Manipulation of Interfacial Diffusion for Controlling Nanoscale Transformation

Asymmetric Self-Assembly of Colloidal Superstructures in Nested Transient Emulsion Aerosols

Emulsions are versatile and robust platforms for colloidal self-assembly, but their ability to create complex and functional superstructures is hindered by the inherent symmetry of droplets. Here the creation of an aerosol of nested transient emulsion droplets with inherent asymmetry is reported, achieved by converging beams of water and 1-butanol mists. Self-assembly of nanoparticles occurs within such emulsion droplets as driven by the rapid two-phase interface diffusion, producing anisotropic superstructures. A unique hollowing process is observed due to the asymmetric diffusion of solvents, akin to the Kirkendall effect. This novel assembly platform offers several advantages, including asymmetric self-assembly in air, surfactant-free operation, and tunable droplet size. It enables the creation of clean, functional nanoparticle superstructures that can be easily disassembled when needed. These advancements pave the way for exploring intricate, anisotropic superstructures with diverse applications that are unavailable in conventional superstructures of spherical symmetry.

Advanced morphological control over Cu nanowires through a design of experiments approach

Copper nanowires (CuNWs), featuring anisotropic highly conductive crystalline facets, represent an ideal nanostructure to fabricate on-demand materials as transparent electrodes and efficient electrocatalysts. The development of reliable and robust CuNWs requires achieving a full control over their synthesis and morphology growth, a challenge that continues to puzzle materials scientists. In this study, we systematically investigated the correlation between the critical synthetic parameters and the structural properties of nanowires using a design of experiments (DOE) approach. Multiparametric variation of experimental reaction conditions combined with orthogonal technical analysis allowed us to develop a sound predictive model that provides guidelines for designing CuNWs with controlled morphology and reaction yield. Beyond these synthetic achievements, voltammetric and electrocatalytic experiments were used to correlate the CuNWs morphology and structure to their catalytic activity and selectivity toward CO2 electroreduction, thus opening new avenues for further intersectoral actions.

Crystal Facet Engineering on SrTiO3 Enhances Photocatalytic Overall Water Splitting

Single-crystal semiconductor-based photocatalysts exposing unique crystallographic facets show promising applications in energy and environmental technologies; however, crystal facet engineering through solid-state synthesis for photocatalytic overall water splitting is still challenging. Herein, we develop a novel crystal facet engineering strategy through solid-state recrystallization to synthesize uniform SrTiO3 single crystals exposing tailored {111} facets. The presynthesized low-crystalline SrTiO3 precursors enable the formation of well-defined single crystals through kinetically improved crystal structure transformation during solid-state recrystallization process. By employing subtle Al3+ ions as surface morphology modulators, the crystal surface orientation can be precisely tuned to a controlled percentage of {111} facets. The photocatalytic overall water splitting activity increases with the exposure percentage of {111} facets. Owing to the outstanding crystallinity and favorable anisotropic surface structure, the SrTiO3 single crystals with 36.6% of {111} facets lead to a 3-fold enhancement of photocatalytic hydrogen evolution rates up to 1.55 mmol·h-1 in a stoichiometric ratio of 2:1 than thermodynamically stable SrTiO3 enclosed with isotropic {100} facets.

Diffusion-Controlled Crystal Engineering with Diverse Antisolvent Intervention for the Preparation of High-Quality Hybrid Perovskite Films

Antisolvent engineering is routinely used to modulate the crystallization of perovskite films as they can offer an additional driving force for nucleation. Actually, the intervention of antisolvent into nucleation is thought to involve some relatively fast and complex processes, which, however, are not fully understood so far. Here, the diffusion of the organic amine cation FA+ (one dominated precursor) and its distribution in a spin-coating process in different antisolvents is simulated by the computational fluid dynamics (CFD) model. It is suggested that a moderate diffusion rate (like that in the case of toluene as an antisolvent) not only enables to form a very uniform distribution of FA+ ions on the substrate, beneficial to the uniform nucleation of the intermediate phase, but also can balance the nucleation and growth rates of the intermediate phase, thereby suppressing undesired heterogeneous nucleation and growth. Results show that the perovskite film fabricated using toluene as an antisolvent has a high quality, based on which higher power conversion efficiencies of up to 24.32% are achieved for perovskite solar cells.

