Adina Magdalena Musuc

Synthesis, spectral characterization, and thermal behavior of mononuclear Cu(II), Co(II), Ni(II), Mn(II), and Zn(II) complexes with 5-bromosalycilaldehyde isonicotinoylhydrazone

A bidentate/tridentate 5-bromosalycilaldehyde isonicotinoylhydrazone Schiff base was synthesized by condensing 5-bromosalycilaldehyde with isonicotinoylhydrazine. Cu(II), Co(II), Ni(II), Mn(II) and Zn(II) complexes of this chelating ligand were synthesized using nitrates of these metals. The ligand and the complexes were characterized by elemental analysis, UV–Vis, IR and EPR spectroscopy, conductance and magnetic susceptibility measurements, fluorescence, cyclic voltammetry and thermogravimetric analysis. The ligand and Zn(II) complex exhibits solid-state photoluminescence at room temperature.

FTIR, XRD, and DSC analysis of the rosemary extract effect on polyethylene structure and biodegradability

Differential scanning calorimetry (DSC) technique enabled the study of the effect of the rosemary (Rosmarinus officinalis) extract on polyethylene foils structure and biodegradability. The polyethylene used for food packaging contains synthetic antioxidants which are often able to migrate and to contaminate the food. Natural extracts with antioxidant properties may be an interesting alternative for the polyethylene fabrication. The influence of the rosemary present in different concentrations in non-irradiated and irradiated polyethylene samples was studied. The biodegradability studies were carried out by incubating the modified polyethylene with the yeast Candida lipolytica. The changes of physical properties and morphological aspects before and after fungal attack were studied by Fourier Transform Infrared Spectroscopy, X-ray diffraction, and DSC. With some exceptions due to the nonuniform character of the investigated samples, the melting peak temperature and crystallization degree were found to decrease with increasing of rosemary content and irradiation. Synergic effects of rosemary and irradiation on the film biodegradability were directly confirmed by optical microscopy.

Additive-free 1,4-butanediol mediated synthesis: a suitable route to obtain nanostructured, mesoporous spherical zinc oxide materials with multifunctional properties

A family of mesoporous, self-aggregated zinc oxide materials with spherical morphologies of high crystalline quality, is obtained through a facile, additive-free polyol procedure. The forced hydrolysis of zinc acetylacetonate in 1,4-butanediol (BD), in various reaction conditions, affords ZnO materials with versatile morphologies and optical properties. The reaction parameters (temperature, time and zinc source concentration) modulate the ZnO nanocrystallites size (from 8.1 to 13.2 nm), the spheres diameter (ranging from 50 up to 250 nm), the internal structure of the spherical aggregates (hollow or solid) and their specific surface area (from 31 to 92 m2 g−1). Polycrystalline spheres with hollow cores are obtained at the lowest temperature (90 °C) and zinc cation concentration (0.1 M), while at higher reaction temperatures (140–180 °C), solid spherical aggregates are developed. A reaction mechanism for ZnO formation via zinc layered hydroxide (LDH-Zn) is proposed based on nuclear magnetic resonance (1H NMR and 13C NMR) and powder X-ray diffraction (XRD) studies. The obtained ZnO materials have a functionalized surface, derived from the polyol and act as a nitrogen selective photocatalyst in the reduction reaction of NO3−. The organic residual attached on the ZnO surface plays a crucial role in the denitrification reaction, since the photo-cleaned sample showed negligible photocatalytic activity. The ZnO materials also exhibited microbicidal and anti-biofilm activity against reference and clinical strains, highlighting their potential for the development of novel antimicrobial formulations.

Sustainable one-pot integration of ZnO nanoparticles into carbon spheres: manipulation of the morphological, optical and electrochemical properties.

ZnO-carbon composite spheres were synthesized via starch hydrothermal carbonization (HTC) in the presence of a soluble zinc salt (acetate), followed by thermal processing under an argon atmosphere. Besides sustainability, the one-pot procedure represents a scalable synthesis of tailored carbon-metal oxide spheres with a structurally-ordered carbon matrix obtained at a relatively low temperature (700 °C). The ability of zinc cations to develop different linkages with starchs hydrophilic functional groups and to act as external nucleators determines an increase in HTC yield; the effect is obvious even in the presence of small concentrations of zinc in the reaction medium (0.005 M), thus providing a way to improve the carbonization process efficiency. It is also shown that zinc content is the control vector of the spherical composites properties: a variation from 0.3 to 4.8 at% not only induces a variation in their size (200 nm-10 μm), interconnectivity (from disperse spheres to necklace-like aggregations), surface area and connected porosity (from micro- to mesoporosity), but also of their electrochemical and white light adsorption and emission features. Since the variation in zinc content is made by a simple adjustment of the raw material concentrations, the functionality of these carbon-based materials can be modulated in a straightforward manner.

