The ultrahigh EMI shielding property of the LG-4 film originates from the excellent electrical conductivity (6740 S cm−1), as well as multi-layer structure composed of graphene laminates and insulated air pores. Moreover, the LG-4 film shows excellent flexibility and high thermal conductivity (803.1 W m−1 K−1), indicating that the film is a promising candidate for lightweight, flexible thermal conducting film with exceptional EMI shielding performance.As the demand for wearable and foldable electronic devices increases rapidly, ultrathin and flexible thermal conducting films with exceptional electromagnetic interference (EMI) shielding effectiveness (SE) are greatly needed. Large-sized graphene oxide flakes and thermal treatment were employed to fabricate lightweight, flexible and highly conductive graphene films. Compared to graphene films made of smaller-sized flakes, the graphene film made of large-sized flakes possesses less defects and more conjugated domains, leading to higher electrical and higher thermal conductivities, as well as higher EMI SE. By compressing four-layer porous graphene films together, a 14 μm-thick graphene film (LG-4) was obtained, possessing EMI SE of 73.7 dB and the specific SE divided by thickness  shielding effectiveness (SE) are greatly needed. Electromagnetic interference (EMI) shielding protection is the most effective way to prevent EM pollution.4–7 According to electromagnetic theory, the main mechanisms to reduce undesirable EM emissions include reflection of EM radiation by impedance mismatching and absorption of the EM wave energies by dielectric or magnetic loss.8 Electrically conductive materials are reflective shielding materials, which could reflect most of the incident waves, due to their high electrical conductivity. For the portion of waves able to enter shielding materials, absorption loss is the dominant consumption of this EM energy, which depends on the interaction between conducting parts of shielding materials and EM waves.7,9,10With the rapid development of information technology in recent years, electromagnetic (EM) pollution caused by electronic components of wearable and foldable equipments, such as flexible electrodes, storage devices, and smart sensors,4,11–13 For instance, the carbon nanotube (CNT) sponge with a thickness of 1.8 mm shows a high EMI shielding effectiveness (SE) of 54.8 dB and specific SE (SSE) of 5480 dB cm3 g−1 in X band.5 By adding conductive polymer and magnetic loss materials, the graphene/CNT film with a thickness of 0.6 mm can achieve EMI SE as high as 133.22 dB.14Hence, materials with high electrical conductivity, such as metals, carbon materials and conductive polymers, have been applied as effective EMI shielding materials. However, metal shielding materials have the disadvantages of high densities and easy corrosion, limiting their application in lightweight, wearable electronic equipment. With a high specific surface, outstanding thermal and electrical conductivities, carbon nanomaterials have been studied as lightweight and efficient EMI shielding materials.15–17 Moreover, the shielding films are also required to be highly thermally conductive, since electronic components of these devices, such as smart sensors and flexible electrodes,15,18,19 produce significant heat emission during operation. If the heat is not effectively dissipated, it will lead to malfunction of these source electronic devices and reduction of their service life.20,21 Hence, ultrathin, flexible and thermal conducting films with exceptional EMI SE are demanded.However, in some cases like foldable and flexible electronic devices, the thickness of the shielding films is highly restricted.−1 K−1) and ultrahigh electrical conductivity (∼104 S cm−1).22,23 Ultrathin graphene films could absorb and reflect EM waves effectively, which was widely studied as efficient shielding materials.24,25 Moreover, large-scale production of graphene films could be achieved through reduction of graphene oxide (GO) films.26,27 Based on these merits, reduced graphene oxide (rGO) films are promising to be applied as ultrathin thermal conducting films with excellent EMI SE. According to Shen's work, a 8.4 μm-thick rGO film with EMI SE of 20 dB and in-plane thermal conductivity of 1100 W m−1 K−1 was obtained by thermal annealing of GO film at 2000 °C.20 Through improving reduction temperature, higher electrical and thermal conductivities, as well as EMI shielding performance were achieved.13,21 By graphitization of GO films at 3000 °C, Xi et al. has fabricated the foam-like graphene films, with EMI SE up to 65–105 dB.28 The ultrahigh EMI SEs of the foam-like graphene films were attributed to significantly improved electrical conductivity and “expansion enhancement effect” of insulating space layers.Graphene has attracted much attention, due to its outstanding thermal conductivity  films were not mechanically robust enough to meet the requirement of harsh deformations for the wearable and foldable equipments. Cracks were found in the PG films after repeated folding or bending  of 25 680 dB cm2 g−1, as well as outstanding thermal conductivity of 803.1 W m−1 K−1. Moreover, the LG-4 film could endure harsh deformation, with tensile strength of 42.61 MPa and elongation at break of 7.85%, proving to be a promising candidate as thermal conducting materials in wearable and foldable electronic devices.In this work, large-sized graphene oxide flakes and compression of porous graphene films were employed to prepare ultrathin flexible graphene films with ultrahigh EMI SEs and excellent thermal conductivity. Herein, the porous graphene films were fabricated with the combination of casting-evaporation of GO suspension and thermal annealing at 2600 °C. Due to their better thermal and electrical performances, the porous film made of large-sized graphene flakes (PLG) shows an increase in EMI SE of 7.8 dB, compared to that made of smaller-sized graphene flakes. And four 35.6 μm-thick PLG films were compressed into a 14 μm-thick film (LG-4), with an excellent EMI SE of 73.7 dB and specific SE divided by the thickness  at 40 kV. Fourier transform infrared (FTIR) spectra were recorded by a Nicolet 10 spectrometer.Sizes of the GO flakes, and morphologies of the GO and graphene films were investigated by scanning electron microscope . Raman spectra were performed on a LabRAM HR Raman Spectroscopy, and a laser excitation of 532 nm was employed. The elemental compositions of the samples were investigated by X-ray photoelectron spectroscopy . X-ray diffraction (XRD) data was collected with a X'Pert Pro  diffractometer using monochromatic Cu Kα1 radiation  at room temperature. The specific heat capacities were measured from differential scanning calorimeter , and densities of the graphene films were calculated based on sample weight and volume. Diameter of graphene films for thermal conductivity testing is around 25 mm.Static uni-axial tensile tests of the film samples were conducted on a dynamic mechanical analyzer . Two ends of the sample, with a length of about 6 mm and width of around 3 mm, were gripped by tension clamps tightly Fig. S3. All tenS-parameters of the samples, including the reflection (S11 or S22) and transmission (S12 or S21) of a transverse EM wave, were measured by a vector network analyzer  using the wave-guide method in X-band. The standard sample dimensions were 22.86 mm × 10.16 mm, and the tested samples were made by attaching slightly larger graphene films onto a polyurethane (PU) foam substrate. As shown in Fig. S4,A, R and T are the absorption, reflection and transmission coefficients, respectively. SEtotal, SEabs and SEref are the total, absorptive and reflective EMI SE, respectively.The Sizes of graphene oxide flakes, and morphology of the LGO film were observed by SEM, as shown in −1), carboxyl stretching vibrations (∼1725 cm−1), aromatic carbon bonds (∼1615 cm−1), and epoxy and alkoxy bonds (∼1065 cm−1). From The chemical compositions and molecular structures of GO and graphene films with varied flakes sizes are systematically characterized by FT-IR, XPS, XRD and Raman spectroscopy. As shown in The XPS spectra of all GO and porous graphene films is shown in d-spacing around 8.8, 8.5 and 8.3 Å, respectively. After graphitization, the 2θ of graphene films were shifted to 26.42°, 26.52° and 26.58° for SG-1, MG-1 and LG-1, respectively. The shift of 2θ suggests that the GO films were well reduced during thermal treatment. Moreover, d-spacing of these compressed graphene films are slightly greater than that of the natural graphite, attributed to residual structural defects. Due to higher degree of compactness and more ordered structure during assembling of graphene flakes, d-spacing of the LG-1 film (3.352 Å) is a bit smaller than that of the SG-1 film (3.368 Å).−1 and 1592 cm−1 for GO films, corresponding to D band and G band. The peak intensity ratio of D band to G band (ID/IG) is used to characterize structural defects and sp2 hybridized domains. The SGO film possesses the ID/IG of 1.74, which is higher than that of the MGO (1.65) and the LGO (1.53). The results demonstrate that larger-sized graphene flakes has less oxygenated groups and fewer defects, which might lead to higher electrical conductivity and better EMI shielding performance. After graphitization, a new peak appears at 2718 cm−1 for the compressed graphene films, corresponding to the 2D peak, which indicates the formation of graphite structure during thermal treatment.Raman spectroscopy of the GO films and graphene films are shown in EMI shielding performance of the PG films and compressed graphene films made of varied flakes sizes were investigated. As shown in 28 As shown in d, which decreased significantly for LG-1 and LG-2 after compression. As shown in τeff) is defined as the ratio of total transmitted EM waves to incident waves, which could be calculated by the 29Z1 and Z2 are wave impedance of free space and graphene materials, r is propagation constant of free space, and d is average distance between adjacent graphene laminates. On the condition that d ranges from 0 to 100 μm and f is from 8.2 to12.2 GHz, τeff is obviously lower than 1. Therefore, the air pores contribute significantly to shielding performance. With smaller d, compressed graphene films show much lower EMI SE, compared with porous graphene films. On the condition that d = λ/2 and r = j × 2 × π/λ (λ is wavelength), τeff is calculated as −1, indicating that destructive interference of waves might happen. Hence, the excellent EMI shielding performance of the porous graphene films is probably because of the interference among the component waves, which is not related to the number of graphene laminates in the multi-layer structure, but related to the size of air pores. For the PLG films, although insulated air pores could not consume waves directly, these air pores produce multiple interfaces of graphene laminates and air pores, contributing to dispersing extra waves due to the wave interference.A multi-layer model and electromagnetic theories are applied to study the effect of air pores on EMI shielding performance of graphene films.Though the PG films possess higher EMI SEs, the insulated air pores would significantly decrease their electrical and thermal conductivities. Hence, compression of PG films is necessary to obtain ultrathin, flexible thermal conducting films. To improve the relatively low EMI SEs of compressed graphene films, adding the thickness of shielding materials is simple and efficient. Four layers of PLG films were compressed together to obtain the 14 μm-thick LG-4 film, leading to ultrahigh EMI SE of 73.7 dB . And, EMtotal, SEref and SEabs at 10 GHz of the graphene films made of large-sized flakes and the SG-4, MG-4 films were calculated  to 8.1 × 108 Ω (LGO), due to less defects and functional groups. After graphitization, electrical conductivity of the porous graphene films show a remarkable increase, due to defects restoration during thermal treatment. The electrical conductivity of the PSG film is measured as 1170 S cm−1, which increases to 1270 S cm−1 for the PLG film. After compression, electrical conductivity of the LG-4 film increases several times, up to 6740 S cm−1. Compared with graphene films made of smaller-size flakes, large-sized graphene films possess higher electrical conductivity, leading to better EMI shielding performance. Moreover, a small increase of electrical conductivity would lead to a significant decrease in the skin depth of a shield.33,34 And the decrease in the skin depth for the LG-4 film results in the significant enhancement of SEabs. The skin depth (δ) is calculated according to the following equation:σ is the electrical conductivity, f is the frequency and μ is the magnetic permeability. On the conditions that the electrical conductivity of LG-4 is 6960 S cm−1, μ keeps constant to be μ0, and f is at 10 GHz, the calculated value of δ is 6.0 μm based on The electrical conductivity of GO and graphene films were investigated, as shown in δ, EMI SE of LG-1 still reaches to 33.1 dB, due to the consumption of more EM energy by the multi-layer structure of shielding materials. With nearly the same thickness, EMI SE of the LG-4 film is higher than that of the SG-4 and MG-4 films, due to smaller σ for the LG-4 film. Complex permittivity  and loss tangent (tan δ) are analyzed to further study shielding mechanism, as presented in Fig. S9.