CPR) is a crucial intervention for patients with out‐of‐hospital cardiac arrest (OHCA). Although a sex disparity in receiving layperson CPR  has been reported in adults, there are few data in the pediatric population, and we therefore investigated sex differences in receiving layperson CPR in pediatric patients with OHCA.Layperson cardiopulmonary resuscitation  with layperson‐witnessed OHCA from 2005 through 2015. The primary outcome was receiving layperson CPR. Patient sex was the main exposure. We fitted multivariable logistic regression models to examine associations between patient sex and receiving layperson CPR. We included a total of 4525 pediatric patients with layperson‐witnessed OHCA in this study, 1669 (36.9%) of whom were female. Female patients received layperson CPR more often than male patients . After adjustment for age, time of day of arrest, year, witnesses persons, and dispatcher CPR instruction, the sex difference in receiving layperson CPR was not significant .From the All‐Japan Utstein Registry, a prospective, nationwide, population‐based OHCA received layperson CPR more often than male patients. After adjustment for covariates, there was no significant association between patient sex and receiving layperson CPR.In a pediatric population, female patients with layperson‐witnessed  In a nationwide cohort study of 4525 pediatric patients with layperson‐witnessed out‐of‐hospital cardiac arrest in Japan, female patients received layperson cardiopulmonary resuscitation more often than male patients, although the sex difference did not persist after adjustment for covariates.The finding suggests the importance of public health efforts to increase provision of cardiopulmonary resuscitation for patients of both sexes.Out‐of‐hospital cardiac arrest (OHCA) is a global public health problem annually affecting more than 350 000 individuals in the United States and 123 000 in Japan.Layperson cardiopulmonary resuscitation (CPR) is a part of the “chain of survival” and plays an essential role in OHCA care.To address this knowledge gap, we analyzed the All‐Japan Utstein Registry.The data, analytic methods, and study materials will not be made available to other researchers for purposes of reproducing the results or replicating the procedure.We conducted a secondary analysis of the All‐Japan Utstein Registry of the Fire and Disaster Management Agency, a prospective, nationwide, population‐based registry system of OHCA that includes the entire population of Japan. The details of this registry have been previously reported elsewhereData were prospectively collected using the Utstein Resuscitation Registry Templates for OHCA.The primary outcome was receiving layperson CPR. Secondary outcomes included 1‐month survival and favorable functional status at 1 month, defined as Cerebral Performance Category scale 1 or 2.First, we reported patient characteristics, stratified by sex. We presented continuous variables with both median and interquartile ranges and categorical variables with proportion. We performed Wilcoxon rank‐sum tests for continuous variables and chi‐squared tests for categorical variables to examine sex differences in patient characteristics.Second, we reported sex differences in proportions receiving layperson CPR and stratified by type of layperson CPR: chest compression–only CPR and conventional CPR. We also stratified sex differences in proportions receiving layperson CPR by characteristics of witnesses: family versus nonfamily. Nonfamily included friends, colleagues, passersby, and others. EMS personnel who resuscitated patients recorded characteristics of witnesses. We performed chi‐squared tests to examine sex differences in proportions of receiving layperson CPR across types of layperson CPR.P<0.05 was considered statistically significant.Third, we fitted univariable and multivariable logistic regression models to predict sex differences in receiving layperson CPR. In the multivariable regression models we included age group , time of day of arrest (daytime/night), years), A total of 1 299 784 OHCAs occurred during the study period, of whom 18 639 pediatric OHCA patients had resuscitation attempts by EMS personnel . Among those with arrest witnessed by family, female patients were significantly more likely to have received layperson CPR . Among those with arrest witnessed by nonfamily, there was no significant sex difference in receiving layperson CPR . We did not observe significant sex difference in receiving layperson CPR in overall layperson‐witnessed OHCA between types of CPR: chest compression–only CPR  and conventional CPR .We reported unadjusted association between patient sex and receiving layperson CPR in Table P‐value for interaction=0.038). After stratifying by age group in overall layperson‐witnessed arrest, female children (1‐11 years) received layperson CPR more often than male children (adjusted OR=1.41: 95% CI 1.14‐1.73) . In arrest witnessed by nonfamily, male infants (0 year) and adolescents (12‐17 years) received layperson CPR more often than female infants and adolescents, although there was no statistical significance  Figure B, wherea) Figure A. Male a) Figure A. The inescents 1‐17 yearsWe found that 18.9% 315/1669) of female and 17.8% (507/2856) of male patients had 1‐month survival .An observational study using a nationwide OHCA registry in Denmark reported that female patients were less likely to receive layperson CPR than male patients among those who were ≥12 years old  and had EMS‐treated OHCA of cardiac cause , whereas among those who were witnessed by nonfamily, male patients tended to receive layperson CPR more often , a difference without statistical significance. Although this is an important finding, the underlying reasons for this difference are unclear, and further investigation is needed to understand the difference and increase provision of layperson CPR. Such work might include a qualitative approach, interviewing witness laypeople to extract the reason why CPR was or was not provided.We observed that male patients who were witnessed by family received layperson CPR less often than female patients .Our study has several clinical and public health implications. First, the observed sex differences in receiving layperson CPR should be a target of quality improvement efforts at the community level to increase the provision of layperson CPR for pediatric OHCA. Second, our results justify further efforts to identify underlying reasons for this observed sex difference in receiving layperson CPR. Such factors may include sex discordance in providing and receiving CPR .Our study has several limitations. First, there may have been unmeasured factors that confounded our results . Second, our inference may not be fully generalizable to other healthcare settings, given the differences in patient characteristics and medical care systems. Third, in this data set, the sex of layperson CPR providers was not available, and we were unable to assess the effect of sex discordance and concordance between CPR providers and patients on receiving layperson CPR. Last, as with all epidemiological studies, data integrity, validity, and ascertainment bias are potential limitations. The use of uniform data collection based on the Utstein‐style guidelines for reporting cardiac arrest, large sample size, and a population‐based design to cover all OHCA in Japan were intended to minimize these potential biases.In this analysis of a prospective, nationwide, population‐based registry system of OHCA in Japan, receiving layperson CPR tended to be different between patient sexes, although there was no significant sex difference after adjustment for covariates. Witnesses impacted sex difference in receiving layperson CPR. Public health efforts to improve the provision of layperson CPR in pediatric patients should increase interventions for both sexes.None.


We therefore conclude that although TDP-43 CTFs are a hallmark of TDP-43-related neurodegeneration in the brain, they are not a primary cause of ALS or FTLD.During neurodegenerative disease, the multifunctional RNA-binding protein TDP-43 undergoes a vast array of post-translational modifications, including phosphorylation, acetylation, and cleavage. Many of these alterations may directly contribute to the pathogenesis of TDP-43 proteinopathies, which include most forms of amyotrophic lateral sclerosis (ALS) and approximately half of all frontotemporal dementia, pathologically identified as frontotemporal lobar degeneration (FTLD) with TDP-43 pathology. However, the relative contributions of the various TDP-43 post-translational modifications to disease remain unclear, and indeed some may be secondary epiphenomena rather than disease-causative. It is therefore critical to determine the involvement of each modification in disease processes to allow the design of targeted treatments. In particular, TDP-43 C-terminal fragments (CTFs) accumulate in the brains of people with ALS and FTLD and are therefore described as a neuropathological signature of these diseases. Remarkably, these TDP-43 CTFs are rarely observed in the spinal cord, even in ALS which involves dramatic degeneration of spinal motor neurons. Therefore, TDP-43 CTFs are not produced non-specifically in the course of all forms of TDP-43-related neurodegeneration, but rather variably arise due to additional factors influenced by regional heterogeneity in the central nervous system. In this review, we summarize how TDP-43 CTFs are generated and degraded by cells, and critique evidence from studies of TDP-43 CTF pathology in human disease tissues, as well as cell and animal models, to analyze the pathophysiological relevance of TDP-43 CTFs to ALS and FTLD. Numerous studies now indicate that, although TDP-43 CTFs are prevalent in ALS and FTLD brains, disease-related pathology is only variably reproduced in TDP-43 CTF cell culture models. Furthermore, TDP-43 CTF expression in both transgenic and viral-mediated  TDP-43 n (FTLD) , and exoTARDBP gene. It is ubiquitously expressed and predominantly locates to the nucleus owing to a nuclear localization signal (NLS)  . TDP-43 al (NLS) , althougal (NLS) . The domal (NLS) . TDP-43 al (NLS) . This enal (NLS) . TDP-43 anscript . This excontrols . This seed cells .In silico analysis predicts that the C-terminal tail is inherently disordered and of low complexity  inclusions , 2009. TVCP), has few cytoplasmic TDP-43 inclusions but many lentiform neuronal intranuclear inclusions throughout the cortical layers  gene are generally associated with type A TDP-43 pathology, whereas hexanucleotide repeat expansions in C9orf72, which is the most common genetic cause of ALS and FTLD-TDP, most frequently result in type B pathology  in the C-terminal domain of TDP-43 consistently detects CTF-25 in the brains of both FTLD-TDP and ALS patients . AlthougThe N-terminal portion resulting from TDP-43 cleavage has proven difficult to detect experimentally in human autopsy tissues , althougAlthough fragments of the C-terminal portion of TDP-43 are often regarded as a molecular signature of TDP-43 proteinopathies, the presence of TDP-43 CTFs does not necessarily correlate with neurodegeneration. Despite the post-mortem evidence for the presence of TDP-43 CTFs in both the ALS and FTLD brain, structural