Publications

Green chemistry principles were used to phytosynthesis of three types of silver nanoparticles (AgNPs) from aqueous extracts of: nettle (Urtica dioica) leaves, black grapes (Vitis vinifera fruits), and their mixture. The combination of these extracts proved to be the most potent bioreductant for Ag+, as compared to each extract alone. UV-Vis absorption and FT-IR spectroscopy proved the formation of silver nanoparticles. Total polyphenols' quantification of vegetal extracts and "green" AgNPs was carried out by Folin-Ciocalteu analysis. Structural (XRD) analysis revealed crystalline nature of bio-developed AgNPs. Morphological studies (AFM) showed spherical shape and the nano-scale dimensions of the obtained metallic nanoparticles. Physical stability of "green" developed nanoparticles was estimated by zeta potential measurements, and their biological activity was checked by evaluating the antimicrobial and the antioxidant potency. AgNPs phyto-generated from a combination of two extracts (nettle and grapes) proved to be the most bio-active, combining in a synergistic manner, the properties of nettle and grapes. These nanoparticles exhibited high antioxidant activity (AA = 89.4%) evaluated through chemiluminescence method, and strong antibacterial effect (showing an inhibition zone diameter of 20 mm) against Escherichia coli.

Graded structures with different architectures were obtained by spark plasma sintering from (Ba1-xSrx)TiO3 (BST, x = 0.10; 0.20; 0.30) powders. The presence of the composition gradient was confirmed by structural and compositional investigations using X-ray diffraction and electron microscopy combined with energy dispersive X-ray spectroscopy. The concentration gradient was either asymmetric (3 layers, starting with x = 0.10 and ending with x = 0.30) or symmetric (5 or 6 layers, starting and ending with x = 0.10, and with a single or double x = 0.30 layer in the middle, respectively). Electrical measurements reveal a decrease of the dielectric constant with increasing the number of the layers. It was found that the symmetric graded structure with 6 layers has the best thermal stability of both, the dielectric constant (variation of only 8% between zero and 100 degrees C) and the py-roelectric coefficient (6% variation between zero and 80 degrees C). In addition, an enhancement of the pyroelectric signal for frequencies above 100 Hz is obtained in symmetric structures, an effect that is attributed to the additive contributions of the signals originated from the layers with different Sr content. (C) 2021 The Author(s). Published by Elsevier B.V.

Wheat is the most cultivated plant and an important source of carbohydrates in the world. The Fe deficiency reduces quality of grain wheat leading to Fe deficiency in human. The purpose of this study was to investigate the effects of foliar and ground application of iron oxide nanoparticles (made in Romania) on growth components, yield and morphological and anatomical modifications of wheat plants. The ground application of iron oxide decreased height of plant, length of root and increased root volume and chlorophyll content more than foliar application. For the wheat plants fertilized with iron oxide nanoparticles, the decrease of root length was compensated by an increase of radicular density, which led to the development of new adventitious roots that could help the plants have a better uptake of water and nutrients. This meant that the production was not negatively influenced by the treatments performed, regardless of the application method. Our studies revealed that the fertilized wheat plants (foliar and root zone) presented anatomical changes in relation to control plants. The studies presented in this paper can contribute to achieve the necessary framework for the innovative development strategy regarding the efficiency of magnetic nanoparticles in foliar and ground fertilization of different crops.

UV-nanoimprint lithography is currently seen like an alternative to the classical lithographic techniques (electron beam or optical lithography) for large scale patterning in industrial applications. The present study is oriented on the fabrication of silicon nano-cones (pyramids) by using the UV-nanoimprint technique with polymeric stamps and deep reactive ion etching using the UV-cured resist as etching mask at cryogenic temperatures. The results show that the resist can act successfully as etching mask for the cryogenic silicon etching process.

