Designing of LaCrO3 − TiO2 nanocomposites p: n heterojunction-based sensor material for the selective detection of volatile petrol vapors (PV) and CO2 gas vapors

In the present research TiO₂ modified LaCrO₃ nanostructure has been designed by simple sol-gel method. The thick films of TiO₂ with different concentrations with LaCrO₃ were fabricated by using screen printing methodology. In present study, the structural properties of TiO₂ doped LaCrO₃ were confirm by using X-ray diffractometer (XRD). While the morphological properties and surface characteristics of fabricated material analyzed using scanning electron microscopy (SEM). The energy dispersive spectroscopy (EDS) was utilized for chemical composition of the prepared material. Transmission electron microscopy (TEM) confirms the orthorhombic crystal lattice structure and morphology of Ti-doped LaCrO₃. While, Fourier transform infrared (FT-IR) spectroscopy was used to investigate the M ? O bonding vibrational stretching frequencies of LaCrO₃ and TiO₂ materials. The zeta potential was recorded for stability of all Ti doped LaCrO₃ nanostructures. The Brunauer-Emmett-Teller (BET) was analyzed for surface area and pore diameter parameters of the fabricated materials. The fabricated materials were checked for application as a sensor for different pollutant gases like Ethanol, CO₂, NO₂, and petrol vapors. The sensor demonstrates the sensitivity for petrol vapors at 150°C for 0.3 M% TiO₂ doped LaCrO₃. And exceptionally 0.5 M% TiO₂ doped LaCrO₃ sensor showed better response for CO₂. The reproducibility confirms the stability of 0.3 M % TiO₂ doped LaCrO₃ sensor and 0.5 M % TiO₂ doped LaCrO₃ sensor. The rapid response and recovery were recorded for both the sensors viz. 0.3 M % and 0.5 M % TiO₂ doped LaCrO₃.     

Hybrid vertical‐cavity laser with lateral emission into a silicon waveguide

We experimentally demonstrate an optically‐pumped III‐V/Si vertical‐cavity laser with lateral emission into a silicon waveguide. This on‐chip hybrid laser comprises a distributed Bragg reflector, a III‐V active layer, and a high‐contrast grating reflector, which simultaneously funnels light into the waveguide integrated with the laser. This laser has the advantages of long‐wavelength vertical‐cavity surface‐emitting lasers, such as low threshold and high side‐mode suppression ratio, while allowing integration with silicon photonic circuits, and is fabricated using CMOS compatible processes. It has the potential for ultrahigh‐speed operation beyond 100 Gbit/s and features a novel mechanism for transverse mode control.

     

Heat Transfer Performance of Milk Pasteurization Plate Heat Exchangers Using MWCNT/Water Nanofluid

Increasing efficacy of plate heat exchanger (PHE) is a method of reducing energy consumption of milk pasteurization and sterilization in dairy industries. In order to enhance heat transfer capability of water as a hot stream in PHEs, multiwalled carbon nanotubes (MWCNT) were added to water. An experimental setup was designed and manufactured to measure heat transfer coefficient and Nusselt number (Nu) as two key parameters for convective heat transfer. This system had two individual loops for hot and cold fluids. The experimental results clearly indicated that heat transfer coefficient and Nu number of pure water increased by adding MWCNT with weight concentration of less than 1 wt%. With increasing weight concentration of the nanoparticles, heat transfer coefficient and Nu number increased. This augmentation was intensified at higher Peclet numbers which showed more effective presence of them at high flow rates of nanofluids. Moreover, at constant weight concentration, both heat transfer coefficient and Nu number increased. Augmentation of heat transfer capability resulted in more heat exchange with milk fluid in a short time; thus, before occurrence of fouling in plates of exchanger, pasteurization of milk and production of the products would be easier.      

Preparation, characterization and adhesive properties of di- and tri-hydroxy benzoyl chitosan nanoparticles

Modified chitosans with 3,4-di-hydroxy benzoyl groups (CS-DHBA) and 3,4,5-tri-hydroxy benzoyl groups (CS-THBA) were synthesized and their nanoparticles were prepared via ionic crosslinking by tripolyphosphate (TPP). The chemical structure and degree of substitution (DS) of di-and tri-hydroxy benzoyl chitosans are determined by FTIR and 1H-NMR spectroscopy. The morphology of particles, size distribution and zeta potential of nanoparticles were studied using transmission electron microscopy (TEM) and dynamic light scattering (DLS), respectively. The mean diameters of particles of CS-DHBA and CS-THBA nanoparticles were 144 nm and 112 nm, respectively. It was found that the particles size decreased slightly with decreasing the degree of substitution and increasing degree of deacetylation (DD), due to increasing of ionic crosslinking of ammonium ions and polyanions of tripolyphosphate. The TEM photographs of CS-DHBA show that these particles are spherical in shape, but the particles of CS-THBA show some aggregation. In addition, the solubility and the mechanical properties of the prepared modified chitosans and their nanoparticles were evaluated for bio-adhesive and biomedical application. The results of solubility tests indicated that, the CS-DHBA and CS-THBA have higher solubility at pH > 7 comparing to CS. Also the CS-DHBA, CS-THBA and their nanoparticles showed a significant adhesive capacity and enhanced tensile strength and tensile modulus.     

