1,720,956 research outputs found
Decorating of nanostructured zincite films with CdSe quantum dots
No full textMogućnost manipulacije svojstava materijala pomoću nanotehnologije na jako maloj skali otvara brojne prilike. Nanostrukturirani ZnO posjeduje odlična kemijska, električna i optička svojstva zbog čega svoju primjenu pronalazi u optoelektroničkim uređajima, solarnim ćelijama, senzorima i još mnogim novim tehnologijama. Također, njegova svojstva se mogu poboljšati dopiranjem ili dekoriranjem česticama poluvodiča nano veličina odnosno kvantnim točkama što dodatno proširuje njegovu primjenu. Cilj ovog rada bio je pripremiti tanke cinkitne (ZnO) filmove te ih dekorirati CdSe kvantnim točkama. ZnO filmovi pripremljeni su metodom oblaganja rotiranjem. CdSe kvantne točke su sintetizirane iz prekusorskih otopina te su nanesene na prethodno pripremljene ZnO filmove metodom drop casting-a i metodom oblaganja rotiranjem. Za detaljnu analizu uzoraka korištene su mikroskopija atomskih sila, rendgenska difrakcija i UV/Vis spektrometrija. Dobiveni rezultati pružaju uvid u primjenjivost korištenih metoda i materijala u sintezi filmova koji se mogu koristiti u solarnim ćelijama.The ability of nanotechnology to manipulate materials on a very small scale opens up numerous opportunities. Nanostructured ZnO has excellent chemical, electrical and optical properties, which is why it finds its application in optoelectronic devices, solar cells, sensors and many other advanced technologies. In addition, its properties can be improved by doping or decorating it with nano-sized semiconductor particles or quantum dots, which further expands its application. The aim of this work was to prepare thin zincite (ZnO) films and decorate them with CdSe quantum dots. ZnO films were prepared by the spin coating method. CdSe quantum dots were synthesized from precursor solutions and were applied to previously prepared ZnO films by drop casting and spin coating methods. Atomic force microscopy, X-ray diffraction and UV/Vis spectrometry were used for detailed analysis of the samples. The obtained results provide insight into the applicability of the used methods and materials in the synthesis of films that can be used in solar cells
Decorating of nanostructured zincite films with CdSe quantum dots
No full textMogućnost manipulacije svojstava materijala pomoću nanotehnologije na jako maloj skali otvara brojne prilike. Nanostrukturirani ZnO posjeduje odlična kemijska, električna i optička svojstva zbog čega svoju primjenu pronalazi u optoelektroničkim uređajima, solarnim ćelijama, senzorima i još mnogim novim tehnologijama. Također, njegova svojstva se mogu poboljšati dopiranjem ili dekoriranjem česticama poluvodiča nano veličina odnosno kvantnim točkama što dodatno proširuje njegovu primjenu. Cilj ovog rada bio je pripremiti tanke cinkitne (ZnO) filmove te ih dekorirati CdSe kvantnim točkama. ZnO filmovi pripremljeni su metodom oblaganja rotiranjem. CdSe kvantne točke su sintetizirane iz prekusorskih otopina te su nanesene na prethodno pripremljene ZnO filmove metodom drop casting-a i metodom oblaganja rotiranjem. Za detaljnu analizu uzoraka korištene su mikroskopija atomskih sila, rendgenska difrakcija i UV/Vis spektrometrija. Dobiveni rezultati pružaju uvid u primjenjivost korištenih metoda i materijala u sintezi filmova koji se mogu koristiti u solarnim ćelijama.The ability of nanotechnology to manipulate materials on a very small scale opens up numerous opportunities. Nanostructured ZnO has excellent chemical, electrical and optical properties, which is why it finds its application in optoelectronic devices, solar cells, sensors and many other advanced technologies. In addition, its properties can be improved by doping or decorating it with nano-sized semiconductor particles or quantum dots, which further expands its application. The aim of this work was to prepare thin zincite (ZnO) films and decorate them with CdSe quantum dots. ZnO films were prepared by the spin coating method. CdSe quantum dots were synthesized from precursor solutions and were applied to previously prepared ZnO films by drop casting and spin coating methods. Atomic force microscopy, X-ray diffraction and UV/Vis spectrometry were used for detailed analysis of the samples. The obtained results provide insight into the applicability of the used methods and materials in the synthesis of films that can be used in solar cells
Degradation of neonicotinoid insecticides using composite photocatalysts