magnetic resonance imaging as well as post-mortem analysis reveals widespread brain atrophy in FTLD , whereasNumerous studies have attempted to correlate the relative abundance of the several TDP-43 CTFs between 18 and 27 kDa detected by immunoblotting with FTLD-TDP subtype or diagnosis of ALS. Despite progress in this area, low sample sizes, poor resolution of the immunoblots and heterogeneity in the neuropathology of patients with TDP-43 proteinopathies have obscured distinction of a reliable immunoblot pattern of CTFs . To addrIn addition to transcriptional autoregulation, TDP-43 may be cleaved into smaller fragments before being enzymatically degraded to maintain physiological levels . TDP-43 Prior to the discovery of TDP-43 as the primary component of insoluble inclusions in ALS and FTLD , elevateD-sorbitol  . ImportaAlternatively, caspase-cleavage of TDP-43 may play a physiological role in the maintenance of TDP-43 homeostasis. Examination of the time-course of fragmentation following overexpression of full-length TDP-43 identified ER membrane-bound caspase-4 as being responsible for initial cleavage at asparagine residue 174 to produce CTF-25 . This su2+ into the cell  and superoxide dismutase 1 (SOD1), may confer vulnerability to caspase-cleavage of TDP-43. Numerous TARDBP mutations are linked to both familial and sporadic ALS or FTD , which is produced by RAN-translation of the C9orf72 hexanucleotide expansion, in cultured cells induces caspase-3 activation and ER stress  in k of ALS . Expressk of ALS . Importak of ALS . It is u3 CTF-35 .Mutations to the SOD1 gene were the first reported cause of ALS . Motor nIn an effort to develop treatments to effectively clear TDP-43 pathology, numerous molecules have been identified as capable of degrading both full-length and fragmented TDP-43, including ubiquilin-2 (UBQLN2)  and polyMolecular chaperones such as heat shock proteins (HSPs) are central to maintaining cellular proteostasis, including protein degradation via chaperone-mediated autophagy, and are commonly dysregulated in neurodegenerative diseases . The degVCP cause rare cases of FTLD-TDP type D. This suggests a potential link between VCP and the clearance of TDP-43. Expression of FTLD-linked VCP mutant proteins in cell culture increases cytoplasmic TDP-43 but does not lead to production of TDP-43 CTFs , cyclin-dependent kinase (CDK), and glycogen synthase kinase 3 (GSK3), attenuates the aggregation of full-length and truncated forms of TDP-43 . HoweverContinued debate surrounds the role of protein aggregation in neurodegeneration. It has been suggested that the large inclusions that characterize ALS and FTLD neuropathology may be the product of an adaptive response aimed at protecting cells from more toxic oligomers or diffusible assemblies that may not be readily detectable by standard biochemical or microscopy techniques . Recent Although CTFs expressed in cell culture reliably form disease-like cytoplasmic inclusions, this does not always induce cellular toxicity or apoptosis. For instance, exogenous expression of full-length TDP-43 induced programmed cell death more readily than CTF-35, whereas CTFs of 25–27 kDa had no effect, despite their cytoplasmic aggregation . By contEvidence from studies of endogenous TDP-43 CTFs also calls into question the relationship between CTF aggregation and disease. In experiments using inducible pluripotent stem cells derived from a patient carrying an ALS-linked M337V TDP-43 mutation, some clones exhibited higher levels of insoluble CTFs but this was not associated with apoptosis . Thus, aEmerging research into the effects of TDP-43 liquid–liquid phase separation on the dynamics of membraneless organelles such as stress granules offers an alternative way of viewing TDP-43 accumulation in ALS and FTLD. The role of the TDP-43 C-terminal domain in liquid–liquid phase separation has been well established ,b. Howevde novo pathology suggests that TDP-43 is capable of being transmitted to nearby or interconnected cells, where it may corrupt endogenous TDP-43 to adopt pathological, aggregation-prone conformations  pre-mRNA, used as a model of TDP-43 function, has been observed for both CTF-25  and CTF-in vitro findings is confirmed in appropriate animal models. While simple model organisms such as Drosophila melanogaster, Caenorhabditis elegans and zebrafish are easily manipulated for microscopy and offer well-characterized genomes, rodent models more faithfully reproduce the cellular and behavioral or motor phenotypes that typify TDP-43 proteinopathies  and neurofilament heavy chain (NEFH) to direct selective transgene expression in neurons of the brain and spinal cord. Some models have employed the Ca2+/calmodulin-dependent kinase II α (CaMKIIα) promoter to restrict expression to forebrain neurons, primarily in the cortex, hippocampus, and striatum  to the neurons of the brain and spinal cord does not induce motor or cognitive defects  and again, no behavioral phenotype was reported  was expressed in neurons using a r system , 2015. Hr system , 2013. Pr system , 2015. Hr system . Hippocar system . Consistr system . At 15 mter maze . OverallA rat model of TDP-43 CTF-25 (amino acids 220–414) has been produced using a viral-mediated strategy, resulting in highest expression in the spinal cord, cerebellum, muscle, heart, and liver . ApproxiDrosophila, transgenic expression of full-length TDP-43 or ALS/FTLD-linked mutations has been shown to shorten overall lifespan  into the mouse motor cortex resulted in phosphorylated micro-aggregates detectable up to 3 weeks of age  forms cytoplasmic aggregates (Studies using TDP-43 CTF mice have yielded disparate results as to the solubility of TDP-43 CTFs. Immunoblotting of mouse brains expressing CTF-25 (216–414) detected the fragments as detergent-soluble in both nuclear and cytosolic fractions , 2015, wgregates . Importagregates . TogetheDrosophila have repeatedly demonstrated that full-length or disease-associated TDP-43 mutants are more toxic to retinal and neuronal cells than CTFs   . TDP-43 In A315T mice. However, this conflicts with studies in various other model organisms which found that CTFs were only detectable at later disease stages. These findings support the argument that CTFs accumulate as a consequence rather than cause of neurodegeneration (Numerous attempts have been made to correlate the abundance of TDP-43 CTFs with disease stage in animal models, in order to disentangle the functional relevance of CTFs to neurodegeneration. A study by neration . For insneration . In a raneration . In a cyneration .in vitro; recombinant TDP-43 M337V was cleaved into C-terminal fragments when incubated with monkey but not mouse brain extracts. This points to potential species-specific differences in the way that TDP-43 is processed. Indeed, the TARDBP gene of mammals is highly homologous with that of Drosophila and C. elegans from the N-terminal to RRM2, and diverges toward the C-terminus (Mice expressing TDP-43 ΔNLS show no or minimal TDP-43 fragmentation, despite a robust motor phenotype . The samterminus . Closer The mechanism through which TDP-43 drives neurodegeneration may differ between the brain and the spinal cord. A prime example of this is the pathological acetylation of TDP-43, which has been detected in the ALS spinal cord but not the brain, likely due to removal of the targeted lysine residues in the N-terminal domain upon cleavage of TDP-43 in the brain . The eviNeurons are particularly diverse cells with highly specialized functions. With regard to motor neurons, subtypes vary dramatically in terms of neurotransmitter secretion, excitability and cytoarchitecture , as wellExperimental data also indicate that alterations to TDP-43, such as its cleavage into CTFs, may proceed in a cell-type-specific manner. For instance, in people with inclusion body myopathy, an inflammatory muscle disease, TDP-43 is ubiquitinated and translocated to the cytoplasm of the muscle cells but does not appear to be cleaved into CTFs . In cellThe distinct features of certain cell populations may also confer vulnerability to TDP-43 pathology. This was recently demonstrated in mice, whereby intra-cortical injection of insoluble protein extracted from FTLD-TDP brains led to a selective spread of pathology to deeper structures that have previously been shown to be affected in the FTLD-TDP brain, such as the nucleus accumbens and basolateral amygdala . DetermiAmyotrophic lateral sclerosis is a rapidly progressing and debilitating disease, and currently available treatments offer only modest benefits. Riluzole may extend survival by 2–3 months, potentially via attenuation of glutamate excitotoxicity . The morTDP-43 CTFs are considered a pathological hallmark in the brains of people with ALS and FTLD-TDP. However, these fragments are rarely detected in the ALS spinal cord, despite the dramatic death of lower motor neurons. Exogenous expression of these fragments in cultured cells has provided mixed results and whether CTFs are more toxic to cells than full-length TDP-43 remains debateable. Critically, transgenic animals expressing TDP-43 CTFs do not exhibit a robust ALS-like phenotype of motor dysfunction, and only display mild deficits that potentially resemble broader aspects of neurodegeneration, but not specifically ALS or FTD, in aged animals. Given the low-level detection of these fragments in ALS cerebrospinal fluid  and FTD BB and AW conceived and wrote the manuscript and compiled the tables.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


As the older adult population grows in the United States, the need for community planning approaches that respond to the needs of older adults is of increasing importance. As a result, lifelong community movements, encompassing models such as Age-Friendly Communities, Livable Communities, and “Aging-in-Place” initiatives are proliferating. Maine, the oldest state by median age, currently hosts the largest number of AARP designated Age-Friendly Communities efforts. Given the size of this network, the purpose of this study was to collect descriptive information about the status of existing lifelong communities initiatives, their training and support needs, and the desired format and configuration of future training programming. An electronic survey was distributed to community representatives from 76 lifelong communities initiatives throughout Maine. A total of 38 communities responded to the survey representing a response rate of 50%. The majority of respondents (80.4%) reported having a committee or other coordinating group guiding their work. A large portion have completed planning phase activities including hosting focus groups (79.5%), carrying out a survey (66.7%), and identifying a list of local assets (59%). Fewer have completed the plan drafting phase (17.9%). A majority reported receiving assistance from AARP (66%) and a regional educational consortium (66%). The areas with highest self-reported training needs (based on mean ratings) are: Volunteer recruitment and retention, specialized trainings on Age-Friendly Community topics, Dementia-Friendly Communities topics, and outreach and community engagement strategies. Implications will be discussed including optimal configuration of training and support for similar such networks.


