Aqua Regia Treatment Research Articles

A metallic nickel site in a complex multimetallic design for controlled CO2 reduction and symmetric supercapacitor device

Single metallic sites are promising for high power density with promising capacitive performance, and for low-energy chemical reduction of CO2 to formate. Here, we present a novel strategy for accessing C-ZIF-700 with metallic nickel (Ni) sites encapsulated by multiwalled nanotube shells from trimetallic imidazolate frameworks (M-ZIF). A X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopic analysis confirmed the zero-valance state of Ni, with no significant positive valance state. C-ZIF-700 showed no sign of leaching of Ni nanoparticles under aqua regia treatment for long, as evidenced from -XANES-EXAFSanalysis. It is demonstrated that the coexistence of Ni and Co in C-ZIF-700 renders more active electrochemical energy storage by regulating charge distribution to improve electronic transportation capability. C-ZIF-700 with predominantly metallic Ni-sites demonstrated superior capacitive performance, presenting a remarkable capacitance value of 262 F/g at a scan rate of 5 mV/s. In an assembled symmetric supercapacitor device , C-ZIF-700 exhibited a very high specific energy value of 21.2 Wh/kg at a current density of 0.05 A/g, which retained up to 9.7 Wh/kg at 10 A/g, and a corresponding specific power value of 25 kW/kg. C-ZIF-700 has offered facile N-formylation of the primary amine group of aniline, with the assistance of alkyl silane as a hydride source under moderate CO2 pressure (15–20 bar) and temperature (maximum 100 °C). Electronic structural evidence of metal sites in C-ZIF-700, by using XANES-EXAFS, electron microscopy, and CO2 adsorption–desorption profile supports that Ni-site is responsible for CO2 activation-reduction. The evidence also supports a possible synergistic effect of Co nanoparticles in capacitance enhancement and CO2 reduction. This strategy,thus, proves the outstanding role of encapsulated Ni sites for enhanced capacitive performance and chemical fixation of CO2.

Wet etching of platinum (Pt) electrodes for piezoelectric transducers using a thick photoresist mask

Platinum (Pt) is widely used in MEMS applications due to its inert nature and high temperature stability. In general, Pt is patterned using dry etching methods which require expensive machinery. In this study, we propose wet etching of Pt electrodes of piezoelectric transducers in hot Aqua Regia at 60 °C using a thick photoresist as a masking material. We showed that this method eliminates the need for metal hard mask and subsequent metal stripping, which may not be compatible with other structures on the process wafer. A stack of Si/Ti/Pt was used as a test sample to verify the effectiveness and chemical stability of AZ® 9260 and SPR™ 220-7 type photoresists in hot Aqua Regia. The optimized process was then successfully applied on a wafer with a pre-patterned pulsed laser deposited lead zirconate titanate (PLD-PZT) using SPR™ 220-7 photoresist. The suitability of the etching process was verified using optical imaging and SEM-EDS analysis. An etch resolution of 3.5 μm was achieved for 100 nm thick Pt thin films after 15 min immersion in hot Aqua Regia at 60 °C without any plasma cleaning. Using descum process with Ar plasma beforehand decreased the etching time down to 3:45 min and improved the minimum feature size down to 1 μm. • Hard baked thick photoresists can withstand hot Aqua Regia treatment. • Platinum films are etched with micron level resolution. • Piezoelectric structures are protected with easily removable photoresist mask. • No hard metal masking is required.

