Biosynthesis of (MWCNTs)-COOH/CdO hybrid as an effective catalyst in the synthesis of pyrimidine-thione derivatives by water lily flower extract

Article abstract of DOI:10.1080/24701556.2020.1841229

Pink Water lily flower, with the scientific name of Nymphaea alba in the family of Nymphaeaceae, was collected from North of Iran, Mazandaran in spring, dried in shade and powdered. The powdered flower material was extracted in 70% (vol/vol) ethanol. Acid

Full text of DOI:10.1080/24701556.2020.1841229

Inorganic and Nano-Metal Chemistry
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Biosynthesis of (MWCNTs)-COOH/CdO hybrid as an
effective catalyst in the synthesis of pyrimidine-
thione derivatives by water lily flower extract
Shahrbano Kaveh , Navabeh Nami , Banafsheh Norouzi & Ali Mirabi
To cite this article: Shahrbano Kaveh , Navabeh Nami , Banafsheh Norouzi & Ali Mirabi (2020):
Biosynthesis of (MWCNTs)-COOH/CdO hybrid as an effective catalyst in the synthesis of
pyrimidine-thione derivatives by water lily flower extract, Inorganic and Nano-Metal Chemistry, DOI:
10.1080/24701556.2020.1841229
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INORGANIC AND NANO-METAL CHEMISTRY
https://doi.org/10.1080/24701556.2020.1841229
Biosynthesis of (MWCNTs)-COOH/CdO hybrid as an effective catalyst in the
synthesis of pyrimidine-thione derivatives by water lily flower extract
Shahrbano Kaveh, Navabeh Nami, Banafsheh Norouzi, and Ali Mirabi
Department of Chemistry, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran
ABSTRACT
ARTICLE HISTORY
Received 25 April 2020
Accepted 18 October 2020
Pink Water lily flower, with the scientific name of Nymphaea alba in the family of Nymphaeaceae,
was collected from North of Iran, Mazandaran in spring, dried in shade and powdered. The pow-
dered flower material was extracted in 70% (vol/vol) ethanol. Acid functionalized multi-walled car-
bon nanotubes/CdO (MWCNTs-COOH/CdO) was fabricated by using the Water lily flower extract.
The presence of CdO nanoparticles and their surface conjugation to MWCNT have been confirmed
by FT-IR, X-ray diffraction, transmission electron microscopy, scanning electron microscopy and
energy-dispersive X-ray spectroscopy. It was used as a highly efficient catalyst for the synthesis of
some pyrazolo[3,4-d]pyrimidine and pyrido[2,3-d]pyrimidine derivatives. These compounds were
synthesized by the reaction of some substituted pyrazole or pyridine, thiourea and I2 in the pres-
ence of MWCNTs-COOH/CdO hybrid (5% mol) in warm water. The assigned structure was further
established by CHN analyses, NMR and FT-IR spectra.
KEYWORDS
Water lily flower extract;
biosynthesis; MWCNTs-
COOH/CdO; nonocomposite;
pyrimidine-thione
derivatives
Introduction
reaction.[23,24] Nymphaea alba belongs to the Nymphaeaceae
family to know as Water lily or Lotus is an aquatic flower-
ing plant.[25] This plant grows in the wetland and slightly
acidic water. The roots and stems of water lily are in the
water; the broad leaves are on the surface of water toward
the sun and flowers are in the air. Nymphaea alba contains
some active chemical compounds like alkaloids, gallic acid,
sterols, flavonoids, glycosides, tannins, and polyphenolic
compounds,[26,27] because of them all parts of the plant
especially the flower extract have been used in
phetochemistry.[28]
According to the above reasons, we predict that the com-
bination of CdO nanoparticles and acid functionalized
multi-walled CNTs can be helpful to increase catalytic activ-
ity for the synthesis of heterocyclic compounds. So in this
paper, we present a simple and inexpensive biosynthesis of
MWCNTs-COOH/CdO hybrid using pink Water lily flower
extract in good yield and under mild reaction conditions.
MWCNT-COOH/CdO hybrid was used as an effective cata-
lyst for the synthesis of some pyrazolo[3,4-d]pyrimidine and
pyrido[2,3-d]pyrimidine derivatives by reaction of some sub-
stituted pyrazole or pyridine with thiourea and I2 in
warm water.
