Range Of Spectrum Research Articles

A theoretical and computational model for the synergy of electrostriction and photovoltaic effect to create photostriction

The phenomenon of photostriction, which involves generating mechanical actuation in response to light, is observed in a very limited number of materials from ferroelectric, semiconductors, and organic material classes. This limited choice of materials, combined with their responsiveness to narrow light spectra, has constrained the broader adoption of photostriction in practical applications. This study introduces a novel approach by integrating photovoltaic and electrostrictive couplings in composites made of a photovoltaic matrix with ferroelectric inclusions, yielding an apparent photostrictive effect. By leveraging the simultaneous action of both photovoltaic and electrostrictive effects, the composite efficiently converts irradiated optical energy into mechanical energy, enabling mechanical actuation across a broader range of materials and light spectra. First, we develop a computational framework for intertwined multiphysics coupling of the photovoltaic effect with nonlinear electrostriction, based on a novel constitutive model. Then, to evaluate all the effective properties that define the composite's behavior, we introduce a multiphysics-coupled homogenization framework capable of computing elastic, electrostrictive, dielectric, and thermal properties. Finally, a shell finite element formulation based on the assumptions of first-order shear deformation theory is used to analyze the behavior of the homogenized photo-electrostrictive composite based actuator. This study demonstrates the feasibility of the proposed composite by examining the deflection response of structures laminated with this photostrictive composite. Several case studies are conducted to provide insights into the development and characterization of photo-electrostrictive composites, which hold great potential for applications in mechanical actuation, shape morphing, and beyond.

Analysis of Enhanced Optical and Electronic Properties of Bismuthene with Pd, Pt Adsorption for Advanced Optoelectronics

This study examines the nanostructures formed after the adsorption of palladium (Pd) and platinum (Pt) metals over bismuthene monolayer. It is emphasized that the adsorption of Pd and Pt significantly influences the optical absorption characteristics of bismuthene. The computational simulations based on density functional theory investigate how adding Pd and Pt metals to bismuthene changes its electronic and optical properties. Pure bismuthene displays substantial optical absorption, primarily in the visible region. When Pd and Pt atoms adsorb over the surface of bismuthene, the absorption coefficient value in the visible and near‐infrared region is enhanced with redshift. Adsorption of Pd and Pt also leads to significant changes in the dielectric constant and refractive index of bismuthene, with distinct peaks observed in the dielectric constant at lower energy after adsorption. Nanostructures composed of Pd/bismuthene and Pt/bismuthene have the potential to predict stable configurations, which makes them appropriate for the absorption of light in the visible and near‐infrared regions. Because of the stable and improved optical absorption accomplished in the desired range of the electromagnetic spectrum, these nanostructures can be utilized for a variety of applications, including but not limited to solar cells and photodetectors, as well as photovoltaics and IR sensor applications.

Comprehensive Study of Highly efficient Rb2AgInX6 (X = Cl, Br, I) based Lead-Free Double Perovskite Solar Cells

Abstract Lead-free Double Perovskite Solar Cells (DPSCs) have generated great study interest recently as a potential perovskite absorber layer, due to their cost-effectiveness, impressive stability, and superior performance. In this study, we investigated Rb2AgInX6(Cl, Br, I) based DPSCs using SCAPS-1D simulation software. Various properties, such as the density of states for conduction and valance bands, carrier concentration, and carrier mobility (electrons and holes), were calculated for simulation. Furthermore, we have optimized defect density, electron affinity, and thickness of absorber layers for Rb2AgInX6-based DPSCs. We investigated how DPSC parameters were impacted by operating temperature and then performed band gap tuning for Rb2AgInBr6-based DPSC along with their temperature stability. Tandem solar cells (TSC) have had an enormous influence on the field of photovoltaics (PV) because of their ability to effectively use a wider range of solar spectrum and reduce unwanted energy loss. In this context, we have also simulated Rb2AgInBr6/Rb2AgInI6 based an all double perovskite tandem solar cells and optimized the same for future experimental applications. The optimized PCE of 12.14 %, 26.49 %, and 13.95 % were obtained for Rb2AgInX6(X=Cl, Br, I respectively) based DPSCs. In comparison, the PCE of 38.70 % was obtained for tandem structure.

