This review highlights the ocular applications of GFNsand systematically covers the most recent advances of GFNs’physicochemical properties, in vitro and in vivo ocular toxicity, and the possible toxicity mechanismsas well as provides some perspectives on the potential risks of GFNsin material development and biomedical applications.Graphene family nanomaterials(GFNs) are rapidly emerging for ocularapplications due to their outstanding physicochemical properties.Since the eyes are very sensitive organs and the contact between theeyes and GFNs in eye drops, contact lenses, intraocular drug deliverysystems and biosensors and even the workers handling these nanomaterialsis inevitable, it is necessary to investigate their ocular toxicitiesand physiological interactions with cells as well as their toxicitymechanisms. The toxicity of GFNs can be extremely affected by theirphysicochemical properties, including composition, size, surface chemistry,and oxidation level as well as dose and the time of exposure. Up tonow, there are several studies on the  The personnel who areworking with nanomaterials are at a high risk of exposure while theyare preparing or handling nanomaterials. Therefore, due to continuouslyexpanding demands of nanomaterials and increasing exposure to them,it is essential to evaluate the potential risks and hazards of nanomaterialsfrom the human health and safety perspective.In the field of pharmaceutical and biotechnology sciences, nanotechnologyis in high demand these days, leading to the desired products or therapeuticoutcomes. Development of nanomaterials has increasingly assigned alarge number of studies in academic and industrial groups to generateengineered advanced materials and biomedical systems.3 Designand development of novel therapy techniques using nanomaterials mightlead to novel therapeutic methods in ophthalmology. Among varioushuman organs, investigation of nanomaterials’toxicity on the eyes is crucially important due to high levels ofeye exposure with nanomaterials during manufacturing, use, and disposal.Moreover, recently, there are several outstanding reports on the applicationsof nanomaterials in ocular applications such as ocular drug delivery,eye drops, and contact lenses.6Among different nanomaterials, the carbonaceous materials, suchas graphene, carbon nanotube (CNT), and fullerene 2 are at 6 Graphene has received tremendous interest from academiato industries owing to its outstanding physicochemical and structuralproperties.11 The 2D sheet of carbon atoms in a honeycombed network provides graphenewith a large surface to volume ratio and high mechanical, thermal,and electrical properties.14 Generally, graphene, a singlesheet of graphite that is held together by a backbone of overlappingsp2 hybrid bonds, is a part of graphene family nanomaterials(GFNs). Graphene, few-layer graphene , graphite,reduced graphene oxide (rGO), graphene oxide (GO), graphene nanoplatelets(GNP), and graphene quantum dots (GQDs) are the most important GFNanalogs  generationin the A549 cell line.28 Also, the hemolyticpotential evaluation of different sizes of GO and rGO sheets showedthat the smaller one had a higher activity, while the minor hemolyticpotential was seen for the aggregated rGO.29 Morover, the size of GFNs is an important determining factor forsubcellular penetration. For instance, rGO nanoplatelets with averagelateral dimension of 11 nm can enter the nucleus of human mesenchymalstem cells (hMSCs) and induce more genotoxicity compared to 3 μmnanoplatelets. The micron-sized rGO nanoplatelets showed a high toxicityat high concentration (100 μg mL–1) after1 h exposure time, while the 11 nm rGO nanoplatelets translocatedto the nucleus and induced genotoxicity at a very low concentration(0.1–1 μg mL–1).30From a toxicological perspective,one of the prime physicochemical properties that influences GFNs’stoxicity is particle size. Decrease in size to a nano level leadsto more cellular uptake due to increasing the surface area and providingfurther sites for cellular interaction. Several papers reported thatthe mechanism and the efficiency of cellular uptake, the circulation,distribution, clearance, and toxicity of GFNs depend on the nanoparticles’size.2.232 The cell membranes’ performance and structure can be disruptedby GFNs due to their different surface chemistries. In addition, theyare able to stimulate receptors and activate mitochondrial pathwaysand induce apoptosis.35GFNs possess varioussurface chemistries that lead to different biological activities.The extent of oxidation (O/C ratio) imparts hydrophobic, partiallyhydrophobic, and intermediate hydrophilic surface chemistry for pG,GO, and rGO, which alter their dispersibility in different solventsand physiologic medium. The hydrophobicity of GFNs causes aggregationbecause of the π–π stacking between the layers.32Compared with rGO, GO is enriched by carboxylicacid and hydroxyl and epoxy functionalities at its edges and basalplane. Therefore, owing to the difference in their structures, GOhas more dispersion ability, binding sites, and higher activity, whichleads to differences in their toxicities. In a study, the ocular toxicityof GO and rGO was evaluated by exposure of GO and rGO to the conjunctivalsacs of mice. GO exposure led to observing intraocular inflammation,an incrassated corneal stromal layer, higher corneal stromal cellcounts, and TUNEL-positive cells in the cornea as well as iris neovascularization.Unlike GO, by rGO exposure, no specific ocular toxicity was observed,which can be due to their structure and physical characteristic differences.–1 for 2 h. The results showed a dose- and oxygen-dependentcytotoxicity response with greater cytotoxicity for pG. The toxicitylevels were correlated with an increase in functionalized oxygen content.The ROS measurements showed that the oxidized graphenes, low oxidizedgraphene (LOG), higher oxidized graphene (HOG), and GO generate higherROS levels comparing with pG. HOG produced higher superoxide molecules,but free radicals might be reduced due to cellular antioxidant mechanismsof graphene within the cells and its redox ability, preventing theobservation of high cytotoxicity.36Additionally, to compare the effect ofoxygen level of graphene-basedmaterial on its biocompatibility and cytotoxic potential, pG, GO,and low and high oxygen functionalized graphene containing 6.6% and24% oxygen contents were investigated. ROS generation evaluation wasexplored using PC12 cells at very low doses of 0.5, 1.0, and 5 μgmL37 Hence, negatively charged GO showed negligible internalization tononphagocytes;38 however, other reportshave proposed that the negatively charged nanoparticles internalizationinto nonphagocytic cells can occur when they bind to the cell surfacecationic sites and then they can be taken up by scavenger receptors.40 Due to the surface charge of nanomaterials, they can absorb severalproteins and form “coronas” with proteins in biologicalsystems. Certainly, the affinity and the mode of interaction of theproteins play a determining factor in the formation of protein corona.41 Negative charged GFNs cause more electrostaticinteraction with the proteins that can alter their circulation, distribution,clearance, and toxicity. Bovine serum albumin-coated GO relieved thecytotoxicity through decreasing its penetration to the cell membrane.Protein corona can decrease GO cellular uptake according to the reportedcell viability and cellular uptake results, leading to GO potentialcytotoxicity reduction.42Another feature that indicates the effect of surface chemistryon cellular uptake is surface charge, the key factor to induce toxicity.The overall charge of cell membrane is negative, which leads to easilybinding and ingestion of positive charge nanomaterials to the cellmembrane using electrostatic interaction.2 (the sample with higher oxidation level) exhibiteda higher cytotoxicity compared with the samples with lower oxidationlevels.43The oculartoxicity investigation of PEGylated GO (polyethyleneglycol (PEG)-GO) with various oxidation levels and/or surface chargeswas performed. The results revealed that while the surface chargecould change the aggregation status of GFNs, it did not affect thecytotoxicity of PEG-GO samples alone, and the oxidation level hada critical effect on the GO toxicity. Among different PEG-GO samples,GO-h-PEG-NH2.345 However, GO still aggregates in physiological buffers because ofthe charge screening effect of salts.46 Consequently, surface modification of graphene and GO is necessary,especially for biomedical applications.47 To improve the deficiencies in the structure of graphene and GO,scientists usually introduce active functional groups to improve theirdispersion in aqueous and biological media.50To controlthe behaviors of GFNs in biological systems and improve their biocompatibility,their surface chemistry plays an important role. Graphene is an extremelyhydrophobic compound since it does not have any oxygen-containinghydrophilic functionalities and has the π–π stackinginteractions that has crucial implications for its dispersion in water.GO is the most widespread of GFNs because it has been employed forthe synthesis of graphene-based nanomaterials on a large scale. GOshows good water dispersion stability and biocompatibility owing tothe presence of oxygen-containing functionalities on its edges andsurface, which make it a potential nanomaterial for various applications.51 Covalent and noncovalent modifications are the most extensivemethods for graphene and GO functionalization, aiming to improve theirbiocompatibility, physiological and colloidal stability, decreasetheir nonspecific binding to biological molecules and cells, and increasetheir in vivo pharmacokinetics ,3 cyclodextrin,18 poly(ε-caprolactone),44 poly,45 pluronic,59 amine,60 carboxyl,and dextran61 groups significantly decreasedtheir toxicity and improved their biocompatibility.Depending on different application purposes,various surface functionalization strategies have been used to improveGFNs biocompatibility to be used in biomedicine.kinetics 1.52−57 U3, and GO-PEG-NH2) were fabricated, and their toxicitieson ocular tissue were investigated. Among different PEGylated GO,the GO-PEG-NH2 showed the most toxicity to ocular cells.The obtained results of this study can be used for biomedical applicationsof GFNs in the future by decreasing their toxicity with the aim ofsuitable surface modifications.43 In anotherstudy, hydroxylated graphene (G-OH) was prepared, and its ocular biocompatibilitywas investigated and compare with GO. G-OH displayed some featuresof GO such