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PublicationImpact of hydrogen concentrations on the impedance spectroscopic behavior of Pd-sensitized ZnO nanorods( 2013-02-11)ZnO nanorods were synthesized using a low-cost sol-gel spin coating technique. The synthesized nanorods were consisted of hexagonal phase having c-axis orientation. SEM images reflected perpendicular ZnO nanorods forming bridging network in some areas. The impact of different hydrogen concentrations on the Pd-sensitized ZnO nanorods was investigated using an impedance spectroscopy (IS). The grain boundary resistance (Rgb) significantly contributed to the sensing properties of hydrogen gas. The boundary resistance was decreased from 11.95 to 3.765 kΩ when the hydrogen concentration was increased from 40 to 360 ppm. IS gain curve showed a gain of 6.5 for 360 ppm of hydrogen at room temperature. Nyquist plot showed reduction in real part of impedance at low frequencies on exposure to different concentrations of hydrogen. Circuit equivalency was investigated by placing capacitors and resistors to identify the conduction mechanism according to complex impedance Nyquist plot. Variations in nanorod resistance and capacitance in response to the introduction of various concentrations of hydrogen gas were obtained from the alternating current impedance spectra.
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PublicationReliability assessment and activation energy study of au and pd-coated cu wires post high temperature aging in nanoscale semiconductor packaging( 2013-06)Wearout reliability and high temperature storage life (HTSL) activation energy of Au and Pd-coated Cu (PdCu) ball bonds are useful technical information for Cu wire deployment in nanoscale semiconductor device packaging. This paper discusses the influence of wire type on the wearout reliability performance of Au and PdCu wire used in fine pitch BGA package after HTSL stress at various aging temperatures. Failure analysis has been conducted to identify the failure mechanism after HTSL wearout conditions for Au and PdCu ball bonds. Apparent activation energies (Eaa) of both wire types are investigated after HTSL test at 150 °C, 175 °C and 200 °C aging temperatures. Arrhenius plot has been plotted for each ball bond types and the calculated Eaa of PdCu ball bond is 0.85 eV and 1.10 eV for Au ball bond in 110 nm semiconductor device. Obviously Au ball bond is identified with faster IMC formation rate with IMC Kirkendall voiding while PdCu wire exhibits equivalent wearout and or better wearout reliability margin compare to conventional Au wirebond. Lognormal plots have been established and its mean to failure (t50) have been discussed in this paper.
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PublicationInfluence of thermal treatment on extraction and characteristics of phytochemicals from rhizome of Acorus calamus L( 2022-01-01)Certain population in rural zones are still getting assistance from the traditional and folkloric medical systems. Before they cease to exist, this practice and knowledge need to be documented. Acorus calamus is a well-known aromatic herb with a rhizome that has been exhibited various therapeutic applications like gastroenteritis, antibacterial, antioxidant, antifungal, neuroprotective, antidiabetic, anti-inflammatory, anticancer, and anti-asthmatic activity. In Siddha system, the thermally treated dried rhizome of A. calamus is generally used to cure gastrointestinal and neurological ailments occur especially in infants by mixing the powder of rhizome with milk, ghee, and water. In this study, we evaluate the effect of thermal treatment on screening of bioactive compounds from A. calamus rhizome. The dried rhizome was thermally treated at different temperatures and incubation periods followed by ethanol extraction for 12 h to obtain the bioactive compounds profile. The temperature was optimized to 500 °C for 100 s of incubation based on the number of identified compounds through GC–MS analysis. The optimized samples were further analyzed by using LC–MS/MS, FTIR, micro-Raman, DLS-zeta potential, and XRD. A number of sesquiterpenoids, alkaloids, fatty acids, amino acid derivatives, sterols, and glucosides were detected in the aforementioned methods. The difference was observed in the size and charge of thermally treated and control dried rhizome. This indicates the short time exposure of thermally treated rhizome to be enough to retrieve the major bioactive compounds and also has tremendous application to revert the ailments, over to dried control rhizome.
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PublicationUltrasensitive and highly selective graphene-based field-effect transistor biosensor for anti-diuretic hormone detection( 2020-05-01)Nephrogenic diabetes insipidus (NDI), which can be congenital or acquired, results from the failure of the kidney to respond to the anti-diuretic hormone (ADH). This will lead to excessive water loss from the body in the form of urine. The kidney, therefore, has a crucial role in maintaining water balance and it is vital to restore this function in an artificial kidney. Herein, an ultrasensitive and highly selective aptameric graphene-based field-effect transistor (GFET) sensor for ADH detection was developed by directly immobilizing ADH-specific aptamer on a surface-modified suspended graphene channel. This direct immobilization of aptamer on the graphene surface is an attempt to mimic the functionality of collecting tube V2 receptors in the ADH biosensor. This aptamer was then used as a probe to capture ADH peptide at the sensing area which leads to changes in the concentration of charge carriers in the graphene channel. The biosensor shows a significant increment in the relative change of current ratio from 5.76 to 22.60 with the increase of ADH concentration ranging from 10 ag/mL to 1 pg/mL. The ADH biosensor thus exhibits a sensitivity of 50.00 µA·(g/mL)−1 with a limit of detection as low as 3.55 ag/mL. In specificity analysis, the ADH biosensor demonstrated a higher current value which is 338.64 µA for ADH-spiked in phosphate-buffered saline (PBS) and 557.89 µA for ADH-spiked in human serum in comparison with other biomolecules tested. This experimental evidence shows that the ADH biosensor is ultrasensitive and highly selective towards ADH in PBS buffer and ADH-spiked in human serum.
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PublicationHigh-performance detection of an abdominal aortic aneurysm biomarker by immunosensing( 2020-05-01)Abdominal aortic aneurysm (AAA) is a serious, life-threatening vascular disease that presents as an enlarged area of the aorta, which is the main artery that carries blood away from the heart. AAA may occur at any location in the aorta, but it is mainly found in the abdominal region. A ruptured AAA causes serious health issues, including death. Traditional imaging techniques, such as computed tomography angiogram, magnetic resonance imaging, and ultrasound sonography, have been used to identify AAAs. Circulating biomarkers have recently become attractive for diagnosing AAAs due to their cost-effectiveness compared to imaging. Insulin-like growth factor 1 (IGF-1), a secreted hormone vital for human atherosclerotic plaque stability, has been found to be an efficient biomarker for AAA identification. In this report, immunosensing was performed by using an InterDigitated electrode (IDE) sensor to detect circulating levels of IGF-1. The detection limit of IGF-1 was found to be 100 fM with this sensor. Moreover, related protein controls (IGF-2 and IGFBP3) were not detected with the same antibody, indicating selective IGF-1 detection. Thus, immunosensing by using an IDE sensor may help to effectively diagnose AAAs and represents a basic platform for further development.
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