Induction of Chirality in MXene Nanosheets and Derived Quantum Dots: Chiral Mixed-Low-Dimensional TiCT Biomaterials as Potential Agricultural Biostimulants for Enhancing Plant Tolerance to Different Abiotic Stresses.

This work presents two advancements in the engineering design and bio-applications of emerging MXene nanosheets and derived quantum dots. First, a facile, versatile, and universal strategy is showcased for inducing the right- or left-handed chirality into the surface of titanium carbide-based MXene (TiCT) to form stable mixed-low-dimensional chiral MXene biomaterials with enhanced aqueous colloidal dispersibility and debonding tolerance, mimicking the natural asymmetric bio-structure of most biomolecules and living organisms. In particular, TiCT MXene nanosheets are functionalized with carboxyl-based terminals and bound feasibly with the D/L-cysteine amino acid ligands. The physicochemical characterizations of these 2D-0D/1D chiral MXene heterostructures suggest the inclusion of TiCT nanosheets and different levels of self-derived MXene quantum dots and surface titanium-oxide nanoparticles, providing enhanced material stability and oxidative degradation resistance for tested months. Further, the interaction and molecular binding at cysteine-TiCT/Ti-oxide interfaces, associated ion transport and ionic conductivity analysis, and charge re/distribution mechanisms are evaluated using density functional theory (DFT) calculations and electrochemical impedance spectroscopy (EIS) measurements. The second uniqueness of this study relies on the multifunctional application of optimal chiral MXenes as potential nano-biostimulants for enhancing plant tolerance to different abiotic conditions, including severe drought, salinity, or light stress. This surface tailoring enables high biocompatibility with the seed/seedling/plant of Arabidopsis thaliana alongside promoting multi-bioactivities for enhanced seed-to-seedling transition, seedling germination/maturation, plant-induced stomatal closure, and ROS production eliciting responses. Given that the induced chirality is a pivotal factor in many agro-stimulants and amino acid-containing fertilizers for enhanced interaction with plant cells/enzymes, boosting stress tolerance, nutrient uptake, and growth, these findings open up new avenues toward multiple applications of chiral MXene biomaterials as next-generation carbon-based nano-biostimulants in agriculture.