A plasmonic metasurface composed of homogeneously self-assembled gold nanoparticles can provide high-contrast fluorescence images confined to the nanointerface. In this study, we successfully ...demonstrated real-time, high-spatiotemporal-resolution imaging of adhered Venus-paxillin-3T3 live cells under a widefield microscope, where not only a high axial resolution but also a high lateral resolution down to the theoretical limit were confirmed through nascent cluster formation of paxillin. The improved lateral resolution on the sheet could be interpreted as the characteristic of localized surface plasmon resonance (LSPR)-mediated enhanced fluorescence and the metasurface acting as a nanothickness plane light emitter. We also found minimized photobleaching, owing to the increase in the emission efficiency via plasmon-exciton coupling. This simple nanomaterial-based technique will be a powerful tool to enhance interfacial signals and improve the quality of live-cell images, not only under widefield microscopes but also in combination with various super-resolution microscope systems in the future.
Ultrathin films of a poly(styrene)-block-poly(2-vinylpyrindine) diblock copolymer (PS-b-P2VP) and poly(styrene)-block-poly(4-vinylpyrindine) diblock copolymer (PS-b-P4VP) were used to form ...surface-induced nanopattern (SINPAT) on mica. Surface interaction controlled microphase separation led to the formation of chemically heterogeneous surface nanopatterns on dry ultrathin films. Two distinct nanopatterned surfaces, namely, wormlike and dotlike patterns, were used to investigate the influence of topography in the nanometer range on cell adhesion, proliferation, and migration. Atomic force microscopy was used to confirm that SINPAT was stable under cell culture conditions. Fibroblasts and mesenchymal progenitor cells were cultured on the nanopatterned surfaces. Phase contrast and confocal laser microscopy showed that fibroblasts and mesenchymal progenitor cells preferred the densely spaced wormlike patterns. Atomic force microscopy showed that the cells remodelled the extracellular matrix differently as they migrate over the two distinctly different nanopatterns.
We have applied nanoporous anodic alumina films as planar optical waveguides and studied changes in the effective dielectric constants of these thin films due to various processes occurring in the ...pores. We demonstrate the potential of the porous anodic alumina waveguide for high sensitivity (bio-) chemical sensing with bovine serum albumin adsorption and desorption at various pH values, with subangstrom sensitivity in the effective thickness of protein adsorbed. We also monitored pore widening (alumina dissolution) with subangstrom sensitivity, which is conceptually the reverse of detecting conformal film deposition on pore surfaces. Furthermore, we monitored the exchange of pore-filling media between phosphate buffer solution and ethanol, which produces qualitatively the same response as complete pore filling with other materials by various deposition techniques. Thus porous anodic alumina films may be employed simultaneously as deposition templates and as highly sensitive detectors of processes within the pores.
The manuscript describes a novel method to fabricate a thin composite film based on spin coating in which surface plasmon bands of Au and Ag nanoparticles are effectively coupled with each other ...because of position-selective deposition of both nanoparticles on a self-assembled block copolymer structure. Simple solution blending and subsequent spin coating of Au nanoparticles (NPs) and a block copolymer micelles containing Ag NPs in the core regions offers a facile route for controlling coupled surface plasmon band (SPB) of the two NPs over 100 nm in wavelength in thin solid films. Effective coupling of two individual SPBs relies upon the self-assembled composite structure where Ag and Au NPs are preferentially located in the core and corona regions of the micelles, respectively, allowing not only a controlled interparticle distance but also homogeneous dispersion of the NPs throughout film.
We report a new concept of tuning plasmonic colors of two-dimensional crystalline silver nanoparticle sheets with layer-by-layer structures. The multilayered crystalline sheets fabricated by the ...Langmuir–Schaefer method keep the localized surface plasmon resonance bands at the same position (
λ
max
= 465 nm) on quartz, while they change their colors drastically on metal substrates depending on the number of layers (one to five layers). The response of the absorption spectra was absolutely nonlinear, with maximum absorption for two or three layers. The obtained results were well reproduced by the finite difference time domain simulation. The simulation confirmed that these plasmonic colors originate not only from near-field coupling of plasmon resonance but also far-field nano-optics of the multilayered silver nanoparticle sheets.
A plasmonic metasurface composed of self‐assembled gold nanoparticles enables high‐speed interfacial imaging with high axial and lateral resolution down to the theoretical limit under a widefield ...microscope. This high‐spatiotemporal resolution imaging method monitors “early molecular events” in the adhesion of 3T3 fibroblasts expressing Venus‐paxillin and LifeAct‐mScarlet, revealing unique transient cell dynamics. Upon attaching to the SiO2‐coated plasmonic metasurface, cells exhibit fibrous nascent adhesions spreading radially at the periphery, together with actively moving membrane blebs. These fibrous nascent structures exist transiently during passive spreading and disappear upon transition to active spreading with mature focal adhesions (FAs). The structure forms on a poor‐cell‐adhesive SiO2‐coated surface but not on a fibronectin‐preadsorbed cell‐adhesive surface, suggesting that it temporarily anchors cells to the interface but maintains freedom before active cell spreading. These momentary molecular‐level phenomena at the nanointerface are successfully captured by the herein described high‐spatiotemporal resolution live‐cell imaging method using a plasmonic metasurface.
Fine fibrous nascent adhesions spreading radially at the cell contact position are observed on a poor‐cell‐adhesive SiO2‐coated surface at the early stage of cell adhesion. These momentary molecular‐level phenomena at the nanointerface are successfully captured by our high‐spatiotemporal resolution live‐cell imaging method using a plasmonic metasurface composed of self‐assembled gold nanoparticles.
In this paper, we report on in situ optical/electrochemical investigations using a combination of surface plasmon resonance spectroscopy and electrochemistry in order to determine the complex ...dielectric constants of poly(3,4-ethylenedioxythiophene) (PEDOT) thin films. The PEDOT films were deposited by in situ electropolymerization. The film thickness was monitored by a quartz crystal microbalance. In the electrochemical surface plasmon resonance (EC-SPR) measurements, three wavelengths corresponding to interband and intraband electronic transition regions were used in order to investigate electrochromic properties. The optical conductivity was also determined by EC-SPR measurement with a near-infrared laser wavelength which corresponds to the region outside the anomalous dispersion.
Biotin-capped gold nanoparticles assembled on flat gold with volume fraction f are studied by surface plasmon resonance (SPR) spectroscopy and atomic force microscopy (AFM) in order to estimate the ...dielectric function of the gold nanoparticles based on the Maxwell−Garnett (MG) theory. The complex dielectric function (ε‘, ε‘‘) of the spherical nanoparticles at three representative wavelengths in the vis−near-IR region, i.e., λ = 543, 632.8, and 1152 nm, is estimated for a surface homogeneously covered with nanoparticles in order to discuss the wavelength dependence of the dielectric function. The SPR response of a surface covered with particles in 2D aggregates is also analyzed. The experimental SPR curve of the particle aggregates deviates from the theoretical predictions, suggesting dipole interactions between particles.
Nanometer scale patterning on 2D self‐assembled silver nanoparticle sheets using local oxidation nanolithography (LON) is successfully conducted. The patterns written by means of this method exhibit ...not only topological changes but also changes in the contact potential difference. The silver nanoparticle sheet as an adjusted work function film, which is patternable by LON, has great potential for nano‐optoelectronic device applications.
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