Abstract
Surface-enhanced spectroscopy (SES) techniques, including surface-enhanced photoluminescence (SEPL), Raman scattering (SERS) and infrared absorption (SEIRA), represent powerful biosensing modalities, allowing non-invasive label-free identification of various molecules and quantum emitters in the vicinity of nanotextured surfaces. Enhancement of multi-wavelength (vis-IR) excitation of analyte molecules of interest atop a single textured substrate could pave the way toward ultimate chemosensing performance and further widespread implementation of the SES-based approaches in various crucial areas, such as point-ofcare diagnostics. In this paper, an easy-to-implement ultrafast direct laser printing via partial spallation of thermally-thick silver films and subsequent large-scale magnetron deposition of nanometer-thick Au layers of variable thickness was implemented to produce bimetallic textured surfaces with the cascaded nanotopography. The produced bimetallic textures demonstrate the strong broadband plasmonic response over the entire visible spectral range. Such plasmonic performance was confirmed by convenient spectroscopy-free Red-Green-Blue (RGB) color analysis of the dark-field (DF) scattering images supported by numerical calculations of the electromagnetic (EM) “near-fields”, as well as comprehensive DF spectroscopic characterization. Bimetallic laser-printed nanotextures, which can be easily printed at ultrafast (square millimeters per second) rate, using galvanometric scanning, exhibited strong enhancement of the SEPL (up to 75-fold) and SERS (up to 106 times) yields for the organic dye molecules excited at various wavelengths. Additionally, comprehensive optical and sensing characterization of the laser-printed bimetallic surface structures allows substantiating the convenient spectroscopy-free RGB color analysis as a valuable tool for predictive assessment of the plasmonic properties of the various irregularly and quasi-periodically nanotextured surfaces.
Highlights
Surface plasmons, resonant oscillations of the electron-ion plasma in the noble-metal nanostructures induced by irradiating photons, are known to provide substantial augmentation of the electromagnetic (EM) field localized near interfaces of the metals with their dielectric environment[1]
By accounting for the average intensity of the several Rhodamine 6G (R6G) Raman bands at 612, 1360 and 1648 cm−1 we found more than an order of magnitude higher surface-enhanced Raman scattering (SERS) yield for Ag-Au bimetallic textures being compared to the monometallic ones (see Fig. 4(h))
An easy-to-implement ultrafast direct laser printing via spallation of thermally thick silver films and subsequent large-scale magnetron deposition of nanometer-thick Au layer was implemented to produce bimetallic textured surfaces with the cascaded nanotopography
Summary
Resonant oscillations of the electron-ion plasma in the noble-metal nanostructures induced by irradiating photons, are known to provide substantial augmentation of the electromagnetic (EM) field localized near interfaces of the metals with their dielectric environment[1]. Development of surface structures and nanotextured surfaces supporting plasmon-mediated EM-field enhancement in a broad spectral range, covering whole visible spectrum, as well as its near infrared (near-IR) part, is of mandatory importance for various crucial applications[2,3,4] Such textured surfaces with superbroadband plasmonic response can be used to build novel high-performance optoelectronic devices[5,6], solar-cell elements[7], as well as to develop versatile and flexible biosensing platforms based on various surface-enhanced spectroscopy (SES) processes - surface-enhanced Raman scattering (SERS), photoluminescence (SEPL) and infrared absorption (SEIRA)[8,9,10,11]. The spectrally broadband and rather strong plasmonic response of the bimetallic spiky textures, which can be printed at high (square millimeter per second) rate using the galvanometric scanning techniques, make the proposed approach promising for various routing biosensing applications
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