Balaprasad Ankamwar

Biosynthesis of Gold Nanoparticles (Green-gold) Using Leaf Extract of Terminalia Catappa

The synthesis of eco-friendly nanoparticles is evergreen branch of nanoscience for biomedical application. Low cost of synthesis and non toxicity are main features make it more attractive potential option for biomedical field and elsewhere. Here, we report the synthesis of gold nanoparticles in aqueous medium using Terminalia catappa (Almond) leaf extract as the reducing and stabilizing agent. On treating chloroauric acid solutions with Terminalia catappa (TC) leaf extract rapid reduction of chloroaurate ions is observed leading to the formation of highly stable gold nanoparticles in solution. TEM analysis of the gold nanoparticles indicated that they ranged in size from 10 to 35 nm with average size of 21.9 nm.

SERS study of bacteria using biosynthesized silver nanoparticles as the SERS substrate

Surface-enhanced Raman scattering (SERS) spectroscopy has great advantages as a spectroscopic analytical tool due to the large enhancement of the weak Raman signal and thereby facilitates suitable identification of chemical and biological systems. SERS can be utilized as a powerful tool to identify pathogens like bacteria. However, it is difficult to fabricate a homogeneous SERS active substrate in biosensing applications to obtain a uniform, stable and highly reproducible SERS signal. In this paper, we have used biosynthesized silver nanoparticles as the SERS active substrate to identify bacteria with different cell wall compositions. The silver nanoparticles were synthesized using the leaf extract of Neolamarckia cadamba as the source of reducing and stabilizing agents. The pathogen detection by using the SERS technique using biosynthesized silver nanoparticles represents a novel approach for rapid microbial diagnostics, where SERS can be directly applied to clinical samples rather than pure cultured bacteria.

Rod-Shaped Magnetite Nano/Microparticles Synthesis at Ambient Temperature

Here, we reported room temperature synthesis of Fe3O4 rod-shaped nano/microparticles by chemical reduction method from FeCl3 precursor and NaBH4 as the reducing agent in the presence of the pyrrole as a capping agent. The magnetic Fe3O4 particles were characterized by several methods, such as SEM, XRD, FTIR, and TGA. The average aspect ratio of Fe3O4 rod-shaped particles was ~2.8. These particles were redispersed in deionised water to form a colloidal solution and showed magnetic properties. This economical synthesis route is scalable, and Fe3O4 particles can be exploited for various applications such as MRI contrast enhancement, biodiseperations, Ni-Fe batteries, and as a catalyst.

Ultrafine Pt–Ru bimetallic nanoparticles anchored on reduced graphene oxide sheets as highly active electrocatalysts for methanol oxidation

The controlled fabrication of bimetallic nanocatalysts with a suitable size, structure and morphology is extremely important to realize direct methanol fuel cells (DMFCs) as promising energy-generating sources. In this paper, a facile approach for depositing platinum–ruthenium (Pt–Ru) bimetallic nanoparticles on a reduced graphene oxide (RGO) support has been demonstrated. Two electrocatalysts denoted as Pt–Ru/RGO-AA and Pt–Ru/RGO-AB were synthesized by synchronously reducing H2PtCl6 and RuCl3 on the graphene oxide (GO) support with reducing agents ascorbic acid and methyl ammonia borane, respectively. For comparison of methanol electrooxidation activity, monometallic Pt nanoparticles supported on RGO sheets (Pt/RGO) were also synthesized. All the catalysts were conveniently synthesized under ambient conditions without using any surfactants. The Pt/RGO, Pt–Ru/RGO-AA and Pt–Ru/RGO-AB electrocatalysts were characterized using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDS). Among all the catalysts, the Pt–Ru/RGO-AB catalyst with an average particle size of 2.8 nm possessed remarkable uniformity on the RGO sheets. The electrochemical performance of RGO-supported Pt and Pt–Ru catalysts towards methanol oxidation was systematically studied using cyclic voltammetry and chronoamperometry. The results demonstrate that the Pt–Ru/RGO-AB catalyst with a high electrochemical active surface area (ECSA) of 130.46 m2 g−1 exhibits a higher mass and ECSA normalized activities towards methanol oxidation. Furthermore, the Pt–Ru/RGO-AB catalyst has a better tolerance towards accumulated CO-like species as realized from its higher ratio of forward peak current density to reverse peak current density (If/Ib) of 3.21. The facile fabrication strategy described here is convenient and could be used for the fabrication of other multi-component nanostructured electrocatalysts for fuel cell reactions.

