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1.
J Pak Med Assoc ; 73(3): 487-493, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36932747

RESUMO

OBJECTIVE: To assess the perception and attitude of physicians related to breaking bad news. METHODS: The cross-sectional study was conducted at three teaching hospitals in Karachi and Mirpurkhas, Pakistan, from April 2019 to February 2020, after approval from Hamdard University, Karachi, and comprised physicians of either gender having direct patient contact. Data was collected using a questionnaire based on literature. The questionnaire was pilot-tested before distribution among the subjects. The responses were categorised with respect to age, gender and professional experience. Data was analysed using SPSS 25. RESULTS: Of the 230 subjects, 119(51.7%) were females. The overall mean age was 34.5±8.8 years and mean professional experience was 9.1±8.2 years. Overall, 19(8.3%) subjects believed they had a very good ability to deliver bad news, while 26(11.3%) avoided telling the patient the truth about diagnosis, prognosis and treatment. Age had a significant association with correctly defining breaking bad news (p<0.05). CONCLUSIONS: The skill level related to breaking bad news was found to be deficient.


Assuntos
Relações Médico-Paciente , Médicos , Feminino , Humanos , Adulto , Masculino , Revelação da Verdade , Paquistão , Estudos Transversais , Comunicação
2.
J Obstet Gynaecol ; 42(6): 1829-1834, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35476609

RESUMO

There is a dearth of literature studying restless leg syndrome (RLS) among pregnant patients in Pakistan. The objective of this study was to determine the prevalence and associated factors of RLS among pregnant Pakistani patients. It was conducted in 2018 among 478 women attending ante-natal check-up in the outpatient department of five hospitals in Karachi, Pakistan. Individuals were interviewed for socio-demographic information, the key criteria for RLS and its associated factors. RLS was reported in 54 (11%) individuals based on International Restless Legs Syndrome Study Group (IRLSSG) criteria. The mean age was 33.44 ± 4.42 years. Association between pregnant women with RLS and those without reveals statistically significant differences with increasing age (p=.01), gravida (p<.01) and para (p<.001). RLS was significant among working women (p=.001), during third trimester (p=.001), with insomnia (p<.001), use of tobacco (p<.001) and among women with gestational diabetes (p<.001), hypertension (p<.001). The study showed a low prevalence of RLS among women during pregnancy. It further reported gestational diabetes, hypertension, insomnia and tobacco use to be independently linked to RLS. Impact StatementWhat is already known on this subject? Pregnancy has been demonstrated to be strongly associated with development of secondary restless leg syndrome (RLS). RLS in pregnancy has also been shown to portend poor maternal and neonatal outcomes such as postpartum depression and preterm birth. Various conditions and lifestyle factors in pregnancy have been shown to be associated with the development of RLS, but there are variations in these across different populations.What do the results of this study add? The prevalence of RLS was only reported twice in pregnant patients in Pakistan and our research helps to address this data shortage. In addition, the results of our study document a strong association of RLS with gestational hypertension and gestational diabetes and also show that smoking and exercise were correlated with RLS during pregnancy, both of which were previously unstudied in the pregnant Pakistani population.What are the implications of these findings for clinical practice and/or further research? Demonstrating the prevalence of RLS in pregnant Pakistani patients highlights the need to screen these patients, particularly those with associated conditions identified in our findings, for RLS during antenatal visits and to treat their condition to improve maternal and neonatal outcomes.


Assuntos
Diabetes Gestacional , Hipertensão Induzida pela Gravidez , Complicações na Gravidez , Nascimento Prematuro , Síndrome das Pernas Inquietas , Distúrbios do Início e da Manutenção do Sono , Adulto , Feminino , Humanos , Recém-Nascido , Paquistão/epidemiologia , Gravidez , Complicações na Gravidez/epidemiologia , Prevalência , Síndrome das Pernas Inquietas/epidemiologia , Síndrome das Pernas Inquietas/etiologia , Distúrbios do Início e da Manutenção do Sono/complicações
3.
Pak J Med Sci ; 38(7): 1986-1991, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36246698

