Optical Absorption Properties Research Articles

Optical properties and tunable luminescence of Ce3+/Dy3+ doped lithium borate glasses for photonic applications

Optical absorption and photoluminescence properties of novel lithium borate glasses, (B2O3)-(MO)-(Li2O)–(Bi2O3) where M stands for Ca, Mg or Sr, doped with Dy and Ce ions have been investigated. The fundamental optical absorption edge of these materials is observed in the region of 315–390 nm, and depends on the nature of alkaline-earth metals used as network modifiers. The photoluminescence spectra of Dy-doped glasses reveal two intensive emission bands in the visible range, which correspond to 4F9/2→6H15/2 (486 nm) and 4F9/2→6H13/2 (580 nm) transitions of Dy3+ ions. Ce-doped glasses show one broad band in the visible range, which corresponds to the 2D →2F5/2 (340 nm) transition of Ce3+ ions. Three photoluminescence lines (980 nm, 1010 nm and 1150 nm) attributed to the Dy3+ ions electronic transitions are observed in the near-IR region of the spectrum for Dy-doped glasses, while only one at 1150 nm is observed for the Dy/Ce co-doped glasses. Peculiarities of excitation energy transfer between rare-earth activator ions are discussed. These glasses are shown to be a promising host matrix for rare-earth doping.

An Interfacial Material with Low Trap Density Enables Efficient Organic Photovoltaic Cells for Multi‐Scene Applications

AbstractOrganic photovoltaic (OPV) cells have great potential in multi‐scene applications because of their easily tunable optical absorption properties. However, the lagging development of the interlayer material limits the practicality of OPV cells. Herein, a naphthalene diimide‐based polymer cathode interlayer named PNDI‐Br is reported. The suitable energy level and improved light utilization enable the PNDI‐Br‐based cells to achieve a high power conversion efficiency of 18.7% under the illumination of AM 1.5G, representing the highest efficiency of inverted OPV cells. Under continuous illumination, PNDI‐Br‐based OPV cells can maintain an efficiency of over 80% after 1000 h, which reveals excellent stability of the cells. Furthermore, the decreased trap density and charge accumulation of PNDI‐Br‐based OPV cells results in limited charge recombination, which enables the cells to obtain a high fill factor and a low voltage loss in multi‐lighting conditions. This work provides a stimulus for multi‐scene applications of OPV cells.

High Carrier Mobility and Controllable Electronic Property of the h-BN/SnSe2 Heterostructure.

Building two-dimensional (2D) vertical van der Waals heterostructures (vdWHs) is one of the effective methods to regulate the properties of single 2D materials. In this paper, we stack the hexagonal boron nitride (h-BN) monolayer (ML) on the SnSe2 ML to construct the stable h-BN/SnSe2 vdWH, of which the crystal and electronic structures, together with the optical properties, are also analyzed by the first-principles calculations. The results show that the h-BN/SnSe2 vdWH belongs to a type-I heterostructure with an indirect bandgap of 1.33 eV, in which the valence band maximum and conduction band minimum are both determined by the component SnSe2 ML. Interestingly, the h-BN/SnSe2 vdWH under the tensile strain or electric field undergoes the transitions both from type-I to type-II heterostructure and from the indirect to direct bandgap semiconductor. In addition, the carrier mobility of the h-BN/SnSe2 heterostructure has a significant enhancement relative to that of the SnSe2 ML, up to 104 cm2 V-1 s-1. Meanwhile, the h-BN/SnSe2 heterostructure presents the superb optical absorption and unique type-II hyperbolic property. Our findings will broaden the potential applications of SnSe2 ML and provide theoretical guidance for the related experimental studies.

The Morphologically Controlled Synthesis and Application of Mesoporous Alumina Spheres.

