Healthcare utilization and associated factors during the first wave of COVID-19 pandemic in Ghana: A cross-sectional survey.

Background and Aims: Understanding healthcare utilization during the coronavirus disease 2019 (COVID-19) pandemic is crucial to inform policy and to prepare health systems for future pandemics. We examined self-reported healthcare utilization and associated factors, including public health preventive practices, perceptions, and coping strategies among the general public in Ghana during the first wave of the COVID-19 pandemic. Methods: We adopted a cross-sectional study design using a public survey to recruit 643 respondents between May 23, and July 11, 2020 during the first wave of confirmed COVID-19 cases and after the fifth week of a partial lockdown in Ghana. Descriptive, bivariate, and binary logistic regression analyses were carried out in Stata version 15. Results: Overall, there was a high level of compliance with COVID-19 public health preventive measures. In terms of perception, 357 (55.5%) of respondents stated unnecessary worry was created about the disease. In relation to coping strategies, 376 (58.5%) of respondents stayed home for more than 6 h, while 35 (5%) reported drinking alcohol to overcome the fear created by the disease. The results showed that 176 (27.4%) of the respondents utilized healthcare while 44 (9.4%) did not utilized healthcare for fear of contracting the disease at the health facility. Marital status (adjusted odds ratio [aOR] = 0.63; 95% confidence interval [CI] = 0.409, 0.963), religion (aOR = 2.34; 95% CI = 1.10, 4.98), and possession of valid health insurance (aOR = 1.51; 95% CI = 1.020, 2.235) were associated with healthcare utilization. Conclusion: There was low healthcare utilization coupled with fear of contracting the COVID-19 disease at the health facilities among the respondents. The findings suggest the need for effective public education that ensures that future pandemics' prevention information and recommendations are easily understandable by the general public. Additionally, investment in health insurance coverage may contribute to healthcare utilization during future pandemics.

Anemia prevalence and its predictors among children under-five years in Ghana. A multilevel analysis of the cross-sectional 2019 Ghana Malaria Indicator Survey.

Background and Aims: Despite the implementation of anemia control interventions in Ghana, anemia prevalence is still high in children under-fives. Reducing the prevalence of anemia requires identifying and targeting associated critical risk factors. This study seeks to identify predictors of anemia among children under-fives in Ghana. Methods: Nationally representative data from the 2019 Ghana Malaria Indicator Survey was used in this study. Both fixed and random effects (multilevel) logistic regression models were applied to 2434 children to identify critical factors associated with anemia. Results: In this study, 54% (95% confidence interval [CI] 52.0-57.0) of children under-5 years were anemic. Infants were more likely to be anemic (66.7%) compared with other children below 5 years. In the multivariable multilevel model, the risk of anemia was found to be higher in younger children especially 6-11 months old (adjusted odds ratio [aOR] = 3.59, CI: 2.54-5.08) and 12-23 months old (aOR = 2.97, CI: 2.08-4.23), children who had malaria (aOR = 1.53, CI: 1.13-2.06), children whose mothers were not registered but not covered with health insurance (aOR = 1.45, CI: 1.21-1.74) or were not even registered for insurance (aOR = 1.49, CI: 1.15-1.93), children born to adolescent mothers (aOR = 2.21, CI: 1.36-3.57), children born to non-Christian mothers (Islam [aOR = 1.53, CI: 1.17-2.00]), children born to families of poorer households (poorest [aOR = 3.01, CI: 1.64-5.51]; poorer [aOR = 2.56, CI: 1.65-3.98]); middle (aOR = 2.03, CI: 1.32-3.11) and richer (aOR = 1.78, CI: 1.19-2.64), and children who lived in either Upper East (aOR = 2.03, CI: 1.26-3.26) or Central (aOR = 2.52, CI: 1.42-4.47) regions. Significant unobserved community-level differences in anemia prevalence were observed. Conclusion: The probability of anemia in children under-fives differs substantially from one community to another, and the prevalence remains high. The identified critical risk factors should be addressed. Multifaceted and targeted approaches are needed to help reduce the anemia prevalence in this setting to achieve the multiple United Nation's Sustainable Development Goals, which are related to risk and prevalence of anemia by 2030.

