Control over the film-substrate interaction is key to the exploitation of graphene’s unique electronic properties. Typically, a buffer layer is irreversibly intercalated “from above” to ensure decoupling. For graphene/Ni(111) we instead tune the film interaction “from below”. By temperature controlling the formation/dissolution of a carbide layer under rotated graphene domains, we reversibly switch graphene’s electronic structure from semi-metallic to metallic. Our results are relevant for the design of controllable graphene/metal interfaces in functional devices. Interfacial interactions play a key role in tailoring the properties of graphene and other surface-supported two-dimensional 2D) materials. Remarkably, the effect of such interactions is not limited to the film, but extends to the structures in contact with it, e.g. adsorbed atoms1D materia3678Nickel is an appealing choice in the attempt to engineer such a model system, as it is one of the most technologically relevant substrates for graphene production. Among transition metals, it has a low-cost and is widely available; further, it can readily sustain graphene growth by chemical vapour deposition (CVD), with the additional advantage of requiring lower temperatures than other catalysts10111317182021620A striking feature of the nickel-graphene system is the formation of interfacial nickel carbides, which segregate from bulk Ni upon cooling from growth to room temperature (RT) and form exclusively below rotated graphene domainsTo optimize the relative coverage and the size of the rotational domains, we grew graphene on clean Ni(111) by exposing the sample to ethylene at 540–610  °C. Subsequently, the sample was cooled to RT with a cooling rate of about 1 K/s. Following this procedure, graphene displays coexisting EG, RG and RGC domains. Our microprobe low energy electron diffraction (μ-LEED) data show that in micron-sized RG domains, the lattice is preferentially oriented ± 17° from one of the Ni main crystallographic directions, even though domains with different rotation angles are also observed. A statistical analysis of the distribution of rotational orientation of RG regions can be found in the The brightfield (BF) LEEM image in To resolve each phase in real space, we imaged the film using darkfield (DF) LEEM, a method that uses secondary diffracted beams to map the lateral extent of a given surface phase. As shown in A  - surface nickel carbide; Cdis  - interstitial carbon dissolved into the near surface Ni layers; Cgr  - weakly-interacting graphene, identified with the RG domains; and CB  - epitaxial graphene, used as binding energy scale reference. We note that both components originating from below graphene (Cdis and CA) have very low intensity, limited by the low effective photoelectron attenuation length (~4.4 Å) at the kinetic energy usedB, thus indicating that carbon has a similar interaction with the substrate in the two cases. The apparent larger width of the CB peak (~28%) in RG regions is to be expected, considering that, while only two distinct sites contribute to the EG phaseB peak, originating from the adjacent RG regions, which contribute to the spectrum due to the limited lateral resolution of the microscope. However, the main peak is of Cgr type, with a small but evident (see inset) carbide component (CA) on the low-binding energy side. Such a component, absent in the spectrum from region II (see inset), confirms that region III corresponds to the RGC phase. Notably, the lower value of the CGr binding energy with respect to CB is typical of systems characterized by a weak interaction between graphene and the metal supportThe identification of the small patches labelled III is less straightforward. Their localization within the RG phase, small lateral size  ≤ 250 nm) and irregular shape suggest that they correspond to RGC areas, as previously imaged by STM150 nm and 2) comprising domains of both RG and RGC phases.The present results correct our previous indication of a different binding energy for C atoms in the EG and RG phasesF, plus a number of minor features at lower binding energies, already attributed to nickel and hybrid graphene-nickel states7F, as suggested by experiments performed at 40 KThe π band dispersion of the three different graphene phases was investigated by microprobe angle-resolved photoelectron spectroscopy (μ-ARPES). Since our data are collected from a region measuring about 2 microns in diameter, the contributions of the RG or RGC phases in the rotated regions cannot be separated. In 1927F, to image the surface. In the micrographs on the right hand side of In the MDC from mixed RG and RGC regions (D = EF – Ekin = 0.01 ± 0.06 eV). The Dirac energy ED was determined after calculating the intersection point of lines fitting the two branches of the π band, calculated in an energy interval extending 2 eV below EF. These lines were obtained after determining the exact position of each point of the π band branches in the  space. The error bar on ED (95% confidence level) is a consequence of the statistical errors on the intercept and slope of the lines, not of the limited energy resolution of the SPELEEM.The question now arises whether it is possible to control the population of the RGC phase in order to obtain a uniform carbidic buffer and whether this process is reversible. Clearly, such a capability would allow a drastic change in the electronic properties of graphene to be obtained and finely controlled. As shown in our previous work, the RGC phase is not present during growth, but forms only upon cooling towards RTUpon annealing , dissolves once more when it is raised (panels i-l), and so on. It is therefore possible to reversibly switch between the decoupled/coupled states by simply changing the temperature. We note that the switch between RGC and RG takes place only in the (220 °C–370 °C) temperature range. The carbide coverage remains constant upon further cooling below this range (not shown), while annealing in excess may lead to nucleation of bilayer graphene, as occurs for the thin bright stripe in panel (l). The fact that the conversion is active only in a narrow temperature range implies that rapid cooling of the sample from growth to room temperature yields an almost completely carbide free graphene layer. The temperature range where the switch is active is in agreement with previous investigations on the kinetics of C segregation on Ni samples. Indeed, in pioneering experiments, Blakely same rotated regions exist in two states: either decoupled or coupled to the substrate.The microprobe ARPES MDCs for the homogeneous RGC and RG phases (panels n and p) provide unequivocal evidence of the effect of the presence of the surface carbide: while direct strong interaction of graphene with Ni induces the formation of hybrid states and a pronounced modification of its electronic structure, carbide formation underneath the graphene sheet decouples microscopic regions of the layer from the substrateFinally, we have measured at high temperature the MDCs of the EG and RG phases see , observiIn summary, a thorough investigation of the electronic structure of graphene grown on Ni(111) and of its temperature dependence allowed us to devise a strategy to control the graphene-metal coupling. If a surface carbide buffer forms above the topmost Ni layer underneath rotated graphene, the 2D carbon network decouples from the substrate and its semi-metal nature is almost completely restored. Clear evidence is provided that micro-scale carbide domains can be reversibly formed and dissolved by just changing the temperature and deciding the time spent by the sample in the narrow temperature range where the conversion is active. A simple way to vary the graphene/substrate coupling is therefore provided, with significant implications for functional device fabrication and spintronics in particular. The lateral dimension of the switchable regions is only limited by the size of the rotated domains. Systematic studies are ongoing to explore the growth parameter space with the aim of obtaining rotated domains on the millimetre scale. + sputtering at 2 keV and annealing at 600 °C. The cleaning cycles were stopped when the sample did not show any C structure at RT in LEEM and μ-LEED measurements. Growth studies were performed in-situ by maintaining the sample at 540-610 °C while back-filling the chamber with C2H4 (p = 3∙10−6 mbar). The surface evolution during growth was monitored with LEEM.The Ni(111) surface was cleaned with Arstart. The kinetic energy of the electrons scattered (or emitted) by the sample is equal to Ekin = eVstart – δWi-s, the latter being the work function difference between the instrument and the specimen. In our measurements, LEEM was used in both bright and dark-field modes, utilizing, respectively, the zero or first order diffraction beam for imaging. The microscope lateral resolution approaches a few tens of nanometres in XPEEM mode, 9 nm in LEEM; the energy resolution is better than 0.3 eV. Besides imaging, the SPELEEM allows diffraction operation mode. Depending whether the beamline photons or low energy electrons are used as probe, μ-ARPES or LEED measurements can also be carried out. The probed area is defined by inserting a field limiting or illumination aperture in the first image plane along the optical path of the instrument. A 2 μm diameter field limiting aperture was used for μ-ARPES, while for μ-LEED three different illumination apertures were employed . Part of the ARPES measurements was performed using the darkfield PEEM methodThe photoemission microscopy measurements were carried out using the spectroscopic photoemission and low energy electron microscope (SPELEEM) at the Nanospectroscopy beamline of the Elettra synchrotron.How to cite this article: Africh, C. et al. Switchable graphene-substrate coupling through formation/dissolution of an intercalated Ni- carbide layer. Sci. Rep.6, 19734; doi: 10.1038/srep19734 (2016).


