Search Results (3,602)

In the framework of fully vertical GaN-on-Silicon device technology development, we report on the optimization of non-alloyed ohmic contacts on the N-polar n+-doped GaN face backside layer. This evaluation is made possible by using patterned TLMs (Transmission Line Model) through direct laser writing lithography after locally removing the substrate and buffer layers in order to access the n+-doped backside layer. As deposited non-alloyed metal stack on top of N-polar orientation GaN layer after buffer layers removal results in poor ohmic contact quality. To significantly reduce the related specific contact resistance, an HCl treatment is applied prior to metallization under various time and temperature conditions. A 3 min HCl treatment at 70 °C is found to be the optimum condition to achieve thermally stable high ohmic contact quality. To further understand the impact of the wet treatment, SEM (Scanning Electron Microscopy) and XPS (X-ray Photoelectron Spectroscopy) analyses were performed. XPS revealed a decrease in Ga-O concentration after applying the treatment, reflecting the higher oxidation susceptibility of the N-polar face compared to the Ga-polar face, which was used as a reference. SEM images of the treated samples show the formation of pyramids on the N-face after HCl treatment, suggesting specific wet etching planes of the GaN crystal from the N-face. The size of the pyramids is time-dependent; thus, increasing the treatment duration results in larger pyramids, which explains the degradation of ohmic contact quality after prolonged high-temperature HCl treatment. Full article

Renal cell carcinoma (RCC) is the sixth most common cancer in men and is often asymptomatic, leading to incidental detection in advanced disease stages that are associated with aggressive histology and poorer outcomes. Various cancer biomarkers are found in urine samples from patients with RCC. In this study, we propose to investigate the use of Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR) on dried urine samples for distinguishing RCC. We analyzed dried urine samples from 49 patients with RCC, confirmed by histopathology, and 39 healthy donors using ATR-FTIR spectroscopy. The vibrational bands of the dried urine were identified by comparing them with spectra from dried artificial urine, individual urine components, and dried artificial urine spiked with urine components. Urea dominated all spectra, but smaller intensity peaks, corresponding to creatinine, phosphate, and uric acid, were also identified. Statistically significant differences between the FTIR spectra of the two groups were obtained only for creatinine, with lower intensities for RCC cases. The discrimination of RCC was performed through Principal Component Analysis combined with Linear Discriminant Analysis (PCA–LDA) and Support Vector Machine (SVM). Using PCA–LDA, we achieved a higher discrimination accuracy (82%) (using only six Principal Components to avoid overfitting), as compared to SVM (76%). Our results demonstrate the potential of urine ATR-FTIR combined with machine learning techniques for RCC discrimination. However, further studies, especially of other urological diseases, must validate this approach. Full article

Organogels are semi-solid pharmaceutical forms whose dispersing phase is an organic liquid, for example, an oil, such as acai oil, immobilized by a three-dimensional network formed by the gelling agent. Organogels are being highlighted as innovative release systems for cosmetic active ingredients such as hyaluronic acid for topical applications. Acai oil was evaluated for its physicochemical parameters, fatty acid composition, lipid quality index, spectroscopic pattern (Attenuated total reflectance Fourier Transform Infrared Spectroscopy), thermal behavior, total phenolic, total flavonoids, and total carotenoids and β-carotene content. The effectiveness of the organogel incorporated with hyaluronic acid (OG + HA) was evaluated through ex vivo permeation and skin retention tests, in vitro tests by Attenuated total reflectance Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry. The physicochemical analyses highlighted that the acai oil exhibited quality standards in agreement with the regulatory bodies. Acai oil also showed high antioxidant capacity, which was correlated with the identified bioactive compounds. The cytotoxicity tests demonstrated that the formulation OG + HA does not release toxic substances into the biological environment that could impede cell growth, adhesion, and efficacy. In vitro and ex vivo analyses demonstrated that after 6 h of application, OG + HA presented a high level of hydration, thermal protection and release of HA. Thus, it can be concluded that the OG + HA formulation has the potential for physical–chemical applications, antioxidant quality, and potentially promising efficacy for application in the cosmetic areas. Full article

