Revisiting semicontinuous silver films as surface-enhanced Raman spectroscopy substrates

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a very promising analytical technique for the detection and identification of trace amounts of analytes. Among the many substrates used in SERS of great interest are nanostructures fabricated using physical methods, such as semicontinuous metal films obtained via electron beam physical vapor deposition. In these studies, we investigate the influence of morphology of semicontinuous silver films on their SERS properties. The morphologies studied ranged from isolated particles through percolated films to almost continuous films. We found that films below the percolation threshold (transition from dielectric-like to metal-like) made of isolated silver structures provided the largest SERS enhancement of 4-aminothiophenol (4-ATP) analyte signals. The substrate closest to the percolation threshold has the SERS signal about four times lower than the highest signal sample.

Gold semicontinuous thin-film-coated mesoporous TiO2 for SERS substrates

“…S4 (SI). This behavior was already described in the literature for continuous Ag coatings [52] and indicates that the roughness of the 15 nm Au layer is not enough to amplify the Raman signal of pNTP. Figure 6 shows the pNTP SERS spectra obtained using TNM/Au5nm-300 and TF/Au5nm-300 systems.…”

“…However, a thin layer of Cr (< 0.3 nm) was used to ensure Au adhesivity over the SiO 2 film. Thus, despite there are several examples in literature in which metallic nanostructures were synthesized over different substrates and used for SERS or LSPR based sensors [49][50][51][52], the use of mesoporous oxides as agents for nanostructuring noble metal thin films was not described.…”

Lithography-Free Plasmonic Color Printing with Femtosecond Laser on Semicontinuous Silver Films

“…[42,44,49,50,52,53,[59][60][61] Such local photomodification results in spectrally and polarization-selective changes in the scattering, transmittance, reflectance, and absorption spectra due to the gradual structural modifications occurring in the nanometer-scale areas. [38,[42][43][44][51][52][53]62,63] A laser scanning setup with linearly polarized femtosecond laser pulses (repetition rate 1 kHz, pulse duration 100 fs) and operating wavelengths both at 𝜆 = 800 𝑛𝑚 and 𝜆 = 400 𝑛𝑚 is used for photomodifications of the studied structure. The setup generates ultrashort femtosecond laser pulses with a bandwidth of ∆𝜈 = 10 𝑛𝑚.…”

“…Recently, semi-transparent random metal films (RMFs), extensively studied as surfaceenhanced Raman spectroscopy substrates, [38][39][40] have been employed for color printing applications. [41][42][43] These semicontinuous metal films absorb in a broad spectrum of light due to their random morphology and fractal-like nanostructures, [44] as these clustered nanostructures have a non-uniform absorption, contributing to significant inhomogeneous broadening.…”

Optically and electrically driven nanoantennas

“…Here, several approaches to create low-cost, large-area SERS substrates that exhibit homogeneous Raman intensity enhancement are introduced. The substrates are based on quasi-hexagonally ordered gold particles prepared by block-copolymer micellar nanolithography and electroless deposition [41], or on dense silver island films created by pulsed laser deposition [42] or physical vapor deposition [43]. In [44], individual plasmonic nanotags are prepared by coating gold nanoparticle clusters with Raman reporters.…”