Kinetically controlled morphology and composition of colloidal nanoparticles: cation exchange reactions from copper sulfide to transition metal (Mn, Zn, Fe, and Co) sulfides.

The cation exchange reaction is a powerful method for generating nanomaterials with unique structures because of the easy control of the size, morphology, composition, and crystal structure of the nanoparticles. This study investigated the kinetically controlled morphology and composition of colloidal nanoparticles (NPs) through cation exchange reactions, specifically focusing on variations from copper sulfide to transition metal sulfides, including Co, Fe, Zn, and Mn sulfides. In the cation exchange reaction, Co exhibited the fastest exchange rate, followed by Fe, Mn, and Zn. The difference in kinetics rates affected the change in morphology; Co, with the fastest rate, was immediately and uniformly distributed in the NPs. For Fe, a sandwich structure was initially formed and this gradually transformed into a solid-solution phase. After exchanging Cu with Mn and Zn, a heterostructure was formed, which became increasingly clear as the reaction progressed. The transformation of the morphology and crystal structure were confirmed using XRD, TEM, and SEM analyses. The findings of this study suggest that the morphology and distinct structures of the exchanged particles can be controlled by manipulating the kinetics rates of cations through cation exchange reactions. This process offers a powerful tool for the tailored synthesis of colloidal nanoparticles and provides a design principle for enabling predictable outcomes through cation exchange reactions.

Morphology Control of Au-Ni Hybrid Nanoparticles: Exploring Heterostructures and Optical Tuning.

Hybrid nanoparticles (NPs) have attracted considerable attention because of their ability to provide diverse properties by integrating the inherent properties of multiple components; however, synthetic strategies to control their morphology remain unexplored. In this study, a new method was used to control the morphology and optical properties of Au-Ni heterostructure (ANH) NPs. Unique morphological changes were observed by varying the Au/Ni precursor ratio from 2:1 to 1:4, exhibiting a shape transformation from dumbbell-like to quasi-spherical owing to the Ni NP size expansion, whereas the Au NP maintained their size. Moreover, increasing the Ni ratio induced plasmonic band broadening and wavelength redshift, resulting in color changes from red to navy and black. In terms of the structure, the atomic orientation of the crystallite showed that even a large lattice mismatch can result in heterojunctions at the NPs. In addition, the reaction aliquots uncovered heterogeneous nucleation and growth of ANH NPs in the colloidal system, demonstrating Ni reduction on the preformed Au NP owing to the reduction in potential gap. This study provides new insights into controlling the morphology of hybrid NPs using colloidal synthesis and the design of optimized materials for various applications.

Formulation Optimization and in Vitro Characterization of Orally Disintegrating Films Using a Factorial Design and Mathematical Modeling for Drug Release.

Even though experimental designs are becoming popular especially for conventional dosage forms, limited studies have been performed to optimize formulations of orally disintegrating films (ODFs). This study aimed to evaluate sildenafil citrate-loaded ODFs for a controlled release with hydroxypropyl methylcellulose as a film-forming polymer. A factorial design was utilized for optimization with three control factors: ethanol ratio, plasticizer ratio, and the type of plasticizer. Tensile strength, disintegration time, water contact angle, and thickness were chosen as responses. For optimization, water contact angle, disintegration time, and thickness were minimized, while the tensile strength was maximized. Based on the conditions, optimal formulations were achieved for each type of plasticizer. Evaluation of desirability indicated that the response values were close to the target. When these optimal formulations were validated, the optimal solutions and target values were similar with small biases. The formulations were characterized using scanning electron microscopy, differential scanning calorimetry, Fourier transform infrared spectroscopy, surface pH, in vitro dissolution, and drug release simulation with a mathematical modeling. After the drug was homogenously dispersed throughout the film, the crystalline form of the drug provided strong hydrogen bonds between the drug and the film components. Moreover, it showed a controlled drug release profiles that were well matched with simulated results. This study suggests that the optimized films may present a better alternative to conventional tablets for the treatment of male erectile dysfunction.