molecule through its amine functional groups. An excellent performance of 197.28 mg fuchsine B/g adsorbent material, in good agreement with the best values mentioned in literature, was achieved by PtNPs-silica material, capable of removing the dye from solutions of 5 × 10-4 M, even in still conditions.

Hybrid Materials Based on Silica Matrices Impregnated with Pt-Porphyrin or PtNPs Destined for CO2 Gas Detection or for Wastewaters Color Removal.

Multifunctional hybrid materials with applications in gas sensing or dye removal from wastewaters were obtained by incorporation into silica matrices of either Pt(II)-5,10,15,20-tetra-(4-allyloxy-phenyl)-porphyrin (PtTAOPP) or platinum nanoparticles (PtNPs) alone or accompanied by 5,10,15,20-tetra-(4-allyloxy-phenyl)-porphyrin (TAOPP). The tetraethylorthosilicate (TEOS)-based silica matrices were obtained by using the sol-gel method performed in two step acid-base catalysis. Optical, structural and morphological properties of the hybrid materials were determined and compared by UV-vis, fluorescence and FT-IR spectroscopy techniques, by atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM) and by Brunauer-Emmett-Teller (BET) analysis. PtTAOPP-silica hybrid was the most efficient material both for CO2 adsorption (0.025 mol/g) and for methylene blue adsorption (7.26 mg/g) from wastewaters. These results were expected due to both the ink-bottle mesopores having large necks that exist in this hybrid material and to the presence of the porphyrin moiety that facilitates chemical interactions with either CO2 gas or the dye molecule. Kinetic studies concerning the mechanism of dye adsorption demonstrated a second order kinetic model, thus it might be attributed to both physical and chemical processes.

X-ray Structure Elucidation of a Pt-Metalloporphyrin and Its Application for Obtaining Sensitive AuNPs-Plasmonic Hybrids Capable of Detecting Triiodide Anions.

The development of UV⁻vis spectrophotometric methods based on metalloporphyrins for fast, highly sensitive and selective anion detection, which avoids several of the practical challenges associated with other detection methods, is of tremendous importance in analytical chemistry. In this study, we focused on achieving a selective optical sensor for triiodide ion detection in traces based on a novel hybrid material comprised of Pt(II) 5,10,15,20-tetra(4-methoxy-phenyl)-porphyrin (PtTMeOPP) and gold nanoparticles (AuNPs). This sensor has high relevance in medical physiological tests. The structure of PtTMeOPP was investigated by single crystal X-ray diffraction in order to understand the metal surroundings and the molecule conformation and to assess if it qualifies as a potential sensitive material. It was proven that the Pt-porphyrin generated 1D H-bond supramolecular chains due to the weak C-H···O intermolecular hydrogen bonding. The presence of ordered voids in the crystal encouraged us to use PtTMeOPP as the sensing material for triiodide ion and to enhance its potential in a novel AuNPs/PtTMeOPP hybrid by the synergistic effects provided by the plasmonic gold nanoparticles. The spectrophotometric sensor is characterized by a detection limit of 1.5 × 10-9 M triiodide ion concentration and a remarkable confidence coefficient of 99.98%.

Potentiometric Sensors for Iodide and Bromide Based on Pt(II)-Porphyrin.

Pt(II) 5,10,15,20-tetra(4-methoxy-phenyl)-porphyrin (PtTMeOPP) was used in the construction of new ion-selective sensors. The potentiometric response characteristics (slope and selectivity) of iodide and bromide-selective electrodes based on (PtTMeOPP) metalloporphyrin in o-nitrophenyloctylether (NPOE), dioctylphtalate (DOP) and dioctylsebacate (DOS) plasticized poly(vinyl chloride) membranes are compared. The best results were obtained for the membranes plasticized with DOP and NPOE. The sensors have linear responses with near-Nernstian slopes toward bromide and iodide ions and good selectivity. The membrane plasticized with NPOE was electrochemically characterized using the EIS method to determine its water absorption and the diffusion coefficient into the membrane.

Improved Optical and Morphological Properties of Vinyl-Substituted Hybrid Silica Materials Incorporating a Zn-Metalloporphyrin.

