Research Topics: Advanced Molecular Assembly and Crystallization Controlled by Light

Our laboratory focuses on the forefront of physical chemistry, utilizing optical trapping with continuous-wave lasers and ultra-short femtosecond laser pulses to actively manipulate molecular assembly, nucleation, and crystallization at the micro- and nanoscale. Rather than using light merely as a probe, we harness photon pressure, optical angular momentum, and plasmonic enhancement to deterministically control the morphology, polymorphism, and even the chirality of materials.

1. Enantioselective Control and Chiral Crystallization

Symmetry breaking and the control of crystal chirality remain significant challenges in science. We have developed non-contact, light-driven methodologies to induce and control chiral crystallization from achiral molecules (e.g., sodium chlorate, ethylenediamine sulfate) with high enantiomeric excess.
Helical Optical Forces and Plasmonics: By coupling circularly polarized light or optical vortices (Laguerre-Gaussian beams) with precisely engineered gold nanostructures, we generate highly localized helical optical force fields. Remarkably, we discovered an unprecedented enantioselectivity switch: simply altering the size of the gold nanoparticles reverses the handedness of the resulting crystal.
Femtosecond Laser-Driven Transitions: We also utilize circularly polarized femtosecond laser pulses to dictate the enantioselectivity during the polymorphic transition from a metastable achiral phase to a stable chiral phase.

2. Spatiotemporal Control of Protein Crystals and Amyloid Fibrils

Controlling the aggregation of biological macromolecules is crucial for structural biology and understanding disease mechanisms. We employ optical tweezers to manipulate local concentration dynamics and structural conformations of proteins.
Anisotropy in Protein Crystallization: By adjusting the laser polarization (linear vs. circular), we successfully controlled the anisotropy within the highly concentrated domains of hen egg-white lysozyme (HEWL). Linear polarization effectively aligns the molecules, dramatically enhancing crystallization efficiency compared to circular polarization.
Targeted Amyloid Fibrillation: For the first time, we have demonstrated the ability to artificially induce the formation of amyloid fibrils (such as cytochrome c) at a specific time and location using optical trapping, enabling us to pinpoint the essential structural regions required for fibril formation.

3. Laser-Induced Nucleation, Polymorphism, and Cocrystallization

Precise control over crystal polymorphism and cocrystallization is vital, especially in the pharmaceutical industry. We use various laser techniques to alter thermodynamic pathways and kinetics.
Accelerated Polymorphic Transitions: Using high-repetition-rate femtosecond lasers, we can exclusively trigger and accelerate the transition between crystal polymorphs (e.g., the β-to-α transition in glycine) at velocities thousands of times faster than spontaneous processes.
Binary-Solute Cocrystallization: We expanded our optical trapping-induced crystallization (OTIC) method to complex binary solutions, successfully controlling the cocrystallization dynamics of active pharmaceutical ingredients (like acetaminophen) with amino acids by manipulating local concentration gradients.
Nanoparticle-Promoted OTIC: Incorporating plasmonic (gold) or dielectric (silicon) nanoparticles with OTIC allows us to modulate localized heating and optical forces, significantly promoting the nucleation and growth cycles of metastable crystals.

4.Supramolecular Assembly and Advanced Photoluminescence

Optical trapping can push molecular systems beyond their conventional thermodynamic limits.
Higher-Order Complexation: By densely concentrating molecules at the focal point, we successfully induced unprecedented higher-order (2:4) supramolecular complexes between cyclodextrins and guest molecules. This localized high-density state completely inverted the regio- and enantioselectivity of subsequent photochemical reactions.
Aggregation-Induced Emission Enhancement (AIEE): We dynamically manipulate the luminescence properties of advanced polymers. By trapping and growing a single sub-micrometer aggregate, we can instantly switch its dual fluorescence behavior and dramatically enhance its emission through targeted photon pressure.