Directional Excitation of Surface Plasmon Polaritons via Molecular Through-Bond Tunneling across Double-Barrier Tunnel Junctions.

Directional excitation of surface plasmon polaritons (SPPs) by electrical means is important for the integration of plasmonics with molecular electronics or steering signals toward other components. We report electrically driven SPP sources based on quantum mechanical tunneling across molecular double-barrier junctions, where the tunneling pathway is defined by the molecules' chemical structure as well as by their tilt angle with respect to the surface normal. Self-assembled monolayers of S(CH)BPh (BPh = biphenyl, = 1-7) on Au, where the alkyl chain and the BPh units define two distinct tunnel barriers in series, were used to demonstrate and control the geometrical effects.

Rectification Ratio and Tunneling Decay Coefficient Depend on the Contact Geometry Revealed by in Situ Imaging of the Formation of EGaIn Junctions.

This paper describes how the intensive (tunneling decay coefficient β and rectification ratio R) and extensive (current density J) properties of Ag-S(CH) CH//GaO /EGaIn junctions ( n = 10, 14, 18) and molecular diodes of the form of Ag-S(CH)Fc//GaO /EGaIn depend on A, the contact area between the self-assembled monolayer and the cone-shaped EGaIn tip. Large junctions with A ≥ 1000 μm are unreliable and defects, such as pinholes, dominate the charge transport characteristics. For S(CH)Fc SAMs, R decreases from 130 to unity with increasing A due to an increase in the leakage current (the current flowing across the junction at reverse bias when the diodes block current flow).

Aptamer/Polydopamine Nanospheres Nanocomplex for in Situ Molecular Sensing in Living Cells.

A nanocomplex was developed for molecular sensing in living cells, based on the fluorophore-labeled aptamer and the polydopamine nanospheres (PDANS). Due to the interaction between ssDNA and PDANS, the aptamer was adsorbed onto the surface of PDANS forming the aptamer/PDANS nanocomplex, and the fluorescence was quenched by PDANS through Förster resonance energy transfer (FRET). In vitro assay, the introduction of adenosine triphosphate (ATP) led to the dissociation of the aptamer from the PDANS and the recovery of the fluorescence.

Silver decahedral nanoparticles-enhanced fluorescence resonance energy transfer sensor for specific cell imaging.

We report on a silver decahedral nanoparticles (Ag10NPs)-based FRET (fluorescence resonance energy transfer) sensor for target cell imaging. Fluorophores-functionalized aptamers (Sgc8-FITC) were bound with Ag10NPs via the SH group on the aptamer to form Ag10-Sgc8-FITC. Then, quencher-carrying strands (BHQ-1) were hybridized with Sgc8-FITC to form a Ag10NPs-based FRET sensor (Ag10-Sgc8-F/Q).

Multifunctional aptamer-silver conjugates as theragnostic agents for specific cancer cell therapy and fluorescence-enhanced cell imaging.

We fabricated a multifunctional theragnostic agent Ag-Sgc8-FAM for apoptosis-based cancer therapy and fluorescence-enhanced cell imaging. For cancer therapy, aptamers Sgc8 and TDO5 acted as recognizing molecules to bind CCRF-CEM and Ramos cells specifically. It was found that aptamer-silver conjugates (Ag-Sgc8, Ag-TDO5) could be internalized into cells by receptor-mediated endocytosis, inducing specific apoptosis of CCRF-CEM and Ramos cells.

Metal-enhanced fluorescent detection for protein microarrays based on a silver plasmonic substrate.

This paper presents an ultrasensitive fluorescent detection method through fabricating a silver microarray substrate. Silver nanoparticles (AgNPs) and Ag@Au core-shell nanoparticles with different sizes were first synthesized by a seed-mediated growth method and the metal-enhanced fluorescence of these nanoparticles on different fluorescent dyes was investigated. The results indicated that AgNPs could act as a versatile and effective metal-enhanced fluorescence material for various fluorophores, whereas the enhanced fluorescence from Ag@Au was limited only to certain fluorophores.

Aptamer-functionalized silver nanoparticles for scanometric detection of platelet-derived growth factor-BB.

In this work, we reported a scanometric assay system based on the aptamer-functionalized silver nanoparticles (apt-AgNPs) for detection of platelet-derived growth factor-BB (PDGF-BB) protein. The aptamer and ssDNA were bound with silver nanoparticles by self-assembly of sulfhydryl group at 5' end to form the apt-AgNPs probe. The apt-AgNPs probe can catalyze the reduction of metallic ions in color agent to generate metal deposition that can be captured both by human eyes and a flatbed scanner.