Abstract
Hydrophilic layers of porous silicon are prepared by single- or two-step anodization and characterized by evaluating their surface hydrophilicity and contents of functional groups using IR spectroscopy and adsorption of acid-base indicators with differentpKavalues. The surface functional composition of the synthesized samples is shown to be adjustable depending on the anodization current density. The surface of samples obtained at anodization current density 30 mA/cm2is predominantly occupied withpKa2.5 corresponding to ≡Si–OH groups. The increase of current density to 80 mA/cm2results in the increase of surface functional nonuniformity with the formation of versatile centers, primarily Lewis acidic sites corresponding to Si atoms, as indicated by selective indicator adsorption in agreement with the disappearance of Si–H bonds in IR spectra and overall surface disordering according to SEM and AFM data.
Highlights
Porous silicon is a promising material for sensors, biosensors, and specific medical purposes [1,2,3,4]
SEM data for splits of Porous silicon (por-Si) samples prepared under anodization conditions corresponding to each stage of series III separately and after the complete two-stage anodization as well as for a sample synthesized in a single stage within the time equal to the overall anodization time for series III at current density 80 m0/cm2 are shown in Figures 1 and 2
Porous silicon layers are prepared by single- and two-stage anodization of monocrystalline n-type silicon (111) with the variation of anodization current density, number of synthesis stages, and their conditions as well as storage time after the preparation
Summary
Porous silicon (por-Si) is a promising material for sensors, biosensors, and specific medical purposes [1,2,3,4]. Modified por-Si layers can be used in biosensors [1, 2, 4, 12,13,14,15,16,17] for various applications including the determination of glucose, DNA, antibodies, bacteria, and viruses [12,13,14]. This application area involves different types of sensors, including electric, electrochemical, optical, and labeling devices [15,16,17]. Por-Si nanocontainers are efficient for in vivo applications since they dissolve in an organism with the rate adjustable by varying the porosity and surface chemistry [4, 24,25,26] and yield only a nontoxic orthosilicic acid that affords a controllable drug release from such nanocontainers
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