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[This corrects the article DOI: 10.7759/cureus.57472.].
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Introduction With the growing acceptance of transgender individuals, the number of gender affirmation surgeries has increased. Transgender individuals face elevated depression rates, leading to an increase in suicide ideation and attempts. This study evaluates the risk of suicide or self-harm associated with gender affirmation procedures. Methods This retrospective study utilized de-identified patient data from the TriNetX (TriNetX, LLC, Cambridge, MA) database, involving 56 United States healthcare organizations and over 90 million patients. The study involved four cohorts: cohort A, adults aged 18-60 who had gender-affirming surgery and an emergency visit (N = 1,501); cohort B, control group of adults with emergency visits but no gender-affirming surgery (N = 15,608,363); and cohort C, control group of adults with emergency visits, tubal ligation or vasectomy, but no gender-affirming surgery (N = 142,093). Propensity matching was applied to cohorts A and C. Data from February 4, 2003, to February 4, 2023, were analyzed to examine suicide attempts, death, self-harm, and post-traumatic stress disorder (PTSD) within five years of the index event. A secondary analysis involving a control group with pharyngitis, referred to as cohort D, was conducted to validate the results from cohort C. Results Individuals who underwent gender-affirming surgery had a 12.12-fold higher suicide attempt risk than those who did not (3.47% vs. 0.29%, RR 95% CI 9.20-15.96, p < 0.0001). Compared to the tubal ligation/vasectomy controls, the risk was 5.03-fold higher before propensity matching and remained significant at 4.71-fold after matching (3.50% vs. 0.74%, RR 95% CI 2.46-9.024, p < 0.0001) for the gender affirmation patients with similar results with the pharyngitis controls. Conclusion Gender-affirming surgery is significantly associated with elevated suicide attempt risks, underlining the necessity for comprehensive post-procedure psychiatric support.
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Little is known about the burden of silicosis in Africa, despite extensive mining and construction operations in the region putting numerous people at risk. The implementation experience and costs of case-finding for occupational lung disease in resource-limited settings are also currently unknown. We describe the first-ever silicosis case-finding project in rural Rwanda using chest X-ray, symptom questionnaires, and spirometry. This was coupled with routine noncommunicable disease case-finding for diabetes and hypertension. We performed an ingredient-based analysis of the costs of all case-finding activities. In 2022, over 25 days, 1,032 mine workers were included in the program, of which 1,014 (98.3%) completed silicosis case-finding activities. The total cost of the program was estimated to be US$38,656, representing a cost of US$37.49 per person. We conclude that conducting large-scale occupational lung disease case-finding is clinically and economically feasible in resource-limited settings and can be effectively integrated with routine noncommunicable disease case-finding.
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População Rural , Silicose , Humanos , Silicose/economia , Ruanda , Masculino , Mineração/economia , Custos e Análise de Custo , Adulto , Mineradores , Espirometria , Pessoa de Meia-Idade , Doenças Profissionais/economia , Inquéritos e QuestionáriosRESUMO
BACKGROUND: Asylum seekers report exposure to human rights violations associated with a range of psychological and medical sequelae. Clinical evaluators can provide forensic evaluations that document evidence associated with their reports of persecution. The aim of this study was to characterize the forms of abuse experienced by asylum seekers, the psychological consequences of abuse, and the frequency with which clinician-evaluators found evidence that corroborated asylum seekers' reports. METHOD: We completed a retrospective chart review of 121 asylum seekers who received pro bono medical-legal evaluations through a human rights program and analyzed data using the constant comparative method. RESULTS: Eighty-eight percent of the clients reported experiencing multiple human rights abuses. Ninety-one percent of the clients who received psychological evaluations presented with symptoms associated with depression, anxiety, or trauma and stressor-related disorders. Clinician-evaluators found physical or psychological evidence consistent with the clients' reports in 97% of cases. Forms, perpetrators, and psychological consequences of abuse varied significantly by gender and geographic region. DISCUSSION: Asylum seekers report diverse forms of persecution in their countries of origin that differ by gender and geographic region. Clinician-evaluators overwhelmingly found physical and psychological evidence consistent with the asylum seekers' accounts of persecution.
