Preparation and optical properties of novel symmetrical hexadecachlorinatedphthalocyaninato zinc(II) spin coated thin films

Article abstract of DOI:10.1016/j.poly.2007.12.020

Novel symmetrical 1,4,8,11,15,18,22,25-octahexyloxy-2,3,9,10,16,17,23,24-octa-(3,5- dichlorophenoxy)phthalocyaninato zinc(II) was synthesized and characterized by ¹H NMR, ¹³C NMR, MS, UV-Vis, XRD, and IR spectrometry. The synthesized

Full text of DOI:10.1016/j.poly.2007.12.020

Available online at www.sciencedirect.com
Polyhedron 27 (2008) 1256–1261
www.elsevier.com/locate/poly
Preparation and optical properties of novel symmetrical
hexadecachlorinatedphthalocyaninato zinc(II) spin coated thin films
a,
b,1
b
b
a
a
*
S.Y. Al-Raqa , A.S. Solieman , A.A. Joraid , S.N. Alamri , Z. Moussa , A. Aljuhani
a
Department of Chemistry, Taibah University, Madinah, Saudi Arabia
b
Department of Physics, Taibah University, Madinah, Saudi Arabia
Received 1 October 2007; accepted 17 December 2007
Available online 8 February 2008
Abstract
Novel symmetrical 1,4,8,11,15,18,22,25-octahexyloxy-2,3,9,10,16,17,23,24-octa-(3,5- dichlorophenoxy)phthalocyaninato zinc(II) was
1
13
synthesized and characterized by H NMR, C NMR, MS, UV–Vis, XRD, and IR spectrometry. The synthesized ZnPc complex is sol-
uble in various organic solvents such as CH Cl , THF, acetone, and ethyl acetate. This property helped to obtain thin films of the new
2
2
ZnPc complex by spin coating method. The surface morphology of the thin films was investigated by atomic force microscopy, AFM,
and showed that the molecules grow in stacks of rows. The spectrophotometric measurements of transmittance (T) and reflectance (R)
spectra were carried out in the wavelength range 190–3000 nm.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Phthalocyanines; Chlorinated-phenoxy; Spin coated thin film; Solubility
1
. Introduction
epitaxy [4], Langmuir–Blodgett film formation [5], self-
assembled monolayer films [6], and spin-coating technol-
ogy [7,8]. The relationship between the physical properties
of Pc films and the molecular orientation was extensively
investigated by using various techniques [5,9].
Unsubstituted phthalocyanines are sparingly soluble in
most organic solvents, hence, limiting their applications.
The solubility of Pcs can be increased by attaching periph-
eral or non-peripheral solubility-enhancing substituents
such as alkyl, alkoxy, phenoxy and macrocylic groups
and/or the central metal [10]. These substituents enhance
the solubility of phthalocyanines and modify the aggre-
gation state in solution and other physical properties
[11,12].
We report the synthesis of novel hexadecasubstituted
phthalocyaninato zinc(II) by the substitution of Pc with
hexyloxy groups in non-peripheral and chlorinated-phen-
oxy groups in peripheral positions. Thin films of the pre-
pared ZnPcs were deposited by using spin coating
technique onto microscope slide substrates, and their struc-
tural and optical parameters are described.
Phthalocyanines are potential materials in many appli-
cations and technologies. This class of compounds is of a
great interest because of their critical role in emerging tech-
nologies that include photoconductors, solar cells, and
chemical sensors [1–3]. Photoconductivity is one of the
most important properties of phthalocyanines, and inten-
sive research has been carried out to improve their electri-
cal conductivity by doping mechanism or polymerization
methods [1].
Electrical, optical, and structural properties of phthalo-
cyanine thin films are dependent on various parameters
such as evaporation rate, substrate temperature, and
post-deposition annealing. Various methods have been
described for deposition of oriented films of phthalocya-
nines such as vacuum deposition, organic molecular beam
*
Corresponding author. Tel.: +966 507 738708; fax: +966 484 70235.
E-mail address: shaya97@hotmail.com (S.Y. Al-Raqa).
On leave from Physics Department, Alazhar University, Assiut, Egypt.
