top of page
This subgroup aims to develop free-standing 2D-nanosheets from a small molecular building block either through "top-down" or "bottom-up" approaches. In the top-down approaches, first, we have synthesized the bulk nanocrystal of the monomer. Latter, by using various exfoliation approaches, we target to achieve the free-standing 2D-nanosheets. In the bottom-up approaches, the monomer unit is self-assembled in solution to form 2D-nanosheets. Mostly, we have tagged a photo/redox-active unit with a proper functional group in the designed monomer to track the recognition or self-assembly process. The developed 2D-nanosheets are used to recognize and separate important explosives, aromatic carcinogens, pesticides, and pharmaceutical isomers.
-
Two-dimensional (2D) Nanosheets for recognition and separation.
The research focus in our group aims to develop novel functional supramolecular materials. By combining synthesis and physical organic chemistry, we study the self-assembly and self-organization of supramolecular architecture. Our group designs and synthesizes relatively simple organic molecules endowed with suitable functional groups to undergo self-assembly. To achieved the desired materials, we generally used the self-assembly process through non-covalent interaction. These supramolecular materials can exhibit enhanced optical, chiral, or mechanical properties compared to the isolated building blocks. For new supramolecular synthons, we seek to gain control over their structural and functional properties to exploit them for different applications by better understanding the formation of these complex hierarchical materials. Currently, we are working on three research directions; these are as follows.
For example, recently, we have developed a new class of lanthanide 2D-nanosheets to detect FOX-7. 1,1-Diamino-2,2-dinitroethene or FOX-7 is an insensitive high explosive; in a binder mixture, it exhibits a slightly superior detonation velocity of 8870 m s-1 comparison to RDX. The insensitive nature of FOX-7 makes it a key component for the development of low vulnerable high explosive compositions for further application in weaponry. The growing demand for FOX-7, for use as a suitable replacement for conventional explosives, is of grave concern to human security. Achieving rapid and efficient detection of this unexplored explosive is a challenging task. The developed luminescent nanosheets were used for the first time for micromolar level detection of FOX-7 both in solution and in the solid-state. Sonication-assisted top-down approach is used to achieve ultrathin 2D-sheets with lateral dimensions in the micrometer scale (0.3–1 mm) and a thickness of around 2–6.5 nm. A visually distinct color change of the nanosheets from red and green to colorless was witnessed upon UV light irradiation during the detection process. Notably, the solid-state detection technique could be exploited for developing a commercial spray kit for the quick onsite screening of this critical explosive.
2.Organic Nanocrystal.
Materials with well-defined three-dimensional nanoscale architectures are crucial for uncovering and understanding their intrinsic properties and many incipient technologies. The bottom-up fabrication of a nanoscale geometric architecture with precise dimension control has far-reaching implications in various embryonic technologies, including catalysis, sensing, and photonics. Rigid, crystalline geometric structures commonly prevail in natural and purpose-built inorganic systems. The generation of such structure through the self-assembly of small organic molecules is relatively scarce. Developing a generalized strategy for engineering specific interactions between molecules and controlling the pathway for their assembly formation is an outstanding challenge. The aim of this subgroup is to develop organic nanocrystal from self-assembly of small molecules for a particular application like photonics and facet selective catalysis to mimic enzymatic reaction.
For example, recently, we have developed nanocrystals with rhombic dodecahedral (RD) morphology with a size up to 23.7 µm through facet selective self-assembly C3-symmetric triaminoguanidium-derivative. Significantly, we could demonstrate the formation pathway of such a unique shape-controlled nanostructure. The growth mechanism explored in different solvents and varying solvent compositions and polarities for providing a rationalized approach. The self-assembly pathway is illustrated in preferential occupancy of the solvent molecules in different crystal facets and growth direction. Single crystal X-ray diffraction analysis expounds the formation mechanism in terms of preferential occupancy of the solvent molecules in (110) crystal facet over (100) favors the growth direction for achieving the rhombic dodecahedral morphology. The crystallographic evidence for understanding the formation mechanism of such rhombic dodecahedral morphology is rare in small organic molecules' self-assembly systems.
3. Conducting 2D-Nanosheets.
Crystalline two-dimensional organic nanosheets (2D-ONs) with atomic or near-atomic thickness with infinite lateral dimensions are crucial for their possible application as a material for energy storage. The presence of nanofluidic channels with a designed array of molecular interlayers in such 2D-ONs, for a favorable lithium-ion transport, has special significance for improving lithium-ion batteries' efficacy. Recently we have developed a unique lithium-ion conducting behavior of zwitterionic 2D-ONs, formed through self-assembly of a small organic molecule. The resulting sheets obtained from both the self-assembly and exfoliation approach exhibit near-atomic (~ 3.5 nm) thickness and remarkable stability, having broad linear planarity of few micrometers. Significantly these nanosheets form a one-dimensional (1D) channel for efficient ion-transport at room temperature. The presence of permanently immobilized ionic centers and the well-designed directional channels in these 2D-ONs helps achieve a lithium-ion conductivity of 5.14 × 10-5 Scm-1.
bottom of page