Graphene Oxide-Chitosan Composite Material for Treatment of a Model Dye Effluent

Zinc oxide/graphene oxide nanocomposites specifically remediated Cd-contaminated soil via reduction of bioavailability and ecotoxicity of Cd

From both environment and health perspectives, sustainable management of ever-growing soil contamination by heavy metal is posing a serious global concern. The potential ecotoxicity of cadmium (Cd) to soil and ecosystem seriously threatens human health. Developing efficient, specific, and long-term remediation technology for Cd-contaminated soil is impending to synchronously minimize the bioavailability and ecotoxicity of Cd. In the present study, zinc oxide/graphene oxide nanocomposite (ZnO/GO) was developed as a novel amendment for remediating Cd-contaminated soil. Our results showed that ZnO/GO effectively decreased the available soil Cd content, and increased pH and cation exchange capacity (CEC) in both Cd-spiked standard soil and Cd-contaminated mine field soil through the interaction between ZnO/GO and soil organic acids. Using Caenorhabditis elegans (C. elegans) as a model organism for soil safety evaluation, ZnO/GO was further proved to decrease the ecotoxicity of Cd-contaminated soil. Specifically, ZnO/GO promoted Cd excretion and declined Cd storage in C. elegans by increasing the expression of gene ttm-1 and decreasing the level of gene cdf-2, which were responsible for Cd transportation and Cd accumulation, respectively. Moreover, the efficacy of ZnO/GO in remediating the properties and ecotoxicity of Cd-contaminated soil increased gradually with the time gradient, and could maintain a long-term effect after reaching the optimal remediation efficiency. Our findings established a specific and long-term strategy to simultaneously improve soil properties and reduce ecotoxicity of Cd-contaminated soil, which might provide new insights into the potential application of ZnO/GO in soil remediation for both ecosystem and human health.

Chitosan-grafted folic acid decorated one-dimensional GONS: A biocompatible drug cargo for targeted co-delivery of anticancer agents

In conventional chemotherapy, the cancer cells can become highly resilient due to a phenomenon known as multi-drug resistance (MDR). The co-delivery of chemotherapeutic agents assisted with novel nanocarrier-based targeted DDS may counter the MDR issues and subsequently improve their therapeutic efficacy. In line with this, the present work deals with the development of 1D graphene oxide nanoscrolls (GONS)-based nano delivery system for co-delivery of chemosensitizer along with the chemotherapeutic agent. Herein, the 1D GONS nanocarrier was initially functionalized with chitosan (CS) biopolymer and folic acid (FA) further to enhance their biocompatibility and target-specific co-delivery. The resultant GONS-CS-FA (GCF) nanocarriers were co-loaded with doxorubicin (DOX) and caffeic acid (CA) at different weight proportions with respect to nanocarrier and drug composition. The optimum loading efficiency of 51.14 ± 1.47 % (DOX) and 49.70 ± 1.19 % (CA) was observed for GCF: drug ratio of 2.5 with drug composition of 1:1. In vitro release at pH 5 yielded ~83 % DOX and 75 % CA, compared to ~71 % DOX and 61 % CA at pH 7.4 over 7 days, suggesting a higher and targeted drug release in the cancer microenvironment. Cytotoxicity tests revealed selective apoptosis in cancer cells (A549) while maintaining cytocompatibility with normal cells (HEK293).

Theoretical and Experimental Analysis of Hydroxyl and Epoxy Group Effects on Graphene Oxide Properties

In this study, we analyzed the impact of hydroxyl and epoxy groups on the properties of graphene oxide (GO) for the adsorption of methylene blue (MB) dye from water, addressing the urgent need for effective water purification methods due to industrial pollution. Employing a dual approach, we integrated experimental techniques with theoretical modeling via density functional theory (DFT) to examine the atomic structure of GO and its adsorption capabilities. The methodology encompasses a series of experiments to evaluate the performance of GO in MB dye adsorption under different conditions, including differences in pH, dye concentration, reaction temperature, and contact time, providing a comprehensive view of its effectiveness. Theoretical DFT calculations provide insights into how hydroxyl and epoxy modifications alter the electronic properties of GO, improving adsorption efficiency. The results demonstrate a significant improvement in the dye adsorption capacity of GO, attributed to the interaction between the functional groups and MB molecules. This study not only confirms the potential of GO as a superior adsorbent for water treatment, but also contributes to the optimization of GO-based materials for environmental remediation, highlighting the synergy between experimental observations and theoretical predictions in advances in materials science to improve sustainability.

A graphene oxide based composite granule for methylene blue separation from aqueous solution: Adsorption, kinetics and thermodynamic studies

Graphene oxide and chitosan composite material using as a high-efficiency and low-cost granular adsorbent for methylene blue removal was fabricated via self-assembling method. The effects of pH value, contact time, initial concentration, adsorbent dose, temperature, and recyclic stability on the adsorption performance of methylene blue in aqueous solution were investigated in detail. Desorption process with the effects of solvents, contact time, and temperature were also conducted carefully in this study. The adsorption kinetics and adsorption isotherm of dye adsorption process showed that dye adsorption process was fitted to the pseudo-second-order kinetic model and the Freundlich adsorption isotherm, indicating a physical adsorption process with multilayer adsorption. The intra-particle diffusion model indicated that the dye adsorption by the granular adsorbent was strongly happened during the first 4 h. The thermodynamic study showed that the adsorption was a spontaneous and exothermic process and dye ions were condensed onto the surface of adsorbent. The maximum adsorption capacity of dye on the granular adsorbent was calculated as 951.35 mg/g and the adsorbent could maintain its adsorption performance after six cycles. In general, this study provided an efficient, cost-effective, and recyclable the granular adsorbent for dye separation from aqueous solution.