Gender Differences in Social Support and Posttraumatic Growth for Survivors of Intimate Partner Violence.

The current study investigated gender differences in perceived social support and posttraumatic growth for survivors of intimate partner violence. Participants for this study included 86 undergraduate students who indicated at least one instance of partner abuse (consisting of physical abuse, sexual abuse, emotional abuse, and harassment). Participants were predominantly female (68%), White/Caucasian (62%), and between 18 and 21 years of age (84%). Participants responded to the Multidimensional Scale of Perceived Social Support, the Composite Abuse Scale, and the Posttraumatic Growth Inventory. Mean differences and correlational analyses were utilized to investigate potential gender differences in the study variables as well as the relationships among them. The prevalence of intimate partner violence was comparable to those found in other studies, with 59% of men and 57% of women indicating experiencing abuse from a partner. Although the prevalence rates were similar, women indicated higher overall partner abuse victimization than did men. Moreover, women indicated statistically significantly higher scores than men in three of the four Composite Abuse Scale subscales, reflecting higher levels of victimization for all forms of abuse except for partner harassment. Further, perceived social support scores were similar for men and women, with the only significant gender difference to emerge being that men indicated higher levels of familial support than did women. No statistically significant gender differences emerged for overall posttraumatic growth or for any of its domains. Finally, social support was correlated with posttraumatic growth for women but not for men. The current study, therefore, suggests that men and women may experience similar levels of personal growth in the aftermath of partner abuse. Moreover, these results imply that the relationship between social support and posttraumatic growth may vary according to the gender of the survivor.

Prevalence of common adverse events experienced following COVID-19 vaccination and its associated factors in Ghana: Cross-sectional study design.

Background and Aims: The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (COVID-19) pandemic devasted the general life of people and various human activities across the globe, and Ghana is of no exception. This led to development of vaccines within record time to combat morbidity and mortality associated with the virus. In Ghana, COVID-19 vaccines were introduced in addition to existing COVID-19 protocols. However, the vaccines have adverse events among those who received them. In this study, we determined the prevalence of some common adverse events of the COVID-19 vaccines and its associated sociodemographic factors in Ghana. Methods: An online snowball cross-sectional survey was conducted between April and June 2021 among 240 people who had taken at least one dose of any of the COVID-19 vaccines approved in Ghana. The penalized binary logistic regression model was used to assess the factors associated with experience of at least one adverse event and the experience of number of adverse events using Stata version 16. Results: Among the 240 participants, 88.2% had experienced at least one adverse event. The most common adverse event after the first dose was pain at injection site (65.8%), headache (57.5%), tiredness (55.8%), fever (51.7%), chills (39.6%), and muscle pains (38.3%). Experience of adverse events was 16 times higher among those who took their vaccines in Ghana (adjusted odd ratio [AOR]: 16.2, 95% confidence interval [CI]: 1.98-132.56, p = 0.009), 94% less among those who took AstraZeneca (India) compared to AstraZeneca (Oxford) (AOR: 0.06, 95% CI: 0.01-0.37, p = 0.002) and 86% less among 40-49 years compared with less than 30 years old (AOR: 0.14, 95% CI: 0.03-0.58, p = 0.007). Conclusion: Pain at the injection site, headache, tiredness, fever, chills, and muscle pains were the most frequently reported adverse events. The study identified country of vaccination, country of origin of AstraZeneca vaccine and age to be associated with adverse events of vaccination.

Mapping the distribution of zero-dose children to assess the performance of vaccine delivery strategies and their relationships with measles incidence in Nigeria.