Theoretical study on fused 1,2,3,4-tetrazine-1,3-dinitroxide derivatives under external electric field.

Considering the excellent properties of 1,2,3,4-tetrazine-1,3-dinitroxides, several types of energetic derivatives have been synthesized from them. Among them, [1,2,5] oxadiazolo [3,4-e] [1,2,3,4]-tetrazine-4,6-Di-N-dioxide (FTDO), 5,7-dinitrobenzo-1,2,3,4-tetrazine-1,3-nitrogen dioxide (DTND), and [1,2,3,4] tetrazino [5,6-e] [1,2,3,4] tetrazine-1,3,8-tetraoxide (TTTO) are considered excellent energetic materials. However, there is limited research on their behavior under electric fields. The effect of electric fields was studied using density functional theory to calculate trigger bond changes, strain energy, chemical reactivity, and surface electrostatic potential. The results indicate that the planar structure of FTDO is more unique than that of DTND and TTTO, and its trigger bond is located at special position. Increased electric field strength can lengthen the trigger bond, increase sensitivity, and reduce strain energy of FTDO. Under a positive electric field, DTND and TTTO have longer trigger bond lengths, increased sensitivity, and increased strain energy, while exhibiting the opposite behavior under a negative electric field. Electric fields can affect the chemical reactivity of the all three derivatives. FTDO is less active under positive electric fields, DTND is more active under both electric fields, and TTTO becomes more active under negative electric fields. Finally, the electric field can expand their absorption spectrum range, affecting electron transfer between fragments. All calculations in this article were completed on Gaussian 16 software. The calculation levels are B3LYP/6-311G**, B3LYP/Def2-TZVPP, and PBE1PBE/6-311G**. Multiwfn and VMD were used for wave function analysis. Electric fields have a strength range of - 0.02 to 0.02 a.u., with a growth gradient of 0.01 a.u.

Vision transformer based cut interruption detection and prediction of laser fusion cutting from monitored melt pool images

Incomplete cuts during laser fusion cutting result in a closed kerf, preventing the workpiece from detaching from the sheet and resulting in rework or rejection. We demonstrate the approach of a vision transformer, used for image classification, to detect cut interruption during laser fusion cutting in steel and aluminum. With events impending an incomplete cut in steel, we attempt to predict cut interruption before they even occur. To build a data set for training, cutting experiments are carried out with a 4 kW fiber laser, forcing incomplete cuts by varying the process parameters such as laser power and feed rate. The thermal radiation from the process zone during the cutting process is captured with a size of 256 × 256 px2 at sample rates of 20 × 103 fps. The kerf is recorded with a spectral sensitivity between 400 and 700 nm, without external illumination, which enables the melt to be observed in the range of the visual spectrum. The vision transformer model, which is used for image classification, splits the image into patches, linearly embedded with an added position embedding, and fed to a standard transformer encoder. For training the model, a set of images was labeled for the respective classes of a complete, incomplete, and impending incomplete cut. With the trained model, incomplete cuts in steel and aluminum can then be recognized and impending incomplete cuts in steel can be predicted in advance.

Nanoscale Effects in the Room-Temperature UV-Visible Photoluminescence from Silica Particles and Its Cancer Cell Imaging.

