Composition and Surface Optical Properties of GaSe:Eu Crystals before and after Heat Treatment.

This work studies the technological preparation conditions, morphology, structural characteristics and elemental composition, and optical and photoluminescent properties of GaSe single crystals and Eu-doped ß-Ga2O3 nanoformations on ε-GaSe:Eu single crystal substrate, obtained by heat treatment at 750-900 °C, with a duration from 30 min to 12 h, in water vapor-enriched atmosphere, of GaSe plates doped with 0.02-3.00 at. % Eu. The defects on the (0001) surface of GaSe:Eu plates serve as nucleation centers of ß-Ga2O3:Eu crystallites. For 0.02 at. % Eu doping, the fundamental absorption edge of GaSe:Eu crystals at room temperature is formed by n = 1 direct excitons, while at 3.00 at. % doping, Eu completely shields the electron-hole bonds. The band gap of nanostructured ß-Ga2O3:Eu layer, determined from diffuse reflectance spectra, depends on the dopant concentration and ranges from 4.64 eV to 4.87 eV, for 3.00 and 0.05 at. % doping, respectively. At 0.02 at. % doping level, the PL spectrum of ε-GaSe:Eu single crystals consists of the n = 1 exciton band, together with the impurity band with a maximum intensity at 800 nm. Fabry-Perrot cavities with a width of 9.3 µm are formed in these single crystals, which determine the interference structure of the impurity PL band. At 1.00-3.00 at. % Eu concentrations, the PL spectra of GaSe:Eu single crystals and ß-Ga2O3:Eu nanowire/nanolamellae layers are determined by electronic transitions of Eu2+ and Eu3+ ions.

Dual-Pulsed Laser Ablation of Oyster Shell Producing Novel Thin Layers Deposed to Saccharomyces cerevisiae.

Dual-pulsed (DPL) laser deposition using oyster shells as targets was studied in order to find out if this method can replace the use of high-power pulsed lasers. Aspects related to changes in the morphological structure of the thin layer but also to the chemical composition of the obtained thin layer were analyzed and compared with the target as well as with the thin layers obtained with a higher power pulsed laser in a single-pulsed (SPL) regime. Orthorhombic structures were noticed with Scanning Electron Microscopy for the thin film obtained in DPL mode compared to the irregular particles obtained in SPL mode. The deacetylation process during ablation was evidenced by Fourier Transform Infrared spectroscopy, resulting in chitosan-based thin films. The effect of the obtained thin films of chitosan on the cells of baker's yeast (Saccharomyces cerevisiae) was studied. Restoration of the yeast paste into initial yeast was noticed mainly when the hemp fabric was used as support for the coating with yeas which was after that coated with chitosan thin film produced by DPL method.

Septicemic Outbreak in A Rainbow Trout Intensive Aquaculture System: Clinical Finds, Etiological Agents, and Predisposing Factors.

On the 23rd of September 2022, a small intensive aquaculture unit populated with rainbow trout (Oncorhynchus mykiss) reported increased mortality in adults and juvenile fish. The unit comprised 12 enclosed concrete basins with a capacity of ten cubic meters of water, populated with 150 kg of fish each. Fish were subjected to a clinical examination on the site, after which whole fish were harvested for a bacteriological and histopathological examination. Water quality parameters were examined using classic biochemical methods and Fourier Transform Infrared Spectroscopy in order to find out whether the environment in which the fish live is also a predisposing factor that could facilitate different pathogens and induce a state of disease in the fish. Real-time PCR was performed on strains of Aeromonas spp. sampled from the fish to accurately identify the pathogen species. The goal was to accurately identify the problems and predisposing factors that lead to disease outbreaks.

Preparation, Chemical Composition, and Optical Properties of (ß-Ga2O3 Composite Thin Films)/(GaSxSe1-x Lamellar Solid Solutions) Nanostructures.

GaSxSe1-x solid solutions are layered semiconductors with a band gap between 2.0 and 2.6 eV. Their single crystals are formed by planar packings of S/Se-Ga-Ga-S/Se type, with weak polarization bonds between them, which allows obtaining, by splitting, plan-parallel lamellae with atomically smooth surfaces. By heat treatment in a normal or water vapor-enriched atmosphere, their plates are covered with a layer consisting of ß-Ga2O3 nanowires/nanoribbons. In this work, the elemental and chemical composition, surface morphology, as well as optical, photoluminescent, and photoelectric properties of ß-Ga2O3 layer formed on GaSxSe1-x (0 ≤ x ≤ 1) solid solutions (as substrate) are studied. The correlation is made between the composition (x) of the primary material, technological preparation conditions of the oxide-semiconducting layer, and the optical, photoelectric, and photoluminescent properties of ß-Ga2O3 (nanosized layers)/GaSxSe1-x structures. From the analysis of the fundamental absorption edge, photoluminescence, and photoconductivity, the character of the optical transitions and the optical band gap in the range of 4.5-4.8 eV were determined, as well as the mechanisms behind blue-green photoluminescence and photoconductivity in the fundamental absorption band region. The photoluminescence bands in the blue-green region are characteristic of ß-Ga2O3 nanowires/nanolamellae structures. The photoconductivity of ß-Ga2O3 structures on GaSxSe1-x solid solution substrate is determined by their strong fundamental absorption. As synthesized structures hold promise for potential applications in UV receivers, UV-C sources, gas sensors, as well as photocatalytic decomposition of water and organic pollutants.