Geographically precise identification and targeting of populations at risk of vaccine-preventable diseases has gained renewed attention within the global health community over the last few years. District level estimates of vaccination coverage and corresponding zero-dose prevalence constitute a potentially useful evidence base to evaluate the performance of vaccination strategies. These estimates are also valuable for identifying missed communities, hence enabling targeted interventions and better resource allocation. Here, we fit Bayesian geostatistical models to map the routine coverage of the first doses of diphtheria-tetanus-pertussis vaccine (DTP1) and measles-containing vaccine (MCV1) and corresponding zero-dose estimates in Nigeria at 1x1 km resolution and the district level using geospatial data sets. We also map MCV1 coverage before and after the 2019 measles vaccination campaign in the northern states to further explore variations in routine vaccine coverage and to evaluate the effectiveness of both routine immunization (RI) and campaigns in reaching zero-dose children. Additionally, we map the spatial distributions of reported measles cases during 2018 to 2020 and explore their relationships with MCV zero-dose prevalence to highlight the public health implications of varying performance of vaccination strategies across the country. Our analysis revealed strong similarities between the spatial distributions of DTP and MCV zero dose prevalence, with districts with the highest prevalence concentrated mostly in the northwest and the northeast, but also in other areas such as Lagos state and the Federal Capital Territory. Although the 2019 campaign reduced MCV zero-dose prevalence substantially in the north, pockets of vulnerabilities remained in areas that had among the highest prevalence prior to the campaign. Importantly, we found strong correlations between measles case counts and MCV RI zero-dose estimates, which provides a strong indication that measles incidence in the country is mostly affected by RI coverage. Our analyses reveal an urgent and highly significant need to strengthen the country's RI program as a longer-term measure for disease control, whilst ensuring effective campaigns in the short term.

Risks of exposure to microbial contamination in eyewash stations.

Emergency eyewash stations are important safety equipment characterized by long water age. Significant increases in microbial contamination were detected in eyewash stations with water ages longer than 1 day. Enterobacter and Mycobacterium were identified in high abundance in eyewash stations with prolonged water age, suggesting eyewash stations as potential sources of pathogen exposure. Proper eyewash flushing was shown to be an effective practice to mitigate risks of exposure to microbial contaminants from eyewash use.

Invariant NKT cell-augmented GM-CSF-secreting tumor vaccine is effective in advanced prostate cancer model.

Invariant natural killer T cells (iNKT cells) express a semi-invariant T cell receptor that recognizes certain glycolipids (including α-galactosylceramide, αGC) bound to CD1d, and can induce potent antitumor responses. Here, we assessed whether αGC could enhance the efficacy of a GM-CSF-producing tumor cell vaccine in the transgenic SV40 T antigen-driven TRAMP prostate cancer model. In healthy mice, we initially found that optimal T cell responses were obtained with αGC-pulsed TRAMP-C2 cells secreting GM-CSF and milk fat globule epidermal growth factor protein-8 (MFG-E8) with an RGD to RGE mutation (GM-CSF/RGE TRAMP-C2), combined with systemic low dose IL-12. In a therapeutic model, transgenic TRAMP mice were then castrated at ~ 20 weeks, followed by treatment with the combination vaccine. Untreated mice succumbed to tumor by ~ 40 weeks, but survival was markedly prolonged by vaccine treatment, with most mice surviving past 80 weeks. Prostates in the treated mice were heavily infiltrated with T cells and iNKT cells, which both secreted IFNγ in response to tumor cells. The vaccine was not effective if the αGC, IL-12, or GM-CSF secretion was eliminated. Finally, immunized mice were fully resistant to challenge with TRAMP-C2 cells. Together these findings support further development of therapeutic vaccines that exploit iNKT cell activation.

Assessing the characteristics of un- and under-vaccinated children in low- and middle-income countries: A multi-level cross-sectional study.

