Characterization of surface changes on silicon and porous silicon after interaction with hydroxyl radicals

Muñoz, Eduardo; Díaz, Claudio; Navarrete, Emilio; Henríquez, Rodrigo; Schrebler, Ricardo; Córdova, Ricardo; Marotti, Ricardo E.; Heyser, Cristopher

doi:10.1016/j.arabjc.2016.11.008

Cited by 10 publications

(7 citation statements)

References 21 publications

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“…For comparison, the contact angle on a flat silicon substrate and a micropillared silicon, which was soaked in a HF solution (10 wt %), was also measured. Soaking in HF solution was to remove the oxide layer on the surface, making the surface hydrogen-terminated, exhibiting hydrophobicity. − As shown in Figure , the apparent contact angle on the HF-treated flat silicon substrate is approximately 89°. It increases to approximately 145° on the HF-treated micropillared substrate.…”

Section: Resultsmentioning

confidence: 99%

“…In contrast to the hydrophobic nature of the HF-treated silicon surface, the silicon surface treated by soaking in hydrogen peroxide (H 2 O 2 ) exhibits hydrophilicity. Soaking in H 2 O 2 solution makes the surface hydrophilic because of the presence of silanol groups (Si–OH). − In a hydrophilic regime, the hydrodynamics of the droplet deposited on a rough surface depends significantly on the intrinsic wettability and surface morphology. The intrinsic wettability (i.e., equilibrium contact angle θ e ) and surface morphology determine an apparent contact angle θ* and a critical angle θ c .…”

Section: Resultsmentioning

confidence: 99%

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Superwicking on Nanoporous Micropillared Surfaces

Zheng

Choi

Sun

et al. 2020

ACS Appl. Mater. Interfaces

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Engineering surfaces with excellent wicking properties is of critical importance to a wide range of applications. Here, we report a facile method to create superhydrophilic nanoporous micropillared surfaces of silicon and their applicability to superwicking. Nanopores with a good control of the pore depth are realized over the entire surface of three-dimensional micropillar structures by electrochemical etching in hydrofluoric acid. After rinsing in hydrogen peroxide, the nanoporous micropillared surface shows superhydrophilicity with the superwicking effect. The entire spreading process of a water droplet on the superhydrophilic nanoporous micropillared surface is completed in less than 50 ms, with an average velocity of 91.2 mm/s, which is significantly faster than the other wicking surfaces reported. Owing to the presence of nanopores on the micropillar array, the wicking dynamics is distinct from the surfaces decorated only by micropillar arrays. The spreading dynamics of a water droplet shows two distinct processes simultaneously, including the capillary penetration between micropillars and the capillary imbibition into the nanopore’s interior. The wicking dynamics can be described by the two stages separated by the time when the contact line starts to recede. The transition between the two wicking regimes is due to the increasing effect of the imbibition of the bulk droplet by the nanopores. While a similar transition of the wicking dynamics is shown on the surfaces with different pore depths, the nanopore structure with a greater depth causes a greater amount of imbibition to slow down the spreading and promote superwicking.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Superwicking on Nanoporous Micropillared Surfaces

Zheng

Choi

Sun

et al. 2020

ACS Appl. Mater. Interfaces

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“…Modification of the surface properties can happen due to the interaction of OH radicals with the ice nucleating surface via etching and increment of hydrophilicity (inversely related to contact angle). Yet, excess O 3 can cause oxidation of Hg(I), without creating a favorable ice nucleating surface.…”

