TG′=G″. The modification mechanisms are different before and after percolation. Before the percolation threshold, graphene which has a molecular structure similar to asphaltene enhances asphalt, like increasing asphaltene components, and after threshold, graphene improves asphalt because of the formed graphene networks. Rotational viscosities test results show that the higher the GC is, the higher the operating temperatures are, but the operating temperatures are higher than 200 °C when GC is above 4%. The percolation helps to further develop conductive asphalt concrete for intelligence pavement, but the operating properties of GMAs need to be improved.Recently, low-cost, high-quality graphene can be obtained readily, so it is potential to prepare conductive graphene modified asphalts (GMAs). In this paper, GMAs were prepared with 0%, 2%, 4%, 6%, 8%, and 10% of graphene by weight of composites. Dynamic shear rheological experiments conducted from −30 to 120 °C illustrate that elasticity at above ambient temperatures and rutting resistance at higher temperatures are enhanced and, especially, the conceived percolation of GMAs occurs at graphene contents (GC) above 8% which were verified from three changes as GC increases, i.e., the curve characteristics of complex moduli, storage moduli at temperatures over 100 °C, temperatures when the phase angle reaches 90° and the trend of  Graphene is a kind of magic nano-material. No matter what material it is added to, it seems to have a positive impact on the properties of the material ,9,10,11.Moreno-Navarro, F. et al. , Yang, QIt is noteworthy that the modification effect of low-content GMAs is not as good as that of polymers. According to the percolation theory, when the concentration of graphene exceeds a certain value, the GMAs’ system performance will take place with an abrupt change. Perhaps, graphene will present its magic properties when it is added with a higher content. However, previous studies of GMAs have not dealt with the performances of higher-content GMAs. The reason for this may be that the price of graphene was too expensive in the near past. To our excitement, Luong, D.X. et al. obtained high-quality and low-defect graphene through fast Joule heating , which iThis paper aims to characterize the application potential of high-content GMAs in a wider temperature range, including mechanical properties, working performances, and the relationship between the microstructure of GMAs and the graphene content. For this purpose, strain sweeps, temperature sweeps and the rotational viscosity tests were conducted by dynamic shear rheometer (DSR) to comprehensively evaluate the different graphene content of GMAs. By analyzing the above results, the influence of graphene on the viscoelasticity, the mixing and compaction temperature of GMAs were determined, based on which the application potential of GMAs in engineering was evaluated, which laid a solid foundation for the future intelligent pavement application of GMAs.Graphene was purchased from Zhongke Time Nano , which is in powder form. The relevant parameters are listed in Firstly, the calculated and weighed control asphalt  was put into the oven at 120 °C for preheating. After that, it was quickly transferred to a constant temperature silicon oil bath at 145 °C for heating to make it reach the melting state. Then, the corresponding proportion of graphene was slowly added into the molten control asphalt in batches, while the graphene and asphalt were stirred at low speed. For 0%, 2% and 4% content of GMAs, they were stirred at 300 rpm for 20 min, 500 rpm for 20 min, 1000 rpm for 20 min, 2000 rpm for 20 min, and 2500 rpm for 40 min in a silicone oil bath at 145 °C to ensure it was homogeneous. For 6%, 8% and 10% content of GMAs, it was kept at constant temperature in a 150 °C silicone oil bath , the stirring process was the same as above, and, finally they were kept at high temperature until the bubbles disappeared, and then cooled to room temperature.The linear viscoelastic regions (LVEs) of GMAs were determined by using DSR, MCR 302 . For asphalt, the higher the temperature is, the longer the LVE plateau is . In viewIn order to explore the mechanical properties of asphalt at high and low temperatures, the temperature sweeps of GMAs were carried out by DSR, MCR 302. Temperature sweeps were performed with strain of 0.01%, oscillation frequency of 10 rad/s, and the temperature range reduced at the interval of 1 °C/min from −30 to 120 °C. A 25 mm parallel plate (PP25) was used to determine the overall trend of GMAs in the temperature range of −30–120 °C. In order to further analyze the results, in the temperature range from −30 to 35 °C, an 8 mm parallel plate with 1 mm gap was used, and when the temperature range was from 35–120 °C, a 25 mm parallel plate with 1 mm gap was used. Checking time continued for 10 min to eliminate thermal history and attain an equilibrium state at each measurement.In order to determine the suitable construction temperature of asphalts and explore the engineering feasibility of GMAs, the rotational viscosities of different content of GMAs were measured by MCR 302. As is known to all, asphalt is a kind of viscoelastic material. There is a glass-forming process of Newtonian fluid state to glassy state, which is shown in θ, Φ, Ψ) describe the random orientation of the platelets. Thus, the percolation threshold of nanocomposites, containing 3D, random-distributed, disc-shaped nanoparticles based on the average interparticle distance approach, can be calculated by the following formulatrV is the threshold of volume fraction of particle, d is the diameter of the graphene disk, t is the thickness of the packed graphene disk, and ipS is the maximum spacing that allows electron-hopping to take place between adjacent conductive fillers owing to quantum-mechanical tunneling. The ipS is expected to be in the order of 10 nm. For the graphene and asphalt binder used in this paper, . A is a regression constant, aE is the visco-flow activation energy (kJ·mol−1), R is the universal gas constant (8.314 J·mol−1·K−1), T is temperature in degrees K.According to the fragile liquid theory, asphalt binders are of typical fragile liquids. Thus, their temperature dependences of viscosity satisfy the Vogel–Fulcher–Tammann (VFT) equationequation . When inequation (4)η=Ae−η) and the reciprocal of the temperature 1/T, we can obtainT coefficient value, that is, Ea can be acquired, which can characterize the thermal susceptibility of asphalt in the corresponding temperature ranges.Take the logarithm from both sides of Equation (4) that is transformed into a linear relationship between the logarithmic value of the viscosity lg  with the increasing of graphene content is in concert with that of the glass transition temperature, and this temperature is much easier accurately verify. As shown in TG′=G″ with graphene content can be obviously divided into three domains. In domain I, graphene, which has a molecular structure similar to asphaltene, enhances the asphalt to some extent, like increasing asphaltene to the asphalt, thus, when graphene content is from 0% to 4%, TG′=G″ rises about 4 °C with every 2% graphene increase. In domain II, at the graphene content from 4–6%, there is a plateau of TG′=G″ at about 18 °C. This is a strong implication that there is the percolation threshold at graphene content about 8%, which is in accord with the inferred result from TG′=G″ in the same content step increasing, i.e., when graphene content increases from 8% to 10%, TG′=G″ improves about by 10 °C, that is, GMAs enter another phase, in which graphene structure plays a crucial role. Similar to the classical percolation theory equation introduced in TG′=G″ versus graphene content after percolation threshold are fitted, as shown in T is TG′=G″, 18 is the base value of transition temperature TG′=G″ as shown in TG′=G″ will be higher than 50 °C. However, due to the viscosity of GMA with high-content graphene is too large to stir homogenously, thus, the content of graphene in this study is limited to 10%.As shown in η) of all asphalt falls with the increase in temperature. Besides, at the same temperature, in comparison to the control asphalt, the viscosity of GMAs comes up along with the increase in graphene content. However, the viscosity of all asphalts is close at 180 °C, which may be due to the weakening of the influence of nanoparticles on the viscosity at higher temperature.The viscosity of an asphalt binder at high temperature is considered to be a significant characteristic to affirm the working temperature. For the sake of ensuring that the asphalt has sufficient mobility in the process of pumping and mixing, the mixing and compaction temperature were determined by measuring the rotational viscosities of control asphalt and GMAs ,33,34. A2 are shown in From the construction point of view, the most suitable viscosity range for asphalt mixing and compaction is (0.17 ± 0.02) Pa·s, (0.28 ± 0.03) Pa·s . In acco(1)At graphene content above 8%, the |G*| of GMAs at above 100 °C remains stable, which differs from those of graphene content below 8%. This implies that the percolation of GMAs occurs and graphene networks form at graphene content above 8%, which means that it is possible to make conductive asphalt concrete when the graphene content is higher than 8%;(2)The GMAs’ modification mechanisms are different before and after the percolation point, i.e., before the percolation threshold, graphene, which has a molecular structure similar to asphaltene, enhances asphalt to some extent, like increasing asphaltene, and after the percolation threshold, graphene improves asphalt because of the