Hydrogels Based on Chitosan and Nanoparticles and Their Suitability for Dyes Adsorption from Aqueous Media: Assessment of the Last-Decade Progresses

Water is one of the fundamental resources for the existence of humans and the environment. Throughout time, due to urbanization, expanding population, increased agricultural production, and intense industrialization, significant pollution with persistent contaminants has been noted, placing the water quality in danger. As a consequence, different procedures and various technologies have been tested and used in order to ensure that water sources are safe for use. The adsorption process is often considered for wastewater treatment due to its straightforward design, low investment cost, availability, avoidance of additional chemicals, lack of undesirable byproducts, and demonstrated significant efficacious potential for treating and eliminating organic contaminants. To accomplish its application, the need to develop innovative materials has become an essential goal. In this context, an overview of recent advances in hydrogels based on chitosan and nanocomposites and their application for the depollution of wastewater contaminated with dyes is reported herein. The present review focuses on (i) the challenges raised by the synthesis process and characterization of the different hydrogels; (ii) the discussion of the impact of the main parameters affecting the adsorption process; (iii) the understanding of the adsorption isotherms, kinetics, and thermodynamic behavior; and (iv) the examination of the possibility of recycling and reusing the hydrogels.

Gelatin-decorated Graphene oxide: A nanocarrier for delivering pH-responsive drug for improving therapeutic efficacy against atherosclerotic plaque

The progressive inflammatory disease atherosclerosis promotes myocardial infarction, stroke, and heart attack. Anti-inflammatory drugs treat severe atherosclerosis. They are inadequate bioavailability and cause adverse effects at higher doses. A new nanomaterial coupled pH-apperceptive drug delivery system for atherosclerotic plaque is outlined here. We have synthesized a Graphene Oxide-Gelatin-Atorvastatin (GO-Gel-ATR) nanodrug characterized by spectroscopic and imaging techniques. The encapsulation efficiency of GO-Gel-ATR (79.2%) in the loading process is observed to be better than GO-ATR (66.8%). The internal milieu of the plaque cells has a pH of 6.8. The GO-Gel-ATR displays sustained and cumulative release profile at pH 6.8 compared to ATR and GO-ATR. Our proposed nanocomposite demonstrated high cytocompatibility up to 100μg/mL in foam cells induced by Oxidized-Low Density Lipoprotein (Ox-LDL) and Lipopolysaccharides (LPS) compared to normal macrophages for 24 and 48 h. The uptake efficacy of the nanodrugs is shown to be enhanced in foam cells compared to normal macrophage. Oil red O staining of foam cells with and without drugs confirmed therapeutic efficacy. Foam cells treated with nanocomposite had more lipids efflux than ATR. The finding of the in-vitro study reveals that the GO-Gel-ATR nanocomposite carriers have the potential to deliver anti-atherosclerotic drugs effectively and inhibit atherosclerotic plaque progression.

Adsorption of Levofloxacin onto Graphene Oxide/Chitosan Composite Aerogel Microspheres

The removal of pharmaceutical residues from water resources using bio-based materials is very important for human safety and health. Bio-based graphene oxide/chitosan (GO/CS) aerogel microspheres were fabricated with emulsification and cross-linking, followed by freeze drying, and were used for the adsorption of levofloxacin (LOF). The obtained GO/CS aerogel microspheres were characterized with scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), and thermogravimetry (TG). The effects of GO content, pH value, and temperature on their adsorption capacity were investigated. With the incorporation of 40 wt% GO, the adsorption capacity increased from 9.9 to 45.6 mg/g, and the highest adsorption capacity, 51.5 mg/g, was obtained at pH = 8 and T = 25 °C. In addition, to obtain deeper insight into the adsorption process, the thermodynamics and kinetics of the process were also investigated with four different models of LOF adsorption. The thermodynamic modeling results revealed that LOF adsorption is exothermic, and the kinetic investigation demonstrated that LOF adsorption is generally consistent with a pseudo-first-order rate law.

Removal of Methylene Blue and Congo Red Using a Chitosan-Graphene Oxide-Electrosprayed Functionalized Polymeric Nanofiber Membrane

Untreated textile effluent may contain toxic organic pollutants that can have negative impacts on the ecosystem. Among the harmful chemicals present in dyeing wastewater, there are two frequently used organic dyes: methylene blue (cationic) and congo red (anionic). The current study presents investigations on a novel two-tier nanocomposite membrane, i.e., a top layer formed of electrosprayed chitosan-graphene oxide and a bottom layer consisting of an ethylene diamine functionalized polyacrylonitrile electrospun nanofiber for the simultaneous removal of the congo red and methylene blue dyes. The fabricated nanocomposite was characterized using FT-IR spectroscopy, scanning electron microscopy, UV-visible spectroscopy, and Drop Shape Analyzer. Isotherm modeling was used to determine the efficiency of dye adsorption for the electrosprayed nanocomposite membrane and the confirmed maximum adsorptive capacities of 182.5 mg/g for congo red and 219.3 mg/g for methylene blue, which fits with the Langmuir isotherm model, suggesting uniform single-layer adsorption. It was also discovered that the adsorbent preferred an acidic pH level for the removal of congo red and a basic pH level for the removal of methylene blue. The gained results can be a first step for the development of new wastewater cleaning techniques.

Chitosan modulated engineer tin dioxide nanoparticles well dispersed by reduced graphene oxide for high and stable lithium-ion storage

Tin based materials are widely investigated as a potential anode material for lithium-ion batteries. Effectively dispersing SnO₂ nanocrystals in carbonaceous supporting skeleton using simplified methods is both promising and challenging. In this work, water soluble chitosan (CS) chains are employed to modulate the redox coprecipitation reaction between stannous chloride (SnCl₂) and few-layered graphene oxide (GO), where the excessive restacking of the corresponding reduced graphene oxide sheets (RGO) has been effectively inhibited and the grain size of the in-situ formed SnO₂ nanoparticles have been significantly controlled. In particular, the CS molecules are gradually detached from the RGO sheets with the GO deoxygenation process, leaving only a small quantity of CS remnants in the intermediate SnO₂@CS@RGO sample. The final SnO₂/CSC/RGO sample with significantly improved microstructure is synthesized after a simple thermal treatment, which delivers a high specific capacity of 842.9 mAh g^-1 at 1000 mA·g^-1 for 1000 cycles in half cells and a specific capacity of 410.5 mAh g^-1 at 200 mA·g^-1 for 100 cycles in full cells. The reasons for the good lithium-ion storage performances for the SnO₂/CSC/RGO composite have been studied.

