Silver Nanocube- and Nanowire-Based SERS Substrates for Ultra-low Detection of PATP and Thiram Molecules
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Silver Nanocube- and Nanowire-Based SERS Substrates for Ultra-low Detection of PATP and Thiram Molecules Govind Kumar 1 & R. K. Soni 1 Received: 28 September 2019 / Accepted: 14 April 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The shape-anisotropic metal nanoparticles support large surface plasmon resonance (SPR) wavelength tuning and higher intrinsic electromagnetic hot spots for excellent surface-enhanced Raman spectroscopy (SERS) performance. Here, two shape-anisotropic nanostructures, silver nanocubes and nanowires with sharp features and high yield, are synthesized using the polyol reduction method. Finite-difference time-domain (FDTD) simulations are performed to understand the origin of the SPR peaks in the absorption spectra and for optimization of excitation wavelengths for large near-field enhancement. Silver nanocubes and nanowires exhibit broad plasmon resonances over the visible region of the electromagnetic spectrum with maxima around 498 nm and 410 nm, respectively. The SERS activity of nanocubes and nanowires are investigated for three molecules of different Raman activity. The SERS spectra show higher activity for nanocubes and ultra-low molecular detection (10−15 M) capability of the fabricated substrates for rhodamine B (RhB) dye, p-aminothiophenol (PATP), and pesticide thiram. Relatively higher enhancement of some Raman modes is observed when excited with laser wavelength 532 nm indicating photo-induced charge transfer from metal to molecule. Keywords Surface plasmon resonance (SPR) . Nanocubes . Nanowires . Finite-difference time-domain (FDTD) simulations . Surface-enhanced Raman spectroscopy (SERS) . PATP . Thiram
Introduction Surface-enhanced Raman spectroscopy (SERS) has emerged as an efficient and selective molecular sensing technique capable of ultrasensitive detection of a wide range of chemical species such as coloring dyes, pesticides, drugs, biomolecules, and explosives [1–5]. This technique is based on the localized surface plasmon resonance (LSPR) supported by metal nanoparticles. The LSPR causes enhancement of electromagnetic fields around metal nanostructures which hugely increases the Raman cross-section of molecule present in the vicinity of the nanoparticle [6]. It has been shown that the enhancement of Raman scattering mainly depends on the morphology of nanoparticles and their concentration on the substrate [7, 8]. ShapeElectronic supplementary material The online version of this article (https://doi.org/10.1007/s11468-020-01172-0) contains supplementary material, which is available to authorized users. * R. K. Soni [email protected] 1
Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
anisotropic metal nanostructures entrap the oscillating metal charges at sharp corners or tips and cause strong localized electromagnetic fields on these highly confined spaces. These regions of intense electromagnetic field are called hot spots and are responsible for the overall Raman intensity enhancement
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