Manoj K. Nayak

Synthesis and visible photocatalytic activities of a Au@Ag@ZnO triple layer core–shell nanostructure

We report a facile route for the synthesis of a Au@Ag@ZnO triple layer core–shell nanostructure with Au as core, Ag as intermediate layer and ZnO as an outer shell. The thickness and surface plasmon resonance (SPR) absorption peak of the Ag shell of Au@Ag bimetal has been controlled by the concentration of AgNO3. In the Au@Ag@ZnO nanostructure two major absorption peaks were seen, one due to SPR of Au and other due to the combined effect of Ag and a ZnO layer. The photoluminescence study shows that the Au@Ag@ZnO has better charge separation compared to the ZnO and Au@ZnO nanostructure. The visible photocatalytic activity for the degradation of methyl orange dye was found to be much higher in the case of the Au@Ag@ZnO core–shell structure than ZnO or Au@ZnO or TiO2.

Selective electrochemical sensing for arsenite using rGO/Fe3O4 nanocomposites.

Herein, we report rGO/Fe3O4 nanocomposites (NCs) free from noble metals, synthesized by facile one step chemical reduction method, for electrochemical detection of arsenite in water by square wave anodic stripping Voltammetry (SWASV). The synthesized NCs were characterized for its optical, morphological and structural properties. The NCs modified glassy carbon (GCE), NCs/GCE, electrodes showed a higher sensitivity (0.281μA/ppb) and lower LOD (0.12ppb) under optimized experimental conditions. The proposed NCs/GCE electrodes show no interference towards arsenite species in the presence of common cationic interferants, namely, Cu(II), Pb(II), Ni(II), Co(II), Cd(II), Cr(II), Zn(II), etc. In addition, the proposed electrode demonstrates a good stability, reproducibility and potential practical application in electrochemical detection of arsenite.

Bacteriophage conjugated IRMOF-3 as a novel opto-sensor for S. arlettae

This article reports the novel assembly of a bacteriophage-based fluorescent sensor for the selective and sensitive detection of a model bacterium ‘Staphylococcus arlettae (S. arlettae)’. A host specific bacteriophage was bioconjugated with a fluorescence metal organic framework ‘IRMOF-3’. Changes in the photoluminescence intensities of this fluorescent probe were correlated with bacterial concentrations. The proposed bacteriophage based opto-sensor provided a low detection limit (100 cfu mL−1) along with specificity in the detection with respect to other some non-specific bacteria, e.g. S. aureus and E. coli. The detection was achieved over a wide range of bacterial concentrations, i.e. 102–1010 cfu mL−1S. arlettae. Compared to antibody and DNA based optical sensors, the use of bacteriophage in conjugation with IRMOF-3 should offer advantages of simplicity and stability. The use of IRMOF-3 as a fluorescent molecule should also offer the development of reproducible sensors because of its well defined structural geometry and hierarchical assembly.

Ultrasensitive and Selective Sensing of Selenium Using Nitrogen-Rich Ligand Interfaced Carbon Quantum Dots

This work reports a label-free, ultrasensitive, and selective optical chemosensory system for trace level detection of selenite (SeO32-), the most toxic form of selenium, in water. The probe, i.e., carbon quantum dots (CQDs), is designed from citric acid by means of pyrolysis and is interfaced with a newly synthesized nitrogen-rich ligand to create a selective sensor platform (functionalized CQDs, fCQDs) for selenite in a water matrix. Spectral (NMR, UV-vis, photoluminescence, Raman, and Fourier transform infrared analyses) and structural (high-resolution transmission electron microscopy) characteristics of the designed new probe were investigated. The developed sensor exhibits high sensitivity (limit of detection = 0.1 ppb), a wide detection range (0.1-1000 ppb range, relative standard deviation: 3.2%), and high selectivity even in the presence of commonly interfering ions reported to date, including Cl-, NO3-, NO2-, Br-, F-, As(V), As(III), Cu2+, Pb2+, Cd2+, Zn2+, Sr2+, Rb2+, Na+, Ca2+, Cs+, K+, Mg2+, Li+, NH4+, Co2+, etc. The observed selectivity is due to designed ligand characteristics in terms of strong Se-N chemistry. Ultrafast spectroscopic analysis of the fCQDs in the absence and presence of selenite was studied to understand the sensing mechanism. The sensor was successfully exemplified for real water samples and exhibits comparative performance to conventional ion channel chromatography as well as flame atomic absorption spectroscopy for selenite analysis. The promising results pave ways for realization of a field deployable device based upon a developed probe for selenite quantification in water.

