Graphene Oxide Synthesis from Agro Waste

Graphene nanosheet reinforcement of polyurethane nanocomposite for green and sustainable photoluminescence, superhydrophobic, and anticorrosive paint

A simple and environmentally friendly method was developed for smart and efficient waterborne polyurethane (PUR) paint. Sugarcane bagasse was recycled into reduced graphene oxide nanosheets (rGONSs). Both lanthanide-doped aluminate nanoparticles (LAN; photoluminescent agent, 7-9 nm) and rGONSs (reinforcement agent) were integrated into a waterborne polyurethane to produce a novel photoluminescent, hydrophobic, and anticorrosive nanocomposite coating. Using ferrocene-based oxidation under masked circumstances, graphene oxide nanosheets were produced from sugarcane bagasse. The oxidized semicarbazide (SCB) nanostructures were integrated into polyurethane coatings as a drying, anticorrosion, and crosslinking agent. Polyurethane coatings with varying amounts of phosphor pigment were prepared and subsequently applied to mild steel. The produced paints (LAN/rGONSs@PUR) were tested for their hydrophobicity, hardness, and scratch resistance. Commission Internationale de l'éclairage (CIE) Laboratory parameters and photoluminescence analysis established the opacity and colourimetric properties of the nanocomposite coatings. When excited at 365 nm, the luminescent transparent paints emitted a strong greenish light at 517 nm. The anticorrosion characteristics of the coated steel were investigated. The phosphor-containing (11% w/w) polyurethane coatings displayed the most pronounced anticorrosion capability and long-persistent luminosity. The prepared waterborne polyurethane paints were very photostable and durable.

Naringin and graphene oxide incorporated Moringa oleifera gum/poly(vinyl) alcohol patch for enhanced wound healing

Patients and healthcare systems stand to gain much from the use of substances that can accelerate wound healing. In this research work, a polymeric patch was fabricated using polymers like poly (vinyl alcohol) (PVA) and Moringa oleifera gum (MO) incorporated with graphene oxide (GO) and naringin (Nar) (drug). This study determined the impact of using PVA/MO/GO/Nar polymeric patch on wound healing via in vitro and in vivo investigations. Graphene oxide was synthesized by modified Hummer's method. The synthesized sample was characterized using XRD, FT-IR, RAMAN Spectroscopy, FESEM and HRTEM. Antibacterial analysis of the GO on four different bacteria was studied through well diffusion, colony count, growth curve and biofilm assay. Biocompatibility was analysed by haemolysis assay. The morphology, antibacterial activity, haemolysis assay, swelling, degradation, porosity, water vapour transmission rate, drug release, blood pump model, in-vitro scratch assay and MTT assay were analysed for the fabricated polymeric patches under in-vitro condition. The PVA/MO/GO/Nar patch has shown enhanced wound healing in in-vivo wound healing experiments on albino Wistar rats.

Proactive Effect of Algae-Based Graphene Support on the Oxygen Evolution Reaction Electrocatalytic Activity of NiFe

The preparation of graphene materials from biomass resources is still a challenge, even more so if they are going to be employed as supports for electrocatalysts for water splitting. Herein, we describe the preparation and characterization of graphene oxides (GOs) from solid macroalgae waste obtained after processing an agar-agar residue. The structural and morphological characterization of the obtained GO confirm the presence of a lamellar material that is composed of few layers with an increased number of heteroatoms (including nitrogen) if compared with those observed in a GO obtained from graphite (reference). Three-dimensional electrodes were prepared from these GOs by depositing them onto a fibrous carbon paper, followed by electrodeposition of the catalyst, NiFe. The electrocatalytic performance of these hybrid systems for the oxygen evolution reaction (OER) showed a proactive effect of both graphene materials toward catalysis. Moreover, the electrode prepared from the algae-based graphene showed the highest electrocatalytic activity. This fact could be explained by the different structure of the algae-based graphene which, due to differences in the nucleation growth patterns and electroactive sites developed during the electrodeposition process, produced more reactive NiFe species (higher oxidation state).

Graphene as a nano-delivery vehicle in agriculture - current knowledge and future prospects

Graphene has triggered enormous interest in, and exploration of, its applications in diverse areas of science and technology due to its unique properties. While graphene has displayed great potential as a nano-delivery system for drugs and biomolecules in biomedicine, its application as a nanocarrier in agriculture has only begun to be explored. Conventional fertilizers and agricultural delivery systems have a number of disadvantages, such as: fast release of the active ingredient, low delivery efficiency, rapid degradation and low stability that often leads to their over-application and consequent environmental problems. Advanced nano fertilizers with high carrier efficiency and slow and controlled release are now considered the gold standard for promoting agricultural sustainability while protecting the environment. Graphene's attractive properties include large surface area, chemical stability, mechanical stability, tunable surface chemistry and low toxicity making it a promising material on which to base agricultural delivery systems. Recent research has demonstrated considerable success in the use of graphene for agricultural applications, including its utilization as a delivery vehicle for plant nutrients and crop protection agents, as well as in post-harvest management of crops. This review, therefore, presents a comprehensive overview of the current status of graphene-based nanocarriers in agriculture. Additionally, the review outlines the surface functionalization methods used for effective molecular delivery, various strategies for nano-vehicle design and the underlying features necessary for a graphene-based agro-delivery system. Finally, the review discusses directions for further research in optimization of graphene-based nanocarriers.

Rice straw derived graphene-silica based nanocomposite and its application in improved co-fermentative microbial enzyme production and functional stability

Cellulases are the one of the most highly demanded industrial biocatalysts due to their versatile applications, such as in the biorefinery industry. However, relatively poor efficiency and high production costs are included as the key industrial constraints that hinder enzyme production and utilization at economic scale. Furthermore, the production and functional efficiency of the β-glucosidase (BGL) enzyme is usually found to be relatively low among the cellulase cocktail produced. Thus, the current study focuses on fungi-mediated improvement of BGL enzyme in the presence of a rice straw-derived graphene-silica-based nanocomposite (GSNCs), which has been characterized using various techniques to analyze its physicochemical properties. Under optimized conditions of solid-state fermentation (SSF), co-fermentation using co-cultured cellulolytic enzyme has been done, and maximum enzyme production of 42 IU/gds FP, 142 IU/gds BGL, and 103 IU/gds EG have been achieved at a 5 mg concentration of GSNCs. Moreover, at a 2.5 mg concentration of nanocatalyst, the BGL enzyme showed its thermal stability at 60°C and 70 °C by holding its half-life relative activity for 7 h, while the same enzyme demonstrated pH stability at pH 8.0 and 9.0 for the 10 h. This thermoalkali BGL enzyme might be useful for the long-term bioconversion of cellulosic biomass into sugar.

