M. BAN, F. SASAKI
114
Figure 6(a). For Figure 6(c), the particles having a shape of
relatively grain were synthesized, and formed sticking to
each other. Therefore, it is noted that at the optimal dis-
charge conditions for generating more ROS, that is to say,
the droplets per discharge of 10 to 20 and the total drop-
lets of 400, the finer needle-like particles were three-di-
mensionally formed as seen in Figure 6(b). Additionally,
the SEM observation results of all ink-jet spotted PDMS
substrates suggested that the particles formation state was
transformed from planar into three-dimensional structure,
and from needle-shaped into grain-shaped particles with
an increase in both the droplets per discharge and the
total droplets.
To investigate the relation between the formation state
of
les formed in the various
di
particles and the ROS production, the total surface
area of the crystalline C60 particles formed on the PDMS
substrate was estimated by the following calculation pro-
cedure. The total amount of the fullerene solution dis-
charged was calculated by the product of an amount of
one droplet (4.2 pl, supposing that the diameter was 20
μm) and the number of total droplets. The weight of all
crystalline C60 particles formed on the PDMS substrate
was calculated with the total discharged amount and the
concentration of the C60 dissolved in the solution, 35
mg/ml. Here, the weight of one crystalline C60 particle
was obtained using the density of C60, 1.73 g/cm3 [11],
and the sizes of the crystalline C60 particles measured
from the SEM images. Assuming that all dissolved fulle-
rene in the fullerene solution was precipitated as the crys-
talline C60 particles, the number of the crystalline C60
particles formed on the PDMS substrate was obtained
from the weight of one crystalline C60 particle and the
calculated weight of all crystalline C60 particles formed
on the PDMS substrate. Multiplying the surface area of
one crystalline C60 particle, which was calculated from
the size measured using the SEM observation results, by
the number of the crystalline C60 particles, the total sur-
face area of the crystalline C60 particles formed on the
PDMS substrate was obtained.
For the crystalline C60 partic
scharge conditions, the variation of the ratio of in-
creasing rate in the case of using DCF-DA (see Figure 5
(a)) as a function of the calculated total surface area of
the particles is shown in Figure 7. The figure revealed
that there appeared to be two tendencies (plots of group I
and II) of the ratio of increasing rate against the total
surface area of the particles. That is to say, for group I
and II, the ratios of increasing rate were increased and
almost unchanged with an increase in the surface area of
the particles, respectively. The crystalline C60 particles
belonging to group I had a three-dimensionally formed
finer structure as observed in the image of Figure 6(b),
and it was suggested that larger exposed particle sur-
face led to more production of ROS. Meanwhile, for the
Figure 7. Variation in the ratio of increasing rate as a fnc-
rystalline C60 particles in group II the increment of the
4. Conclusion
particles were formed on the PDMS
5. Acknowledgements
xpress many thanks to Mr.
REFERENCES
[1] E. Nakamura lized Fullerenes in
u
tion of the total surface area calculated for the crystalline
C60 particles formed under the various discharge conditions.
The dotted lines are drawn to guide the eye.
c
surface area made little contribution to ROS generation
because it was highly probable that the particles were
stuck together to form larger clumps, as seen in Figure
6(c).
The crystalline C60
substrates under the various discharge conditions by the
ink-jet spotting system, and investigated for the relation-
ships among the conditions, the shape and the structure
of particles, and the ROS generation. The fluorescence
measurement results implied that the formed crystalline
C60 particles mediated the generation of ROS, hydrogen
peroxide and superoxide anion. The optimal ink-jet dis-
charge conditions, the droplets per discharge of 10 to 20
and the total droplets of 400, existed for synthesizing the
crystalline C60 particles to generate more ROS. It was
indicated from the SEM observation results that under
the optimal conditions the finer needle-like particles were
three-dimensionally formed. It was found that there was
a possibility that increasing the surface area of crystalline
C60 particles led to an increase in the ROS generation
amount, considering that the particles formed under the
optimal conditions had larger surface area.
The authors would like to e
Manabu Suzuki of Research & Development Center for
Advanced Materials and Technology, Nippon Institute of
Technology for TEM observations and the specimen prepa-
ration. This work was supported by KAKENHI (22510125).
and H. Isobe, “Functiona
Water,” Accounts of Chemical Research, Vol. 36, No. 11,
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