2. Articole
Permanent URI for this collectionhttps://msuir.usm.md/handle/123456789/47
Browse
19 results
Search Results
Item Aero-Ga2o3 nanomaterial electromagnetically transparent from microwaves to terahertz for internet of things applications [Articol](2020) Braniște, Tudor; Dragoman, Mircea; Jucov, Serghei; Aldrigo, Martino; Ciobanu, Vladimir; Iordănescu, Sergiu; Alîabîeva, Liudmila; Fumagalli, Francesco; Ceccone, Giacomo; Raevschi, Simion; Schűtt, Fabian; Adelung, Rainer; Colpo, Pascal; Gorșunov, Boris; Tighineanu, IonIn this paper, fabrication of a new material is reported, the so-called Aero-Ga2O3 or Aerogallox, which represents an ultra-porous and ultra-lightweight three-dimensional architecture made from interconnected microtubes of gallium oxide with nanometer thin walls. The material is fabricated using epitaxial growth of an ultrathin layer of gallium nitride on zinc oxide microtetrapods fabricated using epitaxial growth of an ultrathin layer of gallium nitride on zinc oxide microtetrapods followed by decomposition of sacrificial ZnO and oxidation of GaN which according to the results of X-ray diffraction (XRD) and X-ray photoemission spectroscopy (XPS) characterizations, is transformed gradually in β-Ga2O3 with almost stoichiometric composition. The investigations show that the developed ultra-porous Aerogallox exhibits extremely low reflectivity and high transmissivity in an ultrabroadband electromagnetic spectrum ranging from X-band (8–12 GHz) to several terahertz which opens possibilities for quite new applications of gallium oxide, previously not anticipated.Item Aero-TiO2 prepared on the basis of networks of ZnO tetrapods [Articol](2022) Ciobanu, Vladimir; Ursachi, Veaceslav; Lehmann, Sebastian; Braniște, Tudor; Raevschi, Simion; Zamalai, Victor V.; Monaico, Eduard V.; Colpo, Pascal; Nielsch, Kornelius; Tighineanu, IonIn this paper, new aeromaterials are proposed on the basis of titania thin films deposited using atomic layer deposition (ALD) on a sacrificial network of ZnO microtetrapods. The technol-ogy consists of two technological steps applied after ALD, namely, thermal treatment at different temperatures and etching of the sacrificial template. Two procedures are applied for etching, one of which is wet etching in a citric acid aqua solution, while the other one is etching in a hydride vapor phase epitaxy (HVPE) system with HCl and hydrogen chemicals. The morphology, composition, and crystal structure of the produced aeromaterials are investigated depending on the temperature of annealing and the sequence of the technological steps. The performed photoluminescence analysis suggests that the developed aeromaterials are potential candidates for photocatalytic applications.Item Self-propelled aero-gan based liquid marbles exhibiting pulsed rotation on the water surface [Articol](2021) Braniște, Tudor; Ciobanu, Vladimir; Schűtt, Fabian; Mimura, Hidenori; Raevschi, Simion; Adelung, Rainer; Pugno, Nicola M.; Tighineanu, IonWe report on self-propelled rotating liquid marbles fabricated using droplets of alcoholic solution encapsulated in hollow microtetrapods of GaN with hydrophilic free ends of their arms and hydrophobic lateral walls. Apart from stationary rotation, elongated-spheroid-like liquid marbles were found, for the first time, to exhibit pulsed rotation on water surfaces characterized by a threshold speed of rotation, which increased with the weight of the liquid marble while the frequency of pulses proved to decrease. To throw light upon the unusual behavior of the developed self-propelled liquid marbles, we propose a model which takes into account skimming of the liquid marbles over the water surface similar to that inherent to flying water lily beetle and the so-called helicopter effect, causing a liquid marble to rise above the level of the water surface when rotating.Item Synthesis and properties of Al-doped ZnO thin films for photovoltaics [Articol](Institute of Electrical and Electronics Engineers Inc., 2018-11-27) Potlog, Tamara; Lungu, Ion; Botnariuc, Vasile; Gorceac, Leonid; Raevschi, Simion; Taku, Miyake; Worasawat, Suchada; Mimura, HidenoriPolycrystalline undoped and Al-doped ZnO thin films were deposited by spray pyrolysis using oxygen and argon atmospheres. The influence of postdeposition vacuum annealing on the structure, morphology and optical properties was studied by X-ray diffraction, atomic force microscopy and UV–VIS spectroscopy. The thermal vacuum annealing induces structural and morphological changes, especially in Al-doped ZnO thin films synthetized in oxygen atmosphere. Further on, the electrical conductivity in dependence of the nature of gas atmosphere and Al concentration is discussed.Item Effect of carrier gas and vacuum annealing on the physical properties of ZnO thin films doped with gallium by chemical spray pyrolysis [Articol](Editura "Tehnica-UTM", 2018-05-24) Potlog, Tamara; Lungu, Ion; Botnariuc, Vasile; Raevschi, Simion; Worasawat, Suchada; Mimura, Hidenori; Gorceac, LeonidStructural, optical and electrical properties of zinc oxide thin films doped with 2% Ga, annealed in the vacuum at the same temperature and obtained onto glass substrates by the chemical spray pyrolysis method in the different gas atmospheres were investigated by X-ray Diffraction (XRD), UV-VIS spectrophotometry and Hall measurements, respectively. XRD studies revealed that all films were polycrystalline in nature, with a hexagonal wurtzite