PD-L1 is expressed in many cancers, including non-small cell lung cancer (NSCLC). Immune cells play an important part in blocking the “cancer immunity cycle” by binding PD-1Cancer evades host immune surveillance by using immune checkpoints, which are inhibitory pathways crucial for maintaining self-toleranceEGFR) and translocated anaplastic lymphoma kinase (ALK). Majority of patients do not attain prolonged disease control, and 5-year survival rates remain lowPTEN leads to PD-L1 up-regulation in lung squamous cell carcinomaEGFR-mutant NSCLC may be susceptible to PD-1 blockade immunotherapyEGFR-mutant lung tumors inhibit antitumor immunity by activating the PD-1/PD-L1 pathway to suppress T-cell function and increase levels of proinflammatory cytokines; exposure to EGFR-TKIs leads to PD-L1 downregulationTreatment strategies for NSCLC include chemotherapy regimens based on histology and targeted agents for patients who carry somatic activated oncogenes, such as epidermal growth factor receptor  and the other 95 were EGFR-mutant, KRAS-mutant, or ALK translocated. All cases with moderate (+2) or strong staining (+3) in more than 5% of tumor cellsKRAS-mutant adenocarcinoma. By contrast, patients with PD-L1 positive tumors were more likely to be female and/or never or former smokers with EGFR-mutant or ALK-translocated adenocarcinoma histologyA recent study in the EGFR mutations remain controversial. Gettinger et al.EGFR or KRAS mutations did not correlate with response rate to nivolumab for NSCLC patients. Some researchers found that activation of the EGFR pathway induced PD-L1 expression to help NSCLC tumors evade the antitumor immune response,et al.EGFR, KRAS, BRAF, or ALK status in stage I NSCLC patients. Similarly, Zhang et al.EGFR or KRAS in lung adenocarcinoma. Most recently, Ansen et al.EGFR, KRAS, and STK11 in the two most common histological NSCLC subtypes  in the 2014 ASCO Annual Meeting.Until now, the results of the correlation between PD-1/PD-L1 expression and et al.KRAS mutations, whereas PD-L1 positive status was significantly associated with presence of EGFR mutations. Recent data presented by Rizvi et al.D’Incecco POLD1, POLE, and MSH2. Some of these mutations occur in never-smokers with high mutational burden; this finding may explain why some never-smokers may also respond to therapy with PD-1 inhibitorsBesides smoking-related changes, the researchers were also able to identify other mutations present in lung cancer that may contribute to a high mutation burden and response to PD-1 inhibition. Specifically, they noted deleterious mutations in DNA repair and replication genes that have high mutation burden response and high response to pembrolizumab, such as et al.EGFR-mutant patients, TTP to EGFR TKI was significantly longer in PD-L1 positive than negative tumorset al.et al.D’Incecco et al.+ TILs or explore any correlation that may exist between PD-1-positive TILs and expression of PD-L1 on cancer cells.D’Incecco et al.et al.et al. suggest that EGFR-mutant NSCLC is highly eligible for PD-1/PD-L1 immunotherapy, and PD-L1 may represent a favorable biomarker candidate for response to EGFR-TKIs. If this finding is reconfirmed in prospective studies, then immune checkpoint blockade combination with EGFR TKIs could be a major step forward in improving outcomes of EGFR-mutant NSCLC patients.A suitable test should be created to measure PD-L1 expression levels with established thresholds that can be used as a biomarker for anti-PD-1/PD-L1 therapies. A multitude of questions pertaining to companion predictive biomarkers to anti-PD-1/anti-PD-L1 therapies remain unanswered: Which PD-L1 antibody most accurately and reproducibly measures PD-L1 protein expression and predicts response to therapy? Which cutoff should be utilized to determine PD-L1 positivity/negativity? Should PD-L1 protein be measured in the tumor epithelium, stroma, or both? Should a different measure of PD-L1 expression, such as quantitative immunofluorescence or RNA, be used instead of standard immunohistochemistry protein methodology? Which additional components, such as TILs, PD-1, or PD-L2, play a role in predicting response? Currently, the various assays tend to be propriety to each of the groups developing the antibodies. Most assays examine PD-L1 staining on the tumor. Based on recent data from Herbst


In live Drosophila fat body tissue from third instar larvae, ReZolve-L1™ interacted mainly with lipid droplets, including the core region of these organelles. The presence of polar lipids in the core of these lipid droplets was confirmed by Raman mapping and while this was consistent with the distribution of ReZolve-L1™ it did not exclude that the molecular probe might be detecting other lipid species. In response to complete starvation conditions, ReZolve-L1™ was detected mainly in Atg8-GFP autophagic compartments, and showed reduced staining in the lipid droplets of fat body cells. The induction of autophagy by Tor inhibition also increased ReZolve-L1™ detection in autophagic compartments, whereas Atg9 knock down impaired autophagosome formation and altered the distribution of ReZolve-L1™. Finally, during Drosophila metamorphosis fat body tissues showed increased ReZolve-L1™ staining in autophagic compartments at two hours post puparium formation, when compared to earlier developmental time points. We concluded that ReZolve-L1™ is a new live cell imaging tool, which can be used as an imaging reagent for the detection of polar lipids in different intracellular compartments.Lipids have an important role in many aspects of cell biology, including membrane architecture/compartment formation, intracellular traffic, signalling, hormone regulation, inflammation, energy storage and metabolism. Lipid biology is therefore integrally involved in major human diseases, including metabolic disorders, neurodegenerative diseases, obesity, heart disease, immune disorders and cancers, which commonly display altered lipid transport and metabolism. However, the investigation of these important cellular processes has been limited by the availability of specific tools to visualise lipids in live cells. Here we describe the potential for ReZolve-L1 The. The™ lotructure . The loc675 cm-1 , as the 675 cm-1 , and spe1780cm-1 , which i-1 attributed to the ν(P-O), which is unique to phospholipids, such as phosphatidylcholine, phosphatidylethanolamine and sphingomyelin [ν(P-O) band (from the second derivative) with the ν(C = O) band, for the detection of triglycerides and sterol esters [™ in the lumen of Drosophila fat body lipid droplets.Further interrogation of the second derivative of the spectra taken from the lipid droplet revealed the presence of a band at ~ 1096cmgomyelin  Fig 3C)-1 attribl esters  it was pex vivo models  combined with Raman spectroscopy of both a 3T3 adipocyte cell line and Drosophila tissue provide evidence for the localisation of ReZolve-L1™ in cells with polar lipids. With the Raman data suggesting that lipid droplets are more heterogeneous in lipid composition, which may account for the dispersed staining of lipid droplets with ReZolve-L1™, rather than an interaction with non-polar lipids. However, it should be noted that this does not discount an interaction between ReZolve-L1™ and non-polar lipids (such as CEs and/or TAGs), but that the evidence suggests a preferential interaction with polar lipids. The authors suggest that the observed localisation patterns of ReZolve-L1™ is not due to an interaction with one ‘specific’ lipid, but more closely aligned with the polar lipid families and localisation pattern may in fact be the result of a particular combination of lipid(s).The accumulation of data from both the ™ could also detect autophagosomes, Drosophila fat bodies expressing the autophagic marker Atg8-GFP were stained with ReZolve-L1™ following exposure of the larvae to different autophagy inducing starvation conditions. Staining with Oil Red O was performed in parallel to allow for a comparison between a purely non-polar lipid dye and ReZolve-L1™; and to provide further evidence of the greater affinity for polar lipids.Autophagosomes are cellular compartments that are involved in cell degradation and like lipid droplets can accumulate lipids from a range of cellular components , 60. Pro™ was detected mainly in lipid droplets , these compartments had minimal to no Oil Red O staining  [TorTED reduced the fat body volume in larvae at later developmental time points, which prevented the analysis. TorTED expression increased the number of autophagic compartments detected by LysoTracker® Green in larval fat body tissue [® Green compartments detected in response to TorTED expression were co-stained by ReZolve-L1™, but there were some compartments that appeared to contain either only LysoTracker® Green or only ReZolve-L1™  , 63. Faty tissue , when coolve-L1™ . In contartments  and was artments . This ag™ to autophagic compartments, autophagosome formation was disrupted by RNAi silencing of the core autophagy protein Atg9 [Atg9RNAi, under the control of the fat body specific driver CG-GAL4, were either fed on standard media, or amino acid and sugar starved for four hours. In the control and Atg9RNAi fed larvae ReZolve-L1™ was detected in lipid droplets and was not detected in LysoTracker® Green compartments . At -4 h PF ReZolve-L1™ was detected primarily in lipid droplets and not in LysoTracker® Green compartments  and these compartments had some ReZolve-L1™ staining Drosophilysosomes . In addiysosomes . These fDrosophila fat body tissues. In these tissues ReZolve-L1™ was also localised to lipid droplets and was detected throughout the organelle. Although the mode of action of ReZolve-L1™ requires further analysis, lipid overlay experiments, liposome affinity experiments and Raman mapping of stained adipocytes showed positive correlations between ReZolve-L1™ and polar lipids to a much greater extent than neutral lipids. Although we cannot rule out that the lipophilic nature of ReZolve-L1™ drives the localisation of this molecular probe to the lipid droplet core, it is speculated that ReZolve-L1™ is localising with and hence detecting polar lipids in both the outer membrane and the core of lipid droplets. This hypothesis is supported by Fourier transform infrared microspectroscopy, which demonstrated a correlation between the location of polar lipid species such as phosphatidylethanolamine and sphingomyelin and ReZolve-L1™ in 3T3-L1 adipocytes [™ was most often detected in lipid droplets and was rarely associated with other cellular membrane structures where polar lipids are known to be abundant. This lack of other cell membrane staining may indicate that polar lipid packing in these membranes prevents ReZolve-L1™ interaction or that the interaction site is masked, or alternatively that ReZolve-L1™ only detects certain combinations of polar lipids.Lipid droplets are most often described as cytosolic organelles consisting of a neutral lipid core, surrounded by a monolayer of phospholipids , 70. Altipocytes . Interes™ was detected in autophagic compartments in response to certain starvation conditions, the inactivation of the target of Rapamycin (TorTED), or developmental cues. The ReZolve-L1™ staining of lipid droplets was also altered in response to these cues, and these changes in distribution may involve the trafficking of polar lipids during interactions between lipid droplets and autophagosomes.Autophagy has a pivotal role in lipid localisation, for example, to orchestrate the vesicular traffic and secretion of triglyceride rich lipoproteins, as well as to mediate the transient storage of lipids in lipid droplets , 76, 77.