Programmable liposomes are designed to selectively produce various liposome-nanoparticle hybrids.

A rapid, precise method for identifying waterborne pathogens is critically needed for effective disinfection and better treatment. However, conventional methods, such as culture-based counting, generally suffer from slow detection times and low sensitivities. Here, we developed a rapid detection method for tracing waterborne pathogens by an innovative optofluidic platform, a plasmonic bacteria on a nanoporous mirror, that allows effective hydrodynamic cell trapping, enrichment of pathogens, and optical signal amplifications. We designed and simulated the integrated optofluidic platform to maximize the enrichment of the bacteria and to align bacteria on the nanopores and plasmonic mirror via hydrodynamic cell trapping. Gold nanoparticles are self-assembled to form antenna arrays on the surface of bacteria, such as Escherichia coli and Pseudomonas aeruginosa, by replacing citrate with hydroxylamine hydrochloride in order to amplify the signal of the plasmonic optical array. Owing to the synergistic contributions of focused light via the nanopore geometry, self-assembled nanoplasmonic optical antennas on the surface of bacteria, and plasmonic mirror, we obtain a sensitivity of detecting E. coli as low as 102 cells/ml via surface-enhanced Raman spectroscopy. We believe that our label-free strategy via an integrated optofluidic platform will pave the way for the rapid, precise identification of various pathogens.

The assembly of colloidal metal nanoparticles at immiscible liquid interface has attracted considerable attention because of both enhanced physical properties associated with the assembly and controlled mass transfer at the interface for many sensing and catalytic applications. However, rapid production of 3D assembly of metal nanoparticles at liquid interface is still challenging. Here a facile and robust method is proposed to generate 3D assembly of colloidal metal nanoparticles at oleic acid/water interface, which is based on an interesting observation of the autonomous and rapid interfacial locomotion of nanoparticles from air/water to oleic acid/water interface. This interfacial transfer of these particles is completed within a minute considerably owing to electrostatic interaction between positively charged surface molecule of the particle and the negative end of oleic acid, producing up to 20‐fold denser 3D assembly. To realize one of the benefits of the proposed method, 3D assemblies of gold and silver nanoparticles at oleic acid/water interface are successfully exploited for the detection of trace molecules in both oil and water phases via surface‐enhanced Raman spectroscopy. Molecular Raman signals can be increased by our 3D nanoparticle layers by up to 100 times, compared with that measured from nanoparticle monolayers being transferred onto solid substrates.

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Plasmonic nanocavities between metal nanoparticles on metal films are either hydrophobic or fully occupied by nonmetallic spacers, preventing molecular diffusion into electromagnetic hotspots. Here we realize water-wettable open plasmonic cavities by devising gold nanoparticle with site-selectively grown ultrathin dielectric layer-on-gold film structures. We directly confirm that hydrophilic dielectric layers of SiO 2 or TiO 2 , which are formed only at the tips of gold nanorod via precise temperature control, render sub-10 nm cavities open to the surroundings and completely water-wettable. Simulations reveal that spontaneous wetting in our cavities is driven by the presence of tip-selective hydrophilic layer and tendency of minimizing high energy air/ water interface inside the cavities. Our plasmonic cavities show significant Raman enhancement of up to 4 orders of magnitude higher than those of conventional ones for molecules in various media. Our findings will offer new opportunities for sensing applications of plasmonic nanocavities and have huge impacts on cavity plasmonics.