Alloy nanocrystals:Synthesis paradigms and implications

1.Introduction Noble metal nanocrystals serve as exceptional catalysts across a wide spectrum of industrial processes[1].Moreover,there exists a substantial demand for noble metal catalysts in emerging clean-energy applications,such as water-splitting hydrogen production and fuel cells.Incorporating non-noble transition metals or main-group metals into noble metal nanocrystals can reduce the weight of noble metals in the catalysts,thus remarkably lowering the cost.Furthermore,alloy nanocrystals offer intriguing catalytic properties that surpass those of their monometallic counterparts,thanks to the charge transfer between the constituent components and the expansion or shrinkage of the lattice size[2].

Scalable synthesis of sub-lO0 nm hollow carbon nanospheres for energy storage applications

Sub-100 nm hollow carbon nanospheres with thin shells are highly desirable anode materials for energy storage applications. However, their synthesis remains a great challenge with conventional strategies. In this work, we demonstrate that hollow carbon nanospheres of unprecedentedly small sizes （down to - 32.5 nm and with thickness of - 3.9 nm） can be produced on a large scale by a templating process in a unique reverse micelle system. Reverse micelles enable a spatially confined Stober process that produces uniform silica nanospheres with significantly reduced sizes compared with those from a conventional Stober process, and a subsequent well-controlled sol-gel coating process with a resorcinol-formaldehyde resin on these silica nanospheres as a precursor of the hollow carbon nanospheres. Owing to the short diffusion length resulting from their hollow structure, as well as their small size and microporosity, these hollow carbon nanospheres show excellent capacity and cycling stability when used as anode materials for lithium/sodium-ion batteries.

Optimizing surface-engineered ultra-small gold nanoparticles for highly efficient miRNA delivery to enhance osteogenic differentiation of bone mesenchymal stromal cells

Regulation of osteogenic differentiation of bone mesenchymal stromal cells （BMSCs） plays a critical role in bone regeneration. As small non-coding RNAs, microRNAs （miRNAs） play an important role in stem cell differentiation through regulating target-mRNA expression. Unfortunately, highly efficient and safe delivery of miRNAs to BMSCs to regulate their osteogenic differentiation remains challenging. Conventional inorganic nanocrystals have shown increased toxicity owing to their larger size precluding renal clearance. Here, we developed novel, surface-engineered, ultra-small gold nanoparticles （USAuNPs, 〈10 nm） for use as highly efficient miR-5106-delivery systems to enable regulation of BMSC differentiation. We exploited the effects of AuNPs coated layer-by-layer with polyethylenimine （PEI） and liposomes （Lipo） to enhance miR-5106-delivery activity and subsequent BMSC differentiation capacity. The PEI- and Lipo-coated AuNPs （Au@PEI@Lipo） showed negligible cytotoxicity, good miRNA-5106-binding affinity, highly efficient delivery of miRNAs to BMSCs, and long-term miRNA expression （21 days）. Additionally, compared with commercial Lipofectamine 3000 and 25 kD PEI, the optimized Au@PEI@Lipo-miR-5106 nanocomplexes significantly enhanced BMSC differentiation into osteoblast-like cells through activation of the Sox9 transcription factor. Our findings reveal a promising strategy for the rational design of ultra-small inorganic nanoparticles as highly efficient miRNA-delivery platforms for tissue regeneration and disease therapy.

Customizable Ligand Exchange for Tailored Surface Property of Noble Metal Nanocrystals

It is highly desirable,while still challenging,to obtain noble metal nanocrystals with custom capping ligands,because their colloidal synthesis relies on specific capping ligands for the shape control while conventional ligand exchange processes suffer from“the strong replaces the weak”limitation,which greatly hinders their applications.Herein,we report a general and effective ligand exchange approach that can replace the native capping ligands of noble metal nanocrystals with virtually any type of ligands,producing flexibly tailored surface properties.The key is to use diethylamine with conveniently switchable binding affinity to the metal surface as an intermediate ligand.As a strong ligand,it in its original form can effectively remove the native ligands;while protonated,it loses its binding affinity and facilitates the adsorption of new ligands,especially weak ones,onto the metal surface.By this means,the irreversible order in the conventional ligand exchange processes could be overcome.The efficacy of the strategy is demonstrated by mutual exchange of the capping ligands among cetyltrimethylammonium,citrate,polyvinylpyrrolidone,and oleylamine.This novel strategy significantly expands our ability to manipulate the surface property of noble metal nanocrystals and extends their applicability to a wide range of fields,particularly biomedical applications.