RESUMO

Objectives: To find out the impact of occupational and socio-demographic factors on the health related quality of life of sewerage and sanitary workers in Karachi. Methods: A cross-sectional study was conducted during 2019. Four hundred workers were chosen from five districts of Karachi using a non-probability convenient sampling technique. An Urdu version of WHO BRIEF quality of life questionnaire was used to collect the data about workers general health status and quality of life. Descriptive analysis was done and Chi-square test was used for the association of socio-demographic factors and quality of life. Multiple regression model was used to predict QOL of all domains. P-value<0.05 was considered as statistically significant. Results: Out of 400 sanitary workers, 228 (57.0%) were sweepers and the rest 172 (43.0) were sewerage workers. The majority of the workers 321 (80.3%) were male and 246 (61.5%) were illiterate. The vast majority of the workers 386 (96.5%) were not immunized against typhoid, / hepatitis and tetanus. Ninety-one percent (91%) were not using any kind of safety gadgets while at work. Male workers, married workers of both sexes and those with some education had a little better quality of life than their counterparts. Sanitary employees likewise had a higher quality of life score than sewage workers (P-value<0.05). Conclusion: The majority of workers, particularly sewage workers, have a very poor quality of life. Along with very bad working circumstances, their standard of living is significantly below par. They were not given any safety equipment. They were handling untreated sewage/waste with their bare hands, and they have never received a typhoid/hepatitis /tetanus vaccine.

4.
Anal Chem ; 93(36): 12320-12328, 2021 09 14.
Artigo em Inglês | MEDLINE | ID: mdl-34460223

RESUMO

Electrochemical impedance spectroscopy (EIS) is a powerful tool to measure and quantify the system impedance. However, EIS only provides an average result from the entire electrode surface. Here, we demonstrated a reflection impedance microscope (RIM) that allows us to image and quantify the localized impedance on conductive surfaces. The RIM is based on the sensitive dependence between the materials' optical properties, such as permittivity, and their local surface charge densities. The localized charge density variations introduced by the impedance measurements will lead to optical reflectivity changes on electrode surfaces. Our experiments demonstrated that reflectivity modulations are linearly proportional to the surface charge density on the electrode and the measurements show good agreement with the simple free electron gas model. The localized impedance distribution was successfully extracted from the reflectivity measurements together with the Randles equivalent circuit model. In addition, RIM is used to quantify the impedance on different conductive surfaces, such as indium tin oxide, gold film, and stainless steel electrodes. A polydimethylsiloxane-patterned electrode surface was used to demonstrate the impedance imaging capability of RIM. In the end, a single-cell impedance imaging was obtained by RIM.


Assuntos
Espectroscopia Dielétrica , Ouro , Condutividade Elétrica , Impedância Elétrica , Eletrodos
5.
J Pak Med Assoc ; 71(7): 1910-1913, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34410276

RESUMO

OBJECTIVE: To assess the knowledge, belief and preventive measures taken regarding osteoporosis by students of different non-medical educational backgrounds. METHODS: The descriptive cross-sectional study was conducted from January to March, 2018, at one private-sector and two public-sector universities in Karachi, and comprised female participants aged >15 years from engineering, commerce, social and pure sciences background. Osteoporosis Knowledge Assessment Tool questionnaire was self-administered to collect data which was analysed using SPSS 23. RESULTS: There were 400 females with a mean age of 20.55±1.66 years. The overall mean score was 46.49±12.83 and 43(10.8) subjects had a good score, 204(51%) had an average score and 150(37%) had a poor score regarding knowledge about osteoporosis. Also, 186(47%) subjects identified previous studies as their source about osteoporosis, 103(26%) gained knowledge by health professionals and 62(16%) did it through electronic media. The knowledge on risk factors, protective factors and perceived susceptibility were significant (p<0.05) when compared by type of study and age. CONCLUSIONS: The knowledge of the disease was found to be insufficient, indicating need for generating awareness regarding osteoporosis.


