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On: 11 August 2014, At: 08:08
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Materials and Manufacturing Processes
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Microwave-Assisted Synthesis of Silver Nanoparticles Using Chitosan: A Novel Approach
Ngoan Thi Nguyen a , Binh Hai Nguyen b , Duong Thi Ba a , Dien Gia Pham a , Tran Van Khai c , Loc Thai Nguyen b & Lam Dai Tran b
a Institute of Chemistry, Vietnam Academy of Science and Technology , Ha Noi , Viet Nam b
Institute of Materials Science, Vietnam Academy of Science and Technology , Ha Noi , Viet Nam
c Faculty of Materials Technology , Ho Chi Minh City University of Technology , Ho Chi Minh City , Viet Nam
Accepted author version posted online: 20 Feb 2014.Published online: 01 Apr 2014
To cite this article: Ngoan Thi Nguyen , Binh Hai Nguyen , Duong Thi Ba , Dien Gia Pham , Tran Van Khai , Loc Thai Nguyen
& Lam Dai Tran (2014) Microwave-Assisted Synthesis of Silver Nanoparticles Using Chitosan: A Novel Approach, Materials and Manufacturing Processes, 29:4, 418-421, DOI: 10.1080/10426914.2014.892982
To link to this article: http://dx.doi.org/10.1080/10426914.2014.892982
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Trang 2In this work, microwave-assisted (MwH) synthesis of silver nanoparticles (AgNPs) using chitosan was investigated The new method was compared against chemical reduction (CRed) by NaBH 4 and conventional thermal method (CvH) The as-synthesized AgNPs were char-acterized by UV–Visible spectroscopy, transmission electron microscopy (TEM) and infrared spectroscopy The MwH method was found to effectively synthesize AgNPs of which properties were comparable CRed and CvH The average particle sizes of AgNPs produced by CRed, CvH and MwH were approximately 20, 5 and 7 nm, respectively The proposed approach can provide a viable green route for synthesizing AgNPs with high potential applicability.
Keywords Biodegradable; Chitosan; Green; Heating; Microwave; Nanoparticles; Reduction; Silver.
INTRODUCTION
In recent years, metal nanoparticles (NPs) have
attracted increasing attention due to their unique
phy-sical, chemical properties and numerous prospective
applications [1, 2] In general, metal NPs can be
synthe-sized by chemical or physical pathways The chemical
method in which NPs are formed by reduction of metal
ions in the solution is most widely used [2–6] due to its
cost effectiveness, simple equipment and capability of
large-scale production However, strong reducing agents
such as NaBH4, citrate or ascorbate could be sources of
environmental toxics or biological hazards [6]
There-fore, alternative ‘‘green’’ agents derived from naturally
occurring substances are desirable Natural polymers
such as starch and chitosan (CS) are highly preferred
due to their non-toxic properties and biocompatibility
[7] Chitosan, N-deacethylated derivative of chitin, is a
viable option since it is cheap, easily available [8],
bio-compatible, biodegradable and environmental-friendly
[9] Various studies demonstrate that chitosan could be
successfully used as a reducing and stabilizing agent in
the synthesis of metal NPs [1, 2, 6] Despite the fact that
chemical reducing reactions can generally take place at
ambient conditions [10, 11], they require the input of
additional thermal energy to achieve high reaction rate
Traditional heating method in which the heat transfer is
mainly driven by conduction and convection takes long
time and can result in nonuniform temperature distri-bution Since morphology and properties of metal NPs strongly depend on experimental conditions [2], selection
of an appropriate heating method would be essential to reproducibly synthesize metal NPs of desired properties Microwave-assisted (MwH) heating received consider-able interests in organic synthesis [12, 13] and inorganic materials preparation [14, 15] due to its ability to gener-ate the fast reaction times, high-throughput capabilities and beneficial crystallization effects [15] Rapid and uni-form heating effects of microwave heating were reported
to be conducive to synthesis of metal nanoclusters of small size and uniform dispersity [16] MwH heating was also shown to have marked effects on nucleation and growth mechanisms of NPs [17] In this study, a novel pathway to synthesize silver nanoparticles (AgNPs) using chitosan and MwH heating was investi-gated Properties of AgNPs produced were characterized
by transmission electron microscopy (TEM), UV–vis and (infrared) IR spectroscopy and compared against those obtained by traditional chemical synthesis and conventional heating
EXPERIMENTAL Chitosan was purchased from Tokyo Chemical Co Ltd Other reagents were of analytical grades In this research, MwH synthesis of AgNPs was studied and compared against chemical reduction (CRed) and con-ventional thermal (CvH) methods The schematic diagram of experimental procedures used is given in Fig 1
Chitosan suspension in acetic acid solution was pre-pared by dissolving 0.5 g of chitosan in 100 mL of 2% acetic acid solution The mixture was vortexed until a
Received December 12, 2013; Accepted January 9, 2014
Address correspondence to Lam Dai Tran, Institute of Materials
Science, Vietnam Academy of Science and Technology, 18 Hoang
Quoc Viet Road, Ha Noi, Viet Nam; E-mail: lamtd@ims.vast.ac.vn
Color versions of one or more of the figures in the article can be
found online at www.tandfonline.com/lmmp.