An Overview of Recycling Wastes into Graphene Derivatives Using Microwave Synthesis; Trends and Prospects

It is no secret that graphene, a two-dimensional single-layered carbon atom crystal lattice, has drawn tremendous attention due to its distinct electronic, surface, mechanical, and optoelectronic properties. Graphene also has opened up new possibilities for future systems and devices due to its distinct structure and characteristics which has increased its demand in a variety of applications. However, scaling up graphene production is still a difficult, daunting, and challenging task. Although there is a vast body of literature reported on the synthesis of graphene through conventional and eco-friendly methods, viable processes for mass graphene production are still lacking. This review focuses on the variety of unwanted waste materials, such as biowastes, coal, and industrial wastes, for producing graphene and its potential derivatives. Among the synthetic routes, the main emphasis relies on microwave-assisted production of graphene derivatives. In addition, a detailed analysis of the characterization of graphene-based materials is presented. This paper also highlights the current advances and applications through the recycling of waste-derived graphene materials using microwave-assisted technology. In the end, it would alleviate the current challenges and forecast the specific direction of waste-derived graphene future prospects and developments.

Sustainable Nanomaterials for Biomedical Applications

Significant progress in nanotechnology has enormously contributed to the design and development of innovative products that have transformed societal challenges related to energy, information technology, the environment, and health. A large portion of the nanomaterials developed for such applications is currently highly dependent on energy-intensive manufacturing processes and non-renewable resources. In addition, there is a considerable lag between the rapid growth in the innovation/discovery of such unsustainable nanomaterials and their effects on the environment, human health, and climate in the long term. Therefore, there is an urgent need to design nanomaterials sustainably using renewable and natural resources with minimal impact on society. Integrating sustainability with nanotechnology can support the manufacturing of sustainable nanomaterials with optimized performance. This short review discusses challenges and a framework for designing high-performance sustainable nanomaterials. We briefly summarize the recent advances in producing sustainable nanomaterials from sustainable and natural resources and their use for various biomedical applications such as biosensing, bioimaging, drug delivery, and tissue engineering. Additionally, we provide future perspectives into the design guidelines for fabricating high-performance sustainable nanomaterials for medical applications.

Graphene oxide:Fe2O3 nanocomposites for photodetector applications: experimental and ab initio density functional theory study

In this report, a GO:Fe₂O₃ nanocomposite was synthesized using a one-step covalent attachment approach using a sol-gel technique. The optical absorbance, photoconductive, photo-capacitive, and electrical properties were obtained using spectroscopy, and current-voltage (I-V) measurements. An enhanced optical absorbance with corresponding band gap reduction is observed when Fe₂O₃ nanoparticles are incorporated in GO. A corresponding enhanced photoconductance in the order of ×10¹ was observed due to the impact of band gap narrowing. The enhanced photoconductivity and photo-capacitance can be attributed to energy and charge transfer between GO and Fe atoms, leading to the generation of photo-induced excitons. Density function theory calculations indicate increased charge transfer when GO is doped with Fe-O atoms, which is consistent with experimental data. The observed results could potentially enable the use of GO:Fe₂O₃ nanocomposites for photodetectors and other optoelectronic applications.

Graphene Oxide/Gelatin Nanofibrous Scaffolds Loaded with N-Acetyl Cysteine for Promoting Wound Healing

Purpose

We aimed to develop an antioxidant dressing material with pro-angiogenic potential that could promote wound healing. Gelatin (Gel) was selected to improve the biocompatibility of the scaffolds, while graphene oxide (GO) was added to enhance their mechanical property. The loaded N-Acetyl cysteine (NAC) was performing the effect of scavenging reactive oxygen species (ROS) at the wound site.

Materials and Methods

The physicochemical and mechanical properties, NAC releases, and biocompatibility of the NAC-GO-Gel scaffolds were evaluated in vitro. The regeneration capability of the scaffolds was systemically investigated in vivo using the excisional wound-splinting model in mice.

Results

The NAC-GO-Gel scaffold had a stronger mechanical property and sustainer NAC release ability than the single Gel scaffold, which resulted in a better capacity for cell proliferation and migration. Mice wound-splinting models revealed that the NAC-GO-Gel scaffold effectively accelerated wound healing, promoted re-epithelialization, enhanced neovascularization, and reduced scar formation.

Conclusion

The NAC-GO-Gel scaffold not only promotes wound healing but also reduces scar formation, showing a great potential application for the repair of skin defects.

Optimization of reduced Graphene oxide synthesis using central composite design analysis-A waste to value approach

In recent times, reduced graphene oxide has gained more attention in various fields. In our study, a direct synthesis of reduced graphene oxide using a novel carbon-rich agro-waste from Pennisetum glaucum was used. Ferrocene acted as an oxidizing agent during thermal degradation at 300 °C for 15 and 20 min to promote graphene oxide and reduced graphene oxide formation. The X-ray diffraction peak at 2θ indicating a shift from 16.86 to 24.28°, presence of functional groups like -OH stretching, -C = C-, C = O, C-O, and C-OH by Fourier transmission infrared spectroscopy, prominent D and G bands at 1308 cm^-1 and 1578 cm^-1 by Raman spectra and UV-visible spectroscopy peak shift from 235 to 245 nm (π-π*, C = C bonds) confirmed the reduction of graphene oxide to reduced graphene oxide. The average particle size values 233.3 nm for graphene oxide and 63.57 nm for reduced graphene oxide illustrate the nanoscale range of our synthesized material. The negative zeta potential values in the range - 45.5 mV and - 29.5 mV for graphene oxide and its reduced forms infer the dispersion stability along with surface oxygen group presence. We have also highlighted the formation of graphene oxide quantum dots by magnetic stirring and confirmed by UV transilluminator and photoluminescence spectra. The photodegradation efficiency was optimized using central composite design for dosage, dye concentration, pH, and time for both malachite green and reactive blue dye. The kinetic studies report pseudo-first-order kinetic model for catalytic degradation and statistical Analysis of variance proved the significance of the process for p value < 0.05. Thus, the synthesized graphene materials could be used as a potential candidate for environmental applications.

