Ayan Maity

Understanding adsorption processes at the molecular level has transformed the discovery of engineered materials for maximizing gas storage capacity and kinetics in adsorption-based carbon capture applications. In this work, we studied the molecular mechanism of gas (CO₂, H₂, methane, and ethane) adsorption inside an interconnected porous network of carbon. This was achieved by synthesizing novel macro-meso-microporous carbon (M³C) nanospheres with interconnected pore structures. The M³Cs showed a CO₂ capture capacity of 5.3 mmol/g at atmospheric CO₂ pressure, with excellent kinetics. This was due to fast CO₂ adsorption within the interconnected hierarchical macro-meso-microporous M³C. In situ small-angle neutron scattering (SANS) under various CO₂ pressures indicated that the macro- and mesopores of M³C enable fast diffusion of CO₂ molecules inside the micropores, where adsorbed CO₂ molecules densify into a liquid-like state. This strong densification of CO₂ molecules causes fast CO₂ diffusion in the macro- and mesopores of M³C, restarting the adsorption cycle for fresh CO₂ molecules until all pores are completely filled. Notably, M³C also showed good capture capacities for hydrogen and various hydrocarbons, with excellent selectivity toward ethane over methane.

The discovery of dendritic fibrous nanosilica (DFNS) has attracted great attention to the field of catalysis, CO₂ capture, drug delivery due to its distinct morphology, and pore size distribution. Despite extensive research, the understanding of the DFNS formation process and its internal structure remains incomplete as microscopy and gas sorption techniques were not able to provide necessary in-depth structural information due to their inherent limitations. In the current work, we present a structural model of DFNS derived using small-angle X-ray scattering (SAXS) supported by ¹²⁹Xe nuclear magnetic resonance (NMR), which provided intricate details of DFNS and its internal structure. Mechanistic understanding of the DFNS formation and growth process was achieved by performing time-resolved SAXS measurements during the synthesis of DFNS, which unveils the evolution of two levels of a bicontinuous microemulsion structure responsible for intricate DFNS morphology. The validity and the accuracy of the SAXS method and the model were successfully established through a direct correlation among the functionality of the DFNS scattering profile and its pore size distribution, as well as results obtained from the ¹²⁹Xe NMR studies. It has been established that the DFNS structure originates from direct modulation of the bicontinuous structure controlled by a surfactant, a co-surfactant, and the silicate species formed during hydrolysis and the condensation reaction of the silica precursor.

Efficient RNA extraction is critical for all downstream molecular applications and techniques. Despite the availability of several commercial kits, there is an enormous scope to develop novel materials that have high binding and elution capacities. Here, we show that RNA from the cells can be extracted by dendritic fibrous nanosilica (DFNS) with higher efficiency than commercially available silicas. This could be because of the unique fibrous morphology, high accessible surface area, and nanosize particles of DFNS. We studied various fundamental aspects, including the role of particle size, morphology, surface area, and charge on the silica surface in RNA extraction efficiency. Fourier transform infrared (FTIR) spectroscopy studies revealed the interaction of functional groups of RNA with the silica surface, causing selective binding. Due to the sustainable synthesis protocol of DFNS and the simplicity of various buffers and washing solutions used, this RNA extraction kit can be assembled in any lab. In addition to the fundamental aspects of DFNS–RNA interactions, this study has the potential to initiate the development of indigenous DFNS-based kits for RNA extraction.

The synthesis of solid acids with strong zeolite-like acidity and textural properties like amorphous aluminosilicates (ASAs) is still a challenge. In this work, we report the synthesis of amorphous “acidic aluminosilicates (AAS)”, which possesses Brønsted acidic sites like in zeolites and textural properties like ASAs. AAS catalyzes different reactions (styrene oxide ring-opening, vesidryl synthesis, Friedel−Crafts alkylation, jasminaldehyde synthesis, m-xylene isomerization, and cumene cracking) with better performance than state-of-the-art zeolites and amorphous aluminosilicates. Notably, AAS efficiently converts a range of waste plastics to hydrocarbons at significantly lower temperatures. A Cu-Zn-Al/AAS hybrid shows excellent performance for CO₂ to fuel conversion with 79% selectivity for dimethyl ether. Conventional and DNP-enhanced solid-state NMR provides a molecular-level understanding of the distinctive Brønsted acidic sites of these materials. Due to their unique combination of strong acidity and accessibility, AAS will be a potential alternative to zeolites.