The control of alumina morphology is crucial yet challenging for its various applications. Unfortunately, traditional methods for preparing alumina particles suffer from several limitations such as irregular morphology, poor dispersibility, and restricted application areas. In this study, we develop a novel method for preparing spherical mesoporous alumina using chitin and Pluronic P123 as mixed templates. The effects of reaction temperature, time, and the addition of mixed templates on the phase structure, micromorphology, and optical absorption properties of the samples were investigated. The experimental results indicate that lower temperature and shorter reaction time facilitated the formation of spherical mesoporous alumina with excellent CO2 adsorption capacity. The periodic density functional theory (DFT) calculations demonstrate that both the (110) and (100) surfaces of γ-Al2O3 can strongly adsorb CO2. The difference in the amount of CO2 adsorbed by Al2O3 is mainly due to the different surface areas, which give different numbers of exposed active sites. This approach introduces a novel strategy for utilizing biological compounds to synthesize spherical alumina and greatly enhances mesoporous alumina's application efficiency in adsorption fields. Moreover, this study explored the electrochemical performance of the synthesized product using cyclic voltammetry, and improved loading of electrocatalysts and enhanced electrocatalytic activity were discovered.

Dual function of new Nd(III) and Gd(III) complexes for cytotoxic and optoelectronic fields: Synthesis, characterization, DFT calculations, and PVA composite films

New two lanthanide complexes of Neodymium (III) and Gadolinium (III) ions were prepared based on 2‐Cyano‐N′‐([4‐oxo‐4H‐chromen‐3‐yl]methylene) acetohydrazide as a chelating agent. The prepared Nd(III) and Gd(III) complexes were characterized via elemental analysis, molecular conductance, IR, and TGA. The obtained results showed the chelating agent behaves as tridentate via oxygen of γ pyrone and carbonyl groups and nitrogen of the azomethine group. The antitumor activity of isolated complexes was investigated against the Ehrlich Ascites Carcinoma cell line (E.A.C). The results of antitumor activity cleared that Gd(III) complex has higher activity than Nd(III) complex and moderate activity relative to cisplatin and 5‐Furacil. Besides, DFT calculations were estimated for prepared Nd(III) and Gd(III) complexes by the Gaussian program. Theoretical parameters were calculated. The energy gap values confirmed the higher activity of the Gd(III) complex over the other Nd(III) complex. In addition, the composite films of Nd(III) and Gd(III) complexes were prepared using the cast technique. The electrical and optical absorption properties of these polymer composites were analyzed.

Structural, Optical, and Electromagnetic Microwave Absorption Properties of Bael Leaves: A Simple Approach to Investigate Microwave Absorption Properties with 3D Printed PLA Tubes

Structural, Optical, and Electromagnetic Microwave Absorption Properties of Bael Leaves: A Simple Approach to Investigate Microwave Absorption Properties with 3D Printed PLA Tubes

Photogenerated cathodic protection properties of Fe2O3 nanotubes prepared by anodic oxidation

Photogenerated cathodic protection as a new type of corrosion protection method has evoked great attention. The n-type semiconductor is normally selected as the photogenerated cathodic protection composite. α-Fe2O3 is a typical n-type semiconductor, which is easy to obtain and environmental-friendly. However, it is normally prepared on the FTO substrate and could hardly protect carbon steel. In this study, α-Fe2O3 nanotubes are fabricated on carbon steel by anodic oxidation method at different oxidation potentials. The corresponding surface morphologies, compositions, and optical absorption properties are characterized with SEM, Raman spectroscopy, and UV-Visible spectrometer. The photoelectrochemical tests show that the prepared α-Fe2O3 can supply cathodic protection to carbon steel. The maximum photogenerated potential drop is obtained for the α-Fe2O3 sample prepared under 50 V at 30 ℃ for 450 s anodic oxidation. It is revealed that the fine structure is benefit to capture light and enhances the photogenerated cathodic protection performance to carbon steel.

Disorder effect on intersubband optical absorption of n-type δ-doped quantum well in GaAs

The inevitable structural disorder associated with the fluctuation of the applied external electric field, laser intensity, and bidimensional density in the low dimensional quantum system can affect noticeably optical absorption properties and the related phenomena. In this work, we study the effect of structural disorder on the optical absorption properties in delta-doped quantum wells (DDQWs). Starting from effective mass approximation and the Thomas-Fermi approach as well as using the matrix density, the electronic structure and the optical absorption coefficients of DDQWs are determined. It is found that the optical absorption properties depend on the strength and the type of structural disorder. Particularly, the bidimensional density disorder suppresses strongly the optical properties. Whilst, the disordered external applied electric field fluctuates moderately in the properties. In contrast, the disordered laser holds absorption properties unalterable. So, our results specify that to have and preserve good optical absorption properties in DDQWs, requires precise control of the bidimensional. Besides, the finding may improve the understanding of the impact of the disorder on the optoelectronic properties based on DDQWs.

