ALEXANDRA PALLA-PAPAVLU
@inflpr.ro
Lasers
National Institute for Laser, Plasma and Radiation Physics
Scopus Publications
Scopus Publications
S. I. Voicu, E. Vasile, A. Palla-Papavlu, R. Oprea, M. Ionita, and A. M. Pandele
Royal Society of Chemistry (RSC)
This work presents a new and facile synthesis approach for multiwalled carbon nanotubes (MWCNTs) decorated with ruthenium oxide (RuO2) nanoparticles using a simple and efficient sonochemical method.
Johannes Heitz, Gerda Buchberger, Werner Baumgartner, Marco Meyer, Margret Weissbach, Anna-Christin Joel, Simona Brajnicov, Alexandra Palla-Papavlu, and Maria Dinescu
MDPI AG
We investigated the effect of additional continuous functional coatings, which changed the hydrophilic–hydrophobic properties of the surface without heavily influencing the surface topography at the nanoscale, on the antiadhesive properties of bioinspired laser-induced periodic nanostructures. These nanostructures mimic the antiadhesive structures on the silk-combing area on the legs of cribellate spiders, the calamistrum. The thin films were deposited by matrix-assisted laser deposition and characterized by infrared spectroscopy, X-ray photoelectron spectroscopy, water contact angle measurements, and adhesion tests using capture threads from the cribellate spider webs. In all cases, the nanoripples were preserved and these structured surfaces showed lower adhesion forces compared to flat controls, although not significant. However, this effect was totally overwhelmed by the difference between the adhesion forces on surfaces with different chemical compositions. The largest adhesion forces were observed on hydrophilic surfaces and the lowest ones on hydrophobic surfaces. The fact that the antiadhesion between nanofibers and the nano-structured areas depends strongly on the chemical composition of the surface can be explained by the specific adhesion between individual chemical groups due to frequency dependencies in the theory of van der Waals forces. However, explaining these adhesion properties just by the categories “hydrophilic” or “hydrophobic” is oversimplified.
Mihaela Filipescu, Stefan Dobrescu, Adrian Ionut Bercea, Anca Florina Bonciu, Valentina Marascu, Simona Brajnicov, and Alexandra Palla-Papavlu
MDPI AG
A highly sensitive ammonia-gas sensor based on a tungsten trioxide and polypyrrole (WO3/PPy) nanocomposite synthesized using pulsed-laser deposition (PLD) and matrix-assisted pulsed-laser evaporation (MAPLE) is presented in this study. The WO3/PPy nanocomposite is prepared through a layer-by-layer alternate deposition of the PPy thin layer on the WO3 mesoporous layer. Extensive characterization using X-ray diffraction, FTIR and Raman spectroscopy, scanning electron microscopy, atomic force microscopy, and water contact angle are carried out on the as-prepared layers. The gas-sensing properties of the WO3/PPy nanocomposite layers are systematically investigated upon exposure to ammonia gas. The results demonstrate that the WO3/PPy nanocomposite sensor exhibits a lower detection limit, higher response, faster response/recovery time, and exceptional repeatability compared to the pure PPy and WO3 counterparts. The significant improvement in gas-sensing properties observed in the WO3/PPy nanocomposite layer can be attributed to the distinctive interactions occurring at the p–n heterojunction established between the n-type WO3 and p-type PPy. Additionally, the enhanced surface area of the WO3/PPy nanocomposite, achieved through the PLD and MAPLE synthesis techniques, contributes to its exceptional gas-sensing performance.
A. Bonciu, L. Cremer, A. Calugaru, E. Vlase, C. Coman, Alexandra Palla-Papavlu, Dan Alin Cristian, and F. Grama
Springer Science and Business Media LLC
Anca Florina Bonciu, Florin Andrei, and Alexandra Palla-Papavlu
MDPI AG
Composites based on poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS)—graphene oxide (GO) are increasingly considered for sensing applications. In this work we aim at patterning and prototyping microscale geometries of PEDOT:PSS: GO composites for the modification of commercially available electrochemical sensors. Here, we demonstrate the laser-induced forward transfer of PEDOT:PSS: GO composites, a remarkably simple procedure that allows for the fast and clean transfer of materials with high resolution for a wide range of laser fluences (450–750 mJ/cm2). We show that it is possible to transfer PEDOT:PSS: GO composites at different ratios (i.e., 25:75 %wt and 50:50 %wt) onto flexible screen-printed electrodes. Furthermore, when testing the functionality of the PEDOT:PSS: GO modified electrodes via LIFT, we could see that both the PEDOT:PSS: GO ratio as well as the addition of an intermediate release layer in the LIFT process plays an important role in the electrochemical response. In particular, the ratio of the oxidation peak current to the reduction peak current is almost twice as high for the sensor with a 50:50 %et PEDOT:PSS: GO pixel. This direct transfer methodology provides a path forward for the prototyping and production of polymer: graphene oxide composite based devices.