Recent Advances of Seed-Mediated Growth of Metal Nanoparticles: from Growth to Applications

Unprecedented advances in metal nanoparticle synthesis have paved the way for broad applications in sensing, imaging, catalysis, diagnosis, and therapy by tuning the optical properties, enhancing catalytic performance, and improving chemical and biological properties of metal nanoparticles. The central guiding concept for regulating the size and morphology of metal nanoparticles is identified as the precise manipulation of nucleation and subsequent growth, often known as seed-mediated growth methods. However, since the growth process is sensitive not only to the metal seeds but also to capping agents, metal precursors, growth solution, growth/incubation time, reductants, and other influencing factors, the precise control of metal nanoparticle morphology is multifactorial. Further, multiple reaction parameters are entangled with each other, so it is necessary to clarify the mechanism by which each factor precisely regulates the morphology of metal nanoparticles. In this review, to exploit the generality and extendibility of metal nanoparticle synthesis, the mechanisms of growth influencing factors in seed-mediated growth methods are systematically summarized. Second, a variety of critical properties and applications enabled by grown metal nanoparticles are focused upon. Finally, the current progress and offer insights on the challenges, opportunities, and future directions for the growth and applications of grown metal nanoparticles are reviewed.

Formation of Core-Shell AuCu@Ag Nanocrystals through the Nanoscale Kirkendall Effect

Polymetallic nanocrystals (NCs) consist of multiple metal elements. A powerful platform to achieve the flexible construction of polymetallic NCs is highly desired but challenging. Herein, we devise a model system that realizes metal atom diffusion between different NCs, resulting in the formation of polymetallic NCs. The differential bond strength between different metal atoms is proposed to initiate such metal atom diffusion, and the specific high surface-to-volume ratio of the NCs can expedite the diffusion process. Taking the Au-Cu-Ag trimetallic system as an example, core-shell AuCu@Ag NCs were successfully formed by combining AgCu NCs with Au NCs. The evolution process was explored, and the gradual fusion of simple NCs into AuCu@Ag NCs was unambiguously observed, which could be attributed to the larger bond strength of Au-Cu than that of Ag-Cu. This work offers an opportunity/platform in theory and experiment to expand the synthesis framework as well as the polymetallic NC list.

Single-Site SnOCu Pairs with Interfacial Electron Transfer Effect for Enhanced Electrochemical Catalysis and Sensing

As advanced electrochemical catalysts, single-atom catalysts have made great progress in the field of catalysis and sensing due to their high atomic utilization efficiency and excellent catalytic performance. Herein, stannum-doped copper oxide (CuOSn₁ ) nanosheets with single-site SnOCu pairs as active sites are synthesized as electrocatalysts for biological molecule detection. Compared with CuO-based electrochemical sensors, the CuOSn₁ -based electrochemical sensors have improved detection sensitivity with a rapid electrochemical response. Theoretical calculation reveals that the single-site SnOCu pairs induced interfacial electronic transfer effect can strengthen hydroxy adsorption and thus reduce the energy barrier of the biological molecule oxidation process. As a concept application, electrochemical detection of dopamine and uric acid molecules is achieved, exhibiting satisfactory sensitivity and selectivity. This work demonstrates the advantages of single-site SnOCu pairs in electrochemical catalysis and sensing, which provides theoretical guidance for understanding the structure-activity relationship for sensitive electrochemical sensing.

Solid-State Reaction Synthesis of Nanoscale Materials: Strategies and Applications

Nanomaterials (NMs) with unique structures and compositions can give rise to exotic physicochemical properties and applications. Despite the advancement in solution-based methods, scalable access to a wide range of crystal phases and intricate compositions is still challenging. Solid-state reaction (SSR) syntheses have high potential owing to their flexibility toward multielemental phases under feasibly high temperatures and solvent-free conditions as well as their scalability and simplicity. Controlling the nanoscale features through SSRs demands a strategic nanospace-confinement approach due to the risk of heat-induced reshaping and sintering. Here, we describe advanced SSR strategies for NM synthesis, focusing on mechanistic insights, novel nanoscale phenomena, and underlying principles using a series of examples under different categories. After introducing the history of classical SSRs, key theories, and definitions central to the topic, we categorize various modern SSR strategies based on the surrounding solid-state media used for nanostructure growth, conversion, and migration under nanospace or dimensional confinement. This comprehensive review will advance the quest for new materials design, synthesis, and applications.