418
Trang 3homogeneous product was obtained Then, 20 mL of
0.1 M AgNO3solution was added to 100 mL of chitosan
suspension and the mixture was vigorously agitated by a
magnetic stirrer for 30 min Chemical reduction was
con-ducted at room temperature by adding 2 M NaBH4
sol-ution (10 mL) to AgNO3=chitosan suspension with the
initial molar ratio of NaBH4 to AgNO3 fixed at 1:1
The reaction was allowed to take place for 15 min during
which the suspension turned to dark brown color With
respect to the production of AgNPs by conventional
heating, 100 mL of AgNO3=chitosan suspension was
heated on a hot-plate at 70C and the sample was mixed
by a magnetic stirrer In previous study [2], it was found
that optimal reaction time for conventional heating
method was about 6 hr Therefore, the same holding
time was used for this study Upon completion of the
reaction, the suspension was observed to change from
light-yellowish to light-brown color The MwH synthesis
of AgNPs was conducted at 70C for 2 min in a
micro-wave oven (model MW-ER-01, Lab-kits) with output
power fixed at 200 W The suspension obtained had a
light-brown color
The AgNPs were characterized using UV–visible
troscopy, IR spectroscopy and TEM Prior to
spec-troscopy analysis, colloidal suspension of AgNPs was
diluted by water to concentration of 200 ppm
UV–vis-ible spectra were recorded using a Beckman DU 520
UV–Vis spectrophotometer IR spectra were collected
from 500 to 4000 cm1by Impact 410 (Nicolet)
spectro-photometer (Carl Zeiss Jena) The morphology of the
NPs was examined by Hitachi H7600 transmission
elec-tron microscope at 120 kV
RESULTS AND DISCUSSION UV–Vis Absorption Spectra of Synthesized AgNPs
In Fig 2, UV–Vis spectra of AgNPs obtained by
CRed, CvH and MwH are comparatively presented
The spectra exhibit surface plasmon resonance (SPR)
peaks from 400 to 420 nm which clearly evidenced the formation of AgNPs The change in color of the suspen-sions (inset) further confirmed the UV–Vis data It was worth noting that AgNPs produced by CRed and MwH had significantly higher SPR band intensity than that of AgNPs obtained from CvH Since the intensity
of SPR band depends on AgNPs concentration, it was obvious from UV–Vis spectra that the syntheses of AgNPs by MwH and CRed were more effective than CvH Similar trends were also noticed for the color intensity of the CRed, CvH and MwH suspensions The influence of MwH in the synthesis of noble metal NPs was previously investigated and compared to CvH [16, 17] Enhanced effectiveness was attributed to rapid and uniform heating of MwH [16] or alternately, marked effects of MwH on nucleation and growth mechanism of NPs [17]
Analysis of TEM Images Figure 3 shows the TEM images (Fig 3(a)–(c)) and particle size histograms (Fig 3(d)–(f)) of AgNPs obtained by CRed, CvH and MwH, respectively As illu-strated in images, three methods produced AgNPs with approximate spherical shape Average diameters were estimated to be 20, 5 and 7 nm for AgNPs prepared by CRed, CvH and MwH, respectively Particle sizes varied from 5.0 to 27.0 nm for AgNPs1; 1.0–9.0 nm for AgNPs2 and 1.0–12.0 nm for AgNPs3
Analysis of IR Spectra Figure 4 presents IR spectra of chitosan and AgNPs synthesized by CvH and MwH Broad peaks at
3440 cm1overlap –OH and –NH stretching vibrations Changes in intensity of peaks from 3300 to 3500 cm1 were reportedly attributed to attachment of silver which affected N–H vibrations [18] Other authors suggested
F IGURE 2.—The UV–visible spectra of silver nanoparticles produced by reducing with NaBH 4 at room temperature (AgNPs1), conventional ther-mal method (AgNPs2) and microwave-assisted method (AgNPs3).
