Promising fluorescent dye for solar energy conversion based on a perylene perinone

We describe the synthesis of a dye based on a perylene perinone and evaluate its potential as the functional material for use in the luminescent solar concentrator (LSC). The dye extends the absorption wavelength of LSCs using the perylene-based dye Lumogen Red 305 by more than ~50 nm, translating into the collection of potentially 25% more photons at a reasonable fluorescent quantum yield and photostability. When the new perinone is used in a two-waveguide LSC in conjunction with Red 305, the integrated edge emission of the total LSC system may be increased more than 24% when compared to the Red 305 dye alone.     

Fabrication of gold nanoparticle assembled polyurethane microsphere template in trypsin immobilization

The separation, reusability and high catalytic activity of bioconjugate remain challenging task in proteins bound gold nanoparticles. A facile synthetic route for the fabrication of gold nanoparticle assembled polyurethane microsphere template and immobilization of trypsin on gold/polyurethane surface to form trypsin-nanogold-polyurethane bioconjugate was developed. The bioconjugate was characterized by X-ray diffraction, Field emission scanning electron microscopy, Transmission electron microscopy, UV-visible, Fourier transform infrared, Fluorescence and Circular dichroism spectroscopy. The catalytic studies confirmed retention of approximately 40% of its original activity even after eight consecutive reaction cycles. The bioconjugate is also very effective for its separation from the reaction medium and exhibited significant enhanced stability over a wide range of pH and temperature compared to free trypsin. These findings clearly demonstrate that trypsin immobilized gold nanoparticle assembled polyurethane microsphere acts as an excellent recyclable biocatalyst with enzyme-specific biocompatibility.     

Response surface optimisation of extraction of antioxidants from strawberry fruit, and lipid peroxidation inhibitory potential of the fruit extract in cooked chicken patties

BACKGROUND: Strawberries contain high levels of antioxidants and have beneficial effects against oxidative stress‐mediated diseases, such as cancer. They contain multiple phenolic compounds, which contribute to their biological properties. Hence, a study was carried out to optimise the extraction of antioxidants and evaluate the antioxidant potential of strawberry fruit extract (SE) in cooked chicken patties during refrigerated storage. The activity of SE was compared with that of butylhydroxytoluene (BHT). RESULTS: The effect of solvent type (MeOH and EtOH), concentration (0–70%) of EtOH in the system, temperature (30–60 °C), and time (30–150 min) on DPPH^?‐scavenging activity of SE was investigated. Response surface methodology was used to estimate the optimum extraction conditions for each parameter. The maximum predicted DPPH^? scavenging under the optimised conditions (100% MeOH, 30 °C, 150 min) was 43% at 1 mg SE mL^?1. Freshly prepared chicken patties were treated with 5% and 10% SE and 2% BHT, and stored aerobically at 4 °C for 6 days. SE had no influence (P < 0.05) on any of the sensory attributes of the patties. The values of thiobarbituric acid reactive substances reduced significantly (P < 0.05) from 2.47 mg in control patties to 0.312 mg and 0.432 mg malonaldehyde kg^?1 sample in 5‐SE and 10‐SE patties, respectively, on the day 6 of storage. CONCLUSION: The optimised model depicted MeOH at 30 °C with an extended time of 150 min as the optimum settings for extraction of compounds from strawberry that had the scavenging activity. The study shows that the extraction of natural antioxidants from strawberry can be improved by optimising several key extraction parameters. SE also acted as an effective antioxidant and suppressed lipid peroxidation in cooked chicken patties. Copyright © 2011 Society of Chemical Industry     

Incorporation of tin in different types of pores in SBA-15: Synthesis, characterization and catalytic activity

Mesoporous Sn-SBA-15 has been synthesized by three different methods such as conventional hydrothermal route, using cocatalyst NH₄F and in the presence of organosilane precursor. All the materials are thoroughly characterized by powder X-ray diffraction (XRD), SEM, TEM, N₂ sorption and surface area measurements, diffuse-reflectance UV–visible and FTIR spectroscopy, TG–DTA and elemental analysis through ICP. Nitrogen adsorption data, XRD patterns, and TEM observations suggests that the textural properties are retained during the isomorphous substitution of silicon by tin. ICP chemical analysis indicates that tin can be substituted in the range of Si/Sn = 69–162. UV–visible spectra of samples synthesized by the cocatalytic approach exhibit unique absorption band at 213 nm characteristics of tin atom substituted in the smaller pores (2–3 nm) located inside the walls of mesopores. Further, an additional band at 224 nm can be assigned to Sn atoms located in the distorted tetrahedral position along the primary mesopores. In contrary, only one absorption band centered at 224 nm is observed for all the samples synthesized by conventional hydrothermal as well as in the presence of organosilane precursor. ¹⁹F NMR spectra confirmed (no signal) the absence of occluded F⁻ ions in the samples made with NH₄F. Observed high catalytic activity in Baeyer–Villiger oxidation and Meerwin–Pondorf–Verly reduction under the liquid-phase conditions suggest the incorporation of a portion of tin in the smaller pores for the Sn-SBA-15 materials synthesized through cocatalyst method.     

Effect of Ti(C,N) addition on sintering behaviour and properties of binder-modified WC-10Co cemented carbide

In the present investigation the microstructure and mechanical properties of WC-10Co, WC-8.3Ti(C,N)-12Co, WC-8.3Ti(C,N)-6Co-6Ni and WC-7Ti(C,N)-2Mo₂C-6Co-6Ni cemented carbides were studied. Introduction of Ti(C,N) in WC-10Co cemented carbide imposed sintering difficulties and hot isostatic pressing was required to obtain fully dense material. The modification of the binder cobalt with nickel and molybdenum did not noticeably affect the sintered microstructure. In general the mechanical properties of Ti(C,N)-containing cemented carbides were inferior to those of WC-10Co cemented carbide.     

