Upcycled graphene nanoplatelets integrated fiber-based Janus membranes for enhanced solar-driven interfacial steam generation †

The increasing demand for drinking water and environmental concerns related to fossil fuels have given rise to the use of solar energy in water desalination. Solar-driven interfacial steam generation is a promising method for water purification, particularly in remote areas. Janus membranes, featuring bilayer hydrophobic/hydrophilic structures, offer high functionality and have attracted significant interest in this field. This study explores the integration of novel graphene nanoplatelets (GNP) derived from waste tire pyrolysis through upcycling as a photothermal source in Janus membranes. The membranes consist of polyacrylonitrile (PAN) nanofibrous membranes for water supply and polymethyl methacrylate (PMMA)/graphene nanoplatelets (GNP) nanofibrous membranes for light harvesting. The effects of GNP content and layer thicknesses on photothermal activity, water transport, and overall evaporation rate were analyzed experimentally and numerically. The results showed that a decrease in membrane thickness led to a 19% to 63% enhancement in evaporation rate, highlighting the importance of optimizing membrane design for efficient water desalination

Remnant polarization and structural arrangement in P(VDF-TrFE) electrospun fiber meshes affect osteogenic differentiation of human mesenchymal stromal cells

Highlights The type of solvent had noticeable effects on morphology and piezoelectric properties of P(VDF-TrFE) electrospun fibers. Using MEK as a solvent and specific environmental conditions led to the obtainment of surface nanopores. Uniaxially aligned fibers exhibited higher β phase and mechanical properties than random ones. Randomly oriented fibers had higher remnant piezoelectric properties (Vout, d31 piezoelectric coefficient) than aligned ones. Human mesenchymal stem cells cultured on randomly oriented fibers showed an accelerated osteogenic differentiation. Abstract Many tissues and cells are influenced by mechano-electric stimulation, thus the application of piezoelectric materials has recently received considerable attention in tissue engineering. This report investigated electrospun fiber meshes based on poly(vinylidenefluoride-co-trifluoroethylene) [P(VDF-TrFE)] as instructive biomaterials for osteogenic differentiation of human mesenchymal stromal cells (hMSCs). The influence played by methyl ethyl ketone (MEK), used as a solvent in place of dimethylformamide (DMF)/acetone mixture, and the effect of rotating velocity of the electrospinning collector on fiber morphology, mechanical and piezoelectric properties were studied. The solvent had noticeable effects on morphology and piezoelectric properties of electrospun fibers, with MEK outperforming DMF/acetone. By increasing the collector velocity up to 4000 rpm, the fiber diameter reduced and the mutual alignment of the fibers increased, corresponding to enhanced mechanical properties and piezo-active β-phase content. However, as a consequence of the diverse mechanical properties of random and aligned fibrous architectures, which ultimately affected the piezoelectric properties, randomly-oriented fibers exhibited higher remnant piezoelectric properties (Vout and d31 piezoelectric coefficient) than aligned ones. On these scaffolds, hMSCs showed an excellent capability of early osteogenic differentiation, leading to high calcium production. Fiber surface topology, fiber mesh morphology and remnant piezoelectric properties played a determinant role on hMSC osteogenic commitment

Classification of waste plastics for dimension-controlled graphene growth on natural mineral substrates in terms of polymer processing and thermal techniques

Plastic materials have become inevitable daily-life products in modern life due to their low cost, high strength, and suitability for many applications. However, wide utilization of them in many areas causes significant high-volume plastic wastes that threaten the ecosystem, soil, water, and human health. Indeed, recycling is used to decrease the plastic waste amount; however, recycled plastics do not have the same performance as virgin plastic composites. Converting the plastic wastes into high-value-added carbon materials by upcycling provides several benefits because it is an effective method in terms of cost and sustainability. A wide range of waste plastics such as polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyamide, textile products, organic wastes, and metal wastes are used for upcycling. Moreover, there are few attempts at the growth of carbon-based structures on mineral substrates. Related to recent studies, this chapter focuses on the classification of polyolefin and aromatic polymer-based plastic wastes for the growth of upcycled graphene on natural mineral substrates. In this regard, the impact of both polymer processing techniques and heat-treatment on the chemical, structural, and morphological features of the resultant hybrid additives were comprehended in detail. In addition, an understanding of the influence of polymer backbone on the upcycled graphene growth was provided. Beyond, controlling the dimension of the upcycled graphene growth on natural mineral substrates related to the used mineral size was comprehensively discussed. Consequently, in this chapter, the effect of polymer processing techniques, heat treatment, and mineral size are investigated to choose a selective method for the conversion of plastic wastes into 2D and 3D graphene structures by a circular economy targeted upcycling process in terms of the plastic waste types and their chain length and aromaticity degree

Turning CO2 into sustainable graphene: a comprehensive review of recent synthesis techniques and developments

