P. Saravanan

Adsorption, photodegradation and antibacterial study of graphene–Fe3O4 nanocomposite for multipurpose water purification application

Graphene–Fe3O4 (G–Fe3O4) composite was prepared from graphene oxide (GO) and FeCl3·6H2O by a one-step solvothermal route. The as-prepared composite was characterized by field-emission scanning electron microscopy, transmission electron microscopy, dynamic light scattering and X-ray powder diffraction. SEM analysis shows the presence of Fe3O4 spheres with size ranging between 200 and 250 nm, which are distributed and firmly anchored onto the wrinkled graphene layers with a high density. The resulting G–Fe3O4 composite shows extraordinary adsorption capacity and fast adsorption rates for the removal of Pb metal ions and organic dyes from aqueous solution. The adsorption isotherm and thermodynamics were investigated in detail, and the results show that the adsorption data was best fitted with the Langmuir adsorption isotherm model. From the thermodynamics investigation, it was found that the adsorption process is spontaneous and endothermic in nature. Thus, the as-prepared composite can be effectively utilized for the removal of various heavy metal ions and organic dyes. Simultaneously, the photodegradation of methylene blue was studied, and the recycling degradation capacity of dye by G–Fe3O4 was analyzed up to 5 cycles, which remained consistent up to ∼97% degradation of the methylene blue dye. Although iron oxide has an affinity towards bacterial cells, its composite with graphene still show antibacterial property. Almost 99.56% cells were viable when treated with Fe3O4 nanoparticle, whereas with the composite barely 3% cells survived. Later, the release of ROS was also investigated by membrane and oxidative stress assay. Total protein degradation was analyzed to confirm the effect of the G–Fe3O4 composite on E. coli cells.

Tailored Anisotropic Magnetic Chain Structures Hierarchically Assembled from Magnetoresponsive and Fluorescent Components

The development of methods for controlling the organization of functional objects at a nanometer scale to build larger objects is of fundamental and technological interest. The unique electronic, magnetic, and optical properties of nanomaterials will be best utilized when they are well integrated into larger devices. A great deal of research is focused on such materials, particularly those with magnetic properties that can be exploited for the fabrication of ordered onedimensional (1D) chainlike assemblies. Pertinent targets include the synthesis of materials that have desirable anisotropic properties for electronic and optical devices. As this is a difficult task, different techniques have been employed including magnetic-field-induced (MFI) assembly, electric or magnetic dipole–dipole interactions, crystallographically specific orientation, non-uniform stabilizer distribution, templated synthesis to produce 1D nanostructured materials. However, an elegant approach would be to construct 1D chains consisting of structurally intricate units and functions. Suitable methods are still required to prepare aligned structures from nanoparticles suspended in an aqueous medium and to allow multifunctional properties to be imparted into such directional structures in a way that allows these additional properties to evaluated and exploited. Herein, we describe a method that provides opportunities for synthesizing materials that not only have a preferred 1D structure but that are also multifunctional. The strategy involves both designing and utilizing nanobuilding blocks to be linked together to generate aligned materials with anisotropic morphology and multifunctional properties. In the first step we assemble preformed nanoparticles (NPs) into a confined structure by using positively charged polypeptides as interparticle mediators while preserving the constituent nanoparticles functional properties. We have shown that the cationic polypeptides can undergo counterion condensation to form spherical aggregates by ionic cross-linking with either certain multivalent counteranions or nanoparticles which are capped with anionic species. The unique aggregation characteristics of these polycation–anion systems means that multiple nanoparticles can spontaneously assemble into microstructures. We have further shown that functionalities can also be integrated to give catalytic and optical properties. Herein, our approach is to use poly(l-lysine) (PLL) to cross-link with hydroxy pyrene trisulfonate (HPTS) and citrate-functionalized magnetic nanoparticles (MNPs) to afford magneto responsive fluorescent spheres (MFS). In a second step these spheres are magnetically aligned by virtue of magnetic dipole interactions to construct 1D anisotropic shapes. HPTS is a pyrene-based molecule and has been proved to be a versatile probe molecule in both chemistry and biology. The ability of HPTS, as an anionic multiple-point cross-linking center, to electrostatically bind cations on different polyelectrolyte chains can impart fluorescent properties to the resulting hybrid structures. To incorporate magnetic properties, we use citrate-functionalized Fe3O4 magnetic nanoparticles (MNPs) so that the ionic interaction of citrate with PLL can enable the formation of spherical MNP aggregates. The MNPs, synthesized by a co-precipitation method, are fully characterized to ensure their structure and the presence of the citrate functional group (Supporting Information, Figure S1). Scheme 1 illustrates our method to include both magnetic and fluorescent functions into the microspheres. Simultaneous columbic interactions between positively charged amine groups of PLL and the negatively charged carboxy groups on

Visible-light-driven SnO2/TiO2 nanotube nanocomposite for textile effluent degradation

