Graphene-Supported High-Resolution TEM and STEM Imaging of Silicon Nanocrystals and their Capping Ligands

Panthani, Matthew G.; Hessel, Colin M.; Reid, Dariya K.; Casillas, Gilberto; José–Yacamán, Miguel; Korgel, Brian A.

doi:10.1021/jp308545q

Cited by 81 publications

(84 citation statements)

References 43 publications

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“…Further, the ligand distribution around the cores can be uniform or regions of different ligand density, including cavities can be formed. 28,29,32 Hence, in nanoparticle assemblies different ligand arrangements come along with different cavities within the ligand shells. In addition, the interstitial (tetrahedral and octahedral) sites of 3D superlattices may provide sufficient space for the formation of what we will term unoccupied voids and, thus, can contribute to the porosity of the structure.…”

Section: Introductionmentioning

confidence: 99%

Gold nanoparticle superlattices: structure and cavities studied by GISAXS and PALS

Olichwer¹,

Koschine

Meyer³

et al. 2016

RSC Adv.

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The performance of nanoparticle assemblies with respect to various applications (e.g. sensors, catalysts, filtration membranes) depends on their microporosity. Here, the microcavities within the ligand matrix of superlattice films comprised of 1-dodecanethiol-stabilized gold nanoparticles (GNPs, core diameter $4 and $5.5 nm) were studied by positron annihilation lifetime spectroscopy (PALS). The superlattice composition, the size and spatial arrangement of the GNP cores were characterized by thermogravimetric analysis, transmission electron microscopy and grazing-incidence small-angle X-rayscattering. From these data a structural model was derived to predict the sizes of the voids formed within the interstitial (tetrahedral and octahedral) sites of the superlattices. The comparison of the PALSmeasured cavity sizes (0.50 to 0.74 nm) with the predicted void sizes of the interstitial sites ($0.7 to $1.7 nm) and the free volume in solid dodecane (0.36 nm), previously measured by PALS, indicate that both types of cavities may contribute to the experimentally determined cavity sizes. However, the GNP core sizes had only a minor influence on the measured cavity size. Larger cavities with sizes corresponding to the voids ($1.7 nm) expected within the octahedral sites of the superlattices comprised of $5.5 nm-sized GNP cores could not be detected. Assuming the intensities arising from these voids are measurable, this finding suggests that the octahedral sites are occupied by excess ligands trapped during film preparation.Apart from the voids predicted for the interstitial sites, the larger cavity sizes measured for the GNP superlattices compared to crystalline dodecane may result from some degree of disorder in the ligand arrangement.

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Section: Introductionmentioning

confidence: 99%

Gold nanoparticle superlattices: structure and cavities studied by GISAXS and PALS

Olichwer¹,

Koschine

Meyer³

et al. 2016

RSC Adv.

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“…Die TEM-Aufnahmen wurden unter Verwendung eines Graphenfilms gewonnen und zeigen eindeutig, dass organische Liganden um die SiNK-Oberflächen angeordnet sind (Abbildung 1b). [38] Verständlicherweise trägt die thermisch induzierte Oligomerisierung zur Erhçhung der Stabilität und PL-Quantenausbeuten der SiNKs bei. [39] Demgegenüber stellen die langen, elektrisch isolierenden Alkylketten eine Hürde für mçgliche optoelektronische Anwendungen dar.…”

Section: Hydrosilylierungunclassified

Silicium‐Nanokristalle und Silicium‐Polymer‐Hybridmaterialien: Synthese, Oberflächenmodifikation und Anwendungen

et al. 2015

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Aufgrund der hohen Verfügbarkeit in der Erdkruste und seiner geringen Toxizität im Vergleich zu einigen anderen Halbleitern ist Silicium der Vorreiter in der Elektroindustrie. Daher finden Silicium‐Nanokristalle (SiNKs) insbesondere aufgrund ihrer einzigartigen optoelektronischen Eigenschaften ein hohes Interesse in der Halbleiterindustrie und sie haben das Potenzial, die toxischen Quantenpunkte (Elemente der Gruppen II–VI und III–V) zu substituieren. Dennoch erhielten SiNKs wegen ihrer geringeren Photolumineszenz(PL)‐Quantenausbeuten, einer schwierig zu erzielenden monodispersen Partikelverteilung und ihrer Oxidationsanfälligkeit nicht dieselbe Aufmerksamkeit wie ihre schwermetallhaltigen Analoga. Daher wurde vermehrt an der Funktionalisierung von SiNK‐Oberflächen geforscht und die genannten Faktoren im Wesentlichen verbessert. Vor diesem Hintergrund fassen wir in diesem Aufsatz die neuesten Entwicklungen in der Funktionalisierung von SiNK‐Oberflächen, beschriebene SiNK/Polymer‐Hybridmaterialien und deren Anwendungen in den Bereichen Sensorentwicklung, Leuchtdioden, Katalyse und Akkumulatoren zusammen.

