Porous Substrates for Label-Free Molecular Level Detection of Nonresonant Organic Molecules

Abstract

We report on the design of practical surface enhanced Raman scattering (SERS) substrate based upon 3D alumina membranes with cylindrical nanopores chemically modified with polyelectrolyte coating and loaded with gold nanoparticle clusters. These substrates allow for a molecular-level, label-free detection of common plastic explosive materials (TNT, DNT) down to 5-10 zeptograms or 15-30 molecules and a common liquid explosive (HMTD) down to 1 picogram. Such a sensitive detection of organic molecules by utilizing efficient SERS substrates opens the path for affordable and label-free detection of trace amount of practically important chemical compounds.

Electrospun Nanofibrous Membranes Surface-Decorated with Silver Nanoparticles as Flexible and Active/Sensitive Substrates for Surface-Enhanced Raman Scattering

“…11−15 Hence, there is a growing interest to design novel substrates with desired aggregations to improve SERS activities, for example, the substrates made of three-dimensional hierarchical aggregations of Au/Ag. 16,17 To further facilitate and broaden the SERS application, it is important to explore facile, costeffective, scalable, and reproducible approaches for the preparation of nanostructured SERS substrates with controlled morphologies and structures of nanoparticle aggregations to achieve ultrahigh SERS activities/sensitivities.…”

Three-dimensional SERS hot spots for chemical sensing: Towards developing a practical analyzer

“…Nevertheless, the extension of a SERS substrate from 2D to 3D brings about a larger overall surface area which in turn enables more target molecules to be adsorbed and detected in the third dimension, especially along the z-axis. [4,8,9] Therefore, 3D architecture can achieve higher tolerance in focus Page 4 of 35 misalignment along the z-direction. [7] 3D architecture not only greatly increases the number of hotspots, but also increase the service efficiency of hotspots.…”

Towards Full‐Length Accumulative Surface‐Enhanced Raman Scattering‐Active Photonic Crystal Fibers

“…Similar to work by others, [30,31] we are using polyelectrolyte-mediated surface immobilization of noble nanoparticles. However, in contrast to previous work where Au nanoparticles were attached to $60-mm-long nanocanal walls of porous alumina, [30,31] we focus on controlling nanoparticle density in a wide range, and achieving low and uniform coverage density of Ag nanoparticles inside much longer air channels of PCFs. To mediate nanoparticle attachment, polyallylamine hydrochloride (PAH) was first allowed to adsorb at the surface of the air channels, served as anchoring site for Ag nanoparticles.…”

“…[28] The use of 3D [29][30][31][32] geometry, i.e., substrates obtained by the deposition of noble nanoparticles onto porous silicon [29] or porous aluminum membrane [30][31][32] offered additional advantages of increased SERS intensity due to increased SERS probing area, [29] as well as the membrane waveguiding properties. [30][31][32] Specifically, several orders of magnitude higher SERS intensity, affording pico-or zeptogram-level detection of explosives, has been demonstrated with porous alumina membranes containing $60-mm-long nanochannels, as compared to a solid planar substrate. [30][31][32] SERS-active PCF optofluidics, as a special fiber optic SERS platform, offers easy system integration for in situ flow-through detection, and, more importantly, much longer light interaction length with analyte, thus promising to open a new vista in chemical/biological sensing, medical diagnosis, and process monitoring, especially in geometrically confined or sampling volume-limited systems.…”