Unconventional Method for Morphology-Controlled Carbonaceous Nanoarrays Based on Electron Irradiation of a Polystyrene Colloidal Monolayer
Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea. ACS Nano
(Impact Factor: 12.88).
07/2008; 2(6):1108-12. DOI: 10.1021/nn8001483
An unconventional and straightforward route to fabricate morphology-controlled 2D ordered carbonaceous nanoarrays is presented. This route is based on the electron irradiation of a polystyrene colloidal monolayer followed by thermal decomposition. This strategy has the advantages of low-cost fabrication and easy manipulation compared to conventional lithography technique and furthermore overcomes the disadvantage of the self-assembly technique that generally has the defect of irregular units in ordered arrays. Various nanoarrays with irregular units, including network-like and star-like ordered arrays as well as hexagonal non-close-packed dot arrays, were fabricated by this novel route. These ordered arrays can be used as templates or masks to fabricate other ordered structures and then can be removed completely by thermal decomposition at a high temperature. Additionally, these arrays are carbonaceous materials that have higher thermal stability and higher refractive index compared with those of the pristine polymer, which are important for real applications such as optical devices. This method might also be used for the fabrication of other unique ordered arrays if different polymer precursor materials are used.
Available from: Kazuya Yamamura
- "The scanning electron microscopy (SEM) image of the PS nanoparticle monolayer fabricated on glass substrates is shown in Figure 2a. In Figure 2b, presenting Au nanoshell arrays, even though structural defects coming from its initial structure were observed, the nanoshell has a monodispersive size distribution compared to other methods of achieving isolated nanoparticle arrays [15,16]. We can precisely control the diameter of nanoparticles and the gap distance by changing the plasma etching time. "
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ABSTRACT: In this work, we focused on the label-free detection of simple protein binding using near-infrared light-responsive plasmonic nanoshell arrays with a controlled interparticle distance. The nanoshell arrays were fabricated by a combination of colloidal self-assembly and subsequent isotropic helium plasma etching under atmospheric pressure. The diameter, interparticle distance, and shape of nanoshells can be tuned with nanometric accuracy by changing the experimental conditions. The Au, Ag, and Cu nanoshell arrays, having a 240-nm diameter (inner, 200-nm polystyrene (PS) core; outer, 20-nm metal shell) and an 80-nm gap distance, exhibited a well-defined localized surface plasmon resonance (LSPR) peak at the near-infrared region. PS@Au nanoshell arrays showed a 55-nm red shift of the maximum LSPR wavelength of 885 nm after being exposed to a solution of bovine serum albumin (BSA) proteins for 18 h. On the other hand, in the case of Cu nanoshell arrays before/after incubation to the BSA solution, we found a 30-nm peak shifting. We could evaluate the difference in LSPR sensing performance by changing the metal materials.
Available from: Ghafar Ali
- "In our previous study, we have found that the band-edge positions as well as the bandgap of PCBM can be tuned by electron irradiation at different fluences . We believe that electron irradiation technique can be an alternative and unique method to modify the molecular structure and tune the bandgap [22,23] compared to the conventional methods such as adjusting the particle size of quantum dots [24,25] or modifying the molecular structure of the dyes  for larger light absorption. In addition to the bandgap, the band-edge positions can also be tuned by electron irradiation compared to the conventional methods such as ionic adsorption for specific quantum dots  or by varying the conjugation linkers in organic dyes . "
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ABSTRACT: The photoelectrochemical (PEC) responses of electron-irradiated [6,6]-phenyl-C61-butyric acid methyl ester (PCBM)/TiO2 electrodes were evaluated in a PEC cell. By coating PCBM on TiO2 nanoparticle film, the light absorption of PCBM/TiO2 electrode has expanded to the visible light region and improved the PEC responses compared to bare TiO2 electrode. The PEC responses were further improved by irradiating an electron beam on PCBM/TiO2 electrodes. Compared to non-irradiated PCBM/TiO2 electrodes, electron irradiation increased the photocurrent density and the open-circuit potential of PEC cells by approximately 90% and approximately 36%, respectively at an optimum electron irradiation condition. The PEC responses are carefully evaluated correlating with the optical and electronic properties of electron-irradiated PCBM/TiO2 electrodes.
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ABSTRACT: A novel approach to pattern nanocrystalline gold (Au) octahedra is presented based on electron irradiation combined with thermal treatment and post-cleaning process using HAuCl4-loaded poly(styrene-b-2-vinyl pyridine) (PS-b-P2VP) block copolymer (BCP) as a precursor material. The BCP tends to cross-link under electron irradiation, and thus a patterned film can be prepared by selectively irradiating an electron beam onto a precursor film using a shadow mask. A post-thermal treatment leads to the formation of crystalline Au nano-octahedra inside the patterned film with a help of the BCP acting as a capping agent. Subsequently, the BCP can be removed by O2 plasma etching combined with oxidative degradation, with the Au nanoparticles remaining. As a result, a patterned film consisting of high-purity nanocrystalline Au octahedra is fabricated. The sizes of the Au octahedral nanoparticles can be readily controlled from 49 to 101 nm by changing the thickness of the precursor film. The patterned Au nano-octahedra films exhibit excellent surface-enhanced Raman scattering behavior with the maximum enhancement factor of ~106.
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