We carried out synthesis of shape-controlled ZnO nanoparticles following a polyol route using either ethylene glycol (EG) or polyethylene glycol (PEG) as solvent, which exhibited wurtzite structures as identified by XRD patterns. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analyses of the synthesized structures showed that the size and the shape are strongly dependent on the reaction medium, resulting in nanospheres, rods, hexagonal plates or sheets, which were characterized by different spectroscopy techniques such as: Raman scattering, x-ray photoelectron spectroscopy (XPS), UV–Vis and photoluminescence (PL). The Raman analysis showed that the resulting surface is passivated with acetate molecules and also monitored the presence of superficial defects, whose spectroscopic patterns (Raman spectroscopy) indicated that the passivation with acetate molecules reduces the number of defects, such as oxygen vacancies. This result was confirmed by XPS analyses that identified chemisorbed oxygen species onto the oxide surface and an oxygen-deficient component in the sample prepared as reference, without a passivation with EG or PEG. Photoluminescence results showed that the passivation, size and shape of the particles influenced the optical features, mainly at the emission at the green region of spectrum that has been related with surface defects. This green emission is favoured at the ZnO sample prepared without passivation and with large amount of defects. Current–voltage characteristic ( J – V ) of an inverted organic solar cell showed the potential application of these ZnO nanostructures as electron transport material in organic photovoltaic devices.

We describe a direct deposition method for the manufacture of 2D-colloidal crystal films on flexible substrates using a roll-to-roll technique (R2R). Suspensions of silica (SiO2) particles in ethanol with different concentrations and particle sizes (diameters between 150 nm and 520 nm) were prepared and directly deposited onto PET, ITO/PET and stainless steel substrates via wire-bar R2R. We propose an empirical equation that allows one to predict an optimal concentration of the colloidal suspension as a function of the processing parameters necessary to produce a colloidal monolayer. We argue that the development of a R2R coating technique for the fabrication of 2D nanostructures can overcome some technological obstacles that currently hinder the development of printed photonics, nanofabrication and colloidal lithography.

Experimental and theoretical techniques are commonly utilized to characterization of materials. In this work, TiO2 nanoparticles (TiO2NP) from anatase and rutile were analyzed by X-ray diffraction (XRD), that was used to follow the structural evolution of the amorphous precipitate, and microstructure analysis was realized with Rietveld refinement. By Rietveld refinements, the crystallographic image file are generated for each sample to be able to perform simulations of the material structure. In addition, density functional theory was used to analyze electronic structures, several adsorptions of the H2O molecule onto TiO2 were performed, using –H was displaced in steps 0.01 Å and calculation/optimization energies were obtained up to cleavage H–O–H and O–H formation, taking into account photocatalytic mode of electron density distribution isosurfaces.

Titanium dioxide (TiO 2 ) is used in a range of applications such as photocatalysis and sensor devices. In this work, TiO 2 nanoparticles (TiO 2 NPs) in the crystallographic forms anatase and rutile were prepared by the green route. The method involves dissolving titanium oxysulfate (TiOSO 4 ) powder in hydrogen peroxide (H 2 O 2 ) solution and subsequent thermal treatment of the resultant amorphous precipitate. X-ray diffraction (XRD) was used to follow the structural evolution of the amorphous precipitate, and microstructure analysis was realized with Rietveld refinement. In addition, the photocatalytic activity of the synthesized TiO 2 NPs was evaluated by studying the degradation of Rhodamine B (RhB) dye. The highest photocatalytic activity was observed for TiO 2 obtained at 600 °C in the crystallographic form anatase.

This work describes ultrafast spectroscopy studies of Au triangular pyramid particle arrays deposited over glass (termed Au/glass), and 190 nm indium tin oxide (ITO) film (termed Au/ITO/glass) prepared by nanosphere lithography. The linear absorption spectra of Au/glass and Au/ITO/glass exhibit surface plasmon resonances at 800 and 870 nm, respectively, in good agreement with discrete dipole approximation simulations. Ultrafast pump-probe measurements at wavelengths below resonance, at resonance, and above the surface plasmon resonance for each of these two systems are presented. The pump-probe measurements on both systems can be well fit with a model accounting for electron-electron scattering, electron-phonon coupling, and acoustic oscillations on top of cooling of the gold lattice. Numerical simulations employing a two-temperature model are consistent with the single-color pump-probe exponential decays. The wavelength-dependent pump-probe results are interpreted in terms of the complex wavelength-dependent refractive index of gold. We show that this interpretation is consistent with diffractive-optic four-wave mixing spectroscopy measurements of absorptive and dispersive parts of the third-order nonlinear polarization at 800 nm.