In this paper we present the results obtained by depositing the nanocomposite materials based on nano TiO2/TiO2:N, Ag, SiO2, single-walled carbon nanotube (SWCNTs), single-walled functionalized carboxylic acid, (SWCNT-COOH), poly(2,2' bithiophene) (PBTh) and poly(dipheylamine) (PDPA) by conventional and unconventional methods on the surface of sheepskin leathers. The nanocomposite materials were integrated in film forming polymers and were applied on sheepskin leather surfaces by spraying (conventional method) or by activating the surface with cold atmospheric plasma followed by electrospraying (unconventional methods). The leather surfaces were tested for antimicrobial properties against Grampositive and Gram-negative bacteria and fungi according to ISO 20743: 2007. The photocatalytic properties under visible light exposure were also tested using two organic stain models (methylene blue and orange II). The stain discoloring was evaluated by measuring the color differences between the blank and the samples with DATA Color Check Plus II portable device assisted by CIELab color management software. The evaluation of the physical-mechanical resistance and comfort properties for the sheepskin leathers was determined by measuring the water vapor permeability, rubbing tests and abrasion resistance. The results showed that the sheepskin leather surfaces treated with nanocomposite materials have improved antibacterial, self-cleaning, physical-mechanical and comfort properties as compared to untreated samples, with potential applications for added value multifunctional products. (c) 2021 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conferences & Exhibition on Nanotechnologies, Organic Electronics & Nanomedicine - NANOTEXNOLOGY 2020. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/

Herein we show the terahertz (THz) time-domain ellipsometry investigation of the InSb semiconductor. At room temperature, the carriers of InSb are thermally excited to the conduction band due to its narrow bandgap. We, nevertheless, show that THz ellipsometry can detect subtle differences between carrier densities of undoped and lightly doped InSb bulk semiconductors. The advantage of THz ellipsometry over other THz time-domain spectroscopy techniques is that it does not require reference measurements through an aperture or standard mirrors.

In this paper we introduce a model of cooperation between High School-University-Industry sustained by activities and results obtained in "Cypress - National Instruments Club" started at "Transilvania" University of Brasov - Romania. This strategic collaboration between High School-University-Industry was become necessary because technology is evolving at a rate that is quickly outpacing traditional engineering teaching methods. New methods such as hands-on learning labs, industry-centric curriculum, permanent updating of facilities, and using new adaptive learning software are being adopted. "Transilvania" University is targeting education at the industries of the future rather than industries of the past and for this reason we must apply the same strategies inside the high school in order to well prepare the children's, future students and the new engineers.

We investigate the photoluminescence properties of structures comprising of Si1-xGex nanoparticles (NPs) within SiO2, GeO2, TiO2 and Ta2O5 oxide matrices. Of the investigated structures, it was observed that the structures with GeO2 and TiO2 matrices provide increased spectral response (at similar to 907 and 844 nm respectively) and increased PL intensity. The improved PL characteristic have been attributed to increased diffusion barrier against oxygen which otherwise would result in formation of unwanted oxide at the film-oxide interface, thereby deteriorating the optical properties.

Composites of BaTiO3 (BT) and doped-PZT (d-PZT) micro-particles randomly dispersed in a PDMS matrix were prepared by a molding process. The morpho-structural characterization, performed by SEM and XRD, showed ceramic micro-grains of cubic BT and orthorhombic d-PZT, randomly dispersed in the PDMS matrix. Polarization (P) as a function of the applied field (E) was measured for composite samples, as well as for polymer samples. Hysteresis loops typical for a dielectric material were obtained, but also atypical ones, especially for higher fraction of polymer in composite, lower fields and shorter measuring periods, as a result of the dielectric relaxation in polymer and the presence of interfacial polarization charges at the contact between polymer and ferroelectric. All these composites show very low polarizations (less than 0.2 mu C/cm(2) and 0.05 mu C/cm(2) the maximum and remnant polarization, respectively), caused by the very low dielectric constant of the polymer (less than 10), which drastically reduces, up to 100 times, the electric field effectively applied to the ferroelectric. Weak pyroelectric response was recorded on BT/PDMS, but a typical behavior of a pyroelectric detector was observed. A figure of merit of the material which exceeds 10(-4) m(2) /C was estimated.