Imre Varga

Imre Varga
Eötvös Loránd University · Laboratory of Colloid and Supramolecular Systems

Professor

About

92
Publications
6,815
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3,023
Citations
Citations since 2016
19 Research Items
1437 Citations
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
Introduction
Skills and Expertise

Publications

Publications (92)
Article
Full-text available
The red-emitting fluorescent properties of bovine serum albumin (BSA)–gold conjugates are commonly attributed to gold nanoclusters formed by metallic and ionized gold atoms, stabilized by the protein. Others argue that red fluorescence originates from gold cation–protein complexes instead, not gold nanoclusters. Our fluorescence and infrared spectr...
Article
Full-text available
Reversible control of the 3D structure of polyelectrolyte/surfactant films at the air/water interface is showcased. A recently discovered mechanism is exploited to form highly efficient, stable and biocompatible films by spreading aggregates composed of poly-L-lysine and sodium dodecyl sulfate on the surface of water. Reversible control of: (1) the...
Article
Full-text available
Layered double hydroxides (LDHs) have attracted considerable attention as promising materials for electrochemical and optical sensors owing to their excellent catalytic properties, facile synthesis strategies, highly tunable morphology, and versatile hosting ability. LDH-based electrochemical sensors are affordable alternatives to traditional preci...
Article
Full-text available
Thermoresponsive polymers, with special emphasis on poly(N-isopropylacrylamide) (PNIPAAM) have been the focus of several investigations due to its potential applications in many fields of physical and polymer chemistry. PNIPAAM has a “lower critical solution temperature” at 32°C. The LCST can be finely tuned by copolymerization with hydrophobic or...
Article
Full-text available
The temperature dependence of nanomechanical properties of adsorbed poly-NIPAm microgel particles prepared by a semibatch polymerization process was investigated in an aqueous environment via indentation-based atomic force microscopy (AFM) methods. Poly-NIPAm microgel particles prepared by the classical batch process were also characterized for com...
Article
Biodegradable, biocompatible nanoparticles with tuneable fluorescence - due to their great potential in biology, medicine and sensor development - are widely studied nowadays. Recently it was shown that the complex red emitting spectroscopic feature of Bovine Serum Albumin - gold (BSAAu) bioconjugates can be related to the versatility of conformati...
Article
Full-text available
A novel structural framework is presented to rationalize the foam film stability of polyelectrolyte/surfactant mixtures using neutron reflectivity data. Provision of electrostatic or steric stabilization in thin foam films is related to the spatial distributions of molecules interacting from opposing air/water interfaces. The advance is discussed i...
Article
The self-assembly of two oppositely charged diblock copolymers that have a common thermosensitive nonionic block of poly(N-isopropylacrylamide) (pNIPAAM) has been investigated. The effect of the mixing ratio and total polymer concentrations on the self-assembly of the components and on the phase stability of the mixtures were studied by dynamic lig...
Article
Full-text available
The electrophoretic mobility of poly(N-isopropylacrylamide) and poly(N-isopropylacrylamide-co-acrylic acid) copolymer particles, as well as different core-shell microgel particles (neutral core with charged shell and charged core with neutral shell) was investigated as function of microgel swelling. The swelling of the microgels were varied with in...
Article
Despite the increasing demand for 'as small as possible' responsive poly(N-isopropylacrylamide) (pNIPAm) nanogels with well-defined internal structure, up to date there is no systematic investigation to provide guidance what are the lower limits of nanogel size and what interactions limit its further decrease. In this work both classical batch prec...
Article
Full-text available
In this work, host-guest supramolecular hydrogels were prepared from poly(N-isopropylacrylamide) (pNIPAm) microgels utilizing electrostatic and host/guest self-assembly. First, pNIPAm microgels bearing a poly(acrylic acid) (pAAc) shell were coated with positively charged β-cyclodextrin polymers. Addition of adamantane-substituted dextrans (Dex-Ada)...
Article
Full-text available
The application of protein deuteration and high flux neutron reflectometry has allowed a comparison of the adsorption properties of lysozyme at the air–water interface from dilute solutions with and without strong denaturants, urea and guanidine hydrochloride (GuHCl). The surface excess and adsorption layer thickness were resolved and complemented...
Article
We developed a terpyridine-functionalized microgel (tpy-mG) for its supramolecular assembly. tpy-mG was synthesized by amidation between 3-(4-([2,2':6',2''-terpyridin]-4'-yl)phenoxy)propan-1-amine and carboxylates of thermo-responsive p(NIPAM-co-MMA) microgel (A-mG), which was synthesized by emulsion polymerization. After decorating terpyridine, it...
