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Optical properties of electrochromic materials can be controlled by the application of an electric field allowing recent development of new applications such as smart windows technology for indoor climate control and energy conservation. We report the fabrication of a single-walled nanotube (SWNT) thin film based electro-optical modulator controlled by ionic liquid polarization in which the active electrochromic layer is made of a film of semiconducting (SC-) SWNTs and the counter-electrode is composed of a film of metallic (MT-) SWNTs. Optimization of this electro-optical cell allows the operations with an optical modulation depth of 3.7 dB and a response time in the millisecond range, which is thousands of times faster than typical electrolyte-controlled devices. In addition, a dual electro-optical device was built utilizing electro-optically active SC-SWNT films for each electrode that allowed increasing modulation depth of 6.7 dB while preserving the speed of the response. [ABSTRACT FROM AUTHOR]

Liquid crystals are unique functional soft materials where the direction of alignment can be easily controlled by external fields or by suitably treated surfaces. This simplicity of control has made liquid crystals very attractive materials for applications, particularly as the active medium in displays. These properties open a route for inclusion of carbon nanotubes in liquid crystals where the host's liquid crystalline phase gives an ordering effect on the carbon nanotubes doped into it. This ordering of carbon nanotubes significantly enhances the liquid crystals electro-optic properties and other physical parameters. In this review paper we have briefly reviewed the research on dispersion and alignment of carbon nanotubes liquid crystalline phases. [ABSTRACT FROM AUTHOR]

Abstracts In this work, a series of novel second order nonlinear optical chromophores modified by heteroatom-groups in electron-donor has been synthesized and systematically investigated. The resulting nonlinear optical chromophores exhibited both good thermal stability and good solubility in common organic solvents. UV–Vis spectra and density functional theory calculations were carried out to investigate the influence of heteroatom-groups on the electro-optic activities. The results revealed that increasing the electron-donor strength will not always improve the nonlinear optical activity of chromophore. There is a best match for electron-donor and acceptor. As to electro-optic activities, the doped polymer film- d3 displayed the highest electro-optic coefficient value of 37 pm/v at the doping concentration of 25 wt%. These results indicated that the nonlinear optical activities could be enhanced by finding the best match for electron-donor and acceptor in chromophore design. [ABSTRACT FROM AUTHOR]

To improve visible-light-driven photocatalytic activity of TiO2, the octahedral Bi2Ti2O7 nanoparticles have been successfully supported on TiO2 nanotubes (Bi2Ti2O7/TiO2) for the first time by a simple hydrothermal method. The structure and electro-optical property of the Bi2Ti2O7/TiO2 were characterized in detail. The obtained Bi2Ti2O7/TiO2 exhibited a markedly enhanced photocatalytic activity and good stability for degradation of organic pollutants under visible light. The study presents a new way to synthesize Bi2Ti2O7/TiO2 using TiO2 nanotubes as both supporter and reactant. [ABSTRACT FROM AUTHOR]

In this study, we demonstrated that doping polymer matrix with a small amount of reduced graphene oxide (rGO) component (0.05–0.2%) had significant influence on the polymerisation kinetics and electro-optical performances of polymer-dispersed liquid crystal films (PDLCs) fabricated with macro reversible addition-fragmentation chain transfer agents. The effects of rGO content were studied in terms of morphology, compound viscosity, polymer conductivity, polymerisation kinetics and driving voltage of PDLCs. The results exhibited that higher rGO content increased the compound viscosity and the entire process proceeded slowly. Furthermore, the addition of rGO increased the polymer conductivity and local electric field, and reduced the saturation voltage as well as the threshold voltage from 27.3 to 19.5 V and 13.2 to 6.41 V, respectively. [ABSTRACT FROM PUBLISHER]