(Invite) Cobalt Platinum Bronze As a Versatile Electrocatalyst

Platinum metal-based materials have been mostly used as the catalysts for polymer electrolyte fuel cells and extensively studied to improve their performance by alloying and shape-controlling. Although these advanced technologies are pursued mainly for enhancing the catalytic activities and showed significant improvement in deed, their durabilities under realistic conditions do not often accompany. For wider distribution of fuel cell vehicles, however, both high activity and high durability should be compatibly achieved. Recently we have started fundamental studies on mixed oxides of platinum (so called "platinum bronze") consisting of platinum, oxygen and other metal ions (such as Li, Na, Mg, Ca, Zn, Cd, Co, Ni [1]), which were reported by Shannon et al. as an ORR catalyst for fuel cells. Although their activities were not extremely high, they were reported not to be dissolved with hot aqua regia. This remarkable property made us expect that these materials can exhibit excellent durability under fuel cell conditions (high temperature, high potential and also chloride contaminant). Here, we present the preparation, characterization and electrochemical behavior of Co-Pt bronze for PEFC application. Co-Pt bronze was prepared according to the literature [1] with some modifications. Platinum oxide and Co(NO3)2·6H2O powders were mixed and heat-treated under air conditions at 650 ºC for 5 hours. The obtained powder was washed with heated (80 °C) aqua regia for 3 times and the remaining powder was then thoroughly rinsed with pure water. The electrochemical behaviors including ORR activity of the obtained Co-Pt bronze were evaluated by the thin-film RDE method in 0.1 M HClO4 at 30 ºC. Then, the electrode was subjected with potential cycling (0.05-1.2 V, 500 mV s-1, 100 cycles) before another electrochemical behavior measurement. The Co-Pt bronze powders were characterized as prepared and before and after electrochemical measurement by nitrogen sorption method, XRD, XPS, SEM etc. XRD measurement confirmed that the as-prepared powder after the heat treatment contained a bronze phase and a platinum metal phase and the latter was completely removed by the heated aqua regia treatment. The particle size of the obtained Co-Pt bronze powder was 20-40 nm from SEM observation and the specific surface area evaluated by BET analysis was 18.8 m2 g-1. The elemental composition was Co0.5Pt3O4 from EDX analysis. The ORR current for the Co-Pt bronze was low in the 0.6-1.0 V potential sweep (Figure 1a, before potential cycling). Cyclic voltammogram under anaerobic conditions showed no hydrogen sorption and platinum redox currents before the potential cycling but these currents gradually increased (Figure 1b) over the potential cycling. The ORR current of the Co-Pt bronze after potential cycling was comparable to that of Pt/Vulcan (Figure 1a, after potential cycling). While XRD measurement did not exhibit any change before and after the potential cycling, XPS spectrum indicated presence of metallic platinum after the potential cycling. These results clearly indicated that a thin metallic platinum phase was formed on the surface of the Co-Pt bronze by potential cycling and the metallic Pt was the main active site for ORR. Moreover, the Co-Pt bronze also exhibited an HOR activity due to the metallic site. Therefore, Co-Pt bronze can be used not only for the cathode but also for the anode. The durability of the Co-Pt bronze will be also discussed at the meeting. Moreover, the Co-Pt bronze showed a high and stable catalytic activity for oxygen evolution reaction (OER) without using Ir or Ru, which are conventionally used as essential elements for OER catalysts but are ones of the scariest elements on earth. This study is financially support by the New Energy and Industrial Technology Development Organization.