Article
In this work we demonstrate the ability to tune the formation of extended structures in films of poly(sodium styrene sulfonate)/dodecyltrimethylammonium bromide at the air/water interface through control over the charge/structure of aggregates as well as the ionic strength of the subphase. Our methodology to prepare loaded polyelectrolyte/surfactan...
Article
This work reports a unifying general physical description of the behavior of oppositely charged polyelectrolyte/surfactant mixtures at the air/water interface in terms of equilibrium vs. nonequilibrium extremes. The poly(diallyldimethylammonium chloride)/sodium dodecyl sulfate system with added NaCl at two different bulk polyelectrolyte concentrati...
Article
Polyelectrolyte complex formation of a long chain poly(sodium styrene sulfonate) (NaPSS) with short chain poly(vinylbenzyltrimethylammonium chloride) homopolymer (pVBTA) and block copolymers (PEG-b-pVBTA) was investigated. The effect of the PEG chain and the pVBTA block length was studied on the complex formation. Then the exchange of the complex b...
Article
We describe a new methodology to prepare loaded polyelectrolyte/surfactant films at the air/water interface by exploiting Marangoni spreading resulting from the dynamic dissociation of hydrophobic neutral aggregates dispensed from an aqueous dispersion. The system studied is mixtures of poly(sodium styrene sulfonate) with dodecyl trimethylammonium...
Article
Full-text available
A study of the dilational surface viscoelastic properties of mixed solutions of lysozyme and denaturing agents of different chemical nature allows us to characterize the changes of protein tertiary structure in the surface layer upon adsorption at the liquid–gas interface. We show that guanidine hydrochloride (GuHCl) and urea influence the dynamic...
Article
We discuss different non-equilibrium mechanisms by which bulk aggregates directly modify, and can even control, the interfacial structure and morphology of an oppositely charged polyelectrolyte/surfactant (P/S) mixture. Samples are categorized at the air/water interface with respect to the dynamic changes in the bulk phase behavior, the bulk compos...
Article
In this paper we rationalize the surface tension behavior and nonequilibrium interfacial characteristics of high molecular weight sodium poly(styrene sulfonate)/dodecyltrimethylammonium bromide (NaPSS/DTAB) mixtures with respect to the ionic strength. Excellent agreement is achieved between experimental data and our recent empirical model (Langmuir...
Article
We study the influence of the particle size on the ability of poly(N-isoprolylacrylamide) microgels to stabilize direct oil-in-water Pickering emulsions. The microgel size is varied from 250 to 760nm keeping the cross-linking density constant. The emulsion properties strongly depend on the stabilizer size: increasing the particle size induces an ev...
Article
While the surface tension of complex mixtures determines the fate of lots of important natural processes, the property is notoriously difficult to interpret. Here we announce a new method that successfully predicts the surface tension of two synthetic and one biological polyelectrolyte/surfactant mixtures in the phase separation region after dynami...
Article
The dynamic interfacial adsorption from mixtures of high molecular weight poly(ethylene imine) (PEI) and sodium dodecyl sulfate (SDS) has been studied by neutron reflectometry and ellipsometry at the expanding air–water interface created by an overflowing cylinder. Aggregation of PEI and SDS in the bulk solution has very different consequences on t...
Article
Molecular dynamics simulations of the adsorption layer of five different surfactant molecules, i.e., pentyl alcohol, octyl alcohol, dodecyl alcohol, sodium dodecyl sulfate, and dodecyl trimethyl ammonium chloride are performed at the free surface of their aqueous solution at two surface densities, namely 1 and 4 μmol/m(2) at 298 K. The results are...
Article
We show conclusively that multilayers at interfaces of an oppositely charged polyelectrolyte/surfactant system can result from the transport under gravity of bulk aggregates with internal molecular structure. This process was demonstrated by measurements of poly(diallyldimethylammonium chloride)/sodium dodecyl sulfate solutions at the air/liquid an...
Article
The adsorption isotherms of n-decyl-β-D-glucoside (β-C(10)G(1)) as well as various n-alkyl-β-D-maltosides (β-C(n)G(2)) with n=8, 10, 12 and 14 were determined from surface tension measurements. Based on the analysis of the adsorption isotherms, the total free energy change of adsorption was determined and a novel method was proposed to determine th...