Assuntos
Conhecimentos, Atitudes e Prática em Saúde , Osteoporose , Adolescente , Adulto , Estudos Transversais , Feminino , Humanos , Osteoporose/epidemiologia , Paquistão/epidemiologia , Estudantes , Inquéritos e Questionários , Adulto Jovem
6.
J Pak Med Assoc ; 71(6): 1704-1708, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34111106

RESUMO

OBJECTIVE: To determine the awareness and practices of doctors and dentists in detecting and reporting suspected cases of child physical abuse. METHODS: The cross-sectional study was conducted from November 2017 to June 2018 at the Hamdard College of Medicine and Dentistry, Karachi, and comprised doctors and dentists practising in public and private hospitals across Pakistan. Data was collected using a predesigned questionnaire to assess knowledge of the social indicators of child physical abuse, response to child physical abuse, and actions taken by the professionals when they believed a child abuse case had been detected. Data was analysed using SPSS 22. RESULTS: Of the 575 healthcare professionals, 371(64.5%) were doctors and 204(35.5%) were dentists; 347(60.3%) were males; 446(77.6%) were working in private hospitals; 384(66.8%) had <10 years of experience; and 99(17.2%) had received formal training of child abuse. While 450(78.3%) subjects strongly agreed on the value of identifying and documenting child physical abuse, 336(58%) did not take any action in suspected cases. CONCLUSIONS: Although doctors and dentists had a positive attitude regarding child physical abuse, the majority preferred to remain silent in suspected cases.


Assuntos
Maus-Tratos Infantis , Abuso Físico , Atitude do Pessoal de Saúde , Criança , Maus-Tratos Infantis/diagnóstico , Estudos Transversais , Odontólogos , Feminino , Conhecimentos, Atitudes e Prática em Saúde , Humanos , Masculino , Paquistão , Inquéritos e Questionários
7.
Nanotechnology ; 31(45): 455601, 2020 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-32808596

RESUMO

Biological synthesis of gold nanostructures could potentially offer an environmentally friendly alternative to traditional chemical synthetic methods. During the last decades, various biomolecules, including amino acids, have been successfully used as reducing and capping agents to synthesize multi-shaped gold nanostructures. A grand challenge in this field is to increase our ability to control the size and shape of gold nanostructures formed precisely by systematic synthetic approaches based on the understanding of the mechanism for structural determination. In this study, using glycine as the model amino acid and chloroaurate (AuCl4 -) ions as the precursor solution, we report the finding that the shape of the gold nanostructures synthesized showed a strong correlation with the speciation of gold complexes determined by the pH, precursor concentration and chloride concentration of the solvent system. The gold chloro-hydroxy speciation [AuClx(OH)4-x]- (with x = 0-4) influenced the shape of the gold nanostructures formed, with gold nanoplatelets, nanotriangles, nanokites and nanoribbons observed at x = 4, 3, 2 and 1, respectively, and spherical nanoparticles observed at x = 0. Glycine was found to play a role as a reducing agent, but no significant effect on the morphology was observed, indicating the dominance of gold chloro-hydroxy speciation in the structural formation. These results collectively provide synthetic considerations to systematically synthesize non-spherical to spherical biosynthesized gold nanostructures by controlling the speciation of [AuClx(OH)4-x]-.

8.
J Pak Med Assoc ; 70(Suppl 3)(5): S113-S117, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32515391

RESUMO

Coronavirus disease (COVID-19) pandemic has rendered the world completely unaware and off-balance. Most of the countries of the world are in a lockdown of varying severity to break the chain of transmission. Many non-essential healthcare practices have been shut down to impose social distancing against a population whose slogan has been freedom of movement. Several healthcare providers have also been caught off guard. Many are not well-versed in the use of transmission-based safeguards, and the dental community, is no different. In this article, we identify the challenges faced by the oral and dental care providers, whose procedures generate a significant amount of aerosol, which can be a significant source of disease transmission within the community. It further describes the dynamics of aerosol spread and various strategies to minimise aerosol generation. Guidelines for the delivery of emergency dental treatment are formulated based on different guidelines from various international dental associations and organisations.


