Graphene derivatives show extraordinary mechanical, optical, and electronic properties, which gave rise to high scientific interest and huge potential for a variety of applications. Raman spectroscopy is a versatile tool to characterize and identify the chemical and physical properties of graphene derivatives. We describe essential Raman scattering processes of the first-(G) and second-order (D, G*, 2D, G + D, 2G) modes in GO and r-GO prepared by a high-pressure growth approach. In r-GO, the linewidth is broadened and slightly red-shifted in all the bands, in comparison with GO because of strain development during the high-pressure growth approach (hydrothermal process) as a result of removal of oxygen functionalities. A normalized intensity ratio (ID/IG) for GO and r-GO is discussed. In both the samples, ID/IG is high which indicates the small size of GO and r-GO and the presence of turbostratic carbon and disordered structures. The peak fitting of the 2D band exhibits four Lorentzian peaks, and the intensity of the 2D band with respect to the G band is strongly reduced, which confirms that we have successfully synthesized bilayer/ trilayer GO and r-GO. For GO and r-GO, the crystallite size (La) is calculated. The existence of the 2D band confirms that we have successfully synthesized high-quality GO and r-GO.

Reduced graphene oxide quantum dots (rGOQDTs) play a vital role in a variety of biological, optoelectronics, and environmental applications. The quality of 0D nanodots is compromised when they are cut from big 2D nanosheets. As a result, it is necessary to maintain a balance between quality and yield. Here, we developed a two-step hydrothermal process for producing nanocrystalline rGOQDTs by employing graphene oxide (GO) as an initial precursor. UV-Visible spectroscopy was used to explore the optical properties of rGOQDTs. XRD, Raman, and FTIR spectroscopic experiments were performed to better understand the crystalline and chemical properties and composition of rGOQDTs. The nanocrystalline rGOQDTs have an average crystallite size of 1.67[Formula: see text]nm. Using GO as an initial precursor implies a simple two-step approach for producing nanocrystalline rGOQDTs in a low-cost, highly efficient, and scalable manner.

Cooling sector is highly dominated by conventional vapour compression system which have negative effect on environment. The solar rankine cooling system which runs on renewable energy and with environmental working fluids. Solar rankine system consists of two cycles, one is power cycle and another is cooling cycle. Power cycle is either solar rankine cycle or organic rankine cycle(ORC) and cooling cycle is vapour cooling cycle(VCC). To optimize the system there are some modification discussed in this paper. Solar heat source are widely available, so solar energy as a heat source for generator is an good option. This paper covers the basic rankine cooling system and modification in rankine cooling system to enhance the performance of system. But this cooling system still needed lots of work and research to make it as an alternative to conventional cooling system.