The effect of electrolyte concentration wasstudied, as low concentrations do not lead to a favorable graphiteexfoliation and high concentrations produce fast graphite expansionbut poor layer-by-layer delamination. The optimal concentrations are0.25 M H3PO4 and 0.05 M Na3PO4, which also exhibited the highest phosphorus contents of2.2 and 1.4 at. %, respectively. Furthermore, when PFG-acid at 0.25M and PFG-salt at 0.05 M were tested as an electrode material forcapacitive energy storage in a three-electrode cell, they achieveda competitive performance of ∼375 F/g (540 F/cm3) and 356 F/g (500 F/cm3), respectively. Finally, devicesmade up of symmetric electrode cells obtained using PFG-acid at 0.25M possess energy and power densities up to 17.6 Wh·kg–1 (25.3 Wh·L–1) and 10,200 W/kg; meanwhile,PFG-salt at 0.05 M achieved values of 14.9 Wh·kg–1 (21.3 Wh·L–1) and 9400 W/kg, with 98 and99% of capacitance retention after 10,000 cycles, respectively. Themethodology proposed here also promotes a circular-synthesis processto successfully achieve a more sustainable and greener energy-storagedevice.Phosphate-functionalizedcarbon-based nanomaterials have attractedsignificant attention in recent years owing to their outstanding behaviorin electrochemical energy-storage devices. In this work, we reporta simple approach to obtain phosphate-functionalized graphene (PFG)via anodic exfoliation of graphite at room temperature with a highyield. The graphene nanosheets were obtained via anodic exfoliationof graphite foil using aqueous solutions of H Nonetheless, producinggraphene nanosheets at a mass scale and low cost is still a big challenge.Many works have studied and developed several top-down and bottom-upproduction methods to overcome this challenge. Nonetheless, nowadaysthe electrochemical exfoliation12 (anodicor cathodic), the graphene oxide route,13 and the direct liquid-phase exfoliation method,14 are the most promissory methodologies15 to produce single- or few-layered graphene nanosheets inbulk quantities.Sustainableenergy storage has recently arisen as a need to satisfythe global energy demand in the near future.17 The exfoliation occurs when theions from the electrolyte are intercalated between graphite layersin the graphite electrode, during the feed of an electrical currentin an electrolytic cell. As a result, the interlaminar distance isincreased, leading to exfoliated graphene layers with a high yield.In particular, for electrochemical exfoliation under cathodic conditions,the graphite electrode acts as a cathode and the cations intercalatingfrom the electrolyte can be molten salts, salts in organic solvents,ionic liquids, etc.20 In contrast, anodic electrochemical exfoliation occurswhen the graphite works as the anode, and anions from the aqueouselectrolyte intercalate in the anode. It is worth noting that anodicexfoliation is considered a greener and environmentally respectfulprocess, due to the use of water as the electrolyte which leads toa high yield of exfoliated layers; nevertheless, it can produce oxygen-centeredradicals from the anodic oxidation of water that attack the exfoliatedlayers.16Specifically, the electrochemical exfoliation has become an attractive methodologyby its operative simplicity, easy scalability, and versatility touse a wide variety of electrolytes to get exfoliated graphene nanosheetswith high yields.22 since the new functional groups promote localized effects on thegraphene layer, thus enhancing their physicochemical properties. Inparticular, several heteroatoms, including N, P, S, and B, have beenincorporated into the graphene lattice26 (doping), and nitrogen-, sulfur-,and phosphorus-based functional groups  have been used to chemically functionalize the graphene nanosheets.28 Among them, phosphorus-based functional groups are highly desirablefor electrochemical energy-storage devices since they possess an excellentelectron-donating ability improving the band gap of the functionalizedlayers. In this sense, many methodologies to functionalize or dopegraphene nanosheets with phosphorus groups have been reported; however,they are usually time-consuming or multistep processes that use expensivereagents and high-temperature post-treatments, or involve processesat high pressures.30On the other hand, thechemical surface modification of grapheneprevents the restacking of the exfoliated layers and can potentiallyimprove their electrochemical performance,31 Nonetheless, studies focused on electrochemical energystorage are scarce.32 Here, graphene nanosheets electrochemically exfoliated from graphitefoil and phosphate-functionalized ) were obtained in an expeditious and single-step processvia anodic exfoliation at room temperature. The underlying exfoliation/functionalizationmechanisms by electrochemical exfoliation of graphite using phosphoricacid (H3PO4) or sodium phosphate (Na3PO4) are proposed. Three concentrations of H3PO4  and Na3PO4 , both as the phosphate sources and the electrolytesin an aqueous solution, were studied. On the other hand, regardlessof the phosphate source , as the electrolytemolar concentration decreased, nanosheets with higher phosphate groupswere obtained. Thus, PFG-acid at 0.25 M and PFG-salt at 0.05 M exhibitedthe highest phosphorus contents ,and its specific capacitance was investigated with three- and two-electrodecells, achieving a competitive performance as a more sustainable andgreener energy-storage device.In this context, anodic exfoliation appears potentially asa powerful,affordable, and greener technique to produce exfoliated and phosphorus-containingnanosheets in one-step using mild reaction conditions without complexpost-treatments, as evidenced by recent studies.3PO4, 85% w/w aqueous solution, ACS grade), andsodium phosphate dodecahydrate  were purchased from Alfa Aesar, and sulfuric acid(1 M H2SO4) was purchased from VWR Chemicals.Deionized water was used throughout the experiments.A 500 μm-thick high-purity graphitefoil (Papyex I980) was purchased from Mersen. Phosphoric acid (H2O and deposited by drop-casting onto preheated (50–60°C) circular stainless-steel sample-holders (12 mm in diameter)for analysis by Raman spectroscopy and X-ray photoelectron spectroscopy(XPS). UV–vis absorption spectra of aqueous PFG dispersionswere obtained with a double-beam Heλios α spectrophotometer(Thermo Spectronic). Raman analysis was carried out by using a HoribaJobin-Yvon LabRam instrument at an incident laser power of 2.5 mWand a laser wavelength of 532 nm. The XPS measurements were accomplishedon a SPECS apparatus at 10–7 Pa with a nonmonochromaticMg Kα X-ray source . The recorded spectra werecurve-fitted using the AAnalyzer software, and a Shirley-Sherwoodbackground function and Voigt curve type were used. The thermogravimetricanalysis was carried out in a TA Instruments SDT Q600 apparatus, heatingthe samples from room temperature to 900 °C at 10 °C/minunder ultra-high-purity nitrogen flow (100 mL/min) and using platinumcrucibles of 90 μL as the sampler container. Scanning electronmicroscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyseswere performed using a Quanta FEG 650 apparatus from FEI Company.The samples were supported onto metallic holders with carbon adhesivetape and analyzed at a 20–25 kV voltage. Atomic force microscopy(AFM) imaging was performed in a Nanoscope IIIa Multimode system inthe tapping mode of operation and using rectangular silicon cantileverswith resonance frequencies of 250–300 kHz and nominal springconstants of 40 N m–1. Specimens for AFM were preparedby drop-casting small volumes (∼20 μL) of an aqueousdispersion of the graphene sample (∼0.01 mg mL–1) onto freshly cleaved highly oriented pyrolytic graphite (HOPG)substrates the were preheated to 50–60 °C. Transmissionelectron microscopy (TEM) and selected area electron diffraction (SAED)measurements were carried out using a JEOL JEM 2100F microscope atan acceleration voltage of 200 kV on specimens prepared by drop-casting20 μL of an aqueous dispersion of the sample (0.01 mg·mL–1) onto a copper grid (200 square mesh) covered witha lacey carbon film and allowing them to dry at room temperature.A graphene slurry was immersed in liquid nitrogen (−176 °C)and freeze-dried for 24 h using a Telstar Cryodos apparatus. The N2 adsorption isotherms were recorded at −196 °Cin an ASAP 2420 volumetric apparatus (Micromeritics), after degassingthe resulting powder overnight under vacuum at 110 °C. The specificsurface areas were obtained from the adsorption branch of the N2 isotherms by the standard Brunauer–Emmett–Teller(BET) method in the relative pressure range 0.05–0.35. PFGfilms were prepared by vacuum-filtering aqueous dispersions of thecorresponding sample through PTFE membrane filter. The electricalconductivity of the PFG films was determined through measurement oftheir resistance with a Fluke 45 digital multimeter. To this end,the films were cut into rectangular strips about 10 × 25 mm largeand their thickness was measured with a thickness gauge.PFG nanosheets were dispersed in DIH3PO4 or Na3PO4 ata specific concentration  as the anode and platinum foil(2.5 cm × 2.5 cm × 25 μm) as the cathode. Both electrodeswere located in a face-to-face parallel position at 2 cm from eachother. The electrodes were immersed in 80 mL of an aqueous solutionof Htion see 1. Then, 2SO4 (as the electrolyte). On the other hand, in the two-electrodeconfiguration the PFG nanosheets were used as both the WE and CE inthe same electrolyte (1 M H2SO4). The graphene-basedWE and CE were prepared by pressing a certain amount of dried PFGsample onto a circular piece of graphite foil (1 cm2),to a mass loading of around 1 mg cm–2. The carbonfiber-based CE was incorporated in paste form, which comprised activatedcarbon fiber as the active component, polytetrafluoroethylene as abinder, and carbon black as a conductive additive, in a weight ratioof 90:5:5, respectively. Two stacked nylon membrane filters  were used as the electrode separator.Before the cell was assembled, the WE and CE were individually soakedin 1 M H2SO4, and the assembled cell was vacuum-degassed.The energy storage performance measurements were carried out in aVSP potentiostat (Bio-Logic Science Instruments), recording cyclicvoltammograms at different sweep rates (3–500 mV s–1) and galvanostatic charge–discharge curves at different potentialcurrent densities (0.1–20 A g–1), using anelectrochemical window between −0.2 and 0.9 V vs Ag/AgCl formeasurements in the three-electrode configuration and between 0 and1.0–1.1 V in the two-electrode configuration. Electrochemicalimpedance spectroscopy (EIS) measurements were carried out for thefully discharged cell using a potential amplitude of 10 mV in a frequencyrange from 100 kHz to 0.1 Hz.The electrochemicalenergy storage experiments were performed in both three-electrodeand two-electrode configurations with a Swagelok-type cell. In thethree-electrode configuration PFG nanosheets were used as the workingelectrode (WE), commercial activated carbon fiber as the counter electrode(CE), and Ag/AgCl as the reference electrode (RE) in 1 M H3PO4 or Na3PO4 as the electrolyte and phosphate source, asshown in Graphenenanosheets decorated with phosphate groups were readily obtained ina single step via anodic exfoliation at room temperature in a shorttime using aqueous solutions of H31 concluded that using a graphite source withcompact layer stacking (HOPG) and H3PO4 as theelectrolyte, it was impossible to achieve phosphate-functionalizednanosheets by anodic exfoliation; nonetheless, Zu et al.32 achieved the phosphate functionalization viaanodic exfoliation using a graphite rod and ammonium phosphate asthe electrolyte. Moreover, Munuera et al.16 demonstrated that effective electrochemical exfoliation of graphitein different electrolytes is strongly dependent on the type of graphitesource used . In the same way, we found that the use ofgraphite with noncompact stacking such as graphite foil, readily affordedthe exfoliation and functionalization of the material via anodic exfoliationwith a phosphate-based aqueous electrolyte. As