Stage 2 - P3
Phase no. 6
Responsible: Dr. Lucian GHEORGHE
Title: "Nonlinear optical crystals with controllable properties for laser emission generation at new wavelengths in the visible range"
Abstract: The optical birefringence of La(Ca1-xSrx)4O(BO3)3 nonlinear optical (NLO) crystals can be controlled by changing the compositional parameter x. Therefore, it is possible to achieve non-critical phase matching (NCPM) for type-I second-harmonic generation (SHG) of specific wavelengths in the range of 990 to at least 946 nm. La(Ca1-xSrx)4O(BO3)3 single crystals (with x = 0.0, 0.1, 0.3 and 0.4 starting compositions) of large size and good optical quality were grown by the Czochralski method. X-ray diffraction measurements have been carried out to characterize the structural changes with compositional parameters x. The NCPM wavelengths along the Z-axis were experimentally determined for each grown crystal. According to our assumptions, the obtained results demonstrate that by a proper choice of the compositional parameter x in La(Ca1-xSrx)4O(BO3)3 crystals, we can obtain blue light in the range of 495-473 nm through type-I NCPM SHG of the corresponding fundamental wavelengths, which are very attractive for practical applications.
Phase no. 7
Responsible: Dr. Catalin LUCULESCU
Title: "Preparation and characterization of Surface-Enhanced Raman Scattering (SERS) substrates"
Abstract: Raman spectroscopy is a valuable analytical tool for the identification of molecules and to monitor the changes that occur in the structure of the molecular bonds. Surface-enhanced Raman scattering (SERS) can increase Raman signal intensity up to 1010 based on plasmonic effects. Such growth can improve considerably the scope of Raman spectroscopy. Thus, it was recently reported the detection of a single molecule. Among SERS applications include detection of cancer cells, determining impurities with ppb precision. Until now, commercial SERS substrates are relatively expensive and one use only. In this project we aim to realize such substrates by laser techniques and plasma deposition techniques at competitive costs. We managed to obtain two new types of active SERS substrates, the first based on carbon nanowalls covered with Au, and the second based on a Nb aloy ablated with pulsed laser radiation. Both substrates were characterized morphologicaly and by Raman enhancing factor. We obtained an enhancing factor of over 103, which qualify analyzed substrates for subsequent applications.
Phase no. 8
Responsible: Dr. Ruxandra BIRJEGA
Title: "Layered double hydroxides (Ni,Al-LDHs) deposition via laser techniques. Characterization"
Abstract: The functionality and hence, prospective applicability of layered double hydroxides (LDHs) is huge due to their flexible composition, „ guest” lamellar structure, high anionic exchange capacity, and high specific areas. Their chemical composition is [Ma(II)1-xMb(III)x(OH-)2]x+(Ax/n)n-.mH2O where Ma(II) is a bivalent metal, Mb¬(III) is a trivalent metal, A is the interlayer anion, inorganic or organic. If a transitional metal is used the LDHs become redox active and have prospects for senzoristics developments. The deposition Ni,Al based layered double hydroxide ( Ni,Al-LDH) via pulsed laser deposition (PLD) and matrix assisted pulsed laser evaporation (MAPLE) on conductive substrates as indium tin oxides (ITO) in comparison with Si(001) substrates were studied. The conclusive results were:
- The films display a lamellar structure, preferred orientation growth and good adherence
- The basal lattice parameter is closer to the target basal parameter
- Deposition at 532 nm is effective due to a high absorbance near the surface plasmonic resonance band observed at 610 nm in the optical absorption spectrum of the Ni,Al-LDH target
- Oxidic phased NiO or/and Ni(Al)O are observed in the film deposited by PLD
- The oxidic phases vanish upon immersion in water
- The thin film deposited by MAPLE has no oxidic phase
Phase no. 9
Responsible: Dr. Gabriel SOCOL
Title: "Synthesis of coatings with photocatalytic activity"
Abstract: A main objective of this phase was to build an experimental setup for testing photocatalytic activity of materials in form of thin films, powders or other structures such as surface immobilized nanowires or membranes. The experimental setup allows using different type of UV emitting lamps (low pressure mercury lamp with or without filters which emits at 185 and / or 254, 312 or 366 nm) and a solar simulator. In order to emphasize photocatalytic effects of tested materials, AZO dyes from the same class of organic pollutants, such as methylene blue, methyl orange and rhodamine B were used. The degradation dynamics of organic dyes was observed by measuring their typical absorption bands, at different time intervals, using a UV-VIS spectrophotometer. Our tests were performed at different pH values: acidic (pH = 2), neutral (pH = 7) and basic (pH = 12). TiO2, CdS, copper oxide, iron oxide and ZnO were used as test materials. Thin films, powders and doped nanowires, mixed or covered were synthesized and examined in order to demonstrate the versatility of photocatalysis experimental setup. Thus, it was shown which composition and structure presented the best photocatalytic performance with respect to photodegradation properities.
