National Institute Of Materials Physics - Romania

Drinking water contamination has become a worldwide problem due to the highly negative effects that pollutants can have on human organisms and the environment. Hydroxyapatite (HAp) has the appropriate properties for the immobilization of various pollutants, being considered amongst the most cost-effective materials for water decontamination. The main objective of this study was to use synthesized hydroxyapatite for the elimination of Sr2+ ions from contaminated solutions. The hydroxyapatite used in the decontamination process was synthesized in the laboratory using an adapted method. The hydroxyapatite powder (HAp) resulting from the synthesis was analyzed both before and after the elimination of Sr2+ ions from contaminated solutions. The efficiency of the HAp nanoparticles in removing Sr2+ ions from contaminated solution was determined by batch adsorption experiments. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to study the HAp samples before and after the removal of Sr2+ ions. The ability of HAp nanoparticles to eliminate strontium ions from contaminated solutions was established. Moreover, the removal of Sr2+ ions from the contaminated aqueous solutions was highlighted by ultrasound measurements. The value of the stability parameter calculated by ultrasonic measurements after the removal of Sr2+ ions from the contaminated solution was similar to that of double distilled water whose stability was used as reference. The outcomes of the batch experiments and the parameters obtained from Langmuir and Freundlich models indicated that the HAp nanoparticles had a strong affinity for the elimination of Sr2+ ions from polluted solutions. These results emphasized that HAp nanoparticles could be excellent candidates in the development of new technologies for water remediation. More than that, the outcomes of the cytotoxic assays proved that HAp nanoparticles did not induce any noticeable harmful effects against HeLa cells and did not affect their proliferation after 1 day and 7 days of incubation.

A numerical algorithm for interface analysis of wicking drops was developed. The code identifies the interface points and subsequently calculates the diameter, volume and contact angle of the drop. As the code can work with multiple frames, it can evaluate the evolution in time of these parameters and calculate the spreading velocity and the flow rate. The performance of the code was tested with solutions of poly(ethylene oxide) of 0.5% and 5% (w/v) concentration. The mean execution time was 0.5 seconds per frame. Therefore, the code can greatly improve the analysis of fluids wicking in porous media, where numerous frames are involved.

The purpose of the work is the synthesis and characterization of TiO2 nanoparticles. These were obtained by two different methods, precipitation and sol-gel, starting from titanium(IV) isopropoxide and calcining at 500 degrees C for 2 h. The compositional, structural, morphological and optical properties of the resulting powders were investigated by energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, reflectance spectroscopy and photoluminescence spectroscopy. The thermally treated samples contain TiO2 as single phase with tetragonal structure, known as anatase. SEM analysis showed quasi-spherical particles with a diameter of few nanometres for the calcined samples, while the optical studies revealed band gap values of 3.04 and 3.17 eV, as a function of the preparation route.

Proteins are vital components of living cells and the loss of their native functions has been associated with a wide variety of medical conditions. From this point of view, investigation of the protein microenvironment is crucial to support the development of therapeutic approaches capable of ensuring cellular functions. Therefore, analytical assays for the detection, quantification, and characterization of proteins, drugs, and protein-drug complexes play an essential role in fundamental research and clinical applications. Electrochemistry arises as an alternative methodology for fast assessment of proteins and drugs and is attractive due to the adaptability to miniaturization and scalability of electroanalytical devices, which then can be further employed as strategies towards personalized medical care. Thus, this review summarizes electrochemical investigations in the past 10 years on protein-based analytical devices and biosensors. A general overview of electrochemical assays that integrate proteins with nanostructured materials and conductive polymers is presented. Applications of electrochemical assays and biosensors were divided into four categories. First, those designed for drug screening strategies that focus on targeting specific intracellular, extracellular, or membrane protein subdomains to modulate their functions, aggregation/misfolding of proteins, and protein degradation pathways. Then, drug metabolism assays that involve mimicking natural metabolic pathways to identify potential safety and efficacy issues related to a drug or its metabolites. The third was dedicated to electrochemical drug delivery systems with anchored drugs in the form of bioconjugates, while the fourth was dedicated to electroanalytical methodologies for quantitative drug assays, where the electroactivity of the target species is often used to correlate the electrochemical signal to their concentration.

In this work, polyvinylidene fluoride (PVDF) fibres loaded with mineral powders, such as titanium dioxide (TiO2), barium titanate (BaTiO3), and calcium magnesium silicate (CaxMgSi2Oy), were prepared by electrospinning polymeric suspensions containing 20 wt.% PVDF and 3 wt.% powder. The piezoelectric polymer was combined with powders having antibacterial, piezoelectric, or bioactive properties, respectively, in the desire to obtain multifunctional materials compatible with the requirements of the medical field. All powders were characterized in terms of morphology and crystalline structure, which confirmed the nanometric character of TiO2 samples and micrometric one for the other two, as well as the lower crystallite size for TiO2 specimens as against BaTiO3 and CaxMgSi2Oy. The final fibrous scaffolds were homogeneous, composed of individual fibres with a diameter below 1 mu m and decorated with aggregates of inorganic particles, placed either inside the fibres or attached to their surface. The biological evaluation demonstrated the superiority of the composites towards the plain polymer in terms of cell viability.

