In a magnetic field, combination of quantum Hall physics and the characteristic transport across p–n junctions leads to a fractionally quantized conductance associated with the mixing of electron-like and hole-like modes and their subsequent partitioning. The mixing and partitioning suggest that a p–n junction could be used as an electronic beam splitter. Here we report the shot noise study of the mode-mixing process and demonstrate the crucial role of the p–n junction length. For short p–n junctions, the amplitude of the noise is consistent with an electronic beam-splitter behaviour, whereas, for longer p–n junctions, it is reduced by the energy relaxation. Remarkably, the relaxation length is much larger than typical size of mesoscopic devices, encouraging using graphene for electron quantum optics and quantum information processing.Graphene offers a unique system to investigate transport of Dirac Fermions at  Dirac fermions at a p–n junction can exhibit a wide variety of unusual properties. Here, the authors investigate the dynamics of such fermions in a graphene junction using shot noise measurements and demonstrate the crucial role of junction length. Investigations of charge carrier transport across such a p–n junction (PNJ) have revealed unique phenomena reflecting the Dirac Fermion character in graphene, such as Klein tunneling125B, the conductance across a PNJ shows plateaus at GPNJ=G0|ν1||ν2|/(|ν1|+|ν2|), where G0=e2/h is the conductance quantum (h is Planck's constant), ν1=2, 6, 10, … and ν2=−2, −6, −10, … are the Landau level filling factor in the n and p regions, respectively7810ν1 and ν2, and then partitioned at the exit of the PNJ  becomes out-of-equilibrium and the subsequent partitioning of the modes gives rise to the shot noise. If the mode mixing is quasielastic, fPNJ(E) is a double-step function. At zero temperature, the shot noise generated by the partitioning of the modes with double-step fPNJ(E) is expected to be =. Energy losses towards external degrees of freedom can drive fPNJ(E) towards a Fermi distribution with a chemical potential eVsd/2 (1516fPNJ(E) to relax towards a Fermi distribution with a finite temperature Teff(Vsd) given by the balance between the Joule power dissipated in the PNJ and the heat flowing along the outgoing electronic channels10ν1, ν2)=]. Note that standard transport measurements yield the same value of GPNJ for all cases, and thus cannot distinguish them.characterized by the Fano factor l eVsd/2 151617, csd/2 1516. InelastfPNJ(E) with carrier dwell time in the PNJ, which can be tuned by changing the length of the PNJ. We demonstrate that the amplitude of the noise is consistent with an electronic beam-splitter behaviour when PNJ is short and the energy losses are negligible.In the following, we investigate the evolution of VG, while that in the ungated region is fixed to electron by the doping (Methods). Therefore, the PNJ is formed at the interface between the gated and ungated regions when the carrier type in the gated region is hole for ΔVG≡VG−VCNP<0 . We prepared five samples with different interface lengths L=5, 10, 20, 50, and 100 μm. The direction of B is chosen so that electron and hole modes from the ohmic contacts Vsd is applied to either Cdet = is formed for ΔVG<−10 V, the current injected from SI appears in this regime. As Vsd applied to SI≡SI−SI(Vsd=0) increases = for 20<ΔVG<50 V, on the other hand, the shot noise is zero (solid black circles), proving that the shot noise is indeed generated at the PNJ.The inset of F by fitting ΔSI as a function of Vsd using the relation including temperature broadeningQuantitatively, we extracted GPNJ is obtained by average current measurements. The fit yields F=0.015, which is one order of magnitude smaller than F=0.25 expected for the noise from the double-step energy distribution. This indicates that fPNJ(E) evolves during the charge propagation for L=50 μm, reducing the shot noise.where fPNJ(E) can be investigated using samples with different L. νug, νg)= for the five samples with L between 5 and 100 μm. The data show that the shot noise decreases with increasing L and almost disappears at L=100 μm (fPNJ(E) relaxes to the thermal equilibrium through interactions with external degrees of freedom. An exponential fit of the data yields a relaxation length L0=15 μm. The extrapolation to L=0 gives F∼0.27, consistent with the limit of quasielastic scattering F=0.25. Furthermore, the decrease is well reproduced by a model gradually coupling the modes propagating in the PNJ to cold external states = is formed for B>4 T and between νg=0 and −4 (the region indicated by dashed lines), in which the current is almost constant, consistent with the quantized conductance78L=10 μm becomes small , generating shot noise. For a short PNJ (L<<15 μm), the energy loss towards external states is negligible and the noise is consistent with a quasielastic mode mixing. This suggests that a graphene PNJ can act as a beam splitter. Since 15 μm is much larger than typical length scale of mesoscopic devices, our results encourage using graphene for electron quantum optics experiments and quantum information.In conclusion, we showed that the mode mixing at PNJ in graphene bipolar QH states leads to non-equilibrium 2 atmosphere. After the etching, the surface was covered with 100-nm-thick hydrogen silsesquioxane (HSQ) and 60-nm-thick SiO2 insulating layers. As a result of doping from the SiC substrate and the HSQ layer, graphene has n-type carriers with the density of about 5 × 1011 cm−2. The width of the PNJ roughly corresponds to the thickness of the insulating layers and estimated to be 200 nm at most. In the QH effect regime, because of the Landau level quantization, the width becomes smaller with B. An important advantage of the SiC graphene is its size: it is single domain for 1 cm2, allowing us to investigate the effect of PNJ length.We prepared a graphene wafer by thermal decomposition of a 6H-SiC(0001) substrate. SiC substrates were annealed at around 1,800 °C in Ar at a pressure of <100 torr. For the fabrication of devices, graphene was etched in an Oν=2 and the temperature of the system.For the noise measurement, the current noise is converted into voltage fluctuations across one 2.5 kΩ resistor in series with the sample. A 500-kHz bandwidth 3-MHz tank circuit combined with a homemade cryogenic amplifier is used. After further amplification and digitization, the autocorrelation voltage noise spectra is calculated in real-time by a computer. Accurate calibration of the noise is done using Johnson–Nyquist noise that relies on the quantification of the resistance at How to cite this article: Kumada, N. et al. Shot noise generated by graphene p–n junctions in the quantum Hall effect regime. Nat. Commun. 6:8068 doi: 10.1038/ncomms9068 (2015).Supplementary Figures 1-5, Supplementary Note 1, Supplementary Methods and Supplementary References


In this work, we investigate the physical dynamics of all-optical control on a graphene-on-Si3N4 chip based on thermo-optic effect. In the experimental demonstration, a switching response time constant of 253.0 ns at a switching energy of ~50 nJ is obtained with a device dimension of 60 μm × 60 μm, corresponding to a figure of merit (FOM) of 3.0 nJ mm. Detailed coupled-mode theory based analysis on the thermo-optic effect of the device has been performed.All-optical signal processing avoids the conversion between optical signals and electronic signals and thus has the potential to achieve a power efficient photonic system. Micro-scale all-optical devices for light manipulation are the key components in the all-optical signal processing and have been built on the semiconductor platforms . However, the two-photon absorption (TPA) effect and the free-carrier absorption (FCA) effect in these platforms deteriorate the power handling and limit the capability to realize complex functions. Instead, silicon nitride (Si Based on these semiconductor platforms, micro-scale all-optical devices for light manipulation have been reported with picosecond response time1 or femto-joule energy consumption2. However, the finite bandgap of these semiconductor materials introduces the two-photon absorption (TPA) effect and the free-carrier absorption (FCA) effect in the 1550-nm telecom band3. These effects increase the light propagation loss and even worse, this loss increases with the injected optical power. The latter results in weak power handling, i.e., the maximum optical power which can be effectively utilized in a photonic chip. This further limits the allowed number of cascaded functional blocks in a semiconductor photonic chip and the capability to realize complex functions.All-optical signal processing avoids the conversion between optical signals and electronic signals and thus a power efficient all-optical system has the potential to replace current electronic systems. A main obstacle preventing the development of all-optical system is the limited capability of large-scale integration. Silicon and III-V semiconductors such as InP and GaAs, are promising platforms for photonic integration3N4) is a promising candidate material to improve power handling of photonic integrated circuits because its insulator nature guarantees no TPA and FCA at telecommunication wavelength. Recently, various nonlinear applications based on Si3N4 photonic devices have been demonstrated, including frequency comb generation6, supercontinuum generation7 and so on. Bistability of a graphene-on-Si3N4 micro-ring resonator (MRR) has also been investigated8. However, it is still challenging to effectively manipulate light with Si3N4. A reported Si3N4 all-optical switch based on the Kerr nonlinearity (n2 = 2.4 × 10−15 cm2W−1) has limited extinction ratio (ER) due to the short interaction length on a chip which makes it difficult for practical switching applications9. Thermo-optic effect is another possible solution for all-optical control of light with good extinction ratio11. But the thermo-optic effect (2.5 × 10−5 K−1 12) and the thermal conductivity (30 W·m−1 K−1 13) of Si3N4 are weaker than those of silicon (1.8 × 10−4 K−1 and 130 W m−1 K−1 14), which lead to a low control efficiency and high power consumption. A reported Si3N4 thermo-optic switch based on MRR has a typical switching time of 5 µs and a switching energy more than 1 µJ15. Therefore, a new mechanism is highly desired for the effective all-optical light control in a photonic Si3N4 device.Silicon nitride  to avoid the metal induced huge optical absorption, graphene can directly contact with waveguides since it has a low absorption rate19. These two properties result in a highly efficient heat transfer from graphene to waveguides and allow the possibility to significantly enhance the efficiency of the all-optical control on a graphene-on-Si3N4 integrated platform based on thermo-optic effect.Graphene as a two-dimensional (2D) material, has been widely utilized as an efficient absorber for optical modulation3N4 integrated platform. The high thermal conductivity of graphene and the direct contact between graphene and the waveguide effectively compensate the weak thermo-optic effect and thermal conductivity of Si3N4. The experimental demonstration of all-optical switching with MRR has been realized with a switching time of 253.0 ns, which is 20-fold faster than the abovementioned Si3N4 thermo-optic switch and even 2-fold faster