C. Viswanathan

Conducting polyaniline-graphene oxide fibrous nanocomposites: preparation, characterization and simultaneous electrochemical detection of ascorbic acid, dopamine and uric acid

Polyaniline/graphene oxide (PANI-GO) fibrous nanocomposites have been prepared and the electrochemical catalytic activity towards the electro-oxidation of ascorbic acid (AA), Dopamine (DA) and Uric acid (UA) has been investigated. The nanocomposites were synthesized via an in situ chemical polymerization method. The morphology, composition, thermal and electrochemical properties of the resulting nanocomposites were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, FT-IR spectroscopy, thermo gravimetric analysis and cyclic voltammetry. The catalytic behavior of PANI-GO nanocomposite modified glassy carbon electrode (GCE) towards AA, DA and UA has been investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV). The PANI-GO/GCE showed excellent catalytic activity towards electrochemical oxidation of AA, DA and UA compared to the bare GCE. The electrochemical oxidation signal of AA, DA and UA are well separated into three distinct peaks with peak potential separation of 343 mV, 145 mV and 488 mV between AA-DA, DA-UA and AA-UA respectively in CV studies and the corresponding peak potential separation in DPV mode are 320 mV, 230 mV and 550 mV. Under the optimized DPV experimental conditions, the peak current of AA, DA and UA give linear response over the range of 25–200 μM (R2 = 0.9955), 2–18 μM (R2 = 0.9932) and 2–18 μM (R2 = 0.9902) with detection limit of 20 μM, 0.5 μM and 0.2 μM at S/N = 3, respectively. The attractive features of PANI-GO provide potential applications in the simultaneous detection of AA, DA and UA. The excellent electrocatalytic behavior of PANI-GO may lead to new applications in electrochemical analysis.

Quercetin conjugated superparamagnetic magnetite nanoparticles for in-vitro analysis of breast cancer cell lines for chemotherapy applications

The magnetic nanoparticles attract increasing interest due to their opportunities in cancer therapy and used as drug carriers for several other diseases. The present study investigates the quercetin conjugated superparamagnetic Fe3O4 nanoparticles for in-vitro analysis of breast cancer cell lines for chemotherapy. A simple precipitation method was used to prepare the dextran coated Fe3O4 nanoparticles and the anticancer flavonoid quercetin was conjugated on the surface via carboxylic/amine group using nanoprecipitation method. The structural, morphological and the magnetic properties of the prepared materials were studied by using X-ray diffractometer (XRD), Fourier transformed infer-red spectrometer (FTIR), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). The MTT (3-(4,5-dimethylthiahiazol-2-yl)-2,5-diphenyl tetrazolium) assay of dextran coated Fe3O4 nanoparticles did not exhibit notable toxicity against MCF7 cells, whereas the cytotoxicity of quercetin conjugated Fe3O4 nanoparticles increased significantly in comparison with pure quercetin. The incubation of MCF-7 cells with quercetin conjugated Fe3O4 nanoparticles (QCMNPs) shows significant changes in cellular morphology observed through fluorescent microscopy. The results validate the prepared quercetin conjugated Fe3O4 nanoparticles are promising anticancer agents for targeted drug delivery.

Shape evolution and size controlled synthesis of mesoporous hydroxyapatite nanostructures and their morphology dependent Pb(II) removal from waste water

Nanostructured hydroxyapatite (n-HAp) with tuneable morphology was successfully synthesized by varying the process parameters using a hydrothermal process with CTAB and PEG as surfactants. Systematic experiments were carried out to investigate the influences of process parameters on morphology. The morphology of n-HAp can be modified from nanorods to spheres by replacing the surfactant CTAB with PEG. The prepared materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM). The specific surface area (SSA) and pore size were determined by N2 adsorption–desorption isotherms. The obtained specific surface area of the nanorods is greater compared to the nanospheres of HAp. These nanostructures of HAp have been used for removal of Pb(II) ions from waste water. The kinetic mechanism was best described by a pseudo-second order model and the isotherm data were fitted well by the Langmuir isotherm and Freundlich model. The adsorption of Pb(II) was found to be 714.14 and 526.31 mg g−1 for the HAp nanorods and nanospheres respectively. The effect of pH, contact time and initial concentration of Pb(II) were also studied through batch experiments.