formed graphene networks;(3)In the temperature section of −30–120 °C, in comparison to control asphalt, as the graphene content increases, the moduli of GMAs rises gradually, and the phase angle and damping factor decrease. This illustrates that graphene boosts the elasticity and the high-temperature rutting resistance of asphalt;(4)The differences of moduli at higher temperatures between the GMAs and the control asphalt are greater than those at lower temperatures, predicting that the modification effect of graphene at higher temperatures is superior than those at lower temperatures, which is because the temperature susceptibility of graphene is much lower than that of control asphalt, and the rigid molecular structure of graphene frames GMAs at higher temperatures;(5)The temperature at δ reaching 90° rises gradually as a result of the increase in graphene content, indicating that the temperature of asphalt from viscoelastic fluid to Newtonian fluid is on the increase. When GMAs’ contents are 8% and 10%, they do not even reach 90° in the experimental temperature range. From this perspective, graphene enhances the strength and the high-temperature rutting resistance. This is also evidence that there is a percolation threshold at graphene content above 8%;(6)In terms of viscosity properties, it has been shown that adding graphene promotes the viscosity of all asphalt. The higher the content of graphene is, the bigger the viscosity is. The higher the temperature is, the closer the viscosity of different graphene content of GMAs is. Obviously, graphene improves the mixing temperature and compaction temperature of asphalts, which should be improved in the future to facilitate the pavement construction.To evaluate the potential for the intelligent pavement and modification effect of high-content graphene on asphalts, rheological experiments and rotational viscosity tests were carried out on the control asphalt and GMAs with 2%, 4%, 6%, 8% and 10% of graphene by weight. On this basis, we conclude that:


The two Dimensional (2D) materials such as MXene and graphene, are most promising materials, as they have attractive properties and attract numerous application areas like sensors, supper capacitors, displays, wearable devices, batteries, and Electromagnetic Interference (EMI) shielding. The proliferation of wireless communication and smart electronic systems urge the world to develop light weight, flexible, cost effective EMI shielding materials. The MXene and graphene mixed with polymers, nanoparticles, carbon nanomaterial, nanowires, and ions are used to create materials with different structural features under different fabrication techniques. The aerogel based hybrid composites of MXene and graphene are critically reviewed and correlate with structure, role of size, thickness, effect of processing technique, and interfacial interaction in shielding efficiency. Further, freeze drying, pyrolysis and hydrothermal treatment is a powerful tool to create excellent EMI shielding aerogels. We present here a review of MXene and graphene with various polymers and nanomaterials and their EMI shielding performances. This will help to develop a more suitable composite for modern electronic systems. The proliferation of smart electronic devices and wireless communication in the artificial intelligent age are a source of electromagnetic pollution (EMP) which is a serious universal problem. The EMP creates complexities in the natural electromagnetic environment, and is unwanted radiation which not only disturbs the general function of surrounding electronic systems but also threatens the well−being of humans ,5,6,7,8.In 2020, the world utilizes electromagnetic radiation as a jamming tool or weapon in battlefields or to destroy electronic components of the ships, radars, and flights, and destroy security of the countries. Hence, electromagnetic interference shielding is the inevitable choice around the globe ,13,14,15A), reflection (SER), and multiple reflection (SEMR). SER occurs on the surface whereas SEA and SEMR are happening within the shielding material. The wave propagating on the other side of the shielding materials is called the transmittance (T), the magnitude of which is lower than that of incident wave (I) and value of SEA, SER, and SEMR is smaller than that of I (EMI shielding can be achieved by absorption (SEhat of I . The eleWe focused on a different synthetic route of graphene (GN), MXene, and composites. GN and MXene structural features and synthesis are discussed in detail. In addition, different composite preparation methods are listed, and its effect is discussed in detail with proper comparison in the discussion. In general, aerogel or foam based composite are most attractive to scientists and have excellent EMI shielding with excellent absorption ability. 2 hybridized carbon network formed graphene. In addition, burning the dry ice by using magnesium followed by acid treatment produces GN , electrochemical exfoliation, sonication, radiation based method, and ball−milling are being used to produce GN while bottom–up follows the strategy that those are grown from metal−carbon melt, epitaxial growth on silicon carbide (SiC), dry ice method, and deposition . Multiladuces GN  . Huhickness  .,61.45,61ficantly . Wan et ficantly ,62,63. The MXene ,65.3·g−1, 0.0042 g·cm−3, respectively . The Zhu et al. study just used an electrostatic assemble of nanomaterials on the porous structure that has less effect on EMI SE and CVD, or a hydro thermal process improved porous geometry and minimized the defect of fillers [In addition, the SEed above . Thus, p fillers ,73.−3 of density, 2.4 mm of thickness, and 92.78 (vol.%) loading rate annealed at 1400 °C gave rise to 54.43 dB of highest EMI SE and the corresponding EC is 0.2012 S·cm−1. The higher annealing temperature (2800 °C) destroys EMI shielding of the composite, whereas the higher temperature repairs the defects by removing functional groups, reduced polarization loss, lessens the amorphous nature (higher amorphous nature at 1400 °C) and enhances the ohmic loss. Further, the introduction of the CNT prevents the agglomeration of GN and enhance the electric channels in the 3D network [−1 of EC while GN/PANI, Ni decorated GN/PANI and Ag decorated GN/PANI (5 wt.%) show EMI SE of 24.85, 29.33, and 24.93 dB, respectively. Therefore, metal nanoparticle decoration with GN in PANI matrix improved EMI SE compared to the GN/PANI in polyimide matrix [The many studies use PDMS as a binder to make GN-based EMI shielding materials. The 3D graphene/carbon nanotubes/polydimethylsiloxane composites (GC) was prepared by using freeze drying followed by annealing at a high temperature (2800 °C) and this is similar to the Song et al. study where they used the HC template to create the aerogel ,74. GC w network ,74. Chene matrix ,75,76. The electrical conductivity of the pure materials is high compared to the composite made from corresponding pure materials. Further, MXene based composition showed excellent EC compared to the GN. This is because of the functional group present in the MXene gave rise to a better arrangement in the polymer matrix which promoted a good electron flow path. Due to this, MXene is one of the most attractive materials in the modern electronic world. The SSE and SSE/t is depend on the density and thickness of the composite. Further, proper geometrical arrangement of the fillers is a crucial factor for better EMI shielding. In this review, we have highlighted recent progress in EMI shielding of MXene and graphene composite with different fabrication technique. The global requirement is a lightweight, flexible, cost−effective, and thinner EMI shielding material and EMI shielding over 20 dB, which is the basic requirement for the EMI shielding application in electronic devices. The graphene is synthesized by various methods in which radiative and chemical vapor deposition gives rise to good quality graphene and utilization of other methods is dependent on the types of applications. MXene synthesis also adapts various techniques and the lithium fluoride/hydrochloric acid etching is the most desirable etching method. The 2D MXene and graphene play a major role in creating different structures, especially aerogel. The freezing and freeze-drying process is used to prepare different geometric composite with excellent EMI shielding is a new approach. Further, the pyrolysis and hydrothermal process are important techniques used to achieve higher EMI shielding of the aerogel hybrid structure. The pyrolysis process of MXene created with surface titanium oxide, induces the EMI shielding while annealing of the MXene/polymer composite forms an internal conductive carbon network is another approach for excellent EMI shielding. The high temperature pyrolysis process of MXene or graphene polymer composite destroyed the EMI shielding function. The EMI shielding of graphene can be improved further by doping, decoration, oxidation, reduction, encapsulation, type of polymer, and processing technique. Thus, the proper geometrical arrangement of the fillers is a crucial factor for better EMI shielding and can be tuned by changing thickness, porosity, dielectric loss range, and complex permeability. The addition of inorganic nano composition like nanowire, ions, and nanoparticle further enhances EMI shielding and are being used to make the most powerful EMI shielding composites. The polymer/filler composites are explored to fulfil recent demand in EMI shielding in electronic devices. We hope, we have provided the fundamental understanding of MXene, graphene, and its corresponding composites to achieve a modern electronic goal in the near future.


