Specific Optical Properties Research Articles

Towards visual color display with fast electric field response: Highly chromatic and stable colloidal photonic crystal inks

There is an increasing demand towards reflective color display devices with high contrast as well as eye-protection function. To this point, colloidal photonic crystal inks have attracted intensive attentions in terms of their unique abilities to enable vivid color variation upon external stimuli. In this paper, the SiO2-propylene carbonate (PC)-trimethylolpropane ethoxylate triacrylate (ETPTA)-based resins e-ink has been developed to construct photonic crystal photomodulation devices, which can realize electrophoresis-driven modification of structural color. Specifically, it is found that the addition of reduced graphene oxide (rGO) plays a key role in improving coloration, ink rheology and electrochromic response time simultaneously for its special optical and electrical properties. This work may be helpful for the design of e-inks aiming at reflective displays.

Theoretical Study on the Atom-Substituted Quinazoline Derivatives with Faint Emission as Potential Sunscreens.

Two novel compounds (HQS and HQSe) with excited-state intramolecular proton transfer (ESIPT) properties were designed based on the compound 2-(2-hydroxy-3-ethoxyphenyl)-3H-quinazolin-4-one (HQ). The parameters related to the ESIPT properties and electronic spectra of HQ and its derivatives were calculated using density functional theory and time-dependent density functional theory methods. The obtained geometric configurations, infrared vibrational spectra, and reduced density gradient scatter plots have shown that the intramolecular hydrogen bond O1···H1–N1 has been weakened upon photoexcitation. Moreover, from the scanned potential energy curves, it can be found that the ESIPT processes of the three compounds have no energy barriers. It is noteworthy that HQS and HQSe can strongly absorb light in the UVA region (∼340 nm) and exhibit weak fluorescence emission in the visible light region, which comes from the keto configuration. The special optical properties of HQS and HQSe can promote their application as potential sunscreen agents.

Construction of Molybdenum Disulfide/Biological Structure Carbon Composite Photocatalysts and Their Photocatalytic Hydrogen Production

The hydrothermal calcination method using bamboo leaves as the biological template, thiourea as the sulfur source, and molybdenum chloride as the molybdenum source was employed to synthesize the molybdenum disulfide/biological structure carbon (MoS2/C) photocatalytic composites with different concentrations of molybdenum chloride. The thermal decomposition behavior, surface morphology, phase structure, BET specific surface area, optical and photoluminescence properties, and photocatalytic activity of MoS2/C photocatalytic composites with different concentrations of molybdenum chloride were studied. The results showed that the optimal temperature for synthesizing MoS2/C photocatalytic composites is 700°C. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show that the hydrothermal calcination method can be used to load MoS2 onto the biological carbon and form a structurally stable composite system. Analysis of optical and photoluminescence properties shows that the MoS2/C composites prepared by the hydrothermal calcination method with the concentration of molybdenum chloride of 0.20 mol/L exhibit a high charge transfer and separation efficiency. Photocatalytic experiments show that the MoS2/C composites prepared by the hydrothermal calcination method with the concentration of molybdenum chloride of 0.20 mol/L have a high photocatalytic activity and cyclic stability. This excellent synthesis strategy can be used to synthesize other photocatalytic hydrogen production materials.

Mechanisms driving self-organization phenomena in random plasmonic metasurfaces under multipulse femtosecond laser exposure: a multitime scale study

Abstract Laser-induced transformations of plasmonic metasurfaces pave the way for controlling their anisotropic optical response with a micrometric resolution over large surfaces. Understanding the transient state of matter is crucial to optimize laser processing and reach specific optical properties. This article proposes an experimental and numerical study to follow and explain the diverse irreversible transformations encountered by a random plasmonic metasurface submitted to multiple femtosecond laser pulses at a high repetition rate. A pump-probe spectroscopic imaging setup records pulse after pulse, and with a nanosecond time resolution, the polarized transmission spectra of the plasmonic metasurface, submitted to 50,000 ultrashort laser pulses at 75 kHz. The measurements reveal different regimes, occurring in different ranges of accumulated pulse numbers, where successive self-organized embedded periodic nanostructures with very different periods are observed by post-mortem electron microscopy characterizations. Analyses are carried out; thanks to laser-induced temperature rise simulations and calculations of the mode effective indices that can be guided in the structure. The overall study provides a detailed insight into successive mechanisms leading to shape transformation and self-organization in the system, their respective predominance as a function of the laser-induced temperature relative to the melting temperature of metallic nanoparticles and their kinetics. The article also demonstrates the dependence of the self-organized period on the guided-mode effective index, which approaches a resonance due to system transformation. Such anisotropic plasmonic metasurfaces have a great potential for security printing or data storage, and better understanding their formation opens the way to smart optimization of their properties.