Multi-walled carbon nanotubes (MWCNTs) were the first
kind of carbon nanotubes (CNTs) to be reported and they
have attracted much attention due to their unique physical
and chemical properties and also many potential applica-
tions such as drug delivery,[1,2] electronics,[3] catalysis,[4–6]
biosensors,[7] biomedical,[8] storage,[9] and photovol-
taic[10] activities.
It has been indicated that the MWCNTs properties can
be dramatically influenced by surface modification with
chemical and biological compounds.[11,12] Nanometal and
nanometal oxide particles immobilized MWCNTs have
shown excellent catalytic properties in organic reactions.[13]
Many metal oxides and sulfides have been used to modify
the MWCNTs.[14,15] Due to the presence of a high surface
area of MWCNT–COOH/MxOy hybrid, it can be employed
as an alternative catalyst supports, high dispersion, outstand-
ing stability, and convenient catalyst recycling.[16] On the
other hand, CNTs are effective supports for nanometal par-
ticles (NPs) like zinc oxide, cadmium oxide (CdO), nickel
oxide or manganese oxide, and together they represent
hybrid structures (NP-CNTs) that combine the unique prop-
erties of both.[17] CdO is one of the most attractive semicon-
ductor materials. It has a tunable bandgap, which proves to
be a useful catalyst,[18] sensor,[19] nonlinear material,[20]
solar cell[21] and antibacterial device.[22]
Experimental
Chemicals and instrumentation
The scientists are very interested in the biosynthesis of
nanomaterials using plants because this method focuses on All chemicals and solvents were purchased from Merck and
the production of the desired product without producing Aldrich. The production of nano compounds were moni-
harmful intermediate byproducts during the chemical tored by measuring the UV-Vis spectrophotometer
CONTACT Navabeh Nami
Navabehnami@yahoo.com
Department of Chemistry, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran.
ß 2020 Taylor & Francis Group, LLC

2
S. KAVEH ET AL.
(JENWAY 650), in the wavelength range of A200 to magnetic stirring, the aqueous solution of Cd(NO3)2 (0.02
A800 nm and determined by powder X-ray diffraction
(XRD) PW 3040/60 X’Pert PRO diffractometer system, using
Cu Ka radiation with (k ¼ 1.5418 Å) in the range of
2h ¼ 20–80ꢀ at room temperature. The morphology and
sizes of NPs were evaluated using a scanning electron
microscope (SEM) and transmission electron microscope
(TEM, 150 kV, and Philips-CM 10) by Day Petronic
Company-Iran. FT-IR measurements were recorded on a
Shimadzu 8400s spectrometer with KBr plates. The NMR
spectra were recorded on Bruker XL 400 (400 MHz) instru-
ments; Mass-spectrometric measurements were made on an
Agilent 6890 N Network GC system. The C, H, N analyses
were performed by the microanalytical service of
Daypetronic Company. Melting points were determined on
an Electrothermal 9100 without further corrections.
M, 50 mL) was added dropwise into the reaction mixture
through a dropping funnel and gently stirred at 60 ꢀC using
temperature-controlled magnetic stirrer for 2 h, after that
0.02 M NaOH was added dropwise to the solution to achieve
the pH 10. The mixture was stirred for 24 extra hours. The
completion of the reaction was monitored by UV-Vis spec-
tra at 300–600 nm (kmaxes¼221,274,401 nm). After comple-
tion of the reaction, the precipitate was purified by several
re-dispersions in deionized water and then centrifuged at
8000 rpm for 20 min, dried at 100 ꢀC. The solid samples
were then calcined at 350 ꢀC for 3 h.
General procedure for the synthesis of 4-amino-8H-
pyrido[2,3-d]pyrimidine-2-thione and 1,7-dihydro-
pyrazolo[3,4-d]pyrimidine-6-thione derivatives using
MWCNTs-COOH/CdO
Collection and preparation of purple water lily
flower extract
2-Oxo-1,2-dihydro-pyridine-3-carbonitrile
derivatives
(1 mmol), thiourea (1 mmol) and a catalytic amount of
MWCNTs-COOH/CdO (5 mol %) were mixed in warm dis-
tilled water (10 ml), I2 (1.2 mmol) was added in small por-
tions to the solution and stirred. The progress of the
reaction was monitored by TLC using n-hexane: ethyl acet-
ate (1:1) and detected by a UV lamp (254 and 366 nm). At
the end of the reaction, the catalyst was separated by centri-
fugation, filtered, washed with ethanol and water, dried at
100 ꢀC for 1 h and reused for the same reaction. A small
amount of tar was filtered from the residue of the reaction
mixture; to the clear filtrate was added sodium hydroxide
(2 M) until the solution was just neutered to litmus and the
products precipitate. The light yellow or white precipitate
was filtered, washed with water and recrystallized from etha-
nol. The products were determined by CHN analyses, NMR
and FT-IR spectra.
