Institute for Research and Development in Optoelectronics

This study investigates the potential of combining Cerium-doped bioactive glass (BBGi) with Polyvinylpyrrolidone (PVP) to enhance the properties of titanium (Ti) implant surfaces using the Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique. The primary focus is on improving osseointegration, corrosion resistance, and evaluating the cytotoxicity of the developed thin films towards host cells. The innovative approach involves synthesizing a composite thin film comprising BBGi and PVP, leveraging the distinct benefits of both materials: BBGi’s biocompatibility and osteoinductive capabilities, and PVP’s film-forming and biocompatible properties. Results demonstrate that the BBGi + PVP coatings significantly enhance hydrophilicity, indicating improved cell-material interaction potential. The electrochemical analysis reveals superior corrosion resistance of the BBGi + PVP films compared to BBGi alone, which is critical for long-term implant stability. The mechanical adherence tests confirm the robust attachment of the coatings to Ti substrates, surpassing the ISO standards for implant materials. Biocompatibility tests show promising cell viability and negligible cytotoxic effects, with a controlled inflammatory response, underscoring the potential of BBGi + PVP coatings for orthopedic applications. The study concludes that the synergistic combination of BBGi and PVP, applied through the MAPLE technique, offers a promising route to fabricate bioactive and corrosion-resistant coatings for Ti implants, potentially enhancing osseointegration and longevity in clinical settings.

Between 14 March and 21 April 2022, an extensive investigation of an extraordinary Saharan dust intrusion over Europe was performed based on lidar measurements obtained by the European Aerosol Research Lidar Network (EARLINET). The dust episode was divided into two distinct periods, one in March and one in April, characterized by different dust transport paths. The dust aerosol layers were studied over 18 EARLINET stations, examining aerosol characteristics during March and April in four different regions (M-I, M-II, M-III, and M-IV and A-I, A-II, A-III, and A-IV, respectively), focusing on parameters such as aerosol layer thickness, center of mass (CoM), lidar ratio (LR), particle linear depolarization ratio (PLDR), and Ångström exponents (ÅE). In March, regions exhibited varying dust geometrical and optical properties, with mean CoM values ranging from approximately 3.5 to 4.8 km, and mean LR values typically between 36 and 54 sr. PLDR values indicated the presence of both pure and mixed dust aerosols, with values ranging from 0.20 to 0.32 at 355 nm and 0.24 to 0.31 at 532 nm. ÅE values suggested a range of particle sizes, with some regions showing a predominance of coarse particles. Aerosol Optical Depth (AOD) simulations from the NAAPS model indicated significant dust activity across Europe, with AOD values reaching up to 1.60. In April, dust aerosol layers were observed between 3.2 to 5.2 km. Mean LR values typically ranged from 35 to 51 sr at both 355 nm and 532 nm, while PLDR values confirmed the presence of dust aerosols, with mean values between 0.22 and 0.31 at 355 nm and 0.25 to 0.31 at 532 nm. The ÅE values suggested a mixture of particle sizes. The AOD values in April were generally lower, not exceeding 0.8, indicating a less intense dust presence compared to March. The findings highlight spatial and temporal variations in aerosol characteristics across the regions, during the distinctive periods. From 15 to 16 March 2022, Saharan dust significantly reduced UV-B radiation by approximately 14% over the ATZ station (Athens, GR). Backward air mass trajectories showed that the dust originated from the Western and Central Sahara when, during this specific case, the air mass trajectories passed over GRA (Granada, ES) and PAY (Payerne, CH) before reaching ATZ, maintaining high relative humidity and almost stable aerosol properties throughout its transport. Lidar data revealed elevated aerosol backscatter (baer) and PLDR values, combined with low LR and ÅE values, indicative of pure dust aerosols.

This research investigates novel polymeric composite materials for automotive interior trim applications. The composites utilize recycled polypropylene (PPr) matrix and carboxymethylcellulose (CMC) as filler (PPr/CMC: 100/0, 95/5, and 90/10 wt.%). The materials were processed by extrusion and injection molding. Considering their intended application, the composites were evaluated for resistance to key climatic factors, i.e., temperature, humidity, and UV radiation. In addition, structural analyses and FTIR analyses were performed to assess potential heterogeneity and thermal stability. Following FTIR tests, the incorporation of carboxymethyl cellulose in polypropylene is confirmed by the detection of characteristic CMC bands for -OH, C=O, and C-O-C groups. The results indicate slight structural heterogeneity in the 5% and 10% CMC composites. However, no thermal distortions were observed in either the composites or the PPr matrix itself. The behavior of PPr/CMC composites under the action of the mentioned climatic factors has been assessed from the variation of dielectric characteristics with frequency. The strong polarization of CMC leads to a sharp increase in composites electrical conductivity after submersion in water for 480 h, suggesting weakening of the composite structure. After exposure to UV radiation, a sharp increase in conductivity is observed even after the first cycle (72 h) of UV radiation. Following the experimental results obtained in our study, it is recommended to use the PPr +10% CMC composite for obtaining different interior ornaments (carpets, supports, etc.). At the same time, the use of these materials also has the advantage of lightening the mass of the vehicle due to their lower density than polymers.

