Elżbieta Megiel

• PhD DSc
• Professor (Associate) at University of Warsaw

This study examines the cytotoxicity of two silver nanoparticle formulations—AgNPs conjugated with chlorhexidine (AgNPs-CHL) and AgNPs conjugated with polyethylene glycol and metronidazole (AgNPs-PEG-MET)—as examples of the surface functionalization of silver nanoparticles with drugs via sulfur–silver bonds and nitrogen–silver interactions. We prev...

The fixation of carbon dioxide with epoxides is one of the most attractive methods for the green utilisation of this greenhouse gas and leads to many valuable chemicals. This process is characterised by 100% atom efficiency; however, an efficient catalyst is required to achieve satisfactory yields. Metal–organic frameworks (MOFs) are recognised as...

Human gastrointestinal cells can be exposed to different xenobiotics present in food or drinking water. In this work, we assessed the cytotoxicity of polystyrene nanoparticles (PS-NPs) and how it is impacted by fluoride (F⁻) presence. We decided to examine PS-NPs and F⁻ which can be easily found in drinking water and food. Commercially available am...

The selective oxidation of alcohols, leading to appropriate aldehydes, is widely recognised as one of the most important reactions in organic synthesis. With ever-increasing environmental concerns, much attention has been directed toward developing catalytic protocols that use molecular oxygen as an oxidant. An ideal green oxidation process should...

Herein, we report a novel polymer containing synthetic squaramide-based ion pair receptors, which effectively capture and remove sulfate salts from aqueous source phases during liquid–liquid extraction. The monomer M1 was synthesized in a modular fashion, assuring acidity of the anion binding domain and allowing the receptor to be incorporated into...

Purpose Periodontal disease (PD), defined as oral inflammation caused by dental plaque, is an emerging problem. PD may lead to tooth loss, and treatment options are limited. In this study, we designed, synthesized, and characterized silver nanoparticles (AgNPs) conjugated with chlorhexidine (AgNPs-CHL) or metronidazole (AgNPs-PEG-MET) to determine...

Purpose In the search for new drug delivery platforms for cardiovascular diseases and coating of medical devices, we synthesized eptifibatide-functionalized silver nanoparticles (AgNPs-EPI) and examined the pharmacological activity of AgNPs-EPI on platelets and endothelial cells in vitro and ex vivo. Methods Spherical AgNPs linked to eptifibatide...

Here, we report our studies on photoresponsive poly(meth)acrylates containing azobenzene groups connected to a polymer backbone via a short methylene linker. A series of side-chain azobenzene polymers was synthesized via the atom transfer radical polymerization (ATRP) technique using several catalytic systems. The polymers synthesized under the opt...

In the present work, we report the studies on perfectly homogeneous nanocomposites composed of polystyrene-grafted silver nanoparticles (Ag@PS) as a bioactive fulfilment and a mixture of polystyrene (PS) and polyvinyl alcohol (PVA) as a matrix. The procedure developed by our group of the nanocomposites’ preparation consists of three steps: synthesi...

Modified multi-walled carbon nanotubes (MWCNTs) functionalized by a redox-active ferrocene (Fc-MWCNTs) were successfully synthesized to enhance the electrochemical performance of MWCNTs for supercapacitor application. The ferrocene moieties were attached to the surface of MWCNTs via a thiourea linker with anions-interacting capability. The Fc-MWCNT...

A new synthetic approach is presented for the preparation of Poly(N-isopropylacrylamide-block-styrene) PNIPAM-b-PS via an Atom Transfer Radical Polymerization (ATRP) technique. The proposed method is based on application of 2-chloro-N-(2-hydroxyethyl)propanamide (NCPAE) as a bifunctional initiator, which enables ATRP of two monomers, differing in a...

In this paper we report a simple and effective method to functionalize industrial-grade multi-walled carbon nanotubes (MWCNTs) with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), via oxidation of MWCNTS and followed by carbodiimide coupling of amino-TEMPO. The effective coupling is confirmed and studied by EPR, HRTEM, BET, XPS, FTIR, TGA and XRD tec...

This article provides an overview of the methods for surface modification based on the use of stable radicals: 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and its derivatives. Two approaches are discussed. The first relies on the immobilization of TEMPO moieties on the surface of various materials including silicon wafers, silica particles, organi...

The achievement of uniform nanoparticles distribution in polymer matrix is still a major challenge in the design and fabrication of polymer nanocomposites with desired properties. In this paper we propose a novel approach for the preparation of homogeneous polystyrene/silver nanocomposites utilizing Nitroxide Mediated Radical Polymerization (NMRP)....

Nanomaterials have been extensively studied for heavy metal ions and dye removals from wastewater. This article reviews the role of nanomaterials as effective adsorbents for wastewater purification. In recent years, numerous novel nanomaterial adsorbents have been developed for enhancing the efficiency and adsorption capacities of removing contamin...

In this paper, we describe the facile synthesis and physicochemical characteristic of nitroxide-coated silver nanoparticles. The proposed procedure allows to obtain isolatable, devoid of Ag+ impurities, long-term stable, spherical nanoparticles with an average diameter ca. 7 nm, which exhibit high antibacterial activity towards both Gram-negative a...