Purple Water lily flower, with the scientific name of N. alba,
was collected from the wetland in the north of Iran,
Mazandaran. The flower was first washed thoroughly in DI
water, dried at room temperature for one week and then
ground in a blender before extraction.
The powdered Water lily flower was weight (500 g) in a
beaker and percolated with 70% (vol/vol) ethanol. This bea-
ker was properly covered with aluminum foil and left for
72 h. The solution was then filtered using a funnel filled in a
filter paper and the extract obtained. It was concentrated
using a rotary evaporator and stored in the refrigerator at
4 ꢀC prior to use.
Synthesis and purification of MWCNTs-COOH
a) MWCNT (250 mg) was mixed with 200 mL concentrated
nitric acid and the mixture was refluxed for 8 h followed by
its ultracentrifugation at 10,000 rpm. The functionalized
MWCNTs were dispersed in 500 mL distilled water followed
by filtration through a cellulose nitrate membrane filter
(0.45 lm pore size) using a vacuum filtration assembly. The
sample was repeatedly washed with distilled water till neu-
tral pH of the filtrate. The filtered compound was dried in a
vacuum oven at 80 ꢀC for 24 h and obtained MWCNTs-
COOH were characterized using different techniques.[29]b)
Water Lily flower extract (1 g) and MWCNTs (0.5 g) were
dissolved in 50 ml of ethanol: H2O with a ratio of 1:1. The
mixture was kept in ultrasonicator for 30 min and then
stirred for 2 h at room temperature. The mixture was stirred
for 48 extra hours. The precipitate was washed and then
centrifuged 3–4 times with distilled water, dried at 100 ꢀC
for 2 hand calcined at 350 ꢀC for 3 h.
Characterization methods
4-Amino-7-isopropyl-1H-pyrido(2,3-d]pyrimidine-2-thione 1
Reaction of thiourea with 6-isopropyl-2-oxo-1,2-dihydro-
pyridine-3-carbonitrile and I2.
FT-IR (KBr, cmꢁ1): 3100–3500 (NH, NH2), 3000 (CHAr),
1
2921 (CHAliph), 1653 (C ¼ N, C ¼ C), 1447 (C ¼ S). H-NMR
(DMSO, 400 MHz, d ppm): 8.03 (d, 1H, J ¼ 8.8 Hz, CHAr),
6.61 (s, 1H, NH), 6.25 (dd, 1H, J ¼ 8.8, 4.0 Hz, CHAr), 5.47
(br, 2H, NH2), 2.82 (m, 1H, CH), 1.17 (m, 6H, 2CH3). 13C-
NMR (DMSO, 75 MHz, d ppm):189.29, 160.15, 149.63,
141.64, 117.26, 102.20, 75.58, 32.39, 21.45. Anal. Calc. for
C10H12N4S (220.29): C, 54.52; H, 5.49; N, 25.43, found: C,
54.82; H, 5.58; N, 25.31.
4-Amino-6,7-dimethyl-1H-pyrido(2,3-d]pyrimidine-2-thi-
one 2
Reaction of thiourea with 5,6-dimethyl-2-oxo-1,2-dihydro-
Preparation of MWCNTs-COOH/CdO hybrid
Water Lily Flower extract (0.5 g) and the functionalize pyridine-3-carbonitrile and I2
FT-IR (KBr, cmꢁ1): 3446 (NH, NH2), 3015 (CHAr), 2922
MWCNTs-COOH (0.3 g) were dispersed into 50 ml of etha-
nol: H2O (1:1) by ultrasonication for 30 min. Under constant (CHAliph), 1662 (C ¼ N), 1627 (C ¼ C), 1444 (C ¼ S). 1H-

INORGANIC AND NANO-METAL CHEMISTRY
3
for C13H10N4S (254.31): C, 61.40; H, 3.96; N, 22.03, S, 12.61,
found: C, 61.85; H, 3.90; N, 21.94: S, 12.50.