is well known, theelectrolyte concentration is also a critical factor in the anodicexfoliation process.16 For this reason,to understand the influence of this parameter on the chemical andmorphological characteristics of the resulting PFG nanosheets andtheir energy-storage behavior, both electrolytes (H3PO4 and Na3PO4) were used at differentconcentrations.A few works have made use of anodicexfoliation as a powerful toolto obtain phosphate-based functional groups on graphene nanosheetsor reduced graphene, owing to the fact that this technique is simple,fast, environmentally friendly, and scalable. Lee et al.,3PO4 and Na3PO4 electrolytes tested here. We determined the concentrationrange where the exfoliation process can be successfully achieved forboth electrolytes. As a general rule, when the electrolyte concentrationis too low, no exfoliation process is attained; this phenomenon wasobserved for H3PO4 at 0.10 M and Na3PO4 at 0.01 M. On the other hand, if the electrolyte concentrationis too high, a very fast expansion and detachment of graphite sheetsfrom the anode takes place. As a result, the attainment of well-exfoliatedgraphene nanosheets is not possible, probably because the fast detachmentof graphite fragments, leaves no time for an efficient layer-by-layerintercalation of the material to occur.16 This behavior was observed for H3PO4 at concentrationsabove 1 M. For the Na3PO4, its solubility inwater is not possible at concentrations higher than 0.25 M, so thiswas the upper concentration limit for this electrolyte. It is alsoworth noting that increasing the electrolyte molar concentration promotesan increment in the yield and consequently an improvement in the solutionconductivity.33 Thus, a good formationof intercalating aqueous ions and a better electrical exfoliationare obtained.2 , C-sp3 , C–O/C–OP (285.7 eV), epoxy , carbonyl , and carboxyl .35 The composition values obtained by the curve-fitting are shown in Table S1 (Supporting Information). It is worthhighlighting that regardless of the electrolyte type or concentrationused to obtain PFG-acid or PFG-salt, the final materials possess oxygen-basedfunctional groups. The O/C ratio without contribution from phosphategroups was calculated to determine the presence of the oxygen-basedfunctional groups, which suggested an oxidized material with an oxygencontent within the common range for anodically exfoliated graphene.37High-resolution XPS (HR-XPS) analysis of C 1sand P 2p correspondingto PFG-acid and PFG-salt at different concentrations were carriedout to examine the new chemical states. 38 Using H3PO4 or Na3PO4 as electrolytes at different concentrationsresults in exfoliated graphene with different O/C ratios, as shownin In fact, the oxidation obtained is similar thatof graphene oxideafter being subjected to an efficient reduction process.3.39 This curve comprises the 2p1/2 and 2p3/2 contributions with a gap of 0.95 eV of separationand a ratio of 2:1 (2p3/2: 2p1/2), which istypically observed for phosphate compounds.39 It is worth noting that all characterizations performed here werecarried out after a thorough purification process of all PFG samplesto remove remnants of electrolyte as well as free, nonbonded chemicalspecies. Therefore, it is reasonable to assume that the phosphategroups observed into graphene samples by XPS are those that are chemicallybonded to the graphene nanosheets.Furthermore,to get a more comprehensive insight into the phosphatespecies chemically bonded to graphene layers, HR-XPS P 2p analysiswas performed, as shown in 3PO4 possesses the highest phosphorus content, and indeed it has thehighest oxygen concentration . The oxidized species reduction suggeststhat when the electrolyte concentration is increased, it promotesa faster intercalation, minimizing the graphene oxidation. Thus, usinglow electrolyte concentration (0.25 M H3PO4 and0.05 M Na3PO4) allows a better intercalationand aqueous ions diffusion. As a result, a slower detachment and layer-by-layerexfoliation was obtained. For this reason, the PFG nanosheets producedusing low electrolyte concentrations were exposed to oxidizing conditionsfor longer times, and as such they were more functionalized with oxygen-and phosphate-based functional groups, as shown in Nonetheless, the use of lowermolar concentrations of electrolytesleads to PFG nanosheets richer in phosphorus. Also, as revealed in 3PO4 or Na3PO4 as electrolytes at different concentrationsproduce PFG materials with different thermostability and hygroscopicproperties (weight loss around 100 °C), as shown in On the other hand, thethermostability and the structural informationon the exfoliated material were obtained by thermogravimetric analysis(TGA) and Raman spectroscopy, respectively, as shown in 40 In particular, desorptionof chemisorbed water around this temperature can be reasonably relatedto water molecules associated to the phosphate groups23 and decomposition of nearby-lying oxygen groups locatedon the basal surface of graphene to give CO and CO2 alsotakes place at temperatures around 150–250 °C.41 Decomposition of oxygen groups bound to edges,rather than basal surfaces, leads to CO/CO2 evolution andhence to weight losses across the whole temperature range above ∼300°C. When the electrolyte concentration was increased, a decrementin the weight loss, both at around 200 °C and at higher temperatures,was generally observed for the PFG-acid and PFG-salt materials. Thisresult was consistent with the lower extent of functionalization (oxidationand phosphatation) of the graphene nanosheets with increasing electrolyteconcentration that the XPS measurements revealed. Moreover, the presenceof oxygen-containing and phosphate functional groups favors the interactionof the graphene materials with the atmospheric water molecules, implyingthat the amount of absorbed water will increase; this phenomenon isobserved in both PFG  materials. The wettability isan essential property in the materials applied in the electrochemicalenergy storage since this property promotes a better interaction ofthe aqueous ions with the electrode surface.It is well known that chemisorbed water moleculesand many oxygen-containingfunctional groups in highly oxidized graphenes can be removed at temperaturesaround 200 °C.–1, respectively,37 appeared in the first-order region of the spectra. Also, the 2Dband was seen in the second-order region of the spectra at ∼2700cm–1. The G band corresponds to C–C bond-stretchingvibrations in the sp2 lattice graphite/graphene materials,whereas D and D′ are defect-related bands.42 The intensity ratio between D and G bands (ID/IG ratio) can be used asa quantitative measure of the structural defects and imperfectionspresent in the lattice.42 As is well known,the intensity of the 2D band is also correlated with the amount ofdefects in the graphene lattice:43 a lowintensity of the 2D band implies a high concentration of defects.The presence ofdefects of the PFG nanosheets was evaluated byRaman spectroscopy, as shown in ID/IG ratio and anincrement in the 2D band intensity were observed, indicating moderatelyoxidized graphene materials. As revealed by the ID/IG ratio and the 2D band,the use of H3PO4 as electrolyte leads to PFGmaterials having slightly higher structural disorder than those observedusing Na3PO4-derivated materials. These resultsare in accordance with the O/C ratio behavior. Additionally, the PFGmaterials were analyzed by UV–vis spectroscopy. It can be observedthat the peak for the different PFG-acid or PFG-salt samples is locatedbetween 260 and 270 nm, as shown in Figure S1a,b (Supporting Information). This absorption peak corresponds to π→ π* transitions from electronicallyconjugated domains in carbon materials,21 and its positionat 260–270 nm is associated to graphitic/graphene materialswith low to moderate oxidation levels.37 These results are thus consistent with the O/C ratios obtained byXPS for the present graphene samples  compared with the PFG-salt (22 m2 g–1), as shown in Figure S2 (Supporting Information),which is related to the exfoliation level. The ultrasonic/centrifugationtreatment can be expected to select those nanosheets with similar lateral sizes  and also with a surfacechemistry that has a high affinity toward water , eliminating those (hydrophobic)nanosheets that are not functionalized, if the latter are really presentin the particles. The introduction of a small amount of functionalgroups to graphene nanosheets, it is possible to increase the waterdispersion stability without disturbing the inherent properties.28 On the other hand, it is very difficult to actuallydetermine whether different particles detached from the graphite anodepossess somewhat different surface chemistries. However, this is possiblynot the case: the graphite foil electrode is rather compact and shouldnot be easy to be infiltrated by the aqueous electrolyte. This meansthat, at any given time, only the graphite microparticles that arestrictly located on the surface of the foil will be expanded and finallydetached from the electrode. Only after this happens, new deeper-lyingmicroparticles will become exposed to the electrolyte, so that theycan be expanded by the electrolytic treatment and detached. Such acourse of action implies that the time any given graphite microparticleis actually subjected to the electrolytic treatment before detachingwill be more or less similar for all the particles, and thereforetheir overall characteristics  should also be similar.As shown in the AFM images 4c,d the 44 Specifically, the green and red dotted circles in the reciprocalspace corresponded to electron diffraction by crystallographic planeswith separations of 2.13 and 1.23 Å, respectively, which couldbe assigned to the {10–10} and {11–20} planes. Theseresults confirmed that PFG-acid and PFG-salt possessed substantialcrystallinity in their basal planes,45 eventhough they were functionalized to a significant extent with oxygenand phosphate groups. It is worth highlighting that PFG possessesa competitive electrical conductivity with other materials obtainedvia anodic exfoliation,37 in which thePFG-acid and PFG-salt yielded values of 8300 and 6600 S m–1, respectively, which is related to the substantial crystallinitypreviously observed.Furthermore, TEMand electron diffraction were used to evaluatethe crystalline quality of the as-prepared PFG sheets. A careful examinationon the edge structure confirmed that the PFG-salt and PFG-acid materialswere well exfoliated and appeared as continuous objects with uniformthickness over the area, as shown in Figure S3d,h, Supporting Information) was uniformlyincorporated throughout the nanosheets. The EDS-derived atomic percentagecorresponding to phosphorus was 1.5 and 1.6 at. % for PFG-acid andPFG-salt, respectively, which was comparable to the values determinedby XPS (2.2 and 1.4 at. %). Oxygen was also uniformly distributedthroughout the graphene samples, as expected .In addition, the presence of the phosphate-basedfunctional groupsin the nanosheets was evidenced by EDS mapping of phosphorus (P Ka1).As evidenced by the corresponding EDS elemental maps, phosphorus  undergoes exfoliationby intercalation of ions  with cointeractionof water molecules from an aqueous electrolyte solution.16 Specifically, the H3PO4 and Na3PO4 electrolytes possess differentspecies; X2PO4–, XPO42–, and PO43– . Since H3PO4 and Na3PO4 are a weak acid and weak base, respectively, the predominantspecies are and H2PO4–, andPO4–3 and HPO42–. The second process is electrogeneration of oxygen radicals: the use of a large anodic overpotential ; active intermediatesfrom water decomposition  are obtained at the graphiteinterface.46 These radical oxygen speciestend to oxidize the subsequent exfoliated graphene nanosheets. Onthe other hand, we know from previous electrochemical exfoliationexperiments carried out in our laboratory with different aqueous electrolytesthat working at bias voltages of 8 or even 6 V still affords exfoliationof the graphite anode, although at somewhat lower yields, but exfoliationbecomes