Abstract
Surface-enhanced Raman scattering (SERS) has recently been investigated extensively for chemical and biomolecular sensing. Multilayer silver (Ag) nanofilms deposited on glass slides by a simple electroless deposition process have been fabricated as active substrates (Ag/GL substrates) for arsenate SERS sensing. The nanostructures and layer characteristics of the multilayer Ag films could be tuned by varying the concentrations of reactants (AgNO3/BuNH2) and reaction time. A Ag nanoparticles (AgNPs) double-layer was formed by directly reducing Ag+ ions on the glass surfaces, while a top layer (3rd-layer) of Ag dendrites was deposited on the double-layer by self-assembling AgNPs or AgNPs aggregates which had already formed in the suspension. The SERS spectra of arsenate showed that characteristic SERS bands of arsenate appear at approximately 780 and 420 cm-1, and the former possesses higher SERS intensity. By comparing the peak heights of the approximately 780 cm-1 band of the SERS spectra, the optimal Ag/GL substrate has been obtained for the most sensitive SERS sensing of arsenate. Using this optimal substrate, the limit of detection (LOD) of arsenate was determined to be approximately 5 μg·l-1.
Highlights
Since the discovery of surface-enhanced Raman scattering (SERS) in the late 1970s, SERS has been extensively studied as a sensitive analytical technique for fundamental studies of surface species [1,2,3,4,5,6]
We examined the effect of ions on the arsenate SERS sensing using Ag nanofilms prepared by modified mirror reaction [23]
After air-dried, the SERS spectra were collected in high resolution mode on a Thermo Nicolet Almega XR Dispersive Raman Spectrometer (Thermo Fisher Scientific Inc., Madison, WI, USA) equipped with a CCD detector, an optical microscope and a digital camera, and a 780 nm laser line with a laser source power of 30 mW (50% power was applied in the experiments)
Summary
Since the discovery of surface-enhanced Raman scattering (SERS) in the late 1970s, SERS has been extensively studied as a sensitive analytical technique for fundamental studies of surface species [1,2,3,4,5,6]. The development of SERS substrates with high sensitivity and good reproducibility has been one of the most challenging tasks. Colloidal Ag or Au nanoparticles are the most widely used SERS substrates. The aggregation of the colloidal particles facilitating the formation of “hotspots” appears to be crucial for strong SERS enhancement [7,8,9,10,11]. The aggregation of colloidal particles is difficult to control, leading to poor reproducibility of both substrates and SERS signals [12,13]. The immobilization/assembly of colloidal nanoparticles onto solid supports could improve the controllable aggregation of the nanoparticles to some extent, the synthesis and fabrication processes for such assembled layers are usually laborious and time consuming, and usually
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