Improved fabrication of zero-mode waveguides for single-molecule detection (original) (raw)
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Nanotechnology, 2005
We report on the fabrication of two-dimensional arrays of nano-optical apertures in gold layers by electron beam lithography (EBL) on a transparent glass substrate. 30 × 30 µm 2 large arrays of high aspect ratio sub-wavelength cylinders (400 nm diameter with period of 1.81 µm) and annular apertures (diameters 250/330 nm and 310/330 nm inner/outer with period of 600 nm) were patterned in a 750 nm thick resist layer using a high contrast negative tone resist. The resist structures show sharp and vertical edges after development. The 150 nm thick deposited gold layer ensures optical transmission of less than 1.1 × 10 −4 at 633 nm wavelength. White light based optical characterizations agreed with theory predictions and prove the good quality of the structures.
Applied physics letters, 1998
We have improved the optical characteristics of aluminum-coated fiber probes used in near-field scanning optical microscopy by milling with a focused ion beam. This treatment produces a flat-end face free of aluminum grains, containing a well-defined circularly-symmetric aperture with controllable diameter down to 20 nm. The polarization behavior of the tips is circularly symmetric with a polarization ratio exceeding 1:100. The improved imaging characteristics are demonstrated by measuring single molecule fluorescence. Count rates increase more than one order of magnitude over unmodified probes, and the molecule images map a spatial electric field distribution of the aperture in agreement with calculations.
An optical atto-liter titer plate device is developed for high-speed molecular analyses. The basis of the device is an optical nano-hole array in a thin metal film, where each hole serves as a reaction chamber. The high density of holes, up to several millions per square mm of chip area, allows massive parallel read-out. Nano-hole arrays with the hole size between 100-200nm have been fabricated, using e-beam lithography and lift-off technique, and further optical characterization of the array has been pursued.
Nature Nanotechnology, 2013
Single-molecule fluorescence techniques 1-3 are key for a number of applications, including DNA sequencing 4,5 , molecular and cell biology 6,7 and early diagnosis 8 . Unfortunately, observation of single molecules by diffraction-limited optics is restricted to detection volumes in the femtolitre range and requires pico-or nanomolar concentrations, far below the micromolar range where most biological reactions occur 2 . This limitation can be overcome using plasmonic nanostructures, which enable the confinement of light down to nanoscale volumes 9-13 . Although these nanoantennas enhance fluorescence brightness 14-20 , large background signals and/or unspecific binding to the metallic surface 23-25 have hampered the detection of individual fluorescent molecules in solution at high concentrations. Here we introduce a novel 'antenna-in-box' platform that is based on a gap-antenna inside a nanoaperture. This design combines fluorescent signal enhancement and background screening, offering high singlemolecule sensitivity (fluorescence enhancement up to 1,100fold and microsecond transit times) at micromolar sample concentrations and zeptolitre-range detection volumes. The antenna-in-box device can be optimized for single-molecule fluorescence studies at physiologically relevant concentrations, as we demonstrate using various biomolecules.
Hybrid Metal-Dielectric Zero Mode Waveguide for Enhanced Single Molecule Detection
Chemical Communications, 2019
We fabricated hybrid metal-dielectric nanoslots and measured their optical response at three different wavelengths. The nanostructure is fabricated on a bilayer film formed by the sequential deposition of silicon and gold on a transparent substrate. The optical characterization is done via fluorescence spectroscopy measurements. We characterized the fluorescence enhancement, as well as the lifetime and detection volume reduction for each wavelength. We observe that the hybrid metal-dielectric nanoslots behave as enhanced Zero Mode Waveguides in the near-infrared spectral region. Their detection volume is such that they can perform enhanced single-molecule detection at tens of µM. We compared their behavior with that of a golden ZMW, and we demonstrated that the dielectric silicon layer improves both the optical performance and the stability of the device.
Gold Ion Beam Milled Gold Zero-Mode Waveguides
Nanomaterials
Zero-mode waveguides (ZMWs) are widely used in single molecule fluorescence microscopy for their enhancement of emitted light and the ability to study samples at physiological concentrations. ZMWs are typically produced using photo or electron beam lithography. We report a new method of ZMW production using focused ion beam (FIB) milling with gold ions. We demonstrate that ion-milled gold ZMWs with 200 nm apertures exhibit similar plasmon-enhanced fluorescence seen with ZMWs fabricated with traditional techniques such as electron beam lithography.
Plasmonic zero mode waveguide for highly confined and enhanced fluorescence emission
We fabricate a plasmonic nanoslot that is capable of performing enhanced single molecule detection at 10 μM concentrations. The nanoslot combines the tiny detection volume of a zero-mode waveguide and the field enhancement of a plasmonic nanohole. The nanoslot is fabricated on a bi-metallic film formed by the sequential deposition of gold and aluminum on a transparent substrate. Simulations of the structure yield an average near-field intensity enhancement of two orders of magnitude at its resonant frequency. Experimentally, we measure the fluorescence stemming from the nanoslot and compare it with that of a standard aluminum zero-mode waveguide. We also compare the detection volume for both structures. We observe that while both structures have a similar detection volume, the nanoslot yields a 25-fold fluorescence enhancement
2019
Xavier Zambrana-Puyalto,a* Paolo Ponzellini,a Nicolò Maccaferrib, Enrico Tessarolo,c Maria G. Pelizzo,c Weidong Zhang,d Grégory Barbillon,e Guowei Lu,d and Denis Garolia* a Istituto Italiano di Tecnologia – Via Morego, 30, I-16163 Genova, Italy b Physics and Materials Science Research Unit, University of Luxembourg, L-1511 Luxembourg, Luxembourg c CNR-IFN, Via Trasea 7, Padova (Italy) d State Key Laboratory for Mesoscopic Physics & Collaborative Innovation Center of Quantum Matter, School of Physics, Peking University, Beijing 100871, China e EPF—École d’Ingénieurs, 3 bis rue Lakanal, 92330 Sceaux, France * Corresponding author’s email: denis.garoli@iit.it, xavier.zambrana@iit.it