Silver nanoparticles: Facile synthesis and their catalytic application for the degradation of dyes

Article abstract of DOI:10.1039/c5ra02909k

Derivatives 3, 5 and 7 having aldehyde groups at their periphery have been designed and synthesized. Interestingly, all three derivatives formed aggregates in aqueous media and served as reactors for facile synthesis of spherical silver nanoparticles (AgN

Full text of DOI:10.1039/c5ra02909k

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ARTICLE
Silver Nanoparticles: Facile Synthesis and their
Catalytic Application for the degradation of dyes
Cite this: DOI: 10.1039/x0xx00000x
Kamaldeep Sharma,‡ Gurpreet Singh,‡ Gurpreet Singh,‡ Manoj Kumar and
Vandana Bhalla*
Received 00th January 2012,
Accepted 00th January 2012
DOI: 10.1039/x0xx00000x
Derivatives 3, 5 and 7 having aldehyde groups at their periphery have been designed and synthesized.
Interestingly, all the three derivatives formed aggregates in aqueous media and served as reactors for
facile synthesis of spherical silver nanoparticles (AgNPs) and silver nanorods at room temperature in
aqueous media without the addition of any external reducing agents, stabilizing agents or shape
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directing additives. Interestingly, in-situ generated AgNPs by aggregates of derivatives 3, 5 and 7 exhibit
high catalytic degradation of industrially important organic dyes such as Rhodamine B (RhB), methylene
blue (MB), methyl orange (MO) and eriochrome black T (EBT).
the additives act as strong complexing stabilizers which lead to
generation of large and polydisperse NPs.24 Further, preparation
1.
Introduction
Aquatic systems are extremely important to human beings due
to their utility as source of water, agricultural activities and
animal production. However, great damage to aquatic
environment is being caused due to direct discharge of various
organic pollutants especially azo dyes which are widely used in
textiles, foodstuffs and paper industries.1,2 The uncontrolled
discharge of azo dyes into the environment is alarming due to
the toxic, mutagenic and carcinogenic characteristics of these
dyes and their transformation products.3 These dyes can be
removed by various processes such as flocculation,4
adsorption,5 ion exchange,6 UV radiation,7 ozonization,8
photochemical processes of electrochemical destruction9 etc.,
however, most of these methods suffer from high cost and lead
to secondary pollution due to excessive use of chemicals.
Therefore, development of simple and fast methods for the
efficient degradation of organic dyes has become a challenging
task for environmental chemists. Recently, noble metal NPs
such as gold, silver and palladium have been used as catalyst
for the degradation of various organic dyes.10ꢀ14 In comparison
to gold and palladium, preparation of AgNPs is important due
to its low cost, high photostability, abundance, environmentally
benign nature and size and shape dependent catalytic
properties.15ꢀ19 Among AgNPs of various shapes, preparation of
quasiꢀspherical AgNPs has attracted lot of research interest due
to their excellent catalytic efficiency. The literature reports
show that utilization of additives such as polymers,
oligoprolines, peptides and surfactants in the presence of
reducing agent as the most popular approach for the generation
of quasi spherical AgNPs.20ꢀ23 However, in most of these cases
of quasiꢀspherical AgNPs in aqueous media is difficult due to
secondary nucleation arising from slow reduction of silver ions,
hydrolysis of silver ions and decomposition of newly formed
AgNPs.20 Thus, development of simple and fast method for
generation of stable quasiꢀspherical monodisperse AgNPs in
aqueous media remains a challenge.
Our research work involves development of supramolecular
aggregates in aqueous media and their utilization as reactors for
the preparation of metal NPs such as gold, palladium and
iron.25ꢀ28 Recently, we reported aggregates of pentacenequinone
derivatives having pyridine/nitrile/amino groups which served
as reactors for the preparation of palladium and gold NPs.25ꢀ27
Considering the high price of palladium and gold, silver is
unique due to its excellent qualities in terms of plasmonic
ability, available nanostructures and material cost.17 Thus,
keeping in view the advantages of AgNPs, in the present
manuscript,
we
have
designed
and
synthesized
pentacenequinone derivative
3
having aldehyde groups.