as water solubility and processability, whereas it showedhigher electroactivity and biocompatibility with human retinal pigmentepithelium (RPE) cells than GO.62Toinvestigate the role of GFN functionalities in ocular toxicity,in a study, three kinds of PEGylated GO  and graphene foam (G-foam), forthe synthetic keratoprosthesis skirt and assessed their biocompatibilitiesby in vitro cell culture using human corneal stromalcells and an in vivo rabbit implantation model. For in vitro assessment, human corneal stromal fibroblasts werecultured on the surface of G-film, G-foam and pristine titanium (Ti)discs as a standard, and a tissue culture plastic surface (TCPS).Good biocompatibility with human stromal fibroblasts was observedfor G-film in terms of cell adhesion, viability, and proliferation.The number of cells was higher on G-films compared with TCPS control,and 10% more cell proliferation was seen on graphene in comparisonwith on Ti. Moreover, compared with Ti and G-film, the culture mediumcollected from fibroblasts seeded on G-foam demonstrated lower cytokines(IL-6 and IL-8), which can be due to a lower expression of cytokinesby cells, or adsorption of the inflammatory signal molecules withgraphene materials. No sign of infection, neovascularization, or inflammationwas seen by the implantation of G-film into rabbit stroma, confirmingshort-term biocompatibility of graphene with corneal cells and tissue,which can be developed for cornea tissue engineering.Until now, the toxicity of GFNs on some anteriorsegment of the eyes, including conjunctiva, cornea, iris, and lens,has been investigated. In patients with end-stage corneal blindness,synthetic keratoprostheses are required for visual rehabilitation.To this aim, Tan et al.87 The acute eye irritation tests were performed in this studyin albino rabbits based on the OECD guidelines. They investigatedthe influence of GO exposure to the ocular surface in vitro and in vivo, considering different concentrations(12.5–100 μg mL–1) and times of exposure(–1 of GO (–1) in Sprague–Dawley rats that was alleviatedby glutathione (GSH) (Organisationfor Economic Co-operation and Development (OECD) guidelines for theTesting of Chemicals (Test No. 405) can be used as a standard forinvestigation of acute eye irritation/corrosion. According to theseguidelines, eye irritation is defined as “... the productionof changes in the eye following application of a test substance tothe anterior surface of the eye, which are fully reversible within21 days of application”. Moreover, the eye corrosion is alsodefined as “... the production of tissue damage in the eye,or serious physical decay of vision, following application of a testsubstance to the anterior surface of the eye, which is not fully reversiblewithin 21 days of application”. Aiming to this guideline, thetime- and dose-dependent cytotoxicity of GO through oxidative stresswas reported by Wu et al. using human corneal epithelium cells (hCorECs)and human conjunctiva epithelium cells (hConECs).exposure12. Althoexposure6A. The o–1 of GO 6B. Howevne (GSH) 6C. There120In vivo and in vitro morphological and molecular biologicalanalysis revealed no significant ocular toxicity for rGO, while differentsigns of toxicity, such as intraocular inflammation, an incrassatedcorneal stromal layer, cell apoptosis in the cornea, iris neovascularization,and significant cytotoxicity of rat corneal epithelial cells wereseen by short-term GO exposure. After short-term GO contact with eyes,many lymphoid cells were produced, as shown by the HE staining results.Interleukin expression was induced by lymphoid cell proliferation.In addition, compared with the control group, in the GO treatmentgroup, the level of IL-6 and IL-8 expressions were considerably higher.In addition, the TNF-α expression level, which is one of theimportant inflammatory factors, was also evaluated in vivo using GO and rGO. In the GO model mice, the TNF-α contentwas considerably enhanced in the eye, while it did not change in therGO model mice. Therefore, the inflammatory response had been triggeredby increasing the IL-6, IL-8, and TNF-α in the GO model mice.Moreover, the oxygenation levels of eyes in the three groups of micewere indicated by the malondialdehyde (MDA) content. In addition,the in vitro results demonstrated that the main patternsof GO cytotoxicity during cell injury were necrocytosis, cell death,cell cycle disorder, and cell viability loss.In another study on GFNs, theright conjunctival sacs of the Kunmingmice  were exposed once per day for a total of 7 days to therGO and GO suspensions.2 sample, which had a higher oxidation level, exhibited highertoxicity. To understand the potential toxicity mechanisms and complicatedinteractions between GFNs and biological systems on a whole cell level,a study of gene expression profiles can be used as an important approach.Therefore, in this study, the gene expression profile was studiedand the results demonstrated that the accumulation of ROS inducedby GO-h-PEG-NH2 treatment was attributed to NDUFB9-mediatedbiological pathway.43The toxicity investigationof PEG-GO with various oxidation levelsand/or surface charges including positive, negative, and neutral chargeon hCorECs and intraocular cells (hRCECs) was performed. The resultsrevealed that the viability of both cell types decreased by increasingPEG-GO concentration. Among different PEG-GO samples, the GO-h-PEG-NH3.388 RPE cells exhibited >60% cell viability in GO solutionsand <8% LDH release. Although LDH release into the culture mediumupon cells showed a very low impact on cell morphology, after a long-timeculturing, the change was noticeable as well as aggregation of GO.Moreover, the results showed a negligible cell apoptosis (∼1.5%)with the addition of 100 μg mL–1 GO (similarto the control cells), indicating GO biocompatibility. The biocompatibilityof GO was also investigated in vivo by intravitreallyinjection of 0.1, 0.2, and 0.3 mg of GO into white rabbits’eyes. One eye was injected with GO, and the salt solution  was injected to the other eye of the same rabbit asthe control. As seen in The toxicity of GFNs on some posterior segment of theeye was also investigated, such as retina, macula, and optic nerve.The effect of GO on RPE cells in terms of the cell morphology, viability,membrane integrity, and apoptosis was examined by Yan et al., usingseveral techniques, such as optical micrography, cell counting kit-8,lactate dehydrogenase (LDH), and apoptosis assays.in vitro and the in vivo results obtainedin this study, it can be concluded that there is no severe GO toxicityon the eyes.88 However, still more studies,such as controlling GO aggregation by surface functionalization andGO genotoxicity as well as the impact of physicochemical propertieson the GO toxicity, should be considered before making a certain conclusionabout the safety of GO.In addition, the histopathology studies of the rabbits’eyes revealed that while a very low content of GO remained in theGO-injected eye, by comparing with the control eye, no retinal abnormalitywas seen. These observations suggested that by GO injection, no apparentdamage occurred to the retinal morphology. Considering both the 89 Hydroxylated graphene (G-OH) showed genotoxicity at 4100mg mL–1 concentration. Although the genotoxicityof G-OH in rabbits was decreased gradually through intravitreal injectionafter 4 weeks, it did not show damage to cell morphology, structure,and most parts of the eyes. It led to IOP, ERG, and retinal structurechanges as eyesight-related functions. The cytotoxicity mechanismresults also revealed that through endocytosis and exocytosis, G-OHcould penetrate into and out of the cytoplasm without any cell membranedamage.90In another research work, GO showedmitochondria damage and induceddevelopmental malformation of the zebrafish eyes.121 developedrGO membrane (rGOM) for ocular regenerative medicine application.For ocular tissue engineering, the used membrane should have cellularbiocompatibility and promote wound healing as well as show antimicrobialproperties. Because of these needed criteria, the in vitro and in vivo biocompatibility and genotoxicity ofrGOM were investigated using various human ocular cells. The resultsdemonstrated that no sign of cytotoxicity or genotoxicity was seenafter short-term exposure of rGOM compared with control group culturesand allowed the growth of different ocular cells. Although the obtainedresults of this study were very promising, a long-term follow-up periodand additional in vivo research are needed to findout whether rGOM can be a good candidate for treatment of ocular diseasesor not.GFNs can be used in ophthalmologyto treat different ocular disorders.Recently, Zambrano-Andazol et al.44.1123 Ocular drug delivery using GFN-containing systems has attracteda continual interest of researchers in the past few decade. Nanocompositeoleogels of groundnut oil and stearic acid containing different percentagesof GO were developed to improve corneal permeation of ciprofloxacinHCl (CPH), an antibacterial drug, by Hasda et al.124 The in vitro release study showed thatby increasing the GO content up to 0.05% in the nanocomposite oleogels,a higher cumulative percentage of drug permeation through caprinecornea was seen. Moreover, by incorporation of GO in the oleogels,a higher ex vivo corneal permeation of CPH by Fickiandiffusion model was obtained.Recently,graphene and GO exhibited compatible physicochemical properties, whichmakes them suitable for biomedical applications, such as drug andgene delivery, biosensing and imaging, and tissue engineering.125 Silicon contact lensescontaining HA and rGO were prepared through direct loading of HA andrGO in the contact lens (HA-GO-DL) and also by the conventional soakingmethod (HA-GO-SM). The contact lenses containing lower amounts rGOexhibited acceptable swelling and transmittance properties. In addition,the HA-GO-DL contact lenses demonstrated a water retention propertyaccording to the water evaporation study results. Moreover, the fluxdata revealed that the HA-GO-DL lenses showed low burst with sustainedrelease up to 96 h, whereas a high burst release was seen for HA-GO-SMlenses after 24 h. Furthermore, the results of ocular irritation studyconfirmed the safety of the HA-GO-DL lenses. In comparison to HA-GO-SMand eye drop solution, a high HA-tear fluid concentration was seenby using the HA-GO-DL batch as well as improvement in the fluid volumeof rabbit tears.To treat and manage various cornealdiseases such as keratoconus and dry eye syndrome, eye drop solutionis widely used. However, due to a frequent