Silica nano/microparticles have generated significant interest for the past decades, emerging as a versatile material with a wide range of applications in photonic crystals, bioimaging, chemical sensors, and catalysis. This study focused on synthesizing silica nano/microparticles ranging from 20 nm to 1.2 μm using the Stöber and modified Stöber methods. The particles exhibited photoluminescence emission across a UV-visible range, specifically in the UV (∼290, ∼327, ∼339, and ∼377 nm), blue (∼450 nm), green (∼500 nm), yellow (∼576 nm), and red (∼634 nm) range of the electromagnetic spectrum. These emissions are due to radiative relaxation processes involving oxygen-deficient centers arising due to unrelaxed oxygen vacancies, strong interacting surface silanols, 2-fold coordinated silicon, self-trapped excitons, hydrogen-related species, strain-induced defects, and nonbridging oxygen hole centers excited via two-photon and single photon absorption. The increased PL intensity with a decreasing particle size was attributed to higher concentrations of defect sites in the case of smaller-sized particles. The MTT assay, AO/EB staining, and the DCFDA assay confirmed the biocompatible nature of silica particles in the HepG2 cell line. In addition, the cell viability assay in a normal cell line (HEK293) also showed no substantial cell death. Successful bioimaging of HepG2 cells was performed with silica nano/microparticles, which exhibited blue and green fluorescence, along with Hoechst33258 dye. Even though 20 nm-sized silica particles showed higher PL emission, particles sized above 20 nm showed better fluorescence in HepG2 cells, citing their potential in in vitro bioimaging applications.

Gain performance of Nd-doped fiber in the range of 1050–1140 nm

In this work, we present the gain characteristics of a Nd-doped fiber (NDF) obtained through fiber amplification. The NDFs used include a highly doped 30/125 fiber and a low-doped 20/125 fiber. It was found that the gain spectrum range of the NDF can cover 1050–1140 nm. The main gain region was 1060–1135 nm, providing over 500 times small-signal amplification, with the laser peak energy ratio reaching 80% or more. At the long-wavelength edge of 1140 nm with a 50 mW seed injection, a 2.5 W output can be obtained, corresponding to an amplification factor of 50. The excellent gain performance will greatly change our traditional impressions of NDF and provide new insights for research on high-gain fiber materials in 1.1 µm fiber lasers.

In-situ Raman Investigation on the Phase Transition of Grunerite at High Pressure

Abstract Amphiboles are key rock-forming minerals and play a significant role in the subduction process. Grunerite (Mg,Fe)7Si8O22(OH)2, as an important ferromagnesian amphibole, is known to undergo a phase transition from monoclinic C2/m to P21/m structure at elevated pressures. This study investigates the phase transition of grunerite under high pressure using a diamond anvil cell combined with in-situ Raman spectroscopy, aiming to identify pressure-induced phase transitions and associated structural changes. We have identified mode splits of the OH stretching modes indicative of the C2/m to P21/m phase transition at ∼1.46 GPa and observed another possible phase transition suggested by discontinuity in the OH modes at ∼17.81 GPa. The splitting of the OH stretching modes resulted from the distinct environments of two OH positions in the P21/m phase, in comparison to the crystallographically identical OH positions in the C2/m phase. We have also identified additional M–O modes in the lower-wavenumber spectrum range. The results provide new insights into the structural stability of grunerite under extreme geological conditions, contributing to a deeper understanding of metamorphic petrology and geodynamics.

Artificial neural network detection of pancreatic cancer from proton (1H) magnetic resonance spectroscopy patterns of plasma metabolites

BackgroundRoutine screening to detect silent but deadly cancers such as pancreatic ductal adenocarcinoma (PDAC) can significantly improve survival, creating an important need for a convenient screening test. High-resolution proton (1H) magnetic resonance spectroscopy (MRS) of plasma identifies circulating metabolites that can allow detection of cancers such as PDAC that have highly dysregulated metabolism.MethodsWe first acquired 1H MR spectra of human plasma samples classified as normal, benign pancreatic disease and malignant (PDAC). We next trained a system of artificial neural networks (ANNs) to process and discriminate these three classes using the full spectrum range and resolution of the acquired spectral data. We then identified and ranked spectral regions that played a salient role in the discrimination to provide interpretability of the results. We tested the accuracy of the ANN performance using blinded plasma samples.ResultsWe show that our ANN approach yields, in a cross validation-based training of 170 samples, a sensitivity and a specificity of 100% for malignant versus non-malignant (normal and disease combined) discrimination. The trained ANNs achieve a sensitivity and specificity of 87.5% and 93.1% respectively (AUC: ROC = 0.931, P-R = 0.854), with 45 blinded plasma samples. Further, we show that the salient spectral regions of the ANN discrimination correspond to metabolites of known importance for their role in cancers.ConclusionsOur results demonstrate that the ANN approach presented here can identify PDAC from 1H MR plasma spectra to provide a convenient plasma-based assay for population-level screening of PDAC. The ANN approach can be suitably expanded to detect other cancers with metabolic dysregulation.

