Bilayer and trilayer graphene with controlled stacking is emerging as one of the most promising candidates for post-silicon nanoelectronics. However, it is not yet possible to produce large quantities of bilayer or trilayer graphene with controlled stacking, as is required for many applications. Here, we demonstrate a solution-phase technique for the production of large-area, bilayer or trilayer graphene from graphite, with controlled stacking. The ionic compounds iodine chloride (ICl) or iodine bromide (IBr) intercalate the graphite starting material at every second or third layer, creating second- or third-stage controlled graphite intercolation compounds, respectively. The resulting solution dispersions are specifically enriched with bilayer or trilayer graphene, respectively. Because the process requires only mild sonication, it produces graphene flakes with areas as large as 50 µm(2). Moreover, the electronic properties of the flakes are superior to those achieved with other solution-based methods; for example, unannealed samples have resistivities as low as ∼1 kΩ and hole mobilities as high as ∼400 cm(2) V(-1) s(-1). The solution-based process is expected to allow high-throughput production, functionalization, and the transfer of samples to arbitrary substrates.

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Tungsten oxide (WO3) nanoparticles were synthesised by a simple chemical precipitation method in various media, such as acidic, basic and neutral. Hydrochloric acid and sodium hydroxide were used to maintain the different pH levels and tungstic acid was used as the precursor for the synthesis of tungsten oxide. The resultant nanoparticles were studied by different characterisation techniques. Powder X-ray diffraction shows that the average crystallite size of the WO3 is about 13 nm and exhibits stable orthorhombic phase for different pH values. Particle size and the surface morphology of the synthesised material were studied by TEM analysis. Chemical composition and surface area of the nanoparticles were studied by FTIR and BET measurements. Optical properties of the synthesised nanoparticles were studied by UV-Vis absorption and photoluminescence spectroscopy. Band gap (~2.7 eV) of the synthesised WO3 was investigated from the optical absorption spectra. At room temperature, a strong PL blue emission peak at ~440 nm was observed for the synthesised tungsten oxide nanomaterials. Thermal stability of the synthesised material was studied by TG/DTA analysis. Cyclic voltammetry illustrated the electrochemical response of the WO3 nanoparticles using KCl as electrolyte. The peak separation of 182 mV, 153 mV and 77 mV for the acidic, basic and neutral media were observed. Thus it was confirmed that, tungsten oxide has a low peak separation, a fast reaction rate and electron transfer rate in neutral medium.

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Ordered mesoporous carbon (OMC) is a promising material for oxygen reduction reaction (ORR) in fuel cells owing to its high surface area and more number of catalytic active sites. Herein, OMC was synthesized by hard template method, i. e., nanocasting of sacrificial silica template (SBA-15) and then the sacrificial template was abolished using three different etching chemicals namely, hydrofluoric acid (HF), sodium hydroxide (NaOH) and polyvinylidene fluoride (PVDF) respectively, in order to study the etching effect. The etched OMCs derived from the SBA-15 template was confirmed by various characterization techniques. In OMC, the porous nature, surface morphology and defect density changes with respect to etching chemicals were evidently determined. From the electrochemical studies, it has been concluded that the NaOH etched OMC showed higher electrocatalytic activity than others by exhibiting more positive onset (0.83 V), half-wave potential (0.75 V), high current density (3.3 mA/cm 2 ), Tafel slope (83 mV/ dec) and n-value (2.4). Eventually, the electrochemical impedance study (EIS) was performed to determine the charge transfer resistance (R ct ) of various etched OMCs and has been found that NaOH etched OMC shows the lowest R ct value due to the presence of more defective sites and result in enhancing oxygen adsorption during ORR.[a] V.

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