dosing schedule, it canaffect the routine lifestyle of patients. In one study, hyaluronicacid (HA) and rGO loaded silicon contact lens were developed for cornealepithelial healing, which has the potential for improving the tearfluid volume for controlling numerous ocular diseases, such as dryeye syndrome.126 Owing to the very limited therapeutic efficacy of customarytreatments, such as eye drops and probable intraocular injection sideeffects, hydrogel contact lenses have been considered as suitableocular drug delivery systems due to their comfortable structure anddrug loading capacity. Considering this, in one research study, quaternizedchitosan (HTCC), silver nanoparticles, and GO were used for developmentof hydrogel-based contact lens, which had both antibacterial and antifungalactivities.127Recently, an active targeted drug deliveryvia endocytosis mediatedby ligand–receptors was used for doxorubicin (DOX) deliveryto choroidal melanoma. Transferrin (Tf)-modified pegylated graphenenanocarrier was used for DOX loading and provided a targeted capabilitytoward ocular choroidal melanoma-1 cells, which typically exhibiteda high expression of Tf receptors. DOX was loaded into the nanocarrierthrough π–π stacking architecture. The resultsdisplayed more than 80% tumor cell inhibition, which confirmed thepotential of using Tf-PG-DOX as an extremely effective antitumor drugdelivery system suitable for choroidal melanoma.128Bioinspired compound eyes (BCEs) as micro-optical devicesare tremendouslyinteresting due to their large fields of view (FOV) and various focalcapability. Wang et al. prepared a glycerol/graphene nanosheets (G/GNSs)-basedBCEs through a template-directed self-assembly process 9. For li129One-step laser reducedGO conductive tracks on transparent andflexible poly substrates also showed increasedabsorption toward a shorter wavelength of up to 96% in UV regions,which can significantly protect human eyes from high-energy lighthazards.4.2130 Hence, researchers have developed contact lenses usingelectronic devices for detecting physiological changes for the diagnosisof diseases.131 To develop electronicson soft contact lenses, optical transparency, stretchability, flexibility,and reliability upon repeated eye-blinks for clear vision are theimportant demanding challenges. To overcome these challenges, theycan be worn and produced by transparent, stretchable materials andharmless to the human body. Regarding the development of wearablesoft contact lenses, graphene and its hybrid with metal nanowireswere used as multifunctional sensors with suitable transparency andstretchability for wireless diagnosis and management of diabetes andIOP. Indeed, graphene and its hybrid provided enough transparencyand stretchability, which makes sure for the users that the soft contactlens is reliable and comfortable for unobstructed vision when it isworn.132 Recently, flexibility and transparencyof graphene led to development of liquid contact lenses with a largeFOV, a compact size, and fast response to electric potential.133Currently,contact lenses are used for cosmetic reasons and correction of vision.A unique platform can be provided for ocular diagnostics through continuouscontact of contact lenses with our tear fluids.134 High IOP causes loss of peripheral visual fieldsand leads to irreversible loss of vision fields.135 Unfortunately, glaucoma caused by high IOP is the secondmain cause of blindness in the world. As a result, measuring or monitoringthe IOP is important for glaucoma inhibition and management. Up tonow, many tonometers, the main tool to measure IOP, have also beendeveloped; however, they can be used by professionals for repetitivemeasurements to identify spikes and fluctuations of the patients’daily IOP.137 Zeng et al. developed an IOPsensor using transparent graphene to prevent the sensors from blockingvision and enhancing the flexibility of the wearable sensors to fitseveral sizes or curvatures in the eye.138 Electrooculography (EOG) is a technique to record the cornea-retinalstanding potential induced by eyeball movements. EOG applicationsare an ophthalmological diagnosis and can be used for developing wearablemedical sensors and as human–computer interaction interfaces.140 To resolve the limitation of silver/silver chloride (Ag/AgCl) gel-based,“wet” electrodes, a common method to measure the biopotentials,the graphene-coated textile electrodes were developed for monitoringcardiac biopotentials. Graphene textile electrodes with a high degreeof flexibility and stretchability can be used in various kinds ofpersonal clothing to monitor the epileptic patients and driver drowsiness,diagnostic polysomnogram tests for sleep disorders, and for developingwearable human–computer interfaces.141 Regarding the importance of visual electrophysiology measurements,soft graphene contact lens electrodes were used for conformal, fullcornea recording of electroretinography (ERG) from cynomolgus monkeys.ERG is a test to measure the electrical potential changes at the cornealsurface, which is employed in ophthalmic diagnostic testing for theassessment of retina functional integrity. The softness and opticaltransparency of graphene increased the high-efficacy measurementsof various kinds of ERG signals, including full-field ERG, multifocalERGs, and multielectrode ERG, with negligible corneal irritation.142 Besides, electrical signals in mouse retinawere investigated using a combination of field-effect transistorscontaining graphene and scanning photocurrent microscopy with microfluidicplatforms to detect the neural activity of retina. Results showedthat graphene concentration in the carrier can be modulated by electricalactivity in living retinal tissues, leading to potential gradientsthat can separate photoexcited electron–hole pairs and producephotocurrent signals.143Ocular hypertension is the most importantrisk factor in glaucoma, which has a higher IOP than normal.144 In this study, FLG was used fordevelopment of a sensor with high transparency, sensitivity, linearity,stability, durability, reliability, and biocompatibility for 24 hmonitoring of IOP and parylene-containing rGO and CNT. The sensing performance of preparedcontact lens sensor showed a high sensitivity of 36.01 μV mmHg–1 using an eyeball model made of PDMS to simulate thecurved surface of human eye. High sensitivity to IOP change, goodlinearity, good accuracy and great stability within the clinicallyrelevant IOP range were the outstanding properties of the fabricatedsensor. In another study, a contact lens for detection of IOP wasdeveloped using three-dimensional graphene nanowalls (GNWs) throughthe gold-assisted transfer method. The resistance response of thedeveloped sensor to the normal IOP fluctuation was 1.014 kΩmmHg–1 with a normal sensitivity of 42,250 ppm mmHg–1 and the response range of 0–75 mmHg accordingto the simulated tests on porcine eyes in vitro.The obtained results revealed that the GNWs have significant potentialfor continuous IOP monitoring with high sensitivity and low powerconsumption.146In addition, recently, a wearable contact lens sensor for noninvasivein situ monitoring of IOP was developed by Fan et al.,147 to monitor the IOP  were also employed in contact lensesby Zhang et al. the IOP 11. The G148 In general, it is crucially importantfor diabetic patients to detect their glucose sugar level for earlytreatment, so the noninvasive and real-time detection from tears willbe very valuable. In this study, a high-performance intraocular biosensorcontaining nitrogen-doped graphene was developed, which showed a highelectroactive property that can act as an ophthalmic electrode. Thefabricated chitosan-graphene based biosensor showed a high sensitivityat 9.7 μA mM–1 cm–2, a broadlinear range at 12 mM, and a good detection limit of 9.5 μM.The synthesized graphene-based biosensor also remained stable aftera month of storage. The in vitro ocular biocompatibilityof GC-COOH was investigated using CECs and RPE cells. The as-preparedGC-COOH was highly biocompatible to ophthalmologic cells. Moreover,the effect of biosensing electrode was examined on ocular tissues in vivo, and to monitor the intraocular blood sugar in tears,the electrode was evaluated as an assembled wearable corneal contactelectrode using New Zealand white rabbits as animal models  was fabricated for detection of glucose sugar fromtears.l models 12.148 Ac5124 while othersreported unfavorable biological responses and cytotoxicity.90 These inconsistent results might have been caused by differencesin research groups, experimental models/animals, and physicochemicalcharacterizations of GFNs and their compositions. Once GFNs are preparedand selected for ocular applications, their biocompatibility shouldbe evaluated, and further detailed and accurate experiments regardingtoxicity of GFNs must be done.Over the past few decades, GFNs have been exploredfor ocular therapeuticand diagnosis applications. The high specific surface area and largeπ-conjugated aromatic structure of GFNs make them good candidatesfor the development of ocular materials and devices, such as oculardrug delivery systems and sensors. Besides their advantages, thereare some challenges regarding GFNs’ toxicity especially forclinical use. Currently, since the literature about ocular toxicityof GFNs is limited, it is hard to conclude the potential GFNs’ocular hazards. Until now, there are two opposite opinions in thisresearch field: Some researchers suggested that GFNs are biocompatibleand can be good candidates for ocular applications,In most of the studies detailedherein, the toxicity of GFNs extremelydepends on their physicochemical properties, including size, surfacefunctional groups, oxidative state, and dose of administration aswell as exposure time. GFNs are very large family with huge differencesin size and dimension, which affect the toxicity. In addition, studiesfrequently showed that unmodified graphene and GO were more cytotoxiccompared with functionalized GFNs and rGO. Therefore, useful surfacemodification must be carefully evaluated and used to decrease theGFNs’ cytotoxicity for ocular applications in the future. Surfacefunctionalization of GFNs using biopolymers, such as PEG, can ledto an increase their biocompatibility in ocular applications and improvetheir therapeutic effects. Another physicochemical property that caninfluence the ocular toxicity of GFNs is degree of oxidation. A promisingapproach for reducing the GFNs’ ocular toxicity and improvingtheir safety for ocular applications is minimizing the degree of oxidation.In addition, another important issue