Shape Control of II–VI Semiconductor Nanomaterials

Kumar, Sandeep; Nann, Thomas

doi:10.1002/smll.200500357

Cited by 368 publications

(280 citation statements)

References 90 publications

Supporting

Mentioning

272

Contrasting

Unclassified

Order By: Relevance

“…CdSe nanorods are synthesized via the most widely used approach for the synthesis of colloidal nanocrystals [2,7,13,32]. A typical synthesis system consists of three components: precursors, organic surfactants and solvents.…”

Section: Colloidal Nanorod Growthmentioning

confidence: 99%

Optical phonons in colloidal CdSe nanorods

Lange

Mohr

Artemyev

et al. 2010

Physica Status Solidi (b)

View full text Add to dashboard Cite

Colloidal CdSe nanorods are nanoparticles synthesized in solution. The synthesis allows the growth of CdSe nanorods with well defined diameters and aspect ratios. They have many potential applications in the field of optoelectronics and biotechnology. The nanorods can be epitaxially covered with a graded CdS/ZnS shell of a few monolayers in thickness. The shell leads to an increased quantum efficiency and improved photostability of the nanorods. However, the lattice mismatch between the nanorod core material and the shell material introduces strain into the core lattice. In this work Raman spectroscopy, accompanied by ab-initio calculations, is used to determine the amount of this strain, the exciton-phonon coupling strength in the nanorods and to investigate confinement effects. The longitudinal optical phonons in a nanorod are confined to the nanorod volume. The confinement of a phonon wavefunction leads to a neutralization of the q = 0 rule and the phonon frequency is found to depend on the nanorod diameter. The coupling strength between longitudinal optical phonons and excitons is investigated. It also depends on the nanorod diameter. The total coupling strength is much lower than in bulk material due to a decrease of the influence of the Coulomb interaction in nanoparticles. However, the coupling strength is found to rise for decreasing diameters. This is due to the increasing contributions of higher frequency phonons for smaller nanoparticle sizes. A radial breathing mode with a diameter dependent frequency is deduced from ab-initio calculations and its existence in nanorods is verified experimentally. The diameter-dependence of the modes' frequency can be used to estimate the nanorod diameter from a Raman measurement. In core-shell structures, the coverage of a CdSe nanorod with a ZnS shell leads to a compressive strain of the CdSe core due to the smaller lattice parameter of ZnS compared to CdSe. Ab-initio calculations show that all bonds of the CdSe core are shortened. The bonds in the lateral direction are much more strongly compressed than the bonds parallel to the c-axis. The amount of strain is estimated from the Raman spectra. The compressive nature of the shell decreases for thicker nanorods. The exciton wave function changes with the modified boundary from air to ZnS. This is reflected in a altered exciton-phonon coupling strength and can be monitored in the Raman spectra. ZusammenfassungCdSe Nanorods sind Nanopartikel, die in einer kolloidalen Lösung synthetisiert werden. Für diese existieren viele mögliche Anwendungen im Bereich der Optoelektronik und der Biotechnologie. Der Durchmesser und die Länge der Nanorods lässt sich durch die Syntheseparameter festlegen. Die Nanorods können in eine epitaktische Hülle aus einem Halbleitermaterial mit einer größeren Bandlücke, ZnS, eingebettet werden. Diese Hülle verbessert die optischen Eigenschaften und ermöglicht eine weitere Funktionalisierung der Oberfläche. Der Unterschied der Gitterparameter zwischen ZnS und CdSe führt jedoch zu Verspannung...

show abstract

Section: Colloidal Nanorod Growthmentioning

confidence: 99%

Optical phonons in colloidal CdSe nanorods

Lange

Mohr

Artemyev

et al. 2010

Physica Status Solidi (b)

View full text Add to dashboard Cite

show abstract

“…The formation of nanocrystals usually takes place via two stages: nucleation and growth [11,14,15,39]. It is considered that the suddentemperature-rise process in our synthesis plays similar and important roles in the nucleation of target Figure 6 The changes of state and color at the different stages of the synthesis: (a) and (a') the solid state precursors at room temperature; (b) and (b') the precursors heated at 220 °C ; (c) and (c') the final products after reaction; (a), (b), and (c) indicate the changes during the synthesis of Fe 2 P nanowires; (a'), (b'), and (c') indicate those for Fe 2 P@C nanocables nanocrystals to those of the rapid-injection-of-precursor process in solution-based precursor injection methods [14,15,[22][23][24][25][26], based on the fact that both processes can result in a burst and uniform nucleation of nanocrystals.…”