This study investigates the morphological changes induced by femtosecond (fs) laser pulses in arsenic trisulfide (As2S3) thin films and gold–arsenic trisulfide (Au\As2S3) heterostructures, grown by pulsed laser deposition (PLD). By means of a direct laser writing experimental setup, the films were systematically irradiated at various laser power and irradiation times to observe their effects on surface modifications. AFM was employed for morphological and topological characterization. Our results reveal a clear transition threshold between photoexpansion and photoevaporation phenomena under different femtosecond laser power regimes, occurring between 1 and 1.5 mW, irrespective of exposure time. Notably, the presence of a gold layer in the heterostructure minimally influenced this threshold. A maximum photoexpansion of 5.2% was obtained in As2S3 films, while the Au\As2S3 heterostructure exhibited a peak photoexpansion of 0.8%. The study also includes a comparative analysis of continuous-wave (cw) laser irradiation, confirming the efficiency of fs laser pulses in inducing photoexpansion effects.

(1) Background: A widespread problem in oral health is cavities produced by cariogenic bacteria that consume fermentable carbohydrates and lower pH to 5.5–6.5, thus extracting Ca2+ and phosphate ions (PO43−) from teeth. Dental restorative materials based on polymers are used to fill the gaps in damaged teeth, but their properties are different from those of dental enamel. Therefore, a question is raised about the similarity between dental composites and natural teeth in terms of density and hardness. (2) Methods: We have used Raman spectroscopy and density and microhardness measurements to compare physical characteristics of several restorative dental composites at different polymerization intervals. (3) Results: XRVHerculite®, Optishade®, and VertiseFlow® showed the very different characteristics of the physical properties following four polymerization intervals. Of the three composites, OptiShade showed the highest polymerization rate. (4) Conclusions: Only fully polymerized composites can be used in teeth restoring, because incomplete polymerization would result in cracks, pitting, and lead finally to failure.

A novel lidar simulator based on first principles is presented. Here we describe our approach and initial results for simulating raw lidar signals and system SNR from system parameters and aerosol optical properties. We also include a validation method and sensitivity studies. The main motivation behind this work is to show how low-cost and physically small lidar systems would perform in various atmospheric conditions. The simulator presented herein uses instrument component parameters and, based on known atmospheric scenarios, returns aerosol optical properties and signals. In particular, the simulator accounts for molecular effects, system overlap, different far boundary solutions, and the possibility of depolarization channels and is programmed to function at any UV- NIR wavelength. The simulator’s performance is currently being validated against EARLINET and PollyNet datasets.

Complex demands in the field of cultural heritage preservation often require a multidisciplinary approach and substantial volumes of multimodal data integration and management. The conventional approach to tackling these issues revolves around using different H-BIM (historical building information model) solutions. This paper presents a prototype for a web platform that moves closer to the idea of a digital twin for physical cultural assets. Based on a light development framework, it is designed for online open access and features a versatile custom 3D viewer for intuitive interaction with the presented data. The concept requires a workflow similar to the video game industry's 3D asset optimization to generate highly detailed 3D models and to facilitate the display of multilayered imaging data. The technological stack features a minimal MVC architecture framework and front-end stylesheets. It is designed to be independent of specific databases, enhancing portability for potential future open-source releases. Moreover, the platform employs WebGL libraries to create a dynamic 3D environment interaction. The capabilities of the web platform were tested in a case study regarding the documentation of an important 17th-century church in Romania. Further developments and current limitations of the platform are also discussed.