Optical payloads comprise optical elements like lens or mirrors which are fragile and most susceptible to failure. It is paramount that the design enables the payload to give best performance in terms of optical parameters and survivability is the rudimentary design constraint. Simulation is carried out based on the load levels on a vibration shaker with prescribed input given to the shaker bed.Since the mechanical impedance for the shaker bed is infinite, the constraint forces are higher than what would actually be observed due to the dynamic absorber effect. NASA provides a semi-empirical method which enables us to compute the force limit spectrum based on the payload and deck model. This provides a notched input spectrum which alleviates over testing of the payload. Fabrication of optical elements is a costly affair, so physical testing cannot be carried out until confidence is achieved regarding stress levels in the optical element. This calls for a methodology for analytical stress prediction. In this manuscript, we demonstrate a methodology to predict stresses in components analytically after predicting the notched input profile based on force limits before proceeding to testing at full level. We have also established a methodology to calculate sum of constraint forces in case of multiple constraint system taking into account the phase of the forces.FE and programming tools have been used in this work.A methodology which instils confidence in designer to test optical payloads at full level was successfully developed and demonstrated on an electro-optical payload. Stress profiles were computed analytically on all mirrors before going for actual testing. [ABSTRACT FROM AUTHOR]

The conductance of polymer matrix is an important factor for the property of the polymer dispersed liquid crystal (PDLC). The nanographites are dispersed into the polymer matrix for optimising the dielectric conductive property. The synthesised nanoparticles SiO2was used as photonic crystal (PC) to work as a template for fabricating PDLC films. A mixture of pre-polymer and liquid crystals (LCs) was infiltrated into the void of the PC and polymerised under ultraviolet light. The void of the PC made uniform the dispersion of the liquid crystals in the films. The optical property of the PDLC films was optimised by doped nanographites and negative charge SiO2template. The effect of negative charge SiO2and nanographites on the threshold voltage and driving voltage was researched. The morphology of the PDLC films was studied by the FTIR image. The dispersed LCs droplets were uniformly affected by the addition of the nanographites. The LCs droplets dispersed in the polymer were located in the void of the SiO2photonic crystal. [ABSTRACT FROM PUBLISHER]

A polymer-dispersed liquid crystal based on a biphenol A diglycidyl ether (E-44) and 4-pentyl-4′-cyanobiphenyl was prepared by a method of polymerized-induced phase separation. Electro-optical transmissions of the biphenol-A epoxy resin dispersed liquid crystal were measured as a function of applied alternating voltage over a range of 0–90 V for a liquid crystal cell gap of about 20 μm. Influences of heat treating time and content of firming agent on the electro-optical transmissions of the biphenol A diglycidyl ether dispersed liquid crystal were discussed. [ABSTRACT FROM AUTHOR]

In this article, bistable cholesteric liquid crystal (CLC) light shutters have been fabricated and the effect of dichroic dye on their morphological and electro-optical properties was studied. Experimentally, two different sample cells were prepared for pure CLC and 0.5 wt% dichroic dye (azo orange 3) doped CLC. The morphological behaviour of bistable CLC light shutters observed in transmissive and scattering modes represents planar and focal-conic (FC) states on applied voltages under high and low frequencies, respectively. The voltage-transmission and absorbance characteristics were examined and found the operating voltage lowered with the doping of dichroic dye in CLC. Moreover, dye doped CLC light shutter showed the higher stabilization rate (SR) for planar state along with better contrast ratio (CR) compared with pure CLC light shutter. In addition, phase transition studies of pure and dye doped CLCs have been discussed. • Morphological behaviour of pure and dye doped bistable cholesteric liquid crystals (CLCs) in transmissive and scattering mode. • Bistability of CLC light shutters under zero applied voltage. • Significant reduction of operating voltage with improved contrast ratio (CR) of dye doped bistable CLC light shutter. • Bistability's factor stabilization rate (SR) dependence on electro-optical properties. • Phase transition studies of CLC light shutters. [ABSTRACT FROM AUTHOR]

Polymerisation-induced phase separation method was used to prepare dye-doped polymer-dispersed liquid crystal (DPDLC) films consisting of nematic liquid crystal, photo-curable pre-polymer and a dichroic dye. The change occurring on droplets morphology with the change in dye concentration and voltage was investigated by means of polarising optical microscope and scanning electron microscope. Electro-optic behaviour of these composite films in the presence of an externally applied AC electric field (0–100 V, 200 Hz) and temperature range 25–50°C was evaluated using He–Ne laser. The maximum absorbance of dye and effect of electric field on the absorbance of dye was studied using UV-Vis spectrophotometer. Dielectric relaxation spectroscopy was carried out in the frequency range 20 Hz–20 MHz and over the temperature range 25°C–90°C. Dielectric parameters such as distribution parameter, relaxation frequency, relaxation strength and relaxation time of these DPDLC films were calculated, and the modelling of experimental data was done using Debye and Cole–Cole method. [ABSTRACT FROM AUTHOR]

