Mitali Saha

Green synthesis of zinc oxide nanoparticles using tomato (Lycopersicon esculentum) extract and its photovoltaic application

With an increasing awareness of green and clean energy, zinc oxide-based solar cells were found to be suitable candidates for cost-effective and environmentally friendly energy conversion devices. In this paper, we have reported the green synthesis of zinc oxide nanoparticles (ZnONPs) by thermal method and under microwave irradiation using the aqueous extract of tomatoes as non-toxic and ecofriendly reducing material. The synthesised ZnONPs were characterised by UV–visible spectroscopy (UV–vis), infra-red spectroscopy, particle size analyser, scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction study (XRD). A series of ZnO nanocomposites with titanium dioxide nanoparticles (TiO2) and graphene oxide (GO) were prepared for photovoltaic application. Structural and morphological studies of these nanocomposites were carried out using UV–vis, SEM, XRD and AFM. The current–voltage measurements of the nanocomposites demonstrated enhanced power conversion efficiency of 6.18% in case of ZnO/GO/ TiO2 nanocomposite.

Molecular scale rapid synthesis of graphene quantum dots (GQDs)

Graphene quantum dots (GQDs) as a new series of nanomaterials have drawn great attention in recent years owning to their unique properties. Here we report the single-step synthesis of GQDs using pyrolysis of citric acid which produced GQDs at different pH. The effect of different pH was studied in detail to optimize the conditions of the formation of GQDs. UV–Visible absorption and normalized fluorescence spectra were applied to analyze the optical properties of GQDs. The particle size distribution of the GQDs in case of varying pH was determined to optimize the synthesis conditions. The surface morphology and microstructures were studied by atomic force microscope (AFM).

Synthesis of zinc oxide nanoparticles using tea leaf extract and its application for solar cell

We report the synthesis of zinc oxide (ZnO) nanoparticles and its composite with natural graphite (NG) powder for application in solar cell. ZnO nanoparticles were synthesized using green tea leaf extract as non-toxic and eco-friendly reducing material under microwave irradiation. The formation of ZnO nanoparticles was monitored by the colour changes during the reaction. The synthesized ZnO nanoparticles were characterized by particle size analyzer (dynamic light scattering), scanning electron microscope, UV–visible spectroscopy, atomic force microscope and fluorescence spectroscopy. The average particle size of the ZnO nanoparticles was found to be 26 nm. The synthesized ZnO nanoparticles were further used to prepare ZnO/NG composite material with commercially available NG powder. The current–voltage (I–V) characteristics of thin film of ZnO/NG nanocomposite were investigated. JSC (short-circuit photocurrent), VOC (open-circuit photovoltage), FF (fill factor) and η (efficiency of the solar cell) were measured for ZnO/NG nanocomposite. Interestingly, the cell showed a good power conversion efficiency of 3.54% with high stability.

Microwave Synthesis of Zinc Oxide Nanoparticles Using Coffee Powder Extract and Its Application for Solar Cell

The authors report a single-step, green, and rapid synthesis of zinc oxide (ZnO) nanoparticles using coffee powder extract as a nontoxic and eco-friendly reducing material under microwave irradiation. Excellent reproducibility of ZnO nanoparticles, without the use of any additional capping agent or stabilizer has been observed. Thin film of ZnO/NG nanocomposite was prepared by mixing ZnO nanoparticles with commercially available natural graphite powder in 1:1 ratio to study its suitable application in solar cells. The current–voltage (I–V) performances of ZnO/NG nanocomposite were investigated. Interestingly, ZnO/NG nanocomposite showed a significant efficiency of 3.12% with high stability.

Size-controlled synthesis of silver nanoparticles using Zizyphus mauritiana fruit extract

We demonstrated size-controlled synthesis of silver nanoparticles (AgNPs) using Zizyphus mauritiana fruit extract from an aqueous solution of silver nitrate. The size distribution of the resulting AgNPs were found to be dependent on the con- centration of fruit extract and reaction time, at the same concentration of silver nitrate. The AgNPs were characterised by UV-Visible spectroscopy (UV-Vis), particle size analysis (DLS), atomic force microscopy (AFM), transmission electron microscopy (TEM) and X- ray diffraction (XRD). The sizes of the AgNPs were found to decrease with the increase of concen- tration of fruit extract from 300 nm to 70 nm. The increase in reaction time from 5 min to 20 min significantly decreases the size of the AgNPs from 350 nm to 100 nm.

Synthesis of carbon nanosheet from barley and its use as non-enzymatic glucose biosensor

In this work, carbon nanosheet (CNS) based electrode was designed for electrochemical biosensing of glucose. CNS has been obtained by the pyrolysis of barley at 600–750 °C in a muffle furnace; it was then purified and functionalized. The CNS has been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopic techniques. The electrochemical activity of CNS-based electrode was investigated by linear sweep voltammetry (LSV) and square wave voltammetry (SWV), for the oxidation of glucose in 0.001 M H2SO4 (pH 6.0). The linear range of the sensor was found to be 10−4–10−6 M (1–100 µM) within the response time of 4 s. Interestingly, its sensitivity reached as high as ~26.002±0.01 μA/μM cm2. Electrochemical experiments revealed that the proposed electrode offered an excellent electrochemical activity towards the oxidation of glucose and could be applied for the construction of non-enzymatic glucose biosensors.

Relation of soya bean meal level to the concentration of plasma free amino acids and body growth in white rats

Amino acid (AA) levels in plasma and body growth were determined in rats (n20) fed diets with different soya bean meal levels. Free AA in plasma was determined by reversed-phase high-pressure liquid chromatography. We have used four levels of protein diets like 8%, 15%, 23% and 35% in this trial. Rats which were fed the low-protein (8%) diet with low percentage of soya bean meal were found to be growth-retarded. The body weight gain of high protein group (35%) was lower than that of the 23% groups. In the rats fed with the low-soya bean meal diet, some nonessential AA (NEAA) in plasma like asparagine, aspartic acid, cysteine, glutamic acid and serine increased, whereas the essential AA (EAA), with the exception of arginine, methionine and valine decreased. Here, plasma EAA-to-NEAA ratios were not correlated to growth and experimental diet. We hypothesize that AA metabolism is associated to changes in growth in rats on different protein intake. This study has showed the sensitivity of body mass gain, feed intake, feed conversion rate of rats to four levels of protein in the diet under controlled experimental conditions.