that needs to be consideredis the long-term fate of GFNs after entering the eye or being takenup by cells. In most of the reported studies, the short-term oculartoxicity has been assessed, but long-term follow-up period shouldbe considered. Therefore, extended research is needed to evaluatewhether longer treatment times can affect the toxicity of GFNs inocular applications or not.To improve the safety of using GFNsin ocular applications, itis essential to study their toxicity mechanisms. To date, variousocular toxicity mechanisms of GFNs have been investigated and extensivelyapproved, including mitochondrial damage, oxidative stress, inflammatoryresponse, apoptosis, necrosis, cell membrane damage, cell death, cellcycle disorder, and cell viability loss. However, more specific pathwaysof the ocular toxicity mechanism of GFNs need to be discovered andinvestigated. For a better understanding of complex interactions betweenGFNs and biological systems, gene expression profiles should be studiedas an important approach, which reveals the potential molecular mechanismsof toxicity on a whole cell level.Moreover, hydrogels containingGFNs have been extensively employedand studied in contact lenses since they are highly comfortable andbiocompatible and have a high surface area. However, there will besome drawbacks by changing some conditions, such as increasing thecontent of GFNs and time of exposure. In addition, selecting the rightcell lines and/or animal model in assessment of ocular toxicity iscrucially important to develop ocular formulations with proper safetyand efficiency.in vitro and in vivo ocular toxicities must be evaluated. Therefore,GFNs’ biocompatibility, stability, and biological performancesas well as their side effects in ocular applications can be preliminarilyobtained by considering these items. However, future research is necessaryfor exploring the biological responses and the safety issues of GFNsby taking into consideration the different physicochemical properties.Before doing any research, personal safety protection is cruciallyneeded when dealing with GFNs both in production and in a researchenvironment. All of these provided results will further improve therequired knowledge for developing safe technologies and products usingGFNs appropriate for biomedical applications and minimizing the risksto human health. Consequently, further research is still necessaryto overcome the aggregation problems and genotoxicity of GFNs as wellas their toxicity dependency on the size- and/or functional groupsbefore we can draw a conclusion whether GFNs are safe or not.In conclusion, since ocular devices based onGFNs are developing,for detailed and accurate information about the interactions of GFNsat the molecular, cellular, and tissue levels, their physicochemicalproperties as well as their


Mucopolysaccharidosis type III (MPS III) or Sanfilippo syndrome is a neurodegenerative disease caused by the accumulation of mucopolysaccharides in the body. As the symptoms are wide ranging, it is a challenge to provide a diagnosis and psychological treatment for affected children.The main objective of this study was to describe a form of music therapy treatment applied to three children diagnosed with MPS III. The psychological variables were evaluated by an ad hoc observation recording template, and the physiological variables were measured with a digital meter before and after each session. The perception of the parents was also considered through a semi-structured interview.An improvement in the psychological variables was shown in all cases. Changes in the physiological variables were also noted, although they varied according to each child. The parents report some benefit of music therapy and they share difficulty in assessing the extent of benefits of the music therapy.Findings indicate that music therapy can be a useful form of treatment with multiple benefits for children with conditions such as MPS III or similar conditions. However, further research is needed in this area and in the development of specific ways of evaluating music therapy. Among the approximately 7000 existing rare diseases , mucopolThe MPS group is classified into several subgroups, namely: (1) MPS I or Hurler syndrome; (2) MPS II or Hunter syndrome; (3) MPS III or Sanfilippo syndrome ; 4) MPS IV or Morquio syndrome (variants A and B); 5) MPS VI or Marotaux-Lamy; (6); and (7) MPS IX or Natowicz syndrome .M = 8; SD = 1) diagnosed with Sanfilippo syndrome and residing near the study site participated in this study. The participants were two siblings with MPS III type A (a girl and a boy), and a girl diagnosed with MPS III type B. Non-probabilistic, convenience sampling was used as Sanfilippo is a rare disease and the number of patients in a concentrated location is limited. The inclusion criteria to participate in this study was being a child diagnosed with Sanfilippo who attended the Music Therapy Research Centre in Biscay, Spain.Three children aged between 7 and 9 , diastolic blood pressure (DBP) and heart rate (HR).An additional instrument used was the ad hoc semi-structured interview. This was applied to the participating children’s parents to discover the children's general clinical history, as well as the differences observed after participating in music therapy sessions. Interviews used in similar studies were considered to create the interview –51.Barthel Index was also included [Kappa indices of between 0.84 and 0.97. In terms of validity, Wade and Hewer [The included . This meincluded  was usedincluded  obtainednd Hewer  obtainedFour different instruments were used for data collection:This is a study of three cases with mixed methodology. A qualitative descriptive analysis was used by employing an arbitrary observation code and a semi-structured interview. A quantitative analysis was also used by quantifying observation and taking physiological data using the digital meter. Specifically, data were taken in a prospective and longitudinal manner, since the information was collected at different times along three months, and it was a study with an intra-subject repeated measures design.Children attended 45-min weekly one-to-one sessions at Music Therapy Research Centre in Biscay, Spain. To carry out this study, a total of 20 sessions were observed over three months. All participants obtained permission from their parents through passive consent, after being informed about the study. Before beginning the observational period, the music therapist (MT) provided to the observer the basic sociodemographic data of each case, with the consent of their parents.The patients went to the Music Therapy Research Centre accompanied by their parents or caregivers. Only the music therapist (MT), the co-therapist  and the study's observer were present. The profile of the MT is a pianist who has played in different countries since he was 4 years old, and worked in different fields, including special education and health; he was a university lecturer and held a master's degree in music therapy. The observer was a psychologist specialised in healthcare, with experience with children and adolescents.The MT welcomed each child when they arrived and took them to the room where the sessions were held, which was located at Music Therapy Research Centre. The room was large and had natural light. It was empty except for an acoustic piano tuned to 432 Hz, a Spanish guitar tuned to 440 Hz, a marimba and a cabinet with instruments in another room. Due to the degree of hyperactivity and impulsivity of the patients, an attempt was made before starting the session to eliminate, cover or block any elements that could hinder the course of the session. There were also some instruments that had been previously selected for each session according to the patient and the pre-established objectives.The sessions were structured into three parts: The session started with the child listening to the so-called ‘welcome song’ or ‘welcome passage’. This consisted of a few seconds of silence, followed by an improvised passage played by the MT (who was located near and in front of the child) on the classical guitar. The performance was based on the patient’s needs and lasted about two minutes. After this, there were again a few seconds of silence. In this case, the child's role was receptive.The second part further developed the session by using a more active method, involving vocal or instrumental participation. The patient was invited to sing in an improvised and creative way using their name, the name(s) of siblings, parents, etc. promoting emotional expression, memory and speech. When instruments were used, the patient was offered contact with the instrument  and the patient's musical production began. The MT accompanied the sounds made by the child, trying to harmonise with their creation to communicate and encourage integration between child, MT and co-therapist. The rhythms and tones emitted by the patient were not always the same, which required great attention on the part of the MT to adapt to the different pitches and rhythmic context. According to how the patient was seen to respond in terms of their emotions and movement, the therapeutic relationship was aimed at fostering different aspects; for example, percussion instruments were used to work on gross motor control.The last part of the session used a receptive method, as the first part did. At the end of the session, after asking the patient to take a seat, the MT played a musical passage on the classical guitar for approximately two minutes. Although the passage was improvised, it could be based on the musical passages used during this same session.Information was collected at the beginning and the end of each session. Both psychological and physiological variables were taken in the room before starting, prior to any musical stimulus. The subsequent measurement was taken at the end of the session, in the same conditions as the initial one, although the psychological measurements were collected within (at the most) 5 min after finishing the session. An audio-visual recording of each session was also made with prior written consent in order to complete the assessment in case the scores were lost.A semi-structured interview was conducted by the researcher with the parents to expand the information relating to each case, and to gain a qualitative insight into the possible benefits of the therapy. This interview was carried out after completing the observation process three months afterwards, in order to assess the long-term impact of the intervention and to consider the