Antimicrobial activity of synthesized graphene oxide-selenium nanocomposites: A mechanistic insight

Nanoparticles have recently gained interest as an anti-bacterial agent due to their large surface area/volume ratio and potential to compromise the integrity of bacterial cell membranes. Due to its versatility and anti-bacterial activity, graphene-based materials have drawn significant interest in biomedical applications. One of the greatest threats to life in the modern technological era is the pervasiveness of infectious diseases since bacteria cells are constantly updating themselves to resist antibiotics. In this presented study, GO-Se nanocomposite has been synthesized using polymer solution via a simple dispersion method. The structural and physicochemical properties of nanocomposite were investigated in detail. Staphylococcus aureus, Proteus vulgaris, and Bacillus subtilis bacterial strains were employed to study the anti-bacterial activity of GO-Se nanocomposite. The results show that the synthesized nanocomposites have good efficacy as an anti-bacterial agent. UV-vis spectroscopy, FTIR spectroscopy, HRTEM, XPS, and Raman spectroscopy were used to analyze the as-prepared GO and GO-Se nanocomposite.

Advances in the Physico-Chemical, Antimicrobial and Angiogenic Properties of Graphene-Oxide/Cellulose Nanocomposites for Wound Healing

Graphene oxide (GO) and its reduced form (rGO) have recently attracted a fascinating interest due to their physico-chemical properties, which have opened up new and interesting opportunities in a wide range of biomedical applications, such as wound healing. It is worth noting that GO and rGO may offer a convenient access to its ready dispersion within various polymeric matrices (such as cellulose and its derivative forms), owing to their large surface area, based on a carbon skeleton with many functional groups (i.e., hydroxyl, carboxyl, epoxy bridge, and carbonyl moieties). This results in new synergic properties due to the presence of both components (GO or rGO and polymers), acting at different length-scales. Furthermore, they have shown efficient antimicrobial and angiogenic properties, mostly related to the intracellular formation of reactive oxygen species (ROS), which are advantageous in wound care management. For this reason, GO or rGO integration in cellulose-based matrixes have allowed for designing highly advanced multifunctional hybrid nanocomposites with tailored properties. The current review aims to discuss a potential relationship between structural and physico-chemical properties (i.e., size, edge density, surface chemistry, hydrophilicity) of the nanocomposites with antimicrobials and angiogenic mechanisms that synergically influence the wound healing phenomenon, by paying particular attention to recent findings of GO or rGO/cellulose nanocomposites. Accordingly, after providing a general overview of cellulose and its derivatives, the production methods used for GO and rGO synthesis, the mechanisms that guide antimicrobial and angiogenic processes of tissue repair, as well as the most recent and remarkable outcomes on GO/cellulose scaffolds in wound healing applications, will be presented.

Next-generation graphene oxide additives composite membranes for emerging organic micropollutants removal: Separation, adsorption and degradation

In the past two decades, membrane technology has attracted considerable interest as a viable and promising method for water purification. Emerging organic micropollutants (EOMPs) in wastewater have trace, persistent, highly variable quantities and types, develop hazardous intermediates and are diffusible. These primary issues affect EOMPs polluted wastewater on an industrial scale differently than in a lab, challenging membranes-based EOMP removal. Graphene oxide (GO) promises state-of-the-art membrane synthesis technologies and use in EOMPs removal systems due to its superior physicochemical, mechanical, and electrical qualities and high oxygen content. This critical review highlights the recent advancements in the synthesis of next-generation GO membranes with diverse membrane substrates such as ceramic, polyethersulfone (PES), and polyvinylidene fluoride (PVDF). The EOMPs removal efficiencies of GO membranes in filtration, adsorption (incorporated with metal, nanomaterial in biodegradable polymer and biomimetic membranes), and degradation (in catalytic, photo-Fenton, photocatalytic and electrocatalytic membranes) and corresponding removal mechanisms of different EOMPs are also depicted. GO-assisted water treatment strategies were further assessed by various influencing factors, including applied water flow mode and membrane properties (e.g., permeability, hydrophily, mechanical stability, and fouling). GO additive membranes showed better permeability, hydrophilicity, high water flux, and fouling resistance than pristine membranes. Likewise, degradation combined with filtration is two times more effective than alone, while crossflow mode improves the photocatalytic degradation performance of the system. GO integration in polymer membranes enhances their stability, facilitates photocatalytic processes, and gravity-driven GO membranes enable filtration of pollutants at low pressure, making membrane filtration more inexpensive. However, simultaneous removal of multiple contaminants with contrasting characteristics and variable efficiencies in different systems demands further optimization in GO-mediated membranes. This review concludes with identifying future critical research directions to promote research for determining the GO-assisted OMPs removal membrane technology nexus and maximizing this technique for industrial application.

Advancement in "Garbage In Biomaterials Out (GIBO)" concept to develop biomaterials from agricultural waste for tissue engineering and biomedical applications

Presently on a global scale, one of the major concerns is to find effective strategies to manage the agricultural waste to protect the environment. One strategy that has been drawing attention among the researchers is the development of biocompatible materials from agricultural waste. This strategy implies successful conversion of agricultural waste products (e.g.: cellulose, eggshell etc.) into building blocks for biomaterial development. Some of these wastes contain even bioactive compounds having biomedical applications. The replacement and augmentation of human tissue with biomaterials as alternative to traditional method not only bypasses immune-rejection, donor scarcity, and maintenance; but also provides long term solution to damaged or malfunctioning organs. Biomaterials development as one of the key challenges in tissue engineering approach, resourced from natural origin imparts better biocompatibility due to closely mimicking composition with cellular microenvironment. The "Garbage In, Biomaterials Out (GIBO)" concept, not only recycles the agricultural wastes, but also adds to biomaterial raw products for further product development in tissue regeneration. This paper reviews the conversion of garbage agricultural by-products to the biocompatible materials for various biomedical applications.

GRAPHICAL ABSTRACT

The agro-waste biomass processed, purified, modified, and further utilized for the fabrication of biomaterials-based support system for tissue engineering applications to grow living body parts in vitro or in vivo.

