Hybrids and biohybrids as green materials for a blue planet

There is an urgency to identify novel technological answers to the decreasing availability of important resources together with increasing accumulation of pollution. Among the many ways materials science can contribute to these issues, the enhanced use of renewable resources, the optimal production of alternative energies and the improved monitoring/cleaning of contaminated environments can be identified as area where the sol–gel technology has, and will have, a major role to play. In this short review, we more specifically illustrate recent developments in biohybrid chemistry applied to bioplastics, biofuel cells, biosensors and bioremediation.     

Omega chrome blue green bl as analytical reagent for calcium and magnesium

The behaviour of Omega Chrome Blue Green BL towards various ions was studied. It was used as indicator in the direct ETDA titratiun of both calcium and magnesium and for the titration of magnesium in presence of aluminium.     

Methods for investigation of holographic photopolymer materials

Results obtained by the authors on the development of holographic methods for investigation of photopolymer materials are presented. The work considers the methods for pulse recording of dynamic transmission gratings and characterization of hologram angular selectivity, the double-beam method of twophoton holographic recording, and heterodyne detection of inhomogeneities in volume holograms.     

Removal of cationic methylene blue and malachite green dyes from aqueous solution by waste materials of Daucus carota

In present study adsorption capacity of waste materials of Daucus carota plant (carrot stem powder: CSP and carrot leaves powder: CLP) was explored for the removal of methylene blue (MB) malachite green (MG) dye from water. The morphology and functional groups present were investigated by scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy. The operating variables studied were pH, adsorbent dose, ionic strength, initial dye concentration, contact time and temperature. Equilibrium data were analysed using Langmuir and Freundlich isotherm models and monolayer adsorption capacity of adsorbents were calculated. Kinetic data were studied using pseudo-first and pseudo-second order kinetic models and the mechanism of adsorption was described by intraparticle diffusion model.Various thermodynamic parameters such as enthalpy of adsorption ΔH°, free energy change ΔG° and entropy ΔS° were estimated. Negative value of ΔH° and negative values of ΔG° showed that the adsorption process was exothermic and spontaneous. Negative value of entropy ΔS° showed the decreased randomness at the solid–liquid interface during the adsorption of MB and MG onto CSP and CLP.     

Extraction-spectrophotometric determination of amprolium hydrochloride using bromocresol green, bromophenol blue and bromothymol blue

A new procedure for the determination of amprolium hydrochloride by reaction with bromocresol green (BCG), bromophenol blue (BPB) and bromothymol blue (BTB) has been developed. The method consists of extracting the yellow ion-pair formed into chloroform from aqueous medium. The ion-pairs have absorption maxima at 420, 410 and 415 nm with molar absorptivities of 3.64 × 10⁴, 3.12 × 10⁴ and 2.31 × 10⁴1 mol^–1 cm^–1 for BCG, BPB and BTB, respectively. The method obeys Beer's law over the concentration ranges 0.6–12.0, 0.12–8.8 and 1.2–11.3 ag/ml amprolium hydrochloride for BCG, BPB and BTB, respectively. The method is simple, precise (relative standard deviation 0.665–2.210%), accurate (recovery 97.8–100.8%) and easily applied for pharmaceutical quality assurance for amprolium hydrochloride in raw materials and in formulated veterinary soluble powder.     

3D printed honeycomb bilayer structures based on polylactic acid as lightweight microwave absorbing materials

3D printed honeycomb structures constituted by neat polylactic acid (PLA) and conductive PLA (PLAc) with different cell sizes and thicknesses were manufactured through 3D printing technology based on material extrusion (MEX). These structures were arranged into bi-layer honeycomb structures (BHS) for evaluation of the microwave absorbing properties at the X-band (8.2–12.4 GHz) and Ku-band (12.4–18 GHz) frequency ranges. The effects of cell size, sample thickness, layer thickness ratio and the nature of the top layer on the electromagnetic attenuation performance of BHS samples were investigated in terms of reflection loss (RL). The components geometric characteristics and the arrangement of the layers exerted great influence on the RL values and effective absorption bandwidth (EAB). Overall the bilayer structures with 5 mm total thickness presented the best EM response in terms of EAB and minimum RL, where the component with the larger cell size (7.7 mm), PLAc (1 mm) as the top layer and PLA (4 mm) as the bottom layer exhibited the best results with RL values of −41 dB and EAB of 9.5 GHz. The BHS system with 7.7 mm cell size was more efficient in Ku band frequency range, whereas that with 3.5 mm cell size gave better response in the X-band frequency range. Therefore, RL values and EAB can be adjustable by modifying the building strategy of the printed parts, such as thickness of the sample, cell size and thickness distribution of the conductive and non-conductive layers. The findings in this work show the importance of the building strategy to fabricate components with controllable BHS and improved properties for microwave absorption application.     