F IGURE 1.—Schematic diagram of experimental procedures for
synthesiz-ing silver nanoparticles (AgNPs) via different pathways.
MICROWAVE-ASSISTED SYNTHESIS OF SILVER NANOPARTICLES 419
Trang 4that variations of shape and intensity of peaks in this region resulted from contribution to reduction and stabilizing process [19] The bands from 1350 to
1390 cm1correspond to absorption of C–N vibrations and residual NO3 1[20]; hence change of peak intensity could indicate the presence of NO3 1 after reaction of chitosan with AgNO3 The spectra of AgNPs produced
by CvH and MwH exhibit blue shift of CS peak at
1646 cm1and 1560 cm1to 1634 cm1 and 1544 cm1, respectively Since these bands are associated with amines groups of chitosan, the shift of the peaks prob-ably indicates attachment of AgNPs to amine groups which leads to change in molecular weight and subse-quently, vibration intensity
To verify if the reducing reaction was completed, AgNPs suspensions (AgNPs1, AgNPs3) were tested with solution of NaCl 1 M (Fig 5) The results were negative which meant AgNPs suspensions were completely free from Agþ1
F IGURE 3.—Transmission electron microscopy (TEM) images and particle size histograms of silver nanoparticles produced by chemical reduction (a, d), conventional heating (b, e) and microwave-assisted synthesis (c, f) Scale bar corresponds to 20 nm.
F IGURE 4.—Infrared spectra of chitosan (CS), silver nanoparticles
synthe-sized by conventional heating (AgNPs2) and microwave-assisted method
(AgNPs3).
Trang 5In summary, the proposed MwH synthesis of AgNPs
could successfully produce NPs with properties
compa-rable to those obtained by traditional chemical
reduc-tion The formation of AgNPs was validated by TEM,
UV–Vis and IR spectroscopic analysis The AgNPs
synthesized by MwH had relatively uniform sizes with
average diameter of approximately 7 nm The findings
revealed that the MwH method could serve as an
alter-native to traditional chemical reduction for green
syn-thesis of AgNPs
FUNDING This work was financially supported by the National
Foundation for Science and Technology Development
(NAFOSTED), project number 103.02-2011.57 Financial
support was also provided in part by IFS grant (No
F=5022-1)
REFERENCES
1 Huang, H.; Yang, X Synthesis of polysaccharide-stabilized
gold and silver nanoparticles: a green method Carbohydrate
Research 2004, 339, 2627–2631.
2 Tran, H.V.; Tran, L.D.; Ba, C.T.; Vu, H.D.; Nguyen, T.N.;
Pham, D.G.; Nguyen, P.X Synthesis, characterization,
anti-bacterial and antiproliferative activities of monodisperse
chitosan-based silver nanoparticles Colloids and Surfaces A:
Physicochemical and Engineering Aspect 2010, 360, 32–40.
3 Shiraishi, Y.; Arakawa, D.; Toshima, N pH-Dependent color
change of colloidal dispersions of gold nanoclusters: effect
of stabilizer The European Physical Journal E 2002, 8 (4),
377–383.