Photodetectors of the Short-Wave IR Spectrum Range, Intended for Space Monitoring

Photodetectors of the Short-Wave IR Spectrum Range, Intended for Space Monitoring

The Radio Fundamental Catalog. I. Astrometry

We present an all-sky catalog of absolute positions and estimates of correlated flux density of 21,942 compact radio sources determined from processing interferometric visibility data of virtually all very long baseline interferometry (VLBI) observing sessions at 2–23 GHz from 72 programs suitable for absolute astrometry collected for 30 yr. We used a novel technique of generation of a data set of fused observables that allowed us to incorporate all available data in our analysis. The catalog is the most complete and most precise to date. It forms the foundation and reference for positional astronomy, space geodesy, space navigation, and population analysis of active galactic nuclei (AGNs), and provides calibrators for phase referencing for differential astrometry and VLBI astrophysical observations. Its accuracy was evaluated through a detailed accounting of systematic errors, rigorous decimation tests, comparison of different data sets, and comparison with other catalogs. The catalog preferentially samples AGNs with strong contemporary parsec-scale synchrotron emission. Its milliarcsecond-level positional accuracy allows association of these AGNs with detections in a wide range of the electromagnetic spectrum from low-frequency radio to γ rays and high-energy neutrinos. We describe the innovative data processing and calibration technique in full detail, report the in depth analysis of random and systematic positional errors, and provide a list of associations with large surveys at different wavelengths.

Structural and luminescent properties of a Cr3+/Sm3+ doped GdAlO3 orthorhombic perovskite for solid-state lighting applications.

The Cr3+ and Sm3+ doped GdAlO3 perovskite with formula Gd0.995Sm0.005Al0.995Cr0.005O3, was synthesized via a solid-state reaction method, and its structure, morphology, and photoluminescence properties were thoroughly investigated. The compound crystallizes in the orthorhombic Pbnm space group, with Cr3+ transition-metal ions substituting Al3+ in the octahedral symmetry site, and Sm3+ lanthanide (rare-earth) ions occupying the tetrahedral site. The material's morphology and chemical composition homogeneity were evaluated through Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis. Photoluminescence excitation (PLE) and emission spectra (PL) were used to shed light on the electronic structure of the Cr3+ cations, through crystal field analysis in the O h symmetry site. Theoretical studies enabled the precise assignment of the Cr3+ 3d-3d transitions. The intra-configurational 4f-4f transitions of Sm3+ resulted in a variety of excitation bands appearing in the high-wavelength range of the PLE spectrum. The photoluminescence studies supported the occurrence of energy transfer in the doped GdAlO3 perovskite between Gd3+, Sm3+ and Cr3+ ions. The obtained results suggest the high potential of the synthesized material for solid state lighting applications.

Ferrofluid‐Assisted Dynamic Metasurface 3D Holography Endowed With Rapid, Linear, and High‐Contrast Color Modulation

AbstractMetasurface holography offers a highly promising approach for naked‐eye, full‐color, 3D displays. However, the natural static structure and material of the metasurface limit its ability to dynamically regulate the light field, posing a challenge for achieving photorealistic 3D holography. Here, a ferrofluid‐assisted dynamic metasurface is first demonstrated, conducting a 3D holography endowed with rapid, linear, and high‐contrast color modulation. The ferrofluid has nano‐structural control properties (flow behavior of nanoparticles and emulsion) that enable dynamic manipulation of the extinction (absorption and scattering) intensity in micron region across a broadband spectrum range (400–850 nm). By integrating the ferrofluid with a broadband metasurface, a novel dynamic meta‐hologram is created, which can not only regulate both amplitude and phase of the light field under a single wavelength laser but also in situ linearly changing the color of holographic images under multi‐wavelength lasers. This method provides a new perspective for implementing dynamic metasurface 3D holography capable of continuous color response.