†Although the thickness of LG-1 film (0.0035 mm) is thinner than the calculated t) has been widely used, when taking density and weight into account. Notably, the-14 μm-thick LG-4 film possesses EMI SE of 73.7 dB, which is higher than the 10 μm-thick copper foil , low density (2.05 g cm−3), ultrathin thickness (0.014 mm), anti-corrosion, high flexibility and easy fabrication.To evaluate lightweight EMI shielding materials, like foldable or wearable electronic devices, the specific shielding effectiveness divided by thickness .20 Compared with that of the SG-1 film, a 27.9% improvement of thermal conductivity was observed for the LG-1 film, which is attributed to the reduced phonon-boundary scattering resulted from more compacted and ordered structure of graphene films made of large-sized graphene flakes with fewer defects. With the size of graphene flakes increasing, acoustic phonons with longer wavelengths are available for heat transfer, leading to higher thermal conductivity.52,53 However, the out-plane thermal conductivities of graphene films are quite low, compared with their in-plane thermal conductivities  and elongation at break (εb) are improved for these GO and compressed graphene films. For example, the σ of the SGO film is 35.6 MPa, and the εb is 1.15%. Those of the LGO film are significantly improved to 52.6 MPa and 1.93%, when the average flakes sizes increased from 5–8 μm to 40–50 μm. This size effects induced enhancement is due to less defects and stronger π–π interaction between graphene flakes for the LGO film.9The ultrathin graphene films in this research have not only superior electrical and thermal properties, also excellent mechanical performance. Representative stress–strain curves of GO and graphene films are shown in σ is observed for all graphene samples, while εb of graphene films is dramatically increased. As shown in εb of 7.85%, which is in good agreement with its high flexibility and foldability. And the SEM images (After graphitization, a slight decrease of M images  reveal tThe above results demonstrate that the LG-4 film is promising to be used as thermal conducting films in wearable or foldable electronic devices, which require high EMI SE, low density, ultrathin thickness, excellent thermal conductivity and high flexibility.t of 25 680 dB cm2 g−1, which is one of the highest among the reported values. The superior EMI shielding performance is attributed to less defects, excellent electrical conductivity and multi-layer structure of the LG-4 film. The LG-4 film also shows high thermal conductivity of 803.1 W K−1 m−1, and excellent mechanical flexibility with a elongation at break of 7.85%. The above results indicate that the LG-4 film shows great potential as excellent thermal conducting films applied in wearable or foldable electronic devices, which require lightweight, high flexibility, thermal conductivity, and efficient EMI shielding performance.In conclusion, ultrathin and flexible graphene films were fabricated with large-sized graphene flakes, which displayed outstanding EMI shielding performance, thermal conductivity and mechanical properties. The 14 μm-thick LG-4 film possesses EMI SE of 73.7 dB and the SSE/There are no conflicts to declare.RA-009-C8RA09376H-s001


Control over charge carrier density provides an efficient way to trigger phase transitions and modulate the optoelectronic properties of materials. This approach can also be used to induce topological transitions in the optical response of photonic systems. Here we report a topological transition in the isofrequency dispersion contours of hybrid polaritons supported by a two-dimensional heterostructure consisting of graphene and α-phase molybdenum trioxide. By chemically changing the doping level of graphene, we observed that the topology of polariton isofrequency surfaces transforms from open to closed shapes as a result of doping-dependent polariton hybridization. Moreover, when the substrate was changed, the dispersion contour became dominated by flat profiles at the topological transition, thus supporting tunable diffractionless polariton propagation and providing local control over the optical contour topology. We achieved subwavelength focusing of polaritons down to 4.8% of the free-space light wavelength by using a 1.5-μm-wide silica substrate as an in-plane lens. Our findings could lead to on-chip applications in nanoimaging, optical sensing and manipulation of energy transfer at the nanoscale. 3 heterostructure by tuning the graphene doping level, which enables partial focusing at deep subwavelength.Polaritonic topological transitions of the isofrequency dispersion contour are observed in a graphene/α-MoO In this context, a collection of different phases in magic-angle bilayer graphene has been achieved by changing its carrier density16. Similar concepts have been theoretically explored in photonics using hyperbolic metamaterials composed of subwavelength structures, such as a periodic array of graphene ribbons17 or a stack of graphene dielectric layers18, in which a topological transition in the isofrequency dispersion contour can occur by changing the doping level of graphene. However, these hyperbolic metamaterials rely on a strong anisotropy of the effective permittivity tensor, which is ultimately limited by spatial nonlocal effects that can hinder a practical verification of this concept.The control of charge carrier concentration by either electrostatic or chemical means has been widely studied as a way to induce phase transitions of different nature, such as structural in transition metal dichalcogenides3) films was explored to control the topology of the isofrequency dispersion contour of phonon polaritons (PhPs) by varying the relative twist angle between the two α-MoO3 layers22. Owing to the in-plane anisotropy of the permittivity within the reststrahlen band from 816 to 976 cm−1, the real part of the permittivity is positive along the [001] direction but negative along the [100] direction24, a property that renders α-MoO3 a natural hyperbolic material supporting in-plane hyperbolic PhPs26. The low-loss in-plane hyperbolic PhPs in α-MoO3 thus emerge as an ideal platform to explore further possibilities of doping-driven and electrically tunable topological transitions in photonics.Recently, a twisted stack of two α-phase molybdenum trioxide (α-MoO3 film covered with monolayer graphene by changing the doping level of the latter. We observed the polariton dispersion contour to vary from hyperbolic (open) to elliptic (closed) on increasing the doping level of graphene, leading to the emergence of a mode dominated by its graphene plasmon polariton (GPP) component propagating along the [001] direction at high doping levels. The nature of the polaritons emerging at high doping in the heterostructure evolved from GPP to PhP when moving from the [001] to [100] α-MoO3 crystallographic direction. In addition, when the vdW heterostructure was placed on top of a gold substrate instead of SiO2, a rather flattened dispersion contour was obtained due to a topological transition. As an application, we have designed an in-plane subwavelength focusing device by engineering the substrate.In this work we have achieved the control of polariton dispersion in a van der Waals (vdW) heterostructure composed of an α-MoO2  components along the [100], [001] and [010] crystal directions satisfy εx < 0, εy > 0 and εz > 0, respectively  under a fixed representative incident free-space wavelength of λ0 = 10.99 μm (frequency of 910 cm−1). As the graphene Fermi energy increases from 0 to 0.7 eV, the opening angle φ of the hyperbolic sectors gradually increases due to a change in the PhP wavelength when varying the dielectric environment, and eventually the dispersion contour changes its character from a hyperbolic (open) to elliptic (closed) shape. Note that the Fermi energy at which this topological transition occurs is conditioned to the appearance of well-defined graphene plasmons along the [001] direction at λ0 when increasing its doping level30. When the substrate was changed from SiO2 to gold, we found flatter dispersion contours , the dispersion contours for the hybrid polaritons on both SiO2 and gold substrates display an elliptic-like shape .Numerically simulated field distributions of hybrid polaritons for different graphene Fermi energies are shown in Fig. ate Fig. , highly ape Fig. . As a co3 heterostructures  is recorded simultaneously with the topography, making it possible to directly map the vertical near-field components of the hybrid polariton wavefronts launched by the antenna  on a SiO2 substrate at the same incidence frequency. The image in Fig. x direction, while fringes around the antenna appear in the y direction, indicating that the dispersion contour has evolved into a closed shape, as shown in Fig. EF = 0.3 eV  match quite well the calculated dispersion diagrams in all cases.To visualize the polariton wavefrontsont Fig.  for both eV Fig. , indicatved Fig.  for sampges Fig.  and simuges Fig.  further 3 determines the influence of the dielectric environment , which should not exceed the skin depth of hybrid polaritons  across the amplitude of the canalization mode give a full-width at half-maximum (FWHM) of around 115 ± 5 nm , as shown in Supplementary Fig. Close to θ with respect to the y direction, we could selectively launch and manipulate hybrid polaritons with different in-plane wave vectors. The launching contribution from our antenna can be decomposed into four parts: two endpoints acting as resonant dipoles and two parallel edges behaving as line dipoles (and assimilated to linear arrays of discrete dipoles).By rotating the long axis of the antenna by an angle EF = 0.1 eV) that, at θ = 0°, the field pattern of the exciting hybrid polaritons exhibits vertical fringes parallel to the long axis of the antenna, dominated by the line dipole contributions generated by the edges. Note that the two endpoint dipoles are not well excited when θ = 0° because the polarization direction of the incident light is not aligned with the long axis of the antenna. We can extract the polariton wave vector from the fringes parallel to this long axis. As θ increases from 0 to 90°, the wavefronts produced by the two endpoints gradually show up and interact with those produced by the edges. In the regime with rotation angles θ ≤ 40°, the distance between