consolidation of the effects of the sessions. The interview was held in a quiet, private place at Music Therapy Research Centre, and it was audio recorded to prevent any loss of information. The parents had previously signed an informed consent form describing the objective of the interview and the study, and indicating that the interview would be recorded. Interviews lasted almost one hour and were performed by the researcher who was a health psychologist.Barthel Index, he has a moderate dependency. The most notable symptoms are walking on tiptoes and intestinal problems leading to poor sleep quality. He has never been hospitalised and only takes nutritional and vitamin supplements. He has received treatment for deworming, and once a month the mother refers that he goes to energy-based therapies, like energetic kinesiology which focuses on the energetic processes in the body.A. is a 7-year-old boy who suffers from MPS IIIA. He was diagnosed when he was 1 year old, although his symptoms were not recognized until he was 4 years old. There are seven people in the household and he is the youngest of three siblings who all suffer from MPS IIIA. He currently remains in his school year and follows an adapted curriculum. He has a therapeutic teacher that helps him outside the standard school lessons and he also receives speech therapy sessions. According to the This section analyses the calculations related to the variables observed in A.’s seven sessions through the registration template. This was later converted into means and deviations, resulting in the findings shown in Fig. The researcher’s qualitative observations for the physical, communicative, emotional and cognitive dimensions are described below. A. walked on tiptoes and tried to leave the room and turn off the lights during the sessions. The physical and communication dimensions were particularly remarkable. At the physical level, it was generally difficult to measure his vital signs due to hyperactivity and movements, and it was not possible to carry out measurements in session three. When he listened to the guitar, he moved his legs, although he looked calm (because of his position in the chair), and his breathing was calm and relaxed. However, when he participated actively and played the drum, for example, he did not move his legs. Both verbal and non-verbal communication (sounds) increased when he was stimulated through songs and sounds. At the social-emotional level, positive emotions were strongly expressed and he smiled when he played. Cognitively, his attention was focused on each instrument, and when the MT stopped playing or changed instruments, he also focused on what the MT asked him to do and did himself. He was able to remember as he could repeat his MT’s name and play the instruments; if he could not play a given instrument, he had the capacity to learn. Creative behaviour was observed. For example, if he dropped the drumstick, he continued playing with his hand.His mother said that she had seen a great change in her son A. since he had started going to the Music Therapy Research Centre to receive music therapy sessions. At first, he did not like them; he cried and was upset when he had to go; however, she reported that now he is happy and compared with other children suffering from Sanfilippo, she considered that her son’s level of development had improved. For instance, she explained that hyperactivity was less marked and that he smiled a lot and was more obedient, as he paid attention to the instructions received, although she did not attribute it to anything specific. She was happy with her son's general development and said that he was happy when he arrived home after his music therapy sessions.These variables were analysed by finding the means and standard deviations of diastolic blood pressure, systolic blood pressure and heart rate that were collected before and after the sessions. The results are shown in Fig. Barthel Index, she has a severe dependency level. The most characteristic symptoms are coarse facial features, hyperactivity and impulsivity. She was hospitalised in 2012 for an operation on her adenoids, and in 2014 to remove her tonsils, as it was causing sleep apnoea. She has septal hypertrophy and had many high fevers and ear infections as a child. She has recurrent respiratory infections, so she takes Flixotide daily, and Ventolin on an occasional basis. She also takes risperidone and diazepam to decrease hyperactivity. She has visited an osteopath and physiotherapist for four years.R. is a 9-year-old girl who was diagnosed with MPS III-B when she was 4 years old, although the onset of symptoms was observed at 2 years old, when she stopped talking. She lives with her parents and has had special educational arrangements at school for three years. According to the This section analyses the calculation of the variables observed in the five sessions of R.’s case through the registration template. This was later converted into means and deviations, resulting in the findings shown in Fig. The researcher’s qualitative observations relating the physical, communicative, emotional and cognitive dimensions are described below. Before starting the sessions, rigidity in the muscle tone of R.’s extremities could be seen. Her breathing was unsteady and she was crying when she arrived. In this case, the most remarkable changes were found at the physical social and emotional level. During the sessions she showed hyperactivity, as she constantly wandered around the room; however, when listening to the guitar, she was able to concentrate on the music being played at that moment and to sit in the chair properly without moving, with slower breathing and a greater level of relaxation. At the communicational level, it is important to highlight her non-verbal responses, as she made a large number of sounds as a response to the MT. The greatest social and emotional change was evidenced by the fact that the crying at the beginning of the sessions disappeared when listening to the guitar. She also became involved with the other people in the room, which fostered group integration. Despite R.’s cognitive deterioration, she paid attention to the music therapist while he played during the sessions.The parents highlighted the difficulty in observing changes in their daughter due to the deterioration characteristic of the disease. When she started to attend the sessions, they saw more changes, since they noticed more active participation, more verbal and musical communication, as well as more calmness. Over the past year, they said she had been calm during the session, but when they left, hyperactivity and behaviour problems returned. They also emphasised that it was difficult to see changes due to the subjective nature of the treatment, comparing it with medicine.The means and standard deviations of the systolic, diastolic and heart rate presented by R. both before and after the sessions were used to analyse these variables Fig. .Fig. 4PrBarthel Index, she has a severe level of dependency. The most notable symptoms are motor clumsiness and reduced mobility. She had convulsions once and has poor circulation and intestinal disorders that result in poor sleep quality. She also has three crushed vertebrae and scoliosis. She was hospitalised when she was 5 years old to have her adenoids removed due to apneas at night and otitis. She takes natural enzymatic and vitamin supplements. She usually has intestinal parasites and receives treatment for deworming, and the mother mentions that once a month she goes to energy-based therapies like energetic kinesiology which focuses on the energetic processes in the body.X. is a 9-year-old girl who suffers from MPS IIIA. She was diagnosed when she was 3 years old, at the same age when the symptoms started due to a gait anomaly. There are seven people in the household. She is the middle child, and her two siblings also suffer from MPS III-A. She has special educational arrangements at school and attends speech therapy sessions. According to the This section analyses the calculation of the variables observed in the eight sessions of X.’s case through the registration template. This was later converted into means and deviations, resulting in the findings shown in Fig. The researcher’s qualitative observations relating to the physical, communicative, emotional and cognitive dimensions are described below. Before beginning the sessions, there was restlessness in X.’s legs and strong emotions, notably anguish and general restlessness. Restlessness in her legs diminished with music, and her level of relaxation increased. She communicated by repeating the sounds made by the MT, or creating her own singing, and playing the instrument played by the MT. At the gestural and body level, she frequently held the MT’s hand and maintained visual contact with him. The social and emotional aspects were also intensified, with positive or neutral emotions predominating. X. smiled at the MT and approached the people who were present, showing group integration. At the cognitive level, the most remarkable thing was her ability to pay attention when the MT played an instrument, and her creativity, as she created new harmonies by singing.X.’s mother considered the role of music in people's lives to be fundamental. She mentioned the difficulty in terms of being able to observe changes, and of assessing what remained after leaving the sessions, given the neurodegenerative disease suffered by her daughter. X. really likes music, and she sings and dances daily. This is a way of communicating with her that her mother has used since childhood. X.’s mother reported that, in general, X. was relaxed when she went home after the sessions. For example, there were days that she cried when she went to the session due to back pain. However, when she came out of the session, she felt more relaxed. Her mother stated that X. clearly enjoyed the sessions.These variables were analysed by finding the means and standard deviations of X.'s diastolic blood pressure, systolic blood pressure and heart rate that were collected before and after the sessions. The results are shown in Fig. This study uses a mixed methods approach to describe the effects of music therapy on three patients with Sanfilippo syndrome. This was done by measuring which psychological  and physiological (measured quantitatively) variables in these children increased or decreased after the music therapy intervention.There were higher scores after music therapy sessions in the four psychological variables included in the present study in all