Changes In Optical Properties Research Articles

Micrometric patterning of a borogermanate glass containing terbium by thermal poling to manage luminescence and second order optical properties

Borogermanate glasses containing terbium ions are interesting materials due to their luminescent and magnetic properties. Terbium can present two different oxidation states and the thermal poling technique can be a pertinent way to modulate spatially the oxidation state of these ions. In this work, we demonstrate using a thermo-electrical imprinting process the transfer of micro scaled motifs on the surface of a borogermanate glass containing Tb3+ resulting in a micrometric structuring of the oxidation state of Tb3+/Tb4+ ions. A large change in absorption and luminescence optical properties is observed, arising from the distinct properties of trivalent and tetravalent terbium ions. Correlative micro luminescence, Raman and second harmonic generation measurements were carried out on the patterned poled glass surface. This has demonstrated an accurate concomitant modification of the glass structure accompanying large luminescence changes and the appearance of a second order optical response which could be attributed to a localized space charge implantation. These original results demonstrate how a simple electrical process allows managing multi optical properties but also paves the way to induce static electrical functionalities in a magnetic optical glassy system.

Synergistic advancements in nanocomposite design: Harnessing the potential of mixed metal oxide/reduced graphene oxide nanocomposites for multifunctional applications

Reduced graphene oxide-based nanocomposites find applications in designing and fabrication of smart materials due to their unique optical, electrical, mechanical, sensing, photochemical, and energy-storing capacities. This comprehensive review article explores different synthetic pathways employed in fabricating reduced graphene oxide (rGO)/metal oxides based nanocomposites (NCs) with improved properties for multifaceted applications. The different applications of the mixed metal oxide/rGO NCs were explored in gas sensing, photocatalysis, energy storage, and biomedical applications. Through comparative assessments, this review focuses on the change in optical, physical, chemical, mechanical, electrical, photocatalytic, sensing, charge storing, and antibacterial properties as we move from mixed metal nanoparticles and pure rGO to NCs. This review article opens the door for the design and synthesis of rGO-based multifunctional composite materials by providing insightful information about the development and design of mixed metal oxide/rGO NCs. The findings presented herein hold the potential to revolutionize future endeavors in energy storage, sensing, photocatalysis, adsorption, catalytic processes, purification, separation, protective coatings, and beyond.

Water and methanol soluble aerosol brown carbon over Bhopal, central India – Changes in optical properties and radiative effects during the COVID-19 lockdowns

Water-soluble organic carbon (WSOC) and methanol-soluble organic carbon (MeS-OC) in ambient PM2.5 over Bhopal, central India, were optically characterized during the COVID-19 lockdowns year (2020) to assess the influence of source reductions on these species and the induced changes in their radiative effects. During the lockdowns (23 March – May 31, 2020), the light absorption coefficients (babs-405) of WSOC and MeS-OC had higher values (75 %–105 %) compared to the corresponding period in 2019. MeS-OC light absorption at 365 nm and 550 nm were about thrice and twice, respectively, compared to WSOC absorption at these wavelengths. Increased fire counts and higher MAC405 (Mass Absorption Cross-section) of MeS-OC and WSOC (8 %–58 %) during the lockdowns compared to the corresponding period in 2019, indicated frequent biomass burning events because vehicular and industrial sources were completely shutdown during this period. Fractional solar radiation absorption (f300–400 nm) by MeS-OC and WSOC normalized by EC absorption was higher (15 % ± 9 % and 9 % ± 4 %, respectively) during the lockdowns compared to the corresponding period in 2019. The SFE300–400nm (Simple Forcing Efficiency) values for MeS-OCthisstudy→literature and WSOCthis study→literature were 8 % ± 5 % and 13 % ± 5 % higher, respectively, during lockdowns compared to the same period in 2019. Overall, the results suggested that biomass burning emissions during COVID-19 lockdowns offset (and overtook) any source emissions reduction induced aerosol radiative heating gains.