1-Phenyl-6-thioxo-1,5,6,7-tetrahydro-pyrazolo[3,4-d]pyrimi-
din-4-one 6
Reaction of thiourea with 5-amino-1-phenyl-1H-pyrazole-4-
carboxylic acid ethyl ester and I2
FT-IR (KBr, cmꢁ1): 3454 (br, NH, NH2), 3013 (CHAr),
1
1658 (N-CO-), 1627 (C ¼ N, C ¼ C), 1444(C ¼ S). H-NMR
(DMSO, 400 MHz, d ppm): 7.54–7.56 (m, 2H, CHAr),
7.43–7.49 (m, 3H, CHAr), 7.30 (s, 1H, CHpyrazole). Anal.
Calc. for C11H8N4OS (244.27): C, 54.09; H, 3.30; N, 22.94, S,
13.3, found: C, 54.72; H, 3.51; N, 22.38; S, 13.56.
Figure 1. GC-MS Chromatogram of pink Water Lily flower extract.
NMR (DMSO, 400 MHz, d ppm): 7.94 (s, 1H, CHAr), 6.64
(s, 1H, NH), 5.42 (br, 2H, NH2), 2.23 (s, 3H, CH3), 1.98 (s,
3H, CH3). 13C-NMR (DMSO, 75 MHz, d ppm):184.58,
160.15, 149.63, 141.64, 117.26, 102.20, 75.58, 32.39, 21.45.
Anal. Calc. for C9H10N4S (206.27): C, 52.41; H, 4.89; N,
27.16, found: C, 52.56; H, 4.92; N, 27.21.
4-Amino-3-methyl-1-phenyl-1,7-dihydro-pyrazolo[3,4-d]pyr-
imidine-6-thione 7
Reaction of thiourea with 5-amino-3-methyl-1-phenyl-1H-
pyrazole-4-carbonitrile and I2
FT-IR (KBr, cmꢁ1): 3443 (br, NH, NH2), 3010 (CHAr),
2993 (CHaliph) 1653 (NH-CO-O), 1630 (C ¼ N, C ¼ C), 1452
(C ¼ S). 1H-NMR (DMSO, 400 MHz, d ppm): 7.38–7.536
(m, 5H, CHAr), 6.63 (br, 2H, NH2), 2.16 (s, 3H, CH3). Anal.
Calc. for C12H11N5S (257.31): C, 56.01; H, 4.31; N, 27.22; S,
12.46, found: C, 56.22; H, 4.33; N, 27.34; S, 12.50.
4-Amino-5,7-dimethyl-1H-pyrido(2,3-d]pyrimidine-2-thi-
one 3
Reaction of thiourea with 4,6-dimethyl-2-oxo-1,2-dihydro-
pyridine-3-carbonitrile and I2
FT-IR (KBr, cmꢁ1): 3446 (NH, NH2), 3032 (CHAr), 2922
(CHAliph), 1653 (C ¼ N, C ¼ C), 1447 (C ¼ S). 1H-NMR
(DMSO, 400 MHz, d ppm): 6.98 (s, 1H, CHAr), 6.60 (s, 1H,
NH), 5.48 (br, 2H, NH2), 2.25 (s, 3H, CH3), 2.19 (s, 3H,
CH3). 13C-NMR (DMSO, 75 MHz, d ppm):174.41, 160.32,
158.62, 143.48, 138.54, 113.53, 108.60, 32.45, 25.95. (GC-
Mass): m/z Calculated: 206; Observed: 207 (M þ 1). Anal.
Calc. for C9H10N4S (206.27): C, 52.41; H, 4.89; N, 27.16,
found: C, 52.46; H, 4.88; N, 27.25.
Results and discussion
The present paper reports the results of a research aimed to
verify biosynthesis of the MWCNT-COOH/CdO hybrid
from pink Water Lily flower extract as an effective catalyst
on heterocyclic reactions. GC-Mass analyze (Figure 1) of the
Water Lily flower was performed and various bioactive com-
pounds were identified (Table 1).
