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The demand for the development of chemiresistive sensors for the detection of acetaldehyde has been rapidly increasing, as its concentration needs to be continuously monitored in many industries. Also, exposure to acetaldehyde beyond a permissible limit leads to various health complications including nausea, irritation, headache, and respiratory tract complications. In this context, acetaldehyde-sensing properties of tungsten-doped ZnO thin films deposited using the Successive Ionic Layer Adsorption and Reaction (SILAR) technique by varying the tungsten-dopant concentration from 2 to 10 mM are reported. XRD patterns of both the undoped and tungsten-doped ZnO films divulge the formation of hexagonal wurtzite structure with a preferential plane orientation of (0 0 2). Formation of clustered tiny nanobeads composed of spherical nanograins was observed for undoped ZnO thin film, and the formation of spherical nanoaggregates with dimensions less than ~ 1 μm was observed for the films deposited with tungsten concentrations of 2–8 mM. At 10 mM, formation of homogeneously distributed elongated nanobead-like morphology was observed. Room-temperature vapor-sensing properties of undoped and W-doped ZnO thin films were investigated. Undoped ZnO thin film was selective towards ammonia, whereas the doped ZnO thin films showed a better response towards acetaldehyde. In particular, the film deposited at 10 mM W-doped ZnO exhibited a sensing response of 947 towards 100 ppm of acetaldehyde. The response and recovery times were found to be 53 and 5 s, respectively, with a minimum detection limit of 10 ppm.

Chemical warfare agents (CWAs) have been listed as lethal weapons of mass destruction due to their extreme toxicity and devastating effects. Detection and detoxification are essential to protect ou...

Sapota (Manilkara Zapota) belongs to the Sapotaceae family and is one of the sweetest, delicious, and popular tropical fruits with high nutritional benefits. Due to its high water content (78%), it is easily damaged, which in turn reduces its shelf life. Also, significant post-harvest losses occur due to insufficient storage, poor handling, and transportation conditions, which also increase the microbial or pathogenic contamination. In this context, we have deployed an electronic nose for the first time to rapidly discriminate fresh sapota from bacterial contaminated sapota samples. The electronic nose response was varied from 0.1 to 2.9 V for sapota samples studied from day 1 to day 6. Fourier transform infrared spectra showed a gradual increase in the intensities of OH and H-O-H peaks at 3320 cm−1 and 1636 cm−1for these samples. Also, Staphylococcus bacteria were detected for the same set of sapota samples. Headspace GC-MS results of day 2, day 4, and day 6 sapota samples revealed the increasing trend in bacterial volatiles, namely ethanol, acetaldehyde, and isopropyl alcohol. The sensor data were provided as input to principal component analysis (PCA), Ward’s method analysis, and response surface methodology (RSM) for distinguishing fresh, half-contaminated, and fully contaminated sapota samples.

Broccoli is one of the nutrient-rich vegetables that can easily be affected by bacteria and consumption of bacterial contaminated fresh products leads to a number of food borne illnesses. A multi-dimensional approach has been adapted to evaluate the freshness of broccoli considering four different mutually supporting techniques namely electronic nose, bacterial culture test, head sampler method with Gas Chromatography-Mass Spectrometry (GC–MS) and Fourier Transform Infrared (FTIR) spectroscopy. Electronic nose output variations from 0.05 V to 1.5 V and the presence of Staphylococcus, Salmonella and Shigella in the order of Zero, 106 and 105–107 CFU mL−1 were observed for fresh, half and completely contaminated broccoli samples. GC–MS data revealed the presence of acetic acid, hexanoic acid, nonanol evolved from half and completely contaminated broccoli samples. In addition, Principle Component Analysis, Centroid-link, and Completely-link cluster analyses were used on electronic nose data in correlation with other techniques for decision making.

Microwave irradiation technique provides a simple and quick synthesis route for nanomaterials at controlled experimental conditions. In this view, nanostructures of rGO, ZrO2, and rGO–ZrO2 composite were synthesized using microwave synthesis technique. Herein, we experimented the preparation of rGO using optimized conditions using convection mode at 373 K in a commercial microwave oven. Structural properties revealed the formation of mixed phases of the orthorhombic and rhombohedral crystal structure of ZrO2. The preferential plane orientation was found to be in c-axis (002) for rGO–ZrO2 nanocomposite, which revealed the predominance of rGO in the nanocomposite. Morphology of the prepared nanostructures exhibited agglomerated sheets, denser nanograins and randomly aggregated nanosheets for rGO, ZrO2, and mixed nanocomposite respectively. Room temperature gas sensing properties of the prepared nanostructures were investigated and reported. rGO showed responses of 5.3 and 5.2 towards 200 ppm of trimethylamine (TMA) and methanol. ZrO2 nanostructure showed a response of 35 towards 200 ppm of ammonia with response–recovery times of 91 and 6 s.

