The dependence of magnitude of the electric near-field on the separation between metal nanoparticles for surface-enhanced Raman spectroscopy (SERS) substrates was experimentally verified. Diameters of gold-coated nanopores in a ceramic alumina substrate were varied to study the charge buildup near interparticle junctions and its effect on the enhancement factor due to SERS. The substrates were characterized by sensing a Rhodamine dye and calculating the associated Raman enhancement factors. Decreasing Au interparticle distance increases the electric near-field and shifts the plasmon resonance peak accordingly.
The Raman signal of inelastically scattered photons represents the fingerprint of a chemical molecule. Therefore, surface enhanced Raman spectroscopy (SERS) can be employed as the selective mechanism for an extraordinary optics sensor sensitive enough to detect a single molecule. Such sensitivity makes SERS ideal to detect chemicals at parts per billion to parts per trillion concentrations. SERS studies benefit from a signal enhancing substrate that is both reproducible and cost effective. Commercial substrates produced by electron beam lithography cost approximately $100 a piece to manufacture and can only be used once. The purpose of this study is to design a SERS substrate that offers enhancement equivalent to the commercial standard and is cheaper to produce. Experiments confirm that gold (Au) coated nano-pores can be used as an optimal SERS substrate offering a promising enhancement with durability that rival commercial products.
We investigate commercial nano-engineered SERS (surface enhanced Raman spectroscopy) substrates for the
possibility of recycling them and using them multiple times. Klarite<sup>TM</sup> is a commercial SERS substrate fabricated by
nanoscale lithographic patterning technique on silicon wafer before being coated with a thin layer of Gold. It has
been widely reported that, this substrate results in more reproducible surface enhanced Raman signals. However, it
is designed only for a single measurement and disposable use. In this work, we report a method for recycling one
substrate for multiple SERS measurements by coating a thin layer of Gold/Silver after each application of the
substrate. The results obtained using reprocessed substrates are comparable to the measurements recorded using fresh substrates.
Surface Enhanced Raman Scattering (SERS) is a recently discovered powerful technique which has demonstrated
sensitivity and selectivity for detecting single molecules of certain chemical species. This is due to an enhancement
of Raman scattered light by factors as large as 10<sup>15</sup>. Gold and Silver-coated substrates fabricated by electron-beam
lithography on Silicon are widely used in SERS technique. In this paper, we report the use of nanoporous ceramic
membranes for SERS studies. Nanoporous membranes are widely used as a separation membrane in medical
devices, fuel cells and other studies. Three different pore diameter sizes of commercially available nanoporous
ceramic membranes: 35 nm, 55nm and 80nm are used in the study. To make the membranes SERS active, they are
coated with gold/silver using sputtering techniques. We have seen that the membranes coated with gold layer remain
unaffected even when immersed in water for several days. The results show that gold coated nanoporous membranes
have sensitivity comparable to substrates fabricated by electron-beam lithography on Silicon substrates.