Article
Polyelectrolyte complexes (PECs) self-assembled from bottle-brush polyelectrolytes, having a cationic main chain and uncharged side chains, and linear anionic sodium polystyrenesulfonate (NaPSS) have been investigated with emphasis on (i) the charge density and side chain density of the bottle-brush polyelectrolyte, (ii) the molecular weight of NaP...
Article
This study contributes to the understanding of how the structure of preadsorbed polyelectrolyte layers affects their interaction with oppositely charged surfactants. The adsorbed amount, and thus the adsorption layer structure of poly(ethylene imine), (PEI), was tuned by the pH (4, 6 and 9) of the PEI adsorption. Following the PEI adsorption, each...
Article
Monodisperse microgel latex with homogeneous cross-link density distribution within the particles was prepared by feeding the monomer and cross-linker into the reaction mixture in a regulated way during the polymerization. To determine the appropriate monomer feeding parameters, the kinetics of the particle formation was investigated by HPLC. The s...
Article
The possibility of forming self-organized films using charge-stabilized dispersions of cellulose I nanofibrils and microgel beads of poly-(N-isopropylacrylamide-co-acrylic acid) copolymer is presented. The build-up behavior and the properties of the layer-by-layer (LbL)-constructed films were studied using quartz crystal microbalance with dissipati...
Article
Adsorption properties of stoichiometric and nonstoichiometric polyelectrolyte complexes (PECs) have been investigated by means of dual polarization interferometry (DPI) and X-ray photoelectron spectroscopy (XPS). Poly(sodium styrenesulfonate) (NaPSS) of molecular weight 4300 g/mol was used as polyanion, and two bottle-brush copolymers possessing di...
Article
A quartz crystal microbalance (QCM) and dual polarization interferometry (DPI) have been utilized to study how the structure of poly(allylamine hydrochloride) (PAH)/poly(styrene sulfonate) (PSS) multilayers is affected by the rinsing method (i.e., the termination of polyelectrolyte adsorption). The effect of the type of counterions used in the depo...
Article
We present how dramatically the nonequilibrium nature of an oppositely charged polyelectrolyte/surfactant mixture can affect the interfacial properties. We show for the first time that the cliff edge peak in the surface tension of the poly(diallyldimethylammonium chloride)/sodium dodecyl sulfate system is produced as a direct result of depletion of...
Article
Silica surfaces were coated with a range of cationic bottle-brush polymers with 45 units long poly(ethylene oxide) side chains, and their efficiency in reducing protein adsorption was probed by QCM-D, reflectometry and AFM. Preadsorbed layers formed by bottle-brush polymers with different side chain to charge ratio was exposed to two proteins with...
Chapter
Mixtures of polyelectrolytes and oppositely charged surfactants find applications in many processes and products that are used in our daily life. Such systems also show many interesting features from a scientific point of view. Due to the combined technological relevance and scientific challenge, considerable research efforts have been made in this...
Article
Adsorption properties of bottle-brush polyelectrolytes have been investigated using dual polarization interferometry (DPI), which provides real time monitoring of adsorbed layer thickness and refractive index. The adsorption on silicon oxynitride was carried out from aqueous solution with no added inorganic salt, and the adsorbed polyelectrolyte la...
Article
Solution and adsorption properties of both charged and uncharged bottle-brush polymers have been investigated. The solution conformation and interactions in solution have been investigated by small-angle scattering techniques. The association of the bottle-brush polymers with anionic surfactants has also been studied. Surfactant binding isotherm me...
Article
Solution properties of methylcellulose (MC) and hydroxypropylmethylcellulose (HPMC) have been investigated as a function of temperature and concentration using a broad range of experimental techniques. Novelties include the extensive comparison between MC and HPMC solutions as well as the combination of techniques, and the use of Cryo transmission...
Article
The effect of graft density on the interaction of nonionic bottle brush polymers with an anionic surfactant (sodium dodecyl sulfate) was investigated. The graft density of 45 units long poly(ethylene oxide) (PEO) side chains was varied in a wide range (30, 50, 75, 90, and 100%) on a methacrylate type polymer backbone. The surfactant binding isother...
Article
Full-text available
The structures of interfacial layers formed from mixtures of comb polymers, comprising a high charge density cationic backbone and poly(ethylene oxide) (PEO) side-chains, with the anionic surfactantsodium dodecyl sulfate (SDS) at the silica/water interface, have been determined using neutron reflectivity measurements. The use of mixtures in which o...