adjacent fringes parallel to the antenna edge is reduced from 590 to 380 nm, from which we can obtain the wave vector k perpendicular to the antenna. The extracted wave vectors are shown by red symbols in Fig. θ ≥ 60°  all lie strictly along the x direction  shown in Supplementary Fig. y direction. This focal spot size is less than 1/21 of the corresponding illumination wavelength, thus emphasizing a deep subwavelength focusing effect . This property has allowed us to design a deep-subwavelength device for in-plane focusing of hybrid polaritons, where negative refractive occurs at the boundary between two different substrates. Our study opens promising possibilities to tune topological polaritonic transitions in low-dimensional materials40 with potential applications in optical imaging, sensing and the control of spontaneous emission at the nanoscale18.We have experimentally demonstrated that the topology of the isofrequency dispersion contours for the hybrid polaritons supported in a heterostructure composed of a graphene sheet on top of an α-MoONote added in proof: While preparing this manuscript, two related theoretical and experimental studies on the tuning of highly anisotropic phonon polaritons in graphene and α-MoO3 vdW structures were reported42.3 flakes were mechanically exfoliated from bulk crystals synthesized by the chemical vapour deposition (CVD) method19 and then transferred onto either commercial 300 nm SiO2/500 μm Si wafers (SVM) or gold substrates using a deterministic dry transfer process with a polydimethylsiloxane (PDMS) stamp. CVD-grown monolayer graphene on copper foil was transferred onto the α-MoO3 samples using the poly(methyl methacrylate) (PMMA)-assisted method following our previous report44.High-quality α-MoO46. We designed the gold antenna with a length of 3 μm and a thickness of 50 nm, which provided a high launching efficiency over the spectral range from 890 to 950 cm−1 within the α-MoO3 reststrahlen band. Alternatively, a thicker antenna with a stronger z component of the electric field could be used to launch the polaritons more efficiently in future studies. Note that narrow antennas (50-nm width) were used to prevent their shapes from affecting the polariton wavefronts, especially when their propagation is canalized  on an approximately 350 nm PMMA950K lithography resist. Electron-beam evaporation was subsequently used to deposit 5 nm Ti and 50 nm Au in a vacuum chamber at a pressure of <5 × 10−6 torr to fabricate the Au antennas. Electron-beam evaporation was also used to deposit a 60-nm-thick gold film onto a low-doped Si substrate. To remove any residual organic material, samples were immersed in a hot acetone bath at 80 °C for 25 min and then subjected to gentle rinsing with isopropyl alcohol (IPA) for 3 min, followed by drying with nitrogen gas and thermal baking  was used to image optical near fields. The atomic force microscopy (AFM) tip of the microscope was coated with gold, resulting in an apex radius of ~25 nm (NanoWorld), and the tip-tapping frequency and amplitudes were set to ~270 kHz and ~30–50 nm, respectively. The laser beam was directed towards the AFM tip, with lateral spot sizes of ~25 μm under the tip, which were sufficient to cover the antennas as well as a large area of the graphene/α-MoO3 samples. Third-order harmonic demodulation was applied to the near-field amplitude images to strongly suppress background noise.A scattering scanning near-field optical microscope (Neaspec) equipped with a wavelength-tunable quantum cascade laser  impinged at an angle of 60° relative to the tip axis52. To avert any effects caused by the light polarization direction relative to the crystallographic orientation of α-MoO3, which is optically anisotropic, the in-plane projection of the polarization vector coincided with the x direction  of α-MoO3  is a cover layer, layer 2  is an intermediate layer and layer 3  is a substrate where z is the value of the vertical axis and dh is the thickness of α-MoO3 . The α-MoO3 film was modelled by an anisotropic diagonal tensor diag{εx, εy, εz}, where εx, εy and εz are the permittivity components along the x, y and z axes, respectively. Also, monolayer graphene was located on top of α-MoO3 at z = 0 and described as a zero-thickness current layer characterized by a frequency-dependent surface conductivity taken from the local random-phase approximation model55:EF, the inelastic relaxation time τ and the temperature T; the relaxation time is expressed in terms of the graphene Fermi velocity vF = c/300 and the carrier mobility μ, with e is the elementary charge; kB is the Boltzmann constant; ℏ is the reduced Planck constant; and ω is the illumination frequency.The transfer matrix method was adopted to calculate the dispersion and IFCs of hybrid plasmon–phonon polaritons in graphene/α-MoOrp of the three-layer system admits the analytical expressionrjk denotes the reflection coefficient of the j–k interface for illumination from medium j, with j,k = 1–3; j for a propagation wave vector kp(θ) (where θ is the angle relative to the x axis), which can be expressed as j along the x and y axes, respectively); j along the z axis; and Z0 is the vacuum impedance.Given the strong field confinement produced by the structure under consideration, we only needed to consider transverse magnetic (TM) modes, because transverse electric (TE) components contribute negligibly. The corresponding p-polarization Fresnel reflection coefficient q when the denominator of equation   over a plane 20 nm above the surface of graphene. The boundary conditions were set to perfectly matching layers. Graphene was modelled as a transition interface with a conductivity described by the local random-phase approximation model (see above)57. We assumed a graphene carrier mobility of 2,000 cm2 V–1 s–1. Supplementary Fig. 2 and Au, respectively, at the mid-infrared wavelengths used.We also used a dipole polarized along the Methods, additional references, Nature Research reporting summaries, source data, extended data, supplementary information, acknowledgements, peer review information; details of author contributions and competing interests; and statements of data and code availability are available at 10.1038/s41565-022-01185-2.Supplementary InformationSupplementary Figs. 1–31.


ForAlexa, which has two types of forms, Question-And-Answer (Q&A) and Random-Quote. Both these forms allow the user to build intents (an activity that is invoked by a spoken request from the user), but with slightly different functions. The Q&A form is used to compile answers that Alexa will offer in response to an utterance (question), while the Random-Quote extends the interaction between Alexa and the user, based on the questions asked in the first form. ForAlexa also has a help assistant, as well as a manual, which explains all the steps necessary for the design of an intent. This tool allows educators to develop apps quickly and easily for their classes and this type of app could be an alternative to be used for students with special needs, such as the visually-impaired.Intelligent Personal Assistants (IPAs), such as Amazon’s Alexa, are now widely used for an ample variety of tasks, ranging from personal management to education. These tools have shown considerable promise for student-educator interactions, especially at a distance, a potential that has come to the forefront during the ongoing COVID-19 pandemic. Even so, this potential is still underexploited, even in the current scenario. Alexa’s apps are known as skills, which include all the different commands that Alexa is capable of executing. It is important to note, however, that the use of such technology is work-intensive and can be relatively complex. Given this, to facilitate the development of new skills in Alexa, we have developed an online tool that permits the creation of questions and answers, as well as honing the interaction between Alexa and the user. We have named this tool The online version contains supplementary material available at 10.1186/s12052-022-00169-z. Social distancing, quarantine and the isolation provoked by the COVID-19 pandemic have forced us to modify our way of life in many different ways, which may be more or less permanent . Artificial Intelligence is now a global reality . However, Alexa can also be implemented in devices not produced by Amazon  or manually, in the case of devices with a screen. Once Alexa is activated, a specific skill can be activated by voice or by a touch followed by a voice command. When a skill is requested, its content is processed by the algorithms in Alexa’s AI, such as voice recognition, machine learning, and the understanding of natural language.Alexa processes the user’s request by accessing web-hosted services or its own server (Amazon AWS), and then responds to the user Fig. A. This rThe tools would potentially be extremely valuable as auxiliary teaching aids for specific disciplines, in particular for special needs students. Even so, many of the challenges of teaching the visually impaired will still persist (Orsini-Jones ForAlexa) which explains the steps necessary for the construction of teaching skills. We also developed a skill for a specific, undergraduate-level discipline, population genetics (in Portuguese), and at the end of this discipline, we applied questionnaires to evaluate the students’ use of the skill created using ForAlexa .To facilitate the use of this tool by other educators, in particular those that may be inexperienced in programming, we have created a web-based form page .We chose Alexa, the artificial intelligence (AI) platform from Amazon Inc., for the present study, due primarily to the fact that the development of apps on this platform is facilitated considerably by a specific page on the Amazon system, which provides detailed instructions and examples of codes, and an extremely user-friendly interface for the development of apps, i.e., skills (Johnstone and Razavi intent) is an action that attends to a question (utterance) that the user asks Alexa. It is important to note here that a given intent can be activated by questions formulated in different ways. To ensure this, the developer must consider the different ways in which the user may formulate the same solicitation  with the invocation name (Evolution Professor). The intention .https://developer.amazon.com), and create a new skill , informing its name and standard language, as well as the skill model and its host. The user should then create an account and follow the instructions on the ForAlexa homepage. The ForAlexa workflow is shown in Fig. ForAlexa has a help assistant to facilitate the steps outlined below. This assistant is turned on by default, and allows the user to understand basic concepts, what is permitted or not , and even to build questions and answers rapidly, as well as reinforcing the interaction between the user and Alexa.To begin with, the user must register or login to the Alexa Developer Console . These intents are normally related to the invocation name of the skill (LaunchRequest) and its help request (HelpIntent). There are a number of other required intents, but to simplify, the ForAlexa help assistant only teaches how to edit the LaunchRequest (the edition of required intents is explained below).Once logged in, the user must create a repository, which will present a list of required ork Fig. A. Once eintent has been registered  intents or Random Quotes , the corresponding form will be loaded  and the question that Alexa must be able to answer, e.g., “What is Evolution?”  asking the user a new question (reprompt), for example, asking whether the user requires any more information on the topic —“If you want, you can ask me another question, for example, ask me questions on chapter one or any other chapter you like”.If the form is of the Q&A type, the developer must provide the answer that Alexa will provide in response to the utterance, followed by one of two options—(i) finalizing the intent can also be included here. In this case, the form has the option of creating suggestions for random questions on a given subject or class, such as “would you like to ask more questions about evolution?” or “would you like to ask more questions about class one?”