SERS of molecules that do not adsorb on Ag surfaces: a metal–organic framework-based functionalization strategy

Abstract

The potential for discriminating between analytes by their unique vibrational signature makes surface-enhanced Raman scattering (SERS) extremely interesting for chemical detection. However, for molecules that weakly adsorb to non-functionalized plasmonic materials, detection by SERS remains a key challenge. Here we present an approach to SERS-based detection where a polycrystalline metal-organic framework (MOF) film is used to recruit a range of structurally similar volatile organic compounds for detection by SERS. MOF films were grown on the surface of Ag "films-over-nanospheres" (FONs), which have previously been shown to enhance Raman signals of surface adsorbates by a factor of 10(7). Upon exposing the MOF-coated FON to benzene, toluene, nitrobenzene, or 2,6-di-tert-butylpyridine, the MOF film traps the vapors at the FON surface, allowing the unique Raman spectrum of each vapor to be recorded. By contrast, these analytes do not adsorb to a bare FON surface and thus cannot be detected by conventional SERS substrates. Pyridine was also tested as a Ag-adsorbing control analyte. Concentration dependence and time resolved measurements provide evidence for the hypothesis that the vapors are reversibly adsorbed on the surfaces of MOF nanocrystals exposed at grain boundaries. This represents a generalized approach for confining aromatic molecules through interactions with the MOF surface, which can be applied for future SERS-based sensors.

Smart Nanocomposites of Cu-Hemin Metal-Organic Frameworks for Electrochemical Glucose Biosensing

“…1C). Due to different linkages between metal ions and organic ligands, MOFs could present various morphologies including rod octahedron4244, nanosphere45, hexahedron4546, spindle-shape47, and so on. However, such ball-flower-like structure has not yet been reported in previous works.…”

Ordered array of Ag semishells on different diameter monolayer polystyrene colloidal crystals: An ultrasensitive and reproducible SERS substrate

“…Lots of SERS substrates with “hot spots” have been prepared by different ways including chemical functional method9, electron lithography technique10 and self-assembled aggregation1112. Relatively speaking, as a simple, economic and effective way, nanosphere lithography (NSL) can be used to fabricate uniformly ordered nanoparticle arrays because of its good monodispersity, wide size range and realizable1314151617181920212223242526. For instance, by using NSL, Van Duyne’s group fabricated Au and Ag nanoparticle array on self-assembly monolayer polystyrene or silica nanospheres13141516.…”

“…Relatively speaking, as a simple, economic and effective way, nanosphere lithography (NSL) can be used to fabricate uniformly ordered nanoparticle arrays because of its good monodispersity, wide size range and realizable1314151617181920212223242526. For instance, by using NSL, Van Duyne’s group fabricated Au and Ag nanoparticle array on self-assembly monolayer polystyrene or silica nanospheres13141516. Sugawa’s group prepared periodic Au half-shells and ordered arrays of copper nanostructures on the upper hemispheres of two-dimensional silica1718.…”

Vapor phase SERS sensor based on mesoporous silica decorated with silver nanoparticles

“…At the same time, ordinary materials for SERS with ecological, pharmaceutical, biological and medical applications are commonly designed for the analysis of liquid analytes [1][2][3][4][5][6][7][8][9][10] while a limited number of actual research efforts has focused on vapor phase detection [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. The latter challenge evidently widens the promising application area of SERS and therefore requires novel approaches for the design of SERS-active materials.…”

“…Accordingly, the sensitivity of the analysis becomes even higher if porous silver nanocubes [12], polymer coatings [15], anisotropic nanoparticle aggregates [16,24], metal -organic frameworks [21,26], multihole capillaries [23], graphene oxide surface [28], free -surface microfluidic chips [18], electrodynamic precipitation [17] are applied.…”