Article
Sterically stabilized polyelectrolyte complexes with stoichiometric composition between oppositely charged synthetic polyelectrolytes carrying strong ionic groups and significantly different molecular weights have been prepared. Poly(sodium styrenesulfonate) (NaPSS) was used as polyanion and a range of brush copolymers with various molar ratio (X =...
Article
The formation of complexes with stoichiometric (1:1) as well as nonstoichiometric (2:1) and (1:2) compositions between oppositely charged synthetic polyelectrolytes carrying strong ionic groups and significantly different molecular weights is reported in this contribution. Poly(sodium styrenesulfonate) (NaPSS) was used as polyanion, and a range of...
Article
We have exploited the spatial and kinetic resolution of ellipsometry to monitor the lateral movement of inhomogeneous patches of material in mixed adsorption layers of poly(ethylene imine) and sodium dodecyl sulfate at the air/liquid interface. We show that the choice of sample preparation methods can have a profound effect on the state of the inte...
Article
Mixed micelles formed in aqueous solutions of nonionic surfactants n-dodecyl-hexaethylene-glycol (C12E6) and n-dodecyl-beta-D-maltoside (C12G2) have been studied using small-angle neutron and X-ray scattering (SANS and SAXS) and static light scattering (SLS). Apparent micelle molar masses obtained with SLS were analyzed with a model taking into acc...
Article
Polyethyleneimine (PEI) and Microfibrillated cellulose (MFC) have been used to buildup polyelectrolyte multilayers (PEM) on silicone oxide and silicone oxynitride surfaces at different pH values and with different electrolyte and polyelectrolyte/colloid concentrations of the components. Consecutive adsorption on these surfaces was studied by in sit...
Article
Model fitting to small-angle scattering patterns from a series of dilute sodium- and cesium alkyl sulfate micellar solutions results in two significantly different sets of best-fit parameters for each solution. One of the sets defines nearly monodisperse prolate ellipsoids; the other defines slightly, but significantly, polydisperse oblate ellipsoi...
Article
A number of features of the adsorption of alkyl trimethylammonium bromides with nc=10,12,14, and 16 at the air/water interface were studied. First, the adsorption isotherms were calculated from experimental surface tension vs concentration curves by means of the Gibbs equation. Second, a novel method was used to estimate the adsorption free energy...
Article
The interfacial and bulk behavior of the aqueous solutions of sodium dodecyl sulfate (SDS) and polyethylene oxide (PEO) was investigated by surface tension measurements in the presence of excess NaBr. The Gibbs analysis demonstrated that the surfactant nearly completely displaces the polymer from the surface even below the cac. Furthermore, the ads...
Article
Experimental results are presented on the adsorption of sodium alkyl sulfate homologues (nC = 8-14) at the air/solution interface. The adsorption isotherms calculated from equilibrium surface-tension vs concentration data and the critical micelle concentration change regularly with the length of the alkyl chain; the odd/even effect was not observed...
Article
The effect of different mixing protocols on the charged nature and size distribution of the aqueous complexes of hyperbranched poly(ethylene imine) (PEI) and sodium dodecyl sulfate (SDS) was investigated by electrophoretic mobility and dynamic light scattering measurements at different pH values, polyelectrolyte concentrations, and ionic strengths....
Article
To test the validity of currently used adsorption theories and understand the origin of the lack of their ability of adequately describing existing surface tension measurement data, we have performed a series of molecular dynamics simulations of the adsorption layer of alkali decyl sulfate at the vapor/aqueous solution interface. The simulations ha...
Article
Humic-like substances (HULIS) were isolated by a solid-phase extraction procedure from PM2.5 fraction urban-type atmospheric aerosol samples collected in downtown Budapest, Hungary, in the nonheating season. Their amount was derived, and the surface tension properties of their pure solutions were investigated. Carbon content of HULIS accounted for...
Article
A novel method is presented for the design of robust, sustained nanochemomechanical oscillators. The approach is based on the switching of chemoresponsive nanogel beads between their collapsed and swollen state by coupling them to an appropriately chosen nonlinear reaction. The presented system utilizes a proton activated oscillatory reaction and p...
Article
The adsorption of polyethylene oxide (PEO) homologues in a wide range of molecular weight (from M(PEO)=200 to 10(6)) at the air/aqueous solution interface was investigated by dynamic and static surface tension measurements. An approximate estimate for the lower limit of PEO concentration was given at which reliable equilibrium surface tension can b...