Active site comparison of CoII blue and green nitrite reductases

Copper-containing nitrite reductases (NiRs) possess type 1 (T1) and type 2 (T2) copper sites and can be either green or blue in color owing to differences at their T1 centers. The active sites of a green and a blue NiR were studied by utilizing their T1CuI/T2CoII and T1CoII/T2CoII-substituted forms. The UV/Vis spectra of these derivatives highlight the similarity of the T2 centers in these enzymes and that T1 site differences are also present in the CoII forms. The paramagnetic NMR spectra of T1CuI/T2CoII enzymes allow hyperfine shifted resonances from the three T2 His ligands to be assigned: these exhibit remarkably similar positions in the spectra of both NiRs, emphasizing the homology of the T2 centers. The addition of nitrite results in subtle alterations in the paramagnetic NMR spectra of the T1CuI/T2CoII forms at pH<7, which indicate a geometry change upon the binding of substrate. Shifted resonances from all of the T1 site ligands have been assigned and the CoII--N(His) interactions are alike, whereas the CbetaH proton resonances of the Cys ligand exhibit subtle chemical shift differences in the blue and green NiRs. The strength of the axial CoII--S(Met) interaction is similar in the two NiRs studied, but the altered conformation of the side chain of this ligand results in a dramatically different chemical shift pattern for the CgammaH protons. This indicates an alteration in the bonding of the axial ligand in these derivatives, which could be influential in the CuII proteins.     

New benzo[b]furans as electroluminescent materials for emitting blue light

[structure: see text] New functionalized mono- and bis-benzo[b]furan derivatives were synthesized and developed as blue-light emitting materials. They possessed a CN, CHO, CH=CHPh, CH=CPh(2), or CH=CHCOOH group at the C4-position. Two benzo[b]furan nuclei in bis-benzo[b]furan derivatives were connected by a divinylbenzene bridge. With good volatility and thermal stability, bis-benzo[b]furan 7a was fabricated as a device. It emitted blue light with brightness 53430 cd/m(2) (at 15.5 V) and high maximum external quantum efficiency 3.75% (at 11 V).     

Synthesis of t-butylated diphenylanthracene derivatives as blue host materials for OLED applications

This paper describes the cost-effective synthesis and the photoluminescence of diphenylanthracene derivatives, which are found to be potential blue host materials for organic light emitting diode (OLED) technology.     

Soluble narrow band gap and blue propylenedioxythiophene-cyanovinylene polymers as multifunctional materials for photovoltaic and electrochromic applications

A family of soluble narrow band gap donor-acceptor conjugated polymers based on dioxythiophenes and cyanovinylenes is reported. The polymers were synthesized using Knoevenagel polycondensation or Yamamoto coupling polymerizations to yield polymers with molecular weights on the order of 10 000-20 000 g/mol, which possess solubility in common organic solvents. Thin film optical measurements revealed narrow band gaps of 1.5-1.8 eV, which gives the polymers a strong overlap of the solar spectrum. The energetic positions of the band edges were determined by cyclic voltammetry and differential pulse voltammetry and demonstrate that the polymers are both air stable and show a strong propensity for photoinduced charge transfer to fullerene acceptors. Such measurements also suggest that the polymers can be both p- and n-type doped, which is supported by spectroelectrochemical results. These polymers have been investigated as electron donors in photovoltaic devices in combination with PCBM ([6,6]-phenyl C(61)-butyric acid methyl ester) as an electron acceptor based on the near ideal band structures designed into the polymers. Efficiencies as high as 0.2% (AM1.5) with short circuit current densities as high as 1.2-1.3 mA/cm(2) have been observed in polymer/PCBM (1:4 by weight) devices and external quantum efficiencies of more than 10% have been observed at wavelengths longer than 600 nm. The electrochromic properties of the narrow band gap polymers are also of interest as the polymers show three accessible color states changing from an absorptive blue or purple in the neutral state to a transmissive sky-blue or gray in the oxidized and reduced forms. The wide electrochemical range of electrochromic activity coupled with the strong observed changes in transmissivity between oxidation states makes these materials potentially interesting for application to electrochromic displays.     

