Modification Of Optical Properties Research Articles

A comparative study of gamma radiation-induced modifications in optical and structural properties of PANI/PVC composites

A comparative study of gamma radiation-induced modifications in optical and structural properties of PANI/PVC composites

Modulation of High-Intensity Optical Properties in CdS/CdSe/CdS Spherical Quantum Wells by CdSe Layer Thickness

Spherical quantum wells (SQWs) have proven to be excellent materials for suppressing Auger recombination due to their expanded confinement volume. However, research on the factors and mechanisms of their high-intensity optical properties, such as multiexciton properties and third-order optical nonlinearities, remains incomplete, limiting further optimization of these properties. Here, a series of CdS/CdSe (xML)/CdS SQWs with varying CdSe layer thicknesses were prepared. The modulation effects of CdSe shell variations on the PL properties, defect distribution, biexciton binding energy, and third-order optical nonlinearities of the SQWs were investigated, and their impact on the material’s multiexciton properties was further analyzed. Results showed that the typical CdS/CdSe(3ML)/CdS sample exhibited a large volume-normalized two-photon absorption cross-section (18.17 × 102 GM/nm3) and favorable biexciton characteristics. Optical amplification was observed at 12.4 μJ/cm2 and 1.02 mJ/cm2 under one-photon (400 nm) and two-photon (800 nm) excitation, respectively. Furthermore, different amplified spontaneous emission spectra were observed for the first time under one/two-photon excitation. This phenomenon was attributed to thermal effects overcoming the biexciton binding energy. This study provides valuable insights for further optimizing multiexciton gain characteristics in SQWs and developing optical gain applications.

Reversible Structural Phase Transitions in Zero-dimensional Cu(I)-Based Metal Halides for Dynamically Tunable Emissions.

Exploring structural phase transitions and luminescence mechanisms in Zero-dimensional (0D) metal halides poses significant challenges, that are crucial for unlocking the full potential of tunable optical properties and diversifying their functional capabilities. Herein, we have designed two inter-transformable 0D Cu(I)-based metal halides, namely (C19H18P)2CuI3 and (C19H18P)2Cu4I6, through distinct synthesis conditions utilizing identical reactants. Their optical properties and luminescence mechanisms were systematically elucidated by experiments combined with density functional theory calculations. The bright cyan-fluorescent (C19H18P)2CuI3 with high photoluminescence quantum yield (PLQY) of 77% is attributed to the self-trapped exciton emission. Differently, the broad yellow-orange fluorescence of (C19H18P)2Cu4I6 displays a remarkable PLQY of 83%. Its luminescence mechanism is mainly attributed to the combined effects of metal/halide-to-ligand charge transfer and cluster-centered charge transfer, which effects stem from the strong Cu-Cu bonding interactions in the (Cu4I6)2- clusters. Moreover, (C19H18P)2CuI3 and (C19H18P)2Cu4I6 exhibit reversible structural phase transitions. The elucidation of the phase transitions mechanism has paved the way for an unforgeable anti-counterfeiting system. This system dynamically shifts between cyan and yellow-orange fluorescence, triggered by the phase transitions, bolstering security and authenticity. This work enriches the luminescence theory of 0D metal halides, offering novel strategies for optical property modulation and fostering optical applications.

Modification of Structural, Optical, and Electrical Properties of PVA/PVP Blend Filled by Nanostructured Titanium Dioxide for Optoelectronic Applications

The PVA/PVP/TiO2 films were prepared using different TiO2 concentrations by solvent casting technique. An analysis was conducted to investigate the influence of TiO2 on the characteristics of PVA/PVP blends. The FTIR, UV/visible spectroscopy, and electrical bridge circuits were used to characterize the prepared nanocomposite films. The structural changes of the nanocomposite relative to pure PVA/PVP are indicated by FTIR spectra. The optical studies demonstrate that by increasing the TiO2 concentration inside PVA/PVP blends, the band gaps reduce from 5.40 eV for PVA/PVP to 4.20 eV for PVA/PVP/TiO2 (10 wt%), also the refractive indices the nanocomposites increase from 1.2020 for PVA/PVP blend into 2.5380 for PVA/PVP/TiO2 (10 wt%). Also, the transmittance decreased from 97.6% for PVA/PVP blend to approximately 55.4% at the largest concentration of TiO2. Additionally, studies were conducted on the parameters, as well, ac conductivity (σ ac). The outcomes of dielectric parameters of the prepared films are enhanced by the doping of TiO2 with different concentrations and dielectric relaxation is observed. The hopping mechanism of PVA/PVP/TiO2 films is supported by the ac conductivity. It is found that adding 10 wt% TiO2 inside PVA/PVP matrix at 5 MHz increases the conductivity of the pure PVA/PVP blend by 4.46 times.

