Optical Properties Of Materials Research Articles

Tuning magnetic and optical properties in Mn x Zn1−x PS3 single crystals by the alloying composition

The exploration of two-dimensional (2D) antiferromagnetic (AFM) materials has shown great promise and interest in tuning the magnetic and electronic properties as well as studying magneto-optical effects. The current work investigates the control of magneto-optical interactions in alloyed Mn x Zn1−x PS3 lamellar semiconductor single crystals, with the Mn/Zn ratio regulating the coupling strength. Magnetic susceptibility results show a retention of AFM order followed by a decrease in Néel temperatures down to ∼40% Mn concentration, below which a paramagnetic behavior is observed. Absorption measurements reveal an increase in bandgap energy with higher Zn(II) concentration, and the presence of Mn(II) d-d transition below the absorption edge. DFT + U approach qualitatively explained the origin and the position of the experimentally observed mid band-gap states in pure MnPS3, and corresponding peaks visible in the alloyed systems Mn x Zn1‒x PS3. Accordingly, emission at 1.3 eV in all alloyed compounds results from recombination from a 4T1g Mn(II) excited state to a hybrid p-d state at the valence band. Most significant, temperature-dependent photoluminescence (PL) intensity trends demonstrate strong magneto-optical coupling in compositions with x > 0.65. This study underscores the potential of tailored alloy compositions as a means to control magnetic and optical properties in 2D materials, paving the way for advances in spin-based technologies.

Combining mBJ exchange potential and bootstrap kernel of TDDFT to compute optical spectra of solids

One of the fundamental challenges in calculating the optical properties of crystalline materials is the accurate description of exciton effects so as to make it computationally viable for studying large systems. We combine the modified Becke-Johnson (mBJ) exchange potential and bootstrap kernel (BSK) of time-dependent density functional theory (TDDFT) to compute the imaginary part of the dielectric function of a variety of semiconductors and insulators (Si, GaAs, NiO, TiO2, LiF, LiCl, SrTiO3 and NaMgF3). The results are compared with the experimental data available in the literature. We also compute their dielectric functions using the random phase approximations (RPA) to verify the effect of the BSK method on the optical spectra of these compounds. We conclude that TDDFT+BSK+mBJ calculations can determine the optical spectra of the solids in good agreement with the experimental data (except for small-energy gap materials such as Si and GaAs) with low computational cost, and using a fully ab initio procedure.

Elucidating Solvatochromic Shifts in Two-Dimensional Photocatalysts by Solving the Bethe-Salpeter Equation Coupled with Implicit Solvation Method.

Many studies have focused on tailoring the photophysical properties of two-dimensional (2D) materials for photocatalytic (PC) or photoelectrochemical (PEC) applications. To understand the optical properties of 2D materials in solution, we established a computational method that combined the Bethe-Salpeter equation (BSE) calculations with our GW-GPE method, allowing for GW/BSE-level calculations with implicit solvation described using the generalized Poisson equation (GPE). We applied this method to MoS2, phosphorene (PP), and g-C3N4 and found that when the solvent dielectric increased, it reduced the exciton binding energy and quasiparticle bandgap, resulting in almost no solvatochromic shift in the excitonic peaks of MoS2 and PP, which is consistent with previous experiments. However, our calculations predicted that the solvent dielectric had a significant impact on the excitonic properties of g-C3N4, exhibiting a large solvatochromic shift. We expect that our GW/BSE-GPE method will offer insights into the design of 2D materials for PC and PEC applications.

