Selective SERS Detecting of Hydrophobic Microorganisms by Tricomponent Nanohybrids of Silver–Silicate-Platelet–Surfactant

Abstract

Nanohybrids consisting of silver nanoparticles (Ag), clay platelets, and a nonionic surfactant were prepared and used as the substrate for surface-enhanced Raman scattering (SERS). The nanoscale silicate platelets (SP) (with dimensions of 100 × 100 nm(2) and a thickness of ∼1 nm) were previously prepared from exfoliation of the natural layered silicates. The tricomponent nanohybrids, Ag-SP-surfactant (Ag-SP-S), were prepared by in situ reduction of AgNO3 in the presence of clay and the surfactant. The clay platelets with a large surface area and ionic charge (ca. 18 000 sodium ions per platelet) allowed for the stabilization of Ag nanoparticles in the range of 10-30 nm in diameter. With the addition of a nonionic surfactant such as poly(oxyethylene) alkyl ether, the tricomponent Ag-SP-S nanohybrids possessed an altered affinity for contacting microorganisms. The particle size and interparticle gaps between neighboring Ag on SP were characterized by TEM. The surface tension of Ag-SP and Ag-SP-S in water implied different interactions between Ag and hydrophobic bacteria ( Escherichia coli and Mycobacterium smegmatis ). By increasing the surfactant content in Ag-SP-S, the SERS peak intensity was dramatically enhanced compared to the Ag-SP counterpart. The nanohybrids, Ag-SP and Ag-SP-S, with the advantages of varying hydrophobic affinity, floating in medium, and 3D hot-junction enhancement could be tailored for use as SERS substrates. The selective detection of hydrophobic microorganisms and larger biological cells makes SERS a possible rapid, label-free, and culture-free method of biodetection.

Immobilization and 3D Hot-Junction Formation of Gold Nanoparticles on Two-Dimensional Silicate Nanoplatelets as Substrates for High-Efficiency Surface-Enhanced Raman Scattering Detection

“…Due to their advantageous chemical properties, it has been posited that such clays can form effective adsorbents for stabilizing heavy-metal NPs [33,34,35]. Recently, 3D hot-junctions of AgNP/2D nanomaterial hybrids have been used as SERS substrates for various biochemical analyses [36,37,38,39].…”

Au Nanoparticles Immobilized on Honeycomb-Like Polymeric Films for Surface-Enhanced Raman Scattering (SERS) Detection

“…With that in mind, laser excitation would bring about surface plasmon resonances in AuNP arrays of honeycomb-like polymeric SERS substrates. As a result, the Raman signals of analytes multiplied and produced enormous SERS enhancement, elucidating the multiplied hot-spots effect [40,41].…”

“…However, the detailed causes for such enhanced phenomena were not revealed. Therefore, we set out to investigate the mechanism of Raman enhancement by hot-spots resonance effects in the three-dimensional (3D) honeycomb porous structure along with the flat-film substrates as a control [23,40,41].…”

A Review on Layered Mineral Nanosheets Intercalated with Hydrophobic/Hydrophilic Polymers and Their Applications

“…2D layered mineral nanosheets exhibit highly tuneable properties and are suitable candidates for applications in a large number of fields such as drug delivery, flame retardant, nanohybrids, antibacterial, rheology modifiers, superior thermal transporter, and food packaging . Recently, there have been an enormous number of new developments using 2D layered minerals intercalated with polymer chains to load and in vivo deliver biologically active materials such as porphyrins, nucleoside phosphates, drugs, vitamins, amino acids, and fatty acids .…”