Selenium, which dissolves from the SeS2 cathode, was found to become a component of the anode solid electrolyte interphase (SEI), leading to a significant increase of the SEI conductivity and stability. Moreover, the replacement of lithium metal anode impedes unwanted side reactions between the dissolved intermediate products from the SeS2 cathode and lithium metal and eliminates lithium dendrite formation. As a result, the capacity retention of the lithiated silicon/graphene—SeS2 full cell is 81% after 1,500 cycles at 268 mA gSeS2−1. The achieved cathode capacity is 403 mAh gSeS2−1 .Li-ion batteries dominate portable energy storage due to their exceptional power and energy characteristics. Yet, various consumer devices and electric vehicles demand higher specific energy and power with longer cycle life. Here we report a full-cell battery that contains a lithiated Si/graphene anode paired with a selenium disulfide (SeS Lithium-based batteries employing silicon anodes and sulfur cathodes are promising for combining low cost and high capacity, but have been limited in terms of cycling stability. Here authors present cycling and characterization data supporting beneficial synergies between a selenium disulfide cathode and a silicon anode. Lithium-ion batteries (LiBs) have been successfully commercialized and are widely used in portable electronic devices, electric and hybrid-electric vehicles, aerospace applications and even grid-scale facilities. The continued, rapid technological advancement of these systems requires batteries with higher specific power/energy, longer cycle life and competitive costs124−1, about ten times that of graphite, and sulfur (S)8−1. The successful combination of these two materials would be a breakthrough in the battery research field. Specifically, it is desirable for a high capacity anode to be matched with a high capacity cathode. If a high capacity Si anode is paired with a commercially available metal transition oxide, for example, nickel manganese cobalt oxide (NMC) cathode, the NMC cathode would be much thicker compared with the Si anode. As diffusion time increases with the square of diffusion length, battery performance, especially rate capability, dramatically diminishes.Transition metal oxides (cathode or positive electrode) and graphite (anode or negative electrode) are the predominant active materials used in commercial LiBs. Their material production, processing and electrochemical behaviour are relatively well understood. These two materials have relatively low gravimetric capacities and improvements have nearly plateaued. Therefore, alternative materials are being investigated. Among the many candidates, silicon for the anode and sulfur for the cathode are of great interest due to their natural abundance, low intrinsic cost and high energy-storage capabilities6That being said, combining S and Si to produce a high-capacity battery has been exceedingly challenging. In fact, even adoption of a single material is problematic due to the continuous degradation (capacity fade) during long-term LiB cycling. For instance, Si expands ∼300% during lithiation, resulting in its pulverization and a large irreversible capacity loss6112Sx, x≥4) in the electrolyte and (2) the persistence of unwanted reactions between Li metal and dissolved S species, and (3) dendrite formation on the Li metal anode. The first problem can be partially avoided by adopting porous carbon, which contains the sulfur inside nanopores based on overlapping of adsorption potentials9141516The key challenges in electrochemistry of Li/S battery systems are as follows: (1) the loss of active material due to the dissolution of high-order lithium polysulfides (Li−3 in a Li-free state) and gravimetric (678 mAh g−1) capacities, similar to S. In contrast, the electrical conductivity of Se is several orders of magnitude higher than that of S. The electrical conductivity of Se thin film (0.1∼0.5 μm)−6∼10−8 S cm−1, whereas that of solid sulfur−15∼10−30 S cm−1. In our previous studyxSy would be beneficial to increase gravimetric capacityRecently, several studies reported a full cell employing both S cathodes and Si anodes1920xSy systems (1.7∼2.0 V) are about 1.5∼2.1 V lower than that of traditional lithium metal oxide cathodes (3.7∼4.3 V). However, due to higher specific capacity of both materials , it is notable that the Si-S battery system offers up to ∼2 times higher gravimetric (specific) energy density (up to ∼700 Wh kg−1) than the present graphite-lithium metal oxide systems .The plateau voltage of the Si-S/Se2)/carbide-derived carbon (CDC) for the cathode and Si/graphene for the anode to construct a full-cell battery system. To the best of our knowledge, these complementary materials have not been reported, and for the first time we demonstrate attractive performance of the lithiated Si/Graphene−SeS2/CDC full cell. We further propose a mechanism for the origin of this performance. Selenium, dissolved from the SeS2 cathode, becomes a component of the SEI on the Si/graphene anode, resulting in the significant increase of its conductivity and stability. The replacement of Li metal anode by the lithiated silicon/graphene retards dissolution of intermediate products from the SeS2 cathode and formation of Li dendrite in the anode.For our proof-of-concept studies presented here, we choose selenium disulfide  and micrometre-sized plate-like multi-layered graphene  based electrolyte with 1 M lithium hexafluorophosphate salt at 20 °C. The lithiated Si/graphene anode and SeS2/CDC cathode were cycled between 0.05–1.50 and 1.0–2.85 V, respectively. The rate-capability tests (2/CDC electrode exhibited relatively good rate capability: at 2C 49.5% of the C/5 capacity was preserved. The good rate capability of SeS2-CDC originated mainly from the unique structure of CDC. The CDC is composed of straight mesopores (2−8 nm) and small micropores (< 2 nm). Not only is ion transport greatly improved through aligned pores, but the electron access significantly increases, because SeS2 is trapped in the small pores and is in contact with conductive carbon framework142 results in the better rate capability. 2/CDC electrode with LiB cycling. The Si/graphene and SeS2/CDC electrodes exhibited the CR decrement of 56.4% (963.6→543.8 mAh g−1) for 100 cycles and 58.4% (444.1→259.2 mAh g−1) after 300 cycles. The large decrements could be proven from a result that the CEs of the both electrodes are mostly below 100%. Therefore, from the half-cell results it appears that both electrodes would be impractical—as a guide the US Department of Energy's target for an electric vehicle (EV) battery is 80% CR after 1,000 cycles2 half-cell (including S and Se). In Si systems, capacity fade has been ascribed to the continuous Si pulverization and concomitant SEI growth leading to loss of cyclable Li and conductivity decay729graphene . The sizty tests  were perarticles 0 nm∼4 μm2/CDC cathode are shown in SeS2−1, but decreased to 672 mAh gSeS2−1 after the subsequent delithiation; that is, the first cycle CE is 73.5%. It is due to additional formation of the SEISeS2−1 (98.1% CE). After the fifth cycle, the cell no longer exhibited such obtrusive capacity fade, as shown in SeS2−1, which is 20 times higher than that of initial cycle, the specific capacity was stable between 175 and 195 mAh gSeS2−1. When reducing the current to 268 mA gSeS2−1 after the rate-capability test, the capacity was fully recovered to 441 mAh gSeS2−1, which is the original level at the same rate, implying that there was no degradation during initial rate capability testing. SeS2−1 during the subsequent 1,500 cycles. The curve shows a slight decrease from 498 to 403 mAh gSeS2−1 over 1,500 cycles. Hence, the rate of capacity fade is calculated to be 63 μAh gSeS2−1cycle−1 and the CR is 81% over 1,500 cycles with an average CE of 99.99%. In the magnified CEs of 1113312/CDC full cell is remarkable. The full cells employing S/CDC and Se/CDC electrodes were assembled for the comparative study with the SeS2/CDC full cell. In all cases, lithiated Si/graphene was used for the anode and the cell performances are presented in 2/CDC full cell; however, the specific capacity is about two times smaller than the SeS2/CDC full cell . It is noteworthy that the half-cell of S/CDC also showed better rate capability and then that the capacity could be fully recovered to original level (∼410 mAh gSeS2−1) at 268 mA gSeS2−1 . These results clearly indicate that there is synergistic effect between Si and SeS2.The initial charge/discharge processes of the full cell employing the lithiated Si/graphene anode and SeS gSeS2−1 . This chpability ; however2/CDC coin-type full cell was opened after 1,500 cycles, it was observed that there was no obvious, macroscopic degradation, such as electrolyte dry out, contamination of electrolyte and electrodes, and fracture and separation of electrodes , the S content increased and remained saturated at a constant ratio (bulk content), implying that S is slightly dissolved from surface of both CDC electrodes and a passivating layer containing mainly carbon is formed on the surface of CDC x where x<4) considering the cell voltage of the full cell is ∼0.2 V lower than that of the half cell252Sex (x≥4) in the electrolyte. A recent study reported that if a chalcogen element is confined in a small space, it can directly convert from elemental chalcogen to low-order polychalcogenide showing only one plateau2S(or Se)x where x≥4) decreasing the CE. The SeS2 located in larger pores of CDC formed high-order polychalcogenides and dissolved into the electrolyte. After that, only SeS2 retained in the small pores of CDC did not dissolved into the electrolyte and electrochemically cycled.In the scanning TEM/energy dispersive X-ray spectroscopy (EDS) analysis of Zim-intercept, first high-frequency semi-circle, the second middle-frequency semi-circle and a low-frequency curve. These features are roughly attributed to the resistances of electrolyte, the resistance of the SEI films (mostly on negative electrode), the charge-transfer resistance and diffusion, respectively2/CDC and lithiated Si/graphene–Se/CDC electrodes after 1,000 cycles. Our main interest is on high-frequency resistance (HFR) region, determined by the resistance of electrolyte and SEI. Specifically, the semi-circle presenting in HFR region is directly related to conductivity of SEI, which determines the quality of SEI for high LiB performance3537402/CDC and lithiated Si/graphene–S/CDC full cells, respectively, which can support that the full cells employing Se-containing cathodes has a high-quality SEI with high conductivity. The values are also smaller than those of the 50 cycled Si/graphene half cell (52.6 Ω) and Si/graphene–NCA full cell (44.2 Ω), indicating that Se-containing SEI can keep higher ionic conductivity even after a long-term cycle  than generally formed SEI on Si anode without Se. In particular, from the changes in the EIS curves of the lithiated Si/graphene–SeS2/CDC full cell with cycle number  is a powerful tool to investigate the kinetics of reactions and diffusion processes occurring in the electrodes, surface films and electrolyte4041e number , it was x), however, dissolved Se ions from the cathode become an essential component of the SEI. It is thought that its portion close to Si is electrically conductive, thus connecting individual Si nanoparticles. In addition, Se contributes to making the SEI highly ionically conductive, more mechanically robust and more resistive to solvent penetration. A highly conductive SEI ensures that the Li ion/electron transfer reactions between the electrolyte and active materials are fast and hence impede an unnecessary SEI growth on the surface and the separation the pulverized Si particles to the not-electrochemically active area. Further, the replacement of Li metal by lithiated Si/graphene as an anode can also improve the stability of LiB by impeding the unwanted side reactions between dissolved intermediate products and Li metal, and Li dendrite formation that plague Li/S or Se cells.On the basis of the results presented, the