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“…The ncSi that were too large to be stabilized with allylbenzene caps were removed from the reaction mixture by centrifugation and the ncSi:AB were isolated from the excess un-reacted allylbenzene by vacuum distillation followed by heating under vacuum at 155°C for 5.5 hours to removed excess alkenes. 18 The purified polydisperse ncSi:AB were re-dispersed in toluene, resulting in a clear orange solution that displayed bright orange-red photoluminescence (PL) under photoexcitation (λexc = 365 nm). Size-selective precipitation was performed on the toluene dispersion of polydisperse ncSi:AB, using methanol as the anti-solvent to isolate fractions of relatively monodisperse ncSi:AB.…”

Section: Introductionmentioning

confidence: 99%

Size-Dependent Chemical Reactivity of Silicon Nanocrystals with Water and Oxygen

et al. 2014

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. (2015). Size-dependent chemical reactivity of silicon nanocrystals with water and oxygen. The Journal of Physical Chemistry C: Energy Conversion and Storage, Optical and Electronic Devices, Interfaces, Nanomaterials, and Hard Matter, 119 (1), 826-834. Size-dependent chemical reactivity of silicon nanocrystals with water and oxygen AbstractA detailed investigation examines how the size of allylbenzene-capped silicon nanocrystals (ncSi:AB) affects their chemical reactivity with gaseous O 2 , H 2 O, and O 2 /H 2 O as probed by in situ luminescence spectroscopy. Specifically, changes in the photoluminescence (PL) of size-separated ncSi:AB are monitored through alterations of their PL absolute quantum yield (AQY) as well as the wavelength and intensity of their PL spectra over time. These experiments, conducted under both continuous and intermittent illumination, help elucidate the roles of O 2 , H 2 O, and mixtures of O 2 /H 2 O, with respect to oxidation of ncSi:AB as a function of their size, providing vital information for any perceived application in advanced materials and biomedical devices. ABSTRACT:The effects of exposure to dry and controlled humidity oxygenated atmospheres in the dark and light were examined in situ for monodisperse allylbenzene-capped silicon nanocrystals (ncSi:AB). Changes in photoluminescence (PL) intensity as measured by alterations of the PL absolute quantum yields (AQY) and blue shifting of PL spectra were measured over time under continuous and intermittent illumination to help elucidate the roles of O2 and H2O as well as UV irradiation in the oxidation of the ncSi surface. Size-dependent trends were observed for both PL blue shifting and changes in the PL AQY indicating that nanocrystal size plays an important role in how oxygen species react at the nanocrystal surface. IntroductionSilicon nanocrystals (ncSi) were found to exhibit intense room temperature photoluminescence in 1990, 1 and subsequent study has identified that they possess size-dependant optical and electronic properties, 2a-c similar to other semiconductor nanocrystals composed of heavy metal materials. In particular, quantum and spatial confinement effects result in a widening of the electronic band gap and a blue shift in photoluminescence (PL) as the ncSi particle size decreases. 2a-c,3 Recent studies also report that ncSi show size-dependent PL absolute quantum yields (AQY). 2a,c,4a,b These size-dependent properties as well as a wide PL range that spans the visible to near infrared region, 2c have established ncSi as a promising candidate in optoelectronic and biological imaging applications. 5a-e Currently, there are a variety of methods that exist for the synthesis of ncSi, including the annealing of SiOx powders followed by etching with HF, 6 plasma synthesis, 7 and solution reduction of SiCl4. 8 Colloidal stability of ncSi is easily achieved through a hydrosilylation reaction between surface Si-H groups and terminal alkenes. 9a-c It is well established that surface capping with organic ligands helps to pre...

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Graphene-Supported High-Resolution TEM and STEM Imaging of Silicon Nanocrystals and their Capping Ligands

Cited by 81 publications

References 43 publications

Gold nanoparticle superlattices: structure and cavities studied by GISAXS and PALS

Gold nanoparticle superlattices: structure and cavities studied by GISAXS and PALS

Silicium‐Nanokristalle und Silicium‐Polymer‐Hybridmaterialien: Synthese, Oberflächenmodifikation und Anwendungen

Size-Dependent Chemical Reactivity of Silicon Nanocrystals with Water and Oxygen

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