Milk-derived multi-fluorescent graphene quantum dot-based cancer theranostic system.

An economical green-chemistry approach was used for the synthesis of aqueous soluble graphene quantum dots (GQDs) from cow milk for simultaneous imaging and drug delivery in cancer. The GQDs synthesized using one-pot microwave-assisted heating were multi-fluorescent, spherical in shape having a lateral size of ca. 5nm. The role of processing parameters such as heating time and ionic strength showed a profound effect on photoluminescence properties of GQDs. The GQDs were N-doped and oxygen-rich as confirmed by X-ray photoelectron spectroscopy (XPS) analysis. Cysteamine hydrochloride (Cys) was used to attach an anti-cancer drug berberine hydrochloride (BHC) on GQDs forming GQDs@Cys-BHC complex with c.a. 88% drug loading efficiency. In vitro drug release was studied at the acidic-basic environment and drug kinetics was studied using pharmacokinetic statistical models. The GQDs were biocompatible on L929 cells whereas theranostic GQDs@Cys-BHC complex showed a potent cytotoxic effect on different cancerous cell line models: cervical cancer cell lines such as HeLa cells and breast cancer cells such as MDA-MB-231 confirmed by Trypan blue and MTT-based cytotoxic assays. Furthermore, multi-excitation based cellular bioimaging was demonstrated using confocal laser scanning microscopy (CLSM) and fluorescence microscopy using GQDs as well as GQDs@Cys-BHC complex. Thus, drug delivery (therapeutic) and bioimaging (diagnostic) properties of GQDs@Cys-BHC complex are thought to have a potential in vitro theranostic application in cancer therapy.

Camphor-mediated synthesis of carbon nanoparticles, graphitic shell encapsulated carbon nanocubes and carbon dots for bioimaging.

A green method for an efficient synthesis of water-soluble carbon nanoparticles (CNPs), graphitic shell encapsulated carbon nanocubes (CNCs), Carbon dots (CDs) using Camphor (Cinnamomum camphora) is demonstrated. Here, we describe a competent molecular fusion and fission route for step-wise synthesis of CDs. Camphor on acidification and carbonization forms CNPs, which on alkaline hydrolysis form CNCs that are encapsulated by thick graphitic layers and on further reduction by sodium borohydride yielded CDs. Though excitation wavelength dependent photoluminescence is observed in all the three carbon nanostructures, CDs possess enhanced photoluminescent properties due to more defective carbonaceous structures. The surface hydroxyl and carboxyl functional groups make them water soluble in nature. They possess excellent photostability, higher quantum yield, increased absorption, decreased cytotoxicity and hence can be utilized as a proficient bio imaging agent.

A green route towards highly photoluminescent and cytocompatible carbon dot synthesis and its separation using sucrose density gradient centrifugation.

An efficient, fast and green method for synthesis of Carbon dots (C-dots) using natural precursor Citrus limone under ultrasonic condition is demonstrated. Such as-synthesized C-dots were further purified using Sucrose density gradient centrifugation method (SDGC) which resulted in the separation of water-soluble, photo luminescent, monodispersed, highly photostable and chemically stable C-dot fractions (F1 and F2). They possess very small size (5-20 nm) as evidenced by High angle annular dark field-Scanning Transmission electron microscopy (HAADF-STEM) and very strong luminescence as shown by fluorescence spectroscopic studies. Cytocompatibility and bio imaging properties of both the fractions (F1 and F2) were then studied on Hep-2 cells. Quantum yield of F1 and F2 fraction was found to be 12.1 and 15 %, respectively.

Photocatalysis-assisted water filtration: using TiO2-coated vertically aligned multi-walled carbon nanotube array for removal of Escherichia coli O157:H7.

A porous ceramic was coated with vertically aligned multi-walled carbon nanotubes (MWCNTs) by spray pyrolysis. Titanium dioxide (TiO2) nanoparticles were then coated onto this densely aligned MWCNT. The presence of TiO2/MWCNT interfacial arrays was confirmed by X-ray diffraction (XRD), scanning electron microscope-energy dispersive analysis of X-ray (SEM-EDAX) and transmission electron microscope (TEM). This is a novel report in which water loaded with a most dreadful enterohemorrhagic pathogenic strain of Escherichia coli O157:H7 was filtered through TiO2/MWCNT coated porous ceramic filter and then analysed. Bacterial removal performance was found to be significantly lower in control i.e. plain porous ceramic (P<0.05) as compared to TiO2/MWCNT coated ceramic. The photocatalytic killing rate constant for TiO2-ceramic and MWCNT/TiO2-ceramic under fluorescent light was found be 1.45×10(-2) min(-1) and 2.23×10(-2) min(-1) respectively. Further, when I-V characteristics were performed for TiO2/MWCNT composite, it was corroborated that the current under light irradiation is comparatively higher than that in dark, thus proving it to be photocatalytically efficient system. The enhanced photocatalysis may be a contribution of increased surface area and charge transfer rate as a consequence of aligned MWCNT network.