. The developer can provide to the random questions the utterances created in the Q&A form.If the developer wishes to include a greater level of interaction between Alexa and the user, the random-quote type of intent is substituted by the random quotes field, where the developer defines how many random quotes the AI will use, with a default value of 2. An introductory phrase (which is not obligatory), which defines the possibilities of interaction with the AI, can be introduced here. The developer then provides the random quotes that will be selected when an intent is activated. In the final step, the developer can provide a phrase to be spoken by Alexa following the random quote. While this phrase is not required, it does amplify the potential for interaction between the AI platform and the user. At this point, the developer can save or update the intent by clicking on the respective button  intent name “QuestionsAboutEvolution” , and (ii) an utterance “Questions about Evolution”, followed by an introduction, such as “You can ask me”, and then all the possible questions on a given subject or class, such as “What is Evolution?”, “What is Microevolution?”, “What is Macroevolution?” and so on. Finally, in After Alexa, the developer may choose a sentence of the Q&A type “If you want, you can ask me another question, for example, ask me questions about Evolution”. When Alexa is asked “Questions about Evolution”, it will select questions (2 by default) randomly from the skill to ask the user, and then ask whether the user wants to ask one of these questions or whether the user wants to hear more questions chosen randomly. In other words, the dialog on a theme or a class will continue.An example of a random quotes intent is the LaunchRequest. Here, the developer should edit the Skill Invocation Name, but not the Intent Name. At Skill Invocation Name, the developer must substitute the default sentence with the name of the skill that the users of Alexa will need to say to activate the skill. This is the new name of the skill  option. In this case, Alexa will continue the interaction, saying, for example, “If you want, you can ask me another question, for example, ask me questions about Evolution?” .The second required intents are registered or updated, ForAlexa revalidates the database  whether an utterance is duplicated in the database. Once the absence of duplications is confirmed, the data are saved, but if a duplication is found, the user is redirected to the preceding screen, which will describe the error that requires correction in step 2 .Once all the content is confirmed, the developer is directed to the next phase Fig. , step 4,ile Fig. E , for example, “Tell me about the Hardy-Weinberg equilibrium”, rather than “What is the Hardy-Weinberg equilibrium?”. In these cases, it is possible to include options in ForAlexa that allow Alexa to answer that it has no content on the topic. Alexa will then ask the user if they are interested in hearing some questions on a specific theme (HelpIntent). If the user says “yes”, the Yes.Amazon intent will direct the user to an alternative question. The random question form can also enable Alexa to present random questions on the subject matter (or class) and then ask the user if they would like to hear more questions. These questions are chosen randomly, but Alexa will eventually include the correct question that the developer included, i.e., What is the Hardy-Weinberg equilibrium? The organization of a skill for educational purposes is presented in Fig. One fundamentally important point in the creation of a skill is the Alexa–user interaction, which must ensure the most effective possible communication between the student and the skill. We bore this in mind when developing This interaction with the user is fundamental, because it permits the user to establish a “conversation” with the IPA and not simply ask questions and receive answers. The idea here is for the IPA to lead the user through the skill . While the skill does contain some more general material, which could be used by anyone interested in the theme, it is structured by the topics presented by the educator (Population Genetics) during the classes.A skill was designed in Once the skill has been presented to the students and its use has been demonstrated, they were free to use the skill as they prefer. It is important to emphasize, however, that the skill does not substitute the adequate study of a topic, but rather, provides a reference base for the principal concepts presented in each class. Given this, we monitored the use of the skill by the students in relation to a given topic, in terms of the questions asked and the specific use of the skill. We also asked the students to explain in their own words what they had learnt from Alexa on a specific topic.Overall, the Population Genetics skill was well-accepted by the students, who mostly gave it the most favorable evaluation Fig. . The stuThe creation of a skill is an idiosyncratic task, and each educator will likely adapt it in some way to the content of their discipline and their own personal style of teaching. In our skill, for example, when Alexa is asked what the Hardy-Weinberg Equilibrium is, after providing the answer, Alexa will ask whether the user would like to know something else , VoiceApps (www.voiceapps.com) or Voiceflow (www.voiceflow.com). While no source code is available for Blueprints and only question-and-answers in English, the latter two tools are potentially interesting, but they have only limited function in free plans.Given this, https://github.com/luanrabelo/ForAlexa). After obtaining the code, the user can import the skill to their developer profile, where its different components, including its questions, answers, and invocation name, can be modified. The user can also use the online form for the rapid development of a skill. Even though the development of a skill can be facilitated, it is important to remember that many different types of problems may arise, such as the need to include special characters that are not permitted. This demands a minimum level of knowledge on the part of the developer in order to resolve problems of this type following the upload of the files to Alexa. In particular, we would emphasize, once again, the need for adequate and comprehensive testing to guarantee the creation of the most functional possible skill, which is not a simple task. For this, we would recommend any developer new to this activity to create some test questions and answers to test the efficacy of both the form and the development area in Alexa. To facilitate this, we have created a document with simple questions and answers, and all the interactions necessary for the adequate completion of the forms .The source code of our skill and the forms are open-access, and can be found at GitHub  question-and-answer and(B) and random quotes types. An intent name (C) and utterance (D) are requiredin both forms, while an answer (E) is only required in the question-and-answertype form. The user can then finalize or manifest their interest in asking Alexaa new question (F) or ask a question (G). In the random quotes mode, the usercan choose how many random questions they would like Alexa to proffer (H), anintroductory phrase, which defines the possibilities of interaction with the AI(I), the random questions (J), add space for more random questions (K), anddefine the final phrase or question that Alexa will say (L).


When localized proton transport occurs, it canbe a highly dynamic process, with additional transmission sites “opening”and a small number of sites “closing” under an appliedelectric field on the seconds time scale. Applying a simple equivalentcircuit model of ion transport through a cylindrical nanopore, thelocal transmission sites are estimated to possess dimensions (radii)on the (sub)nanometer scale, implying that rare atomic defects areresponsible for proton conductance. Overall, this work reinforcesSECCM as a premier tool for the structure–property mappingof microscopically complex (electro)materials, with the local ion-fluxmapping configuration introduced herein being widely applicable forfunctional membrane characterization and beyond, for example in diagnosingthe failure mechanisms of protective surface coatings.In 2014, it was reportedthat protons can traverse between aqueousphases separated by nominally pristine monolayer graphene and hexagonalboron nitride (h-BN) films (membranes) under ambient conditions. Thisintrinsic proton conductivity of the one-atom-thick crystals, withproposed through-plane conduction, challenged the notion that grapheneis impermeable to atoms, ions, and molecules. More recent evidencepoints to a defect-facilitated transport mechanism, analogous to transportthrough conventional ion-selective membranes based on graphene andh-BN. Herein, local ion-flux imaging is performed on chemical vapordeposition (CVD) graphene|Nafion membranes using an “electrochemicalion (proton) pump cell” mode of scanning electrochemical cellmicroscopy (SECCM). Targeting regions that are free from visible macroscopicdefects ( These G/A values representedthe intrinsic proton conductivity of the studied 2D crystals ,12 challengingthe widely accepted notion that pristine graphene is impermeable toall atoms, ions, and molecules under ambient conditions.14 Subsequent studies by several research groups18 have suggested that selectiveproton transport may be facilitated at defect sites  that are likely separate fromthe sites that facilitate the transport of other ions .19In 2014, anomalously highproton transport through nominally pristinemonolayer graphene and hexagonal boron nitride (h-BN) membranes  was reported,21 For example,a scalable “electrochemical proton pump cell” configurationin which macroscopic  graphene sheets producedby chemical vapor deposition (CVD) were deposited onto a commerciallyavailable perfluorosulfonic acid polymer (Nafion) film, was reported.12 CVD graphene-on-Nafion membranes  are able to achieve much higher protontransport rates ,11 while maintaining relatively high selectivity .19 Althoughit is well-known that CVD graphene possesses a distribution of intrinsicdefects , as yet there is no direct evidence for heterogeneoustransmission at particular locations on graphene|Nafion membranes.Conventional Raman spectroscopy lacks the spatial resolution and sensitivityto detect defects in high-quality graphene , and although high-resolution microscopy  has sufficient resolution to locally image defects, itis only able to provide a limited view in a macroscopic sense.15There has been interestin scaling up proton-selective membranesbased on graphene and related 2D materials.24 Scanningelectrochemical cell microscopy (SECCM)27 stands out as the idealtechnique for this application, as it uses a fluidic micropipet/nanopipetprobe to carry out local electrochemistry  within a confined region of an electrode surface,with a spatial resolution (down to tens of nanometer29) defined by the area of meniscus contact. In recent years, SECCMhas predominantly been used in conjunction with colocated microscopy/spectroscopyto reveal structure–activity in a diverse range of (electro)materials,30 including 2D materials such as graphene31 and transition metal dichalcogenides, such as MoS2,35 WS2,34 WSe2,36 MoS2/WS2 heterostructures,37etc. However, SECCM with a dual-channelprobe38 can also make real-time, localion conductance measurements on any type of surface, regardless ofelectrical conductivity.39 As we show herein,this configuration is crucial