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Exposição à Violência , Violação de Direitos Humanos/classificação , Abuso Físico , Trauma Psicológico , Refugiados/psicologia , Adolescente , Adulto , Documentação , Feminino , Guias como Assunto , Violação de Direitos Humanos/estatística & dados numéricos , Humanos , Masculino , Pessoa de Meia-Idade , Exame Físico , Refugiados/estatística & dados numéricos , Estudos Retrospectivos , Estados Unidos , Adulto JovemRESUMO
Patients with atrial fibrillation who undergo percutaneous coronary intervention with drug-eluting stent implantation often require oral anticoagulation (OAC) and antiplatelet therapies. Triple antithrombotic therapy (OAC, a P2Y12-receptor inhibitor, and aspirin) has been the default antithrombotic strategy. Evidence from randomized trials indicates, however, that a dual antithrombotic therapy strategy (OAC plus a P2Y12-receptor inhibitor) reduces bleeding risk without increasing the risk of ischemic events. This review provides an overview of advancements in this field as well as European and North American guidelines and consensus documents to inform clinical decision making around antithrombotic therapies for patients with atrial fibrillation who undergo percutaneous coronary intervention.
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Anticoagulantes/uso terapêutico , Fibrilação Atrial/tratamento farmacológico , Doença da Artéria Coronariana/terapia , Fibrinolíticos/uso terapêutico , Intervenção Coronária Percutânea , Administração Oral , Fibrilação Atrial/complicações , Clopidogrel/uso terapêutico , Doença da Artéria Coronariana/complicações , Quimioterapia Combinada , Fibrinolíticos/efeitos adversos , Humanos , Inibidores da Agregação Plaquetária/uso terapêutico , Guias de Prática Clínica como Assunto , Antagonistas do Receptor Purinérgico P2Y/uso terapêuticoRESUMO
BACKGROUND: There is varying evidence regarding the effects of body mass index (BMI) on outcomes of endovascular aneurysm repair (EVAR). This study investigates the effects of BMI on an index of perioperative and postoperative outcomes after EVAR. METHODS: Four hundred ninety-two patients who underwent elective EVAR at Mount Sinai Hospital were included in this study. Patients were classified as either normal weight (BMI = 18.5-25), overweight (BMI = 25-30), or obese (BMI>30). Chi-squared tests were used to determine significant differences between weight classes across an index of outcomes. The following outcomes were collected: intraoperative complications (e.g., conversion to open), perioperative complications (e.g., hematoma, bowel ischemia, and so forth), and postoperative outcomes (endoleak, sac enlargement, sac shrinkage, access site infection, prolonged postoperative length of stay, reintervention, stroke, claudication/lower extremity ischemia, deep vein thrombosis, limb occlusion, renal complications, abdominal aortic aneurysm (AAA) rupture, AAA-related mortality, and all-cause mortality). Kaplan-Meier survival analysis and a log-rank test were used to determine meaningful differences in all-cause mortality following EVAR between the respective weight classes. Subsequently, multivariate Cox proportional hazards were performed for selection of outcomes, with weight classes as predictors. Finally, a multivariate logistic regression was performed for postoperative hospital stay. Subgroup multivariate analysis was also performed examining only class I obese patients, rather than all obese patients. RESULTS: Overweight patients were significantly less likely to experience all-cause mortality up to 9 years after EVAR than normal-weight patients in both Kaplan-Meier and multivariable Cox proportional hazards models. Obese patients similarly had a lower risk of mortality in Kaplan-Meier analysis, but this did not persist in the multivariate analysis. Overweight patients were also significantly less likely to require a postoperative hospital stay longer than 1 day when compared with normal-weight patients. Finally, obese patients were less likely to have a sac shrinkage greater than 5 mm after EVAR, but were also less likely to have an endoleak. CONCLUSIONS: This study adds to the debate on the effects of BMI on outcomes of EVAR. Obesity was not a risk factor for negative perioperative or postoperative outcomes after EVAR with the exception of decreased sac shrinkage. Obese patients were less likely to have an endoleak, and overweight patients were protected against all-cause mortality and longer postoperative hospital stays.