The structure and magnetic properties of CuCo alloys electrodeposited in aqueous solution on n-type Si(100) substrates were investigated as a function of the trisodium citrate concentration in the electrolyte. The compositional analysis show that percentage of Co has a non-monotonic dependence on the increase in concentration of sodium citrate, with a maximum at 300 mM followed by a significant decrease The magnetic measurements in similar samples in terms of composition and thickness show that the coercive field value it differs greatly, from 87 to 20 Oe without and with added citrate, respectivelly, owing to the improved morphological quality and change in crystalline structure induced by the citrate. For electrodeposited films without citrate in the electrolyte, the X-ray diffraction pattern shows two peaks at 2θ = 43.298 and 44.217 typical of fcc (111) planes for copper and cobalt, respectively, while in the presence of citrate only one peak characteristic of fcc of the CuCo alloy was observed.

This manuscript addresses the use of a well-ordered antidot copper nanostructure as a active substrate for surface enhancement fluorescence (SEF). The antidot array was produced by electrodeposition and nanosphere lithography and characterized by microscopy technique, its successful application as SEF-active substrates was verified using polyfluorene (PFO) as a probe layer. Atomic force microscopy (AFM) was used to evaluate the regularity of the metal surface as well PFO coated process and confocal laser fluorescence microscopy (CLSM) to determine the behavior exhibited by the fluorescent layer due to the existence of the nanostructured surface. No accumulation PFO in the cavities was detected and the more intense emission regions coincides with the position of the cavities and is at about one order of magnitude higher.

In the present work, the photoelectrochemical characterization of ITO/TiO2 electrodes electrosynthesized at two distinct TiO2 film charges (0.35 and 1.00 C) was performed. Scanning electron microscopy presented a globular-like nanostructure and a typical morphology that are dependent on the growing charge, where the photoelectrode synthesized at 0.35 C presented a more homogeneous morphology. Such dependence was also observed at the photoelectrochemical response, once the photoactivity for the photoelectrode synthesized at 0.35 C was better than the photoelectrode synthesized at 1.00 C, which was explained by the surface recombination process and the electron lifetime. In order to explore the charge-transfer process and the displacement of the quasi-Fermi level upon illumination, electrochemical impedance spectroscopy (EIS) was performed at distinct applied potentials. EIS results corroborate the previous results, presenting a higher charge-transfer resistance and a lower chemical capacitance for the 1.00 C electrode film, the last one in accordance with the open-circuit voltage decay.

The unique properties of metallic nanostructures of coinage metals that can sustain localized surface plasmon resonances (LSPR) put them at the centre of plasmon-enhanced phenomena. The theory of plasmonic phenomena based on LSPR is well-established. However, the fabrication of plasmonic substrates, reproducibly, is still challenging for applications in surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF). In this work we describe well-ordered copper nanostructures (CuNSs), produced by electrodeposition and nanosphere lithography, as active substrates for SEF. After a detailed spectroscopic and microscopic characterization, CuNSs are successfully applied as SEF-active substrates using a well-known perylene derivative as a target molecule. The signal reproducibility from CuNS substrates was established by comparing the results against those obtained from a simply roughened Cu substrate. Under optimal conditions, signal variability is around 4%.

TiO2 films were produced on ITO using a two-step method: (i) potentiostatic electrosynthesis of an amorphous titanium oxyhydroxide gel and (ii) subsequent crystallization by a thermal treatment (TT). The influence of applied potential on the morphology and on the crystalline structure of the resulting films was studied for three different TT temperatures, using SEM, XRD, and Raman spectroscopy. The films were porous and their morphology was more affected by the potential than by the temperature. The obtained TiO2 presented a high degree of crystallinity. The brookite–anatase coexistence was observed for all synthesis conditions. Nevertheless, the brookite content decreased for samples synthesized at more negative potentials, irrespective of the TT temperature. A relative estimate of brookite content variation among the prepared samples was obtained from an analysis of Raman spectra, and it was shown to be related with the pH variation during electrosynthesis. This correlation is in accordance with reported dependence of brookite-anatase ratio in sol-gel synthesis, which decreases with an increase in pH.

In this report we track the structural changes suffered by ITO along galvanostatic polarization at different current densities by X-ray diffraction and SEM micrographs. The XRD shown that cathodic treatment induces structural change in ITO, characterized by appearing peaks set distinct from ITO original structure associated to metallic phase of the solid solution of In–Sn. It is interesting to note that although the different ions present in the solution are not, at least to a noticeable degree, incorporated in the metallic phase, the SEM images show that they do influence its formation, pointing to some type of adsorptive mechanism of the inert ions during the lateral diffusion of the metallic ions.

This paper deals on the influence of the potentiodynamic stress on structural and morphological proprieties of fluorine-doped tin oxide (FTO, SnO2:F) and indium tin oxide (ITO, In2O3:Sn) commercial substrates. The potential range is between 0.0 and -2.0 (V/SCE) using an electrolyte with neutral pH. The electrochemical behavior was investigated from cyclic voltammetry technique and chronopotentiometric curves. These electrochemical results were associated to the X-ray diffraction (XRD) spectra and morphology images acquired by scanning electron microscopy (SEM). The main results show that structural and morphological properties of FTO substrates after cathodic polarization remain near constant when compared with ITO films. The ITO substrates show morphological changes after treatment and the XRD patterns indicate the formation of a crystalline structure with In metallic characteristic, at neutral pH. (C) 2013 Elsevier B.V. All rights reserved.

