School of Engineering Sciences and Technology

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    3D printing of complex shaped alumina parts
    ( 2018-11-01) Mamatha, Sirisala ; Biswas, Papiya ; Ramavath, Pandu ; Das, Dibakar ; Johnson, Roy
    Alpha-alumina powder was mixed with methyl cellulose as a binder with concentration as low as 0.25% by weight in an aquoes medium and kneaded in a high shear mixer to obtain a printable paste. The paste was subjected to rheological measurements and exhibited a shear rate exponent of 0.54 signifying the shear thinning behavior. The paste was used for printing parts with various shapes according to CAD model by employing a ram type 3D printer. Printed parts were dried and the green density was determined. Further, the parts were also subjected to X-ray radiography in order to evaluate the possible occurrence of printing defects. The samples were sintered under pressureless condition at 1650 °C in a muffle furnace and Hot Isostsically Pressed (HIP) at 1350 °C and a pressure of 1650 bar using a vacuum encapsulated SS CAN. Hot Isostatic pressing resulted in a higher density of 3.94 g/cc in comparison to 3.88 g/cc obtained under pressureless conditions and also shown superior mechanical properties. HIPing of 3D printed samples not only resulted in possible healing of printing defects as reavealed by X-ray radiography but also enhanced the diffusion at low temperature of 1350 °C leading to finer grain sizes as complemented by the microstructure.
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    3D printing of cordierite honeycomb structures and evaluation of compressive strength under quasi-static condition
    ( 2020-01-01) Mamatha, Sirisala ; Biswas, Papiya ; Das, Dibakar ; Johnson, Roy
    Ceramic honeycombs exhibit unique mechanical properties based on engineered formulations and geometry of cells. Extrusion of formable paste through a complex honeycomb die is the commonly practiced technique for the manufacturing of honeycombs globally. Extrusion die fabrication is a complex process which necessitates sophisticated infrastructure facilities that provide high geometrical accuracy and finish to produce defect free honeycombs. Furthermore, every configuration of honeycomb requires a specific tool. Additive manufacturing (AM)/ 3D printing is a rapid prototyping technique which offers flexibility in fabrication of honeycombs with desired geometries from a virtual model directly. Further, this does not require complicated dies. In this study, viscoplastic printable cordierite raw mix paste with a shear rate exponent of 0.87 was printed into honeycombs with hexagonal, square, and triangular cells using a ram type 3D printer. The printed honeycomb samples are found to possess good integrity and near net shape after drying. Sintered 3D-printed honeycomb samples of all configurations have exhibited cordierite as a major phase along with minor phases of magnesium aluminate (MgAl2O4) spinel, clinoenstatite (MgSiO3), and corundum (Al2O3) with sintered density of 2.41-2.48 g/cc. The samples are also subjected to compression testing under quasi-static condition. The study demonstrates 3D printing as a viable and flexible technique for rapid prototyping of honeycombs with desired configurations and engineered properties.
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    A brief notes on metal oxide-carbon nanomaterial-polypyrrole/ polyaniline ternary nanocomposites as hybrid type supercapacitor electrode materials
    ( 2015-12-01) Puttapati, Sampath K. ; Srikanth, Vadali V.S.S.
    Hybrid type supercapacitors store electrical energy through a combination of double layer charging and Faradic processes. The active electrode material plays a pivotal role on the performance of these supercapacitors. In this article, the use of different metal oxide-carbon nanomaterial-conducting polymer ternary nanocomposites as working electrode materials in hybrid supercapacitors is presented.
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    A critical assessment of the microstructure and mechanical properties of friction stir welded reduced activation ferritic-martensitic steel
    ( 2016-02-15) Manugula, Vijaya L. ; Rajulapati, Koteswararao V. ; Madhusudhan Reddy, G. ; Mythili, R. ; Bhanu Sankara Rao, K.