Cobalt Platinum Bronze As a Catalyst for Polymer Electrolyte Fuel Cells

Platinum metal-based materials have been mostly used as the catalysts for polymer electrolyte fuel cells and extensively studied to improve their performance by alloying and shape-controlling. Although these advanced technologies are pursued mainly for enhancing the catalytic activities and showed significant improvement in deed, their durabilities under realistic conditions do not often accompany. For wider distribution of fuel cell vehicles, however, both high activity and high durability should be compatibly achieved. Recently we have started fundamental studies on mixed oxides of platinum (so called "platinum bronze") consisting of platinum, oxygen and other metal ions (such as Li, Na, Mg, Ca, Zn, Cd, Co, Ni [1]), which were reported by Shannon et al. as an ORR catalyst for fuel cells. Although their activities were not extremely high, they were reported not to be dissolved with hot aqua regia. This remarkable property made us expect that these materials can exhibit excellent durability under fuel cell conditions (high temperature, high potential and also chloride contaminant). Here, we present the preparation, characterization and electrochemical behavior of Co-Pt bronze for PEFC application. Co-Pt bronze was prepared according to the literature [1] with some modifications. Platinum oxide and Co(NO3)2·6H2O powders were mixed and heat-treated under air conditions at 650 ºC for 5 hours. The obtained powder was washed with heated (80 °C) aqua regia for 3 times and the remaining powder was then thoroughly rinsed with pure water. The electrochemical behaviors including ORR activity of the obtained Co-Pt bronze were evaluated by the thin-film RDE method in 0.1 M HClO4 at 30 ºC. Then, the electrode was subjected with potential cycling (0.05-1.2 V, 500 mV s-1, 100 cycles) before another electrochemical behavior measurement. The Co-Pt bronze powders were characterized as prepared and before and after electrochemical measurement by nitrogen sorption method, XRD, XPS, SEM etc. XRD measurement confirmed that the as-prepared powder after the heat treatment contained a bronze phase and a platinum metal phase and the latter was completely removed by the heated aqua regia treatment. The particle size of the obtained Co-Pt bronze powder was 20-80 nm from SEM observation and the specific surface area evaluated by BET analysis was 18.8 m2 g-1. The elemental composition was Co0.5Pt3O4 from EDX analysis. The ORR current for the Co-Pt bronze was low in the 0.6-1.0 V potential sweep (Figure 1a, before potential cycling). Cyclic voltammogram under anaerobic conditions showed no hydrogen sorption and platinum redox currents before the potential cycling but these currents gradually increased (Figure 1b) over the potential cycling. The ORR current of the Co-Pt bronze after potential cycling was comparable to that of Pt/Vulcan (Figure 1a, after potential cycling). While XRD measurement did not exhibit any change before and after the potential cycling, XPS spectrum indicated presence of metallic platinum after the potential cycling. These results clearly indicated that a thin metallic platinum phase was formed on the surface of the Co-Pt bronze by potential cycling and the metallic Pt was the main active site for ORR. Moreover, the Co-Pt bronze also exhibited an HOR activity due to the metallic site. Therefore, Co-Pt bronze can be used not only for the cathode but also for the anode. The durability of the Co-Pt bronze will be also discussed at the meeting. This work supported by NEDO, Japan.

Environmentally Friendly Recycling of Fuel-Cell Membrane Electrode Assemblies by Using Ionic Liquids.

The platinum nanoparticles used as the catalyst in proton exchange membrane fuel cells (PEMFCs) represent approximately 46 % of the total price of the cells for a large-scale production, and this is one of the barriers to their commercialization. Therefore, the recycling of the platinum catalyst could be the best alternative to limit the production costs of PEMFCs. The usual recovery routes for spent catalysts containing platinum are pyro-hydrometallurgical processes in which a calcination step is followed by aqua regia treatment, and these processes generate fumes and NOx emissions, respectively. The electrochemical recovery route proposed here is more environmentally friendly, performed under "soft" temperature conditions, and does not result in any gas emissions. It consists of the coupling of the electrochemical leaching of platinum in chloride-based ionic liquids (ILs), followed by its electrodeposition. The leaching of platinum was studied in pure ILs and in ionic-liquid melts at different temperatures and with different chloride contents. Through the modulation of the composition of the ionic-liquid melts, it is possible to leach and electrodeposit the platinum from fuel-cell electrodes in a single-cell process under an inert or ambient atmosphere.

Evaluation of titanium carbide thin film coatings on WC‐Co following surface microstructure treatments

The effects of acid or radio‐frequency (RF) CF4 plasma pre‐treatments before a sputtered titanium carbide (TiC) hard coating thin film were investigated to increase the adhesion strength of TiC on WC‐16wt%Co substrate. The arithmetic average roughness (Ra) was 182.5 nm after a 5‐min aqua regia treatment at 60 °C and 247.8 nm after 30 min of RF CF4 plasma at a substrate temperature of 500 °C. Chemically bonded cobalt disappeared from the WC‐Co substrate surface on treatment with aqua regia for 5 min based on X‐ray photoelectron spectroscopy (XPS). The TiC thin film on substrate with Ra = 150.3 nm after CF4 plasma treatment at 300 °C for 30 min did not delaminate at up to 30 N, in contrast, the substrate with Ra = 182.5 nm after aqua regia treatment at 60 °C for 5 min underwent delamination at below 30 N. The adhesion strength was maximal, with a surface roughness of Ra ≈ 150 nm, with CF4 and aqua regia treatments.

