Different Concentrations Of Graphene Research Articles

Aluminium Hydroxide/Graphene-reinforced Rigid Polyurethane Foam Hybrid Composites

In this study, rigid polyurethane foams (RPUF) were successfully modified using 30 wt.% aluminium hydroxides (ATH), 1.0 pphp silicone surfactant, and different concentrations of graphene, using a one-shot one-step foaming method. This study aims to improve the compressive strength, flame retardancy, and thermal properties of RPUF by creating a synergistic effect between ATH and graphene in fire-retardant RPUF hybrid composites. The effects of a fixed amount of ATH and silicone surfactant and various loadings of graphene on RPUF were investigated. The results show that 0.5 wt.% graphene loading confers the best compression performance on the hybrid composite. Their compressive strength value of 12.58 KPa was higher than virgin RPUF (4.07 KPa) and RPUF/ATH (9.89 KPa). FTIR confirmed the functional groups in the virgin RPUF but could not identify new functional groups in most modified composites. The smallest amount of graphene addition (0.5 wt.%) produced a more stable hybrid composite structure. At 3.0 wt.% graphene addition, the maximum decomposition temperature of the RPUF/ATH hybrid composite was recorded (539oC), which was enhanced by 50% compared to virgin RPUF (296oC), and the highest char residue of 17.46% was observed. The incorporation of graphene enhanced the thermal firmness of the hybrid composite. The study also revealed an enhancement in the fire resistance of the hybrid composite. The LOI and UL-94 results showed that incorporating 3.0 wt.% enables increased LOI value and V-0 classification compared to virgin samples. This hybrid composite can be used in high-performance building insulation applications.

Graphene promotes the growth of Vigna angularis by regulating the nitrogen metabolism and photosynthesis.

Graphene has promising applications in agriculture and forestry. In the current study, six different concentrations of graphene (0mg/L, 0.01mg/L, 0.10mg/L, 1.00mg/L, 10.00mg/L, and 100.00mg/L) were used to investigate its effect on the growth and development of V. angularis plants in soil culture. The results showed that the group treated with 1.00mg/L graphene (G-1) had significantly increased plant height (19.86%), stem diameter (24.33%), and leaf area (13.69%), compared to the control group (CK). Moreover, all concentrations of graphene had positive effects on the total root length, total root surface area, and the number of root tips of V. angularis. Compared to the CK group, the G-1 group had significantly increased leaf water potential (37.89%), leaf conductivity (2.25%), and SOD, POD, and CAT activities (47.67%, 35.22%, and 199.3%, respectively). The G-1 group also showed improved leaf net photosynthetic rate, chlorophyll content, and soluble sugar content (51.28%, 24.25%, and 38.35%, respectively), compared to the CK group. Additionally, 1.00mg/L graphene led to a 23.88% increase in the podding rate and a 17.04% increase in the yield of V. angularis plants. The rhizosphere soil of V. angularis treated with 1.00mg/L graphene had a 25.14% increase in hydrolyzable nitrogen content and a 66.67% increase in available phosphorus content. RNA-seq data indicated that 1.00mg/L graphene induced the expression of photosynthesis and nitrogen transmembrane transport genes, including ATP synthase subunit b, photosystem I reaction center subunit XI, photosystem I reaction center subunit IV A, ferredoxin, and psbP-like protein 1, as well as genes for photosynthesis antenna proteins, glutamine synthetase, glutamate dehydrogenase 1, cyanate hydratase, protein fluG-like, and NRT1/PTR family, suggesting that graphene promoted the growth and development of V. angularis by enhancing the photosynthesis and nitrogen metabolism processes in V. angularis plants. Our results indicated that a suitable concentration of graphene could significantly promote the growth of V. angularis plants in soil.

