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Gabriel Katona

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Papers by Gabriel Katona

Liver-on-a-Chip‒Magnetic Nanoparticle Bound Synthetic Metalloporphyrin-Catalyzed Biomimetic Oxidation of a Drug in a Magnechip Reactor

Micromachines, Oct 1, 2019

Biomimetic oxidation of drugs catalyzed by metalloporphyrins can be a novel and promising way for... more Biomimetic oxidation of drugs catalyzed by metalloporphyrins can be a novel and promising way for the effective and sustainable synthesis of drug metabolites. The immobilization of 5,10,15,20-tetrakis(2,3,4,5,6-pentafluorophenyl)iron(II) porphyrin (FeTPFP) and 5,10,15,20-tetrakis-(4-sulfonatophenyl)iron(II) porphyrin (FeTSPP) via stable covalent or rapid ionic binding on aminopropyl-functionalized magnetic nanoparticles (MNPs-NH 2 ) were developed. These immobilized catalysts could be efficiently applied for the synthesis of new pharmaceutically active derivatives and liver related phase I oxidative major metabolite of an antiarrhythmic drug, amiodarone integrated in a continuous-flow magnetic chip reactor (Magnechip).

Molecular Topology 22.1 Novel Connectivity Descriptors Based on Walk Degrees

Croatica Chemica Acta

An algorithm for generating novel connectivity topological descriptors, denoted SP (subgraph prop... more An algorithm for generating novel connectivity topological descriptors, denoted SP (subgraph property), is proposed and exemplified for P being the number of vertices N, walk degree wt'e), Randić index X, and Wiener index W. SP indices based on wt'e) and x wt'e) (Razinger's extension of x index) are tested for correlation with some physico-chemical properties of octane isomers.

Electrochemical Determination of Dopamine with Ruthenium(III)-Modified Glassy Carbon and Screen-Printed Electrodes

Analytical Letters, 2017

Here is reported for the first time the application of sodium bis[N-2-oxyphenyl-5bromosalicyliden... more Here is reported for the first time the application of sodium bis[N-2-oxyphenyl-5bromosalicylideneiminato-ONO]ruthenate (III) as a mediator with multiwalled carbon nanotubes and Nafion at glassy carbon and screen printed electrodes for the determination of dopamine in the presence of ascorbic acid. Electrochemical studies were done using cyclic voltammetry, differential pulse voltammetry, and flow-injection amperometry. In flow injection mode, the flow rate was 0.4 mL min -1 , the injection volume 250 μL, and the operation potential 0.05 V versus Ag / AgCl. In 0.1 M pH 7.5 phosphate buffer, the sensor provided a linear dynamic range up to 50 mg L 1 dopamine with a detection limit of 0.11 ± 0.04 mg L 1 . The sensor was employed for the determination of dopamine in ampoules of dopamine hydrochloride by cyclic voltammetry, differential pulse voltammetry, and flow-injection amperometry.

Correlations between the anti-corrosion properties and the photocatalytic behavior of epoxy coatings incorporating modified graphene oxide deposited on a zinc substrate