inefficient at even lower voltages. Therefore, a bias voltageof 10 V appears as a reasonable compromise between efficiency of exfoliationand energy consumption. The third process is oxidation byradicals: Radical species oxidize the graphene layers16 and increase the aromatic ring reactivity.47 More specifically, the -OH substituent possessa high resonance donator effect, favoring further functionalizationin ortho- or para-substitutions.48 Furthermore, the presence of •OH radicals can be expectedto induce the formation of phosphate radical species (from phosphateanions), thus increasing the reactivity of this species.50 The fourth process is phosphate functionalization. The radical phosphate functional groups react with carbon atomsfrom the graphene in an addition reaction.51Para-substitution wouldbe favored since the phosphate radicals possess a significant volumeand a steric hindrance phenomenon could be present with -OH substituent.The functionalization routes for both materials are slightly different,since the H3PO4 electrolyte route is an acidmedium and the Na3PO4 electrolyte a basic medium.The formation of one C–O–P is supported by the atomicratio Na/P (2:1) obtained by EDX.The additionof phosphorus-based functional groups to graphenenanosheets is potentially attractive due to their electron-donatingability.39 The presentPFG materials were explored as an electrochemical energy-storage electrodein aqueous 1 M H2SO4 electrolyte using boththree- and two-electrode configurations. The characterization by cyclicvoltammetry(CV) curves and galvanostatic charge–discharge (GCD)profiles at different sweep rates and current densities, as well asby EIS, was carried out for the different electrolyte concentrationsin a three-electrode configuration. The recorded CV curves are shownin Figure S4 (Supporting Information) andexhibited approximately rectangular shapes for a voltage window of1.1 V , which is indicative of a charge storage behaviordominated by capacitive processes.39 All the materialsexhibited pseudocapacitive (Faradaic) reactions in the form of a pairof redox peaks in the 0.3–0.6 V range (vs Ag/AgCl), attributedto reversible C=O/C–O– reactions inquinones and P=O/P–O– in phosphategroups on the carbon surface.25 Remarkably,the samples with higher capacitance were the samples with more functionalgroups. There are two main reasons for this result, owing to the increaseof functional groups: (i) an increment in the hydrophilicity of thenanosheets and (ii) increased redox pseudocapacitance. This phenomenonwas observed for PFG nanosheets obtained with both phosphate sources.Previousstudies on PFG materials as an electrode for electrochemical capacitorsdemonstrated enhanced energy-storage performance owing to the presenceof the phosphate functional group.26 as shown in 3Na2 , whichpermits its use as an efficient auxiliary dispersant in aqueous solutions.52 In the same way, this property allows watermolecules and electrolyte ions to diffuse easier throughout the activematerial, compared with the C–O–PO3H2 functional groups (PFG-acid). This observation is consistentwith the Bode plot analysis , which shows a change in the capacitive processat medium and low frequencies (capacitive and resistance behaviorregion) according to the content of phosphorus-centered functionalgroups.Similarly, EIS measurements can be used to explorethe resistance and capacitive properties of the PFG-acid and PFG-saltsamples from their corresponding Nyquist plots,Figure S6 (SupportingInformation). All profiles exhibited an essentially triangular shape,which is characteristic of a dominantly capacitive process.53 Nonetheless, they showed a very slight slopechange at 0.4–0.5 V (vs Ag/AgCl), associated with the above-mentionedpseudocapacitive reactions. These results are in good agreement withthe observed in CV curves. The specific capacitance values derivedfrom the GCD profiles for the different graphene samples at differentcurrent density are provided in 54 Moreover,in the PFG-salt samples, the material with a higher functional groupscontent is the sample that exhibits a higher specific capacitance(356 F/g), in contrast to materials obtained using other concentrations,where the PFG-salt nanosheets possessed a shorter process (1–2Ω), compared with PFG-acid, as shown in the insets of 39 developed a graphene-based material with a high phosphorus content(3.2 at. %); nonetheless, the energy storage capacitive was 260 F/cm3.The capacitivebehavior of the PFG-acid and PFG-salt is competitivecompared with other products 2, whose In this work, we have obtained graphenematerials with substantialphosphorus content in the form of phosphate groups via a greener,one-step synthesis strategy that is attractive compared to other morecomplex approaches, such as those based on the graphite oxide route.Furthermore, the present graphene materials exhibited good capacitiveperformance. These results arise from: (i) good wettability  and 10,200W·kg–1. On the other hand, the electrode withPFG-salt at 0.05 M yielded values of 14.9 Wh·kg–1  and 9400 W·kg–1.The performance of the PFG devices was investigated by GCDtestsat different current densities at a voltage window of 1.1 and 1 Vfor PFG-acid and PFG-salt, respectively. In this case, the devicesobtained using PFG-acid at 0.25 M possess energy and power densityvalues up to 17.6 Wh·kg–3) together with the eqs S2 and S3. The results found here for thesymmetric device compared favorably to results reported in the literatureusing carbon or graphene materials. For example, the power and energydensities delivered by the PFG materials were comparable to or evenhigher than those of phosphorus-doped graphene,25 as shown in 32 or reduced graphene oxide23 have notreported results for two-electrode devices (only for their three-electrodecounterparts).The gravimetricand volumetric energy and power densities werecalculated using the total electrode mass and the electrode density and 14.9 Wh·kg–1 (21.3 Wh·L–1). Overall, the straightforwardsynthesis conditions as well as fast and facile recovery of electrolytessuggest a circular synthesis, promoting sustainable capacitive energy-storagedevices, combined with a competitive performance in two-electrodesymmetric devices and affordable synthesis.We have successfullydeveloped a straightforward approach to obtainphosphate-functionalized graphene (PFG) in a single-step via anodicexfoliation of graphite. Aqueous H


In wave physics and engineering, directional emission sets a fundamental limitation on conventional simple sources as their sizes should be sufficiently larger than their wavelength. Artificial metamaterial and animal biosonar both show potential in overcoming this limitation. Existing metamaterials arranged in periodic microstructures face great challenges in realizing complex and multiphase biosonar structures. Here, we proposed a physical directional emission model to bridge the gap between porpoises’ biosonar and artificial metamaterial. Inspired by the anatomical and physical properties of the porpoise's biosonar transmission system, we fabricated a hybrid metamaterial system composed of multiple composite structures. We validated that the hybrid metamaterial significantly increased directivity and main lobe energy over a broad bandwidth both numerically and experimentally. The device displayed efficiency in detecting underwater target and suppressing false target jamming. The metamaterial-based physical model may be helpful to achieve the physical mechanisms of porpoise biosonar detection and has diverse applications in underwater acoustic sensing, ultrasound scanning, and medical ultrasonography. Directional emitters can transmit waves to form a narrow beam, increasing the detection resolution and energy in the direction of interest. They have been widely used in applications, such as wireless communications, weather radars, quantum emitters, underwater sonars, medical ultrasonography, etc ,2. ExistMetamaterials provide a promising tool to design physical properties through the programmable design of microstructures . AcoustiHere, we propose a physics-based porpoise model (PPM) via hybrid metamaterial. Based on the complex anatomical and acoustical properties of the porpoise's head, we composed a PPM with steel maxilla, air structures, steel–water and aluminum–water composites. A physical porpoise model with programmable microstructure has been used for the first time to reconstruct complex biosonar components. In comparison with omni-directional systems, the PPM device numerically and experimentally increased directivity and main lobe energy over a broad bandwidth. Its application in underwater target detection is also investigated.Porpoises develop highly sophisticated biosonar for spatial orientation and food acquisition Fig. . Accordiφ = 0.44, aluminum–water composite with φ = 0.62, and aluminum–water composite with φ = 0.66 mimicked the melon, muscle, and connective tissue, respectively. The sound speeds of the system are tunable by changing the filling fraction of these metamaterials. Clearly, the effective medium theory provides a programmable way to design PPM by parameterizing the sound speeds in the porpoise  was placed 1 m away from the source, which was also located along the main beam axis. A second aluminum target, Object 2,  was placed 10 cm behind Object 1 as a jamming object. The hydrophone was placed 10 cm away from the object, between Object 1 and the transducer. In the experiment, the motion of Object 2 was centered on the transducer Fig. . The sout 1 Fig. . The dirNeophocaena phocaenoides) inhabiting Indo-Pacific coastal waters produce directional echolocation clicks to track prey [Finless porpoises (ack prey . Their cack prey . During ack prey . The genack prey  is appliack prey , and thaIn this paper, we have proposed a hybrid metamaterial device inspired by porpoise biosonar. In comparison with existing artificial devices ,24–26 us


In this paper, a switchable and dual-tunable terahertz absorber based on patterned graphene and vanadium dioxide is proposed and analyzed. By controlling the Fermi level of graphene and the temperature of vanadium dioxide, the device’s function can be switched and its absorbing properties can be tuned. When the vanadium dioxide is in an insulator state, the device can be switched from near-total reflection (>97%) to ultra-broadband absorption (4.5–10.61 THz) as the Fermi level of graphene changes from 0 to 0.8 eV. When the vanadium dioxide is changed to a metal state, the device can act as a single-band absorber (when the Fermi level of graphene is 0 eV) and a dual-band absorber with peaks of 4.16 THz and 7.3 THz (when the Fermi level of graphene is 0.8 eV). Additionally, the absorber is polarization-insensitive and can maintain a stable high-absorption performance within a 55° incidence angle. The multilayered structure shows great potential for switchable and tunable high-performance terahertz devices. The efficient absorption of incident waves in terahertz (THz) bands is of significance for a wide range of applications such as imaging, food quality control, communication, spectroscopy, and sensing devices ,3,4,5,6.2) is an important phase change material that represents an insulator-to-metal transition. Its conductivity can be increased by four to five orders of magnitude under light, thermal approaches, and external stimuli [5 S/m is attained. This phase change leads to a reversible transition of infrared light from transmission to reflection [2 can undergo remarkable changes in its electromagnetic characteristics and can also be applied in tunable broadband THz absorber designs [2. By controlling the Fermi levels of graphene and the temperature of VO2, the device’s function can be switched and its absorbing properties can be tuned. When VO2 is in an insulator state, the device can be switched from near-total reflection (>97%) to ultra-broadband absorption 6.11 THz (4.5–10.61 THz) as the Fermi level of graphene changes from 0 to 0.8 eV. When VO2 is transmitted to a metallic state, the device can act as a single-band