Terrestrial geothermal fields and oceanic hydrothermal vents are considered as candidate environments for the emergence of life on Earth. Nevertheless, the ionic strength and salinity of oceans present serious limitations for the self-assembly of amphiphiles, a process that is fundamental for the formation of first protocells. Consequently, we systematically characterized the efficiency of amphiphile assembly, and vesicular stability, in terrestrial geothermal environments, both, under simulated laboratory conditions and in hot spring water samples (collected from Ladakh, India, an Astrobiologically relevant site). Combinations of prebiotically pertinent fatty acids and their derivatives were evaluated for the formation of vesicles in aforesaid scenarios. Additionally, the stability of these vesicles was characterized over multiple dehydration-rehydration cycles, at elevated temperatures. Among the combinations that were tested, mixtures of fatty acid and its glycerol derivatives were found to be the most robust, also resulting in vesicles in all of the hot spring waters that were tested. Importantly, these vesicles were stable at high temperatures, and this fatty acid system retained its vesicle forming propensity, even after multiple cycles of dehydration-rehydration. The remaining systems, however, formed vesicles only in bicine buffer. Our results suggest that certain prebiotic compartments would have had a selective advantage in terrestrial geothermal niches. Significantly, our study highlights the importance of validating results that are obtained under ‘buffered’ laboratory conditions, by verifying their plausibility in prebiotically analogous environments.

Gallium–platinum promoted HZSM-5 is found to be a promising catalyst for ethane aromatization reaction. The influence of Pt as a promoter on the activity of Ga/HZSM-5 catalyst for ethane aromatization has been investigated. Comparative study was performed between bimetallic Ga–Pt based and Mo based HZSM-5, where the GaPt/HZSM-5 showed better aromatic and hydrogen selectivity. Pt promoted Ga/HZSM-5 catalyst exhibited higher activity compared to pure Ga/HZSM-5 catalyst. The presence of platinum in the gallium zeolite considerably accelerated dehydrogenation step in ethane aromatization. In addition, GaPt/HSZM-5 deactivated significantly slower than Mo/HZSM-5 and Ga/HZSM-5. TPO study of spent catalysts revealed that carbonaceous deposit on GaPt/HZSM-5 catalyst was burnt off at lower temperature compared to pure Ga/HZSM-5 catalyst, indicating the presence of Pt facilitated hydrogen spillover resulting in hydrogenolysis of coke precursors. The reaction mechanism associated with aromatic formation is postulated based on the correlation between catalytic performance and surface characterization.

Facile synthesis of ultrasmall gold nanoclusters of size <2 nm dispersible in water using a novel quaternary ammonium ligand is reported. Further, arrays of these nanoclusters are encapsulated in monodisperse silica nanospheres of size 25–30 nm. The photophysical characteristics of the clusters are found to be intact upon encapsulation, rendering the resulting composite material ideal for fluorescence imaging applications. We have further shown the utilization of these materials in catalysis as precursors for Au nanoparticles encapsulated in porous silica.

Catalytic shale gas decomposition for tunable tip/base grown CNTs and CO2-free H2.

We have synthesized g-C3N4 decorated over dendritic fibrous nanosilica (DFNS). The generation of C–N–Si interfaces by coating each fiber of DFNS with g-C3N4 not only provided high surface area but also affected the optical and electronic properties of the composite. The catalyst synthesis reproducibility issue of g-C3N4 was resolved using a vacuum-sealed quartz tube. The extended light absorption in the visible region, enhanced lifetime of photogenerated charge carriers due to the formation of interfaces between silica and g-C3N4 (confirmed by solid-state NMR), and increased surface area result in the improved photocatalytic activity of DFNS/g-C3N4 for hydrogen generation and CO2 conversion.

Si and Zr species grafted on Fe–Al–O catalysts act as an inhibitor and promoter, respectively, in CO2 hydrogenation.

Direct nonoxidative conversion of ethane to aromatics has become an effective way of upgrading shale gas. Metal-promoted shape selective zeolite catalysts are often used for aromatization. Although the coking issue of the catalysts in ethane aromatization has been reported, the deactivation mechanism and the performance of regenerated Ga−Pt promoted HZSM-5 needs to be further investigated. The objective of this study is to elucidate deactivation mechanism of Ga−Pt promoted HZSM-5 and investigate the feasibility of regenerating deactivated catalysts for commercial viability. When using lower concentration of oxygen (2 vol %) for regeneration, decreased catalyst deactivation rate was observed. The metal particle size, crystalline structures, and acidity are characterized by various analytical instrumentations (TEM, XRD, NH 3 -TPD). The change of Bronsted acidity was observed on regenerated catalysts. The results showed that metal agglomeration and leaching of Pt from homogeneous Ga−Pt particle were the main causes of deactivation other than coke deposition, indicating that stabilization of bimetallic metal particles on zeolite surface is critical.

The stability of Fe-and Zn-promoted Mo/ZSM-5 catalysts was studied toward the ethane dehydroaromatization reaction. To elucidate the catalyst deactivation and regeneration mechanism, the catalytic performance was evaluated during five consecutive reaction−regeneration cycles. The addition of Zn to Mo/ZSM-5 resulted in an initial increase in aromatic selectivity; however, the loss of about 50% Zn resulted in a total decrease in aromatic selectivity over five reaction and regeneration cycles. The addition of Fe to Mo/ZSM-5 resulted in no decrease in aromatic selectivity or aromatic yield throughout these reaction cycles. The formation of carbon nanotubes was observed on the Fe-promoted Mo/ZSM-5 catalyst, which was believed to improve gas diffusion to micropores. The presence of Fe-and Mo-agglomerated particles on the catalyst surface was observed at low Fe/Mo atomic ratios, resulting in the formation of base-grown carbon nanotubes. When the Fe/Mo atomic ratio increased, the agglomerated particles were able to leave the zeolite surface, resulting in the formation of tip-growth carbon nanotubes. The temperature-programmed reduction profile of the Fe-promoted Mo/ZSM-5 catalyst also suggested the formation of a more stable Mo and/or Fe species at 615 °C, enhancing carbon nanotube formation. The addition of Fe in the bipromoted Mo/ZSM5 catalyst was found to stabilize the catalyst surface and reduce its Zn loss.