Synthesis and characterization of 9,10-substituted anthracene derivatives as blue light-emitting and hole-transporting materials for electroluminescent devices

New 9,10-substituted anthracene derivatives were designed and synthesized for application as blue-emitting and hole-transporting materials in electroluminescent devices. They were characterized by H NMR, C NMR, FTIR, UV–vis, PL spectroscopy, and mass spectrometry. The theoretical calculation of three-dimensional structure and the energy densities of HOMO and LUMO states, as well as optical properties of these new obtained materials, supported the claim that they had non-coplanar structures. Their optical, thermal, and electrochemical properties could be tuned by varying the peripheral substituents. All of them were electrochemically and thermally stable molecules. Materials having electron donating triphenylamine as peripheral substituents showed promising potential as both blue light-emitting materials and hole-transporting materials for electroluminescent devices. Efficient blue and Alq3-based green OLEDs with maximum luminance efficiencies and CIE coordinates of 1.65 cd/A and (0.15, 0.16) and 6.25 cd/A and (0.26, 0.49) were achieved, respectively.     

Production of malachite green oxalate and leucomalachite green reference materials certified for purity

Malachite green oxalate (MG oxalate) and leucomalachite green (LMG) have been prepared and certified as pure reference materials. The purities of MG oxalate and LMG were assessed by high-performance liquid chromatography–diode array detection (HPLC–DAD), nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), Karl Fischer titration, ashing and thermogravimetric analysis (TGA). MG oxalate was purified by supercritical fluid extraction (SFE). Prior to purification, commercial MG oxalate purity was estimated to be about 90%. The main impurities present in SFE-purified MG oxalate were identified and quantified using HPLC–DAD. The main impurities were found to be monode-MG (monodemethylated MG oxalate synthesis impurity), 4-(dimethylamino)benzophenone (4-DMABP), MG-carbinol and LMG. The homogeneity of both reference materials was also determined. Issues associated with the stability of LMG and MG oxalate in solution forced an extensive study investigating different parameters i.e. solvent, acid, analyte concentration and temperature. MG oxalate (100 μg/mL) was found to be stable in acetonitrile containing 1% v/v glacial acetic acid for at least 155 days and LMG (100 μg/mL) was stable in acetonitrile for at least 133 days. The final purity value for MG oxalate was 94.3 ± 1.4% m/m at the 95% confidence interval (or 67% m/m if MG cation is reported). For LMG, the certified purity was found to be 98.8 ± 0.8% m/m at the 95% confidence interval. Figure Calibration reference materials for malachite green and leucomalachite green, certified for purity, are essential in characterising these key analytes in a fish matrix reference material     

Poly(methyl methacrylate)/soy protein green composites as gas barrier materials

Poly(methyl methacrylate)/soy protein(PMMA/SP) composites were prepared by emulsion polymerization method using potassium persulphate(KPS) as the radical initiator.The interaction of soy protein with PMMA was evidenced by Fourier transformed infrared(FT1R) spectroscopy.The structure of PMMA/SP composites was investigated by X-ray diffraction(XRD) study and scanning electron microscopy(SEM).The thermal properties of soy protein and PMMA/SP composites were compared with soy protein and virgin PMMA sample.PMMA/SP composites were found to be flame retardant materials from the measurement of limiting oxygen index(LOI) of samples.The oxygen permeability of PMMA/SP composites was substantially decreased as compared to virgin PMMA.     

