Alternative Routes toward High Quality CdSe Nanocrystals

Qu, Lianhua; Peng, and Z. Adam; Peng, Xiaogang

doi:10.1021/nl0155532

Cited by 970 publications

(835 citation statements)

References 23 publications

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“…23 In our case, the chelating functional groups of TOPO and SA were different, so separate metal-organic interaction energies might also have contributed to each activation energy.…”

mentioning

confidence: 70%

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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“…23 In our case, the chelating functional groups of TOPO and SA were different, so separate metal-organic interaction energies might also have contributed to each activation energy.…”

mentioning

confidence: 70%

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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“…[67] This size regime was observed earlier, with an estimated diameter of 2.0 nm, [4] with some reported difficulties in determining the diameter of such ultrasmall nanoparticles. [38,68] Attempts to characterise the structure changes by TEM and conventional XRD approaches were unsuccessful due to the small nanoparticle size relative to the capping material. [37] The same challenge has been reported by Bowers et al [38], where they studied the structure of the ultrasmall CdSe nanoparticle (1.5 nm) with an associated band edge absorption centred at 417 nm and refers to as magic-sized CdSe nanocrystals.…”

Section: Nanoparticle Size From Pdf Analysis: the Size Of Crystallinementioning

confidence: 99%

Total scattering atomic pair distribution function: new methodology for nanostructure determination

Masadeh

2016

Journal of Experimental Nanoscience

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The conventional X-ray diffraction (XRD) methods probe for the presence of long-range order towards a solution of the average crystal structure. Experimentally, structural information about longrange, periodic atomic ordering is reflected in the Bragg scattering while local atomic structural deviations from the average structure mainly affect the diffuse scattering intensities. In order to obtain structural information about both average and local atomic structures, a technique that takes in account both Bragg and diffuse scattering needs to be employed, such as the total scattering atomic pair distribution function (PDF) technique. This article introduces a PDF-based methodology that can be applied to extract precise structural information about nanoparticles such as the size of the crystalline core region, the degree of crystallinity, the atomic structure of the core region, local bonding, and the degree of the internal disorder, as a function of the nanoparticle diameter. This article sheds light on a new PDF-based methodology that can yield precise quantitative structural information about small nanocrystals from XRD data, and also describes the essential aspects of this proposed methodology as well as its great potential. This method is generally applicable to the characterisation of the nanoscale solid, many of which may exhibit complex disordered structure.

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“…Peng e colaboradores 14,15 propuseram a substituição do dimetilcádmio por óxido de cádmio, CdO, ou por sais de cádmio contendo ânions de ácidos fracos, como o acetato de cádmio, Cd(Ac) 2 . Outra modificação adotada, na síntese de calcogenetos metálicos, foi a utilização da octadecilamina (ODA) como agente passivante e a substituição do solvente coordenante TOPO pelo solvente não coordenante 1-octadeceno (ODE).…”

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O estado da arte da síntese de semicondutores nanocristalinos coloidais

et al. 2010

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, 74, 36301-160 São João del-Rei -MG, Brasil Recebido em 8/11/09; aceito em 21/4/10; publicado na web em 24/8/10 THE STATE OF THE ART IN THE SYNTHESIS OF COLLOIDAL SEMICONDUCTOR NANOCRYSTALS. Colloidal semiconductor nanocrystals, also known as quantum dots, have attracted great attention since they have interesting size-dependent properties due to the quantum confinement effect. These nanoparticles are highly luminescent and have potential applications in different technological areas, including biological labeling, light-emitting diodes and photovoltaic devices. The synthetic methods of semiconductor nanocrystals have progressed in the last 30 years, and several protocols were developed to synthesize monodisperse nanocrystals with good optical properties, different compositions and morphologies. This review describes the main methods used to synthesize nanocrystals in the II-VI and III-V systems, and the recent approaches in this field of research.Keywords: semiconductor nanocrystals; quantum dots; colloidal synthesis. INTRODUÇÃOA síntese de nanocristais, partículas cristalinas com tamanhos de 1 a 100 nm, tem sido o objeto de inúmeros trabalhos científicos no mundo todo, devido às suas intrigantes propriedades ópticas. Dentre os materiais nanométricos, têm-se os semicondutores nanocristalinos coloidais, também chamados de pontos quânticos, os quais apresentam os portadores de carga (buracos e elétrons) em um estado de forte confinamento quântico, o que faz com que estes materiais possuam propriedades ópticas que podem ser alteradas modificando-se apenas o tamanho das nanopartículas. Uma das propriedades ópticas mais interessantes destes nanocristais, do ponto de vista da aplicação tecnológica, é a forte intensidade de luminescência que apresentam, permitindo que sejam utilizados em dispositivos optoeletrônicos, fotovoltaicos e biomédicos, dentre outros. 1,2A Figura 1 apresenta imagens de dispersões coloidais aquosas de nanocristais de telureto de cádmio (CdTe) com diferentes cores de emissão, em função do tamanho das nanopartículas, bem como os espectros de absorção óptica (UV-Vis) e de fotoluminescência (PL) dessas amostras.3 Na Figura 1b é possível observar um deslocamento da banda de absorção óptica fundamental de 480 para 556 nm (red shift), devido à formação de partículas maiores ao longo da evolução da síntese. De maneira semelhante, na Figura 1c, fica evidente um deslocamento das bandas de emissão em direção a comprimentos de ondas maiores, de 507 nm da primeira amostra para 592 nm na última amostra, o que corresponde a uma variação nas cores de emissão, como mostrado na Figura 1a.Os semicondutores nanocristalinos podem ser divididos em diferentes grupos da tabela periódica, tais como II-VI, III-V e IV-VI, sendo que, nesta revisão, são abordados, principalmente, os métodos experimentais de síntese para produção dos semicondutores dos grupos II-VI e III-V, embora esse último grupo seja ainda muito menos estudado. As sínteses destes materiais podem ser realizadas pelo método top-down, que utiliza técnicas ...

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Alternative Routes toward High Quality CdSe Nanocrystals

Cited by 970 publications

References 23 publications

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

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

Total scattering atomic pair distribution function: new methodology for nanostructure determination

O estado da arte da síntese de semicondutores nanocristalinos coloidais

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