mechanism for synergetic effect from coupling between silicon anode and selenium sulfide cathode, which demonstrated high capacity and long-term stability for LiB, can be proposed as shown in the schemes of 2 full cell, <20% degradation after 1,500 cycles. More important, our studies suggest that the improvements in the electrochemical stability of high-capacity Si anode may be realized by using cathodes containing Se. We expect that our findings will provide new avenues for the improvements in the Si SEI stability by incorporating Se  species exhibiting similar properties or behaviour.In summary, we demonstrated remarkable CR of the lithiated Si/graphene–SeSMv: 450,000 g mol−1), carbon black conductive agent and conductive additive of micro-sized multi-layer granular graphene with very high conductivity of 107 S m−1, and propyleneglycol monomethyl ether solvent (Sigma Aldrich). After mixing the slurry by sonication and stirring with magnetic bar in a jar, the slurry was coated on a 10 μm Cu foil using a doctor blade. The coating on Cu foil was dried for 1 h at a room temperature and then in a vacuum oven at 80 °C overnight. The loading active of active material was between 1.64 and 1.66 mg cm−2.A commercially available Si-graphene composite was used for the anode. The active material was composed of nano Si particles and nano-sized plate-like multi-layer graphene . To make the slurry of adhesive and conductive anode material, the nano-sized active material was combined with polyacrylic acid (PAA) binder  melted at 120 °C and was absorbed into the CDC pores based on capillary action. Both inner and outer surfaces of the carbon were coated during the infiltration process. Any extra SeS2 that coated the outside of the pores, which could easily dissolve and lower the sulfur utilization/the active mass during cycling, was evaporated at 200 °C. From the gas sorption  binder were mixed in ethanol/water solution to prepare the slurry for casting the electrode. Pure black (Superior Graphite) and purified exfoliated graphite (Superior Graphite) were used as conductive additives, and the mass ratio was 75:15:5:5, respectively, SeS2/CDC, PAA binder, pure black and purified exfoliated graphite. The slurry was stirred at room temperature for 12 h and cast on aluminum foil. After drying overnight at room temperature under vacuum, the electrodes were used.The selenium sulfide  on cathode side. One hundred and fifty microlitres of electrolyte was added to 2,032 coin cells with active materials of 1 mg cm−2 in both anode and cathode. The cells were equilibrated for 24 h before operation. For Li addition to the full-cells, the Si/graphene anode was lithiated to 0.005 V at C/10 rate before assembly of the full cell and then the lithiated Si/graphene was used. To see the effects of both the anode and cathode on the capacity fade of the full cell during cycling, the capacity ratio of anode:cathode was designed to be close to 1:1. Using the measured gravimetric capacity (mAh g−1) during initial stable cycle (1–10 cycles at C/5) for the half cells employing of Si/graphene anode, SeS2/CDC, S/CDC and Se/CDC cathodes, the loading weights (g) were determined for full-cell design. The thickness of all the electrodes range between 25 and 33 μm.The coin cells were assembled with 1 M lithium hexafluorophosphate in ethylene carbonate:diethyl carbonate  as electrolyte, Celgard 2325 separator, silicon/graphene composite anode and S/Se/SeSC–V) and EIS test were performed. All cycling tests were conducted at room temperature (∼20 °C) using a battery cycler (Arbin). The half cell of Si-graphene anode was charged to 1.5 V and discharged to 0.01 V (1 h rest time between charge and discharge) at various rates from 134 to 2,680 mA gSeS2−1 for capacity-fade testing. Although the half cells of the Se/S/SeS2 CDC cathodes and full cells employing the electrodes were charged to 2.85 V and discharged to 1.0 V at various rates from 134 mA gSeS2−1 to 2,680 mA gSeS2−1. EIS tests of the full cells were conducted at both a nearly full charged state using a potentiostat (Autolab). The frequency was scanned from 1 MHz∼0.01 Hz using a 5 mV amplitude perturbation. The values for SEI resistances of individual components in high-resistance frequency were determined with a fitting program .To characterize the electrochemical properties of Li-ion batteries employing various fabricated electrodes, capacity–voltage  to remove Li salts fully and the samples were stored in containers filled with Ar before analysis to prevent any contact with air. To observe the surface morphology and phases of nano-sized Si particles and SEI, high-resolution TEM equipped with EDS  was used. From the EDS line scanning in scanning TEM mode, atomic mapping images were obtained. To examine the chemical composition of electrode surface, X-ray photoelectron spectroscopy (Thermo K-Alpha XPS) analysis was performed. The vacuum transfer module was used to prevent air exposure. Using etching by the Ar cluster ion beam, XPS depth profiles were obtained. In addition, high-resolution SEM (Hitachi SU8000) and SEM/EDS (Zeiss Leo 1530) were used to observe the micro-surface morphology and atomic compositions of materials. N2 sorption and thermo-gravimetric analysis were also used to measure surface area and to see thermal properties of CDC and SeS2/CDC materials for cathode, respectively.For material characterization of electrodes, the cells were opened in an Ar-filled glove box and washed gently for 2 min in extra pure dimethyl carbonate .Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.Supplementary Figures


P < 0.001). In subgroup analysis stratified according to histology types, the pooled results demonstrated that increased PD-L1 expression was an unfavorable prognostic factor for non-small cell lung cancer (NSCLC)  and pulmonary lymphoepithelioma-like carcinoma (LELC) , rather than small cell lung cancer (SCLC) . The pooled ORs indicated that PD-L1 expression was associated with gender, smoking status, histology, differentiation, tumour size, lymph nodal metastasis, TNM stage and EGFR mutation. However, PD-L1 expression was not correlated with ALK rearrangement and KRAS mutations.Although many studies have addressed the prognostic value of programmed cell death-ligand 1 (PD-L1) expression in lung cancer, the results remain controversial. A systematic search of the PubMed, EMBASE, and Cochrane Library databases was performed to identify the correlation between PD-L1 expression and driver mutations and overall survival (OS). This meta-analysis enrolled a total of 11,444 patients for 47 studies, and the pooled results showed that increased PD-L1 expression was associated with poor prognosis (HR = 1.40, 95% CI: 1.19–1.65,  More than 70% of patients are diagnosed with advanced disease, which are not amenable to curative therapy. Although much progress has recently been made for lung cancer such as low-dose spiral screening, minimally invasive techniques for diagnosis and treatment, advances in radiation therapy and molecularly targeted therapies, patients with lung cancer are still facing a relatively low 5-year survival rate, merely 17.4%3. Thus, immunotherapies have been considered as a very promising therapeutic strategy for different tumour types.Lung cancer, broadly divided into small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC), is deemed as the leading cause of cancer-related deaths in both the United States and China4. Programmed cell death ligand 1(PD-L1), the mainly ligand of PD-1, is upregulated in different types of tumours, including breast cancer5, NSCLC6, colorectal cancer7, gastric cancer8, testicular cancer9 and papillary thyroid cancer10. PD-L1 delivers negative costimulatory signals and binds PD-1 to reduce cellular immune responses by inducing T-cell apoptosis or exhaustion. Blocking the PD-1/PD-L1 pathway with monoclonal antibodies (MoAbs) is currently considered to be the most promising approach, offering durable activity and long-term survival outcomes11. Several meta-analyses have demonstrated that not only is PD-L1 expression associated with adverse clinical and pathologic features but an increased risk of death in many cancer types15. However, date regarding the prevalence and prognostic role of PD-L1 expression in NSCLC remains controversial, particularly in SCLC and other types of lung cancers.Programmed death 1 (PD-1), a member of the CD28 family, is a key immune checkpoint receptor expressing on the surface of the activated T, B and NK cells and plays a crucial role in tumour immune escape16. However, the relationship between major driver mutations and PD-L1 expression remains unclear. A recent study showed that oncogenic EGFR mutations directly up-regulated PD-L1 protein expression on the surface of cells in NSCLC, and exposure to gefitinib also lead to PD-L1 up-regulation17. Another study showed the upregulation expression of PD-L1 in NSCLC as a result of an EGFR mutation and ALK rearrangement via common downstream signalling pathways mediated by PI3K-AKT and by MEK-ERK18, implicating driver mutations in the regulation of the expression of immunosuppressive molecules.NSCLC is a disease that is characterized by driver mutation-defined molecular subsets, and alterations in epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), and KRAS are major oncogenic drivers in NSCLCWe therefore conducted a comprehensive meta-analysis to investigate the significance of PD-L1 expression as a prognostic marker and to determine the relation of PD-L1 expression to clinicopathological features and driver mutations in lung cancer patients.in vivo/in vitro studies, case reports, reviews, meta-analyses and comments. After reading the full texts of the remaining articles, 45 studies lacking sufficient data for further analysis were discarded. Forty-seven studies with 11,444 patients were finally included for meta-analysis.The literature review process is shown in Fig. 40, thirteen in adenocarcinoma (ADC)53, six in squamous cell carcinoma (SCC)59, two in small cell lung cancer (SCLC)61, and two investigated PD-L1 in pulmonary lymphoepithelioma-like carcinoma (LELC)63, and one investigated PD-L1 in pulmonary pleomorphic carcinoma (PPC)64. Thirty-seven studies were conducted with Asian patients, and 10 studies were conducted with non-Asians patients. Twenty-three studies included non-metastatic lung cancer patients, while 5 studies involved metastatic disease, and 17 studies involved both non-metastatic and metastatic diseases. The Newcastle–Ottawa Quality Assessment Scale (NOS) scores of the studies ranged from 4 to 8, with a mean value of 6.92.Referring to Table P < 0.001) for OS using a random model with significant heterogeneity .The correlation between the expression of PD-L1 and overall survival (OS) in lung cancer is shown in Fig. P = 0.01) and LELC patients , but not SCLC .To further examine the effects of different subtypes of NSCLC on survival, a subgroup analysis was conducted in patients with ADC and SCC. The results revealed that increased PD-L1 expression was associated with poor prognosis in patients with ADC , but not in SCC . In addition, subgroup analyses according to TNM stage showed that increased PD-L1 expression impacted OS negatively for lung cancer patients in stage I-III , but not in stage IV . When grouped according to ethnicity, the combined HRs of Asian studies and non-Asian studies were 1.64  and 0.85 , respectively, indicating that PD-L1 is an indicator of the poor prognosis in Asian populations, but not in non-Asian populations , smoker , patients with SCC , a higher histological grade , larger tumor sizes , positive lymph nodal metastasis  and TNM stage . The analysis of the relation of PD-L1 expression to histological grade , tumour size , and lymph nodal metastasis status  presented no heterogeneity; thus, a fixed effect model was used. The other analyses above were performed using the random effects model.The correlation between PD-L1 expression and clinicopathological parameters of lung cancer is shown in Supplementary Figs P = 0.01), while no associations were identified between