absorber with an absorption band of 0.84 THz (when the Fermi energy level of graphene is 0 eV) and a dual-band absorber with absorption peaks of 4.16 THz and 7.3 THz (when the Fermi energy level of graphene is 0.8 eV). Moreover, the absorber is polarization-insensitive and can maintain a stable high-absorption performance within a 60° incidence angle. In this work, the absorption mechanism is analyzed first with an impedance matching concept [An efficient approach for realizing switchable and tunable terahertz absorbers is to combine other materials with graphene. This achieves switchable functionality and provides extra tunability. Vanadium dioxide σgσgμc=ℏv follows :(4)Zg=1σIn our simulations, we assumed a relaxation time of 2 can be described by the Drude model [−1 expresses the damping frequency, and 2 spans several orders of magnitude when it is changed from an insulator state to a metallic state by thermal and electrical stimuli [2 is difficult to control during its transition, two stable states of VO2 were taken into consideration for investigating the absorber. For the conductivity of VO2 εVO2 which is supported by a back plate. The thicknesses of the SiO2 layers are h1, h2, and h3 from bottom to top, respectively. Here, the dielectric layers act as resonance absorption spaces. The bottom of the structure is a gold mirror with a thickness of d5 = 0.2 μm. This gold mirror is thick enough to block the propagation of electromagnetic waves and reflect the energy reduced in graphene. Absorption is strengthened by this part of the gold mirror. The first layer is an ultra-thin patterned graphene film, formed by subtracting four rectangular films from a disk with a radius of 2.7 μm. The width of the interval between these different parts is d1. For the second layer, eight rectangular films with a side length of l1 and interval width d2 were subtracted from a square patterned graphene. The third layer consists of a crossed-shaped VO2 with four gold parts in the corners of the square. The square has a thickness of d4, and the side length of the outsider square is l1 and the side length of the hollow part is l4. The absorption of the different layers affects each other, which enhances overall absorption and expands bandwidth. The electric field of the patterned graphene design is concentrated to the edge because of the local surface plasmon resonance that contributes to the absorption. Narrow intervals added to the designed pattern can increase the edge of the graphene and can enhance its absorption. Moreover, the whole structure is symmetrical to ensure that the absorber is insensitive to polarizations and incident angles within a large range. The parameters of the absorber proposed are introduced below. 2’s transition is temperature. It can be tuned using electrifying and terahertz radiation. Adulteration is sometimes used to change the transition temperature in order to suit practical working conditions. of 2.25 . Each laμc = 0.8 eV. VO2 is in an insulator state with a conductivity of 10 S/m. Both the finite element method and ANSYS HFSS are applied to analyze the absorption characteristics of the absorber. A THz wave is applied perpendicular to the upper graphene surface. The periodic boundary conditions are used for the x-direction and the y-direction, and the Floquet ports are set in the z-direction. The absorption of the absorber can be calculated as follows:S parameters are obtained from ANSYS HFSS. Due to the ground gold mirror, the The initial chemical potential of the graphene is assumed as 2–gold layers and the thickness of the dielectric layers can affect the input impedance of the whole structure. To facilitate simulation work, the selection and optimization of the proposed structure parameters were conducted by using the Optimetrics function in ANSYS HFSS. The parameters proposed in Therefore, a relatively high absorption can be obtained when the reflection efficiency is close to zero. Furthermore, the equivalent input impedance (fc) is 7.56 THz, and the fractional bandwidth is 80.87%. It can be concluded that the real part of the impedance is close to 1 and that the imaginary part is close to 0, which demonstrates that the impedance of the absorber matches the free space. To further discuss the function of multilayered structures in achieving broadband absorption, the absorption curves of both single-layer and multi-layer structures are displayed in In this section, both the broadband absorption of the proposed structure and the absorptions of different parts of the structure are displayed and analyzed in In order to further disclose the mechanism of the absorber, electric field distributions of the absorber have been plotted. The frequencies corresponding to the absorption peaks of the curves plotted in In order to further discuss the mechanism of the broadband absorption mode of the absorber, the electric field distributions from both an x-y perspective and y-z perspective are given in c is the speed of light in a vacuum. The electric field is trapped in graphene layers, in the VO2 layer, and in the SiO2 dielectric layers. However, the absorption effect of the dielectric layers is less effective than other parts, corresponding to electric distribution. This can be explained by Equation (9); the imaginary parts of graphene and VO2 permittivity are larger than the dielectric layers within the THz range. In resonant frequencies of 4.91 THz and 6.86 THz, energy consumption mainly occurs in the top and second graphene layers. As the resonant frequency rises to 9.85 THz, the energy consumption of the VO2 layer is strengthened since the electric field intensity increased.The electric field intensity distributions in the y-z plane of the absorber at each peak frequency are plotted in the right side of 2. The structure acts as a broadband THz absorber when μc is 0.8 eV and VO2 is in an insulator state and as a dual-band absorber when μc is 0.8 eV and VO2 is in a metallic state. Additionally, when the voltage applied to the graphene layers is set to 0, the device acts as a single-band absorber when the VO2 is in a metallic state and as a broadband reflector when the VO2 is in an insulator state. The reflectivity is greater than 97% because the transmission coefficient of the absorber is 0 and the absorption is less than 0.03. As shown in The switchable function of the THz absorber is achieved by tuning both the Fermi energy level and the phase transition property of the VOθ) range. In this section, absorptions of the proposed absorber are plotted in contour maps to analyze their insensitivities in both the incident angles and polarization angles. In φ and incident angles θ. In φ. From our results, it can be concluded that the absorber is polarization-insensitive. This can be ascribed to the asymmetrical design of the structure. For broadband absorption, spectra with TE and TM polarized waves are represented in It is of great importance to design absorbers equipped with polarization insensitivity and tolerance within a wide incident angle (μc) for two graphene layers are hard to implement. Therefore, the Fermi energy was set the same for each graphene layer. In μc are set to 0.2 eV, 0.5 eV, and 0.8 eV, respectively. Because the relaxation time is in direct proportion to the chemical potential μc, the following expression is given: μ is the electron mobility decided by the quality of the graphene and is fixed on 1250 cm2/Vs. Therefore, the relaxation time in 2 is in an insulator state. The absorption curves of both TE and TM polarized waves are then calculated. The results indicate that the structure proposed can support different polarized incident waves. As μc increases, the absorption increases gradually and absorption peaks start to appear. Additionally, the quantity of the absorption peaks increases and the broadband absorption appears. The relationship between the Fermi energy μc and the conductivity of graphene is introduced in μc, the greater the surface impedance of the graphene. This change leads to an increase in absorption. Moreover, the relationship between central frequency (fc) and consecutive Fermi energy levels varies within a range of 0.75 eV–0.85 eV. Tuning μc in the range of 0.8 eV ± 0.05 eV, the fc of the broadband absorber can be tuned linearly. It can be concluded that the graphene also plays an important role in controlling the structure. The relaxation time (τ) of the patterned graphene is investigated because it can be changed by the quality of the graphene [Finally, we discuss the tunable function for the broadband absorber of Fermi energy level of the graphene and the relaxation time τ. In practical situations, different energy levels  to high absorption over a wide frequency range (4.5–10.61 THz) as the Fermi level of graphene changed from 0 to 0.8 eV. When VO2 was transmitted to a metal state, the device acted as a single-band absorber with absorption band 0.84 THz (when the Fermi energy level of graphene is 0 eV). When VO2 was in a metal state and the Fermi energy level of graphene was tuned to 0.8 eV, the device acted as a dual-band absorber with bands of 3.78–4.61 THz and 6.75–7.94 THz. The absorber was polarization-insensitive and could maintain a stable high absorption performance within a 55° incidence angle. Moreover, the broadband structure could maintain a stable absorption within a τ change of ±50%. With respect to the large absorption bandwidth, flexible tunability, and switchable functionality, the device is promising for various terahertz applications.In summary, a switchable, dual-tunable THz absorber based on patterned graphene and phase-change VO


Graphene is a type of two-dimensional material with special properties and complex mechanical behavior. In the process of growth or processing, graphene inevitably has various defects, which greatly influence the mechanical properties of graphene. In this paper, the mechanical properties of ideal monolayer graphene nanoribbons and monolayer graphene nanoribbons with vacancy defects were simulated using the molecular dynamics method. The effect of different defect concentrations and defect positions on the vibration frequency of nanoribbons was investigated, respectively. The results show that the vacancy defect decreases the vibration frequency of the graphene nanoribbon. The vacancy concentration and vacancy position have a certain effect on the vibration frequency of graphene nanoribbons. The vibration frequency not only decreases significantly with the increase of nanoribbon length but also with the increase of vacancy concentration. As the vacancy concentration is constant, the vacancy position has a certain effect on the vibration frequency of graphene nanoribbons. For nanoribbons with similar dispersed vacancy, the trend of vibration frequency variation is similar. The mechanical property of graphene is crucial for its reliable application, both from a technical point of view and from the perspective of understanding its fundamental interest in physics deformation [Graphene has excellent elastic properties and high intrinsic strength ,2,3,4, aormation ,21,22. Hormation , vacancyormation , grain bormation , and adsormation  are inevormation . Wang etormation  found thormation  investigormation  investigormation  studied ormation  conducteormation ,34 used ormation  measuredIn this paper, the vibration frequencies of monolayer graphene nanoribbons with different defect concentrations and different defect locations were calculated using the Forcite Tools module of MS  software and the molecular dynamics method. It is predictable that ideal graphene nanoribbons and graphene nanoribbons with different vacancy defects produce different vibrations under the same simulation conditions. The structure of graphene nanoribbons was fixed with the width (3.935 nm) and the thickness (2.0 nm), and the length increased from 8.379 nm to 23.718 nm.i  indicates the type of vacancy and i is the number of missing atoms in a supercell. For example, 3(2 + 1) indicates that the number of missing atoms in the supercell