Abstract

Cobalt oxide particles have emerged as one of the promising metal oxide systems for their unique properties and various applications. This article reports syntheses of nano to micrometer sized morphology-controlled cobalt oxide particles by using the sol-gel synthesis method. The method can produce cobalt oxide particles in gram quantity. We explored the effects of various factors such the metal precursor, capping agent, solvent, calcination temperature, etc. on the size and morphology of the synthesized particles. FTIR and XRD studies confirmed the formation of crystalline Co3O4 particles. Field-emission scanning electron microscopy (FE-SEM) show that particles with sizes ranging from 180 nm to 6 μm and morphologies mainly smoothed surfaced octahedra formed depending on the metal precursor, capping agent, solvent and calcination temperature. The effects of three calcination temperatures have been explored based on the thermal behavior of the particles as studied by the thermogravimetric and differential thermal analysis (TGA/DTA). The powdered particles offer ~50 to ~75 m2 /g Brunner-Emmett-Teller (BET) surface area. The sol-gel technique is rapid, straightforward, and cost-effective and requires low processing temperatures to produce the particles compared to solvothermal methods. The present study shows that a proper choice of reaction conditions in a sol-gel method could be used to produce morphology-controlled cobalt oxide particles of nanometer to micrometer sizes in high yield

Abstract

This paper utilizes RF Sensing to develop a facile methodology for the determination of Critical Micelle Concentration (CMC) of surfactants. The study is undertaken with the help of an Interdigitated Capacitor based RF Sensor. Due to change in permittivity, the sensor yields distinct resonant frequencies when introduced to solutions of varying concentration of Sodium Dodecyl Sulphate as the electrolyte. As the surfactant approaches micellization, the resonant frequency shift drastically alters, and this sudden transition is used to determine the value of CMC. The proposed technique estimates the CMC of SDS to be 6.5 x10 -3 M The introduced method is effective and less cumbersome as compared to traditional techniques.

Abstract

In this paper, RF resonant sensor is designed for measurement of complex permittivity of unknown sample. It takes advantage of peano curve fractal geometry (i.e. higher capacitance in minimum area). It operates in the ISM (industrial, scientific and medical) frequency band of 4-5 GHz. An empirical model of sensor is developed for the accurate calculation of complex permittivity of an unknown sample in terms of shifts in the resonant frequencies and reflection coefficients (S11) under loaded condition. Due to homogeneous E-field at fractal capacitor, placement position of sample will not affect the sensitivity. Significant frequency shifts as high as 60 M Hz, 80 M Hz, 116 M Hz and 134 M Hz are observed for relative permittivity of 5.4, 6.5, 8.9 and 10.6 respectively.

Abstract

DESIGN OF RF SENSOR FOR SIMULTANEOUS DETECTION OF COMPLEX PERMEABILITY AND PERMITTIVITY OF UNKNOWN SAMPLE

Abstract

In this paper, a novel microwave planar resonant sensor (using two spiral inductors) is designed and developed for detection of ferritin from the blood sample using non destructive technique. Due to concentration change of ferritin in blood, shift in resonant frequency arise. The frequency range of 15 GHz-16 GHz is used as it is effective for label-free analysis of ferritin. The sensor is designed using the full wave electromagnetic solver, HFSS 13.0, and an empirical model is developed for the accurate calculation of ferritin concentration in terms of shifts in the resonant frequency. Due to homogeneous H-field in spacing between two inductors, placement position of ferritin will not affect the sensitivity. Significant frequency shifts as high as 105 MHz, 192 MHz, 310 MHz and 655 MHz are observed for concentrations as low as 20 ng/ml, 50 ng/ml, 100 ng/ml and 320 ng/ml of ferritin respectively. Simulation results suggest …