Section: Resultsmentioning

confidence: 99%

Influence of Environmentally Relevant Physicochemical Conditions on a Highly Efficient Inorganic Ice Nucleating Particle

et al. 2018

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Ice nucleation microphysical processes are identified to be of high importance in forecasting the magnitude of the Earth’s climate change. The environmental conditions often influence the ice nucleation processes in the Earth’s atmosphere. We herein study the impact of various environmental conditions on FeHg (maghemite–Hg2Cl2 composite), a highly efficient ice nucleating particle with similar freezing point to the best inorganic ice nuclei, AgI. FeHg is formed from FeCl2·4H2O and HgCl2, which are observed in the environment, in contrast to AgI, which is rarely found. The ice nucleation efficacy remained unchanged for FeHg under ambient conditions for a long duration. To mimic the atmosphere, we performed a series of experiments using a suite of complementary techniques, at various levels of radiation intensity, temperature, and pH for FeHg. Experiments were also performed in the presence of atmospheric pollutants, such as ozone (in the presence or absence of light), as well as nine emerging metal oxides and NO2. The emerging metal oxides at various pH levels produced significant effects on the ice nucleation ability of FeHg. Elevated temperatures changed the maghemite of FeHg to β-Fe2O3, whereas other studied environmentally relevant physicochemical conditions could not alter the maghemite phase. We describe potential reaction mechanisms using our observations. To evaluate the effect of surface alterations, the passivation of clay materials, namely, kaolin and montmorillonite, was also performed on FeHg. The observed alteration in crystal structure, as found in X-ray diffraction, was attributed to the change of the extent of lattice mismatch, resulting in a significant variation of ice nucleation ability. Our insights of the ice nucleating particles may help understand real atmospheric ice nucleation processes, in association with the establishment of more in-depth understanding of ice nucleation mechanism in the Earth’s atmosphere.

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“…According to several studies [17][18][19], the value of the contact angle ensuring a successful assembly is in the range from 30° to 75°. In the PS case, such conditions can be set by reducing the free surface energy using surfactants [20] or changing the template wetting behavior by oxidation [21], oxygen plasma treatment [22], or functionalization [23]. The contact angle of the standard PS samples looks to be smaller than the contact angle of RIE-treated samples, but it shows the same behavior in dependence on the current density, i.e., the PS hydrophobicity increases with the increase of current density.…”

Section: Surface Wettabilitymentioning

confidence: 99%

“…According to several studies [17][18][19], the value of the contact angle ensuring a successful assembly is in the range from 30 • to 75 • . In the PS case, such conditions can be set by reducing the free surface energy using surfactants [20] or changing the template wetting behavior by oxidation [21], oxygen plasma treatment [22], or functionalization [23].…”

Section: Surface Wettabilitymentioning

confidence: 99%

Tailoring Mesoporous Silicon Surface to Form a Versatile Template for Nanoparticle Deposition

et al. 2021

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Porous silicon (PS) can be used as a loading template in sensing or as a matrix to develop nanoparticle arrays. We present a comprehensive study of PS morphology and optical properties before and after the pore opening process, including the determination of thickness, pore size, and pore density of PS layers, its surface wettability, and reflectivity. The PS samples were fabricated by electrochemical anodization of monocrystalline silicon wafer in 5–20 wt.% hydrofluoric acid (HF) solution at a current density in the range of 20–200 mA/cm2. Anodization was followed by the pore opening process, i.e., the removal of a parasitic superficial layer with a “bottleneck” structure by reactive ion etching (RIE). The results illustrate that “bottleneck”-free PS allows to achieve a high pore density using a low HF concentration and a reduced current density. We established that this structure demonstrates higher hydrophobicity in comparison to the samples before RIE. The applicability of the developed “bottleneck”-free PS was tested via filling the pores with silver nanoparticles, indicating its potential use as a template for the fabrication of nanoparticle arrays.

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Characterization of surface changes on silicon and porous silicon after interaction with hydroxyl radicals

Cited by 10 publications

References 21 publications

Superwicking on Nanoporous Micropillared Surfaces

Superwicking on Nanoporous Micropillared Surfaces

Influence of Environmentally Relevant Physicochemical Conditions on a Highly Efficient Inorganic Ice Nucleating Particle

Tailoring Mesoporous Silicon Surface to Form a Versatile Template for Nanoparticle Deposition

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