Pentacenequinone is the scaffold of our choice as it can be
functionalized with different moieties at the periphery and in an
aqueous environment pentacenequinone derivatives are known
to form aggregates which can serve as reactors and stabilizers
for the preparation of metal NPs.25ꢀ27 For generation of AgNPs,
we planned to reduce the Ag+ ions with the help of aldehyde
groups that are present at the periphery of the molecules. We
envisioned that during the reduction process, aldehyde groups
will be oxidized to carboxylic acids and the in-situ generated
AgNPs will be stabilized due to their interactions with the
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oxidized form of aggregates of derivative 329,30. To study the observed at 422 nm (Fig.1 A). This new band may be attributed
influence of scaffold on size/shape and catalytic efficiency of to the formation of intermolecular charge transfer (ICT) state as
in-situ
hexaphenylbenzene (HPB) and perylene diimide (PDI) based the aggregation process34,35. Further increase of water fraction
derivatives and having aldehyde groups at their periphery. up to 95% leads to the appearance of levelꢀoff tail (Inset Fig.
generated
AgNPs,
we
also
synthesized the molecules of derivative 3 are packed more closely during
5
7
Being electron rich, HPB derivative having high reduction 1A). The presence of the levelꢀoff tail in the visible region
potential31 (vide infra) is expected to influence rate of suggests the formation of aggregates. The scanning electron
formation of AgNPs. On the other hand, PDI derivatives are microscopy (SEM) image of derivative
3 in the solvent mixture
known for their electron acceptor nature and low reduction of H2O/THF (9.5:0.5) showed flake like morphology of
potential.32 Thus, we were interested to know whether the aggregates (Fig. 1B).
aggregates of PDI derivative
AgNPs or not. Interestingly, all the derivatives
7
will be successful in generating
and 7
Water fraction (%)
3
,
5
formed fluorescent aggregates in aqueous media and these
aggregates served as reactors for the generation of AgNPs.
Furthermore, the in-situ generated NPs exhibited good catalytic
efficiency for the degradation of industrially important organic
dyes such as RhB, MO, EBT and MB. Thus, the present study
has several advantages. First, supramolecular aggregates of
electron rich/electron deficient molecules have been used at
room temperature for generation of AgNPs without the addition
of any external reducing agents, stabilizing agents or shape
directing additives. Second, effect of scaffold and
morphology/nature of aggregates on rate of generation of
AgNPs has been studied and it is found that despite the low
0
10
20
30
(A)
Level off tail
422 nm
Wavelength (nm)
Wavelength (nm)
reduction potential of aggregates of PDI derivative
7 exhibit
(B)
high rate of formation of AgNPs due to its porous morphology.
Third, the present study demonstrates the catalytic efficiency of
aggregates of pentacenequinone/HPB/PDI stabilized AgNPs for
degradation of organic dyes.
2.
Results and Discussion
Derivative
2,3ꢀdibromopentacenequinone 1 33
acid (Scheme 1). The structure of derivative
from its spectroscopic and analytical data (Figs. S37ꢀS38 in
ESI†). The 1H NMR spectrum of derivative
showed four
3
was synthesized by SuzukiꢀMiyaura coupling of
with 4ꢀformylphenylboronic
was confirmed
Fig. 1 (A) UV-vis spectra showing the variation of absorbance of derivative
μM) in H2O/THF mixture with different fractions of H2O. Inset: enlarge UV-vis
spectra of derivative (10 μM) with the addition of H2O/THF mixture in the
3 (10
,
2
3
3
range of 425-600 nm showing level-off tail (B) SEM image of derivative
H2O/THF (9.5/0.5) mixture showing flake like morphology; scale bar 2 µm.
3 in
3
The recognition behaviour of aggregates of derivative
3 (10
singlets at 10.03, 9.04, 8.99 and 8.23 ppm, corresponding to the
aldehyde group and aromatic protons, respectively, two
doublets at 7.83 and 7.43 ppm and two multiplets at 7.74ꢀ7.75
and at 8.15ꢀ8.17 ppm, corresponding to aromatic protons (Fig.
ꢁM) in H2O/THF (9.5/0.5) was studied toward different metal
ions such as Cd2+, Hg2+, Fe2+, Ni2+, Zn2+, Cu2+, Pb2+, Ca2+,
Co2+, Au3+, Na+, K+, Li+, Pd2+, Cr3+, Al3+ ions as their
perchlorate/chloride or both perchlorate and chloride salts by
UVꢀvis spectroscopy (Figs. S1ꢀS2 in ESI†). Upon addition of
S37 in ESI†). The mass spectrum of derivative
3 showed a
parent ion peak at m/z 517.1305 (M+1)+ (Fig. S38 in ESI†).
Ag+ ions (100 equiv.) to the solution of derivative
3 in mixed
These spectroscopic data corroborate the structure
compound.