It was found that the doping site right above C atom (T) was the most stable structure by studying three potential doping positions of the Ge and Cr atom on the graphene surface. Then, the structural parameters, density of states, and difference state density of these adsorption systems were calculated and analyzed based on the density functional calculations. The results show that the adsorption properties of GeG and CrG systems for H2 and C2H2 are obviously better than the IG system. Furthermore, by comparing the two doping systems, CrG system exhibits more outstanding adsorption performances to H2 and C2H2, especially for C2H2 gas. Finally, the highest adsorption energy (−1.436 eV) and the shortest adsorption distance (1.981 Å) indicate that Cr-doped graphene is promising in the field of C2H2 gas-sensing detection. In order to find an excellent sensing material for dissolved gases in transformer oil, the adsorption structures of intrinsic graphene (IG), Ge-doped graphene (GeG), and Cr-doped graphene (CrG) to H The oil-immersed transformer, as the key hub of a power system, undertakes the task of power transmission and transformation of the whole power grid, and its operation condition will directly affect the safety of the power network and users ,2,3,4. H2 , CH4 [10 [4 [2H2 , etc. Th [4 [2H2 ,13,14.2 adsorption behavior on doped  graphene by density functional theory (DFT) calculations and indicated that metal doping can be an ideal method to enhance the performances of a graphene-based gas sensor [2 molecule on intrinsic graphene and transition metal  -doped graphene, suggesting that the latter exhibits stronger adsorption [With the discovery of two-dimensional materials, graphene material has captured widespread attention for its excellent performances and considerable applications ,16,17. Ns sensor . Gao et sorption . Hence, 2CO) molecule in the aspect of atmospheric environment [2 and C2H2 molecules based on density functional theory (DFT). To analyze and compare the sensing mechanism and adsorption capacity of three kinds of graphene models, their geometric structures, adsorption distances, bond lengths, adsorption energies (2 and C2H2 gas molecules.Chromium (Cr) has received considerable investigation with its high electrical conductivity and excellent ductility as a transition metal (TM) atom . Germaniironment . Wang etironment . Gecim eironment . However−5 Ha, 2 × 10−3 Ha/Å, and 5 × 10−3 Ha were set for energy convergence accuracy, maximum displacement, and stress, respectively. The convergence accuracy of the Self-Consistent Field (SCF) and the k-points of the Brillouin zone were set to 1 × 10−6 Ha and 6 × 6 × 1. The setting of density of state (DOS) in Dmol3 calculation properties was selected to qualitatively analyze the electronic structure of the material by outputting the charts of the total density of state (TDOS) and partial density of state (PDOS). All of the above calculations were considered Spin polarization effect [Density functional calculations between gas molecules and three graphene-based materials were carried out in Dmol3 module of Materials Studio (MS) ,39,40. Tn effect .2 and C2H2) on three kinds of graphene-based material is defined in Equation (1).The adsorption energy  supercell with the vacuum slab of 20 Å to avoid layer interaction and the slab position of 10 Å to build a two-dimensional graphene monolayer. The models of GeG or CrG were constructed by different sites doping with a Ge or Cr atom. To obtain the steadiest doped structure, the three potential sites of metal-doped graphene structure are discussed, including the doping site right above C atom (T), the hollow site in the positive center of graphene lattice (H), and the bridge site at midpoint the two C atoms (B), which are shown in The models of Hgraphene , and Equgraphene . In whicT doping structure, while the charge transfers in GH and GB doping structures are 0.135 e and 0.032 e, respectively. The C atom of graphene and the Ge atom form the C-Ge bond by the shortest length of 1.865 Å in the GT doping structure, which is much shorter than that in GH (2.119 Å) and GB (2.279 Å) doping structures. Remarkably, the larger bind energy of 4.725 eV is consumable to form new Ge-C bonds, because the substitution doping of the T site destroys the internal structure of graphene.By comparing the detailed calculated parameters information in T doping structure are shown in The total density of state (TDOS) and partial density of state (PDOS) of GeG in GH and GB show that the tQ is 0.211 e and 0.236 e, while the charge transfer value in the GT doping structure is −0.252 e, which is higher than that of other structures. Moreover, the Cr-C bond (1.856 Å) of the GT doping structure is shortest compared with that of GH (2.031 Å) and GB (1.386 Å), but the consumable bind energy (4.732 eV) of the GT site is larger to form the new Cr-C bonds. The most stable doping configurations obtained by comparing various geometric parameters are depicted in As shown in T doping structure is depicted in Spin-polarized total DOS for IG and CrG in G2 and C2H2 molecules.According to the above analysis results, the most stable structures of doped graphene-based materials are doped by T sites, which are C atoms of the graphene structure substituted with Ge or Cr atoms. The metals doping has a strong effect on the electronic structural performances of graphene. Then, the adsorption effects of the three materials of graphene-based to oil-dissolved gas molecules are investigated based on the stable doped structures, especially the adsorption effects of H2 on intrinsic graphene, Ge-graphene, and Cr-graphene have been established, and the structures after optimization are exhibited in Figure 7. Comparing the three adsorption models, a H2 molecule tends to vertically close to the surface of IG and GeG systems, to form a stable adsorption structure, while H2 molecule adsorbs parallelly on Cr atom in CrG system. 2 molecule have small change in IG and GeG systems. Nevertheless, there are distinct variations of structural parameters in the CrG system, as the adsorption distance is obviously smaller between a H2 molecule and graphene-based material than that in IG (3.026 Å), and the H2-adsorbed Cr-graphene exits significant charge transfer (0.052 e). Therefore, these findings suggest that the CrG system is the steadiest adsorption structure to H2 molecule in metal-doped graphene.The adsorption models of H2 on IG, GeG, and CrG systems, the DOS diagrams of various systems are analyzed. According to the TDOS and PDOS of IG system displayed in 2 adsorption has a small influence on the DOS curve due to less hybridization between H-1s orbital and C-2p orbital. 2 adsorption, while the other distribution of TDOS diagram is almost unchanged in GeG system, and the varied DOS mainly caused by the 1s orbital of H atoms. As for H2 adsorption, the total DOS of the adsorption system does not change distinctly near the Fermi level in the IG and GeG system. Thus, the introduction of H2 molecules has little effect on electron properties of intrinsic graphene and Ge-graphene. As the TDOS of CrG depicted in 2 molecule and Cr-graphene mainly contributes by the hybridization of H-1s and Cr-4s orbitals, while Cr-3d orbital may be main reason for the alpha-spin and beta-spin asymmetry of TDOS. In brief, CrG system shows a stronger adsorption to a H2 molecule than that of IG and GeG systems, because of the clearly varied DOS of CrG system during the adsorption process.To further investigate the adsorption behavior of H2 molecule and Cr atom are surrounded by blue and red, respectively, which indicates that Cr atom obtains electrons from the H2 molecule. This phenomenon further confirms that charges transfer from H2 molecule to CrG, which is uniform with the results of the tQ (0.052 e). In addition, a certain amount of interaction exists because of the continuous electron area between H atom and Cr atom.2H2 in top and side views are shown in 2H2.The adsorption structures of IG, GeG, and CrG systems to C2H2 adsorption on the IG system, the C2H2 molecule is far from the graphene surface because of the weak interaction. adsE and tQ of the IG system are only −0.066 eV and −0.008 e, which are far smaller than those of GeG and CrG systems. For C2H2 adsorption on the GeG system, the C2H2 molecule is distinctly deformed after the captured C atom of C2H2 molecule by the Ge atom, while C2H2 is adsorbed on the top site of the C atom by an H atom in the IG system. It is notable that the C2H2 molecule still exhibits a planar configuration after capturing by graphene monolayer, indicating the nonactivation of C2H2 molecule during the adsorption. By comparing the adsorption parameters of GeG structures in 2H2 molecule and Ge-graphene is shorter, which indicates that the C2H2 molecule is more likely to be absorbed on Ge-graphene surface by C atom. For C2H2 adsorption on Cr-graphene, a C2H2 molecule adsorbs on Cr atom with C-Cr bond, and the bond angle of the C2H2 molecule changes significantly in the adsorption process. The C-H band was a little elongated from 1.071 Å to 1.089 Å, resulting from the impact of strong adsorption of Cr-C bonds. The adsorption energy of Cr-graphene reaches −1.436 eV, the charge transfer amounts 0.079 e, and the distance is 1.981 Å. Comparing to intrinsic graphene and Ge-graphene, Cr-graphene has the best adsorption energy, largest charge transfer, and shortest distance.For C2H2 molecule on the intrinsic graphene and Ge-graphene is relatively weaker, while Cr-graphene exhibits strong adsorption capacity owing to the huge adsorption energy (−1.436 eV). Furthermore, CrG system should be the most stable structure due to the excellent adsorption properties.In conclusion, considering the energy and structures of IG, GeG, and CrG adsorption systems, the adsorption of C2H2 system are displayed in 2H2 molecule and intrinsic graphene and the few charge transfers of adsorption. For the GeG system depicted in 2H2 molecule adsorption, suggesting the notable change of charge density and the easy transfer of electron distribution from valence to conduction band. 2H2 near −7 eV, −3 eV, and 3 eV imply that the appearance of the new peak of TDOS at these place may be caused by C2H2 adsorption. 2H2 adsorption turns magnetic Cr-graphene into a non-magnetic system. From The TDOS and PDOS distributions for C2H2 molecule and Ge atom, which infers a strong interaction between them because of a certain amount of transferred electron. A direct continuous electron region is found in 2H2 is surrounded by blue areas. This phenomenon suggests that a mass of electrons transfer from the C2H2 molecule to CrG system. The findings show that a strong chemical interaction appears between C2H2 and CrG, and results in the appearance of a new Cr-C bond. The above conclusions are uniform with the consequences of the Mulliken analysis.By analyzing the charge density difference as shown in 2 and C2H2) were investigated via a detailed DFT study. The most stable structure was explored by studying structural and electronic properties of various adsorption models. The adsorption energy, charge transfer, density of state, and other structural parameters have been employed to discuss the adsorption mechanism. It is found that both Ge doping and Cr doping by T site have most stable doping structure through researching three typical doping structures. By constructing and optimizing different adsorption models of gas molecules to IG, GeG, and CrG systems, H2 closes to Ge and Cr atom through H atom, but C atom of C2H2 directly adsorbs above Ge and Cr atom. The adsorption energies of H2 and C2H2 molecules absorbed on GeG system are −0.117 eV and −0.287 eV, and those of the CrG system are −0.390 eV and −1.436 eV, respectively. The results show that CrG system has strong adsorption abilities to H2 and C2H2 molecules, while GeG system is relatively weaker. For CrG system, the charge transfer value of Cr-graphene to C2H2 (0.079 e) is distinctly higher than that of H2 (0.052 e), confirming that the interaction between C2H2 molecule and Cr-graphene is stronger. In addition, the strong hybridization between atomic orbitals results in the more excellent adsorption performances of CrG to C2H2. Therefore, the Cr-graphene is expected to be an ideal gas-sensing material for detecting C2H2 gas.In this paper, the adsorption abilities of IG, GeG, and CrG systems towards two oil-dissolved gases (H


