Highly biocompatible jujube polysaccharide-stabilized palladium nanoparticles with excellent catalytic performance

Article abstract of DOI:10.1039/c9nj00950g

The development of stable and biocompatible palladium nanoparticles (Pd NPs) catalysts has been drawing great interest. In this study, Pd NPs were prepared through a green method, where jujube polysaccharide (JP) was employed as both reducing and stabilizing agents for the first time. The JP stabilized palladium nanoparticles (Pd_n-JP NPs) displayed small size, high stability, good biocompatibility and excellent catalytic efficiency. Pd₅₀-JP NPs showed high stability up to two weeks in solutions of a wide pH range (4-9). Pd₅₀-JP NPs showed negligible cytotoxicity against HeLa cells at a high concentration of up to 400 μg mL^-1. Furthermore, Pd_n-JP NPs showed excellent catalytic activity for reduction of 4-nitrophenol (4-NP) in the presence of sodium borohydride (NaBH₄). The normalized rate constant (k_nor) and turnover frequency (TOF) of Pd₅₀-JP NPs were as high as 38.4 s^-1 mM^-1 and 4455 h^-1, respectively. The prepared Pd_n-JP NPs will have various potential applications in bio-related catalysis in the future.

Full text of DOI:10.1039/c9nj00950g

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Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
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Highly biocompatible jujube polysaccharide-stabilized palladium
nanoparticles with excellent catalytic performance
a
b
*a
c
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d
Xiaolei Guo , Jin Zhang , Yanshuai Cui , Shengfu Chen , Haotian Sun , Qinghua Yang , Guanglong
c
*a
a
Ma , Longgang Wang , Jianxin Kang
The development of stable and biocompatible palladium nanoparticles (Pd NPs) catalysts has been drawing great interest.
In this study, Pd NPs were prepared through a green method, where jujube polysaccharide (JP) was employed as both
n
reducing and stabilizing agents for the first time. The JP stabilized palladium nanoparticles (Pd -JP NPs) displayed small size,
high stability, good biocompatibility and excellent catalytic efficiency. Pd50-JP NPs showed high stability up to two weeks in
solutions of wide pH range (4 - 9). Pd50-JP NPs showed negligible cytotoxicity against HeLa cells at high concentration up to
4
00 μg/mL. Furthermore, Pd
n
-JP NPs showed excellent catalytic activity for reduction of 4-nitrophenol (4-NP) in the
). The normalized rate constant (knor) and turnover frequency (TOF) of Pd50-JP NPs
presence of sodium borohydride (NaBH
4
-1
-1
-1
were as high as 38.4 s mM and 4455 h , respectively. The prepared Pd
related catalysis in the future.
n
-JP NPs have various potential applications in bio-
16
the field of nanocatalyst synthesis.
1
Introduction
Green synthesis of nanoparticles is an environmentally friendly, low
Nitro-containing compounds are common organic pollutants in the energy and low cost method. Various microorganisms including
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water. They are extremely harmful to the environment and human fungi, bacteria and plant extracts have been widely used for
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,2
health. Among them, 4-NP is a kind of highly toxic and refractory green synthesis of metal nanoparticles. Among them, the plants
organic pollutant. However, 4-aminophenol (4-AP) is an important extracts has become popular raw material in recent years due to the
2
0
chemical intermediate. It has been widely used in development of easy access. Mahmoud and co-workers used the extract from
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,4
pesticides, pharmaceuticals, dyes and leather.
generation of 4-AP from 4-NP is important for environmental size of less than 32 nm and a non-uniform morphology.
