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Ultra Low Field Sensor Using GMI Effect in NiFe/Cu Wires
Pratap Kollu,Doung Young Kim,Cheol Gi Kim 한국자기학회 2007 Journal of Magnetics Vol.12 No.1
A highly sensitive magnetic sensor using the Giant MagnetoImpedance effect has been developed. The sensor performance is studied and estimated. The sensor circuitry consists of a square wave generator (driving source), a sensing element in a form of composite wire of a 25 ㎛ copper core electrodeposited with a thin layer of soft magnetic material (Ni??Fe₂?), and two amplifier stages for improving the gain, switching mechanism, scaler circuit, an AC power source driving the permeability of the magnetic coating layer of the sensing element into a dynamic state, and a signal pickup LC circuit formed by a pickup coil and an capacitor. Experimental studies on sensor have been carried out to investigate the key parameters in relation to the sensor sensitivity and resolution. The results showed that for high sensitivity and resolution, the frequency and magnitude of the ac driving current through the sensing element each has an optimum value, the resonance frequency of the signal pickup LC circuit should be equal to or twice as the driving frequency on the sensing element, and the anisotropy of the magnetic coating layer of the sensing wire element should be longitudinal.
Development of Sensors Using Giant Magnetoimpedance Effect In Amorphous Ribbons
Pratap Kollu,Lan Jin,Seok Soo Yoon,Hung Tran Quang,Chong-Oh Kim,CheolGi Kim 한국자기학회 2006 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-
Micro Sized magnetic sensors are needed for recent developments such as magnetic recording technology, highly accurate rotary encoding for intelligent robot control, nondestructive testing and sensing in various industrial and environmental measurement tasks, and automotive control applications. Following the demands of industrial and automotive electronics, a direction sensitive micro-magnetic field sensor is developed using the Giant MagnetoImpedance (GMI) effect in a amorphous Co??Fe₄B₁?Si₁? ribbon. Sensor consists of an amorphous ribbon of about 1 ㎝ length, 20㎛ thickness and 1mm width. The ability of the GMI sensor to detect the geomagnetic field is tested in the laboratory. The sensor is tested for its linearity and angle dependence. The permeability and gmi spectrum for as-quenched, annealed and bead coated samples are studied. The sensor is modeled based on these measurements. The resolution of the sensor is found to be 1V/Oe and angle resolution is 1㎷/degree. The permeability spectrum and the GMI profile of the Magnetic Dynabead M-280<SUP>®</SUP>coated amorphous ribbon are studied, and its application in biosensor is proved experimentally.
Prototype Milli Gauss Meter Using Giant Magnetoimpedance Effect in Self Biased Amorphous Ribbon
Pratap Kollu,Seok Soo Yoon,Gun Woo Kim,C. S. Angani,Cheol Gi Kim 한국자기학회 2010 Journal of Magnetics Vol.15 No.4
In our present work, we developed a GMI (giant magnetoimpedance) sensor system to detect magnetic fields in the milli gauss range based on the asymmetric magnetoimpedance (AGMI) effect in Co-based amorphous ribbon with self bias field produced by field-annealing in open air. The system comprises magnetoimpedance sensor probe, signal conditioning circuits, A/D converter, USB controller, notebook computer, and program for measurement and display. Sensor probe was constructed by wire-bonding the cobalt based amorphous ribbon with dimensions 10 ㎜ × 1 ㎜ × 20 ㎛ on a printed circuit board. Negative feedback was used to remove the hysteresis and temperature dependence and to increase the linearity of the system. Sensitivity of the milli gauss meter was 0.3 V/Oe and the magnetic field resolution and environmental noise level were less than 0.01 Oe and 2 mOe, respectively, in an unshielded room.
Electrocatalytic activity of Cu2O nanocubes based electrode for glucose oxidation
FELIX, S.,KOLLU, P.,RAGHUPATHY, B. P.,KWAN JEONG, S.,NIRMALA GRACE, A. Springer Science + Business Media 2014 Journal of chemical sciences Vol.126 No.1
A direct electrocatalytic activity of glucose oxidation on cuprous oxide modified glassy carbon electrode is reported. Cu2O nanocubes were synthesized by a simple wet chemical route in the absence of surfactants. Purity, shape and morphology of Cu2O are characterized by XRD, SEM, XPS and DRS-UV. The Cu2O nanocubes-modified glassy carbon electrode (GCE) exhibited high electrocatalytic activity towards glucose oxidation compared with bare GCE electrode. At an applied potential of +0.60 V, the Cu2O electrode presented a high sensitivity of 121.7 mu A/mM. A linear response was obtained from 0 to 500 mu M, a response time less than 5 s and a detection limit of 38 mu M (signal/noise=3). The Cu2O nanocubes-modified electrode was stable towards interfering molecules like uric acid (UA), ascorbic acid (AA) and dopamine (DA). In short, a facile chemical preparation process of cuprous oxide nanocubes, and the fabricated modified electrode allow highly sensitive, selective, and fast amperometric sensing of glucose, which is promising for the future development of non-enzymatic glucose sensors.
Felix, S.,Kollu, P.,Raghupathy, B.P.C.,Jeong, S.K.,Grace, A.N. Elsevier Sequoia 2015 Journal of Electroanalytical Chemistry Vol.739 No.-
Platelet-like copper oxide nanostructures were prepared by a hydrothermal method. Various techniques like X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) were used to characterize the structure and morphology of the as-prepared products. The electrocatalytic oxidation of carbohydrates and dopamine on the surface of the modified electrode were studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA). Under the optimal experimental condition, the CuO nanoplatelets (CuO NPlts) loaded on glassy carbon electrode (GCE) exhibited excellent sensitivity in the linear concentration range of carbohydrates, good stability and reproducibility. Interferences from other biological compounds were studied and results indicated good selectivity for glucose, sucrose, and fructose. Apart from the detection of carbohydrates, the electrode was tested for detection possibility of dopamine in the range of 10-80μM in phosphate buffer solution (PBS) with a detection limit of 8.25μM.
Kumar, P. Ramesh,Kollu, Pratap,Santhosh, Chella,Eswara Varaprasada Rao, K.,Kim, Do Kyung,Grace, Andrews Nirmala The Royal Society of Chemistry 2014 NEW JOURNAL OF CHEMISTRY Vol.38 No.8
<P>Porous CoFe<SUB>2</SUB>O<SUB>4</SUB> nanoclusters with different concentrations of graphene based composites were synthesized by a simple solvothermal process. The electrochemical properties of prepared CoFe<SUB>2</SUB>O<SUB>4</SUB>–reduced graphene oxide (rGO) composites were evaluated using polyvinylidene fluoride and Na-alginate as binder materials. The CoFe<SUB>2</SUB>O<SUB>4</SUB> + 20% rGO composite with alginate exhibited a high stable capacity of 1040 mA h g<SUP>−1</SUP> at 0.1 C (91 mA g<SUP>−1</SUP>) rate with excellent rate capability. The observed enhancement in electrochemical properties of the CoFe<SUB>2</SUB>O<SUB>4</SUB> + 20% rGO composite with alginate is due to the high stability and good transportation network while charging–discharging.</P> <P>Graphic Abstract</P><P>Porous CoFe<SUB>2</SUB>O<SUB>4</SUB> nanoclusters with different concentrations of graphene based composites were synthesized by a simple solvothermal process. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4nj00419a'> </P>