INVESTIGATION OF BIOGENIC SILVER NANOPARTICLES GREEN SYNTHESIZED FROM CARICA PAPAYA

Objective: This work mainly focuses on the investigation of optical, structural and morphological characteristics of Silver nanoparticles (Ag-NPs) synthesized using Papaya (Carica Papaya) leaf extract and to study the mechanisms involved in the formation.Methods: Ag-NPs were synthesized using colloidal method from silver nitrate using aqueous leaf extract of Papaya as reducing agent. Spectral analysis of Ag-NPs was done using UV-Vis spectroscopy and optical characteristics were studied. Fourier Transform Infrared (FTIR) analysis was done to investigate the mechanisms involved in the reaction. A detailed study of structural and morphological properties was done using X-Ray Diffraction (XRD) and Atomic Force Microscopy (AFM).Results: Spherical shaped Ag-NPs of Face Centered Cubic (FCC) structure were formed and the average particle size was in the range 25-35 nm.Conclusion: Papaya is a good reducing agent for the synthesis of Ag-NPs. Since it is a plant with medicinal values, thus synthesized Ag-NPs can be used for medicinal implications.Â

Synthesis and characterization of CuO nanowires by a simple wet chemical method

We report a successful synthesis of copper oxide nanowires with an average diameter of 90 nm and lengths of several micrometers by using a simple and inexpensive wet chemical method. The CuO nanowires prepared via this method are advantageous for industrial applications which require mass production and low thermal budget technique. It is found that the concentration and the quantity of precursors are the critical factors for obtaining the desired one-dimensional morphology. Field emission scanning electron microscopy images indicate the influence of thioglycerol on the dispersity of the prepared CuO nanowires possibly due to the stabilization effect of the surface caused by the organic molecule thioglycerol. The Fourier transform infrared spectrum analysis, energy dispersive X-ray analysis, X-ray diffraction analysis, and X-ray photoemission spectrum analysis confirm clearly the formation of a pure phase high-quality CuO with monoclinic crystal structure

Efficient and Recyclable Cu Incorporated TiO2 Nanoparticle Catalyst for Organic Dye Photodegradation

Highly efficient Cu-doped TiO2 photocatalysts (CTO) with variation in Cu concentration (4 to 16 wt.%) were prepared via a modified sol-gel technique. X-ray diffraction (XRD) data indicate a pure anatase structure with a small crystallite size of 22.16 nm obtained for CTO-12 (12 wt.% Cu). The average crystallite size and energy bandgap with variation in Cu doping were also studied. All the samples exhibited a spherical morphology. The increment in the Cu concentration caused a systematic decrease in the photoluminescence (PL) intensity, which indicated a lower recombination rate of electron-hole pairs and hence higher separation efficiency. CTO-12 served as the best-suited photocatalyst, tested for photocatalytic degradation of cationic basic (methylene blue, rhodamine B) and anionic acidic (Methyl orange) dyes under UV light irradiation. The comparative study illustrates higher degradation efficiency obtained for cationic dyes than anionic dyes in the order of RhB\u3eMB\u3eMO. The highest degradation (95.3%) was obtained for RhB dye in 180 min. In addition, the further kinetic study suggested the degradation of dyes followed the first-order kinetics. The recyclability data demonstrated superior stability and reliability of the photocatalyst, suggesting its future utilization in potential wastewater treatment applications

Carbon Nanospheres Derived from Lablab Purpureus for High Performance Supercapacitor Electrodes: a Green Approach

Carbon nanospheres derived from a natural source using a green approach were reported. Lablab purpureus seeds were pyrolyzed at different temperatures to produce carbon nanospheres for supercapacitor electrode materials. The synthesized carbon nanospheres were analyzed using SEM, TEM, FTIR, TGA, Raman spectroscopy, BET and XRD. They were later fabricated into electrodes for cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy testing. The specific capacitances were found to be 300, 265 and 175 F g−1 in 5 M KOH electrolyte for carbon nanospheres synthesized at 800, 700 and 500 °C, respectively. These are on a par with those of prior electrodes made of biologically derived carbon nanospheres but the cycle lives were remarkably higher than those of any previous efforts. The electrodes showed 94% capacitance retention even after 5200 charge/discharge cycles entailing excellent recycling durability. In addition, the practical symmetrical supercapacitor showed good electrochemical behaviour under a potential window up to 1.7 V. This brings us one step closer to fabricating a commercial green electrode which exhibits high performance for supercapacitors. This is also a waste to wealth approach based carbon material for cost effective supercapacitors with high performance for power storage devices

Structural and optical investigations of SiO<SUB>2</SUB>-CdS core-shell particles