1
0
277-5387/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.12.020

S.Y. Al-Raqa et al. / Polyhedron 27 (2008) 1256–1261
1257
2
. Experimental
oxy)phthalonitrile (127 mg, 0.196 mmol), zinc acetate
dihydrate 99.999% (excess) and two drops of 1,8-diazabicy-
clo[5,4,0]undec-7-ene (DBU) in dry n-pentanol (10 mL)
was heated to reflux for 12 h under an argon atmosphere.
The reaction mixture was cooled down to room tempera-
ture and the solvent was rotaevaporated under reduced
pressure. The resulting dark green compound was sepa-
rated by silica gel column chromatography using the
appropriate eluent. Column chromatography on silica gel
with n-hexane/DCM 4:1 gave five bands. The required
1,4,8,11,15,18,22,25-octahexyloxy-2,3,9,10,16,17,23,24-
octa-(3,5-dichlorophenoxy)phthalocyaninato zinc(II) (4)
was collected as the final fraction by changing the eluent
to (n-hexane/DCM 3:2) and it was further purified by col-
umn chromatography (silica gel, eluent: petroleum ether
(bp 40–60 °C)/THF 10:1) to afford a waxy green product
All solvents were HPLC grade and used without further
purification. Melting points were determined using Kofler
hot stage melting point apparatus. IR spectra were
recorded on Shimadzu Fourier Transform Infrared Spec-
1
trometer FTIR-400 using KBr disks. H NMR spectra
were recorded on a Bruker AVANCE 400 MHz in the deu-
terated solvents specified, and are reported in parts per mil-
lion (ppm, d).
The films were deposited onto standard microscope slide
substrates of thickness 1 mm at room temperature. The
slide substrates were cleaned ultrasonically in acetone and
then rinsed with deionized water. The films were deposited
using spin coating technique (Specialty Coating Systems
G3P-8 Spin Coater) under nitrogen flow at 2000 rpm for
ꢀ1
2
min. The surface microstructure was measured by atomic
(70 mg, Yield 9%). IR(KBr): m, cm , 3052 (Ar–CH),
2940 and 2850 (CH ). dH (400 MHz, CDCl ): d , ppm
force microscopy (AFM; Veeco CP-II) in non-contact
mode with Si tips at a scan rate of 1 Hz. The film thickness
of 45–50 nm was estimated from AFM measurements.
Transmittance T(k), and reflectance, R(k) spectra of the
films were measured at normal incidence and at an incident
angle of 5°. The measurements were acquired at room tem-
perature in the spectral range 190–3000 nm by using a com-
puter-aided double-beam spectrophotometer Shimadzu
2
3
H
6.90 (8H, t, Ar–H), 6.65 (16H, d, Ar–H), 4.17 (16H, t,
8 ꢁ OCH ), 1.02–1.60 (64H, m), 0.81 (24H, t, 8 ꢁ –CH ).
2
3
d
(400 MHz, CDCl ) ppm 14.0 (CH ), 22.5 (CH ), 25.3
3 3 2
C
(CH ), 29.9 (CH ), 31.4 (CH ), 76.6 (OCH ), 114.4
2
2
2
2
(2 ꢁ CH), 120.4 (C), 123.6 (CH), 135.6 (C), 146.1 (C),
146.9 (C), 157.8 (C), 164.3 (C). MS (GC–FAB): m/z (%)
+
+
2668 [M+H] , MS (GC–FAB): m/z (%) 2668 [M+H] .
3
150 UV–VIS–NIR with a resolution of 0.1 nm. Phthalo-
cyanine diffraction pattern was examined using Shimadzu
3. Results and discussion
XRD-6000 X-ray diffractometer using Cu Ka radiation
˚
(
k = 1.5418 A). The X-ray tube voltage and current were
3.1. Synthesis
4
0 kV and 30 mA, respectively.
Preparation of the phthalonitrile derivative with the
desired substituents is a critical step in phthalocyanine syn-
thesis. In the key intermediate, aryloxy groups substituted
with chlorine atoms were incorporated to increase the sol-
ubility of the resulting phthalocyanine. The oxygen atoms
in the non-peripheral and peripheral positions cause a
bathochromic shift of the long wavelength absorption
maximum which helps to widen the visible window of the
target ZnPc. Therefore, 4,5-bis(3,5-dichlorophenoxy)-3,6-
bis(hexyloxy)phthalonitrile was prepared by the treatment
of 4,5-dichloro-3,6-dihexyloxyphthalonitrile with 3,5-dichlo-
rophenol, 1, and K CO in DMSO, Scheme 1.
