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Urchinlike TiO2 spheres with tunable chamber structure were synthesized using a template-free solvothermal method. The unique sphere-in-sphere chamber structure allows multiple reflections of UV light resulting in greatly enhanced photocatalytic activity. This work provided novel structural platforms for novel materials and device applications.

intermediate frequencies, T u (q) interpolates smoothly between these two limiting behaviours 12 .The behaviour seen in Fig. 2 is consistent with KTB dynamics, if we identify the crossover with T KTB of an isolated bilayer. Above T KTB , the conductivity is predicted to scale according to 13±15 :The scaling function S(q/) is constrained by the physics of the high-and low-frequency limits. As q= !`, S must approach i/q in order for j to assume its superconducting form, equation (1). At low frequencies, S approaches a real constant S 1 (0) which characterizes the d.c. conductivity of the normal state. By comparing the measured complex conductivity to equation (2), we can extract both the phase stiffness and correlation time at each temperature. To analyse the experimental data in terms of equation (2), we note that the phase angle of the complex conductivity, J [ tan 2 1 j 2 =j 1 , equals the phase angle of S(q/). Therefore J depends only on the single parameter , and is independent of T 0 u . With the appropriate choice of (T), all the measured values of J should collapse to a single curve when plotted as a function of the normalized frequency q/. Knowing (T), T 0 u is obtained from a collapse of the normalized conductivity magnitude, (~=k B T 0 v jjqj=j Q , to jSq=j. Figure 3 shows the collapse of the data to the phase angle and magnitude of S. As anticipated, S approaches a real constant in the limit q= ! 0, and approaches i/q as q= !`.When analysed further, the data reveal a con®rmation of thermal generation of vortices in the normal state. In the KTB picture we expect that the d.c. conductivity will equal k B T/n f D© 2 0 , which is thè¯u x-¯ow' conductivity of n f free vortices with quantized¯ux © 0 , and diffusivity D (ref. 16). Together with equation (2), this implies that is a linear function of n f , that is, 0 n f a vc =£, where a vc is the area of a vortex core, £ [ T=T 0 u is the reduced temperature, and 0 [ p 2 S 1 0D=a vc . Moreover, we expect that n f will be a thermally activated function, except for T very close to T KTB . The activation energy is simply Ck B T 0 u , where C is a non-universal constant of order unity. It follows that the¯uctuation frequency depends exponentially on the reciprocal of the reduced temperature, 0 =£exp 2 2C=£. The inset to Fig. 3 is a plot of log(£) versus 1/£ which shows that the exponential relation is observed over nearly four orders of magnitude. This is direct evidence that vanishing of phase coherence in our samples re¯ects the dynamics of thermally generated vortices. From the slope and intercept of a straight-line ®t we obtain C 2:23 and 0 1:14 3 10 14 s 2 1 .In Fig. 4 we present the behaviour of the bare stiffness and phasecorrelation time obtained from our measurement and modelling of j(q). The main panel contrasts T 0 u with the dynamical stiffness T u (q) measured at 150 and 400 GHz. The inset shows t as a function of temperature together with hatching that highlights the region where t ,~=k B T.The parameters displayed in Fig. 4 suggest that while phase ...

Electrical energy storage plays an increasingly important role in modern society. Current energy storage methods are highly dependent on lithium-ion energy storage devices, and the expanded use of these technologies is likely to affect existing lithium reserves. The abundance of sodium makes Na-ion-based devices very attractive as an alternative, sustainable energy storage system. However, electrodes based on transition-metal oxides often show slow kinetics and poor cycling stability, limiting their use as Na-ion-based energy storage devices. The present paper details a new direction for electrode architectures for Na-ion storage. Using a simple hydrothermal process, we synthesized interpenetrating porous networks consisting of layer-structured V(2)O(5) nanowires and carbon nanotubes (CNTs). This type of architecture provides facile sodium insertion/extraction and fast electron transfer, enabling the fabrication of high-performance Na-ion pseudocapacitors with an organic electrolyte. Hybrid asymmetric capacitors incorporating the V(2)O(5)/CNT nanowire composites as the anode operated at a maximum voltage of 2.8 V and delivered a maximum energy of ∼40 Wh kg(-1), which is comparable to Li-ion-based asymmetric capacitors. The availability of capacitive storage based on Na-ion systems is an attractive, cost-effective alternative to Li-ion systems.