Fluorescence-enhanced Cs2Ag0.3-xNaxZn0.35In1-yCl6:yM double perovskites for multimodal optical anti-counterfeiting

The excellent optical properties of lead-free halide double perovskites (LHDPs) Cs2AgInCl6 are of great importance in the field of anti-counterfeiting encryption. However, the fluorescence quantum yield of the existing Cs2AgInCl6-based materials is relatively low, and the fluorescence color is monochromatic, making it difficult to use in advanced multi-mode anti-counterfeiting applications. In this study, we synthesized Cs2Ag0.3-xNaxZn0.35In1-yCl6:yM (M = Cr/Bi) series LHDPs using an anti-solvent assisted co-precipitation method, improving the optical properties of Cs2AgInCl6-based materials by optimizing their composition. The fluorescence quantum yield of Zn–Na substituted Cr-doped Cs2Ag0.3-xNaxZn0.35In1-yCl6 LHDPs increased from 1.53 % to 82.57 % on the basis of Cs2AgInCl6. The Zn–Na substituted Bi-doped Cs2Ag0.3-xNaxZn0.35In1-yCl6 LHDPs exhibited dual-wavelength fluorescence emission at 407 and 650 nm, and the relative intensity between the two emission wavelengths changed via a change in the Bi doping amount, resulting in a change in the material's luminescence color. The as-synthesized LHDPs could be applied to multi-mode anti-counterfeiting, optical coding information storage, and art decoration applications.

Nonlinear Optical Properties of 2D Materials and their Applications.

2D materials are a subject of intense research in recent years owing to their exclusive photoelectric properties. With giant nonlinear susceptibility and perfect phase matching, 2D materials have marvelous nonlinear light-matter interactions. The nonlinear optical properties of 2D materials are of great significance to the design and analysis of applied materials and functional devices. Here, the fundamental of nonlinear optics (NLO) for 2D materials is introduced, and the methods for characterizing and measuring second-order and third-order nonlinear susceptibility of 2D materials are reviewed. Furthermore, the theoretical and experimental values of second-order susceptibility χ(2) and third-order susceptibility χ(3) are tabulated. Several applications and possible future research directions of second-harmonic generation (SHG) and third-harmonic generation (THG) for 2D materials are presented.

Nanomaterials for advanced energy applications: Recent advancements and future trends

Nowadays, one of the most promising and significant challenges for our society is achieving highly efficient energy utilization. To address the upcoming demands in energy applications, which demonstrate considerable potential for future trends, continuous efforts are necessary to develop improved and higher-performing inorganic multifunctional nanomaterials. Multifunctional inorganic nanomaterials have been extensively researched to meet the requirements of various energy applications or to enhance them further. Specific attention is given to inorganic nanomaterials for advanced energy storage, conservation, transmission, and conversion applications, which strongly rely on the optical, mechanical, thermal, catalytic, and electrical properties of energy materials. At the nanometer-scale range, triboelectric, piezoelectric, thermoelectric, electrochromic, and photovoltaic materials have made significant contributions to numerous energy sector applications. Functional inorganic materials possess unique properties, including excellent thermal and electrical conductivity, chemical stability, and a large surface area, which enhance their competitiveness in energy-related applications. Herein, recent research, development, and advances in inorganic multifunctional nanomaterials to enhance their performance are discussed, highlighting how devices combine the functionalities of nanomaterials. In this manner, we aim to provide insights into future applications and elucidate the ongoing research challenges currently facing this field.

Photoluminescence Enhancement and Carrier Dynamics of Charged Biexciton in Monolayer WS2 Coupled with Plasmonic Nanocavity

Monolayer two-dimensional transition metal dichalcogenide (TMD)-based materials have become one of the ideal platforms for the study of multibody interactions due to their rich excitonic complexes. The coupling between optical nanocavity and material has become an important means for manipulating the optical properties of materials, but there are few studies on the coupling of nanocavities and the multi-body effect in materials. In this study, we investigate the optical properties of silver nanodisk (Ag ND) arrays covering a monolayer WS2. In the experimental sample, we observed a ~114.3-fold photoluminescence enhancement of charged biexciton in the heterostructure region, as compared to the monolayer WS2 region, a value which is much higher than those for exciton (~2.2-fold) and trion (~16.4-fold), a finding which is attributed to the Fano resonant coupling between monolayer WS2 and the Ag ND. By means of time-resolved spectroscopy, we studied the carrier dynamics in the hybrid system. Our findings reveal that resonant coupling promotes the formation and radiation recombination processes of the charged biexciton, significantly reducing the radiative recombination lifetime by ~15-fold, which is much higher than the measurement in exciton (~2-fold). Our results provide an opportunity to understand the multibody physics of coupling with nanocavities, which could facilitate the application of multi-body excitons in the fields of light-emitting devices and lasers, etc.