Adsorption of dyestuff by nano copper oxide coated alkali metakaoline geopolymer in monolith and powder forms: Kinetics, isotherms and microstructural analysis

To remove contaminants and pollutants from wastewater systems, adsorbents are widely used. Geopolymers offer a convenient alternative as adsorbents in the wastewater treatment system as they are low-cost, environmentally friendly, and safer. A new adsorbent material prepared by coating nano copper oxide on the surface of alkali-activated metakaolin showed a higher ability to remove methylene blue (MB) dye from wastewater, thus making them attractive in dye removal applications. First, nano copper oxide was prepared by sol gel method and metakaolin geopolymer was produced using sodium silicate solution having a Ms value of 1.1 (M). Afterwards, nano copper oxide (MC) was coated on the surface of the geopolymer. The ability of MB dye to bind to both pristine (M^p, MC^p) and powder forms (M^pr, MC^pr) of the geopolymer was evaluated. X-ray diffraction revealed that the halo found at 27.40°-31.077° (2θvalue) in both samples related to amorphous gel's composition and the major peaks of copper oxide in MC^pr were sited at a 2θ value of 35.45° and 38.88°.The dye removal efficiency can be inferred from the increased adsorption capacity of 11.9 mg/g (M^p) and 14.4 mg/g (MC^p) for the monolith form and 81.43 mg/g (M^pr) and 87.82 mg/g (MC^pr) for the powder form. The adsorption of reused active sites was 73% for M^pr and 83% for MC^pr up to the fifth cycle after regeneration by heat treatment at 400 °C. The models that best suited the adsorption data were pseudo-second-order and Freundlich isotherms, which indicated possible chemisorption with intra-particle diffusion. Furthermore, the binding energy is shifted to lower value in XPS spectra due to dye adsorption arising from electrostatic attraction. A higher electron density is formed due to interaction with an equal contribution of silanol Si-O-H and Si-O-Na/Cu(O1s). The adsorbents are effective over a wide pH range and their improved recycling capability increases their applications for a wide range of uses.

On the Sorbent Ability and Reusability of Graphene-Oxide-Chitosan Aerogels for the Removal of Dyes from Wastewater

One of the most persistent issues affecting people worldwide is water contamination due to the indiscriminate disposal of pollutants, causing severe environmental problems. Dyes are among the most harmful contaminants because of their high chemical stability and consequently difficult degradation. To remove contaminants from water, adsorption is the most widely used and effective method. In this work, we recall the results already published about the synthesis, the characterization and the use of porous graphene-oxide-chitosan aerogels as a sorbent material. Those systems, prepared by mixing GO sheets and CS chains, using APS as a cross-linking agent, and by further lyophilization, were further characterized using nano-computed tomography, supplying more understanding about their micro and nano-structure. Their sorbent ability has been investigated also by the study of their isotherm of adsorption of two different anionic dyes: Indigo Carmine and Cibacron Brilliant Yellow. Those analyses confirmed the potentialities of the aerogels and their affinity for those anionic dyes. Moreover, the possibility of regenerating and reusing the material was evaluated as a key aspect for applications of this kind. The treatment with NaOH, to promote the desorption of adsorbed dyes, and subsequent washing with HCl, to re-protonate the system, ensured the regeneration of the gels and their use in multiple cycles of adsorption with the selected water contaminants.

Chitosan-Graphene Oxide Dip-Coated Polyacrylonitrile-Ethylenediamine Electrospun Nanofiber Membrane for Removal of the Dye Stuffs Methylene Blue and Congo Red

Textile wastewater accommodates many toxic organic contaminants that could potentially threaten the ecosystem if left untreated. Methylene blue is a toxic, non-biodegradable, cationic dye that is reportedly observed in significant amounts in the textile effluent stream as it is widely used to dye silk and cotton fabrics. Congo red is a carcinogenic anionic dye commonly used in the textile industry. This study reports an investigation of methylene blue and Congo red removal using a chitosan-graphene oxide dip-coated electrospun nanofiber membrane. The fabricated nanocomposite was characterized using Scanning Electron Microscopy (SEM), FT-IR Spectroscopy, Raman Spectroscopy, UV-vis Spectroscopy, Drop Shape Analyzer, and X-ray Diffraction. The isotherm modeling confirmed a maximum adsorptive capacity of 201 mg/g for methylene blue and 152 mg/g for Congo red, which were well fitted with a Langmuir isotherm model indicating homogenous monolayer adsorption.

Preparation of Graphene Oxide-Maghemite-Chitosan Composites for the Adsorption of Europium Ions from Aqueous Solutions

The adsorption of Eu(III) on composites synthesised from graphene oxide (GO), maghemite (MGH), and chitosan (CS) has been studied using different approaches. The physicochemical and morphological characteristics of the composites GO-MGH, GO-CS, GO-MGH-CS I, II, and III were determined by XRD, Mössbauer spectroscopy, FTIR, Raman spectroscopy, and TEM. According to the results of batch experiments, the maximum experimental adsorption capacity was 52, 54, 25, 103, and 102 mg/g for GO-MGH, GO-CS, GO-MGH-CS I, II, and III, respectively. The data obtained are in better agreement with the Langmuir, pseudo-second-order, and pseudo-first-order models only for GO-MGH. Thus, the adsorption of Eu(III) on the composites was a favourable, monolayer, and occurred at homogeneous sites. The nature of adsorption is chemical and, in the case of GO-MGH, physical. Tests of the composites in natural waters showed a high removal efficiency for Eu(III), Pu(IV), and Am(III), ranging from 74 to 100%. The ANFIS model has quite good predictive ability, as shown by the values for R², MSE, SSE, and ARE. The GO-MGH-CS composites with the high adsorption capacity could be promising candidates for the removal of Eu(III) and the pre-concentration of Pu(IV) and Am(III) from natural waters.

