Determination of Band Structure Parameters and the Quasi‐Particle Gap of CdSe Quantum Dots by Cyclic Voltammetry

Abstract

Band structure parameters such as the conduction band edge, the valence band edge and the quasi-particle gap of diffusing CdSe quantum dots (Q-dots) of various sizes were determined using cyclic voltammetry. These parameters are strongly dependent on the size of the Q-dots. The results obtained from voltammetric measurements are compared to spectroscopic and theoretical data. The fit obtained to the reported calculations based on the semi-empirical pseudopotential method (SEPM)-especially in the strong size-confinement region, is the best reported so far, according to our knowledge. For the smallest CdSe Q-dots, the difference between the quasi-particle gap and the optical band gap gives the electron-hole Coulombic interaction energy (J(e1,h1)). Interband states seen in the photoluminescence spectra were verified with cyclic voltammetry measurements.

Effect of shell thickness on electrochemical property of wurtzite CdSe/CdS core/shell nanocrystals

“…With the increase of CdSe core's size, the potentials of the anodic and cathodic peaks in each curve are gradually negatively and positively shifted, respectively, so the separation between the anodic and cathodic peaks is generally decreased. The decrease of the LUMO level and the increase of the HOMO level (Table 1) are in good agreement with the theoretical expectations and previous observations, and size-dependent peak shift phenomenon is attributed to the size quantum confinement effect and has been observed previously [11,17,19,21]. As shown in Table 1, the gap (E PL ) determined by PL peak is smaller than that (E Abs ) determined by excitonic absorption as expected.…”

“…[15]. Herein, peak potentials, the points A and B shown in Figure 2, are adopted to calculate HOMO and LUMO levels since the peak potential represents a comprehensive effect which the electrochemical response comes from the ensemble of NCs cast on the electrode surface [5,9,11,13,16,[19][20][21].…”

“…The band structure and electronic properties can be theoretically calculated with tight-binding (TB) model, effective mass approximation (EMA) and density functional theory (DFT) [4,5], these parameters estimated by experiments under specific conditions vary much from those. Some experimental methods, including photoemission spectroscopy in air (PESA) [6], ultraviolet and X-ray photoelectron spectroscopy (UPS and XPS) [7], scanning tunneling spectroscopy (STS) [8] and cyclic voltammetry (CV) [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24], exhibit the capability to measure the values of the NC's band structure parameters in special environment.…”

Quantum confinement induced shift in energy band edges and band gap of a spherical quantum dot

“…On the other hand, the experimental works on quantum confinement by Kucur et al, [55] Inamdar et al, [56] and Querner et al, [57] were performed through cyclic voltammetry method and Jasieniak et al [58] investigated the size dependency of valence and conduction band-edge energies using photoelectron spectroscopy in air (PESA).…”

Electrochemistry of Metal Nanoparticles and Quantum Dots

“…Cyclic voltammetric experiments on QD dispersions [52] and adsorbed on electrode surfaces [53] have been used for determining energy band gaps, the relationship between optical and electrochemical band gaps being expressed by Eq. 5.…”