The task of rapid detection and identification of bacteria remains a major challenge in both medicine and industry. This work introduces a new concept for the design of self-reporting optical structures that can detect and quantify bacteria in real-time. The sensor is based on a two-dimensional periodic structure of porous Si photonic crystals in which the pore size is adjusted to fit the target bacteria cells (Escherichia coli). Spontaneous bacteria capture within the pores induces measurable changes in the zero-order reflectivity spectrum collected from the periodic structure. Confocal laser microscopy and electron microscopy confirm that the Escherichia coli cells are individually imprisoned within the porous array. A simple model is suggested to correlate the optical readout and the bacteria concentration and its predictions are found to be in good agreement with experimental results. In addition, we demonstrate that sensing scheme can be easily modified to potentially allow monitoring of concentration, growth and physiological state of bacteria cells. This generic platform can be tailored to target different microorganisms by tuning the array periodicity and its surface chemistry for rapid and label-free detection outside the laboratory environment.

We report on a method to extend the optical sensing capabilities of conventional RIFTS (reflective interferometric Fourier transform spectroscopy) biosensors for real-time detection of large microorganisms, such as bacteria and cells. Using macro porous silicon based 2D arrays of phase (lamellar) grating, we demonstrate that the zero-order optical reflectivity exhibits a similar interference pattern to that obtained for ordinary RIFTS biosensors, which can be Fourier transformed into optical thickness and exploited for biosensing. The sensing capabilities are demonstrated for Escherichia coli bacteria that were captured inside the macro-pores. The entrapment process is monitored and verified by confocal laser scanning microscopy.

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We report on a novel approach to synthesize hybrid nanostructures of meso porous silicon and conjugated organic polymers that are suitable for solar cell applications. Meso‐porous silicon substrates with relatively large pores (∼100 nm) have been exploited for electrochemical polymerization of organic monomers, which were introduced into the porous silicon matrices and electro‐polymerized to create poly‐vinyl‐carbazole (PVK). We present electrical characteristics of a device having relatively thin films of the hybrid medium, which exhibits a photovoltaic mode of operation (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on the fabrication and characterization of porous‐silicon/conjugated‐polymer hybrids, created by combining a host columnar matrix of mesoporous silicon and a network of organic nanowires made from poly(N‐vinylcarbazole) (PVK). A uniform and homogeneous filling of the pores by the polymers was accomplished by electrochemical polymerization of organic monomers inside the pores by using cyclic voltammetry. Spectroscopic measurements showed that polymerization inside the confined environment of the nanometric pores results in a tighter and denser packing of the polymer due to a change of the polymerization process from the vinyl groups to the conjugated carbazole groups, giving rise to a redshift of the absorption spectra and better electrical conductivity. Current‐voltage characterization of the hybrids under dark conditions and under illumination were investigated. We demonstrate a simple method to control the band alignment between the organic polymer and the porous silicon, altering it from a type‐I to a type‐II interface by changing the doping polarity of the silicon substrate (from p‐type to n‐type, respectively). An efficient photoinduced charge separation was observed for the type‐II interface (n‐type porous‐silicon–polymer interface), while no such effect was observed for the type‐I organic–inorganic interface.