Evidence of oxygenated species in laser-irradiated carbon particles

Combustion-generated carbon nanoparticles exhibit a variety of optical and physicochemical properties. Therefore, when applying laser diagnostic tools for monitoring purpose, it is important to consider the different response of the particles with varying properties as well as the impact of laser irradiation on these properties. In this work, we analyze the possible modification of particle optical and physicochemical properties by coupling extinction measurements with FT-IR and Raman spectroscopy. The aim is to retrieve optical, chemical, and structural properties of the particles under analysis. To our knowledge, the approach proposed in this work has not yet been performed on irradiated particles. Particles are sampled from a premixed flame at two heights above the burner, representing two different aging stages. While extinction measurements are carried out in-flow, FT-IR and Raman spectroscopy are performed on particles collected for ex-situ analysis. Moreover, the analysis is conducted on both pristine and irradiated nanoparticles with one and ten laser shots. While nascent particles do not exhibit relevant modification under laser irradiation, heating mature particles with one or more laser pulses of relatively high energy density is observed to significantly affect absorption properties, particle structures and specific surface functionalities. The presence of oxygenated species in mature particles and in particular the structures spectroscopically correlated with graphene oxide indicates that specific chemical reaction pathways can occur under laser irradiation, likely promoted in the ambient condition under analysis.

Strain-bandgap quasi-linear correlation applied to modulation of NiBr2 monolayer optical properties

Recently, two-dimensional transition metal dihalides have shown diverse applications in spintronics, quantum devices, and optoelectronic devices. In this work, density functional theory (DFT) is adopted to investigate the effect of biaxial strain upon the electronic structure and optical properties of NiBr2 monolayer. The results show that NiBr2 is an indirect semiconductor with band gap 2.62 eV (DFT + U) and 3.18 eV (HSE06), which could vary quasi-linearly from 2.73 eV to 1.71 eV modulated by biaxial strain (6 % to −10 %). Combined with the analysis of the density of states (DOS), the primary reason for the alteration in the band gap is that strain significantly affects the behavior of Ni 3d electrons. When the strain changes from positive to negative, the DOS of Ni 3d shifts towards the Fermi level, resulting in a reduction in the band gap. Within this strain range, all of the optical properties exhibit a quasi-linear tendency similar to the band gap variation. The optical peaks of NiBr2 under compressive strain are not only red-shifted into the visible light (VL) region but also significantly enhanced in the VL and ultraviolet (UV) regions. Applying strain can greatly boost the electrical and optical properties of NiBr2 monolayer, making it a promising candidate in the field of ultraviolet detectors.

Electric field-induced modulation of electronic and optical properties in doped CdTe/CdS core/shell quantum dots embedded in an oxide matrix

This work presents a theoretical analysis of a CdTe/CdS core/shell quantum dots embedded in a dielectric oxide matrix under the influence of hydrogenic impurity and the applied electric field intensity. The eigenstates and their corresponding eigenfunctions are computed by solving the Schrodinger equation using the finite element method within the effective mass approximation. The first-order linear and third-order nonlinear optical absorption coefficients as well as the refractive index changes are computed based on the compact density matrix approach. The obtained result shows that the first-order linear and third-order nonlinear optical properties are more pronounced with the electric field, surrounding oxide matrix and the donor impurity effects. However, the first-order linear and third-order nonlinear optical absorption coefficients and refractive index changes can experience a red or blue shift under the influence of electric field, oxide matrix and hydrogenic impurity. In addition, under all conditions, the height peaks of these optical properties can be raised (fall). Our findings demonstrate the critical importance of considering the roles of electric field, the presence of donor impurity, and the capped dielectric oxide matrix in the design and fabrication of core–shell-based optoelectronic devices.

Insights into impact of shock wave on structural, optical and surface characteristics of ammonium pentaborate tetrahydrate single crystal

In this study, we are emphasizing on growth of bulk size optically transparent single crystals of ammonium pentaborate tetrahydrate (APB) using the slow evaporation solution technique at room temperature. Initially, crystalline phase of the compound was confirmed through the X-ray diffraction technique. Thereafter, APB has been analysed systematically for its crystallographic structural stability in such a way that its structure has been examined periodically at two shock wave (SW) loaded conditions using XRD measurements. Further, our research contains a comprehensive knowledge about effect of shock wave on rocking curve of APB single crystal measured through high resolution XRD measurement system and the changes in crystalline perfection due to shock wave was analysed. Also, modifications in optical properties were studied due to impact of shock waves. The transmittance was checked through UV–visible spectroscopy and the changes in optical band gap were examined. The defects generated in the APB crystal after every two shocks i.e., shockwave - sample interaction was scrutinized by photoluminescence spectroscopy and surface morphology studies in detail.