is three, and (2 + 1) indicates the combination of missing atoms. The structure of graphene nanoribbons was obtained by expanding the supercells of the above model according to the requirement. The types of vacancy defects in graphene we discuss in this paper (based on a supercell with the number of atoms 8 × 8 × 1) are shown in The structure of different vacancy supercells was expanded to study the effect of the vacancy concentration of graphene nanoribbons with different lengths on their vibration frequencies. As the vacancy concentration was certain, the effect of the vacancy position of graphene nanoribbons on their vibration frequency was also explored.The vibration frequency of graphene nanoribbons with different vacancy concentrations were obtained from the energy of the simulation results using molecular dynamics method, as shown in Therefore, the variation of bond length and bond angle mades the C-C bond energy of graphene vancancy-containing nanoribbons smaller than the ideal structure, which meant that the graphene nanoribbons containing vacancies acquired less deformation energy than that of the ideal graphene nanoribbons after bending. In addition, the deformation energy of graphene nanoribbons with multiple vacancies was converted to smaller vibration energy in the NVE system synthesis. Since the vibration energy was proportional to the square of the vibration frequency, the vibration frequency of graphene nanoribbons containing vacancies was less than that of ideal graphene nanoribbons.In contrast, the inset shows that the vibration frequency of graphene nanoribbons containing different vacancy concentrations decreased with increasing length as the nanoribbon length increased from 13 nm to about 17 nm. In particular, the vibration frequency of the graphene nanoribbons containing five vacancies decreased sharply; the reduction was greater than that of other vacancies. When the length exceeded 20 nm, the reduction in the vibration frequency changed slowly. The vibration frequencies of the nanoribbons containing single vacancies were significantly higher than those of other vacancies, mainly because the interactions between atoms around the vacancies changed little. In addition, the bond lengths and bond angles between the carbon atoms in nanoribbons containing single vacancies varied less, which had less influence on the vibration frequency.Except for a single vacancy, the decreasing trend of vibration frequency of other vacancies was not obvious. In general, compared with ideal graphene nanoribbons, the vibration frequency of nanoribbons containing vacancies decreased with increasing vacancy concentration. Therefore, vacancy concentration has a certain effect on the vibration frequency of nanoribbons.In addition, dynamic simulation of graphene nanoribbons with different vacancy positions was carried out while the vacancy concentration was kept constant to further understand the influence of different vacancy positions on the vibration frequency of nanoribbons. As shown in As the number of the vacancy in a supercell was four (V-4), the effect of different vacancy positions on the vibration frequency of graphene nanoribbons with (V-4) were discussed, as shown in Compared with other vacancies, the vibration frequency of graphene nanoribbons containing vacancies (V-6) is significantly smaller than that without vacancies  when the nanoribbon length is small, as shown in Defects are inevitable in the actual preparation and processing of graphene. The effects of vacancy defect concentrations and vacancy positions on the vibration frequency of monolayer graphene were studied using molecular dynamics simulations. The results show that vacancy defects reduce the vibration frequency of the graphene nanoribbon, and both vacancy concentration and vacancy position have an effect on the vibration frequency of graphene nanoribbons. Regardless of the presence of vacancy defects, the vibration frequency of graphene nanoribbons decreases with the increase of length. Compared with ideal nanoribbons, nanoribbons with vacancies have smaller vibration frequencies. The vibration frequency of nanoribbons decreases with increasing vacancy concentration, especially when the length of the nanoribbon is small.Furthermore, the vibration frequency of graphene nanoribbons with different vacancy positions showed little difference. The vibration frequency of the nanoribbon with dispersed vacancy was less than that of the nanoribbon with concentrated vacancy. As the vacancy positions were similar, the vibration frequency of graphene nanoribbons was close. In conclusion, both vacancy concentration and vacancy position have a certain effect on the vibration frequency of graphene nanoribbons, but the size effect of nanoribbons is the main factor.


Soluble PD-L1 (sPD-L1) has been associated with worse prognosis in numerous solid tumors. We determined sPD-L1 levels before and during nivolumab treatment in two prospective clinical trials of metastatic clear cell renal cell carcinoma (RCC) and melanoma patients, and investigated its relationship to clinical factors, biomarkers, and outcome.Using a new Single Molecule Array assay, serum sPD-L1 level were determined in RCC  and melanoma  prior to, and at two time points on treatment. Gene expression data was obtained from biopsies taken prior to, and at day 28 on treatment. Results were integrated with clinical variables, tumor PD-L1 status from immuno-histochemistry, and genomic mutation status.In RCC patients, sPD-L1 levels were higher in patients with progressive disease as their best response. For both RCC and melanoma patients, progressive or stable disease was associated with an increase in sPD-L1 on nivolumab therapy, whereas mean sPD-L1 levels did not change or declined in patients with objective responses. By categorizing RCC patients into transcriptomic molecular subtypes, we identified a subgroup where the associations between sPD-L1 and progressive disease were particularly evident. In baseline biopsies, we identified six biological processes that were associated with sPD-L1 level in both RCC and melanoma: higher sPD-L1 is associated with lower tumor expression of the Hallmark gene sets ‘hypoxia’, ‘fatty acid metabolism’, ‘glycolysis’, ‘MTORC1 signaling’ and ‘androgen response’, and with higher expression of ‘KRAS signaling_Down’.Baseline and on-therapy sPD-L1 levels in RCC have the potential to predict progressive disease on PD-1 inhibitor nivolumab. In a hypothesis-generating analysis of tumor gene expression, high baseline sPD-L1 is associated with a tumor metabolic state reflecting potentially targetable processes in both melanoma and RCC. In both trials, we observed associations between change in sPD-L1 on treatment and outcome metrics. sPD-L1 levels may further refine a nivolumab-refractory subtype of RCC within transcriptionally based subtypes of RCC. An ideal biomarker would be accessible in the periphery, relevant across multiple tumor types, and provide information to guide initial selection, combination and sequencing of therapies. Regulatory approvals for the PD-1 family of therapeutics have outpaced the development of clinically useful biomarkers for their use. Finding biomarkers for immunotherapies has proven to be particularly challenging, in part due to the dynamic nature of the tumor microenvironment and its relationship to the tumor. While sampling tumors for PD-L1 expression, tumor mutational burden (TMB) and inflammation have identified associations with response to PD-1 blockade therapy in multiple cancers including melanoma, renal cell carcinoma (RCC) has remained an outlier with respect to their utility.The PD-1 ligand (PD-L1) is a coinhibitory molecule expressed on immune cells  as well as some non-hematologic cells, such as the placenta. Tumor cells can also express PD-L1 through oncogene activation or induction by interferon-gamma.11Since PD-L1 may be expressed dynamically by both tumor cells and immune cells in the tumor microenvironment, soluble PD-L1 (sPD-L1) may be a more accessible and relevant surrogate for the total expression of PD-L1 by tumors (reviewed in Ref. 13). PD-L1 is a transmembrane protein and primarily expressed on the surface of cells, but multiple forms of sPD-L1 have been described: cleaved, secreted splice variants and exosomal PD-L1.15There is a clear need for liquid biomarkers that are broadly relevant to immunotherapy. We have developed an ultrasensitive capture assay to detect sPD-L1 using the Quanterix Single Molecule Array (SIMOA) technology. In this study, we quantified sPD-L1 in prospectively collected serum samples from patients in two biomarker-directed clinical trials of PD-1 monotherapy: advanced RCC (CheckMate 009) and melanoma (CheckMate 038 part 1). Using sPD-L1 levels at baseline and two on-treatment timepoints, we could also determine the dynamics within each patient. Somatic mutation status and gene expression data from pretreatment and on-treatment biopsies were available for a subset of patients in both trials. This study identifies clinical and biological factors associated with sPD-L1 levels and provides a comprehensive evaluation of the association between sPD-L1 metrics and therapeutic outcomes. We find that sPD-L1 is a dynamic marker of early PD on nivolumab in patients with either kidney cancer or melanoma.CheckMate 009 (NCT01358721) was an open-label, parallel, four-group, phase 1b study of nivolumab in advanced renal cancer . Part 1 of CheckMate 038  was an open-label, single arm, two group phase 1 study of nivolumab in advanced melanoma (Bristol Myers Squibb). Study design, methods, and baseline clinical and demographic features have been previously described.Tumor burden change (maximum reduction or minimum increase in index lesions) and Best Overall Response (BOR) were determined by Response Evaluation Criteria in Solid Tumors V.1.1. For analyses that require a binary definition of response , response status was defined to concur with previously published studies for CheckMate 009A previous ELISA assay (anti-human PD-L1 mAb 29E.12B1/capture and biotinylated anti-PD-L1 mAb 29E.2A3 (Biolegend)/detector) had a lower limit of detection sensitivity of 100 pg/mL of recombinant PD-L1.10.1136/jitc-2021-003527.supp1Supplementary dataPaired fresh frozen biopsies from metastatic lesions at baseline and study day 29 were used to evaluate tumor-associated lymphocytes, PD-L1 status, somatic genome sequence, and gene expression. IHC assessment of tumor-associated lymphocytes  and PD-L1 expression on the tumor cell surface (Dako PD-L1 IHC 28–8 pharmDx) have been described previously.16RNA was labeled by WT-Pico Ovation  and profiled using the HG-U219 array on the GeneTitan platform . Robust multi-array average expression values were determined for 18,562 loci (BrainArray V.10). Affymetrix data were evaluable for 72 patients in CheckMate 009  and 65 patients in CheckMate 038-P1 . Gene signature scores were calculated for the ‘Angiogenesis’, ‘T-effector’ and ‘Myeloid Inflammation’ gene sets described in the IMmotion150 trial publication (5), the Tumor Inflammation Signature (33), and ‘cytolytic’ gene set,26Association of discrete factors with response was evaluated using Fisher’s exact test. Hazard for survival was estimated from Cox proportional hazard models. HRs compare the highest tertile to the lowest tertile , the above median group to the below median group  or nominal patients whose sPDL1 values differ by IQR . Association of discrete factors with sPD-L1 level was evaluated using the Kruskal-Wallis rank sum test, the receiver operating characteristic (ROC) and the area under curve (AUC). Association of numeric factors with sPD-L1 level was evaluated using Pearson, Spearman and Kendall correlation.Gene expression data and annotation are in ArrayExpress . Analyses performed in R V.3.6.3 are available on github.com/rossmacp/sPDL1_ Publication).This study uses samples collected prospectively in two biomarker-focused clinical trials of nivolumab monotherapy. CheckMate 009 enrolled first-line (1L) and