Effective piezoelectric response of substrate-integrated ZnO nanowire array devices on galvanized steel.

Harvesting waste energy through electromechanical coupling in practical devices requires combining device design with the development of synthetic strategies for large-area controlled fabrication of active piezoelectric materials. Here, we show a facile route to the large-area fabrication of ZnO nanostructured arrays using commodity galvanized steel as the Zn precursor as well as the substrate. The ZnO nanowires are further integrated within a device construct and the effective piezoelectric response is deduced based on a novel experimental approach involving induction of stress in the nanowires through pressure wave propagation along with phase-selective lock-in detection of the induced current. The robust methodology for measurement of the effective piezoelectric coefficient developed here allows for interrogation of piezoelectric functionality for the entire substrate under bending-type deformation of the ZnO nanowires.

Anion dependent self-assembly of a linear hexanuclear Yb(III) salen complex with enhanced near-infrared (NIR) luminescence properties.

Reactions of H2salen (H2L, N,N'-ethylene bis(salicylideneimine)) with Yb(CF3SO3)3, Yb(OAc)34H2O and Yb(NO3)36H2O in MeOH­EtOH under reflux gave NIR luminescent complexes [Yb6L9(H2L)2] (1), [Yb3L3(HL)(OH)2] (2) and [Yb2L2(H2L)2(NO3)(MeOH)2]NO3 (3), respectively.

Vertical ZnO nanowire growth on metal substrates.

Vertical growth of ZnO nanowires is usually achieved on lattice-matched substrates such as ZnO or sapphire using various vapor transport techniques. Accomplishing this on silicon substrates requires thick ZnO buffer layers. Here we demonstrate growth of vertical ZnO nanowires on FeCrAl substrates. The pre-annealing prior to growth appears to preferentially segregate Al and O to the surface, thus leading to a self-forming, thin pseudo-buffer layer, which then results in vertical nanowire growth as on sapphire substrates. Metal substrates are more suitable and cheaper than others for applications in piezoelectric devices, and thin self-forming layers can also reduce interfacial resistance to electrical and thermal conduction.

Investigation of Nucleation Mechanism and Tapering Observed in ZnO Nanowire Growth by Carbothermal Reduction Technique.

ZnO nanowire nucleation mechanism and initial stages of nanowire growth using the carbothermal reduction technique are studied confirming the involvement of the catalyst at the tip in the growth process. Role of the Au catalyst is further confirmed when the tapering observed in the nanowires can be explained by the change in the shape of the catalyst causing a variation of the contact area at the liquid-solid interface of the nanowires. The rate of decrease in nanowire diameter with length on the average is found to be 0.36 nm/s and this rate is larger near the base. Variation in the ZnO nanowire diameter with length is further explained on the basis of the rate at which Zn atoms are supplied as well as the droplet stability at the high flow rates and temperature. Further, saw-tooth faceting is noticed in tapered nanowires, and the formation is analyzed crystallographically.

Surface smoothness effect for the direct growth of carbon nanotubes on bulk FeCrAl metal substrates.

We investigate effects of surface smoothness and surface chemistry on the nature of multi-walled CNTs (MWCNTs) grown directly on FeCrAl substrates. A single sample was grown that contained a gradation in surface morphologies ranging from 2.9 nm to 30.2 nm RMS. The MWCNTs were grown using ethylene and H2 gases. Characterization was done using atomic force microscopy (AFM), scanning electron microscopy (SEM), and Auger elemental surface analysis. In smooth regions, MWCNTs demonstrated high-density vertical aligned growths; however, patches of approximately 10-20 microm where poor MWCNT growth occurred. In contrast, rough regions of the surface exhibited a continuous blanket layer of MWCNTs, albeit growth was spaghetti-like throughout this layer. The variation in nature of MWCNT growths was directly dependent on the surface roughness, which can affect surface growth chemistry of MWCNTs. Auger elemental analysis determined carbon was observed everywhere on the surface, but carbon was strongest over the smooth regions of high density growth; while relatively less carbon was detected over the patches with poor MWCNT growth, as well as over the blanket layer of the rough region. Oxygen was also measured, which was detected both within the patches of poor MWCNT growth in the smooth regions and over the blanket layer of the rough region. However, measurements of Cr and Al were exhibiting mixed trends: Cr was detected more strongly than Al over the rough region; whereas the opposite was observed in the patches of poor MWCNT growth in the smooth region. The surface smoothness affects the surface chemistry involving the nature of MWCNT growth and may also affect the surface chemistry involving the metal substrate itself; therefore, comparisons on the nature of MWCNT growths must also take careful consideration of the surface smoothness.

Multinuclear luminescent Schiff-base Zn-Nd sandwich complexes.

Multinuclear 3d-4f complexes with sandwichlike molecular structures are formed with the Schiff-base ligand bis(3-methoxysalicylidene)ethylene-1,2-phenylenediamine(H(2)L). The stoichiometry and structures are dependent on the Zn:Nd ratio and counteranions present. They are trinuclear [Nd(ZnL)2(NO3)2(H2O)2].NO3.EtOH.H2O (1), [Nd(ZnL)2Cl2(H2O)3].Cl.2MeOH.5H2O (2), and tetranuclear [Nd2(ZnL)2Cl6(MeOH)2].MeOH (3). Dinuclear complex [NdZnL(NO3)3MeCN].MeCN (4) was also characterized. Near-infrared (NIR) lanthanide luminescence is observed in these complexes.

Design and synthesis of a near infra-red luminescent hexanuclear Zn-Nd prism.

The use of the Schiff-base ligand N,N'-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine (H2L) and 1,4-benzenedicarboxylate (BDC) enables the construction of the hexanuclear luminescent Zn-Nd complex [Zn4Nd2L4(1,4-BDC)2].[Nd(NO3)5(H2O)].Et2O.2EtOH.3H2O.

Synthesis and near infrared luminescence of a tetrametallic Zn2Yb2 architecture from a trinuclear Zn3L2 Schiff base complex.

Near infrared luminescence is observed in tetrametallic [Zn2Yb2L2(mu-OH)2Cl4].2MeCN which is obtained from the Zn3 Schiff-base complex [Zn3L2(NO3)2].MeOH, (H2L =N,N'-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine).