Green synthesis of supported palladium nanoparticles employing pine needles as reducing agent and carrier: New reusable heterogeneous catalyst in the Suzuki coupling reaction

Article abstract of DOI:10.1002/aoc.3587

A green method for the synthesis of supported Pd nanoparticles (NPs) using pine needle extract as the reducing agent and the extracted residue of pine needle (RPN) as the carrier is described. The Pd/RPN nanocomposites were characterized using Fourier transform infrared, UV–visible, inductively coupled plasma atomic emission and X-ray photoelectron spectroscopies, transmission electron microscopy and X-ray diffraction. The spherical Pd NPs had a mean particle size of 3.25?nm and were evenly distributed on the RPN surface. More importantly, the Pd/RPN nanocomposite, as a heterogeneous catalyst, presented superior catalytic activity for the Suzuki coupling reaction. The yield of the reaction of 4-bromotoluene with phenylboronic acid catalyzed by Pd_0.03/RPN reached 98% with low Pd loading (0.1?mmol%) at room temperature for 30?min. In addition, the catalyst could be easily separated by centrifugation and reused at least six times without significant loss of activity.

Full text of DOI:10.1002/aoc.3587

Received: 13 July 2016
DOI 10.1002/aoc.3587
Accepted: 19 July 2016
F U L L PA P E R
Green synthesis of supported palladium nanoparticles employing
pine needles as reducing agent and carrier: New reusable
heterogeneous catalyst in the Suzuki coupling reaction
1
1,2*
2
Guanghui Liu | Xuefeng Bai
| Hongfei Lv
1
School of Chemistry and Material Sciences,
A green method for the synthesis of supported Pd nanoparticles (NPs) using pine
needle extract as the reducing agent and the extracted residue of pine needle
(RPN) as the carrier is described. The Pd/RPN nanocomposites were characterized
using Fourier transform infrared, UV–visible, inductively coupled plasma atomic
emission and X‐ray photoelectron spectroscopies, transmission electron microscopy
and X‐ray diffraction. The spherical Pd NPs had a mean particle size of 3.25 nm and
were evenly distributed on the RPN surface. More importantly, the Pd/RPN
nanocomposite, as a heterogeneous catalyst, presented superior catalytic activity
for the Suzuki coupling reaction. The yield of the reaction of 4‐bromotoluene with
phenylboronic acid catalyzed by Pd0.03/RPN reached 98% with low Pd loading
Heilongjiang University, Harbin 150080, China
2
Institute of Petrochemistry, Heilongjiang
Academy of Sciences, Harbin 150040, China
Correspondence
Xuefeng Bai, School of Chemistry and Material
Sciences, Heilongjiang University, Harbin 150080,
China.
Email: tommybai@126.com
(0.1 mmol%) at room temperature for 30 min. In addition, the catalyst could be eas-
ily separated by centrifugation and reused at least six times without significant loss
of activity.
KEYWORDS
green synthesis, heterogeneous catalyst, Pd nanoparticles, pine needles, Suzuki
coupling reaction
1
|
INTRODUCTION
Heterogeneous catalysts are preferred over homogeneous cat-
alysts due to their facile separation from a reaction mixture
[
17–19]
The Suzuki coupling reaction is a powerful and straightfor-
ward reaction in the field of organic synthesis due to its wide
application for the selective construction of C─C bonds to
synthesize biphenyl compounds,
ucts,
materials
Traditionally, homogeneous Pd catalysts can form com-
plexes with phosphine ligands or other protective agents,
such as polyvinylpyrrolidone and cetyltrimethylammonium
and the possibility of recycling.
Supported Pd catalysts
play an important role in a lot of catalytic reactions, espe-
cially in the Suzuki coupling reaction. However, there are
many shortcomings, such as aggregation and leaching of Pd
nanoparticles (NPs) on the surface of supports, which result
in a low Pd utilization efficiency. One solution to this prob-
lem is to uniformly disperse Pd NPs on the surface of sup-
[
1–4]
such as in natural prod-
[
5,6]
[7,8]
liquid crystalline polymers,
nonlinear optical
[
9,10]
[11]
and pharmaceuticals.
