Optical Properties Of Materials Research Articles

Cooperative β-Sheet Coassembly Controls Intermolecular Orientation of Amphiphilic Peptide-Polydiacetylene Conjugates

In this work, we elucidated the structural organization of stimuli-responsive peptide-polydiacetylene (PDA) conjugates that can self-assemble as 1D nanostructures under neutral aqueous conditions. The amino acid sequences bear positively or negatively charged domains at the periphery of the peptide segments to promote solubility in water while also driving assembly of the individual and combined components into β-sheets. The photopolymerization of PDA, as well as the sensitivity of the resulting optical properties of the polymeric material to external stimuli, highly depends on the structural organization of the assembly of amphiphilic peptide-diacetylene units into 1D-nanostructures. Solid-state NMR measurements on 13C-labeled and 15N-labeled samples show that positively charged and negatively charged peptide amphiphiles are each capable of self-assembly, but self-assembly favors antiparallel β-sheet structure. When positively and negatively charged peptide amphiphiles interact in stoichiometric solutions, cooperative coassembly dominates over self-assembly, resulting in the desired parallel β-sheet structure with a concomitant increase in structural order. These results reveal that rational placement of oppositely charged residues can control β-strand organization in a peptide amphiphile coassembly, which would have implications on the adaptive properties of stimuli-responsive biomaterials such as the peptide-PDAs studied here.

Optical properties of popular dielectric substrate materials in a wide spectral range from far-infrared to ultraviolet

We investigated the optical properties of 13 different dielectric materials (slide glass, quartz, Al2O3 (c-cut), DyScO3 (110), KTaO3 (001), LaAlO3 (001), (LaAlO3)0.3-(Sr2AlTaO6)0.7 (001) (LSAT), MgF2 (100), MgO (100), SiC, SrTiO3 (001), TbScO3 (110), and TiO2). The single-bounce reflectance spectra of the bulk samples were measured using Fourier transform infrared (FTIR) and monochromatic spectrometers across a wide spectral range, from far infrared to ultraviolet (80–50,000 cm−1). Using the Kramers–Kronig analysis, we obtained the optical conductivity and dielectric function of the dielectric materials from their measured reflectance spectra. Moreover, we measured the transmittance spectra of the materials to obtain their bandgaps. We fitted the measured reflectance spectra using the Lorentz model to obtain phononic structures. Each dielectric material exhibits unique phononic structures and optical bandgaps, associated with the composition and crystal structure of the material. The observed optical properties of these dielectric materials provide valuable information for the optical analysis of thin films grown on them.

Photo- thermo-induce changes in As2S3- and As2S3: Au-nanoparticles filled porous glass composite: Optics and the molecular structure simulation of the responsible chalcogenide transformations

In this study we continue a more detailed investigation of the photoinduced effect in nanoporous glass impregnated with As2S3 NPs and Au NPs and its influence on the material's optical properties. The goal of this research is establishing the quantum chemical peculiarities of these processes taking into account the impact of gold nanoparticles on the photoinduced structural transformations of As-S component using Raman spectroscopy and theoretically investigating the molecular structure of arsenic sulfide As-S through ab initio quantum chemical calculations. These support the possibility of further variations in optical properties of such composite materials and photo-thermo driven elements made on their basis.

Theoretical insight into physical characteristics of lead-free perovskites Rb2TlSbX6 (X = Cl, Br, I) for optoelectronic devices.