Optimized photocatalytic performance of ZnS-SnO2 heterostructures for visible light driven mineralization of Acid violet 7 dye and inactivation of bacteria

The present study aims to decipher the defect-induced photocatalytic activity of ZnS-SnO2 heterostructure for visible light-assisted oxidative mineralization of Acid Violet 7 dye (AV7) and Escherichia coli (E. coli) bacterial disinfection. The prepared ZnS-SnO2 (60ZS) heterostructure/nanocomposite catalysts show improved optical and visible light absorption properties. Photoluminescence findings reveal the existence of defect energy levels/surface states associated with 60ZS heterostructure catalysts. Photo/Electrochemical studies show improved photocurrent response, high capacitance, lower charge transfer resistance, and improved charge-discharge behaviour in 60ZS heterostructure catalysts compared to individual components. The improved photocatalytic performance of 60ZS heterostructure is ascribed to the interactive effect of a reduction in the band gap, improved surface area, and enhanced lifetime of photogenerated charge carriers. The major reactive species that cause the degradation reaction have been identified, and a plausible AV7 dye degradation pathway has been proposed. The 60ZS heterostructure catalyst exhibits good stability and a recycled nature.

Sol-gel synthesis and characterization of neodymium orthoferrite for disposing oily wastewater

The aim of this study was to design and characterize a NdFeO3-based photocatalyst prepared by sol-gel method for treatment of oily wastewater. Different characterization techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), UV–vis spectrophometer were used to elucidate the structure, morphology, surface functional groups, and optical absorption properties of the prepared NdFeO3 photocatalyst. The photo-Fenton degradation performance of the as-prepared NdFeO3 photocatalyst was investigated by degrading oily-containing wastewater under visible light irradiation. The NdFeO3 photocatalyst manifests the high chemical oxygen demand (COD) removal efficiency of 97.6 % for 120 min reaction) thanks to its narrow band gap energy and high crystalline degree.

Self-Powered Sb2Te3/MoS2 Heterojunction Broadband Photodetector on Flexible Substrate from Visible to Near Infrared

Van der Waals (vdWs) heterostructures, assembled by stacking of two-dimensional (2D) crystal layers, have emerged as a promising new material system for high-performance optoelectronic applications, such as thin film transistors, photodetectors, and light-emitters. In this study, we showcase an innovative device that leverages strain-tuning capabilities, utilizing a MoS2/Sb2Te3 vdWs p-n heterojunction architecture designed explicitly for photodetection across the visible to near-infrared spectrum. These heterojunction devices provide ultra-low dark currents as small as 4.3 pA, a robust photoresponsivity of 0.12 A W−1, and reasonable response times characterized by rising and falling durations of 0.197 s and 0.138 s, respectively. These novel devices exhibit remarkable tunability under the application of compressive strain up to 0.3%. The introduction of strain at the heterojunction interface influences the bandgap of the materials, resulting in a significant alteration of the heterojunction’s band structure. This subsequently shifts the detector’s optical absorption properties. The proposed strategy of strain-induced engineering of the stacked 2D crystal materials allows the tuning of the electronic and optical properties of the device. Such a technique enables fine-tuning of the optoelectronic performance of vdWs devices, paving the way for tunable high-performance, low-power consumption applications. This development also holds significant potential for applications in wearable sensor technology and flexible electro-optic circuits.

Mimicking evasive behavior in wavelength‐dependent reconfigurable phototransistors with ultralow power consumption