Synthesis and characterization of stable aqueous dispersions of graphene

A stable aqueous dispersion (5 mg ml−1) of graphene was synthesized by a simple protocol based on three-step reduction of graphene oxide (GO) dispersion synthesized using the modified version of Hummers and Offeman method. Reduction of GO was carried out using sodium borohydride, hydrazine hydrate and dimethyl hydrazine as reducing agents. The chemically synthesized graphene was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible absorption spectroscopy, Fourier transform infrared (FTIR) and Raman spectroscopy, thermogravimetric analysis (TGA), optical microscopy. The stability of aqueous dispersions of graphene was confirmed through zeta potential measurements and the negative zeta potentials of 55–60 mV were obtained indicating the high stability of aqueous graphene dispersions.

Ecofriendly Synthesis of Anisotropic Gold Nanoparticles: A Potential Candidate of SERS Studies

Ecofriendly synthesis of nanoparticles has been inspiring to nanotechnologists especially for biomedical applications. Moreover, anisotropic particle synthesis is an attractive option due to decreased symmetry of such particles often leads to new and unusual chemical and physical behaviour. This paper reports a single-step room-temperature synthesis of gold nanotriangles using a cheap bioresource of reducing and stabilizing agent Piper betle leaf extract. On treating aqueous chloroauric acid solution with Piper betle leaf extract, after 12 hr, complete reduction of the chloroaurate ions was observed leading to the formation of flat and single crystalline gold nanotriangles. These gold nanotriangles can be exploited in photonics, optical coating, optoelectronics, magnetism, catalysis, chemical sensing, and so forth, and are a potential candidate of SERS studies.

Size and Shape Effect on Biomedical Applications of Nanomaterials

Earlier, we studied [1] the I-V response of electron transport within the plain and normal to the film surface of gold nanotriangles formed using the crude lemongrass extract. The I-V plot was fairly linear for the out-of-plane measurement while considerably higher across the film surface (681 kΩ) than within the plane of the film (32 kΩ). This could be due to the field-enhancement effects (FEE) near the sharp vertices of the nanotriangles considerably higher when the electric field was applied parallel to the film surface than when applied normal to the film surface. The FEE near sharp vertices of single crystalline triangular gold nanoprisms (Figure 1A) would be more as compare to truncated (1B) triangular gold nanoprisms. Costa and Dmitriev observed the better field confinement and enhancement in the plane xy for the triangular disk in comparison with the circular disk and circular disk in comparison with the sphere [2]. The FEE could have important application in the use of the sharp vertices biogenic gold nanotriangle as conductive tips in scanning tunneling microscope for studying biological samples. The size of the nanotriangles (thickness: 8-18 nm) makes manipulation on to cantilevers feasible for detection of cancer cells by antibodyantigen mechanism.

Room temperature green synthesis of anisotropic gold nanoparticles using novel biological fruit extract

ABSTRACT Herein, we reported the room temperature green synthesis of anisotropic gold nanoparticles from the aqueous Cordia myxa fruit extract, which can concurrently serve as the source for both the reducing and stabilizing agents. In the X-ray diffraction pattern, the identified Bragg reflections corresponded to the (111), (200), and (220) sets of lattice planes, which can be indexed based on the face center cubic structures of gold. They are in different morphologies such as multiple twinned pentagonal shaped octahedron and hexagonal shaped icosahedron with their size ranging from 20 to 50 nm as evident from the transmission electron microscopy images.

Synthesis of Mesoporous Nanocrystalline Zirconia by Surfactant-Assisted Hydrothermal Approach

In this paper, we have reported the chemical synthesis of thermally stable mesoporous nanocrystalline zirconia with high surface area using a surfactant-assisted hydrothermal approach. We have employed different type of surfactants such as CTAB, SDS and Triton X-100 in our synthesis. The synthesized nanocrystalline zirconia multistructures exhibit various morphologies such as rod, mortar-pestle with different particle sizes. We have characterized the zirconia multistructures by X-ray diffraction study, Field emission scanning electron microscopy, Attenuated total refection infrared spectroscopy, UV-Vis spectroscopy and photoluminescence spectroscopy. The thermal stability of as synthesized zirconia multistructures was studied by thermo gravimetric analysis, which shows the high thermal stability of nanocrystalline zirconia around 900 °C temperature.

Optical, dielectric, electronic and morphological study of biologically synthesized zinc sulphide nanoparticles using Moringa oleifera leaf extract and quantitative analysis of chemical components present in the leaf extract

The biosynthesis of zinc sulphide nanoparticles with ∼30 nm diameter using the leaf extract of Moringa oleifera is reported here. The biosynthesized nanoparticles exhibit high stability for a period of three months as supported by the observed negative zeta potential values of 45–55 mV. Two peaks were observed at 427 and 560 nm in the photoluminescence spectrum of ZnS nanoparticles. The dielectrics as well as electronic properties of ZnS nanoparticles were systematically investigated. Thin-layer-chromatography densitometric technique was employed for the simultaneous quantification of the major chemical components present in the extract of M. oleifera leaves. The average amount of observed biomolecules such as crypto-chlorogenic acid, isoquercetin and astragalin were found to be 0.0423, 0.0467 and 0.0634% dry weight, respectively.