Alexandra Palla-Papavlu, Sorin Vizireanu, Mihaela Filipescu, and Thomas Lippert
MDPI AG
Ammonia sensors with high sensitivity, reproducible response, and low cost are of paramount importance for medicine, i.e., being a biomarker to diagnose lung and renal conditions, and agriculture, given that fertilizer application and livestock manure account for more than 80% of NH3 emissions. Thus, in this work, we report the fabrication of ultra-sensitive ammonia sensors by a rapid, efficient, and solvent-free laser-based procedure, i.e., laser-induced forward transfer (LIFT). LIFT has been used to transfer carbon nanowalls (CNWs) onto flexible polyimide substrates pre-patterned with metallic electrodes. The feasibility of LIFT is validated by the excellent performance of the laser-printed CNW-based sensors in detecting different concentrations of NH3 in the air, at room temperature. The sensors prepared by LIFT show reversible responses to ammonia when exposed to 20 ppm, whilst at higher NH3 concentrations, the responses are quasi-dosimetric. Furthermore, the laser-printed CNW-based sensors have a detection limit as low as 89 ppb and a response time below 10 min for a 20 ppm exposure. In addition, the laser-printed CNW-based sensors are very robust and can withstand more than 200 bending cycles without loss of performance. This work paves the way for the application and integration of laser-based techniques in device fabrication, overcoming the challenges associated with solvent-assisted chemical functionalization.
Florin Andrei, Iulian Boerasu, Mihaela Filipescu, and Alexandra Palla-Papavlu
MDPI AG
In this work, we report the modification of commercially available electrochemical electrodes with tin oxide (SnO2) and Pd doped SnO2 (Pd-SnO2) via pulsed laser-induced forward transfer (LIFT). The pulsed light irradiation working as in situ pulsed photo-thermal treatment allows for the transfer of SnO2 and Pd-SnO2 from UV absorbing metal complex precursors onto flexible, commercially available screen-printed electrodes. The laser transfer conditions are optimized and the material transferred under different conditions is evaluated morphologically and chemically, and its functionality is tested against the detection of copper ions. For example, by applying laser fluences in the range 100–250 mJ/cm2, the shape and the size of the transferred features ranges from nano-polyhedrons to near corner-grown cubic Pd-SnO2 or near cubic Pd-SnO2. In addition, the EDX analysis is consistent with the XPS findings, i.e., following laser transfer, Pd amounts lower than 0.5% are present in the Pd-SnO2 pixels. First sensing tests were carried out and the transferred Pd-SnO2 proved to enhance the cathodic peak when exposed to Cu(II) ions. This photo-initiated fabrication technology opens a promising way for the low-cost and high-throughput manufacturing of metal oxides as well as for electrodes for heavy metal ion detection.
Cristina Craciun, Florin Andrei, Anca Bonciu, Simona Brajnicov, Tatiana Tozar, Mihaela Filipescu, Alexandra Palla-Papavlu, and Maria Dinescu
MDPI AG
This work is focused on the application of a laser-based technique, i.e., matrix-assisted pulsed laser evaporation (MAPLE) for the development of electrochemical sensors aimed at the detection of nitrites in water. Commercial carbon-based screen-printed electrodes were modified by MAPLE via the application of a newly developed composite coating with different concentrations of carbon nanotubes (CNTs), chitosan, and iron (II) phthalocyanine (C32H16FeN8). The performance of the newly fabricated composite coatings was evaluated both by investigating the morphology and surface chemistry of the coating, and by determining the electro-catalytic oxidation properties of nitrite with bare and modified commercial carbon-based screen-printed electrode. It was found that the combined effect of CNTs with chitosan and C32H16FeN8 significantly improves the electrochemical response towards the oxidation of nitrite. In addition, the MAPLE modified screen-printed electrodes have a limit of detection of 0.12 µM, which make them extremely useful for the detection of nitrite traces.
