9 Si Nanopowder for Photoluminescence and Hydrogen Generation Materials
369
generation of hydrogen molecules [38–40]. Therefore, oral administration of Si is
expected to prevent oxidative stress-induced diseases.
To prevent oxidative stress-induced diseases by elimination of OH radicals
generated in the body without side effects, the following three requirements should
be satisfied: (i) a large amount of reducing species is present in the body, (ii) the
concentration of reducing species is always maintained high, and (iii) reducing
species reacts only with OH radicals among ROS. Requirement (i) arises from
the high reactivity of OH radicals, which easily attack and oxidize cells, and
therefore, hydrogen is necessary to react with OH radicals before they damage cells.
Requirement (ii) results from continuous generation of OH radicals in the body
due to mitochondrial respiratory metabolism. Other ROSes possess physiological
functions such as immunity, and therefore, their elimination may cause side
effects. Hydrogen reacts only with the most reactive OH radicals among ROSes
(requirement iii), and therefore, no side effects arise by hydrogen.
Hydrogen-rich water may have effects to prevent oxidation stress-induced
diseases. However, the saturated hydrogen concentration in water is only 1.6 ppm at
room temperature, and even in the case of the saturated concentration, only 18 mL
hydrogen gas dissolves in 1 L water. The hydrogen concentration in hydrogen-rich
water is usually much lower because hydrogen easily diffuses to air even when
it is contained in a container. Moreover, in 1 h, the hydrogen concentration in
every organ returns to the initial values before intake of hydrogen-rich water [41].
Therefore, the effects of intake of hydrogen-rich water on oxidative stress-induced
diseases seem to be limited.
Polyphenol [42, 43], vitamin C [44], and vitamin E [45] can eliminate OH
radicals. However, their reducing power is too strong to react with other ROSes.
Therefore, taking a large amount of these species may cause side effects. Moreover,
keeping a high concentration of these species in the body continuously is almost
impossible.
We have demonstrated that the above three requirements can be satisfied with
intake of Si composition, as explained below.
9.2.2 Experiments
Si nanopowder was fabricated from Si powder (Koujundo Chemical Laboratory,
Si Powder ca. 5 μm) by use of the beads milling method with 0.5 mm zirconia
beads, unless otherwise noted. Fabricated Si nanopowder was etched in a 5wt% HF
solution for 10 min at room temperature, followed by immersion in ethanol to make
the surface hydrophilic.
For the reaction with water in the neutral pH region between 7 and 9, the
generated hydrogen volume was obtained by measuring the hydrogen concentration
in water using a TOA DKK DH-35A potable dissolved hydrogen meter, while that
generated by the reaction with strong alkaline solutions was determined just by
measuring the volume after subtraction of the volume of water vapor.
369
generation of hydrogen molecules [38–40]. Therefore, oral administration of Si is
expected to prevent oxidative stress-induced diseases.
To prevent oxidative stress-induced diseases by elimination of OH radicals
generated in the body without side effects, the following three requirements should
be satisfied: (i) a large amount of reducing species is present in the body, (ii) the
concentration of reducing species is always maintained high, and (iii) reducing
species reacts only with OH radicals among ROS. Requirement (i) arises from
the high reactivity of OH radicals, which easily attack and oxidize cells, and
therefore, hydrogen is necessary to react with OH radicals before they damage cells.
Requirement (ii) results from continuous generation of OH radicals in the body
due to mitochondrial respiratory metabolism. Other ROSes possess physiological
functions such as immunity, and therefore, their elimination may cause side
effects. Hydrogen reacts only with the most reactive OH radicals among ROSes
(requirement iii), and therefore, no side effects arise by hydrogen.
Hydrogen-rich water may have effects to prevent oxidation stress-induced
diseases. However, the saturated hydrogen concentration in water is only 1.6 ppm at
room temperature, and even in the case of the saturated concentration, only 18 mL
hydrogen gas dissolves in 1 L water. The hydrogen concentration in hydrogen-rich
water is usually much lower because hydrogen easily diffuses to air even when
it is contained in a container. Moreover, in 1 h, the hydrogen concentration in
every organ returns to the initial values before intake of hydrogen-rich water [41].
Therefore, the effects of intake of hydrogen-rich water on oxidative stress-induced
diseases seem to be limited.
Polyphenol [42, 43], vitamin C [44], and vitamin E [45] can eliminate OH
radicals. However, their reducing power is too strong to react with other ROSes.
Therefore, taking a large amount of these species may cause side effects. Moreover,
keeping a high concentration of these species in the body continuously is almost
impossible.
We have demonstrated that the above three requirements can be satisfied with
intake of Si composition, as explained below.
9.2.2 Experiments
Si nanopowder was fabricated from Si powder (Koujundo Chemical Laboratory,
Si Powder ca. 5 μm) by use of the beads milling method with 0.5 mm zirconia
beads, unless otherwise noted. Fabricated Si nanopowder was etched in a 5wt% HF
solution for 10 min at room temperature, followed by immersion in ethanol to make
the surface hydrophilic.
For the reaction with water in the neutral pH region between 7 and 9, the
generated hydrogen volume was obtained by measuring the hydrogen concentration
in water using a TOA DKK DH-35A potable dissolved hydrogen meter, while that
generated by the reaction with strong alkaline solutions was determined just by
measuring the volume after subtraction of the volume of water vapor.