Phase no. 10
Responsible: Dr. Monica SCARISOREANU
Title: "Photocatalysts obtained by TiO2 and SnO2 coupling through laser pyrolysis method"
Abstract: In this phase, we report the TiO2/SnO2 nanocomposites obtained by laser pyrolysis of volatile TiCl4 and SnCl4 precursors, introduced together or separately in the reaction zone, in the presence of air as oxidant and ethylene as sensitizer. Prior to the synthesis of TiO2/SnO2 nanocomposites with the different Sn concentrations (1.1-4.8 at %), the optimal experimental conditions were identified for preparing pure anatase phase TiO2 samples, considered as photoactive reference sample. All the samples were characterized using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), RAMAN spectroscopy and UV–vis diffuse reflectance spectroscopy (DRS) techniques. The structural analysis results of the new nanocomposites show the presence of anatase phase majority (65-82%) and mean crystallite dimensions in the 8-22 nm range. Laser synthesized TiO2/SnO2 samples have a lower band gap energy and higher photoactivity in the process of Methyl Orange degradation in aqueous suspensions, when compared with the P25 Degussa commercial sample.
Phase no. 11
Responsible: Dr. Daniel IGHIGEANU
Title: "Linear or crosslinked polymeric materials based on natural and synthetic polymers obtained by electron beam irradiation with energy of 6 MeV"
Abstract: Hydrogels based on acrylamide (AMD), acrylic acid (AA), potassium persulfate (PP) and trimethylolpropane trimethacrylate (TMPT) obtained by electron beam irradiation in the dose range of 2 - 4.5 kGy, may be an option of "soil conditioner" for holders of agricultural crops or greenhouses in geographical areas that are experiencing water deficiency or lack of irrigation, or operate in areas where the water supply for irrigation is poor. Also, the properties of these types of polymeric materials to hold fast and gradually release essential salts for plant development, may represent an option for farmers that experiencing problems connected with the imposibility of crop rotation on some farmland. Through their use can therefore be simultaneously solved the problem of fluid and nutrients contribution on lands depleted of nutrients by the disposition during one or more consecutive seasons of the same crops.The "soil conditioner" properties of hydrogels obtained in the project were highlighted by specific analysis for determining the soluble fraction, gel fraction, degree of crosslinking, porosity and pore size of polymer networks, their morphology and structure. It was also studied the affinity of such polymers for water and aqueous solutions containing salts essential for the growth of plants (sodium, potassium, chloride, calcium, magnesium).
Phase no. 12
Responsible: Dr. Emanuel AXENTE
Title: "Synthesis of doped calcium phosphates compositional libraries by combinatorial laser approaches for bone implants coatings"
Abstract: This project is devoted to the synthesis and characterization of doped calcium phosphates (CaPs) compositional libraries for biomedical applications. If Hydroxyapatite [Ca10(PO4)6(OH)2 – HA] is already a natural choice for metalic implants coatings, its further functionalization with bioactive compounds could significantly improve the performances of the implants. The main challenge in the fabrication of such intelligent biointerface is the optimum choice of the dopant and the identification of its optimum concentration. Moreover, if HA thin films co-doping with two different substances is considered in view of obtaining a synergistic effect of the dopants, the problem became complex, and advanced multi-disciplinary competences and technologies are mandatory. Thus, we performed Strontium and Zoledronate doped HA compositional libraries thin films by Combinatorial Matrix-Assisted Pulsed Laser Evaporation (C-MAPLE), followed by their physical-chemical and biological characterizations.
