Nano-shaping of gold particles on silicon carbide substrate from solid-state to liquid-state dewetting

Abstract This work reports on the effect of annealing temperature on the size, shape and wetting of particles obtained on 4H-SiC substrate by the dewetting process of a deposited nanoscale-thick Au film, with focus on the difference between solid-state dewetting (below Au melting temperature) and liquid-state dewetting (above Au melting temperature). After depositing nanoscale-thick Au film on the SiC substrate, annealings are perfomed so to induce the solid-state or liquid-state dewetting process of the film with the consequent formation of particles. Plan-view and cross-view scanning electron microscopy analyses are carried out to quantify the evolution of the average planar size and vertical size of the particles and of the average contact angle of the particles to the SiC surface versus the annealing temperature. These analyses allow us to extract quantitative information on the wetting behaviour of the particles on the SiC surface by calculating the adhesion work versus the annealing temperature. Energy dispersive x-ray analyses are, also, performed on the dewetted particles to analyze their composition in the various annealing conditions. Overall, we set a general framework connecting process parameters to the nano-shape of the dewetted particles towards specific shape design for selected applications

TiO2 Nanostructures and Nanocomposites for Sustainable Photocatalytic Water Purification

Water, together with energy and food, has been addressed as one of the main urgent problems of humanity. The conventional wastewater treatments suffer some limitations related to the effectiveness in decontamination (mechanical filtration), in the heavy use of chemicals (chlorination), or in elevation of operational costs and energy requirements (desalination and reverse osmosis). In this sense, new materials such as nanocomposites may overcome these issues taking advantage of the peculiar properties of materials at nanoscale. Research on novel nanotechnologies must bring advances in order to contrast and prevent water scarcity and pollution. In order to be effective, these nanotechnologies should run at low operational cost, even in places unequipped by strong infrastructures and in concert with conventional cheap methodologies

Atomic force microscopy investigation of the kinetic growth mechanisms of sputtered nanostructured Au film on mica: towards a nanoscale morphology control

The study of surface morphology of Au deposited on mica is crucial for the fabrication of flat Au films for applications in biological, electronic, and optical devices. The understanding of the growth mechanisms of Au on mica allows to tune the process parameters to obtain ultra-flat film as suitable platform for anchoring self-assembling monolayers, molecules, nanotubes, and nanoparticles. Furthermore, atomically flat Au substrates are ideal for imaging adsorbate layers using scanning probe microscopy techniques. The control of these mechanisms is a prerequisite for control of the film nano- and micro-structure to obtain materials with desired morphological properties. We report on an atomic force microscopy (AFM) study of the morphology evolution of Au film deposited on mica by room-temperature sputtering as a function of subsequent annealing processes. Starting from an Au continuous film on the mica substrate, the AFM technique allowed us to observe nucleation and growth of Au clusters when annealing process is performed in the 573-773 K temperature range and 900-3600 s time range. The evolution of the clusters size was quantified allowing us to evaluate the growth exponent 〈z〉 = 1.88 ± 0.06. Furthermore, we observed that the late stage of cluster growth is accompanied by the formation of circular depletion zones around the largest clusters. From the quantification of the evolution of the size of these zones, the Au surface diffusion coefficient was evaluated in D(T) = [(7.42 × 10−13) ± (5.94 × 10−14) m2/s]exp(−(0.33±0.04) eVkT). These quantitative data and their correlation with existing theoretical models elucidate the kinetic growth mechanisms of the sputtered Au on mica. As a consequence we acquired a methodology to control the morphological characteristics of the Au film simply controlling the annealing temperature and time

Techno-Economic Analysis of Clean Hydrogen Production Plants in Sicily: Comparison of Distributed and Centralized Production

This paper presents an assessment of the levelized cost of clean hydrogen produced in Sicily, a region in Southern Italy particularly rich in renewable energy and where nearly 50% of Italy’s refineries are located, making a comparison between on-site production, that is, near the end users who will use the hydrogen, and centralized production, comparing the costs obtained by employing the two types of electrolyzers already commercially available. In the study for centralized production, the scale factor method was applied on the costs of electrolyzers, and the optimal transport modes were considered based on the distance and amount of hydrogen to be transported. The results obtained indicate higher prices for hydrogen produced locally (from about 7 €/kg to 10 €/kg) and lower prices (from 2.66 €/kg to 5.80 €/kg) for hydrogen produced in centralized plants due to economies of scale and higher conversion efficiencies. How-ever, meeting the demand for clean hydrogen at minimal cost requires hydrogen distribution pipelines to transport it from centralized production sites to users, which currently do not exist in Sicily, as well as a significant amount of renewable energy ranging from 1.4 to 1.7 TWh per year to cover only 16% of refineries’ hydrogen needs

Solid-State Fabrication of Cu2O/CuO Hydroxide Nanoelectrode Array onto Graphene Paper by Thermal Dewetting for High-Sensitive Detection of Glucose