PD-L1 expression and ALK rearrangements  or KRAS mutations .To further understand the role of PD-L1 expression as a biological marker, we investigated the relevance of increased PD-L1 expression and major driver mutations (EGFR/ALK/KRAS). As shown in Fig. P values for these tests were 0.237 and 0.120, respectively 72, and atezolizumab (MPDL3280A)73 have shown promising clinical activity in advanced NSCLC. In the era of precision medicine, it is particularly important to screen patients who are most likely to benefit from PD-1/PD-L1 antibody immunotherapy. Preliminary results suggested that high PD-L1 expression was associated with higher clinical activity of anti PD-1/PD-L1 monoclonal antibodies74. Therefore, the identification of patients with high PD-L1 expression is a vital question for anti-PD-1/PD-L1 therapy. In the present study, we investigated the relation of PD-L1 expression to clinicopathological factors. According to the pooled analysis, the expression of PD-L1 was increased in male, smoker, patients with SCC, a higher histological grade, larger tumour size, positive lymph nodal metastasis, and later clinical stage. These patients might benefit more from treatment targeting the PD-1/PD-L1 pathway. These data suggest that increased PD-L1 expression might promote lung cancer invasion and metastasis, leading to the poor prognosis of patients with lung cancer. It has been reported in several studies regarding the association of smoking status with PD-L1 expression in patients with lung cancer. Some studies have shown that the expression of PD-L1 was significantly higher in smokers46, whereas other studies could not confirm this finding54. In the present study, patients with high PD-L1 expression were associated with smoking status in lung cancer patients.Several clinical trials using anti-PD-1 and anti-PD-L1 monoclonal antibodies, including nivolumab (BMS-936558)75. Moreover, as observed in NSCLC cell lines, there was a high level of PD-L1 expression in NSCLC patients harboring EGFR mutations45. However, some studies have shown that PD-L1 positivity was more frequent in EGFR wild-type46, and other studies have shown no association between PD-L1 expression and EGFR mutations27.The present meta-analysis investigated the correlation of PD-L1 expression with EGFR mutations in lung cancers. The results of the present study showed that high PD-L1 expression was associated with EGFR mutations. The discrepancies among different studies might reflect the heterogeneous study population and variable definitions of PD-L1 expression. Additional studies are needed to further analyze this issue. In addition, we showed that increased PD-L1 is not associated with ALK rearrangements and KRAS mutations.Accumulating evidence revealed the relationship between PD-L1 expression and driver mutations. EGFR mutations represent one of the most frequent driver mutations in NSCLC, particularly in ADC. Previous studies revealed that activating EGFR mutations induced PD-L1 expression in EGFR-driven NSCLC in cell lines and an animal modelThere are several limitations of the present study that should be acknowledged. First, the sample size of SCLC and LELC studies included in the present meta-analysis was relatively small; therefore, the pooled data might be less than the statistical power. Hence, additional well-designed studies with larger sample sizes are needed to provide a more comprehensive evaluation of the prognostic value of PD-L1 expression in patients with SCLC and LELC. Second, the HR values of some studies were extracted from survival curves, which is less reliable than direct data provided in the original literature. Third, the distinct antibodies and different cut-off levels of PD-L1 expression among diverse studies might also impact the accuracy of prognostic estimation for lung cancer. Moreover, some inevitable publication bias might exist in the present meta-analysis, as many negative studies could not be published. Furthermore, significant heterogeneity existed in the results, although we calculated the pooled subgroup data using random-effects models. The observed heterogeneity might reflect differences based on different baseline characteristics, study designs, or treatment protocols. Finally, all of included studies were retrospectively collected, which might have introduced heterogeneity from variable treatments.In conclusion, despite the limitations described above, this study presents the first meta-analysis to systematically assess the association of PD-L1 expression with lung cancer survival and driver mutations. The results demonstrated that high PD-L1 expression represents an unfavorable biomarker in LELC and NSCLC, but not in SCLC. In addition, increased PD-L1 expression is correlated with EGFR wild-type status. To strengthen these findings, the validation of the prognostic value of PD-L1 expression in patients with lung cancer requires further studies.76. The present study was based on data from previously published studies, and therefore, ethical approval was not required.This meta-analysis was performed according to the preferred reporting items for systematic reviews and meta-analysis (PRISMA) statementWe conducted a systematic literature search for published articles in the PubMed, EMBASE, and Cochrane databases from January 1999 to July 2017. The search terms included the following keywords: (PD-L1 OR B7-H1 OR CD274 OR programmed cell death 1 ligand 1 protein) AND (lung cancer OR lung neoplasms OR pulmonary cancers). Furthermore, we manually searched the abstracts of the annual meetings of American Society of Clinical Oncology (ASCO), European Society of Medical Oncology c (ESMO) and the World Conference of Lung Cancer (WCLC) from 1999 to 2017. To explore additional studies, we also reviewed the reference lists of relevant articles.The following inclusion criteria were used: (1) All patients were histologically confirmed as having lung cancer; (2) PD-L1 expression was detected by immunohistochemistry (IHC) or quantitative immunofluorescence (QIF) in primary NSCLC tissue; (3) Studies showed a correlation between PD-L1 expression and overall survival; (4) Studies showed a correlation between PD-L1 expression and clinicopathological features; (5) Studies provided sufficient information to extract the HR and 95% CI date for OS; and (6) articles were published in English. Studies that did not meet the inclusion criteria were excluded. When several studies were conducted using the same cohort of patients, only the most recent study was included.77. Two reviewers (ZS and WY) independently conducted the quality assessment for each study using the NOS, and any discrepancies were resolved after revisiting the original study and discussion until consensus was reached. The NOS maximum possible score was 9 points, and studies that receiving a score of 6 or higher were considered high quality78.Two authors (ZMH and LGL) independently conducted the data extraction, and a third reviewer (WY) resolved any discrepancies. The following information was extracted: name of the author, year of publication, country, tumour type, number of patients, stage, detection method, PD-L1-positive expression, outcome, clinicopathological parameters and HRs and 95% CIs for OS. When the HR values were not directly reported, we obtained the additional data from the original authors. And the data was extracted from survival curves using the methods of Parmar under the circumstances of no response2. A P value <0.1 orI2 values of >50% were indicative of significant heterogeneity, with a random effects model being used; a fixed effects model otherwise. A subgroup analysis was conducted to explore the potential heterogeneity among studies. Potential publication bias was assessed using Egger’s and Begg’s tests. The meta-analysis was performed using Review Manager 5.3  and STATA version12.0 . All statistical analyses were 2-sided, and P values < 0.05 were defined as statistically significant.The HR and its 95% CI values were used to evaluate the association between PD-L1 expression and survival, and the pooled OR and 95% CI values were used to determine the relationship between PD-L1 expression and clinicopathological features. Statistical heterogeneity between studies was assessed using the chi-squared test and ISupplementary Fig.1-7


The as-exfoliated graphene slurry can be directly used for 3D printing, as well as fabricating conductive graphene aerogels and graphene−polymer composites, thus avoiding the use of copious quantities of organic solvents and lowering the manufacturing cost. This non-dispersion strategy paves the way for the cost-effective and environmentally friendly production of graphene-based materials.It is difficult to achieve high efficiency production of hydrophobic graphene by liquid phase exfoliation due to its poor dispersibility and the tendency of graphene sheets to undergo π−π stacking. Here, we report a water-phase, non-dispersion exfoliation method to produce highly crystalline graphene flakes, which can be stored in the form of a concentrated slurry (50 mg mL Large-scale graphene production remains challenging because of the tendency of graphene to stack with itself, which requires its dispersion in large amounts of solvent. Here the authors achieve the environmentally favourable production of highly concentrated graphene in water through a non-dispersion, flocculation strategy. Due to the lack of efficient large-scale production processes, the production of graphene faces a dilemma where a compromise has to be made between scalability and graphene quality14. Liquid-phase exfoliation is a promising approach to realize scalable production of high-quality graphene or graphene oxide. Graphite can be exfoliated in organic or aqueous solutions containing a surfactant15 by applying mechanical force 16. However, large quantities of solvent is always needed in these processes for purification and dispersion due to the limited dispersion stability of graphene flakes. Only a very small amount of graphene, typically <1 mg mL−1, can be dispersed in common solvents, and this is only marginally improved with the help of dispersing agents like superacids17 or ionic liquids19, or through sonication for extended periods of time20. Reducing the amount of solvent destabilizes the graphene dispersion and leads to the re-stacking of graphene by van der Waals interactions. This means that the production of 1 kg graphene by such dispersion approaches requires at least 1 ton of solvent, which is environmentally unfriendly and economically infeasible.Following the discovery of graphene, many optimistic predictions have been made with regards to its applications in fields ranging from electronics to medicine16, the introduction of cation−π interaction between graphene and the solvent18, and the creation of electrostatic repulsion between graphene flakes by protonation21 or adding surfactants22. Generally, these approaches are only partially effective because of the large ratio of area to thickness (>103) and the tendency of graphene flakes to undergo π−π stacking23. Chemical intercalation-exfoliation methods have also been explored to prepare high-quality graphene in high yields25. However, these methods require the use of designer ionic liquids18 and have limited scale-up capability (1 mg per batch)24, and suffer from the drawbacks of producing partially exfoliated flakes (>10 nm in thickness)25. Rheological analysis of graphene dispersions indicates that the viscosity increases steeply with increasing graphene contents; for instance, it was observed that graphene-ionic liquid systems had a critical gel concentration as low as 4.2 mg mL−126. The increased viscosity will reduce the efficiency of liquid phase exfoliation and limit its large-scale production. Furthermore, the strong inclination for graphene to undergo π−π stacking has to be overcome and one way to do this is by introducing segregating agents.Three approaches have been explored previously to increase the concentration of graphene dispersions, which include the selection of a suitable solvent with a low enthalpy