In this work, porous ordered TiO2 films were prepared through sol gel route by using a monolayer of polystyrene spheres as template on indium-tin oxide/glass substrate. These films were characterized by SEM, AFM, Raman spectroscopy, UV–vis absorbance and XRD. The UV–vis absorbance spectrum show a pseudo band gap (PBG) with maxima at 460nm arising from the light scattering and partial or total suppression of the photon density of states, this PBG can be controlled by the size of the pore. We also propose the use of this porous film as electron acceptor electrode in organic photovoltaic cells; we show that devices prepared with porous titania displayed higher efficiencies than devices using compact titania films as electrode. Such behaviour was observed in both bilayer and bulk heterojunction devices.

Among the many methods developed for the synthesis of titanium dioxide, cathodic electrosynthesis has not received much attention because the resulting amorphous oxy‐hydroxide matrix demands a further thermal annealing step to be transformed into crystalline titania. However, the possibility of filling deep recessed templates by the control of the solid–liquid interface makes it a potentially suitable technique for the fabrication of porous scaffolds for photovoltaics and photocatalysis. Furthermore, a careful control of the crystallization process enables the growth of larger grains with lower density of grain boundaries, which act as electron traps that slow down electronic transport and promote charge recombination. In this report, well crystallized titania deposits were obtained by thermal annealing of amorphous deposits fabricated by cathodically assisted electrosynthesis on indium‐tin oxide (ITO)substrates. The combined use of Raman spectroscopy and X‐ray diffraction showed that the crystallization process is more intricate than previously assumed. It is shown that the amorphous matrix evolves into a rutile‐free mixture of brookite and anatase at temperatures as low as 200 °C that persists up to 800 °C, when pure anatase dominates. The amount of brookite in the brookite–anatase mixture reaches a maximum at 400 °C. This very simple method for obtaining a brookite–anatase mixture and the ability to tune their proportions by thermal annealing is a promising alternative whose potential for solar cells and photocatalysis deserves a careful evaluation. Copyright © 2011 John Wiley & Sons, Ltd.

Nanosphere lithography is a simple and accessible technique for nanostructuring of materials. Combined with electrodeposition, it allows the production of compact, ordered antidot networks. In contrast to other lithographic techniques, the resulting nanostructure shows periodicity also along the growth axis. Interesting results are expected for the magnetoresistive behavior of such structures as function of thickness, due to the confinement of electronic routes and the strong shape anisotropy. We were able to electrodeposit cobalt antidot structures of homogeneous and controlled thickness directly over silicon substrates. Room temperature anisotropic magnetoresistance (AMR) as function of thickness and nanosphere diameter are presented, with the magnetic field applied in plane, transverse to the applied current. An overlap of two effects is observed. At fields lower than 2 kOe typical hysteretic AMR peaks appear around the coercive field, and tend to disappear for thicker films. At higher fields, a reversible contribution, caused by the forced magnetization that rotates the spin away from the local current direction, lowers the magnetoresistance, before it reaches its saturation value.

The characteristics of cobalt antidot structures, electrodeposited on Si by nanosphere lithography, is investigated by analysis of current transients and optical and atomic force microscopy. Polystyrene colloidal masks of 1 ML (monolayer) or a maximum of 2, with sphere diameters ranging between 165 and 600nm were fabricated by spin coating. For masks partially covered with bilayer regions, it is shown that the volume of deposited material in bilayer areas corresponds to only 5% of the cobalt deposited in the monolayer areas. This drastic reduction in the deposition rate affects the quality of the deposit. Therefore, the use of colloidal masks of homogeneous thickness is necessary to guarantee the electrodeposition of nanostructured films of controlled thickness. It will also be shown that the use of high quality colloidal masks yields a reproducible electrodeposition process, enabling the use of the current transient as a reliable tool for assessment of the deposition process.

FexNi100−x thin films were produced by galvanostatic electrodeposition on Si (100), nominal thickness 2800nm, and x ranging 7–20. The crystalline structure of the sample was determined by X-ray diffraction (XRD). The magnetic properties were investigated by vibration sample magnetometry (VSM) and room temperature 57Fe Mössbauer spectroscopy. Conversion Electron Mössbauer spectroscopy (CEMS) in both film surfaces for the thick self-supported films showed that the magnetic moment direction is in the plane and conventional transmission (MS) that the directions are out of the plane films. The results were interpreted assuming a three-layer model where the external layer has in-plane magnetization and the internal one, out of plane magnetization.