Spun films of perylene diimide derivative for the detection of organic vapors with host–guest principle

The optical characterization and chemical vapor sensing properties of 1,7-dibromo-N,N′-(bicyclohexyl)-3,4:9,10-perylene diimide thin film against to organic vapors were discussed in this study by using spin coating, UV–Vis spectroscopy, atomic force microscopy, surface plasmon resonance (SPR) and Quartz Crystal Microbalance (QCM) techniques. The perylene diimide thin films were fabricated with a refractive index values from 1.55 to 1.60 and thicknesses in the range between 15.80 and 26.32 nm using different spin speeds from 1000 to 5000 rpm. In this study, perylene diimide thin film sensor was exposed to dichloromethane, chloroform, carbon tetrachloride, tetrahydrofuran and ethyl acetate vapors by using both SPR and QCM techniques. Also, the swelling behaviors of the perylene diimide thin films prepared at different spin speeds were investigated with respect to dichloromethane vapor at the room temperature by using SPR data. Diffusion coefficients were found to be 11.34?×?10^?17 (1000 rpm), 2.56?×?10^?17 (3000 rpm) and 0.38?×?10^?17 cm² s^?1 (5000 rpm) for dichloromethane vapor by using the Fick’s law of diffusion. It might be proposed that perylene diimide thin film optical chemical sensor element has a good sensitivity and selectivity for the dichloromethane vapor at room temperature.     

Double telecom band thermo-optic switch based on dual-line filled photonic liquid crystal fibres

We demonstrate a thermo-optic switch based on photonic liquid crystal fibres (PLCFs) in which two lines of air hole are selective filled with liquid crystal (LC), with a high extinction ratio of more than 20 dB around 1310 nm and 1550 nm. Only in the range of 2.0°C it can perform a turn off and on operation of transmitted light in the second telecom band around 1550 nm while the first telecom bands around 1310 nm is still on. Due to the splitting of the bandgap, the switching function is achieved in this kind of PLCFs. Before the cleaning point (CP) of LC, a broad bandgap from about 1120 nm to 1320 nm splits into two ones, which are continuing inducing huge bandgap extension to shorter wavelength and longer wavelength after the CP of LC, respectively. Moreover, the temperature responses around the CP of LC is also investigated. Its sensitivity is about ?92.32 nm/°C around the CP of LC. Therefore, such kind of selective-filled PLCFs could find potential applications as thermo-optic switch and temperature sensor in the telecom band.     

A Study on Liquid Hybrid Material for Waveguides—Synthesis and Property of PSQ‐Ls for Waveguides

Silicate‐based inorganic‐organic hybrid polymer systems have many unique properties including thermal stability and photo‐stability, chemical resistance with the combination of tunable optical properties. Two kinds of new UV‐patternable hybrid materials PSQ‐Ls were synthesized by a sol‐gel process at room temperature, which can be used for low cost fabrication of optical waveguides. Thick films (up to 8.31 µm) can be coated by a single spin‐coating process without any cracking and the average surface roughness (Ra), detected by atomic force microscopy (AFM), is below 0.5 nm. The optical properties (refractive index, birefringence, and optical loss at 1310 nm and 1550 nm, respectively) of the PSQ‐Ls films are investigated by a prism coupler. The refractive index of PSQ‐Ls can be exactly tuned from 1.4483 to 1.5212 by blending PSQ‐LH (n_TE=1.5212 @ 1310 nm) and PSQ‐LL (n_TE=1.4483 @ 1310 nm). The maximum refractive index contrast is about 4.8%. After post‐baking, birefringences of the films are below 0.0005 and optical losses are about 0.2 dB · cm^?1 at 1310 nm, 0.7 dB · cm^?1 at 1550 nm, respectively. Furthermore, the PSQ‐Ls films also show outstanding thermal stability in air atmospheres.     

Refractive index increase of acrylate‐based polymers by adding soluble aromatic guest‐molecules

This work presents the influence of dopants on viscosity in an uncured liquid state as well as on refractive index, Abbe number, optical loss, and glass transition temperature of different polymer compositions. The base material consists of Genomer 2263, a bisphenol, an epoxy diacrylate as matrix polymer, and benzyl methacrylate as comonomer. As dopants, the soluble aromatic guest‐molecules 9‐bromophenantrene and 9‐vinylcarbazole are investigated. The viscosity can be adjusted by different mixtures of the matrix polymer and comonomer from 3000 down to 4 mPa sec. Depending on the type and content of the dopants, the refractive index, Abbe number, and the glass transition temperature can be adjusted. The refractive indices increase linear at 589 nm and 20°C from 1.572 to 1.638 by doping, with Abbe numbers between 20 and 30. At this wavelength, the optical losses were determined to be around 2 dB · cm^?1. The glass transition temperature can be tailored between 50 and 98°C. A way to use high amounts of optical dopants is presented, which opens up the way for different shaping technologies like inkjet printing of optical components. Copyright © 2016 John Wiley & Sons, Ltd.     