Perovskites can absorb solar energy and are extensively used in various catalytic and photocatalytic reactions. However, noble metal particles may enhance the catalytic, photocatalytic, and antibacterial activities. This study demonstrates the cost-effective green synthesis of the photocatalyst perovskite LaMnO₃ and its modification with noble metal Ag nanoparticles. The green synthesis of nanocomposite was achieved through a hydrothermal method employing aqueous extract derived from Citrus limon (L.) Burm peels. The properties of fabricated perovskites LaMnO₃ and LaMnO₃-Ag nanocomposites were evaluated and characterized by Ultraviolet-Visible spectroscopy (UV-Vis), Diffuse Reflectance Spectroscopy (DRS), X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FT-IR), High-Resolution Transmission Electron Microscopy (HRTEM), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDX) and Brunauer–Emmett–Teller (BET) surface area techniques. The particle size distribution % of LaMnO₃ and LaMnO₃-Ag was observed to be 20 to 60 nm after using TEM images. The maximum percentage size distribution was 37 nm for LaMnO₃ and 43 nm for LaMnO₃-Ag. In addition, LaMnO₃-Ag nanocomposite was utilized as a photocatalyst for the degradation of Rose Bengal (RB) dye and its antibacterial activities against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The surface area and band gap for perovskite LaMnO₃ nanoparticles were calculated as 12.642 m²/g and 3.44 eV, respectively. The presence of noble metal and hydrothermal-bio reduction significantly impacted the crystallinity. The BET surface area was found to be 16.209 m²/g, and band gap energy was calculated at 2.94 eV. The LaMnO₃ nanocomposite with noble metal shows enhanced photocatalytic effectiveness against RB dye (20 PPM) degradation (92%, R² = 0.995) with pseudo-first-order chemical kinetics (rate constant, k = 0.05057 min⁻¹) within 50 min due to the ultimate combination of the hydrothermal and bio-reduction technique. The photocatalytic activity of the LaMnO₃-Ag nanocomposite was optimized at different reaction times, photocatalyst doses (0.2, 0.4, 0.6, and 0.8 g/L), and various RB dye concentrations (20, 30, 40, and 50 ppm). The antibacterial activities of green synthesized LaMnO₃ and LaMnO₃-Ag nanoparticles were explored based on colony-forming unit (cfu) reduction and TEM images of bacterial and nanoparticle interactions for S. aureus and E. coli. An amount of 50 µg/mL LaMnO₃-Ag nanocomposite was sufficient to work as the highest antibacterial activity for both bacteria. The perovskite LaMnO₃-Ag nanocomposite synthesis process is economically and environmentally friendly. Additionally, it has a wide range of effective and exclusive applications for remediating pollutants. Full article

The present study is aimed at the characterization of artifacts excavated in the necropolis surrounding the mausoleum of the Aga Khan in Aswan (Egypt), as part of the Mummies Investigations Anthropological & Scientific West Aswan Necropolis (MIASWAN) project. Four cartonnages and some pottery shards were investigated on-site by means of non-destructive and micro-destructive techniques, such as attenuated total reflection/Fourier transform infrared spectroscopy (ATR/FTIR) and visible reflectance spectroscopy Vis-RS). Thanks to the use of these techniques, several pigments employed in the creation of the artifacts were identified. Due to the impossibility of transporting the investigated objects out of Egypt, a first-ever on-site characterization of the artifacts from this important excavation was carried out through scientific methodologies. These extreme conditions made the use of analytical instrumentation very challenging. Nevertheless, several characteristic pigments and hues were successfully identified. Full article

Raman spectroscopy with the advantages of the in situ and simultaneous detection of multi-components has been widely used in the identification and quantitative detection of gas. As a type of scattering spectroscopy, the detection sensitivity of Raman spectroscopy is relatively lower, mainly due to the low signal collection efficiency. This paper presents the design and assembly of a multi-channel cavity-enhanced Raman spectroscopy system, optimizing the structure of the sample pool to reduce the loss of the laser and increase the excitation intensity of the Raman signals. Moreover, three channels are used to collect Raman signals to increase the signal collection efficiency for improving the detection sensitivity. The results showed that the limits of detection for the CH₄, H₂, CO₂, O₂, and N₂ gases were calculated to be 3.1, 34.9, 17.9, 27, and 35.2 ppm, respectively. The established calibration curves showed that the correlation coefficients were all greater than 0.999, indicating an excellent linear correlation and high level of reliability. Meanwhile, under long-time integration detection, the Raman signals of CH₄, H₂, and CO₂ could be clearly distinguished at the concentrations of 10, 10, and 50 ppm, respectively. The results indicated that the designed Raman system possesses broad application prospects in complex field environments. Full article