Therefore, leaves of Euphorbia esula L. to synthesize Cu NPs with a particle
2
1
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protection and resources regeneration. This is in line with the MubarakAli and co-workers used extract of the Mentha piperita to
green chemical concept. At present, various materials including synthesize Au NPs around 150 nm. However, plant extracts are
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metal nanoparticles,
metal oxide nanoparticles and metal rich in various components such as proteins, pigments and
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nanoparticle-decorated 2D materials
have been studied in this polysaccharide. It is usually difficult for reproducibility of
reduction reaction in the presence of NaBH . It is generally believed morphology and sizes of nanoparticles resulting from the uncertain
4
that the mechanism of this reaction follows the Langmuir- composition. Yu and co-workers synthesized Au NPs by Citrus
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Hinshelwood kinetics.
synthesis of noble metal nanoparticles has many disadvantages such performance. The kapp is only 0.08977 min at a catalyst
However, the commonly used method for maxima water extract and studied their catalytic reduction of 4-NP
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-1
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as strict conditions, toxic solvents and harmful by-products.
concentration of 1 mmol/L, which is lower compared with that in
Therefore, exploring environmentally friendly method to prepare many reports. The low catalytic activity of NPs may be attributed to
noble metal nanoparticle has gradually become a research hotspot in their low stability in water. Thus, it is necessary to isolate the plant
extracts to obtain soluble macromolecules with reducing power.
Natural polysaccharide meet the above criteria and are rich in plant.
Moreover, polysaccharide eliminate oxygen free radicals, which
24
gives them wide application such as improving immunity, anti-
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tumor, anti-virus, anti-aging, anti-infection and anti-ulcer. In
addition, polysaccharide form an independent space at the molecular
level due to the interaction of their hydrogen bonds, which may
serve as good templates for the growth of nano-ions. JP has good
biocompatibility, biodegradability and high molecular weight. Jujube
is a kind of healthy food with nutritional value and medicinal value.
It is also widely distributed and easy to obtain at a low price.
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Pd NPs have been found to be catalytically active in aqueous 2.5 Size and zeta potential measurements
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DOI: 10.1039/C9NJ00950G
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solution, in cell culture and in vivo.
ability in reduction of 4-NP compared with Pt NPs and Au NPs.
Here, we proposed a green method, in which Pd -JP NPs were
prepared using JP as stabilizer and reducing agent. To the best of our
knowledge, there is no report on the synthesis of Pd NPs from JP.
They have higher catalytic
The size and zeta potential measurements of the Pd -JP NPs were
determined using dynamic light scattering (DLS) technology with a
Zetasizer Nano ZS system (Malvern, UK). 100 μL of 5 mg/mL Pd -
JP NPs were dissolved in 900 μL of PBS with different pH (4, 5, 6, 7,
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or 9), respectively. Each sample had triplicate and was measured at
The Pd -JP NPs had small size and narrow size distribution for Pd
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C. The sizes of the Pd NPs were characterized by HT7700
NPs. The stability of Pd -JP NPs in solutions with different pH
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transmission electron microscopy (TEM) operating at 100 kV in
bright field mode.
values and toxicity against cells and bacteria were carefully studied.
More importantly, the catalytic activity of Pd -JP NPs was evaluated
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in reduction of 4-NP by NaBH . The results revealed that Pd-JP NPs 2.6 Biocompatibility
4
are highly stable, biocompatible and efficient as catalysts.
Cell viability assay was performed according to the previous
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reports.
HeLa cells were seeded in 96-well cell culture plates at
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o
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0 cells/well. The cells were cultured in an incubator at 37 C and
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Materials and methods
CO2 concentration of 5%. After 24 h, the original high-glucose
DMEM medium with 10% FBS was replaced by different
concentrations of Pd -JP NPs medium. Each group had 3 replicate
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.1. Materials
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Sodium tetrachloropalladate (Na PdCl ), NaBH , hydrogen peroxide
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wells. The medium was removed after 24 h, and 100 μL of 0.5
mg/mL MTT solution was added. After 4 h, the MTT culture
medium was replaced by 150 μL of DMSO. The culture plates were
shaken for 10 min. The absorbance of the samples at 490 nm was
measured by a microplate reader. Cell viability assay was calculated
by comparison the absorbance of samples with that of control groups.
