Electrodeposition spectroscopy

ZnTe The electrodeposition of ZnTe was published quite recently [58]. The authors prepared a liquid that contained ZnGl2 and [EMIM]G1 in a molar ratio of 40 60. Propylene carbonate was used as a co-solvent, to provide melting points near room temperature, and 8-quinolinol was added to shift the reduction potential for Te to more negative values. Under certain potentiostatic conditions, stoichiometric deposition could be obtained. After thermal annealing, the band gap was determined by absorption spectroscopy to be 2.3 eV, in excellent agreement with ZnTe made by other methods. This study convincingly demonstrated that wide band gap semiconductors can be made from ionic liquids. 

Recently, a eutectic mixture of choline chloride and urea (commercially known as Reline) was used as a medium from which CdS, as well as CdSe and ZnS, thin films were electrodeposited for the first time [53]. Reline is a conductive room-temperature ionic liquid (RTIL) with a wide electrochemical window. The voltammetric behavior of the Reline-Cd(II)-sulfur system was investigated, while CdS thin films were deposited at constant potential and characterized by photocurrent and electrolyte electroabsorbance spectroscopies. 

Duffy NW, Peter LM, Wang RL, Lane DW, Rogers KD (2000) Electrodeposition and characterisation of CdTe films for solar ceU applications. Electrochim Acta 45 3355-3365 Duffy NW, Peter LM, Wang RL (2002) Characterisation of CdS/CdTe heterojunctions by photocurrent spectroscopy and electrolyte electroreflectance/absorbance spectroscopy (EEA/EER). J Electroanal Chem 532 207-214 (see also references therein). 

The UPD and anodic oxidation of Pb monolayers on tellurium was investigated also in acidic aqueous solutions of Pb(II) cations and various concentrations of halides (iodide, bromide, and chloride) [103]. The Te substrate was a 0.5 xm film electrodeposited in a previous step on polycrystalline Au from an acidic Te02 solution. Particular information on the time-frequency-potential variance of the electrochemical process was obtained by potentiodynamic electrochemical impedance spectroscopy (PDEIS), as it was difficult to apply stationary techniques for accurate characterization, due to a tendency to chemical interaction between the Pb adatoms and the substrate on a time scale of minutes. The impedance... 

According to absorption spectroscopy, these nanoribbons were composed of 3R-M0S2. The E/C synthesis of M0S2 wires and ribbons was size selective control over the wire or ribbon size was provided by control of the MoO , nanowire dimensions, which in turn were controlled using the electrodeposition potential and time in the first step of the synthesis. 

Boone BE, Shannon C (1996) Optical properties of ultrathin electrodeposited CdS films probed by resonance Raman spectroscopy and photoluminescence. J Phys Chem 100 9480-9484... 

Air Filter wet ashed in HNO3/HF, purified with cation and anion exchange columns and electrodeposition a -Spectroscopy No data No data Knab1979... 

Air Cellulose filter dry ashed, dissolved in HNO3/HF, H202/HCI04, purified with anion exchange, TRU-spec columns followed by electrodeposition. a -Spectroscopy 0.023 pCi/sample 102% Goldstein et al. 1997... 

Sea water Co-precipitation with iron hydroxide, purified by anion exchange, coprecipitation with BiP04, cation exchange, electrodeposition a -Spectroscopy No data 64-79% Lovette et al. 1990... 

Sediments Sample leached with HNO3/HF, filtered, purified by KL-HDEHP resin columns, solvent extracted, and electrodeposition a -Spectroscopy No data 95-99% Guogang et al. 1998... 

Soil Dry ash, digest in HNO3/HCI, anion exchange, Ca-oxalate and Fe (OH)2 coprecipitation, anion exchange, electrodeposition a -Spectroscopy 27 pCi/g 75-92% Sanchez and Singleton 1996... 

Vegetation Ashed, digested with HN03-H202, oxalate and Fe precipitations, anion exchange, solvent extraction, electrodeposition a -Spectroscopy 0.3 fCi/g 73-109% Cooper et al. 1993... 

Lichen, moss Ashed, leached with HCI, Microthene-TNOA and KL-HDEHP column extractions, solvent extraction, electrodeposition a -Spectroscopy 0.9 fCi/g No data Jia et al. 1997... 

The film electrodeposition process was studied by means of linear sweep voltammetry. The rate of electrochemical reaction was determined from current density (current-potential curves). The film deposits were characterized by chemical analysis, IR - spectroscopy, XRD, TG, TGA and SEM methods. 

Determination of trace metals in seawater represents one of the most challenging tasks in chemical analysis because the parts per billion (ppb) or sub-ppb levels of analyte are very susceptible to matrix interference from alkali or alkaline-earth metals and their associated counterions. For instance, the alkali metals tend to affect the atomisation and the ionisation equilibrium process in atomic spectroscopy, and the associated counterions such as the chloride ions might be preferentially adsorbed onto the electrode surface to give some undesirable electrochemical side reactions in voltammetric analysis. Thus, most current methods for seawater analysis employ some kind of analyte preconcentration along with matrix rejection techniques. These preconcentration techniques include coprecipitation, solvent extraction, column adsorption, electrodeposition, and Donnan dialysis. 

