K. Giribabu

Fabrication of Ni–Fe2O3 magnetic nanorods and application to the detection of uric acid

Doping of Ni into Fe2O3 lattices has been achieved by co-precipitation followed by thermal decomposition method. The structural, morphological, and magnetic properties of the fabricated samples were investigated by X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared (FT-IR) spectroscopy, UV-visible absorption (UV-vis) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The results reveal that the Ni is well doped within the lattices of Fe2O3. The Ni dopant suppresses the formation of more stable α-Fe2O3 at higher calcination temperature. Further, the Ni-doped Fe2O3 nanoparticles were used to fabricate an electrochemical sensor (Ni–Fe2O3/GCE) for the detection of uric acid (UA) in biological conditions by cyclic voltammetry (CV) and chronoamperometry (CA). It was found that 5%Ni–Fe2O3/GCE exhibits best response towards UA with less positive potential and larger current response. Furthermore, the sensor gives good linear current response in the concentration range of 6.6 to 112.4 μM with the higher sensitivity of 0.849 μA (μM cm2)−1. Such fabricated sensors are appropriate for newly emerging non-enzymatic electrochemical nanobiosensors.

Synthesis and characterization of chromium(III) Schiff base complexes: Antimicrobial activity and its electrocatalytic sensing ability of catechol

A series of acyclic Schiff base chromium(III) complexes were synthesized with the aid of microwave irradiation method. The complexes were characterized on the basis of elemental analysis, spectral analysis such as UV-Visible, Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR) spectroscopies and electrospray ionization (ESI) mass spectrometry. Electrochemical analysis of the complexes indicates the presence of chromium ion in +3 oxidation state. Cr (III) ion is stabilized by the tetradentate Schiff base ligand through its nitrogen and phenolic oxygen. From the spectral studies it is understood that the synthesized chromium(III) complexes exhibits octahedral geometry. Antimicrobial activity of chromium complexes was investigated towards the Gram positive and Gram negative bacteria. In the present work, an attempt was made to fabricate a new kind of modified electrode based on chromium Schiff base complexes for the detection of catechol at nanomolar level.

Spectroscopic investigations, antimicrobial, and cytotoxic activity of green synthesized gold nanoparticles

The gold nanoparticles (AuNPs) were synthesized by using naturally available Punica Granatum fruit extract as reducing and stabilizing agent. The biosynthesized AuNPs was characterized by using UV-Vis, fluorescence, high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and thermogravimetric (TGA) analysis. The surface plasmon resonance (SPR) band at 585nm confirmed the reduction of auric chloride to AuNPs. The crystalline nature of the biosynthesized AuNPs was confirmed from the HRTEM images, XRD and selected area electron diffraction (SAED) pattern. The HRTEM images showed the mixture of triangular and spherical-like AuNPs having size between 5 and 20nm. The weight loss of the AuNPs was measured by TGA as a function of temperature under a controlled atmosphere. The biomolecules are responsible for the reduction of AuCl4(-) ions and the formation of stable AuNPs which was confirmed by FTIR measurement. The synthesized AuNPs showed an excellent antibacterial activity against Candida albicans (ATCC 90028), Aspergillus flavus (ATCC 10124), Staphylococcus aureus (ATCC 25175), Salmonella typhi (ATCC 14028) and Vibrio cholerae (ATCC 14033). The minimum inhibitory concentration (MIC) of AuNPs was recorded against various microorganisms. Further, the synthesized AuNPs shows an excellent cytotoxic result against HeLa cancer cell lines at different concentrations.

Synthesis, growth and photoluminescence behaviour of Gd2O2SO4:Eu3+ nanophosphors: the effect of temperature on the structural, morphological and optical properties

Gd2(SO4)3·8H2O, Gd2O2SO4, and Gd2O2SO4:Eu3+ nanoparticles have been synthesized in the presence of Gd3+ ions and sodium dodecyl sulphate (SDS) by the simple complexation-thermal decomposition (CTD) method. The structural analysis, growth mechanism and optical properties of the Gd2(SO4)3·8H2O, and Gd2O2SO4 are described by the diffraction pattern, functional group analysis, Raman, morphology, elemental analysis, and absorbance spectra. The most intriguing factor was that the Gd2O2SO4 nanoplates are in the range of 42–50 nm without adding any external stabilizer. The results revealed that the Gd2O2SO4 nanoparticles with an orthorhombic structure have a band gap of 3.12 eV. Furthermore, Gd2O2SO4 shows an intense red photoluminescence associated with the 5D0 → 7F2 transition in the presence of Eu3+. The results suggest that the Gd2O2SO4:Eu3+ nanophosphors, may have a beneficial approach in the field of biomedical application as luminescent probe/labels.

Fabrication of α-Fe2O3 Nanoparticles for the Electrochemical Detection of Uric Acid

α-Fe2O3 nanoparticles were synthesized using the hydrolysis method. The prepared sample was characterized by various techniques. The synthesized nanoparticles were used to modify glassy carbon (GC) electrode and the modified electrode was used to detect uric acid (UA) by cyclic voltammetry (CV) and chronoamperometry (CA). At the modified GC electrode, UA is oxidized with less positive potential than the bare GC electrode. The effect of scan rate and the substrate concentration on the modified electrode have also been discussed. The electrochemical studies revealed that the product will exhibit potential applications in the development of sensors.