™ appeared to be directed to autophagosomes as a selective response to certain autophagic cues, rather than as a general response to autophagy induction. Under conditions of partial nutrient restriction by amino acid starvation, autophagosomes were formed, but ReZolve-L1™ had little interaction with these autophagic compartments. This would suggest that ReZolve-L1™ did not detect the polar lipids acquired from all cellular organelles that might be degraded under these conditions. ReZolve-L1™ did, however, co-locate with Atg8-GFP autophagic compartments following combined amino acid and sugar starvation, which indicated that it was recognised a specific event during autophagy. Amino acid and sugar starvation did induce lipid droplet degradation via autophagy, as shown by Oil Red O co-localisation with autophagosomes. While it is commonly accepted that neutral lipids are transferred to autophagic compartments in response to autophagy induction, by either combined amino acid and sugar starvation or the inhibition of Tor [™ detects polar lipid sequestration from lipid droplets by autophagosomes under these conditions. The down regulation of autophagy by genetic inhibition is known to reduce lipid transfer from lipid droplets to autophagosomes [™ detection in autophagosomes following autophagic reduction by Atg9RNAi knock down. Atg9RNAi knock down did not completely abrogate autophagic progression [™ positive structures near the periphery of the lipid droplets; which could be indicative of altered autophagosome formation and reduced incorporation of lipid into autophagosome membrane, a process in which Atg9 is suggested to be involved [Drosophila fat body, if lipid membrane content in autophagosomes is increased under certain conditions, however this may be an alternative explanation for the detection of ReZolve-L1™ in autophagic compartments.The lipids detected by ReZolveL1n of Tor , 62, 63,n of Tor , 80. Thuagosomes , 81, andgression , but cauinvolved , 83. Theinvolved . It is u™ had an altered staining pattern upon sugar starvation alone, but unlike exposure to combined amino acid and sugar starvation, similar changes were not observed in Oil Red O staining. This difference in staining patterns supports the interaction of ReZolve-L1™ with lipids that are distinct from the neutral lipids detected by Oil Red O. Furthermore, this suggested that the polar lipids detected by ReZolve-L1™ have increased association with autophagic compartments during the energy depravation induced by sugar starvation. The induction of autophagy by most signalling pathways converge at TOR but in contrast, energy depletion can lead to the direct activation of autophagy via interactions between energy sensing AMPK and the autophagy initiator Atg1/ULK1 [™ staining was detected throughout the cells with some brighter puncta seen localising with autophagic structures, unlike the staining observed following combined amino acid and sugar starvation, which was highly concentrated in autophagic compartments. This suggested a change in polar lipid distribution under these conditions, which may be associated with either an alternative signalling pathway being activated or a specific event in autophagosome maturation.Interestingly, ReZolve-L1tg1/ULK1 . FollowiDrosophila development, autophagy is important for the degradation and remodelling of larval tissue, including the fat body [Drosophila, and these lipids can be mobilised to provide energy or used as structural lipids for developing tissues during metamorphosis [Drosophila, the mobilisation of lipids during metamorphosis is in part facilitated by lipases, such as the lipid droplet associated Brummer and lysosomal acid lipase-1 [Drosophila metamorphosis [Drosophila fat body, at the later developmental stage of +2 h PF, ReZolve-L1™ staining was detected in autophagic compartments that were co-stained by LysoTracker®Green and Atg8a-GFP. Neutral lipids were also detected in these autophagic compartments at +2 h PF, which provided the first evidence of autophagy as a route for lipid delivery to the lysosome during metamorphosis. The detection of both neutral and polar lipids in the autophagosomes at the later developmental time point may also indicate that bulk degradation of lipid droplets is occurring at this stage.During fat body , 86. Theorphosis , 87. In lipase-1 . The invlipase-1  and the lipase-1  has led orphosis . In Dros™ appears to be able to identify the transfer of polar lipids from lipid droplets to autophagic compartments under conditions of high energy demand and during developmental autophagy. By reporting on this dynamic balance between lipid droplets and autophagic compartments during different energy requirements, ReZolve-L1™ has the potential to define new aspects of cellular lipid metabolism. ReZolve-L1™ overcomes many of the critical limitations for conventional molecular probes, including photobleaching, extended sample preparation, and the need for cell fixation, which could enable live cell imaging of specific metabolic events.There is a paucity of live cell imaging molecular probes available, to allow the specific investigation of lipids and to support the wider field of lipid metabolism. ReZolve-L1™ could be used to visualise the pathology in for example: the altered lipid metabolism associated with fatty liver disease; the increased autophagy and altered degradation of lipids observed in Alzheimer’s disease; the altered cholesterol deposition and plaque formation in cardiovascular disease; or the altered balance between lipid metabolism and autophagy in cancer. Therefore ReZolve-L1™ may provide a promising new tool for the live cell imaging of polar lipids and autophagy that has practical applications for both cell biology research and clinical diagnosis/prognosis.The bidirectional interaction of autophagy and lipid metabolism has important implications for disease pathophysiology and there is a defined need to develop new imaging technology for these disease processes . Consequiso-propanol for loading depending on solubility. Following lipid loading, the PVDF membranes were washed for 10 minutes in cold 10% ethanol, methanol or PBS, before they were incubated with 10μM of rhenium molecular probe in PBS for 1h. The neutral rhenium(I) species, ReZolve-L1™, was prepared according to a previously published procedure [To determine the binding properties of the rhenium molecular probe, a lipid overlay was performed. 50 μM of each lipid was loaded on to a PVDF membrane . Ten lipids were analysed including; sphingomyelin , sphingosine , ʟ-α-phosphatidylethanolamine , monosialodanglioside , oleoly-ʟ-α-lysophosphatidic acid , palmitic acid , cholesterol , ceramide , triacylglycerol mix C2-C10  and cholesteryl acetate . Lipids were dissolved in ethanol or sn-glycero-3-phosphocholine  and cholesterol , were dissolved in 2:1 chloroform:methanol at 20 mg/mL. Lipid mixtures were formed by evaporating liquid 666 μL DMPC alone or a mixture containing 443 μL of DMPC and 32 μL of cholesterol (8:1 molar ratio). The lipid mixture was then resuspended in 1 mL PBS and sonicated for 40 minutes. Following sonication liposomes were passed through an extruder with a 100 nm membrane 15 times. Liposome formation was confirmed using a Malvern Zetasizer DLS system. Mixtures were run through a Sephadex G-25 column to ensure no free lipid was present in solution. Fraction containing particles of approximately 100 nm (ascertained by DLS) were incubated with ReZolve-L1™ for 40 minutes. Solutions were then passed through a Sephadex G-25 column to remove unbound stain and fraction containing vesicles of approximately 100 nm were tested for fluorescence’s by flow cytometry and fluorometry.1,2-dimyristoyl-4 events were collected using 40x objective and camera with pixel size of 0.5 μm. Vesicles were identified by their low SSC signal and high fluorescence (405/560-595 nm) values; the accuracy of this separation was proven by viewing the images of single events.For analysis of vesicles by flow cytometry an Amnis ImageStreamX Flow Cytometer mkII (EMD Millipore) was used. Vesicles were excited with 405 nm laser (120 mW) and fluorescent data between 560–595 nm were collected. In parallel, data for forward scatter (FSC) and side scatter (SSC) light  were collected. Core diameter of the flow was 10 μm and flow speed was 66 mm/sec. Calibration beads (2 μm in diameter) were run in parallel to the samples. For each sample, images for 1.5–5.0x10™.For analysis of vesicles by fluorescence a Varian Cary Eclipse spectrophotometer was used. Vesicles were excited at 256 nm and emission was collected from 350–700 nm. Vesicles were tested for fluorescence before and after incubation with ReZolve-L1GAL4-UAS system was used for targeted gene expression [CG-GAL4 [UAS-Atg9RNAi stocks (#34901) and UAS-TorTED stocks (#7013) were obtained from the Bloomington Drosophila Stock Centre . Atg8a-GFP was driven by an endogenous promoter [Mammalian 3T3 adipocytes were obtained from culturing and differentiated the 3T3 pre-adipocyte fibroblast on calcium fluoride slides for Raman microscopy, as previously described  for a mipression . Fat-bod[CG-GAL4 . Transgepromoter  and was Bromophenol-blue was added to the fly media and used to define different developmental time points . Third iThird instar larvae at -8 h puparium formation (PF) were removed from standard media and placed on filter paper either soaked in 5% (w/v) sucrose (for amino acid deprivation), or 5% (w/v) tryptone pancreatic digest of casein , or soaked in water (for amino acid and sugar starvation). Larvae were incubated at 25°C for 4–5 hours prior to tissue isolation and imaging.™ was prepared according to a previously published procedure [™ was dissolved in DMSO to prepare a 10 mM stock solution, which was diluted in PBS to 10 μM for tissue staining. For Raman confocal microscopy, 3T3 cells were fixed using cold methanol and air dried [™ overnight. Fat body tissue was dissected from Drosophila larvae or pupae into PBS. For Raman confocal microscopy, the tissue was fixed in 4% paraformaldehyde  ready for mapping. For live confocal and two photon microscopy, the fat body tissue was incubated with ReZolve-L1™ for 15 minutes at room temperature and washed in PBS for 30 seconds. Tissues were counterstained for acidic compartments with LysoTracker® Green  for 2 minutes at room temperature. Tissues were then mounted in carbomer-940  based optical coupling gel to prevent dehydration prior to imaging; see protocol in [The neutral rhenium(I) molecular probe ReZolve-L1rocedure . ReZolveir dried  before btocol in . For Oil™ HR mapping. The spectrometer was fitted with holographic notch filters and 2400 mm/line (NIR) grating. The attached microscope was a Leica DMLM and was equipped with three objectives  and a trinocular viewer that accommodates a video camera allowing direct viewing of the sample. Sample excitation was achieved using a Modu-Laser  emitting at 785 nm. Calibration of the wavenumber axis is achieved by recording the Raman spectrum of silicon  for both static and extended modes. If necessary an offset correction is performed to ensure that the position of the silicon band is at 520.50 ± 0.10 cm-1. Spectra were not corrected for instrument response. The spectrometer was controlled by PC with instrument control software . The Raman maps were acquired using a step size of 2 μm for both x and y axes over the spectral range of 700–1850 cm-1.Raman spectra were collected using a Renishaw Raman inVia Reflex Microscope , equipped with an air-cooled charge-coupled device (CCD) cameras for StreamLineCosmic rays were removed from the spectral data using a nearest neighbour cosmic ray removal method and noise filtering was applied using the Renishaw WiRE 4.2 software. The false colour maps shown generated from the data using the direct analysis approach by calculating the area under bands of interest using the signal-to-baseline mode.®  was used for live imaging. The images were acquired using a Plan- APOCHROMAT 63X/ NA1.4 oil immersion objective. ReZolve-L1™ was excited at 830 nm using the two-photon pulse laser and detect at 600–654 nm. LysoTracker® Green was imaged by excitation at 488 nm and detected at 497–558 nm. Atg8a-GFP was imaged with ReZolve-L1™ by excitation at 830 nm (to excite both fluorophores) and resolved using spectral un-mixing using the Zen software package . A spectral profile for ReZolve-L1™ was acquired in lambda stack mode .A Ziess LSM710 META NLO confocal microscope , supplemented with a two-photon Mai-Tai™ images and co-location analysis involved at least five separate images from five independent biological replicates, and one representative image from each treatment was selected for presentation. For image quantification, two regions of interest (ROI) were selected at random, with an area of 2500 μm2 and the number of compartments stained with ReZolve-L1™ and LysoTracker®Green were counted to give a minimum of ten counts per treatment group. Comparison of means was performed by ANOVA with a Tukey post hoc tested in GraphPad Prism V.6.01 (USA).The ReZolve-L1S1 FigA) and DMPC and cholesterol vesicles (DMPC:cholesterol 8:1 molar ratio) (B) incubated with ReZolve-L1™ when excited at 405nm and representative fluorescence and transmitted lights images of vesicles by flow cytometry. (C) Fluoroscence spectra of liposomes alone (dashed grey line), ReZolve-L1™ alone (dotted grey line) and liposomes incubated with ReZolve-L1™  when excited at 256nm.Histogram showing fluorescence intensity 560-595nm of DMPC vesicles ((TIF)Click here for additional data file.S2 FigA) Structure and Raman spectrum of ReZolve-L1™ and (B) the second derivative of this spectrum. (C) Second derivatives of Raman spectra taken from a ReZolve-L1™ stained 3T3 adipocytes from a region of high (a) medium (b) and low (c) ReZolve-L1™ presence.((TIF)Click here for additional data file.S3 FigRepresentative Raman spectra from the lipid droplet core of -4 h PF larval fat body tissue. Corresponding second derivatives are presented above each of the five spectra. Important lipid regions are shaded and assigned above.(TIF)Click here for additional data file.S4 FigA) Confocal micrographs of Drosophila fat body cells explanted from +2 h PF from pupae expressing Atg8a-GFP (green) and stained with ReZolve-L1™ (red). (B) Confocal micrographs of Drosophila fat body cells explanted from +2 h PF from pupae expressing Atg8a-GFP (green) and stained with Oil Red O (red). LD indicates lipid droplets arrows indicate co-location between ReZolve-L1 or Oil Red O and Atg8a-GFP autophagic compartments. Scale = 10 μm.((TIF)Click here for additional data file.


