Innovative breakthroughs in fundamental research and industrial applications of graphene material have made its mass and low-cost production as a necessary step toward its real world applications. This one-atom thick crystal of carbon, gathers a set of unique physico-chemical properties, ranging from its extreme mechanical behavior to its exceptional electrical and thermal conductivities, which are making graphene as a serious alternative to replace many conventional materials for various applications. In this review paper, we highlight the most important experimental results on the synthesis of graphene material, its emerging properties with reference to its smart applications. We discuss the possibility to successfully integrating graphene directly into device, enabling thereby the realization of a wide range of applications, including actuation, photovoltaic, thermoelectricity, shape memory, self-healing, electrorheology, and space missions. The future outlook of graphene is also considered and discussed.

Few-layer graphene (FLG) is grown on copper and nickel substrates at high rates using a novel flame synthesis method in open-atmosphere environments. Transmittance and resistance properties of the transferred films are similar to those grown by other methods, but the concentration of oxygen, as assessed by XPS, is actually less than that for CVD-grown graphene under near vacuum conditions. The method involves utilizing a multi-element inverse-diffusionflame burner, where post-flame species and temperatures are radially-uniform upon deposition at a substrate. Advantages of the flame synthesis method are scalability for large-area surface coverage, increased growth rates, high purity and yield, continuous processing, and reduced costs due to efficient use of fuel as both heat source and reagent. Additionally, by adjusting local growth conditions, other carbon nanostructures (i.e. nanotubes) are readily synthesized.

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Abstract:Titanium dioxide (TiO2) nanoparticles containing iron, silicon, and vanadium are synthesized using multiple diffusion flames. The growth of carbon-coated (C-TiO2), carbon-coated with iron oxide (Fe/C-TiO2), silica-coated (Si-TiO2) and vanadiumdoped (V-TiO2) TiO2 nanoparticles are demonstrated using a single-step process. Hydrogen, oxygen, and argon are utilized to establish the flames, with titanium tetraisopropoxide (TTIP) as the precursor for TiO¬2. For the growth of Fe/C-TiO2 nanoparticles, TTIP is mixed with xylene and ferrocene. While for the growth of Si-TiO2 and V-TiO2, TTIP is mixed with hexamethyldisiloxane (HMDSO) and vanadium (V) oxytriisopropoxide, respectively. The synthesized nanoparticles are characterized using high-resolution transmission electron microscopy (HRTEM) with energy filtered TEM for elemental mapping (of Si, C, O, and Ti), x-ray diffraction (XRD), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), nitrogen adsorption BET surface area analysis, and thermogravimetric analysis. Anatase is the dominant phase for the C-TiO2, Fe/C-TiO2, and Si-TiO2 nanoparticles, whereas rutile is the dominant phase for the V-TiO2 nanoparticles. For C-TiO2 and Fe/C-TiO2, the nanoparticles are coated with about 3-5 nm thickness of carbon. The iron based TiO2 nanoparticles significantly improve the catalytic oxidation of carbon, where complete oxidation of carbon occurs at a temperature of 470oC (with iron) compared to 610oC (without iron). With regards to Si-TiO2 nanoparticles, a uniform coating of 3 to 8 nm of silicon dioxide is observed around the TiO2 particles. This coating mainly occurs due to variance in the chemical reaction rates of the precursors. Finally, with regards to V-TiO2, vanadium is doped within the TiO2 nanoparticles as visualized by HRTEM and XPS further confirms the formation of V4+ and V5+ oxidation states.Response to Reviewers: Reviewer #1: Powered by Editorial Manager® and ProduXion Manager® from Aries Systems CorporationThank you for the comments. Below please find our response.Response to General Comments:All the papers listed have been included within the manuscript as well as any relevant discussion. Please see the highlighted parts within the manuscript."In my opinion, the study of carbon oxidation kinetics is the novel part of this work" thank you for the comment, we have carried out additional experiments to further validate the carbon oxidation of the Fe-TiO2 nanoparticles.Individual Comments:1-We have collected 60-80 mg for the silica and vanadia TiO2 cases and this amount increased to ~120 mg for the carbon containing samples. Precursor was injected to the system using a syringe pump with the flowrate of 20 ml/hr. All gaseous flowrates were controlled using calibrated MKS mass flow controllers with the following flowrates: Fuel: hydrogen: 0.77 SLPM Oxidizer: Oxygen: 2.63 SLPM + Argon: 7.5 SLPM Carrier gas: Argon: 0.22 SLPM or Ethylene: 0.234 SLPM All the above details have been added to the modified manuscript.2-The temperature of the burner has been measu...

A novel double-slit curved wall-jet (DS-CWJ) burner was proposed and utilized for flame synthesis. This burner was comprised of double curved wall-jet nozzles with coaxial slits; the inner slit was for the delivery of titanium tetraisopropoxide (TTIP) precursor while the outer one was to supply premixed fuel/air mixture of ethylene (C 2 H 4 ) or propane (C 3 H 8 ). This configuration enabled rapid mixing between the precursor and reactants along the curved surface and inside the recirculation zone of the burner. Particle growth of titanium dioxide (TiO 2 ) nanoparticles and their phases was investigated with varying equivalence ratio and Reynolds number. Flow field and flame structure were measured using particle image velocimetry (PIV) and OH planar laserinduced fluorescence (PLIF) techniques, respectively. The nanoparticles were characterized using high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and nitrogen adsorption Brunauer-Emmett-Teller (BET) for surface area analysis. The flow field consisted of a wall-jet region leading to a recirculation zone, an interaction jet region, followed by a merged-jet region. The DS-CWJ burner revealed appreciable mixing characteristics between the precursor and combustion gases near the nozzle regions, with a slight increase in the axial velocity due to the precursor injection. The precursor supply had a negligible effect on the flame structure. The burner produced a reasonably uniform size (13-18 nm) nanoparticles with a high BET surface area (>100 m 2 /g). The phase of TiO 2 nanoparticles was mainly dependent on the equivalence ratio and fuel type, which impact flame height, heat release rate, and high temperature residence time of the precursor vapor. For ethylene flames, the anatase content increased with the equivalence ratio, whereas it decreased in the case of propane flames. The synthesized TiO 2 nanoparticles exhibited high crystallinity and the anatase phase was dominant at high equivalence ratios (ϕ > 1.6) for C 2 H 4 , and at low equivalence ratios (ϕ < 1.3) for the C 3 H 8 flame. ARTICLE HISTORY

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