A review: synthesis and applications of graphene/chitosan nanocomposites

  • cc icon
  • ABSTRACT

    Recently, with continuous developments in the field of materials science, graphene oxide (GO) has emerged as a promising material with excellent electrical, thermal, mechanical, and optical properties, which play important roles in most fields. Researchers have achieved considerable progress with graphene. Chitosan (CS) is a natural polymer that has been studied intensively owing to its specific formation, high chemical resistance, and excellent physical properties. These outstanding properties have led to its universal use in applications such as textile fabrics, tissue engineering, medicine and health, coatings, and paints. By combining the advantages of GO and CS, different types of promising materials can be obtained. This review discusses the preparation of GO-CS fibers, hydrogel and aerogel, and the applications of GO-CS nanocomposites. In addition, directions for future research on graphene material composites are discussed.


  • KEYWORD

    carbon composites , adsorption , amino acids , dyes , hydrogel

  • 1. Introduction

    Graphene oxide (GO) has many extraordinary properties and has great potential among nanomaterials. Since its discovery, it has been studied by many researchers for a variety of novel applications owing to its excellent chemical and physical properties, including low density, exceptional mechanical properties, large surface area, inherent impermeability, mechanical strength, and excellent electrical conductivity [1-5]. In other words, graphene is promising and gaining increasing attention for different applications [6-7]. The carbon atoms in GO within a single layer are combined via sp2-hybridization with other graphene layers [8-9]. Each carbon atom has an electron that is not involved in bonding, and these electrons form a large delocalized bond in the vertical direction. Thus, the intermolecular van der Waals interactions are strong, and the bond accumulation effect between each layer easily leads to irreversible graphene aggregation [10-17].

    Chitosan (CS) is the product of chitin deacetylation and contains a large quantity of hydrophilic groups (e.g., amino and carboxyl groups). Thus, CS molecules are easily protonated. It has been widely used in medicine and has many excellent biological properties, such as biocompatibility, biodegradability, and coagulation activity [15-17]. Spinning CS into fibers for medical uses, such as for absorbable sutures, wound dressings, and artificial skin, is a particularly important goal for scientists. CS and its derivatives have been applied as clothing, food additives, cosmetics, and antibacterial agents, and have been used in medical treatment and medicinal development [18,19]. It is obvious that CS will bring about considerable economic and social benefits [20].

    Not only does GO contain carboxyl and epoxy groups, it is also possible to insert small molecules or polymers between its layers [21-25]. The surface anionic groups of GO are able to interact with the CS matrix via hydrogen bonding and electrostatic interactions, to achieve good dispersion [15-17]. The composites prepared by combining the advantages of each material are expected to lead to new nanomaterials. In this paper, we present an overview of GO-CS composites and discuss recent theoretical advances in fibers, hydrogels, aerogels, nanocomposites, and their applications (Fig. 1).

    2. Preparation of Graphene Chitosan Fiber

    There are free amino groups in CS molecules; the greater the number of amino groups are, the more clearly the amino features manifest. CS can be dissolved in dilute acid solutions, where it acquires cationic properties. Because its chemical structure is similar to that of cellulose, researchers have considered using it in the synthesis of fibers [25], and this has attracted considerable interest [26]. Graphene CS fibers have a unique combination of properties that will lead to applications in many fields [27].