3 for this
aqueous media (H2O/THF, 9.5/0.5), a broad absorption band at
470 nm was observed after 4 hours (Fig. 2) which is the
characteristic surface plasmon resonance (SPR) of spherical
AgNPs.36 In comparison to the reported absorption band of
AgNPs (ca 390 nm), the SPR band is red shifted.37 Further,
instead of wellꢀknown sharp peak for AgNPs, a broad peak is
observed. The presence of broad and red shifted band may be
attributed to the interactions between AgNPs and aggregates of
Scheme 1. Synthesis of pentacenequinone based derivative 3
The UVꢀvis spectrum of derivative
3 in THF exhibits
derivative 3 38
The intensity of this band increases with time
.
absorption bands at 315 and 406 nm due to л–л* and n–
л*transitions. On addition of water (≤ 70% volume fractions) to
and the rate constant39 for the formation of AgNPs was found to
be 8.31×10ꢀ5 sꢀ1 (page S6 in ESI†).40,41
the THF solution of derivative
3, a new absorption band is
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The formation of AgNPs is also supported by powder Xꢀray
To get insight into effect of morphology and nature of
diffraction (XRD) analysis of the sample containing AgNPs of aggregates on the rate of formation, size and shape of AgNPs,
derivative (Fig. S4 in ESI†) which shows peaks we also designed and synthesized HPB and PDI based
corresponding to diffraction from the 111, 200, 220, 311 crystal derivatives
planes of fcc silver (0).42
Derivatives
3
5
5
and
and
7
7
having aldehyde groups at the periphery.
were synthesized by SuzukiꢀMiyaura crossꢀ
coupling of HPB based derivative 444 and PDI based derivative
After 4 hours
645 with 4ꢀformyl phenyl boronic acid
2 in 70% and 50%
After 2 hours
After 1 hours
Derivative 3
yields, respectively (Scheme 2).
470 nm
Scheme 2. Synthesis of HPB and PDI based derivatives
5 and 7.
Wavelength (nm)
Fig. 2 UV–vis spectra of derivative
3
(10 µm) upon addition of Ag+ ions (100
equiv.) at different time intervals in H2O/THF (9.5/0.5). Inset: photograph of
solution of AgNPs recorded after 4 hours.
To get insight into the mechanism of formation of AgNPs, we
slowly evaporated the solution of aggregates of derivative
3
containing AgNPs. After several days, precipitates were
1
observed which were filtered and washed with THF. The H
NMR spectrum of the residue obtained after evaporation of
THF was recorded and it showed the absence of signal
The structures of derivatives
spectroscopic and analytical data (pages S36ꢀS41 in ESI†). The
UVꢀvis studies of derivative and in H2O/THF mixture show
the presence of aggregates (Figs. S10ꢀS11 in ESI†). The SEM
images of the derivatives and in H2O/THF solution show
5 and 7 were confirmed from their
corresponding to aldehyde protons in derivative
3 with slight
upfield shift of aromatic signals (Fig. S5 in ESI†). Further,
FTIR spectrum of the resulting residue showed the presence of
a new band at 1760 cmꢀ1 which may be assigned to C=O group
of acid (Fig. S6 in ESI†). These results suggest the involvement
of aldehyde groups in the process and their subsequent
oxidation to acid.29 The chemical composition of the resulting
precipitates was determined by energy dispersive Xꢀray (EDX)
analysis. The presence of a peak of Ag in EDX spectrum of
resulting precipitates indicates the presence of Ag metal in the
precipitates40 (Fig. S7 in ESI†). We also studied the behaviour
5
7
5
7
the presence of disc shaped and irregular shaped aggregates
with porous morphology, respectively (Figs. S12ꢀS13 in ESI†).
The porous morphology of derivative
transmission electron microscopic (TEM) images46 (Fig. S14 in
ESI†). The absorption studies of derivatives and (10 ꢁM) in
7 was confirmed from
5
7
H2O/THF solution were carried out towards Ag+ ions and it was
found that aggregates of both derivatives served as nanoreactors
for preparation of AgNPs (Figs. S15ꢀS16 in ESI†). In both
cases, plasmon absorption is observed in the region 430ꢀ460 nm
which indicates the formation of AgNPs36 which was supported
by their powder XRD analysis. (Figs. S17ꢀS18 in ESI†). We
also investigated the electrochemical behavior of the
of derivative
3
towards Ag+ ions in THF but absorption spectra
did not indicate any absorption band corresponding to AgNPs
(Fig. S8 in ESI†). These studies suggest the importance of
water in the preparation of AgNPs. To evaluate the role of
pentacenequinone moiety for the formation of AgNPs, we
tested the generation of AgNPs using benzaldehyde. Upon
addition of Ag+ ions (100 equiv.) to the solution of
benzaldehyde in mixed aqueous media (H2O/THF, 9.5/0.5), no
absorption band corresponding to AgNPs was observed in the
visible region (Fig. S9 in ESI†). This study highlights the
importance of aggregates of pentacenequinone based derivative
derivatives
(1/9, v/v). The cyclic voltammetric (CV) measurements of
derivative in the presence of 0.1 M tetrabutylammonium
3, 5 and 7 in the presence of AgNO3 in H2O/ACN
3/5/7
perchlorate as supporting electrolyte (page S18 in ESI†),