An investigation of the structural and optical properties of modified barium magnesium fluoroborate glasses with hafnium oxide (HfO2)

AbstractGlasses of nominal composition xHfO2–(35-x)B2O3–15MgF2–35BaO, where x ranged from 0 to 0.2 mol% were fabricated using a melt-quenching technique. Structural characterization techniques, including X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and Raman spectroscopy, were employed to elucidate the glass network structure. The XRD patterns confirmed the amorphous nature of the studied glasses, while the FTIR and Raman spectra revealed that the incorporation of HfO2 may led to a transformation of trigonal BO3 units to tetrahedral BO4 units in the borate glass network. Deconvolution analysis of the FTIR and Raman bands provided quantitative insights into the extent of this structural rearrangement as a function of HfO2 content. UV–Vis absorption studies demonstrated that the optical bandgap of the glasses was widened with increasing HfO2 additions. This blue shift in the absorption edge was attributed to the increased formation of bridging oxygen bonds and reduced non-bridging oxygen content in the glass network. The results indicate that the studied glasses exhibit excellent compositional tunability through the incorporation of HfO2. The structural modifications and concomitant optical property enhancements suggest the potential of this glass system for various integrated photonic applications where low phonon energy and tailored transparency are highly desirable. The present work introduces a comprehensive investigation of the structural and optical property modifications in barium magnesium fluoroborate glasses induced by the addition of hafnium oxide (HfO2).

Nanostructured transition metal dichalcogenides-based colorimetric sensors: Synthesis, characterization, and emerging applications.

Nanostructured transition metal dichalcogenides (TMDCs) have garnered significant attention as prospective materials for the development of highly sensitive and versatile colorimetric sensors. This work explores the synthesis, characterization, and emerging applications of TMDC-based sensors, focusing on their unique structural aspects and inherent properties. The synthesis methods involve tailored fabrication techniques, such as chemical vapor deposition and hydrothermal processes, aimed at producing well-defined nanostructures that enhance sensor performance. Characterization techniques, including microscopy, spectroscopy, and surface analysis, are employed to elucidate the structural and chemical features of the nanostructured TMDCs. These analyses provide insights into the correlation between the material's morphology and its sensing capabilities. The colorimetric sensing mechanism relies on the modulation of optical properties in response to specific analytes, enabling rapid and visual detection. The emerging applications of TMDC-based colorimetric sensors span diverse fields, including environmental monitoring, healthcare, and industrial processes. The sensors exhibit high sensitivity, selectivity, and real-time response, making them ideal candidates for detecting various target analytes. Furthermore, their integration with complementary technologies such as microfluidics, can facilitate the development of on-site and point-of-care applications. This work highlights the interdisciplinary significance of nanostructured TMDC-based colorimetric sensors and underscores their potential contributions to addressing contemporary challenges in sensing technology.

Modification in electrical conductivity correlated with surface, structural & optical characteristics of graphite ions implanted CR-39

Ion implantation of laser induced graphite plasma has been performed for modifications in surface, optical, electrical and structural properties of CR-39. KrF Excimer laser (248 nm, 18 ns, 120 mJ), at an irradiance of 2.5 × 108 W cm−2 is utilized for the production of graphite plasma. The energy and fluence of graphite ions are estimated by Thomson parabola technique. The targets are implanted with energy of 710 KeV graphite ions for four fluences ranging from 26 × 1012 to 92 × 1015 ions/cm2, in presence of magnetic field of strength 90 mT. The digital optical analysis reveals well-arranged dendritic and island like structure formation on irradiated polymer surface. Confocal microscopic investigation illustrates the growth of nano/micro sized craters and hillocks for various ion fluences. Dissociation of bonds along with formation of new bonds is confirmed from Raman analysis. UV–Vis spectral analysis reveals that the optical transmittance values for visible regions of CR-39 are drastically reduced from 90 % to 68 % for maximum laser fluence of 92 × 1015 ions.cm−2. Significant improvement in electrical conductivity is achieved from 10−9 to 10−7 Scm−1 for lowest fluence value of graphite ions. SRIM software is utilized for the measurement of stopping power or Linear Energy Transfer (LTE) of 710 Kev graphite ions, is about, 55.53 eV/Ǻ, in the CR-39 targets.