than a recently reported switch with graphene-on-silicon photonic crystal structure20. Detailed modeling and simulation based on coupled-mode theory (CMT) have also been performed to understand the physical dynamics behind the experimental results. Our work reveals the heating and cooling mechanisms of all-optical control of light on an insulator Si3N4 platform by incorporating graphene and may pave the way to a large-scale integrated all-optical signal processor.In this work, we investigate all-optical control of light on graphene-on-Si3N4 MRR with a graphene sheet on top. The MRR has a diameter of 60 μm and is side-coupled to a straight waveguide. The gap distance between the MRR and the straight waveguide is set to 100 nm. The waveguides used to construct both the MRR and the straight waveguide have a width of 1.2 µm and a height of 400 nm. Inverse tapers with 1 µm wide tips are integrated for input and output terminals of the waveguides to enhance the coupling between the waveguides and tapered lensed fibers.The schematic diagram of the all-optical device is shown in Fig. 22r is the radius of the MRR, neff is the effective refractive index of the graphene-on-Si3N4 hybrid waveguide forming the MRR and m is a positive integer known as resonance order. When a pump light at a certain resonance wavelength is injected into the resonator, part of its power is absorbed by the graphene and converted to heat. The heat is then directly transferred to the Si3N4 waveguide under the graphene. Since Si3N4 has a positive thermo-optic coefficient of ~2.5∙10−5 K−1, the resonance wavelength experiences a red shift. If the wavelength of a probe light is set near the resonance wavelength, its transmission will be changed accordingly.The principle of the device is based on the graphene assisted thermo-optic tuning of the resonance wavelength of the MRR. The resonance wavelength of the MRR is given by3N4 layer and a 5-µm-thick SiO2 buried oxide (BOX) layer. The Si3N4 device was defined by standard electron beam lithography (EBL) and inductive coupling plasma (ICP) etching processes. Chemical vapor deposition (CVD) grown graphene on a copper foil was then wet-transferred on top of the device. After the graphene transfer, the graphene layer was patterned by EBL and oxygen plasma etching processes. Thus only part of the MRR was covered by the graphene sheet after oxygen plasma etching process and the absorption from graphene was reduced. As shown in the scanning electron microscope (SEM) image of the device in Fig. The device was fabricated on a commercial wafer with a 400-nm-thick top Si22. The 3-dB bandwidth is 0.52 nm at 1550 nm, corresponding to a Q factor of 2981. Here the graphene induced waveguide propagation loss is estimated to be 113 dB/cm 15, our efficiency is 4 times higher, which confirms the increased heating efficiency by graphene.The static thermo-optic tuning efficiency of the MRR is first characterized by a CW pump laser source and a tunable laser source as shown in Fig. t/τr) and exp(−t/τf), respectively, the time constants are estimated to be τr = 253.0 ns and τf = 888.3 ns. The rising edge is determined by the heating process from the injected pump power and the heat dissipation to the air and substrate whereas the falling edge is only determined by the cooling process from heat dissipation. When the wavelength is biased at point B of 1510.1 nm, a pump pulse induces a switch from “on” state (high transmission) to “off” state (low transmission) of the probe as shown in Fig. τf = 219.6 ns and τr = 860 ns, respectively. In the heating process, the falling edge of the dark pulse is slightly faster than the rising edge of a bright pulse in Fig. Figure ω in the experiment and then the probe signal light is modulated. To clearly understand the dynamic process of the pump light induced switching, the nonlinear time-domain coupled-mode theory has been applied to perform the simulation. The behavior of pump light and the device are described by the following equations23ω is the frequency of the input pump light, ω0 is the resonant frequency of the cold cavity and Δω is the time-dependent cavity resonance shift due to the thermo-optic effect. In the experiment, ω is equal to ω0. a represents the amplitude for the resonant mode (at the pump light frequency) with the unit of J−1/2. 1/τ0 and 1/τe are the decay rates due to the cavity loss and the waveguide-resonator coupling, respectively. κ is the coupling coefficient between the waveguide and the resonator. 1/τe and κ are related to each other by |κ|2 = 2/τe. Pin is the pump power in the input waveguide. ΔT is the temperature change of the graphene-on-Si3N4 hybrid waveguide. It should be noted that here ΔT represents the average temperature change of the whole micro-ring waveguide because the actual heat distribution is not uniform along the micro-ring waveguide  is the group index of the waveguide. By fitting the transmission spectra of the device (see supplement τe = 6.22 ps (unchanged with or without graphene), τ0 = 11.16 ps (with graphene), τ0′ = 23.23 ps (without graphene) and τlinear = 10.73 ps. And |κ|2 = 2/τe = 3.21 × 1011 s−1.Heating process is the key process which determines the device performance. In the heating process, the pump light induces the resonance frequency shift Δmentclass2pt{minim23ω′ is the frequency of the input CW probe light, ω0′ is the resonant frequency of the cold cavity for the probe light. a′ is the resonant mode amplitude. Pin′ is the CW probe light in the input waveguide. Sout′ denotes the amplitude of the output probe wave whose squared magnitude is equal to the power of output probe wave. Note that, there is no mutual coupling between the two resonance modes due to different frequencies.For the resonant mode at the frequency of the probe light, the behavior of the probe light can be similarly described by the following equationsBy using equations –6), the, the6), 3N4 and SiO2 are 2000, 29 and 1.38 W/m∙K, respectively24. The heat convection coefficient for air is 5 W/m2∙K24. The graphene thickness is 0.5 nm. It can be found that the maximum temperature change is ΔTmax = 18.4 K. Then the average temperature change ΔT can be roughly estimated by considering the ratio between the length of graphene layer (43.4 μm) and the length of the micro-ring (π∙60 μm = 188.5 μm), i.e., ΔT = ΔTmax∙43.4/188.5 = 4.23 K. The corresponding control efficiency is ΔT/10 mW = 0.423 K/mW. When the pump power is increased to 200 mW, the ideal temperature change should be 0.423∙200 K = 84.6 K. However, the actual average temperature change obtained by the above CMT based analysis is ~26 K. This is because in the dynamic operation with a pulsed pump, the absorption of the high pump power (200 mW) causes the shift of the MRR resonance wavelength and the actual absorbed pump power decreases. As a result, the control efficiency also decreases. The temperature of the graphene can be estimated as 26 K/43.4∙188.5 = 113 K.A quantitative analysis on the temperature change is also performed based on the simulation of 2D cross section of the graphene covered micro-ring waveguide. The calculated temperature distribution is shown in Fig. A 3D temperature at 10 mW pump power is also simulated for illustration and shown in the inset of Fig. 3N4 integrated platform using thermo-optic effect, a comparison between our work and reported similar works with insulator materials  is provided in Table To further clarify the performance of an all-optical device on graphene-on-Si20. In this geometry, the control light and the incoming data stream are coupled to the first straight waveguide. The data stream can be routed either to the output port of the first waveguide  or the output port of the second waveguide  by the presence or absence of a control light pulse.Our demonstrated device can be used as a switch for all-optical routing. For such an application, another straight waveguide should be added at the other side of the micro-ring resonator to form an “add-drop” configuration3N4 integrated chip using thermo-optic effect. The high thermal conductivity of graphene compensates the low thermo-optic effect in Si3N4 while maintaining the advantages brought by the insulator nature of Si3N4. In our experimental demonstration, the device has a switching time of 253 ns, a switching energy of ~50 nJ and a figure of merit of 3.0 nJ mm. The device has a good balance between power consumption and integration. Moreover, coupled-mode theory based simulation reveals the physical dynamics of the heating and cooling processes of the device. Our demonstration may pave the way for integrated all-optical signal processing in an insulator platform which allows large-scale integration with high power handling.In conclusion, we have investigated all-optical control of light on a graphene-on-SiSupplementary materials


Two-dimensional (2D) graphene emerged as an outstanding material for plasmonic and photonic applications due to its charge-density tunability, high electron mobility, optical transparency and mechanical flexibility. Recently, novel fabrication processes have realised a three-dimensional (3D) nanoporous configuration of high-quality monolayer graphene which provides a third dimension to this material. In this work, we investigate the optical behaviour of nanoporous graphene by means of terahertz and infrared spectroscopy. We reveal the presence of intrinsic 2D Dirac plasmons in 3D nanoporous graphene disclosing strong plasmonic absorptions tunable from terahertz to mid-infrared via controllable doping level and porosity. In the far-field the spectral width of these absorptions is large enough to cover most of the mid-Infrared fingerprint region with a single plasmon excitation. The enhanced surface area of nanoporous structures combined with their broad band plasmon absorption could pave the way for novel and competitive nanoporous-graphene based plasmonic-sensors. Recently, fabrication processes have realised three-dimensional nanoporous graphene. Here, the authors reveal two-dimensional Dirac plasmons in three-dimensional nanoporous graphene disclosing strong plasmonic absorptions tunable from terahertz to mid-infrared via controllable doping level and porosity. Plasmons, the collective oscillations of electrons in metals and doped semiconductors, show notable properties including a strong interaction with the electromagnetic field, reduced wavelength in comparison with that of exciting light and a huge electric field enhancement several orders of magnitude larger than the incident light field. Those properties are at the basis of surface-enhanced Raman and Infrared spectroscopies which are now routinely used in many bio-sensing applications124851048Recently a novel fabrication process allowed researchers to obtain a 3D nanoporous configuration of high-quality monolayer graphene1314151614EF∼70 meV) have a thickness spanning from 10 to 30 μm and their pore size can be engineered from about 200 nm to nearly 1 μm. The samples here investigated were well characterized through photoemission (PES), Raman spectroscopy, and transport measurements131415EF up to 340 meV  method13T(ν) was measured from the THz range (30 cm−1) to the Near Infrared  at room-temperature with a Michelson Bruker 66v Interferometer kept under vacuum. Due to their micrometric thickness the samples of NPG are free-standing so they have been directly mounted onto a metal frame