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Aneurisma da Aorta Abdominal/cirurgia , Implante de Prótese Vascular , Índice de Massa Corporal , Procedimentos Endovasculares , Obesidade/complicações , Idoso , Idoso de 80 Anos ou mais , Aneurisma da Aorta Abdominal/complicações , Aneurisma da Aorta Abdominal/diagnóstico por imagem , Aneurisma da Aorta Abdominal/mortalidade , Implante de Prótese Vascular/efeitos adversos , Implante de Prótese Vascular/mortalidade , Endoleak/etiologia , Procedimentos Endovasculares/efeitos adversos , Procedimentos Endovasculares/mortalidade , Feminino , Humanos , Tempo de Internação , Masculino , Pessoa de Meia-Idade , Cidade de Nova Iorque , Obesidade/diagnóstico , Obesidade/mortalidade , Valor Preditivo dos Testes , Fatores de Proteção , Estudos Retrospectivos , Medição de Risco , Fatores de Risco , Fatores de Tempo , Resultado do TratamentoRESUMO
BACKGROUND: Sex-related differences in outcomes have been identified in patients with peripheral artery disease (PAD). We hypothesized that women with PAD would have equivalent inpatient mortality with men after vascular intervention. METHODS: Patients with a primary diagnosis of critical limb ischemia (CLI) or lifestyle-limiting claudication (LLC) receiving endovascular (EV) or open surgical repair from 2003-2012 were identified from the Nationwide Inpatient Sample. Demographics, comorbidities, and inpatient mortality were analyzed by chi-squared tests of independence and independent-samples t-tests. Logistic regression analysis was performed to identify predictors of inpatient mortality. SPSS 24 software was used with P < 0.05 considered statistically significant. RESULTS: We identified 139,435 (59,432 women and 80,003 men) individuals meeting the aforementioned criteria. Women were older than men (71.5 years vs. 68.2, P < 0.001). There were no differences in racial distribution but women had lower rates of diabetes (38.6% vs. 39.7%, P < 0.001), chronic obstructive pulmonary disease (17.9% vs. 19.5%, P < 0.001), and coronary artery disease (38.6% vs. 47.4%, P < 0.001), while having a higher rate of hypertension (60.0% vs. 56.1%, P < 0.001). There was no sex-related difference in the rate of chronic renal failure. Women had higher inpatient mortality than men after vascular intervention (1.3% vs. 1.1%, P < 0.001). When stratified by surgical technique, women also had higher inpatient mortality after EV repair (1.0% vs. 0.8%, P < 0.05) and open repair (1.9% vs 1.3%, P < 0.001). When separated by admitting diagnosis, women with CLI had higher inpatient mortality than men after open surgery (2.3% vs. 1.9%, P < 0.05) but not after EV intervention. Women with LLC had higher inpatient mortality after both open (0.6% vs. 0.3%, P < 0.05) and EV surgery (0.3% vs. 0.1%, P < 0.05). Regression analysis revealed female sex as an independent predictor of inpatient mortality in patients with LLC (OR, 1.74; 95% CI 1.30-2.32, P < 0.001) but not CLI. CONCLUSIONS: Women had higher inpatient mortality than men after vascular intervention for PAD. Women were also older and more likely to have EV intervention than men. Subgroup analysis suggests that these sex-related differences in inpatient mortality are more pronounced in patients with LLC than with CLI. Furthermore, regression analysis shows that sex is a significant predictor for patients diagnosed with LLC but not with CLI. Treatment guidelines should include consideration of sex in their indications for revascularization, particularly for patients diagnosed with LLC.