    Bead-on-plate friction stir welding was conducted on 6mm thick plate of Reduced Activation Ferritic-Martensitic Steel employing polycrystalline cubic boron nitride tool with rotational speeds of 200, 300, 500 and 700rpm and traverse speed of 30mm/min. The interface temperature between shoulder bottom and top surface of the plate was monitored by non-contact in-line thermography which served to identify the peak temperature attained in the stir zone (SZ). This temperature for 200, 300 and 500, and 700rpm was respectively below Ac1, between Ac1 and Ac3, and above Ac3. In the base metal (BM), the prior austenite grain and martensite lath boundaries were decorated with chromium and tungsten rich M23C6 precipitates while intra-lath regions revealed Ta and V rich MX type carbides. Rotational speeds greater than 300rpm led to martensite formation and simultaneous recovery, recrystallization and grain growth in SZs with wide distribution in grain size whereas SZ of 200rpm and BM possessed similar distribution. The grain boundary M23C6 dissolved and very fine needles of Fe3C precipitated in all SZs. The hardness of all SZs was unacceptably higher compared to the BM. The 200rpm weld exhibited higher impact toughness in the absence of martensite in SZ.
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    A mechanism for multiple goods and interdependent valuations
    ( 2005-12-01) Dash, Rajdeep K. ; Rogers, Alex ; Jennings, Nicholas R.
    This paper reports on the design of an auction mechanism for allocating multiple goods when the buyers have interdependent valuations. We cast the problem as a multi-agent system consisting of selfish, rational agents and develop an auction mechanism which is efficient, incentive compatible and individually rational. We first discuss the necessary assumptions that any mechanism developed for this scenario should satisfy so as to achieve the aforementioned properties. We then present our mechanism and show how it is a generalisation of the Vickrey-Clarke-Groves mechanism. © Springer-Verlag Berlin Heidelberg 2005.
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    A new electrochemical approach for the synthesis of copper-graphene nanocomposite foils with high hardness
    ( 2014-02-11) Pavithra, Chokkakula L.P. ; Sarada, Bulusu V. ; Rajulapati, Koteswararao V. ; Rao, Tata N. ; Sundararajan, G.
    Graphene has proved its significant role as a reinforcement material in improving the strength of polymers as well as metal matrix composites due to its excellent mechanical properties. In addition, graphene is also shown to block dislocation motion in a nanolayered metal-graphene composites resulting in ultra high strength. In the present paper, we demonstrate the synthesis of very hard Cu-Graphene composite foils by a simple, scalable and economical pulse reverse electrodeposition method with a well designed pulse profile. Optimization of pulse parameters and current density resulted in composite foils with well dispersed graphene, exhibiting a high hardness of ∼2.5 GPa and an increased elastic modulus of ∼137 GPa while exhibiting an electrical conductivity comparable to that of pure Cu. The pulse parameters are designed in such a way to have finer grain size of Cu matrix as well as uniform dispersion of graphene throughout the matrix, contributing to high hardness and modulus. Annealing of these nanocomposite foils at 300°C, neither causes grain growth of the Cu matrix nor deteriorates the mechanical properties, indicating the role of graphene as an excellent reinforcement material as well as a grain growth inhibitor.
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    A new insight into Li-staging, in-situ electrochemical exfoliation, and superior Li storage characteristics of highly crystalline few-layered graphene
    ( 2021-09-01) Maseed, Hussen ; Petnikota, Shaikshavali ; Srikanth, Vadali V.S.S. ; Rotte, Naresh Kumar ; Srinivasan, Madhavi ; Bonaccorso, Francesco ; Pellegrini, Vittorio ; Reddy, Mogalahalli V.
    Highly crystalline few-layered graphene (hcFLG) is synthesized using microwave exfoliation of in-house prepared graphene oxide. When hcFLG is tested as an anode material in a Li-ion coin cell, it showed unique lithiation electrochemistry. Cyclic voltammetry (CV), structural and electrochemical impedance spectroscopic analyses of hcFLG showed enhanced surface lithiation above 0.3 V and in-situ exfoliation of hcFLG responsible for excellent storage capacity of hCFLG. Below 0.3 V, the CV data before and after long-term cycling showed a unique Li-staging phenomenon and confirmed that diffusion-controlled lithiation is responsible for stable capacity. hcFLG delivered reversible specific capacities as high as 400 and 330 mAh/g at current rates of 0.1 and 1 C, respectively. hcFLG also exhibited an excellent rate capability by showing a reversible specific capacity of 215 mAh/g at a very high current rate of 10 C. At the end of long-term cycling (i.e., 1175 cycles), hcFLG displayed a significant increase in specific capacity from 330 to 555 mAh/g and 200 to 365 mAh/g at current rates of 1.0 and 2.0 C, respectively, attributed to a safe in-situ exfoliation. The performance of hcFLG is far superior to the commercial graphite and other materials of the same class. hcFLG is best suited for emerging battery technologies like ‘All Graphene Battery”.