Synthesis of hierarchical WO3 nanostructured thin films with enhanced electrochromic performance for switchable smart windows

In our present work, hierarchical WO3 nanostructured thin films were successfully synthesized over pre-deposited seed layered FTO substrates through an electrodeposition method. By adjusting the pH values of the electrolyte, three different morphologies such as nanospindles (W1), nanoplatelets (W2), and hierarchical flower (W3) like nanoarray films have been obtained. The structural, surface, compositional and optical performance of the WO3 nanostructured thin films were characterized by XRD, FESEM, AFM, XPS, UV-VIS and detailed electrochromic functionality was examined by cyclic voltammetry (CV) at different applied potentials. Among the three nanostructured thin film electrodes (W1, W2, W3), W3 exhibits excellent larger optical contrast (79.90% at 550 nm), faster switching response time (tb = 3.82 s and tc = 5.05 s), and superior coloration efficiency (172.08 cm2 C−1) with stability over 2000 cycles. The synthesized WO3 electrode (W3) with flower morphology shows excellent reversibility of around 94.11% compared to the other nanostructures (W1 and W2) due to its enhanced crystallinity and high porosity. Our results suggest that flower-like WO3 nanostructured thin film electrodes will have a great impact on large scale production and make the material a promising candidate for fabrication of efficient electrochromic devices.

Edge-carboxylated graphene anchoring magnetite-hydroxyapatite nanocomposite for an efficient 4-nitrophenol sensor

The surface chemistry and physical properties of edge-carboxylated graphene (ECG) have to date been over looked in terms of understanding the real world practical applications. The accurate identification of each possible oxygenated group on the surface of the basal plane as well as the edges of ECG is necessary to understand the properties for their potential multifunctional applications. Herein, we report the use of a simple high energy ball mill to prepare a large scale production of ECG from natural graphite flakes through interaction with aspartic acid under solid conditions. These 2 dimensional ECG sheets were anchored with magnetite-hydroxyapatite (m-HAp) using a simple hydrothermal process. The prepared materials were systematically investigated by various analytical techniques to realize the structural, morphological, compositional and functional properties. These m-HAp dispersed ECG sheets can be further used to modify the glassy carbon electrode (GCE) for the sensitive and selective detection of 4-nitrophenol (4-NP) by cyclic voltammogram (CV) and differential pulsed voltammetry (DPV). The high specific surface area of 130 m2 g−1 for the m-HAp on ECG displays an excellent catalytic activity with reversible redox behavior of 4-NP. The modified electrode possesses a good detection limit and high sensitivity of 0.27 μM and 0.587 μA μM−1 cm−2, respectively, towards 4-NP, rendering practical industrial applications.

Hydrophilic polymer coated monodispersed Fe3O4 nanostructures and their cytotoxicity

Surface functionalized monodispersed Fe3O4 magnetic nanoparticles were synthesized by the polyol method. Surfactants were used to control size, shape and agglomeration of the magnetic nanoparticles during the preparation. The size of these nanoparticles was in the range of 10–30 nm as observed in transmission electron microscopy (TEM). The formation of monodispersed shapes was controlled by varying the surfactants without changing the reaction conditions. The x-ray diffraction (XRD) pattern validates the phase purity and cubic structure even after the addition of surfactants. The functional groups were observed from Fourier transform infrared (FTIR) spectroscopy analysis, confirming the surface modification with polymer molecules in the polyol medium. The saturation magnetization value decreases from 89 to 59 emu g−1 for the surfactant coated Fe3O4 nanoparticles and it also shows superparamagnetic behavior at room temperature. Cell viability rate and percentage of dead cells were accurately identified in human breast carcinoma cell lines using in vitro cell viability experiments, which confirms that pristine and surfactant coated Fe3O4 nanoparticles are non-toxic and can be used for biomedical applications.

