Woo-Sik Kim

Chiral symmetry breaking (CSB) in crystallization is commonly achieved through strong mechanical perturbations or temperature cycles, whereas the role of interfacial transport remains less understood. Here, we investigate CSB during antisolvent crystallization of aqueous sodium chlorate droplets confined in a dodecane/ethanol/Span 80 system, using surfactant concentration to regulate interfacial transport. Increasing Span 80 concentration progressively delays observable crystallization onset, consistent with slower supersaturation development within the droplet. Crystal growth exhibits a transition from a faster early-stage regime to a slower late-stage regime, consistent with depletion of the finite solute reservoir and the resulting competition between nucleation and growth. These kinetic effects translate directly into chiral outcomes, increasing the critical droplet volume for exclusively single-handed crystallization. Interfacial-tension measurements and molecular dynamics simulations reveal a close correspondence between the critical droplet volume and interfacial surfactant coverage. Together, the results support a mechanistic framework in which surfactant-controlled interfacial transport governs supersaturation development and thereby determines CSB outcomes through nucleation−growth competition. This work establishes interfacial transport as a key factor controlling CSB in confined antisolvent crystallization systems.

Pharmaceutical cocrystals are constructed via non-covalent interactions between active pharmaceutical ingredients and coformers, enabling the improvement of solubility, stability, bioavailability, and processing suitability while preserving the structural integrity of drug molecules. Previous research on pharmaceutical cocrystals has predominantly focused on 1:1 stoichiometric systems; however, recent findings have revealed that stoichiometrically diverse cocrystals exhibit more diverse structural morphologies and greater flexibility in performance modulation. This review comprehensively summarizes the latest advances in synthesis strategies, characterization techniques, physicochemical properties, and application explorations of pharmaceutical cocrystals with different stoichiometric ratios. Stoichiometrically diverse cocrystals can be prepared by methods such as solution crystallization, mechanochemical synthesis, and vapor-induced phase transformation. Their crystal architecture, molecular arrangement, and physicochemical properties are strongly correlated with stoichiometry. Such cocrystals with stoichiometry departing from 1:1 offer significant advantages in solubility regulation, dissolution profile optimization, and bioactivity modulation, and some systems even enable reversible dynamic switching of stoichiometry. Furthermore, this review analyzes current challenges in the prediction of formation rules, stabilization of metastable phases, and scale-up production of stoichiometrically diverse pharmaceutical cocrystals, and outlines future development pathways, including machine learning-assisted design, multicomponent drug−drug cocrystals, and smart responsive cocrystals.

This study characterises a commercial lab-scale Taylor–Couette reactor (TCR) for pharmaceutical particle engineering, focusing on heat transfer, solid suspension, residence time distribution (RTD), and shear effects on particle formation. Net flowrates of 50–300 g/min had little influence on the performance of the reactor, with temperature drop at ∆T=29.4±1.53℃ observed throughout all experiments. Particle suspension correlated directly with rotational velocity, with vortex formation essential for homogeneous suspension of a 5 wt% lactose/ethanol slurry at 190 rpm. RTD analysis revealed significant deviation from plug flow for both phases, with greater dispersion in the solid phase due to vortex interactions and centrifugal effects. During antisolvent crystallisation of lactose, increased shear promoted crystal breakage and reduced agglomeration. Overall, the TCR demonstrated strong heat transfer, effective solid suspension, and tuneable particle size control, highlighting its suitability as a platform for particle engineering applications.

Hydrogen, an essential clean energy carrier, poses challenges in terms of efficient and scalable storage. Liquid organic hydrogen carriers (LOHCs) have gained attention as viable chemical media for hydrogen storage and release, providing advantages such as high energy density and compatibility with zero-emission fuel cells. Nevertheless, a critical bottleneck is the development of cost-effective and stable electrocatalysts for LOHC dehydrogenation, particularly using noble metal catalysts such as Pd, which suffer from high costs and limited durability. In this study, we demonstrate that Pd-based multimetallic alloy nanoparticles on carbon (Pd-M/C, where M = Pt, Ag, Cu, and Ru), synthesized via a Couette-Taylor reactor, demonstrate enhanced electroactivity and stability for piperazine oxidation, a model for LOHC dehydrogenation. Among these, Pd₇₁Cu₂₉/C shows the optimal electronic structure, achieving a specific activity of 20.50 mA cm^-2─1.8 and 2.68 times higher than commercial Pd/C and Pt/C benchmarks, respectively. Density functional theory (DFT) calculations coupled with gas chromatography-mass spectrometry (GC-MS) analysis of reaction intermediates elucidate the electrocatalytic dehydrogenation pathway. These studies reveal that Pd-Cu alloying synergistically modulates the electronic structure via interatomic charge redistribution.

A non-isothermal continuous Taylor vortex, which integrates internal heating and cooling processes, has proven to be highly effective in regulating the crystal size distribution through the mechanisms of dissolution and recrystallization of crystals.