Graphene-enhanced, wear-resistant, and thermal-conductive, anti-/de-icing gelcoat composite coating

Wind power is considered as a sustainable and environmentally friendly energy source. However, the occurrence of icing poses significant challenges to energy production, particularly in frigid regions during the winter season. Conventional strategies employed for preventing and removing ice formation have proven inadequate due to their inability to satisfy intricate requirements or their high energy consumption. In this study, a commercial gelcoat coating was adopted as an anti-/de-icing coating by introducing different concentrations of graphene and boron nitride into the gelcoat coating through physical mixing. Extensive investigations were conducted on the correlation between anti-/de-icing, wear resistance, and thermal conductivity. Notably, the incorporation of nanoparticles induced a rise in the surface roughness, resulting in prolonged resistance to water icing on the coated surface. The wear resistance and thermal conductivity of the composite coating were enhanced through the inclusion of boron nitride and graphene. The building of thermal conductive particle networks improved thermal conductivity which can lead to improved heat transfer and heat distribution. At the same time, the enhanced gelcoat composite coating exhibited exceptional passive anti-/de-icing performance and wear resistance. This coating can replace commercial coatings to improve anti-/de-icing efficiency for the existing active heating anti-/de-icing techniques available in the market.Graphical The graphene was employed to enhance the thermal conductivity, wear resistance, and anti-/de-icing properties of the turbine coating.

Regulatory effect of graphene on growth and carbon/nitrogen metabolism of maize (Zea mays L.).

Leakage of graphene into the environment has resulted from its increasing use. Although the impact of graphene on ecosystems is already in full swing, information regarding its impact on plants is lacking. In particular, the effects of graphene on plant growth and development vary, and basic information on the regulation of carbon and nitrogen metabolism is missing. In the current study, the way in which graphene (0, 25, 50, 100, and 200 g kg-1 ) affects maize seedlings was studied in terms of morphological and biochemical indicators. The purpose of this study was to understand better how graphene regulates plant carbon and nitrogen metabolism and to understand its interactions with leaf structure and plant growth. The results showed that 50 g kg-1 graphene increased plant height, stem diameter, leaf area, and dry weight; however, this was inhibited by the high level of graphene (200 g kg-1 ). Further studies indicated that different concentrations of graphene could increase leaf thickness and vascular bundle area as well as the net photosynthetic rate (Pn) of leaves; 25 and 50 g kg-1 graphene enhanced the leaves stomatal conductance (Cond), transpiration rate (Tr), intercellular carbon dioxide (Ci), and chlorophyll content. Higher concentrations decreased the above indicators. At 50 g kg-1 , graphene increased the activity of carbon/nitrogen metabolism enzymes by increasing carbon metabolites (fructose, sucrose, and soluble sugars) and soluble proteins (nitrogen metabolites). These enzymes included sucrose synthase (SS), sucrose phosphate synthase (SPS), nitrate reductase (NR), glutamine synthase (GS), and glutamate synthase (GOGAT). These results indicate that graphene can regulate the activities of key enzymes involved in carbon and nitrogen metabolism effectively and supplement nitrogen metabolism through substances produced by carbon metabolism by improving photosynthetic efficiency, thus maintaining the balance between carbon and nitrogen and promoting plant growth and development. The relationship between these indexes explained the mechanism by which graphene supported the growth of maize seedlings by enhancing photosynthetic carbon metabolism and maintaining metabolic balance. For maize seedling growth, graphene treatment with 50 g kg-1 soil is recommended. © 2023 Society of Chemical Industry.