AbstractRetinal‐inspired synaptic phototransistors, which integrate light signal detection, preprocessing, and memory functions, show promising applications in artificial vision sensors. In recent years, it has been reported to construct heterojunction in phototransistors to realize positive photoconductance (PPC) and negative photoconductance (NPC) modulations, thereby achieving visible and infrared wavelength discrimination and various visual functions. However, relatively little attention has been paid to wavelength‐dependent switching and reconfigurability between two states (PPC and NPC), limiting further applications for complex simulations of biological visual functions. Here, a mixed organic–inorganic heterojunction synaptic phototransistor was constructed by integrating CsPbBr3 nanoplates (NPLs) with strong blue‐light absorption and poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) with strong red‐light absorption. Compared with the three‐dimensional (3D) structure CsPbBr3 nanocubes (NCs), the two‐dimensional (2D) CsPbBr3 NPLs exhibited more efficient charge transfer with P3HT. Based on the individual optical absorption properties in organic–inorganic heterojunction, the device exhibited wavelength‐selective and reconfigurable behavior between PPC and NPC. A low power consumption of 0.053 fJ per synaptic event was achieved, which is comparable to a biological synapse. Finally, Drosophila's evasive behavior to food under red and blue light can be successfully demonstrated. This work demonstrates the future potential of synaptic phototransistors for visuomorphic computing.

First-principles calculations to investigate optoelectronic and thermodynamic properties of new 1T’-RuOsSe2 hybrid monolayer

The electronic band structure, density of states, optical absorption, phonon spectrum, stability, and thermodynamic properties of 1T’-phase RuOsSe2 hybrid monolayer were systematically studied using ab initio calculations based on Density Functional Theory (DFT) and Density Functional Perturbation Theory (DFPT) within the generalized gradient approximation (GGA) and the HSE06 functional of hybrid correlation–exchange. Indirect bandgaps [Formula: see text][Formula: see text]eV and [Formula: see text][Formula: see text]eV were obtained within the calculation level GGA-PBE and HSE06. The investigation of optical absorption shows that the RuOsSe2 monolayer exhibits a significant absorption in the ultraviolet and visible regions of the electromagnetic spectrum. Thermodynamic potentials and specific heat at constant volume were calculated, of which dependence on the temperature is discussed. We predict a new RuOsSe2 monolayer from the 1T’ phase that could potentially be synthesized for future electronic devices and bring potential technological applications.

The construction of TiO2 NTs/Ag3PO4–AgBr by SILAR deposition as promising photocatalysts for hydrogen production and pollutant treatment

The construction of ternary TiO2 NTs/Ag3PO4–AgBr photocatalysts was carried out by the SILAR deposition of Ag3PO4 and AgBr on TiO2 nanotube arrays (TiO2 NTs) for enhancing the photocatalytic application in H2 evolution and dyeing wastewater remediation. The adjustment of Ag3PO4/AgBr deposition cycles was used to optimize the optical absorption and photocatalytic property. The TiO2 NTs/Ag3PO4–AgBr (5) prepared with 5 cycle deposition of Ag3PO4 and AgBr exhibited the optimal photoelectric activity and photocatalytic performances. The photocatalytic rate constants for the degradation of MO, RhB and MB dyes achieved 1.35 × 10−2, 3.30 × 10−2 and 4.47 × 10−2 min−1, respectively, and the visible light-driven photocatalytic H2 evolution rate achieves 46.87 μmol cm−2 h−1. •O2− radicals exhibited the key influence on the organic dye degradation, and the as-prepared photocatalysts showed exceedingly high photocatalytic activity and stability. Furthermore, the photocatalytic mechanism was proposed based on the ESR result.

Новые деградируемые фотокатализаторы для очистки сточных вод

The weakening of the manmade load on the environment has become a global goal of humanity. The accumulation of toxic substances in effluents can increase the acceleration of pollution of the planet’s watersheds, resulting in biota pollution. To solve this problem, it is necessary to create photocatalysts that cause self-excitation under the ignition of light. Also, important parameters of photocatalysts are simple synthesis and low cost. This article demonstrates a one-step approach to the synthesis of carbon nanostructures (CNS) with photocatalytic activity. For this purpose, the “green chemistry ” method is used – hydrothermal treatment of various polysaccharides (sodium dextran sulfate (SDS), starch, pectin), which opens up the possibility of recycling products. A comprehensive study of the properties of the synthesized CNS has been carried out. To study the optical properties of CNS, absorption and luminescence spectroscopy, and IR spectroscopy, have been used. The CNS obtained have been successfully used in the processes of photocatalytic destruction of a model of the organic dye tartrazine, which is widely used in the fiber and textile industries. The effect of lyophilization on the photocatalytic properties of СNS has been studied, and cytotoxicity has been evaluated.

Unveiling the Intimate Mechanism of the Crocin Antioxidant Properties by Radiolytic Analysis and Molecular Simulations.