Polar anchoring strengths of nematic liquid crystal on high-density polymer brush surfaces

ABSTRACT

Herein, the polar anchoring energy coefficient (A_θ) of nematic liquid crystal (NLC) was examined for high-density polymer brushes via capacitance measurements. The A_θ is 10^?4 J m^?2 for the brushes of poly(methyl methacrylate), poly(ethyl methacrylate) and poly(styrene). The value decreases to 10^?5 J m^?2 for poly(n-butyl methacrylate) and poly(hexyl methacrylate) with lower glass transition temperatures. However, each polymer brush displays a constant A_θ value over a temperature range of ?15°C to 90°C, which is hardly affected by the graft density and brush thickness. At 25°C, A_θ is 10 times greater than the corresponding azimuthal anchoring energy coefficient (A_φ); therefore, NLCs on polymer brushes can be preferentially aligned along the in-plane component of the applied field.     

Crystal growth, spectral, optical, and thermal characterization of glycyl-l-alanine hydrochloride (GLAH) single crystal

A new semi-organic nonlinear optical material glycyl-l-alanine hydrochloride (GLAH) was grown successfully by slow evaporation solution growth method. The solubility of GLAH was estimated for a wide range of temperatures. Large size single crystal of size 15?×?9?×?6?mm³ was grown at room temperature. The grown crystal was subjected to single crystal X-ray diffraction study which confirms that the grown crystal is monoclinic in nature with the space group P2₁. The molecular weight of the title compound was estimated by mass spectrometry. Functional groups and the modes of vibrations were identified by FT-IR spectral analysis. The UV?Cvisible spectral study reveals that the percentage of optical transmission of the sample is very high in the entire visible and UV regions. The second harmonic generation of the crystal was confirmed by the Kurtz and Perry technique. The hardness of the sample was tested by microhardness test which shows that the grown crystal belongs to the soft category of materials. The thermal stability of the compound was studied by TG?CDTA analyses which indicate that the crystal is thermally stable up to 248.6?°C.     

The preparation of superhydrophilic surface of TiO2 coating without ultraviolet irradiation through annealing treatment

The superhydrophilic surface without ultraviolet light irradiation is obtained only through the modulation of annealing process on surface morphology of TiO₂ coating. Meantime, the influence of annealing temperature on the structural, optical and wetting properties of the TiO₂ coating is investigated. As the increase of annealing temperature, the root mean square roughness of the TiO₂ coating surface increases from 8.6 to 30.7 nm and the nanoparticle surface is formed. Meanwhile, the refractive index increases linearly from 2.02 to 2.22, the thickness decreases from 120 to 82 nm, the transmittance varies from 90 to 62 %, and it is more important the WCA is reduced from 68° to 0°. Furthermore, through analyzing the thickness variation, it is illustrated that the structure variation of TiO₂ coating includes the removal process of solvent and the crystallization process with the increase of annealing temperature, and the 400 °C is a critical temperature. When the annealing temperature is above 400 °C, the TiO₂ coating starts to be crystallized and exhibits excellent antifogging property.     

Synthesis,crystal structure and non-linear optical properties of a new cyanide-containing compound

Reaction of K₃[Fe(CN)₆], NiCl₂ and diethylenetriamine (dien) resulted in the formation of a cyanide-containing heterometallic compound [Ni(dien)₂]₂[Fe(CN)₆]·4H₂O 1. The structure consists of two octahedral [Ni(dien)₂]²⁺ cations, one octahedral [Fe(CN)₆]^4? anion and four crystallization water molecules, which are held together by hydrogen-bonding interactions. Its TG curve exhibits two stages of mass loss. Compound 1 in DMF solutions has a very strong third-order non-linear optical (NLO) behavior with an absorption coefficient and refractive index α₂?=?1.10?×?10^?11?m?w^?1, n ₂?=??3.05?×?10^?19?m²?w^?1, respectively, and third-order NLO susceptibility χ⁽³⁾ 4.34?×?10^?13?esu.     