located in the focal plane of a Michelson interferometer. A typical extinction spectrum E(ν)=1−T(ν) of a NPG sample having an average porous size p=200±50 nm and a thickness t=10±1 μm, is reported in α∼2.3%, and therefore a transmittance T=97.7%. This high-frequency absorption is related to Dirac intercone transitions. NPG samples instead, due to their finite (micrometric) thickness show, in the same spectral range, a nearly constant transmittance as low as a few percent or lower corresponding to an extinction E∼99% (σ(ν) by means of a Kramers–Kronig consistent fit (see Methods section). This quantity, shown in σHF evaluated around 7,000 cm−1. Three main features are well evident in −1, σ(ν) increases saturating at higher frequency. This absorption, like in single-layer graphene, can be associated with intercone electronic transitions. The small narrow peak around 1,600 cm−1 roughly coincides with the graphene G phonon which becomes infrared active probably due to disorder. In the following we do not discuss this spectroscopic feature. At low frequency, where for a single layer non patterned graphene having a finite Fermi energy one would expect a Drude absorption, NPG instead exhibits a peak at a finite frequency. This peak, which has been also observed in single-layer disordered grapheneThe optical transmittance on E∼99% . From thThe plasmon and the interband transition are separated by a broad minimum as the Dirac intercone electronic transitions are forbidden for photon energies below the Fermi energy (Pauli-blocking). Thus to separate the plasmon absorption from the interband transition, and tracing the plasmon characteristic frequency versus the Fermi energy and the pore size, we fit the optical conductivity through the sum of two components: a Lorentz oscillator, which describes the low-frequency peak, plus the conventional graphene interband term21νpl and Γpl are the plasmon frequency and linewidth, respectively, while T and EF are the temperature and the Fermi energy. B(C) defines the intensity of the plasmon absorption (interband transition). To the terms of A∼0.3–0.4), depending on the sample, already observed in single layer and few layers graphene, whose origin is probably related to charged impurities and extrinsic scattering centers20here EF, whose slope increases for decreasing temperature. For the NPG sample shown in −1 against an experimental broadening of about 3,000 cm−1. This suggests that both disorder and a spatial inhomogeneity of Fermi Energy should be taken into account in order to describe the experimental data as suggested also for single layer grapheneEF1 and EF2, the convolution yields an analytical expression for σ(ν)  . The resνpl and the average Fermi energy EF=(EF1+EF2)/2 (The convolution model thus provides information on both absorption mechanisms (plasmon and interband), allowing one to retrieve the relevant parameters defining the plasmon behaviour: the plasmon frequency 1+EF2)/2 . This laIn micro- and nano- ordered structures based on conventional metals and 2D electron gas systems352425262728In this section we study the optical conductivity of nanoporous graphene samples as a function of charge-density, that is, of the Fermi energy, for a fixed pore size, which allows one to investigate the effect of doping for a given geometry. We span a Fermi energy interval from 70 meV, for as-grown NPG samples, to 340 meV in intentionally Nitrogen doped systems (N-NPG)31p=200±50 nm) and thickness (t=10±1 μm), versus an increasing Fermi energy. The corresponding optical conductivity normalized to its high-frequency value is plotted in the right panels (from e to h). The Fermi energy values were obtained from fitting to the experimental optical conductivity (see above) and correspond well to the values provided by independent measurements on samples from the same batchEF increases towards higher energies (from e to h), the plasmon peak is blue shifted. This is expected when the carrier density increases due to a stiffening of the plasmonic restoring forceIn νpl versus EF as obtained from fitting of data in νpl clearly increases with EF passing from nearly 60 cm−1 for EF∼70 meV to about 800 cm−1 for the highest doped N-NPG sample with EF∼340 meV. The value of Γpl also increases from 200 to 2,500 cm−1 with increasing EF, and is much larger than the mean values found in 2D graphene2 V−1 S−1. Therefore, although we cannot completely rule-out a possible increase of losses in NPG plasmons with respect to single-layer graphene, we mainly ascribe their broad linewidth Γpl to the statistical distribution of Fermi energy and pore size in the 3D structure  and L is a geometrical factorL depends on the geometrical shape of the micro/nano object , and has been set to 12.5 for a perfect circular disk composed of a single layer graphene. However, one could expect a variation of L with the disk shape  and on the graphene thickness, which has been fixed to 0.5 nm in ref. L as a free fitting parameter, while all other parameters in L=10.5±0.5 and the corresponding fit is reported through a black-dashed line in F, p and L. As evident from Here To further support this finding, we have compared our data to experimental observations available in recent literature, which accounts for plasmons in graphene structures ranging in a variety of sizes (from 50 nm to 4 μm), shapes (disks and ribbons) and interfaces. In particular we superimpose on our data in The good comparison among experimental data, theoretical fit and literature reports suggests that, although we are dealing with a disordered 3D structure, the plasmon excitation in NPG and N-NPG preserves a 2D Dirac character. This indicates further that plasmonic modes in NPG and N-NPG graphene represent the natural extension in 3D of Dirac plasmons in single-layer/few-layers graphene.We also investigated the optical conductivity of nanoporous graphene samples as a function of the pore size for a constant Fermi energy. This allows one to extract the dependence of the plasmon frequency on the pore size at a fixed charge density.EF∼70 meV and an average pore size of 900±100, 650±90 and 200±50 nm, respectively. As evident in SEM images, pore sizes are randomly distributed. While the statistical pore spatial distribution mirrors in spectra independent of light polarization (νpl whose behaviour versus 1/p (p is the average pore size), is plotted in νpl from 80 to 300 cm−1 shows an appreciable dependence on the pore size. Experimental error bars have been estimated through a statistical analysis on several samples having, nominally, the same properties. The behaviour of νpl versus 1/p can be calculated by using the same analytic model summarized in the previous section  well describes the experimental data. The error bars on the theoretical data (represented by a blue shaded area around the dashed black line), take into account the uncertainties on the parameters entering the calculation. The good agreement between data and theory further allows us to attribute this spectral feature to plasmon excitation of Dirac carriers in NPG.In rization , from Fi section . Here wep, frequencies from literature data have been rescaled according to In −1). By taking into account the enhanced surface area of nanoporous structures, the tunability of graphene plasmon and the broad spectral response, the use of 3D NPG could pave the way for novel and competitive graphene based plasmonic-sensors.In conclusion, this work represents a systematic optical investigation of 3D nanoporous structures made of high-quality single-layer graphene. The optical conductivity of this non-periodic array of graphene nano- and micro-pores exhibits both single-carrier interband transitions and collective plasmonic modes resonating at Terahertz and Mid-Infrared frequencies. The plasmonic excitation depends both on doping and on the nanostructure geometry, the latter providing the extra-momentum needed to activate the radiation absorption process. The plasmon frequency dependence on the charge-carrier density (parametrized in terms of the Fermi energy), and pore size are in good agreement with a 2D Dirac character of plasmonic excitations in the 3D architecture of nano-porous graphene. This suggests that the extreme wavelength-compression and field enhancement of graphene plasmons is at work. Furthermore for N-doped samples, the microscopic inhomogeneity of doping and pore sizes yields a macroscopic plasmonic response that covers a wide spectral range  using an Ar-protected arc melting furnace. After annealing at 900 °C for 24 h for microstructure and composition homogenization, the ingots were cold-rolled to thin sheets with a thickness of ≈50 μm at room temperature. Nanoporous Ni substrates were prepared from these sheets, by chemical dealloying them in a 1.0 M (NH4)2SO4 aqueous solution at 50 °C. After de-alloying, the Ni substrates were rinsed thoroughly with water and ethanol and dried in vacuum.Ni2, respectively. After the reduction pre-treatment, benzene  or pyridine  was introduced with the gas flow of Ar  and H2 (100 sccm) for graphene growth. Typical CVD time is 2 min cleaning and 2 min deposition time at 800 °C for 200 nm pore size, 6 min cleaning and 2 min deposition time at 900 °C for 600–700 nm pore size and 18 min cleaning and 2 min deposition time at 900 °C for 1 μm pores. Moreover, typical CVD time of N-doped graphene is 2 min cleaning and 2 min deposition at 800 °C for 200 nm pore size, 8 min cleaning at 900 °C and 2 min deposition time at 800 °C for 600–700 nm pore size and 20 min cleaning at 900 °C and 2 min deposition at 800 °C for 1 μm pores. The furnace was quickly opened to quench the inner quartz tube with a fan to room temperature. The nanoporous Ni substrates were dissolved by 1.0 M HCl solution and then transferred into 2.0 M HCl solution to dissolve the residual Ni and Mn. The samples were repeatedly washed in distilled water for 5 times and floated on water for overnight.Nanoporous Ni substrates loaded in a quartz tube were inserted into the center of a quartz-tube furnace and annealed at 800 or 900 °C under 2,500 sccm Ar and 100 sccm HThe microstructure of the NPG samples was characterized by a scanning electron microscope . The chemical bonding states of the Nitrogen doped NPG were studied by X-ray photoelectron spectroscopy  with Al Ka and X-ray monochromator. Raman spectra were recorded by using a micro-Raman spectrometer  with an incident wavelength of 514.5 nm. Finally, Photoemission spectroscopy was used for investigating the electronic properties of nanoporous graphene around the Fermi energy13−1) to the Near Infrared . Measurements were performed with a Michelson Interferometer Bruker 66v kept under vacuum and at room-temperature. The sample was fixed onto a copper frame with a 2 mm aperture, allowing the film to be free-standing over the aperture. An empty copper frame with an identical aperture was used to collect the reference spectrum I0(ν). Transmittance T(ν) was then computed as the ratio IS(ν)/I0(ν) between the spectrum transmitted by the sample IS(ν) and the reference.The real part of the optical conductivity σ(ν) was obtained from the measured T(ν) by means of a Kramers-Kronig consistent analysis software .We measured the optical transmittance of 3D NPG samples from the THz range (30 cmp can be written for pω=2πν), as:Analytic calculation of the electromagnetic behaviour of NPG can be obtained considering NPG and N-NPG like an incoherent superposition of graphene single layers decorated by circular holes. The polarizability of a hole of diameter A and L are material- and size-independent constantsσ(ω) is the graphene conductivity which takes the following form:Here, e is the elementary charge, ħ is the reduced Plank's constant γ is the scattering rate of Dirac electrons.where By substituting equation (9) in equation (8), the plasmon frequency can be determined by looking for the zero of the real part of the polarizzability. This corresponds to:α is the fine-structure constant. Furthermore inter-layer plasmonic hybridization can be confidently neglected given that the expected energy decay of graphene plasmons is extremely compressed and estimated in the 5 nm rangeEF, p, L and dielectric environments 1 and 2.as reported in the text, where The data that support the findings of this study are available from the corresponding author on request.How to cite this article: D'Apuzzo, F. et al. Terahertz and mid-infrared plasmons in three-dimensional nanoporous graphene. Nat. Commun.8, 14885 doi: 10.1038/ncomms14885 (2017).Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.Supplementary Figures, Supplementary Notes, Supplementary Table and Supplementary References