vascular endothelial growth factor receptor (VEGFR) inhibitor (VEGFi)-experienced (2+L) patients with advanced RCC, while CheckMate 038-part 1 enrolled several types of advanced melanoma and included a cohort that had previously been treated with ipilimumab. Both studies specified characterization of serum cytokine levels and tumor immune infiltration as primary outcomes. To this end, samples of sera were obtained at multiple time points on treatment, and the data available from pretreatment and on-treatment tumor biopsies includes IHC for PD-L1, gene expression and somatic mutation status.We applied our ultrasensitive SIMOA sPD-L1 assay (Methods) with sera samples obtained from patients enrolled in CheckMate 009/RCC (n=91) and CheckMate 038-P1 (n=78). sPD-L1 levels were determined at baseline (prior to initiation of nivolumab), at day 29, and at day 43 for CheckMate 038-P1 or Day 63 for CheckMate 009 . Over 90We evaluated association between baseline sPD-L1 and clinical characteristics of the patient populations . In Chec10.1136/jitc-2021-003527.supp2Supplementary dataIn CheckMate 038-P1/melanoma, we observed no significant association between sPD-L1 level and the time on therapy . We saw We evaluated association between the sPD-L1 level at each timepoint and the patient’s BOR . In CheckMate 009/RCC, median sPD-L1 was higher at all timepoints in patients with PD relative to SD or CRPR . At baseWe also evaluated association between sPD-L1 level and progression-free survival (PFS) or overall survival (OS). Hazard for PFS was increased in the highest tertile in CheckMate 009/RCC (p=0.06 on treatment at day 63), but there was no statistically significant difference in hazard for PFS or OS at any time point in either trial . HRs werGene expression data from baseline biopsies was available for 59 patients in CheckMate 009,In CheckMate 009/RCC, baseline sPD-L1 level had a negative association with the Angiogenesis transcriptional score, and positive association with presence of resting mast cells p<0.05, . We alsoIn CheckMate 038-P1/melanoma, higher baseline sPD-L1 level had negative association with the ‘Myeloid Inflammation’ score p=0.046, . We saw Six Hallmark gene sets were enriched with the same direction in GSEA results from both RCC and melanoma: high baseline sPD-L1 is associated with lower expression of genes from ‘Hypoxia’, ‘Fatty Acid Metabolism’, ‘Glycolysis’, ‘MTORC1 signaling’ and ‘Androgen Response’, and with higher expression of genes from ‘KRAS signaling_Down’. A further eight Hallmark gene sets were enriched but with the opposite direction in melanoma and RCC . These eIn CheckMate 009/RCC and CheckMate 038-P1/melanoma, serum samples were evaluated at two on-treatment timepoints, allowing investigation of the relationship between change in sPD-L1 and outcome. These analyses of paired samples excluded any cases where sPD-L1 values exceeded the ULOQ. It should be noted that patients with PD are under-represented at the later on-treatment timepoint, reducing our ability to detect association .In CheckMate 009/RCC, most patients showed an increase in sPD-L1 on therapy at day 29 and at day 63 . There was an association between the increase in sPD-L1 and BOR. The increase of sPD-L1 was least in CRPR, both at day 29 (median change +79 pg/mL) and at day 43 (median change +70 pg/mL) . At day We also evaluated the association between change in sPD-L1 and survival, and observed that increase of sPD-L1 on therapy is related to worse survival outcome both in CheckMate 009/RCC and in CheckMate 038-P1/melanoma . This reHaving observed an association between increase of sPD-L1 on therapy and poor clinical outcomes, in both CheckMate 009/RCC and CheckMate 038-P1/melanoma, we wished to further characterize the biological basis of the increase. We first compared the change in sPD-L1 at Day 29 to the change in Cibersort immune cell populations in pretreatment vs day 29 biopsies . We did We then analyzed correlation between our scores for published transcriptional gene sets, derived in pretreatment biopsies, and the change in sPD-L1 at day 29 of therapy . We founWe also analyzed correlation between the Cibersort immune cell estimates in pretreatment biopsies and the change in sPD-L1 at day 29 of therapy . In ChecFinally, we observed that in CheckMate 009/RCC patients with ccrcc1 subtype tumors had the highest median change in sPD-L1 at day 29 . We thenWe investigated possible associations to sPD-L1 levels in two prospective trials of nivolumab treatment, and found an association with some clinical characteristics, as well as association with PD and worse survival outcomes in both trials. This study is the first to report an association between serum sPD-L1 levels and clinical outcomes on nivolumab before and during treatment of metastatic ccRCC and metastatic melanoma. Furthermore, the association of PD with change in sPDL1 on treatment is the first biomarker to agree between melanoma and RCC.Our findings are consistent with sPD-L1 being a marker of aggressive disease in both RCC and melanoma,28Our analysis of gene expression in pretreatment biopsies from RCC found a clear association between low baseline sPD-L1 and higher expression of an ‘Angiogenesis’ signature that predicts a positive response to sunitinib in the ImMotion 150 trial.Interestingly, on nivolumab therapy, an increase in sPD-L1 is associated with progression in both RCC and melanoma, suggesting a potential immunologic mechanism of early resistance to PD-1 blockade in both tumor types. sPD-L1 is a noninvasive means of monitoring the early trajectory of the disease on treatment. While the association between the sPD-L1 increase at day 29 and lack of response (PD or SD) was significant in both trials, day 29 is not an optimized time point. Analysis of a full time series could refine the performance of sPDL1 as an indicator of PD. In the CheckMate 009/RCC study, prior investigations focused on exploring predictors of response to nivolumab failed to find a clinically useful predictive biomarker, which may have been due in part to the study having a low response rate relative to other nivolumab clinical trials in kidney cancer.


We report μm scale, few-layergraphene structures formed at moderate temperatures (600–700°C) and supported directly on an interfacial dielectric formedby oxidizing Si layers at the graphene/substrate interface. We showthat the thickness of this underlying dielectric support can be tailoredfurther by an additional Si intercalation of the graphene prior tooxidation. This produces quasi-freestanding, patterned graphene ondielectric SiO While isolation of graphite layersby mechanical exfoliation led the field in characterizing the materialproperties,5 andsemiconductor7 substrates or high-temperatureannealing of SiC10 has gained the most traction for producing high-qualitygraphene films. A large number of routes for further processing arenow available, such as photolithography,12 electron beam lithography,14 scanning probe lithography/etching,16 and direct laser lithography.19 However, these methods each havetheir own disadvantages, e.g., growth on a metal substrate requiresthe graphene to be transferred and patterning induces defects/contaminantsthat reduce device efficacy.21Chemical vapor deposition (CVD) on metal23 Graphene is then formed by annealing in the presence of carbon,and the metal film is subsequently removed chemically, leaving thegraphene in direct contact with the dielectric material. Althoughthis method shows great potential, metal contamination remains a majorissue.24 An alternative approach for removingmetal from the graphene has been demonstrated,25 as has a method for adding a dielectric layer under thegraphene after growth.26 Both modify thegraphene–substrate interaction, which is known to impact theelectronic properties of graphene.30 Although there is no single methodthat suits all device applications, there is a desire for transfer-freemethods that produce graphene free of contaminants and with controlof the substrate interaction, directly on dielectric surfaces. Inthis work, we demonstrate transfer-free, patterned graphene structureson SiC, with optional decoupling by forming SiO2 at thegraphene–semiconductor interface.A promising transfer-freemethod utilizes a transition-metal catalyst(Cu or Ni) deposited directly onto an oxide layer on a Si wafer.232 Thin films of Fe or Ru (1–2nm) on 6H-SiC(0001) were thermally activated by annealing to temperaturesof 600–700 °C for a short duration. This triggered transition-metalsilicide formation at the interface and the associated liberationof carbon reconstructing into graphitic (sp2) layers onthe surface. Following the growth, all samples were subsequently annealedto higher temperatures (T > 700 °C) to diffusethe metal into the bulk of the underlying SiC substrate.32 This left the graphene layers supported directly on a thin filmof Si.In our previous work, few-layer grapheneon transition-metal silicidewas prepared according to the metal-mediated approach as describedelsewhere.To demonstrate the possibility of patterning graphenewe followedthe above approach, but now with predefined metallic regions (priorto graphene growth) in regular arrays of squares or circles by meansof a simple shadow mask. The metals Fe and Ru were deposited underultrahigh vacuum (UHV) onto chemically and thermally cleaned 6H-SiCsubstrates through solid masks made of a Mo foil with openings of50 and 500 μm that were placed in proximity (<0.3 mm) tothe sample surface.32 hybridized carbon is observed at 2708.4 cm–1  a symmetric peak from the C–Si bonds inSiC appears at 1.1 eV lower binding energy.8 The spatially resolved Raman and EF-PEEM thus demonstrate that grapheneforms only within the metalized regions.The spatially resolved C 1s corelevel intensity from a similarlyprepared sample is shown in S1 and S2.These twelve spots have a |k| = 2.50 Å–1, i.e., within ±2% of what is expected for pristine graphenelayers36 and are thus interpreted as twopredominant graphene rotational domains, G1 and G2. Additional spots(M) are also observed that likely originate from an underlying bcc(110)lattice constrained by the hexagonal 6H-SiC(0001) surface. Similarfeatures have been reported for Fe thin films on hexagonal surfaces38 and are removed at a later stage.32The crystalline qualityof the graphene formed is demonstratedfrom the small spot (1.5 μm) low-energy electron diffraction(μ-LEED) pattern in 32 The spatial distributionof C 1s core level signal from this system is resolved in In our earlier work, thermalized thin films of Ru on 6H-SiC havebeen shown to produce graphene of a similar quality to those mediatedby thin films of Fe.41 rather thanby the abruptness of the patterning.The lateral resolution of the patterning can be ascertainedfromthe sharpness of the boundary between the graphene region and theSiC substrate, as shown in the low-energy electron microscopy (LEEM)image in 44 and other 2D materials.45When annealed for a longerduration, the patterned geometry andthe photoemission signal from the graphene in each growth region arewell preserved, as shown in The chemical stabilityof the patterned graphenewas tested by exposing both systems to air for 30 min. In 48 this small energy increase hints at a change in thepotential at the graphene interface. Furthermore, the intensity ofsecondary electrons (SEs) near the low-energy cutoff increases byroughly 1 order of magnitude. This can be explained by the longerinelastic mean-free path of photoelectrons associated with the widerband gap of SiO2.49 Togetherwith the higher background intensity seen from the LEED  and near-edge X-ray absorption fine structure (NEXAFS)measurements were performed both inside and outside of the graphenegrowth regions. Note that to perform spatially resolved, high-resolutionspectroscopy like this, particularly the NEXAFS, samples of metal-mediatedgraphene were produced with a patterning scale of 5 mm to compensatefor the larger spot size of the photoexcitation.To further explore the possibility of electricallydecoupling