One of the sources of environmental threat in recent years is the leakage of toxic gases from various industries. Sensors to detect these gases in trace level concentrations are highly required to ensure a safe living environment. In this context, many types of gas sensors such as calorimetric, conductometric, potentiometric, catalytic, and chemiresistive types have been employed to detect these gases. Among them, chemiresistive type sensors have been widely employed due to high selectivity, sensitivity, simplicity in fabrication, compactness, lower operating temperature, and low power consumption. Chemiresistive sensors are designed with inbuilt micro-heaters for improving the sensing response. However, sensors operated at elevated operating temperatures would significantly affect the stability of the sensor due to grain growth. To address this concern, many efforts have been progressing over the years towards the development of room temperature operated gas sensors. In this review, room temperature operated gas sensors developed for the detection of ammonia, acetaldehyde, ethanol, nitrogen dioxide, ozone, and aromatic VOCs have been discussed. In addition, the major challenges possessed by the sensors operated at elevated temperatures such as grain growth, change of conductivity, and variations in charge transport characteristics have been addressed. Also, the strategies to minimize the aforementioned challenges have been highlighted.

Integration of multifunctional nanomaterials with textiles could be a significant value addition to the bright future of the growing technology "Technical Textiles". Development of textiles with antielectromagnetic radiation and in particular antiultraviolet features could be one of the best solutions to the ozone depletion induced ultraviolet pollution of the environment, which is a major concern in the context of surging skin cancer cases. In this background, multifunctional nanoflower structured partial hydroxide nickel oxide (NiO x) was grown on cotton fabric using a chemical bath deposition technique for the development of UV filter and flexible gas/chemical sensor. X-ray diffraction patterns of bare and NiO x modified cotton fabrics confirmed the micro and poly crystalline nature, respectively. Field emission scanning electron microscopic images revealed the growth of 3D green button chrysanthemum flower-like morphology on the surface of cotton fabric. In addition, X-ray photoelectron spectra revealed the presence of nickel, carbon, and oxygen elements in the NiO x modified cotton cellulose. The increase in hydrophobic nature of surface-treated fabric was observed using a goniometer. A differential scanning calorimeter trace for bare and surface modified cotton fabrics exhibited endothermic behavior at the characteristic onset temperature. The results of thermogravimetric analysis revealed the enhanced thermal stability of up to 800 °C for the surface-treated fabric compared to bare cotton. Further, the ultraviolet protection factor (UPF) of the NiO x nanoflower modified cotton fabric was measured using an in vitro method following the AATCC 183:2004 standard using a UV transmittance analyzer. The enhanced absorbance of ultraviolet rays at 388 nm resulted in the UPF of 2000. The chemical/gas sensing features of the surface modified textile samples were investigated using the homemade gas testing chamber. NiO x modified fabric showed a selective response of 12431 toward trimethylamine at room temperature.

ZnO thin films were deposited onto the glass substrates using successive ionic layer adsorption and reaction (SILAR) technique by varying the deposition cycles from 25 to 100 in steps of 25 cycles. The effect of deposition cycles on the structural, morphological, optical and electrical properties was investigated and reported. Structural analysis revealed the formation of the hexagonal wurtzite crystal structure of ZnO with the preferential plane orientation of (1 0 0) for all deposition cycles. For the film deposited at 25 cycles alone, we observed the meagre diffraction peak at 2θ = 21.27° corresponds to (1 0 1) plane of the orthorhombic phased zinc sulphate, which indicated the incomplete formation of zinc ammonium complex from the precursor. Morphological analysis revealed the formation of nanorod-like morphology for the deposition cycles of 25 and 50, whereas it was found to be deformed at 75 and 100 cycles. The optical bandgap of the deposited thin films was decreased as a function of deposition cycles. However, at 75 deposition cycles, the bandgap was increased to 3.2468 ± 0.0026 eV, and it could be attributed to the variation in the density of states near the conduction band. The significant variations in the electrical parameters namely, carrier concentration, mobility, electrical resistance as a function of deposition cycles were investigated. The variations in the refractive index and static impedance characteristics as a function of deposition cycles were also studied and reported.

In recent times, the development of breath sensors for the detection of Diabetic Keto-Acidosis (DKA) has been gaining prominent importance in the field of health care and advanced diagnostics. Acetone is one of the prominent biomarkers in the exhaled breath of persons affected by DKA. In this background, nanostructured cobalt oxide sensing elements were fabricated using a spray pyrolysis technique at different deposition temperatures (473 to 773 K in steps of 100 K) towards the fabrication of an acetone sensor. The influence of deposition temperature on the various properties of the nanostructured cobalt oxide thin films was investigated. Formation of cubic spinel phase cobalt oxide was confirmed from the structural analysis. The shifting of plane orientation from (3 1 1) to (2 2 0) at 773 K deposition temperature revealed the migration of cobalt atoms to the highly favorable energy positions. Further, the downshifted peak absorption wavelength and upshifted PL profile at higher deposition temperature confirmed the migration of cobalt ions. The sensor fabricated at higher deposition temperature (773 K) showed a sensing response of 235 at room temperature towards 50 ppm of acetone. Also, the fabricated sensor showed a lower detection limit (LOD) of 1 ppm with the response–recovery times of 6 and 4 s, respectively. The LOD reported here is lower than the minimum threshold level (1.71 ppm) signifying the presence of DKA.