The innovative design of sliding transfer based on a liquid substrate can succinctly transfer high‐quality, wafer‐size, and contamination‐free graphene within a few seconds. Moreover, it can be extended to transfer other 2D materials. The efficient sliding transfer approach can obtain high‐quality and large‐area graphene for fundamental research and industrial applications. The successful isolation of high‐quality single‐layer or few‐layer graphene by mechanical exfoliation has unleashed a flurry of research activities in 2D carbon worldwide over the past few years.Here, we develop a novel sliding transfer strategy, which is inspired by the natural phenomenon of a snail secreting mucus .Figure –1 with a full width at half maximum (FWHM) of 27.0 cm–1 is more than four times the intensity of the G peak at 1582 cm–1. The D peak, indicating defects of graphene, is not obvious, which attests to extremely high crystalline quality. The equipment corresponding to Figure 2 monolayer graphene transferred onto a 300 nm SiO2/Si substrate exhibits excellent uniformity and integrality with a clean surface. The ingenious design of sliding transfer actually can be dated back to an institutional technique—floating glass,The core competence of our sliding method results from the ease of metallic atom delocalization at melted state and the applied sliding force. Any original substrate, once melted, can easily achieve facile atom delocalization, which establishes the foundation for the layer–layer separation of liquid metal and the applied sliding force further promotes such a process. Here we take gallium to illustrate our sliding transfer technique.2/Si,Figure Ga has a near room‐temperature melting point of 29.8 °C, which is decided by the strength of the metallic bond that depends on the number of delocalized electrons.Figure 2/Si. The graphene film appears to be highly uniform and intact, with no visible defects such as cracks and folds. To further exhibit the whole quality of the transferred graphene,ID/IG and I2D/IG were calculated by integrating the range of the intensity ratio for 256 spectra with mapping for 15 × 15 μm2 .{101¯0} and outer {112¯0} spots. For monolayer, the inner spots are more intense than the outer spots, as we observe  was employed to demonstrate that the as‐transferred graphene should be totally metal‐free after washing by diluted HCl. 2/Si substrates were obtained by sliding transfer of graphene floating on Ga–In and Ga–In–Sn and the Raman spectra were the feature of single‐layer graphene.We then studied the universality the novel transfer method, and transparent quartz and an emerging 2D material–h‐BN were adopted as examples. The clean scanning electron microscopy (SEM) image and Raman spectrum in Figure S4a,c of the Supporting Information present a defect‐free and single‐layer graphene on quartz. In addition, Figure S4b,d of the Supporting Information also demonstrated the successful transfer of h‐BN by the sliding transfer. These results manifest that the sliding transfer process can be directly extended to other substrates and other 2D materials, which is important for a number of applications of electronic and optical devices. On the other hand, the original support in such a sliding transfer strategy can also be altered to meet various demands. Ga–In (76%–24%) alloy of which the melting point is as low as 16 °C and Ga–In–Sn (62%–25%–13%) of which the melting point is as low as 5 °C,Figure –1 on EVA plastic can be distinctly observed, and it is ascribed to the 2D peak of the graphene. In Figure 2 were conducted, which were corresponding with the locations at the left and the right regions of graphene on EVA plastic as marked in Figure −1, which is much lower than the value (≈5200 Ω sq−1) in the previous report.It is worth mentioning that our sliding transfer method can also transfer large‐area graphene onto the flexible and transparent EVA plastic, which is similar to the roll‐to‐roll transfer. The transfer process is shown in Figure S7 of the Supporting Information. 2/Si, back‐gate field effect transistors were fabricated on 300 nm SiO2/p‐Si substrates using conventional electron beam lithography. The source and drain electrodes were deposited using Ti/Pd/Au (0.5/30/20 nm) with a separation of 5 μm . Figure S8b of the Supporting Information demonstrates the transport characteristics (Ids–Vg) of the field effect transistor that was measured under ambient conditions. The V‐shaped ambipolar property is typical for single‐layer graphene with a zero bandgap. The extracted carrier mobility of electrons for this device is 3625 cm2 V–1 s–1, which is comparable to the average value of graphene at current condition. The slightly positive Dirac point indicates that the transferred graphene is weakly p‐type doped. Moreover, for the better comparison of the electrical property, we also measured the carrier mobility of the mechanical exfoliated graphene under the same test conditions. And the value is 3761 cm2 V–1 s–1, as shown in Figure S8c,d of the Supporting Information.To investigate the electrical quality of the sliding transferred graphene onto SiOTo summarize briefly, we first achieved ultrafast and highly controllable transfer of graphene and put forward a brand new transfer mode based on the original substrate at a melted state. All the characterizations above show that the sliding transferred films exhibit good crystalline integrity and long‐distance continuity without cracks, wrinkles or any smudges. The novel sliding transfer method totally inherits the simplicity and speedability of traditional mechanical cleavage and improves its controllability for uniformity and size. The introduction of rolling–sliding process ensures the large‐area transfer of continuous and uniform graphene, which is an extremely large improvement as compared to traditional mechanical transfer. The selection of liquid metals enables one to obtain high‐quality and strictly uniform monolayer graphene due to its self‐limited catalytic property and the subsequent efficient sliding transfer is resulted from the large delocalization of metallic atoms when in a molten state. In addition, the moderate horizontal sliding force enables the ultracontact and enhanced interaction between graphene and target substrates, which makes it possible to obtain wafer‐size graphene without any cracks, wrinkles, and contaminations. More importantly, this sliding transfer is not strictly limited to the type of the catalytic support or the target substrate. This strategy is also not limited to graphene, and it can be extended to transfer other 2D materials, such as h‐BN. Lower‐temperature sliding transfer via modulating the component of the support and the adherence to various substrates, such as flexible substrates, transparent substrates, and insulated substrates, have been demonstrated and need further exploration for industrial applications in the future.The Design of Graphene/Ga Layers: Owing to the good catalytic activity of Ga for catalyzing graphene growth, we achieved such a unique graphene/Ga layers. First, the Ga pellet was put on the W foil under 30 °C. Following, chemical vapor deposition (CVD) growth of graphene is carried out as follows: Ar and H2 are introduced at a gas flow rate of 300 and 30 sccm, respectively, with the Ga–W substrate heated to 1020 °C. Next, CH4 (10 sccm) is admitted into the chamber for 50 min to initiate graphene growth. After growth, the sample is allowed to cool down in Ar and H2 atmosphere which is the same as the heating process until the temperature is close to the room temperature. Figure S1a of the Supporting Information illustrates the formation of graphene/Ga layers, which includes: (1) heating process, (2) growth process, and (3) cooling process.General Graphene Transfer Methodology: The process of transferring the graphene to the target substrates involves spin‐coating PMMA film onto the graphene‐grown substrate and releasing the PMMA/graphene film by etching out Ga film in a diluted hydrogen chloride (1:4) for 1 h. This was followed by a rinse in ultrapure water to remove the metal ions. The PMMA layer was dissolved with hot acetone after the PMMA/graphene film was transferred onto a SiO2/Si.New Sliding Transfer Methodology with Accurate Control: The novel sliding transfer strategy is schematically illustrated in Figure S3 of the Supporting Information, where graphene/Ga and a SiO2/Si substrate were fixed on the equipment in a face‐to‐face state and contacted with each other by rotating the Z axis controller to a certain value to adjust the contact, and subsequently the two substrates were separated in the horizontal direction to achieve sliding by rotating the X axis controller to a certain value. Finally, the graphene film floating on liquid Ga was separated from the liquid bulk and attached to the SiO2/Si substrate with accurate control both in the spatial displacement and the exerted sliding force. This sliding step only takes several seconds. After the sliding exfoliation process, a trace of Ga was left on the graphene surface, which was rinsed thoroughly by the hydrochloric acid.Characterization: Optical images were taken with an optical microscope (Olympus DX51), and Raman spectroscopy was performed with a laser micro‐Raman spectrometer . The AFM images were taken with a NT‐MDT Ntegra Spectra with graphene transferred onto the 300 nm SiO2/Si. The TEM images were taken with an aberration‐corrected high‐resolution TEM  operating at 80 kV with the graphene samples directly sliding transferred onto a lacey carbon copper TEM grid. XPS was performed on ESCALAB 250Xi using monochromatic Al Kα radiation . The images were obtained by a SEM (Zeiss Merlin Compact). Optical absorbance spectrum was collected at room temperature using UV‐6 100PC double beam spectrophotometer (Mapada). The current (I)–voltage (V) data were collected in a probe station (Keithley 4200) under ambient conditions.As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re‐organized for online delivery, but are not copy‐edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors.SupplementaryClick here for additional data file.


