Tamás Szabó

University of Szeged · Department of Physical Chemistry and Materials Science

TiO2-based mixed oxide–carbon composite support for Pt electrocatalysts provides higher stability and CO tolerance under the working conditions of polymer electrolyte membrane fuel cells compared to traditional carbon supports. Non-traditional carbon materials like graphene nanoplatelets and graphite oxide used as the carbonaceous component of the...

The main goal of this research is to investigate the effectiveness of graphitic carbon nitride (g-C3N4, g-CN) in both bulk and nanosheet forms, which have been surface-modified with silver nanoparticles (Ag NPs), as photocatalysts for the degradation of acid orange 7 (AO7), a model dye. The photodegradation of AO7 dye molecules in water was used to...

Ionogels are an attractive class of materials for smart and flexible electronics and are prepared from the combination of a polymer and ionic liquid which is entrapped in this matrix. Ionogels provide a continuous conductive phase with high thermal, mechanical, and chemical stability. However, because of the higher percentage of ionic liquids it is...

Hypothesis Reduced graphene oxide (rGO/polycation/sulfur) composites are promising cathode materials for Li-S battery applications because homogeneously dispersed sulfur nano/micro clusters in suitable carbon hosts enable remarkable cycle life for Li-S battery cells. New, benign and economic synthesis methods based only on aqueous colloidal dispers...

Homoaggregation of polystyrene microplastics (MPs) and heteroaggregation of MPs with anionic clay minerals, namely, layered double hydroxide (LDH), in different salt (NaCl, CaCl2, and Na2SO4) solutions were systematically investigated using light scattering techniques. The salt type and ionic strength had significant effects on the stability of bot...

This study investigates the enhancement of dairy wastewater treatment using chemical and physical pre-treatments coupled with membrane separation techniques to reduce membrane fouling. Two mathematical models, namely the Hermia and resistance-in-series module, were utilized to comprehend the mechanisms of ultrafiltration (UF) membrane fouling. The...

Designing turbulence promoters with optimal geometry and using them for ultrafiltration systems has been a key challenge in mitigating membrane fouling. In this study, six different turbulence promoters were created using three-dimensional printing technology and applied in dead-end ultrafiltration. Three-dimensional-printed (3DP) turbulence promot...

In line with the global recognition of waste-to-wealth concept aiming for circular economy, scientific articles are published in greatly increasing number on the eco-friendly and sustainable utilization of carbon nanocomposites. However, control on the structure and properties of waste-derived carbon nanomaterials still requires substantial future...

To mitigate the shuttle effect and enhance the electrical conductivity in lithium battery cathode, the unique characteristics of supercritical CO2 solvent (SC–CO2) and the distinctive porous and layered microstructure of reduced graphene oxide (rGO) are exploited in the fabrication of a high-performance rGO/sulfur composite cathode. Exploiting SC-C...

The COVID-19 pandemic has highlighted the importance of air sterilization and disinfection. Besides the regular cleaning and disinfection of surfaces it is at least as important to reduce the number of airborne microorganisms as they are known to play an important role in the spreading of different infections. Herein, we report a facile preparation...

Amino acid complexes of zirconia represent an entirely new class of materials that were synthesized and studied for the first time for the decontamination of fluoride ion containing aqueous solutions. Glutamic and aspartic acid complexes of zirconia assembled with thin carbon (stacked graphene oxide) platelets deriving from graphite oxide (GO) were...

TiO2-C (carbon) hybrid materials are promising electrocatalyst supports because the presence of TiO2 results in enhanced stability. Use of new types of carbonaceous materials such as reduced graphene oxide instead of traditional active carbon provides certain benefits. Although the rutile polymorph of TiO2 seems to have the most beneficial properti...

We present a study on the magnetic hyperthermia properties of graphene oxide/magnetite (GO/MNP) nanocomposites to investigate their heat production behavior upon the modification of the oxidation degree of the carbonaceous host. Avoiding the harsh chemical conditions of the regular in situ co-precipitation-based routes, the oppositely charged MNPs...