The surge in skin cancer cases across the globe has forced the scientific community to develop solutions to protect humans against the ill effects of ultraviolet (UV) radiation. Nowadays, functionalized cotton textiles are employed to protect humans against UV radiation. In this context, nanostructured ZnO modified cotton fabrics towards the enhancement of ultraviolet protection factor (UPF) as well as to develop wearable gas sensors have been developed. The surface of carbon cellulosic fabric was modified by sol-gel and sputter seed layer-coated sol-gel techniques. ZnO grown fabrics were characterized using X-ray Diffractometer (XRD), Field Emission Scanning Electron Microscope (FE-SEM), Thermogravimetric Analysis (TGA), X-ray Photoelectron Spectrometer (XPS) and Fourier Transform Infrared Spectrometer (FTIR). Subsequently, UV-blocking and gas sensing properties of the modified textile samples were investigated. The seed layer initiated sol-gel modified cotton fabric showed a maximum UV protection factor (UPF) of 378. Also, room temperature gas-sensing performance of the functionalized cotton fabric towards volatile organic compounds such as acetaldehyde, ammonia and ethanol vapours was investigated.

Cerium oxide (CeO2) thin films were deposited on glass substrates by spray pyrolysis technique using three different precursors namely cerium chloride heptahydrate, cerium nitrate hexahydrate and cerium acetate hydrate. Structural, morphological, optical, electrical and sensing properties of the CeO2 thin films were examined. X-ray diffraction patterns of spray deposited CeO2 thin films confirmed the formation of polycrystalline cubic fluorite crystal structure. The surface morphologies of CeO2 films were observed using field emission scanning electron microscope. The optical band gap observed from luminescence spectra varied from 3.23 to 3.57 eV. Room temperature sensing characteristics of CeO2 thin films towards acetone, ethanol, xylene and toluene were observed. CeO2 thin film deposited using cerium acetate hydrate at 0.1 M concentration exhibited a better response towards xylene with fast response and recovery times of 224 and 13 s respectively at ambient temperature.

Consumption of fruits leads to increase in glucose level in blood for diabetic patients, which in turn leads to peripheral, vascular, ocular complications and cardiac diseases. In this context, a non-enzymatic hybrid glucose biosensor was fabricated for the first time to detect glucose by immobilizing titanium oxide–manganese oxide (TiO2–Mn3O4) nanocomposite and chitosan membrane on to the surface of Pt working electrode (Pt/TiO2–Mn3O4/chitosan). TiO2–Mn3O4 nanocomposite catalyzed the oxidation of glucose to gluconolactone in the absence of glucose oxidase enzyme with high electron transfer rate, good biocompatibility and large surface coverage. Electrochemical measurements revealed the excellent sensing response of the developed biosensor towards glucose with a high sensitivity of 7.073 µA mM−1, linearity of 0.01–0.1 mM, low detection limit of 0.01 µM, reproducibility of 1.5% and stability of 98.8%. The electrochemical parameters estimated from the anodic process were subjected to linear regression models for the detection of unknown concentration of glucose in different fruit samples.

In the recent past, wearable electronics has emerged as one of the significant products of nanoscience and nanotechnology initiatives. Multi-functional textiles achieved by means of surface modification with nanomaterials are a promising strategy by which flexible and wearable electronics, also called as “next generation electronics” could be developed. Nanostructured metal and metal oxide materials, metal organic frameworks (MOF), nanostructured carbon derivatives and conducting polymers are the major kinds of materials being used to modify the surface of textiles for the fabrication of wearable devices. In this chapter, modification or functionalization of textile surface with nanomaterials through predominantly used techniques like Physical Vapour Deposition (PVD), Chemical Vapour Deposition (CVD) and other chemical techniques have been reviewed. Also, applications of wearable textiles with functionalized surface for energy harvesting, electromagnetic interference filter with special focus on UV, and wearable sensors for healthcare and environment quality monitoring, etc., have been highlighted.

In recent times, the development of breath sensors for the detection of Diabetic Keto-Acidosis (DKA) has been gaining prominent importance in the field of health care and advanced diagnostics. Acetone is one of the prominent biomarkers in the exhaled breath of persons affected by DKA. In this background, nanostructured cobalt oxide sensing elements were fabricated using a spray pyrolysis technique at different deposition temperatures (473 to 773 K in steps of 100 K) towards the fabrication of an acetone sensor. The influence of deposition temperature on the various properties of the nanostructured cobalt oxide thin films was investigated. Formation of cubic spinel phase cobalt oxide was confirmed from the structural analysis. The shifting of plane orientation from (3 1 1) to (2 2 0) at 773 K deposition temperature revealed the migration of cobalt atoms to the highly favorable energy positions. Further, the downshifted peak absorption wavelength and upshifted PL profile at higher deposition temperature confirmed the migration of cobalt ions. The sensor fabricated at higher deposition temperature (773 K) showed a sensing response of 235 at room temperature towards 50 ppm of acetone. Also, the fabricated sensor showed a lower detection limit (LOD) of 1 ppm with the response-recovery times of 6 and 4 s, respectively. The LOD reported here is lower than the minimum threshold level (1.71 ppm) signifying the presence of DKA.

