Supplementary material
Nickel-doped zinc aluminate oxides: starch-assisted synthesis, structural,
optical properties and their catalytic activity in oxidative coupling of methane
Diana Visinescu, Florica Papa, Adelina C. Ianculescu, Ioan Balint and Oana Carp
Diana Visinescu, Florica Papa, Ioan Balint and Oana Carp
Romanian Academy, Institute of Physical Chemistry “Ilie Murgulescu”, Splaiul Independentei
202, 060021 Bucharest, Romania; e-mail:
Adelina C. Ianculescu
University Polytechnica of Bucharest, Gh. Polizu Street no.1-7, 011061 Bucharest, Romania
FTIR spectra of the (Zn,Ni,Al)-starch gel-precursors
The overlaid infrared spectra of starch for two (Zn,Ni,Al)-starch gel precursors,
corresponding to an oxide composition of Ni0.6Zn0.4Al2O4 and Ni0.8Zn0.2Al2O4 are depicted in
Fig. S1. The structured medium intensity band observed on 1000-1050 cm-1 region is attributed
to the stretching vibrations of the C-C and adjacent C-O bonds originated from starch [1].
Significant differences between the two precursors samples are remarked on 1300-1480 cm-1
region, a zone specific to the δ(OCH), δ(COH), δ(CCH) deformations and also to nitrate
characteristic bands. For x = 0.6 an intense and sharp absorption centred at ca. 1384 cm-1 is
present, while for a richer nickel sample (x = 0.8) the band is clearly broadened. The distinct
pattern of the two spectra suggest that the nickel content has determined the assembly of two
different and complicated supramolecular systems in which the (Zn,Ni,Al)-starch incipient
complexe(s) is/are covered and connected through hydrogen bonds to the carbohydrate in excess.
The polysaccharide transformations is more evident for lower quantities of Ni(II) cations. In both
cases is remarked the triplet characteristic for M-O and M-O-M’ bonds of the aluminate spinels
[2] as low-intensity bands , which represents an additional prove that the nucleation centres of
the mixed oxides are already formed in gel-precursors. Water is identified by a medium intensity
band centred at 1639 (for x =0.6) and 1623 (for x = 0.8) cm-1, covering 3000-3500 cm-1 region.
The sharp absorption located at 825 cm-1, observed for both precursors, corresponds to nitrate
anions most probably embedded in the polysaccharide matrix.
Fig. S1. Overlay of the FTIR spectra of starch and (Zn,Ni,Al)-starch gel precursors of
NixZn1-xAl2O4 (x = 0.6, 0.8)
References
[1] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, Part
B, Application in Coordination, Organometallic, and bioinorganic chemistry 6th Ed., 2009.
[2] (a) G.A. Siegel, R.A. Bartlet, D. Decker, M.M. Olmstead, P.P. Power, Charge delocalization
in ruthenium-quinone complexes. Structural characterization of bis(bipyridine)(3,5-di-tertbutylsemiquinonato)ruthenium(II) perchlorate and trans-bis(4-tert-butylpyridine)bis(3,5-di-tertbutylquinone)ruthenium, Inorg. Chem.26 (1987) 1769-1773; (b) R.W. Adams, R.L. Martin, G.
Winter,Possible ligand field effects in metal-oxygen vibrations of some first-row transition metal
alkoxides, Aust. J. Chem.20 (1967) 773-774; (c) A. Kruger, G. Winter, Magnetism, electronic
spectra, and structure of transition metal alkoxides. VIII. Nickel halo methoxides,Aust. J.
Chem.23 (1970) 1-14; (c) C.G. Barraclough, D.C. Bradley, J. Lewis, I.M. Thomas,The infrared
spectra of some metal alkoxides, trialkylsilyloxides, and related silanols, J. Chem. Soc. (1961)
2601-2605.
FTIR spectra for NixZn1-xAl2O4 oxides
FTIR spectra of the corresponding oxides reveal the presence of a broad three-structured
band attributed to the spinelic phase that overlaps the 500-800 cm-1 region (fig. S3). For the
mixed substituted oxides, NixZn1-xAl2O4 (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) the highest energy peak
of the triplet has been associated with vibration of the tetrahedral group (ZnO4), while the bands
located at lower energies are related to tetrahedral (ZnO4)/(NiO4) and octahedral [AlO6]
vibrations [3]. For the two oxide samples, Ni0.6Zn0.4Al2O4 and Ni0.8Zn0.2Al2O4, the differences
remarked for an increased content of nickel, namely the changed pattern of absorptions attributed
to the spinelic phase is most probably resulted from a distinct cations distributions, especially
regarding the Ni(II) metal ions. The weak and sharp band, observed for both samples at
418 cm-1, is an additional prove that indicates that nickel oxide coexist with the spinelic oxide.
Specific bands of starch are still visible in the FTIR spectra of the calcined samples independent
on calcination temperature and time (800oC/1h, for x =0.6 and x = 0.8 and 1000oC/5h for x = 1,
see fig. S4), meaning that the polysaccharide has been strongly associated in (Zn,Ni,Al)-starch
gel precursors and the heating treatment could not remove completely the carbohydrate.
References
[3] L.K.C. de Souza, J.R. Zamian, G.N. da Rocha Filho, L.E.B. Soledade, I.M.G. dos Santos,
A.G. Souza, T. Scheller, R.S. Angélica, C.E.F. da Costa, Blue pigments based on CoxZn1−xAl2O4
spinels synthesized by the polymeric precursor method, Dyes and Pigments 81 (2009) 187-192.
Fig. S2. Overlay of the FTIR spectra of NixZn1-xAl2O4 (x = 0.2, 0.8) oxides
Fig. S3. FTIR spectra of stoichimetric NiAl2O4 calcined at 1000oC for 5h
Fig. S4. SEM images for Ni0.2Zn0.8Al2O4 oxide resulted after
calcination at 800oC for 1 h
Fig. S5. The NIR-UV-Vis spectra of the nickel-doped zinc aluminates oxides, Ni0.2Zn0.8Al2O4
for samples calcinated at 800oC and 1000oC for 1h
Table S1. Color parameters for Ni0.2Zn0.8Al2O4 samples calcinated at 800 and 1000oC.
Ni0.2Zn0.8Al2O4
L*
a*
b*
T = 800oC
20
-4
-2
T = 1000oC
21
-6
-5
(a)
(b)
Fig. S6. The nitrogen adsorption-desorption isotherms for: (a) Ni0.2Zn0.8Al2O4 and (b)
Ni0.2Zn0.8Al2O4 oxides