cases. This showed an improvement in terms of physical, communication, social, emotional and cognitive levels after participating in music therapy sessions. Some variations were found in the dimensions according to each child’s specific needs and limitations, which were shown in the measurements prior to the sessions. In the case of A., the physical and communication dimensions prevailed since the extent of his disability in these areas was less marked than in the other cases. He was the only one that maintained his verbal abilities and used them in the sessions. In the case of R., the changes at the physical level stood out because hyperactivity was particularly marked initially although it decreased considerably during the sessions. Besides, in R.’s case, an improvement was particularly noticeable in the social and emotional aspects, since she cried before starting the sessions and but this decreased as the session progressed. X. experienced improvements especially on a physical level, due to the general restlessness shown before the sessions and the relaxation during the therapy.These results can be compared with those obtained from children with ASD. García  observedOn a different note, the assessments made by the parents varied considerably. However, in all cases, the parents stated that, to a greater or lesser extent, they had seen that music therapy had benefited their children, especially at a social-emotional level. Furthermore, the common point of all the cases was the difficulty in making long-term evaluations of music therapy, due to the degenerative character of the disease. This information highlighted the importance of working with families in this type of study. Parents’ views were essential because their involvement provided a source of external feedback for the researcher that went beyond what was observed in the sessions. In other studies, in which parents have been interviewed, in addition to finding positive opinions about the use of music therapy, researchers also stressed the importance of their collaboration , 36, 38.The physiological variables showed greater variability in the results. This could be due to each child’s varying needs and baseline activation level. In the cases in which it tended to increase, the pre-treatment measurement was low whereas, in those where it tended to decrease, the pre-treatment measurement was in the normal average range or slightly above, so it was adjusted to what each individual needed at the time. To a greater or lesser extent, systolic blood pressure decreased in all cases. The heart rate was found to have increased in the siblings, which may have to do with the level of activation that the sessions produced on them, as a way of preparing the body for the action required. In the case of R., the pre-treatment measurement was higher in all measures, which may be due to the fact that her activation level was higher, especially due to crying and hyperactivity. After the sessions, all the indicators decreased to a normal range level, and a balance was achieved between the sympathetic and parasympathetic nervous systems , 45.Although no studies have been conducted on the measurement of physiological variables in children with MPS III or similar diseases when participating in a music therapy treatment, these results can be compared with research carried out on dimensions that are affected in these children, such as pain, stress and anxiety. In these studies, there was a decrease in the relevant indicators, with increased relaxation and reduced pain, anxiety and stress, as in the case of R. and in all cases in systolic blood pressure –43.This study has some limitations that should be considered for future research. Mainly, it should be noted that, since it is a rare disease and it is difficult to put together a sample, the number of the selected sample is small, with only three participants. Given the small sample size, the results were not compared between the cases, as it was considered that the results would not be relevant and would not be an appropriate representation of reality.Another limitation was the measure used to collect psychological variables. This was an ad hoc template on the direct observation of these variables by the researcher. It could lead to the impression of being subjective judgment, in which the observer’s perspectives and wishes may have influenced observation, although an attempt was made to overcome this limitation by recording the sessions. For future studies, it would be important to introduce different observers and calculate the interjudge agreement as a measurement of reliability. In addition, as it is a non-standardised instrument, despite relying on validated measures, some studies would be needed to determine its reliability and validity.Continuing with the assessment, another limitation is that due to the degree of affectation of the children and their ages, a standardised evaluation of the variables studied was not carried out. As the sample was small, a qualitative descriptive approach was chosen in order to obtain information of clinical and scientific interest. However, it would be interesting, for future studies and for international comparisons, to use standardised instruments, especially through a standardised parental report.A final limitation to note is the lack of previous research on the subject, which makes it very difficult to compare or comment on the results found in this study. Although it has been based on research on music therapy and other diseases that have similarities with Sanfilippo, there are no previous studies on this disease in particular or any type of non-medical treatment. However, this type of limitation can serve as an opportunity to identify new gaps in the literature and consequently stimulate new research.Regarding the implications of this preliminary clinical report, the results could be useful to encourage the development of a music therapy programme not only for children with MPS III but for anyone suffering from a rare disease or a neurodegenerative disorder of this nature that involves verbal and cognitive impairment. It can also influence the creation of a validated test to reliably and validly evaluate music therapy sessions, which could lead to a more quantitative study to determine if the differences are significant. It is also important to highlight the importance of this type of studies where the purpose is to gain a better understanding about the effectiveness of this intervention among this group of patients since it could be applied at an earlier age when the deterioration is not so marked.The results of this study provide preliminary information and indicate positive changes in both psychological and physiological variables after having received music therapy sessions. This leads to the conclusion that this treatment is a promising practice for improving quality of life. The study provides information that has not been published to date and can be of great social importance, as it can be very helpful for professionals and family members of those affected. These data could serve as a basis for future research that has greater resources available, such as a larger sample, rigorous design and a standardised assessment and treatment. Also, further research should be done both on this rare disease and music therapy so that more can be learnt about them and to clarify whether this treatment is effective.


It is well known that a small number of graphene nanoparticles embedded in polymers enhance the electrical conductivity; the polymer changes from being an insulator to a conductor. The graphene nanoparticles induce several quantum effects, non-covalent interactions, so the percolation threshold is accelerated. We studied five of the most widely used polymers embedded with graphene nanoparticles: polystyrene, polyethylene-terephthalate, polyether-ketone, polypropylene, and polyurethane. The polymers with aromatic rings are affected mainly by the graphene nanoparticles due to the π-π stacking, and the long-range terms of the dispersion corrections are predominant. The polymers with linear structure have a CH-π stacking, and the short-range terms of the dispersion corrections are the important ones. We used the action radius as a measuring tool to quantify the non-covalent interactions. This action radius was the main parameter used in the Monte-Carlo simulation to obtain the conductivity at room temperature (300 K). The action radius was the key tool to describe how the percolation transition works from the fundamental quantum levels and connect the microscopic study with macroscopic properties. In the Monte-Carlo simulation, it was observed that the non-covalent interactions affect the electronic transmission, inducing a higher mean-free path that promotes the efficiency in the transmission. The science of polymeric materials has revolutionized today’s science and technology. Today, almost every industrial component has a polymer in it ; there iExperimental and computational studies of conductivity in nanocomposite polymer-graphene present a change in the electrical behavior according to a sigmoid curve ,32,33. IThe percolation threshold for carbon nanotubes embedded in polypropylene is around 5% ,39, wherOur group has proved that quantum effects are the main reason for the percolation threshold occurring so rapidly, and we are developing a methodology to calculate the conductivity of these nano-compounds theoretically. In this work, we simulated the nanocomposites at the microscopic level using an ab-initio computational framework to characterize the quantum effects correctly. Then, we approached the macroscopical level with a Monte-Carlo simulation, which has been proven to give accurate results ,42,43,44The ab-initio calculations were made to characterize the systems’ quantum effects appropriately and then to incorporate them in the macroscopic simulation and phase conductivity analysis.The DFT calculations were carried out using the Perdew–Burke–Ernzerhof (PBE) functional , Grimme More details of the ab-initio calculations are presented in the Deposition Process. The random deposition of the graphene nanoparticles over the polymer matrix within a specific percentage is achieved using a Metropolis Monte-Carlo model. The implementation of this model consists of three subparts: a first-neighbors function, the introduction of a training period, and a condition to generate the random deposition of graphene. The details are in the The graphene-clustering Process. It is well known that the deposition process may produce clustered