Optical and Structural Analysis of TiO2-SiO2 Nanocomposite Thin Films Fabricated via Pulsed Laser Deposition Technique.

TiO2-SiO2 nanocomposite thin films have gained the attention of the scientific community due to their unique physical and chemical properties. In this paper, we report on the fabrication and characterization of a TiO2-SiO2 nanocomposite disk-shaped target. The target was used for the deposition of TiO2-SiO2 nanocomposite thin films on fluorine-doped tin oxide/glass substrates using the pulsed laser deposition (PLD) technique. The thicknesses of the thin films were fixed to 100 nm, and the deposition temperature ranged from room temperature to 300 °C. As revealed by the microstructural and morphological characterizations revealed, the TiO2-SiO2 nanocomposite thin films are amorphous and display homogeneous distribution. The determined values of the indirect optical band gap range from 2.92 to 3.07 eV, while those of the direct optical band gap lie between 3.50 and 3.55 eV. Additionally, as the deposition temperature decreases, the light transmission increases in the visible and in the ultraviolet ranges, which is suitable for flexible perovskite solar cells. This research can uncover new insights into the fabrication of amorphous TiO2-SiO2-based nanostructured thin films using the PLD technique for perovskite solar cell technology.

Urban Exotic Pollution: The Harmful Environmental Footprint for Health and Historical Architecture.

The study in this paper was carried out as a result of the observation of pollution phenomena and foaming effects associated with anthropogenic activities, including street cleaning activity. The processes of dust binding used in order to reduce PM10 and PM 2.5 pollution has been proven to be inefficient, and even contributing to pollution with particulate matter. Our results suggest that the use of dust binders must be integrated in a technique that includes methods of removing agglomerated particle structures resulting from the process of coagulation or flocculation. These are the conclusions of the investigations carried out by spectroscopic methods (FTIR, SEM-EDX) on samples collected from the streets of Iasi on 10 March 2021, and on samples collected from the surface of the Precinct Wall of the historical monument Golia-Iasi Monastery Ensemble (Romania). On the later samples, coloristic analysis was also performed. The alert for investigation was given by the foaming waters that were leaking on the streets. The phenomenon was observed after the streets had been washed by specialized vehicles. Analyses revealed compounds used as dust binders and coagulant type (aluminum sulfate, sodium aluminate and their derivatives, plus anti-skid chemicals such as calcium chlorine and magnesium chlorine), as well as organic compounds included in aggregate type structures, and they showed contamination of the Golia Precinct Wall. The results show that the dust binders or coagulants used as such, or embedded in various products intended for the cleaning process of streets or other outdoor public places, must be subject to regulation. Otherwise, there is a risk of adding more pollutants during an operation with the opposite purpose. The migration of these pollutants on the studied building offers an image on how both our health and all constructions and equipment exposed in the open air are affected.

Nano-Biocomposite Materials Obtained from Laser Ablation of Hemp Stalks for Medical Applications and Potential Component in New Solar Cells.

The study in this paper presents a new material that was produced as a thin film by the Pulsed Laser Deposition technique (PLD) using a 532 nm wavelength and 150 mJ/pulse laser beam on the hemp stalk as target. The analyses performed by spectroscopic techniques (Fourier Transform Infrared Spectroscopy-FTIR, Laser-Induced Fluorescence Spectroscopy-LIF, Scanning Electron Microscopy coupled with Energy Dispersive X-ray-SEM-EDX, Atomic Force Microscopy-AFM and optical microscope) evidenced that a biocomposite consisting of lignin, cellulose, hemicellulose, waxes, sugars and phenolyc acids p-coumaric and ferulic, similar to the hemp stalk target was obtained. Nanostructures and aggregated nanostructures of 100 nm to 1.5 µm size were evidenced. Good mechanical strength and its adherence to the substrate were also noticed. It was noticed that the content in calcium and magnesium increased compared to that of the target from 1.5% to 2.2% and from 0.2% to 1.2%, respectively. The COMSOL numerical simulation provided information on the thermal conditions that explain phenomena and processes during laser ablation such as C-C pyrolisis and enhanced deposition of calcium in the lignin polymer matrix. The good gas and water sorption properties due to the free OH groups and to the microporous structure of the new biocomposite components recommends it for studies for functional applications in medicine for drug delivery devices, filters in dialysis and for gas and liquid sensors. Functional applications in solar cells windows are also possible due to the conjugated structures of the contained polymers.