The tetraethyl orthosilicate (TEOS) and flake graphite was used as original materials. On the one hand, the unique structure of as-obtained composite accommodated the large volume change to some extent. Simultaneously, it enhanced electronic conductivity during Li-ion insertion/extraction. The MR-Si/G composite is used as the anode material for lithium ion batteries, which shows high reversible capacity and ascendant cycling stability reach to 950 mAh·g−1 at a current density of 50 mA·g−1 after 60 cycles. These may be conducive to the further advancement of Si-based composite anode design.Embedded Si/graphene composite was fabricated by a novel method, which was in situ generated SiO In addition, there is abundant silicon in nature, and lithium insertion potential is relatively low (< 0.5 V vs. Li/Li+) [2 as both a template and silicon precursor [−1 at current density 1 A g−1, and the capacity retention after 100 cycles was 95.5%.Anode material plays a significant role in the rechargeable lithium-ion batteries (LIBs). Recently, most people think that the promising candidate for anode material are the silicon-based materials –3. The m Li/Li+) –6.Unfort Li/Li+) . Therefo Li/Li+) , 10. For Li/Li+) . Xuejiaorecursor . It exhiRecently, graphene, an original kind of carbon material, has aroused great concerns in the field of materials science. It has a unique structure with a single-layer sheet-like structure composed of carbon atoms . Demonst2 particles on graphene sheets followed by magnesium thermal reduction. Compared with the previous preparation method, the synthesis of materials in this experiment is relatively simple. At the same time, silicon and graphene are relatively evenly mixed by in-situ generated SiO2 particles on graphene. Embedded structure of the composite accommodated the large volume change, displayed high specific capacity and cycle stability, and increased the electronic conductivity. Another, the raw materials are cheap. All of these may be conducive to the further advancement of Si-based composite anode design.In our work, we designed a novel method to synthesize high-capacity magnesium-thermal reduced Si/graphene (MR-Si/G) composite, which used the tetraethyl orthosilicate (TEOS) and graphene oxide (GO) as the starting materials, and was in situ generated SiOGraphite oxide (GO) was obtained from flake graphite according to the modified Hummers method in literature . DispersThis step is to prepare the Si/G complex by magnesium thermal reduction. Firstly, the above composite was heated at 550 °C for 3 h at 5 °C/min in an argon atmosphere, and then cool it to room temperature. The weight ratio of as-sample and magnesium powder was 1:1 in an agate mortar and grinding 30 min. Then, the mixture was placed in a tube furnace and heated at 800 °C for 4 h in an argon atmosphere. Finally, the as-composite was soaked by 1 M HCl for 10 h then filtered and dried under vacuum at 60 °C for 8 h. This product is MR-Si/G composite.The X-ray diffraction  was used to characterize the phase composition of the materials. The morphology and structure of the products were evaluated by field emission scanning electron microscopy , Transmission electron microscopy . Raman spectra and the FTIR Spectra were measured on RM2000 Raman Spectrometer  and the NICOLET 560 Fourier transform infrared spectrophotometer, respectively. The content of Si in the composite was measured by thermogravimetric analysis , it was from room temperature to 800 °C at a heating rate of 10 °C/min under air.To test the electrochemical performance, which was carried out in two-electrode 2032 coin-type cells, the active material (MR-Si/graphene), conductive additive (Super-P), and sodium carboxymethyl cellulose (CMC) as binder were intermingled at weight ratio of 80:10:10, which was used as the working electrode. The mixture slurry was prepared by using deionized water as a solvent, then equably pasted on pure copper foil current collector via doctor blade processing, followed by drying under vacuum at 105 °C for 12 h. All the cells were assembled in an argon-filled glovebox . The metallic lithium foil was used as the counter electrode. The electrolyte was a solution of 1.0 M LiPF6, which dispersed in mixture of EC: DMC: EMC (1:1:1 by volume). The cells were tested in the potential range from 0.01 V to 3 V (vs. Li+/Li) by CT2001A Land battery testing system.2 particles on graphene sheets followed by magnesium thermal reduction. Figure 2 nano-particles were synthesized by modified Stöber process [2/graphite oxide, the final composite was synthesized by magnesium-thermal reduction.The MR-Si/graphene composite manufactured by in-situ generated SiO process . SubsequFigure Compared Fig. −1(this peak is absent in the SiO2/GO) is in accordance with the spectrum of Si nano-particle [−1 and 1585 cm−1 consistent with the D band and the G band, respectively. The G-peak is the feature of the graphite, representing the carbon of the sp2 structure. The D-peak can be ascribed to the existence of a defective hexagonal graphite structure. The ID/IG is the most important parameter, which was related to the graphitization degree of the carbonaceous material and the defect density in the graphene-based material [D/IG intensity ratios of MR-Si/G composite has increased, which maybe the presence of Si nanoparticles that increases the disorder of the material [D/IG ratio of GO is approximately 0.93 and the ID / IG ratio of MR-Si / G is about 1.19. In order to further study the changes in chemical structure, we conducted FTIR to analyze the functional groups of sample. Figure −1, 816 cm−1, and 1087 cm−1 are corresponding to the O-Si-O bending vibration, symmetric elastic vibration of Si-O-Si and Si-O-Si asymmetric elastic vibration, respectively. The presence of these functional groups is conducive to the formation of a stable structure. And the broad peaks at 3427 cm−1 are related to the O-H stretching vibration.From the Raman diagram in Fig. particle , manifesmaterial . Althougmaterial . After cThe morphology of all prepared materials was studied by SEM and TEM Fig. . Figure The content of the Si in the MR-Si/G composite carried by the TGA measurements, which was implemented from ambient temperature to 800 °C with a heating rate of 10 °C/min in the air. As shown in Fig. −1 and voltage range of 0.01–3.0 V vs Li/Li+. For the pure Si, the initial discharge capacity is 3279 mAh·g−1, while the first charge capacity is only 2391 mAh·g−1(Fig. Figure −1, respectively (Fig. xSi phase [For the MR-Si/G composite, the initial discharge capacity and charge capacity is 1570 and 1178 mAh·gSi phase . As the −1 after 60 cycles. For the pure Si, the cycle performance is highly bad at the first 10 cycles, which the discharge capacity quickly dropped from 3279 to 528 mAh·g−1. After 60 cycles, the capacity was reduced to about 125 mAh·g−1. At the same times, the MR-Si/G compound has superior cycling properties, which the discharge capacity is 1570 mAh·g−1 and the reversible capacity is about 1055 mAh·g−1 in the initial 10 cycles. And the coulombic efficiency is achieved 99% and kept steady in a subsequent loop. It is noted that the specific capacity of complexes has been maintained at about 950 mAh·g−1 after 60 cycles. The results indicate that the graphene layers act as a significant role in the cycling performance of the compound electrode, which due to stabilizes the structure of the electrode and increases the electric conductivity. The rate capability of the MR-Si/G composite at different current densities is displayed in Fig. −1 correspond to at the current densities of 50, 100, 200, 500 mA·g−1, respectively. In an addition, the capacity value is only 950 mAh·g−1 as the current density back to 50 mA·g−1.Figure −1. In the first cycle, the peak at 0.75 V during the cathodic sweep relates with the formation of SEI layer, which disappears in the next cycle. It matches the composite discharge curve (Fig. Figure Figure −1 at a current density of 50 mA·g−1 after 60 cycles. The methodology employed in this study produced a promising unique MR-Si/G composite, which for the next generation of high-capacity lithium-ion battery anode material, provides a reliable basis.Embedded Si/graphene nano-composite was successfully synthesized via combined with the hydrothermal process and Mg-assisted reduction. The Si nano-particles were fabricated by the magnesium-thermal reduction of amorphous silica nanoparticle, which were uniformly adhered on the graphene. The unique structure of the composite eases the volume expansion and manifests excellent electrochemical properties. The MR-Si/G composites exhibited high reversible capacity, which can be up to 950 mAh·g


The temperature dependence of the silicon-graphene conductive photodetector is studied for the first time. It is shown that the silicon-graphene conductive photodetector has ultra-high responsivity when operating at low temperature, which provides the possibility to detect extremely weak optical power. For example, the device can detect an input optical power as low as 6.2 pW with the responsivity as high as 2.4 × 107 A/W when operating at −25 °C in our experiment.Graphene is attractive for realizing optoelectronic devices, including photodetectors because of the unique advantages. It can easily co-work with other semiconductors to form a Schottky junction, in which the photo-carrier generated by light absorption in the semiconductor might be transported to the graphene layer efficiently by the build-in field. It changes the graphene conduction greatly and provides the possibility of realizing a graphene-based conductive-mode photodetector. Here we design and demonstrate a silicon-graphene conductive photodetector with improved responsivity and response speed. An electrical-circuit model is established and the graphene-sheet pattern is designed optimally for maximizing the responsivity. The fabricated silicon-graphene conductive photodetector shows a responsivity of up to ~10 This provides a platform to realize a graphene-based conductive-mode photodetector with high responsivity. For example, Konstantatos et al.7 A/W for an input optical power less than 10 fW, while the response is slow (in the order of ~10 ms) due to carrier trapping effect of quantum dots. Recently, a silicon-based graphene conductive photodetector was demonstrated by putting a graphene sheet on an N-type silicon substrate with a doping level n < 1016 cm−3 (the resistivity ρ ≥ 10 Ω·cm). For this photodetector, the response time is ~1.48 ms, while the responsivity is reduced to be ~106 A/W under an input optical power less than 10 pWet al. demonstrated a silicon-graphene conductive photodetector with further improved response time around 3 μs by using a lightly-doped P-type silicon substrate while the responsivity further decreases to ~104 A/W under an input optical power of 0.112 μWGraphene is a two-dimensional mono-layer material and has attracted intensive attention owing to its unique optoelectronic properties12315 cm−3 (the resistivity ρ is 0.55 ~ 0.8 Ω·cm), and the graphene pattern is designed specially to have optimized metal/graphene contact resistance according to an established electrical-circuit model. The fabricated silicon-graphene conductive photodetector with an optimized graphene-sheet pattern shows a responsivity up to105 A/W for an input optical power P = 10 nW at room temperature (27 °C) and the response time as short as 30 μs. The temperature dependence of silicon-graphene conductive photodetectors is also studied for the first time. It is found that the responsivity increases greatly as the temperature decreases. Our experimental result shows that the silicon-graphene conductive photodetector has ultra-high responsivity when operating at relatively low temperature, and thus enables the detection of ultra-low optical power. For example, when operating at −25 °C, the device can detect an input optical power as low as P = ~ 6.2 pW and the corresponding responsivity is as high as 2.4 × 107 A/W.In this paper, we design and demonstrate an improved silicon-graphene conductive photodetector with high responsivity as well as response speed. Here we choose a silicon substrate with a relatively high N-type doping level of ~7 × 1015 cm−3. 