New strategies for materials fabrication are of fundamental importance in the advancement of science and technology. Organometallic and other organic solution phase synthetic routes have enabled the synthesis of functional inorganic quantum dots or nanocrystals. These nanomaterials form the building blocks for new bottom-up approaches to materials assembly for a range of uses; such materials also receive attention because of their intrinsic size-dependent properties and resulting applications. Here we report a unified approach to the synthesis of a large variety of nanocrystals with different chemistries and properties and with low dispersity; these include noble metal, magnetic/dielectric, semiconducting, rare-earth fluorescent, biomedical, organic optoelectronic semiconducting and conducting polymer nanoparticles. This strategy is based on a general phase transfer and separation mechanism occurring at the interfaces of the liquid, solid and solution phases present during the synthesis. We believe our methodology provides a simple and convenient route to a variety of building blocks for assembling materials with novel structure and function in nanotechnology.

The integration of nanostructured materials into macroscopic devices that can translate phenomena at the nanoscale to the macroscopic level has proved key to paving the way to realizing applications of nanomaterials.[1] To date, although remarkable progress has been made in the self-assembly of building blocks such as nanocrystals, nanotubes, nanowires, and the newly discovered graphenes, [2][3][4][5][6][7][8][9][10] very little success has been achieved with three-dimensional (3D) macroscale assemblies. Herein we report the controlled assembly of single-layered graphene oxide (GO) into 3D macrostructures promoted by a noble-metal nanocrystal (Au, Ag, Pd, Ir, Rh, or Pt, etc.). Although the density of such macroassemblies is very low (ca. 0.03 g cm À3 ), they have shown excellent mechanical properties, and have been utilized as fixed-bed catalysts for a Heck reaction resulting in both 100 % selectivity and conversion. We expect our endeavor may further the research and practical applications of graphene-based materials.Graphene is a well-defined two-dimensional structure of carbon atoms. It has received a great deal of attention because of its unique electronic, thermal, and mechanical properties. [11][12][13] Micromechanical cleavage from highly ordered pyrolytic graphite (HOPG) and the reduction of exfoliated graphite oxide sheets (graphene oxide, GO) are commonly used to produce graphene; [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] the reduction of GO appears to be a viable approach to the large-scale production of graphene. GO is usually prepared by oxidation of graphite powder with strong oxidants such as a mixture of concentrated sulfuric acid and potassium permanganate. The abundant oxygen-containing groups on GO endow it with excellent aqueous dispersion and make it easy to modify. [16][17][18][19][20][21][22][23][24][25] Recently, efforts have focused on the fabrication of graphene films through the self-assembly of the well-dispersed GO or functionalized graphene sheets. [20][21][22][23] Herein, we demonstrate that the 3D assembly of GO into macroscopic porous structures has been achieved successfully with the assistance of noble-metal nanocrystals (Au, Ag, Pd, Ir, Rh, Pt, etc.). The macroscopic size of the obtained samples can be easily controlled by adjusting the volume of the vessel, and the microstructure (the number of the pores and the pore diameter) can be controlled by varying the effective concentration of GO. These results mean that the macroscopic and microscopic structure of the sample can be controlled in one step. It not only provides a simple way to fabricate porous structures from GO, but also shows that the GO can selfassemble into more complicated 3D structures. Furthermore, the combination of noble-metal nanocrystals and the GO single layers may result in some interesting properties. As an example, we show that the Pd-embedded assemblies exhibited excellent catalytic activity and selectivity for the Heck reaction; this indicates that the self-assembled 3D structure is...

SnO2 quantum dots (QDs) and ultrathin nanowires (NWs) with diameters of approximately 0.5-2.5 and approximately 1.5-4.5 nm, respectively, were controllably synthesized in a simple solution system. They are supposed to be ideal models for studying the continuous evolution of the quantum-confinement effect in SnO2 1D --> 0D systems. The observed transition from strong to weak quantum confinement in SnO2 QDs and ultrathin NWs is interpreted through the use of the Brus effective-mass approximation and the Nosaka finite-depth well model. Photoluminescence properties that were coinfluenced by size effects, defects (oxygen vacancies), and surface capping are discussed in detail. With the SnO2 QDs as building blocks, various 2D porous structures with ordered hexagonal, distorted hexagonal, and square patterns were prepared on silicon-wafer surfaces and exhibited optical features of 2D photonic crystals and enhanced gas sensitivity.

Uniform magnetite, hematite, and goethite nanocrystals were prepared through an attractive method based on an oleic acid/alcohol/water system. By adjusting the synthetic parameters (base concentration, alcohol content, categories of alcohols, etc.), the controlled synthesis of uniform magnetite, hematite, and goethite nanocrystals can be easily achieved. Detailed investigations on the effect of the experimental parameters on the morphology of the final products and the phase transitions among the magnetite, hematite, and goethite phases were carried out. Finally, a method of doping other metal ions into magnetite was developed and the magnetic properties of magnetite doped with different metal elements were studied.

In this paper, a hydrothermal synthetic route has been developed to prepare a class of rare-earth fluoride nanocrystals, which have shown gradual changes in growth modes with decreasing ionic radii and may serve as a model system for studying the underlying principle in the controlled growth of rare-earth nanocrystals. Furthermore, we demonstrate the functionalization of these nanocrystals by means of doping, which have shown visible-to-the-naked-eye green up-conversion emissions and may find application in biological labeling fields.

In this Full Paper, a water/alcohol/oleic acid system was developed to prepare NaYF4 nanocrystals with predictable size, shape and phase. The structural and kinetic factors that govern the phase and shape evolution of NaYF4 nanocrystals have been carefully studied, and the influence of NaF to Y3+ ratio, reaction time and temperature on the phase and shape evolution of the as‐prepared NaYF4 samples was systematically investigated and discussed. It was found that the NaF to Y3+ ratio was responsible for the shape evolution while temperature and reaction time was the key for the phase control of the NaYF4 nanocrystals. This study would be suggestive for the precisely controlled growth of inorganic nanocrystals, especially for those usually crystallizing in diverse crystal structures.

A one-pot method was developed to prepare atomic thick nanosheets of metastable TiO(2)(B), which has a unique open structure owing to the coupling of intrinsic channels and the preferentially exposed (010) facets. They display high activity of doping due to the rapid incorporation and diffusion along these open channels.

Regulating the electron transport layer (ETL) has been an effective way to promote the power conversion efficiency (PCE) of perovskite solar cells (PSCs) as well as suppress their hysteresis. Herein, the SnO2 ETL using a cost‐effective modification material rubidium fluoride (RbF) is modified in two methods: 1) adding RbF into SnO2 colloidal dispersion, F and Sn have a strong interaction, confirmed via X‐ray photoelectron spectra and density functional theory results, contributing to the improved electron mobility of SnO2; 2) depositing RbF at the SnO2/perovskite interface, Rb+ cations actively escape into the interstitial sites of the perovskite lattice to inhibit ions migration and reduce non‐radiative recombination, which dedicates to the improved open‐circuit voltage (Voc) for the PSCs with suppressed hysteresis. In addition, double‐sided passivated PSCs, RbF on the SnO2 surface, and p‐methoxyphenethylammonium iodide on the perovskite surface, produces an outstanding PCE of 23.38% with a Voc of 1.213 V, corresponding to an extremely small Voc deficit of 0.347 V.