Anca F. Bonciu, Mihaela Filipescu, Stefan I. Voicu, Thomas Lippert, and Alexandra Palla-Papavlu
MDPI AG
Ammonia is one of the most frequently produced chemicals in the world, and thus, reliable measurements of different NH3 concentrations are critical for a variety of industries, among which are the agricultural and healthcare sectors. The currently available technologies for the detection of NH3 provide accurate identification; however, they are limited by size, portability, and fabrication cost. Therefore, in this work, we report the laser-induced forward transfer (LIFT) of single-walled carbon nanotubes (SWCNTs) decorated with tin oxide nanoparticles (SnO2 NPs), which act as sensitive materials in chemiresistive NH3 sensors. We demonstrate that the LIFT-fabricated sensors can detect NH3 at room temperature and have a response time of 13 s (for 25 ppm NH3). In addition, the laser-fabricated sensors are fully reversible when exposed to multiple cycles of NH3 and have an excellent theoretical limit of detection of 24 ppt.
Alexandra Palla-Papavlu, Stefan Ioan Voicu, and Maria Dinescu
MDPI AG
Since their development, surface acoustic wave (SAW) devices have attracted much research attention due to their unique functional characteristics, which make them appropriate for the detection of chemical species. The scientific community has directed its efforts toward the development and integration of new materials as sensing elements in SAW sensor technology with a large area of applications, such as for example the detection of volatile organic compounds, warfare chemicals, or food spoilage, just to name a few. Thin films play an important role and are essential as recognition elements in sensor structures due to their wide range of capabilities. In addition, other requisites are the development and application of new thin film deposition techniques as well as the possibility to tune the size and properties of the materials. This review article surveys the latest progress in engineered complex materials, i.e., polymers or functionalized carbonaceous materials, for applications as recognizing elements in miniaturized SAW sensors. It starts with an overview of chemoselective polymers and the synthesis of functionalized carbon nanotubes and graphene, which is followed by surveys of various coating technologies and routes for SAW sensors. Different coating techniques for SAW sensors are highlighted, which provides new approaches and perspective to meet the challenges of sensitive and selective gas sensing.
F. Stokker-Cheregi, A.I. Bercea, A. Ojeda-Gonzalez-Posada, A. Palla-Papavlu, T. Acsente, C. Grisolia, P. Delaporte, G. Dinescu, T. Lippert, and M. Dinescu
Elsevier BV
Cristina Craciun, Mihaela Filipescu, Alexandra Palla-Papavlu, Simona Brajnicov, Tatiana Tozar, Fanel Scheaua, Anca Bonciu, Florin Nedelcut, and Maria Dinescu
IEEE
Hereby we report on design of an aerial monitoring platform equipped with sensors for detection of specific contaminants, named AWISEM (Air-Water Innovative System for Environmental Monitoring). The AWISEM system is aimed to be a mobile aerial and aquatic vehicle which should contain: A) an aerial and aquatic mobile monitoring platform, with an innovative sustentation system, having the capability to fly and also to float in an aquatic environment; B) two distinct sets of sensors, based on CNT composites with high sensitivity for the monitoring of either aerial or aquatic contaminants. An important part of this work consists in producing and characterizing sensing membranes (thin layers) for two types of sensors able to detect contaminants such as ammonia - in air and nitrites - in water. These membranes are produced by matrix-assisted pulsed laser evaporation technique. The morphological investigations showed specific structures (“worm”-like, rods, grains) while EDX investigations revealed that all constitutive elements (C, O, Fe, W) of used compounds (CNT, C32H16FeN8, WO3) are present in the corresponding nanostructured layers.