Strengthening the surface and adsorption properties of diatomite for removal of Cr(VI) and methylene blue dye

The main purpose of this work was to boost the surface and adsorption characteristics of diatomite (D) through chemical modifications with chitosan (DC), chitosan/titanium isopropoxide (DCTi), or chitosan/ graphene oxide (DCGr), respectively. Physicochemical characteristics of the prepared samples were investigated using SEM, TEM, XRD, FTIR, TGA, and porosity measurements. The impact of such modifiers into the D surface on the removal efficiency of chromium (VI) ions and methylene blue dye was studied in an equilibrium mode. Langmuir and Freundlich isotherms were used to analyze the adsorption data. Modifiers considerably enhanced the surface and textural properties of D through insertion of the main surface functional groups of chitosan and graphene oxide together compared to chitosan and titanium isopropoxide together or chitosan alone. In addition, the total surface area and total pore volume parameters of the unmodified D sample were improved greatly from 16.5 m2/g, 0.036 cm3/g to 39.8 m2/g and 0.174 cm3/g for DCGr, while they were 17.7 m2/g and 0.132 cm3/g for DC. The best adsorption results were well-defined with the Langmuir isotherm equilibrium model. Accordingly, the DCGr sample exhibited the highest uptake of Cr(VI) (about 167 mg/g) and methylene blue (66.7 mg/g). Hence, the chemical modification strategy of diatomite performed by using chitosan and graphene oxide significantly boosted the surface active sites and porosity properties and thus gave rise to the high adsorption capacity of Cr(VI) and methylene blue dye from wastewater. Hence, these findings affirmed the validity of the current strategy for surface modification of diatomite with chitosan and graphene oxide.

Chitosan-Functionalized-Graphene Oxide (GO@CS) Beads as an Effective Adsorbent to Remove Cationic Dye from Wastewater

In this study, the preparation of graphene oxide@chitosan (GO@CS) composite beads was investigated via continuous dropping techniques to remove methylene blue (MB)-dye from an aqueous media. The prepared beads were characterized using various techniques before and after the adsorption of MB. The experimental results showed that the adsorption processes fit the kinetic pseudo-second-order and Langmuir isotherm models. Moreover, the GO@CS beads achieve maximum adsorption capacities of 23.26 mg g⁻¹, which was comparable with other adsorbents in the literature. An important advantage of our adsorbent is that the GO@CS can remove 82.1% of the real sample color within 135 min.

Fabrication of glutathione functionalized self-assembled magnetite nanochains for effective removal of crystal violet and phenol red dye from aqueous matrix

A novel fabrication of magnetite (Fe₃O₄) nanochains, surface functionalized with glutathione (GSH), has been attempted through a basic wet reduction method, coalesced with oxidative etching for the removal of crystal violet (CV) and phenol red (PR) from an aqueous solution. The structural and functional characterizations of GSH@Fe₃O₄ MNPs were performed using SEM-EDX, DLS, XRD, and FTIR. The nanochain-structured adsorbent was found to have an average size of 24 ± 1.29 nm and a zeta potential value of - 6.44 mV. The batch experiments showed that GSH@Fe₃O₄ MNPs have a brilliant removal efficiency of 97% and 79% for CV and PR dyes, respectively, within a period of 60 min. The influence of different operational parameters like adsorbent dosage, pH, temperature, reaction time, and initial dye concentration on the removal behaviour of the adsorbent was studied in detail. The adsorbate-adsorbent reaction was tested over isotherm models, and the reaction fitted well for Langmuir isotherm with an excellent q_max value of 1619.5 mg/g and 1316.16 mg/g for CV and PR dye, respectively. The experimental results were also validated using different reaction kinetics, and it was found that the pseudo-first-order model fits well for PR dye adsorption (R² = 0.91), while adsorption of CV dye was in best agreement with the pseudo-second-order kinetic model (R² = 0.98). Thermodynamic studies revealed that the adsorption reaction was spontaneous and endothermic in nature. Furthermore, GSH@Fe₃O₄ MNPs can be reused effectively up to 5 cycles of dye removal. Major mechanisms involved in the adsorption reaction were expected to be electrostatic attraction, hydrogen bonding, and π-interactions. The efficiency of GSH@Fe₃O₄ MNPs in real water samples suggested that it has a high potential for dye removal from complex aqueous systems and could be used as an effective alternative for remediation of dyes contaminated water.

Graphene Oxide-Chitosan Network on a Dialysis Cellulose Membrane for Efficient Removal of Organic Dyes

Currently, water pollution is a significant health problem for both humans and animals due to large amounts of dye-containing wastewater. Thus, polymer composite membranes (PCMs) are considered as efficient adsorption/filtration membranes that can be utilized for removing organic dyes from contaminated water/wastewater. In this study, the goal is to explore the modification of the interfacial dialysis cellulose (DC) surface through molecular interactions of an active graphene oxide-chitosan (GO-CTS) composite hydrogel (GCCH) network without the use of an external cross-linker toward an effective dye removal ability using a simple casting process and a low-cost adsorption technique, resulting in the formation of a PCM, i.e., GO/CTS/DC membrane (GCD-mems). Concomitantly, the incorporation of the GCCH network (as an active hybrid network) and DC (as a supporting material) is considered as a promising approach toward a dye-removing PCM. As a result, the GCD-mems showed that cellulose robustly interacted via the chemical bonds of the GCCH network by maintaining the three-dimensional (3D) porous layer structures, and the functional surface of the membrane was enhanced toward specific groups for an effective dye removal approach. In addition, there is a significant improvement in dye removal performance after modification of the interfacial DC surface through molecular interactions of GCCH, i.e., high adsorption capacities of cationic and anionic dye molecules on the GCD-mems, compared to the relevant GO-based adsorbents. Also, the dye flux and rejection of the GCD-mems can simultaneously remove both methylene blue and Congo red. In the adsorption, it is appropriate with the pseudo-second-order and Langmuir models corresponding to chemical adsorption and monolayer approaches, as well as physical sieving through the 3D layers of porous channels of GCD-mems during the filtration process. Moreover, the structural stability and sustainability of the PCMs are enhanced during the recycling process, and the use of ethanol in the recycling process further simplifies the process and reduces the cost of the PCMs. Thus, the GCD-mems are encouraged as potential candidates that can be applied directly in the removal of dyes from the wastewater of textile industries or selective dialysis applications.