Novel hyperbranched polymers as host materials for green thermally activated delayed fluorescence OLEDs

A series of novel hyperbranched polymers(HBPs) consisting of a 2,7-subsituted 9-(heptadecan-9-yl)-9H-carbazole unit(A_2+A_2') and a tetra-substituted green thermally activated delayed fluorescence(TADF) dye of 2,3,5,6-tetra(9Hcarbazol-9-yl)-4-pyridinecarbonitrile(4CzCNPy, B4) have been synthesized via Suzuki cross-coupling reaction following an "A2+A2'+B_4" method. The polymers are named according to the polymerization ratio of 4CzCNPy monomer(5 mol%, 10 mol% and 15 mol% for HBPs of P2-P4 respectively, and 0 mol% for the control linear polymer P1). Their thermal, optoelectronic and electrochemical properties have been characterized by a combination of techniques. All the polymers exhibit high thermal stability with the decomposition temperatures(Td) above 400 ℃ and glass transition temperatures(Tg) up to 98 ℃. Unfortunately, the incorporation of TADF moiety into these HBP materials induced non-TADF characteristics. However, when the HBPs functionalized as the host for our previously developed 4CzCNPy TADF dopant in solution processed devices, maximum external quantum efficiency of 5.7% and current efficiency of 17.9 cd/A have been achieved in P3-based device, which is significantly higher than those of 1.5% and 4.2 cd/A for the linear polymer P1.     

Extending NAA to materials with high concentrations of neutron absorbing elements

Summary The recently discovered universal functions for thermal and epithermal neutron self-shielding were adapted to NAA of cylindrical samples, expressing the magnitude as the product of a nuclear factor, a geometrical factor and the amount of the neutron absorbing element. The theory was tested and the nuclear factors were measured for 1 ml samples containing the halogens Cl, Br and I. Tests on samples containing these elements at a priori unknown concentrations, irradiated in a mixed thermal and epithermal neutron spectrum, showed that self-shielding as high as 30% could be corrected with an accuracy of about 1%, except in cases with significant epithermal shielding of one element by another.     

The origins of the colours of yellow,green and blue sapphires

The absorption spectra of natural yellow sapphires are shown to be due to single Fe³⁺ and Fe³⁺  O²⁻  Fe³⁺ pairs, with the latter dominant. Blue and green sapphires have spectra dominated by Fe³⁺  O²⁻  Ti⁴⁺ and Fe²⁺  O²⁻  Fe³⁺ pairs.     

Use of poorly absorbing materials and low-contrast photometric reactions in thermal lens spectrometry

The capability of thermal lens spectroscopy as a highly sensitive method applicable to indicator reactions, the products of which appear poorly absorbing and/or insufficiently contrasting and, which there-fore cannot be utilized in traditional spectrophotometric analysis, are considered in a study of a number of model systems (phenanthrene, unsubstituted dibenzo-p-dioxin, polysaccharides, lyposaccharides, and other materials). It is shown that, in thermal lens spectrometry, the sensitivity of determination in such reactions can be increased by significantly increasing the sensitivity of thermo-optical measurements due to the formation of colloidal reaction products and the exploitation of the kinetic behavior of such reactions. Along with the increase in the sensitivity of absorbance measurements due to the thermo-optical effect itself, these factors also favor a gain in sensitivity in comparison to the spectrophotometry by 1–2 orders of magnitude.     

Performance of radar absorbing materials by waveguide measurements for X- and Ku-band frequencies

In this work, samples consisting of an elastomeric matrix containing different kinds of active materials in particulate form were prepared for reflectivity measurements. The materials individually used in weight contents of 80% in polychloroprene matrix were: carbonyl-iron (CI) and doped ferrite powders. The microwave reflectivity levels were determined from the magnetic and dielectric properties of the elastomeric composites obtained from scattering data, by fitting the samples in a waveguide, for measurements in the frequency range from 8 to 16 GHz. Better microwave absorption for X-band was obtained for CI while doped ferrite absorbed at higher frequencies (Ku-band).     

Photoacoustic spectroscopic studies of methylene blue and malachite green adsorbed on silica

Spectra and calibration curves of methylene blue and malachite green adsorbed on silica show that photoacoustic spectroscopy can be used for the determination of these compounds. The problem of the existence of an equilibrium between monomer and dimer for methylene blue is considered.