On the Deposition Process of Ceramic Layer Thin Films for Low-Carbon Steel Pipe Protection.

Ceramic thin films with variable thicknesses have been used in many applications. In order to protect the petroleum transportation pipes against the harmful H2S action, two ceramic materials as thin layers are proposed. In this article, pulsed laser deposition (PLD) of ceramic layers by in situ time-resolved optical techniques is investigated. Two ceramic materials were used as targets and real-time monitoring of the PLD process was realized via ICCD fast camera imaging and optical emission spectroscopy. The space-time displacement of the ceramic emissions was analyzed in order to determine the plasma structure and respective kinetic energies. Spectral-resolved investigation allowed the determination of plasma species individual velocities (in the first case: 43 km/s for C ionic species, 11 km/s for Si, from 25 to 5 km/s for atomic species; in the second case: 32 km/s for C ionic species, 11 km/s for W species, and 15 and 53 km/s for neutral species). SEM and AFM techniques were implemented to analyze the resulting ceramic layers showing homogeneous surfaces with characteristic material droplets. The ablation crater also reveals selective ablation during the deposition process. EDX results show that Al/Si is retained in the thin films similar to the target composition.

Optical and Photosensitive Properties of Flexible n (p)-InSe/In2O3 Heterojunctions.

In this work, optical, including photoluminescence and photosensitivity, characteristics of micrometer-sized flexible n (p)-InSe/In2O3 heterojunctions, obtained by heat treatment of single-crystalline InSe plates doped with (0.5 at.%) Cd (Sn), in a water-vapor- and oxygen-enriched atmosphere, are investigated. The Raman spectrum of In2O3 layers on an InSe:Sn substrate, in the wavelength range of 105-700 cm-1, contains the vibration band characteristic of the cubic (bcc-In2O3) phase. As revealed by EDX spectra, the In2O3 layer, ~2 µm thick, formed on InSe:Cd contains an ~18% excess of atomic oxygen. The absorption edge of InSe:Sn (Cd)/In2O3 structures was studied by ultraviolet reflectance spectroscopy and found to be 3.57 eV and ~3.67 eV for InSe:Cd and InSe:Sn substrates, respectively. By photoluminescence analysis, the influence of doping impurities on the emission bands of In2O3:Sn (Cd) was revealed and the energies of dopant-induced and oxygen-induced levels created by diffusion into the InSe layer from the InSe/In2O3 interface were determined. The n (p)-InSe/In2O3 structures display a significantly wide spectral range of photosensitivity (1.2-4.0 eV), from ultraviolet to near infrared. The influence of Cd and Sn concentrations on the photosensitivity and recombination of nonequilibrium charge carriers in n (p)-InSe layers from the heterojunction interface was also studied. The as-obtained nanosized InSe/In2O3 structures are suitable for optoelectronic applications.

Implications and Consequences of SL(2R) as Invariance Group in the Description of Complex Systems Dynamics from a Multifractal Perspective of Motion.

Possible implications and consequences of using SL(2R) as invariance groups in the description at any scale resolution of the dynamics of any complex system are analyzed. From this perspective and based on Jaynes' remark (any circumstance left unspecified in the description of any complex system dynamics has the concrete expression in the existence of an invariance group), in the present paper one specifies such unspecified circumstances that result directly from the consideration of the canonical formalism induced by the SL(2R) as invariance group. It follows that both the Hamiltonian function and the Guassian distribution acquire the status of invariant group functions, the parameters that define the Hamiltonian acquire statistical significances based on a principle of maximizing informational energy, the class of statistical hypotheses specific to Gaussians of the same average acts as transitivity manifolds of the group (transitivity manifolds which can be correlated with the multifractal-non-multifractal scale transitions), joint invariant functions induced through SL(2R) groups isomorphism (the SL(2R) variables group, and the SL(2R) parameters group, etc.). For an ensemble of oscillators of the same frequency, the unspecified circumstances return to the ignorance of the amplitude and phase of each of the oscillators, which forces the recourse to a statistical ensemble traversed by the transformations of the Barbilian-type group. Finally, the model is validated based on numerical simulations and experimental results that refer to transient phenomena in ablation plasmas. The novelty of our model resides in the fact that fractalization through stochasticization is imposed through group invariance, situation in which the group's transitivity manifolds can be correlated with the scale resolution.

