Abstract:With a view to contribute to the understanding the surface effects on optical properties process, and its hole in the electronic properties of the nanoparticles, CdS based nanoparticles are characterised by different experimental techniques and the experimental results compared to density functional theory calculations. Our results indicate that cubic CdS nanoparticles present a strong structural deformation, hexagonal reconstructed structures preserve their lattice behaviour. Both cubic and hexagonal CdS nano… Show more
“…Recently, the hydroxyl groups of starch have also been employed to stabilize metallic particles of Ag and Ag 2 S [33]. In our case, the cadmium-rich semiconductor nanoparticles form a stable complex with starch, though this type of particles is always S-terminated [27]. Consequently, the scheme proposed by Rutot-Houzé [34], displayed in Fig.…”
Section: Resultsmentioning
confidence: 85%
“…4 reveal extra features when the analysis is performed as a function of the measurement temperature. In quantum dots (QD), owing to the high surface-to-volume ratio, the impurity levels into the forbidden band gap are localized at the surface of the particle [26,27]. In order to explain the forbidden interband electronic transitions in CdS-QD, impurity levels have been proposed in a number of works, and in some cases these impurity levels have been associated to the ligand material at the surface of the particle [23,[28][29][30].…”
“…Recently, the hydroxyl groups of starch have also been employed to stabilize metallic particles of Ag and Ag 2 S [33]. In our case, the cadmium-rich semiconductor nanoparticles form a stable complex with starch, though this type of particles is always S-terminated [27]. Consequently, the scheme proposed by Rutot-Houzé [34], displayed in Fig.…”
Section: Resultsmentioning
confidence: 85%
“…4 reveal extra features when the analysis is performed as a function of the measurement temperature. In quantum dots (QD), owing to the high surface-to-volume ratio, the impurity levels into the forbidden band gap are localized at the surface of the particle [26,27]. In order to explain the forbidden interband electronic transitions in CdS-QD, impurity levels have been proposed in a number of works, and in some cases these impurity levels have been associated to the ligand material at the surface of the particle [23,[28][29][30].…”
“…A similar problem has been discussed by Vorokh [14] and Faver [15], who discovered by computer analysis that small CdS NP (AE < 5 nm) have disordered structure differing from the crystal structure of wurtzite and sphalerite characteristic for bulk crystals of this semiconductor. Furthermore, we may propose that the difference in dimensions and, probably, the mechanism for growth of the CdS NP in the case of excess of different ions is related specifically to the difference in the structure of the core of the nanoparticles in the initial stages of growth.…”
mentioning
confidence: 60%
“…Coefficients k 1 …k 15 were determined using the experimental data according to Gorman [11] and Novik [12]. The starting region of compositions of the three components used most often for the preparation of CdS/L-Cys is shown in Fig.…”
A study was carried out on the dependence of the optical properties such as the maxima in the absorption and luminescence spectra, Stokes shift, and quantum yield on the composition of the three-component Cd 2+ -L-Cys-S 2-reaction system under synthesis conditions at 298 ± 2 K and pH 7. Equations describing the dependence of the position of the maximum in the luminescence and absorption spectra of solutions on their composition were obtained by mathematical planning using the Scheffe simplex-lattice design and treatment of the data. The region of compositions for unstable colloidal solutions was determined.Decreasing the size of semiconductor crystals to a size comparable to the region of delocalization of the electron-hole pair substantially alters their physical properties and expands the scope for their practical application. Nanosized cadmium sulfide is a leading material both relative to the number of studies of the interrelationship between the method of preparation of the nanoparticles (NP) and their size and properties and to the scope of their use in optical electronics, photocatalysis, analytical chemistry, biology, and medicine (as biolabels) [1]. In many studies, special attention has been focused on cadmium sulfide nanoparticles stabilized by the biocompatible amino acid L-cysteine (L-Cys) obtained in aqueous solution [2][3][4][5][6][7]. Besides the pH of the medium, the ratio of the amounts of precursors, ionic composition of the solution, and preparation temperature have been varied, leading to a clear-cut understanding of the effect of concentration. As a rule, correlations have generally been sought upon varying the concentration of one of the precursors and holding the concentrations of the others constant. Attempts for a broader understanding of the effect of surfactants (with L-cysteine or glutathione as the stabilizer and bistrimethylsilyl sulfide as the sulfidizing agent) on the width of the forbidden band of CdS NP in the solution pH range from 4 to 10 were undertaken only by Kalasad et al. [7], who used a statistical design for the experiment.In the present work, we have established general rules for changing the optical properties and shape of cadmium sulfide NP obtained in a three-component system consisting of Cd 2+ , S 2-, and L-Cys upon broad variation of the ratios relating the 0040-5760/11/4702-0101
“…Theoretical photoluminescence spectrum corresponding to the spectrum of CdS nanoparticles obtained in Ref. [7] are shown in Figure 5. Nanoparticles were synthesized in water solution of (NH 4 2 S and Cd(NO 3 2 .…”
Section: Fluctuation-dissipative Relation For the Description Of Photmentioning
We present a possibility to model morphology of surfaces of nanostructured semiconductor films by use of methods of nonlinear physics. We also describe experimental photoluminescence and absorption spectra in nanostructured fractal medium. By use of our theory we describe the new experimental fact of light localization in non-crystalline films. We suggest a fractal model for energy spectra of excitons in nanostructured semiconductors with porous structure. We obtain equations for exciton and multi-exciton energy depending on energy of exciting photon.
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