Amplified spontaneous emission and photoresponse characteristics in highly defect tolerant CsPbCl x Br3−x crystal

All inorganic perovskite CsPbX3 with excellent optical properties and a tunable bandgap is a potential candidate for optoelectronic applications, and the amplified spontaneous emission (ASE) is normally reported in low-dimensional structures where the quantum confinement enhances ASE. Herein, we not only demonstrate the ASE in millimeter size CsPbCl x Br3−x crystal with a high defect concentration, but also tune the emission wavelength from the green band to blue band through the ion exchange of Br with Cl. The ASE centered at ∼456 nm is probed at 50 K with a threshold of 106 μJ/cm2. Furthermore, a metal-semiconductor-metal (MSM) structure CsPbCl x Br3−x photodetector is fabricated and shows a distinct response to lights from UV to the blue band; the response spectrum range is quite different from the narrow band (∼30 nm) response of the CsPbBr3 photodetector induced by a charge collection narrowing (CCN) mechanism. The CsPbCl x Br3−x photodetector also exhibits fast response speeds with a rise time of 96 μs and a decay time of 34 μs, indicating the defects have limited influence on the transportation speed of the photo-generated carriers.

Growth‐Based Analyte and Bioanalyte Sensing Applications Using Noble Metal Nanoparticles: Effect of Nanoparticle Growth on the Localized Surface Plasmon Resonance Signal

Noble metal (gold and silver) nanoparticles have found a range of applications as sensors and biosensors. These applications utilize the nanoparticles’ tunable optical properties within the visible range of the electromagnetic spectrum, which originate from localized surface plasmon resonance. Recent applications have focused on analyte and bioanalyte detection through nanoparticle growth while successfully achieving low detection limits. This review focuses on theoretical and empirical models used to quantify and/or optimize the localized surface plasmon resonance response to nanoparticle growth, with representative examples from the literature. The effect of nanoparticle growth on the localized surface plasmon resonance signal in monometallic nanoparticles, bimetallic core‐shell nanoparticles, and monometallic nanoshells will be discussed, including spherical, spheroidal and non‐spheroidal nanoparticle shapes. 1. Introduction 1. Introduction

Ion Intercalation‐Enabled Reconfigurable Photodetector with Low Programming Voltage and Broadband Response Based on Van Der Waals Tin Disulfide

AbstractArtificial neural networks with integrated sensing and computing capabilities, leveraging reconfigurable optoelectronics, can effectively emulate biological neural networks, thereby enabling rapid and efficient information processing. However, realizing reconfigurable photoresponsivity is often blocked by the requirement for high programming voltages and the limits of the detection spectrum range. This greatly restricts the progress of energy‐efficient and precise neuromorphic vision sensing. Herein, a reconfigurable photodetector with low programming voltage and broadband response is presented via in situ intercalation of Cu+ ions into the van der Waals (vdW) gaps of thermoelectric 2D material SnS2. Interestingly, the vdW gaps provide an ionic transport channel with lower energy barriers compared to oxide‐based memristors, resulting in a low programming voltage (0.5 V). Furthermore, reversible conversion of photo‐detection is achieved from photovoltaic to photo‐thermoelectric (PTE) mode via voltage‐controlled ion distribution, which modulates the phonon scattering rate in the neighboring SnS2 layer. As a result, the response spectrum switches from visible (532 nm) to long‐wave infrared (10 µm) with an on/off ratio as high as 104. Thus, dual‐mode conversion and broadband detection functionality in reconfigurable imaging are realized, suggesting a potential pathway for the development of highly energy‐efficient reconfigurable optoelectronics with a spectrum far beyond human vision.