Plausibility of variable coverage high range spraying

Electrostatic force field has been exploited in the development of an air-assisted electrostatic nozzle.Parameters are optimized and engineering design aspects have been addressed.Plausibility of variable coverage high range spraying with simple retrofitted mechanical maneuver.The effects of wind current in electrostatic spraying have been explained.It covers a longer distance with variable coverage, which was not possible earlier. A system for spraying liquid pesticides to crops and orchards combines an induction based electrostatic nozzle and externally air-assisted manually controlled mechanical device. In this paper, an innovative concept has been executed for variable coverage high range spraying through an external air-assistance system, which supplies compressed air to assist the finely divided charged liquid droplets by farming a virtual covering around the fine mist of liquid spray. External air-assistive device consists of movable support for air supplies whose variation of cone angle is from parallel spray center line (0°) to maximum spray cone angle (25°). This provides a means to transport electrostatically charged fine mist of liquid droplets to intended target with variable spray coverage angle of target, applicable in high wind and transient conditions with enhanced performance without degradation of charge-to-mass ratio. The results of applied induction electrification process were characterized by a charge-to-mass ratio as a function of applied voltage, target distance, and wind current. It has been shown that the wind current has an insignificant (p value=0.021615) and significant (p value=0.000325) effects on the performance of the electrostatic nozzle at 99% confidence level with and without external air-assistive mechanical device respectively. The experimental results are in good agreements with proposed concept.

Navigation control of a mobile robotic system in semi-structured and dynamic environment for controlled dose delivery of pesticides

A major portion of the autonomous mobile robotics research has been in the development of reliable means for navigation and control of autonomous systems in a complex, irregular, unstructured and dynamic environment for farm duties such as seeding, pruning, pesticide spraying, reaping etc. Several practices have been established by numerous researchers in the motion planning of mobile robots. This paper presents an ultrasonic multi-sensor fusion based technique for navigation and control of the autonomous mobile robotic system for collision avoidance, target detection and canopy mapping. The autonomous system is a combination of real time monitoring and navigation, detection of the target and canopy mapping which delivers controlled dose of pesticide in a targeted manner according to the information gathered from the sensory attributes of precision farming data set through online and real time monitoring of the objects. Real time monitoring and navigation control, complex algorithm, data acquisition and storage, calculation and processing are designed with motors and sensors interfaced with microcontroller. Test results showed that the ultrasonic sensor fusion technique was capable of performing satisfactory guidance in dynamic environment and desired paths. The sensor fusion navigation was capable of compensating large error and resulting in satisfactory agricultural vehicle guidance.

Comparative analyses of prediction models for inactivation of Escherichia coli in carrot juice by means of pulsed electric fields

This paper reports the prediction capacity of various microbial inactivation models to prefigure the bactericidal effect using pulsed electric field (PEF) on liquid food. The aim of study was to compare the various inactivation models based on accuracy and bias factor to find out the most accurate inactivation model for Escherichia coli present in carrot juice treated with PEF. In this study, E. coli suspended in carrot juice was treated with varying pulsed electric field strength for different intervals. The obtained data were utilized for the evaluation of parameters of Bigelow, Peleg, Hülsheger and Weibull inactivation models. Furthermore, secondary models were developed for Hülsheger and Weibull to predict the microbial inactivation at any level of field strength and treatment time. The secondary model for Hülsheger exhibits 5.8% error as compared to the Weibull model having 8.5% error in prediction of death kinetics of E. coli suspended in carrot juice by means of PEF. The comparative analysis of secondary models to forecast the unknown data set unveiled the superior functioning of Hülsheger model.

Introduction to semiconductor nanomaterial and its optical and electronics properties

Semiconductor nanoparticles is an important class of nanostructured materials that have a plethora of interesting physical, chemical, mechanical, optical, and electronic, properties. This chapter provides an overview of research pertaining to various nanostructured materials in general and core–shell nanoparticles (CSNs) in particular. Different classification criteria of nanostructured materials based on their sources, dimensions, structural configurations, and nature of core/shell materials have been discussed. Semiconducting core–shell nanoparticles are segregated into different types based on the energy levels of the core and shell materials. Optical and electronic properties of CSNs along with synthesis techniques are discussed in details. Moreover, semiconductor core–shell nanostructure materials highlight the key developments and current status in fields, such as electronic, health, agricultural, food processing, sustainable energy, and environmental catalysis. This chapter covers an introduction to the field of semiconductor and core–shell nanostructures and provides comprehensive understanding to various aspects of these materials in details.

An advance air-induced air-assisted electrostatic nozzle with enhanced performance

Electrostatic force field has been exploited in the development of an air-induced air-assisted electrostatic nozzle.Parameters are optimized and engineering design aspects have been addressed.Charge to mass ratio of 10mC/kg at voltage less than 2.5kV and electric power consumption less than 75mW.The deposition and uniformity has increased on both front and backside of the leaves. There is a pressing need of new chemical application sprayer for small scale farms in Indian agricultural pesticides spraying. A new air-assisted electrostatic nozzle has been designed and developed for small scale farms with a specific focus on Indian agricultural and rural developing economies. An air-assisted electrostatic nozzle is a combination of an air-assisted nozzle and induction based electrostatic charging system. Spray droplets are electrified to more than 10mC/kg charge-to-mass ratio by charging voltage less than 2.5kV at liquid flow of 150ml/min and electric power consumption less than 75mW. Higher charge-to-mass ratio ensured the high range spraying distance to overcome the charge neutralization by recombination of naturally occurring ions present in the environment and charged liquid droplets. The results of applied induction electrification process were characterized by a charge-to-mass ratio and the results are in good agreement with the theoretical considerations. There has been 23 fold increase of liquid deposition with better uniformity on the obscured as well as front target. This nozzle is light weight, highly efficient, reduces pesticide use and human health risks, and eco-friendly.