Deposition of CdSe by EC-ALE

A mercury sulfide layer was prepared at the surface of a mercury electrode by an anodic reaction (þ 0.1 V vs. Ag j AgCl j KCl(3 M)) in the presence of thiourea at the micromolar concentration level. Electrochemical reactions of mercury sulfide were investigated by a subsequent cathodic scan at near-neutral pH values and in the absence/ presence of a second metal ion. Two different forms of mercury sulfide were evidenced by characteristic cathodic peaks; the first one (in the form of adsorbed molecules) undergoing a reversible reduction at about À 0.6 V, whereas the second one (probably as nanoaggregates) being reduced in an irreversible process at À 0.9 V. A detailed analysis of the first process was performed by adapting the already existing theoretical approaches. It was proven that the HgS layer prepared by mercury anodization in the presence of thiourea is similar to that prepared by anodization in the presence of sulfide ion. Other metal sulfides were prepared via the exchange reaction of mercury in HgS with a metal ion in solution; namely, Zn 2þ , Ni 2þ , and Cd 2þ; reactions of the latter proceeding in a fair agreement with the theoretical model used (the rapid exchange leading to the single CdS form with no soluble cadmium sulfide species). Evident deviations from this model have occurred with both Ni 2þ and Zn 2þ due to a sluggish exchange reaction, formation of soluble species, and occurrence of various metal sulfide forms. Two different forms of nickel sulfide were detected by characteristic cathodic reactions, namely i) adsorbed free molecules that are reduced at À 1.0 V and are able to take part in a catalytic (EC') reduction of Ni 2þ ; and ii) an aggregated form that is irreversibly reduced at negative potentials beyond À 1.2 V and acts as a catalyst for hydrogen evolution. The method presented herein allows one electrochemical preparation and investigation of metal sulfides with no difficulty due to hydrogen sulfide volatility at pH < 12 and emphasizes that this method can be applied to other systems consisting of a chalcogenide anion and a metal (like mercury or silver) being able of undergoing a reversible electrochemical reaction. In addition, this contribution provides an insight to the intricacy of the electrochemical behavior of the mercury electrode/sulfide anion/second metal ion system and mentions a series of sources of errors related to the interpretation of such data obtained with natural water specimens.

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“…Moreover, electrochemistry of metal chalcogenides is a topic of interest in semiconductor technology [17,18].…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Investigation of Metal Sulfides at Mercury Electrodes Using Thiourea as a Source of Sulfide Ion

et al. 2009

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“…InP is a III-V semiconductor with an energy band of 1.28 eV in the bulk material 9 and is a particularly promising as alternative, because of its energy band gap is relatively close to that of CdSe (1.74 eV). 10 Although the photoluminescence quantum yield (PLQY) and emission band width of colloidal InP QDs have been greatly improved in recent years, [11][12][13] the materials have not yet suitable for replacing widely used CdSe-based colloidal QDs. Among II-VI semiconductors, there is no candidate binary material system; however, ternary CuInS 2 -and CuInSe 2 -based materials have been proposed as alternative materials to CdSe.…”

Section: Introductionmentioning

confidence: 99%

Design of cadmium-free colloidal II–VI semiconductor quantum dots exhibiting RGB emission

Asano

Omata

2017

AIP Advances

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The size and composition dependence of the optical gap of colloidal alloyed quantum dots (QDs) of Zn(Te1−xSex) and Zn(Te1−xSx) were calculated by the finite-depth-well effective mass approximation method. QDs that exhibited red, green and blue emission were explored to develop cadmium-free II–VI chalcogenide-based QD-phosphors. We considered that highly monodisperse colloidal QDs with diameters of 3–6 nm are easy to synthesize and II–VI semiconductor QDs usually exhibit a Stokes shift ranging between 50 and 150 meV. We showed that Zn(Te1−xSex) QDs with 0.02≤x≤0.68, and 0≤x≤0.06, and 0.66≤x≤0.9 may be expected to exhibit green, and blue emission, respectively. Zn(Te1−xSx) QDs with 0.26≤x≤0.37, 0.01≤x≤0.2 and 0.45≤x≤0.61, 0≤x≤0.02, and 0.63≤x≤0.72, should give red, green and blue emission respectively. On the basis of our calculations, we showed that Zn(Te,Se) and Zn(Te,S) QDs are very promising cadmium-free II-VI chalcogenide semiconductor QD phosphors.

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“…However, many studies reveal that the deposition of CdSe is in fact a codeposition of Cd and Se, with the presence of selenium excess inside the deposit [20][21][22][23][24]. To overcome this issue, in 1991, Kressin et al [20] have adopted a cyclic voltammetry deposition technique in order to ensure the good "50-50" stoichiometry.…”

Section: Introductionmentioning

confidence: 99%

Temperature and pH influences on the structural and the emission properties of electrodeposited CdSe nanowires

Mallet

Kante

Fricoteaux³

et al. 2011

J Solid State Electrochem

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Cadmium selenite (CdSe) nanowires have been electrodeposited by potentiostatic method using polycarbonate membranes as template. For the same potential value, the pH modification of the solution or the temperature variation of the substrate leads to drastic differences of the CdSe composition. A meticulous study of the influence of both temperature and pH value on the stoichiometry of electrodeposited CdSe nanowires has been done and several combinations of temperature/pH leading to the 50-50 CdSe composition have been found. The as-electrodeposited CdSe nanowires under these specific conditions reveal a good crystallinity with a <111> preferred growth orientation exhibiting a luminescence band in the visible range corresponding to the CdSe gap.

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Deposition of CdSe by EC-ALE

Cited by 48 publications

References 25 publications

Electrochemical Investigation of Metal Sulfides at Mercury Electrodes Using Thiourea as a Source of Sulfide Ion

Electrochemical Investigation of Metal Sulfides at Mercury Electrodes Using Thiourea as a Source of Sulfide Ion

Design of cadmium-free colloidal II–VI semiconductor quantum dots exhibiting RGB emission

Temperature and pH influences on the structural and the emission properties of electrodeposited CdSe nanowires

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