Ultrafast exciton relaxation dynamics in silicon quantum dots

Cimpean, Carla; Groenewegen, Vincent; Kuntermann, Volker; Sommer, Anja; Kryschi, Carola

doi:10.1002/lpor.200810036

Cited by 23 publications

(29 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…I A 2). The SO interaction is a relativistic effect that has the form h 4m 2 o c 2 rV c ðrÞ Â p ð ÞÁr; (15) where r represents the Pauli matrices. In the LÁS(¼ 1/2(J 2 -L 2 -S 2 )) coupling scheme, the four valence electrons exist in an sp 3 The energy levels of the exciton states are schematically depicted in Fig.…”

Section: Fine Structurementioning

confidence: 99%

Quantum confinement in Si and Ge nanostructures: Theory and experiment

Barbagiovanni

Lockwood

Simpson

et al. 2014

Applied Physics Reviews

200

132

View full text Add to dashboard Cite

The role of quantum confinement (QC) in Si and Ge nanostructures (NSs) including quantum dots, quantum wires, and quantum wells is assessed under a wide variety of fabrication methods in terms of both their structural and optical properties. Structural properties include interface states, defect states in a matrix material, and stress, all of which alter the electronic states and hence the measured optical properties. We demonstrate how variations in the fabrication method lead to differences in the NS properties, where the most relevant parameters for each type of fabrication method are highlighted. Si embedded in, or layered between, SiO 2 , and the role of the sub-oxide interface states embodies much of the discussion. Other matrix materials include Si 3 N 4 and Al 2 O 3. Si NSs exhibit a complicated optical spectrum, because the coupling between the interface states and the confined carriers manifests with varying magnitude depending on the dimension of confinement. Ge NSs do not produce well-defined luminescence due to confined carriers, because of the strong influence from oxygen vacancy defect states. Variations in Si and Ge NS properties are considered in terms of different theoretical models of QC (effective mass approximation, tight binding method, and pseudopotential method). For each theoretical model, we discuss the treatment of the relevant experimental parameters. V

show abstract

Section: Fine Structurementioning

confidence: 99%

Quantum confinement in Si and Ge nanostructures: Theory and experiment

Barbagiovanni

Lockwood

Simpson

et al. 2014

Applied Physics Reviews

200

132

View full text Add to dashboard Cite

show abstract

“…12 In addition, the chemical modifications of the surface of Si QDs induce tuning of the optical properties and quantum yield, and also allow an ultrafast charge transfer across the surface through the organic conjugated capping molecule. 13,14 To investigate the effects of surface chemistry on the optical properties of Si QDs, our groups adopted the microemulsion approach to synthesize hydrogen terminated Si QDs using CuSO 4 for the quenching of LiAlH 4 , 15,16 with subsequent functionalization with three different capping molecules, viz. 1-octene, phenylacetylene, and 1,4-diethynylbenzene to give the octyl capped Si QD, the styryl Si QD, and the 4-ethynylstyryl Si QD, respectively.…”

Section: Introductionmentioning

confidence: 99%

The effects of electronic coupling between capping molecules and quantum dots on the light absorption and emission of octyl, styryl, and 4-ethynylstyryl terminated silicon quantum dots

Jeong

2014

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

Optical properties of silicon quantum dots (Si QDs) are greatly influenced by their size and surface chemistry. We report the micro-emulsion synthesis of hydrogen terminated Si QDs, with the modification of quenching the remaining reducing agent LiAlH4 with CuSO4. Subsequent functionalization was carried out with different capping molecules, including 1-octene, phenylacetylene, and 1,4-diethynylbenzene, to give octyl, styryl, and 4-ethynylstyryl terminated silicon quantum dots, respectively. The optical properties of the three kinds of Si QD synthesized, with the extended conjugation length, were examined. The effects of surface chemistry on the optical properties of the Si QD, obtained using ultraviolet-visible absorption spectroscopy and photoluminescence spectroscopy, were compared to the extension of electron and hole wavefunctions into the capping molecules, which were estimated from modified particles in a box calculation. The observed quantum yield increased from 2% to 2.5% and 9.0% and the average lifetime decreased with increasing conjugation length of the octyl Si QD, the styryl Si QD, and the 4-ethynylstyryl Si QD, which were ascribed to the effect of electronic coupling between the capping molecules and the Si QD. A tentative model in which the strong electronic interaction through covalent bonding induced a more direct band gap character for light emission was proposed by tuning the ground state wavefunctions of the electron and hole in wave vector space.

show abstract

“…Oxide-free, water-soluble, green luminescent 2-vinylpyridine terminated SiQDs (2-vipySiQDs) with sizes between 2 and 3 nm were obtained from a combined HF etching and thermal hydrosilylation procedure [9]. Cells were incubated at 37°C in a 10 % CO 2 /air incubator with 90 % humidity.…”

Section: Methodsmentioning

confidence: 99%

Silicon Quantum Dots Functionalized for siRNA Delivery

et al. 2010

View full text Add to dashboard Cite

Biocompatible, water-soluble, green luminescent silicon quantum dots (SiQDs) were developed as transfection tool for small interfering RNA (siRNA). The research goal was to down-regulate via the RNA interference (RNAi) mechanism the P-glycoprotein expression of the multidrug resistant gene 1 (MDR1) in a human colon carcinoma cell line (Caco-2). The internalization of 2-vinylpyridine terminated SiQDs (2-vipySiQDs) by Caco-2 cells as observed in confocal laser scanning microscopy imaging studies occurs via endocytosis. Experiments employing agarose gel electrophoresis revealed that 2-vipySiQD-siRNA complexes are formed through electrostatic interactions. The release of siRNA in the cytosol with subsequently RNAi induced down-regulation of the P-glycoprotein translation was verified by detecting a reduced ABCB1 mRNA level in transfected Caco-2 cells employing real-time PCR. Additional evidence for successful ABCB1 gene silencing was obtained by measuring a significant decrease of the Pglycoprotein transporter efficiency for the fluorescent substrate Rhodamine 123 (Rh123).

show abstract

Ultrafast exciton relaxation dynamics in silicon quantum dots

Cited by 23 publications

References 32 publications

Quantum confinement in Si and Ge nanostructures: Theory and experiment

Quantum confinement in Si and Ge nanostructures: Theory and experiment

The effects of electronic coupling between capping molecules and quantum dots on the light absorption and emission of octyl, styryl, and 4-ethynylstyryl terminated silicon quantum dots

Silicon Quantum Dots Functionalized for siRNA Delivery

Contact Info

Product

Resources

About