Novel optoelectronic and thermoelectric properties with broad compositional range, non-toxic nature and structural stability make halide-based double perovskites fascinating for flexible optoelectronic devices. In this work, the structural electronic, optical and transport properties of Rb2TlSbX6 (X = Cl, Br, I) were studied using density functional theory for optoelectronic devices. The elastic analysis demonstrates ductile nature, mechanical stability, anisotropic behaviour and feasibility for flexible optoelectronic devices. The band structure study using Tran-Blaha-modified Becke-Johnson (TB-mBJ) potential shows that all studied materials have direct bandgap. In addition, the bandgap of Rb2TlSbCl6 is more appropriate for optoelectronic devices. The small loss and maximum absorption in visible regions make these materials prime candidates for optoelectronic devices. The transport features indicate that all the studied double perovskites reflect p-type semiconducting behaviour as highlighted by positive Seebeck coefficient values. Furthermore, the high power factor values of Rb2TlSbX6 (X = Cl, Br, I) double perovskites make them suitable for thermoelectric device applications at high temperatures. Based on electronic optical and thermoelectric properties Rb2TlSbCl6 is the best candidate for flexible optoelectronic devices. In this paper, structural optimization of Rb2TlSbX6 (X = Cl, Br, I) double perovskites was conducted utilizing the Wien2k software based on first principle calculations with Perdew-Burke-Ernzerhof's generalized-gradient approximation (PBE-sol approximation). The TB-mBJ potential was employed to compute the accurate band gap of studied materials. The thermoelectric properties are evaluated with BoltzTraP code, showing a predominance of P-type charge carriers in all studied perovskites. This methodological strategy verifies the material's remarkable stability and optical properties and offers a solid framework for examining its potential in optoelectronic devices.

Kretschmann configuration as a method to enhance optical absorption in two-dimensional graphene-like semiconductors

Objectives. The optical properties of two-dimensional semiconductor materials, specifically monolayered transition metal dichalcogenides, present new horizons in the field of nano- and optoelectronics. However, their practical application is hindered by the issue of low light absorption. When working with such thin structures, it is essential to consider numerous complex factors, such as resonance and plasmonic effects which can influence absorption efficiency. The aim of this study is the optimization of light absorption in a two-dimensional semiconductor in the Kretschmann configuration for future use in optoelectronic devices, considering the aforementioned phenomena. Methods. A numerical modeling method was applied using the finite element method for solving Maxwell’s equations. A parametric analysis was conducted focusing on three parameters: angle of light incidence, metallic layer thickness, and semiconductor layer thickness.Results. Parameters were identified at which the maximum area of absorption peak was observed, including the metallic layer thickness and angle of light incidence. Based on the resulting graphs, optimal parameters were determined, in order to achieve the highest absorption percentages in the two-dimensional semiconductor film.Conclusions. Based on numerical studies, it can be asserted that the optimal parameters for maximum absorption in the monolayer film are: Ag thickness <20 nm and angle of light incidence between 55° and 85°. The maximum absorption in the two-dimensional film was found only to account for a portion of the total absorption of the entire structure. Thus, a customized approach to parameter selection is necessary, in order to achieve maximum efficiency in certain optoelectronic applications.

Investigation of electrochemical, structural, electronic, thermodynamic, and optical properties of LiTi2O4 cathode material for Li-ion battery: an Ab Initio calculations

Investigation of electrochemical, structural, electronic, thermodynamic, and optical properties of LiTi2O4 cathode material for Li-ion battery: an Ab Initio calculations

Line-field dispersive interference ellipsometry based on an anisotropic crystal

We propose an anisotropic crystal-based line-field dispersive interference ellipsometry, capable of both transmission and reflection measurements. This technique is adept at characterizing the optical polarization properties of transparent materials and is applicable for real-time film thickness monitoring in industrial line-field configurations. Experimental demonstrations include the dynamic line-field birefringent phase of the quarter-wave plate and the Soleil-Babinet compensator in the near-infrared band. The developed method also accurately measured the thickness distribution of a conveyor-based film specimen with thicknesses of 250 nm and 510 nm. A phase stability of 9.5 × 10−4 rad under 200 Hz update rate was demonstrated.

Atomic layer deposition of SnO2 enables fast-dynamics in electrochromic vanadium oxide/polyaniline films

Heterostructure materials hold great promise for electrochromism, but the complexity in coupling the optical and electronic properties of multiple materials remains a challenge. Herein, SnO2 film with excellent transparency and electronic properties is deposited on electro-deposited inorganic-organic vanadium oxide-polyaniline composite films by atomic layer deopisiton (ALD). As a result, the heterostructure strategy stimulated the reaction dynamics, significantly reducing the response time (from 30 s to 5 s). In addition, the thickness of the SnO2 films is found to have a crucial influecne on the electrochromic performance of heterostructure electrodes. Our work highlights the potential of semiconductor films in improving the electrochoromic materials.