As-obtained MGFG is demonstrated in generating controllable local thermal field and defogging efficiently. The strategy of laser-tailoring grid will greatly advance the applications of graphene for transparent electrodes in industry.Applications of graphene as transparent conductive electrodes (TCE) have been hindered either by high cost of single crystal graphene or balance between transparency and sheet resistance of polycrystalline graphene. In this work, we propose to fabricate multilayer graphene film grids (MGFG) to enhance transparency and keep low sheet resistance through IR laser tailoring. It is proved that the transparency of MGFG could be increased by 200 times while remaining its competitive sheet resistance as low as 340 Ω sqThe online version of this article (10.1186/s11671-019-3040-9) contains supplementary material, which is available to authorized users. It is worth noting that the laser tailoring process is rather rapid that tailoring of 5 cm × 5 cm thin film can be finished within 1 min, which guaranteeing wide application for large scale in industry. We demonstrate efficient defogger based on MGFG as well as controllable local thermal field on substrate through designing of the grids’ patterns. The highly transparent and conductive MGFG will have great potential applications as transparent electrodes in touch panel, smart window, and wearable devices.Graphene has been highly prized as candidate for TCE for its outstanding electric and optic properties –6. Large−1) , 8. Howe−1) –13. Alth kΩ sq−1 –17. Ther2 atmosphere. In order to assist the growth of multilayer graphene, Fe ions that coordinated with polyethyleneimine are spun and coated on substrate serving as catalyzer  is applied as carbon source that is evaporated at 300 °C and deposited onto substrate at 1000 °C under Ar/HHererin, FoM of the MGFs with different thickness from 10 nm to 350 nm could be calculated from 0.1 to 0.5 in Fig. How to improve the FoM of as-grown MGF? The most important thing is to balance the contradiction between transparency and sheet resistance described above. Herein, IR laser was applied to ablate MGF for creating micro-grids structures Fig. a. The ta−1 to 340 Ω sq−1 in Fig. −1, which is only 2.5% of MGF (13.5 kΩ sq−1). That is to say, the FoM of the MGFG is increased as high as 3.6 from 0.1 of MGF under the equal transmittance of 80%. Therefore, it could be firmly concluded that the transparency and conductivity of MGFG have been dramatically enhanced than MGF through tailoring into micro-grid. To demonstrate the visual effect, a 5 cm × 5 cm MGF sample is presented in natural light. The sample in Fig. To evaluate the influences on transmittance and sheet resistance from tailored grids parameters, we carried out a series of MGFG with different ablation ratio from Fig. For demonstrating applications of the MGFG, Fig. IR laser is utilized to transform non-transparent MGF into highly transparent and conductive electrodes through tailoring micro-grids structures. Arbitrary multilayer graphene patterns could be obtained under the help of the CAD design and laser direct writing system. It is worth noting that the tailoring process is rather fast for large-scale manufacturing desirable structure. The transparency of the well-maintaining conductive MGF could be significantly enhanced from 0 to 80% through partially ablation and creation of micro-grids. Applications of the MGFG are demonstrated for electrical-thermal device and controllably localized thermal field on the substrate through designing the grid patterns. This route of fabricating graphene grids is effective to open up the possibility for the multilayer graphene or even graphite film for directly being utilized as transparent electrodes without complicated exfoliation process.3+ ion catalyzer is prepared by adding 2.5 g Fecl3 to a solution containing 1 g polyethyleneimine (PEI), 1 g ethylenediaminetetraacetic acid (EDTA), and 30 mL water. After ultrafiltration, the final Fe concentration was 28.20 mg/mL measured by an inductively coupled plasma atomic emission spectrometer . The solution with a concentration of 28.20 mg/ml Fe3+ is diluted into 0.5 mg/ml and then spin-coated onto quartz substrates at 5000 rpm for 30 s. The films were annealed at 1000 °C for 10 min with Polystyrene (PS) put at one side of the tube as carbon source.The precursor of aqueous FeGraphene grid is tailored by 1064 nm IR laser (YDFLP-20-M1+-S) provided by JPT Electronics at scanning speed of 100 mm/s, power of 2 W, frequency of 42 Hz and pulse width of 100 ns.Raman spectra were collected from Horiba Jobin Yvon HR Evolution. Scanning electron microscopy (SEM) analysis was carried out on a FEI Scios, operating at 10 kV. The optical image was obtained from Metallographic microscope CMM-55E. Sheet resistance was tested by the four-probe tester ST2263. Transmittance was tested on a Shimadzu UV-2450. Contour temperature map was measured by an Infrared camera (VarioCAM) from InfraTec.Additional file 1:Supporting information is available online. (DOC 12218 kb)


Single-stranded DNA (ssDNA) molecules in solution typically form coiled structures, therefore stretching ssDNA is extremely crucial before applying any nanotechnology for ssDNA analysis. Recent advances in material fabrication enable the deployment of nanochannels to manipulate, stretch, sort and map double-stranded DNA (dsDNA) molecules, however nanochannels fail to stretch ssDNA molecules due to the ultra-short persistence length and the potential nonspecific-interaction-induced clogging. Given the significance of ssDNA stretching in genome analysis, here we report an ssDNA stretching platform: two dimensional in-plane heterostructure comprising graphene and hexagonal boron nitride (h-BN), and show that ssDNA can be stretched on a h-BN nanostripe sandwiched between two adjacent graphene domains (“nanochannel”). We further show that with a biasing voltage the stretched ssDNA can be electrophoretically transported along the “nanochannel”, allowing easy controls/manipulations. When being conveniently integrated with existing atomic resolution sensors, the heterostructure platform paves the way for sequencing DNA on a planar surface. Single stranded DNA analysis is of interest for a range of applications; however, natural folding of DNA can cause problems with this. Here, the authors report on the in silico analysis of graphene and hexagonal-boron-nitride structures for the stretching and unfolding of DNA to allow for analysis. Amazingly, in a fully stretched ssDNA the spacing a between the neighboring nucleotides can be about 2.1 times of that (~3.4 Å) in the canonical B-form dsDNA2. However, for the purpose of ssDNA sequencing with existing sensing technologies, such as AFM3 and scanning tunneling microscope (STM)6, it requires to stretch ssDNA on a planar surface which is extremely challenging given the nonspecific interaction (or sticking) between ssDNA and the surface. For example, limited studies have demonstrated that ssDNA molecules can be successfully  adsorbed and stretched linearly by a flow on a modified mica surface7, however, the relatively small averaged spacing (a ~ 4.0 Å) indicates a partial stretching and potential intra-strand base stacking between the neighboring nucleotides. Therefore, a platform for stretching ssDNA with a great success rate is of vital importance and highly desirable in order to achieve the base sensing of ssDNA in an attoliter-scale sample8.Stretching ssDNA in solution has been predominantly studied in the past for its mechanical properties13. However, stretching ssDNA in a conventional nanochannel has remained impossible due to the electroosmotic flow14 (as well as the entropy barrier) that prevents the entry of ssDNA. Even after its entry, the analysis of ssDNA in a nanochannel is challenging because of the fast electrically driven translocation15 and possible clogging. With recent advances in fabrication of two-dimensional (2D) nanomaterials, remarkably, different 2D nanomaterials can be integrated together to form an in-plane heterostructure with controlled domain sizes, including seamlessly connected graphene and h-BN16, WS2 and MoS217, MoS2 and MoSe218 as well as MoSe2 and WSe219. Consistent with the adsorption of ssDNA on a flat graphite surface in experiment20, we have previously shown that biomolecules can be preferably adsorbed on a 2D nanomaterial due mainly to the strong van der Waals (vdW) interaction22. Here, with emerging in-plane heterostructures, we are motivated to design a nanochannel/nanostripe on the heterostructure surface to stretch an adsorbed ssDNA molecule sterically (or via an energy trap), as illustrated in Fig. Besides the mechanical stretching, it is straightforward to sterically stretch dsDNA confined inside solid-state nanochannels24. By employing sophisticated force fields for describing molecular interactions (see the “Methods” section), we investigate the dynamic movements of ssDNA on the graphene/h-BN heterostructures using our high performance computing (HPC) clusters. Our results demonstrate that an ssDNA molecule can be efficiently stretched in a linear conformation on the 2D heterostructure, which is excellent for ssDNA analysis by atomic resolution sensors.In order to demonstrate how 2D in-plane heterostructures can be utilized to stretch ssDNA, we carry out the proof-of-principle molecular dynamics simulations that have been widely applied to predict/confirm nanoscopic processes not yet possibly observed in experimentπ–π interaction with graphene after being adsorbed from water  with high level quantum methods, modern force fields used in our simulations were found to be able to capture well the interaction strengths through fitting to experimental data26. Stochastically, one ssDNA nucleotide diffused across the boundary and arrived at h-BN, which is strikingly followed by the remaining nucleotides in ssDNA. Subsequently, ssDNA diffused freely on h-BN and never moved back to graphene. As shown in Fig. Ngph of carbon atoms in graphene that were in contact with ssDNA decreased from about 350 to zero once ssDNA moved across the boundary, meanwhile the number NBN of boron and nitrogen atoms in h-BN in contact with ssDNA increased from zero to a saturated value (~420). This unidirectional motion of ssDNA was confirmed in two independent simulations (Sim-1 and Sim-2).Firstly, we focus on the ssDNA dynamics near the boundary/junction of a graphene/h-BN heterostructure, as shown in Fig. 27. Consistently, interaction energies from Sim-1 and Sim-2 become more negative  during the boundary-crossing