Enhanced bioenergy and nutrients recovery from wastewater using hybrid anodes in microbial nutrient recovery system

Background

The combined microbial fuel cell–microbial nutrient recovery system has lately been thoroughly explored from an engineering standpoint. The relevance of microbial communities in this process, on the other hand, has been widely underestimated.

Results

A lab-scale microbial nutrients recovery system was created in this work, and the microbial community structure was further defined, to give a thorough insight into the important microbial groups in the present system. We reported for the first-time different hybrid anodes of activated carbon and chitosan that were used in the microbial nutrient recovery system for bioenergy production, and, for the removal of COD and recovery of nutrients present in the wastewater. The hybrid anodic materials were studied to adapt electrochemically active bacteria for the recovery of nutrients and energy generation from wastewater without the need for an external source of electricity. The potential of the created hybrid anodes in terms of nutrients recovery, chemical oxygen demand elimination, and energy generation from municipal wastewater was thoroughly examined and compared with each other under similar operating conditions. When the COD loading was 718 mg/L, a total COD removal of ~ 79.2% was achieved with a hybrid activated carbon and chitosan anode having an equal ratio after 10 days of the operation cycle. The maximum power density estimated for hybrid anode (~ 870 mWm⁻²) was found.

Conclusion

Overall, this work reveals a schematic self-driven way for the collection and enrichment of nutrients (~ 72.9% phosphorus recovery and ~ 73% ammonium recovery) from municipal wastewater, as well as consistent voltage production throughout the operation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13068-022-02116-y.

Graphene and Its Derivatives: Synthesis and Application in the Electrochemical Detection of Analytes in Sweat

Wearable sensors and invasive devices have been studied extensively in recent years as the demand for real-time human healthcare applications and seamless human-machine interaction has risen exponentially. An explosion in sensor research throughout the globe has been ignited by the unique features such as thermal, electrical, and mechanical properties of graphene. This includes wearable sensors and implants, which can detect a wide range of data, including body temperature, pulse oxygenation, blood pressure, glucose, and the other analytes present in sweat. Graphene-based sensors for real-time human health monitoring are also being developed. This review is a comprehensive discussion about the properties of graphene, routes to its synthesis, derivatives of graphene, etc. Moreover, the basic features of a biosensor along with the chemistry of sweat are also discussed in detail. The review mainly focusses on the graphene and its derivative-based wearable sensors for the detection of analytes in sweat. Graphene-based sensors for health monitoring will be examined and explained in this study as an overview of the most current innovations in sensor designs, sensing processes, technological advancements, sensor system components, and potential hurdles. The future holds great opportunities for the development of efficient and advanced graphene-based sensors for the detection of analytes in sweat.

Biomass conversion of agricultural waste residues for different applications: a comprehensive review

Agricultural waste residues (agro-waste) are the source of carbohydrates that generally go in vain or remain unused despite their interesting morphological, chemical, and mechanical properties. With rapid urbanization, there is a need to valorize this waste due to limited non-renewable resources. Utilizing agro-waste also prevents the problems like burning and inefficient disposal that otherwise lead to immense pollution worldwide. In addition, conversion of biomass to value-added products like earthen cups, weaving baskets, and bricks is equally beneficial for the rural population as it provides secondary income, creates jobs, and improves rural people's lifestyles. This review paper will discuss an overview of different applications utilizing agro-waste residues. In particular, agro-wastes used as construction material, bio-fertilizers, pulp and paper products, packaging products, tableware, heating applications, biocomposites, nano-cellulosic materials, soil stabilizers, bioplastics, fire-retardant additive, dye removal, and biofuels will be summarized. Finally, several commercially available agro-waste products will also be discussed, emphasizing the circular economy.

Synthesis and characterization of a novel composite of rice husk-derived graphene oxide with titania microspheres (GO-RH/TiO2) for effective treatment of cationic dye methylene blue in aqueous solutions

Graphene oxide (GO) was synthesized utilizing rice husk (RH) as the starting raw material via a modified Hummers' method. Ground pencil leads were used as a control powder of the starting raw material to monitor the consistency of the synthesis method. TiO₂ microspheres were synthesized via a precipitated method using the pluronic F127 solution as the pore template. GO derived from RH (GO-RH) was composited with TiO₂ microspheres as GO-RH/TiO₂ composites by an impregnation method with weight ratios of 3:1, 2:2, and 1:3. Characterized results revealed GO-RH formed a ternary phase material of graphene oxide, graphite oxide, and silica. A typical microstructure of the calcined TiO₂ microspheres was found as the agglomerated anatase nanoparticles. Furthermore, the composites belong to large surface areas and numerous oxygen-containing functionalities on their surfaces. Removal efficiencies of cationic dye methylene blue (MB) from aqueous solutions by the composites, GO-RH and TiO₂, were studied under UV illumination for 180 min. Due to the effective combination of adsorption and photodegradation for the MB removal, the composites provided the higher efficiencies (99-100%) faster than those of GO-RH and TiO₂ and could be reused at least 4 times. Finally, a mechanism of the MB removal by the composites was proposed.

Preparation of photoluminescent and anticorrosive epoxy paints immobilized with nanoscale graphene from sugarcane bagasse agricultural waste

Sugarcane bagasse agricultural waste has been one of the most common solid pollutants worldwide. Thus, introducing a simple method to convert sugarcane bagasse into value-added materials has been highly significant. Herein, we develop a simple and green strategy to reprocess sugarcane bagasse as a starting material for the preparation of graphene oxide nanosheets toward the preparation of novel photoluminescent, hydrophobic, and anticorrosive epoxy nanocomposite coatings integrated with lanthanide-doped aluminate nanoparticles. Environmentally friendly graphene oxide (GO) nanostructures were provided by a single-step preparation procedure from sugarcane bagasse (SCB) agricultural waste using ferrocene-based oxidation under muffled conditions. The oxidized SCB nanostructures were applied as a drier, anticorrosion, and crosslinking agent for epoxy coatings. Different concentrations of pigment phosphor were applied onto the epoxy coating. The generated epoxy-graphene-aluminate (EGA) paints were then coated onto mild steel. The hydrophobic properties and hardness as well as resistance to scratch of the EGA paints were examined. The transparency and colorimetric screening of the EGA nanocomposite paints were determined by the absorption spectral analysis and CIE Lab parameters. The luminescent translucent paints demonstrated a bright green emission at 520 nm when excited at 372 nm. The anticorrosion properties of the painted steel submerged in NaCl_(aq) were inspected by the electrochemical impedance spectral (EIS) method. The EGA paints with phosphor (11% w/w) exhibited the most distinct anti-corrosion properties and long-persistent luminescence. The produced paints displayed high durability and photostability.