[
20]
[21]
ports, such as microporous polymers,
nano‐silica,
[
22]
[23,24]
TiO
or carbon materials.
2
[
12,13]
bromide,
to produce water‐soluble catalysts, which are
The synthesis of Pd NPs is generally carried out using
chemical agents or advanced technical equipment, which
are harmful to the environment and increases the cost of pro-
duction. In recent years, the utilization of biosynthetic tech-
niques for the preparation of metal NPs has emerged as a
new and reliable method due to a growing need to develop
generally applied in the Suzuki coupling reaction and exhibit
excellent catalytic activity.
[14–16]
However, many of these
chemical agents may cause serious problems to the environ-
ment due to their toxicity and lead to high production costs.
The separation of catalyst from reaction system and the reuse
of the catalysts in consecutive reactions are the major limita-
tions for the application of these catalytic systems.
[
25–27]
eco‐friendly processes in nanomaterial synthesis.
Extensive work has been committed to the green synthesis
Appl. Organometal. Chem. 2016; 1–7
wileyonlinelibrary.com/journal/aoc
Copyright © 2016 John Wiley & Sons, Ltd.
1

2
LIU ET AL.
[
28–31]
fungi[25,32–34] and
of metal NPs, employing bacteria,
plants.
with a Bruker D8 Advance diffractometer equipped with Cu
Kα radiation. Transmission electron microscopy (TEM) was
conducted with a JEM‐2100FX (200 kV). Inductively
coupled plasma atomic emission spectrometry (ICP‐AES)
was carried out with an ICP‐7510 (Shimadzu). Fourier trans-
form infrared (FT‐IR) spectra was recorded with an Avatar
Nicolet 6700 using pressed KBr pellets with a scanning range
from 500 to 4000 cm . X‐ray photoelectron spectroscopy
(XPS) was conducted with a Kratos AXIS ULTRA DLD
spectrometer with Al X‐ray source.
[
35–37]
According to these studies, a biosynthetic
method using plants has emerged as a viable alternative to
traditional chemical and physical processes, it being simple,
cost‐effective, safe and eco‐friendly. To date, there is no
report on the synthesis of supported metal NPs using plants
as the reducing agent and carrier.
Pine is an evergreen plant of the Pinaceae family located
throughout the world (Figure 1). The main classes of second-
ary metabolites occurring in pine needles are polyphenolic
compounds, such as tannins, α‐pinene, trans‐caryophyllene,
−
1
[38,39]
α‐terpineol, terpinene‐4‐ol and δ‐cadinene.
Accord-
2
.2 | Preparation of Pine Needle Extract (PNE) and
ingly, there are compounds with potential antioxidant activity
in this plant. Thus, the plant can serve as an effective and
green source for the reduction of Pd ions for the synthesis
of metal Pd NPs. In addition, the foliage is composed of a cel-
which is rich in hydroxyl groups and can
be combined with metal NPs. Therefore, it can serve as a
good carrier for supported Pd NPs.
In this paper, an eco‐friendly and economic process for
the synthesis of supported Pd NPs using pine needles as the
reducing agent and carrier is reported. In addition, the cata-
lytic activity of nanocomposites of Pd and extracted residue
of pine needle (RPN), used as a reusable heterogeneous cata-
lyst, was further investigated in the Suzuki coupling reaction.
RPN
Sundried pine needles were milled. Then, 2 g of the powder
was added into 100 ml of deionized water and refluxed at
[
40]
6
4
0°C for 1 h. The PNE obtained was centrifuged at
000 rpm and filtered through Whatman No. 1 filter paper.
lulose structure,
The filtrate was collected in an Erlenmeyer flask and stored
at 4°C for further use. The filter residue was RPN.
2
.3 | Preparation of Pd/RPN Catalyst
To prepare the Pd/RPN catalyst with 3 wt% Pd, 0.2 g of RPN
was added into 6 ml of Na PdCl solution (0.01 M) and
2
4
impregnated for 12 h at room temperature. Subsequently,
0 ml of PNE was added dropwise to this mixture with mag-
netic stirring at 60°C for 3 h. The product, denoted as Pd0.03
1
/
2
2
|
EXPERIMENTAL
RPN, was separated using a centrifugation step. The sepa-
rated solid was washed two times using deionized water.