High-Power Laser Deposition of Chitosan Polymers: Medical and Environmental Applications.

High-power laser irradiation interaction with natural polymers in biocomposites and Laser-Induced Chitin Deacetylation (LICD) was studied in this work, in order to produce thin films consisting of chitosan composite. The new method can lead to a cutting-edge technology, as a response to the concern regarding the accumulation of "natural biological waste" and its use. The process consists of high-power laser irradiation applied on oyster shells as the target and deposition of the ablated material on different substrates. The obtained thin films we analyzed by FTIR, UV-VIS and LIF spectroscopy, as well as SEM-EDS and AFM. All the results indicated that chitin was extracted from the shell composite material and converted to chitosan by deacetylation. It was, thus, evidenced that chemical transformation in the chitin polymer side-chain occurs during laser irradiation of the oyster shell and in the resulted plasma plume of ablation. The numerical simulation in COMSOL performed for this study anticipates and confirms the experimental results of chitin deacetylation, also providing information about the conditions required for the physico-chemical processes involved. The high sorption properties of the thin films obtained by a LICD procedure is evidenced in the study. This quality suggests that they should be used in transdermal patch construction due to the known hemostatic and antibacterial effects of chitosan. The resulting composite materials, consisting of the chitosan thin films deposited on hemp fabric, are also suitable for micro-filters in water decontamination or in other filtering processes.

The Influence of Abrasive and Acidic Aggressions on the Surface Condition of Flowable Composite Resin.

The aim of this in vitro study was to evaluate the effect of hydrochloric acid associated with the abrasive effect of toothbrushing on the surface condition of three flowable composite resins used for direct restoration. Seventy samples of each composite resin: Grandio Flow (VOCO, Germany)-group A, Filtek Ultimate Flow (3M-ESPE, MN, USA)-group B, G-aenial Flo X (GC Europe)-group C were prepared, submersed in hydrochloric acid 30% for 60 min and then submitted to simulated toothbrushing procedure using 5000 cycles with toothbrushes with medium and hard bristles, immediately after the chemical attack, after 30 min or without any chemical attack. The sample's surface roughness was analyzed using a noncontact profilometer (Dektak XT, Bruker, USA). ANOVA and post hoc Bonferroni tests, with a p < 0.05, were used to analyze the values. Hydrochloric acid action for 60 min and six months of toothbrushing using toothbrushes having medium hardness or firm bristles affects the surface roughness of tested flowable composite resins. Toothbrushing with firm bristles immediately after acidic challenge determines increased surface roughness for two of the three flowable composite resins (Grandio Flow and Filtek Ultimate Flow). Toothbrushing with medium or firm bristles thirty minutes after the acidic aggression determine no effect on surface condition of flowable composite resins.

Study of Physico-Chemical Interactions during the Production of Silver Citrate Nanocomposites with Hemp Fiber.

In the study presented in this paper, the results obtained by producing nanocomposites consisting of a silver citrate thin layer deposited on hemp fiber surfaces are analyzed. Using the pulsed laser deposition (PLD) method applied to a silver target with impurities of nickel and iron, the formation of the silver citrate film is performed in various ways and the results are discussed based on Fourier Transform Infrared (FTIR) and Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM-EDX) spectroscopy analyses. A mechanism of the physico-chemical processes that take place based on the FTIR vibrational modes and the elemental composition established by the SEM-EDS analysis is proposed. Inhibition of the fermentation process of Saccharomyces cerevisae is demonstrated for the nanocomposite material of the silver citrate thin layer, obtained by means of the PLD method, on hemp fabric. The usefulness of composite materials of this type can extend from sensors and optoelectronics to the medical fields of analysis and treatment.

Ge-Sb-Te Chalcogenide Thin Films Deposited by Nanosecond, Picosecond, and Femtosecond Laser Ablation.

Ge-Sb-Te thin films were obtained by ns-, ps-, and fs-pulsed laser deposition (PLD) in various experimental conditions. The thickness of the samples was influenced by the Nd-YAG laser wavelength, fluence, target-to-substrate distance, and deposition time. The topography and chemical analysis results showed that the films deposited by ns-PLD revealed droplets on the surface together with a decreased Te concentration and Sb over-stoichiometry. Thin films with improved surface roughness and chemical compositions close to nominal values were deposited by ps- and fs-PLD. The X-ray diffraction and Raman spectroscopy results showed that the samples obtained with ns pulses were partially crystallized while the lower fluences used in ps- and fs-PLD led to amorphous depositions. The optical parameters of the ns-PLD samples were correlated to their structural properties.