The surface symmetry of the substrate plays an important role in the epitaxial high-quality growth of 2D materials; however, in-depth and in situ studies on these materials during growth are still limited due to the lack of effective in situ monitoring approaches. In this work, taking the growth of MoSe₂ as an example, the distinct growth processes on Al₂O₃ ($11\overline{2}0$) and Al₂O₃ (0001) are revealed by parallel monitoring using in situ reflectance anisotropy spectroscopy (RAS) and differential reflectance spectroscopy (DRS), respectively, highlighting the dominant role of the surface symmetry. In our previous study, we found that the RAS signal of MoSe₂ grown on Al₂O₃ ($11\overline{2}0$) initially increased and decreased ultimately to the magnitude of bare Al₂O₃ ($11\overline{2}0$) when the first layer of MoSe₂ was fully merged, which is herein verified by the complementary DRS measurement that is directly related to the film coverage. Consequently, the changing rate of reflectance anisotropy (RA) intensity at 2.5 eV is well matched with the dynamic changes in differential reflectance (DR) intensity. Moreover, the surface-dominated uniform orientation of MoSe₂ islands at various stages determined by RAS was further investigated by low-energy electron diffraction (LEED) and atomic force microscopy (AFM). By contrast, the RAS signal of MoSe₂ grown on Al₂O₃ (0001) remains at zero during the whole growth, implying that the discontinuous MoSe₂ islands have no preferential orientations. This work demonstrates that the combination of in situ RAS and DRS can provide valuable insights into the growth of unidirectional aligned islands and help optimize the fabrication process for single-crystal transition metal dichalcogenide (TMDC) monolayers. Full article

In this work, nanocellulose aqueous dispersions were studied as a bio-inspired consolidating agent for the recovery and conservation of ancient wood and compared with two of the most used traditional consolidants: the synthetic resins Paraloid B-72 and Regalrez 1126. The morphology of crystalline nanocellulose (CNC), determined using Scanning Electron Microscopy (SEM), presents with a rod-like shape, with a size ranging between 15 and 30 nm in width. Chemical characterization performed using the Fourier-Transform Infrared Spectroscopy (FT-IR) technique provides information on surface modifications, in this case, demonstrating the presence of only the characteristic peaks of nanocellulose. Moreover, conductometric, pH, and dry matter measurements were carried out, showing also in this case values perfectly conforming to what is found in the literature. The treated wood samples were observed under an optical microscope in reflected light and under a scanning electron microscope to determine, respectively, the damage caused by xylophages and the morphology of the treated surfaces. The images acquired show the greater similarity of the surfaces treated with nanocellulose to untreated wood, compared with other consolidating agents. Finally, a colorimetric analysis of these samples was also carried out before and after a first consolidation treatment, and after a second treatment carried out on the same samples three years later. The samples treated with CNC appeared very homogeneous and uniform, without alterations in their final color appearance, compared to other traditional synthetic products. Full article

In this study, a novel supramolecular composite, “photogels”, was synthesized by mixing of cysteine–silver sol (CSS) and methylene blue (MB). A complex of modern physico-chemical methods of analysis such as viscosimetry, UV spectroscopy, dynamic and electrophoretic light scattering, scanning electron microscopy and energy-dispersive X-ray spectroscopy showed that MB molecules are uniformly localized mainly in the space between fibers of the gel-network formed by CSS particles. Molecules of the dye also bind with the surface of CSS particles by non-covalent interactions. This fact is reflected in the appearance of a synergistic anticancer effect of gels against human squamous cell carcinoma even in the absence of light irradiation. A mild toxic influence of hydrogels was observed in normal keratinocyte cells. Photodynamic exposure significantly increased gel activity, and there remained a synergistic effect. The study of free-radical oxidation in cells has shown that gels are not only capable of generating reactive oxygen species, but also have other targets of action. Flow cytometric analysis allowed us to find out that obtained hydrogels caused cell cycle arrest both without irradiation and with light exposure. The obtained gels are of considerable interest both from the point of view of academics and applied science, for example, in the photodynamic therapy of superficial neoplasms. Full article