events  and increased to 96.8 Å after ssDNA’s stretching on the h-BN stripe  of ssDNA on graphene and h-BN surfaces. According to the widely used worm-like chain (WLC) model, the correlation between two unit tangent vectors s) decays exponentially with their (contour) separation distance Na, i.e. θ) = a (=6.25 Å) is the mean distance between the neighboring nucleotides on the 2D surface and N is an integer. The inset of Fig. lp (from slopes) for ssDNA on both graphene and h-BN are comparable (~1.39 nm).From Sim-3 Fig.  and Sim-w ~ 1.8 nm), the case when lp < w < 2lp is categorized in the transition between the Gauss–de Gennes and the Odjik regimes28. With the known contour length lc, the predicated end-to-end distance from the Gauss–de Gennes theory is lclp/w (~96.5 Å) and from the Odjik theory is lc[1 − A(lp/w)−2/3] , agreeing with our current simulation result of 96.8 Å.Theoretically, for a polymer chain confined in a nanochannel/nanostripe . Starting from a stretched conformation of ssDNA on the h-BN stripe, we applied various electric fields  to electrophoretically drive ssDNA. As shown in Fig. V = 0.2 V, ssDNA moved at a nearly constant velocity opposite to the field direction   was screened, highlighting the complex interplay of electrostatic and hydrodynamic screening of ssDNA on the h-BN stripe. Therefore, similar to dsDNA in a conventional nanochannel, the motion of stretched ssDNA can be further controlled or manipulated for various applications (such as sorting and sequencing). It is noteworthy that the sensing of ssDNA bases through electron tunneling currents above a 2D surface and the transport of ssDNA in an electric field can be two independent steps, thus avoiding possible mismatch of the sensing and the transport speeds.Similar to the transport of dsDNA in a nanochannel, we further demonstrate that the graphene/h-BN/graphene heterostructure can be utilized to transport stretched ssDNA in an external biasing voltage ges Fig. , which y(t) Fig. , we calc Δt Fig.  and extrN nucleotides) can spontaneously enter it through the channel’s long edge because of the flatness of the heterostructure and the entropy barrier (~N0.5) outweighed by the stronger interaction (~N) between ssDNA and h-BN. These scalings with the ssDNA length (N) suggest that it is beneficial for a long ssDNA to be stretched on the heterostructure (i.e. a good read length of ssDNA during sequencing). Another advantage is that all DNA bases lie parallelly with the surface (via the π–π stacking), which reduces spatial fluctuations of DNA bases (that exist in other ssDNA-stretching method7) and thus can improve the signal-to-noise ratio for base sensing (i.e. reducing error rate).For conventional nanochannels, it is impossible for a long dsDNA molecule to spontaneously enter a small nanochannel opening due to the large entropy barrier, and typically requires a large biasing voltage or a pressure-driven flow for dsDNA’s entry into the nanochannel. For the current heterostructure nanostripe (or planar surface nanochannel), however, ssDNA (with a ~ 6.25 Å). Inspired by this result, generally one can conclude that selecting a 2D material with its π-electron energy close to HOMO energy levels of DNA-bases is one of the factors for a successful elongation of ssDNA on the nanostripe. Further stretching is possible by decreasing the ion concentration, reducing the width of h-BN, or reducing the dielectric constant of environment. It is worth noting that ssDNA stretching may occur on the h-BN/graphene/h-BN heterostructure surface as well, if the surface of graphene nanoribbon (connected to a power source) becomes positively charged. Besides ssDNA, the same principle can be used to stretch protein molecules on the 2D heterostructure surface. Conceivably, our proposed ssDNA stretching platform is compatible with existing sensors, such as the atomic-resolution AFM3, high-resolution AFM31 and STM6 and allows parallelization when multiple nanostripes are built in the heterostructure. Therefore, it is expected that our findings will benefit future studies in DNA8 and even protein33 sequencing.In conclusion, we have suggested a planar surface nanochannel for ssDNA stretching on the patterned 2D graphene/h-BN/graphene heterostructure surface. The facts of fast diffusion of ssDNA on such surface and stronger interaction energy for ssDNA on the h-BN stripe permit the remarkable spontaneous stretching of ssDNA to a great extent  contains 50% graphene and 50% h-BN connected seamlessly  respectively. In this study, each C atom forming a bond with a N atom has been assigned a charge of +0.133e, and each C atom forming a bond with a B atom a charge of −0.133e, to maintain the “local charge neutrality” . As shown in Supplementary Fig. We applied the CHARMM27 force field39. The temperature was kept constant at 300 K by applying the Langevin thermostat40.The simulation time-step with rigid bonds applied was 2 fs; non-electric (such as vdW and bonded) and electric interactions were calculated every 2 and 4 fs, respectively. The pair-wise vdW interaction was calculated using a smooth (10–12 Å) cutoff. We used the particle-mesh Ewald (PME) method with a mesh size of about 1 Å to calculate the long-range Coulomb interaction. After the minimization/equilibration, production runs were carried out in the NPT ensemble. The pressure was kept at 1 bar using the Nosé–Hoover methodSupporting InformationPeer Review FileMovie S1Movie S2


A dual-band terahertz (THz) absorber using the periodic cross-shaped graphene arrays is presented. It is shown that the dual-band light absorption enhancement of graphene results from the edge graphene plasmon (EGP) resonance, and the locations of the two absorption peaks can be precisely estimated by using the Fabry-Pérot (F-P) cavity model. Slight residual reflection remains at the two absorption peaks because the input impedance of the cross-arm cannot be perfectly matched with the free space impedance. In addition, the locations of the two absorption bands can be simultaneously tuned by changing the Fermi level of graphene, and they can be independently tuned by changing the width or the length of the cross-arm of graphene. Excellent angle-insensitivity dual-band absorption enhancement of graphene can be maintained for both the transverse electric (TE) and transverse magnetic (TM) polarizations. In recent years, terahertz (THz) technology has become one of the most attractive research topics, because of its promising applications in the fields of imaging, spectroscopy, security and communications . The THzVarious groups have been working on graphene-based absorbers in the THz region. Many of these absorbers are based on periodically patterned graphene, like disks ,12, micrIn this work, we numerically investigate a tunable dual-band THz absorber with a high absorption efficiency by using the periodic cross-shaped graphene arrays. The dual-band light absorption enhancement of graphene results from the edge graphene plasmon (EGP) resonance, and a simplified Fabry-Pérot (F-P) cavity model is proposed to estimate the locations of the two absorption peaks. The absorption bands of graphene can be simultaneously tuned by changing the Fermi level of graphene, and they can be independently tuned by changing the width or the length of the cross-arm of graphene. Angle-insensitivity dual-band absorption enhancement of graphene can be maintained for both the transverse electric (TE) and transverse magnetic (TM) polarizations. Besides the advantages of high absorption efficiency and relatively simple structure, the absorption performance of the proposed structure could be tuned more flexibly because it has one more free geometry parameter compared with other simple structures such as graphene disk and nanoribbon.y-axis). The absorber consists of the periodic cross-shaped graphene arrays with width L1, length L2 and period xΛ = yΛ. The cross-shaped graphene adheres to a metallic reflective plate substrate (Au film) separated by a thin silicon dioxide (SiO2) spacer with the thickness of d. Here, the reflective Au plate can be equivalent to the perfect electric conductor, which can efficiently enhance the interaction between the incident light and the patterned graphene arrays, due to the mirror effect. From the point of view of device fabrication, the Au film and thin SiO2 spacer can be deposited by using the conventional electron beam evaporation technique [2 is dε = 3.9 [gσ can be modeled by the Kubo formula including interband and intraband transitions [e is the electron charge, kB is the Boltzmann constant, fE is the Fermi level, T is the temperature, ħ is the reduced Planck constant, τ is the momentum relaxation time, and ω is the angular frequency of optical excitation. The relative permittivity of graphene gε can be characterized as [t = 0.34 nm is the thickness of graphene layer and ε0 is the vacuum permittivity. According to Equations (1) and (2), the relative permittivity of graphene can be modulated because its Fermi level can be tuned by changing the chemical doping or applying bias voltage.echnique , and theechnique . The relεd = 3.9 ,32. The nsitions ,34,35:(1rized as :(2)εg=1+x or y axis, the cross-arm of graphene can be approximatively viewed as a finite-sized graphene nanoribbon. Based on Finite Element Method (FEM) simulation, we firstly perform a modes analysis of the graphene nanoribbon under different widths L and Fermi levels fE. Here, only the dispersion relation of the fundamental mode of the GP is analyzed. effn) of the GP as function of wavelength under different widths L and Fermi levels fE of the graphene nanoribbon. As can be seen in fE and the width L of the graphene nanoribbon, which provides an effective strategy to control the resonant wavelengths of the GP modes.Along the directions of the A = 1 − R, where R is reflection, which is because the transmission channel is blocked by the optically thick Au film. xΛ = yΛ = 2.5 μm, fE = 0.4 eV, τ = 0.5 ps, d = 4 μm, T = 300 K, L1 = 0.8 μm and L2 = 1.7 μm. The incident angle is cθ = 0, and the direction of the incident electric-field is along the x-axis. As shown in xy plane for 37.26 μm and 62.13 μm are illustrated in x-axis, indicating the features of the EGP modes [L1; similarly, the electric-field is well confined on the edges of length L2 for 62.13 μm. Here, we consider the cross-arm as an F-P cavity with different cavity lengths along the x-axis (the direction of the incident electric-field), and an enhanced absorption peak can be realized when the cross-arm is in F-P resonance. The F-P cavity resonance