Article
Solvent isotope effects on the interaction between the hyperbranched cationic polyelectrolyte, polyethylene imine (PEI), and the anionic surfactant sodium dodecyl sulfate (SDS) were investigated using potentiometric titration and eletrophoretic mobility measurements. In the basic pH range, a significantly higher fraction of the amine groups was fou...
Article
A simple one-step synthesis is described for the functionalization of poly(vinyl chloride) used for the preparation of anionic surfactant-selective membrane electrodes. The method is based on the nucleophilic substitution of a fraction of the chlorine atoms bound to the poly(vinyl chloride) backbone by trimethylamine. The prepared slightly charged...
Article
A thermodynamic analysis of the interaction between fourteen different molar mass poly(ethylene oxide)s (PEO) and sodium dodecyl sulfate (SDS) based on the measured surfactant-binding isotherms is given. The surfactant-binding isotherms were determined by the potentiometric method in the presence of 0.1 M inert electrolyte (NaBr). It was found that...
Article
The equilibrium adsorption layers of symmetric chain alkyltrimethylammonium alkyl sulfates (Cn+.Cn- for n = 8, 12) were investigated at the air/water interface by sum-frequency vibrational spectroscopy in the function of the bulk surfactant concentration. To ensure the surface purity of the solutions investigated, an improved version of the foam fr...
Article
Experimental results are presented on the counterion dependence of the adsorption of alkali (Li+, Na+, K+, Rb+ and Cs+) decyl sulfates at the air/solution interface. The adsorption isotherms calculated from equilibrium surface tension vs. concentration data by means of the Gibbs equation show significant counterion dependence. We propose a theoreti...
Chapter
A molecular interaction model of nonionic polymer–surfactant complex formation was developed by modifying the free-energy expression of micelles for interaction with polymer segments. Using the small systems thermodynamics the composition of the surfactant aggregates with respect to the aggregation number, the number of polymer segments involved in...
Article
Monte Carlo computer simulations were used to investigate the adsorption of 1-octanol at the free water surface. The number of the octanol molecules was chosen in order to ensure that the octanol surface density varied in a broad range in the six different systems that were simulated. The interfacial system containing bulk liquid octanol in the apo...
Chapter
Experimental results are presented for the counterion dependence of the adsorption of alkali decyl sulfates (Li+>, Na+>, K+>, Rb+> and Cs+>) at the air/solution interface. The experimental adsorption isotherms calculated from equilibrium surface tension/concentration data by means of the Gibbs equation show significant counterion dependence. A new,...
Article
The role of polymer charge density in the kinetics of the adsorption and desorption, on silica, of the polyelectrolyte poly(ethyleneimine) (PEI) was investigated by stagnation-point flow reflectometry. In the first series of experiments, PEI solutions were introduced at the same ionic strength and pH as the background solvent. It was found that the...
Article
The adsorption features of aqueous PEI/SDS solutions on silica surfaces were investigated by ellipsometry. Results were compared with the interfacial behavior of the SDS solutions on preadsorbed PEI layers. It was shown that the properties of the mixed surface layers can be well interpreted via the individual adsorption properties of PEI as well as...
Article
The adsorption of n-octane at the water liquid–vapor interface has been investigated by Monte Carlo computer simulation. For this purpose, simulation of five different water–apolar interfacial systems have been performed, in which the number of n-octane molecules has been varied. The results clearly show that the apolar n-octane molecules are adsor...
Article
The binding isotherm of sodium dodecyl sulfate (SDS) on a hyperbranched polyethyleneimine (PEI) was determined by an equilibrium dialysis method. Dynamic light scattering, electrophoretic mobility, and coagulation kinetics measurements were also performed in order to monitor the changes in the charged nature and size of PEI/SDS complexes. The exper...
Article
The effect of crosslink density on the structure of poly-(N- isopropylacrylamide) microgel particles prepared by emulsion polymerisation was investigated by static and dynamic light scattering measurements. According to these measurements the gel particles cannot be considered as homogenous spheres. The structure of the gel particles strongly depen...
Article
On the basis of the PoissonBoltzmann cell model a new trace probe electrolyte method was applied to determine the surfactant aggregation number in Poly(ethylene oxide)— Sodium dodecyl sulphate systems. It is demonstrated that activity measurements on a probe electrolyte added to a polymer/surfactant solution in a trace amount can be used for the de...