Cyclic voltammetry as a sensitive method for in situ probing of chemical transformations in quantum dots

Osipovich, N. P.; Poznyak, S.K.; Lesnyak, Vladimir; Gaponik, Nikolai

doi:10.1039/c6cp01085g

Cited by 6 publications

(4 citation statements)

References 33 publications

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“…By simultaneous recording absorption spectra and the electric potential of the system we avoid possible rearrangements of the crystal structure, which may happen on a prolonged time scale, and thus exclude additional processes which might affect the plasmon response. Electrochemistry provides powerful approaches to probe semiconductor nanoparticles, although it has been mostly employed to investigate “classical” cadmium chalcogenide-based quantum dots. − Such electrochemical method as cyclic voltammetry is especially useful in studying redox processes in a wide range of different compounds . Our findings indicate that the two chosen types of nanoparticles (Cu 2– x Se and CuS NCs) behave differently upon similar experimental conditions of the measurements.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Tuning of Localized Surface Plasmon Resonance in Copper Chalcogenide Nanocrystals

et al. 2017

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In this work, we developed a method to study in situ the optical properties of Cu 2−x Se and CuS nanocrystals upon electrochemical reduction and oxidation. Both these materials possess a strong localized surface plasmon resonance (LSPR) in the near-infrared region. First, the nanoparticles were embedded into a transparent film made of a perfluorinated sulfonic-acid copolymer Nafion deposited onto an ITO-coated glass. This substrate was employed as a working electrode for chronoamperometry and cyclic voltammetry measurements directly in a transparent cell allowing for simultaneous acquisition of absorption spectra of the system upon its charging/discharging. We observed that LSPR of the Cu 2−x Se NCs can be well-controlled and tuned in a wide range simply by potentiostatic potential switching. Starting with an intensive plasmon of the initial as-synthesized Cu 2−x Se NCs we were able to completely damp it via reduction (electron injection). Moreover, this electrochemical tuning was demonstrated to be reversible by subsequent oxidation (extracting electrons from the system). At the same time, CuS NCs did not exhibit such prominent LSPR modulation upon the same experimental conditions due to their more metallic-like electronic structure. Hence, our findings demonstrate for the first time a reversible tuning of the LSPR of copper chalcogenide NCs without any chemical or structural modification. Such a wide LSPR tunability is of paramount importance, for example in applications of these materials in photovoltaics to amplify light absorption, in systems involving plasmon−exciton interactions to controllably quench/enhance light emission, and in electrochromic devices to control their transmittance.

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Section: Introductionmentioning

confidence: 99%

Electrochemical Tuning of Localized Surface Plasmon Resonance in Copper Chalcogenide Nanocrystals

et al. 2017

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“…Therefore, a single cyclic voltammetry experiment can readily provide information that could otherwise be obtained by the combination of photoemission, inverse photoemission, and field effect transistor (FET) gating. While reversible electrochemistry is limited by the chemical stability of the materials, irreversible electrochemistry can also be used to learn about chemical processes and decomposition at CQD surfaces. − Another distinction is that the environment must be an electrolyte, allowing for ionic conduction. However, the electrolyte environment may be arguably more natural than a high vacuum for colloidal materials.…”

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confidence: 99%

Reversible Electrochemistry of Mercury Chalcogenide Colloidal Quantum Dot Films

2017

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The absolute positions of the energy levels of colloidal quantum dots of Hg(S, Se, Te), which are of interest as mid-infrared materials, are determined by electrochemistry. The bulk valence bands are at -5.85, -5.50, and -4.77 eV (±0.05 eV) for zinc-blend HgS, HgSe, HgTe, respectively, in the same order as the anions p-orbital energies. The conduction bands are conversely at -5.20, -5.50, and -4.77 eV. The stable ambient n-doping of Hg(S, Se) quantum dots compared to HgTe arises because the conduction band is sufficiently lower than the measured environment Fermi level of ∼ -4.7 eV to allow for n-doping for HgS and HgSe quantum dots even with significant electron confinement. The position of the Fermi level and the quantum dots states are reported for a specific surface treatment with ethanedithiol and electrolyte environment. The positions are however sensitive to different surface treatments, providing an avenue to control doping. Electrochemical gating is further used to determine the carrier mobility in the films of the three different systems as a function of CQD size. HgSe and HgS show increasing mobility with increasing particle sizes while HgTe shows a nonmonotonous behavior, which is attributed to some degree of aggregation of HgTe QDs.

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“…To get an insight into the electrochemical behaviour of the novel MSA-NiSe 2 QDs, the QDs were studied as free diffusing species in solution and as thin films deposited onto the electrode surface. Electrochemical methods, particularly, cyclic voltammetry (CV) is the most commonly employed technique for studying QDs 29,30 In this study, the role of CV analysis on QDs is to (i) understand/identify the nature of electron transfer and (ii) provide information on the stability of QDs upon charge transfer.…”

Section: Resultsmentioning

confidence: 99%