For comparison, Pd0.01/RPN, Pd0.05/RPN and Pd0.10/RPN
nanocomposites were also prepared under the same
conditions.
.1 | Instrumentation and Reagents
Pine needles were collected from Harbin (northeastern
China). All chemicals were purchased from Tiajin Kermel
and Sinopharm Chemical Reagent Co. Ltd. All chemicals
were used without further purification. UV–visible
spectroscopy was performed with a UV‐2450 (Shimadzu).
Powder X‐ray diffraction (XRD) analyses were conducted
2.4 | Catalytic Suzuki Coupling Reaction
Under air atmosphere, aryl halide (1 mmol), K CO (2 mmol)
2
3
and the catalyst (0.1 mmol%) were added into a mixed sol-
vent of 15 ml of EtOH–H O (1:1) with constant stirring at
2
room temperature for 10 min to obtain an evenly dispersed
system. Then, phenylboronic acid (1.5 mmol) was added into
the mixture. After completion of the reaction, the mixture
−
1
(
5 ml) was added to 5 ml of NaOH solution (0.2 mol l )
and extracted two times with EtOAc (10 ml). The combined
organic layers were collected and dried in air to obtain the
crude product. Subsequently, the obtained products were
determined using HPLC analysis.
2
.5 | Catalyst Recycling Experiment
After the reaction, the catalyst was collected by centrifuga-
tion. The separated solid was washed three times using
−
1
NaOH solution (0.2 mol l ) to remove the absorbed
phenylboronic acid. Next, the collected solid was washed
with ethyl acetate and dried under vacuum. Subsequently,
the recovered catalyst was used for another run.
FIGURE 1 Image of pine needles

LIU ET AL.
3
3
3
|
RESULTS AND DISCUSSION
obtained in these samples. From the size distribution histo-
grams, when the Pd load is increased to 10%, the average par-
ticle size is increased to 11.52 nm (Figure 3h). The results
reveal that the Pd/RPN nanocomposites have been success-
fully synthesized and the small Pd NPs are highly distributed
on the RPN without any agglomeration at appropriate Pd
loadings (3 wt% Pd loads). The actual amount of Pd in
Pd0.03/RPN determined using ICP‐AES is 2.72 wt%.
.1 | UV–Visible Analysis
As shown in Figure 2, the UV–visible spectrum of PNE
exhibits a peak at 276 nm, which is in accordance with the
absorption of the gallic acid system. It is related to π–π* tran-
sitions and indicates that polyphenol compounds are present
in the extract. The absorption spectra of Pd colloidal suspen-
sions of various Pd loadings, which were treated for 3 h, are
also shown. The absorption of Na PdCl solution was used as
3
.3 | XRD Analysis
2
4
a reference for comparison. The absorption bands present in
the reference sample spectrum are attributed to the character-
XRD patterns of the as‐prepared Pd/RPN are shown in
Figure 4. The peak intensities of the Pd/RPN nanocomposites
with low Pd loads are not obvious (Figure 4a, b). In combina-
tion with the TEM analysis, this may be due to the relatively
broad reflections, indicating quantitatively sparse or small
particles size. This suggests that no characteristic peaks of
metallic Pd are observed using XRD up to a Pd load of
5 wt%. Only an obvious (111) peak of metallic Pd is observed
at 2θ = 40.1° (Figure 4c). Upon increasing the Pd load to
2−
[41]
istic absorption of PdCl4
species.
The absence of
absorption peak above 420 nm for all of the samples indicates
that the initial bivalent Pd species is adequately reduced to
zero‐valent Pd (Figure 2a). During the reduction process,
the color of the PRN changes from light yellow to deep black
(Figure 2b).
1
0 wt% (Figure 4d), peaks located at 40.1°, 46.1° and 67.9°
3
.2 | TEM and ICP‐AES Analyses
are observed, which are indexed to the (111), (200) and
(
220) Bragg reflections, respectively, of the face‐centered
In Figure 3, the TEM images further confirm the size and
morphology of the Pd NPs, which are dispersed on the
RPN surface. With low Pd loading (Pd0.01/RPN), spherical
Pd NPs with an average particles size of 5.25 nm are quanti-
tatively sparse on the RPN surface (Figure 3a, b). At the
appropriate Pd loading (Pd0.03/RPN and Pd0.05/RPN), the
spherical Pd nanoparticles are evenly dispersed on the RPN
surface (Figure 3c, e). According to the particle size distribu-
tion histograms, the average particle size of Pd0.03/RPN is
[43]
cubic structure of Pd (JPDS 87–0643).