The present study presents the results obtained from evaluating the photocatalytic behavior of a series of sulfated CeO₂ materials in the photocatalytic degradation of the herbicide 2,4-dichlorophenoxyacetic acid. The CeO₂ photocatalytic support was prepared using the precipitation synthesis method. Subsequently, the support was wetly impregnated with different contents of sulfate ions (0.5, 1.0, and 2.0 wt.%). The materials were characterized using X-ray diffraction, nitrogen physisorption, infrared spectroscopy, diffuse reflectance UV–Vis spectrophotometry, and thermal analysis. The characterization results showed that the sulfation of the material promoted an increase in the surface area and a decrease in the average size of the crystallites. Likewise, it was possible to demonstrate the surface sulfation of the support through bidentate coordination of the sulfate groups to the semiconductor metal. Concerning photoactivity, the convenience of the surface modification of CeO₂ was confirmed because the sulfate groups acted as capturers of the electrons generated during the photocatalytic process, reducing the frequency of recombination of the charge carriers and allowing the availability of the gaps to favor the degradation reaction of the contaminant. Finally, it was evident that a percentage of 1.0 wt.% of the sulfate anion is the optimal content to improve the photocatalytic properties of CeO₂. Full article

Quaternary (Al_xGa_1−x)_yIn_1−yP alloys grown on GaAs substrates have recently gained considerable interest in photonics for improving visible light-emitting diodes, laser diodes, and photodetectors. With two degrees of freedom (x, y) and keeping growth on a lattice-matched GaAs substrate, the (Al_xGa_1−x)_0.5In_0.5P alloys are used for tuning structural, phonon, and optical characteristics in different energy regions from far-infrared (FIR) → near-infrared (NIR) → ultraviolet (UV). Despite the successful growth of (Al_xGa_1−x)_0.5In_0.5P/n⁺-GaAs epilayers, limited optical, phonon, and structural characteristics exist. Here, we report our results of carefully examined optical and vibrational properties on highly disordered alloys using temperature-dependent photoluminescence (TD-PL), Raman scattering spectroscopy (RSS), and Fourier-transform infrared reflectivity (FTIR). Macroscopic models were meticulously employed to analyze the TD-PL, RSS, and FTIR data of the (Al_0.24Ga_0.76)_0.5In_0.5P/n⁺-GaAs epilayers to comprehend the energy-dependent characteristics. The Raman scattering and FTIR results of phonons helped analyze the reflectivity spectra in the FIR region. Optical constants were carefully integrated in the transfer matrix method for evaluating the reflectivity $\mathrm{R}\left(\mathrm{E}\right)$ and transmission $\mathrm{T}\left(\mathrm{E}\right)$ spectra in the NIR → UV regions, validating the TD-PL measurements of bandgap energies $\left({\mathrm{E}}_{\mathrm{g}}^{\mathrm{P}\mathrm{L}}\right)$. Full article

Although titanium and its alloys are widely used as dental implants, they cannot induce the formation of new bone around the implant, which is a basis for the functional integrity and long-term stability of implants. This study focused on the functionalization of the titanium/titanium oxide surface as the gold standard for dental implants, with electrospun composite fibers consisting of polyvinylpyrrolidone and Ca²⁺ ions. Polymer fibers as carriers of Ca²⁺ ions should gradually dissolve, releasing Ca²⁺ ions into the environment of the implant when it is immersed in a model electrolyte of artificial saliva. Scanning electron microscopy, energy dispersive X-ray spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy confirmed the successful formation of a porous network of composite fibers on the titanium/titanium oxide surface. The mechanism of the formation of the composite fibers was investigated in detail by quantum chemical calculations at the density functional theory level based on the simulation of possible molecular interactions between Ca²⁺ ions, polymer fibers and titanium substrate. During the 7-day immersion of the functionalized titanium in artificial saliva, the processes on the titanium/titanium oxide/composite fibers/artificial saliva interface were monitored by electrochemical impedance spectroscopy. It can be concluded from all the results that the composite fibers formed on titanium have application potential for the development of osteoinductive and thus more biocompatible dental implants. Full article

