Large-scale self-assembly of meso-, micro-, and nanostructured building components with highly specific morphology and novel properties are of great interest to chemists and material scientists. Remarkable progress has been made in the self-assembly of highly organized building blocks of metals, [1] semiconductors, [2] copolymers, [3] organic-inorganic hybrid materials, [4] and biomaterials [5] based on different driving mechanisms. However, controlling the assembly of primary building units, for example flakes, into curved hollow structures is still a challenge for materials self-assembly.[6] The ability to assemble primary units into hollow structures is in great demand by scientists not only because of the role this plays in better understanding the concept of self-assembly with artificial building blocks but also for its great potential for technological applications. [7] Vanadium oxides, in which the vanadium is known to exist in a wide range of oxidation states, from +2, as in VO, to +5, as in V 2 O 5 , have been extensively studied as a well-known kind of transition-metal oxide because they have unique electrical and optical properties. [8] Regarding the V 5+ and V 4+ oxides, various nanostructures (e.g., nanotubes, nanowires, nanofibers, nanobelts, nanorods, and mesoporous structures) have already been synthesized by a variety of methods, [9] including reverse-micelle transition, the sol-gel process, hydrothermal treatment, and electrochemical deposition. As expected, the various nanostructures of V 4+and V 5+ oxides lead to a wide variety of potential applications, including sensors, [10] optical switching devices, [11] optical datastorage media, [12] and electrode materials for Li secondary batteries.[13] By contrast, there are only limited reports concerning the synthesis of V 3+ oxide nanostructures and their interesting properties, [14] and thus it still remains a challenge to develop simpler and versatile approaches to V 3+ oxide nanostructures.In this communication, we describe a simple hydrothermal method to organize as-formed building blocks of flakes into VOOH hollow curved architectures by means of the "aggregation-then-growth" process: 1) freshly formed VOOH monomers aggregate around the gas/liquid interface to form hollow VOOH spheres and 2) the in situ formed building units of flakes continue to grow during the following hydrothermal process. This one-pot hierarchical organizing scheme relies primarily on the N 2 gas bubbles produced in the reaction process, representing another way of organizing flake building blocks into hollow curved architectures; this is different from previously reported ways using, for example, emulsified soft templates, hydrophobic attraction, or the solid templates resulting from variation of the chemical composition of the building units.[15] The as-obtained VOOH hollow "dandelions", a new-phased and unique V 3+ oxide nanostructure, offer the first opportunity to investigate the Li + charge-and-discharge electrochemical properties for V 3+ oxides.Important info...

Large-scale self-assembly of meso-, micro-, and nanostructured building components with highly specific morphology represents a particularly attractive class of materials because they exhibit many novel characteristics owing to their novel properties while possessing relatively large dimensions. [1] In this regard, remarkable progress has been made in the selfassembly of highly organized building blocks of metals, [2] semiconductors, [3] copolymers, [4] organic-inorganic hybrid materials, [5] and biomaterials [6] based on different driving mechanisms. Moreover, controlling the primary building units of flakes assembled into curved hollow structures represents another challenge for materials self-assembly, while the reported excellent work mainly focused on spheres [7] and cages. [8] For example, gold nanocrystal/silica arrays could be synthesized through the self-assembly of watersoluble micelles with soluble silica. [9] CuO hollow dandelions have also been assembled from nanorods and nanosheets by a simple hydrothermal process. [10] Herein, we extend the assembly of nanoflakes into one-dimensional hollow architecture on a large scale.The Kirkendall effect has proved to be an effective way of manipulating structural template precursors of existing nanostructures to obtain the desired hollow-structured materials without altering the precursor structure or morphology. In particular, an exciting strategic approach has been successfully developed where chemical transformation via the Kirkendall effect occurs without the loss of the original precursor shape in selenide systems, owing to an understanding of thermodynamics, kinetics, and the intrinsic atomic-scale structural mechanism of the nanocrystal reaction. [11] Moreover, Zeng et al. prepared hollow ZnO dandelions from nanorods and nanosheets by a modified Kirken-dall process. [12] Qi et al. reported that rhombododecahedral silver cages have been prepared by self-assembly coupled with a precursor crystal templating approach from Ag 3 PO 4 via the Kirkendall effect. [13] In this work, the Kirkendall effect has been successfully used to construct 3D hollow titanate tubular hierarchitectures from an intermediate precursor.Titanates are well known as functional ceramic materials (dielectric, piezoelectric, ferroelectric, and low infrared absorption), and their characteristic morphologies on the nanoscale are used as structural reinforcements in polymers, metals, and ceramic composites. [14] Moreover, titanium dioxide (titania) is one of the most important metal oxides: Among its three natural crystalline forms (anatase, brookite, and rutile), rutile is the most stable phase, whereas anatase has superior optoelectronic and photochemical properties. Furthermore, there is also great interest in the fabrication of titania with nanoscale dimensions and high morphological specificity from an existing titanate nanoscale motif. For instance, anatase nanowires have been prepared by heating acid-washed titanate nanowires for 4 h in air, where the titanates were initially gene...

Necklace-like hollow carbon nanospheres (CNSs) have been successfully synthesized from the pentagon-including reactants, which provide an auxiliary example for the theoretical prediction that necklace-like hollow CNSs are assumed to be composed of the regular occurrence of nonhexagonal rings at the atomic level. Benefits of the as-obtained hollow CNSs also arise from the high Brunauer-Emmett-Teller value of 594.32 m(2)/g and a narrow pore distribution at 5 nm. The electrochemical hydrogen storage experiments for the as-obtained necklace-like hollow CNSs exhibit a capacity of 242 mAh/g at the current density of 200 mA/g, corresponding to a hydrogen storage of 0.89 wt %, which is higher than the previously reported electrochemical capacities for the multiwalled carbon nanotubes (MWCNTs). Furthermore, the as-obtained necklace-like hollow CNSs show a lithium capacity advantage compared with the carbon solid particles for application in lithium batteries. These results indicate that the necklace-like hollow CNSs provide a new candidate for the application in hydrogen storage and lithium batteries.