of mixing with graphene−1 (5 wt%). The presence of adsorbed ions prevents the re-stacking of graphene flakes and enables their re-dispersion in solution on demand. Partially oxidized graphite is used as the precursor, which is exfoliated by high-rate shearing in an alkaline aqueous solution of pH = 14. Our calculation of inter-sheet interaction energies indicates that under alkaline conditions, the ionization of oxygen-containing groups on graphene layers, even at very low concentrations , can generate a large electrostatic repulsion energy (EE) to counteract the interlayer van der Waals attraction energy (EvdW). Due to the high ionic strength of the solution, exfoliated graphene flakes tend to form low-viscosity, flocculated slurry rather than a stable dispersion. Such graphene slurry can be easily re-dispersed in N-methyl-2-pyrrolidone (NMP) or alkaline water (pH = 12), and serves as a stock solution of graphene. Such graphene slurry possesses a three-dimensional (3D), loosely stacked microstructure with tunable modulus and viscosity, which can be directly used for 3D printing to form graphene aerogels and conductive polymer materials, without additional dispersion processes.In contrast to the conventional exfoliations in a solvent-dispersed system, here, we propose a non-dispersion strategy in which graphene is produced and stored as a flocculated aqueous slurry with concentrations as high as 50 mg mLTo reduce the use of solvent, a non-dispersion strategy was applied to mass produce graphene and fabricate functional materials directly using the flocculated slurry, as opposed to conventional liquid phase method where a large amount of solvent was used Fig. .Fig. 1Pr28. The pretreated graphite was then exfoliated by applying high-speed shear  to generate a low density of ionizable oxygen-containing groups on graphene layers. Partial oxidation-induced peak at 22.5° in the X-ray diffraction (XRD) spectrum indicates the formation of a stage-1 graphite intercalation compound with an interlayer distance of 8.0 Å 26. Although super acids or special ionic liquids may improve the dispersibility of graphene, these systems have high viscosity and limited exfoliation efficiency, and thus impractical for large-scale production18. In contrast, our graphene slurry displays a low shear viscosity of 0.064 Pa s at 50 s−1 at 5 wt% solid content, which is over one order of magnitude lower than those of other dispersion systems in Supplementary Fig. 1730. The viscosity at practical shear rate of 20,000 rpm, corresponding to 2094 s−1, may even be lower due to shear thinning effect. This affords opportunities for high concentration exfoliation and production of high-quality graphene sheets.Meanwhile, the viscosity of system is a critical factor in liquid-phase exfoliation but it is often overlooked−1 (D band) and 1580 cm−1 (G band), corresponding to the contributions from sp3 type carbon from defects and sp2 hybridized aromatic carbon in Fig. ID/IG mapping clearly evidences that most of the defects are located at the edges . The I2D/IG ratio is ~0.45, corresponding to that of ~3 layer graphene31. Since we have to spin-coat NMP dispersion on Si wafer for Raman, it is difficult to avoid the re-stacking of graphene nanosheets during solvent evaporation. The exfoliated graphene only contains a slightly higher oxygen content than pristine graphite (5.9 versus 2.3 atom%) from XPS and elemental analysis in Supplementary Table 1s spectrum shows a strong C=C peak at 284.7 eV together with a small tail at 286.4 eV from C−O bonds, while the carbonyl species at 288.6 eV is negligible32.The quality of graphene produced was assessed by scanning transmission electron microscopy (STEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). In order to probe the quality of individual flakes, as-prepared graphene slurry was washed and re-dispersed prior to test. Atomic-resolution STEM image in Fig. 33. The electrical conductivity is measured as 2.5×104 S m−1 and can be further improved to 4.2×104 S m−1 by HI reduction , scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM and high-resolution TEM images show micron-sized, single-layer graphene flakes with the typical six-fold symmetry selected-area electron diffraction (SAED) pattern in Supplementary Figs. 21. The stability of our graphene aqueous dispersion is pH-dependent, with a maximum dispersion concentration at pH = 12  is a common indicator for the stability of nanomaterials. As shown in Fig. ζ value of −42.4 mV at pH = 12, suggesting a strong electrostatic repulsive interaction between graphene flakes. This observation can be explained by the C1s XPS spectrum, where hydroxyl groups (−OH) are the primary oxygen-containing groups on our graphene. Since the dissociation constant of a phenolic hydroxyl group (pKa) is ~10.036, the degree of ionization (W) increases at higher pH values  due to negatively charged oxygen groups on the surface and adsorbed counter ions determines the dispersion stability  is given by the sum of the electrostatic repulsion energy EE and the van der Waals attraction energy EvdW37 or, ET = EE+EvdW. For graphene flakes, EvdW is given by 22, where d0 = 0.335 nm and γ is the surface energy (70 mJ m−2). EE depends on the electrostatic potential on the graphene surface (ψ0), the electrolyte concentration (c), and the flake separation (h)39. In a previous study, EE was calculated by measuring the value of Zeta potential (ζ), which gives the change of EE as a function of h22. However, this calculation is applicable only when ζ < 25 mV22. To overcome this limit, we have calculated EE from available data for ψ0, h, and other constants (Supplementary Eqs. (39. Using the Poisson−Boltzmann (PB) equation to derive the relationship between ψ0 and surface charge density (σ), we can write 39, where L is the Avogadro constant, e is the elementary electronic charge, k is the Boltzmann constant, κ is the Debye−Hückel parameter, and T is the absolute temperature. Assuming that all oxygen-containing groups on our graphene sheets are hydroxyl group, and σ is dependent on the density of −OH groups together with the degree of ionization W at different pH values, σ can be also expressed as σ=WAe/(2.62×10−20)  theory to explain our experimental observations. Two adjacent graphene flakes in the dispersion are treated as two parallel plates with a separation distance of entclass1pt{minimaary Eqs. 38,39. Usentclass1pt{minimaEE curve for graphene dispersion is presented in Fig. h. After taking EvdW into account, the variation of the total interaction energy ET with h between two adjacent graphene flakes is displayed in Fig. EB = 5.22 mJ m−2) against aggregation is observed, which is ~8 times larger than that of a surfactant-stabilized graphene dispersion (~0.64 mJ m−2)22. Even at oxygen coverage of 1 atom%, the calculation result also shows a relatively large energy barrier (1.83 mJ m−2) in Supplementary Fig. EE and ET curves at different pH values. EE is nearly zero in the pH range of 7~8 due to the lack of ionized oxygen-containing groups, leading to the re-stacking of graphene flakes. In contrast, a large number of counter-ions (Na+) will be adsorbed onto the surface of graphene when pH > 13. This results in the compression of the EDL from 3.0 nm at pH = 12 to 0.3 nm at pH = 14  when the pretreated graphite is exfoliated at pH = 12, even though the dispersion stability is highest at this pH value. This is attributed to the inherent low dispersibility of graphene which sets a limit on the yield of high-concentration exfoliation. In contrast, when exfoliated at pH = 13 or 14, graphene flakes rapidly flocculate due to the compressed EDL, which reduces the system viscosity and facilitates exfoliation. The flocculated graphene flakes are unable to form π−π stacking due to the presence of absorbed ions and the loose stacking, so that they can be re-dispersed in NMP or alkaline solutions.41. In contrast, the slurry at pH = 7 exhibits a face-to-face aggregation due to the lack of electrostatic repulsion from charged functional groups , the flocculated graphene slurry is re-dispersible, even in form of graphene cake with extreme high loading  against storage/loss modulus reveals a critical gel concentration (cg) of ~1.25 wt% for the graphene slurry at pH = 14. Below this cg, the flocculated graphene flakes form individual micro-scale flocs. The system exhibits a liquid-like behavior for which loss modulus (G″) is greater than storage modulus (G′) in the measured frequency range. Beyond cg, where G’′ is larger than G″, the slurry behaves like an elastic gel. Here, we have fabricated various graphene aerogel structures via 3D-printing of highly concentrated slurry at the elastic gel region in Fig. 44. Previous efforts on graphene aerogels rely on the sol-gel chemistry, which is challenging for large-scale production46. The printed aerogel is macroporous −graphene composites were obtained, where PDMS was evenly distributed in the graphene framework. The resulting composite exhibits nonlinear super-elastic behavior and ultra-large, reversible compressibility with a strain up to 40%. Multi-cycle compression test also shows that after the first loading−unloading loop, the stress was still stabilized at 53 kPa in the following nine loops . The exfoliated flakes form loosely stacked, flocculated aggregates due to the presence of adsorbed ions on the weakly oxidized surface. Such graphene slurries possess a 3D loosely stacking microstructure with rheological properties that are markedly different from that of closely stacked graphene flakes; for example, they can be directly 3D-printed to fabricate conductive graphene aerogels and be used to fabricate high graphene content composites. Different from traditional oxidation-reduction approaches, this non-dispersion exfoliation strategy allows a cost-effective, large-scale production, storage and transport of graphene in aqueous medium.In conclusion, we have demonstrated an industrially viable water-phase exfoliation strategy for preparing high-quality graphene and composites. This approach bypasses the destructive chemical oxidation processes, avoids the use of copious quantities of solvent, and addresses the critical issues related to the storage and transportation of graphene. Using this strategy, graphene flakes can be exfoliated in the form of highly concentrated slurries (5 wt%) with high production efficiencies  was added in batches into concentrated H2SO4  over a period of 30 min in an ice-water bath. Then the ice-water bath was removed and natural graphite flake  was added. The system was stirred at 35 °C for 2 h. After reaction, the black flakes were filtered through a 200-mesh sieve  was added into 2 L of 1 M NaOH aqueous solution . The mixture was subjected to shear at 20,000 rpm for 1 h at r.t. by using an FA 40 high shear dispersing emulsifier (Fluko) with a working tool, resulting in a black graphene slurry. For yield calculation, the graphene slurry was centrifuged at 10,000 rpm for 10 min and repeatedly washed by a large amount of water (4~6 times) until pH approaches 10. Then the washed slurry was re-dispersed in NMP at a concentration of ~0.1 mg mLAs-exfoliated graphene slurry at pH = 14 was concentrated to a suitable concentration (from 8 to 23 wt%) by filtration through a G4 funnel and subsequently used as a printable ink without modification. The concentrated graphene slurry was transferred to a 20 mL syringe barrels and printed using a robotic deposition device. The diameter of the printing nozzles ranged from 200 to 600 μm. The pressure was regulated during printing in air to maintain constant ink flow. After printing, the printed structures were frozen at −20 °C for 5 h and freeze-dried for 24 h. Then the dried structures were carefully immersed into water to remove the residual ions. Finally, graphene aerogels was obtained by freeze-drying process for 24 h.2 20 TWIN and JEM-2100F, 200 kV), AFM (Multimode 8), XPS , Rheology , SEM (Ultra 55), Raman , XRD , UV-Vis (Lambda 35), Zeta (ZS90), EA (vario EL III), Conductivity , Contact angle (JC2000 DM), 3D-printing (Bio-Architect®–Pro), Multi-cycle compression (Reger-RWT10).The following equipment was used: High-rate shearing , STEM , TEM/SAED (Tecnai GAll data are available from the authors upon reasonable request.Supplementary InformationPeer Review FileDescription of Additional Supplementary FilesSupplementary Movie 1