This work is focused on a novel class of hybrid materials exhibiting enhanced optical properties and high surface areas that combine the morphology offered by the vinyl substituted silica host, and the excellent absorption and emission properties of 5,10,15,20-tetrakis(N-methyl-4-pyridyl)porphyrin-Zn(II) tetrachloride as a water soluble guest molecule. In order to optimize the synthesis procedure and the performance of the immobilized porphyrin, silica precursor mixtures of different compositions were used. To achieve the requirements regarding the hydrophobicity and the porous structure of the gels for the successful incorporation of porphyrin, the content of vinyltriacetoxysilane was systematically changed and thoroughly investigated. Substitution of the silica gels with organic groups is a viable way to provide new properties to the support. An exhaustive characterization of the synthesized silica samples was realised by complementary physicochemical methods, such as infrared spectroscopy (FT-IR), absorption spectroscopy (UV-Vis) and photoluminescence, nuclear magnetic resonance spectroscopy (29Si-MAS-NMR) transmission and scanning electron microscopy (TEM and SEM), nitrogen absorption (BET), contact angle (CA), small angle X ray and neutron scattering (SAXS and SANS). All hybrids showed an increase in emission intensity in the wide region from 575 to 725 nm (Q bands) in comparison with bare porphyrin. By simply tuning the vinyltriacetoxysilane content, the hydrophilic/hydrophobic profile of the hybrid materials was changed, while maintaining a high surface area. Good control of hydrophobicity is important to enhance properties such as dispersion, stability behaviour, and resistance to water, in order to achieve highly dispersible systems in water for biomedical applications.

Trace Oxygen Sensitive Material Based on Two Porphyrin Derivatives in a Heterodimeric Complex.

The successful preparation of a novel dimer complex formed between 5,10,15,20-tetrakis(3,4-dimethoxyphenyl)-porphyrin Fe(III) chloride and (5,10,15,20-tetraphenylporphinato) dichlorophosphorus(V) chloride using the well-known reactivity of the P-X bond is reported. The obtained complex was characterized by UV-vis, Fourier transform infrared spectroscopy (FT-IR), fluorescence, ¹H-NMR, 13C-NMR, and 31P-NMR spectroscopic techniques and also by additional Heteronuclear Single Quantum Coherence (HSQC) and Heteronuclear Multiple Bond Correlation (HMBC) experiments in order to correctly assign the NMR signals. Scanning electron microscopy (SEM) and EDX quantifications completed the characterizations. This novel porphyrin dimer complex demonstrated fluorescence sensing of H2O2 in water for low oxygen concentrations in the range of 40-90 µM proving medical relevance for early diagnosis of diseases such as Alzheimer's, Parkinson's, Huntington's, and even cancer because higher concentrations of H2O2 than 50 µM are consideredcytotoxic for life. Due to its optical properties, this novel metalloporphyrin-porphyrin based complex is expected to show PDT and bactericidal activity under visible-light irradiation.

A sensitive A3B porphyrin nanomaterial for CO2 detection.

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 1H-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 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%.

Potentiometric detection and removal of copper using porphyrins.

BACKGROUND: Copper is an essential trace element with a great importance in industry, environment and biological systems. The great advantage of ion-selective sensors in comparison with other proposed techniques is that they are measuring the free metal ion activity which is responsible for their toxicity. Porphyrins are known to be among the best ionophores in formulation of ion-selective sensors. RESULTS: A symmetrically substituted meso-porphyrin, namely: 5,10,15,20-tetrakis(4-allyloxyphenyl)porphyrin (TAPP) was used in the construction of a new copper selective-sensor and was also tested for the removal of copper from waste waters. The potentiometric response characteristics (slope and selectivity) of copper-selective electrodes based on TAPP in o-nitrophenyloctylether (o-NPOE), dioctyl phtalate (DOP) and dioctyl sebacate (DOS) plasticized with poly(vinyl chloride) membranes are compared. CONCLUSIONS: The best results were obtained for the membrane plasticized with DOP. The sensor has linear response in the range 1x10-7 - 1x10-1 M with 28.4 ± 0.4 mV/decade near-Nernstian slope towards copper ions and presents good selectivity. Due to its chelating nature, the same porphyrin was also tested for the retention of copper from synthetic copper samples, showing a maximum adsorption capacity of 280 mg/g.

A novel sensor for monitoring of iron(III) ions based on porphyrins.

Three A(3)B porphyrins with mixed carboxy-, phenoxy-, pyridyl-, and dimethoxy-substituent functionalization on the meso-phenyl groups were obtained by multicomponent synthesis, fully characterized and used as ionophores for preparing PVC-based membrane sensors selective to iron(III). The membranes have an ionophore:PVC:plasticizer composition ratio of 1:33:66. Sodium tetraphenylborate was used as additive (20 mol% relative to ionophore). The performance characteristics (linear concentration range, slope and selectivity) of the sensors were investigated. The best results were obtained for the membrane based on 5-(4-carboxyphenyl)-10,15,20-tris(4-phenoxyphenyl)-porphyrin plasticized with bis(2-ethylhexyl)sebacate, in a linear range from 1 × 10(-7)-1 × 10(-1) M with a slope of 21.6 mV/decade. The electrode showed high selectivity with respect to alkaline and heavy metal ions and a response time of 20 s. The influence of pH on the sensor response was studied. The sensor was used for a period of six weeks and the utility has been tested for the quantitative determination of Fe(III) in recovered solutions from spent lithium ion batteries and for the quantitative determination of Fe(III) in tap water samples.