4-Amino-7-methyl-1H-pyrido[2,3-d]pyrimidine-2-thione 4
Reaction of thiourea with 6-methyl-2-oxo-1,2-dihydro-pyri-
dine-3-carbonitrile and I2.
Optimization of different parameters
The effects of the reaction conditions such as the ratio of
plant extract and Cd(NO3)2, MWCNTs-COOH, pH, reaction
time and reaction temperature were studied to maximize the
yield of the nano compounds. The resulting solutions of the
reaction were monitored using a UV-Vis spectrophotometer.
The influence of pH on the synthesis of CdO/MWCNT-
COOH was investigated to 3.0, 5.0, 7.0, 8.0, 9.0, 10 and 11
(pH of Water Lily flower extract solution was about 3.0).
The reaction completion time was studied by monitoring
the absorption spectra of nano compounds formed in the
reaction media at different duration’s time (10 min to 48 h).
Different ratios of plant extract and cadmium nitrate solu-
tion were investigated (1:1, 1:2, 1:3, and 1:4) in order to find
the maximum production of nano powders. The tempera-
ture of the reaction was set at 25 ꢀC, 45 ꢀC, 65 ꢀC and 85 ꢀC
using the Water bath for optimization of the reaction tem-
perature. The optimized condition of the reaction was
obtained at room temperature in pH ¼ 10 after 24 h with
1H-NMR (DMSO, 400 MHz, d ppm): 8.00 (d, 1H,
J ¼ 7.2 Hz, CHAr), 6.93 (s, 1H, NH), 6.21 (d, 1H, J ¼ 7.2 Hz,
CHAr), 5.44 (br, 2H, NH2), 2.26 (s, 3H, CH3). 13C-NMR
(DMSO, 75 MHz, d ppm):186.26, 161.30, 158.16, 154.36,
149.45, 117.26, 105.89, 99.72, 19.64. Anal. Calc. for C8H8N4S
(192.24): C, 49.98; H, 4.19; N, 29.14, found: C, 49.92; H,
4.23; N, 29.36.
4-Amino-7-phenyl-1H-pyrido[2,3-d]pyrimidine-2-thione 5
Reaction of thiourea with 2-oxo-6-phenyl-1,2-dihydro-pyri-
dine-3-carbonitrile and I2
Yellow powder. FT-IR (KBr, cmꢁ1): 3473 (br, NH, NH2),
3000–3020 (CHAr), 1629(C ¼ S), 1442(C ¼ C). 1H-NMR
(DMSO, 400 MHz, d ppm): 8.02 (d, 1H, J ¼ 7.6 Hz, CHAr),
7.49–7.98 (m, 5H, CHAr), 7.21 (d, 1H, J ¼ 7.6 Hz, CHAr),
6.98 (s, 1H, NH), 5.64 (br, 2H, NH2). 13C-NMR (DMSO,
75 MHz, d ppm):182.31, 167.03, 163.20, 160.36, 139.54,
137.14, 129.73, 128.34, 1119.13, 107.28, 102.34. Anal. Calc. the ratio 1:1 of plant extract and cadmium nitrate solution.

4
S. KAVEH ET AL.
Table 1. Phytocomponents of pink Water Lily flower extract by GC-MS.
Molecular formula (MF)
C6H6O3
Name of the compound
Structure
1,2,3-Benzenetriol
C5H11NO2
L-Alanine ethyl ester
C6H18O3Si3
Cyclotrisiloxane, hexamethyl-
Gibberellin A3
C19H22O6
C10H15NO
C7H8N2O4
p-methoxyamphetamine
3,4,5-Trihydroxybenzhydrazid
C16H32O2
C18H24O5
Pentadecanoic acid, 14-methyl
Dicyclohexyl furan-3,4-Dicarboxylate
C6H5AsF2
C7H6O5
Arsine, diethylphenyl
Benzoic acid, 3,4,5-trihydroxy
C10H16
Cyclooctene, 3-ethenyle
C12H22
O
(5E,7E)-Dodecadien-1-ol
Octadecanoic acid
C18H36O2
C15H30O2
C24H38O4
Pentadecanoic acid
Bis(2-ethylhexyl) phthalate
C16H22O4
1,2-Benzenedicarboxylic acid
Eicosane
C20H42

INORGANIC AND NANO-METAL CHEMISTRY
5
Figure 2. UV-Vis spectrum of biosynthesized MWCNT-COOH/CdO after 24 h with the ratio of Cd(NO3)2: water Lily flower extract (a) 1:1, (b) 1:2, (c) 1:3.