Mono-elemental two-dimensional (2D) crystals , termed 2D-Xenes, have been brought to the forefront of scientific research. The stability and electronic properties of 2D-Xenes are main challenges in developing practical devices. Therefore, in this review, we focus on 2D free-standing group-IV graphene analogs  and the functionalization of these sheets with organic moieties, which could be handled under ambient conditions. We highlight the present results and future opportunities, functions and applications, and novel device concepts.  Therefore, free-standing group IV elemental sheets having high stability under ambient conditions is a challenging issue. These challenges include: addressing the gapless nature of graphene and increasing the stability of silicene and germanene under ambient conditions. In this review, to compensate for the weaknesses of mono-elemental classes of 2D-Xenes (X=C (graphene), Si (silicene), Ge (germanene)), we will focus on 2D free-standing group IV graphene analogs . In these materials, every atom in the framework features a covalently bound ligand, thereby removing π-bonding. These ligands directly couple to the half-filled pz orbitals to produce a gapped, semiconducting band structure; and the magnitude of this bandgap depends on both the framework element and the identity of the covalent ligand.While graphite, having a cleavage plane, is mechanically easily exfoliated into the graphene, the structures of the other IV elements do not have cleavage planes. Therefore, these elements cannot be mechanically exfoliated into individual sheets with atomic thickness. In the history of polymer chemistry, many organic chemists have taken up the challenge to synthesize 2D silicon compounds by polymerizing silicon monomers, for example, the Wurtz reaction . Unfortu2.sp, sp2, sp3) enables them to form very diverse structures. Among the diverse carbon allotropes, graphene is a perfect construction of sp2 carbon atoms arranged in a planar honeycomb lattice n), as described below.In the above reaction, the 2D silicon framework of (SiH)3.2.2 single crystal have been analyzed by high-resolution angle-resolved photoemission spectroscopy (ARPES) , naphthyl . D. D116]. 4.Pristine monolayer silicene has been experimentally synthesized on metal substrates and its characteristics have been disclosed by both experimental  and theo4.1.A possible formation process of bilayer silicene was first demonstrated by Morishita et al. using MD simulations . They fo10 K/s. They found that a layered structure was formed at ~ 1700 K inside the slit nanopore.In the MD simulations by Morishita et al. , molten Figure Figure Bai et al.  also per4.2.While the standard classical MD simulation is able to provide dynamical properties in nanoseconds or beyond, the interatomic interactions therein are often approximated by simple functions of the distance of two atoms, which may not be sufficient to accurately characterize a variety of nanoscale structures such as silicene. DFT-based calculations have, thus, been intensively performed for mono- and bilayer silicene, especially those with the honeycomb lattice, by several groups. Here, details of the structural and electronic properties of BHS estimated using DFT are discussed.sp3 hybridization and the tetrahedral bonding. The length of the in-plane and inter-plane bonds in BHS with an AB stacking has also been estimated using DFT calculations [BF4], germanene in Zintl-phase CaGesilicene . The new2 (0.386 nm) and 3C-Si (0.384 nm) was less than 1%, which is comparable to the observational error. Compared with the w-BL structures, the lattice constants, a and b, of w-BLGe were 2–3% larger than those of w-BLSi, and the thickness of w- BLGe  have not been achieved experimentally. Nevertheless, there is a strong resemblance between the organo-modified graphene quantum dots, silicane and germanane in this text and the predicted mono-elemental free-standing 2D materials . Therefore, knowledge of the properties of these is a good starting point for serving as a nanotechnology platform with multi-physical features for fundamental research and applications.The theoretical and experimental studies we have reviewed, thus, far indicate that a variety of bilayer silicenes and germanenes could be synthesized depending on the conditions, such as external stress and charge distribution on the surface. These structural flexibilities mainly originate from the existence of dangling bonds on the surfaces, which place bilayer in a unique position among various nanoscale materials.Finally, on-demand molecular design and control of the surface modification of group IV graphene analogs could be key processes used to develop electronic devices and energy storage materials in the near future. These low-dimensional materials can exist in the form of multi-layered crystals whose length and width are determined by the size of the precursor and can be greater than millimeters – suitable for exfoliation and further device processing.No potential conflict of interest was reported by the authors.This work was supported in by PRESTO; the Japan Science and Technology Agency.


This is due to excellent properties of graphene, such as a high theoretical surface area, electrical conductivity, and mechanical strength. The fundamental structure of graphene is also manipulatable, allowing for the formation of an even more extraordinary material, porous graphene. Porous graphene structures can be categorized as microporous, mesoporous, or macroporous depending on the pore size, all with their own unique advantages. These characteristics of graphene, which are further explained in this paper, may be the key to greatly improving a wide range of applications in energy storage systems.Graphene, 2D atomic-layer of sp In 2 lattice . Since tGraphene possesses excellent mechanical strength with a Young’s Modulus of about 1000 GPa , 5. EffeGraphene sheet can be further assembled or processed into porous structures that exhibit desired physical and chemical properties, Fig. There are several review papers regarding graphene and its application in energy storage –29. HoweGraphene can be produced in a variety of ways including a scotch tape method, chemical vapor depositions (CVD), and chemical oxidations/exfoliation/reduction of graphite using Hummers’ methods , 32–37. Porous graphene can be synthesized using either template or template-free methods. The template approach uses some predetermined structures as the “template” to create the appropriate size and shape of the pores required –45. AlteNanostructured porous graphene could be classified as microporous , mesoporous (2–50 nm), and macroporous (bigger than 50 nm) graphene depending on the pore size according to the International Union of Pure and Applied Chemistry (IUPAC) definition . While iThe “breath figure” method is a promising approach to create the three-dimensional macroporous graphene structures possessing relatively large micrometer size pores , 40. The2SO4 aqueous electrolyte [Kim successfully demonstrated flexible macroporous graphene film with controllable pore size ranging from 1 to 4 um using the breath-figure method . In thisctrolyte . The capctrolyte .Chen also developed a scalable and facile self-assembly of graphene to fabricate macroporous graphene by the breath figure method . Instead3, Na2S, Vitamin C, HI and hydroquinone without stirring, 3D macroporous graphene hydrogel was generated without using any template or cross-linker [3 exhibited a bulk conductivity of 87 S/m, which was higher than crosslinked 3D graphene [A 3D architecture of macroporous graphene can also be created by in situ self-assembly induced by a simple chemical reduction of GO , 47. ThiIn situ self-assembly by chemical reduction was also employed by Wang and coworkers . In this2/g) because of aggregating nature of graphene sheets caused by strong van der Waals interaction [For graphene, it is generally hard to obtain high surface area close to the theoretical value  [2O2 is important for successful creation of holey graphene. It was shown that excessive addition of H2O2 causes aggressive etching that would break the graphene sheets into small pieces [Micro- and mesoporous graphene, so called holey graphene, has also been prepared using other etching agents including H and NaI , 54–57. ng agent . Beginniutoclave . Simultaanopores . This 3Danopores . Freeze-60 m2/g) . In thisl pieces . The coml pieces .2O2 to produce solution processable holey graphene oxide. In this case an aqueous mixture of GO and H2O2 are heated to 100 °C for 4 h while stirring [2O2 the resulting HGO can be re-dispersed to form a stable aqueous dispersion. Via a reduction induced self-assembly process, holey graphene hydrogels were obtained from the holey graphene oxide. The resulting hydrogels displayed an interconnected three dimensional porous network that can be formed in many shapes and sizes simply by changing the reactor used in the reduction process. Similarly, this holey graphene possessed improved electrochemical performance because of highly accessible surface area and pores.More research explored synthesis of holey graphene oxide using Hstirring . After rHeteroatom doping of graphene is one of the most effective way to enhance its electrochemical performance for energy storage applications because of its modified properties such as additional pseudocapacitance, improved electrical conductivity and surface wettability , 59, 60.Apart from porous graphene and heteroatom-doped porous graphene, graphene-based composite materials could be an ideal platform for energy storage owing to tunable composition-dependent properties. In addition, graphene composites having specifically designed properties such as electrochemical properties, surface area, electrical and thermal conductivities can be synthesized by varying controlling composition and synthesis conditions in line with specific applications. Nanoarchitectures of graphene-based composites could lead to superior energy storage capacities due to their additional surface area as well as larger pore volumes, which could facilitate diffusion of electrolytes when the composites are used as electrodes. So far, a wide range of graphene-based composites have been demonstrated with various organic and inorganic materials through template-assisted synthesis, aerosol spray drying process as well as assembly of graphene with other nanomaterials , 64–69.Nanostructured graphene-based hybrid materials can be prepared with the use of a variety of soft and hard templates including polymers, carbon spheres, inorganic particles, micelles, ionic liquids, and nanostructured substrates , 70–76. 