condition can be described as [δ is the phase shift, λ is the resonance wavelength, l is the F-P cavity length of graphene, ϕ is the additional phase, and m is an integer which represents the resonance order. As shown in l = 0.8 μm and l = 1.7 μm with fE = 0.4 eV are 36.92 μm and 61.16 μm, respectively. The theoretical results of the F-P cavity model are in good agreement with the results of 37.26 μm and 62.13 μm calculated by using the FDTD method.In simulation, the 3D finite-difference time-domain (FDTD) models of the commercial software FDTD Solutions are used to analyze the absorption properties of the proposed absorber. The absorption of graphene can be simplified as GP modes . In partS parameters and impedance Z can be expressed as:S11, S21, S12, S22 are S parameters, n is the effective refractive index of the structure, and k the wave vector. The input impedance Z of the structure can be written as [Z0 is the impedance of the free space, and Z are varied abruptly around the two absorption bands, but slight residual reflection remains at the locations of the resonance wavelengths because the input impedance cannot be perfectly matched with the free space impedance.To better understand the selective absorption enhancement of the cross-shaped graphene arrays, the input impedance of the structure are studied by using the impedance theory. According to the impedance theory ,39, the itten as :(6)Z=± of the GP is decreased as fE is increased, thus the locations of the absorption peaks are blue-shifted with the increase of fE according to Equation (3). In addition, the peak absorption of the two bands is slightly increased as fE is increased. This is because the surface conductivity of graphene gσ is increased with the increase of fE, thus the light absorption of graphene at the peak wavelength can be further improved by increasing fE. As shown in fE = 0.3 eV is smaller than that of with fE = 0.5 eV, and stronger EGP resonance can be realized due to the increase of charge oscillations as fE is increased, resulting in enhanced light absorption of graphene for both of the peaks.L1 and length L2 on the absorption performance of the cross-shaped graphene arrays, and other parameters are the same as those in L1 is increased, while the location of the absorption peak at the longer wavelength is almost immune to the variation of L1. This is because the absorption peak at the shorter wavelength is excited by the F-P cavity resonance of L1, thus its location will be redshifted as L1 is increased. Similarly, as shown in L2, the corresponding location of the absorption peak can be effectively tuned by varying L2. Therefore, the locations of the two absorption peaks can be independently tuned by changing the width or the length of the cross-arm. L1 or L2 is altered, the variation of L1 or L2 will influence the intensity of the two absorption peaks. Note because the absorption bandwidth at the shorter wavelength is narrower, thus its intensity at the absorption peak is more sensitive to the variation of L1 or L2.Additionally, because the amplitude of the normalized electric-field of the cross-arm is changed as y-axis) and TM polarizations, whereas other parameters are the same as those in cθ is increased from 0° to 40°, the peak absorption of the two absorption bands is still larger than 48.8%, which is comparable to many graphene-based THz selective absorbers [cθ is increased, and perfect light absorption of graphene with A = 99.4% can be achieved as cθ = 60°. The increase of the light absorption of graphene at the peak wavelength may result from stronger confined electric-fields at oblique incidence for the TM polarization [cθ is altered, the strength of magnetic resonance can be sufficiently kept and further ensures the high ohmic loss in graphene, thus the absorption response of the TM polarization is more robust to the variation of the incident angle [cθ almost does not affect the F-P cavity length of the cross-arm, thus the locations of the two absorption peaks are kept almost the same even if cθ is significantly altered for both the TE and TM polarizations.Finally, we investigate the angular robustness of the proposed graphene-based dual-band THz absorber. bsorbers ,20,21,29rization . In addtnt angle . Note thIn conclusion, we numerically study an angle-insensitive and tunable dual-band THz absorber consisting of periodically patterned cross-shaped graphene arrays. The enhanced light absorption of graphene originates from the EGP resonance, and the locations of the two absorption peaks can be estimated by using the simplified F-P model. Excellent agreements have been achieved between the results of the FDTD and the F-P cavity model. The impedance theory is used to evaluate the absorption properties of graphene, which shows that slight residual reflection remains at the absorption peaks because the input impedance cannot be perfectly matched with that of the free space. In addition, the absorber shows flexible adjustability and excellent angle-insensitive absorption performances. The locations of the dual-band absorption can be simultaneously tuned by changing the Fermi level of graphene, and they can be independently tuned by changing the width or length of the cross-arm of graphene. An excellent angle-insensitivity dual-band absorption enhancement of graphene can be achieved for both the TE and TM polarizations. The results of cross-shaped graphene arrays can be generalized for designing more sophisticated metamaterials and related devices based on the patterned graphene structure.


Grafting thin polymer layers on graphene enables coupling target biomolecules to graphene surfaces, especially through amide and aldehyde linkages with carboxylic acid and primary amine derivatives, respectively. However, functionalizing monolayer graphene with thin polymer layers without affecting their exceptional electrical properties remains challenging. Herein, we demonstrate the controlled modification of chemical vapor deposition (CVD) grown single layer graphene with ultrathin polymer 1,5-diaminonaphthalene (DAN) layers using the electropolymerization technique. It is observed that the controlled electropolymerization of DAN monomer offers continuous polymer layers with thickness ranging between 5–25 nm. The surface characteristics of pure and polymer modified graphene was examined. As anticipated, the number of surface amine groups increases with increases in the layer thickness. The effects of polymer thickness on the electron transfer rates were studied in detail and a simple route for the estimation of surface coverage of amine groups was demonstrated using the electrochemical analysis. The implications of grafting ultrathin polymer layers on graphene towards horseradish peroxidase (HRP) enzyme immobilization and enzymatic electrochemical sensing of H While conventional optical based detection is extremely sensitive ,2, they tructure . The twotructure ,7,8. Fortructure ,10,11,12tructure . Recentltructure ,15, wher3 hybridized bonds that would affect the unique electrical properties of graphene [A wide range of covalent  and non-covalent  functionalization chemistries have been investigated to selectively functionalize the graphene surfaces ,17,18. Tgraphene ,20. Alte2 bonds with aggressive chemicals. Recently, polydiaminonaphthalene (pDAN), a conductive polymer grafted from aromatic diamines, has been reported to exhibit interesting electrochemical characteristics and compatibility to binding biomolecules and to shorten the distance between the electrode surface and enzyme active sites [Grafting thin conducting polymer layers have attracted a great deal of attention over the past decade. Electrodes modified with polymer layers can be achieved by different methods, however, electropolymerization is attractive in the preparation of ultra-thin polymer layers because of its experimental simplicity, room temperature utility, degree of dimensional specificity, and precision over the layer thickness via controlling the charge passed and/or the potential at which the deposition is performed. Additionally, the electrochemical potential applied can shift the Fermi level of graphene, increasing its reactivity as compared to direct attack of the covalent spve sites . Neverthve sites ,23,24,25ve sites . It was 2 groups is critical as it reflects the available active binding sites for the biomolecular immobilization. While a wide range of surface functionalization methods have been reported in literature, to the best of our knowledge, there are only very few articles report on the estimation of amine surface coverage. In 2011, Noel et al. reported the estimation of amino surface densities using calorimetric methods [Furthermore, quantification of -NH methods . Later,  methods  and sili methods . Shiota  methods . While t2O2  were used as received. Monolayer chemical vapor deposition (CVD) grown graphene was purchased from Graphenea and the samples were cleaved with 4 × 4 mm dimension. Sulfuric acid , 1,5-diaminonaphthalene (DAN) , ferrocene carboxylic acid , phosphate buffered saline tablets (Sigma-Aldrich), horseradish peroxidase enzyme (Sigma), N-Hydroxysuccinimide (NHS) , N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC)  and H2SO4 in a three-electrode system, where, monolayer CVD graphene was used as the working electrode, Pt wire as counter electrode and Ag/AgCl served as the reference electrode. The electropolymerization of monomer DAN produces polymer DAN (pDAN) on graphene surface generating NH2 groups on the surface. The thicknesses of the pDAN layers were controlled by controlling the number of cycles during the electropolymerization process. The polymer films were deposited from 10 mM DAN in 0.25 M HThe surface coverage of amines on pDAN modified CVD graphene was estimated by functionalizing the amine groups with electroactive ferrocene carboxylic acid moieties. Typically, 250 µM ferrocene carboxylic acid was prepared in fresh PBS solution containing 5 mM EDC and NHS, which was incubated at room temperature for 40 min to activate the carboxylic functional group of the redox molecule. The resultant solution was drop-casted on a freshly prepared amine terminated pDAN modified CVD graphene surface and incubated at room temperature for 10 min. The electrode functionalization was performed prior to the electrochemical experiments and was used immediately.Aqueous solution of 5% glutaraldehyde was drop-casted onto the pDAN modified electrodes and was incubated for 30 min. Later, the electrodes were rinsed with de-ionized water (DI-water) and dried under nitrogen. The enzyme immobilization was performed by directly drop-casting 10 µL of horseradish peroxidase (HRP) enzyme (1 mg/mL) onto the modified surface and incubated at 4 °C for 18 h. The electrodes were rinsed with DI-water thrice to remove any weakly bound enzymes. The electrodes were freshly prepared and used immediately following the enzyme immobilization.The surface topography of pDAN modified graphene electrode was investigated using atomic force microscopy (AFM), , and the AFM tip was a silicon-SPM sensor (contact mode), thickness 4 μm, length 125 μm, and width 30 μm. The chemical environment was studied using X-ray photoelectron spectroscopy (XPS). Electrochemical analysis was performed using the advanced potentiostat  with the scanning voltage in the range of −0.8 to 0.6 V for evaluating the electrochemical performance of enzyme-functionalized electrodes. Standard 3-electrode system was used for the electrochemical evaluation, where CVD graphene was used as the working electrode, Ag/AgCl as the reference electrode and Pt wire as the counter electrode. 