Achieving equity in vaccination coverage has been a critical priority within the global health community. Despite increased efforts recently, certain populations still have a high proportion of un- and under-vaccinated children in many low- and middle-income countries (LMICs). These populations are often assumed to reside in remote-rural areas, urban slums and conflict-affected areas. Here, we investigate the effects of these key community-level factors, alongside a wide range of other individual, household and community level factors, on vaccination coverage. Using geospatial datasets, including cross-sectional data from the most recent Demographic and Health Surveys conducted between 2008 and 2018 in nine LMICs, we fitted Bayesian multi-level binary logistic regression models to determine key community-level and other factors significantly associated with non- and under-vaccination. We analyzed the odds of receipt of the first doses of diphtheria-tetanus-pertussis (DTP1) vaccine and measles-containing vaccine (MCV1), and receipt of all three recommended DTP doses (DTP3) independently, in children aged 12-23 months. In bivariate analyses, we found that remoteness increased the odds of non- and under-vaccination in nearly all the study countries. We also found evidence that living in conflict and urban slum areas reduced the odds of vaccination, but not in most cases as expected. However, the odds of vaccination were more likely to be lower in urban slums than formal urban areas. Our multivariate analyses revealed that the key community variables-remoteness, conflict and urban slum-were sometimes associated with non- and under-vaccination, but they were not frequently predictors of these outcomes after controlling for other factors. Individual and household factors such as maternal utilization of health services, maternal education and ethnicity, were more common predictors of vaccination. Reaching the Immunisation Agenda 2030 target of reducing the number of zero-dose children by 50% by 2030 will require country tailored analyses and strategies to identify and reach missed communities with reliable immunisation services.

Limiting spread of COVID-19 in Ghana: Compliance audit of selected transportation stations in the Greater Accra region of Ghana.

Globally, little evidence exists on transmission patterns of COVID-19. Recommendations to prevent infection include appropriate and frequent handwashing plus physical and social distancing. We conducted an exploratory observational study to assess compliance with these recommendations in selected transportation stations in Ghana. A one-hour audit of 45 public transport stations in the Greater Accra region was carried out between 27th and 29th March 2020. Using an adapted World Health Organization (WHO) hand hygiene assessment scale, the availability and use of handwashing facilities, social distancing, and ongoing public education on COVID-19 prevention measures were assessed, weighted and scored to determine the level of compliance of stations. Compliance with recommendations was categorized as "inadequate" "basic", "intermediate" and "advanced", based on the overall score. Majority (80%) of stations in Accra have at least one Veronica Bucket with flowing water and soap, but the number of washing places at each station is not adequate. Only a small minority (18%) of stations were communicating the need to wash hands frequently and appropriately, and to practice social/physical distancing while at the station. In most stations (95%), hand washing practice was either not observed, or only infrequently. Almost all stations (93%) did not have alcohol-based hand sanitizers available for public use, while social distancing was rarely practiced (only 2%). In over 90% of the stations, face masks were either not worn or only worn by a few passengers. Compliance with COVID-19 prevention measures was inadequate in 13 stations, basic in 16 stations, intermediate in 7 stations, and advanced in 9 stations. Compliance with COVID-19 prevention measures in public transportation stations in the Greater Accra region remains a challenge. Awareness creation should aim to elevate COVID-19 risk perception of transportation operators and clients. Transport operators and stations need support and guidance to enforce hand washing and social distancing.

Cervical cancer screening practices among women in Ghana: evidence from wave 2 of the WHO study on global AGEing and adult health.

BACKGROUND: Cervical cancer is the third most common cancer that affects women worldwide. It has been and remains the leading cause of cancer mortality among women in Ghana. Despite the fact that cervical cancer is preventable through early detection and treatment of precancerous lesions, anecdotal evidence from gynaecological clinics in Ghana indicates that most patients present with a late stage of the disease. This study assesses the cervical cancer screening practices among women in Ghana. METHODS: Data from the World Health Organization's (WHO) multi-country Study on AGEing and adult health (SAGE) wave 2 conducted between 2014 and 2015 in Ghana was used. We employed binary logistic regression models to analyse data on 2711 women to examine factors associated with having pelvic examination among women aged ≥18 years. Among those who had pelvic examination, we applied binary logistic regression models to analyse factors associated with receiving Pap smear test as a subgroup analysis. RESULTS: Of the 2711 women aged 18 years or older surveyed, 225 (8.3%) had ever had a pelvic examination and only 66 (2.4%) of them reported ever having done a Pap smear test. For those who had pelvic examination, only 26.94% had Pap smear test. Ethnic group, marital status, father's educational level and difficulty with self-care were independently associated with undergoing pelvic examination. Only age and healthcare involvement were independently associated with pelvic examination within the past 5 years to the survey. Marital status, satisfaction with healthcare and healthcare involvement were independently associated with Pap smear test. CONCLUSION: Even though cervical cancer is preventable through early detection of precancerous lesions using Pap smear test, the patronage of this screening test is still very low in Ghana. Factors influencing the low patronage in Ghana include the marital status of women, their level of satisfaction with healthcare as well as their level of involvement with healthcare. These may be the consequences of a weak health system and the lack of a national policy on cervical cancer screening.