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    A Pt-free graphenaceous composite as an electro-catalyst for efficient oxygen reduction reaction
    ( 2019-07-28) Sravani, Bathinapatla ; Maseed, H. ; Chandrasekhar, Y. ; Veera Manohara Reddy, Y. ; Srikanth, V. V.S.S. ; Madhavi, G. ; Subramanyam Sarma, L.
    Use of Pt-based electro-catalysts for the oxygen reduction reaction (ORR) is a major hindrance in large-scale application of proton exchange membrane fuel cells (PEMFCs). Hence, new, cost-effective and high performance electro-catalysts are required for the commercial success of PEMFCs. In this work, a Pt-free magnesium oxide (MgO) decorated multi-layered reduced graphene oxide (MLGO) composite is tested as an electro-catalyst for the ORR. The ORR activity of MgO/MLGO in terms of diffusion-controlled current density is found to be superior (6.63 mA per cm2-geo) than that of in-house prepared Pt/rGO (5.96 mA per cm2-geo) and commercial Pt/C (5.02 mA per cm2-geo). The applicability of less expensive MgO/MLGO not only provides a new electro-catalyst but also provides a new direction in exploring metal oxide-based electro-catalysts for the ORR.
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    A quantitative measure of medium-range order in amorphous materials from transmission electron micrographs
    ( 2003-08-13) Dash, R. K. ; Voyles, P. M. ; Gibson, J. M. ; Treacy, M. M.J. ; Keblinski, P.
    We propose an extension to the technique of fluctuation electron microscopy that quantitatively measures a medium-range order correlation length in amorphous materials. In both simulated images from computer-generated paracrystalline amorphous silicon models and experimental images of amorphous silicon, we find that the spatial autocorrelation function of dark-field transmission electron micrographs of amorphous materials exhibits a simple exponential decay. The decay length measures a nanometre-scale structural correlation length in the sample, although it also depends on the microscope resolution. We also propose a new interpretation of the fluctuation microscopy image variance in terms of fluctuations in local atomic pair distribution functions.
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    A review of nanocrystalline diamond/β-SiC composite films
    ( 2010-01-01) Srikanth, Vadali V.S.S. ; Staedler, Thorsten ; Jiang, Xin
    The idea behind synthesis of nanocrystalline diamond/β-SiC composite films is to obtain films those posses a whole range of combined properties of diamond and β-SiC to serve tribological, thermal barrier, electronics and biological applications. The diamond/β-SiC nanocomposite films are designed in such a way that the resultant material contains required volume of nanometer sized grains of both the components such that the availability of large volume of grain boundaries can be controlled based on the application requirement. In this paper a review of nanocrystalline diamond/β-SiC composite film system with regards to its controlled synthesis, characterization, mechanical properties, and coefficient of friction will be discussed. Microwave plasma enhanced chemical vapor deposition technique was used to carry out the nanocomposite film depositions with the aid of H2-CH 4-Si(CH3)4 gas mixtures. Based on the micro-structural analyses these nanocomposite films are classified as granular type composite films that contain diamond and β-SiC components as nanocrystalline grains distributed contiguously and laterally throughout the thickness of the film in a desired volume fraction combinatorial form. Deposition of gradient natured diamond/β-SiC nanocomposite films and novel diamond/β-SiC composite films containing (001) diamond rounded or square faceted surfaces will also be discussed. β-SiC content and diamond microstructure in the films are identified as the compositional and structural factors respectively that influence the mechanical and friction properties.
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    A risk-based bidding strategy for continuous double auctions
    ( 2004-01-01) Vytelingum, Perukrishnen ; Dash, Rajdeep K. ; David, Esther ; Jennings, Nicholas R.