       2.1 Wet spinning

    One of the most widespread spinning methods used to synthesize chemical fibers is wet spinning. This technique has the advantages of being applicable to multiple materials and being able to prepare bulky concentrates. The procedure is as follows: first, the required spinning solution is prepared. Then, the spinning solution is extruded to form a trickle through a spinneret orifice. Next, the trickle solidifies in a coagulation bath to generate nascent fibers. Finally, the fibers are subjected to stretching, water scrubbing, drying, and other procedures, or reprocessed directly [28]. Wastewater from the textile, dye, paint, papermaking, and plastic industries has severely threatened environmental security, yet wastewater is still handled inefficiently. Du et al. [29] prepared graphene CS silica fibers by wet spinning, and they showed very high adsorption and efficiency for the removal of dye in wastewater. Silica nanoparticles were etched from the graphene CS silica fiber by diluted HF solution to produce GO/CS fibers (GO/CS/ETCH). Tests demonstrated that GO/CS/ETCH could remove Congo red from an aqueous solution, which was used as an environmental protection material for removing Congo red from wastewater. Li et al. [30] prepared GO/CS composites by wet spinning to treat fuchsin acid dye in wastewater, which is harmful to the environment. The addition of GO enhanced the stretched length of CS fibers, and the experiment indicated that the initial PH was one of the most important factors that affected the adsorption capacity of GO/CS fiber for fuchsin acid dye. However due to its complicated preorder procedure, technological process, high cost, and low spinning speed, it is generally not used in industry.

       2.2 Electrospinning

    Electrospinning is a relatively unique method for fabricating fibers, where polymer solutions or melts are subjected to jet spinning by an applied electric field force. In the electric field, spherical drops within a needle become cones, and then fiber filaments extend from the cone tip. Electrospinning is a simple, effective, and widely available new processing technology for synthesizing nanofibers, in which a polymer fluid atomized by static electricity is moved a long distance, and finally stretched into fiber [31-35].

    Liu et al. [33] successfully prepared polyvinyl alcohol (PVA)/CS/graphene biological composite nanofibers using aqueous electrospinning, and was the first to synthesize CS nanofibers with nontoxic, solution-based GO. The addition of GO improved the mechanical properties, hydrophilicity, and antibacterial activity of PVA/CS fibers to some extent. These fibers are promising for drug delivery systems, tissue engineering, and wound healing. Ardeshirzadeh et al. [34] prepared a polyoxyethylene/CS/graphene nanofiber scaffold able to control the release of adriamycin. The nanofibers, obtained by electrospinning, had good stability and demonstrated drug transportation, and they also eliminated previous shortcomings, such as low solubility, stability, and poor mechanical properties, of electrospun CS. In addition, adriamycin could be combined closely with π-π* bonds, and π-π* stacking was beneficial in controlling the release of drugs. Because they lack toxic effects on healthy cells and tissues, polyethylene oxide/CS/GO is ideal materials as delivering vehicles for anti-cancer drugs. The World Health Organization has stated that there are billions of people who do not have access to safe drinking water every year. However, water purification systems require high pressure and membranes to eliminate parvovirus and heavy metal ions. Bai et al. [35] discovered that a composite fiber of CS and GO formed by electrospinning could adsorb membraneless viruses and remove viruses and bacteria from water. Thus, this discovery is significant for areas that are short of fresh water and where filtration membranes cannot be used.

    3. Preparation Chitosan Graphene Hydrogel

    Hydrogel is a soft, cross-linked polymer that uses water as the dispersion medium. It can maintain a definite shape and absorb a large amount of water without being dissolved. Hydrogel is biocompatible and can be used in areas such as drug delivery systems, biomimetic materials, and chemo-mechanical systems [36].

    To cope with the common problem of water pollution, Chen et al. [37] prepared a GO/CS hydrogel as a new type of adsorbent for water supply treatment that is environment friendly. The GO/CS hydrogel could adsorb organic dyestuff and heavy metal ions in wastewater. Absorbent GO-CS offers lower cost and better biocompatibility, which is important in water treatment. Han and Yan [38] conducted special research on CS chains with GO nano sheets, in which GO was used as a two-dimensional cross-linking agent. They fabricated GO-CS super-molecule hydrogel by controlling the GO concentration, rate of CS-GO, and temperature. This type of hydrogel is self-healing and reversible, and can be applied in biomaterials, sewage disposal, and smart materials.