Prevalence, awareness, and associated risk factors of hypertension in older adults in Africa: a systematic review and meta-analysis protocol.

BACKGROUND: The health of older persons has not been a major priority in many African countries. Hypertension is one of the common health problems of older persons. However, there is little information on the prevalence of hypertension in older adults in Africa. This is in spite of the fact that Africa has the highest age-standardized prevalence of hypertension in the world. We therefore present this protocol to conduct a systematic review and meta-analysis on the prevalence of hypertension and the level of its awareness among older persons living in Africa. METHODS: Major databases (EMBASE, MEDLINE, Academic Search Complete, CINAHL, PsycINFO) and unpublished literature will be searched to identify population-based studies on hypertension in adults aged 50 years and older living in Africa. Eligible articles are those which use the 140/90-mmHg cutoff to diagnose hypertension and were published from 1980 to present. We will exclude subjects in restricted environments such as patients and refugees. Articles will be independently evaluated by two reviewers to determine if they meet the inclusion criteria. They will also evaluate the quality of included studies using a validated tool by Hoy and colleagues for prevalence studies. The main outcome is the prevalence of hypertension while the explanatory variables include demographic, socio-economic, dietary, lifestyle and behavioural factors. Effect sizes in bivariate and multivariate analyses will be presented as odds or prevalence ratios. We will explore for heterogeneity of the standard errors across the studies, and if appropriate, we will perform a meta-analysis using a random-effects model to present a summary estimate of the prevalence of hypertension in this population. DISCUSSION: The estimates of the prevalence, the risk factors and the level of awareness of hypertension could help in galvanizing efforts at prioritizing the cardiovascular health of older persons in Africa. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42017056474.

Metal oxide nanoparticle growth on graphene via chemical activation with atomic oxygen.

Chemically interfacing the inert basal plane of graphene with other materials has limited the development of graphene-based catalysts, composite materials, and devices. Here, we overcome this limitation by chemically activating epitaxial graphene on SiC(0001) using atomic oxygen. Atomic oxygen produces epoxide groups on graphene, which act as reactive nucleation sites for zinc oxide nanoparticle growth using the atomic layer deposition precursor diethyl zinc. In particular, exposure of epoxidized graphene to diethyl zinc abstracts oxygen, creating mobile species that diffuse on the surface to form metal oxide clusters. This mechanism is corroborated with a combination of scanning probe microscopy, Raman spectroscopy, and density functional theory and can likely be generalized to a wide variety of related surface reactions on graphene.

Bacteria-polymeric membrane interactions: atomic force microscopy and XDLVO predictions.

Atomic force microscopy (AFM) in conjunction with a bioprobe developed using a polydopamine wet adhesive was used to directly measure the adhesive force between bacteria and different polymeric membrane surfaces. Bacterial cells of Pseudomonas putida and Bacillus subtilis were immobilized onto the tip of a standard AFM cantilever, and force measurements made using the modified cantilever on various membranes. Interaction forces measured with the bacterial probe were compared, qualitatively, to predictions by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory with steric interactions included. The XDLVO theory predicted attractive interactions between low energy hydrophobic membranes with high energy hydrophilic bacterium (P. putida). It also predicted a shallow primary maximum with the most hydrophilic bacterium, B. subtilis . Discrepancies between predictions using the XDLVO theory and theory require involvement of factors such as bridging effects. Differences in interaction between P. putida and B. subtilis are attributed to acid-base interactions and steric interactions. P. putida is Gram negative with lipopolysaccharides present in the outer cell membrane. A variation in forces of adhesion for bacteria on polymeric membranes studied was interpreted in terms of hydrophilicity and interfacial surface potential calculated from physicochemical properties.