UV-Vis studies
DTA peaks at 356 and 486 ꢀC were recorded. After about
480 ꢀC, the samples start to present a significant mass loss,
being. This is attributed to the decomposition of MWCNTs
into CO2 by the O2 atmosphere. The oxidation peak,
observed in DTA curves, occurs at about 529 ꢀC. The con-
stant levels observed after 500 ꢀC in TGA curves should cor-
respond to the oxidation of nanotubes. The final residue
was analyzed as CdO which revealed thermal stability from
800 to 1000 ꢀC.
Completion of the reaction between Water lily flower
extract, MWCNT-COOH, and cadmium nitrate was moni-
tored and optimized by taking the absorption spectrum in
UV-Vis spectrophotometer at different reaction conditions.
As the Water lily flower extract was added to aqueous cad-
mium nitrate solution, the color of the solution changed to
colloidal dark brown with MWCNT-COOH/CdO colloids
formation. The UV-Vis spectra recorded after 10 min,
20 min, 60 min, 16 h and 24 h at different temperatures
(25 ꢀC, 45 ꢀC, 60 ꢀC and 90 ꢀC) from the initiation of reac-
tion at the wavelength of 200–800 nm. Absorption UV-Vis
spectra of biosynthesized MWCNTs-COOH/CdO hybrid
showed k maxes at 221, 274 and 401 nm (Figure 2). These
results were in line with the findings of other studies.[30,31]
It is well known from absorption spectroscopy that the band
gap increases on decreasing particle size. There is also an
opposite ratio between band gap and the wavelength of
absorption. The absorption bands of the synthesized
MWCNT-COOH/CdO nanocomposite have been shows a
blue shift. This optical phenomenon indicates that these
nanoparticles show the quantum size effect and can be due
to a high decrease in particle size.[32,33]
MWCNTs-COOH/CdO characterization
The possible interaction between Cd(NO3)2, MWCNTs-
COOH and N. alba extract was investigated using FT-IR
spectroscopy, which leads the preparation and stabilization
of MWCNTs-COOH/CdO. As shown in Figure 4, typical
FT-IR spectra of MWCNTs, MWCNTs-COOH and
MWCNTs-COOH/CdO can be clarify brieflied.
The bands at around 1300–1550 cmꢁ1 are associated with
the vibration of the carbon skeleton of the CNTs. The bands
at about 2000–2450 cmꢁ1 are corresponding to the C ¼ C
double bonds stretch vibration from the surface of tubes.[34]
The protein and some chemical compounds from plant
extracts might play an important role in the stabilization
nanocomposite by binding or encapsulate them. This action
forms a layer around nanocomposite and protects them
from agglomeration.[35,36] In Figure 3(b,c), the bands at
about 1630–1750 and 1000–1300 cmꢁ1 indicate the existence
of carboxylic groups on the surface of the tube.[37] The weak
peaks around 3500–3900 cmꢁ1 in Figure 3(b,c) can be
assigned to the stretching vibrations of OH groups.[38,39]
The peaks observed at about 500–700 cmꢁ1 in Figure 3(c) is
assigned to the formation of CdO.[40] The Ft-IR spectra
reveal the different surface chemistry of MWCNTs,
MWCNTs-COOH, and MWNTs-COOH/CdO. The peak at
about 2300 cmꢁ1 became narrower and the bands around
1630–1750 and 1000–1300 cmꢁ1 are lower in Figure 3(c)
than those of pure MWCNTs-COOH Figure 3(b). The result
suggested that the surface of MWCNTs-COOH has been
covered almost of surface active sites by CdO.
The UV-Vis spectra showed that MWCNT-COOH/CdO
was obtained rapidly within the first 30 min only and the
MWCNT-COOH/CdO in solution remained stable even
after 24 h of completion of reaction at room temperature.
Thermal properties of (MWCNTs)-COOH/CdO
nanocomposite (TGA/DTA)
Differential thermal analysis (DTA) and thermal gravimetric
analysis (TGA) of (MWCNTs)-COOH/CdO nanocomposite
were carried out. From the thermal decomposition (TGA/
DTA) results, several observations are worth to mention. It
was performed in order to estimate the final amount, and
consequently the thermal behavior of nanocomposite.
