Growth of freestanding nano- and microstructures with complex morphologies is a highly desired aspect for real applications of nanoscale materials in various technologies. Zinc oxide tetrapods (ZnO-T), which exhibit three-dimensional (3D) shapes, are of major importance from a technological applications point of view, and thus efficient techniques for growth of different varieties of tetrapod-based networks are demanded. Here, we demonstrate the versatile and single-step synthesis of ZnO-T with different arm morphologies by a simple flame transport synthesis (FTS) approach, forming a network. Morphological evolutions and structural intactness of these tetrapods have been investigated in detail by scanning electron microscopy, X-ray diffraction, and micro-Raman measurements. For a deeper understanding of the crystallinity, detailed high-resolution transmission electron microscopic studies on a typical ZnO tetrapod structure are presented. The involved growth mechanism for ZnO tetrapods with various arm morphologies is discussed with respect to variations in experimental conditions. These ZnO-T have been utilized for photocatalytic degradation and nanosensing applications. The photocatalytic activities of these ZnO-T with different arm morphologies forming networks have been investigated through the photocatalytic decolorization of a methylene blue (MB) solution under UV light illumination at ambient temperature. The results show that these ZnO-T exhibit strong photocatalytic activities against MB and its complete degradation can be achieved in very short time. In another application, a prototype of nanoelectronic sensing device has been built from these ZnO-T interconnected networks and accordingly utilized for UV detection and H2 gas sensing. The fabricated device structures showed excellent sensing behaviors for promising practical applications. The involved sensing mechanisms with respect to UV photons and H2 gas are discussed in detail. We consider that such multifunctional nanodevices based on ZnO tetrapod interconnected networks will be of interest for various advanced applications.

Magnetoelectric composite materials are promising candidates for highly sensitive magnetic-field sensors. However, the composites showing the highest reported magnetoelectric coefficients require the presence of external d.c. magnetic bias fields, which is detrimental to their use as sensitive high-resolution magnetic-field sensors. Here, we report magnetoelectric composite materials that instead rely on intrinsic magnetic fields arising from exchange bias in the device. Thin-film magnetoelectric two-two composites were fabricated by magnetron sputtering on silicon-cantilever substrates. The composites consist of piezoelectric AlN and multilayers with the sequence Ta/Cu/Mn(70)Ir(30)/Fe(50)Co(50) or Ta/Cu/Mn(70)Ir(30)/Fe(70.2)Co(7.8)Si(12)B(10) serving as the magnetostrictive component. The thickness of the ferromagnetic layers and angle dependency of the exchange bias field are used to adjust the shift of the magnetostriction curve in such a way that the maximum piezomagnetic coefficient occurs at zero magnetic bias field. These self-biased composites show high sensitivity to a.c. magnetic fields with a maximum magnetoelectric coefficient of 96 V cm(-1) Oe(-1) at mechanical resonance.

We present a simple two-stage vapour-solid synthesis method for the growth of bismuth chalcogenide (Bi2Te3, Bi2Se3) topological insulator nanowires/nanobelts by using Bi2Se3 or Bi2Te3 powders as source materials. During the first stage of the synthesis process nanoplateteles, serving as "catalysts" for further nanowire/nanobelt growth, are formed. At a second stage of the synthesis, the introduction of a N2 flow at 35 Torr pressure in the chamber induces the formation of free standing nanowires/nanobelts. The synthesised nanostructures demonstrate a layered single-crystalline structure and Bi : Se and Bi : Te ratios 40 : 60 at% for both Bi2Se3 and Bi2Te3 nanowires/nanobelts. The presence of Shubnikov de Haas oscillations in the longitudinal magneto-resistance of the nanowires/nanobelts and their specific angular dependence confirms the existence of 2D topological surface states in the synthesised nanostructures.

effectively used for multifunctional applications ranging from light-weight space technologies, high-temperature fl exible sensors to stretchable implants on or into human bodies. [ 1b , 5 ] The utilization of Q1D nanostructures from metal oxide semiconductors (ZnO, Fe 2 O 3 , Al 2 O 3 , TiO 2 , etc.) as building units of macroscopic 3D networks is advantageous due to the fact that mechanical fl exibility and excellent electrical/sensing properties [ 3a , 4a , 6 ] of these Q1D nanostructures may be additionally implemented in the 3D networks. The successful fabrication of such multifunctional 3D networks is still a very challenging task and simply not possible with every nanowire synthesis technique. A variety of growth methods starting from conventional vapor-liquid-solid [ 7 ] to advanced lithography [ 8 ] techniques has been utilized for synthesizing the Q1D nanostructures from several metal oxides in different forms, but they still lack with key issues, e.g., appropriate integration, formation of fl exible networks, and others with regard to device applications. To overcome latter integration diffi culties, different strategies for direct fabrication of Q1D nano-and microstructures on microchips have been investigated and the corresponding devices have demonstrated high performances, too. [ 9 ] The 3D fl exible networks made from Q1D nanostructures, in this context, could become better alternates for an easy and direct realization of applications based on the nanoscale materials. However, typical availability of simple, cost-effective, and versatile synthesis techniques of fl exible networks, which is an equally important aspect amongst other listed above, is still not reported extensively.For the fabrication of macroscopic 3D interconnected nanowire networks, some advanced and multistep fabrication techniques have already been utilized. [ 10 ] Although these methods have shown their abilities to fabricate macroscopic 3D networks, they still involve high cost and complex synthesis steps which limit the mass scale production of such networks and hence their appropriate applications. In this regard, the fl ame transport synthesis (FTS) [ 4b ] approach demonstrated an enormous potential for metal oxide nanostructuring in a versatile and cost-effective manner. Structures ranging from singlecrystal ZnO nanoscale rods to centimeter size 3D interconnected network consisting of ZnO nano-and microtetrapods have been successfully synthesized by the FTS approach. The 3D networks have shown various possible and very promising applications in different fi elds. [ 11 ]