Evaluation of Titanium Carbide Thin Film Coatings on Surface Microstructure Controlled WC-Co

Chemical vapor deposited (CVD) or physical vapor deposited (PVD) hard coating technique is widely used the cemented-tungsten carbide (WC-Co) for molds and cutting tools, which plays an important role in a lot of manufacturing industry. For example, titanium carbide (TiC), titanium nitride (TiN) and titanium carbonitride (TiCN) is one of the candidates to control surface properties in order to increase lifetime or to decrease friction coefficient of molds, tools and so on. The film prepared by thermal CVD carried out around 1000°C has good uniformity and mechanical properties, which restricts substrates having low melting points, and also causes deformation of substrates. High temperature sometimes results in decarbonization of WC-Co surface which causes a significant decrease in toughness and transverse rupture strength. Plasma enhanced chemical vapor deposition (PECVD) or PVD has some merits as lower deposition temperature (< 500°C) than thermal CVD and high through-put, however, the film usually has low adhesion strength. Then, life of molds and cutting tools obtained PVD are sometimes shorter than that with CVD. In this study, Several surface pretreatment methods were investigated to remove Co from the WC-Co surface and to increase surface roughness to enhance adhesion strength. The procedure include, Dry etching by CF4 plasma for 15 to 120min in the substrate temperature range from R.T. to 500°C. Chemical treatment with aqua regia (3HCl:HNO3) for 5 min at 25 to 60°C. After pretreatment, TiC coatings were formed by sputtering with TiC target or by PECVD from TiCl4/CH4. Surface roughness was evaluated by AFM. Crystallographic structure of WC-Co and TiC was evaluated by XRD. Hardness was evaluated by dynamic nanoindenter. Atomic concentration was determined by XPS. Figure 1 shows maximum height roughness (Rz) and arithmetic average roughness (Ra) of WC-Co substrates after pretreatment. Rz and Ra got larger as increasing temperature of treatment conditions. In particular, substrate surface with aqua regia treatment at 60°C disappear Co peak. Scratch test for PVD TiC coating on pretreated substrate revealed that critical load was larger than that with the film on non-pretreated substrate. When Ra was 150 nm, critical load was over 30N. The pretreated substrates surface by CF4 plasma and aqua regia have similar Ra value as 150 nm, however, the film with CF4 plasma exhibited no delamination and the film aqua regia exhibited delamination. The opposite trend could be due to the micro-level morphologies. The differences between PVD and CVD films will be discussed. Figure 1

Convenient and Efficient Surface Reforming of LaTiO2 N Photocatalyst: Poly(4-styrenesulfonic acid) Treatment and Microwave Assisted CoO x Deposition

The overall water splitting by solar-energy-driven photocatalysts is a crucial issue as a solution for today’s mass scale energy and environmental problems. The activity of those photocatalysts is to be improved by their surfaces where the water splitting reactions take place. This time we report two useful tips to enhance the efficiency of LaTiO2N, an important candidate oxynitride for photocatalysis. One is to clean off the debris and defects on the particle surface. Domen et al.1 reported a brief, effective aqua regia treatment was in removing surface defects of LaTiO2N. However, aqua regia accompanies drawbacks of its severe reactivity. We need quick, elaborate washing to stop etching of the oxynitride in a contolled manner, and we need to isolate the aqua regia’s corrosive fume from the environment. More convenient and effective altanative surface treatment reagents are wanted in this sense. Two is to modify the surface of LaTiO2N with CoO x nanoparticles as so-called co-catalysts. The co-catalysts are supposed to assist the separation of photogenerated charges as well as promotion of surface reactions to evolve O2. CoO x nanoparticles, composed of earth abundant elements, are conventionally loaded by the liquid impregnation/calcination method.2 However the process of calcination on LaTiO2N brings about a complexity of heating in NH3 flow to avoid surface oxidation, simultaneously introducing chances of CoO x particle sintering and metallization. Our solutions for there problems are by rinsing in aqueous poly(4-styrenesulfonic acid) (PSS) solution followed by loading CoO x with a microwave assisted deposition. Static treatment of the LaTiO2N powder in PSS solution for 17 hours and microwave assisted one-pot loading of CoOx with Co(NH3)3Cl3 in Eyleneglycol solution, prior to fabrication into an electrode, increased the photoanodic current up to 8.9 mA cm-2 at 1.23 VRHE, which is 3 times larger than that without these reforming. We also confirmed that LaTiO2N was treated with PSS solution conveniently and care-freely in comparison with etching in aqua regia, and cocatalyst was coated throughout the surface of LaTiO2N particle by using microwave quick heating. M. Matsukawa, R. Ishikawa, T. Hisatomi, Y. Moriya, N. Shibata, J. Kubota, Y. Ikuhara and K. Domen, Nano Lett. 2014, 14, 1038−1041. F. Zhang, A. Yamakata, K. Maeda, Y. Moriya, T. Takata, J. Kubota, K. Teshima, S. Oishi and K. Domen, J. Am. Chem. Soc., 2012, 134, 8348−8351. Figure 1