Sol-gel derived mesoporous TiO2: Effects of non-ionic co-polymers on the pore size, morphology, specific surface area and optical properties analysis

Titanium dioxide (TiO2) nanoparticles were synthesized using sol-gel method and incorporated with co-polymers polyethylene glycol (PEG), polyvinylpyrrolidone (PVP) and pluronic F127 as pore forming agents. The samples were then calcined at 550 °C for 4 h to evaluate the effect of these co-polymers on the pore size and specific surface area. X-ray diffraction (XRD) analysis revealed a rutile phase with crystalline diffraction peaks. Crystal system of the observed rutile phase for all samples was tetragonal assigned to the group space P42/mm (136). Porous morphology was observed from scanning electron microscopy (SEM) images with spherical nanoparticles from all synthesized samples. Upon calcining at 550 °C, samples showed morphology with more and clear pores compared to as-prepared samples and mesoporous type was observed through Nitrogen adsorption – desorption isotherm measurements. Brunnauer–Emmet–Teller (BET) revealed the specific surface area of ∼69.82, 37.80 and 57.08 m2/g for TiO2@F127, TiO2@PVP and TiO2@PEG, respectively, after calcining at 550 °C. The pore size was found to be ∼13.01, 10.10 and 8.53 nm for TiO2@F127, TiO2@PVP and TiO2@PEG, respectively. Ultimately, the comparison of the non-ionic co-polymers on TiO2 is done to evaluate the morphological properties, specific surface area, porosity and optical properties that could promote TiO2 to act as an efficient electron transport layer in solar cells application.

The comparative study of structural, electronic, and optical properties of hydrogen peroxide and its dihydrate under pressures: first-principle calculations.

Hydrogen peroxide (H2O2) is used as a fuel and propellant in fuel cells and rockets due to its prominent oxidizing and combustion properties. In addition, hydrogen peroxide, as the energetic material with the simplest molecular structure, exhibits general detonation performance under external stimulation. Based on the first-principle method, we calculated the two crystal structure, electronic properties related to sensitivity closely, optical properties of pure hydrogen peroxide, and 48wt.% hydrogen peroxide (H6O4) under pressure. We found that the band gaps of H2O2 and H6O4 become larger under pressure and the former is larger than the latter; neither has the tendency of metallization phase change. The added peak II of TDOS from H6O4 compared with H2O2 come from molecular H2O in crystal structure. The pressure-induced peak (peak 2 and peak II of TDOS from H2O2 and H6O4) splitting is caused by changes (stronger) in the intermolecular hydrogen bond environment in the crystal under pressure. The specific macroscopic optical properties have the characteristics of overall blue-shift under pressure, which is due to the blueshift of the conduction band and the increase of the band gap. We hope to provide some reference and guidance for deeper future research.

Applications and Immunological Effects of Quantum Dots on Respiratory System.

Quantum dots (QDs), are one kind of nanoscale semiconductor crystals with specific electronic and optical properties, offering near-infrared mission and chemically active surfaces. Increasing interest for QDs exists in developing theranostics platforms for bioapplications such as imaging, drug delivery and therapy. Here we summarized QDs’ biomedical applications, toxicity, and immunological effects on the respiratory system. Bioapplications of QDs in lung include biomedical imaging, drug delivery, bio-sensing or diagnosis and therapy. Generically, toxic effects of nanoparticles are related to the generation of oxidative stresses with subsequent DNA damage and decreased lung cells viability in vitro and in vivo because of release of toxic metal ions or the features of QDs like its surface charge. Lastly, pulmonary immunological effects of QDs mainly include proinflammatory cytokines release and recruiting innate leukocytes or adaptive T cells.