Phase no. 13
Responsible: Dr. Cristina GHEORGHE
Title: "Advanced photonic materials with laser emission at new wavelengths in visible with applications for medicine and biology"
Abstract: Sm3+ doped partially disordered calcium-niobium-gallium-garnet (CNGG) and calcium-lithium-niobium-gallium-garnet (CLNGG) as single crystals and ceramics were investigated. Single cristals were grown by the Czochralski method and translucid ceramic samples were obtained by solid state reaction. Spectroscopic characteristics of Sm:CNGG and Sm:CLNGG single crystals and ceramics were obtained by high-resolution absorption and emission spectra and emission dynamics measurements. Partial energy levels of Sm3+ doped CNGG and CLNGG were extracted from the measured spectra. The values for the absorption cross section at ~ 405.5 nm are 2.2×10-20 cm2 and 2.8×10-20 cm2 for CNGG and CLNGG which is suitable for an efficient optical pumping with InGaN/GaN laser diodes. The Judd-Ofelt theory has been applied to evaluate the Ωt (t = 2, 4, 6) intensity parameters Ω2 = 3.06 × 10-20 cm2, Ω4 = 3.89 × 10-20 cm2, Ω6 = 2.6 × 10-20 cm2 for Sm:CNGG and Ω2 = 4.19 × 10-20 cm2, Ω4 = 4.4 × 10-20 cm2, Ω6 = 2.49 × 10-20 cm2 in the case of Sm:CLNGG. The J-O parameteres were use to obtain radiative transition rates Ar, branching ratios β, and radiative lifetime τr of the fluorescent Sm3+ 4G5/2 level. The emission cross-sections for the 4G5/2→6HJ (J=5/2, 7/2, 9/2) transitions of special interest for visible laser application were obtained by the Fuchtbauer–Ladenburg equation. The larger values of emission cross-sections were obtained for 4G5/2→6H7/2 transition at 615 nm as 0.87×10−21 cm2 for CNGG and 1×10−21 cm2 in the case of CLNGG. The interaction between Sm3+ ions is dipole–dipole type and the CDA microparameter for both crystals was calculated based on Inokuty-Hirayama model.
Phase no. 14
Responsible: Dr. Carmen TISEANU
Title: "Lanthanide doped nanosystems for optical imaging applications"
Abstract: We investigate the effects of heterovalent co – dopants on the structural and emission properties of 1% Er - CeO2 nanoparticles. The CeO2 oxide host was selected on the basis of its fairly well understood defect chemistry in either pure or doped state. As a luminescent activator, Er is acknowledged as an interesting one due to its rich luminescence and excitation properties spanning visible to near- infrared range. The optically inactive trivalent La and monovalent Li metal ions with concentration of up to 20 % were chosen to presumably generate a variable amount of defects into the Er - CeO2 lattice. It was found that La and Li co – dopants induced distinct changes related to size, lattice constant, bandgap energy, lattice and surface defects of Er - CeO2. As a result of these changes, a strong modulation of the luminescence intensity and shape was measured using a suite of excitation conditions (charge - transfer absorption band of CeO2, direct/up-conversion into Er absorptions and X-ray excitation modes). The use of Eu as a luminescent probe offered additional information concerning the effects of La/Li co – doping on the local structure surrounding the luminescent activator. A remarkably high percentages of 90 and 98% of the total emission of Er measured between 500 and 1000 nm is measured in the near – infrared at 980 nm under X - ray and up – conversion excitation at ~ 1500 nm, respectively. The optical properties suggest that Li, Er co - doped CeO2 has a good potential for therapy and biological imaging.
Phase no. 15
Responsible: Dr. Cristina SURDU-BOB
Title: "Obtaining thin DLC films on suture-type polymers using the Thermoionic Vacuum Arc plasma (TVA). Chemical and physical characterization of the films."
Abstract: The present project is based on the results of some preliminary in vitro research experiments which demonstrated that TVA obtained DLC thin films are biocompatible. This result conducted to the elaboration of the present project having as main objective the investigation of the possibility of using DLC films prepared by TVA plasma in medicine. In this first phase of the project samples of different comercialy available suture wires made of polymers and polymer coated silk were coated with thin DLC films using TVA method. First of all, sets of coating runs were performed in different conditions in order to find the proper deposition parameters for which the suture wires used as substres will not be deteriorated from plasma radiation. After finding the proper deposition parameters, sets of DLC coatings of different thicknesses were performed using two different plasma powers and the physical and chemical properties of the films obtained were analyzed. The chemical composition of the DLC films was assessed by XPS. Also, the films adherence to the different suture wires used as substrates was investigated. As a result, the proper plasma parameters for which the DLC films withstand bending and/or corrosion without cracking or delaminating by ultrasonic bath in corrosive liquids were determined. Conclusions on the importance of sp3/sp2 relative bonding ratio as well as DLC films thickness on their flexibility were drawn.
Phase no. 16
Responsible: Dr. Andreea MATEI
Title: "Two Photon Polymerization for biomedical applications: Materials/ process parameters tests"
Abstract: The project aims to create a guiding microfluidic system that can be used to build a biosensor. The proposed microfluidic system is in good agreement with the current trend of miniaturization and is based on laser methods for designing channels for a liquid to be guided to the detection electrode where it will be analyzed. Polymeric structures with controlled geometry were produced by laser direct writing using fs and ps lasers, and the optimal processing parameters have been identified. Using laser direct writing with fs pulses (λ = 780 nm) via two photon polymerization, we obtained three-dimensional polymeric structures, whereas after irradiation with a ps laser (λ = 355 nm) we produced two-dimensional structures consisting of a reservoir and a channel with different dimensions. The structures were characterized and preliminary studies on liquid flow through inscribed channels were made.