23P025-O
Fabrication and evaluation of ring-shaped PS@Au metallodielectric nanoshell arrays
リング型PS@Auプラズモニックナノシェルアレイ作製とその評価
Y.Yamamoto1, S.Uchida1, N.Zettsu2 and K.Yamamura1
山本悠人, 内田修平，是津信行，山村和也
1Research Center for Ultra-Precision Science and Technology,
Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan2
Department of Materials, Physics and Energy Engineering Graduate School of Engineering, Nagoya University,Furocho, Chikusa-ku, Nagoya, Aichi 466-8603, Japan1
大阪大学 超精密科学研究センター 〒565-0871 吹田市山田丘2-1
2
名古屋大学 工学研究科 〒466-8603 名古屋市千種区不老町
We have demonstrated the fabrication of two-dimensional periodical non-close packed arrays ofsphere-shaped polystyrene(PS)@Au metallodielectric plasmonic nanoshell. The fabrication process ofnanoshell arrays is constructed by stepwise integration of colloidal self-assembly of PS nanoparticle
monolayer, dry-etching under atmospheric pressure plasma, and surface metallization. Air-plasma
treatment, with filament discharge, enabled to fabricate ring shaped PS array from sphere PS nanoparticles
by combination of etching and sputter deposition. We succeeded in fabrication of ring-shaped PS@Aunanoparticles array in large area and evaluated the optical property.

1. Introduction
Recently, the localized surface plasmon
resonance (LSPR) nanosensor becomes a hot spot
due to their unique characteristics. The LSPR-based
biosensor has many advantages such as
convenience, high sensitivity, wide application,
real-time detection, etc. Optical properties of themetal nanoparticles mainly depend on their size,
shape, metal composition, and refractive index of
the surrounding materials. For use as ultrasentitive
detectors of biomolecular, LSPR peak shift withchange in refractive index by antigen-antibody
reaction is observed, after antibody or antibody
fragments are immobilized on the nanoparticles.
For biomedical applications that require deeper
penetration of near-IR light (800-1200nm) to which
both blood and soft tissues are highly transparent,
we have thought to fabricate PS@Au
metallodielectric nanoshell arrays to make use ofplasmon hybridization [2][3]. In this study, we aim
at fabrication of ring-shaped PS@Au nanoparticles
in large area in order to improve the sensing
sensitivity.
2. Experimental Section
Fabrication procedures of ring-shaped nanoshellarray consists of four main steps as follows: (1)coating a substrate with ultarathin film of PS as
binding layer; (2) deposition of packed spherical PS
nanoparticles of monolayer by spin-coat-assisted
colloidal self-assembly; (3) atmospheric pressureplasma etching to fabricate non-close-packed
periodic array of PS nanoparticles and convert

original
sphere-shaped
intoring-shaped
nanoparticles; (4) Au metalizing by vacuum vapor
deposition.
We used commercially available monodisperse
PS particles with a diameter of 320 nm whose
surface was modified with sulphonic functionalgroup. A densely packed array consisting of asingle layer of spherical PS nanoparticles wasdeposited on a substrate by spin-coating from
aqueous solution at a concentration of 10wt%.
Atmospheric pressure air-plasma, which
modifies the surface of the PS ultrathin film andfabricates non-close-packed array of ring-shaped PS
nanoparticles, was generated by a dielectric barrierdischarge (DBD) plasma reactor. The DBD reactor
consisted of an aluminum plane-electrode and acopper rod-electrode covered by alumina. The gap
between the copper/alumina electrode and sample
was adjusted to 0.5mm. We used a bipolar pulse
power supply with the frequency of 1 kHz and thepulse width of 5 s.
PlasmaPulleyBearingmotor

Fig. 1.
electrode.

Schematic diagram of the rotating

The copper/alumina electrode was rotated togenerate uniform plasma along with longitudinal
direction of rod electrode. The flow of the air
occurred by the rotating electrode and prevented thegeneration of the discharge locally fixed. The
electrode was rotated with a motor, a pulley, apulley belt, and bearings, and applied the pulse
voltage through the bearing (Fig. 1.).
3. Results and Discussion
The DBD generated a gas-phase etchingenvironment which consists of neutrals, electrons,photons, radicals, and positive and negative ions. In
the optical emission spectrum obtained from theplasma, the emission spectra of the second positive
band of N2 were obtained but there was no emission
spectrum from atomic oxygen under the applied
peak voltage of 5kV.
The PS nanoparticles array had been exposed
under the DBD air plasma with the filamentary
discharge by the bipolar pulse power supply (5kV)
to fabricate non-close-packed periodic array. As aresult, the PS nanoparticles were etched and thering-shaped PS nanoparticles were fabricated asshown in Fig. 2.(a). Fig. 1.(b) shows the schematicof preferential etching of the PS nanoparticle andcreating of the PS nanoring. The PS nanosphere and(a)

1m
(b)

1.

2.

3.

4.

Fig. 2. (a) SEM image of PS nanoringarrays. (b) Schematic illustration ofplausible formation mechanism of PSnanoring.

1mFig. 3. SEM image of PS@Au nanoringarrays.
the PS ultrathin film were etched by air plasma
treatment (b-1). The isotropic PS nanospheres weretransformed into the anisotropic shape because theplasma treatment preferentially etched the top of PS
nanoparticles and the different curvature wasobserved between the top and the bottom ofnanoparticles (b-2). The plasma was also used toremove the PS ultrathin film. During the etching,
the secondary sputtering created the deposition
around the base of the nanoparticle (b-3). As theetching progressed, the deposited particles grewlarger because of the sputtering from PS film
whereas the PS nanoparticle was etched smaller.
Finally, the ring-shaped PS nanoparticle remainedon the substrate (b-4).
Fig. 3. shows SEM image of nanorings array
after metalizing of PS nanoparticles surface byusing thermal deposition. Their surface plasmonic
properties were evaluated by UV-vis-near-IR
spectroscopy, and a plasmon peak at 797nm wasobserved. The peak came from the structure of
ring-shaped PS arrays, because the peak was notobserved without the nanoring arrays.
4. Conclusions
Discrete PS nanoring arrays with monolayer
were successively fabricated by the DBD air plasma
etching. The ring-shaped PS@Au nanoparticles
were fabricated by deposition of Au thin film on PS
nanorings. The plasmon peak appeared in nearinfrared. The Au film is deposited on the substrateby thermal vapor deposition. Only PS particles
surface will be metalized by plating.
References[1] E. Prodan, C. Radloff, N. J. Halas, Science 302,(2003)409.
[2] S. Uchida, K. Yamamura, N. Zettsu, Thin
Solid Films 518, (2010) 3581.
[3] S. Uchida, K. Yamamura, N. Zettsu, J.
Nanosci. Nanotechnol. 11, (2011) 2956.