exhibit cathodic peak which corresponds to the reduction of the
silver ions Ag(I) to Ag(0).47 Interestingly, the voltammogram of
3
for the preparation of AgNPs. On the basis of above results,
we suggest that upon addition of Ag+ ions to the solution of
aggregates of derivative , the silver ions enter the network of
interconnected channels, interact with aldehyde moieties and
get reduced. Thus, aggregates of derivative function as
derivatives
3 and 5 in the presence of silver ions show the trace
crossing, thus, suggesting that rate determining step for
reduction of Ag+ ions on electrode is nucleation.48 No trace
3
crossing was observed in the case of CV of derivative
7 in
3
presence of silver ions. On the basis of these CV studies,
reducing agents as well as stabilizing agents for the preparation
of AgNPs.43
derivative
5
was found to have high reduction potential (Table
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S3, in ESI†), thus, it is expected to show higher rate constant 4A). The observed rate constant for the formation of AgNPs by
for the formation of AgNPs. However, on the basis of derivative
in the presence of KI was found to be 1.4 × 10ꢀ4 sꢀ1
absorption studies, the rate constants for the formation of (Fig. S20 in ESI†). The TEM image of AgNPs generated by
5
AgNPs in case of aggregates of derivatives 3, 5 and 7 were aggregates of derivative 5 in the presence of KI, showed the
found to be 8.3×10ꢀ5 sꢀ1, 4.56×10ꢀ5 sꢀ1 and 7.1×10ꢀ5 sꢀ1, presence of only spherical AgNPs and no nanorods were
respectively. These results show that among the derivatives observed (Fig. 4B). These results highlight the role of iodide
3
/
5
/
7
aggregates of derivative
the formation of AgNPs. We believe that flake like morphology
of aggregates of derivative provide large surface area of
3 display higher rate constant for ions in tailoring of growth of AgNPs.
3
(A)
contact which results in stronger interactions with metal ions,
hence, faster rate of reduction is observed in this case. Further,
despite the presence of electron deficient scaffold, aggregates
(b)
(a)
(B)
of derivative
7 exhibit high rate constant for the formation of
AgNPs. We believe that due to the porous morphology and
presence of greater number of heteroatoms in the molecule,
aggregates of derivative
7 bind strongly with silver ions and
50 nm
form a uniform layer around them; hence, rate of reduction is
faster.49 These results suggest that morphology as well as
reduction potential of the reducing/stabilizing agent greatly
influences the rate of formation of AgNPs.
Fig. 4 (A) UV–vis spectra of AgNPs of derivative
after addition of KI. (B) TEM image quasi-spherical AgNPs of derivative
after addition of KI. Inset: electron diffraction pattern of a nanosized region
containing solution of AgNPs of derivative ; scale bar 50 nm.
5 (10 µm) (a) before and (b)
5
The TEM images of AgNPs generated by aggregates of
5
derivatives
(Figs. 3A and 3B) whereas TEM image of AgNPs generated by
aggregates of derivative showed the presence of nanospheres
3 and 7 showed the presence of spherical AgNPs
Further, we investigated the catalytic activities of in-situ
generated AgNPs of aggregates of derivatives and in the
3
,
5
7
5
electronꢀtransfer reaction between organic dyes viz. RhB, MB,
MO, EBT and borohydride ions. For each reaction, three
different samples were studied i.e. in-situ generated AgNPs by
and nanorods (Figs. 3C and 3D).
(B)
(A)
aggregates of
presence of iodide ions and in-situ generated AgNPs by
aggregates of . The progress of the each catalytic dye
3, in-situ generated AgNPs by aggregates of 5 in
7
degradation was monitored through changes in the UVꢀvis
spectra with time as reduction proceeded (Figs. S21ꢀS31 in
ESI†). All the reactions offered a good correlation with first
order kinetics52. First order rate constants were determined
from linear regressions of relative absorbance of dyes plotted
versus time (Figs. S21ꢀS31 in the ESI†).
(D)
(C)
(A)
Derivative 3-stabilized
AgNPs
50 nm
100 nm
Fig. 3 (A) and (B) TEM images of spherical AgNPs of derivative
AgNPs and (D) nanorods generated by aggregates of derivative
corresponding electron diffraction patterns of a nanosized region containing
3
and
7 (C)
2.5 min.
5
. Inset: their
AgNPs of derivative
50 nm.
3, 5, 7; scale bar (A) 20 nm (B) 50 nm (C) 100 nm and (D)
We believe that due to higher rate of formation of AgNPs in
case of aggregates of derivatives and , higher numbers of
reduced AgNPs are available which lead to uniform growth of
nanoparticles in all directions, thus, spherical nanoparticles are
obtained.50
Wavelength (nm)
(C)
3
7
(B)
k = 2.44×10-2 s-1
Earlier, KI has been used to tailor the growth of AgNPs into a
quasiꢀspherical shape via its preferential adsorption on the
(111) facets of nanorods.51 Thus, we studied the effect of iodide
on the shape of AgNPs in case of aggregates of derivatives
and . The UVꢀvis spectrum of AgNPs generated by aggregates
of derivative in the presence of KI exhibited more symmetric
3
,
5
Time (min.)