(
H O ), trichloromethane, butyl alcohol, potassium ferricyanide,
2 2
trichloroacetic acid, iron(III) chloride hexahydrate, sodium chloride,
potassium chloride, dibasic sodium phosphate, potassium phosphate
monobasic,
3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-
diphenyltetrazoliumromide (MTT) and 4-NP were purchased from
Aladdin. Jujube was purchased from a local supermarket. All cell
lines were purchased from China Center for Typical Culture
Collection.
Cellular uptake assay was performed according to the previous
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4
reports.
HeLa cells (5×10 cells/well) were seeded in 24-well cell
culture plates. After 24 h of culture, the original medium was
2
.2 Extraction of JP
replaced by a medium solution of 400 μg/mL Pd -JP NPs. After 24
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0
o
h, the medium was removed, and the cells were washed with PBS
and digested with trypsin. The cells were collected by centrifugation
Dried jujube powder samples were extracted with water at 70 C
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(1:15 (w/v), 3 h, twice).
The water extraction solution was
and washed with PBS. 1 mL of 10% HNO was added, the mixture
was allowed to stand at 80 C overnight. After diluting 10 times on
the next day, the palladium concentration was measured by ICP-MS.
obtained by centrifugation, and pigment was removed by the
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o
o
addition of H O at 50 C (1:15 (v/v), 1.5 h). The resulting solution
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2
was mixed with sevage reagent (5:1 (v/v)) and centrifuged to remove
proteins. The sevage reagent was composed of chloroform and butyl Bacterial toxicity assay was performed according to the previous
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alcohol (5:1 (v/v)). The generated solution was freeze-dried to obtain reports. The bacterial toxicity of Pd -JP NPs was studied using
JP.
n
3
2
Escherichia coli (E. coli, gram-negative bacterium) and
Staphylococcus aureus (S. aureus, gram-positive bacterium). E.coli
and S.aureus colonies were added into nutrient broth (NB). They
2
.3 Determination of reducing power of JP
o
The reducing power of JP was determined according to the previous were both cultured overnight at 37 C with 150 r/min. The next day,
report with slight changes. 1.0 mL of JP aqueous solution with 90 μL of bacterial culture (10 CFU/mL) was added into a 96-well
different concentration (0.0625~2 mg/mL), 2.5 mL of phosphate culture plate. 10 μL of Pd100-JP NPs ranging concentration from 300
33
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buffer saline (PBS) at pH=6.6, and 2.5 mL of potassium ferricyanide to 1200 μg/mL were added to each well. Bacteria were cultured at 37
o
solution with a mass fraction of 1% were added, respectively. The
C and 50 r/min for 24 h. The absorbance value of each well was
mixed solution was rapidly cooled down after being kept in a water measured at 600 nm by a microplate reader.
o
bath at 50 C for 20 minutes. 2.5 mL of 10% trichloroacetic acid
solution was added. After centrifuging the mixed liquid, 2.5 mL of
2.7 Catalytic activity
the supernatant was collected and added into a 10 ml centrifuge tube, (a) Catalytic reduction of 4-NP: 250 μL of 0.6 mM 4-NP and 650 μL
and 2.5 mL of distilled water and 0.5 mL of 0.1% ferric chloride of deionized water were mixed in a cuvette. Then, 100 μL of 20 nM
solution were sequentially added. 10 min later, the absorbance of the Pd -JP and 1 mL of 0.5 M fresh NaBH solution were added. The
50
4
solution at 700 nm was measured.
reaction system was monitored every 3 min using an UV-Vis
spectrophotometer.
2
.4 Preparation of JP stabilized Pd -JP NPs
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(b) In situ detection of 4-NP reduction: 200 μL of 0.6 mM 4-NP
Pd -JP NPs were prepared by using Na PdCl as a metal source and
n
2
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aqueous solution and deionized water (750 μL, 700 μL or 650 μL)
were mixed in a cuvette, respectively. Then, 50 μL, 100 μL or 150
μL of 20 nM Pd -JP and 1 mL 0.5 M of fresh NaBH solution were
JP as reducing agent. Briefly, JP aqueous solution was mixed with 1
mM Na PdCl , where the molar ratio of Na PdCl to JP was 50, 100,
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n
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and 200, respectively. The solutions were incubated for 4 h, and the
color of the solution changed from light yellow to brown.