    4. Preparation of Aerogel

    Aerogels are widely applicable owing to their vast specific surface area, low density, and light weight. Although it is seems fragile, it is in fact very solid and durable and can withstand pressures equivalent to thousands of times its own weight. It can withstand a temperature of up to 1200℃, after which it melts. Its insulating ability is 39 times better than that of the best glass fibers. Aerogels are generally prepared by (1) preparation of solgel and (2) supercritical drying [39-40].

    The sol-gel phase is a wet gel. In this phase, the precursor is dissolved in solvents to obtain a solution with homogeneous dispersion. Hydrolysis or alcoholysis is used to form the sol. Then, the gel is produced by evaporation or drying. The wet gel contains rudimentary solvents and water; therefore, the wet gel volume contracts significantly in the drying process. Holes can collapse due to surface tension in typical drying and this leads to low pore volume and surface area. In order to avoid this effect, supercritical drying is used to turn the liquid into a supercritical fluid by putting it into a pressure vessel under high pressure and temperature. In the critical state where gas and liquid phases coexist, the density of the liquid is identical to its saturated vapor pressure, the interface between the gas phase and liquid phase disappears, the capillary force in the wet gel also disappears, holes cannot collapse, and relatively higher pore volume and surface area are achieved [39,41].

       4.1 Preparation of graphene chitosan aerogel

    Yu et al. [42] prepared graphene CS aerogel because the excessive superposition of GO sheets in GO adsorbent influences its adsorption capacity for pollutants. An aerogel, however, can easily be separated from the system after adsorption. The aerogel had good adsorption for cupric ions, especially with higher pH, lower ionic strength, and higher temperature. They also made a comparison of the qm of GO-CS with that of other adsorbents reported in the literature (Fig. 2). From the graph, it is obvious that GO-CS aerogel could be ranked among the most effective adsorbents of Cu2+, comparable to activated sludge, lignin, carbon nanotubes, and other graphene adsorbents. As air and water pollution become more serious, GO-CS aerogel will play an important role in many fields. Most dyes are difficult to eliminate because they are non-biodegradable. Wang et al. [43] fabricated porous CS aerogels doped with GO by crosslinking and freeze drying. It is expected these will be used extensively in the textile, biological, chemical, plastic, paint, and paper industries, where porous CS-GO aerogels will be a potential alternative for dye removal.

    Supercapacitors possess many extraordinary properties, such as high power density, long lifetime, and safety and have been applied in various fields. At present, high energy-storage capability is usually achieved with activated carbon. However, its high cost and low energy density limit its broad application. GO is superior because of its excellent electrical, thermal, mechanical, and optical properties. Hao et al. [44] produced ‘graphene-based-nitrogen self-doped hierarchical porous carbon’ with outstanding performance by the carbonization of CS aerogel and activation with KOH. The obtained aerogel had macropores, mesopores, and micropores, as well as a high specific surface area. Until now, there has been little research on the fabrication of aerogels for use in supercapacitors; hence, it was a great breakthrough in the field of energy storage.

    5. Preparation of Graphene Chitosan Composite

    The preparation of GO-CS usually involves the GO reduction method. Graphite is a basic element that has good dispersibility and stability after surface modification. It is mixed with a second component to form a composite. According to different combinations of graphene and the second component, there are several categories: (1) graphene is regarded as a continuous phase for the second material, and the second component covers graphene during the formation of nanoparticles; (2) both graphene and the second component are continuous phases; and (3) the second component is a continuous phase, and graphene is a filling phase as the second component (Table 1) [13,14].

       5.1 Solution mixing

    Solution mixing is a process in which graphene and a second component are mixed such that the second component is inserted into the graphene via a solvent. Then, the composite is formed with a reducing agent. Ding et al. [45] fabricated cationic functional hexa-alkylguanidinium ionic liquids and anionic functional tetra-alkylguanidinium ionic liquids; then prepared a magnetic chitosan graphene oxide (MCGO) composite with unique properties. Trypsin, lysozyme, ovalbumin, and bovine serum albumin could be extracted well. MCGO-functional guanidinium ionic liquid can easily be recycled and will find applications for handling other biomolecules. Li et al. [46] prepared an MCGO ionic liquid composite and discovered that it could remove Cr3+ quickly and efficiently. In addition, it has the advantages of economy and environmental friendliness.

