We have developed a nanoscale strurctue measment system based on a digital micromirror device (DMD) based structured illumination microscopy (SIM) capable of wide-range and high-resolution imaging. The DMD based SIM yields the widefield images with the 20 different illumination patterns,a laser source with 349 nm wavelgnth, and a high sensitivity sCMOS camera the UV range. The developed image acquistion and reconstruct process can enhnace the imaging resolution under 150 nm and maximize the imaging area. In order to find practical applications of the SIM system, we prepared metallic nano pattern samples fabricated using FIB milling process and PET film samples fabricated using nano imprinting process that sample has nanohole structure with a diameter of 150 nm. The DMD based SIM system can reconstruct the nanostructure image with an large area and the obtained SIM images were compared with the SEM result to verify the improved resolution.
The surface plasmon erupted by bare metallic film has limitation of localizing high intensity field. Thus, nanostructures on the metallic film (such as nanowire, nanopost) have been used to enhance the Plasmon field by antenna effect. In the case of nanowire, field is highly localized at the sharpened edge of the nanowire. If there is an additional enhancing factor such as a gap between the edges of the nanostructures, area of highly localized field is formed. By adopting reversed trapezoidal structure, we expected to control area and intensity of highly localized plasmon field from both the nano-antenna effect and the gap plasmonic effect. So, we simulated trapezoidal nanowire structure changing the ratio of bottom length and top length of nanostructure. Then we can observe the variation of Plasmon field and intensity. In addition, we can obtain unusual result that the intensity of Plasmon field is highly reduced at specific ratio of bottom length and top length.
The effective confinement of light in a deep-subwavelength volume can be achieved in metallic nanostructures through the electronic resonance, surface plasmons (SPs). There are few ways to enhance the localization of the field such as adopting metallic nanopost or nanowire structures on the precious metallic film. The achieved highly enhanced field localization through SPs can be exploited for surface-enhanced spectroscopy, biosensor, enhancing energy emitter, and enhanced energy generator. Also, many researches have been tried with few-nanometer gap between the metals for achieving large field enhancements. In this paper, by comparing the scattering of gold nanoparticles, the effects of metallic film of substrates were investigated through simulation. In addition, as changing of the gap between gold nanoparticle and metallic surface, different resonance wavelengths were observed in scattering spectra from simulation and practical experiments. We confirmed that the gold film with gold nanoparticles shows the most distinctive scattering spectra. The numerical demonstration was matched with our experimental demonstration, also with the previously introduced papers as well.
Recently, the portable and wearable electronic devices, operated in the power range of microwatt to miliwatt, become available thank to the nanotechnology development and become an essential element for a comfortable life. Our recent research interest mainly focuses on the fabrication of piezoelectric nanogenerators based on smart nanomaterials such as zinc oxide novel nanostructure, M13 bacteriophage. In this talk, we present a simple strategy for fabricating the freestanding ZnO nanorods/graphene/ZnO nanorods double sided heterostructures. The characterization of the double sided heterostructures by using SEM, and Raman scattering spectroscopy reveals the key process and working mechanism of a formation of the heterostructure. The mechanism is discussed in detail in term of the decomposed seed layer and the vacancy defect of graphene. The approach consists of a facile one-step fabrication process and could achieve ZnO coverage with a higher number density than that of the epitaxial single heterostructure. The resulting improvement in the number density of nanorods has a direct beneficial effect on the double side heterostructured nanogenerator performance. The total output voltage and current density are improved up to~2 times compared to those of a single heterostructure due to the coupling of the piezoelectric effects from both upward and downward grown nanorods. The facile one-step fabrication process suggests that double sided heterostructures would improve the performance of electrical and optoelectrical device, such as touch pad, pressure sensor, biosensor and dye-sensitized solar cells. Further, ioinspired nanogenerators based on vertically aligned phage nanopillars are inceptively demonstrated. Vertically aligned phage nanopillars enable not only a high piezoelectric response but also a tuneable piezoelectricity. Piezoelectricity is also modulated by tuning of the protein's dipoles in each phage. The sufficient electrical power from phage nanopillars thus holds promise for the development of self-powered implantable and wearable electronics.
In this presentation, we explore the feasibility of plasmonic nanohole-based sub-diffraction-limited nanoscopy for biomolecular imaging. The technique utilizes near-field distribution localized by surface plasmon localization on metallic nanoholes which is used to sample molecular fluorescence. The optimum geometry of nanohole arrays was determined by numerical analysis. The localization sampling was applied to reconstructing sub-diffraction-limited images of gliding microtubules with a 76 nm effective resolution in the lateral direction. Extraordinary light transmission was also employed to address enhancement of axial resolution using nanohole arrays, based on which extraction of gliding motions of bacteria was demonstrated with an axial resolution down to 50 nm.
We have considered linear nanoaperture arrays for super-resolved live cell imaging. The nanoaperture arrays consist of nanoholes of varying diameter. Each nanohole localizes near-field distribution and produces extraordinary optical transmission (EOT) by surface plasmon localization. Much deeper light penetration was achieved in EOT than under total internal reflection. The results can be used to implement subdiffraction-limited axial resolution when applied to microscopy.