2 layer formed on the silicon substrate by utilizing a thermal oxidation process. This SiO2 layer is removed selectively to open a window so that the graphene sheet can contact with the silicon substrate directly. The Ti/Au electrodes were fabricated with a sputtering process. The thicknesses of the Ti and Au layers are 5 nm and 80 nm, respectively. A monolayer of graphene sheet grown by chemical vapor deposition (CVD) was then wet-transferred onto the top of the chip and was patterned by an oxygen plasma etching process. The graphene-sheet pattern of the photodetector is shown in L and the width W of the graphene sheet on silicon are chosen as 100, 50, 20, and 10 μm, respectively. Finally the negative polymer layer used for patterning the graphene layer is kept for graphene protection. A top-view microscopic image of the fabricated device is shown in Itotal of the silicon-graphene photodetectors with L/W = 50 μm/100 μm under a bias voltage of Vbias = 5 V as a function of the laser power varying from 10 nW to 3.2 mW. Here the operation temperature is fixed as 27 °C and the measured dark current is Idark = ~17.8 mA . The measured responsivity as high as 0.83 × 105 A/W when P = 10 nW. As shown in Itotal decreases, which is different from the results of graphene/P-doped silicon photodetector reported previouslyItotal rises with increasing input optical power and is larger than the dark current Idark. This can be explained from the carrier transport in the Schottky junction formed between the graphene sheet and the silicon substrate. In our design, when the graphene sheet contacts with the N-doped silicon substrate, electrons transport from the silicon substrate to the graphene sheet according to the schematic energy-band diagram  with a fiber pigtail was used as the light source to illuminate the chip from the top side. The output power of the laser ranges from −60 dBm to 16 dBm and the illuminating spot size to the graphene surface is similar to the diameter of the fiber mode spot-size, which is smaller than 20 μm. n is the carrier concentration in graphene. It can be seen that the graphene resistance increases as the carrier concentration decreases. This is why we observed that the total current Itotal with light illumination becomes less than the dark current Idark. As the optical power increases further to a certain value P0 . For the measurement, we use a current source to fix the photodetector bias current Ibias at 10 mA and an oscilloscope to monitor the temporal dynamics of the device voltage under different illumination situations. We consider two cases with different optical powers P1 and P2, where P1 < P0 and P2 > P0. As discussed above, here P0 is the optical power to induce the Fermi-level of graphene to approach the Dirac point , the measured voltage increases quickly when light illumination is switched from off to on. However, when light illumination is switched from on to off, the measured voltage show a sudden rise and then decreases very slowly, which is mainly due to the majority carrier trapping effect at high laser poweron with an optical power P2 > P0 , the graphene sheet becomes P-doped because of the carrier transport through the silicon-graphene Schottky junction, as explained above  and then decreases. Correspondingly, the device voltage increases first and then decreases temporally, as observed in our experiments. Note that the electron-hole combination process lasts for a very long time due to the electron trapped in the N-doped silicon region1 = 10 μW (P1 < P0) in on (off), the voltage becomes high (low) as expected. The rising time τON and the decay time τOFF are about 32 μs and 60 μs, respectively. The response time is mainly determined by the processes of the carrier transport through the silicon-graphene junction and in graphene. It can be seen that this response is much faster than that of quantum-dots/graphene photodetector (~10 ms)We also measure the dynamic response of the silicon-graphene photodetector  is the total serial resistance of the photodetector without (with) light illumination, RC is the contact resistance of the graphene sheet with the Au/Ti electrode, n is the carrier concentration in graphene, ΔN is the carrier number injected to graphene from silicon, Δn is the carrier-concentration variation in graphene, and Iph is the photocurrent. When the illumination power is weak, the carrier-concentration variation in graphene, Δn, is much lower than the carrier concentration n in graphene, where L/W is fixed in the design, the current increment Iph is proportional to Δn. This indicates that the responsivity can be improved by reducing the graphene area to enhance the carrier-concentration variation Δn in the graphene. Note that the graphene area should not be smaller than the spot size of light illumination in order to receive all optical power. On the other hand, when the graphene area is fixed in the design, the current variation Iph varies with the ratio L/W hyperbolically. It can be seen that the current variation Iph reaches maximum when the RC = (L/W)/neμ = RG. In order to verify the dependence of the responsivity on the graphene size, we measured the responsivity of the fabricated photodetectors with different sizes, i.e., L/W = 10 μm/100 μm, 20 μm/50 μm, 20 μm/100 μm, 50 μm/50 μm, 100 μm/50 μm, and 100 μm/100 μm, as shown in L/W = 50 μm/50 μm and 100 μm/100 μm, which have different graphene areas but the same ratio L/W. Therefore, the responsivity for the photodetector with L/W = 50 μm/50 μm (pink line) is higher because of the smaller area, as shown in Rtot_ph and Rtot_D) of the photodetectors with different sizes of the graphene sheet when the light illumination is on or off. Here Rtot_ph and Rtot_D are the resistances for the cases with the illumination power Pin = 3.2 mW and 0 mW, respectively. From the data shown in □ and the contact resistance RC according to □ is given by the slopes of the R~(L/W) curves shown in L/W = 0. For the present case, one has RC = 64.28 Ω, R□_D = 1/(neμ) = ~425.5 Ω at Pin = 0 mW and R□_ph = 1/[(n–Δn)eμ] = ~511.2 Ω at Pin = 3.2 mW. Regarding the devices with the same graphene area but in different aspect ratios L/W, RG are measured to be ~30 Ω and ~192 Ω for photodetectors with L/W = 10 μm/100 μm and 20 μm/50 μm. As the resistance of the photodetector with L/W = 10 μm/100 μm is closer to the contact resistance RC (~64.28 Ω), the responsivity is higher as predicted from A = LW fixed and choosing the ratio L/W = 12.2 μm/81.6 μm, the optimal value to achieve RG = RC according to 5 A/W under 2 nW illumination.According to this simplified equation, if the L/W = 20 μm/100 μm when operating at different temperatures T = 27 °C, 40 °C, 60 °C and 80 °C, respectively. It can be seen that the responsivity decreases notably as the temperature increases. For example, when T = 27 °C, the photocurrent Iph is 0.5 mA under an illumination power P = 2.8 nW and the responsivity is 1.78 × 105 A/W. In contrast, when the temperature increases to 80 °C, the photocurrent Iph is only 0.07 mA even under a stronger illumination power P = 6.2 nW and the corresponding responsivity is 1.34 × 103 A/W. This temperature dependence of the responsivity is mainly due to the following two factors. First, the metal-graphene contact resistance decreases monotonically as the temperature decreases, due to the high carrier transfer efficiency of nearly ballistic transport at low temperaturen > 1011 cm−3) and on the BN substrateAs the temperature dependence of a photodetector performance is a critical characteristic for practical applications, the silicon-graphene photodetector is also characterized at different temperatures. As an example, 2 gas to prevent moisture condensation or freezing on the chip surface. 7 A/W. In our experiment, we can not achieve a temperature lower than −30 °C because of the setup limitation. It can be predicted to obtain an even higher responsivity if operating at lower temperature.Since the responsivity of the photodetector becomes higher when the temperature decreases, here we also characterize the silicon-graphene photodetector when operating at the temperature below 0 °C by setting the thermo electric cooler (TEC). For this measurement, the sample is placed in an enclosed chamber filled with N15 cm−3 has been used and the graphene pattern has been designed optimally to improve the responsivity. An electrical-circuit model has been developed so that one can design the dimension of the graphene-sheet appropriately. The fabricated silicon-graphene conductive photodetector has a response time of as short as 32 μs and a responsivity up to ~105 A/W for a normal-incident illumination power P = 10 nW at room temperature (27 °C). We have also studied the temperature dependence of the silicon-graphene conductive photodetector for the first time. It is shown that the silicon-graphene conductive photodetector has ultra-high responsivity, which provides the possibility to detect ultra-low optical power when operating at relatively low temperature. The device can detect an optical power as low as P = ~6.2 pW with corresponding responsivity as high as 2.4 × 107 A/W when operating at −25 °C in our experiment. The responsivity for the present silicon-graphene conductive photodetector is expected to be improved further when operating at lower temperature.In summary, we have designed and demonstrated a silicon-graphene conductive photodetector with improved responsivity and response speed. A silicon substrate with relatively high N-type doping level of ~7 × 102 layer. This SiO2 layer is removed selectively to open a window by using an electron beam lithography (EBL) process and an wet-etching process with the etchant solution (NH4F: HF = 6:1). A second EBL process and a lift-off process were carried out to form the Ti/Au electrodes with the thickness of 5 nm/80 nm. A monolayer of graphene sheet grown by the chemical vapor deposition (CVD) method was then wet-transferred onto the top-surface and patterned by an oxygen plasma etching process.The N-doped Si was oxidized at 1050 °C for one hour to generate ~100 nm-thick SiOThe monolayer graphene was grown on the copper by the CVD method. A PMMA thin film was formed on the top of the graphene sheet by spin-coating method. Then the copper film was removed by putting it into the Ammonium persulfate solution for 3 hours. After removing the copper film, the graphene-PMMA sample was rinsed on deionized water for ~12 hours, and then dried on the air. Finally, the graphene sheet was wet-transferred and the PMMA film was removed by the acetone.Idark and Itotal) by tuning the optical power with a variable optical attenuator (VOA). The photocurrent is then given by Iph = Itotal − Idark. In order to measure the photodetector’s response time, an optical chopper was adapted to modulate the CW laser with the frequency of 2 kHz. In the experiment, we measured the voltage by an oscilloscope with a current source (Ibias = 10 mA).In the experiment, a continuous-wave (CW) 635 nm semiconductor laser with a fiber pigtail was used as the source. The diameter of the illumination spot size is about 20 μm. Keithley 2400 was used to measure the currents .Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.