Microfibrillated cellulose films for mending translucent paper: an assessment of film preparation and treatment application options

Mending tears in translucent papers is a challenging task that requires mending materials with specific mechanical and optical properties. Recently, translucent films from microfibrillated cellulose have been suggested as an attractive alternative to traditional repair materials. We prepared custom films from a commercial microfibrillated cellulose suspension and compared their mechanical and optical properties as mending supports with commercially manufactured microfibrillated cellulose films and Japanese tissue. Tear mending of modern and historic translucent paper samples using the custom-made films and Klucel G or isinglass as adhesives showed satisfactory strength and resilience, and accelerated ageing tests yielded acceptable visual results. A case study on a translucent paper document from the collection of The National Archives, UK, is detailed. We conclude that custom-made tear mending materials from commercially available microfibrillated cellulose suspensions present a cost-effective and attractive approach for the mending of translucent papers.

Effects of Roughness and Texture on Surface Material Perception in Virtual Environments: The Psychophysics Approach

Effects of Roughness and Texture on Surface Material Perception in Virtual Environments: The Psychophysics Approach

Synthesis and photocatalytic activity of nickel doped zinc ferrite

Nickel Zinc ferrites are of great interest in the research community due to their special optical, magnetic, electrical and catalytic properties. Ferrites can act as an excellent photocatalyst due to their bandgap. This paper discuss the synthesis, structural and photocatalytic behavior of NixZn1-xFe2O4 (x = 0, 0.5, 1). Sol-gel approach is used for synthesizing nanoparticles. The structural evaluation is carried out by using the X-ray diffraction technique. The impact of Nickel substitution on the structural behavior of NixZn1-xFe2O4 is additionally studied. The lattice parameter monotonically decreases with growing Nickel substitution in Nickel -Zinc ferrite. The photocatalytic property of Nickel-Zinc ferrite is used to study the usage of the degradation of fluorescein dye underneath solar irradiation. Ni.5Zn.5Fe2O4 shows the best photodegradation efficiency among Nickel-Zinc ferrite series.

Homogeneous and well-aligned GaN nanowire arrays via a modified HVPE process and their cathodoluminescence properties.

In this work, we demonstrate the growth of homogeneous and well-aligned [0001]-oriented 1-D GaN nanoarrays via a modified hydride vapor phase epitaxy (HVPE) process using GaCl3 and NH3 as precursors. The density and length of the grown nanowires can be easily controlled by the process parameters. It was found that the growth technique provides Cl-rich growth conditions, which lead to special morphology and optical properties of the GaN nanoarrays. Different from reported GaN nanowires, the as-synthesized GaN nanoarrays in this study exhibit a hollow bamboo-like structure. Also, the cathodoluminescence spectrum shows strong visible luminescence between 400 and 600 nm wavelengths centered at 450 nm, and the disappearance of an intrinsic emission peak, which has been investigated in detail with the assistance of first-principles calculations. The strategy proposed in this work will pave a solid way for the controlled nucleation and growth of well-aligned GaN nanowire arrays which are significant for applications in large-scale integrated optoelectronic nanodevices, functionalized sensors and photoelectrocatalysis.

Logarithmic Relaxation of the Specific Volume and Optical Properties of GeS2 Densified Glass

Logarithmic Relaxation of the Specific Volume and Optical Properties of GeS2 Densified Glass

Sol-Gel Derived Mesoporous Tio2: Effects of Non-Ionic Co-Polymers on the Pore Size, Morphology, Specific Surface Area and Optical Properties Analysis

Sol-Gel Derived Mesoporous Tio2: Effects of Non-Ionic Co-Polymers on the Pore Size, Morphology, Specific Surface Area and Optical Properties Analysis

Role Played by Edge-Defects in the Optical Properties of Armchair Graphene Nanoribbons.

