Native oxide formation on pentagonal copper nanowires:a TEM study

Abstract Hydrothermally synthesized copper nanowires were allowed to oxidize in air at room temperature and 30% constant humidity for the period of 22 days. The growth of native oxide layer was followed up by high-resolution transmission electron microscopy and diffraction to reveal and understand the kinetics of the oxidation process. Copper oxides appear in the form of differently oriented crystalline phases around the metallic core as a shell-like layer (Cu2O) and as nanoscopic islands (CuO) on the top of that. Time dependent oxide thickness data suggests that oxidation follows the field-assisted growth model at the beginning of the process, as practically immediately an oxide layer of ∼2.8 nm thickness develops on the surface. However, after this initial rapid growth, the local field attenuates and the classical parabolic diffusion limited growth plays the main role in the oxidation. Because of the single crystal facets on the side surface of penta-twinned Cu nanowires, the oxidation rate in the diffusion limited regime is lower than in polycrystalline films

Self-assembled large scale metal alloy grid patterns as flexible transparent conductive layers

The development of scalable synthesis techniques for optically transparent, electrically conductive coatings is in great demand due to the constantly increasing market price and limited resources of indium for indium tin oxide (ITO) materials currently applied in most of the optoelectronic devices. This work pioneers the scalable synthesis of transparent conductive films (TCFs) by exploiting the coffee-ring effect deposition coupled with reactive inkjet printing and subsequent chemical copper plating. Here we report two different promising alternatives to replace ITO, palladium-copper (PdCu) grid patterns and silver-copper (AgCu) fish scale like structures printed on flexible poly(ethylene terephthalate) (PET) substrates, achieving sheet resistance values as low as 8.1 and 4.9 Ω/sq, with corresponding optical transmittance of 79% and 65% at 500 nm, respectively. Both films show excellent adhesion and also preserve their structural integrity and good contact with the substrate for severe bending showing less than 4% decrease of conductivity even after 105 cycles. Transparent conductive films for capacitive touch screens and pixels of microscopic resistive electrodes are demonstrated

In situ synthesis of catalytic metal nanoparticle-PDMS membranes by thermal decomposition process

Semi-automated processes are becoming more common within the field of waste management. They are often more efficient and improves the waste operators’ work environment in terms of security and health factors. The French company Veolia, engaged in waste management, has for these reasons developed the Tri Télé-Opéré (TTO) - a system where the direct contact between operator and waste is removed, and the waste is separated via a touch screen. The waste line is currently shown with a series of images in the system. This explorative study investigated how a representation of the line was perceived when using dynamic images on the screen. Diverse sequences with various parameters (viewpoint, direction and pace) were studied in order to observe how they supported the recognition and designation of the operators working with the system. Qualitative results from user tests performed with both novices and waste operators identified parameters that should be considered when using dynamic images of the waste line. The study shows that assembled images captured with an angle of 90°, shown in a slideshow mode are preferred. The viewpoint should furthermore be clear and detailed and the information should be displayed in a direction that corresponds to the long side of the screen, while having a size that make use of the screen surface. Moreover, the results suggest that the pace of the waste line could be increased if parameters allowing good recognition are used simultaneously. This study provides a first insight in how users perceive the TTO with dynamic images and which parameters that could facilitate the work. It is furthermore believed that a further development of this representation of information could ameliorate the future work situation for the waste operators, and thus also the efficiency of the sorting process.Halvautomatiserade processer blir allt vanligare inom området avfallshantering. Det är ofta mer effektiva och förbättrar avfallsoperatörernas arbetsmiljö när det kommer till säkerhet- och hälsoaspekter. Det franska företaget Veolia, som arbetar med insamling och hantering av avfall, har på grund utav detta utvecklat Tri Télé-Opéré (TTO) – ett system där direktkontakten mellan sorterare och avfall har avlägsnats och avfallet istället sorteras via en pekskärm. Systemet visar för tillfället upp avfallslinan med en serie stillbilder. Denna explorativa studie har undersökt hur linan uppfattades med dynamiska bilder på skärmen. Diverse sekvenser med olika parametrar (synvinkel, riktning och hastighet) studerades för att se hur de stödde avfallsoperatörernas igenkänning och klassificering i sorteringen vid skärmen. Kvalitativa resultat från användartest utförda med både nybörjare och avfallsoperatörer identifierade parametrar som bör beaktas när en presentation av avfallslinan med dynamiska bilder används. Studien visar att ett bildspel bestående av bilder tagna med en 90° vinkel föredrogs. Synvinkeln bör vara tydlig och informationen bör visas i en riktning som överensstämmer med skärmens långsida, samt ha en storlek som tar vara på bildskärmens yta. Hastigheten på avfallslinan kan ökas om parametrar som möjliggör ett bra igenkännande används simultant. Denna studie ger en första inblick i hur användarna upplever TTO med dynamiska bilder, och vilka parametrar som skulle kunna underlätta arbetet. En vidareutveckling av denna informationspresentation kan förbättra den framtida arbetssituationen för avfallsoperatörer, och därmed också effektiviteten i sorteringsprocessen

Nonlinear electronic transport and enhanced catalytic behavior caused by native oxides on Cu nanowires

Abstract Electrical transport properties of individual nanowires (both in axial and transversal directions) and their random networks suggest rapid oxidation when Cu is exposed to ambient conditions. The oxidation process is elucidated by thorough XRD, XPS and Raman analyzes conducted for a period of 30 days. Based on the obtained experimental data, we may conclude that first, cuprous oxide and copper hydroxide form that finally transform to cupric oxide. In electrical applications, oxidation of copper is not a true problem as long as thin films or bulk metal is concerned. However, as highlighted in our work, this is not the case for nanowires, since the oxidized surface plays quite important role in the contact formation and also in the conduction of percolated nanowire networks. On the other hand, by taking advantage of the mixed surface oxide states present on the nanowires along with their large specific surface area, we tested and found excellent catalytic activity of the oxidized nanowires in phenol oxidation, which suggests further applications of these materials in catalysis

Cu-Pd bimetal and CuPt alloy nanotubes derived from Cu nanowires:novel amplification media for surface-enhanced Raman spectroscopy

Abstract Surface-plasmons of metals have been utilized to enhance the Raman spectra of various adsorbed moieties for over decades. While amplification of the spectral intensity takes place on most of the metals, due to their superb properties, Au, Ag and Cu surfaces represent the benchmark in surface-enhanced Raman spectroscopy. In this paper, we show that Cu-Pd bimetal and CuPt alloy nanotubes derived from Cu nanowires by simple galvanic exchange reactions are suitable for the efficient enhancement of Raman spectra when dispersed on Si surfaces. Amplification factors of 120× on Cu nanowires, 150× on Cu-Pd bimetal nanotubes and 250× on CuPt alloy nanotubes in reference to the substrate are measured for rhodamine 6G and methyl violet model compounds. We also show that the nanotubes dispersed on Au surfaces can contribute to a further intensity enhancement of the substrate and detect analytes adsorbed from 10 −6 M analyte concentrations. Our results obtained using bimetallic and alloy nanomaterials shed light on a new strategy to synthetize and apply new types of metal nanostructures and compositions for surface-enhanced Raman spectroscopy in the future