• The effect of BT2/BT4 NC on the electro-optical and dielectric properties of a NLC is discussed. • The synthesis of BT2/BT4 NC has been performed by in-situ co-precipitation method. • Noticeable change in dielectric properties as the function of frequency, DC bias and temperature observed. • The significant changes observed in dielectric properties of 5CB are due to interaction among LC molecules and NCs. • The BT2/BT4 NC enhanced memory in the NLC. We report here the concentration and temperature dependent optical, electro-optical and dielectric studies on bismuth titanate (Bi 2 Ti 2 O 7 /Bi 4 Ti 3 O 12) nanocomposite (BT2/BT4 NC, ∼42 nm) doped nematic liquid crystal (NLC, 5CB) mixtures using optical polarising microscope and dielectric spectroscopic techniques. The optical textures confirm the uniform dispersion and miscibility of NCs in 5CB for all concentrations (i.e. 0.1, 0.25, 0.5, 1 and 2 wt%) and mixtures appear to be almost agglomeration free. The dielectric studies demonstrate the maximum changes in the dielectric parameters (dielectric permittivity, dielectric loss, loss factor and dielectric anisotropy) of 5CB sample for the 0.1 wt% mixture. Interestingly, the dielectric anisotropy of 5CB in 0.1 wt% mixture is increased by ∼ 11%. However, the dielectric memory effect (bias voltage ON-OFF) is observed maximum in the case of 1 wt% mixture. Similarly, the optical memory examined by bias voltage dependent (ON-OFF) optical textures is also significantly enhanced for 1 wt% mixture. The significant changes observed in dielectric properties of 5CB sample could be due to plausible interaction among NLC molecules and ionic impurities with BT2/BT4 NCs. Moreover, the enhanced volatile memory in BT2/BT4 NC-NLC mixture could be attributed to the dipole–dipole coupling between individual permanent dipole moment of anisotropic NLC molecules with the dipole moments generated by the ionic impurities agglomerated on the surface of high dielectric BT2/BT4 NCs. We strongly believe that such NCs-NLC mixtures would be certainly useful in the advancement of wearable devices (such as smart plenoptic cameras, watches etc.) and smart switchable windows. [ABSTRACT FROM AUTHOR]

Three structural variants of azo substituted achiral bent-core compounds are reported. Here, the effect of symmetrical and non-symmetrical arms at 1,3-positions of the central phenyl ring on the mesogenic properties of the resulting bent-core azo compounds is studied. The structures of all the compounds synthesised are confirmed by the organic spectroscopic methods. The liquid crystalline properties are investigated using polarising optical microscopy, differential scanning calorimetry and X-ray diffraction studies. It was found that the non-symmetrical molecules are more conducive to mesomorphism than the symmetrical ones. We observed B1(Colr), B2(SmCAPA) and B7mesophases in these compounds. The B7mesophase was found to have a modulated layer structure. Interestingly, a reversible field-induced transition from the B7-like structure to the racemic SmCAPFwas also observed. We also report the photo-induced studies in the B7mesophase and make a comparison of these results with those obtained in a B2mesophase. From our studies, we observed that these effects are more profound in the case of B7mesophase when compared to the B2mesophase in such systems. [ABSTRACT FROM AUTHOR]

Here, we report four new homologous series of azo-functionalised achiral bent-core compounds. The paper deals with the design, synthesis and liquid crystalline properties of four new homologous series of photochromic materials. In this study, we have investigated the effect of the presence of –N=N– linkage at different locations of the molecular architecture, on the mesomorphic properties. The molecular structures of all the newly synthesised compounds are established using the organic spectroscopic methods. The liquid crystalline properties are investigated using polarising optical microscopy (POM), differential scanning calorimetry (DSC), X-ray diffraction and electro-optical studies. They exhibit B1(colr) and B2(SmCAPA) mesophases. We find that the presence of the –N=N– linkage at different locations in the molecular architecture does not seem to have much effect on the mesogenic behaviour of such compounds. However, we clearly see a profound effect of the location of the –N=N– linkage on the photo-induced electro-optical properties of these compounds. [ABSTRACT FROM AUTHOR]