Nanocomposites based on the graphene family for food packaging: historical perspective, preparation methods, and properties

Nanotechnology experienced a great technological advance after the discovery of the graphene family (graphene – Gr, graphene oxide – GO, and reduced graphene oxide-rGO). Based on the excellent properties of these materials, it is possible to develop novel polymeric nanocomposites for several applications in our daily routine. One of the most prominent applications is for food packaging, offering nanocomposites with improved thermal, mechanical, anti-microbial, and barrier properties against gas and water vapor. This paper reviewed food packaging from its inception to the present day, with the development of more resistant and intelligent packaging. Herein, the most common combinations of polymeric matrices (derived from non-renewable and renewable sources) with Gr, GO, and rGO and their typical preparation methods are presented. Besides, the interactions present in these nanocomposites will be discussed in detail, and their final properties will be thoroughly analyzed as a function of the preparation technique and graphene family-matrix combinations.

Food packaging based on nanotechnology of polymeric nanocomposites of graphene and graphene oxide results in packaging with better thermal, mechanical, antimicrobial, electrical packaging, moisture barrier and gas properties.

Functionalized Graphene Oxide with Chitosan for Dopamine Biosensing

Detecting biological structures via a rapid and facile method has become a pronounced point of research. Dopamine (DA) detection is critical for the early diagnosis of a variety of neurological diseases/disorders. A study on the real-time optical detection of DA is described here using graphene oxide (GO) functionalized with chitosan (Cs). Hence, a computational model dependent on a high theoretical level density functional theory (DFT) using the B3LYP/LANL2DZ model is carried out to study the physical as well as electronic properties of the proposed interaction between GO functionalized with Cs and its interaction with DA. GO functionalized with a Cs biopolymer was verified as having much higher stability and reactivity. Moreover, the addition of DA to functionalized GO yields structures with the same stability and reactivity. This ensures that GO-Cs is a stable structure with a strong interaction with DA, which is energetically preferred. Molecular electrostatic potential (MESP) calculation maps indicated that the impact of an interaction between GO and Cs increases the number of electron clouds at the terminals, ensuring the great ability of this composite when interacting with DA. Hence, these calculations and experimental results support the feasibility of using GO functionalized with Cs as a DA biosensor.

Graphene-derived antibacterial nanocomposites for water disinfection: Current and future perspectives

Antimicrobial nanomaterials provide numerous opportunities for the synthesis of next-generation sustainable water disinfectants. Using the keywords graphene and water disinfection and graphene antibacterial activity, a detailed search of the Scopus database yielded 198 and 1433 studies on using graphene for water disinfection applications and graphene antibacterial activity in the last ten years, respectively. Graphene family nanomaterials (GFNs) have emerged as effective antibacterial agents. The current innovations in graphene-, graphene oxide (GO)-, reduced graphene oxide (rGO)-, and graphene quantum dot (GQD)-based nanocomposites for water disinfection, including their functionalization with semiconductor photocatalysts and metal and metal oxide nanoparticles, have been thoroughly discussed in this review. Furthermore, their novel application in the fabrication of 3D porous hydrogels, thin films, and membranes has been emphasized. The physicochemical and structural properties affecting their antibacterial efficiency, such as sheet size, layer number, shape, edges, smoothness/roughness, arrangement mode, aggregation, dispersibility, and surface functionalization have been highlighted. The various mechanisms involved in GFN antibacterial action have been reviewed, including the mechanisms of membrane stress, ROS-dependent and -independent oxidative stress, cell wrapping/trapping, charge transfer, and interaction with cellular components. For safe applications, the potential biosafety and biocompatibility of GFNs in aquatic environments are emphasized. Finally, the current limitations and future perspectives are discussed. This review may provide ideas for developing efficient and practical solutions using graphene-, GO-, rGO-, and GQD-based nanocomposites in water disinfection by rationally employing their unique properties.

Natural-Fiber-Reinforced Chitosan, Chitosan Blends and Their Nanocomposites for Various Advanced Applications

There has been much effort to provide eco-friendly and biodegradable materials for the next generation of composite products owing to global environmental concerns and increased awareness of renewable green resources. This review article uniquely highlights the use of green composites from natural fiber, particularly with regard to the development and characterization of chitosan, natural-fiber-reinforced chitosan biopolymer, chitosan blends, and chitosan nanocomposites. Natural fiber composites have a number of advantages such as durability, low cost, low weight, high specific strength, non-abrasiveness, equitably good mechanical properties, environmental friendliness, and biodegradability. Findings revealed that chitosan is a natural fiber that falls to the animal fiber category. As it has a biomaterial form, chitosan can be presented as hydrogels, sponges, film, and porous membrane. There are different processing methods in the preparation of chitosan composites such as solution and solvent casting, dipping and spray coating, freeze casting and drying, layer-by-layer preparation, and extrusion. It was also reported that the developed chitosan-based composites possess high thermal stability, as well as good chemical and physical properties. In these regards, chitosan-based “green” composites have wide applicability and potential in the industry of biomedicine, cosmetology, papermaking, wastewater treatment, agriculture, and pharmaceuticals.

Preparation of new bio-based chitosan/Fe2O3/NiFe2O4 as an efficient removal of methyl green from aqueous solution

Modified chitosan with various functional groups has high potential as an efficient adsorbent in removing water pollution. In this study, new magnetic adsorbent, bio-based chitosan/Fe2O3/NiFe2O4, was successfully prepared by green chemistry route involving mixing of chitosan as core moiety and Fe2O3/NiFe2O4 nanocomposite, and slow evaporation of solvent. Synthesized chitosan/Fe2O3/NiFe2O4 was characterized by FT-IR, TGA, XRD, VSM and FE-SEM. The FT-IR and XRD results confirmed that the successful preparation of chitosan/Fe2O3/NiFe2O4. Uniform dispersion of Fe2O3/NiFe2O4 nanoparticles with low aggregation was confirmed by FE-SEM. The as-prepared magnetic chitosan/Fe2O3/NiFe2O4 was developed as solid phase adsorbent to remove methyl green (MG) dye from aqueous solutions. Several important parameters such as contact time, pH, temperature and adsorbent dosage were investigated systematically. The high and fast MG dye removal (≈ 80%) occurs after 30 min. The optimal conditions for MG removal was recorded at pH = 8, contact time of 60 min, adsorbent dosage of 0.2 g and 25 °C and displayed a high MG dye removal percentage of 96.51% and adsorption capacity of 77.22 mg/g.

