Thermal oxidation of porous silicon: Study on structure

Pap, Andrea Edit; Kordás, Krisztián; Tóth, Géza; Levoska, J.; Uusimäki, A.; Vähäkangas, Jouko; Leppävuori, S.; George, Thomas F.

doi:10.1063/1.1853519

Cited by 101 publications

(57 citation statements)

References 25 publications

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“…The presence of these terminal SiOH groups in CoxPSi, can partly explain the results shown in figure 7, as Si-OH can easily react with APTS molecules according to a partial or total condensation of ethoxy groups [15]. Such a mechanism is less obvious for the terminal SiO 2 present in ToxPSi [20]. These results on surface chemical composition are directly relevant to the further biofunctionalization ( figure 8(c)): the two characteristic protein bands at 1535 and 1653 cm -1 , which are related to the N-H and C=O bonds, respectively [28,29], are stronger in CoxPSi than in ToxPSi.…”

Section: Resultsmentioning

confidence: 76%

“…These results can be explained by the presence of surface SiOH groups in CoxPSi, which can easily react with APTS molecules and induce derivatization according to a partial or total condensation of ethoxy groups [15]. Such a mechanism is not obvious for the terminal SiO 2 present in ToxPSi [20]. Thus, since the APTS molecule functions as a cross-linker between the PSi matrix and biomolecules, biofunctionalization with immunoglobulin is expected to be higher on CoxPSi than on ToxPSi.…”

Section: Resultsmentioning

confidence: 97%

“…• C in a furnace in ambient air [20]. Then, the samples were rinsed in absolute ethanol and derivatized and biofunctionalized with immunoglobulins.…”

Section: Porous Silicon (Psi) Fabrication and Stabilizationmentioning

confidence: 99%

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Chemical stabilization of porous silicon for enhanced biofunctionalization with immunoglobulin

Naveas

Costa

Gallach

et al. 2012

Science and Technology of Advanced Materials

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Porous silicon (PSi) is widely used in biological experiments, owing to its biocompatibility and well-established fabrication methods that allow tailoring its surface. Nevertheless, there are some unresolved issues such as deciding whether the stabilization of PSi is necessary for its biological applications and evaluating the effects of PSi stabilization on the surface biofunctionalization with proteins. In this work we demonstrate that non-stabilized PSi is prone to detachment owing to the stress induced upon biomolecular adsorption. Biofunctionalized non-stabilized PSi loses the interference properties characteristic of a thin film, and groove-like structures resulting from a final layer collapse were observed by scanning electron microscopy. Likewise, direct PSi derivatization with 3-aminopropyl-triethoxysilane (APTS) does not stabilize PSi against immunoglobulin biofunctionalization. To overcome this problem, we developed a simple chemical process of stabilizing PSi (CoxPSi) for biological applications, which has several advantages over thermal stabilization (ToxPSi). The process consists of chemical oxidation in H 2 O 2 , surface derivatization with APTS and a curing step at 120• C. This process offers integral homogeneous PSi morphology, hydrophilic surface termination (contact angle θ = 26• ) and highly efficient derivatized and biofunctionalized PSi surfaces (six times more efficient than ToxPSi). All these features are highly desirable for biological applications, such as biosensing, where our results can be used for the design and optimization of the biomolecular immobilization cascade on PSi surfaces.

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Section: Resultsmentioning

confidence: 76%

Section: Resultsmentioning

confidence: 97%

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Chemical stabilization of porous silicon for enhanced biofunctionalization with immunoglobulin

Naveas

Costa

Gallach

et al. 2012

Science and Technology of Advanced Materials

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show abstract

“…4) which can be attributed to oxide stretching vibrations (νSiO modes). 30,31 The oxide stretching vibrations for H-PSi wafers before the experiments was very weak, but after the reaction, an obvious peak appeared at 950-1250 cm −1 . This change demonstrates that the oxidation of porous Si took place.…”

Section: Resultsmentioning

confidence: 99%

Degradation mechanism of hydrogen-terminated porous silicon in the presence and in the absence of light

Pei

Xiao

et al. 2015

AIP Advances

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Si is well-known semiconductor that has a fundamental bandgap energy of 1.12 eV. Its photogenerated electrons in the conduction band can react with the ubiquitous oxygen molecules to yield ⋅O2− radicals, but the photogenerated holes in the valance band can’t interact with OH− to produce ⋅OH radicals. In this paper, we study the degradation of methyl orange (MO) by hydrogen-terminated porous Si (H-PSi) in the presence and in the absence of light. The absorption spectra of the degraded MO solutions indicated that the H-PSi had superior degradation ability. In the dark, the reduction of dye occurs simply by hydrogen transfer. Under room light, however, some of the dye molecules can be reduced by hydrogen transfer first and then decomposed in the conduction and valance bands. This result should be ascribed to its wide band gap energies centered at 1.79-1.94 eV.

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“…Indeed, previous atomic force microscopy characterization of oxidized PSi shows that the oxide layer tends to form on the needle-like peaks on the PSi surface, rather than in the pores. [52] An additional consideration is that the low pore density might allow an oxide layer to coat the entire surface, sealing off the tops of the pores. [53] However, after the LPSi is cooled, the induced stress on this layer could fracture it, thus exposing the pure silicon pores.…”

Section: Resultsmentioning

confidence: 99%

Selective Response of Mesoporous Silicon to Adsorbants with Nitro Groups

McLeod¹,

Kurmaev²,

Sushko³

et al. 2012

Chemistry A European J

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We demonstrate that the electronic structure of mesoporous silicon is affected by adsorption of nitro-based explosive molecules in a compoundselective manner. This selective response is demonstrated by probing the adsorption of two nitro-based molecular explosives (trinitrotoluene and cyclotrimethylenetrinitramine) and a nonexplosive nitro-based aromatic molecule (nitrotoluene) on mesoporous silicon using soft X-ray spectroscopy. The Si atoms strongly interact with adsorbed molecules to form Si-O and Si-N bonds, as evident from the large shifts in emission energy present in the Si L2,3 X-ray emission spectroscopy (XES) measurements. Furthermore, we find that the energy gap of mesoporous silicon changes depending on the adsorbant, as estimated from the Si L2,3 XES and 2p Xray absorption spectroscopy (XAS) measurements. Our ab initio molecular dynamics calculations of model compounds suggest that these changes are due to spontaneous breaking of the nitro groups upon contacting surface Si atoms. This compound-selective change in electronic structure may provide a powerful tool for the detection and identification of trace quantities of airborne explosive molecules.

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Thermal oxidation of porous silicon: Study on structure

Cited by 101 publications

References 25 publications

Chemical stabilization of porous silicon for enhanced biofunctionalization with immunoglobulin

Chemical stabilization of porous silicon for enhanced biofunctionalization with immunoglobulin

Degradation mechanism of hydrogen-terminated porous silicon in the presence and in the absence of light

Selective Response of Mesoporous Silicon to Adsorbants with Nitro Groups

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