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added. The absorbance at 400 nm was monitored by UV-Vis
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DOI: 10.1039/C9NJ00950G
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Results and discussion
3.1. Reducing power of JP
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JP is a kind of natural biomacromolecule with aldehyde groups, Fig. 2 (a) The photos of Pd
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-JP solution (n=50, 100, 200). (b) UV-Vis spectra of Pd
JP (2 μM), JP (2 μM), and Na PdCl (200 μM). The results indicated the successful
preparation of Pd -JP NPs.
n
-
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hydroxyl groups and ketone groups, which determine its solubility
and reducing power. This property makes it possible to stabilize and
reduce metal nanoparticles. Here, the reducing power of JP was
measured by reducing Fe . In the reduction power measurement, the
antioxidant reduced Fe to generate Fe by providing electrons.
n
Furthermore, the JP and Pd100-JP NPs were measured by using FTIR
spectra. As illustrated in Fig. 3, in the JP spectrum, the absorption
peaks at 3430 cm and 2935 cm were caused by the strong
stretching vibration of O-H and C-H, respectively. The peaks at 1740
and 1630 cm were attributed to stretching vibrations and
asymmetric stretching vibration of C=O. The peaks at 1100 and
020 cm were due to C-OH tensile vibration. In the spectrum of
Pd100-JP NPs, the absorption peak at 1740 cm was weaker than that
of JP, which indicated that the interaction between Pd NPs and the
carbonyl group of JP. In addition, the intensity of the two peaks at
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The formation of Fe could be monitored by measuring the
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absorbance at 700 nm. Thus, the reducing power was linear with
the absorbance. Fig. 1 showed that the reducing power of JP was
positive correlation with its concentration. The absorbance of JP was
0.25 at concentration of 2.0 mg/ml. This reducing power of JP makes
-
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0
it an antioxidant and anti-aging healthcare product.
-
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100 and 1020 cm also significantly was reduced, which should be
attributed to the interaction of Pd NPs with C-OH from the
polysaccharide. Hence, the interaction between the resulting Pd NPs
and various groups of JP can result in the position and intensity
change of transmittance peak in the FTIR spectra of JP and Pd100-JP
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3,44
NPs.
Fig. 1 UV-Vis absorbance at 700 nm with different concentrations of JP. The result
indicated that the reducing power of JP was positive correlation with its
concentration.
3
.2. Pd -JP NPs synthesis and characterization
n
As has been demonstrated, JP had reducing power, which might be
used to reduce PdCl4 to generate zero-valent Pd NPs without using
additional reducing agent. The JP and Na PdCl were mixed together
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-
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Fig. 3 FTIR spectra of JP and Pd100-JP NPs. The result indicated that there was
and incubated for 4 h. Fig. 2a showed that the color of the prepared interaction between the Pd NPs and groups of JP.
Pd -JP NPs solution was gradually deepened as the molar ratio of
n
When nanoparticles are used as catalysts, the relatively narrow size
Na PdCl to JP increased. In addition, Fig. 2b showed the spectra of
2
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dispersion and small particle size generally enhance their catalytic
ability. Small nanoparticles exhibit high specific surface area,
providing more access opportunities for substrate. The size of Pd
NPs was measured by using TEM. As shown in Fig. 4, Pd NPs were
spherical and monodispersed. The calculated average diameters of
Pd NPs were 5.71±1.62 nm for Pd -JP; 6.07±1.84 nm for Pd100-JP;
.17±1.36 nm for Pd200-JP, respectively. Thus, small Pd NPs particle
size (5-7 nm) indicated that Pd -JP NPs had a large specific surface
area. This provided more active sites to enhance catalytic
performance during the catalytic reaction.