2 composite was successfully prepared through vacuum filtration using a sacrificial polystyrene bead template [2 was chemically incorporated into this macroporous graphene to increase its electroactivity [2-graphene composite had significantly increased capacitance (389 F/g at 1 A/g) as compared to the nonporous planar MnO2-graphene counterpart (137 F/g) because of higher surface area and facilitated ion transport within three-dimensional interconnected macropores [2/CMG positive electrode and macroporous CMG negative electrode can be operated in a relatively wide voltage range up to 2 V in NaSO4 aqueous electrolyte [For example, three-dimensional macroporous graphene/MnOtemplate . In thistemplate . After etemplate . Afterwaactivity . This macropores . An asymctrolyte .Fig. 4a2/g than the RGO counterpart having 801 m2/g [A three-dimensional hierarchical carbon nanostructure composed of graphene sheets and mesoporous carbon spheres was also prepared using mesoporous silica spheres (MSS) as a sacrificial template . The app801 m2/g . After t801 m2/g . These r2 was added in GO dispersion, CaCO3 particles were formed on GO sheets, in which CaCO3 were used as template to create a macroporous structure [Hierarchical porous graphene/polyaniline composites are other examples of a successful template-assisted synthesis . In thistructure . After ctructure . This matructure . The eletructure . This retructure . Moreovetructure .Graphene sheets has a tendency to restack and form lamellar structure because of strong van der Waals force between graphene sheets , 77. TheThis development opened up the new opportunities for synthesizing crumpled graphene-based ball-like nanocomposites for energy storage applications , 64–68. Other crumpled graphene nanocomposites were also reported. For instance, a redox-active crumpled graphene/few-walled carbon nanotubes electrode was created using the partially reduced crumpled graphene oxide and functionalized few-walled carbon nanotubes mixture through vacuum-filtration process . It was The aerosol-spray process was further extended to fabricate 3-D crumpled graphene/carbon nanotube/polyaniline (CCP) nanocomposites for supercapacitor applications . First, Layer-by-layer (LbL) assembly is a pervasive film fabrication technique that is characterized by its formation through alternating deposition of complementary species –83. Mult3 was obtained in an acidic electrolyte originating from electric double layer capacitance and redox activity of oxygen-containing functional groups [With the demand for greater energy from micro-power sources, LbL assembly assists in pioneering a new era in micro-batteries or micro-capacitors for thin film devices –95. Poro3 at 0.03 A/g while the 1520 nm thick film exhibited 123 mAh/cm3 [Porous polyaniline nanofiber/reduced graphene oxide (PANI NF/RGO) hybrid films were also demonstrated using dip-assisted LbL assembly followed by electrochemical reduction . The LbL mAh/cm3 .Fig. 6aSpray-assisted LbL assembly was adopted to fabricate the compositionally similar electrodes, PANI NF/RGO and address the previously encountered issues of dip-assisted LbL assembly such as slow processing, cross contamination, and scalability problem . With th2-hybridized graphitic domains. Notably, These LbL films showed excellent mechanical flexibility and durability when subjected to repeated flexure, indicating that this ANFs/graphene LbL films can be used in structural energy systems.For flexible power systems, nanostructured aramid nanofibers (ANFs)/graphene sheets multilayer films were fabricated from ANFs and GO dispersions using dip-assisted LbL assembly . In thisEnergy storage is becoming more important to meet ever-increasing energy demands. To improve current energy storage efficiency, a wide range of materials have been explored as an electrode for energy storage devices. Among various materials, graphene is drawing great interest due to its excellent properties including good mechanical strength, high thermal and electrical conductivities, good chemical stability, and high theoretical surface area , 51, 97.Supercapacitors, also called ultracapacitors, can have higher power density than batteries, which means that supercapacitors can deliver energy much faster (within a few seconds) than batteriers . Supercar is the electrolyte dielectric constant, ɛ0 is the dielectric constant of vacuum, d is the effective thickness of the electric double layer, and A is the effective surface area of the electrode [Capacitor performance of EDLCs can be evaluated based on capacitance, which is the electrostatic charge accumulation at the interface of the electrode/electrolyte, Fig. lectrode , 104. As2SO4 electrolyte comparing with nonporous graphene electrodes [Macroporous graphene structures generally possess larger pore and pore volume as compared to micro- and mesoporous graphene. Electrolytes can be held within large macropores, which could reduce required diffusion path length of electrolyte ions. Indeed, macroporous self-assembled graphene hydrogels prepared by one-step hydrothermal process exhibited relatively high a specific capacitance of 152 F/g at a scan rate of 20 mV/s in 5 M KOH aqueous electrolyte . When 3Dectrodes . These rectrodes , 108.2/g showed promising electrochemical performance in a non-aqueous electrolyte [4/AN) electrolyte, a capacitance of 166 F/g was measured in the voltage window of 3.5 V [2O2 was assembled into 3D frameworks and formed hierarchical porous structures, it displayed an even higher capacity and energy density [4/AN) non-aqueous electrolyte, which led to an excellent energy density of 127 Wh/kg. This excellent supercapacitor performance is ascribed to its unique hierarchical porous network that can accommodate relatively large organic electrolyte ions [Micro- and mesoporous graphene, also called holey graphene, is a particularly promising for supercapacitor applications because extremely high surface area can be obtained in these materials . For supctrolyte . In 1-buof 3.5 V . The eneof 3.5 V . The powof 3.5 V . When ho density . The higyte ions .EDLCs generally suffer from limited energy density because their charge storage relies solely on electric double layer capacitive mechanism . On the 2/macroporous graphene frameworks prepared by template-assisted assembly exhibited an excellent capacitance of 389 F/g at 1 A/g in 1 M Na2SO4 aqueous electrolyte while 3D macroporous graphene showed around 202 F/g under the same measurement conditions [2SO4 electrolyte, resulting from faradaic reactions of PANI as well as facilitated electrolytes transport caused by 3D macroporous networks [For instance, metal oxide/3D macroporous graphene could store large amount of charges because of its additional pseudocapacitve redox reactions of metal oxides with advantageous macroporous structures. The 3D MnOnditions . These rnetworks . This PAnetworks . Its capnetworks . The cornetworks .Fig. 8a2), and an anode (graphite), and non-aqueous electrolyte [Lithium-ion batteries are the most widely used type of battery ranging from handheld devices to electric vehicles due to their relatively high energy density and stable performance . LIBs arctrolyte , 110. Enctrolyte –123. Gractrolyte –121, 1236) based on the intercalation of Li, which gives a theoretical maximum capacity of 372 mAh/g [2C6) because both sides of graphene are able to store lithium ions, giving a theoretical capacity of 744 mAh/g [Graphite is the most widely used anode material in LIBs because of its good reversibility and stability , 110. In72 mAh/g , 125. In44 mAh/g , 127. Fu2/g with pores of 3–8 nm also exhibited a high capacity of 1723 mAh/g at 0.1 C as well as high rate capacity [Indeed, macroporous graphene assembled by the breath figure method showed an extremely high capacity of 3025 mAh/g at a discharge current of 50 mA/g for the first discharge cycle, and lost about 50% of its capacity from the second cycle . This locapacity . Interescapacity .3 gas at 550 °C [4 and (NH4)3PO4) [+ [In order to further improve the performance of porous graphene anode, heteroatom doping has been demonstrated. For example, N-doped 3D macroporous graphene was prepared through a two-step process and tested as an anode in LIBs . First, t 550 °C . The rest 550 °C . The 3D t 550 °C . PhosphoH4)3PO4) . It was H4)3PO4) . This mi3PO4) [+ . It also3PO4) [+ .2, LiFePO4, and LiMn2O4 because of its relatively high capacity and reliable performance [−9 to 10−3 S/cm, which leads to inferior rate capability and low power of LIBs [Current LIBs mostly adopt inorganic cathode materials such as LiCoOformance . However of LIBs , 129–1324 composite was prepared using a spray-drying method followed by thermal annealing process [4 had a substantial void fraction within the 3D micrometer-sized network, which led to improved rate capability and cycling stability [4 could deliver only 54 mAh/g at 30 C [+ caused by its porous structure [4 was also demonstrated as a cathode in LIBs [+ ion can migrate much faster in activated graphene/LiFePO4 than in LiFePO4 and non-activated graphene/LiFePO4 because of additional small pores on activated graphene sheets [4 showed impressive rate capabilities. At a low discharge rate (20 mA/g), activated graphene/LiFePO4, non-activated graphene, and LiFePO4 all showed similar capacities around 145 mAh/g [4 composites could deliver significantly higher capacity of 60 mAh/g whereas both graphene/LiFePO4 and LiFePO4 exhibited very low capacities less than 5 mAh/g at such a high current rate [4 for a cathode in LIBs [A continuous 3D graphene/LiFePO process . This grtability . The cap at 30 C . This entructure . Micro-  in LIBs . It turne sheets . This ac45 mAh/g . On the ent rate . A simil in LIBs . Similar in LIBs .In other literatures, redox-active graphene electrodes and its composites have also been demonstrated for cathode materials in LIBs , 136–138A great amount of effort has been made to develop more advanced energy storage systems, which could deliver higher energy than currently used commercial LIBs. Li–S and Li–air batteries are among those energy storage systems, which have much higher theoretical capacity and energy density . These b2Sx) are formed and dissolved to electrolytes, leading to a loss in capacity and energy density [−1 at 0.5 C and an excellent rate capability showing 809 mAh g−1 at 10 C [3/g, which could accommodate high sulfur content up to 90 wt% in the composite [Li–S batteries have a theoretical capacity of 1675 mAh/g and its theoretical energy density reaches 2600 Wh/kg, which are dramatically higher than those of current LIBs . Despite density , 141. Se density , 143. Gr density . The rel density . Interes density . A hybri density . When us at 10 C . Recentlomposite . A high omposite . Nitrogeomposite .Fig. 9Sc2O2 [2O2 because of strong interaction between defect sites and Li2O2 [Li-air batteries have also great potential because of extremely high theoretical energy density of ~ 11,680 Wh/kg and practical energy density of ~ 3500 Wh/kg, which is even comparable to those of gasoline  . When di2O2 , 148. At2O2 , 148. Re2O2 . This hi2O2 . Defectind Li2O2 . In anotnd Li2O2 . It confnd Li2O2 . After lnd Li2O2 . When cund Li2O2 . Other gnd Li2O2 , 151. FoAs highlighted above, porous graphene has been a subject to extensive research and development in the past years due to its unique properties such as excellent mechanical strength and good electrical conductivity, which makes it a promising material in many applications, especially energy storage. This review paper has introduced various synthesis and processing approaches to preparing porous graphene and porous graphene-based nanocomposites with emphasis on energy storage applications. Overall, porous graphene could result in improved electrochemical performance in energy storage systems because of more available active sites and facilitated ion diffusion throughout the porous structures. However, several issues should be addressed to make porous graphene-based energy storage systems commercially viable. First, the porous architecture of graphene should precisely be controlled during preparation to maximize its electrochemical performance. Morphology and pore size along with a graphene wall thickness affect the behavior and electrochemical properties of graphene. Therefore, it is critical to design hierarchically porous structures with optimized pore size and pore volume for achieving superior performance. Second, production process of porous graphene would essentially be environmentally friendly, simple, affordable and scalable. The advancement of these processes will make graphene more readily available for use in high-performance energy storage devices.Based on the significant effort on porous graphene, it is likely that porous graphene will play important roles in the next-generation energy storage devices. The utilization of porous graphene in supercapacitors, LIBs, Li–S, Li-air and fuel cells will promote manufacturing and commercializing efficient, safe, and more stable energy storage systems. Furthermore, excellent mechanical properties and stability of graphene will provide other opportunities to create multifunctional flexible energy storage devices, which can meet multiple market’s needs simultaneously.