Templating sub-10 nm atomic layer deposited oxide nanostructures on graphene via one-dimensional organic self-assembled monolayers.

Molecular-scale control over the integration of disparate materials on graphene is a critical step in the development of graphene-based electronics and sensors. Here, we report that self-assembled monolayers of 10,12-pentacosadiynoic acid (PCDA) on epitaxial graphene can be used to template the reaction and directed growth of atomic layer deposited (ALD) oxide nanostructures with sub-10 nm lateral resolution. PCDA spontaneously assembles into well-ordered domains consisting of one-dimensional molecular chains that coat the entire graphene surface in a manner consistent with the symmetry of the underlying graphene lattice. Subsequently, zinc oxide and alumina ALD precursors are shown to preferentially react with the functional moieties of PCDA, resulting in templated oxide nanostructures. The retention of the original one-dimensional molecular ordering following ALD is dependent on the chemical reaction pathway and the stability of the monolayer, which can be enhanced via ultraviolet-induced molecular cross-linking.

Quantitatively enhanced reliability and uniformity of high-κ dielectrics on graphene enabled by self-assembled seeding layers.

The full potential of graphene in integrated circuits can only be realized with a reliable ultrathin high-κ top-gate dielectric. Here, we report the first statistical analysis of the breakdown characteristics of dielectrics on graphene, which allows the simultaneous optimization of gate capacitance and the key parameters that describe large-area uniformity and dielectric strength. In particular, vertically heterogeneous and laterally homogeneous Al2O3 and HfO2 stacks grown via atomic-layer deposition and seeded by a molecularly thin perylene-3,4,9,10-tetracarboxylic dianhydride organic monolayer exhibit high uniformities (Weibull shape parameter ß > 25) and large breakdown strengths (Weibull scale parameter, E(BD) > 7 MV/cm) that are comparable to control dielectrics grown on Si substrates.

Self-assembly and photopolymerization of sub-2 nm one-dimensional organic nanostructures on graphene.

While graphene has attracted significant attention from the research community due to its high charge carrier mobility, important issues remain unresolved that prevent its widespread use in technologically significant applications such as digital electronics. For example, the chemical inertness of graphene hinders integration with other materials, and the lack of a bandgap implies poor switching characteristics in transistors. The formation of ordered organic monolayers on graphene has the potential to address each of these challenges. In particular, functional groups incorporated into the constituent molecules enable tailored chemical reactivity, while molecular-scale ordering within the monolayer provides sub-2 nm templates with the potential to tune the electronic band structure of graphene via quantum confinement effects. Toward these ends, we report here the formation of well-defined one-dimensional organic nanostructures on epitaxial graphene via the self-assembly of 10,12-pentacosadiynoic acid (PCDA) in ultrahigh vacuum (UHV). Molecular resolution UHV scanning tunneling microscopy (STM) images confirm the one-dimensional ordering of the as-deposited PCDA monolayer and show domain boundaries with symmetry consistent with the underlying graphene lattice. In an effort to further stabilize the monolayer, in situ ultraviolet photopolymerization induces covalent bonding between neighboring PCDA molecules in a manner that maintains one-dimensional ordering as verified by UHV STM and ambient atomic force microscopy (AFM). Further quantitative insights into these experimental observations are provided by semiempirical quantum chemistry calculations that compare the molecular structure before and after photopolymerization.

Probing the Structure and Chemistry of Perylenetetracarboxylic Dianhydride on Graphene Before and After Atomic Layer Deposition of Alumina.

The superlative electronic properties of graphene suggest its use as the foundation of next generation integrated circuits. However, this application requires precise control of the interface between graphene and other materials, especially the metal oxides that are commonly used as gate dielectrics. Towards that end, organic seeding layers have been empirically shown to seed ultrathin dielectric growth on graphene via atomic layer deposition (ALD), although the underlying chemical mechanisms and structural details of the molecule/dielectric interface remain unknown. Here, confocal resonance Raman spectroscopy is employed to quantify the structure and chemistry of monolayers of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on graphene before and after deposition of alumina with the ALD precursors trimethyl aluminum (TMA) and water. Photoluminescence measurements provide further insight into the details of the growth mechanism, including the transition between layer-by-layer growth and island formation. Overall, these results reveal that PTCDA is not consumed during ALD, thereby preserving a well-defined and passivating organic interface between graphene and deposited dielectric thin films.

