1,720,965 research outputs found
Bipolarons rule the short-range terahertz conductivity in electrochemically doped P3HT
Full text linkDoping of organic semiconductor films enhances their conductivity for applications in organic electronics, thermoelectrics and bioe- lectronics. However, much remains to be learnt about the proper- ties of the conductive charges in order to optimize the design of the materials. Electrochemical doping is not only the fundamental mechanism in organic electrochemical transistors (OECTs), used in biomedical sensors, but it also represents an ideal playground for fundamental studies. Benefits of investigating doping mechanisms via electrochemistry include controllable doping levels, reversibility and high achievable carrier densities. We introduced here a new technique, applying in situ terahertz (THz) spectroscopy directly to an electrochemically doped polymer in combination with spectro- electrochemistry and chronoamperometry. We evaluate the intrin- sic short-range transport properties of the polymer (without the effects of long-range disorder, grain boundaries and contacts), while precisely tuning the doping level via the applied oxidation voltage. Analysis of the complex THz conductivity reveals both the mobility and density of the charges. We find that polarons and bipolarons need to co-exist in an optimal ratio to reach high THz conductivity (B300 S c
Data related to manuscript ['Bipolarons rule the short-range terahertz conductivity in electrochemically doped P3HT', Materials Horizons (2022), https://pubs.rsc.org/en/content/articlelanding/2022/mh/d1mh01343b]
No full textDoping of organic semiconductor films enhances their conductivity for applications in organic electronics, thermoelectrics and bioe- lectronics. However, much remains to be learnt about the proper- ties of the conductive charges in order to optimize the design of the materials. Electrochemical doping is not only the fundamental mechanism in organic electrochemical transistors (OECTs), used in biomedical sensors, but it also represents an ideal playground for fundamental studies. Benefits of investigating doping mechanisms via electrochemistry include controllable doping levels, reversibility and high achievable carrier densities. We introduced here a new technique, applying in situ terahertz (THz) spectroscopy directly to an electrochemically doped polymer in combination with spectro- electrochemistry and chronoamperometry. We evaluate the intrin- sic short-range transport properties of the polymer (without the effects of long-range disorder, grain boundaries and contacts), while precisely tuning the doping level via the applied oxidation voltage. Analysis of the complex THz conductivity reveals both the mobility and density of the charges. We find that polarons and bipolarons need to co-exist in an optimal ratio to reach high THz conductivity (B300 S c
Data related to manuscript ['High resolution phase-sensitive sum frequency generation spectroscopy by time- domain ptychography', Optics Letters (2020), https://doi.org/10.1364/OL.403339]
Full text linkWe demonstrate that time-domain ptychography, when applied to a set of broadband vibrational sum frequency spectra, reconstructs amplitude and phase of the vibrational free induction decay from an interfacial sample with a resolution that is independent of the up-converting pulse bandwidth and spectrometer resolution. These important improvements require no modifications to most standard homodyne setups and the method is applicable to other coherent homodyne spectroscopies like coherent anti-Stokes Raman spectroscopy or transient grating spectroscopy
Time-resolved Spectroelectrochemical Investigation of Organic Mixed Conductors
Full text linkOrganic mixed ionic and electronic conductors (OMIECs) are an emerging class of materials that have been applied for a wide range of electrochemical applications. Due to the complexity inherent to the ionic-electroniccoupling, understanding the underlying mechanisms involved in the OMIEC operation is an exciting and very lively research field. In this work, we highlight the use of time-resolved Vis-NIR spectroelectrochemistry tocharacterize these materials. We discuss an example, where we show that by combining this tool with spectraldecomposition, we are able to understand fundamental aspects of the doping in an OMIEC film. The methodswe present here can be generalized and used to characterize any electrochromic material
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Plataforma universal para a fabricação de transistores eletroquímicos orgânicos e aplicações em biossensores
No full textOrganic bioelectronics is a fast-rising research field that takes advantage of the soft and conducting/semiconducting nature of conjugated polymers to create devices that communicate, interface and mimic biological systems. Bioelectronics encompasses many applications, including tissue engineering, neural interfaces and biosensors. A device that has been extensively explored for such applications is the organic electrochemical transistor (OECT). The main reason is due to its amplification nature and, thus, high fidelity transducer of biological events. Additionally, OECTs convert ionic signals to electronic ones, providing a direct link between biological ion fluxes and electronics. Even though they have been widely explored in the past 10 years, a major drawback that remains unsolved is the lack of hydrophilic polymers that are suitable for applications in biological environment. Hence, in the first part of this dissertation, we propose a novel and universal OECT architecture that enables the use of virtually any type of conjugated polymer. Using the proposed method, which was based on physical chemistry principles, we successfully fabricated transistors that exhibits very high transconductance, good stability and reproducibility, using traditional water-insoluble conjugated polymers. In the second part, we developed a biosensing application using the proposed architecture. In short, the OECT device was functionalized with a cellular membrane model, making it possible to gather quantitative data on the physical and chemical properties of the membrane. This is particularly useful for understanding how different compounds interact with cells. Additionally, we were able to study the working mechanism of lidocaine, a widely used local anesthetic. The concept presented here was then successfully extended to the fabrication of biosensors, enabling thousands of water-insoluble materials that have been developed over the last several decades to be used in organic bioelectronics devices.A bioeletrônica orgânica é um campo de pesquisa que cresce rapidamente. Se beneficiando da natureza condutora/semicondutora e flexível dos polímeros conjugados, seu principal objetivo é o desenvolvimento de dispositivos eletrônicos capazes de interfacear, mimetizar e se comunicar com sistemas biológicos. A bioeletrônica envolve diversos tipos de aplicações, dentre eles engenharia de tecidos, interfaces neurais e biossensores. Um dispositivo que tem sido extensivamente explorado para esses tipos de aplicações é o transistor eletroquímico orgânico (OECT). OECTs convertem correntes ionicas para eletrônicas, atuando como uma conexão direta entre fluxos iônicos, tipícos de eventos biológicos, e a eletrônica. Apesar de terem sido amplamente explorados na última década, uma de suas desvantagens que permanece sem solução é a falta de polímeros adequados para os ambientes biológicos, que devem ser hidrofílicos. Por isso, na primeira parte dessa dissertação, nós propomos uma nova arquitetura universal de OECT, que permite o uso de virtualmente qualquer tipo de polímero conjugado. Utilizando o método proposto, baseado em princípios físico-químicos, fabricamos transistores com polímeros conjugados inssoluveis em água que exibem alta trancondutancia, boa estabilidade e reproducibilidade. Em seguida, desenvolvemos uma aplicação em biossensores utilizando a arquitetura proposta. Em resumo, o OECT foi funcionalizado com um modelo de membrane celular, possibilitando a aquisição de informações quantitativas sobre propriedades físico-químicas da membrana. Isso é particularmente útil para o estudo de como diferentes compostos interagem com células. Além disso, utilizamos a plataforma para estudar o mecanismo de funcionamento da lidocaina, um anestésico local aplamente utilizado. Assim, o conceito aqui apresentado foi estendido para a fabicação de biossensores, permitindo que milhares de materiais insoluveis em água possam ser utilizados na bioeletrônica orgânica
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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