Volumetric Modification of Transparent Materials with Two-Color Laser Irradiation: Insight from Numerical Modeling.

Traditionally, single-color laser beams are used for material processing and modifications of optical, mechanical, conductive, and thermal properties of different materials. So far, there are a limited number of studies about the dual-wavelength laser irradiation of materials, which, however, indicate a strong enhancement in laser energy coupling to solid targets. Here, a theoretical study is reported that aimed at exploring the volumetric excitation of fused silica with dual-wavelength (800 nm and 400 nm) ultrashort laser pulses focused on the material's bulk. Numerical simulations are based on Maxwell's equations, accounting for the generation of conduction electrons, their hydrodynamic motion in the laser field, and trapping into an excitonic state. It is shown that, by properly choosing the energies of the two laser harmonics successively coupling with the material, it is possible to strongly enhance the laser energy absorption as compared to the pulses of a single wavelength with the same total energy. Laser energy absorption strongly depends on the sequence of applied wavelengths, so that the shorter wavelength pre-irradiation can yield a dramatic effect on laser excitation by the following longer-wavelength pulse. The predictions of this study can open a new route for enhancing and controlling the highly localized absorption of laser energy inside transparent materials for optoelectronic and photonic applications.

Multilayered Ru/TiO[formula omitted] hyperbolic material for nonlinear optics

In this work we present the design, fabrication and study of the optical properties of hyperbolic materials based on multilayered metal–dielectric Ru/TiO2 structures. The samples were fabricated using the Atomic Layer Deposition technique, and their structure was designed to have an Epsilon Near Zero point near 800 nm to match the laser wavelength employed to study their response. The linear optical properties were studied using spectrophotometry and spectral ellipsometry. The nonlinear response was studied as a function of incident irradiance using the z-scan technique with fs pulses as a function of wavelength throughout the visible, allowing the determination of the refractive and absorptive contributions to the nonlinear response. Given that a high pulse repetition rate was employed, cumulative pulse to pulse thermal effects can be present, because of this, a modification of the z-scan technique allowed the resolution of the electronic and thermal contributions to the response.

Tailoring the graphene framework by embedding Nb2O5 and silver nanoparticles for electrodes in energy storage applications

In this study, Nb2O5/GNs and Ag/GNs-based nanocomposites were synthesized via a facile single-step hydrothermal approach. Using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, fourier-transform infrared (FTIR) spectroscopy, and UV–vis spectroscopy, the morphology, functional groups, structure, and optical and electrical properties of the as-prepared materials were examined. XPS studies show the predominant signal at 284.8 eV is attributed to the sp2 carbon atoms (C 1) that comprise graphitic areas, indicating that the majority of the C atoms are arranged in a honeycomb lattice. FTIR spectrum confirms bonding, such as CO, CH2, CO, CC, OH, AgO, and NbONb in the nanocomposite. Further, the specific capacitance (Csp) of the Nb2O5/GNs and Ag/GNs was calculated 603 Fg−1 and 810 Fg−1 at different current densities, The Nb2O5/GNs exhibit 109 Wh/kg and 2180 W/kg energy and power density, respectively. However, the Ag/GNs electrode exhibited an energy density of 145.8 Wh/kg and a power density of 3645 W/kg, with cyclic stability retentions of 93.06 % and 97.02 %, respectively. The capacitance retention finished at 1000 cycles. Moreover, the achieved resistance from the I–V characteristics curve shows enhanced electrical conductivity of synthesized nanocomposites. These results suggested that the materials can have bright future in next-generation energy storage devices.