PD-L1 regulates CD8 T cell/Th1 immune responses. PD-L1 expressed in the tumor microenvironment can bind to PD-1 or B7.1 on activated T cells and mediate cancer immune evasion. MPDL3280A is a human mAb containing an engineered Fc-domain designed to optimize efficacy and safety that targets PD-L1 and blocks it from binding to its receptors.Immunologic pharmacodynamics effects were evaluated in tumors and bloods from patients treated with MPDL3280A. MPDL3280A was administered IV q3w in >300 pts with locally advanced or metastatic solid tumors. PD-L1 and CD8 were measured by IHC. PD-L1 expression was evaluated in tumor and intra-tumoral immune cells. CD8 was assessed in the tumor center, periphery and invasive margin. The expression of ≈90 immune-related markers was evaluated at baseline (BL) and on-treatment using a custom-designed immunochip. BL tumor samples were available for 125 pts, and matched on-treatment samples were available for 31 pts. Further, blood-based biomarkers and circulating immune subsets were serially measured in 114 patients by modified ELISA and FACS, respectively.On treatment, responding tumors showed increase in expression of tumor cell PD-L1 and infiltration of CD8+ T-cells and a Th1-dominant immune infiltrate, providing evidence for adaptive PD-L1 up-regulation. Non-responders showed minimal tumor CD8+ T-cell infiltration and an absence of T-cell activation . We also profiled circulating biomarkers for their association with clinical outcomes. A sub-population of patients, including those with RCC and melanoma, exhibited elevated PD-L1 expression on circulating T-cells at BL that was associated with response to MPDL3280A. On treatment, we observed a delayed increase in frequency of CD4+ICOS+ and CD4+PD1+ T-cells in patients responding to MPDL3280A monotherapy. In contrast, frequency of CD8+HLA-DR+Ki67+ T-cells increased shortly following the first dose of MPDL3280A and returned to baseline levels by the end of cycle 2 when assessed in all patients, representing a transient pharmacodynamic measurement of PD-L1 inhibition. On-treatment, increase in plasma IL-6 was associated with disease progression. Associations with other circulating markers of inflammation including CRP with clinical outcomes will be presented.Our data show that changes in pharmacodynamic immune markers are associated with clinical outcomes to MPDL3280A. These data provide mechanistic insights into immune checkpoint inhibition in cancer and identify potential biomarkers that may be monitored as on-treatment markers of clinical activity for patients treated with inhibitors of PD-L1/PD1 pathway.


Pulse generation often requires a stabilized cavity and its corresponding mode structure for initial phase-locking. Contrastingly, modeless cavity-free random lasers provide new possibilities for high quantum efficiency lasing that could potentially be widely tunable spectrally and temporally. Pulse generation in random lasers, however, has remained elusive since the discovery of modeless gain lasing. Here we report coherent pulse generation with modeless random lasers based on the unique polarization selectivity and broadband saturable absorption of monolayer graphene. Simultaneous temporal compression of cavity-free pulses are observed with such a polarization modulation, along with a broadly-tunable pulsewidth across two orders of magnitude down to 900 ps, a broadly-tunable repetition rate across three orders of magnitude up to 3 MHz, and a singly-polarized pulse train at 41 dB extinction ratio, about an order of magnitude larger than conventional pulsed fiber lasers. Moreover, our graphene-based pulse formation also demonstrates robust pulse-to-pulse stability and wide-wavelength operation due to the cavity-less feature. Such a graphene-based architecture not only provides a tunable pulsed random laser for fiber-optic sensing, speckle-free imaging, and laser-material processing, but also a new way for the non-random CW fiber lasers to generate widely tunable and singly-polarized pulses. Q-switching, are generally not applicable to random fiber lasers with random feedbacks14Random lasers have received considerable attention due to the unique properties that distinguish them from conventional resonant cavity lasers, including modeless, cavity-less, low coherence output, simple design, and good reliability operation12457891112Q-switching have been examined31Graphene is an attractive two-dimensional material with a variety of exceptional electronic and photonic properties, and has been proposed in various applications16171920222324262728303133351420213638D-shaped fiber (GDF), the continuous wave (CW) from the arbitrarily-polarized random fiber laser is transformed into coherent sub-nanosecond pulses even in the non-resonant single-pass configuration. The PR and the GDF hybrid waveguide serves simultaneously as the linearly polarized pulse generator (polarization modulation) and the pulse reshaper (saturable absorption). The pulses generated from the GDF not only inherit merits of the CW random fiber laser such as a high pump-power Stokes conversion efficiency, but also offer unique advantages such as a power-dependent singly-polarized output with polarization extinction ratios up to 41 dB, and wide tunability in both pulsewidths and repetition rates, across two and three orders of magnitude respectively.Here we report graphene-based pulse generation with cavity-free random fiber lasers, for the first time. By dynamically modulating the polarization via a polarization rotator (PR) and then transmitting through a designed graphene-coated x-polarization transmission filter. With the x-polarization periodically modulated by the PR, the transmission is a sinusoidal-like temporal wave after passing the GDF. Simultaneously, with Pauli blocking and self-phase modulation at high input powers212228Ex-field distribution is shown in D-shaped fiber without graphene coverage, the x-polarized component and the y-polarized component have almost equal intensity. In comparison, with graphene cladding, the electromagnetic field distribution is pulled close to the graphene film and the x-polarized component is much stronger than the y-polarized component. With the graphene-based evanescent field enhancement, the transmitted CW random lasing field interacts slightly with the graphene film (detailed in With the finite element method (FEM), an example modeled D-shaped fiber was carefully polished with good uniformity and small surface roughness, with an insertion loss less than 10 dB over a polished length of 20 mm. Detailed fabrication process is shown in D-shaped fiber, under 633 nm transmission for clarity. In order to prepare high-quality graphene film and transfer it to the D-shaped fiber properly, monolayer CVD graphene was usedD-shaped fiber surface with good flatness and uniformity, even when the fiber was polished down with 58 μm depth (details in The A high-power CW laser at 1455 nm serves as the pump for the random fiber laser. After the accumulation of Rayleigh scatterings and Raman effects in a 50 km single mode fiber (SMF), a CW random fiber laser at 1550 nm is obtained. Random fiber lasers with other wavelengths are also achievable from their stimulated Raman scattering naturex-polarization was approximately −22 dBm, while the transmission in the y-polarization was approximately −57 dBm for a PER in excess of 34 dB. When the launched power of the GDF increases gradually, saturable absorption begins to occur along the GDF. x-polarized laser launched in the GDF increased from 1 mW to 2.9 W, the transmittance of the GDF increases from ~0.05% to ~3.4%. Contrastingly, for the y-polarized laser with launched power of 2.9 W, the transmission stays predominantly constant with only a 0.0002% increase, within the noise level and negligible. This indicates that much higher power is needed to use the y-polarized light to saturate the GDF. Such a polarization-dependent saturable absorption is determined compositely by the polarization dependent transmission of the waveguide, and the polarization dependent nonlinear response of graphene.The polarization output of the random fiber laser is next modulated periodically using the PR, with a rotation speed tunable from 1 kHz to 3 MHz, prior to launching into the GDF. The power-dependent polarization selectivity and saturable absorption of the GDF are shown in The polarization properties of the graphene based random fiber laser are shown in The intensity dynamics after the PR are measured by a real-time oscilloscope, comparing before and after the GDF. Under 2.8 MHz rotation, The correspondingly pulse spectra is shown in x-polarization. The PER reaches ~41 dB at ~2.88 W, one of the highest values observed for high power polarizers.QP = EFWHM/E0, here EFWHM is the energy in the full width