G Model
ARTICLE IN PRESS
BIOMAC 5139 1–11
International Journal of Biological Macromolecules xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
International Journal of Biological Macromolecules journal homepage: www.elsevier.com/locate/ijbiomac
Montmorillonite/graphene oxide/chitosan composite: Synthesis, characterization and properties
1
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3
Q1
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Mithilesh Yadav, Sharif Ahmad ∗ Materials Research Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi 110025, India
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6 18
a r t i c l e
i n f o
a b s t r a c t
7 8 9 10 11 12
Article history: Received 11 February 2015 Received in revised form 15 May 2015 Accepted 31 May 2015 Available online xxx
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Keywords: Chitosan Graphene oxide Fourier transform infrared spectroscopy
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1. Introduction
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The present work reports the successful preparation, thermal and mechanical characterization of high performance films of Na+ montmorillonite (MMT)/graphene oxide (GO)/chitosan (CS) composite using simple solution mixing evaporation method. The formations of films were verified by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The thermal stability and mechanical properties of these films were investigated by thermogravimetric analysis (TGA) and mechanical testing (Instron 8871). The results obtained from these studies revealed that the composites of chitosan, MMT, and graphene oxide were homogeneous in nature. A synergistic effect of MMT and GO reinforcing on chitosan matrix was observed for the first time, in case of 5 wt.% MMT and 1 wt.% GO. The tensile strength of (5 wt.%) MMT/(1 wt.%) GO/CS composite was formed 9 ± 0.23% and 27 ± 0.25% higher than that of the (1 wt.%) GO/CS composite and chitosan, respectively. © 2015 Published by Elsevier B.V.
Chitosan, a copolymer of  [1]-linked 2-acetamido-2-deoxy-dglucopyranose and 2-amino-2-deoxy-d-glucopyranose, is obtained by deacetylation of chitin, one of the most plentiful natural polymers available on the earth [2]. Because of its good biocompatibility, biodegradability, and multiple functional groups, CS has attracted significant interest in a broad range of applications such as water treatment, separation membrane, food package, tissue engineering, and drug delivery [3]. However, low mechanical properties of CS restrict its use in a wide-range application. Nanocomposite technology using nanofillers such as carbon nanotubes, clay, and hydroxyapatite at low loading has already been proven to be an effective way to overcome the problems [4–6]. A number of novels carbon-based nanomaterials have been developed and studied. Recently, much interest developed in graphene among these materials [7–9], a single atom two dimensional thin film comprised of sp2 -bonded carbon materials has exhibited exponential increase in conductivity [10–12]. The increased application and significant behaviors of graphene can be attributed to the high surface area (theoretically 2620 m2 g−1 for single layer graphene) [13,14], high flexibility, and higher mechanical strength [15]. These unique properties of graphene could possess higher potential for its applications
∗ Corresponding author. Tel.: +91 11 26827508. E-mail address: sharifahmad [email protected] (S. Ahmad).
in the field of batteries [16,17], sensors [18], electrochemical supercapacitors [19], electrocatalysis [20] etc. Literatures report that the perfect graphene does not exist. However, the solution of bulk and processable functionalized graphene materials including graphene oxide (GO) can now be prepared [21]. Graphene oxide (GO) is considered to be an exciting material [22], which is covalently decorated with abundant oxygen-containing groups either on the basal plane or at the edges. The unique optical properties like fluorescence (FL) and electrochemiluminescence (ECL) have been observed in GO [23–25]. Furthermore, GO is most important precursor; find application in the synthesis of graphene ref, which has been widely applied in broad fields due to the low mass density ref, excellent electrical conductivity and high specific surface area. Generally, GO is synthesized by modified Hummers methods [26,27]. The large surface area of GO includes a number of functional groups, such as OH, COOH, O , and C O, which make GO hydrophilic and readily dispersible in water and some organic solvents [28]. On the other hand, as a hydrophilic biopolymer with NH2 and OH in each unit, CS can be protonated to a polycationic material in acidic media, which promotes the interaction between polymer chains and GO sheets ref. Thus, a good dispersion of GO in CS solution becomes possible. Mechanical properties (including the tensile modulus and strength) of a CS film could be greatly improved by introduction of GO. Na+ -montmorillonite (MMT) is one of the most important functionalized layered silicates used for the preparation of these organic-inorganic nanocomposites [29]. MMT is composed of an
http://dx.doi.org/10.1016/j.ijbiomac.2015.05.055 0141-8130/© 2015 Published by Elsevier B.V.
