Gururaj M. Neelgund

Hydroxyapatite grafted carbon nanotubes and graphene nanosheets: promising bone implant materials.

In the present study, hydroxyapatite (HA) was successfully grafted to carboxylated carbon nanotubes (CNTs) and graphene nanosheets. The HA grafted CNTs and HA-graphene nanosheets were characterized using FT-IR, TGA, SEM and X-ray diffraction. The HA grafted CNTs and graphene nanosheets (CNTs-HA and Gr-HA) were further used to examine the proliferation and differentiation rate of temperature-sensitive human fetal osteoblastic cell line (hFOB 1.19). Total protein assays and western blot analysis of osteocalcin expression were used as indicators of cell proliferation and differentiation. Results indicated that hFOB 1.19 cells proliferate and differentiate well in treatment media containing CNTs-HA and graphene-HA. Both CNTs-HA and graphene-HA could be promising nanomaterials for use as scaffolds in bone tissue engineering.

Antimicrobial activity of CdS and Ag2S quantum dots immobilized on poly(amidoamine) grafted carbon nanotubes.

Herein we report the design of antimicrobial nanohybrids, f-MWCNTs-CdS and f-MWCNTs-Ag(2)S developed by covalent grafting of cationic hyperbranched dendritic polyamidoamine (PAMAM) onto multiwalled carbon nanotubes (MWCNTs) and successive deposition of CdS and Ag(2)S quantum dots (QDs). The CdS and Ag(2)S QDs were in situ deposited on PAMAM grafted MWCNTs instead of anchoring the pre-synthesized QDs. The fourth generation, amine terminated hyperbranched PAMAM was grafted on MWCNTs, which was achieved through repetitive reactions of Michael addition of methylmethacrylate to the surface amino groups and amidation of terminal ester groups with ethylenediamine. The covalent grafting of PAMAM onto MWCNTs and the consecutive conjugation of CdS and Ag(2)S QDs were characterized using Fourier transform infrared spectroscopy, elemental analysis, powder X-ray diffraction, Raman spectroscopy, transmission electron microscopy and energy dispersive spectroscopy. The antibacterial activity of f-MWCNTs-CdS and f-MWCNTs-Ag(2)S nanohybrids was evaluated against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus and the results were compared with the activity of carboxylated MWCNTs, PAMAM grafted MWCNTs, PAMAM dendrimer, and CdS and Ag(2)S QDs. It was found that the germicidal action of MWCNTs was enhanced by grafting of PAMAM, which was further improved with immobilization of CdS and Ag(2)S QDs.

ZnO and cobalt phthalocyanine hybridized graphene: efficient photocatalysts for degradation of rhodamine B

A novel method has been developed to synthesize graphene-ZnO composite as a highly efficient catalyst by reduction of graphite oxide and in situ deposition of ZnO nanoparticles by chemical reduction reaction. The graphene-ZnO catalyst is capable of complete degradation of rhodamine B under exposure to natural sunlight. Further, the catalytic efficiency of graphene-ZnO catalyst was enhanced by sensitizing with cobalt phthalocyanine. The formation of graphene-ZnO photocatalyst and its further sensitization with cobalt phthalocyanine was characterized using UV-vis, ATR-IR and Raman spectroscopy, powder XRD and thermogravimetric analysis. The morphology of both graphene-ZnO and graphene-ZnO-CoPC catalysts was analyzed using scanning and transmission electron microscopes.

Adsorption of lead over graphite oxide.

The adsorption efficiency and kinetics of removal of lead in presence of graphite oxide (GO) was determined using the Atomic Absorption Spectrophotometer (AAS). The GO was prepared by the chemical oxidation of graphite and characterized using FTIR, SEM, TGA and XRD. The adsorption efficiency of GO for the solution containing 50, 100 and 150 ppm of Pb(2+) was found to be 98%, 91% and 71% respectively. The adsorption ability of GO was found to be higher than graphite. Therefore, the oxidation of activated carbon in removal of heavy metals may be a viable option to reduce pollution in portable water.

A facile hydrothermal approach for construction of carbon coating on TiO2 nanoparticles

Herein a facile hydrothermal approach is used to construct carbon coated TiO2 nanoparticles employing dextrose as the source of carbon. The procedure is operated at a low temperature of 200 °C. Fourier infrared spectroscopy demonstrated the successful coating of carbon on TiO2 nanoparticles. The phase composition of TiO2 and carbon coated TiO2 nanoparticles were studied using X-ray diffraction and the surface morphology was analyzed by scanning and transmission electron microscopy. The existence of carbon coating on TiO2 nanoparticles was revealed by thermogravimetric analysis through different thermograms exhibited for TiO2 and carbon coated TiO2 nanoparticles. The reported method offers a simple and efficient approach for production of carbon coated TiO2 nanoparticles.

Influence of carbon nanotubes and graphene nanosheets on photothermal effect of hydroxyapatite.

