Research Projects

In reaction to applied mechanical stress, which starts molecular mobility in a way that allows for partial charge separation, piezoelectric materials (PZMs) generate electricity[1]. Besides having many real-world uses, the low piezoelectric coefficient in well-known bio-systems like collagen or bone make them unsuitable for technological applications, prompting the search for novel, high-performing PZMs and their molecular level understanding. The design of non-centrosymmetric/chiral crystals (bearing P21, C2, Pna21, etc space groups) which hold net dipole moment required to exhibit piezoelectricity upon stressing, has paramount importance to develop expected PZMs. In other ways, piezoelectricity in molecular crystals is rarely investigated.[2] Besides, chiral crystal's softness determines the extent of remnant polarization, thus, the softer the crystal, higher the piezoelectric response. However, the majority of crystals are fragile and have little room for deformation. Therefore, developing pathways for the design of non-centrosymmetric crystals with a controlled stiffness calls for the application of advanced crystal engineering,[3] particularly, mechanical property engineering[4]. Different supramolecular synthons, which combine geometric and chemical information, are used in crystal engineering as tools for specific crystal formations. Here, the intended structural types would be achieved using three distinct approaches. (I) Room temperature plastic crystals (RT-PCs), utilising their inherent softness and balancing the stiffness required to enhance charge separation, through the modulation of surrounded molecular connections.[5] (II) Using enantiopure biomolecules (e.g., peptides and amino acids) of varying lengths or by cocrystallizing with PCs, to track contacts and adjust crystal softness. By facilitating greater molecular mobility under mechanical stress, could potentially increase piezoelectricity. (III) Making use of synthons based on C–H···O, π···π and other to enable the adoption of achiral non-centrosymmetric esters or mechanically interlocked systems with chiral functionalities. It can be accomplished by combining and varying the strength of various interactions, such as Me···Me, X···X (X = halogen), O=CH–···O=CH–, and O2N– O=NO–, etc. SCXRD can reveal structural patterns. The degree of softness would subsequently be measured using nanoindentation to investigate the structure-property link. PFM, is a technique for measuring piezoelectric responses. To comprehend the fundamental mechanism, one additional tool is a micro-Raman scattering. All things considered, this effort may help comprehend and develop soft crystalline materials with expected piezo-performances. References: 1. Liu et al. Appl. Phys. Rev. 2018, 5, 041306; 2. Guerin et al. Nat. Mater. 2018, 17, 180; 3. Desiraju et al. Angew. Chem., Int. Ed. 1995, 34, 2311; 4. Saha et al. Acc. Chem. Res. 2018, 51, 29574; 5. Das et al. Chem. Soc. Rev. 2020, 49, 8878.