Green synthesis of biocompatible carbon dots using aqueous extract of Trapa bispinosa peel.

We are reporting highly economical plant based method for the production of luminescent water soluble carbon dots (C-dot) using Indian water plant Trapa bispinosa peel extract without adding any external oxidizing agent at 90 °C. C-dots ranging from 5 to 10nm were found in the solution with a prominent green fluorescence under UV-light (λex=365 nm). UV-vis spectra recorded at different time intervals (30-120 min) displayed signature absorption of C-dots between 400 and 600 nm. Fluorescence spectra of the dispersion after 120 min of synthesis exhibited characteristic emission peaks of C-dots when excited at 350, 400, 450 and 500 nm. C-dots were further analyzed using X-ray diffraction (XRD), Raman Spectroscopy and Thermo-Gravimetric Analysis (TGA). Structure of the C-dots was found to be turbostratic when studied using XRD. C-dots synthesized by our method were found to be exceptionally biocompatible against MDCK cells.

Synthesis of beaded and entwined carbon nanofibers in Ni:Al alloy catalyst.

This paper reports two new types of carbon nanofibers synthesis by thermal decomposition of n-hexane in presence of Ni-Al alloy in hydrogen atmosphere at 1100 degrees C. One type is "beaded fibers" in which spherical carbon beads (approximately 1 microm) are regularly grown from outer surface of fibers (approximately 0.3 microm). The other new microstructure is "entwined fibers" in which multiple nanofibers of diameter approximately 100 nm grow self-entwined like a braid of hair. Both bead-fiber bonding (in beaded fibers) and fiber-fiber interaction (in entwined fibers) are strong to be detached/unfolded by 30-min ultrasonication.

Y-junction multibranched carbon nanofibers.

Multibranched carbon nanofiber (CNF) is produced by a thermal chemical vapor deposition method using camphor as precursor. Nickel and cobalt catalyst was deposited on silicon substrate by e-beam evaporation and used as substrate for the growth of carbon nanomaterials. Branched carbon nanofibers were grown on the nickel thin film at 900 degrees C, whereas spherical carbon beads formed on the cobalt thin film. These fibers followed base growth mechanism devoid of any catalyst particle at the tip of fibers.

Application of the Taguchi analytical method for optimization of effective parameters of the chemical vapor deposition process controlling the production of nanotubes/nanobeads.

Seven variable parameters of the chemical vapor deposition system have been optimized with the help of the Taguchi analytical method for getting a desired product, e.g., carbon nanotubes or carbon nanobeads. It is observed that almost all selected parameters influence the growth of carbon nanotubes. However, among them, the nature of precursor (racemic, R or Technical grade camphor) and the carrier gas (hydrogen, argon and mixture of argon/hydrogen) seem to be more important parameters affecting the growth of carbon nanotubes. Whereas, for the growth of nanobeads, out of seven parameters, only two, i.e., catalyst (powder of iron, cobalt, and nickel) and temperature (1023 K, 1123 K, and 1273 K), are the most influential parameters. Systematic defects or islands on the substrate surface enhance nucleation of novel carbon materials. Quantitative contributions of process parameters as well as optimum factor levels are obtained by performing analysis of variance (ANOVA) and analysis of mean (ANOM), respectively.

Application of carbon nanomaterial as a microwave absorber.

Microwave absorption (8 GHz to 12 GHz) studies have been made with carbon nanomaterials for the first time. Carbon nanomaterials are synthesized by the pyrolysis of camphor. It is observed that film of carbon prepared under certain synthetic condition, can absorb microwave of either some specific wavelengths e.g., 9.5 GHz and 11.5 GHz or full range from 8-12 GHz to the extent of 20 dB depending upon their preparation condition. Carbon nanobeads seems to absorb the microwave in the range of 8-12 GHz.

Nano-octopus: a new form of branching carbon nanofiber.

A new multibranched octopus-type structure of carbon nanofibers is synthesized from a natural precursor, camphor, by a thermal chemical vapor deposition technique. An alloy of Cu:Ni catalyst is prepared by electrochemically coating nickel on a copper sheet, with nickel sulfate as an electrolyte, and heating that nickel-coated copper sheet to a higher temperature. Deposition of carbon on these substrates leads to the formation of a branched nanostructure in the temperature range of 923 K to 1023 K. The fiber diameter increases from 30 nm to 250 nm with increasing pyrolysis temperature. Detailed morphology and the internal structure of these fibers are studied by scanning and transmission electron microscopy.