Nanocellulose and Graphene Oxide Aerogels for Adsorption and Removal Methylene Blue from an Aqueous Environment

The characteristics of aerogel materials such as the low density and large surface area enable them to adsorb large amounts of substances, so they show great potential for application in industrial wastewater treatment. Herein, using a combination of completely environmentally friendly materials such as cellulose nanofibers (CNFs) extracted from the petioles of the nipa palm tree and graphene oxide (GO) fabricated by simple solvent evaporation, a composite aerogel was prepared by a freeze-drying method. The obtained aerogel possessed a light density of 0.0264 g/cm3 and a porosity of more than 98.2%. It was able to withstand a weight as much as 2500 times with the maximum force (1479.5 N) to break up 0.2 g of an aerogel by compression strength testing and was stable in the aquatic environment, enabling it to be reused five times with an adsorption capacity over 90%. The CNF/GO aerogel can recover higher than 85% after 30 consecutive compression recovery cycles, which is convenient for the reusability of this material in wastewater treatments. The obtained aerogel also showed a good interaction between the component phases, a high thermal stability, a 3D network structure combined with thin walls and pores with a large specific surface area. In addition, the aerogel also exhibited a fast adsorption rate for methylene blue (MB) adsorption, a type of waste from the textile industry that pollutes water sources, and it can adsorb more than 99% MB in water in less than 20 min. The excellent adsorption of MB onto the CNF/GO aerogel was driven by electrostatic interactions, which agreed with the pseudo-second-order kinetic model with a correlation coefficient R 2 = 0.9978. The initial results show that the CNF/GO aerogel is a highly durable "green" light material that might be applied in the treatment of domestic organic waste water and is completely recoverable and reusable.

Evolution of graphene oxide (GO)-based nanohybrid materials with diverse compositions: an overview

The discovery of the 2D nanostructure of graphene was in fact the beginning of a new generation of materials. Graphene itself, its oxidized form graphene oxide (GO), the reduced form of GO (RGO) and their numerous composites are associates of this generation. Out of this spectrum of materials, the development of GO and related hybrid materials has been reviewed in the present article. GO can be functionalized with metals (Ag and Mg) and metal oxides (CuO, MgO, Fe₂O₃, Ag₂O, etc.) nanoparticles (NPs), organic ligands (chitosan and EDTA) and can also be dispersed in different polymeric matrices (PVA, PMMA, PPy, and PAn). All these combinations give rise to nanohybrid materials with improved functionality. An updated report on the chronological development of such nanohybrid materials of diverse nature has been delivered in the present context. Modifications in synthesis methodologies as well as performances and applications of individual materials are addressed accordingly. The functional properties of GO were synergistically modified by photoactive semiconductor NPs; as a result, the GO–MO hybrids acquired excellent photocatalytic ability and were able to degrade a large variety of organic dyes (MB, RhB, MO, MR, etc.) and pathogens. The large surface area of GO was successfully complemented by the NPs so that high and selective adsorption capacity towards metal ions and organic molecules as well as improved charge separation properties could be achieved. As a result, GO–MO hybrids have been considered effective materials in water purification, energy storage and antibacterial applications. GO–MO hybrids with magnetic particles have exhibited selective destruction of cancerous cells and controlled drug release properties, extremely important in the pharmaceutical field. Chitosan and EDTA-modified GO could form 3D network-like structures with strong efficiency in removing heavy metal ions and organic pollutants. GO as a filler enhanced the strength, flexibility and functional properties of common polymers, such as PVA and PVC, to a large extent while, GO–CP composites with polyaniline and polypyrrole are considered suitable for the fabrication of biosensors, supercapacitors, and MEMS as well as efficient photothermal therapy agents. In summary, GO-based hybrids with inorganic and organic counterparts have been designed, the unique properties of which are exploited in versatile fields of applications.

GO undergoes synergistic interaction with MO nanoparticles and the hybrid can be used as a heterogeneous catalyst for the photocatalytic degradation of dyes.

Synthesis of EDTA-functionalized graphene oxide-chitosan nanocomposite for simultaneous removal of inorganic and organic pollutants from complex wastewater

Discharging of inorganic and organic pollutants creates a serious threat to the human health and the environment. In the current work, we have synthesized Ethylenediaminetetraacetic acid (EDTA) functionalized graphene oxide-chitosan nanocomposite (GO-EDTA-CS) for simultaneous removal of inorganic (i.e., mercury (Hg(II) and copper (Cu(II)) and organic pollutants (i.e., methylene blue (MB) and crystal violet (CV)) from wastewater via adsorption process. The structural, functional, morphological, elemental compositions, surface area and thermal properties of the synthesized nanocomposite were identified using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), Brunauer-Emmett-Teller (BET), and thermogravimetric analyzer (TGA), respectively. Different batch adsorption experiments such as pH effect, contact time, initial pollutants concentration, reusability etc. were studied in monocomponent system to optimize the results. The adsorption process apparently followed pseudo-second-order (PSO) kinetics for both pollutants, however the adsorption kinetics was also explained by the intra-particle diffusion model. The isotherm data for both metals ions and dyes were well fit by the Langmuir isotherm model. The maximum adsorption capacities of the adsorbent were determined 324 ± 3.30 130 ± 2.80, 141 ± 6.60, and 121 ± 3.50 mg g^-1 for Hg(II), Cu(II), MB, and CV, respectively. The excellent adsorption capacity was attributed to the availability of various active functional groups (e.g., -COOH, -OH, -NH₂, etc.) on the adsorbent. The EDS, elemental mapping and FTIR analysis performed before and after the adsorption of heavy metals and dyes by GO-EDTA-CS confirmed the simultaneous adsorption of the pollutants. Moreover, GO-EDTA-CS could maintain its adsorption capacity for both inorganic and organic pollutants even after seven cycles of adsorption-desorption, indicating itself a promising adsorbent for practical wastewater treatment containing both inorganic and organic toxic pollutants.