2
(
.1. Preparation of 4,5-dichloro-3,6-dihexyloxyphthalonitrile
2)
The compound was synthesized as reported before [13].
2.2. Preparation of 4,5-bis(3,5-dichlorophenoxy)-3,6-
bis(hexyloxy)phthalonitrile (3)
The compound was synthesized following the procedure
reported before [13]. The resulting product was purified by
column chromatography (silica gel, eluent: n-hexane:THF,
2
3
5
:1) to yield 4,5-bis(3,5-dichlorophenoxy)-3,6-bis(hexyl-
It is difficult to synthesize the target ZnPc complex by
direct cylotetramerization of 4,5-bis(dichlorophenoxy)-
3,6-dihexyloxyphthalonitrile in the presence of a catalytic
amount of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) [14].
The steric effect of the bulky substituents on the phthalonit-
rile probably is the reason for the slow reaction progress.
The target ZnPc complex was synthesized according to
the statistical condensation of two different phthalonitriles
procedure [13,15]. The procedure involves the reaction of
4,5-bis(3,5-dichlordphenoxy)-3,6-dihexyloxyphthalonitrile
(3) and 3,6-didecylphthalonitrile (2:1 ratio) in n-pentanol in
the presence of Zn(OAc) ꢂ 2H O and a catalytic amount of
oxy)phthalonitrile (3) as a white solid (280 mg, Yield 85
ꢀ1
%
). IR (KBr): mmax cm 2933, 2851, 1596, 2220 (C„N),
604 (C@C), 1468, 1315, 1263, 1125 (C–O–C), 963, 832.
MS (GC–MS): m/z (CI) 650. dH (400 MHz; CDCl ): d ,
1
3
H
ppm 7.09 (2H, t, Ar–H), 6.71 (4H, d, Ar–H), 4.16 (4H, t,
OCH ), 1.67 (4H, quint, –CH CH (CH ) CH ), 1.2–1.48
2
2
2
2 3
3
(
12H, m, –CH CH (CH ) CH ), 0.82 (6H, t, 2 ꢁ CH ).
2
2
2 3
3
3
2
2
.3. Preparation of 1,4,8,11,15,18,22,25-octahexyloxy-
,3,9,10,16,17,23,24-octa-(3,5-
dichlorophenoxy)phthalocyaninato zinc(II) (4)
2
2
1
,8-diazabicyclo[5.4.0]undec-7-ene (DBU) at 140 °C under
A
mixture of 3,6-didecylphthalonitrile (40 mg
argon atmosphere for 12 h (Scheme 2). The resulting crude
0
.095 mmol), 4,5-bis(3,5-dichlorophenoxy)-3,6-bis(hexyl-
product was subjected to TLC using n-hexane/DCM (3:2)

1258
S.Y. Al-Raqa et al. / Polyhedron 27 (2008) 1256–1261
Cl
OC H
OC H
6
13
6
13
Cl
Cl
Cl
Cl
O
O
CN
Cl
Cl
CN
K2CO3
+
OH
DMSO, 100°C
CN
CN
OC H
6
13
OC H
6
13
1
2
Cl
3
Scheme 1. Synthesis of 4,5-bis(dichlorophenoxy)-3,6-dihexyloxyphthalonitrile (3).
Cl
R'
R'
OC H
6
13
Cl
Cl
O
O
CN
CN
CN
DBU
+
Zn(OAc) .2H O
n-pentanol
2
2
CN
OC H
6
13
R= C H
0 21
1
Cl
Cl
Cl
Cl
Cl
O
O
C6H13O
OC H
6 13
Cl
Cl
OC H
OC H
6
6
13
13
N
N
N
O
O
O
Cl
Cl
Cl
N
Zn
N
Cl
O
N
N
N
OC H
OC H
6
6
13
13
Cl
Cl
C6H13O
OC H
6
13
O
O
4
Cl
Cl
Cl
Cl
Scheme 2. Synthesis of 1,4,8,11,15,18,22,25-octahexyloxy-2,3,9,10,16,17,23,24-octa-(3,5-dichlorophenoxy)phthalocyaninato zinc(II) (4).
as eluent and showed five bands. The first fraction con-
tained the undesired symmetrical octadecylphthalocyanine
Attaching the chlorinated pheneoxy groups to the
peripheral position and hexyloxy groups to the non-periph-
eral position of phthalocyanines enhanced the solubility in
organic solvents [16]. The increased solubility might be due
to that the steric hindrance of peripheral 3,5-dichlorophen-
oxy substituents makes it harder to form dimers of 4. The
prepared ZnPcs show high solubility in various organic sol-
vents such as acetone, benzene, toluene, dichloromethane,
ethyl acetate and tetrahydrofuran.