Manipulating Copper Dispersion on Ceria for Enhanced Catalysis: A Nanocrystal-Based Atom-Trapping Strategy

Due to tunable redox properties and cost-effectiveness, copper-ceria (Cu-CeO2 ) materials have been investigated for a wide scope of catalytic reactions. However, accurately identifying and rationally tuning the local structures in Cu-CeO2 have remained challenging, especially for nanomaterials with inherent structural complexities involving surfaces, interfaces, and defects. Here, a nanocrystal-based atom-trapping strategy to access atomically precise Cu-CeO2 nanostructures for enhanced catalysis is reported. Driven by the interfacial interactions between the presynthesized Cu and CeO2 nanocrystals, Cu atoms migrate and redisperse onto the CeO2 surface via a solid-solid route. This interfacial restructuring behavior facilitates tuning of the copper dispersion and the associated creation of surface oxygen defects on CeO2 , which gives rise to enhanced activities and stabilities catalyzing water-gas shift reaction. Combining soft and solid-state chemistry of colloidal nanocrystals provide a well-defined platform to understand, elucidate, and harness metal-support interactions. The dynamic behavior of the supported metal species can be further exploited to realize exquisite control and rational design of multicomponent nanocatalysts.

Exfoliation-induced O-doped g-C3N4 Nanosheets with improved photoreactivity towards RhB degradation and H2 evolution

Graphitic carbon nitride (g-C3N4) nanosheets exfoliated from bulk-sized counterparts are limited by quantum size effect-induced widened bandgap. In this work, a (NH4)2S2O8 (APS) induced thermal exfoliation approach is introduced to...

Architectural Genesis of Metal(loid)s with Iron Nanoparticle in Water

Reactions of core-shell iron nanoparticles with metal(loid)s in water can form an array of nanostructures such as Ag-seed/dendrite, As-subshell, U-yolk, Co-hollowshell, and Cs-spot. Nonetheless, there is a lack of profound understanding in the genesis of these amazing geometries. Herein, we propose a concept to unravel the interdiffusion between the core-shell iron nanoparticle and metal(loid)s, where several key interactions including the Kirkendall effect, metal(loid) character effect, and reaction condition effect are involved in determining the structure of the final solid reaction products. Particularly, the architectural growths of metal(loid)s with iron nanoparticles in water can be manipulated mutually or singly by the following factors: standard redox potential difference, magnetic property, electrical charge and conductivity, as well as the iron (hydr)oxide shell structure under different solution chemistry and operation conditions. This contribution provides a theoretical basis to rationalize the architectural genesis of various metal(loid)s with iron nanoparticles, which will benefit the real practice for synthesizing functional iron-based nanoparticles and recovering the rare/precious metal(loid)s by iron nanoparticles from water.

Silica Jar-with-Lid as Chemo-Enzymatic Nano-Compartment for Enantioselective Synthesis inside Living Cells

Nanodevices, harvesting the power of synthetic catalysts and enzymes to perform enantioselective synthesis inside cell, have never been reported. Here, we synthesized round bottom jar-like silica nanostructures (SiJARs) with a chemo-responsive metal-silicate lid. This was isolated as an intermediate structure during highly controlled solid-state nanocrystal-conversion at the arc-section of silica shell. Different catalytic noble metals (Pt, Pd, Ru) were selectively modified on the lid-section through galvanic reactions. And, lid aperture-opening was regulated by mild acidic conditions or intracellular environment which accommodated the metal nanocrystals and enzymes, and in turn created an open-mouth nanoreactor. Distinct from the free enzymes, SiJARs performed asymmetric aldol reactions with high activity and enantioselectivity (yield >99 %, ee=95 %) and also functioned as the artificial catalytic organelles inside living cells. This work bridges the enormous potential of sophisticated nanocrystal-conversion chemistry and advanced platforms for new-to-nature catalysis.