Plasmonic-Magnetic Active Nanorheology for Intracellular Viscosity.

We demonstrate active plasmonic systems where plasmonic signals are repeatedly modulated by changing the orientation of nanoprobes under an external magnetic field, which is a prerequisite for in situ active nanorheology in intracellular viscosity measurements. Au/Ni/Au nanorods act as "nanotransmitters", which transmit the mechanical motion of nanorods to an electromagnetic radiation signal as a periodic sine function. This fluctuating optical response is transduced to frequency peaks via Fourier transform surface plasmon resonance (FTSPR). As a driving frequency of the external magnetic field applied to the Au/Ni/Au nanorods increases and reaches above a critical threshold, there is a transition from the synchronous motion of nanorods to asynchronous responses, leading to the disappearance of the FTSPR peak, which allows us to measure the local viscosity of the complex fluids. Using this ensemble-based method with plasmonic functional nanomaterials, we measure the intracellular viscosity of cancer cells and normal cells in a reliable and reproducible manner.

Tricomponent Multiblock Nanorods for Fourier Transform Surface Plasmon Resonance and Its Chemical Sensing.

In this study, we report a new mode of chemical sensing using Fourier transform surface plasmon resonance with tricomponent nanorods (Au, Ni, and Pt). By applying an external magnetic field, magnetically responsive multiblock nanorods fluctuate periodically, producing sigmoidal optical responses that are represented as a dominant frequency peak after Fourier transform conversion. Adding H2O2 to the solution under an external magnetic field perturbed the periodic nanorod rotation due to a catalytic reaction between the Pt segment and H2O2, which produces catalytic random fluctuation states. The target chemicals were detected by measuring the frequency domain recovery time between two competing states, the magnetic dominant state and the catalytic random state. These two states can be controlled and maximized by nanorod block design, demonstrating the effectiveness of our chemical sensing design using Fourier transform surface plasmon resonance.

3D PtAu nanoframe superstructure as a high-performance carbon-free electrocatalyst.

In this work, we demonstrate how to synthesize a three-dimensional (3D) ordered PtAu nanoframe superstructure and evaluated its performance as an electrocatalyst. Compared to carbon supported platinum (Pt) nanocrystal electrocatalysts (wherein the aggregation- and carbon corrosion-induced fast degradation is a well-known drawback), the 3D PtAu nanoframe superstructure is free from aggregation and carbon corrosion. The 3D superstructure was self-assembled via drop-casting and evaporation using truncated octahedral PtAu nanoframes (TOh PtAu NFs) as building blocks that were produced by controlled wet-chemical etching of a TOh Au core whose edges and vertexes were selectively deposited with Pt atoms. Density functional theory calculations revealed that the surface alloy state of PtAu gave rise to an enhanced catalytic activity compared to pure Pt. Experimental investigations showed that such 3D superstructure electrocatalysts exhibited excellent mass transfer efficiency, higher catalytic activity and stability towards the methanol oxidation reaction (MOR) compared to a commercial Pt/C catalyst. The demonstrated 3D nanoframe superstructure shows great potential for practical catalytic application due to its high structural stability, high catalytic activity, high surface area and ease of fabrication.

Fourier Transform Surface Plasmon Resonance of Nanodisks Embedded in Magnetic Nanorods.

In this study, we demonstrate the synthesis and application of magnetic plasmonic gyro-nanodisks (GNDs) for Fourier transform surface plasmon resonance based biodetection. Plasmonically active and magnetically responsive gyro-nanodisks were synthesized using electrochemical methods with anodized aluminum templates. Due to the unique properties of GNDs (magnetic responsiveness and surface plasmon bands), periodic extinction signals were generated under an external rotating magnetic field, which is, in turn, converted into frequency domains using Fourier transformation. After the binding of a target on GNDs, an increase in the shear force causes a shift in the frequency domain, which allows us to investigate biodetection for HA1 (the influenza virus). Most importantly, by modulating the number and the location of plasmonic nanodisks (a method for controlling the hydrodynamic forces by rationally designing the nanomaterial architecture), we achieved enhanced biodetection sensitivity. We expect that our results will contribute to improved sensing module performance, as well as a better understanding of dynamic nanoparticle systems, by harnessing the perturbed periodic fluctuation of surface plasmon bands under the modulated magnetic field.