The synthesis of graphene through environmentally friendly and efficient methods has posed a persistent challenge, prompting extensive research in recent years to access sustainable sources and attain high quality graphene competing with the one obtained from graphite ores. Addressing this challenge becomes even more intricate when aiming to convert captured CO2 into graphene structures, encountering hurdles stemming from the inherent stability of the CO2 molecule and its steadfast transformation. Together with CO2, there is a great potential to create carbon source by using natural biomass, cellulosic plant sources and industrial wastes. This comprehensive review delves into the recent synthesis techniques and developments, exploring both direct and indirect pathways for the integration of CO2 that strive to overcome the complexities associated with transforming CO2 into graphene. The review critically analyzes CO2 capturing mechanisms designed for air, ocean, and alternative sources, outlining the progress made in harnessing captured CO2 as a feedstock for graphene production by evaluating captured CO2 values. This review consolidates the recent advancements by providing a roadmap for future research directions in the sustainable synthesis of graphene from captured CO2 in the pursuit of a greener, circular economy

Upcycled graphene integrated fiber-based photothermal hybrid nanocomposites for solar-driven interfacial water evaporation

Solar-driven interfacial evaporation is an efficient and viable solution for providing freshwater, especially in remote areas that utilize sunlight for water purification and desalination systems. This study proposes a practical preparation method for a photothermal nanocomposite, compromising Polyacrylonitrile (PAN) nanofibrous membrane, crosslinked PVA, and upcycled Graphene Nanoplatelets (GNP). The synergistic effect between the PAN nanofibers and PVA/GNP nanocomposite and the contributing factors to the overall performance is examined. It was found that the initial thickness of the PAN nanofibrous layer has an inverse effect on the evaporation rate. The obtained results indicated that while the GNP content enhances the photothermal activity, it deteriorates the water absorbency of the nanocomposite; thus, an optimized concentration should be obtained. By investigating different parameters for the evaporator, we obtained an evaporation rate of 1.40 kg/m2h under 1 sun of illumination

Electrospun ZnO/poly(vinylidene fluoride-trifluoroethylene) scaffolds for lung tissue engineering

Due to the morbidity and lethality of pulmonary diseases, new biomaterials and scaffolds are needed to support the regeneration of lung tissues, while ideally providing protective effects against inflammation and microbial aggression. In this study, we investigated the potential of nanocomposites of poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)] incorporating zinc oxide (ZnO), in the form of electrospun fiber meshes for lung tissue engineering. We focused on their anti-inflammatory, antimicrobial and mechano-electrical character according to different fiber mesh textures (i.e., collected at 500 rpm and 4000 rpm) and compositions: (0/100) and (20/80) w/w% ZnO/P(VDF-TrFE), plain and composite, respectively. The scaffolds were characterized in terms of morphological, physico-chemical, mechanical and piezoelectric properties, as well as biological response of A549 alveolar epithelial cells in presence of lung infecting bacteria. By virtue of ZnO, the composite scaffolds showed a strong anti-inflammatory response in A549 cells, as demonstrated by a significant decrease of interleukin (IL) IL-1α, IL-6 and IL-8 expression in 6 h. In all the scaffold types, but remarkedly in the aligned composite ones, transforming growth factor β (TGF-β) and the antimicrobial peptide human β defensin 2 (HBD-2) were significantly increased. The ZnO/P(VDF-TrFE) electrospun fiber meshes hindered the biofilm formation by S. aureus and P. aeruginosa and the cell/scaffold constructs were able to impede S. aureus adhesion and S. aureus and P. aeruginosa invasiveness, independently of the scaffold type. The data obtained suggested that the composite scaffolds showed potential for tunable mechanical properties, in the range of alveolar walls and fibers. Finally, we also showed good piezoelectricity, which is a feature found in elastic and collagen fibers, the main extracellular matrix molecules in lungs. The combination of all these properties make ZnO/P(VDF-TrFE) fiber meshes promising for lung repair and regeneration

Adsorption of emerging contaminants by graphene related materials and their alginate composite hydrogels

Graphene nanosheets and nanoplatelets -alginate composite hydrogels were prepared by ionic gelation and the resulting gel beads were exploited for the removal of a mixture of eight selected emerging contaminants (ECs) in tap water, including bisphenol A, ofloxacin and diclofenac. The role of graphene related materials (GRM) on the gel bead structure, adsorption selectivity, kinetic, mechanism, and efficiency was investigated. Combined Scanning Electron Microscopy (SEM) and confocal Raman microscopy mapping showed a porous structure with pore size in the range of 100–200 \ub5m and a homogeneous distribution of graphene nanosheets or nanoplatelets at the pores surface. The adsorption kinetic of GRM was much faster than that of granular activated carbon (GAC), the industrial sorbent benchmark, with removal capacity of ofloxacin from 2.9 to 4.3 times higher. A maximum adsorption capacity of 178 mg/g for rhodamine B was estimated by adsorption isotherm studies for reduced graphene oxide-based beads (a value comparable to that of powered activated carbon). Regeneration test performed on saturated beads by washing with EtOH, and subsequent reiterated reuses, showed no loss of adsorption performance up to the fourth reuse cycle