Radiation-induced defects in the InGaN/GaN superlattice structure

With the molecular dynamics method, this paper investigates radiation-induced defects in the In0.16Ga0.84N/GaN superlattice structure (SLS) and the In0.04Ga0.96N/GaN SLS. In the temporal evolution of cascades, most of vacancies recombine with interstitials. The Monte Carlo simulations about the proportions of PKAs induced by 3 MeV protons were also considered in this work for calculating the weighted averages of surviving defects. For the In0.16Ga0.84N/GaN SLS irradiated by protons, around 82.6 percent of surviving vacancies are Ga vacancies while around 88.9 percent of surviving interstitials are Ga interstitials. For the In0.04Ga0.96N/GaN SLS irradiated by protons, around 87.3 percent of surviving vacancies are Ga vacancies while around 88.6 percent of surviving interstitials are Ga interstitials. N vacancies, N interstitials, and In vacancies also exist in irradiated InGaN/GaN SLS. Details about different types of defects are presented in this paper, which helps explain the microscopic mechanism of irradiated InGaN/GaN SLS. Since different types of defects have different influences on electronic and optical properties, simulations about the proportions of various defects in irradiated InGaN/GaN SLS help experimentalists find the effective factors of radiation-related changes in electronic and optical properties.

Observations on “Mg” incorporated oxides of tungsten for superconducting applications

The present work involves in the synthesis and characterization of pristine and "Mg" associated WO3.H2O nano powders by a high yield irradiation technique using microwaves. The diffraction patterns present phased orthorhombic phase and retained even after annealing process. Clear evidence noticed for pure and doped samples in morphological behavior of the samples. The change in optical properties in terms of energy values revealed the contribution of dopants with the evident at 360 nm wavelength blue shift. The obtained magnetic behavior on the annealed samples revealed the transition offer magnetic state to diamagnetic state may be investigated for super conducting applications.

Sustainable and fast synthesis of zinc-phthalocyanine for gamma radiation dosimeter application

In the present research, the two different systems of dye based on zinc phthalocyanine were prepared by microwave-induced synthesis and conventional methods. They were evaluated as new effective chemical-based dosimeters for gamma irradiation. The sensitivity of the prepared dosimeters was examined by studying the comparative results between them through the changes in structural and optical properties upon exposure to different gamma irradiation doses. The color bleaching of the solutions was followed spectrophotometrically. Gradual changes from blue to light yellow color of zinc phthalocyanine solution, with the increase of the gamma radiation dose, were observed due to the decomposition of the dyes based on the zinc phthalocyanine. The synthesized zinc phthalocyanine chemical-based dosimeters for measurement of gamma irradiation up to 25kGy showed excellent stability after irradiation in terms of morphology and structure, which makes them a suitable novel material as composite-based dosimeters of gamma irradiation.

Experimental and numerical assessment on Pb-free alkaline mixed borate glasses for radiation resisting applications

Melt quenching technique has been used to fabricate calcium boro-phosphate glasses doped with praseodymium oxide ions. With increased P2O5 content, structural parameters like oxygen molar volume (Vo) and oxygen packing density (OPD) indicate an opposing trend. In addition to optical factors like optical electronegativity, absorption edge, and direct and indirect bandgap values being estimated and discussed, optical absorption spectra have been recorded for all the glasses. The presence of ionic bond behaviour confirms the strong structural and optical property changes caused by the P2O5 content. Using the Phy-X software application, the radiation shielding parameters were investigated. The incorporation of B2O3, CaCO3, and P2O5 offers more number of bridging oxygens which further leads to closely packed nature. Considering the glass sample B0PCM:Pr, the highest linear attenuation coefficient (LAC) is determined. The LAC results showed that at high energy levels, the glass's shielding performance became more consistent. The results of the effective atomic number analysis demonstrated the impact that CaCO3 has on the glass's shielding effectiveness, with a higher concentration of CaCO3 improving the material's defence against gamma radiation. For B0PCM:Pr glass, the half value layer (HVL) rises from 2.101 to 3.444 cm at 0.284–1.333 MeV. Certainly, it has been observed that the glass tends to have a smaller HVL when it contains more CaCO3 with lesser P2O5 content.