Structural phase transition and optical properties of zero-dimensional cobalt bromide hybrid material

Zero-Dimensional (0D) metal halide materials have recently emerged as a class of potential optoelectronic materials because of the structural diversity and superior photophysical properties. Here we report a 0D cobalt bromide hybrid material, [Br(CH2)3NH3]2CoBr4 (BPA-CoBr4, BPA=Br(CH2)3NH3, 3-Bromopropylamine), in which the isolated metal halide tetrahedron (CoBr42-) is completely separated each other and surrounded by the organic ligand Br(CH2)3NH3+. Differential scanning calorimetry (DSC) measurements exhibit BPA-CoBr4 undergoes a first-order structural phase transition, as clearly visible to a pair of weak peaks at 340 K (heating) and 317 K (cooling). Single crystal X-ray diffractions were carried out at 293 K and 360 K to explain the phase transformation mechanism, indicating it is an isostructural order–disorder type. The crystal structures which both crystalize in a monoclinic P21/c crystal symmetry and the most distinct difference between room-temperature and high-temperature structures is the order–disorder transition of the 3-Bromopropylamine, which is the driving force of the phase transition. The UV–vis absorption spectra reveal that BPA-CoBr4 has a steep absorption edge at 280 nm corresponding to photo energy of 4.4 eV. The density functional theory (DFT) calculations were performed to study the electronic structure with narrower indirect bandgap 3.9 eV which is lower than the experimental values. PDOS plots show that the electronic states of Co-d and Br-p orbitals are mainly contributed for the VBM and CBM of BPA-CoBr4.

Exploring the structural, electronic, and optical properties of novel two-dimensional ABX-type materials

A first-principles study of the structural, electrical, and optical properties of graphene-like two-dimensional (2D) materials ABX (A=Na/K, B=C/Si/Ge, and X=N/P/As) such as NaCN, KCN, NaCP, KCP, etc was undertaken using state-of-the-art Density Functional Theory (DFT). The investigation encompasses essential parameters such as structural stability through ab initio molecular dynamics (AIMD), electronic structure, and dielectric constants. The AIMD measurements reveal that the structures stay stable for up to 10 picoseconds (ps). Band structure calculations at the PBE level of theory revealed that most materials are semi-conducting with a band gap of 1-3 eV, except NaCN and KCN, which exhibited insulating behaviour. Using hybrid functional (HSE), only eight materials were identified to have a band gap in the visible range. Optical properties have also been investigated to understand their interaction with light. Peaks in the imaginary component of the dielectric function were attributed to inter-band transitions. Several materials were discovered to be optimal for photo-catalysis, while six were found to exhibit conductivity of the order of ∼1012 (Ω−1cm−1s−1) at room temperature.

Phonon Polaritons Launched by Natural Boron Nitride Wrinkles Probed with Nano‐Fourier Transform Infrared Spectroscopy

Nano‐fourier transform infrared spectroscopy (FTIR) is a powerful tool to measure optical and electronic properties of materials at the nanoscale. It is especially useful for visualizing plasmon and phonon polaritons launched from edges of a sample or structures on top of it. Herein, an exfoliated hexagonal boron nitride flake with a thickness of ≈16 nm is transferred onto a gold substrate. The flake is characterized by micro‐Raman and nano‐FTIR spectroscopy. The Raman spectra show no difference between points on the flat surface and points on the wrinkles of the flake. Nano‐FTIR spectra, while comparable to conventional infrared spectra on the flat surface, show a strong change in the form of a second absorption peak appearing near a wrinkle in the flake. This second absorption peak shifts to higher wavenumber and becomes more intense as the probed spot gets closer to the wrinkle. This is consistent with the behavior of phonon polaritons when approaching the scattering point that is reflecting them.