crystal structure and a predominant (002) c-axis orientation. All ZnO:Ga thin films had higher than 80 % transmittances in the visible region. Doping with 2% Ga led to a decrease in the optical band gap indifferent of the nature of the carrier gas. The synthesis of ZnO thin films with 2% Ga doping and annealing in the same conditions in Ar and O2 atmospheres led to the lower conductivity with electron concentration of 1016 cm−3.Item The interaction between Endothelial Cells and Gallium Nitride nanoparticles [Articol](2019) Braniste, Tudor; Andree, Birgit; Benecke, Nils; Raevschi, Simion; Plesco, Irina; Cebotari, Serghei; Haverich, Axel; Tighineanu, Ion; Hilfiker, AndresIn this study, human umbilical vein endothelial cells (HUVECs) were investigated in direct contact with Gallium Nitride (GaN/Fe) based nanoparticles. GaN is a compound semiconduc- tor material, with remarkable characteristics including piezoelectric properties, high thermal stability, radiation hardness and excellent chemical inertness, which make it promising for biomedical applications. There is, however, limited knowledge about the biocompatibility of nanostructured GaN and the impact of GaN nanoparticles on living cells. We report on growth and characterization of GaN/ZnFe2O4 multifunctional piezoelectric and magnetic nanoparticles as well as on their assimilation and interaction with HUVECs. Thin GaN layers were grown on ZnFe2O4 nanoparticles with sizes up to 100 nm, using Hydride Vapor Phase Epitaxy (HVPE). After GaN growth, the sacrificial core of nanoparticles was decomposed at high temperatures in hydrogen flow, the final composition of nanoparticles corresponding to GaN:Fe. The resulted nanoparticles were incubated with human umbilical vein endothelial cells in order to remotely influence the cells activity through nanoparticles. By cultivating cells in medium supplemented with different concentrations of nanoparticles, we show that HUVECs tolerate GaN nanoparticles. The obtained results show that, being uptaken by the cells, the GaN nanoparticles are deposited into vesicles and thus can be used as guiding elements for controlled transportation or designed spatial distribution of cells in a magnetic field, which represent a step forward towards application in cellular therapy.Item Fotodetector pe heterojoncțiune din fosfură de indiu [Articol](CEP USM, 2020) Gorceac, Leonid; Botnariuc, Vasile; Coval, Andrei; Vatavu, Sergiu; Cinic, Boris; Raevschi, Simion; Rotaru, CorneliuItem ZnO nanometric layers used in photovoltaic cells [Articol](Springer Nature, 2020) Botnariuc, Vasile; Gorceac, Leonid; Coval, Andrei; Cinic, Boris; Gaugas, Petru; Chetrus, Petru; Lungu, Ion; Raevschi, SimionThe ZnO thin layers were grown on glass, InP and pInP-nCdS substrates from zinc acetate dissolved in water-acetic acid-methanol solution having a molarity of 0.2 M by using the spray method in the argon flow in the temperature range of (250–450) °C. The dependence of optical properties of ZnO layers on growth temperature have been investigated. The optical transmittance has values of 80–85% in the wavelength range of (200–1000) nm. The using of ZnO of the thickness of (60–80) nm as antireflective layers in nCdS-pInP structures allowed to increase the photovoltaic cell efficiency by 3%. The photosensitivity of the fabricated nZnO-pInP structures covers the wavelength region from 450 nm up to 1100 nm and allows the more efficient utilization of the incident light.Item Electrical properties of thermal annealed in vacuum spray deposited al-doped zno thin films [Articol](Springer Nature, 2020) Potlog, Tamara; Lungu, Ion; Raevschi, Simion; Botnariuc, Vasile; Robu, Stephan; Worasawat, Suchada; Mimura, HidenoriAl-doped ZnO thin films have been prepared by spray pyrolysis, which facilitates the incorporation of a higher percentage of dopant atoms. The vacuum thermally annealed at 420 °C temperature thin films have been characterized by X-ray diffraction (XRD), optical spectroscopy. Electrical conductivity and the Hall effect are investigated in the temperature interval (77–300) K. X-ray analysis results reveal that all the films are polycrystalline with a hexagonal wurtzite structure with a preferential orientation according to the direction (002) plane. Different characters of the temperature dependence of conductibility are observed in the Al-doped ZnO films vacuum thermally annealed at 420 °C temperature. In all cases, the conductivity, mobility carriers and carriers’ concentration of ZnO thin films obtained under Ar are higher than under O2 atmosphere, unless they are not doped. of your paper no longer than 300 words.Item The influence of semiconductor nanoparticles upon the activity of mesenchymal stem cells [Articol](Springer Nature, 2020) Branişte, Tudor; Raevschi, Simion; Cobzac, Vitalie; Ababii, Polina; Pleșco, Irina; Didencu, Alexandru; Manyuk, Mihail; Nacu, Viorel; Ababii, Ivan; Tiginyanu, IonIn this paper, we report on the viability and proliferation of mesenchymal stem cells after exposure to different types of semiconductor nanoparticles. The nanoparticles used for the tests are based on GaN thin layers grown on commercial ZnO and ZnFe2O4 nanoparticles. Different quantities of nanoparticles incubated with mesenchymal stem cells influence the metabolic activity of cells, which was assessed by the MTT assay. The cytotoxic effect of ZnO nanoparticles on MSC was demonstrated and no harmful effect of the other materials.