Nanocomposite of SnO2/TiO2 nanotube (NT) was prepared by a simple two-step procedure, viz., hydrothermal preparation of TiO2 NT followed by chemical precipitation of SnO2 nanoparticle sensitized TiO2 NT. Transmission electron microscopy analysis revealed that the as-synthesized TiO2 NTs exhibit a diameter of 20–30 nm and a length of 1–2 μm with a wall thickness of 2–5 nm. The particle size of SnO2 nanoparticles in the composite was estimated to be 4–6 nm. Both the TiO2 NT and SnO2/TiO2 NT composite were considered for the photocatalytic degradation of textile dye effluent under UV and sunlight irradiation. The SnO2/TiO2 NT composite showed improved degradation efficiency. Photoluminescence spectra of SnO2/TiO2 NT composites showed a decrease in intensity when compared to the TiO2 NT – revealing that the rate of recombination is reduced in the SnO2/TiO2 NT composite, which is responsible for larger photocatalytic activity. Further, an effluent degradation efficiency of 85% was obtained for the SnO2/TiO2 NT composite under sunlight irradiation and this can be considered as one of the best values achieved so far.

Large scale synthesis and formation mechanism of highly magnetic and stable iron nitride (ε-Fe3N) nanoparticles

e-Fe3N magnetic nanoparticles with an average size of 45 nm were synthesized by nitriding the zero valent iron nanoparticle precursors using ammonia gas as a reactive ambience. The technique reported in this study is found to be promising in producing highly stable e-Fe3N magnetic nanoparticles and can be extended to other forms of Fe-nitrides.

Insights into the nitridation of zero-valent iron nanoparticles for the facile synthesis of iron nitride nanoparticles

The process of nitridation of zero-valent iron nanoparticles (ZVINPs) is investigated by employing two different synthesis strategies such as solvothermal method and gas diffusion using N2 and NH3. It is observed that the phase formation of different iron nitrides mainly depends on the reaction chemistry of the nitridation source and temperature. Accordingly, N2 gas diffusion and solvothermal methods yield iron oxide phases, whereas NH3 gas diffusion yields pure iron nitride phase with particle sizes in the nanoscale. X-ray diffraction studies complemented by Rietveld refinement confirm the formation of e-Fe3N and γ′-Fe4N nanoparticles. Field emission scanning electron microscopy images revealed spherical nanoparticles with average particle sizes of 35 and 50 nm for ZVINPs and iron nitride NPs, respectively. From the magnetization studies carried out using a superconducting quantum interference device magnetometer it is found that the field-dependent hysteresis curves indicated the ferromagnetic properties of ZVINPs, e-Fe3N and γ′-Fe4N NPs with coercive fields of 160, 65 and 45 Oe, respectively. Similarly, the temperature-dependent magnetization profiles revealed that the observed ferromagnetic properties of iron nitride phases can be attributed to the redistribution of electronic spin states due to both nitrogen populations and the confinement in the crystallites.

Coercivity enhancement in Mn-Al-Cu flakes produced by surfactant-assisted milling

We herein report the achievement of exceptionally high coercivity (Hc) values: 9.92 and 5.86 kOe at 5 and 300 K, respectively, for Mn55Al43Cu2 flakes produced by surfactant-assisted milling process without employing any heat-treatment. The use of surfactants such as oleic acid and oleylamine during milling yielded high-aspect ratio flakes for the Mn-Al-Cu alloy. Structural studies confirmed the presence of τ- and β-phases as the major constituents in the Mn-Al-Cu flakes. The observed Hc enhancement is due to the increase in anisotropy field and structural defects, which is hypothesized to originate from the domain-wall pinning as a consequence of precipitation of fine Cu-particles present at the grain boundaries.

A surfactant-assisted high energy ball milling technique to produce colloidal nanoparticles and nanocrystalline flakes in Mn–Al alloys

We herein exploit the advantages of surfactant assisted-high energy ball milling (SA-HEBM) for the processing of Mn–Al alloy. In this method, a combination of two surfactants, such as oleic acid and oleylamine, was used along with a solvent, n-heptane, during milling. The use of the SA-HEBM process yielded two different products: a sediment powder consisting of sub-micron sized Mn–Al flakes and a suspension in the milling medium (colloid) containing Mn–Al nanoparticles. The colloid consisted of Mn–Al nanocrystalline particles (5–16 nm) having a lamellar morphology with an average thickness of 1.5 nm and length of 16 nm. Magnetic measurements of these colloidal nanoparticles demonstrated an almost non-magnetic behavior at 300 K. The Mn–Al sediment powders obtained with the SA-HEBM process at regular milling time intervals were investigated for their structural and magnetic performance and also compared with the corresponding powders obtained from the conventional HEBM process. The phase composition of Mn–Al powders processed by both HEBM and SA-HEBM is quite similar and they adhere to the phase constituents of parent alloy: τ-, β-phases with some traces of e-phase. Nevertheless, the estimated magnetic parameters such as saturation magnetization and coercivity for the SA-HEBM powders exhibited improved values, as compared to the HEBM powders. A maximum coercivity of 4.88 kOe was obtained for the 8 h milled SA-HEBM powder and this value is 23% higher than that of HEBM processed powder. The results were explained based on the effect of surfactants on the morphology of the milled powder.

