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The water molecules associated with coal play a significant role in spontaneous ignition and combustion of coal. This paper deals with studies to evaluate the impact of moisture content on crossing point temperature (CPT) and ignition point temperature (IPT) of some low-rank coal and lignite after various stages of drying. Experimental data suggest (i) existence of critical moisture content value determining the propensity of a particular coal toward self-heating and (ii) content of moisture and nature of oxygen-bearing functional groups to be the most influencing factors in self-heating. The auto-oxidation cum self-heating characteristics of coal become more conducive with increase in the ratio of quantity of hydroxyl to carboxyl functional groups. The FTIR studies further corroborate that the initial stages of auto-oxidation cum self-heating occur presumably at the surface of the coal. [ABSTRACT FROM AUTHOR]

By fluorescence spectroscopy it has been established that coal derived asphaltene (CDA) forms aggregates in CCl4medium. The new feature of this compound is that even before aggregate formation it can incorporate water molecules and the critical aggregation concentration (CAC) in nonaqueous medium increases with increase in ω (= water:CDA mole ratio). The fluorescence spectroscopic determination of the equilibrium constant (K) of the molecular complex of [60] fullerenes with CDA in carbon tetrachloride medium has revealed thatKincreases on addition of microquantities of water. This observation has been rationalized by assuming that the nitrogenatoms at one end of CDA molecules attach themselves to the water micropool and thus producing a different conformation with a wider distance at the other end. This pre-organization further facilitates inclusion. By utilizing fluorescence variation of [60]fullerene/CDA complex in CCl4as continuous medium with change in ω a critical ω (=5) has been found. The formation of CDA/[60]fullerene complex has also been established by NMR spectroscopy. [ABSTRACT FROM PUBLISHER]

Herein, blue-emitting carbon nanoparticles (CNPs) were synthesized using the Madhuca longifolia flower for the highly selective and sensitive detection of Cr 6+ ions in aqueous media using a simple, green, and cost-effective approach, and computational experiments were also performed. The prepared CNPs were well-dispersed in water with an average diameter of 12 nm and functionalized with carbonyl, hydroxyl and carboxylic acid groups. The decrease in the fluorescence intensity of the CNPs with an increase in the content of Cr 6+ provided an important signal for the sensitive and selective detection of Cr 6+ in aqueous media. The limit of detection for Cr 6+ in an aqueous medium was found to be 103 ppb, which is more sensitive in comparison with the previously reported study. Furthermore, the validation of the proposed higher sensing feature and more selective nature of the CNPs towards Cr 6+ was also explained using an in silico approach. The results from the theoretical calculations based on the DFT approach demonstrated that the binding energy (BE) of the CNPs with three transition metal (TM) cations (Cr 6+ , Fe 3+ , and Hg 2+ ) follows the order of Cr 6+ > Fe 3+ > Hg 2+ , where the Cr 6+ TM cation associated with the CNPs possesses the highest valence state, showing the highest sensing feature and highest selectivity among the investigated ions, as expected. The metal ions associated with the CNPs having a higher charge and a smaller radius indicated a higher BE and larger degree of deformation of the CNPs. Moreover, to achieve new insights into the structural, stability/energetics, and electronic features, some useful tools, such as NCI-plot, HOMO-LUMO gap, MESP, and QTAIM analysis were employed, which facilitated noteworthy outcomes., Competing Interests: The authors declare that they have no conflict of interest., (This journal is © The Royal Society of Chemistry.)