Kinetics of exothermal decomposition of some ketone-2,4-dinitrophenylhydrazones

In this study, the thermal stability and exothermal decomposition of some ketone-2,4-dinitrophenylhydrazones have investigated using the DSC technique. The synthesized and purified crystalline solids are thermally stable and start to decompose after melting. Non-isothermal DSC curves, recorded at several heating rates, were used to evaluate the melting properties and the kinetics of thermal decomposition. The isoconversional and model-fitting methods were applied to determine the activation parameters from the common analysis of multiple curves measured at different heating rates. Based on the results of the model—free method, a kinetic model was derived, and the kinetic parameters were obtained by means of a multivariate nonlinear regression. The results are discussed in relation to the effect of the ketone structure.

Thermal stabilities of some benzaldehyde 2,4-dinitrophenylhydrazones

The thermal stability of some benzaldehyde 2,4-dinitrophenylhydrazones has been studied using DSC technique. The crystalline solids are thermally stable and start to decompose after melting. Non-isothermal DSC curves, recorded at several heating rates, were used to evaluate the melting properties and the kinetics of thermal decomposition. Both isoconversional and model fitting methods were used for the evaluation of the kinetic parameters. Based on the results of the model free method, a kinetic model was derived and the kinetic parameters were obtained by means of a multivariate non-linear regression. A good agreement between the experimental and fitted data was found.

Kinetic analysis of thermal decomposition in liquid and solid state of 3-nitro and 4-nitro-benzaldehyde-2,4-dinitrophenylhydrazones

A kinetic study on the thermal decomposition of 3-nitro and 4-nitro-benzaldehyde-2,4-dinitrophenylhydrazones was carried out. The isothermal and dynamic differential scanning calorimetric curves were recorded for solids and melts, respectively. The standard isoconversional analysis of the obtained curves from both isothermal and nonisothermal analysis suggests an autocatalytic decomposition mechanism. This mechanism is also supported by the temperature dependence of the observed induction periods. Based on the results of the model-free method from nonisothermal regime, the kinetic model was derived and the kinetic parameters were obtained by means of a multivariate nonlinear regression.

Multifunctional Silver Nanoparticles-Decorated Silica Functionalized with Retinoic Acid with Anti-Proliferative and Antimicrobial Properties

The paper describes a rapid and simple method for preparing a multifunctional biomaterial based on retinoic acid covalently bound on silica@Ag particles. Monodispersed SiO2 particles were prepared by Stöber method and further used for loading the Ag nanoparticles on their surface. This composite was further functionalized with retinoic acid. Characterization of the hybrid materials was made by UV–Visible spectroscopy, Transmission electron microscopy, Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and Thermal analysis. The biological evaluation of the obtained materials revealed their potential use for multiple biomedical applications, from anti-proliferative agents to novel antimicrobial and antibiofilm strategies.

Synthesis, characterization and thermoreactivity of some methylcellulose–zinc composites

Abstract Two methylcellulose–ZnO and one methylcellulose–Zn2+ composites were obtained by precipitation and hydrothermal procedures. The thermal behavior of the composites was examined by simultaneous TG, DTG, DSC-FTIR thermal method. It was found that the thermal reactivity of the methylcellulose contained by the composites is strongly dependent on the composites’ synthetic procedure, but in all cases its stability is shifted toward lower temperatures. For each type of composites, the causes that lead to a change of methylcellulose thermoreactivity were highlighted. The structural, morphological and optical characteristics of the ZnO-based materials are also demonstrated.

Lipoic acid functionalized SiO2@Ag nanoparticles. Synthesis, characterization and evaluation of biological activity

A novel nanocomposite was obtained through the covalent immobilization of lipoic acid on the surface of silver nanoparticles-decorated silica nanoparticles (SiO2@Ag). The hybrid organic - inorganic material obtained was characterized by Fourier transform infrared spectroscopy, thermal analysis, scanning and transmision electron microscopy, X-ray photoelectron spectroscopy and UV-Visible spectroscopy. Its antioxidant, cytotoxic, antimicrobial activity and influence on mammalian cells cycle were evaluated. The results of this study have shown that the functionalization of SiO2@Ag with lipoic acid resulted in a composite with increased specificity of interaction with different mammalian cell lines and antioxidant activity, but with decreased cytotoxicity and antimicrobial properties. Therefore, the SiO2@Ag functionalized with lipoic acid could be successfully used in certain concentrations to modulate the cell cycle, in order to obtain the desired anti-proliferative or stimulatory therapeutic effect.