Transient optical properties change and dense plasma dynamics during water breakdown induced by ultrashort laser pulses

We propose a nonlinear transient coupling model to study the plasma dynamics during the interaction between ultrashort laser pulses and water. We conduct a quantitative characterization of the transient optical properties, energy deposition, and dense plasma dynamics in water with near-infrared ultrashort laser pulses by simulating the spatiotemporal coupling of the laser field with the plasma while calculating the time-varying relative permittivity. The results show that the free electron density in the dense plasma exceeds ≈1.0×1026 m−3, the plasma will move in the reverse direction of the laser pulse propagation, and the velocity is related to the incident laser intensity. An empirical model is established to quantify this reverse movement of dense plasma in the laser field taking into account the energy deposition. We also validate our coupling model by comparing the breakdown thresholds with experimental results and find excellent agreement.

Gold nanoshells with varying morphologies through templated surfactant‐assisted seed‐growth method

AbstractPlasmonic nanoparticles exhibit dramatic changes in optical properties depending on their spatial organization. Therefore, the ability to precisely control their assembly structure is important for both fundamental understanding and practical applications. In this personal account, we describe a templated surfactant‐assisted seed‐growth method to synthesize core–shell‐type gold nanoparticle assemblies with controllable surface morphologies and optical properties. This approach provides a simple procedure for simultaneous growth and assembly of metal nanoparticles on polymer templates, producing well‐defined nanostructures such as spiky nanoshells and raspberry‐like metamolecules with useful and interesting optical properties, such as strong and uniform surface‐enhanced Raman scattering and metamaterial properties. We discuss the factors that control the morphology and collective properties, describe the design rules acquired from the system, and suggest future directions of this research area.

Optical properties of thin films monitored in real-time at high gamma radiation doses using long period fiber gratings

In this work, we report an all-optical-fiber-based method to monitor in real-time the changes in thin film optical properties when exposed to harsh environments such as high doses of gamma radiation. The method is based on a long period grating (LPG) inscribed in a radiation resistant optical fiber, which is coated with a thin film to be analyzed. Due to impact of the environment on the film properties, the transmission spectrum of the LPG changes. To validate this methodology, we deposited oxides of various metals, i.e. aluminum (Al2O3), titanium (TiO2), and tantalum (Ta2O5), as well as a polymeric film, namely polystyrene (PS), on the LPG surface and measured the resonant wavelength shift induced by high doses of gamma exposure (dose rate of 2.3 kGy/h, up to a total dose of 46 kGy). The changes could be observed in real-time up to maximum reached dose and during the recovery period. The results are significantly dependent on thin film material. Among the oxides, TiO2 thin film demonstrated the highest susceptibility to irradiation, whereas Al2O3 exhibited the least impact. Additionally, a good recovery potential for Ta2O5 thin film was observed, hinting at its promising application in dosimetry. Conversely, the PS film exhibited a permanent effect induced by irradiation. This is the first real-time experimental study of the impact of high dose gamma radiation on thin film optical properties using a universal optical-fiber-based device. The findings pave the way for assessing radiation hardness of thin film materials or utilizing such a method to optimize material treatment involving ionizing radiation.

Plasmonic nanosensor and pressure-induced transparency based on coupled resonator in a nanoscale system.

Plasmonic nanosensors and the dynamic control of light fields are of the utmost significance in the field of micro- and nano-optics. Here, our study successfully demonstrates a plasmonic nanosensor in a compact coupled resonator system and obtains the pressure-induced transparency phenomenon for the first time to our knowledge. The proposed structure consists of a groove and slot cavity coupled in the metal-insulator-metal waveguide, whose mechanical and optical characteristics are investigated in detail using the finite element method. Simulation results show that we construct a quantitative relationship among the resonator deformation quantity, the applied pressure variation, and the resonant wavelength offset by combining the mechanical and optical properties of the proposed system. The physical features contribute to highly efficient plasmonic nanosensors for refractive index and optical pressure sensing with sensitivity of 1800 nm/RIU and 7.4 nm/MPa, respectively. Furthermore, the light waves are coupled to each other in the resonators, which are detuned due to the presence of pressure, resulting in the pressure-induced transparency phenomenon. It is noteworthy to emphasize that, unlike previously published works, our numerical results take structural deformation-induced changes in optical properties into account, making them trustworthy and practical. The proposed structure introduces a novel, to the best of our knowledge, approach for the dynamic control of light fields and has special properties that can be utilized for the realization of various integrated components.