Cover Feature: Synthesis and Optical Property Modulation of Substituted [2.2]Paracylophanes through Through‐Space Conjugation (Eur. J. Org. Chem. 25/2024)

Cover Feature: Synthesis and Optical Property Modulation of Substituted [2.2]Paracylophanes through Through‐Space Conjugation (Eur. J. Org. Chem. 25/2024)

Modification of morphological, structural and optical properties of graphene oxide by alteration molarity of aqueous KMnO4 solution

This work reports a nontraditional modified Hummer’s method to synthesize graphene oxide (GO) nanosheets by adjusting the oxidation process via a different-molarity potassium permanganate (KMnO4) solution instead of utilizing its powder. The effect of KMnO4 concentrations on the structural and morphological properties of GO nanosheets was studied. Oxidant solutions of 0.5 M, 1 M and 1.5 M were experimented to control the properties of the GO layers. Then, the samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), Raman and ultraviolet-visible (UV–Vis) spectroscopes. Finally, oxidant concentration was optimized at 1 M by which thinner, high-quality crystalline GO layers and wider bandgap energy ( E g ) were obtained. It is thus confirmed that such a modification in the oxidation is a pioneering process to improve the GO properties.

Strain-induced modulation of electronic and optical properties in hBN/InSe heterostructure

Strain-induced modulation of electronic and optical properties in hBN/InSe heterostructure

ZnMgO Thin Films by Ultrasonic Spray Pyrolysis: Modulation of Optical and Electrical Properties by Post‐annealing and Magnesium Composition

ZnMgO semiconductor is of major interest in sustainable thin‐film solar cells in order to replace buffer layers based on nonabundant or toxic elements. In addition, it has the potential 1) to allow optimal band alignment with absorbers such as CIGS, CZTS, and Cu2O; 2) to have high transparency; 3) to have adjustable properties for use as a window or buffer layer; and 4) to be deposited using low‐cost and energy‐efficient techniques such as ultrasonic spray pyrolysis. This study focuses on modulating ZnMgO properties with the optimization of the ultrasonic spray pyrolysis and post‐annealing parameters. Optical transmission, X‐ray diffraction, and van der Pauw/Hall effect measurements are used to study the material properties. Thin films with a strong <002> preferred orientation are obtained with large crystallite size (42–80 nm), high transparency (>90%), a bandgap increase from 3.28 to 3.34 eV with magnesium composition and annealing, an optimal Urbach energy of 0.068 eV, and electrical properties modulated by magnesium composition and annealing with resistivity varying from 6.520 Ωcm down to 0.022 Ωcm and a carrier concentration from 4.8 × 1017 up to 1.4 × 1020 cm−3.

Ion-irradiation induced structural, electronic, and optical properties modification in a few layered MoS2

Two-dimensional MoS2 is a promising candidate due to its layered structure, high conductivity, and fast charge transfer kinetics. In this work,the structural, electronic, and optical properties of pristine MoS2 have to be done by the ion irradiation technique with different ion fluences.The structural quality of the film has been confirmed by Raman spectroscopy, with peak positions of A1g and E12g indicating a few MoS2 layers. Fourier-transform infrared (FTIR) spectroscopy revealed the conformal fabrication of MoS2 nanosheets. Defect engineering by ion irradiation is an effective approach to tuning the intrinsic properties of Layered MoS2, as analyzed by photoluminescence spectroscopy.

POLarizer-FENestration (POLFEN) a novel concept of a glazing technology to modulate daylighting and glare in buildings

A conceptual new window/glazing technology called POLarizer-FENestration (POLFEN) is presented. In 1935, Edwin Land's pioneering work on polarizers successfully developed a sheet polarizer that was used in various applications. Subsequently, polarizers were employed in windows to modulate daylight and reduce associated glare. Early prototype windows were circular in shape so that the polarizing filter could be rotated to modulate the daylight. However, compared to rectangular-shaped windows that are ubiquitous, circular windows are rare in buildings. Therefore, a new window/glazing technology, discussed in this paper, was developed that utilizes a polarizing film in a conventional rectangular or square window, arranged in the form of strips or a checker-grid over the window panes to modulate daylighting levels and control glare. In this new research, a working prototype of the glazing technology is developed and demonstrated including simulations using the Radiance daylighting simulation software. In the current work, two types of measurements were taken: photographs of the indoor luminous environment and illumination levels (Lux) at selective points on the work-plane both in a physical prototype as well as in the simulation model under two sky conditions: CIE clear sky with sun, and overcast sky. The results indicate that the new glazing technology resulting from this concept can effectively modulate daylighting levels, minimized associated glare to an acceptable level while maintaining a view to the outdoor environment. The technology can be classified as Variable Transmission Glazing (VTG), similar to Electrochromic (EC) glazing since it also offers a dynamic modulation of solar optical properties (Tvis).