3.4 | XPS Analysis
In Figure 5(a), the XPS survey spectrum of Pd0.03/RPN
shows that Pd/RPN nanocomposite consists of C, N, O and
Pd. The XPS spectrum of the Pd 3d region (Pd 3d5/2 and
Pd 3d3/2) consists of four peaks (Figure 5b); the peaks at
0
3
3
35.3 and 340.5 eV belong to Pd , and the other peaks at
3
.25 nm (Figure 3d), which is smaller than that of Pd0.05
RPN (5.18 nm; Figure 3f). The high‐resolution TEM
HRTEM) image further manifests that the Pd crystal plane
is 0.224 nm (inset of Figure 3c), which corresponds to the
/
2+ [44]
37.1 and 342.2 eV are assigned to Pd .
On the basis
of peak area analysis, zero‐valent Pd in Pd0.03/RPN amounts
(
2+
to 65%. A possible reason for the presence of Pd is that the
2+
reduction of Pd does not proceed to completion during the
[42]
lattice spacing of the (111) plane of metal Pd.
As shown
fabrication. Another reason is that the exposed zero‐valent Pd
can be further oxidized into divalent Pd at ambient
conditions.
in Figure 3g, with high Pd loading (Pd0.10/RPN), Pd NPs
with triangular, cubic and rod structures are formed. This
may be due to the lack of biomolecules acting as stabilizing
agents, so that mostly non‐spherical nanoparticles are
3
.5 | FT‐IR Analysis
(
a)
(b)
As shown in Figure 6a, the prominent absorption peaks for
PNE appear at 3415, 2923, 1627, 1515, 1405, 1262 and
1074 cm . Generally, the broad peak at 3415 cm is
PNE
Na PdCl
2
4
2
1
0
Pd
/RPN
/RPN
/RPN
/RPN
0
.01
.03
.05
.10
−1
−1
Pd
0
Pd
0
attributed to the O‐H (phenolic) stretch. The peaks at
Pd
0
−1
1
627, 1515, 1405, 1262 and 1074 cm are assigned to
the stretching vibrations of (NH)─C=O (protein), C=C
(
(
aromatic), C─O─C (esters, ethers) and C─OH/C─H
polyols), respectively. Based on this analysis, the polyphe-
nol compounds, with ‐OH groups, can be used as a reducing
2+
300
400
500
600
agent for the reduction Pd to synthesize Pd NPs. And the
protein compounds, with (NH)─C=O groups, can serve as a
stabilizing agent for protecting the Pd NPs. Comparing the
FT‐IR spectra of RPN and Pd0.03/RPN (Figure 6b), there is
no noticeable change in the characteristic absorption peaks,
Wavelength (nm)
2 4
FIGURE 2 (A) UV–visible spectra of PNE, Na PdCl solution and Pd NP
suspensions with various Pd loadings after 3 h. (B) Color change of RPN
before and after the reaction

4
LIU ET AL.
FIGURE 3 (a) TEM image and (b) size distribution of Pd0.01/RPN; (c) TEM image (inset: HRTEM image) and (d) size distribution of Pd0.03/RPN; (e) TEM
image and (f) size distribution of Pd0.05/RPN; (g) TEM image and (h) size distribution of Pd0.10/RPN

LIU ET AL.
5
(
111)
(
200)
(
220)
(
d)
c)
(
111)
(
200)
(220)
(
(
b)
a)
(
2
0
30
40
50
60
70
80
FIGURE 4 XRD patterns of (a) Pd0.01/RPN, (b) Pd0.03/RPN, (c) Pd0.05
/
RPN and (d) Pd0.10/RPN
FIGURE 6 FT‐IR spectra: (a) PNE and Pd NPs; (b) RPN and Pd0.03/RPN
SCHEME 1 Suzuki reaction catalyzed by Pd/RPN
catalytic performance of the synthesized Pd/RPN complexes
(1, 3, 5, or 10 wt%). The reaction was carried out under rather
mild conditions, using EtOH–H O (1:1) as the solvent and
2
K CO as the base at room temperature under an air atmo-
2
3
sphere in the presence of a low amount of catalyst
(0.1 mmol%).