Design and Characterization of Electroconductive Graphene-Coated Cotton Fabric for Wearable Electronics

Efficient energy storage is becoming a serious niche area nowadays due to exponential growth in energy consumption. Different approaches have been developed and implemented to improve the performance of the devices, in which improving conductivity is a major issue. In the present work, cotton fabric was converted into a conductive material by incorporating graphene, using the Layer-by-Layer (LBL) method, followed by heating at 100 °C. The electrical conductivity of the cotton using different concentrations of graphene was studied. The graphene-coated cotton, at the 17th layer, with a concentration of 168.36 wt.% resulted in a surface resistance of 0.644 Ω/sq and retained the maximum resistance even after two months. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy analysis (EDX) were employed to comprehend the surface morphology and elemental compositions. Fourier transform infrared (FTIR) spectroscopy, UV-vis absorption, and X-ray diffraction (XRD) were used to determine the structural analysis, which revealed a good dispersion of graphene in the cotton samples obtained through dimethyl sulfoxide (DMSO) doping, which reduced the ripple of the cotton. The cotton fabric treated with graphene was thermally stable, as shown through thermal analysis. From the results obtained, it is evident that graphene-treated cotton fabric materials show tremendous potential for use in smart textiles and also as protective clothing.

Enhancing photocatalytic activity: Investigating the synthesis and characterization of BiVO4/Cu2O/graphene ternary nanocomposites

In this study, BiVO4,Cu2O, and grapheneconcentrations have been carefully monitored during the hydrothermalsynthesis of the BiVO4/Cu2O/graphenenanocomposites. The impacts of different concentrations of graphene, time duration and heat treatment temperature have been investigated for synthesized samples. By various characterizations UV–Vis, photoluminescence (PL), FTIR, SEM, XRD and dye degradation, the optical characteristics, vibrational analysis, morphology, structural analysis and photocatalytic activity of the samples examined respectively. The nanocompositeBiVO4/Cu2O with different graphene ratios, the influence on the photocatalytic efficiency and stability of optimal sample has been investigated. BiVO4 and Cu2O concentrations had an impact on the stability of the monoclinic phase of BiVO4, according to X-ray diffraction (XRD) patterns. Nanosheets compositeswith 100 nm average size of nanosheets has observed in SEM micrographs. The e--h+ recombination rate for this sample was lowest according to the PL findings. Also, the optimized sample BiVO4/Cu2O/G5, after 120 min in the visible light spectrum, achieved the greatest degradation of 96% for rhodamine-B (RhB) and 98% for tetracycline (TC) by using optimized photocatalyst BiVO4/Cu2O/G5. Utilizing scavengers, the photocatalytic mechanism has been studied. Recyclability test has been performed to pattern the stability by XRD for optimal sample. To explore the photocatalytic performance, the kinetics of the degradation of RhB and TC have also been examined.

Effect of graphene on soybean root colonization by Bradyrhizobium strains.

Legume crops such as soybean obtain a large portion of their nitrogen nutrition through symbiotic nitrogen fixation by diazotrophic rhizobia bacteria in root nodules. However, nodule occupancy by low-capacity nitrogen-fixing rhizobia can lead to lower-than-optimal levels of nitrogen fixation. Seed/root coating with engineered materials such as graphene-carrying biomolecules that may promote specific attraction/attachment of desirable bacterial strains is a potential strategy that can help overcome this rhizobia competition problem. As a first step towards this goal, we assessed the impact of graphene on soybean and Bradyrhizobium using a set of growth, biochemical, and physiological assays. Three different concentrations of graphene were tested for toxicity in soybean (50, 250, and 1,000 mg/l) and Bradyrhizobia (25, 50, and 100 mg/l). Higher graphene concentrations (250 mg/l and 1,000 mg/l) promoted seed germination but slightly delayed plant development. Spectrometric and microscopy assays for hydrogen peroxide and superoxide anion suggested that specific concentrations of graphene led to higher levels of reactive oxygen species in the roots. In agreement, these roots also showed higher activities of antioxidant enzymes, catalase, and ascorbate peroxidase. Conversely, no toxic effects were detected on Bradyrhizobia treated with graphene, and neither did they have higher levels of reactive oxygen species. Graphene treatments at 250 mg/l and 1,000 mg/l significantly reduced the number of nodules, but rhizobia infection and the overall nitrogenase activity were not affected. Our results show that graphene can be used as a potential vehicle for seed/root treatment.