to land the meniscus cell on any partof the surface, irrespective of the local proton transmissibility.The extraction of large-scale statistics on local proton transmissionthrough graphene|Nafion requires a high-throughput technique thatcan directly probe/map ion flux with high spatial resolution overlarger areas of the membrane.11 graphene|Nafion membrane prepared by a hot-press method.The micropipet probe is deployed as an electrochemical ion (proton)pump cell40 to target regions of the graphene|Nafionmembrane that are free from macroscopic defects , revealing that, in these devices, most of the graphenesurface is impermeable to protons, with transmission typically occurringonly at ∼20–60 localized sites across a ≈0.003mm2 area. This localized proton transport process can alsobe highly dynamic, with a few additional transmission sites “openingup” on the seconds time scale when exposed to a proton-drivingvoltage (from the applied electric field) across the graphene|Nafionmembrane. By analogizing localized proton transmission to ion transportthrough a cylindrical nanopore,41 we can predict a simpleequivalent circuit model in which each site/pore possesses radii onthe (sub)nanometer scale and thus may be attributable to the presenceof one or more atomic defects in the graphene overlayer. All in all,this work further reinforces the status of SECCM as a premier toolfor local ion-flux mapping of microscopically complex (electro)materials.In this work, the synchronous electrochemical activity and ionconductance mapping capabilities of SECCM are exploited to probe localproton transmission through a previously reported–1 under the conditions explored).42 Themonolayer graphene film (situated on top of the Nafion 211 support)is investigated as a proton-selective membrane. Herein, the graphene|Nafionmembrane assembly was fabricated by a hot-press method similar tothat used previously,19 which, as established for themembrane electrode assemblies used in fuel cells,43 should ensure intimate interfacial contact between grapheneand the protogenic groups in Nafion, allowing for efficient protontransmission through the hydrated sandwich structure. Note that afterfabrication of the graphene|Nafion membranes, the quality of the grapheneoverlayer was assessed via SECCM measurements ofthe FcDM0/+ process (FcDM = ferrocenedimethanol). Afterthe tip was positioned, as for the proton conduction measurements(vide infra), this redox process was found to bekinetically facile in randomly selected spots, confirming the graphene preparation yieldeda surface of sufficient quality for electron tunneling measurements .To investigate local proton transport through graphene, spatiallyresolved electrochemical measurements were performed on graphene|Nafionmembranes using SECCM in the dual-channel configuration. The Nafion211 membrane (≈25 μm thickness) behaves as both a solidsupport and a highly conductive proton source/sink  on the scale of the SECCM probes used herein, assuming that intrinsic protontransfer occurs uniformly across the graphene surface via a through-plane conduction mechanism . Indeed, Nafion has previously been used as a graphenesupport for proton transmission measurements with similarly sized5 and larger macroscopic19 devices.Nafion is characterized by a complex, humidity-dependentnanostructure, with distinct domains of high and low ionic conductivity,corresponding to the hydrophilic sulfonate groups and hydrophobicfluorocarbon backbone, respectively.Ebias in idc in idc is highly sensitive to deformationof the meniscus cell,47 meaning that it can be used todetect meniscus–surface contact, enabling accurate positioningof the SECCM probe in three-dimensional (3D) space.48Herein, an “electrochemicalion (proton) pump cell”configuration of SECCM is introduced to measure local proton transmissionthrough graphene|Nafion membranes, as detailed in the Esurf = −(Eapp + Ebias/2) .47 Depending on the value of Esurf (vide infra), two proton-consuming reactions can take placeat the Pt WE, the hydrogen evolution reaction (HER) and/or the oxygenreduction reaction (ORR):Esurf, two scenarios are possible. Case (i):If the graphenefilm is ion-impermeable, the ionic pathway between the Pt WE and Ag/AgClQRCEs is blocked and no electrochemistry can place at the Pt WE, asshown in i.e., there is a continuous ionicpathway between the Pt WE and Ag/AgCl QRCEs) and protons flow fromthe meniscus cell into the Nafion film as the HER and/or ORR takeplace at the Pt WE (while the Ag/AgCl counter reaction takes placeat the QRCE), as shown in 40 whereby protons are “pumped” across the graphene filmin one direction (from meniscus to Nafion) in response to the proton-consumingreactions , through the graphene|Nafion membrane, the effective potentialat the WE surface is eactions 1 and 2 az-position, surface current (isurf), and idc fromrepresentative case (i) (red trace) and case (ii) (blue trace) measurementsare shown in i.e., t <0 s), (2) application of the electrochemical waveform , and (3) retract . From the plot of z-position in –1 in idc set point is triggered ; (2) after establishing meniscus–surfacecontact, zero or nonzero isurf is measuredat the Pt WE at 0 ≤ t ≤ 10 s, indicatingproton-impermeable [case (i)] and proton-permeable [case (ii)] regionsof the graphene|Nafion membrane, respectively; (3) in both cases, isurf returns to zero during retract, as meniscus–surfacecontact is broken. Note that the magnitude of isurf is dependent on Esurf andmay be limited by a combination of the charge-transfer resistance(Rct) associated with the electrode reaction, the micropipettip resistance (Rtip), and the resistanceof the proton transmission site(s) in the graphene film, exploredin greater detail below.In reference to the plotof idc in idc initially adopts a constant value of ≈7 nA, which decreasesduring approach, until reaching the idc set point , idc increases dramatically at 0 ≤ t ≤ 10 s, reflecting a percentage of the countercurrent flowing between the Pt WE and QRCEs ; (3) in both cases, idc tends back toward a stable value during retract , as the meniscus comes away from thesurface. Note that the idc–distancecharacteristic during the approach and retract of the SECCM tip dependson the tip size, initial meniscus size in air (here relatively large),and nature of the meniscus–substrate interaction . The gradual decrease in idc onapproach prior to triggering the feedback threshold at t = 0 s indicates substantial “squashing” of the meniscuscell47 over a distance of ≈500 nmin i.e., on the order of the micropipet probe radius).This idc–distance behavior is similarto that observed previously for SECCM on suspended graphene, wheremeniscus contact to the graphene surface was also evident from directsimultaneous measurements of isurf.49 Here, meniscus contact was additionally confirmedin separate measurements of isurf forthe direct electrochemistry of FcDM0/+ at the graphene|Nafionsubstrate (vide supra). It should also be noted that,herein, the idc set point (±500 pA)is taken relative to the value measured at the beginning of the approach,which means that it is both insensitive to drift in idc  and can be triggered by either a decrease  or increase  in the magnitude of idc, thereforeserving as a sensitive indicator of meniscus–surface contact,irrespective of proton transmission.From the plot of 50 A spatially resolved electrochemicalmovie, comprising 2601 independent cyclic voltammograms (CVs) across an 100 × 100 μm2 area (hopping distance = 2 μm) in the potential range−0.225 to +0.175 V vs Ag/AgClQRCE is shown in the SI Movie S1 (associatedmovie caption presented in the SI). A colocated“quasi-topographical” map, which reflects the (dynamic)topology of the underlying Nafion membrane  collected synchronously with the electrochemical data,is presented in the SI Figure S3. Notethat the ORR , obtained by integrating |isurf| from SI Movie S1 to calculate the charge (|Qsurf|) passedover the entire potential range to be equal to the tip area ]. Notethat the active pixels do not necessarily correspond to obvious featuresin the quasi-topographical map of the graphene|Nafion membrane , and the i–E response is different from that of the Nafion film itself(vide infra). Thus, the data in e.g., defects,18vide infra) across the macroscopic graphene|Nafionmembrane investigated herein. Indeed, due to the high sensitivityand low electronic noise of the SECCM setup, through-plane protonconduction at the “inactive” pixels (N = 2582) can be effectively ruled out in these devices, as the associatedlow isurf values . Considering the weight of statistics presentedin vide infra), and in these locations, proton transmissionrates (currents) are very high. However, as Nafion does not possessa uniform structure on the scale of (atomic) defects , the structure-dependent local proton conductivityof the acceptor Nafion membrane needs to be acknowledged. From theclassical cluster-network (inverted micelle) model for the morphologyof hydrated Nafion,51 proton conductionthrough the graphene|Nafion membrane could only occur if a proton-conductingdefect site  of graphenealigns with a proton-accepting water channel  of Nafion . Given the high hydration state of the Nafionmembrane , there would be an abundance of proton receptor sites on the 1–2μm2 scale , evidenced by the high functionality of graphene|Nafion membranesin previous macroscopic studies.19 Thus, while we are confident that we are not simplymeasuring a sparsity of graphene|Nafion wetting in the proton receptorphase (sink) in our measurements in e.g., 0.007 sites/μm2, vide supra) as a lower limit for these CVD graphene|Nafionmembranes.As discussed above, hydrated Nafion is effectively an isotropic(homogeneous) proton source/sink (electrolyte) on the scale of theSECCM probe  may also vary. In othercases, isurf is nonzero from the beginningof the potential sweep 52 relative to those employedherein. It should be noted, however, that during ultrashort/high-intensityvoltage pulses, the actual magnitude of the potential/electric fieldover the graphene membrane is expected to be dramatically reduceddue to double layer charging and uncompensated resistance, which,as discussed below, can be avoided entirely through the applicationof low-intensity voltage pulses for long times .As shown in the isurf spikesare always followed by a relativelyslow exponential decay with potential/time, taking place on the millisecondto second time scale  of themacroscopic Pt WE], through the uncompensated resistance of the cell,the time scale of which is characterized by the RC time constant (τ).54 As discussedin the next section (and outlined in detail in the SI), over an active proton transport site, R and C are estimated to be on the order of ≈100–1000MΩ and ≈2 nF, respectively, giving rise to τ valuesof 0.2–2 s, consistent with the time scale of the decay in isurf. In addition, in isurf is negative  and shows an exponential dependence on (over)potential,starting at ≈0 V vs Ag/AgClQRCE. This indicates that in the potential range of 0 to −0.225V vs Ag/AgClQRCE, both the relativelysluggish ORR kinetics at the Pt WE surface and the geometry of theactive transmission site may contribute some limitation to the magnitudeof isurf . These pointsare further discussed below.In each of the CVs extractedfrom active pixels 2c–i, indcale see 2g. As alvs Ag/AgClQRCE). A spatially resolved electrochemicalmovie, comprising 2601 independent CVs  across an 100 × 100 μm2 area (hopping distance = 2 μm) is shown in the SI Movie S2. The corresponding static imagesof electrochemical activity obtained for cycles 1 and 2 are shown in SI Figure S4). By consulting Movie S2 and 2. While a large proportion of the proton transmission sites are fixed,there are some sites that “open” and others that (partly)“close” on the time scale of the measurement  or dynamics of the acceptor Nafion phase57 . These are further reasons to consider the density