Exploring the phonon characteristics of novel group-IV binary XC (X = Si, Ge, Sn) carbides and their polymorphs has recently gained considerable scientific/technological interest as promising alternatives to Si for high-temperature, high-power, optoelectronic, gas-sensing, and photovoltaic applications. Historically, the effects of phonons on materials were considered to be a hindrance. However, modern research has confirmed that the coupling of phonons in solids initiates excitations, causing several impacts on their thermal, dielectric, and electronic properties. These studies have motivated many scientists to design low-dimensional heterostructures and investigate their lattice dynamical properties. Proper simulation/characterization of phonons in XC materials and ultrathin epilayers has been challenging. Achieving the high crystalline quality of heteroepitaxial multilayer films on different substrates with flat surfaces, intra-wafer, and wafer-to-wafer uniformity is not only inspiring but crucial for their use as functional components to boost the performance of different nano-optoelectronic devices. Despite many efforts in growing strained zinc-blende (zb) GeC/Si (001) epifilms, no IR measurements exist to monitor the effects of surface roughness on spectral interference fringes. Here, we emphasize the importance of infrared reflectivity $\mathrm{R}\left(\mathsf{\omega }\right)$ and transmission $\mathrm{T}\left(\mathsf{\omega }\right)$ spectroscopy at near normal θ_i = 0 and oblique θ_i ≠ 0 incidence (Berreman effect) for comprehending the phonon characteristics of both undoped and doped GeC/Si (001) epilayers. Methodical simulations of $\mathrm{R}\left(\mathsf{\omega }\right)$ and $\mathrm{T}\left(\mathsf{\omega }\right)$ revealing atypical fringe contrasts in ultrathin GeC/Si are linked to the conducting transition layer and/or surface roughness. This research provided strong perspectives that the Berreman effect can complement Raman scattering spectroscopy for allowing the identification of longitudinal optical ${\mathsf{\omega }}_{\mathrm{LO}}$ phonons, transverse optical ${\mathsf{\omega }}_{\mathrm{TO}}$ phonons, and LO-phonon–plasmon coupled ${\mathsf{\omega }}_{\mathrm{LPP}}^{+}$ modes, respectively. Full article

Using a co-precipitation technique, the anionic form of sulisobenzone (benzophenone-4) sunscreen ingredient was incorporated into the interlayer space of CaFe-hydrocalumite for the first time. Using detailed post-synthetic millings of the photoprotective nanocomposite obtained, we aimed to study the mechanochemical effects on complex, hybridized layered double hydroxides (LDHs). Various physicochemical properties of the ground and the intact LDHs were compared by powder X-ray diffractometry, N₂ adsorption-desorption, UV–Vis diffuse reflectance, infrared and Raman spectroscopy, scanning electron microscopy and thermogravimetric measurements. The data showed significant structural and morphological deformations, surface and textural changes and multifarious thermal behavior. The most interesting development was the change in the optical properties of organic LDHs; the milling significantly improved the UV light blocking ability, especially around 320 nm. Spectroscopic results verified that this could be explained by a modification in interaction between the LDH layers and the sulisobenzone anions, through modulated π–π conjugation and light absorption of benzene rings. In addition to the vibrating mill often used in the laboratory, the photoprotection reinforcement can also be induced by the drum mill grinding system commonly applied in industry. Full article

Using electrospun nanofibers doped with TiO₂ and rare-earth ion Ho³+ as the matrix, and sodium gluconate as the reducing agent, Bi(NO₃)₃ was reduced using hydrothermal technology to produce Bi@Ho³⁺:TiO₂ composite fiber materials. The materials’ phase, morphology, and photoelectric properties were characterized using various analytical testing methods, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), and transient photocurrent (IP). During the hydrothermal process, it was confirmed that Bi³⁺ was reduced by sodium gluconate to form pure Bi nanoparticles, which combined with Ho³⁺:TiO₂ nanofibers to form heterojunctions. By leveraging the surface plasmon resonance (SPR) effect of metallic Bi and the abundant energy level structure and 4f electron transition properties of rare-earth Ho³⁺, the TiO₂ nanofibers underwent dual modification, effectively enhancing the photocatalytic activity and stability of TiO₂. Under visible light irradiation, the rate of hydrogen production through water decomposition reached 43.6 μmol·g⁻¹·h⁻¹. Full article