Graphene fortified polyvinyl alcohol based nanofibre membranes for preserving perishable food

In recent years, graphene as a biomaterial has received considerable attention due to its outstanding physio-mechanical properties. In the present work, we found superior tensile strength, hydrophobic and antibacterial activities in graphene incorporated polyvinyl alcohol (PVA) based nanofibers, prepared by electrospinning. A series of ultrafine graphene-based ink (G-Ink) incorporated PVA nanofiber (GPN) with different concentrations of graphene (0, 0.008, 0.02, 0.04, 0.06, and 0.08% w/v) was fabricated. To overcome difficulty in direct dispersing graphene into the PVA solution, we have prepared graphene-based ink for dispersing into polymer solution. The morphology, composition, mechanical behaviour, and surface wettability of these membranes was investigated. The Fourier transform infrared spectra and the Raman spectra confirmed the successful incorporation of graphene into the GPN. Graphene when used as a nanofiller in polymers, provides excellent mechanical properties (814%), hydrophobicity (40%), and antibacterial properties. In the current study we tested GPN membranes for preserving two fast rotting foods like coriander leaves and tomato. We found that GPN membrane can be used safely for food packaging applications to increase the shelf life of perishing food items, such as up to 3 days for coriander leaves and 8 days for tomatoes.

The Synergistic Effect of Electrical Stimulation and Dermal Fibroblast Cells-Laden 3D Conductive Hydrogel for Full-Thickness Wound Healing.

Clinically, most patients with poor wound healing suffer from generalized skin damage, usually accompanied by other complications, so developing therapeutic strategies for difficult wound healing has remained extremely challenging until now. Current studies have indicated that electrical stimulation (ES) to cutaneous lesions enhances skin regeneration by activating intracellular signaling cascades and secreting skin regeneration-related cytokine. In this study, we designed different concentrations of graphene in gelatin-methacrylate (GelMa) to form the conductive composite commonly used in wound healing because of its efficiency compared to other conductive thermo-elastic materials. The results demonstrated the successful addition of graphene to GelMa while retaining the original physicochemical properties of the GelMa bioink. In addition, the incorporation of graphene increased the interactions between these two biomaterials, leading to an increase in mechanical properties, improvement in the swelling ratio, and the regulation of degradation characteristics of the biocomposite scaffolds. Moreover, the scaffolds exhibited excellent electrical conductivity, increasing proliferation and wound healing-related growth factor secretion from human dermal fibroblasts. Overall, the HDF-laden 3D electroconductive GelMa/graphene-based hydrogels developed in this study are ideal biomaterials for skin regeneration applications in the future.

Graphene-Enhanced Ion Transport in Dual-Conducting Composite Films of Polyacetylene and an Imidazolium Iodide Ionic Liquid

Dual-conducting polymer films were synthesized by dispersing graphene in an aqueous solution of poly(vinyl alcohol) and 1-propyl-3-methylimidazolium iodide ([C3mim]I) ionic liquid and thermally converting the poly(vinyl alcohol) to polyene in the presence of hydroiodic acid catalyst. The electrical and mechanical properties of the resulting free-standing films of the nanocomposite, containing different concentrations of graphene, were analyzed using electrochemical impedance spectroscopy (EIS) and dynamic mechanical analysis (DMA), respectively. Nyquist plots (imaginary vs real components of the frequency-dependent impedance) showed two characteristic arcs representing the composite's electronic and ionic conduction pathways. The conductivity values corresponding to both charge transport mechanisms increased with temperature and the graphene concentration. The enhancement in electronic conductivity is expected because of graphene's high electron mobility. Interestingly, ionic conductivity also showed a significant increase with graphene concentration, approximately triple the extent of the rise in the electronic conductivity, even though the loss and storage moduli of the films increased. (Generally, a higher modulus results in lower ionic conductivities in ionic gels.) Molecular dynamics simulations of the three-component system provided some insights into this unusual behavior. Mean square displacement data showed that the diffusion of the iodide anions was relatively isotropic. The iodide diffusion coefficient was higher in a blend with 5 vol % graphene than in blends with 3 vol % graphene or no graphene. The improvement is attributed to the interfacial effects of the graphene on the free volume of the blend. Furthermore, an exclusion of the iodide ions from the vicinity of graphene was observed in the radial distribution function analysis. The increase in the effective concentration of iodide due to this exclusion and the increase in its diffusion coefficient because of the excess free volume are the primary reasons for the observed enhancement in ionic conductivity by adding graphene.