at half maximum (FWHM) of the pulse, E0 is the energy of the pulse integrated over its periodQP > 70%. However, limited by the background noise and instability of the PR, the measured pulse quality is relatively lower. In the experiment, the maximum measured QP is 50.9%, with launched power 2.88 W and repetition rate 3 MHz.In addition, as the pulses are gradually compressed from the initial sinusoidal-like wave, a weak sinusoidal-like envelope is always persistent at the pulse pedestal, distinct from conventional cavity solitons or cavity mode-locking. Such a residual pedestal would deteriorate the pulse quality, which could be described as Distinct from conventional mode-locking lasers, pulse generated by the single-pass GDF configuration is compressed from sinusoidal-like envelope. To achieve short pulsewidth and acceptable pulse quality, relatively high launched power and fast PR is necessary. However, to generate pulses with cavity-free random fiber lasers, external methods are necessary. Fortunately, the GDF based pulse generation has exceptional properties, and could be further improved in the future, by optimizing the smoothness/uniformity of the GDF, the performance of the PR, and increasing the launched power or the modulation speed of polarization.In addition, beyond the random fiber lasers, the graphene based pulse generator could also be widely applied on typical non-random CW lasers in common fiber systems, as the polarization selectivity and the saturable absorption of the GDF is unique and universal. Hence, it provides a new way for the non-random CW lasers to generate widely tunable and singly-polarized pulses.In summary, we have demonstrated a graphene based 900 ps and widely-tunable pulse generation, with up to 41 dB polarization extinction for random fiber lasers. The single-pass configuration affords unprecedented widely-tunable pulses over two orders of magnitude in pulsewidth and three orders of magnitude in repetition rate, drawing from the synergistic advantages of graphene photonics and random fiber lasers. This not only inspires exploration of the full potential of graphene-based fiber devices for ultrafast photonics, but also the realization of pulsed random fiber lasers towards sensing, imaging and laser-material processing applications.D-shaped fiber (GDF), the polarization-dependent transmission, and fast pulse generation were theoretically investigated and numerically simulated. To estimate the power density in the GDF, the field distribution of the graphene-coated D-shaped fiber was simulated by COMSOL (considering the index of graphene to be determined by its conductivity) by applying εg,eq = −σg,i/ωΔ + iσg,r/ωΔ and ω2μ0ε = n2k02; see D-shaped fiber, the CW light from the random fiber laser would be transformed into highly polarized pulses with power that varies with time.The electric field distribution of the graphene-coated 3 solution, a soft and flexible PMMA/graphene was prepared. Thirdly, the PMMA/graphene hybrid was covered on the polished surface of a D-shaped fiber, which was carefully fabricated with the polished depth of 58 μm and polished length ~20 mm. Finally, the PMMA was removed by acetone vapor. The D-shaped fiber and graphene were clearly identified and characterized using optical microscopes (OPM), scanning electronic microscopes (SEM), and a Raman spectrum analyzer. More details are shown in The GDF samples were fabricated by following steps. Firstly, graphene was grown by using the CVD method on Cu foil. Secondly, after removing Cu by FeClD-shaped fiber can reach 3.5 W. The power meter with resolution of 0.1 dBm was used to detect the output power at 1550 nm. The transmittance could be calculated as PB/PA. Figure S5 in A polarization controller (PC) is used to adjust and fix the input polarization. The power launched into the graphene-coated To verify the broadband polarization selectivity of the GDF, an experimental setup was built as shown in How to cite this article: Yao, B. C. et al. Graphene based widely-tunable and singly-polarized pulse generation with random fiber lasers. Sci. Rep.5, 18526; doi: 10.1038/srep18526 (2015).


A so called all-carbon based graphene field effect transistor (GFET) in which the electrodes are composed of graphite-like nano-sheets instead of metals in the traditional devices is fabricated by one-step e-beam direct writing (EBDW). It is also found that the graphite-like nano-sheets in electrodes are perpendicular to the channel graphene, which is confirmed by the transmission electron microscopy (HRTEM). The one-step fabrication of the carbonaceous electrodes is more convenient and lower-cost comparing to the preparation of traditional metal electrodes and can be applied to many other nano-electronic devices. The resistivity of the carbonaceous electrode is measured to be about 4.8 × 10−3 Ω · cm [Supporting Information], which is much smaller than that of a heavily doped silicon  was employed to analyze the negative PMMA. The sample for the HRTEM was directly prepared on a Cu grid via the same processes and conditions in the et al.40The graphitization of the negative PMMA may originate from two concurrent processes: the lost of oxygen and hydrogen atoms (i.e. the deoxygenation and dehydrogenation) and the self-assembling of carbon-carbon (C-C) covalent bonds. Hydrocarbon gas can be decomposed into amorphous carbon by losing oxygen and hydrogen atoms under high-intensity electron irradiation in electron-beam-induced deposition (EBID) process3840et al.An interesting and important phenomenon revealed by the HRTEM images is that the graphitic nano-sheets in the annealed PMMA film are “standing” rather than “lying” on the substrate. Since the HRTEM gives a top-down view of the sample, the presence of the layer-by-layer structures with the spacing of about 0.33 nm in the HRTEM images taken at different areas of the cross bar on the Cu grid indicates that the graphite sheets in the negative PMMA are perpendicular to the substrate, which is consistence with the report by Duan It is convinced that the electrode/graphene contact could be fabricated as the vertical contact between graphite sheet and graphene if the negative PMMA was used as the electrodes in GFET. Based on the analysis above, the microstructure of the all-carbon based GFET can be sketched diagrammatically, as shown in 2 and etched to a ribbon with the width of 3 μm using O2 plasma with the assistant of EBL. The conductive silicon substrate is used as a back-gate of the GFET. From the scanning electron microscope (SEM) image of the To characterize the graphene in the channel after annealing at the temperature of 800 °C, the Raman spectra of the graphene in the channel before and after the annealing were measured, as shown in 44−4 Pa by a Keithley 4200 analyzer at room temperature, and the carrier mobility of ~3700 cm2/V/s of this GFET was obtained from the fitting of the transfer characteristic curve. The Dirac point (the minimum of the transfer characteristic curve) was at about −2 V, indicating that the device was slightly n-type doped. In our previous work2/V/s to the electrons and ~1750 cm2/V/s to the holes, which is however not so obvious in the all-carbon based GFET as shown in the Any adjacent pair of electrodes in the In summary, we have fabricated a kind of all-carbon based GFET with the carbonaceous electrodes and the channel graphene. The fabrication method of the all-carbon based GFET is simple, convenient and accurate because the electrodes are directly written out by e-beam on a PMMA film. In spite of the simpler and lower cost of the fabrication, the performance of the all-carbon based GFET is totally comparable to the metal contacted GFET from the I–V and field-effect characteristics. It is found that the carbonaceous electrodes are composed by graphite nano-sheets perpendicular to the graphene in the channel. Such vertical contacts between the graphite and graphene supplies a potential choice for the electrode/graphene contact in high-performance GFET.2 for actual) to improve the conductivity of the negative PMMA parts.First, a PMMA  film was spin-coated on a SiO2/Si substrate followed by 180 °C baking on a hot-plate for 1 minute. Second, the PMMA film was irradiated by a focused e-beam (FEB) in an EBL system (FEI 600i) to define the patterns for electrodes. During the irradiation process, the accelerating voltage and the current of the FEB were 10 kV and 1.4 nA, respectively. In order to transform the PMMA film to a negative resist, the irraidaiton dose should be exceeded 50 times more than the normal dose for a positive PMMAHow to cite this article: Chen, W. et al. All-carbon based graphene field effect transistor with graphitic electrodes fabricated by e-beam direct writing on PMMA. Sci. Rep.5, 12198; doi: 10.1038/srep12198 (2015).


