Advances in Carbon Nanomaterial- Based Green Nanocomposites
7.5 Applications of Carbon-Based Green Nanocomposites
epoxy/GO bionanocomposites the homogeneous dispersion of GO into the polymer matrix can significantly enhance thermal stability, tensile strength and elastic modulus, whereas reduces the curing time [85]. GO and xanthan gum (XG) [GO/XG-Fe(III)] NC film exhibited high mechan- ical strength, specific thermal conductivity, and stability against vari- ous organic solvents and acidic solution [86]. Chitosan-carbon dots NC hydrogel film displayed superior UV-visible blocking, swelling, thermal, mechanical and hydrophobic properties as compared to CS hydrogel film [87]. A ternary, bioinspired NC film (WH-MMT-rGO) exhibited good thermal stability and a high strength as compared to other hemicellulose- based films or wood auto-hydrolysate-based films [88]. The compressive modulus of thermoplastic polyurethane/GO composite scaffolds was sig- nificantly enhanced with the addition of GO, as compared to the pure matrix [57]. Small amount of ND can significantly improve the mechani- cal properties of epoxy/ND and poly(vinyl alcohol)/ND NC [89]. Young’s modulus of ND may increase several times compared with the neat poly- mer. ND dispersion can be improved due to the interfacial interaction between matrix/nanofiller.
7.4.3 Electrical Properties
CNTs possess high electrical and thermal conductivity, which improve the charge and heat transportation of green NCs [90, 91]. Thermoelectric materials based on cellulose/CNT NCs were developed. SWCNT-based composites exhibits high electrical conductivity and Seebeck coefficient as compared to MWCNT-based composites. The electrical conductivity for both types were decreased by lyophilization, but did not affect the Seebeck coefficient of MWCNT-based NCs. Higher Seebeck coefficients were mea- sured at 3 and 4 wt% in SWCNT containing aerogels than for films but significant lower values at higher loadings. The CNT addition results in increased thermal conductivity in the films, whereas the lyophilization sig- nificantly reduced it for the aerogels [92].
7.5 Applications of Carbon-Based Green
7.5.1 Wastewater Treatment
CNT-filled CS composites have a huge potential for adsorption of heavy metal ions and treatment of wastewater [93–95]. For example, CNTs-filled CS displayed faster controlled release of dexamethasone as compared to unfilled CS film [96]. Chitin/magnetite/MWCNTs (CMM) NC displayed efficient removal of Cr(VI) with higher surface area and significant mag- netic properties compared with natural chitin [97]. A cheap and eco- friendly NC based on lignin grafted CNTs (L-CNTs) demonstrated an excellent adsorption capability for lead ion and oil droplet [98]. Glycerol plasticized-starch/ascorbic acid-MWCNTs (GPS/AA-MWCNTs) NCs was employed for removal of methylene blue (MB) dye from wastewater [99].
Activated carbon is also an important form of carbon which is been employed for the development of NCs and their utilization in environment applications. For example, multifunctional super paramagnetic NCs using biomaterials such as unripened fruit of Cassia fistula (Golden shower) and Aloe vera displayed excellent pollutant such as Methyl blue (MTB) and Congo red removal (CR) and disinfection properties [55]. GnZVI/PAC NC have been employed to adsorb Cr (VI) from aqueous solutions with high adsorption capacity. [56]. Two types of NC (HAP/TE/GAC) and (HAP/
GAC) were synthesized one using granular activated carbon (GAC) coated with both hydroxyapatite nanoflakes and turmeric extract while the other composite with only HAP nanoflakes coating on GAC. HAP/TE/GAC NC exhibits better adsorption of heavy metals (Pb2+) as compared with HAP/
GAC [100]. Bio-nanocomposite of CS/activated carbon/iron nanoparticles was utilized for the of Cd removal from dilute solution [101].