Time (min.)
Fig. 5 Catalytic properties of in-situ generated AgNPs by aggregates of
Decrease in Rhodamine B absorbance at 554 nm over time using derivative
7
3. (A)
5
3-
stabilized AgNPs as catalyst in the presence of NaBH4 (B) Normalized kinetic
trace of the absorbance at 554 nm during the reduction of Rhodamine B. (C)
Kinetic rate constant.
SPR band in comparison to that observed in absence of KI (Fig.
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The catalytic degradation of RhB in the presence of in-situ band to shorter wavelengths. The degradation ratio was
generated AgNPs by aggregates of derivative
with time is calculated using the following equation54:
presented in Fig. 5. The catalytic degradation process was D (%) = (C0 − C) / C0 × 100% = (A0 − A) / A0 × 100%
3
monitored through the change in intensity of the characteristic Where D represents the degradation ratio, C0 and C are the
absorption peak of RhB at 554 nm. The absorption spectrum of concentrations of RhB in solution at times corresponding to 0
RhB solution showed timeꢀdependent change in the presence of and t moment, and A0 and A are the absorbance of the RhB
AgNPs under visibleꢀlight irradiation. The catalytic degradation solution at times corresponding to 0 and t at the characteristic
process was monitored through the change in intensity of the adsorption wavelength of 554 nm, respectively. It was observed
characteristic absorption peak of RhB at 554 nm. The that after about 2 hrs, the main peak of RhB was blue shifted to
characteristic absorption peak of RhB dye at 554 nm rapidly 15 nm and about 60% degradation ratio was observed. The rate
decreased in intensity as time prolonged and it disappeared constant for the photocatalytic degradation of RhB was found
completely after about 2.5 mins. (Fig. 5) and the color of the to be 2.41×10ꢀ4 sꢀ1. The blue shifting of absorption signal
solution changed from the initial pinkꢀred to almost colorless. suggests Nꢀdeꢀethylation as main path of degradation of
The in-situ generated AgNPs by aggregates of derivatives
were found to exhibit higher catalytic efficiency towards To get insight in to the photocatalytic mechanism, we carried
degradation reaction of RhB as compared to AgNPs of out RhB photodegradation with AgNPs in the presence of 10%
derivative (Table 1). Overall, the degradation rate constant of of triethanolamine (TEOA). The photodegradation rate was
aggregates of derivatives stabilized AgNPs for the dramatically decreased in the presence of TEOA and after 2 hrs
degradation of RhB dye was found to be better than the rate only 38% degradation was observed with no shift in the
constants reported in literature.53
position of absorption peak corresponding to RhB (Fig. S32 in
3
and RhB.55,56
5
7
3
The enhanced degradation observed in case of these ESI†). This result suggests that the photodegradation
nanoparticles may be attributed to several reasons, first, mechanism involves hole transfer from the photoactive material
spherical shape and small size of generated nanoparticles and to the solution.57
secondly, the aggregates of derivatives
heteroatoms assist in bringing the dye molecules closer to degradation of RhB in the presence of NaBH4 aqueous solution
catalytic sites, thus resulting in faster degradation process. was chosen as a model reaction. After the catalytic degradation
The photoefficiency of aggregates of derivative stabilized of RhB, colour changed from pink to colourless. The reaction
3
/5
/7
having To test the reusability of these nanoparticles, the catalytic
3
AgNPs was also checked for photodegradation of RhB under mixture containing AgNPs catalyst was subjected to next
illumination of visible light in the absence of borohydride ions catalytic sequence by adding aqueous solution of RhB and
(Fig. 6).
NaBH4 to reaction mixture. The complete degradation of RhB
occurs up to three cycles in the presence of AgNPs of
(A)
aggregates of derivative
hand, aggregates of derivatives
3
(Fig. S33 in ESI†). On the other
and stabilized AgNPs show
Time (hr)
0
Visible
Irradiation
5
7
complete degradation of RhB upto three and five cycles,
respectively (Figs. S34ꢀS35 in ESI†). Further, recyclability of
2 hours
AgNPs generated by aggregates of derivative
3
as
heterogeneous catalyst was checked by using the same reaction
as model reaction. For this the AgNPs were precipitated after
the completion of reaction by adding dichloromethane to the
reaction mixture. The precipitated AgNPs were filtered and
reused at least three times using this recycling procedure for
2
Wavelength (nm)
k = 2.41×10-4 s-1
(B)
(C)
identical reaction.