SELECTIVE CHEMICAL ETCHING FOR STUDYING THE FRONT SIDE CONTACT IN THICK FILM SCREEN PRINTED CRYSTALLINE P-TYPE SILICON SOLAR CELLS

Crystalline silicon solar cells are currently the leading technology in the photovoltaic market with no great expectable change in the shares. The scientific community works on the further development and improvements of state-of-the-art as well as new solar cell materials. This paper reports on a chemical methodology for selective etching to study the metallization step in monocrystalline silicon solar cells. The object of study is a complete processed silicon solar cell which was cleaved via laser beam on the back side and broken per hand to obtain stripes of the size 15.6×1 cm2. In the following a sequence of etching chemical solutions to selectively remove the components of the front side silver contact was applied. Scanning electron microscopy was used to investigate contact interface after each etching step. The silver finger, the glass and the silver crystallites grown in silicon could be removed. It came out that the silver crystallites preferably grow at the pyramid tips and edges of the textured wafer. A characterization with Energy Dispersive X-Ray Spectrometry was performed to quantify the components of the silver contact after each chemical etching step. While the weight percentage of silver reduced by more than 90% after an aqua regia treatment, it increased by 13% after hydrofluoric acid. Silver was practically eliminated after a second aqua regia bath. Similarly, the content of glass was also determined. The approach serves for interface investigations in semiconductor technology where screen printing approaches are used for the metallization.

Effect of sample preparation procedure for the determination of As, Sb and Se in fruit juices by HG-ICP-OES

Various sample preparation procedures for the simultaneous determination of As, Sb and Se in fruit juices by hydride generation inductively coupled plasma optical emission spectrometry (HG-ICP-OES) were examined. Applicability of total wet digestion with HNO3/H2O2, partial decomposition (solubilisation in aqua regia), 1:1 dilution with 2% (v/v) HNO3 and direct analysis were evaluated. Hydrides were generated in the reaction of an acidified sample with NaBH4 after pre-reduction with KI–ascorbic acid for total As and Sb, and boiling with HCl for total Se. Best results, i.e. limits of detection (LODs) of 0.51–0.73ngmL−1, precision (RSD) within 1.7–3.6% and recoveries for spiked samples between 101% and 106% were found using aqua regia treatment. This procedure simplifying and improving sample preparation step prior to As, Sb and Se measurements in fruit juices by HG-ICP-OES, thus could be adequate for the routine analysis in terms of the quality control of these drinks.

Surface Energy Modification as a Means of Promoting Nanoparitcle-Substrate Electronic Couping

The focus of this paper is to describe studies on the wet chemical treatment of indium tin oxide (ITO) films to promote improved nanoparticle adhesion. Water contact angle measurements, Langmuir Blodgett (LB) film depositions, scanning electron microscopy (SEM) and photoluminescence spectra were used to characterize the treated substrates and the resulting films deposited on them. The authors found a highly diluted aqua regia treatment produced the lowest energy ITO surfaces which in turn saw the highest quality nanocrystal films deposited on them.