A. Muhulet, C. Tuncel, F. Miculescu, A. M. Pandele, C. Bobirica, C. Orbeci, L. Bobirica, A. Palla-Papavlu, and S. I. Voicu
Springer Science and Business Media LLC
M. Filipescu, A. Palla-Papavlu, A. Bercea, L. Rusen, M. O. Cernaianu, V. Ion, A. Calugar, L. C. Nistor, and M. Dinescu
Springer Science and Business Media LLC
Cristian Daniel Alin, Florin Grama, Raluca Papagheorghe, Simona Brajnicov, Valentin Ion, Sorin Vizireanu, Alexandra Palla-Papavlu, and Maria Dinescu
Springer Science and Business Media LLC
Mihaela Filipescu, Alexandra Palla-Papavlu, Paolo M. Ossi, and Maria Dinescu
Elsevier
Massimiliano Benetti, Domenico Cannatà, Enrico Verona, Alexandra Palla Papavlu, Valentina Carmen Dinca, Thomas Lippert, Maria Dinescu, and Fabio Di Pietrantonio
Elsevier BV
Flavian Stokker-Cheregi, Alexandra Palla-Papavlu, Irina Alexandra Paun, Thomas Lippert, and Maria Dinescu
Springer International Publishing
Anna Paola Caricato, Cristian Focsa, Jörg Krüger, and Alexandra Palla Papavlu
Elsevier BV
B Mitu, A Matei, M Filipescu, A Palla Papavlu, A Bercea, T Lippert, and M Dinescu
IOP Publishing
The aim of this work is to demonstrate the potential of laser-induced forward transfer (LIFT) as a printing technology, alternative to standard microfabrication techniques, in the area of flexible micro-electrode fabrication. First, ferrocene thin films are deposited onto fused silica and fused silica substrates previously coated with a photodegradable polymer film (triazene polymer) by matrix assisted pulsed laser evaporation (MAPLE). The morphology and chemical structure of the ferrocene thin films deposited by MAPLE has been investigated by atomic force microscopy and Fourier transformed infrared spectroscopy, and no structural damage occurs as a result of the laser deposition. Second, LIFT is applied to print for the first time ferrocene pixels and lines onto flexible polydimethylsiloxane (PDMS) substrates. The ferrocene pixels and lines are flawlessly transferred onto the PDMS substrates in air at room temperature, without the need of additional conventional photolithography processes. We believe that these results are very promising for a variety of applications ranging from flexible electronics to lab-on-a-chip devices, MEMS, and medical implants.
A. Palla-Papavlu, M. Filipescu, S. Vizireanu, L. Vogt, S. Antohe, M. Dinescu, A. Wokaun, and T. Lippert
Elsevier BV
Alexandra Palla Papavlu, Lukas Urech, Thomas Lippert, Claude Phipps, Jörg Hermann, and Alexander Wokaun
Wiley
The micro-laser plasma thruster (μ-LPT) is a device aimed at orienting and repositioning small satellites above the atmosphere. These devices are based on IR diode lasers utilized for the ablation of polymers and production of thrust for the control of the satellite motion. In this work, different polymer systems, i.e., poly(vinyl chloride) (PVC), glycidyl azide polymer (GAP), and poly(vinyl nitrate) (PVN) with two absorbers, i.e., carbon nanoparticles (C) and an IR-dye (IR), have been investigated for an application in μ-LPT. The properties of a plasma produced by the irradiation of GAP + C, GAP + IR, PVC + C, and PVN + C with 100 fs laser pulses has been investigated by time-resolved plasma imaging and time and space resolved plasma emission spectroscopy.
Alexandra Palla Papavlu, Thomas Mattle, Sandra Temmel, Ulrike Lehmann, Andreas Hintennach, Alain Grisel, Alexander Wokaun, and Thomas Lippert
Springer Science and Business Media LLC
Alexandra Palla-Papavlu, Mihaela Filipescu, Christof W Schneider, Stefan Antohe, Paolo M Ossi, György Radnóczi, Maria Dinescu, Alexander Wokaun, and Thomas Lippert
IOP Publishing
Nanostructured tungsten trioxide (WO3) thin films are deposited by pulsed laser deposition (PLD) and radio-frequency (RF) assisted PLD onto interdigitated sensor structures. Structural characterization by x-ray diffraction and Raman spectroscopy shows the WO3 films are polycrystalline, with a pure monoclinic phase for the PLD grown films. The as-fabricated WO3 sensors are tested for ammonia (NH3) detection, by measuring the electrical response to NH3 at different temperatures. Sensors based on WO3 deposited by RF-PLD do not show any response to NH3. In contrast, sensors fabricated by PLD operating at 100 °C and 200 °C show a slow recovery time whilst at 300 °C, these sensors are highly sensitive in the low ppm range with a recovery time in the range of a few seconds. The microstructure of the films is suggested to explain their excellent electrical response. Columnar WO3 thin films are obtained by both deposition methods. However, the WO3 films grown by PLD are porous, (which may allow NH3 molecules to diffuse through the film) whereas RF-PLD films are dense. Our results highlight that WO3 thin films deposited by PLD can be applied for the fabrication of gas sensors with a performance level required for industrial applications.