TDP-43 protein plays an important role in regulating transcriptional repression, RNA metabolism, and splicing. Typically it shuttles between the nucleus and the cytoplasm to perform its functions, while abnormal cytoplasmic aggregation of TDP-43 has been associated with neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). For the purpose of this study we selected a set of proteins that were misregulated following silencing of TDP-43 and analysed their expression in a TDP-43-aggregation model cell line HEK293 Flp-in Flag-TDP-43-12x-Q/N F4L. Following TDP-43 sequestration in insoluble aggregates, we observed higher nuclear levels of EIF4A3, and POLDIP3β, whereas nuclear levels of DNMT3A, HNRNPA3, PABPC1 and POLDIP3α dropped, and cytoplasmic levels of RANBP1 dropped. In addition, immunofluorescence signal intensity quantifications showed increased nuclear expression of HNRNPL and YARS, and downregulation of cytoplasmic DPCD. Furthermore, cytoplasmic levels of predominantly nuclear protein ALYREF increased. In conclusion, by identifying a common set of proteins that are differentially expressed in a similar manner in these two different conditions, we show that TDP-43 aggregation has a comparable effect to TDP-43 knockdown. TARDBP gene, plays an important role in regulation of several processes, including microRNA processing, apoptosis, cell division, transcription, translation, splicing, axonal transport, and neurite outgrowth1467910TDP-43 protein, encoded by the TARDBP in familial and sporadic ALS cases proved the essential role of abnormal TDP-43 in disease1512171921232Abnormal cytoplasmic and occasional intranuclear aggregation of TDP-43 has been associated with amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD-TDP)12In this study, however, we have specifically investigated whether the aggregation/sequestration of TDP-43 correlated with its loss of function by comparing the expression changes of selected proteins responsive to silencing of TDP-43 in an aggregation and sequestration model cell line HEK293 Flp-in Flag-TDP-43-12x-Q/N F4L. Our results show that differential expression of proteins in TDP-12xQ/N-F4L cells correlated with proteomic results of TDP-43 knockdown in SH-SY5Y, revealing a common set of proteins whose expression is influenced via TDP-43 aggregation or knockdown.TARDBP gene expression.For the purpose of this study, we selected 13 proteins  whose ex6In HEK293 Flp-in Flag-TDP-43-12x-Q/N F4L cells (referred to as HEK TDP-12xQ/N-F4L hereafter) TDP-43 aggregation was induced by addition of doxycycline (DOX) to the growth medium . The aggPOLDIP3 (SKAR) and RANBP1 splicing is under control of TDP-43226POLDIP3 (SKAR) exon 3 and inclusion of RANBP1 exon 5 in both SH-SY5Y and HEK TDP-12xQ/N-F4L in the same pattern  staining  and 4. SIn addition, some discrepancies between the proteomic data obtained for HEK TDP-12xQ/N-F4L in comparison to RNAi in SH-SY5Y may be on account of the difference in experimental model used (knockdown vs. aggregation), the cell line (HEK vs. SH-SY5Y), the experimental conditions , which in turn reflect a moderate difference in the regulation of expression of proteins in question. There is also some variation to be expected from the antibodies used, as some perform better in denaturing conditions of western blot, while others recognise better the proteins in cells (IF). The recognition of the latter can also be influenced by method of fixation of cells  or the accessibility of the epitope against which the antibody was raised due to specific protein conformation.In this study, using a cellular model of TDP-43 sequestration, we have examined expression variations of a series of proteins previously shown to be differentially expressed following TDP-43 knockdownPOLDIP3/SKAR) has been previously noted as a result of the depletion of TDP-4322632POLDIP3 gene has been reported to favour the synthesis of the β isoform in respect to the main α isoform3233POLDIP3 mRNA variant was also observed in ALS patients’ spinal motor neuronsTDP-43 is an RNA/DNA binding protein with multiple functions. For this reason, its downregulation influences a large number of RNA and protein targets. Decreased TDP-43 cellular levels affected splicing of 158 exons in neuroblastoma cells and altered 965 splicing events in adult mouse brain226Our comparative analysis of siRNA-mediated knockdown versus sequestration and aggregation of TDP-43 has allowed us to confirm two possible connections between loss of TDP-43 functional activity and disease. First of all, our analyses add further support to the possible link between TDP-43 and nonsense-mediated decay. In fact, POLDIP3 was also reported to associate with the exon junction complex (EJC), which is recruited to exon junctions during splicing37Drosophila study, ALYREF was singled out as potential modifier of G4C2 expansion related toxicity4C2)n hexanucleotide repeat expansion mutation in the C9orf72 gene, which can span from several hundred to several thousand repeats, is the major genetic cause of ALS and FTLD leading to TDP-43 proteinopathy40414C2 RNA are sequestered in nuclear foci, ALYREF may act as part of a control mechanism that retains unspliced or faulty RNAs in the nucleusSecondly, in a C9orf72 expanded repeats46Thirdly, TDP-43 sequestration impacts several HNRNP proteins by either increasing their concentration in the nucleus, or by nuclear clearance, thus altering RNA metabolism and potentially leading to ALS and FTLD. Following TDP-43 aggregation we observed altered levels of HNRNPA3 and HNRNPL. Previously, HNRNPA3 was found to be aggregated in cytosolic TDP-43 negative inclusions in the brains of patients with RANBP1 transcript, in turn decreasing the level of protein.Finally, we have previously shown in SH-SY5Y that depletion of TDP-43 influences intracellular transport through downregulation of RANBP1 and herein confirmed the expression drop in HEK TDP-12xQ/N-F4L modelin vivo still needs to be determined, our cellular analysis has added further support that aggregation and sequestration model overlaps TDP-43 LOF following its knockdown by siRNA. As a consequence, the major hits from this comparison might represent good candidates to be followed up in further studies that aim to elucidate the causes of ALS/FTLD pathology.In conclusion, although the pathological relevance of these processes HEK293 Flp-in Flag-TDP-43-12x-Q/N F4L cell line was established as previously describedCells were grown in 6-well plates and were harvested in cold CLB buffer , 0.25% Triton X-100, cocktail of protease inhibitors (Roche)) and centrifuged for 5 min at 3000 g at 4 °C. Supernatants were transferred to fresh tubes and re-centrifuged at 16100 g at 4 °C for 10 min. Obtained supernatants were used as cytoplasmic fractions. The first pellets were washed three times in cold CLB, resuspended in 1X SDS loading buffer without bromophenol blue, sonicated, boiled for 5 min and re-centrifuged. Resulting supernatants were saved as nuclear fractions. The protein concentration in the fractions were determined by Bio-Rad DC Protein Assay.Reducing SDS-PAGE was run on 4–12% SDS precast gels (C.B.S. Scientific) loaded with 10–20 μg of protein samples in 1X SDS loading buffer with 100 mM dithiothreitol at 175 V. Wet transfer onto nitrocellulose membrane  was carried out at 200 mA for 90 min. Membranes were blocked with 5% non-fat dry milk in TBS with 0, 05% Tween-20  at room temperature for 1 hour. Primary antibodies  diluted Cells were grown on poly-L-lysine (Sigma) coated glass coverslips and were washed once with PBS and fixed with 4% paraformaldehyde in PBS for 15 min. Then they were permeabilised with 0.1% Trition X-100 (Sigma) in PBS for 5 min. Blocking was performed with 3% BSA (Sigma) in PBS for 1 hour. Cells were incubated with primary antibodies  diluted ImageJ was used to quantify immunofluorescence signal intensities as follows. Several regions of interest (ROI) were selected in the appropriate cellular location, and the mean fluorescence of detected protein was measured, along with several adjacent background readings. The total corrected cellular fluorescence, (CTCF = integrated density−(area of selected cell × mean fluorescence of background readings), was calculated for each ROI. The averages and s.e.m. were determined for several images for each marker in induced cells compared to non-induced, where expression was set to 100%. Statistical analysis (2-sided unpaired Student’s t-tests) was performed.p-value of <0.05 was considered significant.Quantitative values of protein bands in western blots were normalized to GAPDH in cytoplasmic fractions and to fibrillarin (FBL) in nuclear fractions. Relative protein expression levels in TDP-43 aggregating HEK TDP-12xQ/N-F4L were calculated towards non-induced controls. For immunofluorescence quantification, immunofluorescence signal intensities of cells with induced TDP-43 aggregation and non-induced controls were compared and relative protein expression levels were calculated. Statistical significance of differential expression of proteins according to western blot and immunofluorescence was determined with unpaired Student’s t-test analysis. Student’s t-test was performed in Microsoft Excel Professional Plus 2013. A How to cite this article: Prpar Mihevc S. et al. TDP-43 aggregation mirrors TDP-43 knockdown, affecting the expression levels of a common set of proteins. Sci. Rep.6, 33996; doi: 10.1038/srep33996 (2016).