Contamination in Exoplanet Transit Spectroscopy with a Changing Stellar Surface

Abstract Inhomogeneities in the stellar surface can lead to differences between the actual and assumed stellar spectrum below the planet’s transit chord, causing the inferred planet transmission spectrum to have a contamination component. In this study, we present a simple analytical formula for calculating the contamination spectrum in transmission spectroscopy, taking into consideration the variable spot coverage fraction or spot occultation. We took the temperate sub-Neptune, K2-18 b, as an example to demonstrate the range of the possible contamination spectra under fiducial spot coverage and variability assumptions, which is typically around a few to 15%, which is considerably more than when surface changes were ignored, illustrating the importance of considering these higher-order effects in exoplanet transmission spectroscopic observations.

Concentration vs. Optical Density of ESKAPEE Bacteria: A Method to Determine the Optimum Measurement Wavelength.

Optical density measurement has been used for decades to determine the microorganism concentration and more rarely for mammalian cells. Although this measurement can be carried out at any wavelength, studies report a limited number of measurement wavelengths, mainly around 600 nm, and no consensus seems to be emerging to propose an objective method for determining the optimum measurement wavelength for each microorganism. In this article, we propose a method for analyzing the absorbance spectra of ESKAPEE bacteria and determining the optimum measurement wavelength for each of them. The method is based on the analysis of the signal-to-noise ratio of the relationships between concentrations and optical densities when the measurement wavelength varies over the entire spectral range of the absorbance spectra measured for each bacterium. These optimum wavelengths range from 612 nm for Enterococcus faecium to 705 nm for Acinetobacter baumannii. The method can be directly applied to any bacteria, any culture method, and also to any biochemical substance with an absorbance spectrum without any particular feature such as an identified maximum.

Improved piezoelectric energy harvester with dual-impact strategy for small acceleration amplitude vibrations

Increasing the operable frequency range and improving the small acceleration amplitude harvesting performance of the piezoelectric energy harvesting devices is importance due to the wide frequency spectrum and large amplitude range of environmental vibrations. In this Letter, an improved piezoelectric energy harvester with frequency upconversion is proposed, which is comprised of a composite piezoelectric beam and a firing pin. In contrast to the conventional impact-based systems that mainly rely on beam vibrations to enhance harvesting performance, the proposed system employs a dual-impact strategy. In particular, an oblique impact-based harvesting phenomenon is observed, which has not been investigated in previous studies. A multilevel impact nonlinear coupled dynamic model is developed. The experimental results indicate that at an excitation acceleration amplitude of 0.15 g, the proposed system demonstrates a 482.9% increase in the output peak value and introduces dual-band frequency in comparison with the conventional structure. Additionally, the proposed coupled model is validated through adjustments to various load resistances. The highest output power is achieved at a load resistance of 210 kΩ, with the maximum average power reaching 3.96 mW and a power density of 1.59 mW/mm3g2 at an acceleration amplitude of 0.15 g, outperforming other piezoelectric energy harvesters.

One‐Step Fabrication of Carbon Dot‐Based Nanocomposites Powering Solid‐State Random Lasing

Carbon dots (CDs) have attracted much attention for applications in photonics and optoelectronics because of their high emission efficiency and ease of synthesis. Although studies in solution are well established, solid‐state applications are less common because of optical quenching phenomena that critically affect CDs. Herein, the synthesis of amorphous CDs from citric acid, operating as hosts of dye molecules, and their incorporation into organic–inorganic silica matrices through a fast photo‐induced polymerization process are reported. The photocurable sol composition allows easy dispersion of nanometer‐sized scattering centers, such as titania or gold nanoparticles (NPs), which have been incorporated, along with CDs, into nanocomposites. The combination of high‐brightness CDs and nanoscatterers in the hybrid matrices allows for achieving and investigating the random lasing processes occurring in the orange‐red range of the visible spectrum. In situ‐grown gold NPs contribute to a significant improvement in solid‐state lasing, enabling an emission as narrow as 5 nm and a laser threshold as low as 0.3 mJ pulse−1. The present approach reveals the technological and scientific potential of CDs when embedded in solid‐state disordered active media.