A magnetically modified GO/CS/ferrite (GCF) NC material was used for removal of Cr(VI) from wastewater with an adsorption capacity of 270.27 mg g−1 at pH 2.0 [102]. An environment friendly polysaccharide- based NC hydrogel adsorbent (NHA) was employed for the adsorption of different cationic dyes such as like malachite green (MG) dye from aque- ous solution. The NHA possess high regeneration ability after five cycles of dye adsorption-desorption [103]. Ultrasound assisted GO nanoplatelets
Carbon Based Green nanocomposites
Pollution Control Sensing and Detection
Automobiles Catalyst
Packaging and Coating Biomedical Science
Figure 7.2 Applications of carbon-based green nanocomposites.
embedded in CS matrix (GO-Cs-Nc) were employed for the simultaneous adsorption of acid yellow 36 (AY) and acid blue 74 (AB) from their aque- ous solutions. The above NC is cost effective at low dosage and can be used for the treatment of industrial waste rich in mixed dyes [104]. Different forms (fibers, beads, and hydrogels) of sodium alginate/graphene oxide NCs (SA/GO) have been employed for the removal dyes MB from waste- water. The removal of MB is not affected by the pH of the solution, whereas the adsorption capacity increases on decreasing the temperature. The opti- mum desorption can be obtained at acidic pH, which may be attributed to the competition over the adsorption sites of H+ with the positively charged molecules of MB [58]. GO/SA bionanocomposite can also be employed for the drug removal (example, Ciprofloxacin) from wastewater at pH 5.9. The above NC possess higher adsorption capacity (77.9% at GO loading of 6 wt%,) as compared to pure SA (30%) [105]. Magnetic cellulose/GO NC dis- played efficient removal of MB from wastewater under alkaline conditions.
The adsorption depends on NC adsorbent dose and initial concentration of dye [106]. CS/RGO mesoporous NCs were employed for the removal of the anionic azo dye such as Reactive Black 5 [59]. Cationic (basic) fuchsine can also be removed using magnetic CS/GO (RB 5) NCs at pH 5.5 bet- ter as compared to the acidic dye like RB 5. This may be attributed to the increased solubility in water due to the protonation of amido group under acidic conditions [107]. Magnetic CS/GO displayed excellent adsorption of Acid Orange 7 from wastewater under strongly acidic (pH 2) conditions with an adsorption capacity of 90 mg/g [60]. MB, can also be adsorbed on magnetic CS/GO NCs under alkaline conditions with an abdsorption capacity of 180.83 mg/g [108]. Magnetic CS/GO NCs can also be employed to adsorb Cr(VI) from wastewater. The removal decreases on exceeding pH 3 and the NC can be recycled for five cycles with the retention of the adsorp- tion capacity at 92% [109]. CS/GO NCs have been used for the adsorption of Au(III) and Pd(II) with high adsorption capacities under acidic condi- tions with 5 wt% GO [110]. Magnetic CS/GO NCs can also adsorb Pb(II) ions, with lower adsorption capacity, but with an extremely high desorption capacity [111].
7.5.2 Packaging and Coating
Poly(butylene succinate)/MWCNTs NC was used as electronic packaging materials as it possess high antistatic efficiency [112]. Graphene oxide nano- platelets were functionalized with starch biopolymer to proceed with the epoxy ring opening, which has a high-performance epoxy NC for coating applica- tions [113]. A GO and CS biopolymers with TiO2 nanoparticles embedded in
its surface self-assembled film with high antibacterial and preservative prop- erties were employed for food preservation [114]. GO reinforced polyvinyl chloride-waterborne castor alkyd NCs (PVC/WCA/GO) films were utilized in packaging industries [115]. Bulk synthesis of CNs from Desmostachya bipinnatagrass for the development of eco-friendly coating was reported [116].
7.5.3 Sensing and Detection
CNT-based green NCs have been employed to fabricate biosensors. For exam- ple, glassy carbon electrode (GCE) modified by MWCNTs, MWCNTs in CS, and gold nanoparticles (AuNPs) have been employed for the pH dependent selective determination of 2,4-diaminotoluene (TDA), AuNPs/MWCNTs-CS/
GC electrodes displayed highest current response as compared to bare GCE [117]. A bionanocomposite have been prepared by the combination of Glucose oxidase (GOD) and SWNTs for the electrochemical detection of glucose [118].