Charging and aggregation processes were studied in aqueous dispersions of halloysite nanotubes (HNTs) in the presence of monovalent inorganic electrolytes and ionic liquid (IL) constituents. The same type of co-ion (same sign of charge as HNT) was used in all systems, while the type of counterions (opposite sign of charge as HNT) was systematically...

In the present work we report on the effect of the size and the degree of oxidation on the third-order nonlinear optical response and the optical limiting action of water dispersed graphene oxide (GO) sheets. The results show clearly that both the nonlinear optical third-order susceptibility χ(3) and the optical limiting threshold depend importantl...

Graphene oxides (GO) of highly polydisperse size distribution were prepared by the Brodie method and their dispersion stability was characterized. Exfoliation and fractionation led to well-defined particle populations in the Nano, classical Colloidal (submicron) and Micrometer size ranges, as revealed by atomic force microscopy and light scattering...

This study provides a comparative framework on the elucidation of analogies and differences in the interfacial protolytic processes and the associated colloidal behaviour of a typical humic acid (HA) and a set of single-layer graphene oxide (SLGO) and (multi-layered) graphite oxide samples in aqueous electrolyte media. The pH dependence of the surf...

Tetraamminepalladium(II) chloride monohydrate was heterogenized on hydrophilic graphite oxide (GO), synthesized by Brodie's method. Two samples, with Pd contents of 2% and 5%, referred to as Pd2 and Pd5, respectively, were prepared by a simple and scalable impregnation method and tested as catalysts in the Heck coupling reaction of styrene and brom...

Iron oxide nanoparticles are the basic components of the most promising magneto-responsive systems for nanomedicine, ranging from drug delivery and imaging to hyperthermia cancer treatment, as well as to rapid point-of-care diagnostic systems with magnetic nanoparticles. Advanced synthesis procedures of single- and multi-core iron-oxide nanoparticl...

Az elmúlt két évtizedben a szuperparamágneses vas-oxid nanorészecskék (SPIONs) terápiás és diagnosztikai (teranosztikai) célú fejlesztése nagy elõrelépést mutatott. A mag-héj termékekben a mágneses mag MRI kontraszt ágensként, mágneses hipertermiában hõforrásként mûködik, alkalmas mágneses hatóanyag szállításra, a polimer védõréteggel pedig elérhet...

One of the basic surface charge formation mechanisms is the proton association/dissociation or protonation/deprotonation. This charging mechanism is characteristic for sparingly soluble metal oxides, clay * Corresponding Author Etelka Tombácz, Márta Szekeres, Ildikó Y. Tóth et al. 146 minerals, polyelectrolytes with acidic or basic functional group...

Graphite-oxide/TiO2 (GO/TiO2) composite materials were prepared by heterocoagulation method from Brodie’s graphite-oxide (GO) in order to test them as catalysts in the methanol photocatalytic reforming reaction in liquid phase. The preparation of the composite itself resulted in only little changes in the structure of GO as it was indicated by atte...

Nanostructured composite dispersions containing magnetic nanoparticles (MNPs) and graphene oxide (GO) lamellae have been prepared by a simple and easily scalable room temperature procedure. We show that, owing to the enormous surface area and negative surface charge developed in aqueous GO suspensions, large amounts of positively charged MNPs can b...

Aims: Chlamydia trachomatis and herpes simplex virus are the most prevalent bacterial and viral sexually transmitted infections. Due to the chronic nature of their infections, they are able to interact with titanium-dioxide nanoparticles applied as food additives or drug delivery vehicles. The aim of our study was to describe the interactions of t...

Manganese (Mn) is a toxic heavy metal exposing workers in various occupational settings and causing, among others, nervous system damage. Metal fumes of welding, a typical source of Mn exposure, contain a complex mixture of metal oxides partly in nanoparticle form. As toxic effects of complex substances cannot be sufficiently understood by examinin...

Graphene oxide samples prepared in various laboratories following a diversity of synthesis protocols based on Brodie's (BGO) and Hummers/Offeman's (HGO) methods were compared in respect of their in-plane moduli. A simple wrinkling method allowed for a spatial resolution <1.5 μm by converting the wrinkling frequency. Quite surprisingly, a drastic va...

