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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...

A new simple 3-in-1 multi-response thiosemicarbazone-based chemosensor has been synthesized and characterized. The probe not only exhibited high sensitivity towards the most familiar and abundant group 12 metal ions, viz., Zn2+, Cd2+ and Hg2+, in MeCN–H2O (1 : 1, v/v) medium but also can efficiently distinguish them through significant changes in their absorption and emission spectral behavior. The selectivity response was found to follow the order Hg2+, Cd2+, Zn2+ due to the different degrees of stability of their respective complexes, which was further established by TDDFT calculations and interference studies. The binding affinities of the probe towards these metal ions were investigated by absorption, fluorescence emission, fluorescence lifetime, mass spectral and 1H NMR spectral measurements. The effects of solvent polarity on the probe molecule were also examined. Due to the observation of different binding affinities and the ensuing significant changes in absorbance at different wavelengths by a combination of different inputs, L can be judiciously applied for the construction of some basic logic gates (AND, OR, NOT, IMPLICATION and INHIBIT).

Steady state fluorescence spectroscopic technique has been used to investigate the aggregation of coal derived asphaltene (CDA) sourced from Lodna Coke Plant situated at Dhanbad, India. The emission spectra of CDA provide information regarding the various stages of onset of aggregation in carbon tetrachloride medium. Almost similar results have also been inferred from the analysis of corresponding excitation spectra. It has been observed that the onset of aggregation of CDA occurs at concentration beyond a concentration of 10 mg L−1. Studies indicate the formation of a trimer at this concentration range. The association constant (K) for the trimer formation has also been evaluated from the spectroscopic data.

Both petroleum and coal derived asphaltene finds important place on the present research areas of hydrocarbon based liquid and solid fuels. It has earned a name of ‘unwanted’ fame for its deleterious impacts arising mainly due to its self aggregational phenomenon. Over the period of time the asphaltene aggregation has been seriously investigated worldwide even at the molecular scale. Besides several methods, the spectroscopic findings (UV Vis and Fluorescence), in this regard, contribute to substantial meaningful data. The major spectroscopic researches on the aggregation of asphaltene over the last ten years have been reviewed in this present study. A brief discussion on the asphaltene molecular structure and molecular weight also comes as a prelude. Asphaltenes derived from both petroleum and coal have been considered.

The structure of coal derived asphaltene (CDA) proposed by Mullins et al has been corroborated through theoretical and experimental examination by the virtue of its electron donor property. Here, o-chloranil has been used as an electron acceptor. Investigation of o-chloranil/CDA complex in gas phase has been performed by density functional theory (DFT) methods. The Charge transfer (CT) transition energy of the complex in gas phase was calculated by the time-dependent density function theory (TD-DFT) using the ground state optimized geometry at the respective levels of theory. For this, the three semi empirical methods AM1, PM3 and PM3MM were computed under the MPW1PW91, B3PW91, PBE1PBE, BPV86 and RCIS formalism. It is found that the two formalisms MPW1PW91 and PBEPBE under PM3 and PM3MM reproduced values close to the experimental one. However, all of them provide lower charge transfer (CT) transition energy values than that has been experimentally determined. Experimentally, FTIR spectra of the donor, acceptor and the complex further supported the understanding of complex formation and demonstrated close similarity with the theoretically determined CDA frequencies. These findings support the validity of the CDA structure to an extent.

Graphene decorated with Fe clusters is proposed to be a possible alternative catalyst for the hydrogenation and dehydrogenation reactions of MgH2. In particular, graphene decorated with Fe clusters is effective for both hydrogenation and dehydrogenation processes of MgH2. The change in enthalpy and entropy values of hydrogen absorption determined for MgH2 with 5 wt% graphene decorated with Fe clusters is −50.4 ± 2.9 kJ per mole of H2 and 99.8 ± 5.2 J K−1 per mole of H2, respectively. This is significantly lower than those for well-established metal catalysts and nano-interfacial confined MgH2. Moreover, the graphene decorated with Fe clusters facilitates the fast rehydrogenation kinetics of MgH2, which reabsorbed 90% of the total reabsorption capacity in less than 4 minutes at 300 °C and 20 atm. In addition, TEM analysis reveals that MgH2 particles are covered by graphene with Fe clusters, resulting in the reduction of grain growth. Density functional theory shows that the defects in graphene act as the active sites for the dehydrogenation of MgH2, while the Fe clusters reduce the adsorption of dissociated H atoms, resulting in low-temperature dehydrogenation. Thus, graphene decorated with metal clusters could open up a new way of designing a new type of catalyst which could replace transition metal catalysts.

