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. 2020 Apr 24;13(8):1987.
doi: 10.3390/ma13081987.

Porous Silicon-Zinc Oxide Nanocomposites Prepared by Atomic Layer Deposition for Biophotonic Applications

Mykola Pavlenko  1 , Valerii Myndrul  1 , Gloria Gottardi  2 , Emerson Coy  1 , Mariusz Jancelewicz  1 , Igor Iatsunskyi  1
Affiliations

Porous Silicon-Zinc Oxide Nanocomposites Prepared by Atomic Layer Deposition for Biophotonic Applications

Mykola Pavlenko et al. Materials (Basel). .

Abstract

In the current research, a porous silicon/zinc oxide (PSi/ZnO) nanocomposite produced by a combination of metal-assisted chemical etching (MACE) and atomic layer deposition (ALD) methods is presented. The applicability of the composite for biophotonics (optical biosensing) was investigated. To characterize the structural and optical properties of the produced PSi/ZnO nanocomposites, several studies were performed: scanning and transmission electron microscopy (SEM/TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance, and photoluminescence (PL). It was found that the ALD ZnO layer fully covers the PSi, and it possesses a polycrystalline wurtzite structure. The effect of the number of ALD cycles and the type of Si doping on the optical properties of nanocomposites was determined. PL measurements showed a "shoulder-shape" emission in the visible range. The mechanisms of the observed PL were discussed. It was demonstrated that the improved PL performance of the PSi/ZnO nanocomposites could be used for implementation in optical biosensor applications. Furthermore, the produced PSi/ZnO nanocomposite was tested for optical/PL biosensing towards mycotoxins (Aflatoxin B1) detection, confirming the applicability of the nanocomposites.

Keywords: atomic layer deposition; biosensors; photoluminescence; porous silicon; zinc oxide.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
SEM images of porous silicon (PSi) surface before and after 100 cycles of zinc oxide ALD: (a) n-type PSi; (b) p-type PSi; (c,d) n-and p-types PSi after zinc oxide (ZnO) deposition, respectively (insets: an EDX analysis).
Figure 2
Figure 2
(a) TEM imaging of ZnO nanocrystallites on PSi obtained after 100 ALD cycles; (b) FFT of the PSi/ZnO TEM image; (c) GIXRD spectra of PSi/ZnO nanocomposites with 250, 100, and 50 ALD cycles of ZnO in comparison to GIXRD spectrum of PSi. Standard diffraction peaks of wurtzite (pdf card #36-1451) are presented for reference.
Figure 3
Figure 3
XPS survey and core-level spectra of PSi/ZnO with 50, 100, and 250 ALD cycles: (a) total survey spectra; (b–d) O 1s, Zn 2p, Si 2p energy regions, respectively. Corresponding binding energy values obtained by the deconvolution of the detected peaks are shown in the insets.
Figure 4
Figure 4
Optical properties of the fabricated PSi/ZnO nanocomposites: (a) diffuse reflectance spectra of PSi/ZnO nanocomposites; (b) absorption edges and corresponding energy band gap values; photoluminescence spectra for (c) n-PSi/ZnO and (d) p-PSi/ZnO nanocomposites. The energy band diagrams of corresponding excitation mechanisms are depicted in the insets.
Figure 5
Figure 5
PL response of p-type PSi/ZnO toward different AFB1 concentrations. The inset graph indicates the linearity of PL response to three different concentrations of AFB1 in a half-logarithmic scale with an error bar.
See this image and copyright information in PMC

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