Pd -JP, JP, and Na PdCl . The absorption peak at 235 nm was
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assigned to Na PdCl . After the mixed reaction with JP, the
disappearance of the peak at 235 nm indicated that Pd(II) was
reduced to Pd(0).
from light yellow to brown, which also proved the presence of Pd(0).
Both results indicated the formation of Pd -JP NPs. In short, the Pd -
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In addition, the color of the solution changed
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JP NPs were prepared using JP as a green synthetic method.
n
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Fig. 5 The stability (a) and zeta potential (b) of Pd50-JP NPs under different pH.
The Pd50-JP NPs displayed excellent stability from pH 4 to 9 within 2 weeks and
low net charge. The results indicated that the high stability of Pd50-JP NPs was
attributed to the presence of JP.
3
.4 Biocompatibility
When organic pollutants are catalytically degraded in the nature, the
sewage contains a large amount of microorganisms. The strong
interaction between nanoparticles and microorganisms often leads to
high toxicity and reduced catalytic performance. For example, the
generation 5 poly(amido amine) dendrimers encapsulated Pd NPs
47
(
Pd -G5 NPs) have high toxicity against cells and bacteria. Here,
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5
the toxicity of Pd -JP NPs was assessed. Two models (HeLa cells
and bacteria) were incubated with Pd -JP NPs. The cytotoxicity of
Pd -JP NPs was evaluated by MTT assay in vitro. Fig. 6a showed
that the cell viability of Pd -JP NPs and JP was > 90% within 400
n
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n
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μg/mL. In addition, the cytotoxicity of Pd -JP NPs was evaluated by
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observing the morphology of HeLa cells. Fig. 6b showed the HeLa
cell morphology of the control group after 24 h. HeLa cells
incubated with Pd -JP NPs and JP had similar morphology with the
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control groups. Taken together, these results indicated that Pd -JP
Fig. 4 TEM images and size distribution histograms of (a,d) Pd50-JP NPs, (b,e)
Pd100-JP NPs, (c,f) Pd200-JP NPs. The average sizes of Pd NPs were 5.71±1.62 nm NPs displayed very good cytocompatibility. In order to study the
for Pd50-JP; 6.07±1.84 nm for Pd100-JP; 6.17±1.36 nm for Pd200-JP, respectively.
The results indicated that Pd NPs had small size and narrow size distribution.
50
mechanism of high cytocompatibility, the cellular uptake of Pd -JP
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NPs was determined by ICP-MS. Here, the cellular uptake of Pd -
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JP NPs was 1.98 ng/10 cells. As shown in Fig. 6c, the cellular
uptake of Pd -JP NPs was a little higher than that of control group,
3.3 Stability
5
0
Catalytic degradation of organic pollutants is usually carried out in while the cellular uptake of Pd -G5 NPs was 12 to 13 times that of
water. Good dispersion of nanoparticles without aggregation under Pd -JP NPs. The results indicated that Pd -JP NPs showed little
various conditions is beneficial to their high catalytic performance. accumulation in HeLa cells. This was attributed to the natural green
Here, the stability of Pd -JP NPs was evaluated as an example JP template and the negative charge of the Pd -JP NPs surface,
through the change of their hydrodynamic size. The hydrodynamic limiting the entry of Pd -JP NPs into the cell. However, Pd -G5
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size of Pd -JP NPs in PBS with different pH was measured using NPs have highly positive charge on their surface, resulting in their
DLS. As shown in Fig. 5a, the hydrodynamic size of Pd -JP NPs high accumulation in HeLa cells and high cytotoxicity.
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0
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was about 30 nm in the pH range of 4-9 after 24 h. In addition, after
weeks, there was no significant change of the hydrodynamic size
of Pd -JP NPs. Thus, Pd -JP NPs had excellent stability in different
In addition, the bacterial viability of Pd100-JP NPs was detected by
incubating them with the bacteria (E.coli and S.aureus) in NB for 24
hours. Bacterial viability was defined as comparison the optical
density of samples with the control groups at 600 nm. Fig. 6d shows
bacterial viabilites of E.coli and S.aureus were ≥ 96.6%. The results
indicated that Pd -JP did not suppress the growth of both bacteria.
