Indian Institute of Technology Guwahati

About: Indian Institute of Technology Guwahati is a education organization based out in Guwahati, Assam, India. It is known for research contribution in the topics: Adsorption & Catalysis. The organization has 6933 authors who have published 17102 publications receiving 257351 citations.

Formation mechanism of graphene quantum dots and their edge state conversion probed by photoluminescence and Raman spectroscopy

Abstract: We investigate the formation mechanism of graphene quantum dots (GQDs) from a graphene oxide (GO) precursor and study the inter-conversion of edge states during thermal annealing of GQDs through various microscopic and spectroscopic tools. Monitoring the early stages of growth of GQDs reveals that the in-plane epoxy (C–O–C) functional groups attached at the defect sites essentially cut the oxidized GOs into small pieces of GQDs during the hydrothermal reaction. By conducting a series of controlled annealing experiments under oxygen and hydrogen gas environments, we monitor and quantify the inter-conversion of edge states and functional groups in GQDs from Raman and photoluminescence (PL) studies. The deconvolution of the Raman spectrum allowed us to monitor the evolution of new Raman bands at ∼1260 and ∼1438 cm−1, which are assigned to the edge functional groups. Through the fitting of the PL spectra and a quantitative analysis of integrated intensities of PL, we unambiguously assign the blue PL emission bands at ∼407 and ∼440 nm to zigzag and armchair free edge states in GQDs, respectively, for the first time. On the other hand, the green emission bands at ∼490 and ∼530 nm are attributed to COOH/C–OH and CO/C–O edge functional groups, respectively. Our conclusions are corroborated by XPS and FTIR spectroscopic analyses of the as-grown and annealed GQDs.

A comprehensive review on the application of emulsions as an alternative fuel for diesel engines

Abstract: Diesel engine is one of the most efficient and reliable energy conversion devices available till date. During the beginning of twentieth century, the plenty of low cost diesel have engrossed people to run diesel engines with diesel. However, after more than a century, the scenario has just been reversed. The frantic use of diesel has now led to a situation where the global fossil diesel storage may last merely for a few decades. As a result, the price of diesel has reached to a momentous height. This is coupled with the serious environmental pollution created by its burning. These facts have stimulated researchers around the globe to search for suitable, sustainable, renewable, and cheap alternative to diesel fuel, which is environmentally benign too. Among many solutions proposed, emulsified fuel is one of them, which comes under the fuel modification techniques. In this method, two or more mutually immiscible fluids are mixed together, which is expected to run a diesel engine and replicate its performance, combustion and emission characteristics. The most explored emulsified fuel in a diesel engine is the water in diesel emulsion. Alongside, the emulsions prepared with animal fat, methanol, ethanol and few studies with emulsified biodiesels have also been reported. The present paper attempts to accumulate most of these studies under a single shed. Efforts have been made to analyze the numerous studies on emulsified fuel both qualitatively and quantitatively. The paper starts giving an introduction to the types of emulsion, their characteristics, and the criteria of preparing an effective emulsion, followed by the review of their performance, combustion, emission and spray characteristics when run in a diesel engine. At the end, some of the significant points have been addressed based on the extensive review on the state-of-the-art literature, followed by some possibilities of future research.