Intensification of organic pollutant degradation under visible light irradiation using ZnO nanostructured photocatalysts doped with praseodymium

Zinc oxide nanostructures doped with praseodymium (ZnO:Pr) at varying Pr content (0.05 % to 1.0 % w/w) were synthesized using the electrospinning-calcination technique. Comprehensive morphological and structural characterizations were conducted through SEM, XRD, and XPS analyses. In addition, diffuse reflectance and photoluminescence spectroscopy measurements were performed to assess the optical properties of materials. The produced photocatalysts (ZnO:Pr) were then employed for the degradation of methylene blue dye and oxytetracycline under visible-light irradiation. ZnO:Pr(0.1 %) demonstrated the best photocatalytic performance against methylene blue showing a pseudo-first-order rate constant of k = 3.630 × 10-2 min−1. Investigation of oxytetracycline photodegradation with ZnO:Pr(0.1 %) revealed a pseudo-second-order rate constant of ks = 1.165 × 10-1 L mg−1 min−1, resulting in a reaction half-life (τ½) of approximately 1 min under optimal conditions. Total organic carbon and mass spectrometry analyses highlighted mineralization and identified the main reaction intermediates, respectively, for the oxytetracycline photodegradation. The photodegradation mechanism of oxytetracycline was proposed by the photocatalytic degradation measurements in the presence of scavengers such as hydroquinone and isopropanol. These nanostructures exhibited robust photocatalytic activity over multiple cycles, demonstrating excellent stability. This study underlines the promising potential of ZnO:Pr(0.1 %) as an efficient photocatalyst able to intensify the photodegradation of organic pollutants.

Exploring the Regulatory Mechanism of ZnS Materials under Stress and Re Doping: Insights from Density Functional Theory

The application prospects of ZnS stress luminescent materials cover many fields such as high‐precision structural monitoring, smart materials, biomedical imaging, and new sensor technologies, which bring broad application prospects and significance to them in the fields of engineering, medicine, and scientific research. In this article, the electronic structure and optical properties of ZnS materials are successfully regulated by applying pressure and doping rare earth metals (Re), and it is found that the regulation of the luminescence properties of ZnS is the result of stress and doping interactions. Specifically, when pressure is applied or Re metal doping, the lattice structure is deformed and the atomic spacing is adjusted, which affects the electronic energy level distribution and optical properties of ZnS materials. Computational analysis of density functional theory (DFT) reveals the microscopic mechanisms behind these changes, including changes in lattice parameters, adjustment of bond length, and changes in band structure. This study provides theoretical guidance for the design and synthesis of high‐performance and high‐stability ZnS light‐emitting materials, and is of great significance for expanding the application of ZnS in the field of lasers and sensors.

Growth and characterization of physical properties of photovoltaic (K,Ba)(Ni,Nb)O3 single crystals

The substitution of fossil energy for green-energy sources is a world demand. Photovoltaic devices are a well-known safety solution to convert solar energy into electricity. Ferroelectric materials are one of the most promising candidates for substituting Si-based compounds in solar-energy conversion devices due to their relatively low cost and bulk photovoltaic effect instead of the classical p-n junction. In this work, (K,Ba)(Nb,Ni)O3 single crystal was grown by vertical Bridgman-Stockbarger method, and structural, chemical, and optical properties of the as-grown material were characterized. Growth parameters were chosen based on the thermal properties of the precursor oxide and on theoretical models.