Integration of multifunctional nanomaterials with textiles could be a significant value addition to the bright future of the growing technology "Technical Textiles". Development of textiles with antielectromagnetic radiation and in particular antiultraviolet features could be one of the best solutions to the ozone depletion induced ultraviolet pollution of the environment, which is a major concern in the context of surging skin cancer cases. In this background, multifunctional nanoflower structured partial hydroxide nickel oxide (NiO

Hierarchically connected low-dimensional metal oxide nanostructures have been preferred to fabricate gas-sensing elements owing to their enhanced sensing response. In this juncture, hierarchical architectures of WO3 nanowires were synthesized using electrospinning technique with polyvinyl alcohol and ammonium metatungstate hydrate as precursor. X-ray diffraction analysis revealed the polymer evaporation and metal oxide formation with phase transformation of WO3 nanowires from monoclinic to orthorhombic and back to monoclinic as an effect of calcination temperatures (673–973 K). The variation in the interconnected grain features of WO3 nanowires as a function of calcination temperature was observed using field emission scanning electron microscope and transmission electron microscope. The formation of higher oxidation states of tungsten (W6+) and increased oxygen vacancies were observed for the samples calcined at higher temperatures through X-ray photoelectron spectrometer. Electrical studies for 873 K sample showed the maximum mobility of electrons due to the highly interconnected nanowires with minimum grain boundary resistance. The gas sensing responses of WO3 nanostructures were investigated and WO3 sample calcined at 873 K with maximum mobility showed a selective response of 5537 towards 75 ppm of acetaldehyde at room temperature.

The consumption of melamine and urea contaminated cow milk causes indigestion, acidity, ulcers and kidney stones in humans. In this context, a highly sensitive acetylcholinesterase cyclic voltammetric biosensor based on zinc oxide nanospheres modified Pt electrode has been successfully developed for the simultaneous determination of melamine and urea in cow milk sample. The fabricated bioelectrode showed 100% permeability to the binary mixture of melamine and urea, which in-turn enhanced selectivity. In addition, linear regression models for the estimation of binary mixture of melamine and urea in cow milk were formulated by keeping added melamine and urea as dependent variables and the estimated electrochemical paremeters as independent variables. The prediction performance of linear regression models was validated using %recovery, relative prediction error and root mean square error for cross-validation. The developed Pt/ZnO/AChE/Chitosan bioelectrode detected melamine and urea over a range of 1–20 nM with a limit of detection of 3 pM and 1 pM respectively. The proposed sensor exhibited good recovery (99.96–102.22%), thus providing a promising tool for analysis of melamine and urea in cow milk samples.

Glucose, a chief energy source in cellular metabolism, has a significant role in cell proliferation. Cancer cells utilize more glucose than normal cells to meet the energy demand arising due to their uncontrolled proliferation. The present work reports the development of a nano-interfaced amperometric biosensor for rapid and accurate monitoring of glucose utilization by cancer cells. A hybrid nano-interface comprising a blend of carbon nanotubes (CNTs) and graphene (GR) was employed to enhance the surface area of the working electrode and favour direct electron transfer. Glucose oxidase (GOx) immobilized on the interface serves as the sensing element due to its high selectivity and sensitivity towards glucose. Utilization of glucose was monitored at pre-determined time intervals in MiaPaCa-2 cancer cells. The results obtained from the amperometric technique were compared with the values obtained from a commercial glucometer. Alamar blue assay was performed to check the proliferation rate of the cells. A good correlation was obtained between the proliferation rate and glucose utilization. The designed biosensor was found to be unaffected by the presence of potential interferents and hence may serve as a novel in vitro tool to rapidly quantify the proliferation rates of cancer cells in response to different treatment strategies.

Undoped and different molar concentrations of Mg-doped ZnO thin films were deposited on glass substrates via. spray pyrolysis process. Doping concentration was varied from 0.002 to 0.01 M in steps of 0.002 M. Structural, morphological, optical, electrical and room temperature gas sensing characteristics of undoped and Mg-doped ZnO thin films were investigated using X-Ray Diffractometer (XRD), Field Emission Scanning Electron Microscope (FE-SEM), UV–Vis Spectrophotometer and an electrometer respectively. Structural analysis revealed that all the films were polycrystalline in nature with hexagonal wurtzite crystal structure. Spherical shaped uniformly distributed grains were observed for all the films with slight change in size. The optical absorption edge shifted towards the lower wavelength with an increase in Mg-dopant concentration confirmed the blue-shift. Films with lower Mg-dopant concentration showed maximum response towards ammonia at room temperature with quick response and recovery times.