RSC advances, 2024

This research aimed to create a substrate-coating system based on zinc and an epoxy resin incorpo... more This research aimed to create a substrate-coating system based on zinc and an epoxy resin incorporating modified graphene oxide, which possesses two key characteristics: effective resistance against corrosion and the ability to harness photocatalytic properties. Furthermore, correlations between the anticorrosion properties and the photocatalytic behaviour of the coatings were made. Thin epoxy (EP) layers embedding 0.1 wt% graphene oxide (GO), reduced graphene oxide (rGO), and modified graphene oxide with (3-aminopropyl)-triethoxysilane (APTES) or poly(amidoamine) (PAMAM) dendrimer were applied on a zinc (Zn) substrate using the dip-coating method. Anti-corrosion properties of coated Zn samples were investigated through electrochemical impedance spectroscopy (EIS) measurements. They showed that the corrosion protection effect is more prominent for EP containing functionalized GO, the highest in the case of GO-PAMAM. The results of the EIS measurements indicated also that the corrosion protection provided by EP-rGO is smaller than that of EP. The photocatalytic properties of the coatings were studied by exposure of the samples to Methylene Blue (MB) solution followed by monitoring the model dye degradation through UV-Vis measurements. To determine the changes in the anti-corrosion properties due to photocatalysis, the coated Zn samples were put through additional EIS measurements. The same coatings applied to a glass substrate lacked photocatalytic properties, indicating that the Zn substrate is accountable for the degradation of MB. Furthermore, the incorporation of GO or functionalized GO into the coating amplifies this effect. From EIS spectra, it was determined that the protective properties loss observed after 3 days is due to coating delamination during exposure to MB solution, the EP-GO-APTES retaining the best adhesion of the coating, 98% remaining on Zn after a cross-hatch test. The corrosion measurements were complemented by examining the morphology and structure of the coatings and the modified GO particles. All things considered, the Zn/EP-GO-APTES system shows the best ability to break down organic pollutants, keeping a good anti-corrosive property and adhesion.

Temporary Anti-Corrosive Double Layer on Zinc Substrate Based on Chitosan Hydrogel and Epoxy Resin

Gels

In practice, metal structures are frequently transported or stored before being used. Even in suc... more In practice, metal structures are frequently transported or stored before being used. Even in such circumstances, the corrosion process caused by environmental factors (moisture, salty air, etc.) can occur quite easily. To avoid this, metal surfaces can be protected with temporary coatings. The objective of this research was to develop coatings that exhibit effective protective characteristics while also allowing for easy removal, if required. Novel, chitosan/epoxy double layers were prepared on zinc by dip-coating to obtain temporary tailor-made and peelable-on-demand, anti-corrosive coatings. Chitosan hydrogel fulfills the role of a primer that acts as an intermediary between the zinc substrate and the epoxy film to obtain better adhesion and specialization. The resulting coatings were characterized using electrochemical impedance spectroscopy, contact angle measurements, Raman spectroscopy, and scanning electron microscopy. The impedance of the bare zinc was increased by three or...

Hydrogen production by ethanol steam reforming over Cu-Ni/SBA-15 supported catalysts prepared by direct synthesis and impregnation

Applied Catalysis A: General, 2007

Cu-Ni/SBA-15 supported catalysts prepared by the incipient wetness impregnation method were teste... more Cu-Ni/SBA-15 supported catalysts prepared by the incipient wetness impregnation method were tested in the ethanol steam reforming reaction for hydrogen production. The effect of reaction temperature and metal loading was studied in order to maximize the hydrogen selectivity and the CO2/(CO+CO2) molar ratio. The best catalytic performance was achieved at 600°C. Products distribution was the result of the combined effects

Platinum Recovery From Used Auto Catalysts: Dissolution and Precipitation Studies

Studia Universitatis Babeș-Bolyai Ambientum

"Noble metals are used in a plethora of applications, from electronic and communication equi... more "Noble metals are used in a plethora of applications, from electronic and communication equipments, to aerospacial engines, mobile phones and catalytic convertors. Currently, there is a continuous interest in the recovery of noble metals from waste, as their natural reserves are limited. Herein, the paper presents studies on the recovery of platinum from spent automotive catalysts. The process involves two steps - dissolving of platinum, followed by its precipitation into a hexacloroplatinum complex. The optimum reaction conditions for dissolving Pt from the spent automotive catalyst use a mixture of H2O2 + HCl (1:5.5 molar ratio) at 30°C, for 8 h. For the full recovery of platinum from the solution, the volumetric ratio of 4:1 between the platinum solution and the precipitating ammonium chloride solution is optimum. In addition, studies regarding the precipitation time and temperature have also been performed. All the obtained precipitates were analyzed by X-ray powder diffraction and showed the structure of the hexachloroplatinic (NH4)2[PtCl6] complex, with high purity. Upscaling of the processes for technological transfer show promising results in the recovery of platinum from spent automotive catalysts. Keywords. Spent automotive catalyst, Pt recovery, (HCl + H2O2) leaching, precipitation. "