Assuntos
Betacoronavirus , Infecções por Coronavirus , Serviços de Saúde Bucal , Pandemias , Pneumonia Viral , COVID-19 , Atenção à Saúde , Humanos , Guias de Prática Clínica como Assunto , SARS-CoV-2
9.
J Pak Med Assoc ; 70(Suppl 3)(5): S169-S174, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32515406

RESUMO

OBJECTIVE: To measure the awareness of COVID-19 infection among the general population following the outbreak in China. METHODS: This descriptive cross-sectional study was carried out during January and February 2020 amongst the general population of Karachi, Pakistan. A pre-tested, self-administered questionnaire was used among 399 young adult participants. The questionnaire was developed keeping in view of the already published study on severe acute respiratory syndrome (SARS) and the available literature on COVID-19. It included sociodemographic information, assessment of knowledge, beliefs regarding coronavirus and the perception of precautionary measures taken by an individual. Chi-square test was used for categorical variables and p<0.05 was used as statistically significant. RESULTS: There were more females 299 (75%) than male participants 100 (25%). The mean age was 20.9 ±2.30 years and 232 (58%) had graduate degrees. There is lack of knowledge and awareness about coronavirus as 226 (56.6%) participants claimed that coronavirus is actually the most dangerous virus in the world, and 171 (43%) did know that the common flu virus is potentially more lethal than coronavirus. Although a large majority of participants correctly identified sources of transmission, measures and precautions to be taken for coronavirus, their knowledge for symptom identification was deficient. The most pursued platform for information for coronavirus was found to be social media, followed by television and print media. CONCLUSIONS: The study highlighted the level of awareness of coronavirus among young adults in Karachi, Pakistan. The study further pointed out the public knowledge gaps for the authorities concerned to help them develop more effective and successful awareness campaigns using preferred channels.


Assuntos
Betacoronavirus , Infecções por Coronavirus , Conhecimentos, Atitudes e Prática em Saúde , Pandemias , Pneumonia Viral , Adolescente , Adulto , COVID-19 , Estudos Transversais , Feminino , Humanos , Masculino , Paquistão/epidemiologia , SARS-CoV-2 , Adulto Jovem
10.
J Pak Med Assoc ; 70(11): 2077-2081, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33341867

RESUMO

Environmental hazards increase the health morbidity and mortality burden. This study compared the knowledge and perceptions about the health effects of environmental hazards among medical and engineering students of Hamdard University Karachi. A total of 263 (44.1%) engineering students, and 333 (55.9%) medical students participated in the study. Cumulatively, the three most commonly identified environmental hazards included tobacco smoking 561 (94.1%), global climate change 518 (86.9%), and solar ultraviolet radiation 511 (85.7%). The study results suggest the need for better quantifying the magnitude of understanding environmental hazards, and for health education and promotion programmes at the graduate level for medical and engineering students in Karachi.


Assuntos
Estudantes de Medicina , Universidades , Estudos Transversais , Conhecimentos, Atitudes e Prática em Saúde , Humanos , Percepção , Inquéritos e Questionários , Raios Ultravioleta
11.
J Pak Med Assoc ; 70(2): 381-385, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32063644

RESUMO

Organ transplantation is often the only hope for patients with end-stage organ failure. Organ transplant surgeries are increasingly becoming available in Pakistan. From May-July 2017, using convenience sampling and statistical programme R 3.4.1, we assessed and compared the organ donation attitudes among medical and allied health undergraduate students of the Hamdard University in Karachi. Compared to non-medical students, medical students were more likely to be concerned that family members of brain-dead patients would be upset if approached for organ donation, and felt that appropriate time for bringing up organ donation would be after the declaration of brain death has taken place. Medical students also considered prolonging life by using human organ transplants more appropriate, and considered organ donation desirable when a patient has been declared brain dead. As demand of human organs for transplantation far exceeds the supply, there is need to better understand the dynamics underpinning positive attitudes towards organ donation, and to improve educational activities by encouraging debate and acceptance of organ donation for saving lives.


Assuntos
Atitude do Pessoal de Saúde , Transplante de Órgãos , Estudantes de Odontologia , Estudantes de Medicina , Estudantes de Farmácia , Morte Encefálica , Feminino , Humanos , Masculino , Medicina Tradicional , Paquistão , Estudantes de Ciências da Saúde , Obtenção de Tecidos e Órgãos , Universidades
12.
J Pak Med Assoc ; 70(4): 772-775, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32296237

RESUMO

Violence against women is a human rights issue and a major public health problem. The objectives of this study were to determine the magnitude and type of emotional and physical domestic violence perpetrated by fathers on mothers of female students of a private university. A total of 564 questionnaires were duly filled and returned with a response rate of 94.0%. The most common form of violence was reported by 93 (16.5%) of the respondents who witnessed their fathers either saying or doing something to humiliate the respondents' mothers. While the most common physical violence witnessed was fathers slapping their mothers as reported by 39 (6.9%) of the respondents. Empowerment of women, and effective endeavours in education of both sexes are important steps towards addressing and preventing domestic violence.