Synthesis, crystal structure, and electrochemical properties of hollandite-type K0.008TiO2

A single-phase specimen of hollandite-type K0.008TiO2 was synthesized by the ion extraction method using aqua regia treatment. Rietveld refinement from X-ray powder diffraction data for K0.008TiO2 showed it to have the hollandite-type structure (tetragonal; space group I4/m; a=10.1631(6) Å and c=2.9639(2) Å; Z=8). The K0.008TiO2 specimen worked as a rechargeable electrode material. An initial capacity of 161mAh/g (cut-off voltage: 1.0V) could be achieved, and the reversible capacity after 50 cycles was 147mAh/g. After lithium insertion–deinsertion cycling tests, the hollandite structure was still retained without structure collapse.

Effect of boiling aqua regia on MOCVD and MBE p-type GaN surfaces and Cr/p-GaN interfaces

The effect of boiling aqua regia treatment on MOCVD and MBE p-GaN surface and p-GaN/Cr interface is examined with I-V measurements and X-ray photoelectron spectroscopy. The MBE p-GaN/Cr/Au contacts are of lower resistance in all cases, as compared to their MOCVD counterparts. Upon boiling aqua regia treatment, the surface of the MBE p-GaN material appeared to be more stable, as opposed to the increased sensitivity of the MOCVD one. As a result of the different behavior of the two samples surfaces was the fact that surface Fermi energy levels of MOCVD and MBE p-GaN moved towards opposite directions, which improved the contacts formed on the MOCVD sample in contrast to the MBE one, as confirmed by electrical characterization. Finally, the formation of Ga-Cr phase at the MOCVD p-GaN/Cr interface is detected, without any thermal treatment of the contacts. A possible formation mechanism which might explain the binary phase formation is presented and discussed.

A Procedure for Rapid Determination of the Silicon Content in Plant Materials

An efficient, reliable and low-cost procedure to determine the silicon content in plant material is presented which allows to monitor the agricultural aspects like growth and yield. The presented procedure consists of a hydrochloric acid pre-treatment and a subsequent thermal oxidation. The method is compared to other processes like dissolution in hydrofluoric acid combined with ICP OES, energy-dispersive X-ray fluorescence spectroscopy (EDXRF) or aqua regia treatment.

Recycling of WC–Co hardmetal sludge by a new hydrometallurgical route

A hydrometallurgical process based on aqua regia treatment of WC–Co hardmetal sludge was developed to simultaneously extract cobalt in solution and forming tungstic acid as residue in a single step. The parameters such as aqua regia concentration, temperature and time of reaction, and pulp density were optimized to process the sludge containing 60.9 wt.% W, 5.99 wt.% Co, 3.38 wt.% Fe and 12.64 wt.% C as the major components. Almost complete leaching of cobalt was achieved with 100 vol.% of aqua regia at 100 °C temperature, 60 min reaction time and 400 g/L pulp density. Complete conversion of tungsten carbide of the sludge to tungstic acid was observed at and below the pulp density of 150 g/L under this condition. The progress of reaction and conversion of tungsten carbide to tunstic acid (H 2WO 4) were investigated by XRD phase identification of the residues under different conditions. The tungstic acid produced from the acid treatment was purified by dissolving tungsten in 11.20 mol/L of ammonia solution at 60 °C while rejecting insoluble metallic impurities as a residue. Tungsten from the ammoniacal solution was recovered by evaporation–crystallization process as high purity (99.97%) ammonium paratunstate (APT, (NH 4) 10·H 2W 12O 42·4H 2O) with low levels of impurities.

Reactivation of a Carbon-supported Gold Catalyst for the Hydrochlorination of Acetylene

Acetylene hydrochlorination using a carbon-supported gold catalyst is studied. Reactivation of the catalyst is demonstrated using a brief treatment of the spent catalyst with boiling aqua regia and the process of reactivation and deactivation is characterised using X-ray photoelectron spectroscopy. Deactivation is considered to be due to loss of Au3+ which is restored by the aqua regia treatment.