particles over the substrate. In particular, the graphene nanoparticles in a polymer tend to make clusters or fragments that fit together, forming a two-dimensional coverage. In the previous procedure, we could obtain a small concentration of graphene particles or isolate them. Thus, we establish a minimum number of connected graphene particles to be considered a cluster. The detailed algorithm is presented in the i-th to the j-th cluster. Then we defined the transition rate matrix or the intensity matrix (M) as a function of the Euclidean distance between clusters and each nanocomposite potential. The interaction potential (iju) between the i-th and the j-th clusters was expressed as an expansion of the van der Walls interaction potential proposed by Hamaker [R−6, R−8, and R−12) [dist is the minimal distance between clusters, the parameter R is entirely determined by the nanocomposite and represents the action radius obtained in the ab-initio simulation. The M matrix is defined using Equation (2) and is given by the last-passenger model. The inversion of the M matrix is almost the Green matrix of the system [Transmission probabilities. The transmission probability is measured using stochastic theory. The transition rate is defined as the probability to pass from the  Hamaker . The intnd R−12) . In partnd R−12)  form thee system  and alloThe stochastic simulation is made to emulate the experimental situation as accurately as possible. The simulation is made in three parts: the deposition process of the graphene nanoparticles on the polymer; the accumulation process; and, finally, the electronic transport in the nanocomposite modeling. A summary of the details is:M matrix is called the transmission matrix. In particular, in phase-type distribution theory, the M matrix is defined i,ju and U = (−T)−1, where U is the expected value in state j prior to absorption given initiation in the state i [U. We repeat this procedure 50,000 times and the output data are the saturation of the simulated polymer. In the In electronic transport theory, the  state i . Then, wG =σA/L, in which A and L are in nanometric dimensions 100 nm2 and 10 nm, respectively.To prove our model, we compared the simulation with experimental results, in which the graphene nanoparticles are obtained from graphene oxide nanoparticles and added to the polymer matrix. The simulations made with PS-graphene nanocomposites were compared with the experimental results obtained by Qi et al. , in whicThe systems were optimized to obtain the most stable geometries by performing a systematic search, as was mentioned in the methodology section. These geometries are shown in The adsorption energies and the HOMO-LUMO gap are shown in A monomer of polystyrene in gas phase presents a gap around 2.37 eV, and polystyrene’s monomers in the presence of graphene have a gap of 0.599 eV. The PET monomer has a HOMO-LUMO gap of 3.58 eV in gas phase and 0.20 eV with graphene interaction. The PEK monomer has a gap of 2.82 eV alone and 0.19 eV with graphene. The linear polymers present the same HOMO-LUMO gap of 0.9 eV representing a huge diminishment from the pristine form of the polymer, which is 3.66 eV for the PP and 5.83 eV for PU. The gas-phase polymers have a big HOMO-LUMO gap in agreement with the insulator properties of the polymer. As soon as graphene nanoparticles are incorporated into the systems, the HOMO-LUMO gap diminished drastically, according to a semiconductor material.With the optimized structures, adsorption energies, and HOMO-LUMO gap, it was noticed that there is an increasing tendency to improve the electronic transfer when the graphene nanoparticles are introduced in the polymers. The interactions between the graphene and polymers are also weak, forming non-covalent bonds; π-π and CH/π bonds are the predominant interactions presented on the systems.The direct consequence of the non-covalent bonds is that graphene nanoparticles are stacked parallel to the polymer and enhance the electronic interchange between polymer and graphene.Following the proposed methodology ,57, the z-axis contains the normal vector of the surface. When the polymer interacts with graphene, carbon atoms can be pushed down (z < 0) or pulled up (z > 0). The action radius is the distance between the maximum and minimum heights near the polymer and directly reflects the internal tensions induced by the polymer–graphene interactions  of electrons. The electronic transport obeys the potential of Equation (2), that consists of some terms of the power series of the dispersion correction. All the results presented here are computed at room temperature (300 K).The macroscopic calculation was carried out in three parts. The first part is the deposition of graphene nanoparticles on the polymer matrix using a Metropolis Monte-Carlo model. The second part is the formation of graphene clusters over the polymer matrix, incorporating the quantum effects and the internal tensions obtained in the previous section. The third part used a phase-type distribution function to obtain the transmission probabilities  as a function of graphene nanoparticles percentage of each simulated set, and we adjust a curve with the sigmoidal Boltzmann equation: σmax as the upper limit of the sigmoidal, (σmax − σmin) is the difference between the upper and lower limit, PT is the percolation threshold, which represents the critical point in which the conductivity changes drastically, and dx represents the slope at the center of the curve. We extrapolate the electrical conductivity , we have two terms whose interactional nature presents a subtle difference. The term R−6, indicating that the electrons find a large mean-free path to promote electronic transport, accelerating behavior change from insulating material to a conductor. Therefore, the percolation threshold comes with a percentage much lower than expected. This accelerating is directly a consequence of the π-π stacking and the action radius. The systems in which the long-range terms are predominate are PS-graphene, PET-graphene, and PEK-graphene and have an action radius long enough to transport the electrons. The electronic transfer mechanism acts via the dispersion forces R−12) are PP-graphene and PU-graphene. The action radius is small due to the CH/π stacking, and the nanofillers have a weak interaction with the polymer, so the electrons are transported locally. The mean-free path of the electrons is short, producing low electronic transport compared with other systems studied here. A larger quantity of graphene nanoparticles are introduced to change insulating material to a conductor and improved the trajectories in which electrons can move. As a consequence of this, the percolation threshold occurs with a more significant nanoparticles percentage. The systems with dominant short-range terms . We constructed a robust simulation at room temperature with microscopic, macroscopic, and experimental facts to simulate the non-covalent interactions as accurately as possible. The non-covalent interactions were characterized in detail with an ab-initio framework and, then, they were included in a Monte-Carlo simulation. The electronic transport is simulated using phase-type distribution, stochastic percolation theory, and Landauer formulation. The electric conductivity of the systems was successfully reproduced in strong agreement with experimental results. We also proved that a stochastic percolation theory with a phase-type distribution is a more appropriate tool because it can incorporate more details than other models, such as considering room temperature or non-covalent interactions. Polymers with aromatic rings in their structure are more compatible with graphene nanoparticles to maximize the conductivity, inducing a π-π stacking that increases the transport of electrons from the graphene to the polymer and vice-versa. For polymers with linear structures, the non-covalent interactions are present mainly by the CH/π stacking. Electronic transport is still promoted, although the electrons are not that accelerated compared with the aromatic polymers. It was observed that the non-covalent interactions dominate the electronic transport mechanism and promoted electrons to be transferred efficiently, diminishing the HOMO-LUMO gap. R of electrons to be transported in the percolation theory. The Monte-Carlo simulation also allows for incorporating the effect of graphene clusterization and considers quantum effects given by graphene–graphene and polymer–graphene interactions. The non-covalent interaction increased the deformation of the nanocomposites. The systems that present a more significant deformation have a higher structural coupling; these are the systems that have cyclic rings and higher adsorption energy. We take the aspect ratio as the deformation radius because it characterizes the neighborhood in which the non-covalent interactions are predominant and connects them with the macroscopic properties. The deformation is used on the Monte-Carlo simulation as the aspect ratio, i.e., the action radius For compounds with low percolation thresholds, such as PS, PET, and PEK, the predominant interactions with the graphene nanoparticles are long-range terms, which produces a long mean-free path for the electrons, which are transported efficiently in the nanocomposite. For high percolation thresholds, such as PP and PU, the prevalent interactions are of the short-range type; this means that the effects induced by graphene on the polymer act locally, so the mean-free path of the electrons is shorter than other polymers. It is observed that this model is the most appropriate to describe these systems.It was proved that the combination of Monte-Carlo simulation with stochastic process based on the phase-type distribution with the last-passenger percolation theory is an excellent approach. As a consequence of the simulation, the electrical conductivity as a function of the percentage of fillers is defined by the Boltzmann sigmoid curve, which allows us to predict the percolation threshold and saturation state correctly at room temperature. The average error of our simulation is around 3%. Specifically, for systems with predominant short-range interactions, our simulation is excellent (≈1% of error). We recognize that interactions of attractive nature contribute significantly to the efficiency of electronic transport by increasing the mean free path of the electrons. The comparison with several experimental studies demonstrates that our model describes the electric transport accurately in polymer-graphene nanocomposites.