    We develop a novel bidding strategy that software agents can use to buy and sell goods in Continuous Double Auctions (CDAs). Our strategy involves the agent forming a bid or ask by assessing the degree of risk involved and making a prediction about the competitive equilibrium that is likely to be reached in the marketplace. We benchmark our strategy against two of the most common strategies for CDAs, namely the Zero-Intelligence and the Zero- Intelligence Plus strategies, and we show that our agents outperform these benchmarks. Specifically, our agents win in 100% of the simulations against the ZI agents and, on average, 75% of the games against the ZIP agents.
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    A study of piezoelectric properties of (Ba < inf > 0.85 < /inf > Ca < inf > 0.15 < /inf > )(Zr < inf > 0.9 < /inf > Ti < inf > 0.1 < /inf > )O < inf > 3 < /inf > ceramics synthesized by sol-gel process
    ( 2013-07-18) Praveen, J. Paul ; Kumar, Kranti ; James Raju, C. K. ; Das, Dibakar
    Lead free piezoelectric ceramics 'Barium calcium zirconium titanate (Ba0.85Ca0.15)(Zr0.9Ti0.1)O 3 have been prepared by sol-gel synthesis method. The structure and piezoelectric properties were investigated for the given BCZT system. X-ray diffraction (XRD) and transmission electron microscope (TEM) studies confirmed the formation of single phase BCZT nanoparticles ( < 50nm). The calcined and compacted powders sintered at 1550°C resulted in a complete perovskite structure. BCZT sample showed a high remnant polarization of 11.55 μC/cm 2 and a low coercive field (Ec) of 0.166 kV/cm. A high piezoelectric co-efficient of d33∼490 pC/N was obtained for the electrically poled sample. The study of microstructure on its piezoelectric properties of BCZT ceramics is discussed in this paper. © 2013 AIP Publishing LLC.
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    A Study on Corrosion Resistance and Mechanical Performance of 6061 Aluminium Alloy: Galvanized Mild Steel Electron Beam Welds at Varying Welding Parameters
    ( 2020-04-01) Sravanthi, S. S. ; Acharyya, Swati Ghosh ; Joardar, Joydip ; Chaitanya, V. N.S.K.
    Dissimilar welds of steel and aluminium alloys have an inherent problem of the vast difference in solid solubility which questions their integrity. The present study elaborates on the mechanical failure and corrosion degradation of 6061 Al—galvanized mild steel lap joints fabricated by electron beam welding as a function of varying parameters such as processing speed, voltage and current. The interfaces of two weld specimens were examined using scanning electron microscopy, phase analysis by micro-area X-ray diffraction and hardness testing by Vickers micro-hardness tester. Results showed the generation of the intermetallic layer at the weld seam–mild steel interface in the specimens. The composition of the Al–Fe intermetallics in the layer was confirmed by micro-XRD analysis. The layer width increased with increased heat input and average width varied between 11 and 16 µm in the specimens. The micro-hardness of the layer was found to increase with a decrease in processing speed during welding. The corrosion resistance and mechanical strength of welds were evaluated as per ASTM G 67-04 and D 1002, respectively. The microstructures at weld interfaces have shown intergranular corrosion after nitric acid exposure for 24 h according to ASTM G 67-04. Weight loss analysis was done after the corrosion test. It was identified that welds fabricated at higher voltage exhibited greater weight loss of 55.9 mg and specimen joined at lower voltage was found to exhibit a weight loss of 41.1 mg, respectively. High intermetallic layer thickness in the welds resulted in failure at the weld seam region during lap shear testing.
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    A transparent and Pt-free all-carbon nanocomposite counter electrode catalyst for efficient dye sensitized solar cells
    ( 2019-11-15) Gurulakshmi, M. ; Meenakshamma, A. ; Susmitha, K. ; Charanadhar, N. ; Srikanth, V. V.S.S. ; Narendra Babu, S. ; Venkata Subbaiah, Y. P. ; Venkateswarlu, Katta ; Raghavender, M.