By fluorescence spectroscopy it has been established that coal derived asphaltene (CDA) forms aggregates in CCl4 medium. 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 that K increases 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 CCl4 as continuous medium with change in ω a critical ω (=5) has been found. The forma...

Coal-derived asphaltene (CDA) has been shown to form electron donor–acceptor-type molecular complexes with electron acceptor such as 2,5-cyclohexadiene-1,4-diylidene also known as tetracyanoquinodimethane (TCNQ) in homogeneous medium of carbon tetrachloride and heterogeneous medium of aqueous SDS. This has been investigated both by UV-Vis and fluorescence spectrophotometric method. The Charge transfer (CT) absorption peaks have been detected by difference spectral method and the wavelengths of the CT peaks are close in both the medium. The formation constants (K) have been determined using the Benesi–Hildebrand equation. The magnitudes of K are in the order of 103 L mol−1 that are comparable to some supramolecular or inclusion complexes. The study reveals the presence of π-donor (i.e., aromatic) type of compounds in CDA molecule. It also supports the view that CDA molecules exist in solution forming micellar aggregate, in the cavities of which the TCNQ molecules are included. The remarkable increase (thre...

The evolution of thermogenic gases during coalification has not yet been theoretically attempted. Examinations on Indian Permian vitrinites of various ranks ranging from Cwt% 76 to 92 were performed. Fourier Transform Infra-red spectroscopy (FTIR) provided insight into the structural changes where the aliphatic CH increases with increase in percentage of carbon up to ~85% and then decreases. In contrast, the aromatic CH, the ratio of aromatic CH to aliphatic CH and aromaticity (fa) increase monotonically with the advancement of rank. A relationship between fa and atomic H/C ratio as fa = 1.12–0.45H/C was established to predict fa from elemental analysis. The structural data from FTIR served as an input to construct six representative hypothetical models of coal of varying Cwt% (76, 80, 83, 86, 87 and 89). Density Functional Theory (DFT) has been applied to these coal models and the formation of principal thermogenic gases, viz. CO2 for the low-(76%C)and CH4 for the high-rank (87%C), with simultaneous increase in the rank was demonstrated considering the smaller structural units extracted from the relevant coal models. The suggested reaction pathways are supported by the negative values of changes in free energies of the reactions computed from the Gaussian thermo-chemistry. The studies could, therefore, show that gas evolution as a natural (spontaneous) process with feasibility of rank advancement.

Desmoplastic small round cell tumor (DSRCT) is a rare pathologic entity that most frequently affects the peritoneal cavity and presents in pediatric and adolescent boys. It often presents at an advanced stage and has a generally poor prognosis. Sometimes it may involve liver at diagnosis. We present an unusual case of DSRCT who was present with mass in lower abdomen, pain, hepatomegaly and mild ascites. This tumor is characterized by nests of small undifferentiated cells that show immunohistochemical evidence of epithelial, mesenchymal and neural differentiation. In our patient histologicaly tumor had the characteristic features of DSRCT and were composed of small round cells with hyperchromatic nuclei and scanty cytoplasm. With various difficulties in diagnosis we ultimately reached at diagnosis by open biopsy and immunohistochemistry. Now patient is on multidrug chemotherapy (modified p6 protocol). Diagnosis and management of a rare tumor needs high level of suspicion and in time intervention.DOI: http://dx.doi.org/10.3329/jpsb.v2i2.19552

Coal derived asphaltene (CDA) has been observed to form molecular complexes with electron acceptors such as [60]- and [70]fullerenes in carbon tetrachloride medium. The UV–vis spectroscopic studies show that CDA forms an inclusion complex of 2(CDA):1(fullerene) stoichiometry with [60]fullerene. On the other hand, CDA forms similar complex of 3(CDA):1(fullerene) stoichiometry with [70]fullerene. This is established by determining the thermodynamic parameters such as formation constants, enthalpies and entropies of the complex formation. The results also indicate that the process of complex formation in both the cases is entropy driven one.