4 Bhui, D.K.; Bar, H.; Sarkar, P.; Sahoo, G.P.; De, S.P.; Misra,
A Synthesis and UV–vis spectroscopic study of silver
nanoparticles in aqueous SDS solution Journal of Molecular
Liquids 2009, 145, 33–37.
5 Songping, W.; Shuyuan, M Preparation of ultrafine silver powder using ascorbic acid as reducing agent and its appli-cation in MLCI Materials Chemistry and Physics 2005, 89, 423–427.
6 Wei, D.; Sun, W.; Qian, W.; Ye, Y.; Mac, X The synthesis of chitosan-based silver nanoparticles and their antibacterial activity Carbohydrate Research 2009, 344, 2375–2382.
7 Hu, B.; Wang, S.B.; Wang, K.; Zhang, M.; Yu, S.H Microwave-assisted rapid facile ‘‘green’’ synthesis of uniform silver nanoparticles: self-assembly into multilayered films and their optical properties Journal of Physical Chemistry C 2008,
112, 11169–11174.
8 Ma, G.P.; Yang, D.Z.; Zhou, Y.S.; Xiao, M.; Kennedy, J.F.; Nie, J Preparation and characterization of water-soluble N-alkylated chitosan Carbohydrate Polymers 2008, 74, 121–126.
9 Jigar, M.J.; Sinha, V.K Ceric ammonium nitrate induced grafting of polyacrylamide onto carboxymethyl chitosan Carbohydrate Polymers 2007, 67, 427–435.
10 Sun, Y.G.; Xia, Y.N Shape-controlled synthesis of gold and silver nanoparticles Science 2002, 298, 2176–2179.
11 Sun, Y.G.; Mayers, B.; Herricks, T.; Xia, Y.N Polyol synthesis of uniform silver nanowires: A plausible growth mechanism and the supporting evidence Nano Letters 2003,
3, 955–960.
12 Kappe, C.O Controlled microwave heating in modern orga-nic synthesis Angewandte Chemie International Edition 2004,
43, 6250–6284.
13 Lidstrom, P.; Tierney, J.; Wathey, B.; Westman, J Micro-wave assisted organic synthesis: a review Tetrahedron 2001,
57, 9225–9283.
14 Bilecka, I.; Niederberger, M Microwave chemistry for inorganic nanomaterials synthesis Nanoscale 2010, 2, 1358–1374.
15 Nadagouda, M.N.; Speth, T.F.; Varma, R.S Microwave-assisted green synthesis of silver nanostructures Accounts of Chemical Research 2011, 44, 469–478.
16 Tu, W.X.; Liu, H.F Rapid synthesis of nanoscale colloidal metal clusters by microwave irradiation Journal of Materials Chemistry 2000, 10, 2207–2211.
17 Dahal, N.; Garcia, S.; Zhou, J.P.; Humphrey, S.M Beneficial effects of microwave-assisted heating versus conventional heating in noble metal nanoparticle synthesis ACS Nano
2012, 6, 9433–9446.
18 Wei, D.; Sun, W.; Qian, W.; Ye, Y.; Ma, X The synthesis of chitosan-based silver nanoparticles and their antibacterial activity Carbohydrate Research 2009, 344, 2375–2382.
19 Venkatesham, M.; Ayodhya, D.; Madhusudhan, A.; Babu, N.V.; Veerabhadram, G A novel green one-step synthesis of silver nanoparticles using chitosan: catalytic activity and antimicrobial studies Applied Nanoscience 2012 DOI:10.1007=s13204-012-0180-y.
20 Lv, Y.; Long, Z.; Song, C.; Dai, L.; He, H.; Wang, P Preparation of dialdehyde chitosan and its application in green synthesis of silver nanoparticles Bioresources 2013, 8, 6161–6172.
F IGURE 5.—Testing of residual Agþ1in AgNPs1 and AgNPs3 using 1 M
NaCl solution.
MICROWAVE-ASSISTED SYNTHESIS OF SILVER NANOPARTICLES 421