Assuntos
Consanguinidade , Abuso Emocional/estatística & dados numéricos , Exposição à Violência/estatística & dados numéricos , Pai , Mães , Núcleo Familiar , Abuso Físico/estatística & dados numéricos , Maus-Tratos Conjugais/estatística & dados numéricos , Estudos Transversais , Violência Doméstica/estatística & dados numéricos , Feminino , Violência de Gênero/estatística & dados numéricos , Humanos , Paquistão/epidemiologia , Estudantes , Inquéritos e Questionários , Universidades
13.
Educ Health (Abingdon) ; 30(2): 140-145, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28928344

RESUMO

BACKGROUND: Publication is a central element in research dissemination and scientific misconduct in publication is relatively ignored in biomedical research. This study is to assess the knowledge of scientific misconduct in publication among private and public sector medical students. METHODS: A questionnaire-based cross-sectional study was carried in four (two public and two private) medical colleges of Karachi in 2015. After ethical approval, data were collected through convenient sampling and analyzed in SPSS 16.0. Descriptive statistics was used to summarize the data and Chi-square test was used for cross tabulation with sex, type of medical colleges, and knowledge of scientific misconduct in publication. RESULTS: A total of 592 medical students participated with mean age of 22.2 ± 1.47 years. The majority (491, 79%) of medical students had heard about the word "publication ethics," higher among public sector students than from private sector (P < 0.001). Only 78 (13.2%) reported to had published original articles, and 64 (10.8%) and 53 (9%) medical students had heard of "ICMJE authorship criteria" and "COPE," respectively. Knowledge about fabrication of data and scientific misconduct in publication was found to be statistically significant (P < 0.05) among males than female students. Statistically significant differences were also observed between public and private medical students for knowledge regarding salami slicing, ghost author, fabrication, and photomanipulation (P < 0.001) and for plagiarism (P < 0.005). Participants from public sector colleges scored significantly better in all above variables than private medical colleges except knowledge about salami slicing in which participants from latter performed significantly better than public sector students. DISCUSSION: The study demonstrates deficiencies in knowledge regarding several aspects of publication ethics among medical students of both public and private medical colleges in Karachi. There is a need to increase the awareness of research and publication ethics among students during their academic years.


Assuntos
Editoração/ética , Má Conduta Científica , Estudantes de Medicina/psicologia , Adolescente , Autoria/normas , Estudos Transversais , Feminino , Humanos , Masculino , Paquistão , Fotografação/ética , Plágio , Editoração/normas , Faculdades de Medicina , Inquéritos e Questionários
14.
J Pak Med Assoc ; 67(11): 1747-1750, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-29171573

RESUMO

Puberty heralds the onset of adulthood, and is fraught with complex physiological and psychological changes and emotions. In this study, we looked at the sources of information about puberty and sex education among males and females, age at which they learned about them, and the opinions on the role of schools and parents in imparting this education among medical students.A cross-sectional pilot study, using convenience sampling was conducted among 153 medical students of the Hamdard College of Medicine and Dentistry (HCM&D) in Karachi. Regarding most common source of information about puberty; 23 (25.3%) males identified friends as the most important source of information. While 31 (50.0%) women identified their mothers as the most important source.Regarding most common source of information about reproductive systems and sex; 17 (27.4%) women identified school teachers as the most common source of information, while 26 (28.6%) men identified books and magazines.