Tailored fabrication of a self-rolled-up AlGaN/GaN tubular structure with photoelectrochemical etching.

Group III-nitride semiconductors with tubular structures offer significant potential across various applications, including optics, electronics, and chemical sensors. However, achieving tailored fabrication of these structures remains a challenge. In this study, we present a novel, to the best of our knowledge, method to fabricate micro-sized tubular structures by rolling the layered membrane of group III-nitride alloys utilizing the photoelectrochemical (PEC) etching. To customize the geometry of the tubular structure, we conducted an analytic calculation to predict the strain and deformation for the layered membrane. Based on the calculations, we designed and fabricated an AlGaN/GaN/InGaN/n-GaN/ sapphire structure using metal-organic chemical vapor deposition (MOCVD). Photolithography and PEC etching were employed to selectively etch the sacrificial InGaN layer. We investigated the changes of optical properties of the rolled-up structure by utilizing micro-photoluminescence (µ-PL) and micro-Raman spectroscopy.

Polymer dispersed cholesteric liquid crystals with combined photo- and mechanochromic response

The development of stimuli-sensitive systems is one of the newest and most promising directions in the field of modern materials science. The combination of various types of sensitivity in the same material opens the possibility of creating complex devices with a wide range of potential applications. This work deals with the design and preparation of new composite materials based on plasticized polyvinyl alcohol (PVA) films containing droplets of cholesteric liquid crystals (CLC). Mechanical stretching of elastic composite films results in a change in optical properties, namely selective light reflection (SLR), from CLC droplets. This in turn transforms the structure and optical properties of the entire polymer matrix. Such a process represents a certain mechano-optic response of the polymer matrix to the influence of mechanical deformation. The introduction of a chiral photochromic dopant into a composite film makes it possible to transform such a film into a photochromic material with the ability to control its optical properties using, for example, UV irradiation. Therefore, mechanical deformation of a polymer composite leads to a change in its optical properties (SLR) caused by a change chiral supramolecular structure of cholesteric mesophase. At the same time, UV irradiation of a polymer film induces E-Z isomerization process in the chiral photochromic dopant, altering its molecular shape and helical twisting power. This enables the using of this process for remote and contactless control of the composite optical properties. In addition, this feature allows one to implement the photopatterning and the recording of a latent image, which appears under the influence of a mechanical field.

Naturalization of treated wastewater by a constructed wetland in a water-scarce Mediterranean region

The effluents from conventional wastewater treatment plants (WWTP), even if accomplishing quality regulations, substantially differ in their characteristics with those of waters in natural environments. Constructed wetlands (CWs) serve as transitional ecosystems within WWTPs, mitigating these differences and restoring natural features before water is poured into the natural environment. Our study focused on an experimental surface-flow CW naturalizing the WWTP effluent in a semiarid area in Eastern Spain. Despite relatively low pollutant concentrations entering the CW, it effectively further reduced settled organic matter and nitrogen. Dissolved organic matter (DOM) reaching the CW was mainly protein-like, yet optical property changes in the DOM indicated increased humification, aromaticity, and stabilization as it flowed through the CW. Flow cytometry analysis revealed that the CW released less abundant but more active bacterial populations than those received. MiSeq Illumina sequencing highlighted changes in the prokaryotic community composition, with phyla Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria dominating the CW outflow. Functional prediction tools (FaproTax and PICRUSt2) demonstrated a shift towards microbial guilds aligned with those of the natural aquatic environments, increased aerobic chemoheterotrophs, photoautotrophs, and metabolic reactions at higher redox potentials. Enhanced capabilities for degrading plant material correlated well with changes in the DOM pool. Our findings emphasize the role of CWs in releasing biochemically stable DOM and functionally suited microbial populations for natural receiving environments. Consequently, we propose CWs as a naturalization nature-based solution (NBS) in water-scarce regions like the Mediterranean, where reclaimed discharged water can significantly contribute to ecosystem's water resources compared to natural flows.

