Preparation of CuO mesocrystals via antlerite intermediate for photocatalytic applications

CuO mesocrystals were synthesized by thermal decomposition of antlerite (Cu₃(OH)₄SO₄) formed as an intermediate by the reaction between CuSO₄.5H₂O and urea under specific experimental conditions. Antlerite possessing spindles of sea urchin‐like morphology was obtained via controlled hydrolysis process using ethylene glycol as a co‐solvent. Antlerite and CuO mesocrystals were characterized by X‐ray diffraction (XRD), fourier transform‐infrared spectrum (FT‐IR), thermo gravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). A probable mechanism for formation of such morphologies has been proposed. The photocatalytic and optical properties of CuO mesocrystals were also evaluated.     

Head‐to‐Tail Intermolecular Hydrogen Bonding of OH and NH Groups with Fluoride

To explore the anion‐recognition ability of the phenolic hydroxyl group and the amino hydrogen, we synthesized three different acridinedione (ADD) based anion receptors, 1 , 2 and 3 , having OH, NH, and combination of OH and NH groups, respectively. Absorption, emission and ¹H NMR spectral studies revealed that receptor 1 , having only a phenolic OH group, shows selective deprotonation of the hydroxyl proton towards F^?, which results in an “ON–OFF”‐type signal in the fluorescence spectral studies. Receptor 2 , which only has an amino hydrogen, also shows deprotonation of the amino hydrogen with F^?, whereas receptor 3 (having both OH and NH groups) shows head‐to‐tail intermolecular hydrogen bonding of OH and NH groups with F^? prior to deprotonation. The observation of hydrogen bonding of the OH and NH groups in a combined solution of 1 and 2 with F^? in a head‐to‐tail hetero‐intermolecular fashion, and the absence of head‐to‐head and tail‐to‐tail intermolecular hydrogen bonding in 1 and 2 with F^?, prove that the difference in the acidity of the OH and NH protons leads to the formation of an intermolecular hydrogen‐bonding complex with F^? prior to deprotonation. The presence of this hydrogen‐bonding complex was confirmed by absorption spectroscopy, 3D emission contour studies, and ¹H NMR titration.     

Estimation of ultrasound induced cavitation bubble temperatures in aqueous solutions

Mean acoustic cavitation bubble temperatures have been measured in a series of aqueous solutions containing C(1)-C(5) aliphatic alcohols, at 355 kHz. The method relies on the distribution of hydrocarbon product yields produced from the recombination of methyl radicals generated on the thermal decomposition of the alcohols. The mean bubble temperature was found to decrease with increasing concentration of alcohol with the effect being more pronounced the higher the molecular weight (the lower the vapour pressure) of the alcohol. It is shown that the decrease in the temperatures measured correlates very well with an increase in the surface excess of the alcohol, similar to that previously reported for the quenching of sonoluminescence in aqueous solutions containing alcohols [J. Phys. Chem. B 101 (1997) 10845; J. Phys. Chem. B 103 (1999) 9231]. The measured temperatures ranged from 4600+/-200 K at zero alcohol concentration to 2300+/-200 K at 0.5 M t-butanol. The validity of the method is discussed and it is concluded that even though a number of assumptions need to be applied the results appear to indicate that the method gives an accurate measure of the mean bubble temperature.     

Dynamics of counterion binding during acoustic nebulisation of surfactant solutions

A metal ion (Cu(2+)) and a complex copper species, copper (II) bis-bipyridine, were used as alternate counterions in an aqueous surfactant solution of sodium dodecylbenzenesulfonate (SDBS) to investigate the dynamics of counterion interactions in an acoustic field. Sonoluminescence spectral studies showed that such counterions were able to replace sodium ions at the interface, even when the interface was rapidly oscillating under the acoustic field. Ultrasound induced nebulisation was then used to probe the interfacial profile of surfactant and bound counterions in a dynamic environment. At low bulk concentrations, the copper (II) bis-bipyridine cation was more effective at enhancing the loading of the dodecylbenzenesulfonate anion on the interface, due to its documented greater binding ability. However, at higher bulk concentrations, the movement of this cation is limited by its larger size and the smaller Cu(2+) cation is more effective in enhancing the loading of the dodecylbenzenesulfonate anion. The results show that under dynamic conditions, the surface concentrations are governed by mass transfer kinetics rather than equilibrium thermodynamics.     

Phytochemical variations among four distinct varieties of Indian cardamom Elettaria cardamomum (L.) Maton

Abstract

Elettaria cardamomum (L.) Maton prestigiously called as Indian cardamom and is mostly cultivated in south India at higher altitudes ranging from 900 to 1400 msl. The chemical composition of dry capsules essential oil of the four distinct varieties was chemo-profiled by gas chromatography-mass spectrometry (GC-MS). Results revealed a higher concentration of major monoterpene 1, 8-Cineole ranging between 28.94% and 34.91% in PV 1 and PV 2 varieties respectively. Other monoterpenes like α-Pinene, Sabinene, Linalool, α-Terpineol and Nerol were present considerable quantities in all of the four cardamom varieties. Two sesquiterpenic constituents namely, ç-Elemene and 1,6,10-dodecatrien-3-ol (Nerolidol) were identified in all varieties. Three ester constituents were also obtained in PV 1 in which α-Terpinyl acetate (26.68%) exhibited as a major ester constituent followed by Ocimenyl acetate (0.80%) and E5-Dodecenyl acetate (0.30%). This is the first published report on the phytochemical concentration of recent varieties of Indian cardamom.