Nanoparticles do not exist in thermodynamical equilibrium because of high surface free energy,thus they have only kinetic stability. Spontaneous changes can be delayed by designed surface coating. In biomedical applications,superparamagnetic iron oxide nanoparticles (SPIONs) require an optimized coating in order to fulfil the expectation of medicin...

Carboxylated magnetite nanoparticles (MNPs) are frequently used to develop materials with enhanced properties for MRI and hyperthermia. The controlled clustering of MNPs via covalent or electrostatic approaches provides opportunity to prepare high quality materials. MNPs were prepared by co-precipitation and coated by poly(acrylic acid-co-maleic ac...

We demonstrate that a simple spectrophotometric method can be efficiently applied for the characterization of structural and chemical stability and adsorption properties of composite graphene oxide (GO) films in various solutions. The immersion stability of GO layer-by-layer (LbL) self-assembled with a polycation into ultrathin multilayered films w...

The effect of poly(amido amine) (PAMAM) dendrimers of generations G2, G6, and G10 on the dispersion stability of titanate nanowires (TiONWs) as potential nanocarriers was clarified in order to develop biocompatible delivery systems. The PAMAMs adsorbed strongly on the oppositely charged TiONWs even under slightly alkaline conditions where the macro...

Electrophoretic and dynamic light scattering (DLS) measurements revealed that aggregation in aqueous dispersion of titanate nanowires (TiONWs) can be tuned by poly(diallyldimethyl ammonium) chloride (PDADMAC) polyelectrolyte. The nanowires possessed negative charge under alkaline conditions which was compensated by the oppositely charged PDADMAC ad...

A Pd(II) complex with chloride and tridecylamine ligands (PdCl2(TDA)(2)) was immobilized on graphite oxide modified with the cationic surfactant octadecyltrimethylammonium bromide (C(18)TABr). Samples with different Pd loadings were synthesized and tested for the liquid-phase hydrogenation of 1-pentyne and the Heck coupling reactions of styrene-bro...

We have recently focused on preparation and dispersion characteristics of lamellar structures such as layered double hydroxides, titanates and graphite oxide. They are multifunctional materials with applications ranging from the preparation of solar cells through sensor development to catalysis. One of the most promising ways to tune the aggregatio...

Copper-intercalated graphite oxides (GO) were prepared by adding complex solutions of cupric ions and 2,2′-bipyridine (L) ligands to exfoliated GO dispersion at pH = 7. High adsorption capacity (>140 mg Cu/g GO) was found for adsorption from equimolar solution of Cu2+ and L, while the excess of ligand results in progressively decreasing adsorbed am...

Aggregation of sub-micron and nano-sized polystyrene latex particles was studied in room temperature ionic liquids (ILs) and in their water mixtures by time-resolved light scattering. The aggregation rates were found to vary with the IL-to-water molar ratio in a systematic way. At the water side, the aggregation rate is initially small, but increas...

Titanate nanowires (TiONWs) are synthesized through the hydrothermal method and characterized in acidic aqueous dispersions by using electrophoresis, dynamic light scattering, and atomic force microscopy. The TiONWs have a rodlike shape with an average length of about 600 nm and a thickness of 35 nm. They are positively charged under the conditions...

The structure of graphene oxide (GO) membranes was studied in situ in liquid solvents using synchrotron radiation X-ray diffraction in a broad temperature interval. GO membranes are hydrated by water similarly to precursor graphite oxide powders but intercalation of alcohols is strongly hindered, which explains why the GO membranes are permeated by...

A series of nanocomposite photocatalysts was prepared from aqueous dispersions of Degussa P25 TiO2 and exfoliated graphite oxide (GO) by heterocoagulation. The structure and catalytic activity of samples in the photooxidation of phenol were characterized in line with their separability by controlled settling experiments at different pHs, irradiatio...

In this work we report on the preparation of some aqueous graphene oxide (GO) dispersions and the investigation of their nonlinear optical response under visible (532 nm) and infrared (1064 nm), picosecond and nanosecond laser excitation. The GO colloids were prepared under specific and well-defined conditions resulting in finely dispersed heavily...

Graphite oxides (GOs) synthesized by Brodie's and Hummers' methods are significantly different with respect to hydration, solvation and exfoliation properties. Hummers GO is more easily intercalated by liquid water and alcohols, exhibiting osmotic type of swelling. In contrast, Brodie GO shows crystalline swelling in alcohol solvents with step-like...