The motivation behind this work is to study the gas phase chemical sensing characteristics of optical (plasmonic) nano-antennas (ONA) and graphene/graphene oxide-covered versions of these structures. ONA are devices that have their resonating frequency in the visible range. The basic principle governing the detection mechanism for ONA is refractive index sensing. The change in the concentration of the analyte results in a differing amount of adsorbate and correlated shifts in the resonance wavelength of the device. In this work, bare and graphene or graphene oxide covered ONA have been evaluated for gas sensing performance. Four different analytes  were used in testing. ONA response behavior to different analytes was modified by adsorption within the graphene and graphene oxide overlayers. This work is a preliminary study to understand resonance wavelength shift caused by different analytes. Results imply that the combination of well-structured ONA functionalized by graphene-based adsorbers can give sensitive and selective sensors but baseline drift effects identified in this work must be addressed for applied measurements. Presently, solid-state sensors are most prominently used for gas phase chemical detection1Plasmonic structures have been widely used for biological sensing810In this work, an array of dipole structures is designed as an ONA with resonance frequency in the visible spectrum. The array structure enhances the spectrum response of the ONA. The ONA was chosen with a bulk sensitivity of 450 nm/RIU. Response of the bare ONA for four different analytes  was studied. A shift of 0.5 nm to 3.5 nm in the resonance peak was observed. Motivated by a desire to attain greater sensitivity and selectivity than the bare ONA, we tested the same four analytes on graphene coated and graphene oxide coated ONA structures. We observed a much larger frequency shift with graphene and graphene oxide covered ONA. Bare ONA exhibits only a red shift when exposed to all the analytes. Graphene and graphene oxide coated ONA exhibited a blue shift when exposed to toluene and a red shift when exposed to the other three analytes. In this work, there was no baseline drift observed for the bare ONA sensor. However, graphene and graphene oxide coated ONA exhibited baseline drift apparently arising from residual adsorbed gas molecules. We propose a suggested mechanism for the frequency shifts observed for graphene and graphene oxide coated ONA for different analytes.μm as shown in ONA were prepared using e-beam lithography, metal deposition and lift-off as mentioned in the literatureThe testing setup is as shown in μmol/mol, and toluene and nitrogen dioxide with concentrations of  μmol/mol were examined. Analytes were delivered from cylinders, pre-diluted with zero air, and then further diluted to testing levels using our gas-flow manifold  were tested on the three different ONA configurations. Three configurations of ONAs were tested: (i) bare ONA, (ii) graphene covered ONA and (iii) graphene oxide covered ONA. Acetone and ethanol with concentrations of  manifold . While mThe intensity was determined by the following Equation Itransmission is the transmission spectrum of the device. Idevice is the spectrum when ONA are illuminated. Isource is the spectrum of the light passing through the fused silica without the ONA. Idark is the spectrum collected when the light source is turned off. The data processing was done using MATLAB (Disclaimer). A linear fit was used to determine the slope of concentration-wavelength shift curve for a given device. The linear fit was used only for those readings for which the response was not saturated. We don’t observe any variation in the resonance wavelength beyond the measurement capabilities of the spectrometer . In these feasibility studies each sample was tested once for all the analytes.where λ, is given by Equation 2In this work, we study the change in the resonance frequency of ONA when exposed to gas-phase analytes. We note that this proof-of-concept study uses three different ONA arrays to demonstrate the feasibility of using them for gas-phase sensing. Furthermore, we explored the possible utility of employing modifying layers to affect the response phenomena for two of the ONA arrays. The shift in the resonance wavelength, Δnanalyte and nair are the refractive indices of the analyte and air. d is the thickness of the analyte layer on top of the dipole structure. ld is the exponential field decay length. m is the bulk refractive index sensitivity of the bare ONA. For graphene/graphene oxide covered ONA, m is the bulk refractive index sensitivity of the combined device (ONA + graphene or graphene oxide). Using Lumerical’s FDTD (Finite Difference Time Domain) tool (Disclaimer) we determined that m is similar for bare ONA and graphene/graphene oxide covered ONA (which lies in the range of 450 nm/RIU to 730 nm/RIU). The values in where, λ > 0) is predicted for all the analytes used. The responses of the bare ONA are shown in μmol/mol and 100 μmol/mol for acetone and ethanol, and 10 μmol/mol and 20 μmol/mol for nitrogen dioxide and toluene). Bare ONA also has a fast response to different analytes. Bare ONA exhibits the highest sensitivity to toluene, which can be attributed to the high refractive index of toluene amongst all four analytes.Based on Equation Motivated by a desire to attain greater sensitivity and selectivity, we also tested two more sensor types with the same four analytes. We characterized the modifying layers with Raman spectroscopy to estimate the coverage level. From the Raman spectra of the covered ONA, we estimate that there are more than 4 layers of graphene oxide stacked on top of each other, while we observe evidence for only a monolayer of graphene covering the ONA See .λ > 0) for the graphene-covered ONA, in response to all the analytes, but a blue shift (Δλ < 0) is observed for toluene as shown in The response of graphene covered ONA for four different analytes is as shown in The responses of graphene oxide covered ONA are shown in μmol/mol) and detection limit is calculated as the smallest concentration that can give a spectral shift detected by the spectrometer. The slope was calculated using a linear fit on each sensitivity curve shown in Graphene, though apparently one atom thick when placed on top of the bare ONA, results in a shift of 13 nm, and graphene oxide having multiple layers, results in a shift of 45 nm. Response strengths of the three types of sensors to the four analytes are plotted as a function of analyte concentration in λ > 0). For ONA covered with graphene or graphene oxide depending on the analyte, the shift is either blue (Δλ < 0) or red (Δλ > 0). However, there may be an adsorbate history contribution to this effect (as discussed below).From The bare ONA resonates at 746.2 nm. As indicated above, when a monolayer of graphene is placed on top of the bare ONA to form graphene covered ONA, the resonance frequency is red shifted to 759 nm. The shift of around 13 nm was expected due to graphene as seen beforeThe baseline values before and after analyte adsorption for the bare ONA, graphene covered ONA and graphene oxide covered ONA are given in s and Rs. The gap between the two arms of the dipole is modeled by Cs. Cp and Rp denote capacitance and resistance connected to the ambient conditions1215s, and more dominantly Cp. Bare ONA has a fast response and is reversible, as the response comes back to its baseline value once the analyte flow is stopped. We also observe that the response saturates at higher concentrations. In the equivalent circuit diagram this corresponds to the larger values reached by capacitor Cs and Cp. The bare ONA response has no obvious selectivity towards any analyte. The bare ONA gives a red shift to all the analytes, making it hard to differentiate between analytes. However, among all the four analytes tested, bare ONA exhibited its maximum sensitivity towards toluene and nitrogen dioxide.The red shifts observed in the responses of the bare ONA can also be explained with the help of the left portion of the equivalent circuit diagram in Fig. 8p and Rp, and would yield a red shift in the peak resonance since all the analytes have a refractive index larger than air  or red shifted . A possible mechanism underlying the wavelength shift for graphene and graphene oxide coated ONA is discussed. Baseline drift was observed in the response of the graphene and graphene oxide coated ONA. Graphene and graphene oxide coated ONA have a slower response as compared to bare ONA.How to cite this article: Mehta, B. et al. Gas Sensing with Bare and Graphene-covered Optical Nano-Antenna Structures. Sci. Rep.6, 21287; doi: 10.1038/srep21287 (2016).


This generic technique paves the way for using a whole new range of eutectic substrates for the large-area synthesis of 2D materials.Large-area synthesis of high-quality graphene by chemical vapour deposition on metallic substrates requires polishing or substrate grain enlargement followed by a lengthy growth period. Here we demonstrate a novel substrate processing method for facile synthesis of mm-sized, single-crystal graphene by coating polycrystalline platinum foils with a silicon-containing film. The film reacts with platinum on heating, resulting in the formation of a liquid platinum silicide layer that screens the platinum lattice and fills topographic defects. This reduces the dependence on the surface properties of the catalytic substrate, improving the crystallinity, uniformity and size of graphene domains. At elevated temperatures growth rates of more than an order of magnitude higher (120 μm min Innovative substrate engineering is necessary to improve the quality of CVD-synthesized graphene. Here the authors demonstrate in situ fabrication of an eutectic Pt-Si alloy that forms a wetting liquid surface on polycrystalline Pt foils, allowing millimetre-sized graphene crystals to grow in minutes. Graphene is a two-dimensional material that has great potential for use in a wide variety of applications such as transparent flexible electrodes, photonic and electronic devices, energy storage, sensors and coatings to name a fewAtmospheric pressure chemical vapour deposition (APCVD) has received much attention due to its simplicity, improved safety and lower cost over alternative procedures. When a solid substrate is used with APCVD, graphene growth is strongly influenced by the crystallographic lattice of the substrate, its defects, roughness and grain boundaries2347in situ for graphene growth when heated, over the entire substrate surface. This significantly reduces the influence of the defects, roughness and the crystallographic orientations of the substrate on the quality of graphene. Substrates covered with the film exhibit increased growth rates of up to 120 μm min−1 at elevated temperatures, one of the fastest reported to date. While metal alloys121314In this investigation we combined the advantages of both approaches by using widely available, scalable, solid polycrystalline substrates in conjunction with a thin, liquid layer on the surface of these substrates. The layer is formed by coating polycrystalline Pt foils with a silicon-containing film, which forms a wetting liquid silicide surface 2 film was deposited on pristine Pt with a tetraethyl orthosilicate (TEOS) precursor in a CVD-based process, where TEOS was introduced by an Ar carrier gas (Methods). Other techniques such as evaporation and sol-gel deposition of Si/SiO/SiO2 were also investigated and showed similar trends after the optimisation of the procedure. CVD of TEOS is fast, cheap and can be performed in a single CVD system before synthesis. Upon annealing the SiO2 layer disappeared resulting in the formation of silicidated Pt (discussed later in the paper). To synthesize graphene, pristine Pt or the Pt/SiO2 stack was subjected to a CVD procedure that consisted of an annealing stage, synthesis stage and a cooling stage at atmospheric pressure (Methods). A compromise had to be made between the length of an experiment versus the size and quality of graphene flakes because the ratio of H2 to CH4 needed to be kept high2:CH4 ratio of 100:1. The ratio of H2 to CH4 on silicidated Pt compared with pristine Pt had to be increased by as much as 50%  to reduce the carbon deposition and achieve flakes of comparable size to those on pristine Pt. The comparison of the synthesis parameters on pristine and silicidated Pt is presented in −1  is high −1 ref. ), but stl−1 ref. ) present2 to CH4 ratios on Cu is usually such that experiments often need to be conducted for hours or days−1(S/2)−2, is also shown in Interestingly, the high melting point of Pt allowed us to probe unexplored temperatures above 1,100 °C in CVD, at which single crystal graphene flakes of up to 1.8 mm were obtained in 15 min on silicidated Pt. For comparison, the window of useful Het al.et al.A number of techniques were used to extensively assess the properties of the synthesized graphene, such as size, shape, crystallinity, number of layers and its electronics properties. 