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Mortalidade Hospitalar , Claudicação Intermitente/cirurgia , Isquemia/cirurgia , Admissão do Paciente , Doença Arterial Periférica/cirurgia , Procedimentos Cirúrgicos Vasculares/mortalidade , Fatores Etários , Idoso , Comorbidade , Estado Terminal , Bases de Dados Factuais , Procedimentos Endovasculares/efeitos adversos , Procedimentos Endovasculares/mortalidade , Feminino , Disparidades nos Níveis de Saúde , Mortalidade Hospitalar/tendências , Humanos , Claudicação Intermitente/diagnóstico por imagem , Claudicação Intermitente/mortalidade , Isquemia/diagnóstico por imagem , Isquemia/mortalidade , Masculino , Doença Arterial Periférica/diagnóstico por imagem , Doença Arterial Periférica/mortalidade , Medição de Risco , Fatores de Risco , Fatores Sexuais , Fatores de Tempo , Resultado do Tratamento , Estados Unidos/epidemiologia , Procedimentos Cirúrgicos Vasculares/efeitos adversos , Procedimentos Cirúrgicos Vasculares/tendênciasRESUMO
BACKGROUND: The long-term durability of Roux-en-Y gastric bypass (RYGB) remains ill-defined in the American population secondary to poor follow-up after bariatric surgery. OBJECTIVES: This study evaluated the population lost to follow-up to better define the long-term durability of RYGB for weight loss and co-morbidity amelioration. METHODS: All patients (n = 1087) undergoing RYGB at a single institution between 1985 and 2004 were evaluated. Univariate differences in preoperative co-morbidities, postoperative complications, annual weight loss, and 10-year co-morbidities were analyzed to compare outcomes between patients with routine follow-up and those without. Using electronic medical record review for all encounters at our academic medical center and telephone survey, we obtained data for patients lost to follow-up. RESULTS: Among 1087 RYGB patients, 151 (14%) had consistent 10-year follow-up in our prospectively collected database, with yearly clinic visits beyond 2 years postoperatively. Electronic medical record review and telephone survey data were collected on an additional 500 (46%) patients, resulting in 60% of patients having 10-year follow-up after RYGB. There was no statistical difference in any preoperative or postoperative variables between the 2 groups. We found no difference in co-morbidity prevalence preoperatively or at 10 years between groups. Examination of percent excess body mass index lost at yearly intervals revealed no difference between the groups at each interval up to 10 years (P = .36). CONCLUSION: We found no difference in 10-year outcomes, including weight loss and co-morbidity reduction, between patients with routine clinic visits and those lost to follow-up. These 10-year data address the gap in knowledge resulting from poor long-term follow-up after bariatric surgery.
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Derivação Gástrica , Obesidade Mórbida/cirurgia , Adulto , Estudos Epidemiológicos , Feminino , Humanos , Peso Corporal Ideal , Masculino , Obesidade Mórbida/complicações , Satisfação do Paciente , Resultado do Tratamento , Redução de Peso/fisiologiaRESUMO
OBJECTIVE(S): The aim of the study was to evaluate the clinical effectiveness and long-term durability of Roux-en-Y Gastric Bypass (RYGB) at an accredited center. BACKGROUND: Short-term data have established the effectiveness of RYGB for weight loss and comorbidity amelioration. The long-term durability of this operation remains infrequently described in the American population. METHODS: All patients (N = 1087) undergoing RYGB at a single institution over a 20-year study period (1985-2004) were evaluated. Univariate differences in preoperative comorbidities, operative characteristics (laparoscopic vs. open), postoperative complications, annual weight loss, and current comorbidities were analyzed to establish trends and outcomes 10 years after surgery. RESULTS: Among 1087 RYGB patients, 651 (60%) had complete 10-year follow-up, including 335 open RYGB and 316 laparoscopic RYGB. Patients undergoing open RYGB had a higher preoperative body mass index. Otherwise, preoperative characteristics were similar. Postoperative incisional hernia rates were expectedly higher in open (vs laparoscopic) RYGB (16.9% vs 4.7%; P = 0.02). Annual % reduction in excess body mass index significantly improved over time, peaking at 74% by 24 months, with a slow trend down to 52% at 10 years (all P < 0.001). Importantly, a highly significant decrease in obesity-related comorbid disease persisted at 10 years of follow-up after RYGB. CONCLUSIONS: Roux-en-Y Gastric Bypass remains an excellent and durable operation for long-term weight loss and treatment of obesity-related comorbid disease. Laparoscopic RYGB results in highly favorable outcomes with reduced incisional hernia rates. These 10-year data help to more clearly define long-term outcomes and demonstrate outstanding reduction in comorbid disease following RYGB.
