Decoding the Biomimetic Mineralization of Metal-Organic Frameworks in Water.

This study unveils the "green" metal-organic framework (MOF) structuring mechanism by decoding proton transfer in water during ZIF-8 synthesis. Combining in situ small- to wide-angle X-ray scattering, multiscale simulations, and quantum calculations, we reveal that the ZIF-8 early-stage nucleation and crystallization process in aqueous solution unfolds in three distinct stages. In stage I, imidazole ligands replace water in zinc-water cages, triggering an "acidity flip" that promotes proton transfer. This leads to the assembly of structures from single zinc ions to 3D amorphous cluster nuclei. In stage II, amorphous nuclei undergo a critical transformation, evolving into crystalline nuclei and subsequently forming mesoscale-ordered structures and crystallites. The process proceeds until the amorphous precursors are completely consumed, with the transformation kinetics governed by an energy barrier that determines the rate-limiting step. In stage III, stable crystallite nanoparticles form in solution, characterized by a temperature-dependent thermal equilibrium of molecular interactions at the crystal-solution interface. Beyond these core advancements, we explore the influence of encapsulated pepsin and nonencapsulated lysozyme on ZIF-8 formation, finding that their amino acid proton transfer capacity and concentration influence the resulting biomolecule-MOF composite's shape and encapsulation efficiency. The findings contribute to understanding the molecular mechanisms behind biomimetic mineralization and have potential implications for engineering proteins within amorphous MOF nuclei as protein embryo growth sites.

Cu nanoclusters with aggregation induced emission enhancement.

A facile and versatile method for preparing water-soluble, stable, luminescent Cu nanoclusters (NCs) via the process of size-focusing etching from nonluminescent nanocrystals is presented. Using glutathione as a model ligand, the smallest cluster, Cu2 , is selectively synthesized to form a nearly monodisperse product, eliminating the need for tedious size fractionation. Evolution of photoluminescence and absorption spectra reveal that the formation of stable cluster species occurs through surface etching. Intriguingly, the as-prepared CuNCs exhibit an aggregation-induced emission enhancement effect. The CuNCs emit a faint light when dispersed in aqueous solution, but generate a striking fluorescence intensity enhancement upon aggregation. Armed with these attractive properties, the emissive CuNCs are expected to open new opportunities for the construction of light-emitting diodes, chemosensors, and bioimaging systems.

Traveling through the Desalting Column Spontaneously Transforms Thiolated Ag Nanoclusters from Nonluminescent to Highly Luminescent.

This letter reports an unexpected observation in the purification of ultrasmall (<2 nm) thiolate-protected Ag nanoclusters (NCs) via a common separation technique (e.g., desalting column and ultrafiltration), where the nonluminescent Ag NCs were spontaneously transformed to highly luminescent NCs during the separation. This interesting finding was then used to develop a facile and fast (<5 min) synthesis method for highly luminescent Ag NCs. The key strategy was to use the separation process to selectively remove small species (e.g., salts and excess protecting ligands) from the Ag NC solution, which induced a size or structure-focusing of Ag NCs in the solution, leading to the formation of highly luminescent Ag NCs. The concurrent synthesis and purification of highly luminescent Ag NCs via a common "physical separation unit" could be further advanced in a continuous mode for large-scale production of luminescent Ag NCs.