Surface Modification of CdSe and CdS Quantum Dots-Experimental and Density Function Theory Investigation

Chena, Liang-Yih; Chou, Hung‐Lung; Chenc, Ching-Hsiang; Tseng, Chia-Hung

doi:10.5772/48675

Cited by 9 publications

(8 citation statements)

References 70 publications

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“…Therefore, this postsynthesis treatment shows a distinctly different behavior from CdSe QDs and hence it is not an effective tool for optimizing the emission of CdS QDs. The strong decrease in emission due to the addition of Olam and other amine-based ligands have been previously reported for CdS QDs . This has been explained using DFT calculation to be due to the effects of net charge transfer between the ligand and the CdS QDs, effecting the carrier recombination dynamics by controlling the radiative recombination surface state centers and therefore lowering the resulting PLQY and can produce an increase in the surface deep trap state emission.…”

Section: Resultsmentioning

confidence: 60%

Investigation of Quantum Dot–Metal Halide Interactions and Their Effects on Optical Properties

2018

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Quantum dots (QDs) are a class of important light-emitting nanomaterials, which have shown considerable potential for a range of applications. Here, we report detailed studies of the interactions between cadmium halide salts and II–VI-based quantum dots affecting their optical properties. A specific set of experiments have been utilized to better understand these effects using a range of core and core–shell quantum dots as model systems, examining CdSe, CdS, CdS/CdSe, CdTe/CdSe, CdSe/CdS, CdSe/ZnS QDs, and CdSe/CdS dots in rod nanostructures. In our studies, we have demonstrated that significant increases in photoluminescent (PL) and photoluminescent quantum yields (PLQY) can be achieved, producing a 1.5–4-fold increase for CdSe QDs and 1.4–1.8-fold increase for a number of other Cd-based core–shell nanostructures. To explain these phenomena, the interaction’s efficiency for three alternative ligand-capped CdSe QDs have been examined, with results showing a weak dependency on capping ligand. By contrast, we have demonstrated that variation of the halide anion of the cadmium salt shows a strong dependence, with decreasing effectiveness found when comparing Cl– to Br– and I–. In addition, we have been able to show a large increase of PLQY for reverse type I (CdS/CdSe) and type II (CdTe/CdSe) QDs, both nanostructures which display strong surface-sensitive PL properties, while type I (CdSe/CdS) nanostructures showed a weaker effect, with an inverse relationship relative to shell thickness. Finally, it was also found that ZnS or ZnS-shelled QDs show the onset of cation exchange, causing PL red shifting and a significant reduction of PLQY. Therefore, the culmination of these results can be best explained using standard covalent ligand classification, and points to this treatment working via a three-pronged approach, in which surface passivation takes place through the presence of the L-type ligand oleylamine, the Z-type ligand, Cd(oleylamine), and the X-type ligand Cl– anion, the combination of which produces the total optimal effect observed. Overall, this study presents important approaches to increase quantum yields in a range of widely utilized QDs and provides important insights into the underlying interactions of this type of surface treatments as means to improve the resulting optical properties.

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Section: Resultsmentioning

confidence: 60%

Investigation of Quantum Dot–Metal Halide Interactions and Their Effects on Optical Properties

2018

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“…22,33 The slow reaction kinetics assures higher quality of the obtained nanomaterials with a large number of radiative surface-states and low nonradiative surface quenching defects. 34 The high QY and short t also suggest that the observed emission band broadening is likely due to the CdS tetrapod size distribution, which can be in fact seen in the TEM images and size distribution histograms (Fig. 1a and c).…”

Section: Methodsmentioning

confidence: 83%

Two-photon absorption in penicillamine capped CdS tetrapods

Wawrzyńczyk

2017

J. Mater. Chem. C

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“…The PL intensity diminishes with the growth time. The increment of reaction time causes departure of the ligand from the surface of the quantum dots and it weakens the PL intensity because of deterioration in the surface passivation [18]. However, there is no a considerable shift in the PL peak position.…”

Section: Resultsmentioning

confidence: 99%

Kolloidal CdSe Kuantum Noktalarının Sentezi ve Optik Karakterizasyonu

Allahverdi¹

2019

Academic Platform Journal of Engineering and Science

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Kolloidal CdSe kuantum noktaları, koordine olmayan oktadesen çözücü içerisinde sıcak-enjeksiyon tekniği kullanılarak yaklaşık 300 o C'de 15 s çekirdekleştirildi ve 272 o C'de 245 dakikaya kadar büyütüldü. CdSe kuantum noktalarının sentezinde stearik asit bir kaplama ajanı olarak kullanıldı. Bu çalışmada kullanılan çekirdekleşme zamanı literatürdekilere göre oldukça uzundu ve optik özelliklere olan etkisi incelendi. Birinci eksiton soğurma ve karşılık gelen rekombinasyon tepeleri, sırasıyla, optik soğurma ve fotolüminesans spektrumlarında gözlendi. Stokes kayma değeri 70 meV'ye kadar değişti. 20 dakika için büyütülen numunenin optik soğurma ve fotolüminesans spektrumlarında bir tepe ve omuz yapısı elde edildi. Yüksek sıcaklık altında yeterince uzun bir sürede çekirdekleştirilen bu kuantum noktalarının çift büyüklük dağılımına sahip olabileceği gösterildi. CdSe kuantum noktalarının görüntüleri geçirgenlik elektron mikroskopi vasıtasıyla elde edildi. Resimleri, ImageJ görüntü işleme programı ile işlendi. 12 dakika büyütülen CdSe kuantum noktalarının ortalama büyüklüğü 2.63 nm olarak bulundu. Büyüklük dağılımı tekil dağılımlı kuantum noktalarınkine nazaran 4.6 kat arttı. Cd ve Se elementlerine ait X-ışınları enerji geçiş tepeleri enerji dağılımlı X-ışınları spektrumlarında gözlendi. Bu kuantum noktalarını saran stearik asit moleküllerinin simetrik ve asimetrik tireşim modları Fourier dönüşümlü kızıl ötesi spektroskopi kullanılarak, sırasıyla, 2848 cm-1 ve 2914 cm-1 civarında belirlendi.

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Surface Modification of CdSe and CdS Quantum Dots-Experimental and Density Function Theory Investigation

Cited by 9 publications

References 70 publications

Investigation of Quantum Dot–Metal Halide Interactions and Their Effects on Optical Properties

Investigation of Quantum Dot–Metal Halide Interactions and Their Effects on Optical Properties

Two-photon absorption in penicillamine capped CdS tetrapods

Kolloidal CdSe Kuantum Noktalarının Sentezi ve Optik Karakterizasyonu

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