Figure 7 shows the yields of biphenyl at different inter-
vals with various catalysts. Among all the catalysts with dif-
ferent Pd loads, Pd0.03/RPN exhibits the best catalytic
activity; the yield of the reaction of 4‐bromotoluene with
phenylboronic acid reaches 98% with 0.1 mmol% catalyst at
room temperature for 30 min. Lower catalytic activity is
obtained with higher Pd load (10 wt%) and lower Pd load
FIGURE 5 (a) XPS survey spectrum of Pd0.03/RPN; (b) Pd 3d core‐level
XPS spectrum
which indicates that there is a non‐covalently coupled inter-
action between the Pd species and RPN in the Pd/RPN
nanocomposites.
(1 wt%), due to the increase of the particle size and reduction
of the degree of dispersion, respectively. The results are also
supported by the TEM analysis. Therefore, the dispersion and
size uniformity are the key factors determining the activity of
catalyst. This result may be attributed to the relatively strong
interaction between the Pd species and RPN in the Pd/RPN
nanocomposites.
3.6 | Catalytic Activity Evaluation
The Suzuki coupling reaction of 4‐bromotoluene with
phenylboronic acid (Scheme 1) was used to compare the

6
LIU ET AL.
a
TABLE 2 Recycling study of Pd0.03/RPN
Run
1
2
3
4
5
6
Yield (%)
98
96
93
91
89
84
a
Reaction conditions: 4‐bromotoluene (1 mmol), phenylboronic acid (1.5 mmol),
Pd0.03/RPN (0.1 mmol%), K
2
CO
3
2
(2 mmol), ethanol–H O (6 ml/6 ml) at room
temperature for 30 min.
of Pd in the Pd0.03/RPN determined using ICP‐AES is
1
.98 wt%.
4
| CONCLUSIONS
In summary, an effective and reusable Pd/RPN catalyst was
designed and successfully prepared via a low‐cost and green
method using PNE as the reducing agent and RPN as the car-
rier. Pd NPs with small size and highly dispersed were suc-
cessfully prepared at appropriate Pd loading (3 wt%). The
Pd0.03/RPN catalyst demonstrated excellent catalytic perfor-
mance for the Suzuki coupling reaction and could be reused
at least six times without significant loss of activity. The
excellent catalytic activity can be attributed to the close inter-
action between the Pd NPs and abundant hydroxyl groups on
the surface of RPN, which is beneficial for obtaining well‐
dispersed and small Pd NPs. This method provides a simple
and eco‐friendly route for the synthesis supported Pd NPs,
which will find potential application in other nanometal
materials.
FIGURE 7 Yields of biphenyl at different intervals with various catalysts
To survey the substrate generality for Pd0.03/RPN cata-
lyst, the general applicability of the coupling reaction
between aryl halide and phenylboric acid was studied, and
the results are summarized in Table 1. Various p‐substituted
aryl bromides, containing either electron‐donating groups
(Table 1, entries 1 and 4) or electron‐withdrawing groups
(Table 1, entries 2 and 3), undergo the coupling reaction
smoothly and produce the corresponding products with
excellent yields. The m‐substituted nitrobenzene (Table 1,
entry 5) also gives the corresponding product with a high
yield. The o‐substituted aryl bromides (Table 1, entries 6
and 7) give the corresponding products in poor yields due
to steric effects. The substrate scope was further extended
to aryl chlorides (Table 1, entries 8 and 9). Poor yields are
observed even after prolonging the reaction times to 6 h.
The reusability and stability of a catalyst are essential
from an economic standpoint and for industrial applications.