In case of a population-wide infectious disease outbreak, such as the novel coronavirus disease (COVID-19), people’s online activities could significantly affect public concerns and health behaviors due to difficulty in accessing credible information from reliable sources, which in turn causes people to seek necessary information on the web. Therefore, measuring and analyzing online health communication and public sentiment is essential for establishing effective and efficient disease control policies, especially in the early stage of an outbreak.This study aimed to investigate the trends of online health communication, analyze the focus of people’s anxiety in the early stages of COVID-19, and evaluate the appropriateness of online information.We collected 13,148 questions and 29,040 answers related to COVID-19 from Naver, the most popular Korean web portal . Three main methods were used in this study: (1) the structural topic model was used to examine the topics in the online questions; (2) word network analysis was conducted to analyze the focus of people’s anxiety and worry in the questions; and (3) two medical doctors assessed the appropriateness of the answers to the questions, which were primarily related to people’s anxiety.A total of 50 topics and 6 cohesive topic communities were identified from the questions. Among them, topic community 4 (suspecting COVID-19 infection after developing a particular symptom) accounted for the largest portion of the questions. As the number of confirmed patients increased, the proportion of topics belonging to topic community 4 also increased. Additionally, the prolonged situation led to a slight increase in the proportion of topics related to job issues. People’s anxieties and worries were closely related with physical symptoms and self-protection methods. Although relatively appropriate to suspect physical symptoms, a high proportion of answers related to self-protection methods were assessed as misinformation or advertisements.Search activity for online information regarding the COVID-19 outbreak has been active. Many of the online questions were related to people’s anxieties and worries. A considerable portion of corresponding answers had false information or were advertisements. The study results could contribute reference information to various countries that need to monitor public anxiety and provide appropriate information in the early stage of an infectious disease outbreak, including COVID-19. Our research also contributes to developing methods for measuring public opinion and sentiment in an epidemic situation based on natural language data on the internet. The recent appearance of the novel coronavirus disease COVID-19) has been devastating worldwide. In South Korea, hundreds of new cases have been diagnosed daily since late February 2020. The cumulative number of confirmed cases at the time of writing  exceeded 9000. Internationally, over 800,000 cases have been confirmed in more than 200 countries, areas, and territories  and [바이러스 or 폐렴]) or (코로나19 or 코로나 19 or 신종코로나 or 신종코로나 or COVID19 or COVID 19 or COVID-19). English and Korean words were mixed in the search criteria because Koreans use both languages commonly. The English translations of the Korean words used here are as follows: 코로나=corona, 우한=Wuhan, 바이러스=virus, 폐렴=pneumonia, 신종코로나=novel corona. Therefore, we included biological words such as virus or pneumonia, or a relatively formal name referring to this disease, such as COVID19 or corona19, in the search criteria. These criteria were used to identify questions and answers that were related to COVID-19 and contained at least a fraction of biological perspective, as we assumed that the biological words and formal name reflect the perspective at least a little. Since COVID-19 is a controversial issue in domestic politics, we searched for posts that contained at least some biological perspective and excluded posts written purely from a political viewpoint.Third, we isolated the questions from the selected data and again selected the questions satisfying the following search criteria: (코로나 or corona or 우한 or COVID). Questions including irrelevant words  were removed. Since dogs or cats could be infected with a different type of coronavirus than COVID-19, there were questions about it. We excluded the questions related to pets. Questions related to “corona,” the guitar-producing company in Korea, were also excluded. The advanced criteria were applied only to the questions because some users supplied answers without considering the questions’ contents. In other words, although rare, there were cases in which answers related to COVID-19 were attached to questions unrelated to COVID-19. This ensured that both questions and answers were related to COVID-19.Fourth, the duplicate questions were deleted. Q&A forum users sometimes reposted the same question or posted a similar question with a slight change in the wording, which were unhelpful. The criteria used to find duplicate questions were whether the first 50 or the last 50 characters of the question, including blank spaces, were duplicated.Fifth, the few questions (n=14) posted before January 20, 2020, were deleted, as the data in this period cannot represent public concern properly. As a result, 13,148 questions and 29,040 answers, which were assumed to be related to COVID-19, were collected. Several text-mining techniques, including structural topic modeling and word network analysis, were used to analyze public concerns from 13,148 questions. Language data analyses have often used human interpretation capability . These sAlthough text mining allows us to examine a huge amount of data, these techniques usually cannot capture delicate nuances. For example, using basic text mining techniques, determining whether the answer is correct information or a rumor is somewhat difficult. This poses a challenge to the researcher because rumors, especially convincing rumors, use similar words and connection of words with valid information. To compensate for this, we also used a method that allows medical doctors  to categorize answers to questions on a particular topic and then analyze the characteristics of those answers.In summary, three main methods were used for analysis: the structural topic model (STM), network analysis, and professional qualitative classification. Each method is described in the following sections.The STM, a type of topic modeling method, was selected to extract the overall themes or focus of 13,148 questions and examine how the theme or focus changed over time.Like most topic modeling methods developed after the latent Dirichlet allocation (LDA), the STM can extract multiple topics and the topics’ probability distribution in each document from a large number of documents. The extracted topics and their distribution are information that summarizes the given documents ,18.The topic estimation process is based on several assumptions. Topic modeling methods assume that a document is a simple set of words and a topic is a probability distribution of words . Each document contains multiple topics with specific probability distributions . It is then assumed that individual documents were randomly generated from the topics and their distribution per document, and were not directly written by humans; thus, the most probable topics and their distributions are estimated considering the given data -19.Naturally, the probability distribution of words itself does not have intuitive meaning; however, we can interpret the meaning of the topic from the probability distribution of words. When a topic is expressed qualitatively, it mainly appears as an unequal use of words. For example, suppose a topic of “cancer screening test” exists in the language materials. Certain words like “screen” or “mammography” would be used more frequently in this material than other words. Therefore, if we can deduce the word probability distributions, which are likely to produce the given documents, we can also deduce the topics’ meanings by noting the high probability words in the corresponding probability distributions.Distributions of topics in each document are also important information for interpreting the topics because they can be used to identify how each topic is realized into language material. We can also identify documents that have the highest proportion on each individual topic. For example, we can identify the top ten documents with the highest proportion of topic 2 among all documents. After reading the ten documents, we can understand the detailed context and intuitive meaning of topic 2 more accurately.In short, the topic modeling method estimates topics and their probability distributions per document that explain the given documents appropriately. Although the probability distribution itself does not provide intuitive meaning, researchers could interpret the topics’ meaning.Besides this general function of topic modeling, the STM estimates how much of the document’s meta information affects the topics’ proportion or content ,21. MetaThe application of the STM to the questions is described as follows. Of the 13,148 questions, 12 questions were additionally eliminated in the preprocessing for the STM. We only used the words that appeared in at least 2 questions and questions that contained at least 2 words, as a word that only appears in a single document or a question that contains only 1 word carries little information for topic modeling. We estimated 50 topics from the remaining 13,136 questions. The number of topics was set at 50 because there was no significant improvement in topic modeling performance after 50 as measured by the held-out likelihood  when chaAll the topics were interpreted and labeled by considering three kinds of information: the words given high probability in each topic, the words with a high frequency and exclusivity (FREX) score in each topic, and the documents with a high proportion of each topic. The importance of the high probability words and the documents estimated to have a high proportion of each topic in interpreting topics has been explained previously. The words with a high FREX score supplement the high probability words by considering exclusivity and frequency together . That isWe also used the STM to sample representative questions containing subjects related to anxiety and worry. To analyze the appropriateness of the answers to the questions related to the public’s anxiety and worry, most representative questions needed to be reselected from the entire batch of questions. Since it is impossible for a small group of human researchers to review 13,148 questions directly, the STM results were used to select questions that contained anxiety- and worry-related topics. We extracted questions that contained a high proportion of topics discussing physical symptoms and self-protection methods against COVID-19 because they were revealed as the main targets of anxiety and worry.Topic modeling is useful for identifying broad topics in a large volume of documents; however, a researcher cannot control the model to see results on specific subjects. Therefore, analyzing the relationship between particular words of interest is important in achieving our research goals.One of our research objectives was to identify the objects and contexts of anxiety and worry expressed by people. To identify the source of anxiety and worry, we extracted the top 20 words that appeared most frequently in the questions including the words “불안” or “걱정,” which are Korean words for “anxiety” and “worry,” respectively. We considered both words appearing in the same question as a linkage or an association between the words.Additionally, we created a word network using the top 50 words linked to the two Korean words referring to anxiety and worry to analyze the context of people’s anxiety and worry comprehensively. Observing individual words associated with anxiety and worry cannot accurately analyze the full context of anxiety and worry. A network of words linked to anxiety and worry allowed us to further analyze the context of anxiety and worry. Therefore, the top 50 words associated with the two Korean words referring to anxiety and worry