Alexandra Mocanu

Design of Antimicrobial Membrane Based on Polymer Colloids/Multiwall Carbon Nanotubes Hybrid Material with Silver Nanoparticles

The aim of this study was to obtain membranes with antimicrobial activity presenting a complex sandwich-type structure. The outer layers are comprised of poly(methyl methacrylate) membranes, whereas the inner active layer consists of a modified commercial membrane to achieve antimicrobial properties. This activity arises due to the presence of silver nanoparticles in a material with a hybrid composition deposited on a commercial membrane. This hybrid material consists of polymer colloids and multiwall carbon nanotubes used for both the stabilization of the active layer by the interconnections of the polymer particles and as active component. The filtration tests revealed a good stability of the materials and an increased hydrophilicity of the hybrid membranes. The antimicrobial properties have been evaluated using Staphylococcus aureus and Escherichia coli, and have been correlated with the content and migration rate of silver ions.

Silver nanoparticles influence on photocatalytic activity of hybrid materials based on TiO 2 P25

The aim of the present study consists in the obtaining of a hybrid material film, obtained using TiO2 P25 and silver nanoparticles (AgNPs). The film manufacturing process involved realization of physical mixtures of TiO2 P25 and AgNPs dispersions. The size distribution of the AgNPs proved to be a key factor determining the photodegradation activity of the materials measured using methyl orange. The best result was 33% degradation of methyl orange (MO) after 150 min. The second approach was the generation of AgNPs on the surface of TiO2 P25. The obtained hybrid material presents photocatalytic activity of 45% MO degradation after 150 min. The developed materials were characterized by UV-VIS, SEM, and DLS analyses.

Fluorescence properties of photonic crystals doped with perylenediimide.

This study aims to present the fabrication of colloidal photonic crystals (PC) with increased fluorescence properties. The use of a highly fluorescent perylenediimide derivate (PDI) during the soap-free emulsion polymerization of styrene-acrylic acid resulted in monodisperse core-shell particles which allowed the fabrication of PC films. The properties of the hybrid material were studied in comparison with hybrid materials obtained by impregnation of films with chromophore solutions. In both cases an increase of the fluorescence response was observed in addition to a blue shift for the PDI core particles, proving the incorporation of the dye inside the copolymer particles.

Optical Properties of the Self-Assembling Polymeric Colloidal Systems

In the last decade, optical materials have gained much interest due to the high number of possible applications involving path or intensity control and filtering of light. The continuous emerging technology in the field of electrooptical devices or medical applications allowed the development of new innovative cost effective processes to obtain optical materials suited for future applications such as hybrid/polymeric solar cells, lasers, polymeric optical fibers, and chemo- and biosensing devices. Considering the above, the aim of this review is to present recent studies in the field of photonic crystals involving the use of polymeric materials.

Polymer colloids and silver nanoparticles hybrid materials

The present study presents two different methods to obtain hybrid material formed by the poly [styrene (ST)–poly(ethylene glycol) methyl ether methacrylate (PEGMA) 1100] and silver (Ag0). The aim has been to cover the polymeric particles with Ag0 shell. The first method consisted of mixing Ag0 nanoparticles dispersion with poly (ST-PEGMA 1100) dispersion, while in the second method, the Ag0 nanoparticles have been generated in situ. The hybrid materials have been characterized by MO, dynamic light scattering, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray energy dispersive spectrometry, and ultraviolet–visible spectrophotometry. The results confirm the obtaining of two types of morphologies. In the first case, the nanoparticles have been arranged in the interspatial zones of the polymer particles, while in the second method, the Ag0 nanoparticles have covered the polymer particles. Thus, the film obtained using the second method is more suitable for the practical application, as a separation membrane, using the antiseptic properties of Ag0.

Superficial Grafting of Water-Soluble Polymers on Brominated MWCNT by ATRP Technique

Multiwall carbon nanotubes (CNTs) have been brominated by photochemical bromine addition. XPS analysis has been used to determine the amount of bromine reacted. By measuring the concentrations of the co-initiator and the monomer, multiwall carbon nanotubes functionalized with hydrosoluble polymers—polyhydroxyethylacrylate (PHEA) and polyacrylamide (PAAM)—have been obtained and characterized using the Raman, SEM, and XPS depth profile techniques. The 3-D structure of the composite films obtained from the functionalized CNTs has been studied as well.

Atom transfer radical emulsion polymerization (emulsion ATRP) of styrene with water-soluble initiator

This study presents styrene emulsion polymerization initiated in aqueous media through an atom transfer radical polymerization (ATRP) mechanism. The water-soluble initiator employed in this process has been synthesized by our team by reacting diethanolamine with α-bromoisobutyryl bromide. The complexation of CuBr was realized by using a bicomponent complexation system comprised of 2,2′-bipyridine and N,N,N′,N′,N″-pentamethyldiethylenetriamine. The initiator ratio influence on the obtained emulsion was studied. The obtained latexes and polymer particles have been characterized by dynamic light scattering, scanning electron microscopy, and gel permeation chromatography.

Anionic polymerization by an electron transfer process from a CdSe quantum dot–perylenediimide (PDI) system

Reversible physical interactions between CdSe quantum dots (QDs) and perylenediimide (PDI) derivatives have been investigated. Original processes, dependent on the concentration of the two species, contact time, temperature and pH, were observed. The combining of the two solutions resulted in the formation of an electron transfer complex (ETC) due to the transfer of an electron from CdSe nanoparticles to PDI, followed by the formation of the final particularly stable dianion PDI2− species through another electron transfer process. The anionic species was employed for the polymerization initiation of glycidyl methacrylate (GMA). Some aspects of the anionic polymerization mechanism have been investigated.

Novel facile method for obtaining CdSe/polyaniline/C60 composite materials.

This study presents a novel method for the oxidative polymerization of aniline (ANI) by employing fullerene C60/cadmium selenide (CdSe) quantum dots, as promoting agent of the polymerization system. The polymerization initiation mechanism is based on the difference between the HOMO-LUMO energy levels of the components which permits the formation of a continuous donor-acceptor exchange. Both the polymerization reaction evolution and the molecular weights of the obtained polymers have been characterized. The novelty of the paper consists in the synthesis of a novel nano-composite material through a novel polymerization technique. The resulting material containing PANI, CdSe quantum dots and C60 has been characterized by UV-Vis, NIR, fluorescence, TEM and GPC analyses.

Electrochemical Deposition of Zinc Oxide on the Surface of Composite Membrane Polysulfone-Graphene-Polystyrene in the Presence of Water Soluble Polymers

The aim of this study consisted in the development of an alternative synthesis procedure for hybrid ultrafiltration membranes for water purification. The membranes were obtained by wet-phase inversion method based on aliquots of polysulfone (PSF) and graphene nanoplatelets modified with poly(styrene) (G-PST). The hybrid materials were modified by electrochemical deposition of zinc oxide (ZnO) on one side of the membranes in the presence of water soluble polymers. Raman, XPS, and TGA analyses were used to characterize the chemical and thermal characteristics of the PST-G. SEM analysis showed the formation of asymmetric porous configuration in all cases and the generation of ZnO with different shapes/structures on the bottom surface of the membrane or inside the porous channels. EDS analysis confirmed the formation of ZnO.