The result suggests carriers in the doped graphene are no longer massless, and an effective mass as small as one percent of free electron mass is sufficient to confine carriers within a 2D hetero space with energy 10 times larger than the room-temperature thermal energy. The interlayer excitons arise within 1 ps. Their formation effectively blocks charge recombination and improves charge separation efficiency for more than one order of magnitude.Phase transitions of electron–hole pairs on semiconductor/conductor interfaces determine fundamental properties of optoelectronics. To investigate interfacial dynamical transitions of charged quasiparticles, however, remains a grand challenge. By employing ultrafast mid-infrared microspectroscopic probes to detect excitonic internal quantum transitions and two-dimensional atomic device fabrications, we are able to directly monitor the interplay between free carriers and insulating interlayer excitons between two atomic layers. Our observations reveal unexpected ultrafast formation of tightly bound interlayer excitons between conducting graphene and semiconducting MoSe 2.The investigation into the dynamical transitions of charged quasiparticles on interfaces remains technically challenging. Here, the authors use ultrafast, mid-infrared micro-spectroscopy to unveil the formation of tightly bound interlayer excitons between conducting graphene and semiconducting MoSe The electrostatic interaction between the depleted valence band states (holes) and excited electrons can lead to the formation of long-lived insulating excitons4. The evolution of these electron/hole states on interfaces in the devices, which arises from interactions among phonons, photons, and charged quasiparticles, determine their fundamental properties, e.g., luminescence, heat generation, charge separation and transport, redox reaction kinetics, and outcomes7. In the past, the interfacial dynamics of excited optoelectronic materials were often studied on bulk or nano-sized samples that contain both interfacial and bulk components with absorption, photoluminescence, and visible pump/probe experiments close to the bandgap9. Despite providing a wealth of important information, these techniques are sensitive to creation and destruction of excitons and thus only probe the quasiparticles with negligible center-of-mass momentum because of the small photon momentum. However, the majority of excitons can assume finite momenta as a result of scattering and is optically dark in these measurements11.In optoelectronic and optoelectro-chemical devices composed of semiconductors and conductors, photo excitation can generate transient conducting free carriers by promoting electrons from the occupied valence band into the empty conduction band of the semiconductors14, photons with lower energy, e.g., the near- and mid-infrared (IR) or THz, can probe photo-generated excitons at center-of-mass momenta well outside the optically accessible range  heterostructures composed of only two atomic layers17 provides an ideal laboratory for the studies of pure interfacial dynamical transitions of charged quasiparticles. However, limited by spatial resolution, it remains a challenge for regular IR setups to probe electron/hole pairs in 2D heterostructures of which the sizes are typically smaller than the IR beam size. In this work, combining microscope, ultrafast visible/near-infrared/mid-infrared frequency-mixed spectroscopy  materials18 promise ideal combinations for atomically thin optoelectronic devices in which 2D TMDC functions as photon absorbers and graphene layers serve as transparent electrodes17.In our experiments, photo-excited electrons/holes are quantum confined within the 2D space of two atomic layers. We investigate heterostructures composed of one monolayer of MoSeene Fig. . The mon2/graphene heterostructure is illustrated in Fig. 2 is around 2.0 eV26. The Dirac point of graphene is 0.9 eV below CBM of MoSe2. The Fermi level of graphene in heterostructure is -0.17 eV, 0.02 eV higher than the monolayer graphene because of charge transfer from the n-doped MoSe2. The photoluminescence  and 400 nm (3.1 eV), respectively. The optical density change  with a Lorentzian width of 280 cm−1 remains in heterostructure that lasts for more than 20 ps , and e is the elementary charge, Γ is the broadening of the interband transitions, whereas τe is the relaxation time due to intraband carrier scattering. Quantitative analyses of the graphene signal according to Eqs. 31.The huge difference in signal reveals distinct evolutions of electrons/holes in graphene and heterostructure. The excitation photon energy 1.03 eV is lower than the excitonic transition energy (1.59 eV) of MoSe32. A similar 1s-2p transition peak was also observed in the mid-IR range for monolayer WSe2 on a diamond11. In this work, different from the two previous experiments, the graphene/MoSe2 heterostructure sample is not a pure substance, but a combination of two monolayers. Thus, the nature of the exciton that give rise to the resonant peak at 2185 cm−1 can have several possible origins: 1, the internal neutral and charged excitons, e.g., regular excitons and trions33 in graphene; 2, the internal neutral and charged excitons in MoSe2; and 3, the interlayer neutral and charged excitons.In the heterostructure, the detection frequency dependent signals and dynamics Fig.  resemble11. In brief, the binding energy of trions is only about 30 meV33. The binding energy of excitons with more particles is even smaller. At room temperature, where our experiments were carried out, most of the trions had dissociated due to thermal motions34, which has been verified with temperature-dependent photoluminescence34. Second, the intralayer exciton in graphene is not likely. Although the carriers in doped graphene are no longer massless due to the Fermi level shift from the Dirac point and a slight symmetry breaking35, tightly bound excitons cannot form because the bandgap of graphene in the heterostructure is too small  are not likely either. The combination of the experiments with 3.1 and 1.03 eV excitations in Fig. 2. Excitation with it cannot produce detectible amounts of free carriers or excitons in MoSe2 4 than the free carriers created with 3.1 eV excitation in the monolayer MoSe2. However, experimentally, the free-carrier dynamics detected at 1860 cm−1 of the heterostructure excited with 1.03 eV is significantly faster than that inside the monolayer MoSe2, and essentially the same as graphene  of the two monolayers. It is conceivable that the formation of interlayer excitons need carriers to diffuse in both the layers and the faster partner dominates.In the following, combining experimental data and literature, neutral interlayer excitons are concluded to be the dominant species that produce the resonant signals. First of all, the contribution of the charged excitons (including trions and other excitons composed of more than three carriers) is very minor in room temperature optical/IR pump/probe experiments. This has been completely addressed in the SI of the previous work −1 Fig.  was due ene Fig. . The detene Fig.  is inter−1 (0.27 eV) seem to be unlikely and completely unexpected if estimated with conventional hydrogen-like 3D model. It is well known that pristine graphene has massless carriers, which cannot form excitons36. In most CVD grown graphene, which is effectively doped, like the one used in our experiments, the Fermi level is not at the Dirac point. Because of the Fermi level shift and the slight symmetry breaking due to the formation of heterostructure35, the carriers are no longer massless , similar to 0.012 m0 reported for an epitaxy-grown graphene37. Estimated with this effective mass and the conventional 3D hydrogen-like model in which the binding energy is linearly proportional to the reduced mass, the binding energy of graphene/MoSe2 would be only 1/60 of the MoSe2 intralayer excitons. The binding energy of MoSe2 intralayer excitons has been computed to be between 0.4 and 0.6 eV19. Our experiments  , the 980 nm photoexcitation, which excites only graphene but not MoSe2, produces external photocurrent flowing from the portion of graphene that is on the top of Si (with a thin layer of SiO2) to that on the top of MoSe2, which is a clear signal that the quasi-equilibrium of MoSe2 (hole)/graphene (electron) inside the heterostructure is reached by the 980 nm photoexcitation. The results have a very interesting indication: under the experimental condition, graphene functions as a photon absorber and MoSe2 serves as a charge acceptor, rather than their traditional roles, in which graphene is the transparent electrode and MoSe2 is the chromophore.In summary, the excitation of MoSeeV) Fig. . As showons Fig. . Kinetic2. Figure 2 and MoSe2/graphene heterostructure detected in three different IR ranges at 16 ps after excitation with 3.1 eV photons. In the low-frequency range (1280–1380 cm−1), signals of both graphene and heterostructure are zero. Between 1900 and 2230 cm−1, the spectrum of graphene is very close to zero, whereas the spectrum of the heterostructure is at peak. In the high frequency range (2500–2800 cm−1), the signal of graphene remains zero, but that of heterostructure is a flat spectrum with an amplitude of about 30–40% of the peak value at 2156 cm−1. Similar to those following 1.03 eV excitation  is significantly higher than that of graphene (4.14%) at 3.1 eV42, overall the interlayer charge transfers result in higher electronic temperature in graphene. Excluding the free carriers remaining in MoSe2, the effect is around equal to 200% excitation flux increase for graphene monolayer, assuming semi-instantaneous interlayer charge transfers27 and electronic thermalization22. Our calculations show that the temperature increase with additional 200% flux slows the graphene electronic dynamics for about 30%, from 130 to 170 fs  interlayer charge transfers27 send both electrons and holes into graphene45, where they recombine within a couple of hundred fs25. The commonly accepted but oversimplified pictures, however, cannot account for the complex many-body dynamics in real systems and our experiments. Quasiparticles that excitons are composed of cannot be treated separately. In a photo-excited electron/hole gas, the ultrafast Coulomb interactions result in fundamentally new properties through pairing and higher-order correlations46. Some of these can be intuitively visualized by processes such as a pair of free electron and hole forming an exciton by transferring their energy and momenta to other free carriers or redistributions among pairs through collisions  keep the charged quasiparticles on different layers for more than 20 times longer. The greatly improved intrinsic charge separation efficiency is important for many applications that utilize the conversion of photo energy into electronic energy or electricity, e.g., solar cells, photo-detections, and photo-electrochemistry. We anticipate that the microspectroscopic IR response uncovered here will enable realtime and precise studies of the new non-equilibrium states on atomic interfaces that are critical for future developments and applications of atomically thin and other optoelectronic devices, but cannot be studied with other means.The transition of conducting free carriers into insulating interlayer excitons observed in the semiconductor/semimetallic 2D heterostructure reveals the significance of many-body interactions in mediating and thus producing sophisticated electronic dynamics and states on interfaces. The unexpected formation of the tightly bound interlayer excitons suggest that carriers in the doped graphene of the heterostructure is no longer massless, and an effective mass as small as one or two percent of 2 in our prior publication47 using Selenium pellets and Molybdenum oxide as sources.We follow the CVD method of growing high-quality monolayer MoSe2/Ar was used as a carrier gas and the pressure was kept around 1 torr during the whole process.CVD method was used to grow graphene on an electropolished copper foil with methane as a precursor. The copper foil was annealed at 1000 ℃ for 20 min, followed by graphene growth for 9 min using 3.5 sccm of methane under the same temperature. 15% H2 are transferred onto the CaF2 substrates for transmission mode laser experiments. The process is: at first, a thin layer of PMMA (PMMA-B4 4%wt) is spin-coated onto the sample on SiO2 substrate twice at the speed of 4000 rpm, and then the sample is carefully placed in a Buffer HF (1:5) and allowed to float. After 20 h, the PMMA sheets are separated from the SiO2 substrate and fished with glass plate, and then moved to Di-water for rinsing for a few times. The pre-cleaned CaF2 windows are used to fish the PMMA sheets. The CaF2 windows with PMMA and samples stay in room temperature and vacuum for 24 h. Finally, acetone is used to remove the PMMA. The MoSe2 triangles on the CaF2 substrate are confirmed by optical microscope. Graphene on the Cu foils spun with PMMA is dissolved in Cu2Fe3, and the PMMA sheet is fished and transferred like the same method above onto the MoSe2 monolayers. PMMA is removed with acetone. Finally, the sample is annealed in vacuum at 300 °C for 3 h.The as-grown MoSeRaman and PL spectroscopy were carried out using a Horiba Jobin Yvon LabRAM HR-Evolution Raman microscope. The excitation light is a 532 nm laser, with an estimated laser spot size of 1 μm and the laser power of 1 mW.4 of the ultrafast visible-NIR/infrared microspectroscopy is illustrated in Fig. 49 or a near-IR-2 pulse. In ultrafast experiments, the visible or NIR-1 pulse is the pump light with the central wavelength and excitation power adjusted based on need. The interaction spot on the samples varies from 120 to 250 micron. The mid-IR super-continuum pulse or NIR-2 pulse acts as the probe light, which is focused at the sample by the reflective objective lens  to reduce the spot size to the level of the sample area (<40 μm). A 300-megapixel microscope digital camera is used to align the pump/probe beam to proper sample area. The probe light is detected by a liquid-nitrogen-cooled mercury-cadmium-telluride (MCT) array detector or InSb detector after frequency resolved by a spectrograph with a resolution of 1–3 cm−1, which is dependent on the central frequency. The time delay between the pump light and probe light is controlled by a motorized delay stage.The experimental setupThe data that support the findings of this study are available from the corresponding author upon request.Supplementary InformationPeer Review File