Elżbieta Megiel

The role of nanomaterials as effective adsorbents and their applications in wastewater treatment

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 contaminants from wastewater. The innovation, forthcoming development, and challenges of cost-effective and environmentally acceptable nanomaterials for water purification are discussed and reviewed in this article. This review concludes that nanomaterials have many unique morphological and structural properties that qualify them to be used as effective adsorbents to solve several environmental problems.Graphical Abstract

High-density polystyrene-grafted silver nanoparticles and their use in the preparation of nanocomposites with antibacterial properties

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). In the first step of the developed procedure, the polystyrene grafted silver nanoparticles (Ag@PS) with well-defined core-shell structure and exceptionally high grafting density (from 2 chains/nm2 to 5.9 chains/nm2) have been synthesized through late injection of nitroxide-coated silver nanoparticles (N-AgNPs) into a TEMPOL mediated styrene polymerization system. Afterwards, the synthesized Ag@PS have been used for the preparation of nanocomposites (PS/Ag@PS) by mixing them with narrow-dispersity polystyrenes and thermoforming at 140°C. Due to the high flexibility of polymer chains attached to silver surface through nitroxide linker, free volume effect enables interpenetration of polystyrene molecules that provides excellent mutual miscibility of Ag@PS with polymer matrix. The synthesized nanohybrids (Ag@PS) and their nanocomposites (PS/Ag@PS) exhibit effective antibacterial activity with respect to pathogenic bacteria: Pseudomonas aeruginosa (Gram-negative representative) and Staphylococcus aureus (Gram-positive representative).

Nitroxide-coated silver nanoparticles: synthesis, surface physicochemistry and antibacterial activity

In this paper, we describe the facile synthesis and physicochemical characteristics of nitroxide-coated silver nanoparticles. The proposed procedure allows us 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 and Gram-positive strains. The determined Minimum Bactericidal Concentrations (MBCs) are significantly lower than the values reported for other thiolate-capped silver nanoparticles and range from 4 μg ml−1 (against Pseudomonas aeruginosa) to 12 μg ml−1 (against Staphylococcus aureus). Our studies proved that the nitroxide coverage favours the antibacterial activity of silver nanoparticles, probably due to the ability of nitroxides to be oxidized by reactive oxygen species (ROS) to positively charged oxoammonium ions which can interact strongly with the bacterial membrane. Furthermore, the mechanism of chemisorption of disulphide bisnitroxide on a silver surface has been discussed on the basis of XPS, FTIR and ESR results.

TEMPO coated Au nanoparticles: synthesis and tethering to gold surfaces

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 nanoparticles was evaluated based on cyclic voltammetry measurements. The TEMPO–nanoparticle modified electrode was found more efficient in electrocatalytic oxidation of benzyl alcohol than the electrode modified with a monolayer of TEMPO molecules directly bound to the gold surface.

A smart synthesis of gold/polystyrene core-shell nanohybrids using TEMPO coated nanoparticles†

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-TEMPO) mediated styrene polymerization system. Thermal analyses have shown that the thus obtained polystyrene modified gold nanoparticles are significantly more stable to the thermal treatment than only thiol-stabilized gold nanoparticles (aggregation has not been observed even at 300 °C). The obtained materials exhibit intensive surface plasmon resonance (SPR) observed near 520 nm that provides an opportunity to apply them as high-temperature optical sensors. The proposed procedure allows for precise synthesis of tailor-made nanohybrids via macroradical coupling.

Excess volumes of binary systems formed by a 2,4,6-trimethylpyridine and n-alkane

Abstract 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, V E , for a 2,4,6-trimethylpyridine + a C 6 to C 10 n-alkane have been measured at 25 °C. For these systems no V E values were available in the literature. We have compared the experimental V E data for the investigated systems with the results calculated by applying the Prigogine-Flory-Patterson theory (PFP) (Flory et al., 1964, 1982), Extended real associated solutions by Heintz (1985) (ERAS), and Treszczanowicz-Benson-Patterson (TB), (Treszczanowicz et al., 1989). We concluded that Treszczanowicz-Benson-Patterson Method (Treszczanowicz et al., 1989) gave the best results of V E .

Volumes of mixing 2,4-dimethylpyridine withn-alkanes

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 experimentalVE was used to test the Prigogine-Flory-Patterson theory (PFP), Extended Real Associated Solutions model (ERAS) and the Treszczanowicz-Benson method (TB).

Heats of mixing of binary mixture of pyridine bases and o-xylene. Experimental results and description according to the theory

Abstract 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.

Surface modification using TEMPO and its derivatives

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, organic polymers as well as diverse nanomaterials. Applications of such materials with spin labeled surface/interface, in (electro)catalysis, synthesis of novel hybrid nanostructures and nanocomposites as well as in designing of organic magnets and novel energy storage devices are also included in the discussion. The second approach utilizes TEMPO and its derivatives for the grafting of polymer chains and polymer brushes formation on flat and nanostructure surfaces via Nitroxide Mediated Radical Polymerization (NMRP). The influence of such polymer modification on surface/interface physicochemical properties is also presented.

Enthalpy of mixing for binaries: m-xylene + pyridine bases. Experimental data at 298.15 K and theoretical description

Abstract 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 experimental results.