Efficient visible light photocatalysis and tunable photoluminescence from orientation controlled mesoporous Si nanowires

Ghosh, Ramesh; Giri, P. K.

doi:10.1039/c6ra05339d

Cited by 14 publications

(17 citation statements)

References 54 publications

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“…In our experiments, one-dimensional zigzag SiNWs were obtained on Si (111) substrate, in agreement with existing reports (Fig. 2 b) [ 7 , 19 ]. Compared with the SiNWs prepared on Si (111), the majority of the nanowire morphologies on Si (110) wafers are more uniform.…”

Section: Resultssupporting

confidence: 92%

“…Superwetting surface with drop sliding angle (α) less than 5° and water contact angles (CA) lower than 5° or higher than 150° has drawn much more attention in recent years because of the limited contact angle and rollability [ 1 , 2 ]. The superwetting properties of solid surface has crucial applications in our daily life as well as engineering fields, such as self-cleaning, digital microfluidic devices, biomedical engineering, and silicon hybrid solar cells [ 3 – 7 ]. There are two ways to obtain the superwetting properties of existing artificial surface.…”

Section: Introductionmentioning

confidence: 99%

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Stable Superwetting Surface Prepared with Tilted Silicon Nanowires

et al. 2016

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Large-scale uniform nanostructured surface with superwettability is crucial in both fundamental research and engineering applications. A facile and controllable approach was employed to fabricate a superwetting tilted silicon nanowires (TSNWs) surface through metal-assisted chemical etching and modification with low-surface-energy material. The contact angle (CA) measurements of the nanostructured surface show a large range from the superhydrophilicity (the CA approximate to 0°) to superhydrophobicity (the CA up to 160°). The surface becomes antiadhesion to water upon nanostructuring with a measured sliding angle (α) close to 0°. Moreover, the fluorinated TSNWs surface exhibits excellent stability and durability because strong chemical bonding has been formed on the surface.Graphical Abstract

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Section: Resultssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Stable Superwetting Surface Prepared with Tilted Silicon Nanowires

et al. 2016

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“…If the oxidant concentration remains constant during etching, we expect the etch depth to increase linearly in time, an observation that has been confirmed experimentally (Ghosh and Giri, 2016; Toor et al, 2016a). If we assume Arrhenius behavior and that the kinetic order is independent of temperature, the etch rate is given by the depth along the etch direction divided by time, and a plot of the etch rate vs. inverse temperature should yield a straight line as long as the concentration of the oxidant is essentially invariant during the etch (as it is for wafer etching, but not necessarily for high-surface area powder etching).…”

Section: Resultsmentioning

confidence: 59%

“…Pei et al (2017) found that [111]-oriented nanowires are observed for 20 mM H 2 O 2 but [001]-oriented SiNWs are formed at 400 mM H 2 O 2 . Ghosh and Giri (2016) similarly reported that the etch direction changed from the vertical 〈111〉 direction to slanted and eventually to wavy as H 2 O 2 concentration is increased.…”

Section: Introductionmentioning

confidence: 99%

Crystallographically Determined Etching and Its Relevance to the Metal-Assisted Catalytic Etching (MACE) of Silicon Powders

et al. 2019

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Metal-assisted catalytic etching (MACE) using Ag nanoparticles as catalysts and H2O2 as oxidant has been performed on single-crystal Si wafers, single-crystal electronics grade Si powders, and polycrystalline metallurgical grade Si powders. The temperature dependence of the etch kinetics has been measured over the range 5–37°C. Etching is found to proceed preferentially in a 〈001〉 direction with an activation energy of ~0.4 eV on substrates with (001), (110), and (111) orientations. A quantitative model to explain the preference for etching in the 〈001〉 direction is developed and found to be consistent with the measured activation energies. Etching of metallurgical grade powders produces particles, the surfaces of which are covered primarily with porous silicon (por-Si) in the form of interconnected ridges. Silicon nanowires (SiNW) and bundles of SiNW can be harvested from these porous particles by ultrasonic agitation. Analysis of the forces acting between the metal nanoparticle catalyst and the Si particle demonstrates that strongly attractive electrostatic and van der Waals interactions ensure that the metal nanoparticles remain in intimate contact with the Si particles throughout the etch process. These attractive forces draw the catalyst toward the interior of the particle and explain why the powder particles are etched equivalently on all the exposed faces.

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“…A Gaussian peak yields 1.9 eV for the energy of the peak and a full-width half max (FWHM) of 0.3 eV, which is consistent with the literature 29,40,41 . Prior studies suggest that the origin of this red band is associated with the porous Si/SiO x layer, where the local electrochemical etching creates Si nanocrystals (< 10 nm in size) 29,[42][43][44] as well as active defect sites, such as non-bridging oxygen hole centers (NBOHC, ≡Si-O•). The emission peak for NBOHC is centered around 1.9 eV 41,42 , whereas the luminescence of Si nanocrystals is in the range of ultraviolet (3.5 eV) to infrared (1.5 eV), depending on the cross-sectional area of the Si nanocrystals 45 .…”

Section: Resultsmentioning

confidence: 99%

Heterogeneous optoelectronic characteristics of Si micropillar arrays fabricated by metal-assisted chemical etching

Yang

Magginetti

Jeon

et al. 2020

Sci Rep

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Recent progress achieved in metal-assisted chemical etching (MACE) has enabled the production of high-quality micropillar arrays for various optoelectronic applications. Si micropillars produced by MACE often show a porous Si/SiOx shell on crystalline pillar cores introduced by local electrochemical reactions. In this paper, we report the distinct optoelectronic characteristics of the porous Si/SiOx shell correlated to their chemical compositions. Local photoluminescent (PL) images obtained with an immersion oil objective lens in confocal microscopy show a red emission peak (≈ 650 nm) along the perimeter of the pillars that is threefold stronger compared to their center. On the basis of our analysis, we find an unexpected PL increase (≈ 540 nm) at the oil/shell interface. We suggest that both PL enhancements are mainly attributed to the porous structures, a similar behavior observed in previous MACE studies. Surface potential maps simultaneously recorded with topography reveal a significantly high surface potential on the sidewalls of MACE-synthesized pillars (+ 0.5 V), which is restored to the level of planar Si control (− 0.5 V) after removing SiOx in hydrofluoric acid. These distinct optoelectronic characteristics of the Si/SiOx shell can be beneficial for various sensor architectures.

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Efficient visible light photocatalysis and tunable photoluminescence from orientation controlled mesoporous Si nanowires

Abstract: Efficient visible light photocatalysis and visible photoluminescence from orientation controlled mesoporous Si nanowires grown by Ag assisted chemical etching of Si have been discussed.

Cited by 14 publications

References 54 publications

Stable Superwetting Surface Prepared with Tilted Silicon Nanowires

Stable Superwetting Surface Prepared with Tilted Silicon Nanowires

Crystallographically Determined Etching and Its Relevance to the Metal-Assisted Catalytic Etching (MACE) of Silicon Powders

Heterogeneous optoelectronic characteristics of Si micropillar arrays fabricated by metal-assisted chemical etching

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