Gut microbiome interactions with graphene based nanomaterials: Challenges and opportunities

Rapid growth of nanotechnology has accelerated immense possibility of engineered nanomaterials (ENMs) exposure by human and living organisms. In this context, wide range applications of graphene based nanomaterials (GBNMs) may inevitably cause their release into the environment. Consequently, potential risks to the ecological system and human health is consistently increasing due to the probable ingestion of GBNMs by mean of contaminated water or food sources. Further, gut microbiome is known to play a profound impact on the health status of human being and has been recognized as the most exciting advancement in the biomedical science. Recent studies has shown vital role of ENMs to alter gut microbiome and thereby changed pathological status of organisms. Therefore, in this review results of numerous studies dedicated to explore the impact of GBNMs on gut microbiome and thereby various pathological status have been summarized. Dietary exposure of different types of GBNMs [e.g. graphene, graphene oxide (GO), partially reduced graphene oxide (PRGO), graphene quantum dots (GQDs)] have been evaluated on the gut microbiome through numerous in vitro and in vivo models. Moreover, emphasis has been made to evaluate different physiological responses with the short/long-term exposure of GBNMs, particularly in gastrointestinal tract (GIT) and its correlation with gut microbiome and the health status. It is reviewed that exposure of GBNMs can exert significant impact which alter the composition, diversity and function of gut microbiome. This may further appear in terms of enteric disorder along with numerous pathological changes e.g. IEC (intestinal epithelial cells) colitis, lysosomal dysfunction, inflammation, shortened colon, resorbed embryo, retardation in skeletal development, low weight of fetus, early or late dead of fetus and IBD (inflammatory bowel disease) like symptoms. Finally, potential health risks due to the exposure of GBNMs have been discussed with future perspective.

Fabrication and Characterization of Effective Biochar Biosorbent Derived from Agricultural Waste to Remove Cationic Dyes from Wastewater

The main aim of this work is to treat sugarcane bagasse agricultural waste and prepare an efficient, promising, and eco-friendly adsorbent material. Biochar is an example of such a material, and it is an extremely versatile and eco-friendly biosorbent to treat wastewater. Crystal violet (CV)-dye and methylene blue (MB)-dye species are examples of serious organic pollutants. Herein, biochar was prepared firstly from sugarcane bagasse (SCB), and then a biochar biosorbent was synthesized through pyrolysis and surface activation with NaOH. SEM, TEM, FTIR, Raman, surface area, XRD, and EDX were used to characterize the investigated materials. The reuse of such waste materials is considered eco-friendly in nature. After that, the adsorption of MB and CV-species from synthetically prepared wastewater using treated biochar was investigated under various conditions. To demonstrate the study’s effectiveness, it was attempted to achieve optimum effectiveness at an optimum level by working with time, adsorbent dose, dye concentration, NaCl, pH, and temperature. The number of adsorbed dyes reduced as the dye concentrations increased and marginally decreased with NaCl but increased with the adsorbent dosage, pH, and temperature of the solution increased. Furthermore, it climbed for around 15 min before reaching equilibrium, indicating that all pores were almost full. Under the optimum condition, the removal perecentages of both MB and CV-dyes were ≥98%. The obtained equilibrium data was represented by Langmuir and Freundlich isotherm models. Additionally, the thermodynamic parameters were examined at various temperatures. The results illustrated that the Langmuir isotherm was utilized to explain the experimental adsorption processes with maximum adsorption capacities of MB and CV-dyes were 114.42 and 99.50 mgg⁻¹, respectively. The kinetic data were estimated by pseudo-first and pseudo-second-order equations. The best correlation coefficients of the investigated adsorption processes were described by the pseudo-second-order kinetic model. Finally, the data obtained were compared with some works published during the last four years.

Graphene Oxide (GO) Materials-Applications and Toxicity on Living Organisms and Environment

Graphene-based materials have attracted much attention due to their fascinating properties such as hydrophilicity, high dispersion in aqueous media, robust size, high biocompatibility, and surface functionalization ability due to the presence of functional groups and interactions with biomolecules such as proteins and nucleic acid. Modified methods were developed for safe, direct, inexpensive, and eco-friendly synthesis. However, toxicity to the environment and animal health has been reported, raising concerns about their utilization. This review focuses primarily on the synthesis methods of graphene-based materials already developed and the unique properties that make them so interesting for different applications. Different applications are presented and discussed with particular emphasis on biological fields. Furthermore, antimicrobial potential and the factors that affect this activity are reviewed. Finally, questions related to toxicity to the environment and living organisms are revised by highlighting factors that may interfere with it.

Nano-Structured Carbon: Its Synthesis from Renewable Agricultural Sources and Important Applications

Carbon materials are versatile in nature due to their unique and modifiable surface and ease of production. Nanostructured carbon materials are gaining importance due to their high surface area for application in the energy, biotechnology, biomedical, and environmental fields. According to their structures, carbon allotropes are classified as carbon nanodots, carbon nanoparticles, graphene, oxide, carbon nanotubes, and fullerenes. They are synthesized via several methods, including pyrolysis, microwave method, hydrothermal synthesis, and chemical vapor deposition, and the use of renewable and cheaper agricultural feedstocks and reactants is increasing for reducing cost and simplifying production. This review explores the nanostructured carbon detailed investigation of sources and their relevant reports. Many of the renewable sources are covered as focused here, such as sugar cane waste, pineapple, its solid biomass, rise husk, date palm, nicotine tabacum stems, lapsi seed stone, rubber-seed shell, coconut shell, and orange peels. The main focus of this work is on the various methods used to synthesize these carbon materials from agricultural waste materials, and their important applications for energy storage devices, optoelectronics, biosensors, and polymer coatings.