Breath analysis has emerged as one of the accurate diagnostic techniques, which can be used to correlate disease conditions with the abnormal concentrations of certain biomarkers present in the exhaled breath. In this background, thin film based chemi-resistive Cerium-doped ZnO sensors were developed for detecting acetone and ethanolamine, which are the notable biomarkers of diabetes mellitus and carcinoma respectively. Ce-doped ZnO thin films were deposited on glass substrates using spray pyrolysis technique. X-ray diffraction patterns confirmed the formation of Ce-doped ZnO thin films with polycrystalline hexagonal wurtzite structure. Scanning electron micrographs and optical absorption spectra of Ce-doped ZnO thin films revealed the decrease in average grain size and increase in band gap respectively with an increase in Ce-dopant concentration. ZnO films with 0.004 and 0.008 M of Ce-dopant concentrations showed a better room temperature sensing response towards acetone and ethanolamine respectively. Highly selective nature of the developed sensing elements towards acetone and ethanolamine with swift response and recovery times can be considered as a non-invasive and cost effective method for the detection of diseases like diabetes mellitus and carcinoma.

Arsenic in water is considered as a global problem affecting human health as well as world’s economy. Intake of toxic arsenic leads to cytological effects leading to cancer and disorders such as black foot disease, hypertension and dermatitis. A low—cost spray deposited nanocauliflower like fluorine doped cadmium oxide (F-doped CdO) thin film based working electrode was developed to detect arsenic with lower detection limit. The structural properties of F-doped CdO thin film exhibited face centered cubic structure with high crystallinity. Morphological characterization of F-doped CdO highlighted the cauliflower like building blocks. F-doped CdO thin film showed a resistivity, sheet concentration and mobility of 0.13 Ω cm, 8.18 × 10 12 cm −2 and 3151 cm 2 V −1 s −1 respectively. F-doped CdO showed a redox peak at −0.10 and 0.05 V ( vs Ag/AgCl ) respectively without the use of arsenite oxidase or arsenate reductase enzymes and mediators. The redox reaction of arsenic was due to the inherent catalytic behaviour of F-doped CdO. The electrocatalytic activity of F-doped CdO helped in detecting arsenic with a detection limit of 4.55 × 10 −3 ppb and a sensitivity of 5.747 × 10 −3 μA ppb −1 . This suggests, F-doped CdO electrocatalyst can replace electrodes such as platinum, gold and glassy carbon electrodes and can be operated at wider potential ranges.

Chemiresistive gas sensors play a significant role in human exhaled breath analysis for non-invasive disease diagnosis applications. Ammonia has been considered as one of the prominent biomarkers, which is present in the exhaled breath of persons affected by chronic kidney disease (CKD). In this context, polyvinyl pyrrolidine (PVP) - zinc oxide (ZnO) nanofibers based chemiresistive gas sensor has been developed for the detection of ammonia at room temperature. PVP-ZnO nanofibers were synthesized using electrospinning technique with an applied potential of 20 kV. The synthesized nanofibers were calcined in the temperature range of 200–700°C in steps of 100°C. The influence of calcination temperature on the structural, morphological, electrical and optical properties were investigated using various characterization techniques. Further, calcinated samples were drop cast onto the Ag/Pd electrode for sensing studies using a homemade gas chamber integrated with high resistance electrometer. The sample calcined at 500°C showed a selective response towards ammonia with a response of 20 towards 50 ppm, and response and recovery times of 88 and 65 s.

LiTi y Co 1-y O2 (y = 0, 0.02, 0.05, 0.1) thin films were deposited on metalized Si substrates using RF magnetron sputtering technique. The films were deposited at a substrate temperature of 250 °C with subsequent annealing at 600 °C for 3 h in controlled oxygen environment. The films exhibited predominant (003), (101), and (104) orientations representing single-phase hexagonal structure with R $$ \overline{3} $$ m space group. Two well-defined Raman peaks observed at 489 and 598 cm−1 corresponding to E g and A1g modes confirm the hexagonal layered structure. The grain size and grain distribution were observed using atomic force microscopy. The cyclic voltammetry studies on Pt//LiTi y Co1-y O2 film cathodes in aqueous region exhibited perfect redox peaks at expected potentials. The Pt//LiTi0.02Co0.98O2 film cathode exhibited better discharge capacity of about 65 μA h cm−2 μm−1 with good cycling stability compared to pure Pt//LiCoO2. The electrochemical impedance analysis revealed a lower charge transfer resistance in Ti doped LiCoO2 film cathode, resulting better discharge capacity.