The spectral (both absorption and steady-state fluorescence) studies of interaction of asphaltene with o-chloranil have been carried out in aqueous micellar media of cationic cetyl trimethyl ammonium bromide (CTAB), and neutral triton X-100 (TX-100). Spectroscopic results indicate formation of a complex between asphaltene and o-chloranil. The fluorescence band positions of the complexes are identical in both the medium. The absorption spectrum of the complex has been detected by difference spectral method. The position of maximum absorption of the complex in these micellar media have been compared and found in the order of SDS > CTAB > TX-100. The formation constant (K) has been determined using Benesi–Hildebrand equation utilizing absorption spectral data. Formation of ground state complex involving asphaltene and o-chloranil has also been observed from the study of quenching of asphaltene fluorescence by o-chloranil. The value of K, as obtained by Stern–Volmer plot, agrees well with that obtained by absorption spectrophotometric method.

Ultraviolet-visible absorption and steady-state fluorescence of asphaltene in sodium dodecyl sulphate (SDS) micellar medium containing o-chloranil have been studied. Spectroscopic results indicate formation of a complex between asphaltene and o-chloranil. The absorption spectrum of the complex has been detected by difference spectral method. The position of maximum absorption of the complex in micellar medium agrees well with that of the complex in the carbon tetrachloride medium studied previously. The formation constant (K) has been determined using Benesi-Hildebrand equation utilizing absorption spectral data. Formation of ground state complex involving asphaltene and o-chloranil has also been evidenced from the study of quenching of asphaltene fluorescence by o-chloranil. The value of K, as obtained by Stern-Volmer plot, agrees well with that obtained by absorption spectrophotometric method.

The effect of water to the self-aggregational phenomenon of coal-derived asphaltene (sourced from coal liquefaction plant at CIMFR, Dhanbad, India) has been studied tensiometrically and fluorimetrically in CCl4 medium. Although asphaltene molecule contains small number of hydrophilic groups such as –NH, –SH, and sometimes –OH, the main force behind the aggregation of asphaltene is π-π stacking interaction between the asphaltene molecules. This has been established by showing that critical micelle concentration (CMC) of asphaltene/CCl4 system increases with addition of microquantity of water and also by studying the variation of surface tension (ST) with addition of water to asphaltene solution above its CMC.

It has been shown by UV−vis spectrophotometric method that p-bromanil forms inclusion complex of 1:2 stoichiometry with coal-derived asphaltenes. The absorption peak for the complex has been detect...

Steady-state fluorescence spectra of coal derived asphaltenes sourced from the Barari coke plant situated in Dhanbad, India, have been studied in carbon tetrachloride solution. Quenching of the asphaltene fluorescence in solutions containing fixed concentrations of asphaltene (10 and 0.05 mg/L) has been studied in the presence of the two isomeric chloranils. Quenching has also been studied by varying the excitation wavelength. Time-resolved fluorescence studies indicate that the average lifetime of asphaltene in the excited-state remains unaltered in the presence of the quencher, indicating static quenching involving ground-state complexation of asphaltene with the chloranils. The value of the average lifetime does not depend on the concentration of asphaltene in the concentration range studied. The equilibrium constant (K) for the formation of the electron donor–acceptor complex has been determined from Stern−Volmer plots. The dependence of the K values on the excitation and emission wavelengths and also...

Fluorescence spectra of coal derived asphaltenes sourced from Barari coke plant situated at Dhanbad, India, have been studied as a function of concentration in benzene, toluene and carbon tetrachloride with an eye to study the self-aggregation of the solute. Aggregation has been found to be a gradual process and the concentration characterizing onset of aggregation process coincide for the solvents. The critical aggregation constants (CAC) appear to be ca 90–100 and 180–200 for all the solvents. A small red shift of fluorescence band is observed when traces of water (∼0.05%, v/v) are present in carbon tetrachloride solution.

Coal derived asphaltene has been observed spectrophotometrically to form molecular complexes of charge transfer type with o - and p -chloranils. The CT absorption peaks have been detected by difference spectral method and the wavelengths of the CT peaks are in the expected order of electron affinities of the chloranils. The formation constants ( K ) have been determined using the Benesi–Hildebrand equation. The magnitudes of K are large compared to those of weak charge transfer complexes (for which K ≈10 1 –10 3 dm 3 mol −1 ) but are comparable to those of some recently reported supramolecular or inclusion complexes. The study reveals the presence of π -donor (i.e. aromatic) type of compounds in asphaltene molecule. It also supports the view that asphaltene molecules exist in solution forming micellar aggregate, in the cavities of which the chloranil molecules are included.