of transmissionsites that we report as a lower limit. In any case, most of the graphene|Nafionmembrane is impermeable to protons, clearly demonstrated in the averageCVs (N = 2544) shown in To explore the dynamics of protontransport, particularly the potentialdependence, a voltammetric hopping mode SECCM experiment was performedon another area of the graphene|Nafion membrane, performing two cycleswithin the same potential window .Individual CVs extracted from representative active pixels areplotted in  landing 3c or aft landing 3d–gand st e.g., 3c–f, alt41 Applying the equivalent circuitmodel59 derived and discussed in the SI, the local electrochemical response  is rationalized and furtherused to estimate the geometry of the active transmission sites. Toachieve the latter, potential-step experiments were performed in the SECCM configuration, targeting bothdamaged and more intact areas of the graphene|Nafion membrane. Spatiallyresolved electrochemical movies, comprising 1421 independent chronoamperograms(CAs) across 120 × 70 μm2 areas  at Esurf = −0.5 V vs Ag/AgClQRCE (pulsetime = 10 s) are shown in the SI Movies S3 and S4. The corresponding static imagesof electrochemical activity ,obtained from damaged and more intact areas of the graphene|Nafionmembrane, are shown in Proton conductionthrough local transmission sites on the graphene|Nafionmembranes is likened to ion transport through an atomically thin,solid-state nanopore.i–t curve shown in e.g., cracks and holes) where the underlying Nafion extrudes throughthe graphene overlayer, relatively large isurf values of ≈−23 nA are measured throughout the entire i–t pulse, also shown in N = 24/1421), surrounded by contiguousareas of intact, proton-impermeable graphene. While many of the activepixels exhibit large isurf values  orafter an onset time , before decaying onthe millisecond to second time scale  tosteady values in the 270–1100 pA range. Again, the pixel-dependentdelayed onset of the isurf spike in Movies S3 and S4).Contrary to the SECCM scans shownabove 2 and 3, vs Ag/AgClQRCE  and long pulsetime of 10 s applied duringthese potential-step experiments permits quantitative treatment ofthe data, allowing the pore resistance (Rpore) to be calculated and the pore radii (rp) to be estimated. As seen from SI Figure S6, assuming Cdl and Rct can be neglected, and under conditions where Rpore is negligible , the series resistance(Rseries) ≈ Rtip, meaning that isurf is limitedby the resistance of the micropipet probe. Applying Ohm’s law(SI eq S13), Rseries is estimated to be ≈9 MΩ from isurf = −23 nA . Thus, landing on the Nafion film provides the “tip-limited” i–t response, and pixels with isurf values approaching approximately −23nA .The large driving potential of −0.5V Rtip is known (≈9MΩ), Rpore can be calculated (SI eq S14) for each of the individual activepixels highlightedin Rpore values of 730, 460, 320, and 170 MΩare calculated for isurf values of 270,430, 600, and 1100 pA, for the green-, red-, blue-, and pink-labeledpixels (–1 for 0.1 M HCl60) and taking Lp = 0.6 nm (theapparent thickness of graphene in water7), we estimated rp values of 0.4, 0.5,0.6, and 1.0 nm (SI eq S12) for the green-,red-, blue-, and pink-labeled pixels , both the access resistance(Rg ∝ 1/rp) and geometric resistance (Ra ∝ Lp/rp2) contribute significantly to Rpore,and the calculated rp values are sensitiveto Lp (SI eq S12). For instance, taking Rpore = 460 MΩ, rp is estimated to be 0.4 and 0.6 nm for Lp values of 0.34 nm  and 1 nm , respectively. In anycase, the estimated (sub)nanometer pore geometry from this simplemodel indicates that the local proton transmission sites through themacroscopic graphene|Nafion membrane likely coincide with relativelyrare atomic-scale defects  in the graphene overlayer film, consistent withsome previous reports.18Since dpixels 4a-ii,red pixels 4a-ii, reG/A valuesreported in previous studies, alongside the graphene preparation methodand size of the measured membrane, is reported in the SI Table S1. The G/A valuespreviously reported for macroscopic graphene|Nafion membranes variesover several orders of magnitude (≈0.09 to 30 S cm–2),19 which is perhapsunsurprising given that macroscopic defects such as pinholes, cracks,and other imperfections are known to be present. Indeed, comparing A summary of example –2) required to achieve the reported G/A values is also calculated, assumingan individual defect resistance of 170 MΩ·defect. As shownin Table S1, the lower end of defect densities(0.005 defects μm–2), obtained from high-quality,small-area graphene membranes produced by exfoliation  or CVD ,is in good agreement with the number of defects detected on the morepristine areas of the graphene|Nafion membrane, with values of 0.007,0.02, and 0.008 defects μm–2 calculated for G/A values of up to ≈1000mS cm–2),17 the densityof defects would need to increase by >2 orders of magnitude (assuminga constant defect resistance of 170 MΩ·defect) up to ∼2μm–2, such that on average each meniscus cellof size ≈2 μm2 , previousreports have shown that such defects can be introduced readily duringthe growth17 or postgrowth treatment  of CVDgraphene, producing highly conductive, proton-selective membranes.To contextualizethe results reported herein, the density of defects was employed to target a relativelydefective area of the membrane. A static map of electrochemical activitymade up of 4760 pixels across an 13.4 × 13.8 μm2 area  is shown in rt ≈ 0.6–1μm), with a small number of isolated (single-pixel) defectspossessing low activity  and alarge number of continuous (multipixel) defects possessing high activity. The synchronously collected,colocated quasi-topography map shown in e.g., vide supra), whereas the larger multipixel sitesrepresent areas where the underlying Nafion film has extruded throughthe graphene overlayer, most likely at pre-existing cracks or grainboundaries. Indeed, macroscopic defects of this type can also be observedby scanning electron microscopy (SEM) imaging, carried out on a nearbyarea of the graphene|Nafion membrane, as shown in To provide a closer inspectionof graphene|Nafion membranes, a much smaller nanopipet probe , relatively large areas of membrane can be coveredin a single SECCM scan. In addition, to accurately estimate Rpore from Rseries (SI eq S13), Rtip ≪ Rpore, which puts a lower limiton the probe size since Rtip ∝1/rtip (eq S6).It should be pointed out thatwhile a small SECCM probe provideshigh-resolution images, a relatively large probe (2) of the membrane, it canbe stated with confidence that the majority of the graphene overlayerdoes not conduct protons in the investigated CVD graphene|Nafion membranedevices. Proton transmission was shown to be a site-specific process,occurring at ∼0.007–0.02 sites μm–2, giving rise to very high local conductance values . In addition, protontransmission was strongly potential- and time-dependent, with additionaltransmission sites dynamically “opening” and a smallnumber shutting off during the measurements. Reasons for this behaviorhave been suggested. A simple equivalent circuit model was proposed,analogizing these transmission sites to electrolyte-filled circularnanopores in the graphene film, which were estimated to possess dimensions(radii) on the (sub)nanometer scale, implying that atomic defectsare responsible for local proton transport, in agreement with recentmodeling16 and experimental18 works. The potentiality of SECCM for rapidly assessing the qualityof ion-selective membranes was further demonstrated by deploying afine nanopipet probe, producing high-throughput, high-resolution electrochemicaland (quasi-)topographical images that gave a more detailed pictureof the local proton transmission sites.In this study, an “electrochemicalion (proton) pump cell”configuration of SECCM has been used to probe the spatially dependentproton permeability of CVD graphene|Nafion membranes. Due to the sheerweight of statistics  over severallarge areas  and conversion ; separation technologies; and biological systems.Beyond membranes, SECCM may also have application in any areas whereion transport and/or reactive flux is a highly localized phenomenon,for example, in the characterization of corrosion-resistant coatings.Graphene has been proposed as a corrosion-resistant coating,61 and based on the results presented herein, itis clear that high-resolution, dual-channel SECCM could be deployedto rapidly assess local protection efficiency, in particular, by identifyingactivity “hot-spots” where the protective barrier maybe compromised.Overall, the resultspresented herein demonstrate the strong potentialof SECCM as a multifunctional membrane characterization tool, producinghigh-fidelity images that provide a wealth of information on spatiallyresolved ion-selective transport/transmission. Although CVD graphene|Nafionmembranes have been exclusively considered herein, ion-selective transportthrough membranes plays an important role in many applications, toname a few: electrochemical energy storage , 1,1′-ferrocenedimethanol , and potassium chloride  were used as supplied by the manufacturer. All aqueous solutionswere prepared with ultrapure deionized water .vide infra) are high-quality, with nodetectable D-peak near 1350 cm–1, indicating a relativelack of graphene defects with edge-plane character.19 Further characterization with X-ray photoelectron spectroscopy (XPS)revealed successful graphene transfer onto the Nafion membrane, withno detectable impurities or surface contamination from copper . The XPS survey reveals the expectedelemental composition  for both unmodified Nafion 211 and graphene|Nafion membranes(see SI Table S2). The C 1s spectra ofan unmodified Nafion 211 membrane show only one major main carbonpeak at 291 eV, attributed to the CF2 group of the fluorocarbonbackbone (the other low intensity peak at 284.8 eV is assigned toadventitious carbon impurities). In contrast, C 1s spectra from thegraphene|Nafion membranes show two main peaks, corresponding to theCF2 groups of Nafion and sp2 carbon atoms ofgraphene at 291 and 284.1 eV, respectively.The Nafion 211 membraneswere purchased from the Fuel Cell Store . Themonolayer CVD graphene (supported on copper foil) was purchased fromACS Material . In previous studies, Raman spectroscopyindicated that these graphene-on-copper substrates , prior to use as a WE. Ag/AgClQRCEs were prepared by anodizing 125 μm diameter Ag wire  in an aqueous saturated KCl solution. The Ag/AgClQRCEs possessed a stable reference potential  on the hours timescale in 0.1 M HCl, consistent with a previous report.62The nanocrystallinePt WE was prepared by evaporating a 2 nm Cradhesion layer followed by a 75 nm Pt layer on a borosilicate glassmicroscope slide. The glassy carbon plate was purchased from HTW Germanyand was polished with a suspension of 0.05 μm Al19 In brief,a ≈2 × 2 cm2 square of copper-supported graphenewas placed on top of a Nafion 211 disk with a diameter of ≈1.9cm and a thickness of ≈25 μm. Furthermore, two piecesof Teflon-reinforced fiberglass (of diameter ≈1.9 cm) wereplaced below and atop the Nafion|graphene on copper to serve as protectivelayers. This assembly was then placed into a hot press  and pressed at 140 °C for 2 min. Next, the Nafion|graphene|copperassembly was placed into a 0.3 M ammonium persulfate solution andallowed to react until the copper layer was fully etched away by visualinspection. Note that in previous studies,19 monolayer graphene sheets were shown to survive the Nafion hot-pressingand copper-etching processes intact, without any significant creationof additional defects or contamination from the copper substrate,as revealed by Raman spectroscopy and XPS.Nafion|graphenesandwich structures were fabricated at Clemson University, U.S.A.,using a previously reported procedure.2 nanocrystalline Pt WE withadhesive tape, ensuring intimate contact between the Nafion and Pt.The constructed