Abstract

Studies of metal nanoclusters can provide valuable information on how various properties evolve in the nanoscale materials. Previously often mixed-sized products have been separated in order to study their size-related properties. We present here a one-pot aqueous synthesis protocol that allows direct observations of the evolutions of size-dependent optical and electrochemical properties of the gold nanoclusters while the clusters grow from a few-atom, ultra-small size to the plasmonic nanoparticle stage. Our selection of a mixed ligand system comprising of methionine and CTAB for the aqueous synthesis of gold nanoclusters by the chemical reduction of gold ions led to the slow growth of the nanoclusters making direct observations of the cluster growth and concomitant evolution of properties possible. UV-visible spectrophotometric and dynamic light scattering studies demonstrated the size-dependent transition from the molecule-like, non-plasmonic to plasmonic properties in the evolving nanoclusters. Differential pulse voltammetry studies demonstrated how the electrochemical properties changed from the molecule-like redox behavior to a quantized double-layer charging type with the growth of the nanocluster with time. Thermogravimetric analysis, MALDI-TOF mass spectrometry, etc. were employed to further characterize the nanocluster systems. This report will inspire further studies in understanding the evolution of the size-dependent

Abstract

In this paper, biotin streptavidin interaction has been sensed at microwave frequencies with the help of designed sensor. It takes advantage of two pole filter topology where interdigitated capacitor (IDC) is used as a coupling zone between resonators for higher sensitivity. Due to permittivity change of biotin streptavidin combination, shift in resonant frequency arise whereas due to conductivity, magnitude of reflection coefficient changes. The frequency range of 10 GHz - 25 GHz (γ-dispersion region) is used as it is effective for label free analysis of biotin streptavidin. Due to homogeneous E-field between the fingers of IDC, placement position of biotin-streptavidin will not affect the sensitivity. Significant frequency shifts as high as 19 MHz, 45 MHz and 70 MHz are observed for concentrations as low as 10 ng/ml, 20 ng/ml and 30 ng/ml of biotin-streptavidin respectively. Simulation results suggest that proposed biosensor …

Abstract

Recent reports have demonstrated that nanoclusters of silver and gold can act as substrates for Raman signal enhancements. This article presents a density functional theory (DFT)-based study to explore how the variations in the nature of the cluster-binding heteroatom in the ligand molecule and the relative orientation of the alkyl group attached to the heteroatom affect the Raman signal enhancement in the ligand molecules. Our calculations involved nitrogen and phosphorus heteroatoms in two simple model molecules, methylphosphine and methylamine, as ligands and four small gold clusters, Aun (n = 6–9). In order to understand the interactions in the cluster-molecule systems, we have calculated various geometrical parameters such as Au–X (X = P, N) distances, ffC–X–Au angles and different bond lengths of free and cluster-bound molecules as well as various interaction energies. We have performed natural bond order (NBO) analysis and have calculated second order stabilization energies for the molecules bound to the gold clusters from the NBO analysis. In addition, we have performed detailed calculations pertaining to the change in polarisability, quantity of molecule to cluster charge transfer as well as molecular orientations relative to the clusters and have studied how these factors influence the Raman scattering cross-sections and vibrational frequency shifts. The quantity of charge transfer and the orientation effect have been found to be important contributors in the chemical Raman enhancement mechanism of the ligand molecules.

Abstract

There has been a constant demand for the development of non-invasive, sensitive glucose sensor system that offers fast and real-time electronic readout of blood glucose levels. In this article, we propose a new system for detecting blood glucose levels by estimating the concentration of acetone in the exhaled breath. A TGS822 tin oxide (SnO2) sensor has been used to detect the concentration of acetone in the exhaled air. Acetone in exhaled breath showed a correlation with the blood glucose levels. Effects of pressure, temperature and humidity have been considered. Artificial Neural Network (ANN) has been used to extract features from the output waveform of the sensors. The system has been trained and tested with patient data in the blood glucose ranges from 80 mg/dl to 180 mg/dl. Using the proposed system, the blood glucose concentration has been estimated within an error limit of±7.5 mg/dl.

Abstract

The past few years have witnessed the development of non-spherical metal nanoparticles with complex morphologies, which offer tremendous potential in materials science, chemistry, physics and medicine. Covering all important aspects and techniques of preparation and characterization of metal nanoparticles with controlled morphology and architecture, this book provides a sound overview-from the basics right up to recent developments. Renowned research scientists from all over the world present the existing knowledge in the field, covering theory and modeling, synthesis and properties of these nanomaterials. By emphasizing the underlying concepts and principles in detail, this book enables researchers to fully recognize the future research scope and the application potential of the complex-shaped metal nanoparticles, inspiring further research in this field.