Nanostructures of Cu2O/CuO hydroxide suitable for the electrochemical determination of glucose are obtained by solid‐state dewetting of CuO layers 6, 8, and 31 nm thin deposited by sputtering onto 240 μm‐thick graphene paper. Solid‐state dewetting in nitrogen produces a partial decomposition of CuO into Cu2O and Cu. X‐ray diffraction patterns reveal the presence of high‐index crystallographic facets, which are reactive and useful toward glucose oxidation to gluconolactone. Typically, morphology studied by scanning electron microscopy reveals faceted nanoparticles with an average size below 200 nm. X‐ray photoelectron spectroscopy shows that the nanostructure surfaces of Cu2O and metallic copper exposed to natural ambient are promptly reoxidized and hydroxidized to a mixture of CuO and Cu(OH)2. Electrochemical characterization in amperometric mode reveals linear response to glucose concentration in the range from 50 to 10 × 10−3 m, sensitivity up to 83 μA cm−2 mm −1, and limit of detection up to 3.6 × 10−6 m. Good combination of low cost and simplicity of preparation with low limit of detection, high sensitivity, and wide linear range makes the proposed electrodes suitable for a variety of applications ranging from health to food and beverage industries

Regional reductions of gray matter volume in familial dyslexia

An in vivo anatomic study of gray matter volume was performed in a group of familial dyslexic individuals, using an optimized method of voxel-based morphometry. Focal abnormalities in gray matter volume were observed bilaterally in the planum temporale, inferior temporal cortex, and cerebellar nuclei, suggesting that the underlying anatomic abnormalities may be responsible for defective written language acquisition in these subjects

Nanoporous Ge electrode as a template for nano-sized (<5 nm) Au aggregates

none8In this paper we present the extremely peculiar electrical properties of nanoporous Ge. A full and accurate electrical characterization showed an unexpected and extremely high concentration of positive carriers. Electrochemical analyses showed that nanoporous Ge has improved charge transfer properties with respect to bulk Ge. The electrode behavior, together with the large surface-to-volume ratio, make nanoporous Ge an efficient nanostructured template for the realization of other porous materials by electrodeposition. The pores were efficiently decorated by Au nanoparticles of diameter as low as 1–5 nm, prepared by electrochemical deposition. These new results demonstrate the potential and efficient use of nanoporous Ge as a nanostructured template for nano-sized Au aggregates, opening the way for the realization of innovative sensor devices.openG.Impellizzeri; L.Romano; B.Fraboni; E. Scavetta; F.Ruffino; C.Bongiorno; V. Privitera; M.G.GrimaldiG.Impellizzeri; L.Romano; B.Fraboni; E. Scavetta; F.Ruffino; C.Bongiorno; V. Privitera; M.G.Grimald

Memory effects in annealed hybrid gold nanoparticles/block copolymer bilayers

We report on the use of the self-organization process of sputtered gold nanoparticles on a self-assembled block copolymer film deposited by horizontal precipitation Langmuir-Blodgett (HP-LB) method. The morphology and the phase-separation of a film of poly-n-butylacrylate-block-polyacrylic acid (PnBuA-b-PAA) were studied at the nanometric scale by using atomic force microscopy (AFM) and Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS). The templating capability of the PnBuA-b-PAA phase-separated film was studied by sputtering gold nanoparticles (NPs), forming a film of nanometric thickness. The effect of the polymer chain mobility onto the organization of gold nanoparticle layer was assessed by heating the obtained hybrid PnBuA-b-PAA/Au NPs bilayer at T >Tg. The nanoparticles' distribution onto the different copolymer domains was found strongly affected by the annealing treatment, showing a peculiar memory effect, which modifies the AFM phase response of the Au NPs layer onto the polar domains, without affecting their surfacial composition. The effect is discussed in terms of the peculiar morphological features induced by enhanced mobility of polymer chains on the Au NPs layer

Experimental Analysis on the Molten-Phase Dewetting Characteristics of AuPd Alloy Films on Topographically-Structured Substrates

AuPd nanoparticles are formed on fluorine-doped tin oxide (FTO) by a nanosecond laser irradiation-induced dewetting process of deposited AuPd films. In particular, we analyze the effect of the surface topography of the substrate on the dewetting process and, so, on the final mean size of the formed nanoparticles. In fact, we used two supporting FTO substrates differing in the surface topography: we used a FTO layer which is un-intentionally patterned since it is formed by FTO pyramids randomly distributed on the glass slide as result of the deposition process of the same FTO layer, namely substrate A. We used, also, a further FTO substrate, namely substrate B, presenting, as a result of a chemical etching process, a higher roughness and higher mean distance between nearest-neighbor pyramids with respect to substrate A. The results concerning the size of the obtained AuPd NPs by the laser irradiations with the laser fluence fixed shows that the substrate topography impacts on the dewetting process. In particular, we found that below a critical thickness of the deposited AuPd film, the NPs formed on substrates A and B have similar size and a similar trend for the evolution of their size versus the film thickness (i.e., the dewetting process is not influenced by the substrate topography since the film does not interact with the substrate topography). On the other hand, however, above a critical thickness of the deposited AuPd film, the AuPd NPs show a higher mean size (versus the film thickness) on substrate B than on substrate A, indicating that the AuPd film interacts with the substrate topography during the dewetting process. These results are quantified and discussed by the description of the substrate topography effect on the excess of chemical potential driving the dewetting process

Plasmonic Coatings

Thin films and nanoscale-sized materials used as functional coatings with plasmonic properties have contributed to the development of modern and innovative optical, photonic, energy conversion, and sensing devices [...