Please cite this article in press as: M. Yadav, S. Ahmad, Int. J. Biol. Macromol. (2015), http://dx.doi.org/10.1016/j.ijbiomac.2015.05.055
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G Model BIOMAC 5139 1–11 2 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89
ARTICLE IN PRESS M. Yadav, S. Ahmad / International Journal of Biological Macromolecules xxx (2015) xxx–xxx
aluminate sheet sandwiched between two silicate sheets, stacked together by weak ionic and van der Waals forces, which allow MMT to be easily intercalated and/or exfoliated [30]. The swelling ratio and mechanical behavior of the poly (N-isopropylacrylamide) hydrogel were improved by the introduction of MMT [31]. The NH2 groups of CS are protonated in acidic aqueous solution and can intercalate into layers of MMT to form CS/MMT composites [5]. The CS/MMT composite film was seldom investigated until now; although CS/MMT systems have been applied in many fields. There have been many reports on graphene oxide based chitosan composite with enhanced mechanical properties by simple physical mixing of two components [32]. To the best of our knowledge, the synergistic effect of MMT and GO on the mechanical properties of chitosan composites has not been reported yet. Henceforth in this study, in order to expand the various applications of CS, a simple solution evaporation method was used to prepare novel MMT/GO/CS composites. Considering the high performance and unique properties of CS, GO, and MMT, their combination may generate a novel material that holds great potential for pharmaceutical and biological applications. The main objective of this study is to investigate the synergistic effect of MMT and GO on the material properties of MMT/GO/CS composites.
2. Experimental
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2.1. Materials and methods
91
CS (average molecular weight = 350,000 gmol−1 , 90% degree of deacetylation), potassium permanganate (analytical grade), sodium nitrate, hydrogen peroxides and graphite with an average particle size of
ARTICLE IN PRESS
BIOMAC 5139 1–11
International Journal of Biological Macromolecules xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
International Journal of Biological Macromolecules journal homepage: www.elsevier.com/locate/ijbiomac
Montmorillonite/graphene oxide/chitosan composite: Synthesis, characterization and properties
1
2
3
Q1
4
Mithilesh Yadav, Sharif Ahmad ∗ Materials Research Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi 110025, India
5
6 18
a r t i c l e
i n f o
a b s t r a c t
7 8 9 10 11 12
Article history: Received 11 February 2015 Received in revised form 15 May 2015 Accepted 31 May 2015 Available online xxx
13
17
Keywords: Chitosan Graphene oxide Fourier transform infrared spectroscopy
19
1. Introduction
14 15 16
20Q2 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
The present work reports the successful preparation, thermal and mechanical characterization of high performance films of Na+ montmorillonite (MMT)/graphene oxide (GO)/chitosan (CS) composite using simple solution mixing evaporation method. The formations of films were verified by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The thermal stability and mechanical properties of these films were investigated by thermogravimetric analysis (TGA) and mechanical testing (Instron 8871). The results obtained from these studies revealed that the composites of chitosan, MMT, and graphene oxide were homogeneous in nature. A synergistic effect of MMT and GO reinforcing on chitosan matrix was observed for the first time, in case of 5 wt.% MMT and 1 wt.% GO. The tensile strength of (5 wt.%) MMT/(1 wt.%) GO/CS composite was formed 9 ± 0.23% and 27 ± 0.25% higher than that of the (1 wt.%) GO/CS composite and chitosan, respectively. © 2015 Published by Elsevier B.V.