To sum up, Pd -JP NPs had very good biocompatibility in vitro.
The high biocompatibility exhibited by Pd -JP NPs should be
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pH solutions for a long time. As for Pd -JP NPs, the hydrodynamic
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size value measured by DLS was larger than the size measured by
TEM, which was because the sample measured by DLS contained
the JP template with hydrated states, while size measured by TEM
was Pd NPs with dried states. The zeta potential of Pd -JP NPs was
also measured. As shown in Fig. 5b, the zeta potential of Pd -JP
NPs was in the range from -0.19 to -1.53 mV. This indicated that
there was weak electrostatic repulsion between the Pd -JP NPs. This
prevented mutual attraction or aggregation of Pd -JP NPs in solution
to some extent.
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attributed to the JP template. The high biocompatibility of Pd -JP
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NPs was beneficial to make them environmentally friendly catalyst
for bio-related catalytic applications.
n
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In short, the Pd -JP NPs displayed excellent
n
stability in different pH buffer solutions, showing their potential
catalytic application in a wide pH range solution.
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Fig. 7 (a) The UV-Vis spectra of 4-NP and 4-NP+NaBH
the reduction of 4-NP using Pd50-JP NPs every 3 min. The results indicated that 4-
NP was quickly reduced to 4-AP using Pd50-JP NPs with NaBH4.
4
. (b) The UV-Vis spectra of
.
Fig. 6 (a) Cell viabilities of HeLa cells for Pd50-JP NPs and JP. (b) Cell morphology of
the HeLa cells for the control group. (c) ICP-MS measurements for Pd contents. (d)
The relationship between bacterial viability and the concentrations of Pd100-JP
NPs in NB after incubation with E.coli and S.aureus for 24 hours. The results
indicated the high cell viability was due to the low cellular uptake of Pd50-JP NPs.
Pd100-JP NPs did not suppress the growth of bacterial.
Scheme 1 Schematic representation of catalytic reduction of 4-NP by Pd NPs in
7
4
the presence of NaBH .
3.5 Catalytic efficiency
The mechanism of reduction of 4-NP catalyzed by noble metal
As described above, Pd -JP NPs were synthesized by a green method.
They were small, monodisperse, stable and biocompatible in vitro.
Furthermore, the catalytic activity of Pd -JP NPs was investigated
using catalytic reduction of 4-NP as a model. 4-NP is mainly derived
from common pollutants in industry and agriculture. If 4-NP is
directly discharged into the water, it will cause serious pollution to
the environment. Therefore, it is necessary to treat the 4-NP of
wastewater. It has been reported that the 4-NP can be reduced to
useful 4-AP by using the Pd NPs. Here, the catalytic properties of
14,53
n
nanoparticles has been reported by many groups.
This reaction
should follow Langmuir-Hinshelwood kinetic model. The catalytic
reaction was carried out on the surface of the Pd NPs. As shown in
Scheme 1, the 4-NP and hydrogen produced by hydrolysis of
borohydride are first adsorbed on the surface of the catalyst. Electron
transport and atom exchange were then carried out on the surface of
n
4
9
54
the catalyst to produce the intermediate 4-Hx. Finanlly, 4-Hx was
reduced to the product 4-AP. The 4-AP was then released from the
surface of the catalyst. The vacant active sites continue to be
occupied by the reactants.