Anti-corrosive Polystyrene Coatings Modified with Tannic Acid on Zinc and Steel Substrates

Journal of Electrochemical Science and Engineering

Polystyrene (PS) polymer layers were prepared and studied as anti-corrosive barrier layers on bot... more Polystyrene (PS) polymer layers were prepared and studied as anti-corrosive barrier layers on both carbon steel and zinc substrates. To increase the corrosion resistance of the coatings, two different approaches were considered: (i) the use of mesoporous silica-nanocontainers impregnated with a corrosion inhibitor (tannic acid) introduced into the polystyrene matrix and (ii) direct impregnation of polystyrene coatings with the same corrosion inhibitor. The impregnated nanocontainers were characterized by Transmission Electron Microscopy. The thickness and the adhesion of the coatings were measured, and their corrosion behavior was investigated by Electrochemical Impedance Spectroscopy. Results showed that the used inhibitor slightly decreased adhesion, but significantly increased the corrosion resistance of the coatings. The direct introduction of tannic acid into the polymer matrix offers higher corrosion resistance than in the case of polystyrene coatings doped with impregnated si...

Structural, morphological and dissolution properties of ZrO2-based biocomposites for dental applications

Studia Universitatis Babeș-Bolyai Chemia, 2020

In the present work, zirconia-based biocomposites were prepared by adding different amounts of an... more In the present work, zirconia-based biocomposites were prepared by adding different amounts of antibacterial magnesium oxide and bioactive and biocompatible hydroxyapatite (HAP). The biocomposites were synthesized by the conventional ceramic processing route. The structure and morphology of the materials were investigated using X-ray powder diffraction (XRPD), scanning and transmission electronic microscopy (SEM and TEM). The stability of the tetragonal structure of ZrO2 was confirmed by XRPD analyses. Moreover, their bioactivity was studied by soaking the samples in artificial saliva (AS) to evaluate the effect of MgO and HAP on the biological performances of the prepared biocomposites. UV-VIS analyses carried out on artificial saliva after immersion of the prepared materials showed that MgO plays an important role in the post-immersion dissolution process.

New fluorescent phenothiazine carboxylates for fluorescent nanomaterials

Journal of Molecular Structure, 2021

Abstract Fluorescent electrospun polymers doped with new 10-ethyl-10H-phenothiazine-3-carboxylate... more Abstract Fluorescent electrospun polymers doped with new 10-ethyl-10H-phenothiazine-3-carboxylate derivatives were prepared, and their optical properties were investigated. The fluorescence emission properties were studied in solution and solid state for 10-ethyl-10H-phenothiazine-3-carboxylic acid (2) and for two if its salts (3a, b). The quantum yields and fluorescence lifetimes were also determined for 10-ethyl-10H-phenothiazine-3-carboxylates before and after incorporation in polymeric matrices. From fluorescence emission in solid state and in solution, large Stokes shifts were recorded in all investigated solvents for the salts 3a, b.

Efficient and Stable Magnetic Chitosan-Lipase B from Candida Antarctica Bioconjugates in the Enzymatic Kinetic Resolution of Racemic Heteroarylethanols

Molecules, 2020

Lipase B from Candida antarctica immobilized by covalent binding on sebacoyl-activated chitosan-c... more Lipase B from Candida antarctica immobilized by covalent binding on sebacoyl-activated chitosan-coated magnetic nanoparticles proved to be an efficient biocatalyst (49.2–50% conversion in 3–16 h and >96% enantiomeric excess) for the enzymatic kinetic resolution of some racemic heteroarylethanols through transesterification with vinyl acetate. Under optimal conditions (vinyl acetate, n-hexane, 45 °C), the biocatalyst remains active after 10 cycles.