Antimicrobial Activity of a 3D-Printed Polymethylmethacrylate Dental Resin Enhanced with Graphene.

The present study aimed to test, in vitro, the antimicrobial activity against Candida albicans and Streptococcus mutans and the surface roughness of a 3D-printed polymethylmethacrylate dental resin enhanced with graphene. A 3D-printed polymethylmethacrylate dental resin was reinforced with four different concentrations of graphene: 0.01, 0.1, 0.25 and 0.5 wt%. Neat resin was used as a control. The specimens were printed in a liquid crystal display printer. Disc specimens were used in antimicrobial evaluation, and bar-shaped specimens were used to measure surface roughness. The study of antimicrobial activity included the inhibition of the growth of C. albicans and S. mutans and their adhesion to the resin’s surface. Surface roughness increased with the increase in the graphene concentration. The growth inhibition of C. albicans was observed in the different concentrations of graphene after 24 h, with no recovery after 48 h. The specimens doped with graphene were capable of inactivating S. mutans after 48 h. The surface-adhesion studies showed that the density of microbial biofilms decreases in the case of specimens doped with graphene. Graphene, despite increasing the resin’s surface roughness, was effective in inhibiting the growth and the adhesion to the resin’s surface of the main inducers of prosthetic stomatitis.

The Third-Order Nonlinear Optical Properties of Sb2S3/RGO Nanocomposites

Antimony sulfide/reduced graphene oxide (Sb2S3/RGO) nanocomposites were synthesized via a facile, one-step solvothermal method. XRD, SEM, FTIR, and Raman spectroscopy were used to characterize the uniform distribution of Sb2S3 nanoparticles on the surface of graphene through partial chemical bonds. The third-order nonlinear optical (NLO) properties of Sb2S3, RGO, and Sb2S3/RGO samples were investigated by using the Z-scan technique under Nd:YAG picosecond pulsed laser at 532 nm. The results showed that pure Sb2S3 particles exhibited two-photon absorption (TPA), while the Sb2S3/RGO composites switched to variable saturated absorption (SA) properties due to the addition of different concentrations of graphene. Moreover, the third-order nonlinear susceptibilities of the composites were also tunable with the concentration of the graphene. The third-order nonlinear susceptibility of the Sb2S3/RGO sample can achieve 8.63 × 10−12 esu. The mechanism for these properties can be attributed to the change of the band gap and the formation of chemical bonds supplying channels for photo-induced charge transfer between Sb2S3 nanoparticles and the graphene. These tunable NLO properties of Sb2S3/RGO composites can be applicable to photonic devices such as Q-switches, mode-locking devices, and optical switches.

High-sensitivity electrical properties measurement of graphene-based composites using interferometric near-field microwave technique

High-sensitivity electrical properties measurement of composite materials using an interferometric near-field microwave technique is proposed in this paper. A one-port calibration model is developed to relate the measured transmission coefficient to the local properties of the material. To represent the probe–composite sample interaction, an electrical model based on lumped elements is developed. As a demonstration, the complex permittivity and conductivity of composite materials prepared with polyvinyl chloride and different concentrations of graphene are experimentally determined at 2.45 GHz. The obtained results show that the proposed technique is sensitive for the detection of small contrasts of permittivity and conductivity in the composite material. When the graphene concentration increases from 1% to 30%, the conductivity increases from 0.0061 s m−1 to 0.056 s m−1.