0.01 M phosphate buffer saline (PBS) solution (pH = 7.4) was used as the electrode unless otherwise stated. −1 is shown in Cyclic voltammogram for the electropolymerization of 10 mM 1,5-DAN on monolayer CVD graphene at a sweep rate of 50 mVsThe surface topography of the pDAN functionalized graphene was analyzed using atomic force microscopy (AFM) analysis. 2/Si substrate; whereas, the O peaks might be originating from both SiO2/Si substrate as well as graphene (edges and defects of the graphene lattice had bonds with oxygen). The atomic percentage of C, O, and N were determined from the XPS spectra and are presented in 2/Si substrate, which might be masked by the pDAN layer (>5 nm). To further analyze the nature of C, O, and N species, the C 1s (aromatic (~284.8 eV), Caliphatic (~285.4 eV), C=C-N/C-NH2/C-O (~286.5 eV), and C=O/C=N (~287.5 eV) [2+, respectively [2 groups on the graphene surface. X-ray photoelectron spectroscopic measurements were carried out on CVD graphene and pDAN modified CVD graphene surfaces  to studythe C 1s b, O 1s  . The N 1ectively , confirm−1 sweep rate. −1), and A is the geometrical area of the electrode (cm2). The surface coverage of ferrocene moieties were found to be 58.04, 62.60, 83.95, 109.52, and 179.99 pmol cm−2 for the electrodes modified with 5, 10, 25, 50, and 75 cycles of pDAN layers, respectively. Assuming an effective binding (100%), these surface coverage’s reflect the amine surface coverage on pDAN modified CVD graphene substrates. Thus, the amine surface coverage increases with an increase in the thickness of the pDAN layer. The surface coverage of amine groups on pDAN modified CVD graphene was estimated via functionalizing the electrodes with an electroactive ferro-centered molecule, ferrocene carboxylic acid, using a standard EDC/NHS coupling reaction. Ferrocene carboxylic acid functionalized electrodes were scanned between −0.1 V and 0.3 V at 5 mVs2+/Fe3+ redox couple at scan rates 2–200 mVs−1. The pristine graphene modified electrode shows the typical oxidation and reduction peaks at 0.25 V and 0.1 V, which is ascribed to Fe2+/Fe3+ redox reaction. However, the pDAN modified graphene electrodes showed that the redox potentials moved to a more positive value (0.5 V and 0.042 V), indicating the occurrence of additional chemical reactions. The peak current ipc is linear with the square root of scan rate , A is the area of the electrode, D is the charge transfer diffusion coefficient, C is the concentration of redox couple (5 mM), and υ is the scan rate. The pristine CVD graphene electrodes shows a typical DCT of 1.023 × 1010 cm2 s−1 (10 cm2 s−1) around 25 cycles, after which the DCT decreases. This confirms that the electron transfer rates are affected by the thickness of the pDAN layer  in the ground state . The nat−1, the surface coverage of HRP enzyme was found to be 9.5617 × 10−10 mol·cm−2, 2.43 × 10−9 mol·cm−2, and 3.0026 × 10−9 mol·cm−2 for HRP immobilized on pristine CVD graphene, 5pDAN layers and 25pDAN layers modified CVD graphene electrodes, respectively. It is found that the pDAN surface modifications increases the enzyme immobilization that could be ascribed to the increased binding sites upon polymer grafting. Additionally, the enzyme surface obtained via pDAN modifications shows higher enzyme loading that the previously reported values [−1) in PBS. The linear change in the cathodic peak current with square root of scan rate given in the inset of 2 = 0.98985). The enzymatic electrochemical sensor performance of the modified electrodes (2O2. It is clear from 2O2. The inset figure shows the current response of the electrodes (@−0.25 V) at different concentrations of H2O2. This increase in the redox current can be ascribed to the increased electron transfer between the heme protein HRP and the electrode upon the reduction of H2O2 into H2O, as shown in −3 M to 100 × 10−3 M with 100 × 10−6 M limit of detection compared to earlier reports [The surface coverage of immobilized HRP enzyme on the electrodes can be estimated using the reduction peaks. As anticipated, the redox peaks of heme protein increases with an increase in the pDAN cycles indicating higher loading of HRP enzymes upon pDAN modification. From the integration of the reduction peaks of HRP functionalized modified graphene electrodes at 50 mVsd values ,39,40. Fectrodes c were st reports ,42,43,442 peaks upon electropolymerization. The electrochemical analysis showcase that the pDAN polymers exhibit thickness dependent electron transfer phenomenon. A simple electrochemical tool was demonstrated for the estimation of total amine surface coverage, which can be adapted for other similar systems. The enzymatic electrochemical sensing ability of these electrodes were demonstrated using a standard H2O2 detection system via functionalizing the HRP. The experimental results evidence that the electrochemical sensing efficiency increases, owing to the synergistic effects of better electron transfer as well as higher enzyme loading on pDAN modified electrodes.A controlled deposition of 1,5-diaminonaphthalene (DAN) was achieved on CVD graphene surfaces using direct electropolymerization process. The surface morphology analysis of pristine and pDAN modified CVD graphene shows uniform deposition of the polymer layer on CVD graphene. The XPS analysis shows that the atomic percentage of C increases from 25.64% to 71.76%, whilst the atomic percentage of N drastically improves from 0 to 9.12%. Additionally, it is observed from the XPS analysis that the increase in the N atomic percentage corresponds to the formation of new -NH


Moreover, all NrGOm-4 show high tolerance to methanol poisoning in comparison with the state-of-the-art ORR electrocatalyst Pt/C and good stability. N-doped (NrGO) and non-doped (rGO) graphenic materials are prepared by oxidation and further thermal treatment under ammonia and inert atmospheres, respectively, of natural graphites of different particle sizes. An extensive characterization of graphene materials points out that the physical properties of synthesized materials, as well as the nitrogen species introduced, depend on the particle size of the starting graphite, the reduction atmospheres, and the temperature conditions used during the exfoliation treatment. These findings indicate that it is possible to tailor properties of non-doped and N-doped reduced graphene oxide, such as the number of layers, surface area, and nitrogen content, by using a simple strategy based on selecting adequate graphite sizes and convenient experimental conditions during thermal exfoliation. Additionally, the graphenic materials are successfully applied as electrocatalysts for the demanding oxygen reduction reaction (ORR). Nitrogen doping together with the starting graphite of smaller particle size (NrGO In recent years, the interest in graphene has grown due to its many outstanding electronic, thermal, chemical, and mechanical properties . These pAn extensive number of works have been devoted to the preparation of graphene and N-doped graphene. The synthesis of graphene can be performed using different methods, among them the micromechanical cleavage method , chemica3 .Then, the ORR kinetics at different potentials were assessed with the Koutecky-Levich (K-L) plots obtained with the application of the K-L equation to the LSVs in  at rotatO2n (ñO2) values estimated from Equation 3 in ESI are depicted in nO2 with the applied potential. For the non-doped materials, as the potential decreases from 0.46 to 0.26 V versus RHE, there is an increase in nO2 values with ΔE values of 1.0, 0.53, and 0.71 V for rGO10-3, rGO100-3, and rGO325-3, respectively. The variation for the N-doped materials is less significant with 0.40 ≥ ΔE ≥ 0.22 V versus RHE. The results of mean nO2 values obtained suggest that rGO100-3 and rGO325-3 proceed through the indirect pathway, while rGO10-3, NrGO10-4, and NrGO100-4 seem to proceed through a mixed mechanism, similar to ñO2 ≈ 3. This behavior has already been reported for other N-doped structures [325-4, a one-step four-electron transfer mechanism seems to be the leading process, since O2ñ = 3.9. This value is equal to the one obtained for Pt/C. Additionally, this result is better than that obtained for the other N-doped carbon nanotubes and graphene [The mean ructures . On the graphene ,60.jL and ñO2) of the N-doped materials in comparison with the non-doped may be related to the presence of nitrogen as explained before, while the differences between the three N-doped materials to the percentages and types of N species found could also be related to the particle size of the starting graphite. As discussed above in 3, leading to the incorporation of nitrogen in the structure, which will favor ORR. Elemental analysis showed that NrGO325-4, NrGO100-4, and NrGO10-4 presented 5.0%, 3.8%, and 1.8% of N, respectively, whereas the XPS results indicated percentages of 3.4%, 3.3%, and 3.2%. The NrGO325-4 sample presents a higher N% at the surface and has also a higher percentage of pyridinic nitrogen. The latest have been reported to work as ORR electrocatalytic sites due to the electron donated to the conjugated π-bond of graphene and to the lone pair of electrons they have [The better ORR performances , which is in accordance with the high ñO2 value (ñO2 = 3.9), while a value of 3% was obtained for Pt/C.To confirm the excellent result obtained for NrGO2 at 1600 rpm. The Tafel slopes obtained between E = 1.00 to 0.70 V versus RHE were 65, 48, 98, 78, 99, 62, and 89 mv dec−1 for rGO10-3, rGO100-3, rGO325-3, NrGO10-4, NrGO100-4, NrGO325-4, and Pt/C, respectively. All electrocatalysts except for rGO325-3 and NrGO100-4 presented Tafel slopes lower than those obtained for Pt/C, which suggests that the graphene materials can easily adsorb O2 onto their surface and activate it, promoting a robust electrocatalytic activity toward ORR. The different Tafel slopes obtained for rGO325-3 and NrGO100-4 are most likely associated to fluctuations in the oxygenated intermediates adsorption strength or to an incomplete electrocatalyst, which is used as a consequence of mass transport losses [− is the rate-determining step, whereas for the remaining electrocatalysts, the conversion of MOO− to MOOH rules the overall reaction rate  [Tafel plots b were obt losses ,64. It isurface) .