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Derivação Gástrica , Laparoscopia , Obesidade Mórbida/cirurgia , Redução de Peso , Adulto , Índice de Massa Corporal , Conversão para Cirurgia Aberta , Feminino , Seguimentos , Derivação Gástrica/métodos , Humanos , Laparoscopia/métodos , Tempo de Internação , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores de Risco , Fatores de Tempo , Resultado do TratamentoRESUMO
The concept of the Kennedy Terminal Ulcer (KTU) has been ubiquitous in attempting to explain the development of pressure based tissue injuries in patients with actual or presumed terminal conditions. The concept is problematic in that it uses factors other than pressure to explain the development and progression of pressure based tissue injuries, specifically the presence of a terminal condition. Based on the most current understanding of how pressure based tissue injuries develop and progress, the concept of The Kennedy Terminal Ulcer appears to be without physiologic basis and based solely on observation. Since systemic factors affect all tissues with relative equality, the development of a single locus of injury must logically be based on a single locus of cause and affect. The presumption that a single locus of injury will develop in an arbitrary location based on a systemic set of factors is untenable. A new concept called Miller Pressure Equivalent Injuries is proposed to refute the concept of a single pressure based tissue injury developing based solely on terminal systemic factors and why these previously presumed terminal condition associated pressure based injuries occur.
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BACKGROUND: There is limited outcome data for super-super-obese (SSO) patients, those with Body Mass Index (BMI) ≥ 60 kg/m(2), who seek surgical treatment with Laparoscopic Roux-en-Y Gastric Bypass (LRYGB). A large single center LRYGB experience was reviewed to compare the safety and efficacy of LRYGB in SSO patients to the standard obese population undergoing this procedure. METHODS: The American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database and an Institutional Review Board approved prospective database was used to identify all patients undergoing LRYGB by multiple surgeons at a single institution between 1/1/1994 and 11/15/2013. Preoperative co-morbidities, postoperative complications, 30-day outcomes, and weight loss at yearly intervals were analyzed to determine difference between SSO patients and NonSSO patients (BMI < 60 kg/m(2)). RESULTS: Of the 2009 patients undergoing LRYGB over the past 20 years; 328 had BMI ≥ 60 kg/m(2). Preoperative co-morbidities, conversion to open, and length of stay were significantly increased among SSO patients; however there was no significant difference in postoperative outcomes or complications. Percent reduction of excess BMI beyond 12 months was significantly improved among NonSSO patients with less than 30% follow-up beyond 2 years. CONCLUSIONS: LRYGB appears well tolerated for super-super-obese patients with BMI ≥ 60 kg/m(2) in experienced centers. These patients still have significant reduction in excess BMI despite being less than NonSSO patients undergoing RYGB. The ACS NSQIP database provides excellent tracking of institutional progress with bariatric surgical outcomes to facilitate the improvement of best practice techniques.