Eventual MWCNTs oxidation is expected to form CO2 gas,
leaving the sample and resulting in composite weight loss as
a function of temperature. It was investigated in the
25–1000 ꢀC temperature range. typical thermal TGA and
DTA curves are given in Figure 3. There is no weight loss
in the range 0–350 ꢀC, which indicates the absence of coor-
XRD can be used to characterize the crystallization and
average size of MWCNT-COOH/CdO. The XRD pattern of
MWCNTs-COOH/CdO shows ten intense peaks in the
dinated or uncoordinated water molecules. The exothermic whole spectrum of 2h values ranging from 5ꢀ to 80ꢀ.

6
S. KAVEH ET AL.
Figure 3. TGA and DTA curves of (MWCNTs)-COOH/CdO nanocomposite.
Presence of six distinct high diffraction peaks at 2h values of and the analysis reveals the presence of Cd, O and C which
26.598ꢀ, 33.0530ꢀ, 38.351720ꢀ, 55.310ꢀ, 65.931ꢀ and 69.268ꢀ, emphasize the successful of decoration process with CdO
respectively (JCPDS Number. C: 00-026-1080, and JCPDS nanoparticles (Scheme 1).
Number. CdO: 01-075-0591)[41–43] confirmed that the
MWCNTs-COOH/CdO was used as a highly efficient
catalyst for the synthesis of some heterocyclic compounds.
Some pyrimidine derivatives were synthesized by the reac-
tion of thiourea, pyridine or pyrazole derivatives and I2 in
the presence of MWCNTs-COOH/CdO (5% mol) in warm
water solution. The assigned structure was further estab-
lished by CHN analyses, NMR and FT-IR spectra. Because
of excellent capacity, the exceedingly simple workup and
good yield, eco-friendly catalyst MWCNTs-COOH/CdO
were proved to be a good catalyst for this reaction.
In the preliminary stage of the investigation, the model
reaction of thiourea, 6-methyl-2-oxo-1,2-dihydro-pyridine-3-
carbonitrile, and I2 was carried out by using various
amounts of NPs in various solvents and solvent-free condi-
tions. The optimum amount of MWCNTs-COOH/CdO was
5 mol% as shown in Table 2. Increasing the amount of cata-
lyst does not improve the yield of the product any further,
whereas decreasing the amount of catalyst leads to a
MWCNTs-COOH/CdO had been formed using Water Lily
flower extract (Figure 5). The other diffraction peaks could
be due to some bioorganic chemical compounds and crystals
on the surface of the nanoparticle. The broad X-ray diffrac-
tion peaks around their bases indicate that the MWCNTs-
COOH/CdO is in nano sizes. With the XRD pattern, the
average diameter which can be evaluated from Scherrer
equation[17,44] (D＝Kk/bcosh, where K is constant, k is X-
ray wavelength and b is the peak width at half maximum) is
obtained about 76.7 nm.
The morphology and size of MWCNTs-COOH/CdO
were studied using transmission electron microscopy (TEM)
in Figure 6. It shows the TEM images of MWCNTs-COOH/
CdO nanopowders. The TEM image clearly indicates that
nanoparticle shape of CdO particle is incorporated on multi
wall CNTs and this result is in a good agreement with the
result obtained from XRD.
Figure 7 shows the typical SEM images of MWCNTs- decrease in the product.
It was found that in the absence of MWCNTs-COOH/
CdO, the yield of the product on the TLC plate even after
2 h of the reaction wasn’t good. The best results were
COOH/CdO. It is shown that CdO nanoparticles have
grown as nanoparticles on the surface of the
MWCNTs-COOH.
In Figure 8, energy-dispersive X-ray spectroscopy (EDX) obtained with 5 mol% of MWCNTs-COOH/CdO in warm
analysis was performed in order to confirm the elements water under mild reaction conditions (Table 1, entry 4). To
which presented in the resulted MWCNTs-COOH/CdO, evaluate the scope and limitations of this methodology, we

INORGANIC AND NANO-METAL CHEMISTRY
7
Figure 4. FT-IR spectrum of (a) MWCNTs, (b) biosynthesized MWCNTs-COOH, (d) biosynthesized MWCNTs-COOH/CdO.