We prepared copper oxide thin films as electrode of supercapacitors. Films of Cu–O were grown by rf-magnetron sputtering on stainless steel substrates maintained at 350 °C under different O2/Ar ratios by keeping the sputtering pressure at ~1 Pa and rf-power at 220 W. The changes in the phase of copper oxide thin films from metallic copper to Cu2O, Cu2O to Cu4O3 and then to CuO were observed by varying O2/Ar ratio from 1:25 to 1:1. Electrochemical impedance spectroscopy studies show a low charge transfer resistance of 0.3 Ω cm−2 for copper oxide thin films prepared at 1:11 O2/Ar. The cyclic voltammetric studies exhibited a high rate ratio pseudocapacitance of 357 mF cm−2 at 0.5 mV s−1 for these copper oxide thin films with very good cycling capacitance even after 1000 cycles.

Hypertension results due to dysfunction of different metabolic pathways leading to the increased risk of cerebral ischemia, atherosclerosis, cardiovascular and inflammatory disorders. Hypertension has been considered a one of the major contributors to metabolic syndrome and is often referred to as a ‘silent killer’. Its incidence is on the rise across the globe owing to the drastic life style changes. The diagnosis of hypertension had been traditionally carried out through measurement of systolic and diastolic blood pressure but in most cases, this form of diagnosis is too late and the disease has already caused organ damage. Therefore, early detection of hypertension by monitoring subtle changes in specific biochemical markers from body fluids can minimize the risk of organ damage. However, a single marker may be insufficient for accurate diagnosis of hypertension thereby necessitating quantification of multiple markers. Concerted efforts to identify key markers for hypertension and their quantification, especially using chemical and biosensors, are underway in different parts of the world. Constant evolution of the sensing elements and transduction strategies have contributed to significant improvements in the diagnosis field, especially in the context of sensitivity, response time and selectivity and this when applied to the detection of hypertension markers may prove beneficial. This review summarizes advances in the field of sensor technology towards the detection of biologically relevant entities, arrays and the next generation ‘lab-on-a-chip’ systems for hypertension.

Foodborne pathogens cause serious health issues and have a strong impact on the economy of the country. In this context, quality testing of royal delicious apple by detecting pathogen contamination using an electronic nose, which contains an array of six ready-made sensors, has been proposed. To estimate the types of pathogens, fresh, half and completely contaminated apple samples were considered for bacterial studies. This study revealed the presence of Staphylococcus, Salmonella and Shigella bacteria, which were in the order of zero, 102, 103−104 CFU/mL. Further, the recorded headspace GC–MS spectra of contaminated samples confirmed the presence of bacterial spoilage markers namely acetone, ethyl acetate, ethyl alcohol and acetaldehyde. Voltage swing of 0.2 and 0.5 V was observed for half and completely contaminated apple samples respectively with reference to the fresh sample. Voltage responses of the sensors fed to Principal component analysis and Ward's method of hierarchical cluster algorithms helped to assess the quality of apple samples. By correlating the results of tri-layers namely bacterial count, GCMS data and classification results, reference table was developed and embedded in the ATmega processor of the electronic nose for real-time quality estimation of apple samples.

Increased consumption of fried foods such as grilled chicken contains elevated levels of methylglyoxal (MG), which is associated with diabetes mellitus. Hence, in this work, glyoxalase 1(GLO 1) based, zinc oxide (ZnO) flakes interfaced mediator free electrochemical biosensor was developed to detect MG in grilled chicken. ZnO flakes were synthesized by direct precipitation method. X-ray diffractometer and field emission scanning electron microscope were used to study the structural and morphological characteristics of ZnO flakes. The immobilization of GLO 1 on Pt/ZnO flakes modified electrode was confirmed by Fourier transform infrared spectroscopy. Cyclic voltammetric and amperometric studies were carried out using Pt/ZnO flakes/GLO 1 working electrode. The developed biosensor exhibited linear range of 0.6–2.0 µM, sensitivity of 0.281 µA µM−1, LOD of 9 nM with a response time of

Influence of Si substrate texturing on growth, microstuctural and electrochemical properties of lithium cobalt oxide (LiCoO2) cathode films was investigated. A batch of rf magnetron sputtered LiCoO2 films were prepared on both Au/Ti/SiO2/(polished) Si and Au/Ti/SiO2/(textured) Si substrates and the film properties were studied, systematically. As-grown films on polished Si substrates were exhibited partially ordered rock-salt structure with a very poor electrochemical performance. However, the as-grown films on textured Si substrates exhibited relatively predominant (0 0 3) orientation with R 3 ¯ m symmetry and exhibited an initial discharge capacity of 57.5 μAhcm−2 μm−1 with an appreciable capacity fade rate of 0.07%, even after 50 cycles. Electrochemical performance of these films was in close comparison with the annealed (650 °C) LiCoO2 films of Au/Ti/SiO2/(polished) Si substrates. The experimental observations were thoroughly demonstrated and suggested that the as-grown LiCoO2 films on textured Si substrates can be useful for all types of 2D solid state Li+-ion microbattery applications.