Fundamental performance limits of carbon nanotube thin-film transistors achieved using hybrid molecular dielectrics.

In the past decade, semiconducting carbon nanotube thin films have been recognized as contending materials for wide-ranging applications in electronics, energy, and sensing. In particular, improvements in large-area flexible electronics have been achieved through independent advances in postgrowth processing to resolve metallic versus semiconducting carbon nanotube heterogeneity, in improved gate dielectrics, and in self-assembly processes. Moreover, controlled tuning of specific device components has afforded fundamental probes of the trade-offs between materials properties and device performance metrics. Nevertheless, carbon nanotube transistor performance suitable for real-world applications awaits understanding-based progress in the integration of independently pioneered device components. We achieve this here by integrating high-purity semiconducting carbon nanotube films with a custom-designed hybrid inorganic-organic gate dielectric. This synergistic combination of materials circumvents conventional design trade-offs, resulting in concurrent advances in several transistor performance metrics such as transconductance (6.5 µS/µm), intrinsic field-effect mobility (147 cm(2)/(V s)), subthreshold swing (150 mV/decade), and on/off ratio (5 × 10(5)), while also achieving hysteresis-free operation in ambient conditions.

Seeding atomic layer deposition of high-k dielectrics on epitaxial graphene with organic self-assembled monolayers.

The development of high-performance graphene-based nanoelectronics requires the integration of ultrathin and pinhole-free high-k dielectric films with graphene at the wafer scale. Here, we demonstrate that self-assembled monolayers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) act as effective organic seeding layers for atomic layer deposition (ALD) of HfO(2) and Al(2)O(3) on epitaxial graphene on SiC(0001). The PTCDA is deposited via sublimation in ultrahigh vacuum and shown to be highly ordered with low defect density by molecular-resolution scanning tunneling microscopy. Whereas identical ALD conditions lead to incomplete and rough dielectric deposition on bare graphene, the chemical functionality provided by the PTCDA seeding layer yields highly uniform and conformal films. The morphology and chemistry of the dielectric films are characterized by atomic force microscopy, ellipsometry, cross-sectional scanning electron microscopy, and X-ray photoelectron spectroscopy, while high-resolution X-ray reflectivity measurements indicate that the underlying graphene remains intact following ALD. Using the PTCDA seeding layer, metal-oxide-graphene capacitors fabricated with a 3 nm Al(2)O(3) and 10 nm HfO(2) dielectric stack show high capacitance values of ∼700 nF/cm(2) and low leakage currents of ∼5 × 10(-9) A/cm(2) at 1 V applied bias. These results demonstrate the viability of sublimated organic self-assembled monolayers as seeding layers for high-k dielectric films in graphene-based nanoelectronics.

Preparation, characterization, and application of polypropylene-clinoptilolite composites for the selective adsorption of lead from aqueous media.

A polymer composite of polypropylene (PP) and clinoptilolite (CLI) for the adsorption of lead has been prepared using the melt-mixing compounding technique in a rheomixer. Characterization of the composite was performed using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), Brunuer-Emmett-Teller (BET), and Fourier transform infrared spectroscopy (FTIR). The influence of contact time, pH, initial metal-ion concentration, temperature, and pretreatment on the adsorption of lead (Pb) by the PP-CLI composite was investigated. Optimum pH was found to be between pH 6 and pH 8 while the maximum sorption of lead at optimal pH was 95%. No difference was observed between the adsorption behavior of composites functionalized with 20% and 30% clinoptilolite, respectively, while the pretreatment with HCl and NaCl made a slight difference to the adsorption capacity of composites. The findings from this study on the lead adsorption behavior of CLI-PP composite may have potential applications in wastewater and water purification works.