EGFR) mutations, implying lower PD-L1 expression in EGFR-mutant NSCLC than in EGFR-wild type.Current clinical trials have suggested poorer efficacies of anti-programmed death-1 (PD-1)/PD-ligand 1 (PD-L1) immunotherapies for non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor  was 3 , whereas EGFR-wild-type (n=31) was 8  (p=0.0075). Using H-scores ≥1, ≥5, and ≥10 cut-offs, incidence of PD-L1+ in EGFR-mutant vs. EGFR-wild-type samples were: 85% (55/65) vs. 94% (29/31) (p=0.2159); 42% (27/65) vs. 74% (23/31) (p=0.0027); and 22% (14/65) vs. 48% (15/31) (p=0.0074), respectively. Patient-oriented (n=77) univariate analysis for strong PD-L1+ found age of sample (p=0.0226) and EGFR mutation status (p=0.0490) as significant factors. Multivariate analysis identified EGFR mutation status as the only significant factor  for strong PD-L1+. H-scores of PD-L1 expression varied in all 11 cases receiving multiple rebiopsies, and categories of positivity migrated in 10 (91%) of 11 patients.We investigated 96 available histologic samples in 77 pretreated patients with NSCLC. Median H-score in EGFR-mutant NSCLC samples than in EGFR wild-type samples. Its expression could be dynamic and affected by age of sample.PD-L1 expression was significantly lower in  Lung cancer is the leading cause of cancer deaths worldwide. Non-small cell lung cancer (NSCLC) accounts for approximately 80% of lung cancers, and the majority are already unresectable and metastatic upon their initial diagnosis. Cytotoxic chemotherapies such as platinum-based regimens were once the primary therapeutic option for metastatic NSCLC, but their advancement has reached a plateau. Molecular-targeted therapies have been recently developed, and they have provided a remarkable benefit to patients harboring specific genetic alterations such as epidermal growth factor receptor (EGFR) gene mutations or anaplastic lymphoma kinase (ALK) gene fusions –3. EfficOn the other hand, current advancement of immunotherapies is evolving. Among them, anti-programmed death-1 (PD-1)/PD-ligand 1 (PD-L1) antibodies have demonstrated their splendid efficacies in pretreated NSCLC. Anti-PD-1/PD-L1 antibodies, such as nivolumab, pembrolizumab, and atezolizumab have shown survival benefit in pretreated patients with NSCLC after failure of platinum doublet chemotherapies, in randomized phase III trials compared to docetaxel monotherapy –9. BasedEGFR mutations [EGFR-mutant NSCLC. Practical predictive markers are necessary to select patients who benefit from anti-PD-1/PD-L1 antibody immunotherapies.In cases responding to such immunotherapies, durable response is expected over 1-2 years, much longer than common cytotoxic agents –9. Unforutations –9. HowevSeveral predictive markers for anti-PD-1/PD-L1 antibodies have been developed . Among tEGFR-mutant NSCLC samples than in EGFR-wild type. The aim of this study was to investigate correlation between PD-L1 expression and EGFR mutation status in pretreated NSCLC.We thus hypothesized lower PD-L1 expression in ALK-fusion positive samples were excluded, and a total 103 EGFR-mutant and wild-type tissue samples of NSCLC were examined. Fifteen samples were unavailable, and 8 samples contained insufficient cancer cells to perform PD-L1 IHC. We registered 80 rebiopsied histologic samples of 63 EGFR-mutant and wild-type. In the second cohort, 17 surgical tissue samples were available in 17 NSCLC patients receiving surgery after neoadjuvant chemoradiation therapy. After exclusion of one ALK-fusion positive sample, 16 of these surgical tissue samples were registered. Finally, we combined pretreated rebiopsy samples and surgical tissue samples, and the number of final investigated samples was 96 (65 EGFR-mutant and 31 wild-type) in 77 (47 EGFR-mutant and 30 wild-type) NSCLC patients.Flow chart of final investigated samples and patients is shown in Figure EGFR were: deletional mutation in exon 19 ; L858R point mutation in exon 21 ; L861Q point mutation in exon 21 , and wild-type . Radiotherapy before rebiopsy for sampled tissue was performed in 24 (31%) of patients. Median number of chemo-regimens before rebiopsy was 2 . Approximately 90% of patients underwent cytotoxic chemotherapies. EGFR-TKIs were prescribed to 47 all EGFR-mutant and only 3 EGFR-wild-type patients. Rebiopsy was performed to lung lesions in approximately 80% of patients. Extra-lung lesions included: 8 lymph nodes ; 2 pleural; 2 liver; 2 rib; 1 muscle; and 1 adrenal metastases. Eleven (14%) patients underwent multiple rebiopsies. Median duration from rebiopsy/surgery to PD-L1 IHC evaluation (age of sample) was 21.3  months.Characteristics of final 77 patients investigated are shown in Table EGFR-mutant samples (n=65) was 3 , whereas EGFR-wild-type (n=31) was 8    vs. 94% (29/31) (p=0.2159), 42% (27/65) vs. 74% (23/31) (p=0.0027), 22% (14/65) vs. 48% (15/31) (p=0.0074), 5% (3/65) vs. 19% (6/31) (p=0.0205), and 3% (2/65) vs. 10% (3/31) (p=0.1735), respectively  (H-score: 0); B, EGFR-mutant (L858R) (H-score: 10); and C, EGFR wild-type (H-score: 134).Median H-score in ) Figure . Using HEGFR mutation status (mutant vs. wild-type); radiation before rebiopsy for sampled tissue (irradiated vs. non-irradiated); cytotoxic chemotherapy before rebiopsy (received vs. none) rebiopsy site (lung vs. extra-lung); and age of sample (<12 months vs. 12 months≤). EGFR-TKIs before rebiopsy (prescribed vs. none) was eliminated because of strong confounding to EGFR mutation status. Univariate analysis found EGFR mutation status (p=0.0490) and age of sample (p=0.0226) as significant factors for strong PD-L1+ .Patient-oriented (n=77) univariate and multivariate analyses for strong PD-L1+ were performed at H-score ≥10 cut-off. In patients receiving multiple rebiopsy, first rebiopsy results were adopted in these analyses. Univariate analysis was performed on: age (<70 vs. 70≤); gender ; smoking status (never vs. former vs. current); histology (adeno vs. non-adeno); Eleven 14%) patients underwent multiple rebiopsies. H-scores of PD-L1 expression varied in all 11 cases receiving multiple rebiopsies  are more desirable for studies to investigate PD-L1 expression. Moreover, anti-PD-1 antibodies, nivolumab and pembrolizumab are approved only in pretreated patients with EGFR-mutant NSCLC. To properly investigate this issue, it is preferable to examine pretreated samples for best reflection of study results into clinical practice. Thus, our study focused on histological samples of pretreated NSCLC patients, which is more clinically valuable than studies using chemo-naïve surgical samples.Meanwhile, some studies using surgical samples of chemo-naïve NSCLC have shown lower PD-L1 expression in nstrated , 14. Othild-type –18. Thisild-type , 19. Preutations , 21. NotEGFR status as the only significant factor for strong PD-L1+. Based on results of pivotal studies regarding nivolumab, PD-L1 expression was associated with clinical efficacies in non-squamous NSCLC population [EGFR mutational analysis, which is performed in most cases. Therefore, EGFR status could be useful as a predictive marker of anti-PD-1/PD-L1 antibody therapies in pretreated patients with NSCLC.Our multivariate analysis identified pulation . Althougpulation , 13, 22,pulation . ClinicaAge of sample was identified as a significant factor for strong PD-L1+ in our univariate analysis, but multivariate analysis failed to confirm this result. Older samples revealed lesser prevalence of strong PD-L1+. This result implies a possible underestimation of PD-L1 expression in older samples. Several studies suggested that tissue processing and storage could alter the ability to detect PD-L1 in tumor samples . The decIssues of PD-L1 IHC contain not only tissue processing and storage but also interpretation of the test by pathologists. Reproducibility is another issue in PD-L1 IHC scoring. We adopted a digital pathological systematic procedure (Aperio). This system can digitally evaluate PD-L1 IHC scores, and demonstrated highly similar IHC staining results to visual evaluation by a pathologist . Our patOur study includes several limitations. First is the selection of antibody for PD-L1 IHC. Our study adopted the 28-8 PD-L1 antibody. Four anti PD-L1 antibodies  are clinically used for PD-L1 IHC, but PD-L1 IHC is not globally standardized . Each IHEGFR-mutant NSCLC samples than in EGFR wild-type samples. As several studies have shown [EGFR-mutant population appear to be poorer than those in EGFR wild-type population. Priority of anti-PD-1/PD-L1 immunotherapies might be lower in EGFR-mutant population than in EGFR wild-type population. Our multiple rebiopsied cases suggested PD-L1 expression dynamism. Age of sample could affect PD-L1 expression, and rebiopsied fresh samples may be better for PD-L1 IHC. Further studies are warranted to investigate association between PD-L1 expression and EGFR mutation status.In conclusion, our study has demonstrated a significantly lower PD-L1 expression in ve shown –9, efficEGFR/ALK. The second was surgical tissue samples after neoadjuvant chemoradiation therapy. After exclusion of samples with ALK-fusion, we examined whether each sample contained sufficient cancer cells to perform PD-L1 immunohistochemistry (IHC). After confirmation of cancer cell sufficiency, PD-L1 IHC was carried out. Never smoker