We explore the implementation of specific optical properties of armchair graphene nanoribbons (AGNRs) through edge-defect manipulation. This technique employs the tight-binding model in conjunction with the calculated absorption spectral function. Modification of the edge states gives rise to the diverse electronic structures with striking changes in the band gap and special flat bands at low energy. The optical-absorption spectra exhibit unique excitation peaks, and they strongly depend on the type and period of the edge extension. Remarkably, there exist the unusual transition channels associated with the flat bands for selected edge-modified systems. We discovered the special rule governing how the edge-defect influences the electronic and optical properties in AGNRs. Our theoretical prediction demonstrates an efficient way to manipulate the optical properties of AGNRs. This might be of importance in the search for suitable materials designed to have possible technology applications in nano-optical, plasmonic and optoelectronic devices.

Comparative Study of Modified Mueller Matrix Transformation and Polar Decomposition Parameters for Transmission and Backscattering Tissue Polarimetries

Mueller matrix polarimetry is widely used in biomedical studies and applications, for it can provide abundant microstructural information about tissues. Recently, several methods have been proposed to decompose the Mueller matrix into groups of parameters related to specific optical properties which can be used to reveal the microstructural information of tissue samples more clearly and quantitatively. In this study, we thoroughly compare the differences among the parameters derived from the Mueller matrix polar decomposition (MMPD) and Mueller matrix transformation (MMT), which are two popular methods in tissue polarimetry studies and applications, while applying them on different tissue samples for both backscattering and transmission imaging. Based on the Mueller matrix data obtained using the setups, we carry out a comparative analysis of the parameters derived from both methods representing the same polarization properties, namely depolarization, linear retardance, fast axis orientation and diattenuation. IN particular, we propose several modified MMT parameters, whose abilities are also analyzed for revealing the information about the specific type of tissue samples. The results presented in this study evaluate the applicability of the original and modified MMT parameters, then give the suggestions for appropriate parameter selection in tissue polarimetry, which can be helpful for future biomedical and clinical applications.

Porphyrin-infiltrated SiO2 inverse opal photonic crystal as fluorescence sensor for selective detection of trace mercury ion

Sensing of heavy metal irons in aqueous medium is essential because the presence of heavy metals is very hazardous for environmental safety and human health. Here, a porphyrin-infiltrated inverse opal photonic crystal of silica (TPP-SiO2 IOPC) as the solid optical sensor has been prepared for the selective detection of mercury iron (Hg2+) in aqueous medium, while porphyrin is served as a fluorescence probe and the photonic crystal (PC) provides support as the backbone with special optical property. The intensity of fluorescence during the detection of Hg2+ on the TPP-SiO2 IOPC sensor is 38.9 times larger than that of control sample. The sensor has good linear response to the concentration of Hg2+ from 1.0 × 10−8 to 1.5 × 10−6 mol/L and the lower detection limit observed for Hg2+ concentration is 1.18 nM. Furthermore, the sensor exhibits excellent selection for Hg2+ rather than other metal ions. Therefore, the TPP-SiO2 IOPC sensor can be utilized for fast and simple monitoring of Hg2+.

Metal Filled Light Emitting Porous Silicon as Platform for Tunable Optical and Magnetic Properties