No full textZbog prekomjerne primjene pesticida u posljednjim desetljećima, dolazi do njihove bioakumulacije u okolišu te postaju sve veća prijetnja za ljude i ekosustav. Stoga se razvijaju različiti postupci za njihovo uklanjanje iz otpadnih voda i tla, pri čemu posebnu važnost imaju napredni postupci fotokatalitičke razgradnje. U ovom radu izučavana je fotokatalitička aktivnost novih kompozitnih fotokatalizatora TiO2- SBA-15 i TiO2-MCM-41 te je njihova fotoaktivnost uspoređena sa aktivnošću polaznih mezoporoznih materijala SBA-15 i MCM-41 koji nisu sadržavali TiO2 koji predstavlja uobičajeni poluvodički materijal koji se primjenjuje za fotorazgradnju. Fotokatalitička razgradnja provedena je u kotlastom reaktoru sa fotokatalizatorom suspendiranim u reakcijskoj smjesi. Kao izvor zračenja za fotokatalitičku razgradnju korištena je Pen-Ray lampa. Mjerenja su provedena pri konstantnoj početnoj koncentraciji imidakloprida od 10 ppm. Reakcija je praćena mjerenjem konverzije imidakloprida u određenim vremenskim intervalima, a za tu svrhu primijenjena je tekućinska kromatografija visoke učinkovitosti. Eksperimentalna istraživanja uključivala su i mjerenje promjene pH, promjene koncentracije otopljenog kisika te promjene ukupnog organskog ugljika na početku i nakon provedene fotokatalitičke razgradnje. Rezultati istraživanja pokazali su da je razgradnja imidakloprida moguća jedino uz primjenu TiO2 katalizatora i odgovarajućeg izvora zračenja (u našem slučaju UVA). Mezoporozni materijal MCM-41 pokazao se učinkovitijim od SBA-15.. U završnom dijelu ispitivanja dobiveni eksperimentalni podaci testirani su na model kotlastog reaktora uz kinetički model za reakciju prvoga reda te su određene konstante brzine reakcije, k i korijeni srednjeg kvadratnog odstupanja, SD.Excessive usage of pesticides for the last several decades resulted in their bioaccumulation in the environment and thus presenting growing threat to humans and ecosystem. In order to remove the remains of pesticides from wastewaters and soil, different methods are being developed, whereas advanced procedures of photocatalytic degradations become more and more important. This work studied photocatalytic activity of new composite photocatalysts TiO2-SBA-15 and TiO2-MCM-41. Their photoactivity was compared to the activity of the initial mesoporous materials SBA-15 and MCM-41 that did not contain TiO2. TiO2 represents ordinary semiconductor material that is used for photocatalytic degradation. Photocatalytic degradation was performed in batch reactor with photocatalyst suspended in the reaction mixture. Pen-Ray lamp was used as a radiation source for photocatalytic degradation. Measurements were conducted at the constant initial imidacloprid concentration of 10 ppm. The reaction was observed by measuring conversion of imidacloprid at certain time intervals, and high performance liquid chromatography (HPLC) was used for that purpose. Experimental measurements included the changes in pH, in concentration of dissolved oxygen, and in changes of total organic carbon at the beginning and after the photocatalytic degradation. The results showed that the degradation of imidacloprid is possible only with application of TiO2 catalyst and adequate radiation source (UVA in this case). Mesoporous material MCM- 41 proved to be more efficient than SBA-15. In the final part of the test, the achieved experimental results were tested on the batch reactor model with the kinetic model for firstorder reaction, and the reaction rate constants, k, and the root mean square deviation, SD, were determined
Decorating of nanostructured zincite films with CdSe quantum dots
No full textMogućnost manipulacije svojstava materijala pomoću nanotehnologije na jako maloj skali otvara brojne prilike. Nanostrukturirani ZnO posjeduje odlična kemijska, električna i optička svojstva zbog čega svoju primjenu pronalazi u optoelektroničkim uređajima, solarnim ćelijama, senzorima i još mnogim novim tehnologijama. Također, njegova svojstva se mogu poboljšati dopiranjem ili dekoriranjem česticama poluvodiča nano veličina odnosno kvantnim točkama što dodatno proširuje njegovu primjenu. Cilj ovog rada bio je pripremiti tanke cinkitne (ZnO) filmove te ih dekorirati CdSe kvantnim točkama. ZnO filmovi pripremljeni su metodom oblaganja rotiranjem. CdSe kvantne točke su sintetizirane iz prekusorskih otopina te su nanesene na prethodno pripremljene ZnO filmove metodom drop casting-a i metodom oblaganja rotiranjem. Za detaljnu analizu uzoraka korištene su mikroskopija atomskih sila, rendgenska difrakcija i UV/Vis spektrometrija. Dobiveni rezultati pružaju uvid u primjenjivost korištenih metoda i materijala u sintezi filmova koji se mogu koristiti u solarnim ćelijama.The ability of nanotechnology to manipulate materials on a very small scale opens up numerous opportunities. Nanostructured ZnO has excellent chemical, electrical and optical properties, which is why it finds its application in optoelectronic devices, solar cells, sensors and many other advanced technologies. In addition, its properties can be improved by doping or decorating it with nano-sized semiconductor particles or quantum dots, which further expands its application. The aim of this work was to prepare thin zincite (ZnO) films and decorate them with CdSe quantum dots. ZnO films were prepared by the spin coating method. CdSe quantum dots were synthesized from precursor solutions and were applied to previously prepared ZnO films by drop casting and spin coating methods. Atomic force microscopy, X-ray diffraction and UV/Vis spectrometry were used for detailed analysis of the samples. The obtained results provide insight into the applicability of the used methods and materials in the synthesis of films that can be used in solar cells
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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