Strain modulation is crucial for heteroepitaxy such as GaN on foreign substrates. Here, the epitaxy of strain-relaxed GaN films on graphene/SiC substrates by metal-organic chemical vapor deposition is demonstrated. Graphene was directly prepared on SiC substrates by thermal decomposition. Its pre-treatment with nitrogen-plasma can introduce C–N dangling bonds, which provides nucleation sites for subsequent epitaxial growth. The scanning transmission electron microscopy measurements confirm that part of graphene surface was etched by nitrogen-plasma. We study the growth behavior on different areas of graphene surface after pre-treatment, and propose a growth model to explain the epitaxial growth mechanism of GaN films on graphene. Significantly, graphene is found to be effective to reduce the biaxial stress in GaN films and the strain relaxation improves indium-atom incorporation in InGaN/GaN multiple quantum wells (MQWs) active region, which results in the obvious red-shift of light-emitting wavelength of InGaN/GaN MQWs. This work opens up a new way for the fabrication of GaN-based long wavelength light-emitting diodes. Currently, the high cost of native substrates makes group III-nitrides usually grow on foreign substrates, such as sapphire, SiC, and Si6. However, there are lattice and thermal mismatches between nitride films and foreign substrates, leading to the formation of high-density point defects, threading dislocations, and residual stress in the prepared films and devices, which degrade the working lifetime and efficiency of GaN-based optoelectronic devices9.Due to direct wide bandgap and high stability, group III-nitride semiconductors have been widely used in light-emitting diodes (LEDs), laser diodes and photodetectors13. The epitaxial growth of GaN on graphene forms weak covalent bonds at the interface between graphene and epitaxial layer, which makes the lattice at the interface produce no large strain as the traditional heteroepitaxy, and the stress in films greatly reduced14. This provides a new path for heteroepitaxial growth of GaN films. In addition, the weak force between the epitaxial layer and graphene can make the epitaxial layer be easily released from the substrate and transferred to other materials, realizing some novel device applications, such as flexible devices16. However, the lack of dangling bonds on graphene suppresses the GaN nucleation, limiting the growth of continuous and smooth GaN films on graphene17. To solve this problem, some researches have achieved the epitaxial growth of nitrides on graphene by introducing interfacial buffers or defects on graphene. For instance, Chung et al. realized the epitaxial growth of the GaN-based LED structures on graphene/sapphire substrates by using of high-density, vertically distributed ZnO nanowalls as the interfacial buffer10. Besides, Chen et al. reported the epitaxial growth of AlN films on graphene by nitrogen-plasma pre-treatment18. Although there are a few reports on the epitaxial growth of GaN on graphene, the epitaxial growth mechanism of GaN on graphene is still not clear enough, and the role of graphene in the GaN epitaxial growth process is unclear.Recently, GaN films grown on graphene and other two-dimensional materials have attracted extensive attentionHere, we successfully grew a strain-relaxed GaN film on graphene/SiC substrates by metal-organic chemical vapor deposition (MOCVD). Graphene was directly prepared on SiC substrates by thermal decomposition. The nitrogen-plasma pre-treatment was performed on graphene surface, introducing the C–N-related dangling bonds, which promoted the subsequent epitaxial growth of GaN films. The scanning transmission electron microscopy (STEM) measurements reveal that part of graphene surface was etched by nitrogen-plasma pre-treatment. The growth behavior on different areas of nitrogen-plasma-treated graphene was studied, and then a growth model was proposed based on the STEM results to explain the epitaxial growth mechanism of GaN on graphene. It is worth noting that, the graphene is found to be effective to reduce the biaxial stress in GaN films. Then, we prepared InGaN/GaN multiple quantum wells (MQWs) on the strain-relaxed GaN films. The strain relaxation in GaN films leads to the improvement of indium-atom incorporation efficiency in the MQWs, resulting in the obvious red-shift of light-emitting wavelength. Our work enhances the understanding of epitaxial growth of nitrides on graphene, and provides a new way for the fabrication of nitride long wavelength GaN-based LEDs.−1) and 2D peak (~2700 cm−1) of graphene can be seen in Raman spectra of five measured positions, which indicates that the prepared graphene on SiC substrate by thermal decomposition has good uniformity20. In addition, we calculated the intensity ratio of the characteristic 2D-to-G peak (I2D/IG) of graphene, and the intensity ratio of the defect-related D peak (~1350 cm−1) to the characteristic G peak (ID/IG) of that. The results show that the prepared graphene on SiC substrate is the multilayer one with good quality  measurement results also confirm that AlN buffer is polycrystalline  measurements were performed on the as-grown GaN on untreated graphene. As shown in Fig. ID/IG ratio of the graphene in Raman spectra increases from 0.3 to 0.5. The defect density in graphene can be calculated based on the ID/IG ratio, and it increases from 9.0 × 1010 cm−2 to 2.0 × 1011 cm−223. In order to further study the effect of nitrogen-plasma pre-treatment, X-ray photoelectron spectroscopy (XPS) measurements were conducted for untreated and nitrogen-plasma-treated graphene. Figure 2C–sp2C bond (~284.6 eV) from graphene24. After nitrogen-plasma pre-treatment, two different kinds of C–N bonding configurations appeared in C 1s peak, corresponding to N–sp2C bond (~285.5 eV) and N–sp3C bond (~286.5 eV), as shown in Fig. 4c25. Since the pyrrolic N atom in N–sp3C bond is more reactive than the pyridinic N atom in N–sp2C bond18, N–sp3C bond can provide more nucleation sites for subsequent epitaxial growth of GaN films.The Raman spectra in Fig. Figure To determine the macroscopic orientation and crystal structure of GaN films on nitrogen-plasma-treated graphene, we also performed XRD measurements on GaN films. The XRD 2θ and φ scan results show that GaN film on graphene is a well-aligned single crystal with hexagonal wurtzite structure  phonon mode in Raman spectra is sensitive to the biaxial strain of GaN films, and therefore it can be used to evaluate the biaxial stress in III-nitrides26. For stress-free GaN bulk materials, its E2 (high) phonon frequency is 568 cm−127. Figure 2 (high) phonon frequencies of GaN films grown on graphene and directly on SiC are both less than 568 cm−1, indicating that both GaN films are under tensile stress state28. While, the E2 (high) phonon frequency of GaN on nitrogen-plasma-treated graphene is closer to that of stress-free GaN, which is 567.9 cm−1. The specific biaxial stress value σ of GaN epilayers can be calculated by the formula: σ = Δω/κ, where κ is the stress coefficient, Δω is the Raman frequency shift relative to the E2 (high) phonon frequency of stress-free GaN films. Here, κ = −3.4 cm−1 GPa−1 is adopted for the calculation29. The calculated residual tensile stress value for the GaN films on graphene is only 0.03 GPa, which is much lower than that of GaN films grown directly on SiC substrate (0.74 GPa). This result shows that the residual stress in GaN films can be significantly reduced by inserting graphene.The stress in as-grown GaN films is further evaluated by Raman spectroscopy. The Ec-axis orientation growth. The c-axis-oriented AlN nucleation islands gradually occupy the dominant role, and a single crystal AlN layer with the same orientation is formed by lateral epitaxy. The subsequent GaN films are grown on the AlN layer, as shown in Fig. Based on the above results, we propose a growth model to explain the growth mechanism of GaN films on graphene. As shown in Fig. Based on above results, InGaN/GaN MQWs were grown on the as-grown GaN/graphene/SiC template. For comparison, we also prepared InGaN/GaN MQWs with the same structure on GaN/SiC template under the same conditions. The two samples were grown in one run. Figure 3C dangling bonds, which facilitate the nucleation and growth of subsequent epitaxy. STEM results provide direct evidence that the surface of graphene is partially etched by nitrogen-plasma pre-treatment. Based on the growth behavior on different etched areas of graphene surface after pre-treatment, a growth model is proposed to explain the epitaxial growth mechanism of GaN films on graphene. It is worth noting that, graphene can effectively reduce the biaxial stress in GaN films and the strain relaxation improves the incorporation efficiency of In atoms in InGaN/GaN MQWs. This work provides a feasible way for the epitaxy of strain-relaxed GaN films and opens up a new avenue for the fabrication of GaN-based long wavelength LEDs.In conclusion, we realized the epitaxy of strain-relaxed GaN films on graphene/SiC substrates. Graphene was directly prepared on SiC substrates by thermal decomposition. The pre-treatment of graphene with nitrogen-plasma can generate N–spGraphene was prepared on Si-face 4H-SiC substrates by thermal decomposition. Firstly, 4H-SiC substrates were annealed in an Ar atmosphere at 800–1000 °C for 1 h to remove scratches and oxygen on the surface of SiC substrate. Then, SiC substrates was heated to 1600–1700 °C in an ultra-high purity Ar atmosphere under 800 mbar for 2–5 h to realize surface graphitization.3) were used as Ga, Al, and N precursors, respectively. H2 and N2 were used as carrier gases. Prior to the deposition, graphene/SiC substrates were thermally cleaned in H2 atmosphere at 1100 °C for 5 min. The growth began with the low-temperature AlN buffer layer of about 40 nm thickness grown at 780 °C. Then, the growth temperature ramped up to 1080 °C for the growth of high-temperature AlN buffer layer with thickness of about 160 nm. Subsequently, a 2 μm thick undoped GaN layer was grown at 1050 °C. After that, the InGaN/GaN MQWs were grown on the undoped GaN layer. The MQWs consist of 5 pairs of 2.5 nm thick InGaN quantum well (QW) layers and 15 nm thick GaN quantum barrier (QB) layers. QW and QB layers were grown at 712 and 840 °C, respectively, and they were undoped. For comparison, InGaN/GaN MQWs without graphene interlayer were fabricated directly on SiC substrate. It is worth noting that these two kinds of MQWs samples were grown in one run.GaN films were grown on graphene/SiC substrates by an AIXTRON 3 × 2″ FT MOCVD system. Trimethylgallium (TMGa), trimethylaluminum (TMAl), and ammonia (NHThe surface morphology of graphene and GaN films were measured by SEM (Jeol-7500F) and AFM in tapping mode (Bruker Dimension ICON-PT). Raman spectroscopy  was performed to characterize the quality of graphene and the stress state of GaN films. The chemical states of graphene were measured by an ESCALab 250 Analytical XPS spectrometer with a monochromatic X-ray source . The binding energies of the spectra were referred to that of the C 1s peak at ~284.8 eV. The crystalline quality of GaN films characterized with a Rigaku Ultima IV XRD with Cu Kα radiation (0.154056 nm), and the structural properties of GaN films were investigated by aberration corrected Thermo Fisher Scientific Titan Cubed Themis G2 transmission electron microscope operated at 300 kV and equipped with Bruker Super-X EDX detector. The PL spectra of InGaN/GaN MQWs were measured by a PL system which includes a He-Cd laser  as an excitation source, a Jobin Yvon iHR550 spectrometer, a Syncerity charge coupled device (CCD) and a closed circle helium cryostat.Supplementary information for demonstration of epitaxial growth of strain-relaxed GaN films on graphene/SiC substrates for long wavelength light-emitting diodes.