Light-emitting-diodes based on ordered InGaN nanocolumns emitting in the blue, green and yellow spectral range.

The growth of ordered arrays of InGaN/GaN nanocolumnar light emitting diodes by molecular beam epitaxy, emitting in the blue (441 nm), green (502 nm), and yellow (568 nm) spectral range is reported. The device active region, consisting of a nanocolumnar InGaN section of nominally constant composition and 250 to 500 nm length, is free of extended defects, which is in strong contrast to InGaN (planar) layers of similar composition and thickness. Electroluminescence spectra show a very small blue shift with increasing current (almost negligible in the yellow device) and line widths slightly broader than those of state-of-the-art InGaN quantum wells.

Molecularly imprinted polymer diffraction grating as label-free optical bio(mimetic)sensor.

Micropatterned molecularly imprinted polymer (MIP) transmissive 2D diffraction gratings (DGs) are fabricated and evaluated as label-free antibiotic bio(mimetic)sensors. Polymeric gratings are prepared by using microtransfer molding based on SiO(2)/Si molds. The morphology of the MIP gratings is studied by optical and atomic force microscopes. MIP 2D-DGs exhibit 2D optical diffraction patterns, and measurement of changes in diffraction efficiency is used as sensor response. The refractive index of the micropatterned MIP material was estimated, via solvent index matching experiments, to be 1.486. Immersion of a MIP 2D-DG in different solutions of target-antibiotic enrofloxacin leads to significant variations in diffraction efficiency, demonstrating target-molecule detection. On the other hand, no significant response is observed for both control experiments: MIP grating exposed to a non-retained analyte and an equivalent non-imprinted polymer grating exposed to the target analyte, showing highly specific antibiotic label-free optical recognition.

Bio-Photonic Sensing Cells over transparent substrates for anti-gestrinone antibodies biosensing.

In a previous work we introduced the term Bio-Photonic Sensing Cells (BICELLs), referred to periodic networks of nano-pillar suitable for biosensing when are vertically interrogated. In this article, we demonstrate the biosensing capabilities of a type of micrometric size BICELLs made of SU-8 nano-pillars fabricated over transparent substrates. We verify the biochips functionality comparing the theoretical simulations with the experimental results when are optically interrogated in transmission. We also demonstrate a sensitivity enhancement by reducing the pitch among nano-pillars from 800 to 700 nm. Thus, the Limit of Detection achievable in these types of BICELLs is in the order of 64 pg/mL for 700 nm in pitch among nano-pillars in comparison with 292 pg/mL for 800 nm in pitch when are interrogated by Fourier Transform Visible and Infrared Spectrometry. The experiments exhibited a good reproducibility with a relative standard deviation of 0.29% measured within 8 days for a specific concentration. Finally, BICELLs functionality was tested in real conditions with unpurified rabbit serum for detecting anti-gestrinone antibodies, demonstrating the high performance of this type of BICELLs to detect specific antibodies having immobilized the suitable bioreceptors onto the sensing surface.

Label-free biosensing by means of periodic lattices of high aspect ratio SU-8 nano-pillars.

We developed biophotonic sensing arrays of 60x60 microm(2) made of periodic lattices of high aspect ratio SU-8 nano-pillars in order to demonstrate their capability for label-free molecule detection, as well as the sensitivity enhancement in comparison with a single layer of SU-8. The biophotonic sensing arrays, that we call BICELLs (Biophotonic sensing cells), are interrogated vertically by using micron spot size Fourier transform visible and IR spectrometry (FT-VIS-IR). We monitored the surface immobilization of bovine serum albumin (BSA) antigen and anti-BSA antibody (aBSA) recognition. The bioassay exhibits a limit of detection (LOD) in the order of 2 ng/ml limited by the wavenumber uncertainty during the interrogation process. We also estimated and compared the theoretical biolayer thickness with previous results.