were gathered, and the network was created. Connection criterion is a coappearance of words in the same question. This network is extremely dense because the network is made of words that are used in a similar context. Only the most prominent links were required to be selected to extract particularly prominent meanings. For this, only the links with the highest weight,  were extracted to create a subnetwork. This subnetwork was assumed to contain the most prominent contexts related to people’s anxiety and worry.The network community detection algorithm was applied to this subnetwork to extract distinguished themes from the network. This algorithm identifies relatively more cohesive communities of nodes within a network -25. WhenWalktrap was selected from the various network community detection algorithms because of its excellent performance while overcoming the “resolution problem” ,26. A reThe Walktrap algorithm was also used to identify cohesive communities of topics related to each other. The STM estimates the correlation between topics ,27. A poThat is, after estimating 50 topics from 13,136 questions, these topics were summarized into 6 topic communities using the Walktrap algorithm and then interpreted. This additional step was employed due to the fact that, although 50 topics is a great summary, it is still a lot of information for a person to grasp intuitively.Using the results of the aforementioned methods, we assessed the appropriateness of the answers to questions dealing with the main targets of anxiety and worry, and found that the main themes were physical symptoms and self-protection methods. We selected sample questions and answers that addressed these two subjects. Two medical doctors, who are family medicine specialists and the authors of this paper, classified the answers into 5 independent categories: appropriate answers, unrelated answers, wrong answers, advertisement, and other. If there was a disagreement on an answer’s category, they discussed until they reached an agreement and recorded the agreed result.The sample questions were selected by considering the proportion of topics in each question that resulted from using the STM. The themes of physical symptom and self-protection correlated with the fourth and fifth topic communities, respectively. Choosing high proportion questions from each community of topics could form good sample questions that appropriately represent each theme. Therefore, the proportion of the topic communities 4 and 5 was calculated for each question based on the topic proportion information per question. It was created by adding up the proportion of topics belonging to each topic community. The top 100 questions were selected for both topic communities 4 and 5, and the answers to each question were identified. The number of answers was 250 and 306, respectively.For the previously mentioned methods, especially STM and network analysis, to function properly, morphemes need to be extracted from our language data. That is, we need information about what kinds of words appeared from where and at what frequency. The program used to determine this is called a morphological analyzer. From the many types of morphological analyzers applicable to Korean, Komoran was used because it is resilient to the spacing problem in Korean and is sufficiently qualified, as it won awards from the National Institute of Korean Language in 2016.We would like to mention in advance a caveat regarding the words extracted from the data by Komoran; Korean and English do not respond 1:1. For example, there are several Korean words that can be translated as fever (“열” and “발열”). When translating such words into English, we numbered them .Our data included a total of 13,148 questions. Of the words that appeared in the questions, About 50 topics were estimated from 13,136 questions using the STM and were interpreted by the authors. Most topics had an apparent subject or consistent contents that allowed a precise interpretation. Some topics, however, were extracted because of expressions that appeared repeatedly in various questions, regardless of the content of the question. This is because topic modeling captures the coappearance patterns of multiple words observed in documents without considering the meanings of words. For example, if many questions on different subjects contain similar expressions, like “please answer my question or you could be cursed,” the topic model would capture that pattern and estimate the topic based on the pattern. In our model, several topics were extracted because of unique Korean language usages. In this case, we unified the interpretation of the topic as “Questions involving particular Korean language expressions without a common subject.” Additionally, we presented the most prominent Korean expression in these topics in Korean in parentheses and translated its meaning into English.The third column in The STM calculates the proportions of topics on a per-document basis. This allowed us to calculate the proportion of each topic in the entire document, which could also be used to calculate the proportion of the topic communities in the entire document. We aggregated proportions of topics belonging to the same community. Additionally, the STM calculated the proportion variation of all topics over time because the time variable was set as a covariate in our STM. The estimates of topics’ proportion changes over time could also be aggregated to produce the proportion change of the topic communities over time. Topic community 4 (questions suspecting possible COVID-19 infection after developing a particular symptom) occupied the largest proportion of all the questions. It increased sharply in late February when the number of infections had begun to increase earnestly in Korea. In We extracted 20 words that were most frequently connected with words referring to anxiety and worry  from the questions posted from January 20 to March 1, 2020. We also checked whether the list of words associated with anxiety and worry would vary with time. The period  was divided into 6 weeks, and the top words associated with anxiety and worry was extracted from the data of the 6 subperiods . During We formed a word network using the top 50 words linked to anxiety and worry and extracted its subnetwork based on the most prominent 500 links. By applying the Walktrap algorithm to the subnetwork, we could extract three cohesive word communities or three distinct themes. The answers to questions about physical symptoms were often appropriate and relatively less distorted. On the other hand, there were many advertising answers to questions related to self-protection measures.In the event of a novel infectious disease outbreak, the general population cannot easily assess the accuracy of the information regarding the disease, and there is increased reliance on online information. Obtaining appropriate and accurate information is extremely difficult, especially in the early stage of an outbreak, due to the uncertainty about the disease. There may be a delay before the governance body, such as health authorities, announces official statements regarding the disease, including symptoms, treatment, or preventive measures. However, it is unlikely that the public would refrain from seeking information and patiently wait until the accurate information becomes publicly available. In this scenario, it is more probable that the members of the populace would seek to acquire the much-needed information from other sources such as the internet.anxiety and worry in the word network analysis. This implies that the people were mainly concerned about whether developing a particular physical symptom was relevant to COVID-19 and ways to protect them from COVID-19.Consistent with previous studies, our data showed that people sought information regarding COVID-19 on the web. The analysis of 13,136 questions revealed that the largest proportion of topics was regarding anxiety and worries about possible COVID-19 infection after developing a particular symptom. The proportion of topics regarding concerns over working conditions also slightly increased as the COVID-19 outbreak became prolonged. Physical symptoms such as cough, throat pain, and sputum as well as self-protective measures such as wearing a mask were some top key words that simultaneously appeared with the words We also analyzed the appropriateness of the answers that replied to the questions. About 63% of the total answers to questions on suspecting possible COVID-19 infection after developing particular symptoms were evaluated as appropriate, while 15.6% of the answers were incorrect, implying a potential dissemination of misinformation. For questions regarding self-protective measures, such as questions asking how to wear masks properly, as much as 66.3% of the answers were advertisements. Thus, it can be assumed that the general population may have difficulty in obtaining appropriate information on self-protective measures.This study contributes to the establishment of early health communication about public concerns and anxiety observed at the early stage of COVID-19. The initial stage of the epidemic is when neither the health authorities’ policies nor people’s understanding of the epidemic has stabilized. Under these circumstances, people’s online exchange of information and emotion can have a great influence. Governments should implement proper measures to establish online health communication in the early stage of an outbreak to provide appropriate and accurate information. Considering that web data-based studies related to COVID-19 are rare at present, our research’s policy and academic value is more pronounced. Although there are studies that use web data to analyze various characteristics of public psychology for other infectious diseases, there are few studies related to COVID-19. Given that numerous countries have been affected recently and are in the initial stage of the COVID-19 outbreak, our study on South Korea, which experienced COVID-19 relatively early, could be a reference point for policy making in other countries.This study also contributes to devising methods of measuring public psychology using language data in the circumstance of an infectious disease outbreak. Understanding public psychology and culture is essential when dealing with infectious diseases  because Additionally, this study is differentiated from other studies in how we used text mining techniques. Previously, papers using health-related text data often used frequency as the main information, such as the number of Twitter mentions , or applVarious advanced analyses are possible using the data and results of this study. One of the notable results in our study is that the proportion of topic community 4 (questions suspecting possible COVID-19 infection after developing a particular symptom) seems to be linked to the actual number of confirmed patients. Considering that the symptoms observed in topic community 4  were reported as common symptoms of COVID-19 in other clinical reports, this linkage might not be a coincidence. This suggests that information extracted from web data may help identify and even predict the actual trend of infectious diseases. Future research could use sophisticated time series analyses to scrutinize this possibility. Additionally, it is noteworthy that a certain kind of question could have a high proportion of answers written from commercial motivations . This imThis study has limitations concerning the range of data. Although Naver is the most popular portal website in Korea, people are not just using this one service. For further comprehensive analysis of information and emotion exchange in online spaces, various sources of web data, including various social network services, need to be incorporated. Furthermore, since the internet user population does not appropriately represent the entire population, it is necessary to consider using the data produced through traditional methods such as surveys and the internet natural language data together.Nevertheless, this study showed how health information exchanged based on the disease transmission related to people’s anxiety and commercial interest in new infectious disease outbreak via a novel approach using online data analysis and topic modeling.