       5.2 In-situ polymerization

    In in-situ polymerization, graphene and monomers are mixed, and monomers aggregate between the layers of graphene via an initiator. The discovery of and research on new materials must finally apply theory to practice. Zhou et al. [47] abandoned former means of reducing graphene and created a process for the vat dye industry where GO was reduced using sodium dithionite, and by which graphene CS composites were produced by insitu polymerization. The study indicated that sodium dithionite could reduce GO to graphite efficiently and that the addition of graphene could greatly improve the mechanical and electrical properties when graphene was dispersed uniformly within the polymer matrix.

    6. Applications of Graphene-Chitosan Composites

    Most current research on carbon nanomaterials, including carbon nanotubes, graphite, and GO, has been focused on their unique physical and chemical properties [48]. As soon as their basic properties have been fully described, the next level of research should be focused on their potential and practical applications [49]. They will be promising candidates for applications in diverse fields.

       6.1 Applications in biomedicine

    The structure of GO-CS composites produced with chemical synthesis using thin pieces or layers of graphite is symmetrical, which means that GO-CS composites can be applied as antibacterial agents in stem cell proliferation and nanostructural templates. Mazaheri et al. [50] discovered that the strength and elastic modulus of the layers increased by improving the concentration of GO in CS. In addition, the GO-CS composite showed a significant resistance to Staphylococcus aureus bacteria. Traditionally, the reduction of GO uses chemical substances to dispose of GO, which is not beneficial for the development of GO in biomedicine, because these chemical substances are harmful to human health and cells. In the process of drug delivery, cells and drugs cannot tolerate high temperature; therefore, we should determine a green reduction process. Justin et al. [51] reduced GO with CS at body temperature (37℃) for the first time, which allowed GO to be reduced without harming cells or decreasing the effectiveness of the therapeutic drugs.

       6.2 Applications in sewage treatment

    Fouling of reverse osmosis membranes remains a challenging and restrictive aspect of membrane filtration performance, so it is necessary to find new methods to enhance membrane antifouling properties. Hegab et al. [52] used GO functionalized CS (GO/f-CS) in a commercial brackish water thin-film composite using a novel surface modification. The GO/f-CS/polyamide (PA) composite membranes showed superior performance compared to the unmodified PA membrane in terms of hydrophilicity, surface smoothness, water flux, and antifouling. Travlou et al. [53] researched magnetic GO-CS, and thermomechanical analysis suggested that this material has a high adsorption capacity for sewage.

       6.3 Applications in batteries and electrochemistry

    Nowadays, lithium-ion batteries (LIBs) are essential energy storage systems in portable electronic devices, owing to their high energy density, high working voltage and low self-discharge rate [54-55]. Therefore, new electrode materials with good compatibility with LIBs electrolyte are obviously significant. Ma et al. [56] prepared ultrathin MoS2/graphene hetero structures that had excellent electrochemical properties and large specific surface areas. They achieved this using a facile CS-assisted hydrothermal and subsequent calcination approach. It is believed that this simple and efficient strategy will be a milestone for large-scale production of various hetero structures with many potential applications in fuel cells, supercapacitors, and lithium ion batteries.

    It is difficult to detect dimethyl disulfide (DMDS); especially volatile sulfur compounds (VSCs). Today, the most popular method for the quantitative analysis of sulfur compounds in environmental samples relies on gas chromatography (GC) [57-59]. However, GC analysis of VSCs requires efficient sample pretreatment and enrichment methods, and such procedures are complicated, time consuming, and tedious [60-61]. In contrast, electrochemistry has much higher sensitivity, much lower detection limits, and lower cost. Rajabzadeh et al. [62] first published on graphene-CS sensing of DMDS in liquid samples, which is simple, fast and environmentally friendly.