−3 of methanol were added at t = 500 s  for 20,000 s applying a potential of E = 0.50 V versus RHE at 1600 rpm. The results obtained for Pt/C and all graphenic materials are presented in 325-4 electrocatalyst showed the best result from all the graphene materials with a current retention of 85%, which is only 3% less than Pt/C. For the other ECs, the current retention percentages were 63%, 72%, 82%, 80%, and 78% for rGO10-3, rGO100-3, rGO325-3, NrGO10-4, and NrGO100-4, respectively. The best performance of the NrGO325-4 electrocatalyst can be ascribed to the combination of two features, the N-doping and the smaller particle size of the starting graphite.The EC stability is also of extreme importance. So, this was evaluated, for all graphene materials, using chronoamperometric runs in KOH electrolyte  allow to successfully introduce nitrogen within the graphenic structure, enhancing the electronic properties and basicity of the doped materials. For the N-doped samples, the amount of nitrogen introduced and surface areas could be also tailored. The use of different reduction atmosphere (NH−1), and good jL values (−3.03–−4.05 mA cm−2). The better performance of NrGO325-4 was attributed not only to the higher content of nitrogen but also to the smaller particle size of the starting material. Moreover, all the graphene materials presented good durability/stability and very low sensitivity to methanol. This work has led to a new class of metal-free ORR electrocatalysts with good efficiency and stability.As a result of their tailored enhanced properties, these optimized NrGO and rGO samples were successfully applied as ORR electrocatalysts. The NrGO samples showed better ORR performance in alkaline medium with onset potentials ranging from 0.79 and 0.82 V versus RHE, low Tafel slopes (62–99 mV dec


Electro-optic modulators based on micro-electromechanical systems have found success as elements for optical projectors, for simplified optical spectrometers, and as reflective-type screens that make use of light interference (Interferometric Modulator Display technology). The latter concept offers an exciting avenue for graphene nanomechanical structures to replace classical micro-electromechanical devices and bring about enhancement in performance, especially switching speed and voltage. In this work we study the optical response of electrically actuated graphene drumheads by means of spectrometric and stroboscopic experiments. The color reproducibility and speed of these membranes in producing the desired electro-optic modulation makes them suitable as pixels for high refresh rate displays. As a proof of concept, we demonstrate a Graphene Interferometric Modulator Display prototype with 5 μm-in-diameter pixels that compose a high resolution image (2500 pixels per inch)—equivalent to a 5″ display of 12K—whose color can be changed at frame rates of at least 400 Hz. The electro-optical response of suspended graphene membranes measured by change in wavelength-dependent reflectance can enable interferometric modulation display (IMOD) technology. Here, the authors report suspended double layer graphene based IMOD drums with 2500 pixels per inch. In contrast to modulation devices that rely on plasmonic or electronic effects, micro-electromechanical system (MEMS)-based modulators can have wider tuning ranges albeit at a lower operating frequency. These properties make electro-optic mechanical modulators ideal for reflective-type display technologies as has been demonstrated previously with SiN membranes in Interferometric Modulator Displays (IMODs)5. Despite their low-power consumption and performance in bright environments, IMODs suffer from low frame rates and limited color gamut.Graphene, the carbon monolayer and two-dimensional allotrope of graphite, has the potential to impact technology with a wide range of applications such as optical modulators for high-speed communications6. Here, we report on the electro-optical response of CVD DLG mechanical pixels by measuring the change in wavelength-dependent reflectance of a suspended graphene drumhead as a function of electrical gating. We use a spectrometer to measure the wavelength spectrum at different voltages, and find a good agreement with a model based on light interference. Moreover, to verify that gas compression effects do not play an important role, we use a stroboscopic illumination technique to study the electro-optic response of these graphene pixels at frequencies up to 400 Hz. Based on these findings, we demonstrate a continuous full-spectrum reflective-type pixel technology with reduced flicker effect by fabricating a Graphene Interferometric Modulator Display (GIMOD) prototype of 2500 pixels per inch (ppi) equivalent to more than 12 K resolution.Double-layer graphene (DLG) membranes grown by chemical vapor deposition (CVD) can also recreate the interference effect like in IMODs as proven with drumheads displaying Newton’s rings2 layers (300 to 1180 nm in depth depending on the sample) on silicon substrates by means of reactive-ion etching. DLG layers, fabricated by stacking two CVD single-layer graphene (SLG) layers, are transferred onto the patterned substrate using a semi-dry transfer technique. This results in an optical cavity with a movable absorbing membrane made out of CVD DLG . A series of color filters with wavelengths ranging from 450 nm to 650 nm (bandpass linewidth of 5–10 nm) are mounted on a motorized computer-controlled wheel, and placed in front of the camera imager as shown schematically in Fig. 2/Si structure (area of ~1 cm2) was measured to be 0.6 nF. Figure λ = 580 nm) at 0 V to green (λ = 550 nm at 12.5 V and λ = 510 nm at 20 V).Electrostatic actuation of the graphene drums is achieved by using a computer-controlled DC source connected to the suspended graphene electrode, while keeping the silicon substrate grounded. For these measurements a sample with 1180 nm oxide thickness was chosen. The capacitance of the graphene/SiOk1), the cubic elastic force (stiffness k3), and the hydrostatic force due to the pressure of trapped gas inside the cavity, we develop a 1-degree-of-freedom graphene membrane electromechanical model where the bending rigidity is neglected  and B(λ) are wavelength-dependent constants, g the cavity depth. This model is applied to our devices and shown in Fig. The spectral response of the graphene drums allows us to extract the deflection of the drum, which can be used to relate the electromechanical and optomechanical performance of the pixel. By applying a force equilibrium condition between the electrostatic force, the linear elastic force , which is powered by short duration pulses that are synchronized to a sinusoidal actuation voltage: Vact = (17.5 + 2.5sin(ωactt + ϕact)) V (see Methods). By sweeping the phase difference between the illuminating pulse and the actuation signal, we are able to reconstruct the time-domain response of the structure. An example is shown in Fig. Given the gas impermeability of grapheneWe stroboscopically measure 5 drumheads of 15 μm in diameter with actuation frequencies ranging from 0.5 to 2000 Hz. The measured structures do not exhibit a first-order low-pass filter response indicative of squeeze-film effect for frequencies up to 400 Hz, beyond which the cut-off frequency of the capacitively loaded amplifier is reached. The frequency response of the drum’s center reflectance is shown in Fig. 11. The large electro-optic modulation and absence of mechanical delays at frequencies up to 400 Hz make these devices interesting to enable display rates beyond the flicker fusion threshold that require color reproducibility in the millisecond range for applications such as virtual or augmented reality (VR/AR)13. Figure Flicker effect in displays is usually perceived negatively and can be reduced or eliminated by increasing the refresh rate14, demonstrating the electro-optical modulation from yellow to blue of these pixels.By analyzing the RGB  channels of one of the pixels, we obtain its average color gamut and its evolution upon applied voltage. Figure If more graphene layers are added, then the colorimetric response should improve. However, that response is no longer captured by the analytical model in Supplementary Equation 17, in this work we investigate the far-from-resonance, quasi-static, large deformation regime of graphene membranes19. For such a regime of operation the hydrostatic pressure component near the zero-deflection position While electrostatic transduction is used extensively as an actuation mechanism for MEMS/nanoelectromechanical system (NEMS) devices, including graphene nanoelectromechanical structuresIt is interesting to note that among the five 15 μm in diameter membranes measured stroboscopically, one drum shows larger static and dynamic deflections compared to the others  pixel technology would greatly reduce power consumption as it is an IMOD technology. The use of graphene allows the large deformation of small membranes without mechanical failure or hysteresis allowing the fabrication of diffraction-limited devices for ultra-high resolution displays. Moreover, by using different voltages to actuate the pixels, each device is able to generate natural colors in the full spectrum and in a continuous manner. This eliminates the need for RGB subpixels and reduces the addressing bandwidth to only one channel, which enables a further reduction of power consumption.7. Pictures are taken with a Canon EOS 600D and a 20× Olympus UMPlanFI objective lens . A TE-cooled linear CCD array spectrometer (B&W Tek Glacier X) is attached to the optical microscope in such a way that it collects the light reflected from an area slightly larger than the selected drum (about 595 μm2)  controls the LED by outputting a narrow (Supplementary InformationPeer Review FileDescription of Additional Supplementary FilesSupplementary Movie 1