The quenching of fluorescence (FL) at the vicinity of conductive surfaces and, in particular, near a 2-D graphene layer has become an important biochemical sensing tool. The quenching is attributed to fast non-radiative energy transfer between a chromophore  and the lossy graphene layer. Increased emission rate is also observed when the QD is coupled to a resonator. Here, we combine the two effects in order to control the emission lifetime of the QD. In our case, the resonator was defined by an array of nano-holes in the oxide substrate underneath a graphene surface guide. At resonance, the surface mode of the emitted radiation is concentrated at the nano-holes. Thus, the radiation of QD at or near the holes is spatially correlated through the hole-array’s symmetry. We demonstrated an emission rate change by more than 50% as the sample was azimuthally rotated with respect to the polarization of the excitation laser. In addition to an electrical control, such control over the emission lifetime could be used to control Resonance Energy Transfer (RET) between two chromophores. The quenching of fluorescence in the vicinity of metals ,2 and itIntensity studies need to be complemented by time-resolved emission rates . ConcentScreening near the Dirac point by charged carriers depends on the amount of charge placed within a small distance away from the graphene . Again, Our ultimate goal is to explore energy transfer from one QD to another via a surface guide as a mediator. To do so effectively, we first need to control the lifetime of the energy donating QD through a simple mechanism; in our case, this will be an azimuthal rotation of the substrate.The Coupling Process and its Theoretical Considerations: the coupling process may be broken into several steps . A surface mode is sustained due to the large refractive index of graphene (ngraphene~2.6), QDs and hafnia, but not necessarily through a plasmonic mode for which the dielectric constant of graphene needs to be negative [Excitation of the chromophore  by a pump laser at frequency ωnegative .i1→f1 with i1—the initial, excited state of QD and f1—the final state, the excited dipole in the graphene. The final state, f1 may transfer its energy to another QD nearby or thermally relax. If the graphene is coupled to a resonator , then the QD may relax at a rate of Γi1→f2 with i1—the initial, excited state of the QD and f2—the final electromagnetic state within the surface resonator. That mode may propagate back and forth along the surface resonator and eventually be coupled to free space modes or back to the lossy graphene film. Coherence in our case is achieved when the surface mode is at resonance with the local periodic perturbations.The excited QD dipole is coupled non-radiatively to a charge dipole in the graphene via energy transfer ,10,11 atA third interaction channel between the standing surface mode and the dipole generated in the graphene may be possible. Its mutual coupling may be sensitive to nonlinear photonic, or phononic effects  and coulThe surface mode is coupled to free-space radiation modes and detected by a faraway detector.Furthermore,(a)when all the other parameters are kept the same, the emission rate of a chromophore coupled to a 2-D system is smaller than a chromophore coupled to a 3-D system;(b)the conductive graphene increases the emission rate through non-radiative energy transfer process, which is enabled by charge screening;(c)ET = Γi1→f1 + Γi1→f2 in the absence of other nonlinear processes (see ET/(ΓET + ΓD), where ΓET and ΓD are, respectively, the non-radiative rate of energy transfer and the radiative decay rate of a stand-alone donor. Thus, increasing or decreasing of ΓET provides an active control over the entire process. Long lifetime donors  are preferred;the effect of a resonating spatial perturbation is to further increase the emission rate of the chromophore due to an increase in the DOS near resonance . The measses see . The pro(d)the efficiency of the coupling between the QDs and the surface mode is enhanced because the resonating electromagnetic mode is mostly confined to the structure holes as we shall see below. A photon travelling back and forth within a resonating structure  forms a standing wave at resonance conditions. The resonance conditions result in enhanced intensity at some particular tilt and azimuthal rotation angles with respect to the nano-hole array ,26.see also :Excitatiβs. A standing wave is formed if a Bragg condition is met: |βs-G| = βs; G is the reciprocal wave vector of the spatial square array of holes with a pitch. The wavenumber of the surface mode may be written as, βs~k0neff = (2π/λ0) × neff. Here, λ0 is the free-space emission wavelength and neff is the effective refractive index of the surface mode .Following , once coβs = oksinθ + qG with q integer (positive or negative). At normal incidence, we may pick up the x and y coordinate along the square hole-array coordinates, βscos(φ) = q1Gx and βssin(φ) = q2Gy with q1,2–integers and for square array, Gx = Gy = G  and the coupling to the surface guide is made with every other hole-plane q = 1/2. When excited by an s-polarizations  there is a non-zero z-component (perpendicular to the guide surface) mostly in the air pillars. This implies that excited QDs, situated in, or nearby holes, are spatially correlated.The simulations indicate that the propagation along the x-direction in the surface guide may be polarized along either the y-direction  or z-direction (perpendicular to the guide surface) for excitation and emission modes. For the emission wavelength, λPolarization and dephasing: At normal incidence, the incident laser beam is polarized parallel to the guide’s surface. Simulations suggest that the pillar-interfaced, graphene surface guide supports Transverse Electric (TE) modes for the excitation and emitted wavelengths . At normal incidence and through momentum conservation, this s-polarized excitation mode is coupled to two counter-propagating TE guided modes. The de-polarization [βsL, βse are the surface wavevectors for the incident (laser) and emitted (fluorescence) modes, then, for a co-linear case, βsL + βse + G = 2π × neffcos(φ)/λL + 2π × neff/λe − 2π/Λ = 0 within 1% if we assume neff = 1.15 (see below). For a square array, we expect the transition rate to have a 90° rotation symmetry, considering two orthogonal Bragg reflectors along the x- and y-directions. Discussion on the fitting curve to the azimuthal data is provided in the rization  through Since the energy transfer depends on the distance between the graphene and chromophore, a spacer may be used to control their mutual interaction. While very thin, this spacer—a 10 nm hafnia film on the graphene—in addition to the QDs and the graphene itself, may construct a surface optical waveguide. Coupling the excitation laser to this guide, or coupling the emission to free-space radiation modes may be conveniently made through a periodic array of nano-holes in the oxide substrate under the graphene layer. The array of holes provides for spatial confinement of the surface mode, effectively increasing its propagation lifetime but also increasing the emission rate of a nearby QD via an increase in the emission’s density of states (DOS) (Purcell effect).2. A square hole-array, with a pitch of 250 nm, a hole-diameter of 30 nm and a hole-depth of ca 30 nm was defined by e-beam lithography and etched into the SiO2 layer by using CHF3. The wafer was coated with ZEP diluted 1:4 anisole, spun at 4 krpm for 30 s and baked at 150 °C. A JEOL 8100 was used to write the pattern using 2 nA current and a dose of 300 μC/cm2. The sample was developed in n-amyl acetate for 60 s, rinsed in Isopropyl Alcohol (IPA) for 30 s and then dried with N2. The devices were etched for 2 min in DC reactive ion etching (50 sccm CHF3 2 sccm O2) 50 W power at 10 mTorrAll samples were made on a 500-micron-thick p-Si wafers coated with 150 nm SiOA monolayer graphene was grown by the Chmical Vapor Deposition (CVD) method as described in . The graThe QDs  were pu2. The dots, suspended in toluene were either dip-coated or spun at 2500 RPM for 30 s.Raman spectra were taken with a 633 nm HeNe laser (above the excitation and emission wavelengths of the QD) at an intensity of 2 mW as an excitation source and a × 20 objective. Stresses in the graphene from the hafnia and the QDs may affect its 2-D line, albeit its position remained in the vicinity of 2650 1/cm. The QD emitting in the wavelength of ca 575 nm were pumped with a 90 ps, 250 μW, 405 nm laser at a pulse rate of 25 MHz. The fluence was 1000 W/cm2 spot onto a well-defined spot that was visible through the set of filters and could be visited time and again. The sample area could be viewed using a home built optical microscope that could be separated from the measurement system by a prism and which was equipped with a white light illuminator and a Charge Coupled Device (CCD) camera while viewing through the same objective. An error in repeating the measurement of the same spot was estimated as less than 10%. Uncertainties in the exact spot position may have contributed to coefficient variations. For the fluorescence data, the detector was equipped with a cut-off low-pass filter whose cut-off wavelength was 450 nm. For the time-resolved measurements, a bandpass filter between 500 and 700 nm was used (with a different detector than the one used for the fluorescence measurements).For the time-resolved and fluoresce measurements, the laser beam at 405 nm was focused by an × 5 objective to a ca 25 micron−1. It is attributed to dots that are in close proximity to the graphene guide. The medium rate is of the order of 0.2 ns−1 and is attributed to dots that are less impacted by the graphene layer. The smallest decay rate is of the order of 0.05 ns−1 and serves as a background component and could be also attributed to the photon lifetime in the waveguide. As the focal point moves away from the graphene surface, the weight of the three ensembles is shifted towards dots that are less impacted by the graphene surface.The FL curves exhibited multiple decay rates and could be properly fitted with three decay constants. In each case, the entire curve (from the stating pulse at ca 6 ns to 200 ns) was used for fitting. The largest decay rate is of the order of 2 nsHere are some considerations to the fit process that led to the evaluation of the emission rates.(1).The geometrical effect of the laser spot on the overall emission rate assessment is not straight forward. The Gaussian beam has features of a plane wave only at the focal point; yet, excitations of the dots with varying degrees of efficiency occur with the unfocused beam as well.(2).Limiting the fit to mainly one time component that is prevalent in a finite time range  runs the risk that the solution will be affected by the boundaries of the time window.(3).Having too many time constants may blur the physics of the processes.