    7. Conclusions

    GO-CS is a new type of nanomaterial that combines carbon and the natural polymer. Then new material possesses not only large specific surface area and good electrical properties, but also specific functional groups with properties different from those of iron-carbon. Therefore, by creating a composite material, the advantages of both materials can be combined, and is expected to be applied extensively. However, research on it is not sufficient and must be improved. Modification and research in the future can be considered from the following points of view: (1) we can discover more suitable polymers to combine with GO and obtain a more valuable nanomaterial. (2) Polyvinylpyrrolidone (PVP) is also a linear polymer, which has a high solubility in water and good biocompatibility. We can consider combining PVP, CS, and GO to prepare composites [15,17]. (3) The surface of GO still has many defects; thus we need to find other materials to modify it in order to utilize its properties better.

  • 1. Lee EJ, Choi SY, Jeong H, Park NH, Yim W, Kim MH, Park JK, Son S, Bae S, Kim SJ, Lee K, Ahn YH, Ahn KJ, Hong BH, Park JY, Rotermund F, Yeom DI (2015) Active control of all-fibre graphene devices with electrical gating [Nat Commun] Vol.6 P.6851 google doi
  • 2. Li W, Wang X, Zhang X, Zhao S, Duan H, Xue J (2015) Mechanism of the defect formation in supported graphene by energetic heavy ion irradiation: the substrate effect [Sci Rep] Vol.5 P.9935 google doi
  • 3. Zhu C, Han TYJ, Duoss EB, Golobic AM, Kuntz JD, Spadaccini CM, Worsley MA (2015) Highly compressible 3D periodic graphene aerogel microlattices [Nat Commun] Vol.6 P.6962 google doi
  • 4. Kostarelos K, Novoselov KS (2014) Exploring the interface of graphene and biology [Science] Vol.344 P.261 google doi
  • 5. Celebi K, Buchheim J, Wyss RM, Droudian A, Gasser P, Shorubalko L, Kye JI, Lee C, Park HG (2014) Ultimate permeation across atomically thin porous graphene [Science] Vol.344 P.289 google doi
  • 6. Geim AK (2009) Graphene: status and prospects [Science] Vol.324 P.1530 google doi
  • 7. Bonaccorso F, Colombo L, Yu G, Stoller M, Tozzini V, Ferrari AC, Ruoff RS, Pellegrini V (2015) Graphene, related two-dimensional crystals, and hybrid systems for energy conversion and storage [Science] Vol.347 P.1246501 google doi
  • 8. Moradi O, Gupta VK, Agarwal S, Tyagi I, Asif M, Makhlouf ASH, Sadegh H, Shahryari-ghoshekandi R (2015) Characteristics and electrical conductivity of graphene and graphene oxide for adsorption of cationic dyes from liquids: kinetic and thermodynamic study [J Ind Eng Chem] Vol.28 P.294 google doi
  • 9. Johra FT, Lee JW, Jung WG (2014) Facile and safe graphene preparation on solution based platform [J Ind Eng Chem] Vol.20 P.2883 google doi
  • 10. Meng LY, Rhee KY, Park SJ (2014) Enhancement of superhydrophobicity and conductivity of carbon nanofibers-coated glass fabrics [J Ind Eng Chem] Vol.20 P.1672 google doi
  • 11. Meng LY, Park SJ (2012) Influence of pH condition on colloidal suspension of exfoliated graphene oxide by electrostatic repulsion [J Solid State Chem] Vol.186 P.99 google doi
  • 12. Yang YG, Chen CM, Wen YF, Yang QH, Wang MZ (2008) Oxidized graphene and graphene based polymer composites [New Carbon Mater] Vol.23 P.193 google
