Lanthanide Luminescence Enhancements in Porous Silicon Resonant Microcavities

Abstract

In this paper, the covalent immobilization and luminescence enhancement of a europium (Eu(III)) complex in a porous silicon (pSi) layer with a microcavity (pSiMC) structure are demonstrated. The alkyne-pendant arm of the Eu(III) complex was covalently immobilized on the azide-modified surface via ligand-assisted "click" chemistry. The design parameters of the microcavity were optimized to obtain an efficient luminescence-enhancing device. Luminescence enhancements by a factor of 9.5 and 3.0 were observed for Eu(III) complex bound inside the pSiMC as compared to a single layer and Bragg reflector of identical thickness, respectively, confirming the increased interaction between the immobilized molecules and the electric field in the spacer of the microcavity. When comparing pSiMCs with different resonance wavelength position, luminescence was enhanced when the resonance wavelength overlapped with the maximum emission wavelength of the Eu(III) complex at 614 nm, allowing for effective coupling between the confined light and the emitting molecules. The pSiMC also improved the spectral color purity of the Eu(III) complex luminescence. The ability of a pSiMC to act as an efficient Eu(III) luminescence enhancer, combined with the resulting sharp linelike emission, can be exploited for the development of ultrasensitive optical biosensors.

Acetylcholinesterase immobilization and characterization, and comparison of the activity of the porous silicon-immobilized enzyme with its free counterpart

“…During the experiment the following were used: acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7, acetylcholinesterase from human erythrocytes), acetylthiocholine iodide, 5,5 -dithio-bis(2-nitrobenzoic acid), neostigmine methyl sulfate and MgCl 2 , purchased from Sigma-Aldrich, NaCl (Daejung Chemical and Metals Co., Ltd), ethanol, water (Samchun Chemicals), HF (48 %, w/w; Merck) and boron-doped p-type silicon wafers with a resistivity of [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] cm and thickness 500-550 μm (obtained from Cree Co.). The photoluminescence spectra and relative photoluminescence intensities were measured on an FS-2 fluorescence spectrometer (Scinco) and LabRam HR-800 spectrometer (Horiba Jobin Yvon) with a He/Cd laser source (325 nm).…”

“…The silicon wafer (boron-doped p-type silicon wafers with resistivity [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] cm and thickness 500-550 μm) was cut into chips sized 1×1 cm 2 and degreased with an ultrasonic bath of acetone for 5 min, and then rinsed in deionized water. After drying with nitrogen gas, silver paste was simply sputtered on to the back of the wafer to provide a back ohmic contact for anodization.…”

“…etching time and anodization current density [2]. The unique features of porous silicon make this material a frontline candidate for enzyme immobilization [3][4][5][6][7][8][9], drug delivery [10,11], energyharvesting devices [12][13][14][15][16][17] and biosensing [18,19], due to its large internal surface area, prodigious pore volume, biodegradability, and tunable pore geometry via variation of both porosity and crystallite size [20][21][22][23][24].…”

Development of l-lactate dehydrogenase biosensor based on porous silicon resonant microcavities as fluorescence enhancers

“…The Q value, i.e. the amount of energy stored within the microcavity (Jenie et al, 2014;Ouyang and Fauchet, 2005), was 27 and 20 for MC-1 and MC-2, respectively. Pore sizes were in the range of 39-48 nm for the L layer and 65-100 nm for the H layer.…”

Light-Confining Nanoporous Anodic Alumina Microcavities by Apodized Stepwise Pulse Anodization

“…The quality factor (Q C ), defined as the ratio of the resonance band wavelength (λ R ) to its full width at half maximum (FWHM R ) (Equation 5), is an important criteria in assessing the strength of photon confinement within optical microcavities. 64,65 The Q C of these NAA-µCVs was estimated by fitting the resonance bands shown in Figures 5 and 7 to Gaussian envelopes, using as a baseline the lower love of the PSB as indicated by the horizontal dotted black lines showed in these graphs. Tables S1-S3 (Supporting Information) along with the quality (R 2 ) of these Gaussian fittings.…”