Sensitivity of Raman spectra excited at 325 nm to surface treatments of undoped polycrystalline diamond films

AbstractAbout 20 μm thick films were deposited in the same run by MPCVD at 900 °C on Si substrates and then hydrogenated in situ during 30 min with a hydrogen plasma at the same temperature. Their surfaces were kept as prepared or more or less strongly oxidized by annealing at 600 °C under ambient atmosphere or by sulphochromic acid or aqua regia treatments. Raman spectra were excited at 325 and 632.8 nm. Spectra of the as‐prepared sample exhibit structures around 2835 and 2895 cm–1 from monohydride carbon–hydrogen ascribed to the atomically flat (111) and (100) areas, respectively, on the facets of the sample surface crystallites. The decrease of these structures in the normalized spectra after the various oxidation treatments confirms these assignments. The decrease is smaller for the aqua regia treatment than for the two other treatments which give similar effects. Other Raman signals from sp2 C around 1589 cm–1 and CHx bonds around 2930, 2952, 3025 and 3050 cm–1 originate from species at the surface and within the films. Their variation with the oxidizing treatments indicates a significant contribution from the surface species. (© 2006 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Effect of surface treatment and functionalization on the ITO properties for OLEDs

The relation between ITO morphology and surface properties has been studied by wettability measurements and AFM microscopy. Different wet cleaning procedures have been investigated leading to different surface properties: ultrasonic degreasing, RCA and Aqua regia treatment. After full elimination of the organic surface contaminants, the ITO surface shows a main basic surface component. RCA and Aqua regia treatments are the most efficient techniques for cleaning ITO surfaces from organic contamination. Nevertheless, Aqua regia treatment induces ITO surface degradation, which is evidenced by AFM observations and resistance sheet measurements. The ITO surface has been derivatized with a SAM layer of phosphonic acid to improve the ITO/polymer interface. Effect of 2-chloroethylphosphonic acid layer on the different components of the surface energy was determined: acid component is increased whereas basic component is decreased, showing the good coverage of the ITO surface by the SAM layer. A more compact coating of POMX polymer is obtained after SAM functionalization of ITO samples cleaned with RCA treatment.

Simultaneous determination of hydride (Se) and non-hydride-forming (Ca, Mg, K, P, S and Zn) elements in various beverages (beer, coffee, and milk), with minimum sample preparation, by ICP–AES and use of a dual-mode sample-introduction system

A method has been developed enabling direct analysis (i.e. after dilution only) of beer, instant coffee, milk, and milk powder by ICP-AES. Analysis of the beverages after dilution with a low concentration of HNO3 was used for accurate determination of essential minor and trace elements (Ca, Mg, K, P, S, and Zn). Selenium, introduced as the hydride, was determined simultaneously with the other non-hydride-forming elements using the commercial multi-mode sample-introduction system (MSIS). To obtain accurate results, however, some simple pre-treatment was needed. Analysis was also performed after microwave-assisted decomposition of the samples. Three different modes of sample-preparation, i.e. dilution only, partial decomposition (aqua regia treatment), and complete decomposition were compared. The results obtained by use of the three different sample-preparation methods were in very good agreement. Results from analysis of certified reference material (SRM 1459 non-fat milk powder) also verified the accuracy of the methods. The limit of detection obtained for Se using dual-mode sample introduction was 0.5 ng mL(-1), which corresponds to approximately 2 ng g(-1) in beer and approximately 4 ng g(-1) in coffee and milk when using the recommended procedure.

Effect of Surface Treatment on Schottky Barrier Height of p-Type GaN

The chemical bonding state and atomic composition at the surface of p-type GaN were studied by synchrotron radiation photoemission spectroscopy. Ga-related oxides existed even after surface treatment using HCl solution, causing pinning of the surface Fermi level at 0.62 eV above valence band maximum Meanwhile, aqua regia treatment is effective in removing the surface oxide, resulting in the movement of the Fermi level toward This resulted from the existence of Ga vacancies underneath the surface oxide. As a result, the slope in the plot of Schottky barrier height with the metal work function was increased. © 2003 The Electrochemical Society. All rights reserved.