was defined as patients who had never smoked in their lifetime. Current smoker was categorized as those who had smoked within 1 year of the diagnosis. The rest were regarded as former smoker. The study was approved by the institutional review board, and complied with the Declaration of Helsinki.We retrospectively screened electronic medical records of patients with NSCLC in our institute. Two sampling cohorts were adopted to collect histological samples in pretreated patients with NSCLC. The first was histological rebiopsied samples after several chemotherapies, regardless of driver oncogene alterations such as EGFR mutations using highly sensitive assays: the peptide nucleic acid-locked nucleic acid PCR clamp method [We isolated tumor DNA from each specimen, and analyzed p method  or the cp method .Paraffin-embedded tumor tissue was sectioned at a thickness of 4 μm, and the sections were then pasted on coated glass slides for PD-L1 IHC. PD-L1 IHC was performed using the 28-8 antibody for tumor cell membrane staining. Slides were stained with Dako Autostainer Link48. Antigen retrieval was performed in Target Retrieval Solution Low pH. The primary antibody of PD-L1 (clone: 28-8) was diluted at 1:600, and incubated for 45 min at room temperature. The antibody was detected with Rabbit (LINKER) and EnVision FLEX/HRP. Digital image was captured using Aperio Scanscope AT Turbo slide scanner  under 20x objective magnification. Scoring of PD-L1 was performed using digital image analysis software, namely Aperio membrane v9 and Aperio Genie Classifier. Score of PD-L1 was represented as H-score to evaluate both percentage and intensity. Semiquantitative H-score  was determined by multiplying the percentage of stained cells by an intensity score . Our pathologists also confirmed PD-L1 IHC score, and no significant difference was found in PD-L1 scores between digital procedure and pathologists. We defined H-scores ≥1 as PD-L1+, scores ≥5 as moderate PD-L1+, and scores ≥10 as strong PD-L1+.EGFR-mutant and wild-type samples, we used the Wilcoxon rank sum test. Chi-square test was done to compare the incidence of PD-L1+. Multivariate analysis for strong PD-L1+ was performed using the logistic regression model. Final investigating variables were selected by backward elimination method. A P-value less than 0.05 was considered significant. The statistical analyses were performed using JMP 12 .To compare H-scores between


L1Mab-4 reacted with oral cancer cell lines  in flow cytometry and stained oral cancers in a membrane-staining pattern. L1Mab-4 stained 106/150 (70.7%) of oral squamous cell carcinomas, indicating the very high sensitivity of L1Mab-4. These results indicate that L1Mab-4 could be useful for investigating the function of hPD-L1 in oral cancers.Programmed cell death-ligand 1 (PD-L1), which is a ligand of programmed cell death-1 (PD-1), is a type I transmembrane glycoprotein that is expressed on antigen-presenting cells and several tumor cells, including melanoma and lung cancer cells. There is a strong correlation between human PD-L1 (hPD-L1) expression on tumor cells and negative prognosis in cancer patients. In this study, we produced a novel anti-hPD-L1 monoclonal antibody (mAb), L •Programmed cell death-ligand 1 (PD-L1) is expressed in many cancers.•PD-L1 expression has not been fully investigated in oral cancers.•1Mab-4 was developed in this study.A novel anti-PD-L1 mAb L•1Mab-4 stained 70.7% of oral SCCs in a membrane-staining pattern.L Clinically, nivolumab, a complete human IgGPD-L1, also known as B7-H1 and CD274, is a type I transmembrane glycoprotein, which is expressed on antigen-presenting cells and some tumor cells, including melanoma, ovarian, and lung cancer cells et al. have revealed a correlation between high PD-L1 expression and metastasis and poor prognosis in oral SCC Lin 22.1Ca9-22, HO-1-u-1, SAS, HSC-2, HSC-3, HSC-4, and HEK-293T cells were obtained from the Japanese Collection of Research Bioresources Cell Bank . LN229 and P3U1 cell lines were obtained from the American Type Culture Collection . LN229/human PD-L1 (hPD-L1) was produced by transfecting pCAG/PA-hPD-L1-RAP-MAP into LN229 cells using a Gene Pulser Xcell electroporation system . The stable transfectant of LN229/hPD-L1 was established by limiting dilution. HEK-293T/hPD-L1 was produced by transfecting pCAG/PA-hPD-L1-RAP-MAP into HEK-293T cells using Neon transfection system . A few days after transfection, PA tag-positive cells were sorted using a cell sorter . PA tag system (GVAMPGAEDDVV (12 a.a.) vs. clone: NZ-1), RAP tag system (DMVNPGLEDRIE (12 a.a.) vs. clone: PMab-2), and MAP tag system GDGMVPPGIEDK (12 a.a.) vs. clone: PMab-1) have been previously established in Tohoku University Graduate School of Medicine and described in detail 2 and 95% air, both of which were supplemented with 10% heat-inactivated fetal bovine serum . One hundred units/mL penicillin, 100 μg/mL streptomycin, and 25 μg/mL amphotericin B  were added to the culture medium. Zeocin  was added to the culture medium of LN229/hPD-L1 and HEK-293T/hPD-L1.Ca9-22, HO-1-u-1, SAS, HSC-2, HSC-3, HSC-4, LN229, LN229/hPD-L1, HEK-293T, and HEK-293T/hPD-L1 cells were cultured in Dulbecco's Modified Eagle's Medium , and P3U1 cell line was cultured in RPMI 1640 medium  at 37 °C in a humidified atmosphere containing 5% CO2.2Female 4-week-old BALB/c mice were purchased from CLEA Japan  and kept under specific pathogen-free conditions. The Animal Care and Use Committee of Tohoku University approved all animal experiments described in this study. Oral cancer tissue arrays were purchased from US Biomax, Inc. : Cases 1–38 from Cat. # OR480, Cases 39–88 from Cat. # OR601b or from Cybrdi, Inc. , and Cases 89–159 from Cat. # 27-10-001. The study examined one patient (Case-160) with oral cancer who underwent surgery at the Tokyo Medical and Dental University. The Tokyo Medical and Dental University Institutional Review Board reviewed and approved the use of human cancer tissues, and written informed consent was obtained for using the human cancer tissue samples.2.38 cells) together with Imject Alum (Thermo Fisher Scientific Inc.). After three additional immunizations, a booster injection of LN229/hPD-L1 was intraperitoneally administered 2 days before harvesting the spleen cells. Spleen cells were then fused with P3U1 cells using PEG1500 . The resulting hybridomas were grown in RPMI medium supplemented with 10% FBS and hypoxanthine, aminopterin, thymidine selection medium supplement (Thermo Fisher Scientific Inc.), and 5% BriClone Hybridoma Cloning Medium . One hundred units/mL penicillin, 100 μg/mL streptomycin, and 25 μg/mL amphotericin B  were added to the medium. Plasmocin  was also used to prevent Mycoplasma contamination. Culture supernatants were screened by SA3800 Cell Analyzers (Sony Corp.) using LN229 and LN229/hPD-L1. MAbs were purified from the supernatants of hybridomas and cultured in Hybridoma-SFM medium (Thermo Fisher Scientific Inc.) using Protein G Sepharose 4 Fast Flow .One BALB/c mouse was immunized using intraperitoneal (i.p.) injections of LN229/hPD-L1 (1 × 102.41Mab-4 (produced in this study), for 30 min at 4 °C and subsequently with Alexa Fluor 488-conjugated anti-mouse IgG . Fluorescence data were collected using EC800 Cell Analyzers (Sony Corp.).Cells were harvested by briefly exposing to 0.25% trypsin/1-mM ethylenediaminetetraacetic acid . After washing with 0.1% bovine serum albumin (BSA)/phosphate-buffered saline, the cells were treated with 1 μg/mL of anti-PD-L1 mAbs, such as clones 29E.2A3 2.51Mab-4 for 1 h at room temperature, treated using an Envision+ kit (Agilent Technologies Inc.) for 30 min. Color was developed using 3,3-diaminobenzidine tetrahydrochloride  for 2 min, and counterstained with hematoxylin .Histological sections of 4-μm thickness were deparaffinized in xylene and subsequently rehydrated and autoclaved in citrate buffer  or EnVision FLEX Target Retrieval Solution, High pH  for 20 min. Sections were then incubated with 10 μg/mL of L33.11 subclass and three as IgG2b subclass. Only one clone, L1Mab-4 , reacted with lung SCC tissue, which was previously diagnosed as PD-L1-positive in an immunohistochemical analysis (data not shown). Although both L1Mab-4 and 29E.2A3  1Mab-4 was higher for LN229/hPD-L1 than LN229  were diagnosed as 3+. Although the samples were limited, adenoid cystic carcinomas (ACCs) and mucoepidermoid carcinomas (MECs) also showed positive staining by L1Mab-4.We then stained oral cancer tissue arrays, and the typical results  are shown in 1Mab-4, a novel anti-hPD-L1 mAb, using the CBIS method. This method is very advantageous because it does not require the membrane protein to be purified in all steps of mAb production. L1Mab-4 is very useful in the detection of hPD-L1 using flow cytometry and immunohistochemical analysis. In the near future, studies investigating the reactivity of L1Mab-4 for other human cancers need to be conducted. Furthermore, we should consider the possibility that L1Mab-4 might cross-react with other membrane proteins or react with post-translational modification, including glycosylation, on PD-L1 because the reaction of L1Mab-4 is much higher than those of 29E.2A3 against LN229 and HO-1-u-1 (In conclusion, we successfully produced LHO-1-u-1 , Fig. 2.