Template Synthesis of Nanostructured Metals Using Cellulose Nanocrystal - The Nanoscience and Technology of Renewable Biomaterials - page 323

(4)

(4)

(3)

(2)

(3)

(1)

10 20 30 40 50 60 70 80 30 40 50 60 70 80

2 q
(a)

2 q

(b)

Figure 12.6 XRD patterns of metallic nickel obtained by thermal reduction at different
temperatureofNi(II)-depositedCNXLfilms(a);(1)200,(2)300,(3)400,and(4)500 ◦ Cunder
N 2 . (b) ismagnified (x5) diffractionpatterns of (3) and (4) in (a) (reprintedwith permission
fromref46).Copyright2007Elsevier.

3 . 5237 ˚ A(JCPDSfileNo.
04-0850). The broadening in diffraction peaks shows that the product is very small
particles. An average particle size of 8.0 nm was calculated from the half-width of the
peak (111) of the XRD pattern using the Scherrer formula (47). Ni(II) and Cu(II) are
reduced to corresponding metal nanoparticles by high reaction temperature (

=

cubic phase (Fm-3 m (225)) Ni with lattice parameters a

300 ◦ C).
FESEM image of Ni nanoparticles is in Figure 12.7a. Ni nanoparticles of 5-15 nm
diameter are well-dispersed on carbonized CNXL surfaces after thermal treatment at
500 ◦ C. Figure 12.7b shows a high-resolution TEM image of Ni nanocrystals on the car-
bonized CNXL at 500 ◦ C. The sizes of the Ni nanocrystals are in the range of 5-12 nm,
which is in good agreement with XRD and FESEM results. The metallic Ni product was
shown to be a nanocrystal and shows crystalline lattice fringes in a high resolution TEM
image. The Ni crystals grow along the (111) phase with a d spacing of 2.1 A. A selected
area electron diffraction (SAED) pattern exhibited as an inset in Figure 12.7b reveals
reflections from (111), (200), and (220) of crystalline Ni, which is in good agreement
with XRD results. Cu nanoparticles generated show uniform size distribution ( 20 nm)

in diameter on carbonized CNXL, where Cu nanoparticles are embedded into carbon
(Figure 12.7c and d). As the reaction temperature was increased, the crystallinity of
Cu was gradually increased (300

∼

500 ◦ C), aggregation of Cu nanoparticles was also

→

observed.
The proposed mechanism for the formation of nickel and copper nanoparticles is shown
in Equations (12.2) and (12.3). The CNXL releases electrons during the carbonization
process (48). The major part of the CNXL simply degrades into noncrystalline carbon
during the thermal treatment ( 300 ◦ C) under N 2 . The overall carbonization reaction of

CNXL (Equation 12.2), is based on the carbon measurement by XPS. The glucose unit
released 4.8-5.3 carbons according to the XPS results. Then, metal ions are reduced to
elemental metals by electrons released from the CNXL (Equation 12.3).