A review on graphene / graphene oxide supported electrodes for microbial fuel cell applications: Challenges and prospects

Microbial Fuel Cell (MFC) has gained great interest as an alternative green technology for bioenergy generation along with reduced sludge production, nutrient recovery, removal of COD and color, etc. during wastewater treatment. However, the MFC has several challenges for real-time applications due to less power output and high ohmic resistance and fabrication (electrode and membrane) cost. Several kinds of research have been carried out to increase energy production by reducing various losses associated with electrodes in the MFC. Though, carbonaceous electrodes (carbon and graphite) are the key materials for the anode and cathode side, since these have a higher surface area, good biocompatibility, low cost, and good mechanical strength. Graphene or graphene oxide-based nanocomposite can be an ideal substitute for electrode modifications and an alternative for an expensive anode and cathode catalyst in MFC. Graphene oxide synthesis from waste material such as waste biomass, agricultural, plastic waste, etc. is added advantages of minimizing the cost of the electrodes. But, the synthesis of graphene is quite expensive and has limitations in economic feasibility for bioelectricity production in MFC. Hence, the present review deals with the anode and cathode electrode modification with graphene-based nanocomposites, synthesis of graphene/graphene oxide from various raw materials, and its application in MFC. The current challenges and future outlook on graphene-based composites on MFC performance are also discussed.

Graphene and graphene oxide with anticancer applications: Challenges and future perspectives

Graphene-based materials have shown immense pertinence for sensing/imaging, gene/drug delivery, cancer therapy/diagnosis, and tissue engineering/regenerative medicine. Indeed, the large surface area, ease of functionalization, high drug loading capacity, and reactive oxygen species induction potentials have rendered graphene- (G-) and graphene oxide (GO)-based (nano)structures promising candidates for cancer therapy applications. Various techniques namely liquid-phase exfoliation, Hummer's method, chemical vapor deposition, chemically reduced GO, mechanical cleavage of graphite, arc discharge of graphite, and thermal fusion have been deployed for the production of G-based materials. Additionally, important criteria such as biocompatibility, bio-toxicity, dispersibility, immunological compatibility, and inflammatory reactions of G-based structures need to be systematically assessed for additional clinical and biomedical appliances. Furthermore, surface properties (e.g., lateral dimension, charge, corona influence, surface structure, and oxygen content), concentration, detection strategies, and cell types are vital for anticancer activities of these structures. Notably, the efficient accumulation of anticancer drugs in tumor targets/tissues, controlled cellular uptake properties, tumor-targeted drug release behavior, and selective toxicity toward the cells are crucial criteria that need to be met for developing future anticancer G-based nanosystems. Herein, important challenges and future perspectives of cancer therapy using G- and GO-based nanosystems have been highlighted, and the recent advancements are deliberated.

Low-Cost High Performance Polyamide Thin Film Composite (Cellulose Triacetate/Graphene Oxide) Membranes for Forward Osmosis Desalination from Palm Fronds

Novel low-cost cellulose triacetate-based membranes extracted from palm fronds have been fabricated through the phase-inversion procedure. The cellulose tri-acetate (CTA) membrane was modified by incorporation of graphene oxide (GO) prepared from palm fronds according to the modified Hummer method as well as the preparation of polyamide thin film composite CTA membranes to improve forward osmosis performance for seawater desalination. The surface characteristics and morphology of the prepared CTA, GO, and the fabricated membranes were investigated. The modified TFC prepared membrane had superior mechanical characteristics as well as permeation of water. The performance of the prepared membranes was tested using synthetic 2 M Sodium chloride (NaCl) feed solution. The water flux (Jw) of the thin-film composite (TFC) (CTA/0.3% GO) was 35 L/m2h, which is much higher than those of pure CTA and CTA/0.3% GO. Meanwhile, the salt reverse flux TFC (CTA/0.3% GO) was 1.1 g/m2h), which is much lower than those of pure CTA and CTA/0.3%. GO (Specific salt flux of TFC (CTA/0.3% GO) substrate membrane was 0.03 g/L indicating good water permeation and low reverse salt flux of the TFC membrane compared to CTA. A real saline water sample collected from Hurgada, Egypt, with totally dissolved solids of 42,643 mg/L with NaCl as the draw solution (DS) at 25 °C and flow rate 1.55 L/min, was used to demonstrate the high performance of the prepared TFC membrane. The chemical analysis of desalted permeated water sample revealed the high performance of the prepared TFC membrane. Consequently, the prepared low-cost forward osmosis (FO) thin-film composite CTA membranes can be introduced in the desalination industry to overcome the high cost of reverse osmosis membrane usage in water desalination.

Bio-inspired graphene-based nano-systems for biomedical applications

The increasing demands of environmentally sustainable, affordable, and scalable materials have inspired researchers to explore greener nanosystems of unique properties which can enhance the performance of existing systems. Such nanosystems, extracted from nature, are state-of-art high-performance nanostructures due to intrinsic hierarchical micro/nanoscale architecture and generous interfacial interactions in natural resources. Among several, bio-inspired nanosystems graphene nanosystems have emerged as an essential nano-platform wherein a highly electroactive, scalable, functional, flexible, and adaptable to a living being is a key factor. Preliminary investigation project bio-inspired graphene nanosystems as a multi-functional nano-platform suitable for electronic devices, energy storage, sensors, and medical sciences application. However, a broad understanding of bio-inspired graphene nanosystems and their projection towards applied application is not well-explored yet. Considering this as a motivation, this mini-review highlights the following; the emergence of bio-inspired graphene nanosystems, over time development to make them more efficient, state-of-art technology, and potential applications, mainly biomedical including biosensors, drug delivery, imaging, and biomedical systems. The outcomes of this review will certainly serve as a guideline to motivate scholars to design and develop novel bio-inspired graphene nanosystems to develop greener, affordable, and scalable next-generation biomedical systems.

Hydroxypropyl methylcellulose/graphene oxide composite as drug carrier system for5-Fluorouracil

AIM

This study aims to prepare green nanocomposite (HPMC/5-FL@GO) from the most biocompatible materials, hydroxypropyl methylcellulose (HPMC) and graphene oxide (GO), to enhance the drug activity of immobilized 5- Fluorouracil (5-FU) with decreasing the side effect of long-run treatment protocols with highly efficient drug-drug activity.