Pt|Nafion|graphene electrode assembly was then fittedinto a custom sample holder with a surrounding moat of deionized water,47 effectively fixing the local relative humidity at >70%. Due tothereportedly long equilibration times associated with Nafion hydration,63 the electrode assembly was stored under these conditions overnight.Following this procedure ensured that, during SECCM experiments onthe several hours time scale, the prehydrated Nafion 211 membrane(1) possessed high bulk proton conductivity (on the order of 0.02–0.06S cm–1)42 and (2) didnot undergo significant changes in volume . An electrical connection was made by fixinga copper wire to the Pt WE surface with conductive silver epoxy resin, taking care to avoid making a connection  with the graphene overlayerfilm. Scanning electron microscopy imaging was carried out on thePt|Nafion|graphene electrode assembly, after SECCM, with a GeminiSEM500 system .Prior to scanningwith SECCM, the graphene|Nafion assembly was rinsed in deionized waterand fixed to a 2 × 2 cmi.e., calculated from the overalldiameter of the dual barrel) in the ≈10–11 to ≈10–9 cm2 (nanopipets) and≈10–8 cm2 (micropipets) ranges,were fabricated from filamented quartz and borosilicate  theta capillaries, respectively, using a CO2 laser puller . After fabrication,both barrels of the probes were backfilled with analyte solution  using a MicroFil syringe , before adding a thin layerof silicone oil  on top to minimize evaporationfrom the back of the pipet during prolonged scanning, as previouslyreported.33 Ag/AgCl QRCEs were then insertedinto each barrel, through the silicone oil layer, into the analytesolution, to finalize the SECCM probe, rendering it ready for use.After being scanned, the SECCM probes were carefully emptied and rinsedwith deionized water (using a clean MicroFil syringe) before imagingthe tip on a GeminiSEM 500 system.Double-barreledpipet probes, withtotal tip areas  was mounted on a z-piezoelectric positioner , and the Pt|Nafion|grapheneelectrode assembly  was mounted atop an xy-piezoelectric positioner.As schematized in Ebias) of0.05 V was applied between the QRCEs to induce a dc ion current (idc) between the barrels to enable meniscus positioningon the substrate.48 The SECCM probe wasinitially positioned above the WE using coarse xy-micropositioners  and subsequentlylowered into the near-surface position using a stepper motor in tandemwith an optical camera .Local electrochemicalmeasurements were carried out in the SECCM format on a home-builtscanning electrochemical probe microscopy (SEPM) workstation at theUniversity of Warwick, U.K., as previously reported.–8 cm2) was approached to the graphene overlayer film  surface using an idc thresholdof ∼500 pA to detect when the meniscus–surface contacthad been made and to stop further translation. Note that the glassportion of the probe never contacted the graphene surface. Electrochemicalmeasurements  wereperformed in the confined area defined by the meniscus cell createdbetween the SECCM probe tip and graphene surface  at voltammetricscan rates (υ) of 0.1 or 0.2 V s–1 for 1 or2 cycles, respectively. During chronoamperometry, the potential atthe Pt WE was held at −0.5 V vs Ag/AgClQRCE (0.1 M Cl–) for 10 s. Mapping was carriedout using a standard hopping mode protocol, as previously reported.50 In brief, the SECCM probe was approached to the graphene surfaceat a series of locations in a predefined grid pattern, and upon eachlanding, an independent electrochemical measurement was made, buildingup spatially resolved chronoamperometric (i–t) or voltammetric (i–E) “images” of the substrate surface. In addition, thefinal position of the z-piezoelectric positionerat approach was used to synchronously construct a “quasi-topographical”map of the Pt|Nafion|graphene electrode assembly surface. Note that,in context, “quasi” refers to the fact that the underlyingNafion membrane possesses a dynamic physical structure (topology)due to small changes in volume  on the time scale of SECCM scanning(vide supra).The SECCMprobe , held at a common ground, was measuredwith a home-built electrometer. Note that during the SECCM measurements,unless otherwise stated , the graphene membrane itself was floating .The isurf and idc were measured every 4 μs and averaged in 256 blocks to givean effective data acquisition rate of 4 × (256 + 1) = 1028 μs,where one extra iteration was used to transfer the data to the hostcomputer. A home-built eighth-order (low-pass) brick-wall filter unit(time constant = 1–10 ms) was utilized during data (current)collection. Instrumental control and data acquisition were carriedout using an FPGA card (PCIe-7852R) controlled by a LabVIEW 2016  interface running the Warwick ElectrochemicalScanning Probe Microscopy  software.The SEPM setup was located ona vibration isolation platform  located within an aluminum faraday cage equippedwith heat sinks and acoustic foam to minimize mechanical vibration,electrical noise, and thermal drift (<10 nm per minute) duringprolonged scanning.isurf data, log10|isurf|, was plotted vs xy position to create a seriesof time-resolved (chronoamperometry) or potential-resolved (cyclicvoltammetry) images, which were combined and presented as dynamicelectrochemical movies.30 The static images ofelectrochemical activity ,presented in the main text, were constructed by integrating |isurf| with respect to time to calculate surfacecharge, |Qsurf|, which was plotted aslog10|Qsurf| vs xy position. In all electrochemical images and movies, pixels withlog10|isurf| or log10|Qsurf| values less than 3× theelectrical noise level are assigned a gray color and represent proton-impermeable regionsof the graphene|Nafion membrane. The proton transmission site densitywas estimated as ≈active pixels/,taking the area wetted by the meniscus cell during contact to be equalto the tip area of the employed pipet probe. Data plotting was carriedout using the Matlab R2020 and OriginPro 2019b  software packages. Note that all electrochemical maps and moviesare presented without any data interpolation.Afteracquisition, theraw SECCM data were processed using the Matlab R2020a  software package. The logarithm of


Because these models are carefully designed to avoid a serious deformation of graphene in the tension of sandwich-like composite models, the strengthening mechanism close to the experimental theory where graphene just serves to transfer a load can be studied dynamically. The boundary comprising of two phases is confirmed to hinder the motion of dislocations, while the crack grows along the interface beside graphene, forming a fracture surface of orderly arranged Al atoms. The results indicate that single-layer graphene (SLG) gives rise to an increase of 1.2 or 0.4 GPa in tensile strength when stretched in in-plane or normal direction, while bilayer graphene (BLG) brings a clear rise of 1.2–1.3 GPa in both directions. In both in-plane and normal stretching directions, the mechanical properties of the composite can be improved clearly by graphene giving rise to a strong boundary, new crack path, and more dense structure.The powder metallurgy process of the Al–graphene system is conducted by molecular dynamics (MD) simulations to investigate the role of graphene. During the sintering process, graphene is considered to reduce the pore size and metal grain size based on the volume change and atomic configuration of the Al parts in the composite. Compared with the pure Al system, the space occupied by the same number of Al atoms in the sintered composite is 15–20 nm Owing to the superior mechanical properties, graphene is naturally expected to work as an effective reinforcement phase to improve metal matrix composite materials. Existing studies have provided quite a number of methods to fabricate metal–graphene composites such as powder metallurgy sintering, composite electroplating, differential speed rolling, etc. In those techniques, powder metallurgy sintering is supposed to be an efficient way to prepare metal–graphene composite in bulk because of the simple process and precise control, drawing considerable attention of researchers recently ,2,3.Generally, most of the investigations on sintering metal–graphene composites are performed by experiments. Some focus on problems of graphene dispersion hindering the preparation of a homogeneous structure. Mu et al. applied an electroless plating method to prepare Ni-decorated graphene nanoflakes as a reinforcement to be uniformly dispersed in a Ti matrix, and then spark plasma sintering (SPS) and hot-rolling are followed to gain a titanium matrix composite with an enormous strength increase . Ju et aThe experimental studies listed in Nevertheless, most of the MD papers only consider the system of pure metal particles ,13 or meIn the sintering systems of Al–graphene composites, MD models shown in During the sintering process, the composite structure will be heated from 300 K to 773 K in 300 ps, with the external pressure increasing from 1 atm to 500 atm (50 MPa). Then, the system maintains such temperature and pressure for 300 ps. At last, the external conditions of sintered composite will return to 300 K and 1 atm after a cooling stage of 300 ps. The NPT ensemble is also applied in the entire sintering process. It should be noted that parameter settings above such as the heating and cooling rate are selected according to the similar sintering process of the Al–graphene system in reference .Then, tensile simulation is conducted on sintered composite to examine the mechanical behaviors. Another relaxation process will be carried out at 300 K for 100 ps to eliminate thermal stress before tensile testing. The NVE ensemble is applied to operate quasi-static tension by changing the shape of the simulation box in both in-plane and normal directions, and the temperature is reset by explicitly rescaling their velocities. Verlet algorithm is used to solve Newton’s equations of motions and the time step is set to 1.0 femtosecond. The eam potential is applied to the interaction between Al atoms [airebo potential is used to link carbon atoms in graphene [morse potential [All the MD simulations are carried out by LAMMPS and the generated data are visualized by VMD software. The velocity Al atoms , the filgraphene , as commgraphene ,21,22 tootential , which iotential . 3 to 816.9 nm3 in the heating process, while the configures in 3 to 801.0 nm3; the surface morphology of sintered bulk has been basically established and the final drop of volume can be simply attributed to cold shrink in the cooling stage. This change is mainly in line with expectations, which have been reported in many experimental studies [As is known to all, the powder metallurgy process can promote densification of metal particles by virtue of plastic deformation and material transfer during the sintering, leading to a decline in porosity, a shrinkage in volume, and an increase in density. To validate the MD model in this paper, a sintering process of pure Al particles is operated, firstly, after relaxation on the initial model, followed by monitoring of the changes in system volume and surface morphology. As expected, the system temperature and pressure are successfully controlled during the sintering process a. The bl studies ,9. 3 to 806.3 nm3 during the heating stage, which keeps a lower than pure Al curve after about 150 ps, and then falls to 777. 