thegraphene, insulating SiO2 as previously demonstrated for CVD graphene grownon transition-metalsubstrates.26 In the first step, patternedgraphene was subjected to Si atoms at a flux of 0.15 Å/min for40 min while being heated to 450 °C. K-edge and the Si 2p and C 1s core levels for Fe- and Ru-mediatedgraphene samples. During deposition, the intensities and shapes ofthe 1s → π* excitations  are attenuatedstrongly. New and prominent peaks (Si2) appear at lower binding energiesrelative to the surface Si–C and silicide (Si1) in the Si 2pregion .52With Op signal 4c of Reg56 Inside the pattern (Region I), the graphene does not show any signsof oxidation: the π* resonances of the NEXAFS appear to be unchanged,and the energies, shapes, and intensities of the graphene core levelsare well preserved. In 5/2 signal from the Ru-mediated graphene system can no longer be distinguishedat this stage. With the presence of SiO2 verified fromthe Si 2p signal, the robustness of the graphene peaks suggests thatthe graphene is now supported directly on top of the SiO2.As expected,no signatures of graphene can be observed in the regionpreviously shadowed by the mask (Region II). The NEXAFS shows no π*resonance, and the only C 1s signals present are those correspondingto the C–C and C–Si bonds of the SiC surface.42 layer can easily be formed throughstepwise intercalation of Si and O2, in principle yieldingoxides with precise thicknesses by controlling the dosage of eachof the two constituents. Hence graphene–dielectric–semiconductorheterostructures with tailored and tunable oxide thicknesses can beproduced. This simplistic approach is suitable for producing someof the building blocks for graphene-based device applications thatrely on a semiconducting substrate/body, such as graphene-based field-effecttransistors (GFETs)58 and radiation sensors.59 Our results thus demonstrate the principle andfeasibility of transfer-free growth of graphene on dielectric, whichmay open up avenues for integrating the techniques presented intothe established framework of semiconductor device processing.The demonstrated concepts oftransfer-free and patterned grapheneformation directly on dielectric thin films is an exciting developmentthat allows structured graphene to be defined in a simple and straightforwardmanner with minimal extra processing required. Transition metals Feand Ru can be used interchangeably to predefine the growth regions,and at moderate temperatures (600–700 °C), both will yieldhigh-quality graphene that is robust against subsequent exposure toair. An underlying SiO


Therefore,we add herein a new dimension for controlling the formation of theTICT state, in addition to the solvent polarity and acceptor strengthparameters. These findings are not limited to the studied dyes, andwe expect that numerous organic carboxylic acids dyes show similarproperties.Organic dyes haveshown high efficiencies in solar cells, whichis mainly attributed to the push–pull strategy present in suchdyes upon attaching to the semiconductor surfaces. We deeply studiedthe fundamental photophysical properties of cyanoacrylic dyes, mostlythe L1 dye, and found unique emission properties that depend on manyfactors such as the solvent polarity and the concentration of thedye and could present a complete emission picture about this familyof dyes. The L1 dye shows an intramolecular charge transfer (ICT)emission state at low concentrations and shows a twisted intramolecular charge transfer (TICT) emissionstate in specific solvents upon increasing the concentration to themicromolar scale. Moreover, the associated emission lifetimes of theICT and TICT states of the L1 dye depend on solvent basicity, highlightingthe role of hydrogen bond formation on controlling such states. Densityfunctional theory calculations are performed to gain insight intothe photophysical properties of the dye and revealed that H-bondingbetween the carboxylic groups triggers the dimerization at low concentrations.Using femtosecond transient absorption, we assigned the rate of TICTformation to be in the range (160–650 fs) This dye wasdesigned as a photosensitizer in DSSCs and comprises a triphenylamineas a primary donor and the cyanoacrylic acid (CyA) as a primary acceptorand anchor group see 1b. Remar20The L1 dye (5-[4-(diphenylamino)phenyl]thiophene-2-cyanoacrylicacid (CAS 762269-56-7) was obtained from Dyenamo AB. However, thesynthesis of L1 was described earlier.Absorption andemission spectra were performed at a right angle in a 1 cm cuvetteby using a Varian Cary 5000 and an Horiba Jobin Yvon Fluorolog, respectively.Emission measurements were automatically corrected for wavelength-dependentinstrument sensitivity.21 Briefly, the sample was excited with a picosecond diode laser  at 404.6 nm (77.1 ps pulses), giving an instrumentresponse function of ca. 100 ps.The TCSPC setuphas been described in detail previously.21 Briefly, excitationof the sample with ultrafast laser pulses was performed by using afrequency-doubled Ti:Sa oscillator (Coherent Mira) output (400 nm).Fluorescence at a right angle to the excitation was passed througha Bruker SPEC 250IS spectrograph and onto the streak camera (Hamamatsustreak camera and blanking unit C5680 in combination with a SynchroscanUnit M5675). The charge-coupled device (CCD) camera (Hamamatsu Orca-ERC4742-95) was used in binning mode (2 × 2 pixels) to give a 512× 512 pixel matrix.The streak camera setup hasbeen described earlier.22 Briefly, the ca. 100 fs (1 kHz) output pulsesfrom a Coherent Legend amplifier were split, and one part was frequencydoubled for 400 nm excitation. Another part of the output was sentinto a moving CaF2 plate to produce white light as theprobe beam. After passing through the sample and a spectrograph, thelight was detected from ∼390 nm to up to 700 nm by a 512 pixelphotodiode array.A detaileddescription of thetransient absorption setup can be found in a previous publication.0) and first excited state (S1), and the absorption and emission spectra were calculatedwith the time-dependent DFT method.23 Thesecalculations were performed in acetonitrile, described implicitlyby using the polarized continuum model (PCM), with the Gaussian 16program.24 Density functional theory (DFT)calculations were performed with the 6-31G(d) basis set and the CAM-B3LYPfunctional.25 This functional is chosenas it takes long-range interactions into account, which is importantto describe ICT states.26 Relaxed potentialenergy scans of the dihedral angles ϕ1, ϕ2, and ϕ3 of L1  analysis wasperformed to quantify the degree of intramolecular charge transferin the two states. Intermolecular interactions and its impact on theabsorption spectra of L1 were investigated by using the (L1)2 dimer as a model. The S0 geometry of the (L1)2 dimer was optimized in the gas phase starting from various initialbinding conformations, and the interaction energies of all stablestructures (no imaginary frequencies) are calculated29 without (E) and with (ECP) correction for basis set superposition error (BSSE) by using thecounterpoise procedure of Boys and Bernardi.30Quantum chemicalcalculationsare performed to gain insight into the change of the absorption andemission spectra of L1 in response to its charge  and molecular aggregation (monomer vs dimer). Thegeometry of L1 and its deprotonated and various protonated forms wasoptimized in the ground of 7.3 D and by 30°, 26°, and 0° for ϕ1, ϕ2, and ϕ3, respectively. Incomparison, L1 is more polar (μ = 12 D) and more planar  in the S1 state. NBO analysis revealscharges of 0.17 and 0.28 for the triphenylamine moiety in the S0 and S1 states, respectively. This indicates thatICT occurs to a greater extent in the excited state, which is consistentwith the larger polarity of the S1 vs S0 state.This ICT is responsible for the observed trigonal planar rather thantriagonal-pyramidal geometry of the triphenylamine moiety . Sucha high association constant is matching with the low concentrationutilized for such observations.32 Thesespectral changes are not only limited to the L1 dye but are also observedin other cyanoacrylic dyes with different molecular weights such asthe D131 and L0 dyes .The new spectral bands that appear upon increasingthe L1 concentrationare assigned here to the dimers formed between L1 molecules throughthe CyA groups according to the following simple equation:Figure S4). We have excluded the possibility of L1 deprotonation atlow concentrationsby the possible traces of water present in aprotic MeCN by measuringthe absorption spectra of L1 in the presence of water and in EtOH(pure protic solvents) see S4. FigurFigure S5). The additionof the dioctylamine base is expected to deprotonate the L1, whichinhibits the formation of the dimers, giving an absorption spectrumsimilar to the monomer form of L1 . In addition, measuring the L0Br dye (a derivativeof L0 with Br instead of CN) yields similar absorption behavior tothat of L0 . These evidencespreclude the role of the CN group in the dimerization process itself.Interestingly, the equilibrium between monomers and dimers of L1can be shifted as well by only adding organic bases 3b and ac2L1a–2L1c) are less stable than those with planarorientation of the interacting pair (2L1d–2L1g), indicating that dimerization is attributed to H-bondingrather than hydrophobic association of the aromatic groups. The moststable structure (2L1g) is stabilized by two (O–H···O=C)H-bonds between the carboxylic groups and display an interaction energy ECP = −20.7 kcal/mol. Structure 2L1f is 6.3 kcal/mol less stable than 2L1g, confirmingthat dimerization is derived by the carboxylic rather than the cyanogroup.The structures of the various stable conformers of (2L1) calculatedwith CAM-B3LYP/6-31G(d) in the gas phase are given in 2L1g) wasalso optimized in acetonitrile, and its absorption spectra were calculated(see max relative to thisof the isolated monomer (429 vs 415 nm), confirming that the observedincrease in λmax with increasing the concentrationof L1 and the polarity of the environment, we excluded the formation ofexciplex or excimers.With regard to the emission data of L1, we assign the emissionat 570 nm to the ICT state, in which the charge is transferred fromthe triphenylamine to the CyA moiety as shown previously by TD-DFT.3. Apparently, a highly stablecomplex species can be formed between formamide and L1 dye . This reflects the tendency of thecyanoacrylic group to interact with the solvent molecules throughhydrogen bonding.38 Despite, the absence of monomer–dimerequilibria of L1 in formamide, the formamide complex species showas well an emission–temperature relationship reflecting thepresence of an actively excited state process, as shown in We have also measured the L1 dye in awide range of solvents withdifferent properties to correlate between the monomer–dimerequilibrium and the solvent effect on the ICT and TICT states.  