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Work function measurement using Kelvin probe method has been demonstrated as an effective and novel approach towards detection of NH3 and NO2 gases using ZnO–NiO based nanocomposites. For this the nanocomposites were synthesised in different compositions using the solvothermal method. Formation of ZnO–NiO nanocomposites was confirmed using XRD and EDS studies. It is found that the nanoparticle morphology of NiO changes with different percentages of Zn addition. The work function of the sensing film was found to decrease and increase upon exposure to NH3 (1.51) and NO2 (1.18) gases owing to the reducing and oxidising nature of the test gases. Of the different composites, Zn0.75Ni0.25O exhibited highest sensor response towards the test gases. The increased response is attributed to the nanostructured morphology of the nanocomposite and the formation and collapse of the p-n heterojunction formed between p-type NiO and n-type ZnO. Besides, incorporation of NiO enhances the oxygen adsorption on the sensor surface assigned to the Ni2+ ions getting readily oxidised to Ni3+. Our results clearly suggest that the work function measurements could also be used as an effective way for NO2 and NH3 detection. [ABSTRACT FROM AUTHOR]

Heavy metal ions (HMIs) are known to cause severe damages to the human body and ecological environment. And considering the current alarming situation, it is crucial to develop a rapid, sensitive, robust, economical and convenient method for their detection. Screen printed electrochemical technology contributes greatly to this task, and has achieved global attention. It enabled the mass transmission rate and demonstrated ability to control the chemical nature of the measure media. Besides, the technique offers advantages like linear output, quick response, high selectivity, sensitivity and stability along with low power requirement and high signal-to-noise ratio. Recently, the performance of SPEs has been improved employing the most effective and promising method of the incorporation of different nanomaterials into SPEs. Especially, in electrochemical sensors, the incorporation of nanomaterials has gained extensive attention for HMIs detection as it exhibits outstanding features like broad electrochemical window, large surface area, high conductivity, selectivity and stability. The present review focuses on the recent progress in the field of screen-printed electrochemical sensors for HMIs detection using nanomaterials. Different fabrication methods of SPEs and their utilization for real sample analysis of HMIs using various nanomaterials have been extensively discussed. Additionally, advancement made in this field is also discussed taking help of the recent literature. [ABSTRACT FROM AUTHOR]

The threat of heavy metal ions (HMIs) in aqueous media to public health is gaining its concern all around the world. Thus, to measure the concentration, lower than the regulated level, synthesis of MoO3 nanostructures using hydrothermal method was carried out. In this study, MoO3 was synthesized from an aqueous solution containing ammonium heptamolybdate and different concentrations (0.1 and 0.3 M) of polyvinylpyrrolidone (PVP). Here, PVP stabilizes the particles and prevents them from agglomeration. X-ray diffraction analysis revealed an orthorhombic structure. Field emission scanning electron microscopy revealed that various concentrations of PVP are responsible for morphological modifications. A structure resembling a plate-like morphology were observed at 0.3-M PVP. According to UV–Vis spectroscopy, the bandgap energy is directly proportional to PVP concentration. Electrochemical analysis was used to evaluate the capabilities of synthesized nanostructures for HMIs detection. According to electrochemical experiments, the linear detection range for Pb (II) is 0.02–90 ppb. The higher surface area induced by the presence of PVP improved the material sensitivity by ~ 2 times as compared to material synthesized without PVP. Additionally, synthesized MoO3 showed good selectivity toward Pb (II) than other HMIs. According to electrochemical studies, this research gives a valuable insight for understanding the effect of morphology on HMIs detection. [ABSTRACT FROM AUTHOR]

A novel nanobipyramidal structure along with nanowires and cubes of tin oxide are synthesized by employing RuO2 as a promoter/nucleating gent. The nanobipyramids are collected in the downstream where the temperature is between 2090 and 500 degree Celsius, whereas nanowires and cubes are formed on the substrate containing the reaction mixture.