Comparative study on physicochemical and mechanical characterization of newnanocarbon-based hydroxyapatite nanocomposites

TURKISH JOURNAL OF CHEMISTRY, 2019

This study evaluated the effect of different additives such as nanocarbon compounds (0.5, 1.0, an... more This study evaluated the effect of different additives such as nanocarbon compounds (0.5, 1.0, and 2.0 wt.%) with different morphologies and gelatin (Gel) (10 wt.%) on the mechanical properties of hydroxyapatite (Hap)based nanocomposites (NCs). The NCs were prepared using the innovation process "SmartBox" based on the Internet of things (IoT), which provides process control and reproducibility, and they were characterized by X-ray diffraction, particle size distribution, transmission electron microscopy, Fourier transform infrared spectroscopy, and thermal analysis. The compressive strength tests demonstrated that the use of grapheme oxide (Hap_GO_2.0-133 N/mm 2) , and/or Gel (Hap_Gel-152 N/mm 2) as additives to reinforce Hap (106 N/mm 2) is more appropriate than the use of single functionalized multiwalled carbon nanotubes (Hap_fMWCNT_1.0-110 N/mm 2) and fullerene (Hap_Ful_0.5-106 N/mm 2) .

Design, synthesis and structure of novel G-2 melamine-based dendrimers incorporating 4-(n-octyloxy)aniline as a peripheral unit

Beilstein Journal of Organic Chemistry, 2018

Background: 4-(n-Octyloxy)aniline is a known component in the elaboration of organic materials wi... more Background: 4-(n-Octyloxy)aniline is a known component in the elaboration of organic materials with mesogenic properties such as N-substituted Schiff bases, perylene bisimide assemblies with a number of 2-amino-4,6-bis[4-(n-octyloxy)phenylamino]-s-triazines, amphiphilic azobenzene-containing linear-dendritic block copolymers and G-0 monomeric or dimeric dendritic liquid crystals with photochromic azobenzene mesogens. The present ab initio study explores a previously unknown use of 4-(n-octyloxy)aniline in the synthesis, structure and supramolecular behaviour of new dendritic melamines.Results: Starting from 4-(n-octyloxy)aniline, seven G-2 melamine-based dendrimers were obtained in 29–79% overall yields. Their iterative convergent- and chemoselective synthesis consisted of SN2-Ar aminations of cyanuric chloride and final triple N-acylations and Williamson etherifications (→ G-2 covalent trimers) or stoichiometric carboxyl/amino 1:3 neutralisations (→ G-2 ionic trimers). These transf...

Synthesis and Characterization of Derivatized Carbon Nanostructures

Studia Universitatis Babeș-Bolyai Chemia, 2017

Carbon nanotube-triethanolamine and carbon nanotubedendrimer structures were obtained from carbox... more Carbon nanotube-triethanolamine and carbon nanotubedendrimer structures were obtained from carboxyl functionalized nanotubes (SW-, DW-, MW-COOH). The synthesized compounds were characterized by elemental analysis, scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy (STEM-EDX). The toxicity of the obtained derivatized carbon nanostructures was tested on human immortalized keratinocyte cell line (HaCaT). The viability of the cells was determined using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium-bromide (MTT) cell proliferation assay.

Aminated Single-walled Carbon Nanotubes as Carrier for Covalent Immobilization of Phenylalanine Ammonia-lyase

Periodica Polytechnica Chemical Engineering, 2017

A new and efficient immobilized form of phenylalanine ammonia-lyase (PAL) was obtained by covalen... more A new and efficient immobilized form of phenylalanine ammonia-lyase (PAL) was obtained by covalent linkage onto amino functionalized single-walled carbon nanotubes (SwCNTNH2) as carrier. The catalytic properties of the resulted nanostructured biocatalyst (SwCNTNH2-PAL) were tested in the kinetic resolution of racemic 2-amino-3-(thiophen-2-yl)propanoic acid 1 by ammonia elimination and in the enantiotope selective addition of ammonia onto (E)-3-(thiophen-2-yl)acrylic acid 2. SwCNTNH2-PAL was a durable biocatalyst in batch mode for ammonia elimination from 1 (>85% of original activity after 7 cycles) and in ammonia addition to 2 (>70% of original activity after 3 cycles in 6 M NH3 , pH 10.0). The ammonia addition onto 2 was also studied in a continuous-flow microreactor packed with SwCNTNH2-PAL (2 M NH3, pH 10.0, 15 bar) in the 30-80 °C temperature range. No significant loss of PAL activity was observed over 72 h in the microreactor up to 60 °C. Productivity of SwCNTNH2-PAL at 3...