Indium-doped tungsten oxide architectures anchored on 2D rGO Matrix with enhanced visible-light-response and efficient charge separation for photocatalytic degradation of organic pollutants

Visible-light-responsive photocatalysis has been recognized as a sustainable strategy to address environmental pollution, but semiconductor-based photocatalysts often suffer from many shortcomings, including low visible light absorption and rapid recombination of photo-generated charge carriers. In this regard, rationally designed composite materials have gained substantial prominence, as achieving an ideal photocatalyst's characteristics in a single component material is frequently difficult. In the present study, we have synthesized pure (WO3) and indium-doped tungsten oxide (In-WO3) by the facile solvothermal route. The doped material was anchored on a 2D rGO matrix to fabricate the In-WO3/rGO composite. The structural, morphological, electrical, and optical properties of the as-synthesized materials were investigated as a function of doping and composite fabrication by various physical and electrochemical techniques. The comparative photocatalytic performance was evaluated by degrading Congo Red (CR) dye and paracetamol (PCM) drug. The composite material shows degradation efficiencies of ∼96 % (K=0.0174 min−1) and ∼91 % (K=0.0144 min−1) for CR dye and PCM drug, respectively. The boosted catalytic performance corresponds to the declined band gap (2.53 eV) and increased conductivity (0.1270 Sm−1), which enhances its visible light absorption and a surge in the charge carrier's population. The kinetics, relative contribution of different active species generated, and the potential mechanism of photodegradation reaction are discussed in detail. The significant increase in photocatalytic performance of the fabricated In-WO3/rGO composite discloses its promising catalytic potential for the degradation of recalcitrant organic pollutants.

Dynamical sensitivity on thermal fluctuations of torsional homogeneous and nonhomogeneous microsystems under the influence of Casimir and electrostatic torques: Nonlinear actuation towards chaotic motion

We have studied how the mechanical Casimir torque between the components of a torsional double beam microdevice under the influence of thermal fluctuations could play significant role on the dynamics of the device, and under what conditions can even lead to chaotic behavior. The influence of thermal fluctuations on the dynamical behavior of torsional microsystems, whether homogeneous or nonhomogeneous, has been revealed through bifurcation and phase diagrams, and Poincare maps. For nonhomogeneous microsystems, the device with low conductivity reveals significant sensitivity to thermal fluctuations. Moreover, it is shown the significant dependence of the optimal voltage distribution, which leads to a significant increase in the stable operation range of the device, on the ambient temperature conditions and the optical properties of the constituent materials. For nonconservative torsional microsystem, the use of the Melnikov method and Poincaré plots have shown how thermal effects increase the probability of chaotic behavior. This is because different temperature enhances the effective Casimir torque and the possibility of chaotic motion. Furthermore, it is illustrated how the use of the optimal voltage distribution, by taking into consideration thermal fluctuations and optical properties, can keep the device away from chaotic behavior. This is because by dividing the electrostatic torques the influence of the effective Casimir torque is reduced. Finally, it is demonstrated that by transforming a homogeneous system into a heterogeneous one, the response of the system to thermal fluctuations is reduced making it possible to avoid to increase the possibility for chaotic behavior by changing the temperature.

Unlocking Giant Third‐Order Optical Nonlinearity in (MA)2CuX4 through Introducing Jahn‐Teller Distortion