2 substrates for Raman measurements (Graphene was transferred to Si/SiOurements . The D-purements  providedurements . In addiurements . The rou2/Si substrates (methods) from silicidated Pt. The carrier density n and mobility μ of the device were determined from the low-field Hall measurements with n=(e·∂ρxy/∂B)−1 and μ=(enρxx)−1. Small p-type doping was observed in our device, which is also commonly seen in transferred graphene on SiO2/Si substrates and considered to be due to the adsorption of water molecules between the interfaces27ρxx and ρxy as functions of magnetic field from −19 to +19 T for a typical device. We observed a very high hole mobility of 5,525 cm2 V−1 s−1 at a hole density of 5.86 × 1011 cm−2. Recently, graphene has been shown to be an exceptional candidate for quantum Hall metrologyB|>12 T, well-defined ν=2 quantum Hall states was clearly observed with ρxy=h/2e2 and ρxx=0, consistent with its carrier density 2/Si substrates, and are comparable to those in epitaxial graphene grown on SiC , fused silica or quartz may be described similarly due to the strong Si—O bond, which can be broken by hydrofluoric acid or some strong bases. However, when these compounds are in contact in a reducing H2 atmosphere at elevated temperatures silica may reduce to silicon, catalysed by Pt, and react with Pt to form various phases of eutectic Pt silicides as reported by numerous studies333435It is commonly known that Pt is a noble metal that is very inert; only hot aqua regia can react with it. Silicon dioxide  film was deposited on Pt to get the material in excess, resulting in the formation of a Pt3Si phase that matched well with the literatureCharacterization of the annealed and cooled substrate before graphene synthesis was performed. The cooling was rapid (quenched) to obtain the closest possible condition to that during the synthesis. 2 film before and after annealing we propose a simple mechanism of the liquid silicide formation that explains why the morphologies of graphene are so different on pristine and silicidated Pt. Most Pt silicide phases have reduced (eutectic) melting points3Si phase melts at around 830 °C  effects. For example, the silicide route may produce silicon carbide as an intermediate state. Precise in situ studies would be needed to confirm the correct chemical mechanism. We also suggest that such eutectic materials may be suitable for use as liquid-surface substrates at low synthesis temperatures, bringing all the associated benefits.On the basis of experimental observations of the SiO °C ref. . Figure  surface . The silGood crystallinity is an important quality factor of CVD-grown graphene, as it offers superior electronic and tensile properties, chemical resistivity and impermeabilityAlthough there is as yet no confirmed theory that explains the poor crystallinity of graphene on pristine Pt via CVD that we have observed, it is well known that the face-centred cubic (FCC) lattice of Pt has the largest lattice constant compared with the commonly used transition metals for graphene synthesis. On Cu(111) the lattice constant mismatch with graphene is 3.6%, whereas on Pt(111) this is significantly higher at 12.5%. This may result in incommensurable growth and the observed poor crystallinity.−2 and enhanced growth rates of up to 120 μm min−1 at elevated temperatures, allowing millimetre-sized flakes to grow easily in minutes. The silicide film formation on the substrates is an important parameter for graphene growth and may have beneficial effects if controlled. To our knowledge no current reports focusing on graphene synthesis via CVD consider the effects of the formation of the silicides, though commonly used reaction tubes are made of fused silica. It is likely that previous results were influenced by these silicides but were overlooked by other reports. In particular, we explicitly verify the dependence of the amount of silica on the crystallinity of graphene flakes on Pt. All of these beneficial effects may make the silicidation feasible commercially, especially if the procedure is extended to other metals. There is significant potential for further use of the method, such as a liquid surface for low temperature graphene synthesis or the possibility to oxidize the silicide layer to achieve transfer-free graphene. This approach is generally applicable and paves the way for a whole new field of eutectic substrates for the growth of superior quality 2D materials.In this study, we demonstrate a novel, low-cost substrate processing procedure to achieve rapid, efficient synthesis of millimetre-sized single crystal graphene. Silicidation of polycrystalline foils may be used as a replacement for expensive single-crystal substrates or as an alternative to polishing and grain enlargement. Large topographic defects, such as grain boundaries, are locally smoothed and the lattice of the grains is screened by a liquid surface, making silicidated polycrystalline foils superior to single crystals due to epitaxy-free synthesis. This ensures that graphene grows as a single crystal in its undistorted hexagonal shape. Silicidated polycrystalline Pt also exhibits low graphene flake nucleation density of up to 0.3 mm2 stack, a film of SiO2 of specified thickness (2 film of about 1 μm thickness can be deposited on pristine Pt with CVD by passing Ar gas (350 sccm) through a TEOS precursor (in a ‘bubbler') that is carried to a furnace with the substrates heated to 700 °C for 30 min. Other methods, such as Si, SiO, SiO2 evaporation, sputter coating, sol-gel processes or ion implantation are also applicable.Pristine Pt substrates  were used as received from the supplier after cleaning in acetone and deionized water. To form a Pt/SiOhickness  was depo2 stack was placed on a boron nitride holder inside a fused silica tube (28 mm inner diameter) at sufficient distance from the walls of the tube. The tube was then purged with Ar (99.999% purity) and shifted into a pre-heated furnace, followed by annealing in H2  to allow Pt silicide formation and to stabilize the temperature of the furnace. The useful annealing time to form silicidated Pt strongly depended on the temperature and the silica thickness. For example, at 1,070 °C with 1-μm-thick silica layer, 30 min was suitable . However, at 1,050 °C with a 1 μm silica film after 30 min, 10% of the SiO2 film still remained. In the experiments where reusing silicidated Pt was tested, we shortened the annealing time to 5 min to simply re-heat the solidified silicide. To synthesize graphene, a mixture of CH4 (99.5%) and H2 was introduced. The gas ratio and the duration of the synthesis depended greatly on the temperature and the silica layer thickness and are given in the 4 and 600 sccm H2 for 20 min, resulting in ∼0.5-mm-sized graphene flakes. Directly after this step, the tube was shifted from the furnace and purged with Ar to quench graphene growth.Pristine Pt or the Pt/SiOet al.2 wafer, followed by heating at 140 °C for 5 min to improve the adhesion of graphene to SiO2. The stack was then placed in acetone  for 6 h and after dried with a N2 gun. For the TEM transfers, the PMMA layer was burnt in air at 350 °C after the transfer to a gold TEM grid, as outlined in Huang et al.41The ‘bubbling transfer' method outlined in Gao Raman spectra and maps were recorded with a Horiba LabRAM Aramis microscope equipped with a 532 nm laser. Routine SEM characterization was done with a JEOL JSM-6500F microscope at 5 kV. TEM images and SAED patterns were recorded with a JEOL JEM-2010 microscope at 80 kV. AFM measurements were performed using a Cypher AFM (Asylum Research). The scan was done in contact mode by looking at the lateral motion due to changes in friction as the probe scanned over the surface. To eliminate the effects of the direction of probe movement and also any topographic effects the trace scan was subtracted from retrace for the lattice-resolved image in real space. 2D fast Fourier transforms were taken of the AFM scans, the absolute values of which were then calculated and plotted on log scale; the contrast of the final images was adjusted to reduce the background.B were applied perpendicular to the sample surface. A small AC current with peak amplitude of 40 nA was applied in the longitudinal direction (Ixx). The longitudinal voltage Vxx and the Hall voltage Vxy ˙Vxx/Ixx and Vxy/Ixx, respectively, where L and W are the length and the width of the device.Eight-leg Hall bars (15 μm × 130 μm) were fabricated using e-beam lithography followed by oxygen plasma etching. A two-step ohmic contacting methodtage Vxy  were sim2 films was measured with a Nanometrics Nanospec AFT interferometer on co-deposited Si tiles. Some samples were also analysed with ellipsometry directly on a Beaglehole Instruments Picometer Ellipsometer. The XPS measurements were performed at base pressure of 5 × 10−10 torr on a VG nine channel CLAM4 electron energy analyser with a 250 W Al X-ray excitation. XRD analysis was performed on the Bruker D5000 diffractometer.The thickness of the SiOP) squared to area (A) was calculated for each geometric shape. This unit-less number is usually indicative of specific geometric shapes. For example, for a circle it is 4π≈12.57 , for an octagon it is ≈13, for a hexagon √192≈13.86, for a pentagon ≈15, for a square it is 16 and so on. Concave polygons have higher P2/A values. If the calculated ratio (P2/A) for a shape is X, then we define the hexagonality as ≈1−|X−√192|/√192 . This means that a shape with a value close to 100% is close to a perfect hexagon. The s.d. of the % hexagonality for a sample indicates how non-uniform the shape distribution is. It is understood that rounded convex or concave polygons may introduce an uncertainty in the measurement, since, for example, a rounded cube may have the ratio of the perimeter squared to area similar to a hexagon. However, we usually have either hexagonal shapes (silicidated Pt) or concave polygons (pristine Pt); thus, for a large number of graphene domains the approach characterizes the samples sufficiently.MATLAB was used to find an automatic threshold value of SEM micrographs, which were then converted into binary images. The ratio of the perimeter .Supplementary Figures 1-3