(
AAAA) compound. The following three bands were pos-
sibly AAAB, AABB and ABBB which can be isolated in
a very small quantity. The final separable green fraction
was the symmetrical phthalocyanine derivative (BBBB),
4
, which was further purified by a new column using petro-
leum ether (bp 40–60 °C)/THF 10:1 as eluent to yield
0 mg (8.4%) as green waxy product. The aromatic region
6
showed two broad signals integrated for 24 protons and
assigned to the phenoxy ring protons. A triplet at
3.2. Electronic absorption spectrometry
4
.17 ppm was assigned to the 16 methylenoxy protons.
The FAB–MS showed an isotopic cluster at 2668 m/e cor-
responding to the expected structure.
The UV–Vis spectrum of 4 in THF solution is typical of
phthalocyanine compound, having a soret and Q-bands

S.Y. Al-Raqa et al. / Polyhedron 27 (2008) 1256–1261
1259
1
0
0
0
0
0
.0
.8
.6
.4
.2
.0
3
00
400
500
600
700
800
900
λ (nm)
Fig. 1. UV–Vis absorption spectrum of 4 in THF solution at room
temperature.
(
Fig. 1). The introduction of dichlorphenoxy groups onto
the phthalocynine periphary increases the Q-band absorp-
tion wavelength of these molecules. The absorption spec-
trum of 4 is characterized by a strong absorption in the
red region and a weaker absorption in the blue region. It
is clear that the absorption bands of the chlorinated phene-
oxy phthalocyanine 4 are shifted to a longer wavelength
compared with the unsubstituted Pc. The spectral shift is
attributed to the distortion of the ZnPc macrocycle and
the electron withdrawing chlorine substituents on the phe-
nyl rings. It is possible that the high electron withdrawing
character of chlorine atoms tends to depopulate the p-sys-
tems, which would lead from a highly symmetrical planar
state to low symmetry state molecule. However, there is
no apparent change in the spectral features by comparing
the chlorinated-phenoxy with the fluorine substituted
phthalocyanines [13].
Fig. 2. 5 lm ꢁ 5 lm AFM surface pattern of thin film of 4: (a) 2-D as-
deposited and (b) 3-D as-deposited.
3
.3. Structural studies
The structure and morphology of phthalocyanine thin
film was examined by using AFM. Many investigations
on the morphology of metal–phthalocyanine have been
reported especially CuPc complexes [17–19]. The molecular
orientation strongly depends on the growth conditions and
substrates. The regular structure of phthalocyanine thin
films is described as a stack of needle-like molecules with
alternating tilt angles so that the molecules are arranged
in zig-zag chains. The growth direction of the molecule col-
umns (b-axis) is normally found either with the b-axis par-
allel to the surface or standing up from the substrate face
with an angle of about 32° from the surface plane [17–19].
Fig. 2a and b shows 5 ꢁ 5 lm 2D and 3D AFM images
of the thin film surface. The molecular arrangement of the
ZnPc crystallites is visible. The phthalocyanine molecules
are growing in aggregation rows rather in the parallel or
in the zig-zag arrangement. The roughness of the films
was estimated to be about 4.2 nm.
0
10
20
30
40
50
2θ (deg.)
Fig. 3. X-ray diffraction pattern of as-deposited thin film of 4.
linity as indicated by the small intensity of the diffraction
peak at 2h = 5.08°. The pattern shows the a form because
it does not show the characteristic double intense peak that
is observed with the b form. The individual crystallite grain
size was determined using Scherrer’s relation [20] and was
found in the order of 16.56 nm.