Other nonꢀbiodegradable dyes, such as MB, MO and EBT
were also examined using AgNPs of aggregates of derivatives
3
,
5
and
7 as catalysts (Table 1). In the presence of aggregates
of
3 stabilized AgNPs, the coloration of methylene blue is
visibly reduced within 18 minutes (Fig. S21 in ESI†). The
intensity of characteristic wavelength of MB at 665 nm is
gradually decreased as the reaction proceeds and nearly 100%
reduction is observed. Under similar conditions as used for
degradation of RhB, we also carried out degradation of MO and
EBT using in-situ generated AgNPs of aggregates of
Time (hr)
Time (hr)
Fig. 6 (A) UV-vis spectral changes of RhB over time using derivative 3-stabilized
AgNPs as catalyst under visible light irradiations. Inset: photographs show
colour change of aqueous RhB solution after 2 hours under visible light
irradiations (B) Normalized kinetic trace of the absorbance at 554 nm during
the photodegradation of RhB. (C) Kinetic rate constant.
derivatives
3, 5, 7 and results are summarised in table 1.
Visible light irradiation of the aqueous RhB/AgNPs solution
A blank experiment was carried out for the degradation of
leads to a decrease in absorption with a wavelength shift of the RhB, MB, MO and EBT with NaBH4 in the absence of AgNPs
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1
and no change in absorption corresponding to each dye was of compound
observed after 24 hours (Fig. S36 in ESI†).
3
as yellow solid; m. p. >260oC; H NMR (500
MHz, CDCl3): δ = 7.42 [d, 4H, J = 5.0 Hz, ArH], 7.74ꢀ7.76 [m,
Table 1. Summary of rate constants for the catalytic degradation of organic dyes by AgNPs of aggregates of derivatives 3, 5 and 7 in the presence of
NaBH4.
Dyes
RhB
MO
MB
EBT
Rate constants for degradation of dyes by in-situ generated
AgNPs of derivative 3
2.44×10ꢀ2 secꢀ1
3.05×10ꢀ3 secꢀ1
2.81×10ꢀ3 secꢀ1
3.2×10ꢀ3 secꢀ1
Rate constants for degradation of dyes by in-situ generated
AgNPs of derivative 5 in the presence of KI
1.8×10ꢀ2 secꢀ1
6.6×10ꢀ3 secꢀ1
5.9×10ꢀ3 secꢀ1
5×10ꢀ3 secꢀ1
3.8×10ꢀ3 secꢀ1
2.4×10ꢀ3 secꢀ1
4.3×10ꢀ3 secꢀ1
1.88×10ꢀ3 secꢀ1
Rate constants for degradation of dyes by in-situ generated
AgNPs of derivative 7
2.
Experimental Section
2H, ArH], 7.83 [d, 4H, J = 10.0 ArH], 8.15ꢀ8.17 [m, 2H, ArH],
8.23 [s, 2H, ArH], 8.99 [s, 2H, ArH]; 9.04 [s, 2H, ArH]; 10.03
[s, 2H, CHO]; TOF MS ES+: 517.1305 [M+1]+; Elemental
analysis: Calcd. for C36H20O4: C 83.71; H 3.55; O 12.39 Found:
C 83.68; H 3.51; O 12.35. Due to poor solubility of compound
2.1.
Instruments
UVꢀvis spectra were recorded on a SHIMADZU UVꢀ2450
spectrophotometer, with a quartz cuvette (path length, 1 cm).
The cell holder was thermostatted at 25 0C. The fluorescence
3
, its 13C NMR spectrum could not be recorded.
Compound 5. To a solution mixture of (0.4 g, 0.578 mmol)
and (0.22 g, 1.5 mmol) in THF (20 mL) were added K2CO3
spectra were recorded on
a
SHIMADZU 5301 PC
4
spectrofluorimeter. Scanning electron microscope (SEM)
images were obtained with a fieldꢀemission scanning electron
microscope (SEM CARL ZEISS SUPRA 55). TEM images
were recorded from Transmission Electron Microscope (TEM)
ꢀ JEOL 2100F. Elemental analysis was performed on a Flash
EA 1112 CHNS/O analyzer of Thermo Electron Corporation.
The 1H and 13C NMR spectra were recorded on a JEOLꢀFT
NMRꢀAL 300 MHz and BrukerꢀFT NMRꢀAL 500 MHz
spectrophotometers using CDCl3 and DMSOꢀd6 as solvent and
tetramethylsilane (SiMe4) as internal standards. UVꢀvis studies
were performed in THF and H2O/THF mixture. Data are
reported as follows: chemical shifts in ppm (δ), multiplicity (s =
singlet, d = doublet, br = broad singlet, m = multiplet), coupling
constants J (Hz), integration and interpretation.