These data were related to the hydraulic data as well as the sample type, location, and time. Temporal and spatial variation was observed between and within wastewater communities and biofilm communities. The bacterial communities in biofilm were distinctly different from the communities in wastewater and exhibited greater spatial variation, while the wastewater communities exhibited variability between different months of sampling. This study highlights the variation of bacterial communities between biofilm and wastewater, and has shown both spatial and temporal variations in bacterial communities in combined sewers. The temporal variation is of interest for in‐sewer processes, for example, sewer odor generation, as field measurements for these processes are often carried out over short durations and may therefore not capture the influence of this temporal variation of the bacterial communities.This study describes the temporal and spatial variability of bacterial communities within a combined sewer system in England. Sampling was conducted over 9 months in a sewer system with intensive monitoring of hydraulic conditions. The bacterial communities were characterized by 16S  Combined sewers are a key part of the urban infrastructure and play a vital role in safeguarding public health and reducing water pollution in the environment. Sewage released into the urban environment can potentially expose people to waterborne pathogens, and sewer overflows impact upon the natural aquatic environment as well as producing esthetic pollution including noxious odors. During the transport of wastewater within a combined sewer network, it undergoes physicochemical and biological changes  which release excess sewage into a small watercourse when the sewer network is overloaded during intense rainfall events; five of these are located on the main intercepting sewer Fig. . The catThe sites for the sampling of material for bacterial community analysis were chosen based on an analysis of the flow data from the seven flow monitors  located on the intercepting sewer, as well as excluding sites where the access manhole was located in the main road as this would limit safe accessibility. Table The measured wastewater velocity from these sites was chosen as the parameter defining the sampling program as it can be related to the shear stress on the biofilms covering the submerged pipe wall in the sewer, with the assumption that the pipe geometry and wall roughness is fixed. Based on the dry weather data, the average daily velocity profile for each measuring station was calculated and is shown in Figure Based on the velocity profiles in Figure am). Wastewater samples were collected in November 2009, March 2010, and June 2010. For each manhole, 1 L of wastewater was collected in triplicate at each time point in sterile glass bottles, and biofilm samples were collected in March 2010 and June 2010. The biofilm samples were collected using a biofilm sampler constructed from a sponge attached to a piece of PE plastic. These were sterilized by autoclaving prior to use and kept in sterile 50 mL falcon tubes. The biofilm samples were collected by scraping the sponge over the pipe wall immediately above the water line to avoid mixing with the wastewater. The samples were collected in the upstream sewer pipe discharging into the manhole rather than in the actual manhole. Triplicate biofilm samples were again collected at each location. The samples were transported to the laboratory within 12 h of sampling in a cool bag to ensure stable temperature following sampling.Samples of wastewater and biofilms were collected by entering the manholes at the same time as the routine maintenance of the flow monitors, and the samples were collected during the day  for the biofilm samples and eluted in a final volume of 50 μL nuclease‐free water.Upon return to the laboratory, 50 mL samples of wastewater were filtered through a 0.22‐μm, 47 mm diameter, polycarbonate membrane filter . The filters were then stored at −20°C until the DNA was extracted. The biofilm samples were frozen at −20°C upon return to the laboratory. DNA was extracted using the MoBio Ultra Clean Soil DNA isolation kit  following the manufacturer's instructions. DNA was extracted from half a filter for the wastewater samples, corresponding to 25 mL of the original 50 mL sample volume, and from a quarter of a sponge .After DNA extraction, bacterial 16S rRNA genes were amplified using the polymerase chain reaction (PCR) with primers FAM63f and HEX1389r  test with a 5% confidence level  for FM004, 0.6 m/sec (standard deviation 0.01 m/sec) for FM012, and 3.1 m/sec (standard deviation 0.05 m/sec) for FM019. These average velocities are based on dry weather data defined as described in There were two sampling times where samples of wastewater and biofilms were collected at all three sites, that is, the March and June samples. Figure When comparing bacterial community structure between the three individual sampling locations in the network Fig. , the wasSeparating all of the biofilm communities from the wastewater communities shows that the biofilm communities overall formed three separate clusters Fig. B with seThe catchment where the sampling was carried out is located in an area where infiltration of groundwater into the sewer networks is typically observed. Groundwater infiltration is a seasonal process, and is much more influential during certain months in which the local ground water levels are elevated due to previous rainfall (Kracht et al. Figure In this study, variations in the structure of bacterial communities in sewer wastewater were investigated at three locations along the same intercepting sewer and at three separate points in time. Variation in biofilm community structure was also investigated at the same locations, but at only two time points. In addition to the samples for microbial analysis, an extensive dataset of flow data and rain data were available for the catchment. From the bacterial community profiling it was clear that the biofilm communities were different from the wastewater communities at each sampling point and at each time Figs. , 4. TherLooking only at the wastewater communities in Figure In addition to the general difference between the communities in the wastewater and the biofilms, the communities also indicate a higher variability overall in the biofilms than is found in the wastewater samples. This is particularly seen for samples collected at the same time in March and June Fig. . The higThe variability in microbial communities in sewers is of interest mainly due to their influence on in‐sewer processes which contributes to problems such as odor generation in the urban environment or corrosion of the sewer pipe walls. In addition, the vision of enhancing the naturally occurring in‐sewer processes to provide safe in‐sewer treatment of wastewater without the need for large energy inputs at large end of pipes wastewater treatment plants (Hvitved‐Jacobsen None declared.


The optical characteristics of graphene oxide (GO) were explored to design and fabricate a GO-based optical humidity sensor. GO film was coated onto a SU8 polymer channel waveguide using the drop-casting technique. The proposed sensor shows a high TE-mode absorption at 1550 nm. Due to the dependence of the dielectric properties of the GO film on water content, this high TE-mode absorption decreases when the ambient relative humidity increases. The proposed sensor shows a rapid response (<1 s) to periodically interrupted humid air flow. The transmission of the proposed sensor shows a linear response of 0.553 dB/% RH in the range of 60% to 100% RH. These functional groups include hydroxyl, epoxy and carboxylic acid moieties [3 hybridized carbon atoms turn GO into an insulator by decreasing its conductivity, and enhance its hydrophilic properties, [Aside from the basic needs of high sensitivity and wide detection range additional demands for fast response and short recovery time exist for humidity sensors to meet industry requirements. Consequently, research on humidity-sensitive nanomaterials such as silicon nanostructures, ceramic nanomaterials, semiconductor nanoparticles and metal oxide nanowires have attracted much attention due to its high surface to volume ratio ,2. Latelmoieties ,3. The sperties, ,6. Besidperties, , which eCapacitive-based sensors having high response time, low temperature dependence, low hysteresis, low drift with good performance in harsh environment are desirable in various applications –14. Duri2.The experimental setup of the humidity sensor is shown in On the other hand, GO solution was prepared by an improved version of Hummer's method . The GO A gas tube providing controlled humidity vapour was placed about 1 cm above the GO-coated waveguide (sensing region) of the proposed sensor. Humid nitrogen gas was produced by bubbling dry nitrogen gas through water before flowing out from the gas tube. The response time of the proposed sensor to humid air (∼90% RH) was measured using a photodiode and by placing a mechanical shutter in between the gas source and the sensing region to control the exposure intervals. Measurement of the change in transmitted power to different relative humidity values was carried out by placing the proposed sensor in a humidity control box. Relative humidity in the box was controlled by mixing dry nitrogen gas and humid nitrogen gas with different mixing flow rates before flowing into the box. Before each optical measurement, the relative humidity of the gas flow or inside the humidity control box was measured using a HI 8562 hygrometer from Hanna Instruments. A long working distance optical microscope  was used to monitor the sensing region during the experiment. Throughout the optical measurement, the polarization of the incident light was set to be TE-polarized using a polarization controller (PC). Extra care in the handling of the launch fibre was taken to ensure that the linear polarization state of the incident light was not scrambled by minor disturbances on the fibre. Also, the polarization dependent loss between TE- and TM-polarized modes of the incident light for another uncoated polymer waveguide was measured and found to be lower than 0.5 dB, limited only by the performance of the PC.3.Prior to the introduction of humid air (up to the 6th second), no water condensation was observed on either the GO film or the substrate, as shown in To study the response time of the proposed sensor, the output of the sensor was connected to a photodiode and the transmitted power was observed using an oscilloscope, and the results are shown in The polarization state of the transmitted light was measured when the proposed sensor was exposed to a relative humidity of 100% RH, and was TE-polarized. In fact, rotating the PC only rotates the polarization state and does not affect the transmitted power. The water saturated GO film seems to lose its polarization capability and becomes transparent to both TE- and TM-polarized light. There are reports showing that, at high relative humidity, water molecules can easily permeate in and out of the GO film of up to 10 μm in thickness . The per4.The humidity sensing ability of a GO-coated optical waveguide has been studied. The optical transmission characteristics of the proposed sensor are found to be affected by the relative humidity of its surroundings. The increase in transmitted power at higher humidity is due to a change in the dielectric properties of the GO film where the conductivity of the GO film is reduced in the presence of water molecules. The proposed sensor exhibits fast response of less than 1 s to humid air breezes. In addition, it shows a good linear response of 0.553 dB/% RH in the humidity range from 60% to 100% RH. The all optical nature of the proposed sensor enables its application in long distance humidity sensing with fast response.


Processes of selective allocation of visual attention play a prominent role for survival, but also for development and maintenance of clinically relevant symptoms such as in anxiety or depression. Previous research provided evidence for increased attentional orienting and preoccupation with biologically relevant and mood-congruent stimuli, indicating tendencies of attentional biases. For instance, in anxiety, the visual-attentional system may be overly sensitive toward threat- and avoidant of reward cues.Behavioral and physiological bases of attentional biases: paradigms, participants, and stimuli cover these topics and give a comprehensive overview on current directions and challenges in attentional bias research. Our driving motivation was to critically evaluate parameters that may directly or indirectly influence attentional biases and may thus be important for our understanding of attentional biases.The research articles appearing in the E-book dot-probe task (MacLeod et al., Our first aim was to demonstrate the variety of experimental paradigms and outcome measures used. So far, the Our second aim was to demonstrate the variety of populations and stimuli, which may show, or elicit, differing attentional biases. Wittekind et al.  examinedInvestigating the impact of participant sex on attentional biases, Pfabigan et al.  applied Kappenman et al.  investigChallenges in attentional bias research become quite clear in the course of the articles in this E-book. There is no common agreement as to whether particular stimuli or experimental set-ups are more reliable than others. For example, only a few studies addressed the topic of different presentation durations and their impact on attentional bias measures so far (e.g., Koster et al., Nevertheless, the current research topic also points toward future directions of attentional bias research. In particular, Kappenman et al.  emphasizThe 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.