Synthesis of new phosphorus-containing (co)polyesters using solid-liquid phase transfer catalysis and product characterization.

This paper is directed towards the development of safe, and thermally stable solid polymer electrolytes. Linear phosphorus-containing (co)polyesters are described, including their synthesis, thermal analysis, conductivity, and non-flammability. Polycondensation of phenylphosphonic dichloride (PPD) with poly(ethylene glycol) (PEG 12000) with and without bisphenol A (BA) was carried out using solid-liquid phase transfer catalysis. Potassium phosphate is used as base. Yields in the range of 85.0-88.0%, and inherent viscosities in the range of 0.32-0.58 dL/g were obtained. The polymers were characterized by gel permeation chromatography, FT-IR, (1)H- and (31)P-NMR spectroscopy and thermal analysis. Their flammability was investigated by measuring limiting oxygen index values. The polymers are flame retardants and begin to lose weight in the 190 °C-231 °C range. Solid phosphorus- containing (co)polyesters were complexed with lithium triflate and the resulting ionic conductivity was determined. Conductivities in the range of 10(-7)-10(-8) S cm(-1) were obtained.

Manganese(III) porphyrin-based potentiometric sensors for diclofenac assay in pharmaceutical preparations.

Two manganese(III) porphyrins: manganese(III) tetraphenylporphyrin chloride and manganese(III)-tetrakis(3-hydroxyphenyl)porphyrin chloride were tested as ionophores for the construction of new diclofenac-selective electrodes. The electroactive material was incorporated either in PVC or a sol-gel matrix. The effect of different plasticizers and additives (anionic and cationic) on the potentiometric response was studied. The best results were obtained for the PVC membrane plasticized with dioctylphtalate and having sodium tetraphenylborate as a lipophilic anionic additive incorporated. The sensor response was linear in the concentration range 3 × 10(-6) - 1 × 10(-2) M with a slope of -59.7 mV/dec diclofenac, a detection limit of 1.5 × 10(-6) M and very good selectivity coefficients. It was used for the determination of diclofenac in pharmaceutical preparations, by direct potentiometry. The results were compared with those obtained by the HPLC reference method and a good agreement was found between the two methods.

Syntheses, spectroscopic and AFM characterization of some manganese porphyrins and their hybrid silica nanomaterials.

The present work is concerned with the manganese complexes of 5,10,15,20-tetraphenylporphyrin and of 5,10,15,20-tetra(3-hydroxyphenyl)porphyrin, which were prepared by metallation of the corresponding porphyrin ligands, and the study of their spectroscopic and photophysical behavior under strongly acidic and alkaline conditions. The second objective was to obtain and study some new hybrid materials, with special optoelectronic and surface properties, by impregnation of silica gels obtained by one step acid and by two steps acid-base catalysis with these Mn-porphyrins. The resulting nanomaterials exhibited interesting bathochromic and hyperchromic effects of their second band in the emission spectra in comparison with the Mn-porphyrins and also they have distinct orientation of the aggregates on surfaces, as shown by AFM images, making them useful for applications in medicine, formulation of sensors and for environmental-friendly catalysts for photodegradation of organic compounds.

Free Base Porphyrins as Ionophores for Heavy Metal Sensors.

Two functionalized porphyrins: 5,10,15,20-tetrakis(3,4-dimethoxyphenyl) porphyrin (A) and 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin (B) obtained and characterized by us were used as ionophores (I) for preparing PVC-based membrane sensors selective to Ag⁺, Pb2+ and Cu2+. The membranes were prepared using three different plasticizers: (bis(2-ethylhexyl)sebacate (DOS), dioctylphtalate (DOP), o-nitrophenyl octyl ether (NPOE) and potassium tetrakis(4-chlorophenyl)borate (KTClPB) as additive. The functional parameters (linear concentration range, slope and selectivity) of the sensors with membrane composition: (I:PVC:KTClPB:Plasticizer) in different ratios were investigated. The best results were obtained for the membranes in the ratio I:PVC:KTClPB:Plasticizer 10:165:5:330. The influence of pH on the sensors response was studied. The sensors were used for a period of four months and their utility has been tested on synthetic and real samples.