Ganesh Kumar Mani

Effective Ammonia Detection Using n-ZnO/p-NiO Heterostructured Nanofibers

Metal-oxide heterostructures are very important materials for developing various toxic gas/chemical detection sensor systems. However, the major factors, such as sensitivity, selectivity, stability, response, and recovery times of the sensors, still need to be optimized for practical technological applications. Low-dimensional materials have shown tremendous potential to solve majority of the critical issues due to their surface chemistry than that of their bulk form. In this paper, the role of nanostructured n-ZnO/p-NiO heterostructure as room temperature (RT) ammonia sensor has been investigated. Toward this paper, the electrospinning method was employed to prepare heterostructure metal-oxides blended with polyvinyl alcohol (n-ZnO/p-NiO) nanofibers. The systematic characterizations of the obtained n-ZnO/p-NiO heterostructure were performed using X-Ray diffractometer, scanning electron microscope, and photoluminescence spectrophotometer. Furthermore, the RT ammonia sensing characteristics were investigated.

A simple and template free synthesis of branched ZnO nanoarchitectures for sensor applications

Strong electrophilic natured acetaldehyde present in various food and beverages damages genetic material and induces diseases like atherosclerosis. Detection and quantification of such a carcinogen poses a major challenge. In this context, a novel room temperature acetaldehyde sensor made up of hierarchical ZnO nanostructures and prepared by a simple and template-free method has been reported. ZnO nanostructures were grown on glass substrates by a chemical spray pyrolysis technique at the substrate temperature of 523 K. Different nanostructures, namely tiny nanoplatelets, branched nanorods and thicker nanoplatelets, were formed by an annealing process. The crystal structures, morphologies and optical absorbances of the hierarchical ZnO nanostructures were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and UV-vis spectrophotometry, respectively. The branched nanorods showed an excellent sensing response towards 20 to 500 ppm of acetaldehyde vapour. The role of high density junctions of the branched ZnO architecture in enhancing the vapour sensing performance has been highlighted. The observed selectivity, range of detection and stability of the branched ZnO nanorods have proven their potential as a sensing element for the detection of acetaldehyde.

Selective recognition of hydrogen sulfide using template and catalyst free grown ZnO nanorods

Hydrogen sulfide is an important endogenous signaling molecule which can play a key role in regulating blood pressure, cardiovascular and age-associated diseases. But it is extremely toxic if inhaled and can even cause death at higher concentrations. This work reports a systematic investigation of template and catalyst free grown ZnO nanorods through simple chemical spray pyrolysis technique and their room temperature hydrogen sulfide sensing characteristics such as sensitivity, selectivity, stability, response and recovery times. The structural, morphological, optical and electrical properties of ZnO nanostructures were investigated using X-ray diffractometer (XRD), field emission scanning electron microscope (FE-SEM), UV-Vis spectrophotometer and electrometer respectively. The role of density of nanorods formed on the glass substrates through spray cycle modulation has been used as an effective tool for achieving better sensing response. ZnO nanorods with the diameter ranging from 200–250 nm exhibited high selectivity towards hydrogen sulfide and the mechanism has been reported. The challenge of selectivity has also been solved efficiently through ZnO nanorods.

ZnO-Based Microfluidic pH Sensor: A Versatile Approach for Quick Recognition of Circulating Tumor Cells in Blood

The present study is concerned about the development of highly sensitive and stable microfluidic pH sensor for possible identification of circulating tumor cells (CTCs) in blood. The precise pH measurements between silver-silver chloride (Ag/AgCl) reference electrode and zinc oxide (ZnO) working electrode have been investigated in the microfluidic device. Since there is a direct link between pH and cancer cells, the developed device is one of the valuable tools to examine circulating tumor cells (CTCs) in blood. The ZnO-based working electrode was deposited by radio frequency (rf) sputtering technique. The potential voltage difference between the working and reference electrodes (Ag/AgCl) is evaluated on the microfluidic device. The ideal Nernstian response of -43.71165 mV/pH was achieved along with high stability and quick response time. Finally, to evaluate the real time capability of the developed microfluidic device, in vitro testing was done with A549, A7r5, and MDCK cells.

Microneedle pH Sensor: Direct, Label-Free, Real-Time Detection of Cerebrospinal Fluid and Bladder pH

Acid-base homeostasis (body pH) inside the body is precisely controlled by the kidneys and lungs and buffer systems, such that even a minor pH change could severely affect many organs. Blood and urine pH tests are common in day-to-day clinical trials and require little effort for diagnosis. There is always a great demand for in vivo testing to understand more about body metabolism and to provide effective diagnosis and therapy. In this article, we report the simple fabrication of microneedle-based direct, label-free, and real-time pH sensors. The reference and working electrodes were Ag/AgCl thick films and ZnO thin films on tungsten (W) microneedles, respectively. The morphological and structural characteristics of microneedles were carefully investigated through various analytical methods. The developed sensor exhibited a Nernstian response of -46 mV/pH. Different conditions were used to test the sensor to confirm their accuracy and stability, such as various buffer solutions, with respect to time, and we compared the reading with commercial pH electrodes. Besides that, the fabricated microneedle sensor ability is proven by in vivo testing in mouse cerebrospinal fluid (CSF) and bladders. The pH sensor procedure reported here is totally reversible, and results were reproducible after several rounds of testing.

Template-free synthesis of vanadium sesquioxide (V2O3) nanosheets and their room-temperature sensing performance

Until recently, it has been relatively hard to prepare vertically aligned vanadium sesquioxide (V2O3) nanosheets on glass substrates due to their extreme sensitivity to the atmosphere, doping, external pressure, and temperature. In this study, we present a simple one-step sputtering technique for the preparation of high-density vertically aligned V2O3 nanosheets on glass substrates without the use of any catalyst or template. To date, this structure has not been achieved using the V2O3 phase through sputtering. The definite oxidation state and phase of V2O3 with V3O5 inclusions were confirmed from the binding energies of the V2p3/2 and O1s peaks via X-ray photoelectron spectroscopy (XPS). The growth mechanism of nanosheets has been briefly explained. In this way, hierarchical V2O3 nanosheets interconnected with each other, which would allow easy electron transport between electrodes, favour remarkable sensing performance. The nanosheets exhibited trace-level ammonia (NH3) detection under ambient conditions for a wide concentration range of 10–500 ppm. Moreover, the selectivity and stability of the V2O3 nanosheets was studied. The present study may permit the design and fabrication of new electronic materials with multiple advantages based on V2O3 nanosheets.

A novel electrolyte free solid state pH sensor for Bio-MEMS applications

This research work is focused on development of solid state electrolyte free pH sensor for biomedical applications. Thin films of silver — silver iodate (Ag/AgIO3) and antimony oxide (Sb2O3) was deposited on glass substrates and successfully employed them as reference and working electrodes respectively. The structural, morphological, and electrical properties of the working and reference electrodes were investigated using X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM) and high resistance electrometer respectively. Open circuit potential was measured in a universal pH solutions. The developed sensor exhibited the sensitivity of ∼ 43.1552 mV pH−1. Time domain pH monitoring for continuous usage was recorded over a period of several hours and reported.