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Time Evolution of the Wettability of Supported Graphene under Ambient Air Exposure.

ABSTRACT: The wettability of graphene is both fundamental and crucial for interfacing in most applications, but a detailed understanding of its time evolution remains elusive. Here we systematically investigate the wettability of metal-supported, chemical vapor deposited graphene films as a function of ambient air exposure time using water and various other test liquids with widely different surface tensions. The wettability of graphene is not constant, but varies with substrate interactions and air exposure time. The substrate interactions affect the initial graphene wettability, where, for instance, water contact angles of ?85 and ?61° were measured for Ni and Cu supported graphene, respectively, after just minutes of air exposure. Analysis of the surface free energy components indicates that the substrate interactions strongly influence the Lewis acid-base component of supported graphene, which is considerably weaker for Ni supported graphene than for Cu supported graphene, suggesting that the classical van der Waals interaction theory alone is insufficient to describe the wettability of graphene. For prolonged air exposure, the effect of physisorption of airborne contaminants becomes increasingly dominant, resulting in an increase of water contact angle that follows a universal linear-logarithmic relationship with exposure time, until saturating at a maximum value of 92-98°. The adsorbed contaminants render all supported graphene samples increasingly nonpolar, although their total surface free energy decreases only by 10-16% to about 37-41 mJ/m2. Our finding shows that failure to account for the air exposure time may lead to widely different wettability values and contradicting arguments about the wetting transparency of graphene.

SUBMITTER: Aria AI

PROVIDER: S-EPMC4754094 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature

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Time Evolution of the Wettability of Supported Graphene under Ambient Air Exposure.

Aria Adrianus I AI Kidambi Piran R PR Weatherup Robert S RS Xiao Long L Williams John A JA Hofmann Stephan S

The journal of physical chemistry. C, Nanomaterials and interfaces 20160107 4

The wettability of graphene is both fundamental and crucial for interfacing in most applications, but a detailed understanding of its time evolution remains elusive. Here we systematically investigate the wettability of metal-supported, chemical vapor deposited graphene films as a function of ambient air exposure time using water and various other test liquids with widely different surface tensions. The wettability of graphene is not constant, but varies with substrate interactions and air expos ...[more]

PMID: 26900413

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Project description:ImportanceAir pollution is associated with structural brain changes, disruption of neurogenesis, and neurodevelopmental disorders. The association between prenatal exposure to ambient air pollution and risk of cerebral palsy (CP), which is the most common motor disability in childhood, has not been thoroughly investigated.ObjectiveTo evaluate the associations between prenatal residential exposure to ambient air pollution and risk of CP among children born at term gestation in a population cohort in Ontario, Canada.Design, setting, and participantsPopulation-based cohort study in Ontario, Canada using linked, province-wide health administrative databases. Participants were singleton full term births (≥37 gestational weeks) born in Ontario hospitals between April 1, 2002, and March 31, 2017. Data were analyzed from January to December 2022.ExposuresWeekly average concentrations of ambient fine particulate matter with a diameter 2.5 μm (PM2.5) or smaller, nitrogen dioxide (NO2), and ozone (O3) during pregnancy assigned by maternal residence reported at delivery from satellite-based estimates and ground-level monitoring data.Main outcome and measuresCP cases were ascertained by a single inpatient hospitalization diagnosis or at least 2 outpatient diagnoses for children from birth to age 18 years.ResultsThe present study included 1 587 935 mother-child pairs who reached term gestation, among whom 3170 (0.2%) children were diagnosed with CP. The study population had a mean (SD) maternal age of 30.1 (5.6) years and 811 745 infants (51.1%) were male. A per IQR increase (2.7 μg/m3) in prenatal ambient PM2.5 concentration was associated with a cumulative hazard ratio (CHR) of 1.12 (95% CI, 1.03-1.21) for CP. The CHR in male infants (1.14; 95% CI, 1.02-1.26) was higher compared with the CHR in female infants (1.08; 95% CI, 0.96-1.22). No specific window of susceptibility was found for prenatal PM2.5 exposure and CP in the study population. No associations or windows of susceptibility were found for prenatal NO2 or O3 exposure and CP risk.Conclusions and relevanceIn this large cohort study of singleton full term births in Canada, prenatal ambient PM2.5 exposure was associated with an increased risk of CP in offspring. Further studies are needed to explore this association and its potential biological pathways, which could advance the identification of environmental risk factors of CP in early life.