Electronic and optical properties of two-dimensional Janus Sn0.5Ge0.5S monolayer

Janus two-dimensional (2D) materials have received widespread attention in recent years due to their out-of-plane asymmetric structures which makes them promising candidates for sustainable energy devices. In this work, using first-principles calculations, we study a novel 2D Janus monolayer Sn0.5Ge0.5S for recently synthesized SnS monolayer. We investigate structural, electronic and optical properties of this new 2D Janus material. Our results show that monolayer Sn0.5Ge0.5S is an indirect band gap semiconductor with the lowest conduction band is nearly flat around the band minimum. Atom projected band structure reveals that this flattened valley is mainly originated from orbitals of Sn atom. In addition, the inclusion of spin–orbit coupling leads to splitting of the bands, largely along Γ-Y direction. Optical absorption spectra indicate superior sunlight absorption in the visible and ultraviolet regions. Interestingly, absorption spectra of Janus monolayer Sn0.5Ge0.5S are polarization dependent owing to its anisotropic crystal structure along zigzag and armchair directions.

La-Doped Sm2Zr2O7/PU-Coated Leather Composites with Enhanced Mechanical Properties and Highly Efficient Photocatalytic Performance.

Flexible La-doped Sm2Zr2O7/polyurethane (PU) coated leather composites were synthesized using a one-step hydrothermal method, with highly efficient photocatalytic degradation properties by coating the La-doped Sm2Zr2O7/PU emulsion onto the leather and drying it. The phase composition and optical properties of the as-prepared photocatalytic material were systematically characterized. The result revealed that La was doped in Sm2Zr2O7 successfully, and the prepared samples still possessed pyrochlore structure. The absorption edge of the prepared samples exhibited a red-shift with the increase in La doping, indicating that La doping could broaden the absorbance range of the La-doped Sm2Zr2O7 materials. The catalytic performance of La-doped Sm2Zr2O7/PU composite emulsion coating on the photocatalytic performance of leather was studied with Congo red solution as the target pollutant. The results showed that the best photocatalytic property was found in the 5% La-doped Sm2Zr2O7 nanomaterial at a concentration of 3 g/L. The resulting 5% La-doped Sm2Zr2O7 nanomaterial exhibited a high specific surface area of 73.5 m2/g. After 40 min of irradiation by a 450 W xenon lamp, the degradation rate of Congo red reached 93%. Moreover, after surface coating, the La-doped Sm2Zr2O7/PU coated leather composites showed obviously improved mechanical properties, as the tensile strength of La-doped Sm2Zr2O7/PU coated leather composites increased from 6.3 to 8.4 MPa. The as-prepared La-doped Sm2Zr2O7/PU coated leather composites with enhanced mechanical properties and highly efficient photocatalytic performance hold promising applications in the treatment of indoor volatile organic compounds.

DFT Study of Electronic, Optical, Thermoelectric, and Thermodynamic Properties of the HfO2 Material

DFT Study of Electronic, Optical, Thermoelectric, and Thermodynamic Properties of the HfO2 Material

A Metastructure Based on Amorphous Carbon for High Efficiency and Selective Solar Absorption.

Efficient solar thermal conversion is crucial for renewable clean energy technologies such as solar thermal power generation, solar thermophotovoltaic and seawater desalination. To maximize solar energy conversion efficiency, a solar selective absorber with tailored absorption properties designed for solar applications is indispensable. In this study, we propose a broadband selective absorber based on amorphous carbon (a-C) metamaterials that achieves high absorption in the ultraviolet (UV), visible (Vis) and near-infrared (NIR) spectral ranges. Additionally, through metal doping, the optical properties of carbon matrix materials can be modulated. We introduce Ti@a-C thin film into the nanostructure to enhance light absorption across most of the solar spectrum, particularly in the NIR wavelength band, which is essential for improving energy utilization. The impressive solar absorptivity and photothermal conversion efficiency reach 97.8% and 95.6%, respectively. Notably, these superior performances are well-maintained even at large incident angles with different polarized states. These findings open new avenues for the application of a-C matrix materials, especially in fields related to solar energy harvesting.