    Recently, substantial focus has made in the development of cost effective Pt-free dye sensitized solar cells (DSSCs). In this article we report a potential, Pt-free, carbon based nanocomposite as counter electrode catalyst for dye sensitized solar cells. Graphene oxide (GO) was made into reduced graphene oxide (SSrGO) by irradiating with light (Xe source). Suspension of SSrGO in DMF was spray coated onto fluorine doped tin oxide (FTO) coated glass substrate, followed by spray coat of single walled carbon nanohorns (SWCNH) suspension in DMF. SSrGO and SWCNH coated FTO glass substrate was investigated as an effective Pt-free composite counter electrode (CE) for DSSC and also showed the comparable catalytic activity with Pt. The test cell reveals power conversion efficiency (PCE) of 8.27%, whereas the DSSC module exhibited a PCE of 5.18%. By using the fabricated DSSC module, an electric motor (15 mW) was operated both in indoor and outdoor light conditions. The procedures followed in this work pave a way for the easy fabrication of composite CE towards transparent DSSC modules and further the integration of the DSSC module with the standard Si solar cell is of great potential for various real-time application.
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    A unique solar radiation exfoliated reduced graphene oxide/polyaniline nanofibers composite electrode material for supercapacitors
    ( 2015-08-01) Gedela, Venkataramana ; Puttapati, Sampath Kumar ; Nagavolu, Charanadhar ; Srikanth, Vadali Venkata Satya Siva
    Solar radiation exfoliated reduced graphene oxide (SRGO) and polyaniline nanofibers (PANi NFs) containing composite is synthesized using the typical chemical oxidative polymerization. The composite exhibits an excellent specific mass capacitance of ~655 F/g owing to an optimal chemical interaction between SRGO and PANi NFs in the composite. Specific mass capacitance of the composite remains almost constant at different current densities making it expedient as a working electrode material in supercapacitors.
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    A utility-based adaptive sensing and multihop communication protocol for wireless sensor networks
    ( 2010-06-01) Padhy, Paritosh ; Dash, Rajdeep K. ; Martinez, Kirk ; Jennings, Nicholas R.
    This article reports on the development of a utility-based mechanism for managing sensing and communication in cooperative multisensor networks. The specific application on which we illustrate our mechanism is that of GlacsWeb. This is a deployed system that uses battery-powered sensors to collect environmental data related to glaciers which it transmits back to a base station so that it can be made available world-wide to researchers. In this context, we first develop a sensing protocol in which each sensor locally adjusts its sensing rate based on the value of the data it believes it will observe. The sensors employ a Bayesian linear model to decide their sampling rate and exploit the properties of the Kullback-Leibler divergence to place an appropriate value on the data. Then, we detail a communication protocol that finds optimal routes for relaying this data back to the base station based on the cost of communicating it (derived from the opportunity cost of using the battery power for relaying data). Finally, we empirically evaluate our protocol by examining the impact on efficiency of a static network topology, a dynamic network topology, the size of the network, the degree of dynamism of the environment, and the mobility of the nodes. In so doing, we demonstrate that the efficiency gains of our new protocol, over the currently implemented method over a 6 month period, are 78%, 133%, 100%, and 93%, respectively. Furthermore, we show that our system performs at 65%, 70%, 63%, and 70% of the theoretical optimal, respectively, despite being a distributed protocol that operates with incomplete knowledge of the environment. © 2010 ACM.
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    A utility-based sensing and communication model for a glacial sensor network
    ( 2006-12-01) Padhy, Paritosh ; Dash, Rajdeep K. ; Martinez, Kirk ; Jennings, Nicholas R.
    This paper reports on the development of a utility-based mechanism for managing sensing and communication in cooperative multi-sensor networks. The specific application considered is that of GLACSWEB, a deployed system that uses battery-powered sensors to collect environmental data related to glaciers which it transmits back to a base station so that it can be made available world-wide to researchers. In this context, we first develop a sensing protocol in which each sensor locally adjusts its sensing rate based on the value of the data it believes it will observe. Then, we detail a communication protocol that finds optimal routes for relaying this data back to the base station based on the cost of communicating it (derived from the opportunity cost of using the battery power for relaying data). Finally, we empirically evaluate our protocol by examining the impact on efficiency of the network topology, the size of the network, and the degree of dynamism of the environment. In so doing, we demonstrate that the efficiency gains of our new protocol, over the currently implemented method over a 6 month period, are 470%, 250% and 300% respectively. Copyright 2006 ACM.