A first-principles investigation of BF3 and ClF3 gas sensing on N-defected AlN nanosheets

We conducted theoretical calculations to examine the energetic stability of pristine aluminum nitride (AlN) and N-defected AlN nanosheets, along with their structural, electronic, and optical properties, utilizing density functional theory. Furthermore, we explored the adsorption properties of BF3 and ClF3 toxic gases on both pristine AlN and N-defected AlN nanosheets. Our findings reveal that the N-defect on the AlN nanosheet enhances the gas adsorption energies (−1.354 and −13.263 eV) compared to the pristine AlN nanosheet. Additionally, the absolute value of the bandgap for the N-defected AlN nanosheet increases to 3.032 eV, exceeding the 2.997 eV value of the pristine AlN nanosheet. The gas molecules suffer significant deformation due to their interaction with adsorbents. Upon BF3 gas adsorption, the bandgap of the N-defected AlN nanosheet diminishes to zero. Moreover, the recovery time after gas adsorption on the N-defected AlN nanosheet surpasses that of the pristine AlN nanosheet. Both adsorbents showed a high absorption coefficient of over 104 cm−1 in the UV region. Significant peak shifting in the optical spectra of the N-defected AlN nanosheet was observed due to gas adsorption. The pronounced changes in structural, electronic, and optical properties following toxic gas adsorption suggest that N-defected AlN nanosheets are suitable for the adsorption (dissociation) of BF3 (ClF3) gases.

Unveiling the optical, electrical, and thermodynamic properties of γ-(Cs, Rb)PbBr3

The all-inorganic perovskite CsPbBr3 has garnered significant attention in the fields of optoelectronic devices owing to its favorable bandgap. However, CsPbBr3 undergoes polymorphic phase transitions, existing in three light-active phases: Pbnm (γ), P4/mbm (β), and Pm-3m (α). Although extensive investigations have been conducted on the α-phase, the room-temperature γ-phase has received limited investigation. The present work explores the thermodynamic properties and optoelectronic characteristics of the (Cs, Rb)PbBr3 perovskite system by means of a combinatorial density-functional-theory (DFT) and CALPHAD method. An increase in Rb doping of CsPbBr3 induces structural distortion of γ-phase, resulting in a widened bandgap from 2.12 eV to 2.28 eV. The bandgap increase will eventually lead to changes in optical properties, such as poor absorptivity and energy consumption under high Rb doping. Moderate doping enables (Cs, Rb)PbBr3 to retain the excellent optical properties and energy consumption of CsPbBr3. Especially when Rb doping is 0.25, the solid solution has the lowest reflection coefficient. The thermodynamic phase diagram shows that the solid solution (Cs, Rb)PbBr3 maintains excellent thermodynamic stability. In addition, the phase diagram quantifies the temperature range of the γ-phase, α-phase, and coexistence of two phases, which provides the theoretical guidance for the preparation of (Cs, Rb)PbBr3 solid solution films in the future.

Black TiO2@Ag core-shell nanoparticles combined with WO3 nanorods on rGO nanosheets for PEC analysis

Well-coated black TiO2 and Ag core-shell nanoparticles (NPs) were prepared using a simple wet-chemical approach, which is combined with the WO3 nanorods over rGO nanosheets. The inherent properties of the composite nanostructures were examined thoroughly by diffuse reflectance spectroscopy, X-ray diffraction, Raman scattering, X-ray photoelectron spectroscopy, transmission electron microscopy, and photoelectrochemical (PEC) analysis. The formation of surface oxygen vacancies in the black TiO2 NPs facilitated tuning the optical properties in the visible region, which was enhanced by the surface plasmon resonance behavior of the Ag NPs. While combining the black TiO2@Ag core-shell NPs with intermediate bandgap WO3 nanorods and rGO nanosheets promoted PEC performance in the visible light irradiation. The composite nanostructure exhibited enhanced PEC efficiency (Jp=0.97 mAcm−2 and ABPE=0.62%) compared to the bare NPs. This work discusses the possible PEC mechanism based on the change in optical and structural properties.