Manganese sesquioxide to trimanganese tetroxide hierarchical hollow nanostructures: effect of gadolinium on structural, thermal, optical and magnetic properties

Various hollow manganese oxide (bixbyite Mn2O3 and hausmannite Mn3O4) nanoparticles (NPs) with different morphologies were obtained from a single precursor, manganese oxalate (MnC2O4). To synthesize a Mn3O4 stacked nanostructure rather than coral-like Mn2O3 nanospheres, as synthesized MnC2O4 was thermally decomposed at 700 °C in the presence of Gd3+, through the oriented arrangement mechanism. The formation process and structural variation arising from varying the thermal treatment (450 °C and 700 °C) and the cationic dopant Gd3+ were analyzed by FTIR, TGA, and XRD. The unexpected size reduction, and significant physicochemical properties were analyzed using various techniques such as FESEM coupled with EDAX, HR-TEM, DRS-UV-vis, EPR, EIS and VSM. The addition of gadolinium induces particle size reduction and a phase transition from cubic Mn2O3 to tetragonal Mn3O4, which leads to the suppression of the electrical conductivity, and changes in the optical band gap. The prepared Mn3O4 nanocrystals exhibit ferromagnetic behavior below Tc ≈ 45 K and weak paramagnetic behavior at room temperature.

BiVO4 nanoparticles: Preparation, characterization and photocatalytic activity

Abstract Bismuth vanadate (BiVO4) nanoparticles were synthesized by a simple thermal decomposition method. The synthesized bismuth vanadate nanoparticles were characterized by X-ray diffraction analysis, it is found that the synthesized sample belongs to monoclinic BiVO4. Fourier transform infrared spectroscopy confirms the formation of Bi-O bond in the sample. Ultraviolet–Visible (DRS-UV–Visible) spectroscopy and photoluminescence spectroscopy reveal the optical property of the BiVO4 nanoparticles. The morphology was identified by both scanning electron microscopy and high-resolution transmission electron microscopy. Further, the photocatalytic activity of BiVO4 nanoparticles was investigated by photodegradation of methylene blue as a model organic pollutant.

Copper vanadate nanoparticles: synthesis, characterization and its electrochemical sensing property

Copper vanadate (Cu2V2O7) nanoparticles were synthesized by a simple thermal decomposition method. The synthesized copper vanadate nanorods were characterized by X-ray diffraction analysis, and it is found that the synthesized sample belongs to monoclinic Cu2V2O7. Fourier transform infrared spectroscopy (FT-IR) confirms the formation of Cu–O bond in the sample. Ultraviolet–visible (DRS-UV–visible) spectroscopy and photoluminescence spectroscopy reveals the optical property of the Cu2V2O7 nanoparticles. The nanobar-like morphology was confirmed by both scanning electron microscopy and high resolution transmission electron microscopy. Further, the electrochemical sensing behavior of Cu2V2O7 nanoparticles was investigated by cyclic voltammetry using lidocaine as an analyte. The electrochemical sensing experiment suggests that the Cu2V2O7 nanoparticles will become a potential candidate in the field of drug sensor.

Synergistically strengthened 3D micro-scavenger cage adsorbent for selective removal of radioactive cesium.

A novel microporous three-dimensional pomegranate-like micro-scavenger cage (P-MSC) composite has been synthesized by immobilization of iron phyllosilicates clay onto a Prussian blue (PB)/alginate matrix and tested for the removal of radioactive cesium from aqueous solution. Experimental results show that the adsorption capacity increases with increasing the inactive cesium concentration from 1 ppm to 30 ppm, which may be attributed to greater number of adsorption sites and further increase in the inactive cesium concentration has no effect. The P-MSC composite exhibit maximum adsorption capacity of 108.06 mg of inactive cesium per gram of adsorbent. The adsorption isotherm is better fitted to the Freundlich model than the Langmuir model. In addition, kinetics studies show that the adsorption process is consistent with a pseudo second-order model. Furthermore, at equilibrium, the composite has an outstanding adsorption capacity of 99.24% for the radioactive cesium from aqueous solution. This may be ascribed to the fact that the AIP clay played a substantial role in protecting PB release from the P-MSC composite by cross-linking with alginate to improve the mechanical stability. Excellent adsorption capacity, easy separation, and good selectivity make the adsorbent suitable for the removal of radioactive cesium from seawater around nuclear plants and/or after nuclear accidents.

Visible light photocatalytic property of Zn doped V2O5 nanoparticles

The Zn doped V2O5 nanoparticles were synthesized by thermal decomposition method. The prepared samples were characterized by various techniques like Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) studies, UV-Visible spectroscopy (UV-Vis) and field emission scanning electron microscopy (FE-SEM). The photocatalytic activities of pure and Zn doped V2O5 nanoparticles were examined based on the photodegradation of Rhodamine B (RhB). Experimental results indicated that the Zn doped V2O5 photocatalyst (the molar ratio of V to Zn is 99: 1) exhibited maximum photocatalytic activity.