Single-particle electron cryomicroscopy (cryoEM) has now proved to be the method of choice for determining the structure of biological macromolecules and complexes. Yet success in determining a structure by cryoEM depends on being able to prepare a frozen specimen on a small metal support called a grid. This process is poorly controlled at present because of molecule–surface interactions. Here we used a modified form of graphene, in conjunction with a stable grid made of gold, to control these surface effects. Functionalized graphene-on-gold grids improve the reliability of specimen preparation and enhance image quality. This technology has the potential to take specimen preparation for cryoEM from a trial and error art to a controlled and reproducible process. With recent technological advances, the atomic resolution structure of any purified biomolecular complex can, in principle, be determined by single-particle electron cryomicroscopy (cryoEM). In practice, the primary barrier to structure determination is the preparation of a frozen specimen suitable for high-resolution imaging. To address this, we present a multifunctional specimen support for cryoEM, comprising large-crystal monolayer graphene suspended across the surface of an ultrastable gold specimen support. Using a low-energy plasma surface modification system, we tune the surface of this support to the specimen by patterning a range of covalent functionalizations across the graphene layer on a single grid. This support design reduces specimen movement during imaging, improves image quality, and allows high-resolution structure determination with a minimum of material and data. High-resolution structural studies by electron cryomicroscopy (cryoEM) require the biological specimen to be embedded in a thin layer of amorphous water ice , 2. Duri5SI Appendix, Fig. S1). We aimed to reduce the number of graphene crystal grain boundaries in the film to increase the mechanical and chemical robustness during subsequent functionalization and imaging. To combine the stability of all-gold specimen supports .We optimized a chemical vapor deposition (CVD) graphene growth process  to produsupports  with thesupports , we devisupports B and C. SI Appendix, Fig. S5). We tested four precursor chemicals with different terminal reactive groups ; in principle this method of functionalization can be used with any small-molecule compound provided it has a vapor pressure sufficient to inject into the chamber. We note that the orientation and length of the functional groups are not specifically controlled by this technique, implying there will possibly be a mixture of functional fragments on the surface. Similar plasma-assisted chemical modification and deposition methods are often used in the semiconductor manufacturing industry . The integrity of the graphene lattice was preserved after these treatments, as demonstrated by electron diffraction ; the graphene lattice is also directly visible in electron micrographs at suitably high magnification . The surface properties of functionalized grids are preserved when stored in vacuum; contamination in air occurs in 1–10 h, depending on the storage vessel .The covalent functionalization of the graphene was confirmed by X-ray photoelectron spectroscopy E. An iniSI Appendix, Fig. S6) and serial patterning of the same region with multiple chemicals. At the typical plasma process pressure of SI Appendix, Fig. S5A). With more complicated masks, a distinct functionalization for each of the hundreds of grid squares on a grid is possible; smoother surface patterning transitions or gradient functionalization can also be achieved by increasing the distance between the mask and the graphene surface. This patterning method also enables us to selectively deposit amorphous carbon onto a 100-SI Appendix, Fig. S9).We also designed a noncontact method to pattern multiple functionalizations across the graphene surface of a 3-mm support B and C, SI Appendix, Fig. S10 A–D). We also compared these distributions to those on partially hydrogenated graphene and in unsupported ice . We were able to identify a combination of functionalized surfaces which increased the efficiency of the orientation distribution . The clear differences between all observed distributions indicate the particles are interacting with the functionalized graphene; a tomographic reconstruction shows that the particles are in a monolayer on the graphene surface in a layer of ice just thicker than the particle diameter   .SI Appendix, Fig. S10B), consistent with the low pKa of a thiol group. The next most frequent orientation on the carboxylated graphene is with the 50S side of the 30S subunit facing the surface . In contrast, it is underrepresented on amylamine-treated partially hydrogenated graphene which is consistent with the high pKa of an amine group. Of all surfaces tested here, the amylamine/hydrogen-functionalized graphene minimized orientation bias for the specimens tested. Still, some acidic amino acid residues  . Importantly, besides reducing the rate of random (uncorrelated) particle motion, the addition of the graphene layer also reduces the movement during the first few electrons of irradiation, improving the quality (B-factor) of these initial frames  from 41 EM maps . The dec dataset D is simi dataset , 20. We l frames C and D, Multifunctional graphene-on-gold supports provide several improvements over previously described graphene oxide and graphene-on-carbon supports , 21, 22.−/Å2 , which rapidly become uncorrelated. The reduction of the movement in the second, uncorrelated phase may be due to a reduction in the degrees of freedom of the particle adhered to the graphene surface. Still, complete elimination of the initial movement of the specimen would improve the images even further, reducing the movement to the limit set by pseudodiffusion of the particles in ice . One strategy to reach the pseudodiffusion limit is to improve motion correction algorithms by using the graphene lattice as a fiducial, as suggested previously for graphene oxide  in our in-house–constructed graphene CVD system with a 25-mm-diameter reaction tube. Copper foil was cut to 65-mm .8 mTorr . After tSI Appendix, Fig. S2A) was chosen after many tests since it preserves the structural integrity of the gold foil, while keeping the large graphene sheet intact, and provides optimal plastic adhesion for the transfer, conformal coating of the surface of the grid, and subsequent removal of the polymer. Approximately 100 Graphene was transferred onto all-gold grids  using a compliant form of collodion polymer. This method . Transmission electron diffraction experiments were performed on the suspended graphene to assess the structure of the crystals. Weak and monotonic variation of the intensity of the graphene diffraction spots with tilt unambiguously identified suspended monolayer graphene  , meaning one could expect to encounter only one to two grain boundaries per grid square. For this measurement the number of different grain orientations observed in the selected-area electron diffraction pattern was counted while traversing the whole grid in the TEM. We and others have previously characterized the background signal of graphene and hydrogenated graphene vs. thin layers of amorphous carbon and graphene oxide  in secondary electron mode using an Everhart–Thornley detector (A and B) . The meane oxide , 8. We hfor PMMA . We obsePlasma treatments were performed in an extensively modified commercial plasma cleaner (Fischione 1070), equipped with a custom grid and mask holder, a custom gas-injection system A, and a t 656 nm D. We hypX-ray photoelectron spectroscopy (XPS) was used to study the covalent modifications to graphene. The beam from an Al KSI Appendix, Fig. S6F) and to determine the effect of various storage conditions on these properties over time . We used a custom instrument to measure the contact angle of pure water on the grids  which become contaminated and lose their hydrophilicity within 1–10 h. Further work is needed to provide a simple and commercially viable long-term storage container for functionalized grids; a sealed, evacuated glass vial similar to those used for storing chemicals is one possibility.Contact angle measurements were performed to evaluate the surface properties of the support after varying doses of functionalization .Amorphous carbon was deposited directly onto graphene-coated gold grids in an Edwards 306A evaporator evacuated to Specimens were prepared by manual plunge freezing in a −/pixel per frame, 80 K specimen temperature). The illumination was centered over each exposed hole and the beam diameter was set to be slightly larger than the hole to minimize beam-induced motion  were provided by the Ramakrishnan laboratory. The concentration was adjusted to 8 mg/mL, except for the specimen on partially hydrogenated graphene, where the concentration was 1.7 mg/mL. All graphene-coated grids used were first exposed to Purified Micrographs of 30S ribosomes in ice on functionalized graphene were acquired on a Tecnai Polara microscope operated at 300 kV using a Falcon 3 detector in integrating mode. The nominal magnification was 93,000SI Appendix, Fig. S6E). The micrographs were motion corrected in Relion 3 . The bandwidth for the kernel density was set to SI Appendix, Fig. S11).The sectors of the functionalized grids were identified using the asymmetric center mark  was conme  at 37,000× nominal magnification. The movies were motion corrected in MotionCorr  was buffer exchanged into TBE  at pH 8.3 and adjusted to 0.8 mg/mL concentration. Four-quadrant grids were prepared by exposing one-half of the grid to 180 s hydrogen plasma and then rotating the mask by −/Å2/s and the exposure time was 2 s; a 70-μm objective aperture was used. The nominal magnification was 59,000×, corresponding to 1.34 Å/pixel, calibrated using the (101) reflections from anatase .Micrographs were acquired on a Titan Krios microscope operated at 300 kV using a Falcon 3 detector in integrating mode. The flux was set to 17 eEquus caballus) spleen apoferritin (Sigma) was buffer exchanged into 100 nM PBS at pH 7.4 and adjusted to 11.7 mg/mL concentration. Graphene-coated grids treated with He plasma carrying amylamine for 30 s were used. Vitrification was done in the same way as above.Horse . The previously published model  (SI Appel (4V1W ) was fitel (4V1W  and refiel (4V1W , followeel (4V1W . Illustrel (4V1W . This waSupplementary FileSupplementary File