Effect of sol–gel-based silica buffer layer on the formation of NaA zeolite membrane

The support substrates were modified with sol?Cgel-based silica coating as intermediate buffer layer followed by NaA zeolite seed (prepared hydrothermally at 85?°C for 3?h) coating with 2?wt% aqueous dispersion. The secondary crystallization of NaA zeolite in the silica-seed-coated supports was carried out hydrothermally through crystal growth process at 65?°C for 4 and 8?h (single-stage each), (6?+?4) and (6?+?6)?h (double-stage each), and (6?+?4?+?2) and (6?+?4?+?4)?h (triple-stage each). The crystallization behaviours of the prepared NaA membranes were studied by X-ray diffraction, and the microstructures of the same films were observed by field emission scanning electron microscope. The efficiency of the membranes was tested with gas permeation study. The double-stage secondary crystallization at 65?°C for (6?+?4)?h showed highly interlocked NaA grains in the membrane and it rendered the permeance values of 3.7?×?10^?8?mol?m^?2?s^?1?Pa^?1 and 15.9?×?10^?8 for single gas, nitrogen (N₂) and hydrogen (H₂) respectively with the ideal selectivity of 4.3.     

Design of two-dimensional photonic crystal biosensor using DNA detection

Abstract

In this paper, the photonic crystal biosensor is investigated theoretically with, concomitantly, high quality factor, transmission and sensitivity. This biosensor is made out of two waveguide couplers and one L2 resonant cavity formed by removing two air holes. For biosensor analysis, the 2D finite difference time domain (FDTD) method and the plane-wave expansion (PWE) approach are applied. Four slots placed into the cavity and the three rows of functionalized holes nearby the resonant cavities are filled with DNA. For the optimized structure, the biosensor quality factor is found to be over 3.7468?×?10⁶ and the sensitivity is of order 460?nm/RIU. The designed structure has high sensitivity, which is an important parameter in biosensing applications.     

Tailoring of morphology and crystal structure of nanomaterials in MgO–TiO2 system by controlling Mg:Ti molar ratio

The morphological manipulation and structural characterisation of TiO₂?CMgO binary system by an aqueous particulate sol?Cgel route were reported. Different crystal structures including pure MgTiO₃, mixtures of MgTiO₃ and TiO₂ and mixtures of MgTiO₃ and Mg₂TiO₄ were tailored by controlling Mg:Ti molar ratio and annealing temperatures as the processing parameters. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that all compounds crystallised at the low temperature of 500?°C. Furthermore, it was found that the average crystallite size of the compounds depends upon the Mg:Ti molar ratio as well as the annealing temperature, being in the range 3?C5?nm at 500?°C and around 6?nm at 700?°C. Field emission scanning electron microscope (FE-SEM) analysis revealed that the deposited thin films had nanocrystalline structure with the average grain size of 25?C30?nm at 500?°C depending upon the Mg:Ti molar ratio. Moreover, atomic force microscope (AFM) images presented that the thin films had a hill-valley like morphology made up of small grains.     

Hydrothermal synthesis,crystal structure and third-order nonlinear optical properties of a 3D coordination polymer containing 3,3′,4,4′-benzophenone-tetracarboxylate (BPTC) and pyrazine ligands

A mixed-ligand compound, [Ni₂(BPTC)(pyz)?·?2H₂O] _n (0.5H₂O) _n (BPTC?=?3,3′,4, 4′-benzophenone-tetracarboxylate, pyz?=?pyrazine), has been prepared hydrothermally by assembly of BPTC, NiCl₂·6H₂O and pyz. X-ray diffraction analysis of a single crystal reveals the three-dimensional framework assembled from pyz-pillared two-dimensional sheets. Three types of channels in one direction are established inside the structure. The third-order nonlinear optical (NLO) properties in DMF have been studied by Z-scan technique using an 8?ns laser at 532?nm. The results reveal that the new compound exhibits strong NLO absorption and self-focusing refractive performance (n ₂?=?2.7?×?10^?17?m²?W^?1).     

Negative thermal expansion of a polydiacetylene single crystal

Macroscopic thermal expansion in the chain direction has been measured for the first time on organic polymeric single crystals. Negative linear thermal expansion coefficients αM are reported and related to chain torsional motion and equilibrium point-defect formation for a solid-state polymerized phase of 2,4-hexadiyne-1,6-diol bisphenylurethane (HDU) which contains crystallographically located interstitial dioxane and for a dioxanefree phase obtained by thermal annealing. Data for as-polymerized single crystals (which are probably of extended chain morphology) between ?50 and 100°C give αM = ?(1.686 ± 0.039) × 10^?5 ? (1.35 ± 0.18) × 10^?7 t with t in °C. During volatilization of 11.7 ± 1.0 wt-% interstitial dioxane and a resulting crystal structure change, the as-polymerized fibers fibrillate and shrink irreversibly by 0.16 ± 0.04%. Although dichroism and diffraction measurements indicate both a high degree of crystallinity and chain alignment for the dioxane-free phase, the average thermal expansion coefficient, (?3.0 ± 1.0) × 10^?6 °C^?1 between ?50 and 150°C, is about an order of magnitude less than for the as-polymerized single crystals.     

