Facile synthesis of anisotropic Au@SiO2 core–shell nanostructures

DuChene, Joseph S.; Almeida, Renan Pereira; Wei, W. David

doi:10.1039/c2dt30409k

Cited by 15 publications

(18 citation statements)

References 41 publications

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“…Small Au NPs ( d = 10 ± 1 nm) served as the plasmonic‐metal core for the subsequent deposition of conformal SiO 2 shells of various thickness (5–25 nm) to yield Au@SiO 2 NPs (Figure S7, Supporting Information). Since it is expected that a near‐field enhancement strategy will be most effective at wavelengths where the Cu 2 O absorption coefficient is small ( λ = 500–600 nm), spherical Au NPs exhibiting a maximum LSPR absorption ( λ max ) at 521 nm were chosen to ensure sufficient spectral overlap with the optical response of the Cu 2 O NWs (Figure S8, Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

“…As shown in Figure 2 a, a slight red shift in λ max was observed from 521 to 525 nm upon the deposition of a 5 ± 2 nm SiO 2 shell onto the Au NP core (inset of Figure a). This red shift is attributable to the increased refractive index of SiO 2 compared to H 2 O . After synthesis of the desired core@shell motif, these Au@SiO 2 NPs were intimately mixed with the Cu 2 O NWs during device assembly to confer the maximum plasmonic enhancement to the Cu 2 O/Au@SiO 2 photocathode.…”

Section: Resultsmentioning

confidence: 99%

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Elucidating the Sole Contribution from Electromagnetic Near‐Fields in Plasmon‐Enhanced Cu₂O Photocathodes

DuChene

Williams

Johnston‐Peck

et al. 2015

Advanced Energy Materials

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semiconductor for photoelectrochemical H 2 production as it consists of earth-abundant elements, displays a direct optical band gap ( E g ) suitable for solar energy conversion ( E g = 2.0 eV), and exhibits a so-called "built-in" overpotential for H 2 evolution. [ 2,3 ] Despite these auspicious properties, the performance of Cu 2 Obased photocathodes is ultimately limited by the small optical cross section of this p-type oxide near the band edge. [ 2a-c ] The abrupt decrease in Cu 2 O absorption coeffi cient below 2.5 eV effectively narrows the spectral sensitivity of this ostensibly 2.0 eV band gap semiconductor. [ 2a-c ] Consequently, a signifi cant portion of the solar spectrum ( λ = 500-600 nm) theoretically available for driving H 2 evolution with a Cu 2 O photocathode is often ineffi ciently harvested by the device. [ 2,3 ] Attempts to mitigate this constraint by fabricating thicker semiconductor fi lms have met with limited success: such a strategy ultimately restricts device performance by adversely affecting charge carrier collection due to the incommensurate length scales between the optical penetration depth ( α −1 = 1-3 µm) and the minority carrier diffusion length ( l d ≈ 50 nm). [ 2a , 4 ] Innovative approaches to augment the optical cross section of the semiconductor without signifi cantly altering the internal device architecture are therefore required to achieve viable solar-to-fuel conversion effi ciencies.Plasmonic-metal nanostructures (e.g., Au, Ag, Cu, Al, etc.) offer intriguing opportunities for solar photocatalysis due to their unique ability to confi ne freely propagating optical radiation into subwavelength volumes. [ 5,6 ] Optical excitation at their localized surface plasmon resonance (LSPR) frequency induces a local enhancement (≈10 3 ) of electromagnetic (EM) fi elds near the nanoparticle (NP) surface that can markedly boost the absorption cross section of a nearby semiconductor photocatalyst. [5][6][7] Panchromatic light-harvesting devices are envisioned by tailoring the LSPR frequency to amplify the absorption profi le of the semiconductor in regions of the solar spectrum that would otherwise be incompletely collected by the device. [ 8 ] While promising reports abound, [ 6,7 ] the pursuit of plasmonic photocatalysts is plagued by the daunting complexity of these systems. [ 5,6 ] Numerous plasmonic processes may coexist spatiotemporally, [ 6,9 ] resigning most studies to invoke a multitude of Despite many promising reports of plasmon-enhanced photocatalysis, the inability to identify the individual contributions from multiple enhancement mechanisms has delayed the development of general design rules for engineering effi cient plasmonic photocatalysts. Herein, a plasmonic photocathode comprised of Au@SiO 2 (core@shell) nanoparticles embedded within a Cu 2 O nanowire network is constructed to exclusively examine the contribution from one such mechanism: electromagnetic near-fi eld enhancement. The infl uence of the local electromagnetic fi eld intensity is correlated with ...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Elucidating the Sole Contribution from Electromagnetic Near‐Fields in Plasmon‐Enhanced Cu₂O Photocathodes

DuChene

Williams

Johnston‐Peck

et al. 2015

Advanced Energy Materials

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“…The inset shows the high resolution image of CuCrO 2 nanocrystals with a typical size of about 15 × 5 nm 2 1115. The Au@SiO 2 NPs were prepared by a standard chemical reduction synthesis method27. A representative TEM image of Au@SiO 2 NPs is shown in Figure 2b.…”

Section: Resultsmentioning

confidence: 99%

Near Field Enhanced Photocurrent Generation in P-type Dye-Sensitized Solar Cells

Cui

Han

et al. 2014

Sci Rep

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Over the past few decades, the field of p-type dye-sensitized solar cell (p-DSSC) devices has undergone tremendous advances, in which Cu-based delafossite nanocrystal is of prime interest. This paper presents an augment of about 87% improvement in photocurrent observed in a particular configuration of organic dye P1 sensitized CuCrO2 delafossite nanocrystal electrode coupled with organic redox shuttle, 1-methy-1H- tetrazole-5-thiolate and its disulfide dimer when Au nanoparticles (NPs, with diameter of about 20 nm) is added into the photocathode, achieving a power convert efficiency of 0.31% (measured under standard AM 1.5 G test conditions). Detailed investigation shows that the local electrical-magnetic field effect, induced by Au NPs among the mesoporous CuCrO2 film, can improve the charge injection efficiency at dye/semiconductor interface, which is responsible for the bulk of the gain in photocurrent.