Electrical conductivity of cement mortar with the addition of graphene

With the development of technological innovations in the field of construction, increasing the efficiency of energy-saving materials used, more and more attention is paid to electrically conductive materials. Electrical conductivity studies were carried out on samples of concrete with graphene addition to obtain the current–voltage characteristics of the material. In order to identify the mechanism of the effects of different concentrations of graphene on electrical conductivity, a series of samples with different concentrations of graphene was made. As a result of the research, it was found that the dependence: the resistivity of the materialthe concentration is percolation, the concentration of graphene in the amount of 8% of the mass of cement is the percolation threshold.

Optimization of graphene based minimum quantity lubrication of Inconel718 turning with multiple machining performances

Inconel 718 is a ‘hard to machine’ material due to its toughness and work hardenability. Researchers are working on possible methods to improve its machinability. In the initial part of the work, different concentrations of graphene based cutting fluids are used for machining Inconel718 and best concentration of graphene in cutting fluid is determined based on tool wear. In the second part of the work, turning parameters for machining Inconel 718 are optimized while machining using MQL application of best concentration of graphene based cutting fluid. Single response optimization is performed to identify input parameters which optimize resultant cutting forces, surface roughness, cutting temperature, tool wear and metal removal rate individually. Mutliresponse optimization is also performed giving equal importance to multiple machining performances in one case and by giving unequal importance in other case.

Efficient room temperature methanol sensors based on polyaniline/graphene micro/nanocomposites

The chemically prepared pristine and graphene-doped polyaniline (PANI) samples are utilized for the fabrication of room temperature methanol sensors. For the fabrication of PANI/graphene-based sensing devices, four samples of PANI/graphene composites were prepared with four different concentrations of graphene (2, 4, 6 and 8 wt%). The surface morphology of the prepared composites was analyzed under field emission scanning electron microscopy (FE-SEM), which revealed the agglomerated structures of PANI/graphene composites. X-Ray diffraction studies carried out on these samples revealed the semi-crystalline nature of the samples, whereas, Raman studies confirmed the growth of PANI with the presence of all fundamental bands of PANI in the pristine as well as in its doped state. The prepared PANI/graphene composites devices were tested for alcohol detection at two different concentrations (50 and 100 ppm) of methanol. The change in electric current with the change in environment has been recorded as a sensing parameter and is employed to determine other sensor parameters such as percentage response, response time and recovery time. The sensing response of the prepared samples is found to increase with graphene doping concentration as well as methanol ppm level. The PANI/graphene composite with 8 wt% doping of graphene has shown the highest response (~ 61.5% at 100 ppm) and the lowest response time (55 s). The mechanism of gas sensing has also been discussed in details with the possible theoretical analogy with the adsorption and desorption of gas molecules in accordance with Langmuir kinetic theory.

A New Industrial Technology for Mass Production of Graphene/PEBA Membranes for CO2/CH4 Selectivity with High Dispersion, Thermal and Mechanical Performance.