  • 13. Kuang D, Hu WB (2013) Research progress of graphene composites [J Inorg Mater] Vol.28 P.235 google doi
  • 14. Hu ZL, Chen YF, Li N, Ding YH, Liu FS, Zhang W (2014) The structure, preparation method and theory of graphene composites [J Funct Mater] Vol.45 P.16 google
  • 15. Zha N, Zhang H, Wen SY, Jiang Q, Zhu DC, Yu JL (2014) The review of the graphene/chitosan composite application [Guangdong Chem Ind] Vol.41 P.86 google
  • 16. Ma ZW, Ge HC (2014) Review on preparation and adsorption of the graphene oxide/chitosan composite [Mater Rev] Vol.28 P.60 google
  • 17. Lu JJ, Feng M, Zhan HB (2013) Preparation of graghene oxide/chitosan composite films and investigations on their nonlinear optical limiting effect [Acta Phys Sin] Vol.62 P.014204 google
  • 18. Akbari A, Derikvandi Z, Rostami SMM (2015) Influence of chitosan coating on the separation performance, morphology and anti-fouling properties of the polyamide nanofiltration membranes [J Ind Eng Chem] Vol.28 P.268 google doi
  • 19. Sadeghi-Kiakhani M, Gharanjig K, Arami M (2015) Grafting of prepared chitosan-poly (propylene) imines dendrimer hybrid as a biopolymer onto cotton and its antimicrobial property [J Ind Eng Chem] Vol.28 P.78 google doi
  • 20. Bie YQ, Liu WJ (2008) The advance in application and preparation of chitosan fiber with high tenacity [Chem Fiber & Text Technol] Vol.1 P.10 google
  • 21. Liu D, Yang P, Yuan X, Guo J, Liao N (2015) The defect location effect on thermal conductivity of graphene nanoribbons based on molecular dynamics [Phys Lett A] Vol.379 P.810 google doi
  • 22. Ebrahimi S, Rafii-Tabar H (2015) Influence of hydrogen functionalization on mechanical properties of graphene and CNT reinforced in chitosan biological polymer: multi-scale computational modeling [Comput Mater Sci] Vol.101 P.189 google doi
  • 23. Ramesh P, Bhagyalakshmi S, Sampath S (2004) Preparation and physicochemical and electrochemical characterization of exfoliated graphite oxide [J Colloid Interface Sci] Vol.274 P.95 google doi
  • 24. Nipane SV, Korake PV, Gokavin GS (2015) Graphene-zinc oxide nanorod nanocomposite as photocatalyst for enhanced degradation of dyes under UV light irradiation [Ceram Int] Vol.41 P.4549 google doi
  • 25. Harish S, Orejon D, Takata Y, Kohno M (2015) Thermal conductivity enhancement of lauric acid phase change nanocomposite with graphene nanoplatelets [Appl Therm Eng] Vol.80 P.205 google doi
  • 26. Choi KE, Seo MK (2013) A study on the preparation of the eco-friendly carbon fibers-reinforced composites [Carbon Lett] Vol.14 P.58 google doi
  • 27. Jin FL, Park SJ (2015) Preparation and characterization of carbon fiber-reinforced thermosetting composites: a review [Carbon Lett] Vol.16 P.67 google doi
  • 28. East GC, Qin Y (1993) Wet spinning of chitosan and the acetylation of chitosan fibres [J Appl Polym Sci] Vol.50 P.1773 google doi
  • 29. Du Q, Sun J, Li Y, Yang X, Wang X, Wang Z, Xia L (2014) Highly enhanced adsorption of congo red onto graphene oxide/chitosan fibers by wet-chemical etching off silica nanoparticles [Chem Eng J] Vol.245 P.99 google doi
  • 30. Li Y, Sun J, Du Q, Zhang L, Yang X, Wu S, Xia Y, Wang Z, Xia L, Cao A (2014) Mechanical and dye adsorption properties of graphene oxide/chitosan composite fibers prepared by wet spinning [Carbohydr Polym] Vol.102 P.755 google doi