Carbon paste matrix/pectin-MWCNT (CPE/PEC-MWCNT) bionanocom- posite electrode have been employed for the efficient sensing of creatinine in urine samples [119]. Myoglobin-gold nanoparticles- polydopamine-graphene (MGPG) polymeric bionanocomposite can be employed as biosensors for the detection of H2O2 released by cells [120].
Graphene-based green NCs have been also used for sensing and detec- tion of chemical changes taking place in various systems. Recently, CS/
graphene NC was utilized for accurate detection and quantification of Sunset Yellow with a wide linear range and low detection limit [121]. Also, the ionophore doped graphene-based bionanocomposite was employed as novel optical material for metal ion sensing with high potential [122]. A rGO-CS NC immobilized with a hemoglobin protein exhibited bioelec- trocatalytic activity toward H2O2. The NC provides a favorable micro- environment for the protein to retain its native structure while rGO accelerates the electron transfer at the sensing interface, due to which the polyelectrolyte- rGO sensor displayed broad linear range, low detec- tion limit, and high stability. Despite of these impressive sensing abilities, enzymatic sensors cannot provide long-term stability due to the intrinsic nature of enzymes. Thus, most polyelectrolyte-graphene NCs for H2O2 sensing are actually based on enzyme free strategies [123]. Another bio- sensor based on a bionanocomposite (laccase-thionine-car bon black)- modified screen-printed electrode has been developed as a tiny and cost-effective device for the BPA detection [124]. The above biosensor displayed better results when compared with laccase carbon paste biosen- sor and tyrosinase-thionine GCE [125, 126]. A GO/methyl cellulose (MC) hybrid has been developed as sensor for the detection of nitroaromatics by
instaneous photoluminescence quenching with a detection limit of 2 ppm [127]. 4-Aminophenol, which is the main hydrolytic degradation product of paracetamol, can be easily determined using a RGO/CS film modified GCE [128]. CS/RGO NC film has been employed to modify carbon ionic liquid electrode which can be employed for the detection of trace amounts of bisphenol-A in plastics samples [129]. Molecularly imprinted CS/RGO NC was employed to modify the carbon glassy electrode for the determi- nation of dopamine [130].
Dopamine, urea, and ascorbic acid can be simultaneous determined employing CS/RGO modified GCE [131]. In another case, graphene-based potentiometric sensor has been developed to determine the intracellular glucose concentration [132]. Starch/graphene NCs was used for the prepa- ration of graphene sheet-starch paste electrode which have been used in the selective determination of iodide in seafood samples [133].
7.5.4 As Catalyst
Eco-friendly CS/Au NP/CNTs NC membrane has been employed for the reduction of 4-nitrophenol to 4-aminophenol. CNTs increases the rate of the reaction, mainly by reducing the induction time. The above mem- branes could be reused several times without any loss of catalytic activity [134]. CS-GO NC film as ecofriendly material has been developed for cat- alytic conversion and adsorption of CO2 on industrial scale [135]. A green and efficient NCs from carbon dots (CDs) for photocatalytic activity obtained from guava, red pepper, peas, and spinach have been developed.
The desired NCs was prepared by the combination of spinach-extracted CDs with TiO2 nanoparticles and nanotubes. The H2 generation rates are enhanced for TiO2NP/CD and NT/CD NCs as compared to bare NPs and NTs which may be attributed to the favorable electron transfer property of CDs [136]. Nanoparticles (monometallic Co, Ag, and Cu and bimetal- lic Co + Cu and Co + Ag) were synthesized on the surface of green NC (CB-CS) based on carbon black dispersed in CS fibers. The nanoparti- cle-loaded CB-CS displayed excellent catalytic activity for the reduction of para- nitrophenol, CR, and methyl orange (MO) dyes. Also, above NC fibers exhibits good antimicrobial activities against Escherichia coli. The catalyst can be recycled for several times with high catalytic efficiency (Figure 7.3) [137].