This work reports the effect of dye on the photopolymerisation and electro-optical properties of polymer dispersed liquid crystal (PDLC) composite films. Dichroic PDLC (DPDLC) films based on a photocurable polymer and nematic liquid crystal (LC) with an azo dichroic dye were prepared by photopolymerisation-induced phase separation method. Polarising optical microscopy has been used for monitoring the phase separation kinetics and two-phase morphology evolution in the DPDLC system. LC domains with radial structures during initial period of phase separation adopted a resultant morphology of bipolar configuration over the course of polymerisation. The phase separation and morphology of LC domains was found to be dependent on the amount of dye used. Moreover, the addition of small amount of dye reduced the switching voltage, and enhanced the contrast ratio with improved switching time in the PDLC films. It was shown that, under the application of an electric field, the molecular orientation and absorbance of dichroic dye can be controlled in DPDLC to induce non-linearity and colour contrast without the use of polarisers. [ABSTRACT FROM AUTHOR]

This work reports a recently developed electro-optical (EO) device that can potentially be used as a light shutter or a privacy window. By using nanocrystalline cellulose rods, we were able to improve some of the most relevant parameters characterising the EO behaviour. A brief description of the proposed working mechanism for these devices is presented, and numerical simulations based on this mechanism of both the optical transmission and the cells' electrical capacitance are compared with the obtained results, validating the underlying working model considered. [ABSTRACT FROM PUBLISHER]

A water-soluble ionic polyacetylene, poly(2-ethynyl-N-pentylpyridinium iodide) [PEPPI] was prepared by the uncatalyzed polymerization of 2-ethynylpyridine by using 1-iodopentane in high yield. PEPPI-iron(III) chloride complex was prepared by the reaction of PEPPI and iron(III) chloride in DMF and its properties were characterized. The electrical conductivity of PEPPI-iron(III) chloride complex was 4.3 × 10−4 S/cm. The photoluminescence (PL) spectra of PEPPI-iron(III) chloride complex showed that the photoluminescence peak is located at 578 nm, corresponding to a photon energy of 2.15 eV. The cyclic voltammograms of PEPPI-iron(III) chloride complex exhibited irreversible electrochemical behaviors between the doped and undoped peaks. It was found that the kinetics of the redox process of polymer is controlled by the reactant diffusion process. [ABSTRACT FROM PUBLISHER]

Macro reversible addition-fragmentation chain transfer (RAFT) agents, i.e. RAFT polystyrene (RAFT-PS) and RAFT poly( n-butyl acrylate) (RAFT-PBA), were mixed. Polymer-dispersed liquid crystals (PDLCs) were prepared using the mixture together with methyl acrylate and liquid crystal E7. The electro-optical properties of the PDLCs obtained were investigated. The results showed that the advantages of the electro-optical properties of RAFT-PS- and RAFT-PBA-dependent PDLCs could be combined in RAFT agent mixture-dependent PDLCs. Copyright © 2011 Society of Chemical Industry A reversible addition-fragmentation chain transfer agent mixture can greatly improve the electro-optical performance of polymer-dispersed liquid crystals. [ABSTRACT FROM AUTHOR]

We examine the differences in electro-optical behavior of weakly polymer stabilized cholesteric liquid crystals (PSCLC) when formed using either a flood lit UV lamp, a flood lit UV laser, or a holographically patterned UV laser. Both samples formed with the UV laser exhibit symmetry in their dynamic electro-optical properties relative to the front and rear surface of the polymerized cell. These cells exhibit a reversible ∼100 nm blue shift tuning of the notch upon application of a field when the reflectivity is measured from either side. The UV lamp sample exhibits large differences in behavior when examined from the front or back relative to the direction of the polymerizing source. The front surface exhibits tuning of the notch while measurements from the back surface yield only the typical binary switching behavior of a CLC. The overall switching fields in flood lit UV laser and UV laser holographically patterned samples are also considerably lower. These differences are explained due to the presence of a strong polymer gradient across the cell gap in the UV lamp flood lit samples which is not present for the UV laser stabilized samples. We also present novel electro-optical results when these laser cured cells are examined in transmittance mode. Strong anchoring at the two surfaces causes a strong anisotropic local LC structure across the cell gap when a field is applied. The two local environments next to each surface act to strongly pin the CLC structure whereas within the bulk, ample reorientation of the LC molecules occurs. When probed in transmission, unusual fringe patterns which change with the strength of the applied field are observed. [ABSTRACT FROM AUTHOR]