The electrochemical filling of luminescent microporous silicon (PSi) with magnetic metals (Ni, Co) is presented which results in a composite system with specific magnetic and optical properties. The achieved physical properties are compared with mesoporous silicon loaded with Ni nanoparticles (NPs) of comparable size.The light emitting PSi samples are fabricated by electrochemical etching of a moderately doped p-type silicon wafer in a 10 wt% hydrofluoric acid solution. The achieved porous silicon offers a branched morphology with structure sizes in the range of a few nanometers. The observable visible luminescence is due to quantum confinement effects [1]. The challenging metal filling of these pores is carried out under cathodic conditions by pulsed electrodeposition. As electrolytes aqueous NiSO4 and CoSO4 solutions are employed. Correlated to the branched morphology of the PSi and thus also the deposited nanosized metal structures are interconnected. The structure size of the porous samples is estimated by photoluminescence measurements to 5 nm which also determines the diameter of the deposits.Mesoporous silicon is produced by anodization of a highly n-doped silicon wafer resulting in oriented pores with an average diameter of 50 nm [2]. The loading of these samples with Ni NPs is also carried out by electrodeposition. In contrast to microporous silicon the morphology of mesoporous silicon (mPSi) shows straight pores, grown perpendicular to the sample surface with a diameter up to 50 nm.Magnetic filling of meso- and microporous silicon, respectively means a change in the morphology as well as in the structure size of the magnetic precipitations and both influence the magnetic behavior of the composite system drastically.In the case of light emitting PSi also the luminescence is influenced in its intensity and wavelength by the magnetic filling. With enhanced metal filling a blueshift of the photoluminescence peak is observed.The magnetic properties are investigated with a Vibrating Sample Magnetometer (VSM) and a SQUID, respectively. A luminescence spectrometer is used to measure the intensity and the peak position with respect to the wavelength of the photoluminescence spectrum. The structure is investigated by SEM and TEM.Field dependent magnetization measurements show a distinct difference between metal filled luminescent PSi and mPSi loaded with Ni NPs. Considering luminescent PSi filled with Ni and Co, respectively a strong magnetic anisotropy between the two magnetization directions applying a magnetic field perpendicular and parallel to the surface, is observed, whereas in the case of Co this behavior is even more pronounced. The coercivities do not vary in a broad range between Ni and Co samples, mostly around 10% but the saturation field differs drastically between the two materials. Figure 1 depicts field dependent magnetization curves of luminescent porous silicon filled with Ni and Co, respectively. In contrast mesoporous silicon loaded with Ni NPs offers only a small magnetic anisotropy and also the role of easy axis and hard axis is changed. This different behavior of the two systems can be explained by the differing magnetic interactions between the metal deposits in the two systems. The presented systems which merge optical and magnetic properties within on system are of interest for optoelectronics and magneto optical on-chip devices.[1] Handbook of Porous Silicon, Ed. L. Canham, Springer Int. Publishing (2018).[2] P. Granitzer, K. Rumpf, Front. Phys. 8, 121 (2020). Figure 1

Investigation of the luminescence properties of ZnO clusters induced by single-photon and two-photon excitation

By using a luminescence spectrometer and femtosecond laser, we have investigated the specific optical properties and excitation mechanism of ZnO clusters with one-photon and two-photon excitations. When the excitation wavelength was chosen to be 360 nm, the strongest luminescence intensity was observed. However, the luminescence intensity decreased gradually and the emission peak was red shifted slowly with increasing excitation wavelength (from 360 to 400 nm). When the excitation wavelength was chosen to be 780 nm, the luminescence intensity increased nonlinearly with increasing excitation intensity. What is even more interesting is that ZnO clusters could be used in the imaging of living cells under two-photon excitation, implying the potential applications for the optical properties of ZnO clusters in the field of biophotonics.

Mechano‐Optical Response of Novel Polymer Composites Based on Elastic Polyurethane Matrix Filled with Low‐Molar‐Mass Cholesteric Droplets

AbstractAmong the various types of liquid crystalline (LC) structures, the cholesteric mesophase attracts special attention in view of helical supramolecular structure determining their specific optical properties. The helix pitch of cholesteric liquid crystals is very sensitive to mechanical stress, resulting in change of their optical properties and position of selective light reflection peak. Here, films of polymer‐dispersed cholesteric liquid crystals based on polyurethane elastomer are prepared and studied. Liquid crystal mixtures based on chiral cholesterol derivatives are uniformly dispersed in the form of micrometer‐sized droplets in an elastomeric matrix. A significant mechano‐optical response of the composites under the action of deformation is demonstrated, and the change in the position of the selective light reflection band during mechanical stress is studied in detail. A shift in the selective light reflection peak by 100 nm or more is found. This process is accompanied by color transformations of brightly colored films. Such materials can be promising for creating stress and deformation sensors, ripple and bending sensors, and other technical devices.

Structure–Property Relationships for Weak Ferromagnetic Perovskites

Despite several decades of active experimental and theoretical studies of rare-earth orthoferrites, the mechanism of the formation of their specific magnetic, magnetoelastic, optical, and magneto-optical properties remains a subject of discussion. This paper provides an overview of simple theoretical model approaches to quantitatively describing the structure–property relationships—in particular, the interplay between FeO6 octahedral deformations/rotations and the main magnetic and optic characteristics, such as Néel temperature, overt and hidden canting of magnetic sublattices, magnetic and magnetoelastic anisotropy, and optic and photoelastic anisotropy.