This paper describes a novel route to the synthesis of core–shell nanostructures utilizing Nitroxide Mediated Radical Polymerization (NMRP). The hybrid nanostructures with nanogold cores and precisely designed polystyrene shells (PDI < 1.3) have been synthesized through late injection of TEMPO coated gold nanoparticles into a TEMPOL (4-hydroxy-TEMP...

Gold nanoparticles covered by derivatives of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) with well-defined coverage and narrow size distribution were synthesized and self-assembled on the gold electrode. The TEMPO nanoparticle-coated electrode was characterized using STM and AFM. The kinetics of oxidation of the nitroxide radicals attached to the...

The ketone functionalized N-alkoxyamine, a derivative of 4-oxo-2,2,6,6-tetramethylpiperidin-1-oxyl (4-oxo-TEMPO) was synthesized and applied as an initiator in the nitroxide mediated polymerization of styrene in bulk at 120 C. In the presence of the prepared initiator: 1-phenyl-1-(4-oxo-2,2,6,6-tetramethylpiperidinoxy)propanone polymers with well-d...

Three new ketone functionalized N-alkoxyamines derived from 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) were prepared: N-(1-phenylpropyloxy)-2,2,6,6-tetramethylpiperidin-4-one, 1-phenyl-1-(2,2,6,6-tetramethylpiperidinoxy)propanone, 1-phenyl-1-(4-oxo-2,2,6,6-tetramethylpiperidinoxy)propanone. The rate constants of C-ON bonds homolysis in the synthes...

Homolytic bond dissociation energy (BDE) of the (CON) bond for several N-alkoxyamines derived from 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and the corresponding (CH) bonds were determined from quantum-mechanical calculations including the B3-LYP6-31G(d), B3-LYP/6-311++G(2df,p), UB3-LYP/6-311+G(3df,2p), and integrated IMOMO (G3:ROMP2/6-31G(d))...

The geometries and energetics of transition states (TS) for radical deactivation reactions, including competitive combination and disproportionation reactions, have been studied for the modeled 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-mediated free-radical polymerization of acrylonitrile with quantum mechanical calculations at the DFT/UB3-LYP/6...

The geometries and electronic properties of substrates, transition structures (TS), and product radicals in modeled elementary propagation reactions were studied for the styrene-acrylonitrile monomer system by use of quantum-mechanical calculations: (DFT/B3-LYP/6-31G(d), ROMP2/6-311+G(3df,2p)//DFT/B3-LYP/6-31G(d), and DFT/B3-LYP/6-311+G(3df,2p)//DF...

Penultimate unit effects in the free-radical copolymerization of styrene with acrylonitrile were investigated by the consideration of the theoretical thermochemistry of three subsequent propagation steps in the copolymerization process at 298 K and the electronic properties of the relevant reactants. The total energies, zero-point energies incorpor...

[structure: see text] (1)H NMR measurements and ab initio calculations were used to study the interactions between hindered/nonhindered phenols and carboxylic acid esters. The dihedral angle (phi) between the OH group and a plane of the aromatic ring is close to 0 degrees in the hydrogen-bonded nonhindered phenols, whereas for 2,6-di-tert-butyl-4-m...

The molecular geometry and electronic structure of styrene and methyl methacrylate as well as corresponding radicals formed by the addition of a methyl radical to the β-carbon of the monomer were determined using the density functional theory at the B3LYP/6-311+G** level. Results were in good agreement with the theoretical and experimental data ava...

The 14N NMR spectra of liquid pyridine and its mixtures with n-heptane were measured over a full concentration range. The chemical shifts of the pyridine nitrogen were found to vary in the spectra of the mixtures as compared with the value for the pure base. These variations were compared with theoretical results, i.e. with the difference in shield...

The excess enthalpies for 4-methyltoluene + pyridine bases were measured at 298.15 K. The pyridine bases which have been used were as follows: pyridine, 2-methlpyridine, 9-methylpyridine, 4-methylpyridine,2,4-dimethylpyridine, 2,6-dimethylpyridine, 2,4,6-trimethylpyridine.

In continuation of our work on excess thermodynamic properties of non-electrolyte solutions containing pyridine bases withn-alkanes, we have determined excess molar volumesVE for 2,4-dimethylpyridine + C6 to C10n-alkanes at 25°C. For the investigated systems noVE values were available in the literature for comparison with our data. The experimental...

Enthalpies of mixing for the binaries m-xylene + pyridine and its methyl derivatives have been measured at 298.15 K. The pyridine bases used for the measurements were pyridine, 2-, 3-, and 4-methylpyridine, 2,4-, and 2,6-dimethylpyridine, and 2,4,6-trimethylpyridine.The Prigogine-Flory-Patterson (PFP) model has been applied to describe the experime...

As an extension of our investigation of the effect of chain length of an n-alkane, as well as the number and position of methyl groups in a pyridine ring, excess molar volumes, VE, for a 2,4,6-trimethylpyridine + a C6 to C10 n-alkane have been measured at 25 °C. For these systems no VE values were available in the literature. We have compared the e...

Excess heats of mixing of the binary systems pyridine, or 2-picoline, or 3-picoline, or 2,4-lutidine, or 2,6-lutidine, or 2,4,6-collidine and o-xylene have been measured at 298.15 K as a function of composition. The Prigogine—Flory—Patterson (PFP) theory is applied to describe the experimental results.