3.4. Optical studies
Fig. 4 shows the UV-near infrared spectral behavior of
transmittance T(k) and reflectance R(k) of the as-deposited
ZnPc thin film. In Fig. 5, we report the absorption spectra
The XRD results of the as-deposited ZnPc film are
shown in Fig. 3. The film showed a low degree of crystal-

1260
S.Y. Al-Raqa et al. / Polyhedron 27 (2008) 1256–1261
0
0
0
.20
.15
.10
1
1
1
4
2
0
8
6
4
2
0.90
0.85
0.80
0.75
0.70
0
400
0.05
1600
600
800
1000
1200
1400
400
600
800
1000
1200
1400
λ (nm)
λ (nm)
Fig. 6. The variation of absorption coefficient a as a function of
wavelength of thin film of 4.
Fig. 4. Spectral behavior of transmittance T(k) and reflectance R(k) of
thin film of 4.
2
2
2
ðn ꢀ 1Þ þ k
1
0
0
0
.0
.8
.6
.4
R ¼
ð4Þ
2
ðn þ 1Þ þ k
where n is the refractive index.
Using Eqs. (2) and (3), the variation of absorption coef-
ficient, a, with the wavelength was calculated as shown in
Fig. 6.
The spectral distribution of refractive index n(k) for 4 in
the range 200–2800 nm is shown in Fig. 7. The spectrum
shows an anomalous scattering in the range 300–760 nm
with various peaks and a normal dispersion in the wave-
length range 760–2700 nm. A very high rate of decrease is
seen the refractive index in the range of wavelength 760–
1400 nm followed by a very low rate of decrease until about
1
.0
1.2
1.4
1.6
hν (eV)
1.8
2.0
2.2
2.4
2
550 nm whereas the refractive index becomes wavelength-
Fig. 5. Spectral distribution of absorbance A (m) of thin film of 4.
independent. Finally a sudden drop around ꢄ2700 nm
occurs.
of ZnPc thin film as a function of photon energy, hm. There
The variation of absorption coefficient a with photon
are two main absorption bands: Q at about 728 and Q at
I
II
energy hm and the optical energy gap E is obtained from
the following formula [20]:
g
about 655 nm and identified as the Q-band and attributed
to the monomer and dimer, respectively [21].
S
The optical parameters were calculated from the trans-
mission, absorption, and reflectivity data. The average
transmission of a thin film on a substrate is given by [20]:
a ¼ a
0
ðhm ꢀ E
g
Þ
ð5Þ
where a is a constant
0
2
2
2
ð1 ꢀ RÞ ð1 þ k =n Þ
T ¼
ð1Þ
2.6
2
expðadÞ ꢀ R expðꢀadÞ
2
2
.4
.2
where
ak
k ¼ 4
ð2Þ
p
The parameters a, k, d, n, and k are the absorption coeffi-
cient, absorption index, thin-film thickness, refractive in-
dex, and wavelength of the incident light in air,
2.0
1
1
.8
.6
2
2
respectively. In any practical experiments, where k ꢃ n ,
the average transmission is simplified as
2
ð1 ꢀ RÞ expðꢀadÞ
1.4
T ¼
ð3Þ
400
800
1200
1600
2000
2400
2800
2
1
ꢀ R expðꢀ2adÞ
λ (nm)
The reflectivity of an absorbing medium of indices n and k
Fig. 7. Spectral distribution of refractive index n(k) of thin film of 4 in the
in air for normal incidence is given by:
range 200–2800 nm.

S.Y. Al-Raqa et al. / Polyhedron 27 (2008) 1256–1261
1261
1
1
1
1
600
400
200
000
5
Studies using AFM showed that the phthalocyanine mole-
cules are growing in aggregation rows.
4
3
2
1
0
The optical properties of the ZnPc thin film were studied
in the range 200–2800 nm. The absorption spectra recorded
show two main Q-bands: Q at about 728 and Q at about
I
II
655 nm. The spectral distribution of refractive index n(k),
8
6
4
2
00
00
00
00
0
was obtained. The optical band gap of the indirect and
direct transitions were found to be equal to 3.81 and
4.48 eV, respectively.
References
3
.6
3.8
4.0
4.2
4.4
4.6
4.8
5.0
hν (eV)
[1] C.C. Leznoff, A.B.P. Lever, Phthalocyanine-Properties and Applica-
tions, vol. 3, VCH, New York, 1993.
1
/2
2
Fig. 8. Variation of a and a with photon energy hm of as-deposited thin
film of 4.
[2] G. Winter, H. Heckmann, P. Haisch, W. Eberhard, M. Hanack, J.
Am. Chem. Soc. 120 (1998) 11663.