Project description:BackgroundPopulation-based short-term air pollution health studies often have limited spatiotemporally representative exposure data, leading to concerns of exposure measurement error.ObjectiveTo compare the use of monitoring and modeled exposure metrics in time-series analyses of air pollution and cardiorespiratory emergency department (ED) visits.MethodsWe obtained daily counts of ED visits for Atlanta, GA during 2009-2013. We leveraged daily ZIP code level concentration estimates for eight pollutants from nine exposure metrics. Metrics included central monitor (CM), monitor-based (inverse distance weighting, kriging), model-based [community multiscale air quality (CMAQ), land use regression (LUR)], and satellite-based measures. We used Poisson models to estimate air pollution health associations using the different exposure metrics. The approach involved: (1) assessing CM-based associations, (2) determining if non-CM metrics can reproduce CM-based associations, and (3) identifying potential value added of incorporating full spatiotemporal information provided by non-CM metrics.ResultsUsing CM exposures, we observed associations between cardiovascular ED visits and carbon monoxide, nitrogen dioxide, fine particulate matter, elemental and organic carbon, and between respiratory ED visits and ozone. Non-CM metrics were largely able to reproduce CM-based associations, although some unexpected results using CMAQ- and LUR-based metrics reduced confidence in these data for some spatiotemporally-variable pollutants. Associations with nitrogen dioxide and sulfur dioxide were only detected, or were stronger, when using metrics that incorporate all available monitoring data (i.e., inverse distance weighting and kriging).SignificanceThe use of routinely-collected ambient monitoring data for exposure assignment in time-series studies of large metropolitan areas is a sound approach, particularly when data from multiple monitors are available. More sophisticated approaches derived from CMAQ, LUR, or satellites may add value when monitoring data are inadequate and if paired with thorough data characterization. These results are useful for interpretation of existing literature and for improving exposure assessment in future studies.Impact statementThis study compared and interpreted the use of monitoring and modeled exposure metrics in a daily time-series analysis of air pollution and cardiorespiratory emergency department visits. The results suggest that the use of routinely-collected ambient monitoring data in population-based short-term air pollution and health studies is a sound approach for exposure assignment in large metropolitan regions. CMAQ-, LUR-, and satellite-based metrics may allow for health effects estimation when monitoring data are sparse, if paired with thorough data characterization. These results are useful for interpretation of existing health effects literature and for improving exposure assessment in future air pollution epidemiology studies.

Project description:BackgroundOlfactory dysfunction affects millions of people worldwide. This sensory impairment is associated with neurodegenerative disease and significantly decreased quality of life. Exposure to airborne pollutants has been implicated in olfactory decline, likely due to the anatomic susceptibility of the olfactory nerve to the environment. Historically, studies have focused on occupational exposures, but more recent studies have considered effects from exposure to ambient air pollutants.ObjectivesTo examine all relevant human data evaluating a link between ambient pollution exposure and olfaction and to review supporting animal data in order to examine potential mechanisms for pollution-associated olfactory loss.MethodsWe identified and reviewed relevant articles from 1950 to 2015 using PubMed and Web of Science and focusing on human epidemiologic and pathophysiologic studies. Animal studies were included only to support pertinent data on humans. We reviewed findings from these studies evaluating a relationship between environmental pollutant exposure and olfactory function.ResultsWe identified and reviewed 17 articles, with 1 additional article added from a bibliography search, for a total of 18 human studies. There is evidence in human epidemiologic and pathologic studies that increased exposure to ambient air pollutants is associated with olfactory dysfunction. However, most studies have used proxies for pollution exposure in small samples of convenience. Human pathologic studies, with supporting animal work, have also shown that air pollution can contact the olfactory epithelium, translocate to the olfactory bulb, and migrate to the olfactory cortex. Pollutants can deposit at each location, causing direct damage and disruption of tissue morphology or inducing local inflammation and cellular stress responses.ConclusionsAmbient air pollution may impact human olfactory function. Additional studies are needed to examine air pollution-related olfactory impacts on the general population using measured pollution exposures and to link pollution exposure with olfactory dysfunction and related pathology. Citation: Ajmani GS, Suh HH, Pinto JM. 2016. Effects of ambient air pollution exposure on olfaction: a review. Environ Health Perspect 124:1683-1693; http://dx.doi.org/10.1289/EHP136.

Dataset Information

Time Evolution of the Wettability of Supported Graphene under Ambient Air Exposure.

Publications

Time Evolution of the Wettability of Supported Graphene under Ambient Air Exposure.

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