As evident from Table 2, the Pd0.03/RPN catalyst can be
recycled simply using a centrifugation step. In addition,
although the yield gradually reduces, a yield of 84% is still
obtained in the sixth cycle. After six recycles, the amount
ACKNOWLEDGMENTS
This project was financially supported by the National Natu-
ral Science Foundation of China no. 21276067, NSFC‐RFBR
no. 214111301884, Program of International S&T coopera-
tion no. 2013DFR40570 and Science Foundation of Heilong-
jiang Academy of Sciences.
REFERENCES
[
1] A. Suzuki, J. Organometal. Chem. 1999, 576, 147.
TABLE 1 Suzuki coupling reactions of various aryl halides with
phenylboronic acid
[2] T. X. Zhang, Z. Li, Comput. Theor. Chem. 2013, 1016, 28.
a
[
[
[
3] C. Xu, X. Q. Hao, Z. Q. Xiao, Z. Q. Wang, X. E. Yuan, W. J. Fu, B. M. Ji, M.
P. Song, J. Org. Chem. 2013, 78, 8730.
4] P. D. Thornton, N. Brown, D. Hill, B. Neuenswander, G. H. Lushington, C.
Santini, K. R. Buszek, Abstr. Pap. Am. Chem. Soc. 2012, 244.
Entry
R
X
Time (min)
Yield (%)
5] M. C. Kozlowski, B. J. Morgan, E. C. Linton, Chem. Soc. Rev. 2009, 38,
1
2
3
4
5
6
7
8
9
4‐CH
3
Br
Br
Br
Br
Br
Br
Br
Cl
Cl
30
30
98
97
92
98
96
68
28
46
34
3193.
4‐NO
4‐CN
2
[6] X. Shen, G. O. Jones, D. A. Watson, B. Bhayana, S. L. Buchwald, J. Am.
Chem. Soc. 2010, 132, 11278.
30
4‐OCH
3‐NO
2‐CH
3
3
30
[7] M. Suzuki, J. C. Lim, T. Saegusa, Macromolecules 1990, 23, 1574.
[8] Z. Bao, Y. Chen, R. Cai, L. Yu, Macromolecules 1993, 26, 5281.
2
30
3
30
[9] A. Yokoyama, H. Suzuki, Y. Kubota, K. Ohuchi, H. Higashimura, T.
Yokozawa, J. Am. Chem. Soc. 2007, 129, 7236.
2‐OCH
30
[
10] A. Yokoyama, H. Suzuki, Y. Kubota, K. Ohuchi, H. Higashimura, T.
H
360
360
Yokozawa, J. Am. Chem. Soc. 2007, 129, 7236.
4‐NO
2
[
[
11] L. Ackermann, S. Barfüsser, J. Pospech, Org. Lett. 2010, 12, 724.
12] R. Narayanan, M. A. El‐Sayed, J. Phys. Chem. B 2004, 108, 8572.
a
Reaction conditions: aryl halide (1 mmol), phenylboronic acid (1.5 mmol),
CO (2 mmol), Pd0.03/RPN (0.1 mmol%), EtOH–H O (6 ml/6 ml) at room
temperature.
K
2
3
2
[13] C. C. Wang, D. H. Chen, T. C. Huang, Colloids Surf., A 2001, 189, 145.

LIU ET AL.
7
[
14] N. T. Phan, M. Van Der Sluys, C. W. Jones, Adv. Synth. Catal. 2006, 348,
[32] Y. Qian, H. Yu, D. He, H. Yang, W. Wang, X. Wan, L. Wang, Bioproc.
Biosyst. Eng. 2013, 36, 1613.
609.
[
[
[
15] A. Datta, K. Ebert, H. Plenio, Organometallics 2003, 22, 4685.
[33] Y. S. Chan, M. M. Don, Mater. Sci. Eng. C 2013, 33, 282.
16] J. P. Wolfe, S. L. Buchwald, Angew. Chem. Int. Ed. 1999, 38, 2413.
[34] C. Borelli, M. Schaller, M. Niewerth, K. Nocker, B. Baasner, D. Berg, R.
Tiemann, K. Tietjen, B. Fugmann, S. Lang‐Fugmann, H. C. Korting, Che-
motherapy 2008, 54, 245.
17] Y. Kitamura, S. Sako, A. Tsutsui, Y. Monguchi, T. Maegawa, Y. Kitade, H.
Sajiki, Adv. Synth. Catal. 2010, 352, 718.