(4).Considering the fit quality by only its R-square value is insufficient. One needs to consider the distribution of the residuals about the fitting parameter see . The res2, the graphene film was much larger, approximately 5 × 5 mm2. The maps are overlaid on an image of the substrate; some cracks formed in the hafnia during the transfer of the hafnia/graphene film are noted.In A typical full fluorescence (FL) curve for sample S7 (with 10-hafnia layer on top of the graphene) exhibits a 470 nm line that is attributed to color centers of the 10 nm hafnia on graphene a. The liThe effect of focusing the laser beam on the measured time rates is shown in A more detailed description is provided below for sample S7. The QDs were deposited on the hafnia/graphene layer by use of dip-coating. Plotting the maximum count vs. azimuthal angle, φ, between the laser polarization and the hole-array orientation yields mainly two peaks, at 0° and at 180°, that allude to the stability and repeatability of the measurements  but do n−1) and the medium (of ca 0.2 ns−1) rates. The medium decay rate distribution as a function of the azimuthal rotation angle φ is shown in We concentrate on the first two major decay rates: the largest (of ca 2 nsThe error in the decay rate fit is less than 1% (and hence is contained within a data point); the error in the azimuthal angle is 0.5°. We attempted to maintain the same spot position during sample rotation. The error of maintaining that spot is estimated at less than 10%. Yet, uncertainties in the exact spot position may have contributed to coefficient variations.eff = 1.15. The largest decay rate coefficient as a function of azimuthal angle φ for samples S8 (QD under the graphene) and S9 (QD on top of graphene) are shown in If surface guide is interfaced with a relatively top thick polymer instead of air the surface guide becomes more symmetric. The 250 nm PMMA layer, used during the transfer stage of graphene was retained and no oxide was deposited on top of the graphene. Sample S2 was made of spun QD in the nano-hole array and under the graphene layer. Judged by the emission rates, the dots resides away from the graphene. As exhibited by There are a few more questions that need to be addressed:What is the role of the graphene thickness? As the graphene thickness increases so does its conductivity and thus its screening effect. If the QD are placed above the surface guide, their interaction with the hole-array would be decreased. An increase in the graphene thickness will also increase its electromagnetic losses. The effect of multilayer graphene on the lifetime of the QDs was studied by us  and otheWhat is the effect of temperature? It has been shown that the specific conductance of graphene decreases with an increase in temperature in the range 0–180 K and increases with an increase in temperature in the range 180–800 K ,34. ThisFinally, what about QDs at longer wavelengths? The effects described here are scalable up to λ~10 μm when the graphene becomes plasmonics . Beyond that wavelength, the surface guide becomes much more effective  and highWe observed variations in the quenched fluorescence’s lifetime of QDs embedded with patterned quasi two-dimensional graphene surface guides upon azimuthal rotations. These variations were as large as 50%. Since coupling to spatially resonating surface modes is also associated with large emission rates for nearby chromophore, one, in principle, could control an energy transfer from one type of dot to another via the graphene surface guide. In addition to an electrical control ,35, spat


Transparent conducting electrodes (TCEs) have attracted considerable attention towards the development of flexible optoelectronic devices. In this study, mixed-dimensional TCEs are fabricated based on the two-dimensional graphene and one-dimensional electrospun metal fiber that can address the shortcomings of each electrode. In comparison with other TCEs, the Ag fiber/graphene hybrid electrodes exhibited a highly stable morphology , low sheet resistance (approximately 11 Ω/sq), high transmittance (approximately 94%), high oxidation stability with excellent flexibility, and outstanding chemical stability. The multiple functionalities of the transparent and flexible hybrid structure highlight its potential for applications in emerging electronics and highly stable optoelectronics. As interest in these flexible optoelectronic devices increases, researches on TCEs for implementing such devices are being actively conducted. Conventional indium tin oxide (ITO) electrode has been applied in optoelectronic devices owing to high transmittance and conductivity5. However, the ITO electrode has fatal shortcomings, and its strain values are significantly low (approximately 1.1%), rendering it unsuitable for use as an electrode for emerging optoelectronic devices. Additionally, it has a high refractive index, and it requires a high vacuum and high-temperature deposition which makes ITO unsuitable for roll-to-roll manufacturing6. In this regard, various alternatives, such as carbon nanotubes (CNTs)7, graphene9, metal nanowires11, metal nanogrids12, and thin films13, that can replace ITO have been investigated in TCEs.Recently, as the demand for wearable devices increases, optoelectronic devices, such as, liquid-crystal displays (LCD)15 have been stimulated owing to their excellent electrical properties (10 Ω/sq), high optical transmittance (approximately 90%), and high strain value (approximately 11%), compared to ITO. Furthermore, these 1D metal networks do not require a high vacuum and high-temperature deposition process, which could be implemented in a roll-to-roll manufacturing16. Among the metal-network–based electrodes, the electrospun Ag fiber has attracted considerable interest because of its lower percolation threshold, as a result of its longer length (a few cm), compared to that of Ag nanowires (AgNWs), and thus has been applied in various optoelectronic devices17. Moreover, the surface roughness of the junction-free electrospun Ag fiber can be simply controlled by modifying the thickness of its Ag thin-film deposition, which is a critical problem for AgNWs.Among these alternatives, one-dimensional (1D) metal networks, such as metal nanowires and metal fiber electrodes, have been studied extensively as promising substitutes for ITO. Numerous studies on metal networks have been conducted and their applications18. Therefore, an OLED with Ag fiber electrodes exhibits non-uniform emissions at a low luminance because the current only flows through the fiber electrodes19. Thus, the fabrication of an ultrathin, gas- and thermal-stable, conductive, and flexible buffer layer for the Ag fiber electrodes is required, which can improve the non-uniform current flow caused by the network structure while maintaining the durability of the Ag fiber electrodes.However, because Ag fiber electrodes are also made of metal, their electrical characteristics are deteriorated by heat and chemical treatments when applied in device fabrication. Furthermore, owing to the nature of the metal when exposed to air and moisture, the Ag fiber electrodes are oxidized easily, which leads to a significant increase in resistance and haziness. Therefore, an additional buffer layer is required that can prevent the oxidation of the Ag fiber electrodes while maintaining their electrical characteristics. Additionally, because the Ag fiber electrodes are fabricated in a network form, current only flows through the Ag fiber, and no current flows into the empty space between the Ag fiber electrodes21. Graphene, a two-dimensional (2D) graphite structure, is considered the most promising material with outstanding electrical, optical, and thermal properties23. Particularly, graphene has excellent mechanical strength as it has surprisingly high strain values (approximately 25%). Furthermore, graphene has its unique honeycomb structure as a result of its single atomic carbon layer, which prevents small molecules such as hydrogen and water from passing through and keeps it stable against chemical agents24. Therefore, several studies have used graphene as a protection layer to prevent the oxidation of metals such as copper and nickel25. Additionally, graphene exhibits absorption of only 2.3% in the NIR range to visible light wavelengths, which minimizes the loss of transparency from the Ag fiber electrodes26.In recent studies, hybrid structures of graphene and metal nanowires have been considered alternatives to existing electrodes such as ITO for emerging electronicsIn this study, highly stable and flexible mixed-dimensional TCEs were fabricated by wet-transferring graphene manufactured by the chemical vapor deposition (CVD) method onto junction-free Ag fiber electrodes for applications in optoelectronic devices. The new nanomaterial derived from the 1D Ag fiber and 2D graphene features excellent electrode properties by complementing each other’s disadvantages while highlighting their advantages. By raising the graphene buffer layer on top of the Ag fiber electrodes, additional current flowed through the graphene, and the percolation threshold was decreased accordingly, thereby improving the overall current characteristics. Furthermore, graphene’s properties markedly improved the thermal and chemical durability of the electrodes. These Ag-fiber/graphene hybrid electrodes are expected to be applied to emerging optoelectronic devices that can feature excellent characteristics while replacing the existing electrodes.Figure −1 and 2D peak, showing the number of layers of graphene at 2,700 cm−1. Here the 2D-to-G intensity ratio was larger than 1 and there was no D band, showing the presence of disordered structure, around 1,350 cm−1. This result confirms that the wet-transfer of CVD monolayer graphene onto the Ag fiber electrodes was successful without any damage27.A Raman spectrum was acquired directly from the Ag-fiber/graphene hybrid electrodes to confirm the presence of graphene on the hybrid electrodes. Figure 28. High peak-to-valley ratio can cause electrical shorts and current leakage, which can degrade the performance of the device. 1D metal networks are not suitable for many device applications owing to their intrinsic roughness, and this causes a high leakage of currents, which leads to severe device failures30. Hence, even if the surface roughness is lower than that of AgNW, the highly porous surface morphology of the single Ag fiber is not appropriate for applications in thin-film devices. In this regard, the surface roughness of the Ag fiber can be controlled by simply modifying the thickness of its Ag thin-film deposition. A Ag thickness of 40 nm was used to fabricate the Ag fiber electrodes. Figure Rrms) with the larger width of the Ag fiber electrodes. The average RMS surface roughnesses and average peak-to-valley ratio for the Ag fiber and Ag-fiber/graphene electrodes are summarized in Table Rrms values of the Ag fiber and Ag-fiber/graphene electrodes were 32.719 and 15.676, respectively. These results demonstrate that the Ag-fiber/graphene hybrid electrodes are suitable for applications in emerging thin-film optoelectronic devices.Morphological images of the Ag fiber and Ag-fiber/graphene hybrid electrodes were acquired by using AFM. A lower surface roughness enables strong bonding and easier post-processing, and it improves the device performanceThe optical and electrical properties of the Ag fiber and Ag-fiber/graphene hybrid electrodes were investigated. First of all, Fig. 30. On the contrary, as the surface coverage increased, the network of the Ag fiber also increased, and the overall conductivity improved. Figure For both Ag fiber electrodes and Ag-fiber/graphene hybrid electrodes, the transmittance of the substrate decreased as the spinning time of PS fiber increased owing to the increase in surface coverage with increase in the spinning time. The surface coverage of Ag fiber electrodes, as a function of spinning time, is discussed in our previous paperCompared to those of the Ag fiber electrodes, the transmittance and sheet resistance of the Ag-fiber/graphene hybrid electrodes were higher and lower, respectively, which suggests that the Ag-fiber/graphene hybrid electrodes delivered better optical and electrical performances than the Ag fiber electrodes. This is because, as mentioned earlier, since the Ag fiber electrodes feature a network form, there are empty spaces where the electrodes are not present, which eventually leads to an open-circuit fault. In other words, the sheet resistance increased as the connection between the Ag fiber electrodes and the conductive probe was partially broken, and for the Ag-fiber/graphene hybrid electrodes, the CVD graphene layer covered the entire Ag fiber electrodes, which means that the current could flow through