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Taranu BO, Fagadar-Cosma E. The pH Influence on the Water-Splitting Electrocatalytic Activity of Graphite Electrodes Modified with Symmetrically Substituted Metalloporphyrins. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3788. [PMID: 36364562 PMCID: PMC9656975 DOI: 10.3390/nano12213788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 10/19/2022] [Accepted: 10/24/2022] [Indexed: 06/16/2023]
Abstract
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.
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Affiliation(s)
- Bogdan-Ovidiu Taranu
- National Institute for Research and Development in Electrochemistry and Condensed Matter, Dr. A. Paunescu Podeanu Street No. 144, 300569 Timisoara, Romania
| | - Eugenia Fagadar-Cosma
- Institute of Chemistry “Coriolan Dragulescu”, Mihai Viteazu Ave. 24, 300223 Timisoara, Romania
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Catalytic Properties of Free-Base Porphyrin Modified Graphite Electrodes for Electrochemical Water Splitting in Alkaline Medium. Processes (Basel) 2022. [DOI: 10.3390/pr10030611] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Hydrogen generation via electrochemical water splitting is considered an eco-friendly pathway for obtaining this desired alternative energy source, and it has triggered an intensive search for low cost and efficient catalysts. Within this context, four free-base porphyrins were studied as heterogeneous catalysts for the oxygen and hydrogen evolution reactions (OER and HER) in alkaline aqueous solutions. TEM and STEM analyses of samples obtained by drop-casting the porphyrins from different organic solvents on TEM grids revealed a rich variety of aggregates due to the self-assembling property of the porphyrin molecules. Modified electrodes were manufactured by applying the four tetrapyrrolic macrocycles from various solvents on the surface of graphite supports, in one or more layers. Experiments performed in 0.1 M and 1 M KOH electrolyte solutions allowed the identification of the most electrocatalytically active electrodes for the OER and HER, respectively. In the first case, the electrode was manufactured by applying three layers of 5-(4-pyridyl)-10,15,20-tris(4-phenoxyphenyl)porphyrin on the graphite substrate from N,N-dimethylformamide solution was identified as overall catalytically superior. In the second case, the electrode obtained by applying one layer of 5,10,15,20-tetrakis(4-allyloxyphenyl)-porphyrin from benzonitrile solution displayed an HER overpotential value of 500 mV at i = −10 mA/cm2 and a Tafel slope of 190 mV/dec.
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Pascu B, Negrea A, Ciopec M, Duteanu N, Negrea P, Nemeş NS, Seiman C, Marian E, Micle O. A Green, Simple and Facile Way to Synthesize Silver Nanoparticles Using Soluble Starch. pH Studies and Antimicrobial Applications. MATERIALS 2021; 14:ma14164765. [PMID: 34443288 PMCID: PMC8399506 DOI: 10.3390/ma14164765] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 08/15/2021] [Accepted: 08/17/2021] [Indexed: 11/25/2022]
Abstract
Along with the progress of nanoscience and nanotechnology came the means to synthesize nanometric scale materials. While changing their physical and chemical properties, they implicitly changed their application area. The aim of this paper was the synthesis of colloidal silver nanoparticles (Ag-NPs by ultrasonic disruption), using soluble starch as a reducing agent and further as a stabilizing agent for produced Ag-NPs. In this context, an important parameter for Ag-NPs preparation is the pH, which can determine the particle size and stability. The physical-chemical behavior of the synthesized Ag-NPs (shape, size, dispersion, electric charge) is strongly influenced by the pH value (experiment being conducted for pH values in the range between 8 and 13). The presence of a peak located at 412 nm into the UV-VIS spectra demonstrates the presence of silver nano-spheres into the produced material. In UV/VIS spectra, we observed a specific peak for yellow silver nano-spheres located at 412 nm. Samples characterization was performed by scanning electron microscopy, SEM, energy-dispersive X-ray spectroscopy, EDX, Fourier-transform infrared spectroscopy, and FT-IR. For all Ag-NP samples, we determined the zeta and observed that the Ag-NP particles obtained at higher pH and have better stability. Due to the intrinsic therapeutic properties and broad antimicrobial spectrum, silver nanoparticles have opened new horizons and new approaches for the control of different types of infections and wound healing abilities. In this context, the present study also aims to confirm the antimicrobial effect of prepared Ag-NPs against several bacterial strains (indicator and clinically isolated strains). In this way, it was confirmed that the antimicrobial activity of synthesized Ag-NPs was good against Staphylococcus aureus (ATCC 25923 and S. aureus MSSA) and Escherichia coli (ATTC 25922 and clinically isolated strain). Based on this observation, we conclude that the prepared Ag-NPs can represent an alternative or auxiliary material used for controlling important nosocomial pathogens. The fungal reference strain Candida albicans was more sensitive at Ag-NPs actions (zone of inhibition = 20 mm) compared with the clinically isolated strain (zone of inhibition = 10 mm), which emphasizes the greater resistance of fungal strains at antimicrobial agent’s action.
