Synthesis of Highly Luminescent Silica-Coated CdSe/CdS Nanorods

Pietra, Francesca; Moes, Relinde J. A. van Dijk; Ke, Xiaoxing; Bals, Sara; Tendeloo, Gustaaf Van; Donegá, Celso de Mello; Vanmaekelbergh, Daniël

doi:10.1021/cm401169t

Cited by 51 publications

(93 citation statements)

References 49 publications

(75 reference statements)

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“…Moreover from panel D it can be seen that the SiO2 growth process started at the ends of the NRs, which leads to dumbbell-like structures. Both these observations reproduce the results described by Pietra and coworkers 4. 8 mmol (about 400µL) of TEOS results in 30 nm thick silica shells, the use of about 0.4 mmol TEOS should yield a thickness of about 17 nm according to a rough calculation.…”

supporting

confidence: 89%

“…Pietra et al proposed for the formation of NR-SiO2 dumbbell-like structures, as reproduced in our work, a mechanism after which the initial SiO2 coverage at the tips of the NRs is due to a favorable ligand exchange with Igepal at the tips because of atomic and hence electronic, or geometric anisotropy. 4 Based on these models we propose a growth mechanism as sketched in Fig. 3.…”

Section: Resultsmentioning

confidence: 99%

“…[18][19][20] Also, different facets induce different stabilities of the micellar surrounding and exhibit different reactivities. 4,13 As a result, during the silanization process, TEOS molecules can typically more easily attach on the two tips of the NRs. 4 With the reaction proceeding, the nucleated silica species first grow into two distinct spheres, to form a dumbbell-like structure; then with the size increasing, the two spheres eventually unify to form a large (thickness ≥ 20 nm) silica ellipsoid.…”

Section: Introductionmentioning

confidence: 99%

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Ultrathin and Highly Passivating Silica Shells for Luminescent and Water-Soluble CdSe/CdS Nanorods

Tang¹,

Kröger²,

Nielsen³

et al. 2017

Langmuir

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Microemulsion (water-in-oil) methods enable the encapsulation of individual nanoparticles into SiO spheres. The major drawbacks of this method, when applied for silica encapsulation of anisotropic nanorods (NRs), are spatially unequal silica growth and long reaction times (24 h at least). In this work, various tetraalkoxysilanes [tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), and tetrapropyl orthosilicate (TPOS)] with different alkyl-chain lengths were used as silica precursors in attempt to tune the silanization behavior of CdSe/CdS NRs in a microemulsion system. We find enhanced spatial homogeneity of silica growth with decreasing alkyl-chain length of the tetraalkoxysilanes. In particular, by use of TMOS as the precursor, NRs can be fully encapsulated in a continuous thin (≤5 nm) silica shell within only 1 h reaction time. Surprisingly, the thin silica shell showed a superior shielding ability to acidic environment, even compared to the 30 nm thick shell prepared by use of TEOS. Our investigations suggest that the lower steric hindrance of TMOS compared to TEOS or TPOS strongly promotes homogeneous growth of the silica shells, while its increased hydrolysis rate decreases the porosity of these shells.

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supporting

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ultrathin and Highly Passivating Silica Shells for Luminescent and Water-Soluble CdSe/CdS Nanorods

Tang¹,

Kröger²,

Nielsen³

et al. 2017

Langmuir

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“…64−69 As shown in Figure 10, this process results in the heterogeneous nucleation of silica (SiO 2 ) shells on top of CdS x Se 1−x nanorods. 70 When CdSe is used (x = 0), SiO 2 nucleates starting from the two tips of the nanorods at similar times (concomitantly) (Figure 10a and Scheme 3a). However, when axially anisotropic, drumstick-like CdS 0.4 Se 0.6 nanorods are used, SiO 2 first nucleates starting from the thinner, CdS end of the nanorods, followed at a later coating stage by slower nucleation from the thicker, CdSe-rich end of the nanorods (Figure 10c and Scheme 3b).…”

Section: Chemistry Of Materialsmentioning

confidence: 97%

How Robust are Semiconductor Nanorods? Investigating the Stability and Chemical Decomposition Pathways of Photoactive Nanocrystals