The interaction of hen egg white lysozyme (HEWL) with Na- and Cs-exchanged saponite was investigated using sorption, structural, and spectroscopic methods as a model system to study clay-protein interactions. HEWL sorption to Na- and Cs-saponite was determined using the bicinchoninic acid (BCA) assay, thermogravimetric analysis, and C and N analysi...

Hydration of graphite oxide by excess of water was studied in the temperature interval 295–230 K. A structural breathing effect is found for fully hydrated graphite oxide near the water solidification/melting point. Expansion of hydrated graphite oxide structure due to insertion of additional water occurs upon cooling down from ambient temperature...

Magnetic drug nanocarriers are synthesized following an arrested mineralization of magnetic spinel iron oxides in the presence of the biopolymer of sodium carboxymethylcellulose. Based on the experimental results, the polyelectrolyte corona probably attains a brushlike configuration around the magnetic particles. The inner core of these colloids ma...

Graphite oxide immersed in excess of basic or acidic water media was studied using synchrotron X-ray diffraction at high pressure using diamond anvil cells. The lattice spacing of graphite oxide in excess of NaOH solution increases by the enormous value of 85% at 1.6 GPa. In contrast, structure expansion of graphite oxide immersed in liquid water w...

Low-loaded, organophilic Pd/graphite oxide (Pd/GO) nanocomposites were synthesized from different Pd complex precursors by applying graphite oxide as a host material and tetradecyltrimethylammonium bromide (C14TAB) as a stabilizer. Structural investigation of the Pd/GO samples was performed by ICP-AES, XRD, N2 sorption and TEM measurements. It was...

Highly ordered monolayers of graphite oxide (GO) were assembled on hydrophilic substrates by the Langmuir–Blodgett technique. AFM observations confirm that the film architecture can be controlled by the pH and GO concentration in the subphase. At pH 10, films drawn over a 50 mg/L GO suspension consist of well-aligned, closely interlocked single or...

The sizes and shapes of single clay mineral layers are difficult to determine though they are important parameters which determine the final properties of clay polymer nanocomposites and of ultrathin clay mineral films. To determine these sizes and shapes, hybrid monolayers of clay minerals (saponite, hectorite, Wyoming bentonite, and Laponite) and...

Graphite oxide (GO) immersed in an excess of methanol and ethanol media is found to undergo a phase transformation at about 0.2-0.8 GPa, with an expansion of the unit cell volume by approximately 40%, due to pressure-induced insertion of solvent into interlayer space. The pressure at which the structural expansion occurs does not correlate with the...

Thermal decomposition of graphite oxide into nanocarbons at pressures from ambient to 5 GPa has been studied by using X-ray diffraction, Raman spectroscopy and TEM. The temperature of graphite oxide decomposition at 5 GPa is close to the temperature of graphite oxide exfoliation at ambient pressure; however, materials formed are strongly dependent...

Zinc peroxide and zinc oxide nanoparticles were prepared and self-assembled hybrid nanolayers were built up using layer-by-layer (LbL) technique on the surface of glass substrate using the layer silicate hectorite and an anionic polyelectrolyte, sodium polystyrene sulfonate (PSS). Light absorption, interference and morphological properties of the h...

Plasmonic structures are prepared on bimetal films evaporated onto glass substrates applying a multi-step process, and atomic force microscopy is utilized to study the structures after each step. Sub-micrometer gratings are generated on polycarbonate films spin-coated onto silver-gold bimetal layers by interference lithography (IL) applying the fou...

Journal article

Due to the increased importance of bionanocomposites, protamine and papain proteins were adsorbed on Na+ and on Cs+-exchanged saponite from aqueous solution. protein analysis of equilibrium solutions and thermogravimetric analyses of biocomposites were used to prepare adsorption isotherms, Based on the isotherm shape, and on the amounts of protein...

Loading of graphite oxide (GO) with tris(2,2'-bipyridyl) iron(II) ions and subsequent calcination affords a novel graphene-based composite with magnetic and electrically conductive properties. The pH of the starting aqueous suspension and the washing procedure play a crucial role in the successful immobilization of the iron precursor, which is main...