Plasmonic black gold converts CO₂ to methane using solar energy.

Morphology-controlled nanomaterials such as silica play a critical role in the development of technologies for use in the fields of energy, environment (water and air pollution) and health. Since the discovery of Stöber's silica, followed by the discovery of mesoporous silica materials (MSNs) such as MCM-41 and SBA-15, a surge in the design and synthesis of nanosilica with various sizes, shapes, morphologies and textural properties (surface area, pore size and pore volume) has occurred. Dendritic fibrous nanosilica (DFNS; also known as KCC-1) is one of the recent discoveries in morphology-controlled nanomaterials. DFNS shows exceptional performance in large numbers of fields, including catalysis, gas capture, solar energy harvest, energy storage, sensors and biomedical applications. This material possesses a unique fibrous morphology, unlike the tubular porous structure of various conventional silica materials. It has a high surface area to volume ratio, with improved accessibility to the internal surface, tunable pore size and pore volume, controllable particle size and, importantly, improved stability. However, synthesis of DFNS with controllable size, textural properties and fiber density is still tricky because of several of the steps involved. This protocol provides a comprehensive step-wise description of DFNS synthesis and advice regarding how to control size, surface area, pore size, pore volume and fiber density. We also provide details of how to apply DFNS in catalysis and CO2 capture. Detailed characterization protocols for these materials using scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption and thermal gravimetric analysis (TGA) studies are also provided.

In this work, we report the synthesis protocol for carbon coated dendritic fibrous nanosilica (DFNS@Carbon) and high surface area wrinkled carbon nanospheres using phenol formaldehyde polymerization chemistry. We have shown that the choice of hard template, i. e. DFNS with different sizes and fiber density, can lead to the synthesis of carbon‐coated DFNS and wrinkled carbon nanospheres with tunable properties, having high surface area (1090 ±50 m ² /g), large pore volume (1.18 ±0.02 cm ³ /g) and distinct pore size distribution (from 3.5 nm to 15 nm). The CO2 capture value of 1.47 mmol/g was obtained without any amine functionalization. This value is comparable or better than reported non‐amine functionalized CO2 sorbents, indicating the contribution of textural properties and morphology of carbon cages on their CO2 capture capacity.

Although the range of photocatalysts with controllable size, shape and morphology has developed in recent years with a large number of silica‐supported TiO₂ catalysts, the details of photocatalytic interfaces between nanosilica and TiO₂ them and the mechanisms of TiO₂ functionalization of silica surfaces are not yet well understood. It is worth mentioning that the understanding of a mechanism from a molecular point of view has always been a challenge in the field of materials science. Here, we probe interfaces in (dendritic fibrous nano‐silica (DFNS) supported TiO₂ photocatalysts as well as propose and prove the formation mechanism of the photocatalyst, DFNS/TiO₂, by ammonia‐assisted functionalization of DFNS by titanium butoxide (TBOT). The proposed formation mechanism includes the following steps: i) the deprotonation of silica surface (silanols) by ammonia and the hydrolysis of TBOT to titanium hydroxide [Ti(OH)₄], ii) the donation of electron lone pair from ammonia to the Ti⁴⁺ ion of Ti(OH)₄, iii) the release of hydroxide ions, followed by hetero‐condensation of dehydroxylated titanium ions with the deprotonated silanols, generating Si−O−Ti oxobridges, iv) the formation of oxy‐anion of titanols and its reaction with another molecule of ammonia‐activated titanium hydroxide to generate Ti−O−Ti oxobridges, and v) the continuation of the above cycle of steps until the titanium hydroxide precursor is consumed to produce silica supported titanium hydroxide. During thermal treatment, the titanols condense, yielding DFNS/TiO₂ photocatalysts. To prove this mechanism, detailed solid‐state ¹H, ²⁹Si, ^47,49Ti NMR and in situ FTIR studies were carried out, based on which different surface species formed during TiO₂ growth on DFNS were identified. This has led to fundamental insights into the reaction of TBOT with DFNS silica surface and interfaces between DFNS and TiO₂.