dye see S7. This  dye see S7. This 3, dioxane,tetrahydrofuran, toluene, and benzene), no changes in absorption andemission bands were observed upon changes in concentration; however,L1 is expected to be in dimeric form . The absorption spectrum of L1 in CHCl3 is slightlychanged after adding the carboxylic acid but significantly changedupon adding the organic base, which confirms the presence of the L1molecules in the dimer form in nonpolar solvents. Thus, On the other hand, in nonpolar solvents +, and (L1–H+)− speciesare reported in max = 349nm. In line with experiment, the RCNH+ and R2SH+ protonated forms show red-shifted absorption spectra. However, thelower basicity of the R2S vs RCN group and the fact thatthe R2SH+ structure is 24 kcal/mol less stablethan RCNH+ indicate that the latter is the protonationform of L1 in the presence of strong acids such as HCl and TFA. Similarto experiment, calculations predicts a blue-shifted absorption ofthe deprotonated species (λmax = 366 nm) relativeto the neutral molecule. The fact that calculations overestimate andunderestimate λmax of the protonated and deprotonatedspecies, respectively, is likely due to the implicit description ofthe solvent. Charge transfer from and toward the solvent moleculessurrounding the protonated and deprotonated species would improvethe agreement with the experiment. Calculations predict an emissionspectrum of L1 with λmax = 555 nm, in a very goodagreement with the experimental value (570 nm). In comparison, theRCNH+ protonated form displays emission spectra with λmax = 645 nm, while the acetate anion possesses λmax = 505 nm. The ϕ1, ϕ2,and ϕ3 dihedral angles for the RCNH+ protonatedform in the S0 state are  andare  in the S1 state. As canbe seen, the calculations provide more accurate results for the protonatedform than the pure L1 dimers . This indicates that the TICT stateof the L1 dimer will be more stable than the ICT state of the L1 monomer.As stated previously, adding organic bases or acidsto solubleL1 shows similar effects to the monomer–dimer equilibrium invarious solvents. To investigate the impact of strong acids and baseson the absorption and emission spectra of L1, we calculated the absorptionand emission spectra of the protonated and deprotonated forms of L1in MeCN. We consider the S and two N atoms as possible protonationsites in L1. The geometry of these three protonated forms and thegeometry of the deprotonated molecule (carboxylate ion) were optimizedin the Smers see 4; thus, 39 of the solvent in 41 Clearly, the large scale motions of L1, in either ICT or TICT, dependon the H-bond interactions in the excited state. Similar solvent effectshave been detected previously but a carboxylic acid dye.32 As can be seen, only at high concentrations(dimers) and in sufficiently polar solvents, TICT is enabled as afaster deactivation channel. In nonpolar solvents, such as benzene,the L1 is expected to be in the dimeric form; however, the lifetimemeasurements are independent of concentration, and the dimers in thesenonpolar solvents show long-lived ICT emission. To check the suppressionof TICT state in L1, we measured the embedded form of L1 in the PMMAmatrix (poly(methyl methacrylate)), and as expected long-lived emissionspecies with lifetime of ca. 3.5 ns (81%) and 1.2 ns (16%) were measured.The minor 1.2 ns component is likely to represent L1 in a slightlydifferent environment, possibly interacting with specific groups ofthe PMMA.39 Comparing the lifetime emissionof L1 embedded in PMMA and in CH3Cl confirms the inabilityof dimers in nonpolar solvents to populate efficiently the TICT state.The 3.5 ns component is assumed to be close to the radiative lifetimeof L1 and a sign of a complete inhibition of the TICT formation. Similarly,the TICT formation could be completely prevented in frozen formamideby lowering the temperature to 77 K (see The time-resolved emission data were measured with a streak cameraand time-correlated single photon counting (TCSPC) to further characterizethe two emission bands. The ICT and the TICT bands were found to besolvent-dependent, showing emission lifetimes of 0.5–3.0 nsfor the ICT state and ca. 50–200 ps for the TICT state 2. The em77 K see 5b. These42 and 175 ps for the decay of the TICT state.To monitor the spectral changesof emission for L1, the transientemission of L1 in DMSO is shown herein, as it shows the most strikingspectral changes with variation of concentration. At low concentration(monomer case), the main emission centered at 550 nm is assigned primarilyto the ICT state of monomers 7, top. HFigure S10). The larger formation lifetime in D131 than in L1 can be assignedto the larger molecular size of D131. Similar correlations betweenthe dye molecule size and such large-scale motions have been discussedpreviously.15Femtosecond transient absorption spectroscopy (TA) was used tocharacterize the transition between the initially excited ICT stateand the TICT state according to the scheme shown in The observations from absorption and fluorescencespectroscopyas well as from DFT calculations are summarized in 14 indicatingthat the TICT state should have long-lived emission that the ICT state.This apparent contradiction can be understood via the degree of freedomthat the molecules have in solution and not on semiconductor surfacesor in the single crystals. In either way, it is clear now that furtherincrease of the acceptor strength of the cyanoacrylic group by dimerizationin polar solvents or by attaching it to a semiconductor surface willfacilitate the population of the TICT state, leading to red emissionin polar solvents and minimize the charge recombination in solar cells.It is worth mentioning to compare between the nature of TICT forL1 in solution and on mesoporous surfaces. We previously interpretedthat presence of the TICT state in the L1 on semiconductor surfaceshinders the charge recombination process,14 Thus,our study contributes to both fundamental and applicable understandingsfor such organic dyes.We have studied the photophysical properties of cyanoacrylic dyesin solution taking the L1 dye as model for this class of organic dyesutilized primarily in solar cells as photosensitizers. Our study revealedthe presence of monomer/dimer equilibrium with high association constant.The dimerization has been confirmed experimentally and theoreticallyto be through the carboxylic acid group. The formation of the L1 dimermodifies the strength of the acceptor group and thereby shifts theenergy level of the two lowest excited states (ICT and TICT) in polarsolvents such that TICT is stabilized sufficiently to become the lowestand fluorescent state. This opens possibilities for tuning the emissionacross the visible spectrum solely by changes in dye’s concentration.Also, we could correlate the high performance of cyanoacrylic dyesin solar cells due to the population of the TICT state through increasingthe acceptor strength of the cyanoacrylic dye.


Pancreatic cancer is a highly lethal gastrointestinal malignancy. Most patients are already in the middle to advanced stages of pancreatic cancer at the time of diagnosis and cannot be treated completely. As a single-atom planar two-dimensional crystal, graphene’s unusual electronic structure, specific electronic properties and excellent electron transport capacity make it uniquely advantageous in the field of electrochemical sensing. In this mini-review, we summarize the potential application of graphene in pancreatic cancer detection. K-Ras gene, CEA and MicroRNA are important in the early diagnosis of pancreatic cancer. Pancreatic cancer is a malignant tumor of the gastrointestinal tract with a high mortality rate. Currently, the diagnosis and treatment of pancreatic cancer are difficult . Since tA suitable tumor marker should be highly specific, sensitive and easy to detect. However, numerous clinical studies have shown that it is very difficult to find an ideal tumor marker with 100% specificity and sensitivity and whose level correlates with tumor size, stage and prognosis . In the Graphene is a new type of carbon nanomaterial discovered in 2004. With its ideal flat two-dimensional structure, unique electronic, thermal, optical and mechanical properties, it has excellent prospects for high-tech applications in electronics, mechanics, medicine and aerospace. After carbon nanotubes, it is an emerging carbon nanomaterial with great theoretical and application prospects after carbon nanotubes. As a single-atom planar two-dimensional crystal, graphene’s unusual electronic structure, specific electronic properties and excellent electron transport capacity make it uniquely advantageous in the field of high-sensitivity detection . GraphenIn this mini-review, we summarize the potential application of graphene in pancreatic cancer detection. K-Ras gene, CEA and MicroRNA are important in the early diagnosis of pancreatic cancer. Therefore, this mini-review was divided into three sections. Each section first described the value of the clinical application of the analyte. Then, we described how the electrochemical sensor can achieve sensitive detection with the assistance of graphene.A large number of studies have shown that the mutation rate of K-Ras gene in pancreatic cancer patients can reach more than 90%, and the product of K-Ras gene expression is K-Ras protein with GTPase activity . The K-RGraphene quantum dots (GQDs) were used for electrochemiluminescence (ECL) detection of K-Ras genes . To imprRecent studies have found that aberrant expression of microRNA, a highly conserved class of endogenous non-coding RNA molecules of 18–25 nucleotides in length, is also associated with pancreatic cancer . It is wCarcino-embryonic antigen (CEA), which is widely present in digestive system cancers of endodermal origin, is also present in the digestive tract of normal embryos . CEA is 2 (CS-Fc-TiO2) composite membranes onto GCE. Then, AuNPs and graphene nanohybrids were self-assembled onto the CS-Fc-TiO2 composite membrane modified electrode. This combination utilizes the strong interaction between AuNPs and carcinoembryonic antibody (anti-CEA) to further immobilize anti-CEA on the modified electrode surface, resulting in a CEA immunosensor. Due to the high surface free energy, strong adsorption affinity, good adaptability and conductivity of AuNPs, they provide more binding sites and a more suitable microenvironment for the immobilization of biomolecules. The synergistic effect of graphene and AuNPs leads to high conductivity and sensitivity, with linear detection range of 0.01–80 ng/ml for CEA and detection limit of 3.4 pg/ml (S/N = 3). The sensor showed excellent selectivity for CEA by detecting some possible interferents. The relative deviations of the results for six plasma samples were less than 10% compared with those of the commonly used clinical ELISA method. The good agreement between the two methods was obtained, and the simplicity and rapidity of the electrochemical assay showed great potential for its clinical application and for the detection of low levels of protein. 2SnZnS4 (CZTS) as the antibody marker material, with a wide linear range of 0.5 pg/ml to 20 ng/ml and a detection limit of 0.16 pg/ml.2+)-dependent DNA enzyme-assisted signal amplification and graphene quantum dot ionic liquid-ion (GQDs-IL-NF) composite membrane for highly sensitive determination of CEA. The CEA-containing nucleic acid aptamer and the hairpin DNA of the DNAzyme chain recognize the target and form a CEA-nucleic acid aptamer complex in the presence of CEA. In the presence of Pb2+, a DNAzyme-assisted signal amplification reaction was performed to produce large amounts of ssDNA. Adsorption of ssDNA onto GQDs-IL-NF-modified GCEs by π-π stacking. As a result, methylene blue-labeled substrate DNA (MB-substrate) is immobilized on the electrode and generates an electrochemical signal. Under optimal conditions, the biosensor shows a linear range of 0.5 fg/ml to 0.5 ng/ml with a detection limit of 0.34 fg/ml.Graphene, a novel material with a monolayer, two-dimensional carbon nanostructure, has a great specific surface area and excellent electronic, chemical, and mechanical properties. It also has excellent biocompatibility, which makes it extremely useful in all bioelectrical analyses. In the detection of pancreatic cancer, graphene-based biosensors can show excellent sensitivity and selectivity for both proteins (cancer markers) and DNA, making it an ideal material for the construction of efficient, fast, and sensitive detection biosensors. However, there are still some factors affecting the application of graphene in biosensors that need further detailed study. These issues include 1) the effect of the oxygen-containing functional group fraction in graphene on its electrochemical properties; 2) how to prepare graphene with high electrical conductivity and good solution dispersion; 3) the effect of heteroatom doping on the electrochemical properties and stability of graphene; 4) the connection mode and interaction between biomolecules and graphene in sensors; 5) the biocompatibility of graphene in different biosensing applications issues. These studies related to graphene-based materials will open new directions in the field of biosensor research.