  • 31. Yang DX, Li EZ, Guo WL, Wang HD, Xu BS (2011) Research and industrial development of nanofibers prepared by electrospinning [Mater Rev A] Vol.25 P.64 google
  • 32. Miao YE, Liu TX (2012) Recent progress in hierarchically organized polymer nanocomposites based on electrospun nanofibers [Acta Polym Sin] P.801 google
  • 33. Liu Y, Park M, Shin HK, Pant B, Choi J, Park YW, Lee JY, Park SJ, Kim HY (2014) Facile preparation and characterization of poly(vinyl alcohol)/chitosan/graphene oxide biocomposite nanofibers [J Ind Eng Chem] Vol.20 P.4415 google doi
  • 34. Ardeshirzadeh B, Anaraki NA, Irani M, Rad LR, Shamshiri S (2015) Controlled release of doxorubicin from electrospun PEO/chitosan/graphene oxide nanocomposite nanofibrous scaffolds [Mater Sci Eng C] Vol.48 P.384 google doi
  • 35. Bai B, Mi X, Xiang X, Heiden PA, Heldt CL (2013) Non-enveloped virus reduction with quaternized chitosan nanofibers containing grapheme [Carbohydr Res] Vol.380 P.137 google doi
  • 36. Yang XD, Wu GJ, Lin WJ (2005) Preparation and properties of chitosan hydrogels [New Chem Mater] Vol.33 P.48 google
  • 37. Chen Y, Chen L, Bai H, Li L (2013) Graphene oxide: chitosan composite hydrogels as broad-spectrum adsorbents for water purification [J Mater Chem A] Vol.1 P.1992 google doi
  • 38. Han D, Yan L (2014) Supramolecular hydrogel of chitosan in the presence of graphene oxide nanosheets as 2D cross-linkers [ACS Sustainable Chem Eng] Vol.2 P.296 google doi
  • 39. Li A, Pei CJ, Zhu ZQ, An J, Qin XJ, Bao XM (2013) Progress in graphene aerogels [Mod Chem Ind] Vol.33 P.20 google
  • 40. Jeon DH, Min BG, Oh JG, Nah C, Park SJ (2015) Influence of nitrogen moieties on CO2 capture of carbon aerogel [Carbon Lett] Vol.16 P.57 google doi
  • 41. Hao LF, Gao ZH, Yin LH, Huang W (2005) Preparation of aerogels and their application in catalysis [Natural Gas Chem Ind] Vol.30 P.49 google
  • 42. Yu B, Xu J, Liu JH, Yang ST, Luo J, Zhou Q, Wan J, Liao R, Wang H, Liu Y (2013) Adsorption behavior of copper ions on graphene oxide: chitosan aerogel [J Environ Chem Eng] Vol.1 P.1044 google doi
  • 43. Wang Y, Xia G, Wu C, Sun J, Song S, Huang W (2015) Porous chitosan doped with graphene oxide as highly effective adsorbent for methyl orange and amido black 10B [Carbohydr Polym] Vol.115 P.686 google doi
  • 44. Hao P, Zhao Z, Leng Y, Tian J, Sang Y, Boughton RI, Wong CP, Liu H, Yang B (2015) Graphene-based nitrogen self-doped hierarchical porous carbon aerogels derived from chitosan for high performance supercapacitors [Nano Energy] Vol.15 P.9 google doi
  • 45. Ding X, Wang Y, Wang Y, Pan Q, Chen J, Huang YH, Xu K (2015) Preparation of magnetic chitosan and graphene oxide-functional guanidinium ionic liquid composite for the solid-phase extraction of protein [Anal Chim Acta] Vol.861 P.36 google doi
  • 46. Li L, Luo C, Li X, Duan H, Wang X (2014) Preparation of magnetic ionic liquid/chitosan/graphene oxide composite and application for water treatment [Int J Biol Macromol] Vol.66 P.172 google doi
  • 47. Zhou TN, Chen F, Deng H, Zhang Q, Fu Q (2011) Reduction of graphene oxide and properties of chitosan nano materials [The 2011 national polymer academic report] Vol.9 P.24 google
  • 48. Meng LY, Park SJ (2014) Superhydrophobic carbon-based materials: a review of synthesis, structure, and applications [Carbon Lett] Vol.15 P.89 google doi