Citation: Elisa, M.; Sava, B.A.; Eftimie, M.; Nicoara, A.I.; Vasiliu, I.C.; Rusu, M.I.; Bartha, C.; Enculescu, M.; Kuncser, A.C.; Oane, M.; et al. A Nanocomposite Sol-Gel Film Based on PbS Quantum Dots Embedded into an Amorphous Host Inorganic Matrix. Materials 2023, 16, 7105. Abstract: In this study, a sol-gel film based on lead sulfide (PbS) quantum dots incorporated into a host network was synthesized as a special nanostructured composite material with potential applications in temperature sensor systems. This work dealt with the optical, structural, and morphological properties of a representative PbS quantum dot (QD)-containing thin film belonging to the Al 2 O 3-SiO 2-P 2 O 5 system. The film was prepared using the sol-gel method combined with the spin coating technique, starting from a precursor solution containing a suspension of PbS QDs in toluene with a narrow size distribution and coated on a glass substrate in a multilayer process, followed by annealing of each deposited layer. The size (approximately 10 nm) of the lead sulfide nanocrystallites was validated by XRD and by the quantum confinement effect based on the band gap value and by TEM results. The photoluminescence peak of 1505 nm was very close to that of the precursor PbS QD solution, which demonstrated that the synthesis route of the film preserved the optical emission characteristic of the PbS QDs. The photoluminescence of the lead sulfide QD-containing film in the near infrared domain demonstrates that this material is a promising candidate for future sensing applications in temperature monitoring.

As part of a detailed investigation project focused on the painting materials and technical features used in Wallachia during the 17th and 18th century, the imperial icon “Mother of God with Child” from the Orthodox Church of the “Annunciation” in Râmnicu Vâlcea, Romania, was investigated before the restoration intervention. A minimally invasive multi-analytical approach consisting of high-resolution digital radiography, hyperspectral imaging, UV fluorescence imaging, portable X-ray fluorescence, and Fourier transform infrared spectroscopy was used. The results emphasized several key features, such as: the structure of the wooden panel, the nature of pigments and of the painting technique frequently used at that time, and various defects of the pictorial layer including traces of previous restoration works, most probably made at the end of the 18th century.

The use of MAPLE synthesized thin films based on BG and VD3 for improving the osseointegration and corrosion protection of Ti-like implant surfaces is reported. The distribution of chemical elements and functional groups was shown by FTIR spectrometry; the stoichiometry and chemical functional integrity of thin films after MAPLE deposition was preserved, optimal results being revealed especially for the BG+VD3_025 samples. The morphology and topography were examined by SEM and AFM, and revealed surfaces with many irregularities, favoring a good adhesion of cells. The thin films’ cytotoxicity and biocompatibility were evaluated in vitro at the morphological, biochemical, and molecular level. Following incubation with HDF cells, BG57+VD3_ 025 thin films showed the best degree of biocompatibility, as illustrated by the viability assay values. According to the LDH investigation, all tested samples had higher values compared to the unstimulated cells. The evaluation of cell morphology was performed by fluorescence microscopy following cultivation of HDF cells on the obtained thin films. The cultivation of HDF’s on the thin films did not induce major cellular changes. Cells cultured on the BG57+VD3_025 sample had similar morphology to that of unstimulated control cells. The inflammatory profile of human cells cultured on thin films obtained by MAPLE was analyzed by the ELISA technique. It was observed that the thin films did not change the pro- and anti-inflammatory profile of the HDF cells, the IL-6 and IL-10 levels being similar to those of the control sample. The wettability of the MAPLE thin films was investigated by the sessile drop method. A contact angle of 54.65° was measured for the sample coated with BG57+VD3_025. Electrochemical impedance spectroscopy gave a valuable insight into the electrochemical reactions occurring on the surface.

A convenient and low-cost sol–gel approach for the one-step synthesis of ZnO–P2O5–rGO nanostructures with tuned bandgap and fluorescence was investigated. The obtained hybrid nanostructures exploit the properties of zinc oxide, graphene oxide and phosphorous oxide as promising candidates for a wide range of optoelectronic applications. A predominant amorphous structure, ZnO–P2O5–rGO, containing ZnO nanorods was evidenced by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The estimated size of the ZnO nanorods in nanostructures with P2O5 was noticed to decrease when the P2O5/ZnO ratio was increased. The presence of ZnO, P2O5 and rGO was confirmed by Fourier-transform infrared spectroscopy (FTIR) and Raman investigation. P2O5 was noticed to tune the bandgap and the fluorescence emissions of the nanostructured films, as estimated by UV–Vis–NIR and fluorescence spectroscopy, respectively. The electrical measurements performed at room temperature showed that the main influence on the film’s resistivity does not come from the 1% rGO doping but from the P2O5/ZnO ratio. It was found that a 10/90 molar ratio of P2O5/ZnO decreases the resistivity almost seven-fold compared with rGO-doped ZnO films.