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Affiliation(s)
- Bogdan Pascu
- Faculty of Industrial Chemistry and Environmental Engineering, Politehnica University of Timisoara, 300006 Timisoara, Romania; (B.P.); (P.N.)
- Renewable Energy Research Institute, Politehnica University of Timisoara, 300501 Timişoara, Romania
| | - Adina Negrea
- Faculty of Industrial Chemistry and Environmental Engineering, Politehnica University of Timisoara, 300006 Timisoara, Romania; (B.P.); (P.N.)
- Correspondence: (A.N.); (M.C.); (N.D.); (N.S.N.)
| | - Mihaela Ciopec
- Faculty of Industrial Chemistry and Environmental Engineering, Politehnica University of Timisoara, 300006 Timisoara, Romania; (B.P.); (P.N.)
- Correspondence: (A.N.); (M.C.); (N.D.); (N.S.N.)
| | - Narcis Duteanu
- Faculty of Industrial Chemistry and Environmental Engineering, Politehnica University of Timisoara, 300006 Timisoara, Romania; (B.P.); (P.N.)
- Correspondence: (A.N.); (M.C.); (N.D.); (N.S.N.)
| | - Petru Negrea
- Faculty of Industrial Chemistry and Environmental Engineering, Politehnica University of Timisoara, 300006 Timisoara, Romania; (B.P.); (P.N.)
| | - Nicoleta Sorina Nemeş
- Renewable Energy Research Institute, Politehnica University of Timisoara, 300501 Timişoara, Romania
- Correspondence: (A.N.); (M.C.); (N.D.); (N.S.N.)
| | - Corina Seiman
- Faculty of Chemistry, Biology, Geography, West University Timisoara, 300115 Timisoara, Romania;
| | - Eleonora Marian
- Faculty of Medicine and Pharmacy, University of Oradea, 410068 Oradea, Romania; (E.M.); (O.M.)
| | - Otilia Micle
- Faculty of Medicine and Pharmacy, University of Oradea, 410068 Oradea, Romania; (E.M.); (O.M.)
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Patel N, Swavey S, Robinson J. A Cationic Porphyrin, ZnPor, Disassembles Pseudomonas aeruginosa Biofilm Matrix, Kills Cells Directly, and Enhances Antibiotic Activity of Tobramycin. Antibiotics (Basel) 2020; 9:E875. [PMID: 33291344 PMCID: PMC7762324 DOI: 10.3390/antibiotics9120875] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Revised: 11/28/2020] [Accepted: 12/03/2020] [Indexed: 12/14/2022] Open
Abstract
One of the greatest threats to human health is the rise in antibiotic-resistant bacterial infections. Pseudomonas aeruginosa (PsA) is an "opportunistic" pathogen known to cause life-threatening infections in immunocompromised individuals and is the most common pathogen in adults with cystic fibrosis (CF). We report here a cationic zinc (II) porphyrin, ZnPor, that effectively kills planktonic and biofilm-associated cells of PsA. In standard tests against 16-18 h-old biofilms, concentrations as low as 16 µg/mL resulted in the extensive disruption and detachment of the matrix. The pre-treatment of biofilms for 30 min with ZnPor at minimum inhibitory concentration (MIC) levels (4 µg/mL) substantially enhanced the ability of tobramycin (Tobra) to kill biofilm-associated cells. We demonstrate the rapid uptake and accumulation of ZnPor in planktonic cells even in dedicated heme-uptake system mutants (ΔPhu, ΔHas, and the double mutant). Furthermore, uptake was unaffected by the ionophore carbonyl cyanide m-chlorophenyl hydrazine (CCCP). Cells pre-exposed to ZnPor took up the cell-impermeant dye SYTOXTM Green in a concentration-dependent manner. The accumulation of ZnPor did not result in cell lysis, nor did the cells develop resistance. Taken together, these properties make ZnPor a promising candidate for treating multi-drug-resistant infections, including persistent, antibiotic-resistant biofilms.
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Affiliation(s)
- Neha Patel
- Department of Biology, University of Dayton, Dayton, OH 45469, USA;
| | - Shawn Swavey
- Department of Chemistry, University of Dayton, Dayton, OH 45469, USA;
| | - Jayne Robinson
- Department of Biology, University of Dayton, Dayton, OH 45469, USA;
- Integrated Science and Engineering Center, University of Dayton, Dayton, OH 45469, USA
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