ZnO nanoparticles were prepared and self-assembled hybrid nanolayers were generated on the surface of silicon wafers using the layer silicate hectorite and PSS (sodium polystyrene-sulfonate) polyelectrolyte. The thickness, light absorption and interference properties of the hybrid films were studied. The influence of layer silicates and polymers on...

Mono- and multilayered clay mineral−protein films were constructed with the layer-by-layer deposition technique. The clay mineral saponite and three proteins (protamine, lysozyme, and papain) were tested. Multilayers with up to 15−15 alternating layers of saponite and protein were built up on glass, quartz, and ZnSe. In some cases these supports we...

Magnetic iron oxide nanoparticles were synthesized on two different clay supports: natural montmorillonite and synthetic laponite. The nanocomposites obtained, characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), x-ray diffraction (XRD), transmission electron microscopy (TEM), N 2 adsorption, small-angle x-ray scatter...

In contrast to graphite intercalation compounds, graphite oxide GO is hydrophilic. However, the information about the mobility of the water molecules is still sparse. We show in this report that the degree of hydration and the kinetics of water uptake depend crucially on the preparation and aging conditions. The best sample we have ever got shows l...

This study contributes to the sustained effort to unravel the chemical structure of graphite oxide (GO) by proposing a model based on elemental analysis, transmission electron microscopy, X-ray diffraction, 13 C magic-angle spinning NMR, diffuse reflectance infrared Fourier transform spectroscopy, X-ray photoelectron spectroscopy, and electron spin...

Chemical flaking of graphite has been performed by reacting natural graphite with a strong oxidizing agent, NaClO3/HNO3. The formed hydrophilic, negatively charged graphite oxide (GO) colloids can be dispersed in water which allows the deposition of thin GO/cationic polymer (poly(diallyldimethylammoniumchloride, PDDA) multilayer films on a glass su...

The changes on the IR spectrum of graphite oxide (GO) caused by prolonged drying and isotope exchange with D2O were analyzed. Graphite oxide was prepared from natural flaky graphite by Brodie's method. The spectrum of air-dry GO features a set of overlapping to O-H stretching vibrations of absorbed water molecules and structural OH groups which doe...

This pH-potentiometric study explores the factors influencing the surface charge developed in aqueous dispersions of graphite oxide (GO) after a series of oxidation treatments. Surface charging curves demonstrate that lamellar surfaces of GO are negatively charged in the entire pH range studied. While these curves were found to be independent from...

This study has been conducted to determine whether the nanosized semiconductor crystals qualify as photocatalysts also in that case when they are self-assembled to form ultrathin films in the thickness range of 10–500 nm. For this purpose, multilayer films of Zn(OH)2 and ZnO nanoparticles were prepared by the layer-by-layer self-assembly method on...

The chemical reduction of graphite oxide (GO) to graphite by either NaBH4 or hydroquinone and also its surface modification with neutral, primary aliphatic amines and amino acids are described. Treatment of GO with NaBH4 leads to turbostatic graphite that upon calcination under an inert atmosphere is transformed to highly ordered graphitic carbon,...

The interlamellar space of layer structured materials, such as montmorillonite, kaolinite, graphite oxide can be regarded as a nanophase reactor, in which size-quantized semiconductor and noble metal particles can be prepared. Particle growth is sterically hindered in the interlamellar space between neighboring lamellae which favors the formation o...

TiO2 nanosol particles were prepared by acidic hydrolysis of titanium tetraisopropoxide, and the incorporation of the anatase nanoparticles was next carried out between the layer silicate sheets by heterocoagulation method. TiO2/montmorillonite nanocomposites with high specific surface areas (asBET = 130-284 m2 g-1) were characterized and tested as...

The photooxidative degradation of poorly soluble organic compounds in water (oleic acid, β-naphthol); toluene and asphaltene/toluene solubilized, oleic acid emulsified in sodium dodecylsulphate at various compositions and selfemulsifiable crude oil in water were investigated in TiO2 aqueous (0.1 m/v%) suspension in photoreactor (γ = 240-375 nm). Th...