METHOD AND RESULTS

Different samples were characterized by ATR-FTIR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), Thermogravimetric analysis (TGA), and dynamic light scattering (DLS) along with cytotoxicity and anticancer study. A homogenous and compatible nanocomposite structure with a homogenous drug distribution was confirmed. The results suggested that the prepared nanocomposite has a low cytotoxicity effect against normal Vero cell lines compared with 5-FU. The antitumor activities of the same nanocomposite (20.4 and 74.3 μg/ml on A549 and HepG-2) were lower than that of 5-FU (54.1and 103 μg/ml on A549 and HepG-2).

CONCLUSION AND IMPLICATIONS

According to the attained results, the HPMC/5-FL@GO can be expected to be widely applied in a biomedical application such as cancer therapy with the unique biocompatible to human cells. This article is protected by copyright. All rights reserved.

Direct-Deposited Graphene Oxide on Dental Implants for Antimicrobial Activities and Osteogenesis

Objective

To determine the effects of graphene oxide (GO) deposition (on a zirconia surface) on bacterial adhesion and osteoblast activation.

Methods

An atmospheric pressure plasma generator (PGS-300) was used to coat Ar/CH₄ mixed gas onto zirconia specimens (15-mm diameter × 2.5-mm thick disks) at a rate of 10 L/min and 240 V. Zirconia specimens were divided into two groups: uncoated (control; Zr) group and GO-coated (Zr-GO) group. Surface characteristics and element structures of each specimen were evaluated by field emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and contact angle. Additionally, crystal violet staining was performed to assess the adhesion of Streptococcus mutans. WST-8 and ALP (Alkaline phosphatase) assays were conducted to evaluate MC3T3-E1 osteoblast adhesion, proliferation, and differentiation. Statistical analysis was calculated by the Mann–Whitney U-test.

Results

FE–SEM and Raman spectroscopy demonstrated effective GO deposition on the zirconia surface in Zr-GO. The attachment and biofilm formation of S. mutans was significantly reduced in Zr-GO compared with that of Zr (P < 0.05). While no significant differences in cell attachment of MC3T3-1 were observed, both proliferation and differentiation were increased in Zr-GO as compared with that of Zr (P < 0.05).

Significance

GO-coated zirconia inhibited the attachment of S. mutans and stimulated proliferation and differentiation of osteoblasts. Therefore, GO-coated zirconia can prevent peri-implantitis by inhibiting bacterial adhesion. Moreover, its osteogenic ability can increase bone adhesion and success rate of implants.

Electrochemical detector based on a modified graphite electrode with phthalocyanine for the elemental analysis of actinides

The quantification of actinides in aqueous solutions involves complex and expensive separation processes. Electrochemical methods have been widely used for the quick and accurate identification and quantification of organic and inorganic compounds directly or indirectly. Therefore, this work proposes the use of modified graphite with phthalocyanine for electrochemical detection and quantification of Th, U, Pu, Am, and Cm, in aqueous media by cyclic voltammetry. The electrodes were characterized by Raman and infrared spectroscopy, and the cyclic voltammetry data were modeled with Aoki's model. The detection limits (DL) and the quantification limits (QL) reached by the electrochemical detection of these actinides were of the order of ppt. Aoki's model fitted perfectly with the experimental data. The functionalization of graphite electrodes promotes the formation of phthalic anhydride, and the phthalocyanine is anchored on the epoxy groups of the graphite. The electrochemical detection process of these actinides is indirect. This electrochemical detector is cheap and disposable and can be an alternative for an initial characterization of actinides in liquid waste.

Graphene, Graphene-Derivatives and Composites: Fundamentals, Synthesis Approaches to Applications

Graphene has accomplished huge notoriety and interest from the universe of science considering its exceptional mechanical physical and thermal properties. Graphene is an allotrope of carbon having one atom thick size and planar sheets thickly stuffed in a lattice structure resembling a honeycomb structure. Numerous methods to prepare graphene have been created throughout a limited span of time. Due to its fascinating properties, it has found some extensive applications to a wide variety of fields. So, we believe there is a necessity to produce a document of the outstanding methods and some of the novel applications of graphene. This article centres around the strategies to orchestrate graphene and its applications in an attempt to sum up the advancements that has taken place in the research of graphene.

Structural and Morphological Characterization of Bio-templated Reduced Graphene Oxide and their Antibacterial Efficacy

We would like to report the eco-friendly synthesis of reduced graphene oxide using aqueous extract of Acorus calamus (rhizome), dried fruit and seed parts of Terminalia bellirica, Helicteres isora and Quercus infectoria and the whole shell part of Turbinella pyrum by simple steam bath technique. The structural and morphological characteristics of prepared reduced graphene oxides were determined by UV-Visible spectroscopy, Fourier Transform Infra-Red spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM) and Raman spectroscopy. The Surface Plasmon Resonance at 260-280 nm ensured the reduced graphene oxide formation. The antibacterial efficacy of synthesized reduced graphene oxide was evaluated against both gram-positive and gram-negative pathogens such as Staphylococcus aureus, Bacillus subtilis, Salmonella paratyphi and Escherichia coli. Among the selected samples Quercus infectoria mediated reduced graphene oxide showed excellent inhibition efficiency (27 and 28 mm) against Escherichia coli and Staphylococcus aureus, respectively as compared to the standard Gentamycin (29 mm). Quercus infectoria showed significant inhibition of 22 mm and moderate inhibition of 18 mm against Bacillus subtilis and Salmonella paratyphi, respectively. The results suggest selected plants and chank shell-mediated reduced graphene oxide as potential antibacterial agents for various therapeutic applications.

Two-Dimensional Disposable Graphene Sensor to Detect Na+ Ions

The monitoring of Na⁺ ions distributed in the body has been indirectly calculated by the detection of Na⁺ ions in urine. We fabricated a two–dimensional (2D) Na⁺ ion sensor using a graphene ion–sensitive field–effect transistor (G–ISFET) and used fluorinated graphene as a reference electrode (FG–RE). We integrated G–ISFET and FG on a printed circuit board (PCB) designed in the form of a secure digital (SD) card to fabricate a disposable Na⁺ ion sensor. The sensitivity of the PCB tip to Na⁺ ions was determined to be −55.4 mV/dec. The sensor exhibited good linearity despite the presence of interfering ions in the buffer solution. We expanded the evaluation of the PCB tip to real human patient urine samples. The PCB tip exhibited a sensitivity of −0.36 mV/mM and linearly detected Na⁺ ions in human patient urine without any dilution process. We expect that G–ISFET with FG–RE can be used to realize a disposable Na⁺ ion sensor by serving as an alternative to Ag/AgCl reference electrodes.