Comparing the Effect of In2O3 and Eu2O3 Impurities on the Structural and Optical Properties of Cerium Oxide

This work compares the changes in optical and structural properties of cerium oxide (CeO2) when doped with different concentrations (3%,5%,7%, and 9%) of two oxides, In2O3 and Eu2O3. X-ray diffraction and spectrophotometry were employed in the visible, ultraviolet, and near-infrared regions. The findings demonstrated that CeO2 doped with In2O3 and Eu2O3 thin films were polycrystalline and had a cubic structure. The crystal size increased from 20.5 to 32.15 when Eu2O3 doping ratio increased from 0% to 7% and then decreased to 28.46 nm at 9%. While the crystal size showed an increase from 20.5 to 21.42 nm with the increase of the In2O3 doping ratio, while the lattice constant measured for cubic CeO2 changed opposite to that. The optical measurement showed that Eu2O3 and In2O3 doped CeO2 thin films have a direct band gap with allowed transition with 3.0 eV for the undoped CeO2. The band gap energy changed in a non-regular manner with the increase of the doping ratio of both oxides. The minimum band gap energy was 1.2 eV obtained for 7% Eu2O3 doped CeO2 thin film, and the minimum band gap energy was 1.4 eV obtained for 9% In2O3 doped CeO2. These results qualify them for use as absorbers in solar cell applications.

Investigation of the effect of amine and thiol as functional groups on gold Nanobipyramids properties

Metal nanoparticles are increasingly popular due to their unique properties, such as their vast surface area, tiny size, strong reactivity in live cells, and high-temperature stability. Gold nanoparticles, as one of the metal nanoparticle types, are frequently utilized in biosensor applications because of their adjustable Localized Surface Plasmon Resonance (LSPR) characteristics, less cytotoxic nature, and increased sensitivity to changes in the surrounding medium. The anisotropic metal nanoparticle of gold nanobipyramids (GNBPs) provides for higher Refractive Index Sensitivity (RIS) and Figure of Merit (FOM) value than others, allowing for higher sensitivity. This work lies in the comprehensive investigation of GNBPs functionalized with amine and thiol groups over varying shorter time durations (0.5 – 12 h) through the immediate change in optical, structural, morphological, electrical surfaces, and molecular properties. The findings show amine groups enable the red-shifted spectrum, whereas thiol groups impact the blue-shifted spectrum. By employing amine groups, it is able to produce side peaks in the XRD pattern made up of amine atoms. The use of thiol groups, meanwhile, has an impact on the growth increase in the (111) direction. Then, the highest surface density is obtained in 3 h, 59.78 % for amine-functionalized GNBPs (a-GNBPs) and 75.49 % for thiol-functionalized GNBPs (t-GNBPs). Next, a-GNBPs generate the highest angle slope compared to t-GNBPs, i.e., 140.422⁰. In addition, for the electrical surface effect, amine functionalization increases the zeta potential value from 0.3 to 2.5 mV, indicating the inhibition of nanoparticle agglomeration. On the other hand, thiol functionalization affects the decreasing of zeta potential value from 0.3 to -0.5 mV, allowing for nanoparticle agglomeration. Subsequent FTIR characterization analysis obtained shifts in the wave numbers, with the -OH bond exhibiting changes within the range of 3306.75 – 3269.95 cm-1, C=-CH bond providing for 2138.48 – 2136.56 cm-1 range, and the C = O bond showing alterations between 1637.59 – 1637.33 cm-1 following amine and thiol functionalization. Extended observation reveals that both a-GNBPs and t-GNBPs exhibit significant signal responses in glucose detection applications utilizing LSPR-based sensors, suggesting the feasibility of functionalizing GNBPs with amine and thiol groups for potential biosensor development.

A bacterial biosensor based on gold nanoparticles functionalized by a hydrophobin-chimera and combined with machine learning for user-friendly detection

A chimeric protein, in which a cationic antimicrobial peptide was fused to the adhesive self-assembling moiety of a fungal class I hydrophobin, was produced and used to easily functionalize gold nanoparticles (f-AuNPs). f-AuNPs are able to bind Escherichia coli and Staphylococcus epidermidis bacteria, tested as model organisms. A reverse colorimetric assay was then set up based on the induced aggregation of the free f-AuNPs. This leads to changes in optical properties of the solution, visible even by naked eyes. This approach allows detection of 10 CFU mL−1 of E. coli within 15 min and can be applicable to detect bacterial contamination in real matrices. Notably, the colorimetric variation was combined to machine-learning methodologies inferring data from photos of the colored solutions, acquired by smartphones. This fast, highly practical and flexible system, would enable on-site measurements and, therefore, help to prevent significant contaminations.