Marius Dobromir

Humidity sensor characteristics and electrical properties of Ni–Zn–Dy ferrite material prepared using different chelating-fuel agents

Abstract Humidity sensor characteristics and electrical properties of Ni–Zn ferrite material doped with Dy were studied after synthesis via sol–gel self-combustion method. In order to obtain different micro configurations of the material reflected in different porosities, four different fuel agents were involved: citric acid, tartaric acid, cellulose and urea. XRD and XPS techniques were used to certify the composition. The influence of fuel agent and structural features on the electrical properties of ferrite sintered pellets was investigated at room temperature as a function of frequency and humidity. Because the electrical characteristics of a porous material can significantly affect by the humidity, the electrical measurements were carried out in controlled humidity environments. Conduction mechanism is explained in terms of fuel agent influence on phase composition, grain size value, cation distribution and induced strain within spinel lattice by dissolution of voluminous Dy3+ ions. The humidity sensors applicative characteristics of the material are highlight by analyzing the sensitivity, response and recovery times of nickel–zinc–dysprosium ferrite used as active material.

Synthesis and hydrophilic properties of Mo doped TiO2 thin films

Amorphous undoped TiO2 and Mo-doped TiO2 thin films were obtained by spray pyrolysis. By heat treatment, they became polycrystalline consisting in anatase, or mixed anatase/rutile phases, if deposited on glass or silicon, respectively. Mo enters in the TiO2 matrix as Mo5+, determining a slight red shift of the absorption edge. Based on Fourier transmission infrared analysis, performed on the studied films, before and after irradiation, providing information on the relationship between hydrophilicity and the amount of the adsorbed hydroxyl groups, we certify once again that the anatase phase (present in proportion of 100% in the films deposited on glass) is superior concerning the hydrophilic properties. Mo enhances wettability for the films deposited on silicon, compared to the undoped one, even if determines a rise in the rutile weight percentage, as a combined effect with the substrate nature. The decomposition of the oleic acid confirms that titania films with higher hydrophilic performances are also g...

Hybrid Nanostructures Containing Sulfadiazine Modified Chitosan as Antimicrobial Drug Carriers

Chitosan (CH) nanofibrous structures containing sulfadiazine (SDZ) or sulfadiazine modified chitosan (SCH) in the form of functional nanoparticles attached to nanofibers (hybrid nanostructures) were obtained by mono-axial and coaxial electrospinning. The mono-axial design consisted of a SDZ/CH mixture solution fed through a single nozzle while the coaxial design consisted of SCH and CH solutions separately supplied to the inner and outer nozzle (or in reverse order). The CH ability to form nanofibers assured the formation of a nanofiber mesh, while SDZ and SCH, both in form of suspensions in the electrospun solution, assured the formation of active nanoparticles which remained attached to the CH nanofiber mesh after the electrospinning process. The obtained nanostructures were morphologically characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SDZ release profiles and kinetics were analyzed. The SDZ or SCH nanoparticles loosely attached at the surface of the nanofibers, provide a burst release in the first 20 min, which is important to stop the possible initial infection in a wound, while the SDZ and SCH from the nanoparticles which are better confined (or even encapsulated) into the CH nanofibers would be slowly released with the erosion/disruption of the CH nanofiber mesh.

Polyurethane-extracellular matrix/silver bionanocomposites for urinary catheters

Polyurethane–extracellular matrix membranes with bionanocomposites or coatings containing a small amount of biocompatible polymers such as hydrolyzed collagen, elastin, hyaluronic acid or chondroitin sulfate, and silver were obtained by solvent casting or electrospinning/electrospraying of the polyurethane–extracellular matrix–Ag formulations onto pure polyurethane membrane in order to achieve improved antibacterial biomaterials for urinary catheters. Using Fourier transform infrared spectroscopy, the interaction of the incorporated silver nanoparticles with polyurethane–extracellular matrix was found, while X-ray photoelectron spectroscopy and X-ray diffraction analyses ws used to determine the presence of metallic Ag for polyurethane membrane and Ag only in oxidized state for polyurethane–extracellular matrix membranes due to the stabilizing effect of polymeric components. The in vitro antimicrobial tests against Escherichia coli, Salmonella typhymurium, and Listeria monocytogenes were used for the evaluation of the antimicrobial efficiency.

Bactericidal effect on Foley catheters obtained by plasma and silver nitrate treatments

New medical, materials, and surgical procedures keep improving current health-care practices. Many of these innovations involve polymeric devices that must meet certain clinical and cost requirements. Novel antimicrobial technologies and nanotechnologies are being implemented in more applications such as implant interphases, coatings, and others to avoid postoperatory infections. Here we present a novel approach to create antimicrobial surfaces on Foley catheters widely used in hospitals in order to avoid a variety of harms including infection, pain, and trauma. The combination of plasma and silver nitrate wet treatments demonstrates to be a fast, easy, and convenient method for obtaining colonization-resistant catheter surfaces.