Chitosan, a copolymer of  [1]-linked 2-acetamido-2-deoxy-dglucopyranose and 2-amino-2-deoxy-d-glucopyranose, is obtained by deacetylation of chitin, one of the most plentiful natural polymers available on the earth [2]. Because of its good biocompatibility, biodegradability, and multiple functional groups, CS has attracted significant interest in a broad range of applications such as water treatment, separation membrane, food package, tissue engineering, and drug delivery [3]. However, low mechanical properties of CS restrict its use in a wide-range application. Nanocomposite technology using nanofillers such as carbon nanotubes, clay, and hydroxyapatite at low loading has already been proven to be an effective way to overcome the problems [4–6]. A number of novels carbon-based nanomaterials have been developed and studied. Recently, much interest developed in graphene among these materials [7–9], a single atom two dimensional thin film comprised of sp2 -bonded carbon materials has exhibited exponential increase in conductivity [10–12]. The increased application and significant behaviors of graphene can be attributed to the high surface area (theoretically 2620 m2 g−1 for single layer graphene) [13,14], high flexibility, and higher mechanical strength [15]. These unique properties of graphene could possess higher potential for its applications
∗ Corresponding author. Tel.: +91 11 26827508. E-mail address: sharifahmad [email protected] (S. Ahmad).
in the field of batteries [16,17], sensors [18], electrochemical supercapacitors [19], electrocatalysis [20] etc. Literatures report that the perfect graphene does not exist. However, the solution of bulk and processable functionalized graphene materials including graphene oxide (GO) can now be prepared [21]. Graphene oxide (GO) is considered to be an exciting material [22], which is covalently decorated with abundant oxygen-containing groups either on the basal plane or at the edges. The unique optical properties like fluorescence (FL) and electrochemiluminescence (ECL) have been observed in GO [23–25]. Furthermore, GO is most important precursor; find application in the synthesis of graphene ref, which has been widely applied in broad fields due to the low mass density ref, excellent electrical conductivity and high specific surface area. Generally, GO is synthesized by modified Hummers methods [26,27]. The large surface area of GO includes a number of functional groups, such as OH, COOH, O , and C O, which make GO hydrophilic and readily dispersible in water and some organic solvents [28]. On the other hand, as a hydrophilic biopolymer with NH2 and OH in each unit, CS can be protonated to a polycationic material in acidic media, which promotes the interaction between polymer chains and GO sheets ref. Thus, a good dispersion of GO in CS solution becomes possible. Mechanical properties (including the tensile modulus and strength) of a CS film could be greatly improved by introduction of GO. Na+ -montmorillonite (MMT) is one of the most important functionalized layered silicates used for the preparation of these organic-inorganic nanocomposites [29]. MMT is composed of an
http://dx.doi.org/10.1016/j.ijbiomac.2015.05.055 0141-8130/© 2015 Published by Elsevier B.V.
Please cite this article in press as: M. Yadav, S. Ahmad, Int. J. Biol. Macromol. (2015), http://dx.doi.org/10.1016/j.ijbiomac.2015.05.055
41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67
G Model BIOMAC 5139 1–11 2 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89
ARTICLE IN PRESS M. Yadav, S. Ahmad / International Journal of Biological Macromolecules xxx (2015) xxx–xxx
aluminate sheet sandwiched between two silicate sheets, stacked together by weak ionic and van der Waals forces, which allow MMT to be easily intercalated and/or exfoliated [30]. The swelling ratio and mechanical behavior of the poly (N-isopropylacrylamide) hydrogel were improved by the introduction of MMT [31]. The NH2 groups of CS are protonated in acidic aqueous solution and can intercalate into layers of MMT to form CS/MMT composites [5]. The CS/MMT composite film was seldom investigated until now; although CS/MMT systems have been applied in many fields. There have been many reports on graphene oxide based chitosan composite with enhanced mechanical properties by simple physical mixing of two components [32]. To the best of our knowledge, the synergistic effect of MMT and GO on the mechanical properties of chitosan composites has not been reported yet. Henceforth in this study, in order to expand the various applications of CS, a simple solution evaporation method was used to prepare novel MMT/GO/CS composites. Considering the high performance and unique properties of CS, GO, and MMT, their combination may generate a novel material that holds great potential for pharmaceutical and biological applications. The main objective of this study is to investigate the synergistic effect of MMT and GO on the material properties of MMT/GO/CS composites.
2. Experimental
90
2.1. Materials and methods
91
CS (average molecular weight = 350,000 gmol−1 , 90% degree of deacetylation), potassium permanganate (analytical grade), sodium nitrate, hydrogen peroxides and graphite with an average particle size of
