In-situ grown CuO and ZnO nanowire (NW) arrays were evaluated for their gassensing performance. The metal structures were fabricated by standard e-beamlithography, thermal evaporation and lift-off process onto a silicon substratewith gold electrodes. After integration onto a test structure with resistiveheater and thermocouple for temperature control, the samples were thermallyoxidized at 400°C. During thermal oxidation, nanowires were grownbetween the oxidized metal structures. The gas sensing performance of the NWarray was tested for carbon monoxide, - and a hydrocarbon-mixture (acetylene,ethane, ethene, and propene) at three relative humidity levels.

Titanium dioxide (TiO2) loaded with gold (Au) as noble metal, acts asan efficient photocatalyst that has been extensively investigated for watersplitting processes. In this paper, we report on the microstructure of atomiclayer deposited titanium dioxide and the crystallinity modification of thematerial using energetic electron beam irradiation. A rapid high-energy electronbeam induced crystallization of the nanostructures has been observedin-situ inside a High-Resolution Transmission ElectronMicroscope (HRTEM). The systematic crystallization of the nanomaterial occurringunder the electron beam irradiation (300 KV) indicates the transformation of thenear amorphous material into a mixture of two nuances of TiO2polymorphs, namely rutile and anatase. We believe that this transformation willenhance the efficiency of water splitting process, as the mixed phases of rutileand anatase are known to possess better optical properties than the individualpolymorphs of TiO2. This finding may be of particular interest indeveloping appropriate heat treatment methods for these nanostructures dedicatedto water splitting to increase their efficiency.

We recently demonstrated a sub-bandgap photoresponse with our wafer-scaleAu/TiO2 metallic-semiconductor photonic crystals (MSPhC). Thesub-bandgap energy with 590 nm peak could be absorbed in the form of hotelectron and injected to TiO2, which provides 5.28 times more energyfor photolysis than that of energy absorbed to flat TiO2. If thesolar energy already absorbed above 700 nm could be injected to the catalyst,higher than 10 times improvement will be achieved, and above 20% solar to fuelefficiency will be feasible with the robust but inefficient TiO2catalyst. In order to achieve photocurrent near and above 700 nm spectrum, wedeposited gold nanorods on the surface of MSPhC to incur localized surfaceplasmon (LSP) modes absorption and subsequent injection to the TiO2catalyst. We used electrophoretic deposition (EPD) method to deposit nanorods onthe top, sidewall and bottom well surface of the photonic nanocavities. Thedeposition of nanorods was achieved reasonably uniform and sparse not to blockthe optical cavities of MSPhC. Flat gold surfaces were tested at 4 differentsuspension densities to get the optimum gold nanorods density. Under 10V appliedelectric field, positively charged gold nanorods at the concentration of6.52×1013 #/mL could deposit MSPhC surfacewith the density of 230 #/µm2, which was reasonablyuniform and sparse. Preliminary tests show an absorbance increase near 700 nm onflat device coated with gold nanorods. Photocurrent measurement is under way todemonstrate the enhanced hot electron transfer over full visible light andnear-infrared solar spectrum.

Improved solar spectrum optical absorption in multilayered nanostructuresconsisting of metal, semiconductor and dielectric layers increase theirpotential for efficient photon to electron conversion. In this work, we analyzethe influence of different nanostructure shapes and dimensions on the opticalabsorption in the vacuum wavelength range of 400 nm to 1500 nm based on FiniteDomain Time Difference (FDTD) method. A periodic metallic photonic crystalcomposed of nanorods of gold, titanium oxide, and alumina is proposed byoptimizing thickness of Au and TiO2, aspect ratio, sidewall angle,and geometry of the elemental shape. A high aspect ratio structure consisting ofelliptical nose cone elements with optimized dimensions is seen to absorb morethan 90% of the solar spectrum in the range considered.

Glucose sensor based on ITO/ZnO NRs/GOx/nafion is fabricated andtested under different glucose concentrations. Hydrothermal growth method alongwith sol-gel technique is used to grow high quality ZnO nanorods that havewell-alignment and high density with an acceptable aspect ratio. The as-grown ofZnO nanorods are used to fabricate a working electrode that can be used forglucose detection in blood after a modification process with GOx andnafion membrane. Annealing at 110 °C helped in improves thecrystallinity of the seed layer and as a result, a high density and wellalignment as-grown ZnO nanorods were obtained. High sensitivity and shortresponse time were obtained from the fabricated device with an acceptable lowerlimit of detection.

The paper describes a novel electrochemical method of metal nanowire synthesisvia coherent cocrystallization of metal with metal salt. Using the methoddescribed, iron, copper, and tin nanowires as well as lead nanowalls in thematrix of ferrous chloride FeCl2 salt were synthesized. Influence ofelectrolyte composition and electrolysis regime on the deposit structure isrevealed. Morphology, chemical composition, and structure of the NW@salt nanocomposite isstudied and discussed.

An electrochemical glucose sensor based on zinc oxide (ZnO) nanorods isfabricated, characterized and tested. The ZnO nanorods are synthesized on indiumtitanium oxide (ITO) coated glass substrate, using the hydrothermal sol-geltechnique. The working principle of the sensor under investigation is based onthe electrochemical reaction taking place between cathode and anode, in thepresence of an electrolyte. A platinum plate, used as the cathode andNafion/Glucose Oxidase/ZnO nanorods/ITO-coated glass substrate used as anode, isimmersed in pH 7.0 phosphate buffer solution electrolyte to test for thepresence of glucose. Several amperometric tests are performed on the fabricatedsensor to determine the response time, sensitivity and limit of detection of thesensor. A fast response time less than 3 s with a high sensitivity of 1.151 mAcm-2mM-1 and low limit of detection of 0.089 mM isreported. The glucose sensor is characterized using the cyclic voltammetrymethod in the range from -0.8 – 0.8 V with a voltage scan rate of 100mV/s.

Two segments of horizontally grown crystalline ZnO nanorods (NRs) connected withan amorphous layer have been successfully and reproducibly synthesized usingone-step hydrothermal technique by controlling the growth rate. The confocalphotoluminescence (PL) imaging and spectroscopy of twin ZnO NRs at differenttemperatures shows intense red emission with comparably week UV emission. Thestrong red emission from the twin NRs is a consequence of structuralimperfections. Both UV and red bands showed signatures of strong temperaturedependent exciton-phonon scattering. Using the intensity ratio of the UV and redemissions, we show that the individual ZnO NRs can be used as highly sensitivecryogenic temperature sensors below ∼175 K.

We present here a reactive ion etching recipe to fabricate germanium nanowires.We used a combination of Cl2, N2 and O2 andstudied the influence of both the gas pressure and the O2 mass flowon the morphology of the nanowires. 5 µm long nanowires with an aspectratio of 20 are demonstrated with smooth surfaces and a tapering below 20nm/µm. We also show that both gold and aluminum can be used as hardmask; the latter achieving a selectivity with germanium above 100.