Lithium iron phosphate (LiFePO4) cathode material has been prepared by hydrothermal synthesis. The XRD spectrum exhibited different characteristic peaks along with (311) predominant orientation corresponding to orthorhombic crystal structure with Pnma space group. Electric and dielectric properties were studied over a frequency range of 1 Hz–1 MHz at different temperatures. The conductivity was found to be increased with increasing temperature following Arrhenius relation with an estimated activation energy of 0.44 eV. The dielectric properties were analyzed in the framework of complex dielectric permittivity and complex electric modulus formalisms. The complex permittivity as a function of frequency and temperature was investigated. Several important parameters, such as activation energy, ionic hopping frequency, carrier concentration, ionic mobility, and diffusion coefficient, etc., were determined. The electrochemical characteristics of LiFePO4 are examined in aqueous region. It exhibited a good reversible cyclic voltammogram on sweeping the potential upward and downward with discharge capacity of 140 mAh/g.

LiMn2O4 thin films are deposited on gold coated polyimide flexible substrates using RF magnetron sputtering technique maintained at a moderate substrate temperature of 300℃. The films exhibited characteristic peaks with predominant (111) orientation representing cubic spinel structure of Fd3m symmetry with an evaluated lattice parameter of 8.199 ?. The surface topography of films exhibited pyramidal shaped grains oriented vertical to the substrate surface with root mean square surface roughness of 90 nm. The Pt/LiMn2O4 electrochemical cell in aqueous region exhibited two step de-insertion and insertion kinetics of Li ion during oxidation and reduction reaction with an initial discharge capacity of 36 μAh?cm_2?μm_1.

Increased consumption of raw and par-boiled rice results in the formation of methylglyoxal (MG) at higher concentration and leads to complications in diabetic patients. Highly sensitive electrochemical biosensor was developed using glutathione (GSH) as a co-factor with vanadium pentoxide (V2O5) as a nano-interface for MG detection in rice samples. The Pt/V2O5/GSH/Chitosan bioelectrode displayed two well-defined redox peaks in its cyclic voltammograms for MG reduction. This occurred as two electron transfer process where MG gained two electrons from oxidized glutathione disulfide and formed hemithioacetal. The current density response of the fabricated bioelectrode was linear towards MG in the concentration range of 0.1–100 μM with the correlation coefficient of 0.99, sensitivity of 1130.86 μA cm−2 μM−1, limit of detection of 2 nM and response time of less than 18 s. The developed bioelectrode was used for the detection of MG in raw and par-boiled rice samples.

Acetylcholinesterase (AChE) enzyme has been predominantly used for the detection of pesticides and metal ions. But, these sensors respond to pesticides as well as metal ions at certain concentration, which results in poor selectivity. Hence in this work, the amount of thiocholine produced during AChE inhibition has been estimated to detect the residual activity of AChE enzyme in-turn to enhance the efficiency of the biosensor. In this context, Pt/ZnO–CeO2/AChE/Chitosan based biosensor has been developed for sensitive voltammetric quantification of thiocholine in AChE. The sensor exhibited enhanced electron transfer rate, good conductivity and biocompatibility. Both the intrinsic and extrinsic parameters were simultaneously optimized using second order polynomial regression to get the best conditions for ATCh determination. Under optimized experimental conditions, the redox peak current was linear over the concentration range of 0.1–1.5 mM with detection and quantification limit of 0.05 and 0.15 μM respectively and the sensitivity of 1.47 μA mM−1.

Films of LiCoO2 are prepared on metallized silicon substrates using RF-magnetron sputtering technique. The microstructural properties of the films are investigated by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The films deposited at a substrate temperature of 250 °C with subsequent annealing at 650 °C exhibited hexagonal layered structure with R $$ \overline 3 $$ m symmetry. The kinetics of lithium ions in LiCoO2 film cathode host matrix and its cycleability are studied in aqueous Pt//LiCoO2 and nonaqueous Li//LiCoO2 cell. Both the electrochemical cells at same current density of 50 μA cm−2 delivered the same initial discharge capacity of about 60 μA h cm−2 μm−1 with a chemical diffusion coefficient of ca. 10−11 cm2 s−1 for Li+ ions. The capacity fade rates for the Pt//LiCoO2 and Li//LiCoO2 cells, in average are 3.0 and 0.15 % per cycle, respectively, for the first 20 cycles. The Pt//LiCoO2 cell is found to be advantageous for small number of cycles and is cost effective than the Li//LiCoO2 cell.

