Effective Bonding Parameters for the Prediction    of Electronic Transition of CdS Clusters

Okano, Kiyohisa; Hayashi, Tadao

doi:10.1143/jjap.37.l177

Cited by 2 publications

(4 citation statements)

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“…From published data on similar CdS clusters, we estimate the number of Cd atoms per cluster to be between 17 to 32 atoms. [35][36][37][38][39][40] Over the course of the 1000 mM reaction (6 h at 130°C), the peak at 324 nm increases in intensity but does not shift, indicating continuous formation of MSCs (Figure S1). At the highest concentration, 1000 mM, the peak at 324 nm is dominant with only a small contribution from a broad NP peak (~300 meV FWHM) that shifts during growth from 375 to 404 nm (NPs account for <0.1% of total product based on particle concentration, see SI).…”

Section: Resultsmentioning

confidence: 99%

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Mesophase Formation Stabilizes High-Purity Magic-Sized Clusters

et al. 2018

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Magic-sized clusters (MSCs) are renowned for their identical size and closed-shell stability that inhibit conventional nanoparticle (NP) growth processes. Though MSCs have been of increasing interest, understanding the reaction pathways toward their nucleation and stabilization is an outstanding issue. In this work, we demonstrate that high concentration synthesis (1000 mM) promotes a well-defined reaction pathway to form high-purity MSCs (>99.9%). The MSCs are resistant to typical growth and dissolution processes. On the basis of insights from in situ X-ray scattering analysis, we attribute this stability to the accompanying production of a large (>100 nm grain size), hexagonal organic-inorganic mesophase that arrests growth of the MSCs and prevents NP growth. At intermediate concentrations (500 mM), the MSC mesophase forms, but is unstable, resulting in NP growth at the expense of the assemblies. These results provide an alternate explanation for the high stability of MSCs. Whereas the conventional mantra has been that the stability of MSCs derives from the precise arrangement of the inorganic structures (i.e., closed-shell atomic packing), we demonstrate that anisotropic clusters can also be stabilized by self-forming fibrous mesophase assemblies. At lower concentration (<200 mM or >16 acid-to-metal), MSCs are further destabilized and NPs formation dominates that of MSCs. Overall, the high concentration approach intensifies and showcases inherent concentration-dependent surfactant phase behavior that is not accessible in conventional (i.e., dilute) conditions. This work provides not only a robust method to synthesize, stabilize, and study identical MSC products but also uncovers an underappreciated stabilizing interaction between surfactants and clusters.

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Section: Resultsmentioning

confidence: 99%

“…The small deviation in size (which is approximately 1/5th of a Cd–S bond) suggests that each cluster has an identical number of Cd atoms. From published data on similar CdS clusters, we estimate the number of Cd atoms per cluster to be between 17 to 32 atoms. − …”

Section: Resultsmentioning

confidence: 99%

Mesophase Formation Stabilizes High-Purity Magic-Sized Clusters

et al. 2018

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“…5) Calculations were performed using the program for quantitative determination of molecular geometry and MOs taking the solvent effect or adsorption on a solid surface into account (GEOMOS). 8) However, since CdS ufp after synthesis and separation were investigated in this work, neither the orbitals φ r and φ s which are on atoms A and B, respectively, and R AB is the distance between atoms A and B.…”

Section: Molecular Orbital Calculationsmentioning

confidence: 99%

“…3) In these applications, it is important to obtain an insight into the surface atomic structures on which certain phenomena such as relaxation of photogenerated carriers and charge separation strongly depend. 4) In a previous paper, 5) we reported a new method of molecular orbital (MO) calculation which can be used for semiconductor cluster molecules with the intention of improving the calculation of electronic states and surface structures of semiconductor ufp consisting of a large number of atoms compared to clusters. Namely, the complete neglect of differential overlap (CNDO) method was applied to CdS molecular clusters as good models of CdS ufp.…”

Section: Introductionmentioning

confidence: 99%

Molecular Orbital Approach to the Electronic Structure of CdS Ultrafine Particles

Okano

Hayashi

Miyamoto

1999

Jpn. J. Appl. Phys.

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The electronic structure of CdS ultrafine particles was studied by the semiempirical molecular orbital (MO) method. A practical procedure to perform MO calculations on a very large molecule which contains roughly one thousand atoms was established. The aimed electronic structure was obtained and characterized. A tendency which corresponds to the so-called size quantization effect usually observed in semiconductor ultrafine particles was confirmed. An electronic transition energy, which was almost comparable to experimental data, was obtained. The influence of surface structures on the electronic state was directly calculated by the MO method. Low-coordinated Cd atoms were found to produce surface states. A surface defect site associated with excess Cd was simulated by introducing a sulfur vacancy. A new MO that originated from the defect site, which may act as a trapping site of excited electrons, was identified.

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Effective Bonding Parameters for the Prediction of Electronic Transition of CdS Clusters

Cited by 2 publications

References 28 publications

Mesophase Formation Stabilizes High-Purity Magic-Sized Clusters

Mesophase Formation Stabilizes High-Purity Magic-Sized Clusters

Molecular Orbital Approach to the Electronic Structure of CdS Ultrafine Particles

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