The paper is a review of surface plasmon resonance (SPR) structures containing amorphous chalcogenide (ChG) films as plasmonic waveguides. The calculation method and specific characteristics obtained for four-layer SPR structures containing films made of amorphous As2S3 and As2Se3 are presented. The paper is mainly based on our previously obtained and published scattered results, to which a generalized point of view was applied. In our analysis, we demonstrate that, through proper choice of the SPR structure layer parameters, we can control the resonance angle, the sharpness of the SPR resonance curve, the penetration depth, and the sensitivity to changes in the refractive index of the analyte. These results are obtained by operating with the thickness of the ChG film and the parameters of the coupling prism. Aspects regarding the realization of the coupling prism are discussed. Two distinct cases are analyzed: first, when the prism is made of material with a refractive index higher than that of the waveguide material; second, when the prism is made of material with a lower refractive index. We demonstrated experimentally that the change in reflectance self-induced by the modification in As2S3 refractive index exhibits a hysteresis loop. We present specific results regarding the identification of alcohols, hydrocarbons, and the marker of E. coli bacteria.

Despite the large number of unguentaria vessels generally discovered in Roman archeological sites, very little information is available concerning the nature and chemical composition of the products that were originally contained within these artifacts. In this study a combined non-destructive approach that included Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and X-ray fluorescence was used for the characterization of some brownish-black residues preserved in a series of glass unguentaria recovered from excavations at the Roman baths from Mălăiești. The obtained results highlighted the presence of different inorganic substances (an earth-based pigment rich in iron and manganese oxides, admixed with traces of lead- and mercury-based compounds) impregnated with an organic binder such as animal glue and possible natural essential oils, a powdered product associated most probably with a cosmetic/pharmacological use. The study allowed a first insight into the composition and origin of these ancient remains, providing important clues that may help to understand the original function of these unguentaria vessels.

Oxygen is essential for cellular respiration and energy production. Tissue oxygenation refers to delivering oxygen to cells throughout the body. Microcirculation brings blood through small sanguine vessels to maintain the cells' supply of nutrients and oxygen. Optimal tissue oxygenation and microcirculation are essential for maintaining healthy tissue. Conversely, poor oxygenation can cause tissue damage, impair wound healing, and increase infection risk. Several factors can affect tissue oxygenation and microcirculation, including age, lifestyle factors (such as smoking and stress), and underlying medical conditions (such as diabetes and high blood pressure). To improve tissue oxygenation and microcirculation, individuals can engage in healthy lifestyle habits such as regular exercise, healthy eating, stress management, and avoiding smoking. Tissue oxygenation can also be looked therapeutic, given that topical and cosmetic treatments such as massage, pelotherapy, hydrotherapy, moisturizers, and certain skin care products can help pro-mote healthy microcirculation at the somatic level. In the scientific literature, the focus is on hypoxia rather than tissue oxygenation. This article proposes a paradigm shift and emphasizes the homeostatic importance of microcirculation and tissue oxygenation in pathophysiological and therapeutic circumstances. The systematic review of the data from the last 2 years (2021-2022) and the meta-analysis performed on tissue oxygenation will contribute to the practical approach to the pathology circumscribed to tissue oxygenation. Keywords: Tissue oxygenation; Hypoxia; Microcirculation; Homeostasis; Microenvironment

Oxygen is essential for cellular respiration and energy production. Tissue oxygenation refers to delivering oxygen to cells throughout the body. Microcirculation brings blood through small sanguine vessels to maintain the cells' supply of nutrients and oxygen. Optimal tissue ox-ygenation and microcirculation are essential for maintaining healthy tissue. Conversely, poor oxygenation can cause tissue damage, impair wound healing, and increase infection risk. Several factors can affect tissue oxygenation and microcirculation, including age, lifestyle factors (such as smoking and stress), and underlying medical conditions (such as diabetes and high blood pres-sure). To improve tissue oxygenation and microcirculation, individuals can engage in healthy lifestyle habits such as regular exercise, healthy eating, stress management, and avoiding smoking. Tissue oxygenation can also be looked therapeutic, given that topical and cosmetic treatments such as massage, pelotherapy, hydrotherapy, moisturizers, and certain skin care products can help promote healthy microcirculation at the somatic level. In the scientific literature, the focus is on hypoxia rather than tissue oxygenation. This article proposes a paradigm shift and emphasizes the homeostatic importance of microcirculation and tissue oxygenation in pathophysiological and therapeutic circumstances. The systematic review of the data from the last 2 years (2021-2022) and the meta-analysis performed on tissue oxygenation will contribute to the practical approach to the pathology circumscribed to tissue oxygenation. Keywords: Tissue oxygenation; Hypoxia; Microcirculation; Homeostasis; Microenvironment