2
(0.63 g, 4.6 mmol), distilled H2O (1 mL), and [Pd(PPh3)4]
(0.330 g, 0.288 mmol) under N2 atmosphere. The reaction
mixture was degassed with nitrogen for three times and was
refluxed at 90 °C under the inert atmosphere for 24 hrs. The
THF was then removed under vacuum, and the residue so
obtained was treated with water, extracted with chloroform and
dried over anhydrous Na2SO4. The organic layer was
evaporated, and compound was purified by column
chromatography using (10:90) (Hexane/Chloroform) as an
eluent to give 0.255 g (60%) of compound 5, recrystallized
1
from methanol as pale yellow solid; mp: 270ꢀ272 °C; H NMR
(300 MHz, CDCl3, ppm). δ = 9.97 ( S, 2H, CHO), 7.82 (d, J = 9
Hz, 4H, ArꢀH), 7.57 (d, J = 9 Hz, 4H, ArꢀH), 7.19 (d, J = 9 Hz,
4H, ArꢀH), 6.98 (d, J = 6 Hz, 4H, ArꢀH), 6.94ꢀ6.87 (m, 20H,
ArꢀH); 13C NMR (CDCl3, 75 MHz, ppm) 192.53, 147.12,
141.64, 141.30, 140.96, 140.85, 139.95, 136.55, 135.32,
132.58, 131.83, 130.55, 127.65, 127.25, 127.13, 126.05,
125.89, 125.80; ESI/MS, m/z = 765.2743 [M+Na]+. Elemental
analysis: Calculated for C56H38O2: C 90.54; H 5.16; O 4.31;
Found: C 90.47 %; H 5.12 %; N 4.29 %.
2.2.
Materials
All reagents were purchased from Aldrich and were used
without further purification. THF was dried over sodium and
benzophenone and kept over molecular sieves overnight before
use. Silica gel (60–120 mesh) was used for column
chromatography.
Compound 7. To a solution mixture of
6 (0.5 g, 0.565 mmol)
2.3.
Synthesis
and (0.187 g, 1.2 mmol) in 1,4ꢀdioxane (20 mL) were added
2
Compound 3. To a solution of
1
(0.50 g, 1.07 mmol) and 2
K2CO3 (0.624 g, 4.5 mmol) in distilled H2O (1ꢀ2 mL) and
[Pd(PPh3)4] (0.323 g, 0.280 mmol) under N2 atmosphere. The
reaction mixture was degassed with nitrogen for three times and
was refluxed at 90° C under the inert atmosphere for 24 hrs.
The 1,4ꢀdioxane was then removed under vacuum and the
residue so obtained was treated with water, extracted with
dichloromethane and dried over anhydrous Na2SO4. The
organic layer was evaporated and compound was purified by
column chromatography using (10:90) (Hexane/Chloroform) as
(0.34 g, 2.25 mmol) in 1,4ꢀdioxane (20 mL) were added K2CO3
(1.18 g, 8.56 mmol), distilled H2O (2.10 mL), and [Pd(PPh3)4]
(0.28 g, 0.24 mmol) under N2 atmosphere and the reaction
mixture was refluxed overnight. The 1,4ꢀdioxane was then
removed under vacuum, and the residue so obtained was treated
with water, extracted with dichloromethane, and dried over
anhydrous Na2SO4. The organic layer was evaporated and
compound was purified by column chromatography using
70:30 (Chloroform: Hexane) as an eluent to give 0.191 g (35%)
an eluent to give 0.265 g (50%) of compound 7, recrystallized
1
from methanol as dark red solid; mp: 265ꢀ267 °C. H NMR
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

Page 7 of 9
Journal Name
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View ArticAle ROnTliInCeLE
DOI: 10.1039/C5RA02909K
(300 MHz, CDCl3, ppm). δ = 10.15 (s, 2H, CHO), 8.61 (s, 2H, spectra were recorded. Under visible illumination, the dye is
ArꢀH), 8.18 (d, J=9 Hz, 2H, ArꢀH), 8.05 (d, J = 9 Hz, 4H, Arꢀ deꢀethylated in a stepwise manner indicated by color change of
H), 7.76 (d, J = 9 Hz, 4H, ArꢀH), 7.65 (d, J = 9 Hz, 2H, ArꢀH), solution and blue shift in absorption spectra. After about 2 hrs,
4.18 (t, J = 6 Hz, 4H), 1.72 (br, 4H), 1.25 (br, 30H), 0.87 (t, J = the main peak of RhB was blue shifted to 15 nm and about 60%
6 Hz, 12H); 13C NMR (CDCl3, 125 MHz, ppm) 191.48, 163.14, degradation ratio was observed.
148.00, 139.66, 136.14, 134. 85, 132.48, 131.51, 130.75,
130.36, 127.87, 129.95, 122.62, 122.34, 117.65, 40.65, 31.80,
29.52, 29.26, 28.00, 26.98, 22.57, 14.06; Maldi TOF MS ES+:
936.5 [M+2]+. Elemental analysis: Calculated for C62H66N2O6:
C 79.63; H 7.11; N 3.00; O 10.26; Found: C 79.60 %; H 7.09
%; N 2.96 %; O 10.21 %.