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Índice de Massa Corporal , Derivação Gástrica/métodos , Laparoscopia/métodos , Obesidade Mórbida/cirurgia , Redução de Peso , Adulto , Feminino , Humanos , Masculino , Obesidade Mórbida/diagnóstico , Estudos Prospectivos , Estudos Retrospectivos , Índice de Gravidade de Doença , Resultado do TratamentoRESUMO
For over 20 years, template stripping has been the best method for preparing ultrasmooth metal surfaces for studies of nanostructures. However, the organic adhesives used in the template stripping method are incompatible with many solvents, limiting the conditions that may subsequently be used to prepare samples; in addition, the film areas that can be reliably prepared are typically limited to â¼1 cm(2). In this article, we present chemical-mechanical polishing (CMP) as an adhesive-free, scalable method of preparing ultrasmooth gold surfaces. In this process, a gold film is first deposited by e-beam evaporation onto a 76-mm-diameter silicon wafer. The CMP process removes â¼4 nm of gold from the tops of the grains comprising the gold film to produce an ultrasmooth gold surface supported on the silicon wafer. We measured root-mean-square (RMS) roughness values using atomic force microscopy of 12 randomly sampled 1 µm × 1 µm areas on the surface of the wafer and repeated the process on 5 different CMP wafers. The average RMS roughness was 3.8 ± 0.5 Å, which is comparable to measured values for template-stripped gold (3.7 ± 0.5 Å). We also compared the use of CMP and template-stripped gold as bottom electrical contacts in molecular electronic junctions formed from n-alkanethiolate self-assembled monolayers as a sensitive test bed to detect differences in the topography of the gold surfaces. We demonstrate that these substrates produce statistically indistinguishable values for the tunneling decay coefficient ß, which is highly sensitive to the gold surface topography.
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This paper compares rates of charge transport across self-assembled monolayers (SAMs) of n-alkanethiolates having odd and even numbers of carbon atoms (nodd and neven) using junctions with the structure M(TS)/SAM//Ga2O3/EGaIn (M = Au or Ag). Measurements of current density, J(V), across SAMs of n-alkanethiolates on Au(TS) and Ag(TS) demonstrated a statistically significant odd-even effect on Au(TS), but not on Ag(TS), that could be detected using this technique. Statistical analysis showed the values of tunneling current density across SAMs of n-alkanethiolates on Au(TS) with nodd and neven belonging to two separate sets, and while there is a significant difference between the values of injection current density, J0, for these two series (log|J0Au,even| = 4.0 ± 0.3 and log|J0Au,odd| = 4.5 ± 0.3), the values of tunneling decay constant, ß, for nodd and neven alkyl chains are indistinguishable (ßAu,even = 0.73 ± 0.02 Å(-1), and ßAu,odd= 0.74 ± 0.02 Å(-1)). A comparison of electrical characteristics across junctions of n-alkanethiolate SAMs on gold and silver electrodes yields indistinguishable values of ß and J0 and indicates that a change that substantially alters the tilt angle of the alkyl chain (and, therefore, the thickness of the SAM) has no influence on the injection current density across SAMs of n-alkanethiolates.
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Alcanos/química , Compostos de Sulfidrila/química , Alcanos/síntese química , Transporte de Elétrons , Ouro/química , Prata/química , Compostos de Sulfidrila/síntese químicaRESUMO
We report the formation and characterization of self-assembled monolayers (SAMs) of dialkyldithiophosphinic acid adsorbates [CH3(CH2)n]2P(S)SH (R2DTPA) (n = 5, 9, 11, 13, 15) on ultrasmooth gold substrates prepared by the template stripping method. The SAMs were characterized using X-ray photoelectron spectroscopy, reflection-absorption infrared spectroscopy, contact angle measurements, lateral force microscopy, and electrochemical impedance spectroscopy. The data show these SAMs exhibit an unusual trend in alkyl chain crystallinity; SAMs formed from adsorbates with short alkyl chains (n = 5) are ordered and crystalline, and the alkyl groups become increasingly disordered and liquidlike as the number of methylene units is increased. This trend is the opposite of the typical behavior exhibited by n-alkanethiolate SAMs, in which the alkyl layer becomes more crystalline and ordered as the alkyl chain length is increased. We discuss four factors that operate together to determine how R2DTPA self-organize within SAMs on TS gold: (i) adsorbate-substrate interactions; (ii) gold substrate morphology; (iii) lateral van der Waals interactions between alkyl groups; and (iv) steric demands of the alkyl groups. We also present a model for the structures of these SAMs on the basis of consideration of the data and the structural parameters of a model (n)Bu2DTPA adsorbate. In this model, interdigitation of short alkyl chains stabilizes a trans-extended, crystalline arrangement and produces an ordered alkyl layer. As the alkyl chain length is increased, the increased steric demands of the alkyl groups lead to liquidlike, disorganized alkyl layers.