Structural and Magnetic Properties of FeCuNbSiB Thin Films Deposited by HiPIMS

Using high-power impulse magnetron sputtering (HiPIMS) technique, Fe73.5Cu1Nb3Si15.5B7 thin films with thickness between 40 and 700 nm were deposited. The influence of deposition conditions (deposition time and argon pressure) and of the annealing temperature on the structure and coercive magnetic field of the magnetic films was analyzed. In the as-deposited state, the coercive magnetic field presents a minimum at about 10 mtorr argon pressure. The X-ray diffraction studies show that in the as-deposited state, the samples are amorphous, while after annealing at temperatures between 400°C to 525°C, α-Fe(Si) grains start to nucleate, the grain size varying from 2 to 18 nm. The Curie temperature of as-deposited amorphous phase and the onset of the primary crystallization are 355°C and 460°C, respectively. The lowest coercive magnetic field was obtained after annealing at 475°C.

Ethyl chitosan synthesis and quantification of the effects acquired after grafting it on a cotton fabric, using ANOVA statistical analysis.

Three ethyl chitosans (ECSs) have been prepared using the ethyl chloride (AA) that was obtained in situ. Each ECS was applied on a 100% cotton fabric through a pad-dry-cure technology. Using the ANOVA as statistic method, the wrinkle-proofing effects have been determined varying the concentrations of AA (0.1-2.1mmol) and chitosan (CS) (0.1-2.1mmol). Alkylation and grafting mechanisms have been confirmed by the results of FTIR, (1)H NMR, XPS, SEM, DSC and termogravimetric analyses. The performances of each ECS as wrinkle-proofing agent have been revealed through quantitative methods (taking-up degree, wrinkle-recovering angle, tensile strength and effects durability). The ECSs confer wrinkle-recovering angle and tensile strength higher than those of the witness sample. Durability of ECSs grafted on cotton have been demonstrated by a good capacity of dyeing with non-specific (acid/anionic and cationic) dyes under severe working conditions (100°C, 60min) and a good antimicrobial capacity.

Poly (Ethylene Glycol-Co-Styrene) Films Deposited by Plasma Polymerization Reactions at Atmospheric Pressure

Atmospheric pressure plasma co-polymerization of ethylene glycol and styrene was applied to produce poly (ethylene glycol-co-styrene) using a dielectric barrier discharge. The chemical structure of polymerized films was studied by Fourier-transform infrared spectroscopy which confirms that we obtained copolymerized films with hydroxyl groups incorporated. Chemical composition of films was studied by X-ray Photoelectron Spectroscopy and oxygen containing groups (C-O and C=O) were identified. Topography of polymer films was revealed using Atomic Force Microscopy technique and the film root mean square roughness (Rrms) was found to be 1.6 nm. Surface wettability was analyzed using water contact angle technique.

Cavity-hollow cathode-sputtering source for titanium films

A cavity-hollow cathode was investigated as low-cost sputtering source for titanium. An argon discharge is produced inside a hollow cathode consisting of two specifically formed disks of titanium. An additional cavity further enhances the pendulum effect of the electrons. Measurements with small Langmuir probes yielded evidence for the formation of a space charge double layer above the cathode. The sputtered atoms form negatively charged clusters. After further acceleration by the double layer the clusters impinge on the substrates. Titanium thin films were produced on highly oriented pyrolytic graphite. The films were investigated by a scanning tunnel microscope and X-ray photoelectron spectroscopy.

Platinum role in hydrophilicity enhancement of Cr-doped TiO2 thin films

Abstract In this paper, we have investigated the hydrophilic properties of the titania films doped with increasing chromium percentages (from 2.1 at.% till 4.0 at.%). Cr-doping induces an increase in the rutile weight %, a more compact structure, and a significant red shift of the TiO2 absorption edge, the last property being very important in the self cleaning applications. For the chosen Cr concentrations, the films did not show promising hydrophilic properties. To improve them, we have applied a novel surface modification method, reported in literature mainly for powders, namely, surface metallisation. We have observed that, by depositing Pt islands on the film with the highest Cr content, its hydrophilic properties improve for a certain metal coverage area. The explanation was based on FT-IR and X-ray photoelectron spectroscopy analysis, performed on the UV irradiated and non-irradiated films, which gives information on the relationship between hydrophilicity and the amount of the adsorbed hydroxyl groups.