Lignin-based carbon/ZnO NC exhibited excellent photocatalytic per- formance for the degradation of organic dyes such as MO as compared to pure ZnO and other ZnO/GRs which may be due to a homogeneous struc- ture and stronger absorption ability for organic dyes [54].
7.5.5 Biomedical Applications
CNTs incorporated in the polymer matrix have found application in a vari- ety of regenerative medicine areas [138]. SWCNTs/poly(propylene fuma- rate) NC can act as a model for bone tissue engineering scaffold due to the enhanced mechanical properties of poly(propylene fumarate) after rein- forcing with ultra-short SWCNTs [139]. Starch-based NCs, consisting very minute quantities of MWCNT, were used to prepare tissue scaffolds or bone- regenerating treatments [72]. A biodegradable monetite (DCPA, CaHPO4) cement with surface-modified multi-walled CNTs (mMWCNTs) has been developed as promising bone defect repair materials. The addition of mMWCNTs shortened the setting time and enhanced the comprehensive strength of DCPA [140]. Biodegradable and biocompatible CNT/CS compos- ites with distinct microchannel porous structure support have been employed for culture growth [141]. CNT-PDA have been employed as a scaffold mate- rial for bone tissue regeneration and implantation [142]. The collagen/CNTs composites form rigid fibril bundles, which polarizes the growth and differ- entiation of human embryonic stem cell [143].
Nanodiamond-based materials is another class that can be employed for various biomedical applications [144, 145]. Owing to biocompatiblity and bioresorbablity polymer/ND NC can be employed in drug delivery of biologically active molecules, bioimaging, in tissue scaffolds, and surgical implants. They are used to form mechanically robust implants. Hardness and Young’s modulus of such bioimplants have been found closer to natural
Chitosan Carbon black
Chitosan-Carbon black solution
Gel extrusion to NH2·H2O
Chitosan-Carbon black f ibres Metal ions loaded f ibres
Nanoparticles loaded f ibres
Figure 7.3 Nanoparticle-loaded carbon black-chitosan fibers.
human bone. These NC can act as platform for growth of protein-coated materials [146]. PLLA and PLGA diamond NCs effectively enhance the adhesion and growth of osteoblast-like MG 63 cells and human bone mar- row MSCs. In the case of PLLA films, fluorescent DNPs were employed to localize these materials in tissues and to monitor their behaviour in vivo [38, 39]. In case of nanofibrous PLGA scaffolds, the DNP-loaded scaffolds improved the growth of MG 63 cells similar to pure scaffolds, although it can increase the growth of MSCs [41].
Nanocomposites of graphene and its derivatives have also been employed in the manufacture of biomaterials and their implementation in various biomedical fields [147]. Recently, CN-reinforced protein-based NCs have been found to be ideal candidates for various suture, textile, and biomedi- cal tissue materials. These NCs have been employed for drug encapsulation and release, except for drug removal [148]. A series of pH sensitive konjac glucomannan/sodium alginate (KGM/SA) and KGM/SA/graphene oxide (KGM/SA/GO) hydrogels for anticancer drug loading and controlled release have been developed [149]. The cell adhesion and their compatibil- ity can be enhanced by the modification of GO with hydrophilic molecules or encapsulation in hydrophilic matrices [150]. The porosity of CS scaf- folds was improved on addition of 3 wt% GO due to which the NC attain a better defined and well interlinked pore structure, without introducing significant cytotoxicity [151]. Graphene/CS NC films exhibited faster cell attachment with graphene content 0.1–0.3 wt%, with minimized cytotox- icity [152]. Graphene-based CS NCs fibers were used for wound healing applications [153].
7.5.6 Miscellaneous
Chitosan/grapheneoxide NCs have been developed which can prevent the corrosion of carbon steel. GO has a good interfacial interaction with CS chains. The corrosion protection property gets improved by hundred folds on functionalization of the NC with oleic acid [154].