Absorption Cross-Section and Related Optical Properties of Colloidal InAs Quantum Dots

Abstract

We report the absorption cross-section of colloidal InAs quantum dots of mean radii from 1.6 to 3.45 nm. We find excellent agreement between the measured results and calculated values based on a model of small-particle light absorption. The absorption cross-section per dot is 6.2 x 10(-16)R(3) cm(2) at 2.76 eV and 3.15 x 10(-16)R(1.28) cm(2) at the first-exciton absorption peak, with the dot radius R in nm. We find that the per-quantum-dot particle oscillator strength of the first-exciton transition is constant for all sizes studied. The radiative lifetime of the first exciton calculated from the oscillator strength increases with dot size and ranges from 4 ns for the smallest dots to 14 ns for the largest ones.

Large‐Scale Synthesis of Ultrathin Bi2S3 Necklace Nanowires

“…The reason might lie in the giant oscillator strength effect predicted by the EMA which has thus not been observed consistently in quantum dot systems. [19,20,22,23] This effect predicts that the oscillator strength (per volume) of optical transitions in semiconductors would be proportional to r À3 and thus would justify such a strong oscillator strength in such diminutive structures as the ones we report here. [24] While single-wire measurements are beyond the scope of this report, the electrical properties of Bi 2 S 3 nanowire films could be easily measured and the results are shown in Figure 3.…”

Spectroscopic characterization of streptavidin functionalized quantum dots

“…In this work we have relied on the theoretical and experimental framework established by the earlier work of Brus et al (10,11,44,45), Bawendi et al (18,19,22,23,(46)(47)(48)(49) and others (15,24,25,50,51). Experimental data have shown a strong correlation between the method of dot preparation and excited state behavior (23).…”

Direct determination of absorption anisotropy in colloidal quantum rods

“…For QDs like InAs, 13 wz-and zb-CdSe, 12,17 PbS, 14 PbSe, 16 and ZnO, 15 it has been shown that μ i is independent of the QD size at energies well above the band-gap energy. Within the Maxwell Garnett model, the absorption coefficient can be written in terms of the refractive index n s of the solvent and the dielectric function ε = ε R + iε I of the dispersed particles: 26…”

“…[12][13][14][15][16][17] In Eq. (2), the local-field factor f LF gives the ratio between the (optical) electric field outside (E 0 ) and inside (E) a QD.…”

“…Especially at photon energies considerably higher than that of the first exciton transition, experimental values agree with theoretical predictions using bulk dielectric constants. [12][13][14][15][16][17] The local-field approximation has also been applied to one-dimensional nanowires, where it predicts that μ takes different values for light that is polarized parallel (μ ) and perpendicular (μ ⊥ ) to the long axis of the wire. In the case of InP nanowires, the observation of polarized emission and emission excitation has been accordingly interpreted in terms of anisotropic local-field factors.…”