Design and fabrication of Fourier plane diffractive optical elements for high-power fibre-coupling applications

In industrial processes using fibre beam delivery of high peak power laser light, diffractive optical elements are a very useful and flexible tool in maximising the amount of light reaching the work surface. This is due to the ability of diffractive optical elements to accurately couple light into multiple fibres, while conditioning the light in order to maximise the throughput for each fibre. We discuss the design techniques for diffractive optical elements and the application of these techniques to fibre-coupling problems. The flexibility of diffractive optical elements is demonstrated by their application to several fibre-coupling geometries, including a fibre bundle, a linear array of fibres, and a rotationally symmetric fibre connector. The diffraction efficiencies for the elements approach 90% with uniformity errors of less than 5%.     

Calculation of the rate constant for the ultrasonic degradation of aqueous solutions of polyvinyl alcohol by viscometry

Ultrasonic degradation of polyvinyl alcohol (PVA) was carried out in aqueous solution at 25 degrees C. In this experiment, the effect of solution concentration on the rate of degradation was investigated. Kinetics of degradation was studied by viscometry method. The calculated rate constants indicate that degradation rate of PVA solutions decreases with increasing of solution concentration (C= g lit(-1)). The calculated rate constants correlated in terms of reverse concentration and relative viscosity of PVA solutions. This behavior in the rate of degradation was interpreted in terms of viscosity and concentration of polymer solution. With increasing solution concentration, viscosity increases and it causes a reduction in the cavitation efficiency thus, the rate of degradation will be decreased.     

Superprism effect in all-glass volumetric photonic crystals

This paper focuses on the superprism effect which can be obtained in low-contrast photonic crystals. The modelling is related to the newly developed method for all-dielectric photonic crystals. This places material constraints on the simulated crystals which limit the refractive index difference to 0.1 for all-glass photonic crystals and 0.6 for air-glass structures and forces us to focus on hexagonal lattices. The simulations show the existence of superprism effect in both types of structure for realistic glasses. In both cases various linear filling factors are studied in order to maximize the frequency range of the superprism effect. For the air-F2 glass structure it reaches 0.108 normalized frequencies and for the air-NC21 glass structure it reaches 0.99 normalized frequencies for TM polarization. For the double glass structures, the largest range is for the F2/NC21 photonic crystal and spans 0.012 normalized frequencies. In the F2/NC21 crystal the frequency range reaches 0.005 for TE polarization.     

Diaza-crown-N,N-dialkanoic acids copper(II) and dicopper(II) complexes

Twelve-, fifteen-, and eighteen-membered diaza-crown-N, N-′dialkanoic acids LH₂ and their inner salt copper(II) complexes CuL and dicopper complex [CuL(3). CuCl₂. CH₃OH_n were obtained. The complexes of 15- and 18-membered ligands contain Cu²⁺ ion inside the ring.     

Mathematical morphology operations with a comparator array processor

We present a demonstrator photonic system for mathematical morphology image processing. Optically interconnected arrays of differential pairs of optoelectronic transceivers realize morphological erosion and dilation in an 8x8 pixel size image.     

(Photo)electrochemical behavior of selected organic compounds on TiO2 electrodes. Overall relevance to heterogeneous photocatalysis

Oxidation potentials of resorcinol, 4-chlororesorcinol, 4,6-dichlororesorcinol, catechol, 3,4-dihydroxybenzoic acid and 1,2,4-trihydroxybenzene were measured on particulate TiO₂ (Degussa P-25) thin films, immobilized on optically transparent SnO₂ conducting glass electrodes, by cyclic voltammetry in 0.5M KCl aqueous electrolyte solutions. The effect of adsorption on oxidation potentials was examined with the compounds adsorbed on the TiO₂ particle surface. Scan rate dependencies of oxidation peak currents indicate that adsorbed species are consistently characterized by less positive oxidation potentials compared to those attributed to solution free species; the difference ranges from about 0.2 to 0.8 V. Results show that depending on the nature of the working electrode, associating a single oxidation potential to such compounds does not adequately describe their electrochemical behavior. Such observations have relevance in heterogeneous photocatalysis in that predictions of whether a substance will be photooxidized or photoreduced cannot be based on Fermi levels (redox potentials) of the redox couples in homogeneous solutions.