The microstructural and electrochemical properties of rf-sputtered LiMn2O4 films were investigated as a function of post-deposition process. The degree of crystallization in the films gradually increased with the increase of annealing temperature (T a). The films annealed at T a = 973 K exhibited characteristic peaks with predominant (111) orientation representing the cubic spinel structure of Fd3m symmetry. The estimated Mn–Mn and Mn–O distances obtained from the X-ray diffraction data were observed to be increased slightly with T a. Characteristic changes in surface morphological features were observed as a function of T a as evidenced from scanning electron microscopy. The estimated root mean square (RMS) roughness of the films increased from 97 to 161 nm with augmentation of T a. The electrochemical studies, viz. cyclic voltammetry (CV), specific discharge capacity and Li ion diffusion coefficient were carried out for annealed LiMn2O4 films in saturated aqueous electrolyte (Li2SO4) in the potential window of 0–1.2 V and correlated with surface morphology and grain size. The LiMn2O4 films annealed at T a = 973 K exhibited better electrochemical performance and demonstrated a discharge capacity of about 53.5 μA h cm−2 μm−1 with diffusion coefficient of 1.2 × 10−13 cm2 s−1.

Thin films of Lithium transition metal oxides (LTMOs) have wide applications as a cathode material in the fabrication of all solid state thin film microbatteries. Among various LTMOs, LiMn2O4 with spinel structure is one of the most promising cathode material as it offers high energy density, high cell voltage, low cost and low toxicity. Hence in the present investigation thin films of LiMn2O4 were prepared by RF magnetron sputtering on gold coated silicon substrates maintained at a constant substrate temperature of 573 K with different RF powers ranging from 40 to 150 watts. The influence of RF power on micro structural and electrochemical properties of LiMn2O4 films was studied. The lattice parameter, Mn-Mn-O interatomic distance and grain size was found to be increased with the increase of RF power as evidenced from XRD and SEM studies. The films deposited at a moderate substrate temperature of 573 K with RF power 100 W exhibited predominant (111) orientation with cubic spinel structure. The calculated...

Polycrystalline HT-LiCoO2 films were successfully synthesized by rf magnetron sputtering. The films were characterized by the studying their phase, structure, and morphology using ex-situ measurements of X-ray diffractometry (XRD), Raman Spectroscopy, Atomic force micrometry (AFM). Electrochemical performance evaluation indicated that the as grown LiCoO2 films The anodic electrochemical performances of the films have been evaluated by cyclic voltammetry (CV) at a scan rate of 0.5 mV/s and by galvanostatic cycling, with lithium metal as the counter and the reference electrode, and cycled in the range of 3.0 - 4.2 V at a current density of 50 μA/cm2. The films show a discharge capacity at the 20th cycle of 58 μAh cm−2μm− Keywords: LiCoO which exhibited excellent capacity retention with a small capacity fade which exhibited excellent capacity retention with a small capacity fade.

Thin films of LiCoO2 prepared by RF magnetron sputtering on Si/SiO2/Ti/Au substrates are investigated microstructural and electrochemical properties. The as deposited film shown layered with (003) preferred orientation. After annealing at 923 K in presence of O2 ambient (5×10−2 mbar), HT hexagonal phase LiCoO2 is obtained for the films deposited at O2 to Ar ratio 1:9 and at substrate temperature 523 K. LiCoO2 deposit is unambiguously shown two Raman bands at 465 and 545 cm−1 confirming layered hexagonal structure. Also, studied the performance of the LiCoO2 as positive electrode in aqueous (Pt// LiCoO2) and non‐aqueous (Li// LiCoO2) Li‐ion rechargeable batteries.

Thin films of LiCoO2 were grown by rf magnetron sputtering technique and studied the influence of In situ annealing treatment on microstructural and electrochemical properties of the films. Annealing treatment in presence of O2 ambient develops characteristic (104) plan in relative to (003) plane texture indicating that the films have HT‐layered structure with R3¯m symmetry. The effect is discussed in terms of grain size, cycling stability, reversibility and the specific discharge capacity.

Lithium transition metal oxides have received considerable attention in recent years as high voltage positive electrode materials in the fabrication of all solid state microbatteries. Among various lithium-based cathode materials, LiMn2O4 is one of the most promising cathode materials as it offers high energy density, high cell voltage, low cost, and low toxicity over the other electrode materials. Thin films of LiMn2O4 were prepared by radio frequency magnetron sputtering on gold-coated silicon substrates under various substrate temperatures ranging from 373 to 673 K in a partial pressure of 3 × 10−3 mbar with rf power 100 Watts. In the present investigation, the influence of substrate temperature on the growth and microstructural properties was studied. The films deposited at a substrate temperature less than 473 K was found to be X-ray amorphous. The initial crystallization has been observed at a substrate temperature of 523 K. The X-ray diffraction patterns of the films deposited in the substrate temperature range 523–673 K exhibited predominant (111) orientation representing cubic spinel structure with Fd3m symmetry. The grain size was found to be increased with the increase of substrate temperature as evidenced from SEM studies. However, additional impurity phases like Mn3O4 were observed for the films deposited at higher substrate temperatures (>673 K) because of re-evaporation of Li+ ions in the films. The electrochemical (EC) studies were carried for the films deposited at Ts = 673 K in aqueous media in the potential window of 0.0–1.2 V exhibited better electrochemical performance suggesting that the films are well suited as binder free thin film cathode material for commercially viable Li-ion secondary batteries.