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“…metal NPs into highly stable porous inorganic nanostructures (for example, CeO 2 , 24-26 TiO 2 , 27-34 SiO 2 , [35][36][37][38][39] ZrO 2 40,41 ) and encapsulating noble metal NPs within metal oxides to form core-shell or yolk-shell nanostructures are common strategies. Three requirements must be satisfied simultaneously: (1) the sheath must maintain its chemical inertness in the specific working environment; (2) mass transformation must be avoided during the long-term synthetic and catalytic process, especially under high-temperature treatment; (3) after heat treatment, the active sites should maintain their original particle size, shape and catalytic activities.…”

Section: Introductionmentioning

confidence: 99%

CeO2-encapsulated noble metal nanocatalysts: enhanced activity and stability for catalytic application

2015

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Encapsulation of small noble metal nanoparticles has received attention owing to the resulting highly increased stability and high catalytic activity and selectivity. Among the types of inert metal oxides, CeO 2 is unique. It is inexpensive and highly stable, and, more importantly, the unique electronic configuration gives it a strong capability to provide active oxygen. The method of fabricating CeO 2 -encapsulated noble metal nanocatalysts is determined by the requirements of the application. In this review, we first describe the various types of encapsulated noble metals and then the current developments of synthesis in detail, including the types of hybrid nanostructures and successful synthetic strategies. The following section, concerning catalytic applications, is divided into three topics: anti-sintering capabilities, catalytic activities and selectivities. We hope that this review of the recent achievements and the proposed strategy for addressing the emerging challenges will inspire further developments in this research area. NPG Asia Materials (2015) 7, e179; doi:10.1038/am.2015.27; published online 8 May 2015 INTRODUCTIONNoble metal catalysts have received much attention in the past decade because of their unique chemical and physical properties, and they have been widely applied in industrial use. [1][2][3][4][5][6][7][8][9][10] With the help of noble metal catalysts, environmental friendly catalysis resulting in the decreased production of pollutants, waste minimization and new synthetic routes that circumvent modern synthetic techniques such as Sonogashira-, Heck-and Miyaura-Suzuki-type reactions can be easily realized. 11-15 However, for most technologically important chemical processes, noble metal catalysts spontaneously aggregate and grow to reduce the surface energy, which limits the catalysts' lifetime and efficiency. The ultra-high prices of noble metals have also seriously limited their further development. Because of the development of modern industry, there remains a critical need for robust, simple and readily controllable routes to fabricate highly active, stable and recyclable nanocatalysts.To maximize the catalytic performance of noble metals and reduce the quantity used, it is necessary to load the active centers on a substrate. [16][17][18][19][20] A suitable substrate not only provides a high surface area to stabilize small nanoparticles (NPs) under long-term catalysis but also renders hybrid junctions with rich redox reactions on the two-phase interface. With the development of synthetic techniques in nanoscience, small noble metal NPs, especially atomically precise nanoclusters/metal oxide hybrid nanostructures, have been successfully fabricated very recently, and these materials exhibit remarkable enhanced catalytic activity and selectivity. [21][22][23] However, this simple loading form cannot meet the growing demand for the stability, because the noble metal catalysts contain numerous exposed surfaces

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Facile synthesis of anisotropic Au@SiO2 core–shell nanostructures

Cited by 15 publications

References 41 publications

Elucidating the Sole Contribution from Electromagnetic Near‐Fields in Plasmon‐Enhanced Cu₂O Photocathodes

Elucidating the Sole Contribution from Electromagnetic Near‐Fields in Plasmon‐Enhanced Cu₂O Photocathodes

Near Field Enhanced Photocurrent Generation in P-type Dye-Sensitized Solar Cells

CeO2-encapsulated noble metal nanocatalysts: enhanced activity and stability for catalytic application

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Facile synthesis of anisotropic Au@SiO2 core–shell nanostructures

Cited by 15 publications

References 41 publications

Elucidating the Sole Contribution from Electromagnetic Near‐Fields in Plasmon‐Enhanced Cu2O Photocathodes

Elucidating the Sole Contribution from Electromagnetic Near‐Fields in Plasmon‐Enhanced Cu2O Photocathodes

Near Field Enhanced Photocurrent Generation in P-type Dye-Sensitized Solar Cells

CeO2-encapsulated noble metal nanocatalysts: enhanced activity and stability for catalytic application

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Elucidating the Sole Contribution from Electromagnetic Near‐Fields in Plasmon‐Enhanced Cu₂O Photocathodes

Elucidating the Sole Contribution from Electromagnetic Near‐Fields in Plasmon‐Enhanced Cu₂O Photocathodes