We report a facile particle mediated aggregation protocol to synthesize "sea urchin"-like gold mesoparticles with tailored surface topography via a secondary nucleation and growth process. Surprisingly, these multitip Au mesoparticles are capable of self-assembling into monolayer or multiple layer arrays on Si substrates with a convincing reproducibility and homogeneity over large areas. Raman measurements show that these individual sea urchin-like multitipped gold mesoparticles exhibit a high enhancement of surface-enhanced Raman scattering (SERS). In addition, the sea urchin-like mesoparticle arrays display a further enhancement of SERS by 1 or 2 orders of magnitude over the individual mesoparticle due to the formation of additional hot spots between the particles. The current protocol stands out as a potentially interesting approach for the fabrication of technologically important SERS-based sensors.

In this study, a well-defined dendritic silver nanostructure can be large-scale synthesized in AgNO 3 (aqueous) at room temperature. The nonequilibrium and anisotropic growth at different silver ion concentrations result in controllable morphologies and morphological evolution. At high silver ion concentrations, a strong anisotropic growth contributes to a fine single crystalline silver dendrite. As the reaction proceeds, the dendritic structure transforms into a thermodynamically stable hexagonal structure. At a relatively low silver ion concentration, a particle-aggregated fractal pattern can be obtained due to relatively small anisotropy. As the reaction time increases, the transition from polycrystalline aggregates to a single crystal during silver dendritic growth can be observed. An oriented attachment mechanism can be used to explain the structural and morphological evolution of silver nanostructures. Silver nanostructures with various morphologies are expected to have significant potential applications in superhydrophobic surfaces, surface-enhanced Raman scattering, and others.

A hierarchical nanoparticle strategy to simultaneously gain super Raman signal amplification, high uniformity, and reproducibility is presented. Using hollow Au-Ag alloy nanourchins, an ultrahigh sensitivity, e.g., down to 1 fM concentrations for DEHP molecule is obtained. A small standard deviation of <10% is achieved by simply dropping and evaporating sub-100 nm nanourchins onto a substrate.

Self-assembly of nanoparticles has emerged as a powerful technique to integrate nanoparticles into well-defined ensembles with collective properties that are different from those of individual nanoparticles and bulk materials with the same chemical composition. Compared with the classical ion/molecule-mediated crystal growth, particle-mediated crystallographically ordered self-assembly is considered as "non-classical crystallization" and the resultant product is termed a "mesocrystal". In this tutorial review, we begin by summarizing the progresses of this field during last decade. Secondly, we outline developments in related fields such as grain rotation and oriented attachment as well as mesocrystals. Thridly, the recent progress in the syntheses of mesocrystals particularly in metals, and the related properties are introduced. Finally, some of the current open questions are discussed.

Metal species have a relatively high mobility inside mesoporous silica; thus, it is difficult to introduce the metal precursors into silica mesopores and suppress the migration of metal species during a reduction process. Therefore, until now, the controlled growth of metal nanocrystals in a confined space, i.e., mesoporous channels, has been very challenging. Here, by using a soft-enveloping reaction at the interfaces of the solid, liquid, and solution phases, we successfully control the growth of metallic nanocrystals inside a mesoporous silica template. Diverse monodispersed nanostructures with well-defined sizes and shapes, including Ag nanowires, 3D mesoporous Au, AuAg alloys, Pt networks, and Au nanoparticle superlattices are successfully obtained. The 3D mesoporous AuAg networks exhibit enhanced catalytic activities in an electrochemical methanol oxidation reaction. The current soft-enveloping synthetic strategy offers a robust approach to synthesize diverse mesoporous metal nanostructures that can be utilized in catalysis, optics, and biomedicine applications.

In this paper, through a simple and fast electroless metal deposition route, gold dendritic nanostructures are synthesized in aqueous conditions. The gold dendrites with a threefold symmetric characteristic were built up of numerous nanoparticles roughly 5–10 nm in size. The aggregated nanoparticles spontaneously experience a self-assembly process along crystallographic orientations and finally form a monocrystalline dendrite. An oriented attachment mechanism can be used to explain the nanoparticle-aggregated self-assembly process.

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Local electromagnetic enhancement excited from collective oscillations of free electrons on a highly roughened mental surface can induce greatly enhanced Raman scattering. Herein gold mesoparticles with various morphologies and highly roughened surfaces, including sea urchin-like, flower-like, starlike, meatball-like, and dendritic nanostructures are prepared using pentanol/water interface as a growth ''bed''. The morphologies of the prepared gold mesoparticles are well controlled by varying the concentrations of additives such as gold ions, ascorbic acid (AA) and cetyltrimethylammonium bromide (CTAB). Due to the unique structures such as rough surface, high internal porosity as well as complex morphology, these as-prepared mesocrystals exhibit a remarkable performance in surfaceenhanced Raman scattering (SERS) compared with polyhedral mesoparticles.