every space tightly, leading to a seamless physical contact with the conductive probe. Furthermore, the CVD graphene layer is known to be a highly stable and efficient electron transport layer. Thus, the current measurement between the Ag-fiber/graphene hybrid electrodes and the conductive probe could be highly effective, which means that the Ag-fiber/graphene hybrid electrodes are expected to provide stable electric signals and power supply. An improved electrical connection increases the potential of the Ag-fiber/graphene hybrid electrodes for application as an alternative to the existing electrodes for practical optoelectronic devices.rb) or rolled around and subsequently unrolled under a 5 mm bending radius at a speed of 3 mm s−1. The sheet resistance of each electrode was compared to its initial value . The tensile strain applied to the bent substrate was estimated by31The Ag-fiber/graphene hybrid electrodes exhibited superior mechanical flexibilities, essential for emerging flexible optoelectronic devices such as OLEDs and OSCs. A repetitive bending test was performed to investigate their mechanical durability. During the test, pieces of the Ag-fiber/PEN and Ag-fiber/graphene/PEN were rounded at various bending radius (rb). It is well known that the ITO is made of brittle materials, so it cracks upon exposure to a minimal strain. Therefore, the resistance of the ITO film rapidly increased up to 100% above rb = 5 mm. Both Ag fiber film and Ag-fiber/graphene film exhibited changes in resistance approximately smaller than 15% at difference rb values, although the resistance change of the Ag fiber film was 5% larger than that of the Ag-fiber/graphene film. Figure In Fig. To further evaluate whether the graphene layer acted as a chemically protective layer against the Ag fiber electrodes, various solutions with different pH values of 2 to 12 were prepared. The Ag fiber and Ag-fiber/graphene electrodes were then covered in each pH solution for 20 min, respectively. As shown in Fig. 33. As shown in Fig. 32. It is well known that Ag electrodes, such as the Ag nanowires and the Ag fiber, quickly oxidize when exposed to air. While the Ag electrodes are oxidized, the silver oxides are formed on the Ag fiber electrodes surface, which leads to an increase in the electrical resistivity and junction resistance of the Ag fiber34, as shown in Fig. To further evaluate the thermal stability of the Ag-fiber/graphene hybrid electrodes through the thermal-stable property of the graphene protection layer, the Ag fiber and Ag-fiber/graphene electrodes on the PEN substrates were annealed on a hot plate at 85 °C for 120 h. Their variations in resistance were measured after every 24 h. The melting point of the Ag fiber was significantly low (85 °C), even though the melting point of silver is approximately 962 °C, owing to the increased influence of the loosely bounded surface atoms of the nanostructureThe performances of Ag fiber electrodes and Ag-fiber/graphene hybrid electrodes are summarized in Table The highly transparent, flexible and stable Ag-fiber/graphene hybrid electrodes were fabricated by wet-transferring the CVD graphene onto the Ag fiber electrodes. The Ag-fiber/graphene hybrid electrodes featured excellent optical and electrical properties, chemical stability, and mechanical flexibility, and they exhibited very low surface roughnesses, as the CVD graphene layer simultaneously served as an efficient current pathway by filling the voids. Furthermore, the Ag-fiber/graphene hybrid electrodes exhibited superior long-term stability under harsh environments, such as high temperature or chemical disturbances. Overall, the use of graphene as the buffer layer in the Ag fiber electrodes ensures high stretchability, low surface roughness, and high chemical and thermal stabilities while retaining the properties of the Ag fiber electrodes. The proposed unconventional approach can advance the development of transparent electrodes for emerging electronics.2) plasma under a pressure of 500 mTorr at 90 W during 5 min to oxidize the Ag thin film not covered with the PS fiber mask. Then the substrate was immersed in an H2O2 solution to etch the oxidized Ag thin film (AgOX) and then immersed in deionized (DI) water for 30 s for complete removal of AgOX. Finally, it was left for 5 min in chloroform to remove the remaining PS fiber. The fabrication is also presented in detail in our previous report30.First, The Ag-fiber/graphene hybrid electrodes were fabricated by wet-transferring CVD graphene layer on top of the Ag fiber electrodes. A graphene monolayer was transferred by using the poly (methyl methacrylate) (PMMA)-based technique . A PMMA layer was spin-coated on a graphene/copper foil at 500 rpm for 15 s and 2,000 rpm for 30 s. The PMMA layer could act as a support layer for the graphene. After the coating, the sample was annealed at 100 °C for 60 s and dried in air. The sample was floated on an ammonium persulfate etchant (0.1 M in DI water) for 12 h until the copper foil was fully etched away. A PEN substrate with electro-spun Ag fiber electrodes was used to lift off the PMMA/graphene and then dried in air for 8 h to remove water residues trapped between the graphene and PET substrate. The sample was then immersed in acetone, isopropyl alcohol, and DI water (for 15 min in each of them) to remove the PMMA layer.A four-probe system was used to measure the sheet resistance over randomly selected points of each sample to estimate the electrical properties of the Ag-fiber/graphene hybrid electrodes. The Ag-fiber/graphene hybrid electrodes were analysed by field-emission scanning electron microscopy . Their optical properties were measured by using a Cary 5000 UV–visible spectrophotometer (Varian/Agilent). The surface topography and profiles of the hybrid electrodes were measured by using atomic force microscopy . A bending tester  with a digital multimetre was used to perform a cyclic bending test. Raman spectroscopy  at a laser excitation wavelength of 532 nm was employed to measure the graphene quality. pH solutions were prepared by mixing a solution of hydrochloric acid (HCl) and sodium hydroxide (NaOH) with DI water to test the chemical stabilities.


In recent decades we have seen an exponential growth in the amount of data gathered within psychological research without a corresponding growth of theory that could meaningfully organize these research findings. For this reason, considerable attention today is given to discussions of such broader, higher-order concepts as theory and paradigm. However, another area important to consider is the nature of the questions psychologists are asking. Key to any discussion about the scientific status of psychology or about progress in the field (scientific or otherwise) is the nature of the questions that inspire psychological research. Psychologists concerned about scientific progress and the growth of theory in the field would be well served by more robust conversations about the nature of the questions being asked. Honest, curiosity-driven questions—questions that admit to our ignorance and that express an active and optimistic yearning for what we do not yet know—can help to propel psychology forward in a manner similar to the development of theory or paradigm. However, existing as it does in the “twilight zone” between the natural sciences and the humanities, psychology is fertile ground for questions of wide-ranging natures, and thus the nature of progress in the field can be variously understood, not all of which will be “scientific.” Recent psychological research in three areas  are discussed as examples of how curiosity-driven questions being asked from a position of informed ignorance can lead to progress in the field. It is “the right question, asked the right way, rather than the accumulation of more data, that allows a field to progress.” , psychology is considered a “soft science” relative to the natural sciences . More recently, it has come to be seen as a linear, collective-level accumulation of external, objective data from a mechanistic world. The philosopher Charles Taylor . What is more, the limitations or suggestions for future research are often actually backhanded suggestions in support of the given claims . Such practices in effect anchor psychological questions to the past and to the already-known, rather than projecting them into the future and the as-yet-unknown. In as far as we root for a hypothesis, and do so at the expense of genuine, curiosity-driven questions, we run the risk of silencing the data and ignoring the subject. This can also happen when our constructs are too rigidly defined, indicating that a lack of universal agreement about even core constructs in the field is not necessarily a bad thing, that is, as long as this flexibility allows us to turn meaningfully to the data, or rather, to the subject under study. In fact, intentionally loosening up on widely held definitions can shift priority from the researcher and the past (the known), to the subject and the future (the as-yet-unknown), and yet, “That principle is one that is difficult for many scientists to swallow, because it relaxes control, gets the experimenter out of the driver’s seat, and leaves it up to the subjects […] to produce the results”  in particular. What is more, given the nature of curiosity-driven questions arising from informed ignorance, it is impossible to identify such questions on face value . In other words, while we have been referring to this as a “question,” or rather a type of question, it is in reality more of an approach or practice. Just as the question “Why am I sick?” can be scientific, moral, rhetorical, etc. Sehon , any parAn example of such a process can be seen in psychological research on consciousness. The notion of consciousness is of fundamental importance within psychology, but also in broader, non-academic discussions. It is also one of those often used, but incredibly “fuzzy,” concepts within the field . DSD should not be confused with what is known as “gender dysphoria” APA , that isnecessarily those that lead to scientific progress. In fact, psychological work in this area is often clearly non-scientific. There also remains considerable disagreement regarding just what the science is supposed to say beyond the realms of method. Taken together, this is an example of the “twilight zone” of which Ichheiser spoke and with which he was both comfortable and confident.Scientific knowledge regarding various DSDs has increased over the past several decades . As discussed above, within discussions of the scientific status of psychology it is worth reflecting on the assumptions contained in the questions posed, the degree to which they are future-oriented, and the degree to which they are responsive to, and receptive of, the subject. At the same time, not all meaningful and valuable questions need to lay the foundations for scientific progress, or any kind of progress for that matter . In our concern for the progress of “psychological science,” it is worth reflecting on the potentially progressive quality of our questions. Do they reflect an honest curiosity about the world? Are they boldly expressive and humbly receptive? To the extent that they balance between the known and the unknown, and between the “trivial order” and the “barbaric vagueness” of the given field, it is important that we recognize that not all questions are equal. Questions come in a wide range of types and they serve all sorts of ends, not all of which bespeak the possibility of scientific progress as currently understood. This is not in itself problematic, far from it. Yet, for psychologists concerned with the scientific status of the field or with the possibility of its progress as an empirical science, it is worth asking if our questions provide fertile ground for the notion of such progress in the first place.