In contrast, the coupling of electrochemical and spectroscopic techniques, e.g., electrodeposition of a metal followed by detection by atomic absorption spectrometry, has received limited attention. Wire filaments, graphite rods, pyrolytic graphite tubes, and hanging drop mercury electrodes have been tested [383-394] for electrochemical preconcentration of the analyte to be determined by atomic absorption spectroscopy. However, these ex situ preconcentration methods are often characterised by unavoidable irreproducibility, contaminations arising from handling of the support, and detection limits unsuitable for lead detection at sub-ppb levels. 

Chong et al. [742] have described a multielement analysis of multicomponent metallic electrode deposits, based on scanning electron microscopy with energy dispersive X-ray fluorescence detection, followed by dissolution and ICP-MS detection. Application of the method is described for determination of trace elements in seawater, including the above elements. These elements are simultaneously electrodeposited onto a niobium-wire working electrode at -1.40 V relative to an Ag/AgCl reference electrode, and subjected to energy dispersive X-ray fluorescence spectroscopy analysis. Internal standardisation... 

Electronic spectra (Table 1.1, Fig. 1.2) have been measnred for the orange soln-tions of (RuO ] in aqueous base from 250-600 nm. [212-215, 222], and reproduced [215, 222]. There are two at 460 and 385 nm. [212, 213, 222] or three bands in the visible-UV region, at 460, 385 and 317 nm [214, 215]. These appear to be at the same positions as those for [RuO ] but the intensities and hence the general outline of the two spectra are very different. Woodhead and Fletcher reviewed the published molar extinction coefficients and their optimum values / dm (mol" cm" ) are 1710 for the 460 nm. band, 831 for the 385 nm. band and 301 for the 317 nm. band - the latter band was not observed by some workers [214]. The distinctive electronic spectrum of ruthenate in solution is useful for distinguishing between it, [RuO ]" and RuO [212, 222]. Measurements of the electronic spectra of potassium ruthenate doped in K CrO and K SeO and of barium ruthenate doped into BaSO, BaCrO, and BaSeO (in all cases the anions of these host materials are tetrahedral) indicate that in that these environments at least the Ru is tetrahedrally coordinated. Based on this evidence it has been suggested that [RuO ] in aqueous solution is tetrahedral [RuO ] rather than franx-[Ru(0H)3(0)3] [533, 535]. Potential modulated reflectance spectroscopy (PMRS) was used to identify [RuO ] and [RuO ] " in alkaline aqueous solutions during anodic oxidation of Ru electrodeposited on platinum from [Ru3(N)Clg(H30)3] [228]. 

The influence of benzylidene acetone on the electrodeposition mechanism of Zn-Co alloy was investigated [436]. A relationship between corrosion resistance, microstructure, and cobalt content in Zn-Co alloys was investigated [437] using X-ray photoelectron spectroscopy (XPS) and Auger spectroscopy [438]. The role of vitreous carbon, copper, and nickel substrates in Zn-Co deposition from chloride bath was analyzed [439]. 

Electrodeposition on transparent material such as indium tin oxide (ITO) can be used for electrochromic applications [328]. Pb deposition on indium-tin oxide electrode occurs by three-dimensional nucle-ation with a diffusion-controlled growth step for instantaneous nucleation [329], and the electrode process has also been studied using electrochemical impedance spectroscopy [328]. 

Sorenson etal. [449] have carried out similar studies on electrodeposition of atomic Te layers on Au(lll) surfaces from aqueous solutions. Similarly as in earher works, in this study also, the following techniques were utilized voltammetry, in situ STM, low-energy electron diffraction, and Auger electron spectroscopy. Prior to the deposition, tellurium oxide species coated the surface. Two steps were distinguished in the UPD process. Deposition process was Idnetically slow. 

Auger electron spectroscopy. X-ray photoelectron spectroscopy, low-energy electron diffraction, and in situ STM have been employed to investigate two-step alternate electrodeposition of Cd and Te atomic layers, forming finally, CdTe monolayers (electrochemical ALE on Au(lll)) [451]. STM images suggest that previously proposed hexagonal structures for CdTe may not be correct. 

Although the theoretical studies predict solvent medium breakdown before the onset of actinium electrodeposition, there have been reports of Ac(0) electrodeposition from aqueous solutions utilizing several different methods [8, 9]. One set of studies [8] describes the electrodeposition of actinium from nitric acid solutions, with varying pH values (1.0-4.0) being set to the appropriate level by the addition of sodium hydroxide. The anode and cathode in these studies were platinum metal, and the current density was varied from 50 to 200 mA cm . The authors found that quantitative electrodeposition of actinium could be achieved under various conditions, with the shortest electrolysis time of 1 h being obtained with a current density of200 mA cm and a pH of 2.0. A second study employed a saturated aqueous solution of urea oxalate (ca 6.6% at 30 °C) as an electrolyte for the electrodeposition of Ac onto a nickel foil cathode [9]. The authors of this study found that the yield of electrodeposited Ac increased with time and reached a near quantitative maximum yield of 97% at a current density of 53 mAcm after 2 h. The Ac electrodeposits were suitable for further study using nuclear spectroscopy. 

The electrodeposition of uranium as an oxide is routinely employed as a means of preparing sources for quantitative analytical measurement through alpha spectroscopy. Recently dos Santos et al. studied the electrodeposition of uranium with... 

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