Facile in situ growth of Fe3O4 nanoparticles on hydroxyapatite nanorods for pH dependent adsorption and controlled release of proteins

A general one-pot hydrothermal process was used to prepare different sizes of Fe3O4 nanoparticles dispersed on hydroxyapatite nanorods with CTAB as a surfactant. We also explore the role of hydrothermal reaction temperature and the surfactant on the crystallinity and formation of the rod like morphology of HAp. The obtained nanoparticles are systematically studied by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy (FESEM) with EDS for elemental mapping, transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) nitrogen sorptometry and vibrating sample magnetometry (VSM). The as-synthesized Fe3O4/HAp nanocomposites are further explored to study the pH dependent protein adsorption and controlled release using hemoglobin (Hb) as a model protein. A maximum protein adsorption (Qo) of 166.67 mg g−1 is observed for the Fe3O4/HAp nanocomposite and it increases to 200.07 mg g−1 upon increasing the concentration of Fe3O4 nanoparticles. The pH controlled sustained release process is observed for Hb at various pH values of 4.0, 7.4 and 9.0 in phosphate buffer saline (PBS) solution at room temperature. The maximum protein release was obtained for the lower pH values. The dosage dependent in vitro cytotoxicity assays are also performed to confirm biocompatibility of the prepared samples.

Highly monodispersed Ag embedded SiO2 nanostructured thin film for sensitive SERS substrate: growth, characterization and detection of dye molecules

Highly monodispersed Ag embedded SiO2 nanostructured thin films are synthesized and their sensitivity towards SERS investigated. The possible mechanism for the formation of a highly monodispersed SiO2 nanostructured thin film and its self-assembled nanogap with Ag are discussed. It is found that the architecture of Ag embedded SiO2 (Ag@SiO2) are drastically influenced by precursor concentration and the reaction time. The morphology and monodispersity of the silica thin film were confirmed using FESEM and AFM. The crystallinity and existence of Ag on SiO2 were confirmed using XRD and XPS. The substrate shows enhanced SERS efficiency due to the reduced size (around 15 nm) of the Ag nanoparticles and the nano gap of (below 3 nm) between SiO2 and Ag. Based on the FDTD (finite-difference time-domain) simulation, the creation of hotspots was confirmed for the obtained nanogap. The prepared thin film possesses strong Surface Plasmon Resonance (SPR) with widely tunable peaks between 407–430 nm in the UV visible spectrum. The Ag@SiO2 nanosphere-based SERS platform provides highly enhanced effects and reveals a reproducible enhancement (EF = 7.79 × 108) of R6G (Rhodamine 6G), allowing a detection limit from a 10–18 mol L−1 solution. The prepared substrate was also used to detect trace levels of melamine from a 10–8 mol L−1 solution.

Influence of Growth Parameters on the Formation of Hydroxyapatite (HAp) Nanostructures and Their Cell Viability Studies

Morphology controlled hydroxyapatite (HAp) nanostructures play a vital role in biomedical engineering, tissue regenerative medicine, biosensors, chemotherapeutic applications, environmental remediation, etc. The present work investigates the influence of temperature, pH and time on the growth of HAp nanostructures using a simple, cost effective and surfactant free chemical approach. The obtained HAp nanostructures were systematically investigated by analytical techniques such as XRD, FESEM, EDX, FTIR and Raman spectroscopy. The XRD analysis showed that the hexagonal structure of the hydroxyapatite and average crystallite size was estimated from this analysis. The electron microscopic analysis confirmed the different morphologies obtained by varying the synthesis parameters such as temperature, pH and time. The elemental composition was determined through EDS analysis. FTIR and Raman spectroscopic analysis confirmed the presence of functional groups and the purity and crystallinity of the samples. The biocompatibility and adhesion nature of samples was examined with mouse preosteoblast cells. The obtained results demonstrated good biocompatibility and excellent focal adhesion.

An in vitro analysis of H1N1 viral inhibition using polymer coated superparamagnetic Fe3O4 nanoparticles

Monodispersed Fe3O4 nanoparticles were prepared by a polyol assisted solvothermal method and their activity against H1N1 influenza A virus was studied. The present study also elucidates the influence of size, shape and surface properties of the pristine, as well as polymer coated, magnetite nanoparticles. X-ray diffraction and Fourier transform infrared spectroscopic observations confirm the high crystallinity and the polymer attachment with the magnetite nanoparticles. Transmission electron microscopy (TEM) images confirm the monodispersed nanoprisms and flower like morphologies of the magnetite nanoparticles. The superparamagnetic behavior and other magnetic properties were also studied by measuring the hysteresis loop using a vibrating sample magnetometer. The cell viability studies of the magnetite nanoparticles using a standard MTT assay confirm the non-toxic nature of the samples. Reverse transcription polymerase chain reaction (RT-PCR) analysis confirms the Fe3O4 nanoparticles inhibit influenza viral RNA synthesis in MDCK cells.