Single crystalline ultrathin films of (Ba,Sr)TiO3 (BST) and BiFeO3 (BFO) on MgO (001) substrate were fabricated by RF sputtering at high oxygen pressure, electric filed in planar geometry was applied by interdigital electrode system. Based on the obtained materials switchable ferroelectric and multiferroic nanostructures were fabricated by focused ion beam milling. The structure, dielectric, linear-optical and nonlinear (electro)optical properties of the films of different thicknesses in wide range of frequencies of applied voltage were studied. High efficiency of planar ferroelectric switching is shown. Nanostructuring allows to change dielectric and optical properties of ferroelectric materials and increase in this way the range of switchability of functional parameters. Fabricated structures with high switchability efficiency and low dielectric losses are very promising for fabrication of electro-optical modulators; small size combined with high switching contrast provides conditions for efficient integration in planer geometry. [ABSTRACT FROM AUTHOR]

In this study, polymer dispersed liquid crystal (PDLC) films comprising a phase separated low molecular weight thermotropic liquid crystal (LC) and high molecular weight polymer were, prepared using the polymer–induced phase separation method. In order to enhance the optical efficiency of the PDLC films, LC was doped with dichroic azo dye. Various characterization techniques were employed to determine the properties of the components and, the operating principles of the dye–doped PDLC (DPDLC) films. Morphological studies using polarizing optical microscopy and scanning electron microscopy indicated that the LC droplet configuration changed with various dye concentrations and voltages. Electro-optical analysis showed that the performance of the DPDLC film with a low dye concentration (0.007%) was excellent, with a high contrast ratio (241) and transmittance difference (ΔT = 98.57%), low threshold (V TH = 0.85 V/μm) and saturation voltages (V SAT = 1.45 V/μm), and a minimum hysteresis effect. The effects of temperature on the electro-optical properties of the DPDLC films were studied. Absorbance analyses were conducted using ultraviolet–visible spectrophotometry to complement the transmittance analyses. Dielectric relaxation spectroscopy was employed to measure relaxation frequency/time of DPDLC films. Debye and Cole – Cole modeling were conducted to understand nature of the relaxation process. The zero values of the distribution parameter (α) for all of the DPDLC composite films confirmed their Debye type relaxation process. • Alignment of guest dye molecules with host liquid crystal (LC) to control electro-optic properties. • Properties of polymer dispersed LC (PDLC) films enhanced by doping with dye molecules. • Cole–Cole plots demonstrated Debye type relaxation in doped PDLC films. [ABSTRACT FROM AUTHOR]

Abstract: In order to investigate the electro-optical property variations among the target topology-varied polymers with diverse molecular architectures, a series of polymers (P0–P2), having sterically hindered side chains, based on fluorene and pyridine derivatives were successfully synthesized via simple synthetic route and fully characterized via various spectroscopic methods and cyclic voltammetry measurements. The experiments demonstrate that all polymers with almost equivalent absorption and photoluminescence emission properties take on a wide band gap with blue emission in THF solution and thin solid film. However, their energy levels derived from the onset of electrochemical potential in thin solid films exhibit significant differences, which are considered to be due to the branched molecular frameworks on the basis of theoretical calculations. It is demonstrated that the electro-optical properties of wide band gap rigid noncoplanar copolymers are tunable by the sterically hindered pyridine moieties, and these experiments can serve as an excellent exploratory example for fine band gap and photophysics control principle in the p–n heterostructure polymers through the partial planarization of the π-system. [Copyright &y& Elsevier]

The electro-optical and electrochemical properties of poly(2-ethynylpyridine) was studied and discussed. Poly(2-ethynylpyridine) was prepared by the polymerization of 2-ethynylpyridine by using the catalyst of WCl6-EtAlCl2. The photoluminescence (PL) spectra of the polymer showed that the photoluminescence peak is located at 581 nm, corresponding to a photon energy of 2.14 eV. The cyclic voltamograms of polymer exhibited reversible electrochemical behaviors between the doped and undoped peaks. The kinetics of the redox process of polymer was controlled by the diffusion process from the experiment plotting the oxidation current density of polymer versus the scan rate. [ABSTRACT FROM AUTHOR]

