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In recent times, the importance of nanostructure of metal oxide semiconductor (MOS) as a gas sensing material is rising tremendously. Among various metal oxide semiconductors ZnO has potential to be used as a sensor for several toxic gases. In this work, we investigated the influence of Fe doping into ZnO to detect various concentrations of ethanol vapour. Pristine and Fe doped ZnO (Fe-ZnO) films were deposited on glass substrates using a spin coating technique wherein the concentration of Fe can be easily controlled. The crystallite size and surface morphology of ZnO samples were characterized by XRD, SEM and EDX techniques. The sensor performance in terms of gas response (R) of ZnO and Fe-ZnO gas sensors towards ethanol vapour were measured in the 100 to 300°C temperature range using DC electrical resistance. Fe doped ZnO samples showed enhancement in gas response due to increase in specific surface area originated from reducing grain size after doping. The 2% Fe-ZnO sample showed the good response of 40.9 for 400 ppm of ethanol vapour exposure at 260°C. This was found to be better than reported values for ZnO prepared by different methods.

Manganese nanoparticles are promising material for various applications such as water remediation, catalytic oxidation reactions, bio sensors, etc for their superior adsorbing, electrochemical, catalytic, magnetic, supercapactive like properties additionally, MnNPs possess significant medicinal values, hence, this research aims at synthesizing MnNPs biogenically, characterize them to explore antibacterial activity. Aqueous cabbage extract was allowed to react with precursor KMnO4 solution to synthesize the MnNPs. Then, MnNPs were characterized by: visual observation, UV-visible spectroscopy (UV-vis), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDX). Finally, agarwell diffusion was employed to study antibacterial activity against human pathogenic bacteria: staphylococcus aureus ATCC 25923, escherichia coli ATCC 25922 and salmonella typhi. Turning of purple color solution to reddish brown after stirring was the indication of the formation of nanoparticles. The formation of MnNPs was confirmed by appearance of sharp peak at 420 nm, the assigned band for MnNPs and the energy absorption band at 6 keV in EDX spectrum. Diffraction pattern of MnNPs revealed polycrystalline type with crystallite size of 10.70 nm. FT-IR result showed the chief biomolecules: flavoniods, alkaloids, proteins present in the extract which acts as reducing agent. FE-SEM confirmed the formation of spherical and ellipsoidal shaped agglomerated MnNPs. Agarwell diffusion method showed zone of inhibition (ZOI) of range 10-13 mm with (gram + ve and gram –ve) bacteria. Cabbage mediated biosynthesis of MnNPs is found simple, ecofriendly. This work revealed the formation of agglomerated MnNPs confirmed from uv-vis spectra and FE-SEM. Chief biomolecules of the extract act as reducing agent and stabilizing agent. Results of agarwell diffusion method depicted MnNPs are promising material for its antibacterial properties.

Bio-synthesis of metal nanoparticles (CuNPs) is regarded as one of the recently developed, economic and environmentally benign method. In the present investigation, Copper nanoparticles were synthesized reacting garlic (Allium sativum) extract with Copper Sulphate (CuSO4∙5H2O) solution over magnetic stirrer at 80 °C for 1 hour. So-prepared CuNPs were studied by observing the color change at various time intervals.  Further, the nanoparticles were characterized using UV-Visible spectroscopy, Energy Dispersive X-ray spectroscopy (EDX) and Fourier Transform Infrared spectroscopy (FTIR). The results of UV-Vis   spectroscopy   clearly showed presence of absorption peak at 595 nm which confirmed   the   formation   of   copper nanoparticles. Likewise, the EDX spectrum depicts the presence of optical band at 8 eV which is the characteristic peak of Copper consisting of 38.747 % by weight and FTIR spectra revealed presence of various phytochemicals possessing characteristic functional groups such as carbonyl and phenolic at the surface of CuNPs. Thus, natural products available in the garlic extract help in reduction and stabilization of Copper nanoparticles.  The antibacterial activity of Copper nanoparticles was investigated against Gram +ve (Staphylococcus aureus) and Gram –ve bacteria (Escherichia coli) using Agarwell diffusion method. The results of antibacterial test showed that CuNPs were found to be much sensitive towards Gram –ve bacteria compared to gram +ve bacteria.  BIBECHANA 17 (2020) 12-18  

This research mainly aims at implementing green approach for synthesizing multifunctional manganese nanoparticles (MnNPs) using aqueous extract of banana peel (Musa paradiasca) and potassium permanganate (KMnO4) as the precursor. As synthesized MnNPs were confirmed initially by a color change and later on characterized by UV-visible (UV-vis) Spectrophotometer, Energy Dispersive Spectroscopy (EDX), X-ray Diffraction Spectroscopy (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). Green approach was carried at various parameters like concentration of precursor solution, reaction time, temperature, etc for optimization. The formation of MnNPs was confirmed by the presence of surface plasmon absorbance band  (450 nm) and band at 6 and 6.5 keV of EDX spectrum. Likewise, so formed MnNPs were crystalline nature depicted from the sharp peak observed at 28.5º and 41° in X-ray diffraction pattern. Various types of biomolecules associated with the banana peel extract acting as natural reducer and stabilizer were analyzed from characteristic absorption bands present in the FT-IR spectrum.

Over the past few decades, nanomaterials of metal oxide such as zinc oxide (ZnO) have been significantly researched for sensing various toxic gases like ethanol, acetone and ammonia.  The sensing performance of semiconducting materials depends primarily on their surface structure and the interaction behavior with target gas molecules. The surface quality of ZnO is highly influenced by deposition methods.  Although several ZnO surfaces have been rigorously studied for detecting gas leakages, it still possesses drawbacks such as high operating temperature, slow response and recovery times. Henceforth, this investigation was carried out to resolve these issues in the fabrication of future ZnO-based gas sensors. In this work, we report the major findings of the ZnO-based nanoparticle film gas sensor prepared by a doctor blade method to gain insight towards detecting various concentrations of acetone gas at different temperatures. The XRD and FTIR results confirmed the phase purity of ZnO. The results showed the highest response ratio of 25.697 0.012 at 285 oC with an exposure of 800 ppm of acetone along with the quick response and recovery times of 39 sec and 79 sec, respectively. This operating temperature was found to be lower than the reported value for a similar system than that prepared via different methods.