4 nm3 at constant temperature and pressure. The curves also indicate a possibility of further decline in volume, as reported in [3, which is a little less than 759.6 nm3 of the pure Al model, even though there is an extra SLG. Therefore, the same number of Al atoms in the Al-SLG composites occupies a smaller space, as presented in Based on the pure Al model, Al–graphene composite bulks are sintered to investigate the role of graphene on the powder metallurgy process. The initial structures for sintering are prepared by inserting the graphene nanoplatelet into the gap between Al particles. Firstly, a single-layer graphene (SLG) is placed in the center gap of the pure Al model. It means both sides of the SLG are adjacent to four Al particles, forming a pore containing graphene, as marked in orted in  with impTo gain insights into the inner structure of sintered bulk, centro-symmetry parameter (CSP) analysis is performed, and the local lattice disorder is tinted in CSP values. Blue balls stand for Al atoms with bulk lattice, red balls represent surface atoms, and other colorful balls are classified as defects such as atoms in dislocation or grain boundary. Therefore, the size of Al grains can be directly determined by color configurations of atomic structures. Since red atoms imply surface atoms appearing inside, the pores can be easily found in the sintered structure. As marked with yellow circles in In order to study the effect of multilayer graphene on the powder metallurgy process, SLG in the models is substituted by bilayer graphene (BLG) to gain the Al–BLG composite. Then, the sintering simulation and structure analysis are performed as before. In comparison with the composite structure of SLG, BLG is likely to make little difference in the volume and structure of the Al–graphene composite. Based on The strengthening mechanism of graphene has been illumined experimentally by some static micro images of composite structures, where high density of dislocations accumulates around the boundary comprising two phases and this boundary is expected to hinder the motion of dislocations effectively ,28. It sy or z axis where the tension is roughly parallel or normal to graphene. Then, the stress–strain curve is drawn to compare strength and deformation, and CSP analysis of Al atoms is used to trace the change of inner structure including dislocation motion, propagation of the cavities, and morphology of fracture surface. Uniaxial tensile simulations are performed here to investigate the enhancement mechanism of graphene in metal matrix composites, and the stretching direction is along the It is remarkable that quite a few studies simply attribute the wonderful mechanical performance to graphene sharing most of the stress, where the sizes of graphene are the same as the plane size in models. However, the distribution of atom stress in The stress–strain curves of models stretched in in-plane and normal directions are drawn in 3 smaller than the pure Al structure, and the amount of arranged Al atoms in the sintered composite is about 5000 fewer too. The effect of graphene in the mechanical property is studied minutely through the tensile process on the sintered composite. The composite with the SLG can exhibit an increase of 1.2 or 0.4 GPa in tensile strength when stretched in in-plane or normal direction, while the composite with the BLG can achieve a clear rise of 1.2–1.3 GPa in both directions. This suggests that graphene is of great importance for composites to improve the mechanical performance whether in in-plane or normal tensile direction. This improvement can be attributed to the effect of graphene, contributing to the formation of two-phase boundary, new crack path, and more compact structure, which can be easily found in view of the atomic configures. MD simulations on the powder metallurgy process are performed to study the sintering process and the strengthening mechanism of the Al–graphene system. Details on volume and local crystal structure of Al atoms in a composite, which cannot be measured through the experimental method, indicate that graphene is helpful for promoting the sintering progress, improving the density of sintered structures, and refining metal grain size. The space occupied by the same number of Al atoms in the sintered composite is 15–20 nm


Sarcoidosis is an inflammatory, systemic, idiopathic disease characterized by multisystem involvement, of which mediastinal and pulmonary involvement is the most frequent. Mammary sarcoidosis is exceptional.We report the case of a 50-year-old, diagnosed with mediastinal and mammary sarcoidosis. Therapeutic abstention with clinical and radiological surveillance was recommended. The evolution was marked by a clear improvement .Mammary sarcoidosis is a rare anatomical and clinical entity which poses a problem of differential diagnosis with other granulomatous diseases and especially with breast carcinoma. The coexistence of systemic manifestations should lead to the discussion of sarcoidosis.Mammary sarcoidosis involvement is rare and is manifested by a mass with a smooth or spiculated border, requiring the exclusion of malignancy. •Mammary sarcoidosis is a rare clinical entity.•The final diagnosis is based on a combination of clinical, biological, radiological, and pathological findings.•The main differential diagnosis of mammary sarcoidosis is tuberculosis and breast cancer.•Corticosteroid therapy is the reference treatment for breast sarcoidosis. The tru2A 50-year-old diabetic female patient, who has been on oral hypoglycemics for seven years. She had never been treated for tuberculosis and had no recent history of a tuberculosis contact. She reported the appearance of bilateral cervical lymphadenopathy two months before her admission, without any other associated respiratory or extra-respiratory signs, all evolving in a context of fever, night sweats, and preservation of her general condition. The physical examination revealed a patient in a good general condition (PS 1) with multiple lymphadenopathies of different sizes, painless and without any inflammatory signs, located in the cervical, axillary, epitrochlear, and inguinal regions. The rest of the physical examination was unremarkable.The chest X-ray showed a left hilar opacity and a right paracardiac opacity . The comThe patient was put on anti-tuberculosis as tuberculosis was highly suspected due to the epidemiological context, the clinical symptomatology and the strong positivity of the tuberculin test. On the fifteenth day, she developed a generalized pruritic erythematous rash that required the interruption of the treatment. A thoracic CT scan was performed, which revealed mediastinal hilar and axillary adenopathy without parenchymal involvement and a right breast lump b.Fig. 2aBronchoscopy showed thickening of the left upper lobar spur, bronchoalveolar lavage was predominantly lymphocytic (42%), staged bronchial biopsies were negative as well as the search for AFB in the bronchial aspiration fluid.Bilateral mammography and mammary ultrasound showed a right and left breast lump which is classified respectively BI-RADS V and BI-RADS IV b. The brThe phosphocalcic balance, the electrocardiogram, and the ophthalmic exam were without abnormalities. The biopsy of the accessory salivary glands showed the presence of a giant cellular epithelioid granuloma without caseous necrosis compatible with sarcoidosis. The pulmonary function test showed a correct total lung capacity (TLC). Beta microglobulinemia, serum protein electrophoresis, and abdominal ultrasound were without abnormalities.The diagnosis of sarcoidosis was based on clinical, radiological, biological, and histological criteria .Therapeutic abstention was recommended with clinical and radiological surveillance. The evolution was marked over two years by the disappearance of arthralgias, hilar adenopathies  and peri3Sarcoidosis is a granulomatous pathology with multi-systemic involvement that is pathologically manifested by the formation of non-caseating epithelioid granulomas . It mainThe etiology of sarcoidosis is still poorly understood; numerous investigations into the existence of an infectious agent that may induce the disease have been conducted in recent years. The frequent presence of mycobacterial DNA has been reported in patients with sarcoidosis. Other infectious agents have also been incriminated, such as herpes or Epstein-Barr virus (EBV), but also other bacteria such as Borrelia burgdorferi. Other theories have also emerged, including exposure to environmental  .Sarcoidosis is a systemic inflammatory disorder that is characterized by an immune response involving T-helper cells in which CD4 lymphocytes and activated macrophages accumulate in the affected organs, leading to granuloma formation. An undiscovered antigen, processed by activated macrophages, induces an immune response modulated by T cells and macrophages that release a broad spectrum of mediators, including cytokines, chemokines, and oxygen radicals involved in the etiopathogenesis .Breast involvement in sarcoidosis is rare and represents about 1% of cases . It may Mammography may show well-limited heterogeneous opacities or single or multiple spiculated opacities simulating a malignant mass, small round well-defined masses have also been described, reflecting intramammary lymph node involvement, and ultrasound may show the mass as well or poorly limited hypoechoic opacities ,12. BreaThe diagnostic criteria for sarcoidosis include a suggestive clinical and radiological background, demonstration of epithelioid and giant cellular granuloma without caseous necrosis, and elimination of other known causes of granuloma . BronchoTuberculin anergy is present in 75% of cases; positive TST does not exclude sarcoidosis, as in our patient's case where a positive TST was found. The diagnostic value of serum angiotensin-converting enzyme is low ,15. The Histological investigations should be performed in a hierarchical manner . The senThe differential diagnosis is mainly with other granulomatosis  and in pTuberculosis and sarcoidosis are both granulomatosis diseases that have similar clinical and radiological aspects that are sometimes very difficult to differentiate between the two pathologies, many cases of tuberculosis are initially misdiagnosed as sarcoidosis and vice versa . As in tIn this context, the diagnosis of tuberculosis is established by a positive culture from body fluids or tissues, but may not be possible in some organs because of difficulties in non-invasive access or because of the inability to obtain results. In this case, the positivity of interferon-gamma release assays (IGRA) and tuberculin intradermal reaction at a threshold of 13 mm remains strongly associated with tuberculosis infection with a sensitivity of 54% and specificity of 90% ,21.+ T lymphocytes [+ T cells, regulatory T cells, Th17 and B cells) is organized [The granuloma without caseous necrosis, the main but non-specific lesion, is composed of macrophages, epithelioid and giant cells in the center, in close contact with CD4phocytes . Around rganized . Howeverrganized .In our patient, non-necrotizing granulomas were found in three different sites . Corticosteroid therapy is the reference treatment for breast sarcoidosis, allowing a satisfactory clinical and radiological improvement . Immunos4Breast sarcoidosis is rare and appears clinically as a palpable mass or incidentally discovered on screening mammography. It has a differential diagnosis problem with breast cancer and tuberculosis, so histological examination should be mandatory to establish an early and conclusive diagnosis of breast sarcoidosis.No ethical approval necessary.The author(s) received no financial support for the research, authorship and/or publication of this article.Meriem Rhazari, Abdelbassir Ramdani: Writing, review and editing of the manuscript.Sara Gartini, Siham Bouali, Mohammed Aharmim, Afaf Thouil, Hatim Kouismi: Contributed for diagnose and treatment of the patient.Jamal Eddine Bourkadi: Supervised the writing of manuscript.Our paper is a case report; no registration was done for it.Meriem Rhazari, Abdelbassir Ramdani.Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.Not commissioned, externally peer reviewed.Data will be made available on request.The authors declared no potential conflicts of interests with respect to research, authorship and/or publication of the article.