1,721,172 research outputs found
Single nanoparticle SERS probes of ion intercalation in metal-oxide electrodes
No full textProbing ion-intercalating processes in electrodes is hugely important for batteries, super-capacitors and photovoltaic devices. In this work we use single-nanoparticle probes to see real-time molecular changes correlated to electrochemically modulated ion-intercalation in metal-oxide electrodes. Using surface-enhanced Raman spectroscopy (SERS) transduced by single nanoparticle probes we observe that the Raman frequencies and spectral intensities of the adsorbed molecules vary on cycling the electrochemical potential on a vanadium-oxide electrode. The potential dependent frequency shifts in SERS from an electrochemically inert molecule are attributed to a Stark effect induced by chemical and structural changes as a result of ion-intercalation processes in vanadium-oxide. Our study opens up a unique strategy to explore adsorbates and molecular reaction pathways on ion-intercalating materials and semiconducting interface
Single molecule SERS and detection of biomolecules with a single gold nanoparticle on mirror junction
No full textUsing the bianalyte method we unambiguously demonstrate that a single gold nanosphere on a metal film junction, in the so-called nanoparticle on a mirror configuration, is capable of single molecule detection with surface-enhanced Raman spectroscopy (SERS). Also this configuration serves as a convenient and highly sensitive SERS sensor for detection of biomolecules. Such simple nano-junction based systems are ideal for chemical and biomedical analysis
Hierarchical electrohydrodynamic structures for surface-enhanced Raman scattering
No full textSurface enhanced Raman scattering (SERS) is a well-established spectroscopic technique that requires nanoscale metal structures to achieve high signal sensitivity. While most SERS substrates are manufactured by conventional lithographic methods, the development of a cost-effective approach to create nanostructured surfaces is a much sought-after goal in the SERS community. Here, a method is established to create controlled, self-organized, hierarchical nanostructures using electrohydrodynamic (HEHD) instabilities. The created structures are readily fine-tuned, which is an important requirement for optimizing SERS to obtain the highest enhancements. HEHD pattern formation enables the fabrication of multiscale 3D structured arrays as SERS-active platforms. Importantly, each of the HEHD-patterned individual structural units yield a considerable SERS enhancement. This enables each single unit to function as an isolated sensor. Each of the formed structures can be effectively tuned and tailored to provide high SERS enhancement, while arising from different HEHD morphologies. The HEHD fabrication of sub-micrometer architectures is straightforward and robust, providing an elegant route for high-throughput biological and chemical sensing
Tunable microstructured surface-enhanced Raman scattering substrates via electrohydrodynamic lithography
Full text linkReadily fine-tuned structures are an important requirement for the optimization of surface-enhanced Raman scattering (SERS) to obtain the highest enhancements. Here, a lateral modulation of an electric field applied to a dielectric interface enables the rapid replication of nearly any topographic morphology with micrometer resolution by electrohydrodynamic lithography (EHL). Gold-covered periodic EHL-generated arrays yielded the reproducible enhancement of adsorbed SERS-active molecules. Periodic arrays of micropillars with square and circular cross sections give rise to the effective coupling of surface plasmon modes, which generate enhanced SERS signals. The overall enhancement factors depend on the geometry of the gold-coated structures, and intriguingly, a strong correlation is found with the gap-to-width ratio of the square pillar morphology. A numerical simulation of the EHL-based SERS substrates is consistent with this dependence. The EHL surface architectures can be easily tailored at micrometer-to-submicrometer dimensions, allowing the fabrication of reliably engineered and cost-effective highly sensitive SERS substrates
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
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
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