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We present new flexible, transparent, and conductive coatings composed of an annealed silver nanowire network embedded in a polyurethane optical adhesive. These coatings can be applied to rigid glass substrates as well as to flexible polyethylene terephthalate (PET) plastic and elastomeric polydimethylsiloxane (PDMS) substrates to produce highly flexible transparent conductive electrodes. The coatings are as conductive and transparent as indium tin oxide (ITO) films on glass, but they remain conductive at high bending strains and are more durable to marring and scratching than ITO. Coatings on PDMS withstand up to 76% tensile strain and 250 bending cycles of 15% strain with a negligible increase in electrical resistance. Since the silver nanowire network is embedded at the surface of the optical adhesive, these coatings also provide a smooth surface (root mean squared surface roughness<10 nm), making them suitable as transparent conducting electrodes in flexible light-emitting electrochemical cells. These devices continue to emit light even while being bent to radii as low as 1.5 mm and perform as well as unstrained devices after 20 bending cycles of 25% tensile strain.
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Eletrônica , Nanofios/química , Prata/química , Dimetilpolisiloxanos/química , Técnicas Eletroquímicas , Eletrodos , Vidro/química , Polietilenotereftalatos/química , Resistência à Tração , Compostos de Estanho/químicaRESUMO
We report the formation and characterization of self-assembled monolayers (SAMs) based on dialkyldithiophosphinic acid adsorbates {[CH(3)(CH(2))(n)](2)P(S)SH (n = 5, 9, 11, 13, 15)} on gold substrates. SAMs were characterized using X-ray photoelectron spectroscopy, reflection-absorption infrared spectroscopy, contact angle measurements, and electrochemical impedance spectroscopy. Data show that there is a roughly 60:40 mixture of bidentate and monodentate adsorbates in each of these SAMs. The presence of monodentate adsorbates is due to the numerous and deep grain boundaries of the underlying gold substrate, which disrupt chelation. Comparing the characterization data of dialkyldithiophosphinic acid SAMs with those of analogous n-alkanethiolate SAMs shows that both SAMs follow a similar trend: The alkyl chains become increasingly organized and crystalline with increasing alkyl chain length. The alkyl groups of dialkyldithiophosphinic acid SAMs, however, are generally less densely packed than those of n-alkanethiolate SAMs. For short alkyl chains (hexyl, decyl, and dodecyl), the significantly lower packing densities cause the alkyl chains to be liquid-like and disorganized. Long-chain dialkyldithiophosphinic acid SAMs are only slightly less crystalline than analogous n-alkanethiolate SAMs.
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Ouro/química , Ácidos Fosfínicos/química , Estrutura Molecular , Ácidos Fosfínicos/síntese química , Propriedades de SuperfícieRESUMO
We report the fabrication and characterization of new self-assembled monolayers (SAMs) formed from dihexadecyldithiophosphinic acid [(C(16))(2)DTPA] molecules on gold substrates. In these SAMs, the ability of the (C(16))(2)DTPA headgroup to chelate to the gold surface depends on the morphology of the gold substrate. Gold substrates fabricated by electron-beam evaporation (As-Dep gold) consist of â¼50-nm grains separated by deep grain boundaries (â¼10 nm). These grain boundaries inhibit the chelation of (C(16))(2)DTPA adsorbates to the surface, producing SAMs in which there is a mixture of monodentate and bidentate adsorbates. In contrast, gold substrates produced by template stripping (TS gold) consist of larger grains (â¼200-500 nm) with shallower grain boundaries (<2 nm). On these substrates, the low density of shallow grain boundaries allows (C(16))(2)DTPA molecules to chelate to the surface, producing SAMs in which all molecules are bidentate. The content of bidentate adsorbates in (C(16))(2)DTPA SAMs formed on As-Dep and TS gold substrates strongly affects the SAM properties: Alkyl chain organization, wettability, frictional response, barrier properties, thickness, and thermal stability all depend on whether a SAM has been formed on As-Dep or TS gold. This study demonstrates that substrate morphology has an important influence on the structure of SAMs formed from these chelating adsorbates.