Figure 5. XRD of MWCNTs-COOH/CdO synthesized with Water lily flower extract.
Figure 6. TEM image of MWCNTs-COOH/CdO synthesized with Water lily flower extract.
extended our studies to include a variety of structurally dif- primarily are activated by MWCNTs-COOH/CdO, and
ferent pyridine or pyrazole derivatives with thiourea. The afforded intermediate. At least NH2 groups of thiourea
results are summarized in Table 3 (entries 1–9). In almost attack at the C-2 position and CN group of intermediate to
all cases, the reactions proceeded smoothly within obtain
4-Amino-1H-pyrido[2,3-d]pyrimidine-2-thione
60–90 min, providing the corresponding products in good derivatives.
isolated yields.
The catalyst was simply recovered by centrifugation,
A plausible mechanism for the reaction is envisaged in washed with ethanol, and dried at 100 ꢀC for 2 h. The recov-
(Scheme 2). It is proposed that the carbonyl group and I2 ered catalyst was then added to a fresh reaction mixture

8
S. KAVEH ET AL.
Figure 7. SEM micrograph of MWCNTs-COOH/CdO synthesized with Water lily flower extract.
Figure 8. EDX of MWCNTs-COOH/CdO.
Scheme 1. Preparation of MWCNTs-COOH/CdO nanocomposite with Water lily flower extract
Table 2. Reaction of thiourea (1.2 mmol) with 6-methyl-2-oxo-1,2-dihydro-pyridine-3-carbonitrile (1 mmol) and I2 (1.2 mmol) under different conditions.
Entry
Solvent
THF
Amount of catalyst MWCNTs-COOH/CdO (mol%)
Time (min)
Yielda (%)
1
2
—
3
120
60
Trace
51
58
THF
THF
3
4
60
4
THF
5
60
66
5
THF
7
60
65
6
7
H2O
H2O
—
3
60
60
Trace
60
8
H2O
4
60
85
9
H2O
5
40
95
10
11
12
13
14
15
16
17
18
19
19
20
21
22
23
24
H2O
EtOH
EtOH
EtOH
EtOH
EtOH
7
—
3
4
5
7
—
3
4
5
7
—
3
4
5
7
40
120
60
60
60
60
60
60
60
60
60
120
120
120
120
120
96
Trace
51
64
73
71
—
33
36
45
46
40
50
68
74
76
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
aIsolate yield.

INORGANIC AND NANO-METAL CHEMISTRY
9
Table 3. Production of pyrimidine derivatives using MWCNT-COOH/CdO.
Entry
1
Amine
Product
Reaction time (min) in H2O
60
m.p.(oC)
Yield%
85
>300
2
60
148
95
3
60
142
93
4
60
228
96
5
90
174
95
6
90
300
97
7
60
231
93
8
60
>300
95
(continued)

10
S. KAVEH ET AL.
Table 3. Continued.
Entry
9
Amine
Product
Reaction time (min) in H2O
60
m.p.(oC)
Yield%
96
>300
inherent property of nanocatalyst, MWCNT-COOH/CdO
hybrid exhibited exceptionally high catalytic activity in het-
erocyclic chemistry and increases reaction speed without
pollution. This method is easier and less expensive than
other methods.
Acknowledgment
The authors wish to thanks Islamic Azad University in Qaemshahr
Branch for the institutional support.
Disclosure statement
No potential conflict of interest was reported by the authors.
Scheme 2. A plausible mechanism for synthesis of 4-Amino-1H-pyrido[2,3-
d]pyrimidine-2-thione derivatives using MWCNTs-COOH/CdO
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Table 4. Recycling of the MWCNT-COOH/CdO catalyst.
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In this study, we describe biosynthesis of MWCNT-COOH/
CdO hybrid by water Lily flower extract and synthesized
nanocomposite characterized with UV-Vis spectroscopy, FT-
IR, XRD, SEM, EDX and TEM analyses. The results showed
Water lily flower extract to be an excellent agent for the
synthesis of MWCNT-COOH/CdO hybrid in comparison to
some other plant extract. This plant may have the potential
for the production of different nanocomposit under mild
reaction conditions. In continuation, MWCNT-COOH/CdO
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