Theoretical investigations on some rigid-rod polymers used as high-performance materials

This review focuses on a new type of para-catenated aromatic polymer being used in the preparation of high-performance films and fibers of exceptional strength, thermal stability, and environmental resistance, including inertness to essentially all common solvents. Polymers of this type include cis and transpoly(p-phenylene benzobisoxazole) (PBO), and the cis and trans forms of the corresponding poly(p-phenylene benzobis-thiazole)(PBT). The purpose of this paper is to summarize the authors' theoretical work on the structures, conformational energies, intermolecular interactions, and electronic properties of PBO and PBT chains, including the protonated forms known to exist in strong acids. The emphasis is on how such studies provide a molecular understanding of the unusual properties and processing characteristics of this new class of materials.     

A novel and simple approach to enhance ultraviolet photosensitivity: activated-carbon-assisted growth of ZnO nanoparticles

An activated-carbon (AC) assisted route is developed to synthesize a ZnO nanoparticle network. The route involves simple addition of AC to the solution containing the zinc salt and finally removing them by burning at higher temperature to form a sponge-like porous ZnO nanoparticles. The surface area measurements show that AC-assisted ZnO nanoparticles (AC-ZnO) have a higher surface area than those synthesized without AC (B-ZnO), which is further confirmed by the field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM) images. Ultraviolet (UV) absorbance results show that the optical quality remains almost unchanged for both types of nanoparticles. Enhanced and faster UV photosensitivity has been observed for the AC-ZnO. The change in the UV photosensing properties demonstrated here provides a new approach to synthesizing other high surface area materials for novel physical and chemical properties.     

Development of mineral oil free offset printing ink using vegetable oil esters

Until the middle of this century, fats and oils are the major raw material source for paints, coating and lubricating applications. These markets are completely taken over by petroleum based stocks due to their abundance and versatility. However, recent public awareness to use environmentally acceptable products that minimize pollution, are compatible to human health and readily biodegradable created opportunities for vegetable oils for application in paints and printing inks. The formulation of vegetable oil methyl ester based 'green' offset printing ink that reduces the volatile organic compounds (VOC) has been discussed in the present study. Methyl esters of rapeseed, soybean, rice bran and palm oil have been prepared and their physical properties have been measured and compared with standard petroleum feed stock. Varnishes were prepared with these esters and their properties are also compared with that of the petroleum based products. Rheological properties of the inks are also evaluated and compared with standard printing ink using petroleum based solvent. In general performance of the ester-based printing inks are comparable with that of the mineral oil based product. On the basis of tack stability and gloss, ester based inks are much superior than the mineral oil based products. In conclusion, a new non-volatile diluent for printing ink has been developed. The diluent is made from common vegetable oils like rapeseed, soybean, rice bran and palm oil, a renewable source that is environmental friendly. Vegetable oil esters offer a cost effective solution for mineral oil based printing ink to meet VOCs regulations.     

Enhanced emission from single component organic core-shell nanoparticles

By one-step mixed-solvent mediated approach, we have prepared fluorescent organic core-shell nanoparticles with an oligomer (1) derived from the Schiff base condensation reaction of 2,6-diformyl-4-methylphenol and o-phenylenediamine at room temperature. The core and shell structures are generated by the same oligomer (1) featuring the aggregation structure in core different from that in shell. The radial packing factor distribution of oligomer cluster depending on the solvent interaction in the time of nucleation is mainly responsible for the single component core-shell formation. Different morphologies of the core-shell nanospheres (CSNS) and core-shell nanohemispheres (CSNHS) were generated simply by changing the concentration of 1 in chloroform-methanol mixed solvent (1:2). We observed that fluorescent emission from those core-shell nanoparticles is intense whereas as-synthesized oligomer (1) itself is non-fluorescent in dilute solution. The enhanced emission in the core-shell form with more than 50 times increase in fluorescent quantum yield vis-à-vis 1 is a remarkable feature of the study. As UV absorption spectra of nanoparticles are blue-shifted relative to their properties in solution, the observed strong emission in the solid state makes the oligomer an outstanding exception to a well-established rule based on the molecular exciton model. The core-shell nanoparticles have been characterized by FE-SEM, TEM, XRD, nanosecond (ns) time-resolved fluorescence dynamics, UV-Vis and fluorescence spectroscopy. The longer fluorescence lifetimes (tau) of core-shell nanoparticles (3.50 ns and 3.52 ns for CSNS and CSNHS respectively) than 1 as-synthesized (1.28 ns) implies that the formation of the nanoparticles restricts the rotation and vibration of the groups in the molecules. The factor that induces fluorescent enhancement of nanoparticles is mainly ascribed to the increase of radiative rate constant (k(r)) and simultaneous decrease of nonradiative rate constant (k(nr)).     

Tack and Green Strength of Blends of Bromobutyl and EPDM Rubbers. I. Unfilled Gum Blends

Polymer blends are gaining importance in recent years because they provide a compromise of properties. In this paper, tack and green strength of several blends of EPDM and bromobutyl rubbers (BIIR) have been studied over a wide range of temperaures, contact times and rates.

Tack increases with increase in contact time and with increase in contact temperature up to 47°C for a particular blend. At a much higher temperature the tack strength falls gradually. Green strength increases with increase in bromobutyl content and decreases with temperature. Tack index, a ratio of tack strength divided by the cohesive strength under the same geometry, decreases slowly with the test temperature. At a 50:50 ratio of BIIR:EPDM, the two rubbers form an interpenetrating network as observed under the phase contrast microscope.