The evolution of an amorphous-like to a polycrystalline microstructure and the composition of Ta–Si–N nanocomposites was controlled by nitrogen flow ratios during reactive cosputtering. It influences the chemical bonding, electrical resistivity and optoelectronic luminescent properties of Ta–Si–N films. Amorphous-like Ta–Si–N films formed at a Si/(Si+Ta) ratio larger than 6% had much finer grains, smoother morphology, lower Ta 4f7/2 binding energy and lower resistivity compared to polycrystalline films. A strong visible photoluminescence was observed at Ta53Si7N40 compositions for a peak maximum at 554nm (2.24eV). [Copyright &y& Elsevier]

Abstract: Based on an optimized bonding technique for semiconductor lasers, parametric investigations of different bonding configurations were performed using AuSn solder. No abrupt electrical degradation was observed for both face-up and face-down bonding configurations. The typical optical output achieved for face-up and face-down bonding approach was about 100 mW/facet and 150 mW/facet, respectively. Face-up bonded LDs exhibited a steady differential quantum efficiency η D of ∼0.425 mW/mA before gradual degradation at 200 mA, while face-down bonded LDs improved its performance beyond 350 mA. The characteristic temperature T 0 also improved to as much as 643 K for face-down bonded LDs. Spectrally-resolved emission measurement showed that the temperature rise in unbonded, face-up bonded and face-down bonded LDs were approximately 11, 7–8 and 2–3 °C, respectively. These investigations showed that the improved performances for face-down bonding approach compared to face-up approach were due to better thermal management. [Copyright &y& Elsevier]

Abstract: Indium tin oxide (ITO) thin films were deposited on glass substrates by RF sputtering system at different sputtering pressure (SP) (20–34mTorr) and room temperature. The sputtering pressure effects on the deposition rate, electro-optical and structural properties of the as-deposited films were systematically investigated. The optimum sputtering pressure of 27mTorr, giving a good compromise between electrical conductivity and optical transmittance was found to deposit films. The films were heat-treated in vacuum (200–450°C) and their electro-optical and structural properties investigated with temperature. A criterion factor Q, which is the ratio between the normalized average transmission to normalized resistivity was defined. It has been observed that Q has its maximum value for heat treatment at 400°C and the X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis proves the films have preferred crystal growth towards (222) direction and average size of grains are 35–40nm. [Copyright &y& Elsevier]

This paper presents the CN2 model for calculating the micrometeorological influences on the refractive index structure parameter. The CN2 model is a semi-empirical algorithm developed by the U.S. Army Research Laboratory to provide realistic values for the refractive index structure parameter over land given two vertical levels of conventional wind speed, temperature, and humidity data as input. The CN2 model is based on the structure function formulations of Tatarski. Equations for the real index of refraction are expressed in terms of temperature, pressure, and moisture (preferably the conserved elements potential temperature and specific humidity). Calculations of micrometeorological profile structure are carried out via Monin–Obukhov theory for the surface layer. Model results can be derived for unstable, stable, and near-neutral atmospheric conditions. The CN2 model algorithm is validated in comparison to optical scintillometer data collected at 2 m above ground level over a 450 m path. The paper reported here contains technical and user’s guide information on the CN2 model. [Copyright &y& Elsevier]

The evolution of the intensity profile of TEA CO2 laser pulses along the pulse length is investigated both analytically and experimentally. A simple scalar model of the pulse amplitude is introduced, which gives the loaded-cavity modes as a linear combination of bidimensional Hermite-Gauss functions. According to this model a number of equations are derived which link the time-varying spatial structure of the pulse to its time-resolved second-order intensity moments, namely, the beam width and the M2 parameter. [ABSTRACT FROM AUTHOR]

