Nanoscale, tunable, and highly sensitive biosensor utilizing hyperbolic metamaterials in the near-infrared range.

A plethora of research in recent years has been reported on biosensing in the surface plasmon resonant systems. However, very little research has reported a tunable and highly sensitive biosensor in a nanoscale platform. In this regard, we propose a nanoscale hyperbolic metamaterial (HMM)-based prism coupled waveguide sensor (PCWS) in the near-infrared range. The HMM layer makes up one of the constituents of the PCWS-comprised of a periodically arranged assembly of silver nanostrips. The structure is numerically simulated by the finite difference time domain method. It is demonstrated that the sensitivity of the reflected light can be tuned through the refractive index (RI) of the solution. Moreover, the effects of alteration of constituents of PCWS on the sensitivity have been analyzed. Results show that the sensitivity of PCWS can be harnessed by altering the thickness, slant angle of HMM layer, volume fraction (f) of metal in the HMM layer, and the incidence angle of light. For this purpose, the structure is numerically simulated by the finite difference time domain method. In the optimum design of the proposed sensor, the maximum value of sensitivity is achieved as high as S=3450 nm/refractive index unit with θ=10° and ϕ=10° and a metamaterial thickness of 250 nm. Moreover, the structure has a nanoscale footprint of 600 nm×400 nm×200 nm.

Enhanced decomposition of reactive blue 19 dye in ultrasound assisted electrochemical reactor.

Textile industry effluents contain reactive dyes that may harm our receiving waters. A typical reactive blue (RB) 19 dye is frequently detected in significant concentrations in textile industry effluents. Such dyes have generally shown resistance to decomposition and tend to persist in the environment for long periods and multiply the impacts to water and environment. Therefore, the present investigation focused on high-rate decomposition of a typical reactive dye RB 19 under various ultrasound and electrochemical process conditions. The decomposition of un-hydrolyzed and hydrolyzed forms of reactive blue (RB) 19 dye by ultrasound assisted electrochemical process was investigated using various parameters including dye concentration, pH, ultrasonic frequency and reaction time. Reaction kinetics, organic carbon and mechanism for dye decomposition were determined using UV-Visible spectrophotometry, TOC (total organic carbon) analysis and gas chromatography-mass spectrometry (GC-MS). Almost complete 90% color removal and a maximum of 56% TOC removal for 50 mg L(-1) dye concentration of un-hydrolyzed RB 19 dye was achieved at an ultrasonic frequency of 80 kHz, pH of 8 after 120 min. GC-MS analysis showed that a sonoelectrochemical treatment of un-hydrolyzed RB 19 dye for 30 min resulted in the formation of products e.g. acetic acid, benzoic acid etc. with the complete removal of dye. For hydrolyzed dye, a treatment of 10 min was enough and the results were comparable with 30 min treatment of un-hydrolyzed dye. Kinetics of ultrasound assisted electrolysis showed that the dye decomposition followed 1st order. The ultrasound assisted electrolysis for dye decomposition and hence decolorization proved to be more effective and the total energy consumption reduced to half as compared with simple electrolysis/sonochemical decomposition. Therefore, ultrasound assisted electrolysis was found to be more effective technique for dye decomposition of an otherwise environmentally persistent reactive dye.

Sonochemical degradation of organophosphorus pesticide in dilute aqueous solutions.

Ultrasonic irradiation was found to accelerate the rate of hydrolysis of omethoate in aqueous solution over the pH range of 2-12. Process parameters studied include pH, steady-state temperature, concentration, and the type of gases. Greater than 96% hydrolysis was observed in 30 minutes through this process and the rate of destruction increased with the help of more soluble and low thermal inert gas. So with Krypton, omethoate was found to undergo rapid destruction as compared with Argon. In the presence of ultrasound, the observed first-order rate of hydrolysis of omethoate is found to be independent of pH. The formation of transient supercritical water (SCW) appears to be an important factor in the acceleration of chemical reactions in the presence of ultrasound. A detailed chemical reaction mechanism for omethoate destruction in water was formulated. Experimental results and theoretical kinetic mechanism demonstrated that the most of the omethoate undergo destruction inside the cavitating holes. A very less effect of temperature on the degradation of omethoate within a temperature range of 20-70 degrees C proves that a small quantity of omethoate undergoes secondary destruction in the bulk liquid.

Removal of copper from a copper sulphate solution using an ultrasonic-electrolysis process.

The application of ultrasonic-electrolysis process for the removal of copper is studied. In the ultrasonic field cavitation acts as jets and agitates the solution and breaks the barrier layer between the cathode surface and the bulk of the solution. Thus increases metal deposition on the cathode surface. The results show that an ultrasonic field is successful for the removal of low copper concentrations in solution.

Effect of ultrasound on the removal of copper from the model solutions for copper electrolysis process.

A novel combination of an ultrasonic field with electrolysis for the removal of copper is studied. In the ultrasonic field, cavitation acts as jets and agitates the solution and breaks the barrier layer between the cathode surface and the bulk of the solution, thus increases the metal deposition on the cathode surface. The results show that an ultrasonic field is successful for the removal of low copper concentrations in solution.