Pd -JP were investigated by the reduction of 4-NP in the presence of
n
excess of NaBH . As shown in Fig. 7a, 4-NP had an absorption peak
at 312 nm. After adding NaBH the mixed solution had maximal Fig. 8a-c showed the relationship between ln(C /C
absorption peak at 400 nm, which corresponds to new generated 4- reaction was linear. C and C are the concentration of the 4-NP at
t 0
hydroxyaminophenol (4-Hx). The color of the 4-NP solution reaction time t and initial time, respectively. The catalytic reduction
changed from pale yellow to deep yellow. As shown in Fig. 7b, after of 4-NP was a pseudo-first-order reaction. This is because the
the addition of Pd -JP, the intensity of the absorption peak at 400 nm concentration of NaBH was very high and could be considered as a
4
decreased with increasing time. At the same time, a new absorption constant during our reaction. The apparent rate constant kapp can be
peak at 295 nm appears, which indicated the formation of the obtained from equation (1).
4
) and time in our
4
,
t
0
5
0
n
5
5
1
,51
reduced product of 4-AP.
About 18 min later, the color of this
Ct
At
solution became colorless. On the contrary, the reduction of the 4-
NP without the catalyst was very slow, and the absorbance at 400
nm decreased only 15% after 210 minutes. The reduction of 4-NP by
ln
 ln =-kapp
t
（1）
C0
A0
As shown in Fig. 8d, the relationship between apparent rate
constants kapp and the amounts of Pd -JP NPs was linear. This was
due to an increase of the active site of Pd -JP. Here, two important
NaBH and JP has been carried out. The absorbance at 400 nm did
4
not decrease over 12 minutes, indicated that the intermediate 4-Hx
did not react to give the final product 4-AP. JP only acted as a
stabilizer for Pd NPs and did not participate in the catalytic process,
while Pd NPs were the catalytic center. The increase in 4-NP
reduction is due to the presence of Pd -JP. Pd -JP could enhance
n
n
parameters were introduced to compare the catalytic performance of
56
the catalyst. They are normalized rate constant (knor= kapp/c(Pd)
)
and
turnover frequency (TOF). The TOF is defined as the number of
n
n
8
-
52
moles of 4-NP reduced by per mole of catalyst per hour. Pd -JP
electrons transfer from BH ions to 4-NP nitro groups.
50
4
had the highest knor and TOF in the Pd -JP. The k and TOF of
n
nor
-1
-1
-1
Pd -JP (1.0 nM) were calculated to be 38.4 s mM and 4455 h ,
5
0
respectively. More importantly, after one month, the k and TOF of
nor
-1
-1
-1
Pd -JP (1.0 nM) were still as high as 37.3 s mM and 4334 h ,
5
0
indicating that the catalytic activity kept a long time. Table 1 showed
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knor and TOF of the Pd -JP NPs and other catalyst reported in the standing for one month, the k and TOF of Pd -JP (1.0 nM) were
literature.
knor and TOF, indicating they had the highest activity. The high simple, green, it does not require the use of any external reducing
catalytic performance of Pd -JP NPs should depend on the small agent. The prepared Pd -JP NPs can be used in various bio-related
particle size of Pd NPs and high stability of Pd -JP NPs in aqueous application in the future.
solution. Small particle size of Pd NPs typically had large specific
surface areas and more active sites. In addition, the high stability of
50
nor
50
View Article Online
5
6-60
-1
-1
-1
DOI: 10.1039/C9NJ00950G
The results revealed that Pd -JP NPs had the highest still as high as 37.3 s mM and 4334 h . This synthesis method is
50
n
n
n
6
1
Acknowledgements
Pd -JP NPs in aqueous solution facilitated the rapid adsorption and
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release of the reactants, improving the effective contact between the
reactants and the catalytically active sites. Therefore, Pd -JP NPs
had excellent catalytic activity.
The authors appreciate financial support from the National Nature
Science Foundation of China (21474085 and 21674092), the national
n
development
project
on
key
basic
research
(973
Project,2015CB655303), Natural Science Foundation of Hebei
Province (B2017203229), Youth Foundation Project supported by
the Hebei Education Department of China (QN2015034), China
Postdoctoral Science Foundation (2016M601284), Postdoctoral
Science Foundation of Hebei Province (B2016003017).
Notes and references
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Jujube polysaccharide-stabilized palladium nanoparticles provide active sites for efficient catalysis of
4-nitrophenol to 4-aminophenol.