A paradigm for high-quality factor (Q ) with a substantial fulfillment for appraising sensing ability and performance has been investigated. Through constructing a 1D (one-dimensional) topological photonic crystal (PhC) mirror heterostructure, which is formed by the image view of 1D topological PhC stacking with its original one. In the 1D topological PhC-mirror heterostructure, there is an interesting mode that appeared with the symmetric, typical Lorentzian-line shape with 100% transmittance in the topological mirror edge-state mode (hybrid resonance mode) at the heterostructure interface. Physically, such a mode is a defect mode, but the defect is introduced through topological operations. The high Q -factor of 5.08 × 104 is obtained due to the strong optical localization of the defect mode at the topological edge area. Consequently, this device acts as a narrow passband filter. Moreover, due to the narrow bandpass property, it may be an advantageous reference for many applications in filtering, switching, and sensing. Thus, introducing an electro-optical (EO) polymer layer at the interface to modify the edge defect can tune the defect mode both in frequency and Q -factor for higher spatial pulse compression and higher EO sensitivity. Accordingly, the Q -factor of 10 5 , the sensitivity of 616 nm/RIU, and the figure of merit of 49,677.42 RIU−1 are obtained. The sensing ability and performance are attributable to the strong optical localization in the interface region and enhanced light-matter interaction. We predict that the 1D topological PhC mirror heterostructure will be an outstanding point in the field of optical sensing, filters, and optical switching in different fields. [ABSTRACT FROM AUTHOR]

In this study, the microstructure and stoichiometry of ZnO seed layer driven by a novel electrospun method were evaluated for fabricating a thin film of ZnO nanorods (NRs). The impact of Al and Cu dopants on the morphology, microstructure, composition, and hydrophobicity of seed layers was investigated to understand the stoichiometry role of the seed layer in the optical and photoelectrochemical (PEC) properties of ZnO NRs. The results revealed that nanofibers (NFs) were completely transformed into the uniform coating composed of ZnO wurtzite nanoparticles (NPs) with an average size of 18.2 nm suitable sites for conducting the ZnO NRs. With increasing of the stoichiometry of the ZnO seed layer the homogeneity of morphology, the potential growth factor of (002) plane, and the hydrophobicity behavior of seed layers increased, and eventually, the ZnO NRs with a higher l/d ratio, photon absorption, intrinsic defect points, and lower bandgap were formed. The PEC assays indicated that the maximum photocurrent density (0.06 mA cm−2) and photon conversion efficiency (0.35%) were obtained for the ZnO NRs grown on the electrospun ZnO seed layer with the highest stoichiometry. Furthermore, the electrochemical impedance spectroscopy (EIS) and Mott-Schottky (M − S) tests confirmed that the charge transfer resistance and the charge carrier density depend on the stoichiometry of the ZnO seed layer. [Display omitted] • Stoichiometric and non-stoichiometric electrospun ZnO seed layers were provided. • Electro-optical properties of ZnO NRs depend on stoichiometry of seed layer. • Growth of (002) plane in seed layer has severe impact on the morphology of ZnO NRs. • Charge transfer resistance and carrier density depend on seed layer stoichiometry. • Maximum photon conversion efficiency obtains by pure ZnO seed layer. [ABSTRACT FROM AUTHOR]

Lanthanum doped Z n 0.5 C o 0.5 L a x F e 2 − x O 4 spinel ferrites were synthesized through the co-precipitation technique. To characterize the structural, vibrational, electro-optical, dielectric, and thermoelectric properties, the following characterization techniques X-ray diffraction (XRD), Fourier transformation infrared (FTIR) and Raman spectroscopy, I–V measurement analysis, UV–vis spectroscopy, LCR meter, Seebeck analysis, and Energy dispersive X-ray analysis (EDX) were used. The XRD patterns showed nano-crystalline single-phase structure formation. Moreover, the lattice constant increased from 8.3909 ± 0.0042 Å to 8.3994 ± 0.0042 Å, and the crystallite size reduced from 33.6 to 17.5 nm with increasing La3+ cations. The bond angles showed stronger A – A and A – B interactions and weak B – B interactions with the addition of La3+. FTIR spectra showed the existence of the M − O stretching band and functional group study. The resistivity, optical band gap, and activation energy had maximum values at x = 0.1. At room temperature (RT), the dielectric parameters were recorded between the range of 8 Hz to 8 MHz. The Seebeck voltage coefficient was obtained for the as-prepared nano-ferrites to determine the charge carrier type. The EDX spectra showed a compositional distribution of the elements in all the samples. • Z n 0.5 C o 0.5 L a x F e 2 − x O 4 nano ferrite powder was prepared via the co-precipitation route. • Single-phase crystal structure and crystallite size decreased with La3+ in Zn–Co ferrites. • The optical band gap and DC resistivity were maximum at x = 0.1. • Z n 0.5 C o 0.5 L a 0.1 F e 1.9 O 4 has a small dielectric tangent loss at low frequency. [ABSTRACT FROM AUTHOR]