Assuntos
Conhecimentos, Atitudes e Prática em Saúde , Educação Sexual , Estudantes de Medicina/psicologia , Estudantes de Medicina/estatística & dados numéricos , Adulto , Estudos Transversais , Feminino , Humanos , Masculino , Paquistão/epidemiologia , Educação Sexual/métodos , Educação Sexual/estatística & dados numéricos , Adulto Jovem
15.
J Pak Med Assoc ; 67(9): 1369-1373, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28924276

RESUMO

OBJECTIVE: To assess the nutritional status of children living in Tharparkar. METHODS: This cross-sectional study was conducted in four villages of Tharparkar district of Sindh, Pakistan, in 2014, and comprised children aged between 6 and 59 months. Data was collected from mothers and anthropometry of children was done using standard techniques. Nutritional status was assessed by using age- and sex-specific World Health Organisation standard charts for underweight, stunting and wasting. Data was analysed using SPSS 16. RESULTS: Of the 304 children assessed, 117(38.5%) were stunted, 58(19.1 %) were wasted and 101(33.2 %) were underweight with no gender discrimination. Under-nutrition was particularly observed in the second year of life. Statistically significant factors associated with stunting were illiteracy of mother, family size of >5 members, pregnancy>4 times, child mortality in last 6 months, absence of breastfeeding and no history of child vaccination(p<0.05 each). Logistic regression revealed family size of <5 members, pregnancy ?4 times, breastfeeding and vaccination were protective factors for stunting (p<0.05 each). Mortality of a child in the last 6 months in the family was 3 times more likely to have a stunted child. CONCLUSIONS: Stunting was the most common type of under-nutrition with no sex discrimination.


Assuntos
Aleitamento Materno/estatística & dados numéricos , Transtornos da Nutrição Infantil/epidemiologia , Escolaridade , Características da Família , Transtornos da Nutrição do Lactente/epidemiologia , Alfabetização/estatística & dados numéricos , Paridade , Vacinação/estatística & dados numéricos , Mortalidade da Criança , Pré-Escolar , Feminino , Transtornos do Crescimento/epidemiologia , Humanos , Lactente , Modelos Logísticos , Masculino , Paquistão/epidemiologia , Fatores de Risco , Magreza/epidemiologia , Síndrome de Emaciação/epidemiologia
16.
J Am Chem Soc ; 138(4): 1114-7, 2016 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-26807600

RESUMO

Plasmonic metal/semiconductor heterostructures show promise for visible-light-driven photocatalysis. Gold nanorods (AuNRs) semi-coated with TiO2 are expected to be ideally structured systems for hydrogen evolution. Synthesizing such structures by wet-chemistry methods, however, has proved challenging. Here we report the bottom-up synthesis of AuNR/TiO2 nanodumbbells (NDs) with spatially separated Au/TiO2 regions, whose structures are governed by the NRs' diameter, and the higher curvature and lower density of CnTAB surfactant at the NRs' tips than on their lateral surfaces, as well as the morphology's dependence on concentration, and alkyl chain length of CnTAB. The NDs show plasmon-enhanced H2 evolution under visible and near-infrared light.

17.
Nano Lett ; 15(3): 2132-6, 2015 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-25664666

RESUMO

The optical resonances of plasmonic nanostructures depend critically on the geometrical details of the absorber. We show that this unique property of plasmons can potentially be used to create panchromatic absorbers covering most of the useful solar spectrum, by measuring the light-to-hydrogen conversion capabilities of a series multielectrode photocatalytic devices, based on functionalized gold nanorods of appropriately chosen aspect ratios. Judiciously combining nanorods of various aspect ratios almost doubles the H2 production of the device over what is optimally possible with a device using gold nanorods of a single aspect ratio (all other key parameters being equal). The estimated quantum efficiency (absorbed photons-to-hydrogen) averaged over the entire solar spectrum of the best performing plasmonic multielectrode array was approximately 0.1%, and the measured H2 production rate for all of the devices was found to be approximately proportional to the hot electron generation. The device was monitored continuously for over 200 hr of operation without measurable diminution in the rate.