Herein we present a successful strategy for enhancement of photothermal efficiency of hydroxyapatite (HAP) by its conjugation with carbon nanotubes (CNTs) and graphene nanosheets (GR). Owing to excellent biocompatibility with human body and its non-toxicity, implementation of HAP based nanomaterials in photothermal therapy (PTT) provides non-replaceable benefits over PTE agents. Therefore, in this report, it has been experimentally exploited that the photothermal effect (PTE) of HAP has significantly improved by its assembly with CNTs and GR. It is found that the type of carbon nanomaterial used to conjugate with HAP has influence on its PTE in such a way that the photothermal efficiency of GR-HAP was higher than CNTs-COOH-HAP under exposure to 980nm near-infrared (NIR) laser. The temperature attained by aqueous dispersions of both CNTs-COOH-HAP and GR-HAP after illuminating to NIR radiations for 7min was found to be above 50°C, which is beyond the temperature tolerance of cancer cells. So that the rise in temperature shown by both CNTs-COOH-HAP and GR-HAP is enough to induce the death of tumoral or cancerous cells. Overall, this approach in modality of HAP with CNTs and GR provide a great potential for development of future nontoxic PTE agents.

Synthesis and characterization of reduced graphite oxide–polymer composites and their application in adsorption of lead

Herein, we report the in situ polymerization of 1,5-diaminonaphthalene (15DAN) and 1,4-diaminoanthraquinone (14DAA) on the surface of reduced graphite oxide (RGO). Synthesized RGO-P15DAN and RGO-P14DAA were characterized by FTIR, Raman, SEM, TGA and XRD. The adsorption capacity and adsorptivity of the synthesized composites were investigated by Atomic Absorption Spectroscopy (AAS) using 100 ppm aqueous solution of Pb(2+) ions. Further, we compared the results of the composites with those of poly 1,5-(diaminonaphthalene) (P15DAN), poly 1,4-(diaminoanthraquinone) (P14DAA), RGO, graphite oxide (GO) and graphite. Among the tested adsorbents, RGO-P15DAN demonstrated the high adsorptivity.

Synthesis, characterization and stability of chitosan and poly(methyl methacrylate) grafted carbon nanotubes

The single walled carbon nanotubes (CNTs) were effectively functionalized through grafting with chitosan (CTS) and poly(methyl methacrylate) (PMMA). Prior to grafting reaction, the carboxylated SWNCTs (SWNCTs-COOH) were obtained by treating pristine CNTs with a mixture of 3:1 (v/v) H(2)SO(4) and HNO(3), and the successive treatment of SWNCTs-COOH with SOCl(2) yielded the acylated CNTs (CNTs-COCl). The functionalized derivatives of CNTs were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, atomic force microscopy, scanning electron microscopy and transmission electron microscopy. Both CTS and PMMA grafted CNTs showed better dispersability in acetic acid and tetrahydrofuran, in addition to higher stability in solution.

Photothermal effect: an important aspect for the enhancement of photocatalytic activity under illumination by NIR radiation

A key auxiliary role of photothermal effect (PTE) in the enhancement of photocatalytic activity under illumination to near-infrared (NIR) radiations has been experimentally revealed. It was found that the photoexcitation of electrons, required for the process of photocatalysis does not occur in presence of NIR radiations alone without the support of both UV and visible radiations. Herein, a binary heterogeneous nanophotocatalyst, GR-ZnO was fabricated by a novel approach using hydrothermal process. In which ZnO nanotrapezoids were deposited over the surfaces of graphene nanosheets. In the reported unique approach, reduction of graphene oxide to graphene has been accomplished using water by an entirely alternative mechanism compared to traditional reduction processes those employ the hazardous reducing agents. Thus produced GR-ZnO photocatalyst has exhibited the excellence in rapid degradation of industrially voluntarily employing perilous dye, methyl orange. It is explored that PTE is mainly responsible for the rapid degradation of methyl orange transpired under illumination to NIR laser. Further, it has been established that PTE could not emerge with NIR radiations alone without the support of both UV and visible radiations. In consideration of its importance, PTE of GR-ZnO nanocatalyst has been revealed and compared with its individual components, viz., graphene and ZnO. Moreover, the photothermal conversion efficiency of GR-ZnO nanocatalyst was evaluated. Overall, the excellent catalytic activity found in GR-ZnO nanocatalyst was accounted for its decreased band gap, transpired by hybridization of ZnO with graphene could efficiently prevent the recombination of photo-generated charge carriers. In addition, admired catalytic activity of GR-ZnO nanocatalyst was attributed to improved optical absorption and enhancement in the adsorption affinity to methyl orange molecules.

Advancement in Photothermal Effect of Carbon Nanotubes by Grafting of Poly(amidoamine) and Deposition of CdS Nanocrystallites

A robust, near-infrared (NIR) active photothermal agent, CNTs-PAMAM/G4-CdS, is designed by covalent grafting of fourth generation poly(amidoamine) (PAMAM) to carbon nanotubes (CNTs) and successive deposition of cadmium sulfide (CdS) nanocrystallites. The systematic advancement in photothermal effect of CNTs was achieved by grafting of first, second, third, and fourth generation PAMAM through the repeated process of Michaels addition. The subsequent deposition of CdS nanocrystallites over fourth generation PAMAM grafted CNTs has further improved the photothermal effect (PTE) of CNTs. The photothermal effect of CNTs-PAMAM/G4-CdS was accessed by illuminating with 980 nm NIR laser. During measurement of PTE, maximum temperature attained by CNTs-PAMAM/G4-CdS was 64.1 °C which far exceeds the survival temperature of cancer cells. The photothermal conversion efficiency estimated for CNTs-PAMAM/G4-CdS was 32%, which is higher than the value reported for popular gold and copper based photothermal agents. Apart from its outstanding photothermal effect, CNTs-PAMAM/G4-CdS possessed excellence in both antiphoto-bleaching and antiphoto-corrosiveness.