An Integrated Optical Biosensor (IOBS)

Abstract

We have demonstrated an integrated optical biosensor (IOBS) employed as differential refractometer with a resolution down to n_C.=5 × 10^?5. The minimum volume required for measurements is V=L_x?L_y?L_z=1?10^?4 microlitres where L_x?L_y=1mm?0.1mm is the illuminated grating area and L_z is the penetration depth of the evanescent field of the guided mode into the cover medium.

The sensor described was successfully used to monitor enzyme activities by measuring the change of refractive index of a substrate converted by an enzyme. Because the sensor responds not only to refractive index changes of a cover medium but also to thickness changes of absorbed layers it should be possible to measure biological interactions such as between antigen/antibody, inhibitor/enzyme or receptor/cell by coupling of either respective biomolecule onto the waveguiding film. Thus we have shown in preliminary experiments that on coupling covalently to the grating rabbit anti-human-IgG (both of similar molecular weight around 150 000) a pronounced attenuation of the intensity of the guided mode was observed due to the increased adlayer thickness (to be published).

It should be possible to miniaturize the unit using channel waveguides fabricated by a combination of photolithography and etching techniques with the aim to obtain implantable clinical integrated optical biosensors.

The sensitivity can be further improved electronically by measuring directly the intensity of the guided mode using a second grating as an output coupler. This will increase the signal to noise ratio substantially.     

A Superacid-catalyzed Synthesis of Fluorescent Covalent Triazine Based Framework Containing Perylene Tetraanhydride Bisimide for Sensing to O-nitrophenol with Ultrahigh Sensitivity

Abstract

A mesoporous covalent triazine framework, PCPDI, was synthesized via an aromatic nitrile trimerization reaction of N,N′-di(4-cyanphenyl)- 3,4,9,10-tetracarboxydiimide (CPDI) by CF₃SO₃H catalyzed at 40?°C and this method avoids the use of noble metal catalyzers or high temperature reaction. PCPDI exhibits high thermal stability and strong fluorescence. The PCPDI shows ultrahigh sensitivity to tracing o-nitrophenol in chloroform with K_SV constant of 1.74?×?10⁵ L mol^?1 and detection limit (LOD) of 1.72?×?10^?11?mol L^?1.     

Preparation and nonlinear optical properties of Au nanoparticles doped TiO2 thin films

Nano-sized noble metal nanoparticles doped dielectric composite films with large third-order nonlinear susceptibility due to the confinement and the enhancement of local field were considered to be applied for optical information processing devices, such as optical switch or all optical logical gates. In this paper, sol–gel titania thin films doped with gold nanoparticles (AuNPs, ~10 nm in average size) were prepared. AuNPs were firstly synthesized from HAuCl₄ in aqueous solution at ~60 °C, using trisodium citrate as the reducing agent, polyvinylpyrrolidone as the stable agent; then the particle size and optical absorption spectra of the AuNPs in aqueous solutions were characterized by transmitting electron microscopy and UV–Vis–NIR spectrometry. Sol–gel 2AuNPs–100TiO₂ (in %mol) thin films (5 layers, ~1 μm in thickness) were deposited on silica glass slides by multilayer dip-coating. After heat-treated at 300–1,000 °C in air, the AuNPs–TiO₂ thin films were investigated by X-ray diffraction, scanning electron microscopy and atomic force microscopy. The nonlinear optical properties of the AuNPs–TiO₂ thin films were measured with the Z-scan technique, using a femtosecond laser (200 fs) at the wavelength of 800 nm. The third-order nonlinear refractive index and nonlinear absorption coefficient of 2AuNPs–100TiO₂ films were at the order of 10^?12 cm²/W, and the order of 10^?6 cm/W, respectively, and the third-order optical nonlinear susceptibility χ⁽³⁾ was ~6.88 × 10^?10 esu.     

