THE MORPHOLOGY DEPENDENCE ON GROWTH PARAMETERS IN NANOSTRUCTURED SEMICONDUCTORSMiha Gunde
, 2014, diplomsko delo
Opis: Poly(3-hexylthiophene) (P3HT) is an organic semiconductor material that is widely studied in the photovoltaics and transistor fields of research. The polymer exhibits a relatively high charge carrier mobility when the molecules are ordered in a crystalline way. In this
case the material exhibits a fibril-like morphology, which is usually studied by atomic force microscopy (AFM). Previous studies show that blending P3HT with graphene can further improve the charge carrier transport properties of the film. In this experiment, the scanning electron microscope (SEM) has been chosen, due to its practical aspects such as speed of operation and ease of use. Three sets of samples have been analyzed, containing films made of P3HT+graphene blends at different concentrations. The aims of the experiment are:
i) to find good conditions for the observation of the morphology features of the film
ii) to perform a morphological analysis of the surface of three sets of samples containing both pure P3HT, and P3HT+graphene blend, and possibly to highlight correlation between morpholgy and the charge transport properties.
Surface analysis is done by detecting the secondary electron (SE) emission, which is sensitive to topographical features of the surface. Good observation conditions were established by coating the specimen with a thin layer of conductive coating, using a high energy beam (30 keV), and tilting the sample to an angle (30 ◦ ). In two out of three of the analyzed pure P3HT films, the presence of fibrilles indicated a possibly good charge mobility, which has
been confirmed by electrical measurements using time-of-flight photoconductivity method (TOF). The presence of graphene has only slightly modified morphology of the film. Features of graphene flakes, which lie flat in the film, have been observed such as flake edges and folds. The flakes are homogeneously dispersed in the film without forming any connected network. TOF measurements have shown an increase in mobility of the charge carriers in the P3HT+graphene film.
Najdeno v: ključnih besedah
Povzetek najdenega: ...Previous studies show that blending P3HT with graphene can further improve the charge carrier transport...
Ključne besede: scanning electron microscope, organic semiconductor thin film, P3HT, graphene, morphology
Objavljeno: 01.12.2016; Ogledov: 951; Prenosov: 12
Polno besedilo (30,93 MB)
HETEROGENEOUS PHOTOCATALYTIC OXIDATION FOR THE REMOVAL OF BISPHENOL A FROM AQUEOUS SOLUTION OVER TiO2/GRAPHENE OXIDE (GO) BASED NANOCOMPOSITESAna Veternik
, 2017, magistrsko delo
Opis: Since water is an essential substance for all life on earth, it is therefore vital to prevent its pollution and to improve wastewater purification processes. There is a vast number of pollutants which can contaminate water, of which bisphenol A (known as an endocrine disruptor) is the pollutant studied herein. In this study, several TiO2/GO based nanocomposites with various GO loadings (2, 4, 10, 20 and 40%) and differently shaped nanocrystalline TiO2 phases (titanate nanotubes (TNTs) and calcined titanate nanotubes (TNTs_500)) were synthesised. All of the nanocomposites were characterised through SEM, UV-vis-DR, TGA, BET, FT-IR and CHNS analyses and were used in the heterogeneous photocatalytic degradation of bisphenol A and compared to the activity of pure TNTs and TNT_500 photocatalysts. All TiO2/GO nanocomposites exhibit much better activity than pure TNTs and TNTs_500 catalysts. The conversion of the BPA was analysed using HPLC and the mineralisation was analysed using a TOC analysis. The best experiment was performed with TNTs_500 + 10% GO composite, which can be attributed to the TiO2 crystalline structure obtained. According to the results obtained, TiO2 + 10% GO was found to exhibit the best degradation ratio, which can be ascribed to the fact that excessive GO can act as a charge carrier recombination centre and promotes the recombination of electron-hole pairs in reduced GO.
Najdeno v: ključnih besedah
Ključne besede: heterogeneous photocatalysis, titanium dioxide, graphene oxide, bisphenol A
Objavljeno: 23.02.2017; Ogledov: 672; Prenosov: 89
Polno besedilo (2,96 MB)
Interface-controlled growth of organic semiconductors on grapheneJinta Mathews
, Saim Emin
, Egon Pavlica
, Matjaž Valant
, Gvido Bratina
, 2017, izvirni znanstveni članek
Opis: We have studied submonolayer coverages of N,N-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDIF-CN2) on mechanically exfoliated graphene transferred onto SiO2 substrates. Our atomic force microscopy (AFM) data show that PDIF-CN2 forms irregularly-shaped 1.4 nm-high islands. From the selected area diffraction performed with transmission electron microscope (TEM) we conclude that this height corresponds to π−π
stacks of molecules, which are inclined for 43° relative to the graphene surface. AFM also showed complete absence of PDIF-CN2 on single-layer graphene (SLG). Electric force microscopy revealed a marked difference in surface charge density between a single-layer graphene and bilayer graphene, with a higher surface charge on SLG than on the bilayer graphene. We associate this behavior with p−
type doping of graphene due to the electrostatic dipole induced by the molecular water layer present at the graphene/SiO2 interface. The crucial role of the graphene/SiO2 interface in determining growth of PDIF-CN2 was further confirmed by TEM examination of PDIF-CN2 deposited onto unsupported SLG.
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Ključne besede: afm, organic semiconductors, graphene
Objavljeno: 18.05.2017; Ogledov: 560; Prenosov: 0
Polno besedilo (2,02 MB)