Section: Resultsmentioning

confidence: 99%

“…The presence of this large number of small Fe nanoparticles favors the growth of an Fe-rich Fe 2 P phase, and the size-uniform Fe nanoparticles with their high surface energy will quickly interact with reactive liquid PPh 3 to form a large number of uniform Fe 2 P seeds at a fast rate. In this way, a burst nucleation [14,15,39,40] of Fe 2 P with uniform sizes can be realized in a short period of time by the sudden rise of reaction temperature. The size-uniform Fe 2 P seeds favor the subsequent growth of Fe 2 P@C nanocables with uniform sizes.…”

Section: Resultsmentioning

confidence: 99%

“…Meanwhile, the solution-mediated reaction between Fe particles and PPh 3 at temperatures of 380-400 °C offers a suitable kinetic growth regime. In the growth of 1-D Fe 2 P nanocrystals, the diffusion between Fe and P atoms occurs at a considerable rate in liquid PPh 3 , and a high flux of conversion of Fe 2 P monomers into initial Fe 2 P seeds is created via diffusional growth [11,14,39,40], which favors the preferential 1-D growth of monomers on the highest energy (001) surface [11,14,39], and finally yields the 1-D Fe 2 P nanostructures grown along the [001] direction (as verified by HRTEM and SAED studies). As the kinetic-dominating growth regime will be destroyed by adding extra surfactants or stabilizing ligands, the shape of the Fe 2 P products will be changed.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Magnetic Fe2P nanowires and Fe2P@C core@shell nanocables

et al. 2010

View full text Add to dashboard Cite

We report the synthesis of one-dimensional (1-D) magnetic Fe 2 P nanowires and Fe 2 P@C core@shell nanocables by the reactions of triphenylphosphine (PPh 3 ) with Fe powder (particles) and ferrocene (Fe(C 5 H 5 ) 2 ), respectively, in vacuum-sealed ampoules at 380-400 °C . The synthesis is based on chemical conversion of micrometer or nanometer sized Fe particles into Fe 2 P via the extraction of phosphorus from liquid PPh 3 at elevated temperatures. In order to control product diameters, a convenient sudden-temperature-rise strategy is employed, by means of which diameter-uniform Fe 2 P@C nanocables are prepared from the molecular precursor Fe(C 5 H 5 ) 2 . In contrast, this strategy gives no obvious control over the diameters of the Fe 2 P nanowires obtained using elemental Fe as iron precursor. The formation of 1-D Fe 2 P nanostructures is ascribed to the cooperative effects of the kinetically induced anisotropic growth and the intrinsically anisotropic nature of hexagonal Fe 2 P crystals. The resulting Fe 2 P nanowires and Fe 2 P@C nanocables display interesting ferromagnetic-paramagnetic transition behaviors with blocking temperatures of 230 and 268 K, respectively, significantly higher than the ferromagnetic transition temperature of bulk Fe 2 P (T C = 217 K).

show abstract

“…ZnSe NCs were fabricated by using the hot injection method with ZnO as a precursor [30,31]. A typical synthetic procedure includes adding 2 mmol (0.1644 g) zinc oxide, 10 mmol (2.3068 g) myristic acid, 16 mmol HDA (4.2926 g) into a three-necked flask.…”

Section: Nanocrystal (Nc) Synthesismentioning

confidence: 99%

Solution-Processed CdTe Thin-Film Solar Cells Using ZnSe Nanocrystal as a Buffer Layer

et al. 2018

View full text Add to dashboard Cite

Abstract:The CdTe nanocrystal (NC) is an outstanding, low-cost photovoltaic material for highly efficient solution-processed thin-film solar cells. Currently, most CdTe NC thin-film solar cells are based on CdSe, ZnO, or CdS buffer layers. In this study, a wide bandgap and Cd-free ZnSe NC is introduced for the first time as the buffer layer for all solution-processed CdTe/ZnSe NC hetero-junction thin-film solar cells with a configuration of ITO/ZnO/ZnSe/CdTe/MoOx/Au. The dependence of the thickness of the ZnSe NC film, the annealing temperature and the chemical treatment on the performance of NC solar cells are investigated and discussed in detail. We further develop a ligand-exchanging strategy that involves 1,2-ethanedithiol (EDT) during the fabrication of ZnSe NC film. An improved power conversion efficiency (PCE) of 3.58% is obtained, which is increased by 16.6% when compared to a device without the EDT treatment. We believe that using ZnSe NC as the buffer layer holds the potential for developing high-efficiency, low cost, and stable CdTe NC-based solar cells.

show abstract

Shape Control of II–VI Semiconductor Nanomaterials

Cited by 368 publications

References 90 publications

Optical phonons in colloidal CdSe nanorods

Optical phonons in colloidal CdSe nanorods

Magnetic Fe2P nanowires and Fe2P@C core@shell nanocables

Solution-Processed CdTe Thin-Film Solar Cells Using ZnSe Nanocrystal as a Buffer Layer

Contact Info

Product

Resources

About