AbstractNonlinear absorption coefficient and modulation depth stand as pivotal properties of nonlinear optical (NLO) materials, while the existing NLO materials exhibit limitations such as low nonlinear absorption coefficients and/or small modulation depths, thereby severely impeding their practical application. Here we unveil that introducing Jahn–Teller distortion in a Mott‐Hubbard system, (MA)2CuX4 (MA=methylammonium; X=Cl, Br) affords the simultaneous attainment of a giant nonlinear absorption coefficient and substantial modulation depth. The optimized compound, (MA)2CuCl4, demonstrates a nonlinear absorption coefficient of (1.5±0.08)×105 cm GW−1, a modulation depth of 60 %, and a relatively low optical limiting threshold of 1.22×10−5 J cm−2. These outstanding attributes surpass those of most reported NLO materials. Our investigation reveals that a more pronounced distortion of the [CuX6]4− octahedron emerges as a crucial factor in augmenting optical nonlinearity. Mechanism study involving structural and spectral characterization along with theoretical calculations indicates a correlation between the compelling performance and the Mott‐Hubbard band structure of the materials, coupled with the Jahn–Teller distortion‐induced d‐d transition. This study not only introduces a promising category of high‐performance NLO materials but also provides novel insights into enhancing the performance of such materials.

Unlocking Giant Third-Order Optical Nonlinearity in (MA)2CuX4 through Introducing Jahn-Teller Distortion.

Nonlinear absorption coefficient and modulation depth stand as pivotal properties of nonlinear optical (NLO) materials, while the existing NLO materials exhibit limitations such as low nonlinear absorption coefficients and/or small modulation depths, thereby severely impeding their practical application. Here we unveil that introducing Jahn-Teller distortion in a Mott-Hubbard system, (MA)2CuX4 (MA=methylammonium; X=Cl, Br) affords the simultaneous attainment of a giant nonlinear absorption coefficient and substantial modulation depth. The optimized compound, (MA)2CuCl4, demonstrates a nonlinear absorption coefficient of (1.5±0.08)×105 cm GW-1, a modulation depth of 60 %, and a relatively low optical limiting threshold of 1.22×10-5 J cm-2. These outstanding attributes surpass those of most reported NLO materials. Our investigation reveals that a more pronounced distortion of the [CuX6]4- octahedron emerges as a crucial factor in augmenting optical nonlinearity. Mechanism study involving structural and spectral characterization along with theoretical calculations indicates a correlation between the compelling performance and the Mott-Hubbard band structure of the materials, coupled with the Jahn-Teller distortion-induced d-d transition. This study not only introduces a promising category of high-performance NLO materials but also provides novel insights into enhancing the performance of such materials.

In vitro evaluation of the mechanical and optical properties of 3D printed vs CAD/CAM milled denture teeth materials

This laboratory research aimed to assess the Flexural strength, fracture toughness, Volumetric wear and optical properties of various recent 3D-printed denture tooth materials and compare them to CAD/CAM milled materials. Four 3D-printed denture tooth materials (Lucitone Tooth, OnX, Flexcera Ultra +, and VarseoSmile Crown Plus) and one CAD/CAM milled denture teeth material (Ivotion Dent) were used to fabricate fifteen specimens for each material (with total no. of 300 specimens). Tests were conducted according to ISO standards to assess flexural strength, fracture toughness, color staining, and volumetric wear. All materials were printed, washed, cured, or milled following the manufacturer’s instructions. Flexural strength and fracture toughness values were obtained by a universal testing machine. Volumetric wear was evaluated using a non-contact optical profilometer. Color stability outcomes were obtained via a spectrophotometer for determining L*a*b* values, with color change (ΔE2000) based on the CIEDE2000 formula. Data were analyzed using one-way ANOVA and Tukey post-hoc analysis (α = 0.05). All 3D-printed materials exhibited higher flexural strength values than the milled material (p < 0.05). For fracture toughness, two of the 3D-printed materials showed higher values than the milled material, while the other two had lower values. Insignificant variances in volumetric wear were detected between the materials (p > 0.05). Color staining results varied, with milled materials generally demonstrating better-staining resistance compared to the 3D-printed materials. 3D-printed denture tooth materials exhibit good mechanical and optical properties, presenting a cost-effective and efficient alternative to CAD/CAM milled materials for denture tooth fabrication.