The successive steps of the oxidation mechanism of crocin, a major compound of saffron, by the free OH• radical are investigated by pulse radiolysis, steady-state (gamma) radiolysis methods, and molecular simulations. The optical absorption properties of the transient species and their reaction rate constants are determined. The absorption spectrum of the oxidized radical of crocin resulting from the H-abstraction presents a maximum of 678 nm and a band of 441 nm, almost as intense as that of crocin. The spectrum of the covalent dimer of this radical contains an intense band at 441 nm and a weaker band at 330 nm. The final oxidized crocin, issued from radical disproportionation, absorbs weaker with a maximum of 330 nm. The molecular simulation results suggest that the OH• radical is electrostatically attracted by the terminal sugar and is scavenged predominantly by the neighbor methyl site of the polyene chain as in a sugar-driven mechanism. Based on detailed experimental and theoretical investigations, the antioxidant properties of crocin are highlighted.

Construction of CdS/Ti-Nb-O composite photoanode with favorable optical absorption and charge transfer for dramatically boosted photoelectrochemical water splitting

Rational design and construction of highly effective Ti-based photoanodes with advantageous structures are crucial to enhance photoelectrochemical (PEC) water splitting. In this work, we reported a CdS/Ti-Nb-O composite photoanode with satisfactory charge transfer and optical absorption for dramatically boosted PEC performance, which was constructed by bulk-phase Nb-doping synergistically with CdS quantum dots (QDs) sensitization of Ti-based oxide nanostructures. The composite system exhibited a remarkable photocurrent density of 16.11 mA cm-2, which was 34 times higher than pure TiO2 (0.47 mA cm-2). The electron lifetime was substantially increased and the solar-to-hydrogen (STH) conversion efficiency could be as high as 9.45%. Bulk-phase Nb-doping improved the conductivity of Ti-Nb-O, which enabled speedy and sustained charge separation in the composite-electrolyte solid-liquid interface. Meanwhile, CdS sensitization extended light absorption from 410 nm to 640 nm, thereby generating more photogenerated carriers. Simultaneously, Nb-doping negatively shifted the valence band (VB) and conduction band (CB) of Ti-Nb-O, which made the energy band more compatible with CdS. And the well-matched energy band structures of CdS and Ti-Nb-O not only improved separation-transfer properties of photogenerated electrons and holes but also increased overall optical absorption property of the composite system. This work involved dual-regulation charge separation strategy through bulk-phase doping synergetically with QDs sensitization may contribute to constructing high-efficient Ti-based photoanodes for PEC water splitting.

Tuning the optical properties of zirconium-based metal-organic frameworks by post-synthetic modifications

Functionalization of linkers of robust UiO-66-NH2 MOFs is performed by a post-synthetic modification process. The chemical modifications of linkers, an extension of conjugation by several organic molecules, are authenticated by PXRD, NMR and IR characterization techniques. Diffuse reflectance UV–Vis spectroscopic studies showed significant variation in their optical absorption properties, and computational methods validate these results.

Design of graphene-like nanowall arrays and their optical absorption properties

Design of graphene-like nanowall arrays and their optical absorption properties

Physical Mechanism of Nonlinear Spectra in Triangene.

In this work, we theoretically investigate the linear and nonlinear optical absorption properties of open triangulene spin chains and cyclic triangulene spin chains in relation to their lengths and shapes. The physical mechanism of local excitation within the triangular alkene unit and the weak charge transfer between the units are discussed. The uniformly distributed electrostatic potential allows the system to have a small permanent dipole moment that blocks the electronic transition in the light excitation such that the electronic transition can only be carried out between adjacent carbon atoms. The one-photon absorption (OPA) spectra and two-photon absorption (TPA) spectra are red-shifted with the addition of triangulene units compared to N = 3TSCs (triangulene spin chains, TSCs). Here, TPA is mainly caused by the first step of the transition. The length of the spin chain has a significant adjustment effect on the photon cross-section. TSCs of different lengths and shapes can control chirality by adjusting the distribution of the electric dipole moment and transition magnetic dipole moment. These analyses reveal the photophysical properties of triangulene and provide a theoretical basis for studying the photophysical properties of triangulene and its derivatives.