Macrocycle‐Based Charge Transfer Cocrystals with Dynamically Reversible Chiral Self‐Sorting Display Chain Length‐Selective Vapochromism to Alkyl Ketones

AbstractChirality‐driven self‐sorting plays an essential role in controlling the biofunction of biosystems, such as the chiral double‐helix structure of DNA from self‐recognition by hydrogen bonding. However, achieving precise control over the chiral self‐sorted structures and their functional properties for the bioinspired supramolecular systems still remains a challenge, not to mention realizing dynamically reversible regulation. Herein, we report an unprecedented saucer[4]arene‐based charge transfer (CT) cocrystal system with dynamically reversible chiral self‐sorting synergistically induced by chiral triangular macrocycle and organic vapors. It displays efficient chain length‐selective vapochromism toward alkyl ketones due to precise modulation of optical properties by vapor‐induced diverse structural transformations. Experimental and theoretical studies reveal that the unique vapochromic behavior is mainly attributed to the formation of homo‐ or heterochiral self‐sorted assemblies with different alkyl ketone guests, which differ dramatically in solid‐state superstructures and CT interactions, thus influencing their optical properties. This work highlights the essential role of chiral self‐sorting in controlling the functional properties of synthetic supramolecular systems, and the rarely seen controllable chiral self‐sorting at the solid‐vapor interface deepens the understanding of efficient vapochromic sensors.

Macrocycle-Based Charge Transfer Cocrystals with Dynamically Reversible Chiral Self-Sorting Display Chain Length-Selective Vapochromism to Alkyl Ketones.

Chirality-driven self-sorting plays an essential role in controlling the biofunction of biosystems, such as the chiral double-helix structure of DNA from self-recognition by hydrogen bonding. However, achieving precise control over the chiral self-sorted structures and their functional properties for the bioinspired supramolecular systems still remains a challenge, not to mention realizing dynamically reversible regulation. Herein, we report an unprecedented saucer[4]arene-based charge transfer (CT) cocrystal system with dynamically reversible chiral self-sorting synergistically induced by chiral triangular macrocycle and organic vapors. It displays efficient chain length-selective vapochromism toward alkyl ketones due to precise modulation of optical properties by vapor-induced diverse structural transformations. Experimental and theoretical studies reveal that the unique vapochromic behavior is mainly attributed to the formation of homo- or heterochiral self-sorted assemblies with different alkyl ketone guests, which differ dramatically in solid-state superstructures and CT interactions, thus influencing their optical properties. This work highlights the essential role of chiral self-sorting in controlling the functional properties of synthetic supramolecular systems, and the rarely seen controllable chiral self-sorting at the solid-vapor interface deepens the understanding of efficient vapochromic sensors.

Forecasting optical response in lieu of electronic properties of TlCaF3 via halogen substitution for UV filtration: a DFT perspective

ABSTRACT It is demonstrated that the substitution of Cl, B, and I at different concentrations in TlCaF3 significantly alters the phase, electronic band structure and optical, elastic, mechanical and anisotropic properties of the material. At 2.81% and 5.63% concentrations of all substituted elements, the cubic phase of TlCaF3 transforms into a pseudo-cubic tetragonal phase. With the addition of substitutional atoms, a systematic considerable narrowing of the bandgap is seen, and it can be either direct or indirect depending on the symmetrical positions. The bandgap shrinking can be addressed, in part, via the total/partial/elemental density of states (DOS) in line with structural variations. From the optical response, the refractive index rises with substitution atoms. According to the mechanical stability requirements for each substitution, the determined elastic constants for cubic and tetragonal structures match. Additionally, using elastic parameters, it is possible to estimate the unique mechanical features to evaluate the ductility and brittleness of pure and substituted compounds. Furthernore, Cl, Br and I-atoms’ substitution would make them a suitable choice for improved optimisation in ultraviolet filters (UVF) due to the existence of their absorption spectra in the ultra-violet region and the modification in structural, electrical, optical, elastic and mechanical properties.