2014

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Anisotropic II-VI semiconductor nanostructures are important photoactive materials for various energy conversion and optical applications. However, aside from the many available surface chemistry studies and from their ubiquitous photodegradation under continuous illumination, the general chemical reactivity and thermal stability (phase and shape transformations) of these materials are poorly understood. Using CdSe and CdS nanorods as model systems, we have investigated the behavior of II-VI semiconductor nanorods against various conditions of extreme chemical and physical stress (acids, bases, oxidants, reductants, and heat). CdSe nanorods react rapidly with acids, becoming oxidized to Se or SeO 2 . In contrast, CdSe nanorods remain mostly unreactive when treated with bases or strong oxidants, although bases do partially etch the tips of the nanorods (along their axis). Roasting (heating in air) of CdSe nanorods results in rock-salt CdO, but neither CdSe nor CdO is easily reduced by hydrogen (H 2 ). Another reductant, n-BuLi, reduces CdSe nanorods to metallic Cd. Variable temperature X-ray diffraction experiments show that axial annealing and selective axial melting of the nanorods precede particle coalescence. Furthermore, thermal analysis shows that the axial melting of II-VI nanorods is a ligand-dependent process. In agreement with chemical reactivity and thermal stability observations, silica-coating experiments show that the sharpest (most curved) II-VI surfaces are most active against heterogeneous nucleation of a silica shell. These results provide valuable insights into the fate and possible ways to enhance the stability and improve the use of II-VI semiconductor nanostructures in the fields of optics, magnetism, and energy conversion. KeywordsCadmium compounds, Cadmium sulfide, Chemical stability, Energy conversion, melting, oxidants, surface chemistry, thermoanalysis, thermodynamic stability, X ray diffraction, chemical decomposition, heterogeneous nucleation, optical applications, photoactive materials, semiconductor nanorods Disciplines Chemistry CommentsReprinted (adapted) with permission from Chemistry of Materials 26 (13) ABSTRACT: Anisotropic II−VI semiconductor nanostructures are important photoactive materials for various energy conversion and optical applications. However, aside from the many available surface chemistry studies and from their ubiquitous photodegradation under continuous illumination, the general chemical reactivity and thermal stability (phase and shape transformations) of these materials are poorly understood. Using CdSe and CdS nanorods as model systems, we have investigated the behavior of II−VI semiconductor nanorods against various conditions of extreme chemical and physical stress (acids, bases, oxidants, reductants, and heat). CdSe nanorods react rapidly with acids, becoming oxidized to Se or SeO 2 . In contrast, CdSe nanorods remain mostly unreactive when treated with bases or strong oxidants, although bases do partially etch the tips of the nanorods (along th...

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“…[1][2][3][4][5] The vast majority of research has been directed into improving the optical properties of quantum dots by increasing quantum yields (QYs), [6][7][8] photostability, [9,10] increasing the range of optical activity [11][12][13] and eliminating "blinking". [14][15][16] Enhancement of the optical properties and QYs relies on the reduction of surface defects in the QD lattice fringes.…”

mentioning

confidence: 99%

Doping Group IIB Metal Ions into Quantum Dot Shells via the One‐Pot Decomposition of Metal‐Dithiocarbamates

Bear

Hollingsworth

Roffey

et al. 2015

Advanced Optical Materials

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(2015). Doping group IIB metal ions into quantum dot shells via the one-pot decomposition of metaldithiocarbamates. Advanced Optical Materials. DOI: 10.1002/adom.201400570 Citing this paper Please note that where the full-text provided on King's Research Portal is the Author Accepted Manuscript or Post-Print version this may differ from the final Published version. If citing, it is advised that you check and use the publisher's definitive version for pagination, volume/issue, and date of publication details. And where the final published version is provided on the Research Portal, if citing you are again advised to check the publisher's website for any subsequent corrections. General rightsCopyright and moral rights for the publications made accessible in the Research Portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognize and abide by the legal requirements associated with these rights.•Users may download and print one copy of any publication from the Research Portal for the purpose of private study or research.•You may not further distribute the material or use it for any profit-making activity or commercial gain •You may freely distribute the URL identifying the publication in the Research Portal Take down policy If you believe that this document breaches copyright please contact librarypure@kcl.ac.uk providing details, and we will remove access to the work immediately and investigate your claim. Quantum dots were characterised and interrogated using TEM, HRTEM, electron diffraction, ToF-SIMS, XPS, EDS spectroscopy, photoluminescence emission and lifetime spectroscopy and UV/vis spectroscopy.

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Synthesis of Highly Luminescent Silica-Coated CdSe/CdS Nanorods

Cited by 51 publications

References 49 publications

Ultrathin and Highly Passivating Silica Shells for Luminescent and Water-Soluble CdSe/CdS Nanorods

Ultrathin and Highly Passivating Silica Shells for Luminescent and Water-Soluble CdSe/CdS Nanorods

How Robust are Semiconductor Nanorods? Investigating the Stability and Chemical Decomposition Pathways of Photoactive Nanocrystals

Doping Group IIB Metal Ions into Quantum Dot Shells via the One‐Pot Decomposition of Metal‐Dithiocarbamates

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