Phonon-mediated ultrafast energy- and momentum-resolved hole dynamics in monolayer black phosphorus.

The electron-phonon scattering plays a crucial role in determining the electronic, transport, optical, and thermal properties of materials. Here, we employ a non-Markovian stochastic Schrödinger equation (NMSSE) in momentum space, together with abinitio calculations for energy bands and electron-phonon interactions, to reveal the phonon-mediated ultrafast hole relaxation dynamics in the valence bands of monolayer black phosphorus. Our numerical simulations show that the hole can initially remain in the high-energy valence bands for more than 100fs due to the weak interband scatterings, and its energy relaxation follows single-exponential decay toward the valence band maximum after scattering into low-energy valence bands. The total relaxation time of holes is much longer than that of electrons in the conduction band. This suggests that harnessing the excess energy of holes may be more effective than that of electrons. Compared to the semiclassical Boltzmann equation based on a hopping model, the NMSSE highlights the persistence of quantum coherence for a long time, which significantly impacts the relaxation dynamics. These findings complement the understanding of hot carrier relaxation dynamics in two-dimensional materials and may offer novel insights into harnessing hole energy in photocatalysis.

Synthesis, solvent role, absorption and emission studies of cytosine derivative

The (E)-4-((4-hydroxy-3-methoxy-5-nitrobenzylidene) amino) pyrimidin-2(1H)-one (C5NV) was synthesized from cytosine and 5-nitrovanilline by simple straightforward condensation reaction. The structural characteristics of the compound was determined and optimized by WB97XD/cc-pVDZ basis set. The vibrational frequencies were computed and subsequently compared to the experimental frequencies. We investiated the electronic properties of the synthesized compound in gas and solvent phases using the time-dependent density functional theory (TD-DFT) approach, and compared them to experimental values. The fluorescence study showed three different wavelengths indicating the nature of the optical material properties. Frontier molecular orbital (FMO) and molecular electrostatic potential (MEP) analyses were conducted for the title compound, and electron localized functions (ELF) and localized orbital locators (LOL) were used to identify the orbital positions of localized and delocalized atoms. Non-covalent interactions (H-bond interactions) were investigated using reduced density gradients (RDGs). The objective of the study was to determine the physical, chemical, and biological properties of the C5NV. The molecular docking study was conducted between C5NV and 2XNF protein, its lowest binding energy score is −7.92 kcal/mol.

Coordination of Thermally Activated Delayed Fluorescent Molecules for Efficient and Stable Perovskite Light‐Emitting Diodes

AbstractThe bandgap and operation stability of metal halide perovskites (MHPs) based light‐emitting diodes (PeLEDs) have been compromised by the substantial surface defect densities in the matrix. Today's defect passivation strategies rely on coordination actions of small‐molecular and/or polymeric ligands, which effectively enhance the optical properties of materials. However, the non‐trivial insulating characteristics of the molecules concurrently sacrifice the operation stability and external quantum efficiency (EQE) of the PeLEDs by augmenting the charge injection barrier at the interface. Herein, a coordinative, charge‐polarized organic semiconductor exhibiting thermally activated delayed fluorescence (TADF), namely 9,9‐dimethyl‐10‐(4‐(phenyl sulfonyl)phenyl)‐9,10‐dihydroacridine (SO‐DMAc) is coordinated, into the MHPs matrix for deep‐red PeLEDs. Owing to the distinctive charge transfer (CT) between the molecule and MHPs with exclusive coordination at the MHP's bottom, SO‐DMAc serves as a molecular bridge that significantly augments the hole injection into the PeLEDs. Encouraged by these improvements, efficient and stable deep red PeLEDs offering EQE of 21.8% and respective half lifetimes (T50) of luminance and EQE exceeding 6 and 35 h are demonstrated. It is revealed that the molecular coordination to the MHP surface is pivotal to manifesting the interfacial CT process for favorable energy level tuning.