Hydrothermal synthesis of phosphorylated chitosan and its adsorption performance towards Acid Red 88 dye

Phosphorylated chitosan (P-CS) was successfully synthesized using a facile experimental setup of hydrothermal method that was applied to the adsorption of anionic Acid Red 88 (AR88) from aqueous media. The adsorption process obeyed the pseudo-second-order (PSO) kinetic model. In contrast, the adsorption isotherm conformed to the Langmuir model, with the maximum adsorption capacity (q_m = 230 mg g^-1) at 303 K. Both external and intraparticle diffusion strongly influenced the rate of adsorption. The insights from this study reveal that P-CS could be easily prepared and regenerated for reusability applications. The adsorption mechanism and intermolecular interaction between P-CS and AR 88 were investigated using Fourier transform infrared (FTIR) spectroscopy and calculations via Density Functional Theory (DFT). The key modes of adsorption for the P-CS/AR 88 system are driven by electrostatic attractions, H-bonding, and n-π interactions. The findings herein reveal that P-CS is a promising adsorbent for the removal of anionic dyes such as AR88 or similar pollutants from water.

Surface-decorated graphene oxide sheets with nanoparticles of chitosan-Arabic gum for the separation of bioactive compounds: A case study for adsorption of crocin from saffron extract

This work provides a new perception toward the application of the graphenic-biopolymeric composites as a solid-bed for separation and purification of bioactive compounds. Graphene oxide nanocomposites with functionalized sheets by soluble and insoluble nanocomplexes of chitosan and Arabic gum, were successfully synthesized and employed for the adsorption and purification of crocin, a nutraceutical from saffron. The composites exhibited a nanostructured scaffold with a particle size of 10 nm and experienced an unprecedented increase in the surface area by about 300% and improved d-spacing sheets by 17%. The optimum conditions for crocin separation were temperature = 318 K, stirring rate = 300 rpm, initial concentration = 100 mg L^-1 and pH = 6. Under these conditions, the nanocomposites separated 99.1% of crocin in an equilibrium time of 30 min. The adsorption data were best represented by Freundlich isotherm and pseudo-second-order kinetic models. The thermodynamic studies indicated that the crocin adsorption on nanocomposites was an endothermic, spontaneous and physisorption process. The high-performance liquid chromatography (HPLC) analysis revealed that produced nanocomposites adsorbed crocin efficiently from saffron extract with a purity similar to the standard sample. The possible interaction mechanisms between crocin and nanocomposites were electrostatic interactions and hydrogen bonding.

Effect of Graphene Oxide as a Reinforcement in a Bio-Epoxy Composite

Graphene oxide (GO) has gained interest within the materials research community. The presence of functional groups on GO offers exceptional bonding capabilities and improved performance in lightweight polymer composites. A literature review on the tensile and flexural mechanical properties of synthetic epoxy/GO composites was conducted that showed differences from one study to another, which may be attributed to the oxidation level of the prepared GO. Herein, GO was synthesized from oxidation of graphite flakes using the modified Hummers method, while bio-epoxy/GO composites (0.1, 0.2, 0.3 and 0.6 wt.% GO) were prepared using a solution mixing route. The GO was characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscope (TEM) analysis. The thermal properties of composites were assessed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). FTIR results confirmed oxidation of graphite was successful. SEM showed differences in fractured surfaces, which implies that GO modified the bio-epoxy polymer to some extent. Addition of 0.3 wt.% GO filler was determined to be an optimum amount as it enhanced the tensile strength, tensile modulus, flexural strength and flexural modulus by 23, 35, 17 and 31%, respectively, compared to pure bio-epoxy. Improvements in strength were achieved with considerably lower loadings than traditional fillers. Compared to the bio-epoxy, the 0.6 wt.% GO composite had the highest thermal stability and a slightly higher (positive) glass transition temperature (Tg) was increased by 3.5 °C, relative to the pristine bio-epoxy (0 wt.% GO).

Graphene-Based Composites for Phosphate Removal

A variety of methods, including chemical precipitation, biological phosphorus elimination, and adsorption, have been described to effectively eliminate phosphorus (P) in the form of phosphate (PO₄ ^3-) from wastewater sources. Adsorption is a simple and easy method. It shows excellent removal performance, cost effectiveness, and the substantial option of adsorbent materials. Therefore, it has been recognized as a practical, environmentally friendly, and reliable treatment method for eliminating P. Nanocomposites have been deployed to remove P from wastewater via adsorption. Nanocomposites offer low-temperature alteration, high specific surface area, adjustable surface chemistry, pore size, many adsorption sites, and rapid intraparticle diffusion distances. In this Mini-Review, we have aimed to summarize the last eight years of progress in P removal using graphene-based composites via adsorption. Ultimately, future perspectives have been presented to boost the progress of this encouraging field.

Comparative Study of Nanocarbon-Based Flexible Multifunctional Composite Electrodes

Although nanocarbon-based nanofillers have been widely used to improve the energy-storing and sensing functions of porous materials, the comparison of the effects of different nanocarbon-based fillers on the capacitive and flexible sensing properties of nanocarbon-based porous sponge composite supercapacitor electrodes by combining a carbon nanotube, graphene, and graphene oxide with porous sponge is incomplete. The specific capacitance of carbon nanotube-based electrodes is 20.1 F/g. The specific capacitance of graphene-based electrodes is 26.7 F/g. The specific capacitance of graphene oxide-based electrodes is 78.1 F/g, and the capacity retention rate is 92.99% under 20 000 charge-discharge cycles. Under a bending load of 180°, the capacitance retention rate of graphene oxide sponge composite electrodes is 67.46%, which indicates that the prepared electrodes of supercapacitor have the advantages of high capacitance and good flexibility at the same time. To demonstrate their performance, an array of three graphene oxide supercapacitors in series was constructed, which could light up a red light-emitting diode (LED). The tensile strength of carbon nanotube sponge composite electrodes is 0.267 MPa, and the tensile linearity is 0.0169. The experimental results show that graphene oxide-based sponge composite supercapacitor electrodes have the best capacitance performance and carbon nanotube sponge composites have the most potential as a flexible sensor.

