Fabrication of a Lateral Gradient Rugate in Porous Silicon for a Miniature Spectrometer Application

Abstract

Here, we report on an application of bipolar electrochemistry utilizing an interfacial potential gradient that is distributed on a silicon electrode to generate a porous silicon film, which behaves as an optical rugate filter with a stop‐band that varies in wavelength across the film surface. While the electrode employed is not bipolar because only oxidation is required to etch the silicon wafer, the fundamental concept of bipolar electrochemistry is exploited to generate the anodic current gradient on the silicon anode. When imaged with a smartphone camera and analyzed with the appropriate image processing algorithm, the gradient filter acts as a rudimentary spectrometer. Test spectra are obtained and benchmarked to a conventional CCD spectrometer.

Porous Silicon Fabry–Pérot Interferometer for N-Acetyl-β-d-Glucosaminidase Biomarker Monitoring

“…In the present work, we describe a label-free optical device for monitoring the biochemical activity of NAGase found in whole milk samples. The porous Si (PSi) Fabry–Pérot interferometer is a matured sensing and biosensing platform for diverse applications. − The versatility stems from several tunable features that are beneficial for biosensor’s design. For example, the electrochemical anodization process can refine the physical properties of the nanostructure upon target’s dimensions for optimized sensitivity and enhanced optical performance. , Moreover, the pores’ external surface can be chemically and biologically decorated with capture probes according to the final sensing requirements or to minimize the matrix effects gained from interfering molecules. ,,, The optical properties are effectively monitored using reflective interferometric Fourier transform spectroscopy (RIFTS), which is a highly sensitive technique for monitoring average refractive index alterations within the porous void. ,,− Herein, the PSi nanostructure is applied for detection and identification of BM through evaluating the lysosomal activity of NAGase in different milk samples by spectral acquisition using a miniaturized portable platform.…”

Botulinum Neurotoxin C Dual Detection through Immunological Recognition and Endopeptidase Activity Using Porous Silicon Interferometers

“…Novel BoNT detection techniques focus on the aforementioned limitations to refine, improve, and, at advanced stages, replace the current gold standard method. ,,− Biosensor technology can potentially justify this niche, as it offers substantial benefits over conventional assays, such as high sensitivity and selectivity, continuous measurement, fast response and analysis, robustness, miniaturization toward lab-on-chip technology, and reproducibility. − Specifically, Fabry–Pérot interferometers fabricated from porous nanomaterials ( i.e ., silicon, alumina, or polymer membranes) endure enormous interest in the development of effective optical biosensing platforms. − This can be accredited to the inherent tunable characteristics that present several advantages over competing methods. This includes high surface area, straightforward fabrication process, and tunable optical and physical features that enhance the sensitivity and overall performance of the noted device .…”

Botulinum Neurotoxin-C Detection Using Nanostructured Porous Silicon Interferometer

“…The porous nanostructure owes several beneficial features for the design and development of a sophisticated sensing platform. This includes a rapid and tunable fabrication process resulting in high surface area, various photonic structures, enhanced sensitivity, and label-free practical detection of any biorecognition event occurring within the porous void [32,33]. The reflectivity spectra of the porous scaffold are monitored in real-time by interferogram average over wavelength (IAW) or reflective interferometric Fourier transform spectroscopy (RIFTS), two highly sensitive approaches influenced by refractive index alterations [28].…”