18.
Nano Lett ; 14(6): 3328-34, 2014 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-24784236

RESUMO

Control and optimization of optically excited charge and energy transport across solid-liquid interfaces are essential for many applications including artificial photosynthesis, photocatalysis, and photopolymerization. Nanostructures are especially suited for this purpose, because the exciton diffusion length is typically much larger than the dimension of the particle, enabling efficient charge transport from the bulk to the nanoparticle surface for use in chemical transformations. However, characterization of charge transfer processes at nanoscale interfaces involving either isolated or assembled optoelectronic components remains a major challenge. Here, we use conductive probe-atomic force microscopy (cp-AFM) to spatially characterize the photovoltaic and photoelectrochemical properties of individual nanostructured photosynthetically active heterostructure (PAH) units in large area scans and compare them to thin-film photoelectrode devices. For CuInSe2/Au Schottky barrier PAH devices electrochemically synthesized inside porous anodic aluminum oxide, we observed a significant increase in solid-state photovoltages (∼0.5 V) and applied bias photocurrents (∼5 pA at +2 V) with much less spatial variation compared to thin film devices (<0.1 V and ∼2 pA at +2 V). We identified that the key reasons for the low performance of CuInSe2/Au thin film devices were an increased number of short-circuit pathways formed as a result of the fabrication process, and a lower density of grain boundaries leading to reduced photoelectrochemically active surface area. When photoanodes were fabricated with these PAH units, the electrodes showed superior and stable photoelectrochemical performance due to their inherent fault tolerance. Our results demonstrate the potential of using cp-AFM as a tool to characterize spatially resolved photoelectrochemical performance over device structures designed for areal production of chemicals and to provide us with a means of investigating optimal structural configurations and to better understand charge transfer processes across solid-liquid interface.

19.
Nano Lett ; 13(5): 2110-5, 2013 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-23586680

RESUMO

Efficient and cost-effective conversion of solar energy to useful chemicals and fuels could lead to a significant reduction in fossil hydrocarbon use. Artificial systems that use solar energy to produce chemicals have been reported for more than a century. However the most efficient devices demonstrated, based on traditionally fabricated compound semiconductors, have extremely short working lifetimes due to photocorrosion by the electrolyte. Here we report a stable, scalable design and molecular level fabrication strategy to create photoelectrochemically active heterostructure (PAH) units consisting of an efficient semiconductor light absorber in contact with oxidation and reduction electrocatalysts and otherwise protected by alumina. The functional heterostructures are fabricated by layer-by-layer, template-directed, electrochemical synthesis in porous anodic aluminum oxide membranes to produce high density arrays of electronically autonomous, nanostructured, corrosion resistant, photoactive units (~10(9)-10(10) PAHs per cm(2)). Each PAH unit is isolated from its neighbor by the transparent electrically insulating oxide cellular enclosure that makes the overall assembly fault tolerant. When illuminated with visible light, the free floating devices have been demonstrated to produce hydrogen at a stable rate for over 24 h in corrosive hydroiodic acid electrolyte with light as the only input. The quantum efficiency (averaged over the solar spectrum) for absorbed photons-to-hydrogen conversion was 7.4% and solar-to-hydrogen energy efficiency of incident light was 0.9%. The fabrication approach is scalable for commercial manufacturing and readily adaptable to a variety of earth abundant semiconductors which might otherwise be unstable as photoelectrocatalysts.

20.
Nano Lett ; 12(9): 5014-9, 2012 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-22916955

RESUMO

We report a plasmonic water splitting cell in which 95% of the effective charge carriers derive from surface plasmon decay to hot electrons, as evidenced by fuel production efficiencies up to 20-fold higher at visible, as compared to UV, wavelengths. The cell functions by illuminating a dense array of aligned gold nanorods capped with TiO(2), forming a Schottky metal/semiconductor interface which collects and conducts the hot electrons to an unilluminated platinum counter-electrode where hydrogen gas evolves. The resultant positive charges in the Au nanorods function as holes and are extracted by an oxidation catalyst which electrocatalytically oxidizes water to oxygen gas.


Assuntos
Eletroquímica/instrumentação , Eletrodos , Hidrogênio/química , Nanoestruturas/química , Oxigênio/química , Energia Solar , Ressonância de Plasmônio de Superfície/instrumentação , Titânio/química , Água/química , Desenho de Equipamento , Análise de Falha de Equipamento , Hidrogênio/isolamento & purificação , Luz , Nanoestruturas/efeitos da radiação , Nanoestruturas/ultraestrutura , Oxigênio/isolamento & purificação , Titânio/efeitos da radiação
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