Cadmium sulfide nanoparticles (~5 nm), chemically capped using thioglycerol molecules, have been anchored onto silica particles (~80 nm) functionalized with 3-aminopropyltrimethoxysilane. Transmission electron microscopy clearly showed that at a low concentration of cadmium sulfide, nanoparticles were discretely and more or less uniformly attached onto the silica particles. At a high concentration of cadmium sulfide nanoparticles, an approximately 6-nm-thick compact shell of cadmium sulfide was formed on the silica particles. In both cases the nanocrystalline nature of cadmium sulfide particles was preserved, as is evident from X-ray diffraction and optical absorption spectra

Photocatalytic performance of a novel semiconductor nanocatalyst: Copper doped nickel oxide for phenol degradation

In this study, the degradation of phenolic compounds was performed in the presence of pure and Cu doped nickel oxide (Cu–NiO) nanocatalysts. A wet chemical method was utilized for the catalyst preparation. The crystallinity and phase were determined using X-ray diffraction, optical properties were analyzed by UV–Vis spectroscopy and morphology was analyzed by a transmission electron microscope. Fourier transform infrared spectroscopy confirms the formation of pure NiO and the existence of copper in doped nanocatalyst samples. Cu–NiO nanocatalyst samples showed a reduction in average crystallite size as compared to pure NiO sample, where it was 24.0, 22.8 and 19.03 nm for 2Cu–NiO and 4Cu–NiO, respectively. The average particle size as determined by using transmittance electron microscopy were about 28.0, 26.6 and 22.8 nm for NiO, 2Cu–NiO and 4Cu–NiO, respectively. In addition, the energy bandgap values were found to be 3.26, 3.64 and 3.87 eV for undoped NiO, 2Cu–NiO and 4Cu–NiO, respectively. Comparative study of the photocatalytic performance of Cu–NiO and pure NiO were systematically performed at various reaction times and Cu doping ratios (2–4 wt %). Different molar concentrations of phenol were also considered for this study. The obtained results showed that the Cu–NiO nanocatalyst exhibited the highest phenol degradation efficiency as compared to their undoped counterpart. This material is first reported and successfully used in efficient removal of phenol from real industrial effluent. The nanocatalyst efficiency for phenol removal was tested in real leather industrial wastewater effluent which could remove about 85.7% within 150 min

Photoluminescent core-shell particles of organic dye in silica

Using a single silica precursor, Rhodamine 6G organic dye molecules have been entrapped in silica particles resulting into core-shell particles of ~500 nm diameter. Energy dispersive X-ray analysis, X-ray photoelectron spectroscopy and transmission electron microscopy analysis reveals that dye molecules are trapped inside the silica particles. Photoluminescence investigations show that highly luminescent and photostable core-shell particles are formed. Such core-shell particles can be easily suspended in water and would be useful for a variety of applications. However, there is a blue shift in the photoluminescence wavelength in case of core-shell particles compared to bare dye powder sample

Adsorption kinetic, equilibrium and thermodynamic investigations of Zn(II) and Ni(II) ions removal by poly(azomethinethioamide) resin with pendent chlorobenzylidine ring

This paper reports the application of poly(azomethinethioamide) (PATA) resin having the pendent chlorobenzylidine ring for the removal of heavy metal ions such as Zn(II) and Ni(II) ions from the aqueous solutions by adsorption technology. Kinetic, equilibrium and thermodynamic models for Zn(II) and Ni(II) ions adsorption were applied by considering the effect of contact time, initial metal ion concentration and temperature data, respectively. The adsorption influencing parameters for the maximum removal of metal ions were optimized. Adsorption kinetic results followed the pseudo-second order kinetic model based on the correlation coefficient (R2) values and closed approach of experimental and calculated equilibrium adsorption capacity values. The removal mechanism of metal ions by PATA was explained with the Boyd kinetic model, Weber and Morris intraparticle diffusion model and Shrinking Core Model (SCM). Adsorption equilibrium results followed the Freundlich model based on the R2 values and error functions. The maximum monolayer adsorption capacity of PATA for Zn(II) and Ni(II) ions removal were found to be 105.4 mg/g and 97.3 mg/g, respectively. Thermodynamic study showed the adsorption process was feasible, spontaneous, and exothermic in nature

Facile synthesis of reduced graphene oxide aerogel in soft drink as supercapacitor electrode

A facile approach is reported to produce reduced graphene oxide (rGO) aerogel. The proposed approach involves the reduction of GO by utilizing the reduction capability of carbonic acid in soft drinks. The presence of carbonic acid reduces the oxygen functionalities in GO to produce rGO and simultaneously provides carboxyl groups for hydrogen bonding in the three-dimensional self-assembly of aerogel. It is also proven that the as-synthesized rGO aerogel possesses a pseudocapacitive effect, owing to the presence of carboxyl groups. This facile reduction approach by an easily available source successfully produces rGO aerogel with 20-fold charge storage capacity enhancement (121 F/g at 0.4 A/g) as compared to the GO. It suggests this facile approach has great potential to construct lightweight graphene aerogel for energy storage applications