title: 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.
authors.affiliation: Institute of Polymer Science and Engineering, National Taiwan University , Taipei 10617, Taiwan.
authors.forename: Jun-Ying
authors.initials: JY
authors.lastname: Ho
authors.forename: Ting-Yu
authors.initials: TY
authors.lastname: Liu
authors.forename: Jiun-Chiou
authors.initials: JC
authors.lastname: Wei
authors.forename: Juen-Kai
authors.initials: JK
authors.lastname: Wang
authors.forename: Yuh-Lin
authors.initials: YL
authors.lastname: Wang
authors.forename: Jiang-Jen
authors.initials: JJ
authors.lastname: Lin
mesh_terms: D001419:Bacteria / Q000187:drug effects / Q000302:isolation & purification*; D004926:Escherichia coli / Q000187:drug effects; D057927:Hydrophobic and Hydrophilic Interactions; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D020102:Mycobacterium smegmatis / Q000187:drug effects; D010316:Particle Size; D056951:Photoelectron Spectroscopy; D017640:Silicates / Q000494:pharmacology*; D012834:Silver / Q000494:pharmacology*; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013211:Staphylococcus aureus / Q000187:drug effects; D013501:Surface-Active Agents / Q000494:pharmacology*
chemical_list: D017640:Silicates; D013501:Surface-Active Agents; D012834:Silver