4.
Conclusion
Pentacenequinone, HPB and PDI based derivatives 3, 5 and 7
having aldehyde groups have been synthesized. All the
derivatives formed aggregates in aqueous media and served as
reactors and stabilizers for the preparation of AgNPs.
Synthesis of AgNPs. Synthesis of AgNPs was carried out at
room temperature which involves the preparation of mixed
Aggregates of derivatives
3 and 7 having flake like and porous
morphology display high rate of formation of AgNPs, thus,
showing the importance of morphology on rate of formation of
AgNPs. Interestingly, in-situ generated AgNPs of aggregates of
aqueous solutions of derivatives
(H2O/THF 7/3) and (H2O/THF 5/5) containing aqueous
solution of AgNO3. In a typical procedure, the reaction
solutions were prepared by mixing 0.1 M AgNO3 (30 ꢁL for
3 (H2O/THF 9.5/0.5), 5
7
derivatives
3, 5 and 7 exhibit higher catalytic efficiency for
3
,
degradation of industrially important organic dyes.
60 ꢁL for
derivative
5
, 60 ꢁL for
7) with mixed aqueous solution of
3
,
5
and (3 mL, 10 µM) to obtain a homogeneous
7
5.
Acknowledgment.
reaction mixture. The reaction mixture was stirred at room
temperature and formation of NPs take place. These NPs
solution was used as such in the catalytic experiment.
V. B. is thankful to CSIR [(ref. no. 02(0083)/12/EMRꢀII)]. M.
K. is thankful to DRDO [(Ref. No.
ERIP/ER/1003922/M/01/1429)] and UGC [ref. no. 42ꢀ
282/2013(SR)]. We are thankful to UGC for the UPE project.
2.4.
Catalytic degradation of Rhodamine B.
The catalytic degradation of RhB was carried out at room
temperature in the presence of aqueous solution of AgNPs of
derivatives 3, 5 and 7. Firstly, same volume of aqueous solution
6.
Notes and references
of NaBH4 (0.2 M) and RhB (2 mM) solution were mixed to
obtain the mixture solution of NaBH4 and RhB dye and diluted
100 times in deionized water. Addition of catalytic amount of
Department of Chemistry, UGC SponsoredꢀCentre for
Advanced StudiesꢀI, Guru Nanak Dev University, Amritsarꢀ
143005, Punjab, India. Fax: +91 (0)183 2258820; Tel: +91
(0)183 2258802ꢀ9 ext. 3202; Email vanmanan@yahoo.co.in
AgNPs solution generated by aggregates of derivative
3 (3 µL,
3 nmol), (3 µL, 6 nmol) and (3 µL, 6 nmol) to the solution
5
7
†
Electronic Supplementary Information (ESI) available:
of RhB results in colour change from pink to colourless which
is indicated by the gradual decrease in absorbance band at the
RhB dye at 554 nm. The degradation of RhB takes 2.5 min in
[Optical and
spectroscopic
data
of
derivatives
3
,
5
,
7
].
See
DOI: 10.1039/b000000x/
case of derivative
3
(Fig. 5), 4 min in case of derivative
5 (Fig.
1
H. Zhang, D. Chen, L. V. Xiaojun, Y. Wang, H. Chang and J. Li,
S24 in ESI†) and 9 min. in case of derivative
7
(Fig. S30 in
Environ. Sci. Technol. 2010, 44, 1107ꢀ1111.
ESI†). The characteristic extinction peak of RhB at 554 nm
peak is used as the reference extinction peak for the reaction
kinetic study.
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C. A. MartınezꢀHuitle and E. Brillas, Appl. Catal. B, 2009, 87, 105–
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4
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Murugesan,
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Journal of Hazardous Materials B, 2002, 89, 303ꢀ
The in-situ generated AgNPs by aggregates of derivative
3
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RhB dye in the presence of visible light. The irradiation source
was a 200 W tungsten filament lamp located inside the reactor.
The RhB (2 mM) solution diluted 10 times in deionized water
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adsorption/desorption equilibrium. The dye solution in the
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withdrawn at regular intervals of time (after 1 hour) and UVꢀvis
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This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 7

RSC Advances
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8 | J. Name., 2012, 00, 1-3
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RSC Advances
View Article Online
DOI: 10.1039/C5RA02909K
TOC graphic
EBT
NaBH4
TOC synopsis
Pentacenequinone, HPB and PDI derivatives 3, 5 and 7 having aldehyde groups
have been synthesized. All the derivatives form aggregates in aqueous medium,
bind strongly with Ag+ ions and serve as reactors and stabilizers for the
preparation of AgNPs at room temperature. Further, in-situ generated AgNPs by
aggregates of derivative 3, 5 and 7 exhibit high catalytic efficiency for the
degradation of industrially important organic dyes.