Optical, mechanical, and dielectric properties of Bi1/2Na1/2TiO3 thin film synthesized by sol–gel method

The Bi_1/2Na_1/2TiO₃ (BNT) thin film has been researched as an excellent candidate of lead-free ferroelectric materials. We synthesized BNT thin film on Si wafers or quartz glass by sol–gel spin coating method. The homogeneous and crack-free BNT thin film was synthesized by cost effective solution sol gel coating method. The main crystal phase of the film was identified as Bi_1/2Na_1/2TiO₃. The BNT thin film which was coated 3 times and heat-treated at 700 °C had about 70% of transmittance in the ultra-violet visible (UV–VIS) light wavelength region. The calculated band gap energies from the UV transmittance spectra were 3.0 and 3.5 eV for indirect and direct transition, respectively and the refractive index of BNT thin film was 2.16 at 898 nm of wavelength. The hardness and elastic modulus of the film were about 9 and 136 GPa at 10 mN load, where the penetration depth was about 220 nm. BNT thin film showed the diffuse type of dielectric properties due to its Na⁺ and Bi³⁺ ions in A′_1/2A″_1/2BO₃-type perovskite structure and the dielectric constant was about 10 until 300 °C and showed maximum value at 550 °C, 450 at 1 kHz.     

New soluble polyamides with high transparence and improved gas separation properties

Abstract

Based on the aromatic diamine monomer containing di-tert-butylbenzene and methyl groups, this work proposes its polymerization with four different dicarboxylic acids. The prepared polyamides (PA 3a–3d) were characterized by GPC, FTIR, ¹H NMR, mechanical, thermal, optical and gas separated techniques. They exhibited high solubility and good optical transparency. Their optical transmittance at 450?nm wavelength was in the range of 81.4%–86.8%, and the cutoff wavelength was in the range of 327–352?nm. The membranes also had good mechanical properties with tensile strength of 79.7–91.4?MPa, elongations at breaks of 9.0–10.9% and initial modulus of 1.5–1.9?GPa. Meanwhile, these membranes possessed good thermal properties with glass transition temperature (T _g) values of 226–246?°C. The permeability of CH₄, N₂, and CO₂ for these membranes was tested by constant pressure-variable volume method. The PA 3d containing tert-butyl moiety in the diacid units exhibited highest permeability (P_CO2 = 31.4 and P_N2 = 1.9) whereas PA 3c containing hexafluoroisopropylidene moiety exhibited highest selectivity (CO₂/CH₄ = 22.2).     

Dispersion of polymeric-coated–silica aerogel particles in unsaturated polyester composites: Effects on thermal-mechanical properties

The thermal-mechanical properties of unsaturated polyester (UP) composite were enhanced by the dispersion of silica aerogel (SA) with preserved pores. Low-cost SA was prepared from rice husk via the sol-gel process and ambient pressure drying. A new method was proposed to encapsulate the hydrophobic aerogel surface pores with hydrophilic polyvinyl alcohol (PVA) film using the fluidized-bed coating process. The dispersion of PVA-coated aerogel with preserved pores in the polyester matrix resulted in an increase of specific compressive strength (44.1?MPa?·?cm³?g^?1), thermal insulation (0.23?W?m^?1?K^?1), and thermal stability (T_onset?=?310°C), but decreased the glass transition temperature (T_g?=?260°C).     

Thermal, structural, magnetic and photoluminescence studies on cobalt ferrite nanoparticles obtained by citrate precursor method

Magnetic nanoparticles of cobalt ferrite have been synthesized by citrate precursor method. TG-DSC studies have been made to get the idea of the optimum temperature of annealing that could lead to the formation of nanoparticles. Annealing the citrate precursor was done at 450, 650, and 973?°C. The X-ray diffraction (XRD) studies and the scanning electron microscopy (SEM) have been used for characterization. The data from vibrating sample magnetometer and photoluminescence spectrometer (PL) have been analyzed for exploring their applications. Using the Scherrer formula, the crystallite size was found to be 25, 32, and 43?nm, respectively, using the three temperatures. The particle size increased with annealing temperature. Rietveld refinements on the X-ray (XRD) data were done on the cobalt ferrite nanoparticles (monoclinic cells) obtained on annealing at 650?°C, selecting the space group P2/M. The values of coercivity (1574.4?G) and retentivity (18.705?emu g^?1) were found out in the sample annealed at 650?°C while magnetization (39.032?emu g^?1) was also found in the sample annealed at 973?°C. The photoluminescence (PL) property of these samples were studied using 225, 330, and 350?nm excitation wavelength radiation source. The PL intensity was found to be increasing with the particle size.