The effects of silver nanoparticles on behavior, apoptosis and nitro-oxidative stress in offspring Wistar rats

Nanomedicine (London, England), 2017

To investigate the comparative effects of prenatal exposure to silver nanoparticles (AgNPs) funct... more To investigate the comparative effects of prenatal exposure to silver nanoparticles (AgNPs) functionalized with citrate and polyphenols on spatial cognition and also on nitro-oxidative stress and apoptosis in the hippocampus and cerebellum of offsprings. Pregnant Wistar rats were orally administered substances from day 10 of gestation until day 21. Six weeks postpartum, six male offsprings from each group were used for behavioral evaluation and determination of oxidative stress and apoptosis. Both groups exhibited hyperactivity and anxiety especially after AgNPs-Sambucus nigra L. administration. AgNPs-S. nigra L. group showed increase in induced nitric oxide synthase activity and decrease in superoxide dismutase activity and apoptosis in the hippocampus, while AgNPs-citrate coated administration exerted a moderate toxicity and induced apoptosis. AgNPs functionalized with natural extracts had a lower toxicity than citrate-coated silver particles.

Enhancement of peroxidase-like activity of N-doped graphene assembled with iron-tetrapyridylporphyrin

RSC Advances, 2016

Non-covalently iron-porphyrin functionalized N-doped graphene shows a higher peroxidase-like acti... more

Albumin adsorption study onto hydroxyapatite-multiwall carbon nanotube based composites

Materials Chemistry and Physics, 2016

h i g h l i g h t s Carboxyl functionalized MWCNT, HAP or HAP-Si/chitosan composites were prepare... more

Nanobioconjugates of Candida antarctica lipase B and single-walled carbon nanotubes in biodiesel production

Bioresource Technology, 2016

Carboxylated single-walled carbon nanotubes (SWCNTCOOH) were used as support for covalent immobil... more Carboxylated single-walled carbon nanotubes (SWCNTCOOH) were used as support for covalent immobilization of Candida antarctica lipase B (CaL-B) using linkers with different lengths. The obtained nanostructured biocatalysts with low diffusional limitation were tested in batch mode in the ethanolysis of the sunflower oil. SWCNTCOOH-CaL-B proved to be a highly efficient and stable biocatalyst in acetonitrile (83.4 % conversion after 4 h at 35 C, retaining >90% of original activity after 10 cycles).

Designing chitosan–silver nanoparticles–graphene oxide nanohybrids with enhanced antibacterial activity against Staphylococcus aureus

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2015

Designing hybrid nanomaterials that exhibit multiple mechanisms of antibacterial action provides ... more Designing hybrid nanomaterials that exhibit multiple mechanisms of antibacterial action provides a new paradigm in the fight against resistant bacteria. Herein, we present such a new hybrid nanomaterial which integrates the antibacterial and physico-chemical properties of silver nanoparticles, graphene oxide and chitosan biopolymer. The formation, stability and structure of the integrated three-component chitosan-silver nanoparticles-graphene oxide (chit-AgNPs-GO) nanomaterial is analyzed by UV-Vis extinction spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and zeta potential measurements. The antibacterial activity is evaluated against two representative methicillinresistant Staphylococcus aureus (MRSA) strains (UCLA 8076 and 1190R) and relative to individual components (GO, chit-GO, AgNPs-GO) by determining the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). The three-component nanocomposites (chit-AgNPs-GO) exhibit higher antibacterial activity than most of the antibacterial agents based on AgNPs or AgNPs-GO reported so far and, more interestingly, their activity can be controlled by the ratio between the amount of chitosan and AgNPs-GO. The results presented in this study demonstrate the promising potential of the chit-AgNps-GO hybrids as effective nanomaterial to fight against the bacterial infections.