Study the optical properties of polymer material and its applications

Study the optical properties of polymer material and its applications

The Study of Lead-Free CH3NH3GeX3 (X=F, Cl, Br, I and At) for Optoelectronic Applications Using First-Principle

Organometallic perovskites, with their exceptional electric, magnetic, piezoelectric, and optical properties, are prominent in materials science research. The environmental and health concerns associated with lead-based perovskites have spurred the search for lead-free alternatives, such as methylammonium germanium halides. This study investigates the optical and electronic properties of organometallic perovskite materials, focusing on methylammonium germanium halides (CH3NH3GeX3, where X = F, Cl, Br, I, At). Using computational methods, the analysed properties including band gap energies, dielectric constants, extinction coefficients, optical conductivity, absorption coefficients, reflectivity, refractive indices, and lattice constants. The results show a decreasing trend in band gap energies from 3.987 eV (CH3NH3GeF3) to 0.821 eV (CH3NH3GeAt3), indicating weaker bonding interactions with larger halide ions. Lattice constants increase from 4.981 Å (CH3NH3GeF3) to 6.068 Å (CH3NH3GeAt3), reflecting the larger ionic radii of the heavier halides. CH3NH3GeI3 displayed the highest dielectric constant, demonstrating a strong response to external electric fields. Extinction coefficients were significant within the 0 to 10 eV frequency range, with CH3NH3GeI3 showing the highest values. Optical conductivity peaked in CH3NH3GeI3, suggesting its potential for photovoltaic and light-emitting applications. The absorption coefficients indicated strong visible range absorption for CH3NH3GeI3. Reflectivity analysis revealed that CH3NH3GeF3 and CH3NH3GeCl3 had higher static reflectivity, suitable for applications requiring minimal reflection, whereas CH3NH3GeI3 exhibited minimal reflection, beneficial for high-efficiency photovoltaic cells. The refractive index analysis showed that CH3NH3GeI3 had the highest static refractive index, indicating significant optical density and light-slowing capabilities. These findings highlight the relationship between halide substitution and the optical properties of organometallic perovskite materials, providing insights for tailored technological applications.

Lead‐Free Halide Perovskite Nanoparticles for Up‐Conversion Lasing and Efficient Second Harmonic Generation

AbstractLead‐free halide perovskites is a novel class of environment‐friendly nonlinear optical materials, that already demonstrate high potential for second harmonics generation (SHG). Here a synthesis protocol is optimized to create single‐crystal CsGeI3 nanoparticles (NPs) supporting optical Mie resonances that efficiently convert infrared light to visible both via lasing and SHG mechanisms. Such high‐quality resonant NPs allow us to achieve up‐conversion lasing in the broadband excitation wavelength (1200–1520 nm), which is accompanied by efficient spectrally tunable SHG with intensity comparable with that for lasing depending on temperature. Experimental and theoretical study of linear and nonlinear optical properties of CsGeI3 material in the form of high‐quality thin film and NPs of different sizes reveal that coupling incident light with a magnetic dipole resonance leads to a strong enhancement of SHG by one order of magnitude. As a result, the study provides a novel strategy where individual NPs can support both up‐conversion lasing and SHG in a broad range of excitation wavelengths.

Investigation of the physical characteristics of Bi4Ti3O12, Bi2Ti4O11, Bi12TiO20, Bi2Ti2O7 ternary semiconductors

The mechanical, thermodynamics, electronic, optical properties of Bi4Ti3O12, Bi2Ti4O11, Bi12TiO20 and Bi2Ti2O7 ternary semiconductor materials were calculated and analyzed using first-principles calculations. The structural optimizations demonstrate that four ternary semiconductors are structurally stable. The mechanical parameters of Bi2Ti2O7 exhibit the highest resistance to deformation and average bonding strength, while Bi2Ti4O11 demonstrates the high shear deformation resistance. The Debye temperatures for these bismuth titanate semiconductors are in the following order: Bi2Ti4O11>Bi2Ti2O7>Bi4Ti3O12>Bi12TiO20. Both Bi12TiO20 and Bi2Ti2O7 exhibit high light absorption energies within specific ranges. Through the computational analysis presented in this paper, the theoretical data of bismuth-based semiconductors are enriched for further experimental investigations.