High density (94-98% of the theoretical density) MgB2 samples added with C6H10Ge2O7 and cubic BN with compositions (MgB2)(1-x)(Ge2C6H10O7)(0.0028)(cBN)(x) (x = 0.003, 0.005, 0.007, 0.01) and (MgB2)(1-y)(Ge2C6H10O7)(y)(cBN)(0.005) (y = 0.0014, 0.0028, 0.005, 0.0075) were obtained by spark plasma sintering technique. For optimum doped samples with x = 0.005-0.007 and y = 0.0028-0.005, a weak enhancement of zero-field critical current density J(c0), irreversibility field H-irr, and volume pinning force F-p,F-max was determined. This behavior is very different from similar samples added with a single additive for which H-irr has a large enhancement. Consequently, it suggests the presence of opposite structural and microstructural effects induced by the additives. These effects, on the one hand, are discussed to decrease the sensitivity of MgB2 superconducting properties in the co-added samples comparative to samples added with C6H10Ge2O7, and, on the other hand, they contribute to anomalies that were found when assessing the pinning force-related parameters by the universal scaling law.

The properties of organic heterostructures with mixed layers made of arylenevinylene-based polymer donor and non-fullerene perylene diimide acceptor, deposited using Matrix Assisted Pulsed Laser Evaporation on flat Al and nano-patterned Al electrodes, were investigated. The Al layer electrode deposited on the 2D array of cylindrical nanostructures with a periodicity of 1.1 mu m, developed in a polymeric layer using UV-Nanoimprint Lithography, is characterized by an inflorescence-like morphology. The effect of the nanostructuring on the optical and electrical properties was studied by comparison with those of the heterostructures based on a mixed layer with fullerene derivative acceptor. The low roughness of the mixed layer deposited on flat Al was associated with high reflectance. The nano-patterning, which was preserved in the mixed layer, determining the light trapping by multiple scattering, correlated with the high roughness and led to lower reflectance. A decrease was also revealed in photoluminescence emission both at UV and Vis excitation of the mixed layer, with the non-fullerene acceptor deposited on nano-patterned Al. An injector contact behavior was highlighted for all Al/mixed layer/ITO heterostructures by I-V characteristics in dark. The current increased, independently of acceptor (fullerene or non-fullerene), in the heterostructures with nano-patterned Al electrodes for shorter conjugation length polymer donors.

We have investigated the pinning potential of high-quality single crystals of superconducting material CaKFe4As4 having high critical current density and very high upper critical field using both magnetization relaxation measurements and frequency-dependent AC susceptibility. Preliminary studies of the superconducting transition and of the isothermal magnetization loops confirmed the high quality of the samples, while temperature dependence of the AC susceptibility in high magnetic fields show absolutely no dependence on the cooling conditions, hence, no magnetic history. From magnetization relaxation measurements were extracted the values of the normalized pinning potential U*, which reveals a clear crossover between elastic creep and plastic creep. The extremely high values of U*, up to 1200 K around the temperature of 20 K lead to a nearly zero value of the probability of thermally-activated flux jumps at temperatures of interest for high-field applications. The values of the creep exponents in the two creep regimes resulted from the analysis of the magnetization relaxation data are in complete agreement with theoretical models. Pinning potentials were also estimated, near the critical temperature, from AC susceptibility measurements, their values being close to those resulted (at the same temperature and DC field) from the magnetization relaxation data.

In the present work, stannite Cu2CoSnS4 (CCTS) films were elaborated using spray pyrolysis method on soda-lime glass, at different deposition temperatures (T-d = 250, 300, and 350 degrees C), followed by different chosen sulfurization temperatures (T-s = 450, 500, and 550 degrees C). X-ray diffraction (XRD) revealed the nearly single-phase formation of CCTS films at 300 degrees C deposition temperature. After sulfurization in argon flow, the XRD lines become narrower, the average crystallite size expanding above 70 nm. The Raman spectroscopy analysis confirmed the stannite structure formation, as well as the presence CoS2 secondary phases, which reduces at higher sulfurization temperature (550 degrees C). The energy dispersive spectroscopy results indicated atomic ratios of Cu/Co/Sn/S close to the ideal stoichiometric ratio 2:1:1:4. The room temperature photoluminescence emission is recorded with maximum in the 1.35-1.40 eV range. Thermoelectric properties are measured up to 130 degrees C, the films show poor power factor as a result of small positive Seebeck coefficients 10-45 Of K -1 and low electrical conductivity despite of having relatively high carrier concentration (similar to 10(20) cm(-3)).

The present work reports the synthesis and characterization of polycaprolactone fibers loaded with particulate calcium magnesium silicates, to form composite materials with bioresorbable and bioactive properties. The inorganic powders were achieved through a sol-gel method, starting from the compositions of diopside, akermanite, and merwinite, three mineral phases with suitable features for the field of hard tissue engineering. The fibrous composites were fabricated by electrospinning polymeric solutions with a content of 16% polycaprolactone and 5 or 10% inorganic powder. The physico-chemical evaluation from compositional and morphological points of view was followed by the biological assessment of powder bioactivity and scaffold biocompatibility. SEM investigation highlighted a significant reduction in fiber diameter, from around 3 mu m to less than 100 nm after the loading stage, while EDX and FTIR spectra confirmed the existence of embedded mineral entities. The silicate phases were found be highly bioactive after 4 weeks of immersion in SBF, enriching the potential of the polymeric host that provides only biocompatibility and bioresorbability. Moreover, the cellular tests indicated a slight decrease in cell viability over the short-term, a compromise that can be accepted if the overall benefits of such multifunctional composites are considered.