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    Abrasive free chemical mechanical planarization of semi-polar (11-22) GaN: Effect on structural and surface properties and subsequent homoepitaxial growth
    ( 2018-01-01) Parthiban, P. ; Azizur Rahman, A. ; Bhattacharya, Arnab ; Das, D.
    The implementation of abrasive free chemical mechanical planarization (AFCMP) as an intermediate step to improve the structural and surface qualities of semi-polar (11-22) GaN device layer has been investigated. As-grown semi-polar (11-22) GaN surfaces were polished and characterized for surface finish using AFM and optical surface profiler to investigate the effect of surface planarity. Atomically flat surface with rms roughness of 4 Å was achieved over a scan area of 5 × 5 μm2 with a polishing rate of ∼2.50 μm/hr. Further, this polished wafer was used as a template for the homoepitaxial re-growth of semi-polar (11-22) GaN epilayer. In comparison to as-grown and polished surfaces, the re-grown surface showed a good crystal quality with a reduced full width at half maximum (FWHM) value of 535 arc sec, obtained from X-ray Rocking Curve (XRC) along [11-2-3] direction. Around 0.3 GPa of in-plane stress relaxation has been observed for the re-grown epilayer in comparison to as-grown surface further indicating the improved structural quality. An improved rms surface roughness (∼58% over a scan area of 1.26 × 0.90 mm2) has been achieved for the re-grown GaN epilayer (grown on the AFCMP treated atomically flat surface) as compared to the as-grown surface.
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    Allylamine-mediated DNA attachment to polycrystalline diamond surface
    ( 2009-10-19) Zhuang, H. ; Srikanth, Vadali V.S.S. ; Jiang, X. ; Luo, J. ; Ihmels, H. ; Aronov, I. ; Wenclawiak, B. W. ; Adlung, M. ; Wickleder, C.
    Allylamine, an unsaturated short carbon chain amine was used to mediate ss-DNA attachment to an H-terminated polycrystalline diamond thin film surface for biosensoric applications. At first, allylamine was photochemically tethered onto the diamond film surface; ss-DNA was then attached via the allylamine linkage. The DNA molecules are then hybridized with the complementary DNA molecules containing fluorescence labels followed by denaturing. Time-of-fight secondary ion mass spectrometry and fluorescence spectroscopy are used to confirm the allylamine bonding and the covalent DNA bonding to the diamond film surface, respectively. © 2009 American Institute of Physics.
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    An ultra-sensitive electrochemical sensor for the detection of acetaminophen in the presence of etilefrine using bimetallic Pd-Ag/reduced graphene oxide nanocomposites
    ( 2018-01-01) Veera Manohara Reddy, Y. ; Bathinapatla, Sravani ; Łuczak, T. ; Osińska, M. ; Maseed, H. ; Ragavendra, P. ; Subramanyam Sarma, L. ; Srikanth, V. V.S.S. ; Madhavi, G.
    In this study we report a one-step procedure for the fabrication of Pd-Ag bimetallic nanoparticles on the surface of a graphene oxide (rGO) support. A controlled reduction of Pd2+ and Ag+ ions on an rGO support was achieved by using a methyl ammonium borane reducing agent. The fabricated Pd-Ag/rGO bimetallic nanocomposites were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FT-IR). A Pd-Ag/rGO based electrochemical sensor was fabricated by immobilizing the as-prepared Pd-Ag/rGO bimetallic nanocomposites on to a bare glassy carbon electrode (GCE). The resulting Pd-Ag/rGO/GCE electrochemical sensor was proved to be ultrasensitive and selective towards the detection of acetaminophen (APAP) in the presence of etilefrine (ET). The linear dynamic range (LDR) for the detection of APAP was found to be 1.2-30 nM with a good limit of detection (LOD) and the limit of quantification (LOQ) of 3.26 nM and 13 nM, respectively. The newly prepared Pd-Ag/rGO/GCE-modified electrode makes a good analytical tool for the accurate determination of APAP either in its pristine conditions or in the presence of both real human samples and pharmaceutical formulations. The convenient fabrication protocol shown here can be extendable to other types of bimetallic configurations for various electrochemical sensing applications.