  • 49. Ibrahim KS (2013) Carbon nanotubes?properties and applications: a review [Carbon Lett] Vol.14 P.131 google doi
  • 50. Mazaheri M, Akhavan O, Simchi A (2014) Flexible bactericidal graphene oxide: chitosan layers for stem cell proliferation [Appl Surf Sci] Vol.301 P.456 google doi
  • 51. Justin R, Chen BQ (2014) Body temperature reduction of graphene oxide through chitosan functionalisation and its application in drug delivery [Mater Sci Eng C] Vol.34 P.50 google doi
  • 52. Hegab HM, Wimalasiri Y, Ginic-Markovic M, Zou L (2015) Improving the fouling resistance of brackish water membranes via surface modification with graphene oxide functionalized chitosan [Desalination] Vol.365 P.99 google doi
  • 53. Travlou NA, Kyzas GZ, Lazaridis NK, Deliyanni EA (2013) Functionalization of graphite oxide with magnetic chitosan for the preparation of a nanocomposite dye adsorbent [Langmuir] Vol.29 P.1657 google doi
  • 54. Goodenough JB, Park KS (2013) The Li-ion rechargeable battery: a perspective [J Am Chem Soc] Vol.135 P.1167 google doi
  • 55. Moon HS, Lee JH, Kwon S, Kim IT, Lee SG (2015) Mechanisms of Na adsorption on graphene and graphene oxide: density functional theory approach [Carbon Lett] Vol.16 P.116 google doi
  • 56. Ma L, Zhou X, Xu L, Xu X, Zhang L, Chen W (2015) Chitosan-assisted fabrication of ultrathin MoS2/graphene heterostructures for Li-ion battery with excellent electrochemical performance [Electrochim Acta] Vol.167 P.39 google doi
  • 57. Hashimoto S, Tanaka T, Yamashita N, Maeda T (2001) An automated purge and trap gas chromatography mass spectrometry system for the sensitive ship-board analysis of volatile organic compounds in seawater [J Sep Sci] Vol.24 P.97 google doi
  • 58. Wardencki W (1998) Problems with the determination of environmental sulphur compounds by gas chromatography [J Chromatogr A] Vol.793 P.1 google doi
  • 59. Simo R (1998) Trace chromatographic analysis of dimethyl sulfoxide and related methylated sulfur compounds in natural waters [J Chromatogr A] Vol.807 P.151 google doi
  • 60. Abalos M, Prieto X, Bayona JM (2002) Determination of volatile alkyl sulfides in wastewater by headspace solid-phase microextraction followed by gas chromatography?mass spectrometry [J Chromatogr A] Vol.963 P.249 google doi
  • 61. Napier A, Hurt JP (1996) Voltammetric and amperometric studies of selected thiols and dimethyldisulfide using a screen-printed carbon electrode modified with cobalt phthalocyanine: studies towards a gas sensor [Electroanalysis] Vol.8 P.1006 google doi
  • 62. Rajabzadeh S, Rounaghi GH, Arbab-Zavar MH, Ashraf N (2014) Development of a dimethyl disulfide electrochemical sensor based on electrodeposited reduced graphene oxide: chitosan modified glassycarbon electrode [Electrochim Acta] Vol.135 P.543 google doi
  • [Fig. 1.] Synthesis and applications of GO-CS composites. GO, graphene oxide; CS, chitosan.
    Synthesis and applications of GO-CS composites. GO, graphene oxide; CS, chitosan.
  • [Fig. 2.] Maximum adsorption capacity (qm) of various adsorbents for Cu2+ [42]. CNT, carbon nanotubes; GO, graphene oxide; CS, chitosan.
    Maximum adsorption capacity (qm) of various adsorbents for Cu2+ [42]. CNT, carbon nanotubes; GO, graphene oxide; CS, chitosan.
  • [Table 1.] List of GO-CS composites made by different processes
    List of GO-CS composites made by different processes