A comprehensive review on the synthesis of PANI nanocomposites and their applications as gas sensors and biosensors has been presented.

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This work represents a state-of-the-art technique developed for the preparation of graphene from graphite-metal electrodes by the arc-discharge method carried out in a continuous flow of water. Because of continuous arcing of graphite-metal electrodes, the graphene sheets were observed in water with uniformity and little damage. These nanosheets were subjected to various purification steps such as acid treatment, oxidation, water washing, centrifugation, and drying. The pure graphene sheets were analyzed using Raman spectrophotometry, x-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and tunneling electron microscopy (TEM). Peaks of Raman spectra were recorded at (1300-1400 cm À1 ) and (1500-1600 cm À1 ) for weak D-band and strong G-band, respectively. The XRD pattern showed 85.6% crystallinity of pure graphite, whereas pure graphene was 66.4% crystalline. TEM and FE-SEM micrographs revealed that graphene sheets were overlapped to each other and layer-by-layer formation was also observed. Beside this research work, we also reviewed recent developments of graphene and related nanomaterials along with their preparations, properties, functionalizations, and potential applications.

A nanosize CaCO 3 filler was synthesized by an in situ deposition technique, and its size was confirmed by X-ray diffraction. CaCO 3 was prepared in three different sizes (21, 15, and 9 nm). Styrene-butadiene rubber (SBR) was filled with 2-10 wt % nano-CaCO 3 with 2% linseed oil as an extender. Nano-CaCO 3 -SBR rubber composites were compounded on a two-roll mill and molded on a compression-molding machine. Properties such as the specific gravity, swelling index, hardness, tensile strength, abrasion resistance, modulus at 300% elongation, flame retardancy, and elongation at break were measured. Because of the reduction in the nanosize of CaCO 3 , drastic improvements in the mechanical properties were found. The size of 9 nm showed the highest increase in the tensile strength (3.89 MPa) in comparison with commercial CaCO 3 and the two other sizes of nano-CaCO 3 up to an 8 wt % loading in SBR. The elongation at break also increased up to 824% for the 9-nm size in comparison with commercial CaCO 3 and the two other sizes of nano-CaCO 3 . Also, these results were compared with nano-CaCO 3 -filled SBR without linseed oil as an extender. The modulus at 300% elongation, hardness, specific gravity, and flame-retarding properties increased with a reduction in the nanosize with linseed oil as an extender, which helped with the uniform dispersion of nano-CaCO 3 in the rubber matrix.