This research is about surface-enhanced Raman spectroscopy based on the gap-plasmonic effects between the silver nanoisland (AgNI) substrate and gold nanoparticles (AuNPs). With calculation, we prove that plasmonic-coupling phenomena between AuNPs and AgNIs were formed, which eventually affect to the signal enhancements, and we simulate the field enhancement according to the AuNPs position on the AgNI substrates. Consequently, we experimentally confirm the Raman signal enhancement using target as AuNP attached DNA, which were distributed on the AgNIs substrate randomly. Raman spectra measured on the AgNI substrate exhibit approximately 20-fold signal enhancements compare to the signals measured on a uniform silver film, and the experimental spectra agreed well with the results of simulation. This method has merit in that significant Raman signal enhancements can be achieved for large areas without a complicated nano-lithographic process.
A super-resolved axial imaging technique was investigated based on extraordinary transmission (EOT) of light using metallic gradient nanoaperture arrays. Light through subwavelength nanoapertures at thick metal film can be transmitted and amplified by several orders of magnitude due to plasmonic coupling. Here, the feasibility of EOT-based axial imaging with super resolution is explored. Since light penetration of EOT is much deeper than that of evanescent waves, the axial range to obtain the distance information of fluorescence signals can be extended by EOT. The axial distribution of ganglioside in mouse macrophage cells was measured with sub-diffraction-limited resolution after reconstruction using differential fluorescence excitation on gradient aperture arrays.
Surface enhanced Raman spectroscopy (SERS) based on plasmonic colocalization between DNA attached gold nanoparticles and silver nanoislands substrates. Raman spectra measured on a silver nanoislands substrate were observed 20 and 1.8 folds signal enhancements relative to them on a film substrate with high and low numerical apertures of lenses, respectively. By comparison between calculations and experiments results, we proved that distinct differences of the signal enhancements came from changing field of view on random nanoislands substrate. Consequently, we show that nanoislands substrates with a precise position control can be a good candidate for a SERS substrate which can achieve significant signal enhancements without a complicated lithographic process.
In this study, we investigated light transmission based on a metallic nano-lens for imaging applications. The nano-lens
consists of multiple nano-rings formed in a thin metal film. Four types of nano-lens structures in a 50-nm thick gold film
were simulated using rigorous coupled-wave analysis. Each nano-lens is designed to operate as a lens element that
focuses transmitted light. The results show the focal power increasing with the ring number and the enhancement of
achievable numerical aperture compared to that of conventional lenses.
In this study, we explore the relation between near-field and far-field characteristics of plasmon-enhanced total internal
reflection fluorescence (TIRF) imaging. It was found that a significant disparity exists between near-field intensity
maximum of evanescent fields and reflectance minimum in the far-field. The disparity tends to be larger when plasmons
are localized by surface nanostructures. Experimental data with nanogratings and nanoislands as well as theoretical
results are presented. The disparity can be considered to optimize plasmon-enhanced TIRF microscopy.
We present the enhancement of total internal reflection fluorescence microscopy by the excitation of
localized surface plasmons using nanoisland embedded subwavelength grating. The presence of
nanoislands may provide additional field enhancement even at moderate grating period. For fabrication of
nanoisland embedded grating patterns, a silver film was first evaporated on a glass substrate. Next, silver
grating was patterned by e-beam lithography. Subsequently, nanoisland shapes were chemically formed.
Field enhancement was measured by fluorescent excitation of microbeads on periodic silver nanoislands.
The performance is compared to the microbead excitation on a silver nanograting without nanoislands
and nanoislands formed on a thin film without grating patterns as controls. The result confirms additional
field enhancement by nanoisland embedded periodic patterns.
We present the sensitivity improvement of total internal reflection fluorescence microscopy for imaging intracellular molecular movements near cell membranes. We investigated employing dielectric films on a prism substrate for the enhancement of fluorescence emission intensity. A two-layer dielectric thin film structure using Al2O3 and SiO2 was designed and fabricated to provide the maximal field enhancement for 442 nm excitation at a reasonable angle of incidence (&Thgr;). The field enhancement achieved by the design was 8.5 at &Thgr; = 53.8º for TE polarization and confirmed experimentally using microbeads. Preliminary results in live cell imaging were obtained using quantum dots.
For investigatoin of intracellular protein interactions, quantum dots are widely used for fluorescent live cell imaging such
as total internal reflection fluorescence (TIRF) microscopy and confocal microscopy. In this paper, we performed a
quantitative analysis based on fluorescent intensity. For the measurement, A431 cell lines are imaged live with quantum
dots using TIRF microscopy. The distribution of quantum dots is affected by a TATHA2 peptide sequence in live cells.
This paper also presents the location change of quantum dots due to a nuclear localization signal in A431 cell lines.
Confocal microscopy was used to confirm the relation with fluorescent intensity and quantum dot concentration in live
cells.
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