[3] Z.L. Yang, H.Z. Chen, L. Cao, H.Y. Li, M. Wang, Mater. Sci. Eng. B
1
06 (2004) 73.
The exponent S determines the type of transition and
can take the values 1/2, 2, or 3/2 for direct, indirect, and
forbidden transitions, respectively [20]. A satisfactory fit
was obtained for a and a as a function of hm, Fig. 8. This
indicates that the absorption mechanism is due to both the
indirect and direct transitions. The optical band gap of the
[4] D.A. Evans, H.J. Steiner, R. Middleton, T.S. Jones, C.H. Chen, K.
Horn, S. Park, T.U. Kampen, D. Tenne, D.R.T. Zahn, A. Patchett,
I.T. McGovern, Appl. Surf. Sci. 175-176 (2001) 374.
[5] R. Rella, A. Serra, P. Siciliano, A. Tepore, L. Valli, A. Zocco,
Supramol. Sci. 4 (1997) 461.
1
/2
2
[6] M.J. Cook, J. Mater. Chem. 6 (1996) 677.
[7] B.M. Hassan, H. Li, N.B. McKeown, J. Mater. Chem. 10 (2000) 39.
[
8] Z. Ali-Adib, G.J. Clarkson, N.B. McKeown, K.E. Treacher, H.F.
Gleeson, A.S. Stennett, J. Mater. Chem. 8 (1998) 2371.
9] H. Nakahara, K.Z. Sun, K. Fukuda, N. Azuma, H. Nishi, H. Uchida,
T. Katsube, J. Mater. Chem. 5 (1995) 395.
indirect and direct transitions (E ,E ) can be obtained
gi gd
1
/2
from the intercept of a versus hm plots with the energy
axis and a versus hm, respectively (Fig. 8). The results
[
2
obtained for indirect and direct optical band gaps for the
[10] T. Kudo, M. Kimura, K. Hanabusa, H. Shirai, T. Sakaguchim, J.
as-deposited 4 thin film were determined as 3.81 and
Porphyr. Phthalocya. 3 (1999) 65.
11] R.M. Christie, Dyes Pigments 27 (1995) 35.
12] N.B. McKeown, Phthalocyanine Materials, Synthesis Structure and
Function, Cambridge University Press, 1998.
13] S.Y. Al-Raqa, Dyes Pigments 77 (2008) 259.
[
[
4
.48 eV, respectively.
4
. Conclusions
[
[
14] H. Tomoda, S. Saito, S. Ogawa, S. Shiraishi, Chem. Lett. (1980) 1277.
The present work describes the preparation, character-
[15] S.Y. Al-Raqa, J. Porphyr. Phthalocya. 10 (2006) 55.
[
[
16] S. Wie, D. Huang, L. Li, Q. Meng, Dyes Pigments 56 (2003) 1.
17] R. Hiesgen, M. Rabisch, H. Bottcher, D. Meissner, Solar Energy
Mater. Solar Cell 61 (2000) 73.
18] S. Zhu, C.E. Banks, D.O. Frazier, B. Penn, H. Abdeldayem, R.
Hicks, H.D. Burns, G.W. Thompson, J. Crystal Growth 211 (2000)
308.
ization and spin coated film of novel hexadec-
achlorinatedphthalocyaninato zinc(II), which have been
peripherally substituted with eight chlorinated-phenoxy
groups and non-peripherally substituted with eight hexyl-
oxy groups. The synthesized complex possesses excellent
solubility in various organic solvents such as CH Cl ,
[
[
[
19] M.J. Cook, I. Chambrier, in: K.M. Kadish, K.M. Smith, R. Guilard
2
2
(
Eds.), Phthalocyanine Thin Films: Deposition and Structural Stud-
THF, acetone and ethyl acetate.
ies, The Porphyrin Handbook, vol. 17, Academic Press, 2003.
The structure and optical properties of the spin coated
ZnPc thin films of thickness about 45–50 nm have been
studied. X-ray studies revealed the typical structure of
phthalocyanines with the diffraction peak at 2h = 5.08°.
20] S.N. Alamri, A.A. Joraid, S.Y. Al-Raqa, Thin Solid Films 510 (2006)
2
65.
[21] R. Rella, J. Spadavecchia, G. Ciccarella, P. Siciliano, G. Vasapollo,
L. Valli, Sensors Actuators B 89 (2003) 86.