Mechanisms of the Shape Evolution of CdSe Nanocrystals

Peng, Zhé; Peng, Xiaogang

doi:10.1021/ja0027766

Cited by 1,707 publications

(2,041 citation statements)

References 31 publications

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“…In our investigation, size focusing and existence of nearly monodispersed, fully grown CdSe nanocrystals also indicates that the formation process did not follow Ostwald ripening growth (i.e., defocusing and broad size distribution), but rather maintained a diffusion-controlled process (size-focusing) 55,57,59 as a form of the livingpolymerzation model.…”

Section: Investigation Of Thementioning

confidence: 61%

Mechanistic Study of the Formation of Bright White Light-Emitting Ultrasmall CdSe Nanocrystals: Role of Phosphine Free Selenium Precursors

Dolai¹,

Dutta

Muhoberac³

et al. 2015

Chem. Mater.

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ABSTRACT:We have designed a new non-phosphinated reaction pathway, which includes synthesis of a new, highly reactive Se-bridged organic species (chalcogenide precursor), to produce bright white light-emitting ultrasmall CdSe nanocrystals of high quality under mild reaction conditions. The detailed characterization of structural properties of the selenium precursor through combined 77 Se NMR and laser desorption ionization-mass spectrometry (LDI-MS) provided valuable insights into Se release and delineated the nanocrystal formation mechanism at the molecular level. The 1 H NMR study showed that the rate of disappearance of Se-precursor maintained a single-exponential decay with a rate constant of 2.3 x 10 -4 s -1 at room temperature. Furthermore, the combination of LDI-MS and optical spectroscopy was used for the first time to deconvolute the formation mechanism of our bright white light-emitting nanocrystals, which demonstrated initial formation of a smaller key nanocrystal intermediate (CdSe)19. Application of thermal driving force for destabilization resulted in (CdSe)n nanocrystal generation with n = 29-36 through continuous dissolution and addition of monomer onto existing nanocrystals while maintaining a living-polymerization type growth mode. Importantly, our ultrasmall CdSe nanocrystals displayed an unprecedentedly large fluorescence quantum yield of ~27% for this size regime (<2.0 nm diameter). These mixed oleylamine and cadmium benzoate ligand-coated CdSe nanocrystals showed a fluorescence lifetime of ~90 ns, a significantly large value for such small nanocrystals, which was due to delocalization of the exciton wavefunction into the ligand monolayer. We believe our findings will be relevant to formation of other metal chalcogenide nanocrystals through expansion of the understanding and manipulation of surface ligand chemistry, which together will allow the preparation of "artificial solids" with high charge conductivity and mobility for advanced solid-state device applications.3

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Section: Investigation Of Thementioning

confidence: 61%

Mechanistic Study of the Formation of Bright White Light-Emitting Ultrasmall CdSe Nanocrystals: Role of Phosphine Free Selenium Precursors

Dolai¹,

Dutta

Muhoberac³

et al. 2015

Chem. Mater.

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“…Peng & Peng observed that the reaction solvent strongly affected synthesis kinetics. 13 Early theoretical studies of nanocrystal growth rates emphasized Ostwald ripening, [14][15][16][17] whereby larger particles grow and smaller particles dissolve, thus widening particle size distributions when reactants are scarce. Researchers concluded that narrower size distributions could be achieved when nanocrystal growth was limited by diffusion rather than by reaction rate.…”

mentioning

confidence: 99%

Synthesis kinetics of CdSe quantum dots in trioctylphosphine oxide and in stearic acid

Dickerson

Irving

Herz

et al. 2005

Applied Physics Letters

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A diffusion-barrier model described the early evolution of size-dependent photoluminescence emission from CdSe quantum dots formed by organometallic synthesis. Emission peak widths, emission redshift rates, and nanocrystal growth rates all decreased to a minimum at a reaction completion time. Growth after the completion time by Ostwald ripening was marked by a doubling of the activation energy. The temperature dependence of both reaction completion rates and photoluminescence redshift rates followed Arrhenius behavior governed by activation energies that increased with solvent molecular weight, in this limited case. In stearic acid and in trioctylphosphine oxide, the typical activation energies were 0.6±0.1 and 0.92±0.26eV∕molecule, respectively.

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“…Instead, an excited but electrically neutral state, called and exciton 4 , is created which requires additional energy (E B ) to separate into charge carriers [38,41]. This energy is gained form the offset of energy states at the heterojunction [41][42][43][44][45][46]. Figure 7 gives a ba di ram for the p-n rmed in an inorganic/organic PV cell.…”

Section: Inorganic and Organic Semiconductors Lar Cell Would B Affectmentioning

confidence: 99%

Progress on a Photovoltaic Cell Design Consisting of Silicon Nanowires and Poly (3‐ hexylthiophene)

Noice¹

2006

McNair Scholars Online Journal

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Citation: Noice, Lori. Progress on a photovoltaic cell design consisting of silicon nanowires and poly (3-hexylthiophene). Portland State University McNair Scholars Online Journal, Vol. 2, 2006Vol. 2, -2008. Progress on a photovoltaic cell design consisting of silicon nanowires and poly(3-hexylthiopenen)Lori Noice 1 , Gary Goncher 1 , Raj Solanki 1, 2 Abstract A bulk-heterojunction photovoltaic cell design made from silicon nanowires (SiNW) and poly(3-hexylthiophene) (P3HT) could provide the photon absorption and charge transport needed for a high efficiency hybrid PV cell. Since the mechanisms associated with the inorganic/organic semiconductor heterojunction are not yet well understood, the simple design of the proposed PV cell and tunable properties of both SiNW and P3HT affords experimental optimization opportunities.

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Mechanisms of the Shape Evolution of CdSe Nanocrystals

Cited by 1,707 publications

References 31 publications

Mechanistic Study of the Formation of Bright White Light-Emitting Ultrasmall CdSe Nanocrystals: Role of Phosphine Free Selenium Precursors

Mechanistic Study of the Formation of Bright White Light-Emitting Ultrasmall CdSe Nanocrystals: Role of Phosphine Free Selenium Precursors

Synthesis kinetics of CdSe quantum dots in trioctylphosphine oxide and in stearic acid

Progress on a Photovoltaic Cell Design Consisting of Silicon Nanowires and Poly (3‐ hexylthiophene)

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