Enhanced shielding effectiveness in nanohybrids of graphene derivatives with Fe3O4 and ε-Fe3N in the X-band microwave region

Novel nanocomposites of reduced graphene oxide (rGO)–Fe3O4, denoted as ‘rGO:IO, and nitrogen doped rGO–e-Fe3N, denoted as ‘NrGO:IN’, were prepared by a modified polyol method, wherein both the reduction of graphene oxide and oxidation of Fe2+/Fe3+ ions occurred simultaneously, followed by ammonia nitridation. The electron microscopy analysis of the rGO:IO and NrGO:IN nanocomposites revealed unique morphologies. In rGO:IO, the Fe3O4 nanoparticles having a mean diameter of 38 nm were found to be uniformly anchored to the rGO sheet surface, whereas in NrGO:IN, the e-Fe3N nanoparticles (∼150 nm) were shielded by the NrGO sheets. Superparamagnetic and weak ferromagnetic characteristics with saturation magnetization values of 39.5 and 46 emu g−1 were observed in the rGO:IO and NrGO:IN nanocomposites respectively, which can be attributed to the nature of the constituent magnetic nanoparticles, Fe3O4 and e-Fe3N. In addition, the graphene derivatives such as rGO and NrGO contributed to the enhanced electrical properties of the nanocomposite. The electrochemical impedance spectroscopy analysis showed that, compared to pure Fe3O4 and e-Fe3N nanoparticles, the total electrical resistance of rGO:IO and NrGO:IN was reduced by 33 344.8 and 1569.87 Ω cm−2, respectively, when combined with the rGO and NrGO sheets. Further, the electromagnetic shielding performance of the NrGO:IN nanocomposite was investigated for the first time and was compared with the other samples. Of the two prepared nanocomposites, NrGO:IN exhibited electromagnetic shielding effectiveness of 35.33 dB at 11.4 GHz, which is considerably larger than that of rGO:IO (14.4 dB at 8 GHz). This enhanced shielding effectiveness is not only due to the high inherent magnetic and electrical properties of e-Fe3N nanoparticles, but also due to the ‘particle shielded by sheet’ morphology of the NrGO:IN, which enhances the charge accumulation at the heterogeneous interfaces of NrGO sheets/e-Fe3N nanoparticles.

One-Step Pyrolytic Synthesis of Multiwalled Carbon Nanotubes: The Role of Resupply of Carbon Species on the Quality Control

An investigation on varying experimental parameters such as solution quantity (2.5, 5 and 7.5 mL) and reaction time (15, 30, 45 and 60 min) was carried out for the production of high-quality multiwalled carbon nanotubes (MWCNTs) in one step pyrolysis. Structural analysis revealed the uniform diameter distribution and the length of nanotubes in the range of 60-80 nm and 0.4-2 μm, respectively. Raman and X-ray diffraction analysis showed a remarkable reduction in defect density with increase in graphitization degree, upon increasing the solution volume and reaction time. MWCNTs prepared at higher solution quantity (7.5 mL) with higher reaction time (60 min) showed higher crystallinity (70% graphitization) and lower defect density (ID/IG: 0.56). The attainment in equilibrium of evaporation cum precipitation in formation of high quality nanotubes structure is evaluated. An effective resupplying of condensed precursors by re-evaporation leads for the achievement of low defect density nanotubes with higher product yield is achieved.

Snake Bite - Translating Protocols into Practice

There are many protocols available for treating poisonous snake bites and every treating physician thinks that he is always right. We submit a prospective study done over a period of seven months in a tertiary care hospital in Tamil Nadu. This study emphasizes on low dose ASV as a measure for better clinical response and reducing the morbidity and mortality. Aim of the Study: The aim of the study is to prove that low dose ASV can reduce morbidity and mortality, if the guidelines given by state/ national/ WHO are followed on the basis of individual requirements. Material And Methods: This is a prospective observational study in a tertiary medical care hospital, Dharmapuri, Tamil Nadu, south India, between Jan 2016 to July 2016 with 545 patients all are presented with history of snake bite and285 patients with signs of envenomation exclusion criteria all patients with pre existing renal disease, those who are on drugs like aspirin and clopidogrel, and patients with previous history of bleeding diathesis are excluded from this study Results: Totally we encountered 2295 snake bite patients over a period of 3 years from 2013 – 2015. Among them, 112 (4.88%) patients died of snake bite related AKI. Average number of ASV vials used per patient ranged from 9.27 to 14.83, thus showing the efficacy of low dose ASV regimen. Conclusion: Our study shows that when the signs and symptoms are carefully and constantly observed, low dose ASV is not inferior to high dose ASV in effectively treating snake bite patients as ASV neutralizes only unbound, free flowing venom.