Graphene Oxide-Coated Gold Nanorods: Synthesis and Applications

The application of gold nanorods (AuNRs) and graphene oxide (GO) has been widely studied due to their unique properties. Although each material has its own challenges, their combination produces an exceptional material for many applications such as sensor, therapeutics, and many others. This review covers the progress made so far in the synthesis and application of GO-coated AuNRs (GO-AuNRs). Initially, it highlights different methods of synthesizing AuNRs and GO followed by two approaches (ex situ and in situ approaches) of coating AuNRs with GO. In addition, the properties of GO-AuNRs composite such as biocompatibility, photothermal profiling, and their various applications, which include photothermal therapy, theranostic, sensor, and other applications of GO-AuNRs are also discussed. The review concludes with challenges associated with GO-AuNRs and future perspectives.

Development of Green and Sustainable Cellulose Acetate/Graphene Oxide Nanocomposite Films as Efficient Adsorbents for Wastewater Treatment

: Novel ecofriendly adsorbents, cellulose acetate/graphene oxide (CA-GO) nanocomposite, were prepared from sugarcane bagasse agro-waste for removing Ni²⁺ ions from wastewater. Graphene oxide (GO) was prepared by the oxidation of sugarcane bagasse using ferrocene under air atmosphere. Cellulose acetate (CA) was also prepared from sugarcane bagasse by extraction of cellulose through a successive treatments with sulfuric acid (10% v/v), sodium hydroxide (5% w/v), ethylenediaminetetraacetic acid, and hydrogen peroxide, and finally , followed by acetylation. CA-GO was prepared via mixing of GO and CA in the presence of calcium carbonate and different concentrations of GO, including 5, 10, 15, 20, 25, and 30 wt% relative to the weight of CA. The CA-GO nanocomposite showed porous microstructures with high surface area, which enhance their ability towars the adsorption of Ni²⁺ ions from wastewater. The morphological properties of the prepared adsorbents were explored by scanning electron microscope (SEM) and Fourier-transform infrared spectroscopy (FT-IR). The efficiency of the CA-GO towards the adsorption of Ni²⁺ ions from wastewater was explored against as time, temperature, and total content of Ni²⁺ ions. The adsorption measurements of Ni²⁺ ions were investigated within the concentration range of 10-40 mg/L, time range between 15 and 90 minutes, and temperature range between 25 °C and 55 °C. The results displayed a considerable improvement in the adsorption process of Ni²⁺ ions by CA-GO-2 with a removal efficiency of 96.77%. The isotherms were monitored to best fit the Langmuir model. Finally, the adsorption performance of the prepared CA-GO nanocomposite films demonstrated promising properties as green, sustainable and cheap adsorbents for water pollutants.

Nanomaterials application in greenhouse structures, crop processing machinery, packaging materials and agro-biomass conversion

The discovery of nanomaterials has flagged off crucial research and innovations in science and engineering. Its unique properties and diverse applications present it as the material for the future. The aim of this study is to presents the relative applications of nanomaterial in some aspects of agriculture production. The study discussed nanotechnology applicability in climate control and photosynthesis in the greenhouse farming, hydroponic systems, solar drying, fabrication of crop processing machine components, oxygen scavengers in crop packaging, and micro-organism stimulant in anaerobic digestion for agro biomass conversion. Some highlights from the review revealed that Nanotechnology can be applied to increase water surface area to volume ratio and heat transfer in the air moving into a greenhouse farming. Water cluster can be changed when treated with nanoparticles through ultraviolet absorption spectrum and nuclear magnetic resonance (NMR) spectroscopy resulting in lower micelles to manipulate water delivery in green house farming. Nano-fluids or Nano-composites can be used to recombine the reactive parts of thermal storage materials after broken at elevated temperature to recover the stored heat for drying purpose during the off-sunshine periods in solar drying of crops. Nanomaterials can be a source of electroluminescence light in hydroponic system and act as coatings and surface hardener in crop processing machinery for post-harvest machines. The reviewed work showed that nanotechnologies has good prospect in adding value in agricultural production in the aspects discussed.

Synthesis of Graphene Oxide Using Atmospheric Plasma for Prospective Biological Applications

INTRODUCTION

This paper presents a novel technique for the synthesis of graphene oxide (GO) with various surface features using high-density atmospheric plasma deposition. Furthermore, to investigate the use of hydrophobic, super-hydrophobic, and hydrophilic graphene in biological applications, we synthesized hydrophobic, super-hydrophobic, and hydrophilic graphene oxides by additional heat treatment and argon plasma treatment, respectively. In contrast to conventional fabrication procedures, reduced graphene oxide (rGO) formed under low pressure and high-temperature environment using a new synthesis method-developed and described in this study-offers a convenient deposition method on any kind surface with controlled wettability.

METHODS

High density at atmospheric plasma is used for the synthesis of rGO and GO and its biocompatibility based on various wetting properties was evaluated using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and the viability of cells in response to rGO and GO with various surface features was investigated. Structural integrity was characterized by Raman spectroscopy, FESEM and FE-TEM. Wettability was measured via contact angle method and confirmed with XPS analysis.

RESULTS

We found that GO coating with a hydrophilic feature is more biocompatible than other surfaces as observed in case of fibroblast cells. We have shown that wettability-controlled by GO deposition-influences biocompatibilities and antibacterial effect of biomaterial surfaces.

DISCUSSION

Measuring the contact angle, it is found that contact angle for hydrophobic is increased to 150.590 and reduced to 11.580 by heat and argon plasma treatment, respectively, from 75.880 that was initially in the case of hydrophobic surface. XPS analysis confirmed various oxygen-containing functional groups transforming as deposited hydrophobic surface into superhydrophobic and hydrophilic surface. Thus, we have proposed a new, direct, cost-effective, and highly productive method for the synthesis of rGO and GO-with various surface properties-for biological applications. Similarly, for the dental implant application, the Streptococcus mutans was used as an antibacterial effect and found that S. mutans grows slowly on hydrophilic surface. Thus, antibacterial effect was prominent on GO with hydrophilic surface.