[
[
[
[
35] M. Atarod, M. Nasrollahzadeh, S. M. Sajadi, J. Colloid Interface Sci. 2016,
[
18] S. W. Kim, M. Kim, W. Y. Lee, T. Hyeon, J. Am. Chem. Soc. 2002, 124,
465, 249.
7642.
36] M. Nasrollahzadeh, S. M. Sajadi, A. Rostami‐Vartooni, M. Bagherzadeh,
J. Colloid Interface Sci. 2015, 448, 106.
[
19] T. Kang, Q. Feng, M. Luo, Synlett 2005, 2005, 2305.
[
20] K. Okumura, T. Tomiyama, S. Okuda, H. Yoshida, M. Niwa, J. Catal. 2010,
37] D. Baruah, R. N. Das, S. Hazarika, D. Konwar, Catal. Commun. 2015, 72,
2
73, 156.
21] A. Fihri, D. Cha, M. Bouhrara, N. Almana, V. Polshettiwar, ChemSusChem
012, 5, 85.
73.
[
38] M. P. Kähkönen, A. I. Hopia, H. J. Vuorela, J. P. Rauha, K. Pihlaja, T. S.
2
Kujala, M. Heinonen, J. Agric. Food Chem. 1999, 47, 3954.
[
22] M. Nasrollahzadeh, S. M. Sajadi, J. Colloid Interface, Sci. 2016, 465, 121.
23] C. Liu, X. Rao, Y. Zhang, X. Li, J. Qiu, Z. Jin, Eur. J. Org. Chem. 2013,
[
[
[
[
[
39] K. Y. Kim, H. J. Chung, J. Agric. Food Chem. 2000, 48, 1269.
[
40] R. L. Parfitt, R. H. Newman, Plant Soil 2000, 219, 273.
4345.
41] X. Xie, G. Gao, Z. Pan, T. Wang, X. Meng, L. Cai, Sci. Rep. 2015, 5, 8515.
42] H. M. Song, B. A. Moosa, N. M. Khashab, J. Mater. Chem. 2012, 22, 15953.
43] F. Harraz, S. El‐Hout, H. Killa, I. Ibrahim, J. Catal. 2012, 286, 184.
[
[
[
24] X. Wang, Y. Tang, Y. Gao, T. Lu, J. Power Sources 2008, 175, 784.
25] M. Sastry, A. Ahmad, M. I. Khan, R. Kumar, Curr. Sci. 2003, 85, 162.
26] J. E. van de Mortel, L. A. Villanueva, H. Schat, J. Kwekkeboom, S.
Coughlan, P. D. Moerland, E. V. L. van Themaat, M. Koornneef, M. G.
Aarts, Plant Physiol. 2006, 142, 1127.
[44] J. Moulder, W. Stickle, P. Sobol, K. Bomben, Handbook of X‐ray Photoelec-
tron Spectroscopy, Perkin‐Elmer, Eden Prairie, MN 1992.
[
[
27] C. S. Cobbett, Curr. Opin. Plant Biol. 2000, 3, 211.
28] N. Yousefi, M. Pazouki, M. Alizadeh, F. A. Hesari, Synth. React. Inorg.
Met.‐Org. Chem. 2016, 46, 464.
How to cite this article: Liu, G., Bai, X., and Lv, H.
(
2016), Green synthesis of supported palladium
[
[
[
29] J. A. Bennett, I. P. Mikheenko, K. Deplanche, I. J. Shannon, J. Wood, L. E.
Macaskie, Appl.Catal. B 2013, 140, 700.
nanoparticles employing pine needles as reducing
agent and carrier: New reusable heterogeneous catalyst
in the Suzuki coupling reaction, Appl. Organometal.
Chem., doi: 10.1002/aoc.3587
30] M. Eugenio, N. Mueller, S. Frases, R. Almeida‐Paes, L. M. T. R. Lima, L.
Lemgruber, M. Farina, W. de Souza, C. Sant'Anna, RSC Adv. 2016, 6, 9893.
31] Rahisuddin, S. A. Al‐Thabaiti, Z. Khan, N. Manzoor, Bioproc. Biosyst. Eng.
2015, 38, 1773.