     

Sonoluminescence quenching in aqueous solutions of aliphatic diols and glycerol

The multibubble sonoluminescence (MBSL) signals that were generated using 358kHz ultrasound in aqueous solutions of ethylene glycol, 1,3-propanediol, 1,4-butanediol and glycerol, over a range of concentrations, have been studied. It was found that the intensity of the MBSL was either reduced or enhanced, relative to the signal in water, depending on the concentration of the solute. It was concluded that the reduction in the MBSL intensity was dependent on the strength of the intermolecular forces, in particular hydrogen bonding, between the solute molecules and water. The enhancement in the MBSL signal was ascribed to presence of the solute molecules at the bubble/solution interface that hinder the coalescence of the bubbles in the multibubble clouds produced at the antinodes in the system.     

Sonochemical degradation of martius yellow dye in aqueous solution

The sonolytic degradation of the textile dye martius yellow, also known as either naphthol yellow or acid orange 24, was studied at various initial concentrations in water. The degradation of the dye followed first-order kinetics under the conditions examined. Based on gas chromatographic results and sonoluminescence measurements of sonicated aqueous solutions of the dye, it is concluded that pyrolysis does not play a significant role in its degradation. The chromatographic identification of hydroxy added species indicates that an OH radical induced reaction is the main degradation pathway of the dye. Considering the non-volatility and surface activity of the dye, the degradation of the dye most probably takes place at the bubble/solution interface. The quantitative and qualitative formation of the degradation intermediates and final products were monitored using HPLC and ESMS. The analytical results suggest that the sonolytic degradation of the dye proceeds via hydroxylation of the aryl ring and also by C-N bond cleavage of the chromophoric ring, either through OH radical attack or through another unidentified process. The identification of various intermediates and end products also imply that the degradation of martius yellow proceeds through multiple reaction pathways. Total organic carbon (TOC) analyses of the dye solutions at various times following sonication revealed that sonolysis was effective in the initial degradation of the parent dye but very slow in achieving mineralization. The slow rate of mineralization is likely to be due to the inability of many of the intermediate products such as, the carboxylic acids, to accumulate at the bubble (air/water) interface and undergo decomposition due to their high water solubility (low surface activity).     

Dynamical analysis and FPGA implementation of a chaotic oscillator with fractional-order memristor components

Memristor-based chaotic and hyperchaotic systems are of great interest in the recent years, and addition of meminductor and memcapacitors to the family has widened the applications. In this paper, we propose a new chaotic system with fractional-order memristor and memcapacitor components. Nonlinear chaotic properties of the proposed system are investigated with equilibrium points, eigenvalues, Lyapunov exponents, bifurcation and bicoherence plots. We show that a small model disturbance can make the system to show self-excited and hidden attractors. We use the Adomian Decomposition method for implementing the proposed system in Field Programmable Gate Arrays.     

Ultrasound initiated miniemulsion polymerization of methacrylate monomers

The ultrasound initiated emulsion polymerization of methyl methacrylate (MMA), n-butyl methacrylate (BMA) and 2-ethylhexyl methacrylate (2EHMA) in the presence of sodium dodecylsulfate as a stabiliser produced latex particles in the size range of 70 nm to 110 nm with molecular weights of the order of 2-6 x 10(6) g mol(-1). The experimental data obtained show significant differences in the rates of polymerization of the methacrylate monomers in the order 2EHMA>BMA>MMA. The rate trend is discussed with respect to the physicochemical properties of the monomers. It is suggested from the results obtained that the mechanism involved in sonochemical formation of the latex particles is very similar to that of a conventional miniemulsion polymerization process.     

Experimental and theoretical investigations on sonoluminescence under dual frequency conditions

The multibubble sonoluminescence (MBSL) intensities from water exposed to the simultaneous ultrasonic irradiation from 20 kHz (fixed at 6.3 W) and 355 kHz (variable power) ultrasound sources have been compared to the MBSL from the individual ultrasound sources under the same power conditions. A synergistic enhancement of the sonoluminescence (SL) signal, >30-fold, at low powers (4.6 W) of the higher frequency was observed. At a higher acoustic power level (15.8 W) the dual frequency operation produced a decrease in the SL signal. These results are in agreement with previously reported data [P. Ciuti, N.V. Dezhkunov, A. Francescutto, F. Calligaris, F. Sturman, Ultrasonics Sonochem. 10 (2003) 337; N.V. Dezhkunov, J. Eng. Phys. Therm. 76 (2003) 142] under similar experimental conditions. Numerical single bubble (SB) dynamics calculations have been used to help interpret the experimental results. It is suggested that the observed effects are caused by a combination of changes to the peak collapse temperature of individual bubbles as well as to changes in the active bubble population.