Carbon-based sustainable nanomaterials for water treatment: State-of-art and future perspectives

The supply of safe drinking and clean water is becoming increasingly challenging proposition throughout the world. The deployment of environmentally sustainable nanomaterials with unique advantages namely high efficiency and selectivity, earth-abundance, recyclability, low-cost of production processes, and stability, has been a priority although several important challenges and constraints still remained unresolved. Carbon nanomaterials namely activated carbon, multi-walled- and single-walled carbon nanotubes, have been developed and applied as adsorbents for wastewater treatment and purification; graphene and graphene oxide-based nanomaterials as well as carbon and graphene quantum dots-derived nanomaterials have shown significant promise for water and wastewater treatment and purification, especially, for industrial- and pharmaceutical-laden wastes. This review encompasses advanced carbonaceous nanomaterials and methodologies that are deployed for the elimination of contaminants and ionic metals in aqueous media, and as novel nanosorbents for wastewater, drinking and ground water treatment. Additionally, recent trends and challenges pertaining to the sustainable carbon and graphene quantum dots-derived nanomaterials and their appliances for treating and purifying wastewater are highlighted.

Development of triaminotriazine functionalized graphene oxide capped chitosan porous composite beads for nutrients remediation towards water purification

The porous, definite and nitrogen rich triaminotriazine (TAT) grafted graphene oxide (GO) known as TATGO composite was developed for nutrients (NO₃^- and PO₄^3-) retention. Additionally, the structural property of TATGO composite was improved with the use of chitosan (CS) to produce easily separable TATGO@CS hybrid beads which possess the significant NO₃^- and PO₄^3- adsorption capacities of 58.46 and 61.38 mg/g respectively than their individual materials. The instrumentations such as SEM, TGA, FTIR, EDAX, XRD and BET studies were executed for adsorbents. The optimization of the parameters accountable for adsorption process was performed in batch scale. The effect of isotherms (Langmuir, Freundlich and Dubinin-Radushkevich (D-R)), kinetics (pseudo-first/second order and particle/intraparticle diffusion) and thermodynamic parameters (ΔG°, ΔH° and ΔS°) of the adsorption was explored. The removal mechanism of TATGO@CS hybrid beads was to be electrostatic attraction on NO₃^- and PO₄^3-. The field applicability and reuse of TATGO@CS hybrid beads was also inspected.

Graphene Oxide as a Nanocarrier for Biochemical Molecules: Current Understanding and Trends

The development of an advanced and efficient drug delivery system with significant improvement in its efficacy and enhanced therapeutic value is one of the critical challenges in modern medicinal biology. The integration of nanomaterial science with molecular and cellular biology has helped in the advancement and development of novel drug delivery nanocarrier systems with precision and decreased side effects. The design and synthesis of nanocarriers using graphene oxide (GO) have been rapidly growing over the past few years. Due to its remarkable physicochemical properties, GO has been extensively used in efforts to construct nanocarriers with high specificity, selectivity, and biocompatibility, and low cytotoxicity. The focus of this review is to summarize and address recent uses of GO-based nanocarriers and the improvements as efficient drug delivery systems. We briefly describe the concepts and challenges associated with nanocarrier systems followed by providing critical examples of GO-based delivery of drug molecules and genes. Finally, the review delivers brief conclusions on the current understanding and prospects of nanocarrier delivery systems.

Preparation of Chitosan-Graphene Oxide Composite Aerogel by Hydrothermal Method and Its Adsorption Property of Methyl Orange

Graphene based aerogel has become one of the most likely functional adsorption materials that is applicable to purify various contaminated water sources, such as dye wastewater, because of its high porosity, structural stability, large specific surface area, and high adsorption capacity. In this study, chitosan and graphene oxide were first selected as the matrix to prepare the composite hydrogel through the hydrothermal method, which was further frozen and dried to obtain the target aerogel. The microscopic structures and adsorption capacity of the composite aerogel were then characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and N₂ (nitrogen) physical adsorption and desorption tests. The results show that the specific surface area of the composite aerogel was reached at 297.431 m²/g, which is higher than that of graphene oxide aerogel and chitosan aerogel. The aperture was reduced to about 3 nm. The adsorption rate of the composite aerogel for the methyl orange solution was as high as 97.2% at pH = 1, and the adsorption capacity was 48.6 mg/g. The adsorption process of the composite aerogel satisfies the Langmuir equation and can be described by the second-order adsorption kinetics. In addition, it is worth noting that this composite aerogel can provide a striking adsorption characteristic on methyl orange due to the combining effects from massive amino groups on chitosan and the structural conjugation of graphene oxide.

Uptake of Methylene Blue from Aqueous Solution by Pectin–Chitosan Binary Composites

To address the need to develop improved hybrid biopolymer composites, we report on the preparation of composites that contain chitosan and pectin biopolymers with tunable adsorption properties. Binary biopolymer composites were prepared at variable pectin–chitosan composition in a solvent directed synthesis, dimethyl sulfoxide (DMSO) versus water. The materials were characterized using complementary methods (infrared spectroscopy, thermal gravimetric analysis, pH at the point-of-zero charge, and dye-based adsorption isotherms). Pectin and chitosan composites prepared in DMSO yielded a covalent biopolymer framework (CBF), whereas a polyelectrolyte complex (PEC) was formed in water. The materials characterization provided support that cross-linking occurs between amine groups of chitosan and the –COOH groups of pectin. CBF-based composites had a greater uptake of methylene blue (MB) dye over the PEC-based composites. Composites prepared in DMSO were inferred to have secondary adsorption sites for enhanced MB uptake, as evidenced by a monolayer uptake capacity that exceeded the pectin–chitosan PECs by 1.5-fold. This work provides insight on the role of solvent-dependent cross-linking of pectin and chitosan biopolymers. Sonication-assisted reactions in DMSO favor CBFs, while cross-linking in water yields PECs. Herein, composites with tunable structures and variable physicochemical properties are demonstrated by their unique dye adsorption properties in aqueous media.

Environmental Remediation Applications of Carbon Nanotubes and Graphene Oxide: Adsorption and Catalysis

Environmental issues such as the wastewater have influenced each aspect of our lives. Coupling the existing remediation solutions with exploring new functional carbon nanomaterials (e.g., carbon nanotubes, graphene oxide, graphene) by various perspectives shall open up a new venue to understand the environmental issues, phenomenon and find out the ways to get along with the nature. This review makes an attempt to provide an overview of potential environmental remediation solutions to the diverse challenges happening by using low-dimensional carbon nanomaterials and their composites as adsorbents, catalysts or catalysts support towards for the social sustainability.