Polyether block amide (PEBA) nanocomposite membranes, including Graphene (GA)/PEBA membranes are considered to be a promising emerging technology for removing CO2 from natural gas and biogas. However, poor dispersion of GA in the produced membranes at industrial scale still forms the main barrier to commercialize. Within this frame, this research aims to develop a new industrial approach to produce GA/PEBA granules that could be used as a feedstock material for mass production of GA/PEBA membranes. The developed approach consists of three sequential phases. The first stage was concentrated on production of GA/PEBA granules using extrusion process (at 170–210 °C, depending on GA concentration) in the presence of Paraffin Liquid (PL) as an adhesive layer (between GA and PEBA) and assisted melting of PEBA. The second phase was devoted to production of GA/PEBA membranes using a solution casting method. The last phase was focused on evaluation of CO2/CH4 selectivity of the fabricated membranes at low and high temperatures (25 and 55 °C) at a constant feeding pressure (2 bar) using a test rig built especially for that purpose. The granules and membranes were prepared with different concentrations of GA in the range 0.05 to 0.5 wt.% and constant amount of PL (2 wt.%). Also, the morphology, physical, chemical, thermal, and mechanical behaviors of the synthesized membranes were analyzed with the help of SEM, TEM, XRD, FTIR, TGA-DTG, and universal testing machine. The results showed that incorporation of GA with PEBA using the developed approach resulted in significant improvements in dispersion, thermal, and mechanical properties (higher elasticity increased by ~10%). Also, ideal CO2/CH4 selectivity was improved by 29% at 25 °C and 32% at 55 °C.

Corrosion and Wear Behavior of PEO Coatings on D16T Aluminum Alloy with Different Concentrations of Graphene

The effect of added graphene concentration on the microstructure, phase composition, corrosion- and wear- resistance of plasma electrolyte oxidation (PEO) coatings formed on D16T aluminum alloy in silicate electrolyte with different concentrations of graphene were investigated. The results show that the morphologies of the coatings with graphene were obviously different ascribed to the mode of graphene incorporated into the coating. The coatings consisted of mainly α-Al2O3, γ-Al2O3, and Al, which were divided into an outer porous layer and a dense inner layer. The thickness of the coatings increased non-linearly with graphene concentration. The corrosion resistance of the coatings with graphene was significantly improved. The wear resistance of the coatings was also greatly improved apart from the coating with 3 g/L graphene. The coating produced in the electrolyte with 2 g/L graphene exhibited the optimal comprehensive properties because graphene successfully incorporated into the coating via the pores and spread on the surface of the coating.

Effect of graphene on the growth and development of Raspberry tissue culture seedlings

Raspberry subcultured tissue seedlings were used as test materials for the effect of different concentrations of graphene on the growth of raspberry seedlings and the development of adventitious roots. The graphene was characterized by a laser particle size analyzer, STEM, TEM, XPS and Raman spectroscopy. A root analysis system and SEM were used to systematically characterize the seedling height, root length, root specific surface area, number of branches, number of root tips and root micromorphology, thus determining the optimum concentration of graphene for the growth of raspberry tissue culture seedlings. The results showed that with increasing graphene concentration, the seedling height, root length, root tip number and root specific surface area of the seedlings all showed a trend of first increasing and then decreasing. The optimum concentration of graphene was 2 mg·L-1, the seedling height of tissue culture seedlings was 1.46 times that of the control group, and the root length, specific surface area, number of root tips and their bifurcation number were about twice that of the control group.

Experimental Investigation on the Influence of Graphene Nanoplatelets Dispersion on the Thermal Conductivity of Sunflower Oil

In the past decades, considerable efforts have been made for the development of energy-efficient and eco-friendly convective heat transfer and lubricating agents because of growing energy demands, precision manufacturing, miniaturization and sustainability issues. In this study, different concentrations of graphene–sunflower oil nanofluid were prepared and their thermal conductivity was experimentally investigated and compared with the correlations of similar researches found in the literature. The morphology of graphene nanoplatelets was appraised by X-ray diffractometer (XRD) and scanning electron microscope (SEM). The results show that the thermal conductivity of nanofluid was enhanced with temperature and nanoparticles weight fraction. The nanoconvection at high temperatures, less meandering mobility of graphene nanoplatelets and high kinematic viscosity of graphene nanofluids at low temperatures were identified as the key factors for the thermal conductivity enhancement. Further, the concentration and temperature-dependent theoretical correlation were proposed for estimating the thermal conductivity of graphene nanofluids using backpropagation algorithm of artificial neural network (ANN) with the minimum margin of deviation.