With the rapid scientific and technological changes that occur every day, a new kind of necessity, real-time, rapid, and accurate detection methods, preferably also non- or minimally invasive and non-destructive, has emerged. One such method is laser-induced fluorescence spectroscopy (LIF), applied in various fields of activity in recent decades, ranging from industry and biochemistry to medicine and even heritage sciences. Fluorescence-based spectroscopic methods have all of the above-mentioned characteristics, and their functionality has been proven in many studies. Yet, they have not known great success as other molecular techniques. This paper is a short synthesis of the role of the laser-induced fluorescence spectroscopy technique in heritage sciences, the main applications in this field, along with its advantages and limitations. The article focuses on the most common types of lasers used, the merging of two or more methods into hybrid techniques, the enhancement of the analytical capabilities of LIF and post-processing methods, and also explores some future development possibilities of LIF.

This study highlights the decomposing role through the hydrolytic activities of fungi isolated from natural environments represented by brackish and hypersaline lakes in Romania. Novel strains belonging to the Penicillium, Aspergillus, and Emericellopsis genera were isolated and screened for the ability to produce extracellular hydrolytic enzymes, i.e., proteases, lipases, amylases, cellulases, xylanases, and pectinases. According to salt requirements, they were classified as moderate halophilic and halotolerant strains. Agar plate-based assays with Tween 80, slide cultures with organic deposits, and quantitative evaluation allowed the selection of Aspergillus sp. BSL 2-2, Penicillium sp. BSL 3-2, and Emericellopsis sp. MM2 as potentially good decomposers of organic matter not only in lakes but also on deposits covering the mural paintings. Experiments performed on painted experimental models revealed that only Penicillium sp. BSL 3-2 decomposed Paraloid B72, transparent dispersion of casein, beeswax, sunflower oil, and soot. Moreover, using microscopic, spectroscopic, and imaging methods, it was proved the efficiency of Penicillium sp. BSL 3-2 for decomposition of organic deposits artificially applied on frescoes fragments.

This study evaluated both the possible fungal metabolites involved in the degradation of the commercial consolidant known as Paraloid® B72 and the national artisanal consolidant named transparent dispersion of casein and the deteriorative potential of melanised fungi. Fungi were found to have the capacity to produce organic acids, proteases and esterases when they grow on consolidants, which can be used as nutrients. Mycelia produced by melanised fungi affected the appearance, as well as the integrity, of consolidants applied on painted experimental models and fragments of frescoes. In treatment trials with biocides (Biotin R®, Biotin T® and Preventol® RI 80), the morphology of the consolidants, as well as the vitality of the fungi, were assessed 30 days after the inoculation with melanic fungi. Direct observation, optical microscopy, colourimetry and microbiological analysis highlighted the degradation of the consolidants by fungi and their acquired resistance after biocidal treatments. Biotin R® applied by brushing on the surface of the consolidants proved to be the most effective treatment, followed by Biotin T®. Considering the overall results for both Paraloid® B72 and transparent dispersion of casein, use of Biotin R® applied by brushing is recommended for preventive conservation.

Natural minerals and earths with coloring properties have been widely used as artistic pigments since prehistoric times. Despite being extensively studied, the complex chemistry of earth pigments is still unsatisfactory described with respect to their mineralogical and structural variability and origin. In this study, a large group of earth pigments from various geographical locations was investigated using easily accessible spectroscopic techniques and multivariate analysis with the aim to identify distinctive mineralogical and chemical characteristics of natural pigment sources. Portable X-ray fluorescence (p-XRF), Fourier transform infrared spectroscopy (FTIR) and fiber optic Raman spectroscopy were used for the elemental, molecular and structural characterization of the investigated pigments. Diagnostic spectral features and chemical patterns (fingerprints) were identified and discussed with respect to their geological sources. Due to the occurrence of similar accompanying minerals, it was observed that the differentiation of red and yellow ochers is more challenging compared to green, brown and black pigments. However, for some of the investigated pigments, the presence of certain accessory minerals and/or of certain chemical patterns can have diagnostic value. Principal component analysis (PCA) of the FTIR and XRF data matrices showed promising results in terms of geological attribution, highlighting a promising tool for provenance research. The results of the study demonstrate the potential benefits of this rapid and nondestructive approach for the characterization and differentiation of earth pigments with similar hues coming from different geological sources.