Controlled assembly of SERS substrates templated by colloidal crystal films

Abstract

Convective assembly at high volume fractions was used to assemble gold nanoparticles into structured porous films templated by colloidal crystals. These gold nanofilms have hierarchical porosity and were proven to be stable and efficient substrates for surface-enhanced Raman spectroscopy (SERS). The control over the film structure allowed optimization of their performance for potential sensor applications.Colloidal crystals are materials with periodic structure on the submicrometre length scale made by self-assembly of colloidal particles. Colloidal crystals can be used as a basis for fabrication of photonic materials, 1-7 optical coatings and filters, [8][9][10] lithographic etching masks, 11-13 and sensors. 14-17 The colloidal crystals can also serve as templates for a variety of other self-assembled materials with controlled and reproducible structure. In this review we highlight results based on our process for rapid and reproducible deposition of colloidal crystal films by convective assembly at high volume fractions. 18These crystal films serve as templates of controlled structure for surface-enhanced Raman spectroscopy substrates. 16,19The hallmark of SERS is selectivity, potential for remote sampling through fiber optics, and capability for detection of analytes in aqueous solvents. Despite these advantages the widespread use of SERS-based analytical technology has been slow. Before SERS-based sensors can find broad application in routine chemical analysis new SERS materials must be developed that yield consistently high signals and provide detection generality towards a wide range of chemical and environmental analytes. The major requirements for the SERS substrate materials include controlled nanoscale structure, periodicity and chemical stability. One of the well-studied methods for making SERS substrates uses mono-and bi-layers of close-packed microsphere

Nanostructures and nanostructured substrates for surface—enhanced Raman scattering (SERS)

“…They have demonstrated 10-fold enhancements when compared to similar but disordered templated structures. 41 Recently, three-dimensional ordered nanoparticle metal films have been prepared by using self-assembled amino-modified silicon spheres as a template. 42 In this procedure, the self-assembled silicon film is immersed in a gold nanoparticle solution and the solution stirred for several minutes.…”

Nanofabricated periodic arrays of silver elliptical discs as SERS substrates

“…19 Colloid crystal films have been used as templates to assemble gold nanoparticles in a controlled arrangement to create SERS platforms. 20 Unique SERS substrates have been formed in arrays of pyramidal shaped pits that have shown tunability of surface plasmons by altering pit dimensions while maintaining the pitch. 21 Another technique widely used in creating ordered SERS substrates is nanosphere lithography.…”

Silver nanoparticles deposited inverse opal film as a highly active and uniform SERS substrate

“…These substrates provide an amazingly high enhancement factor and reproducibility of the SERS signals. Among these nanostructures, three-dimensionally (3D) ordered porous structure has advantages of large surface area available for the formation of the so-called "hot spots" and the adsorption of target analytes [13][14][15][16].…”