Gold nanowire synthesis by semi-immersed nanoporous anodic aluminium oxide templates in potassium dicyanoaurate-hexacyanoferrate electrolyte

Publisher Copyright: © The Institution of Engineering and Technology 2014.The synthesis reaction of potassium dicyanoaurate-hexacyanoferrate electrolyte and the pertinence of this electrolyte for gold nanowire synthesis are reported. Gold nanowires were synthesised in anodic aluminium oxide (AAO) nanopores using an improved design of the electrochemical cell. AAO templates with thick gold layers were placed on the surface of the electrolyte, thus the ends of the nanopores were opened, allowing the electrolyte to freely diffuse into the nanopores, extruding gases. The presented procedure simplifies the preparation before nanowire synthesis: AAO templates before synthesis do not need to degas and isolate themselves from contact with the electrolyte by a parafilm or a non-conductive adhesive. A considerably faster nanowire growth in the given conditions in the case of a semi-immersed AAO template when compared with the complete immersion method is reported. For comparison with literature data, gold nanowires were synthesised by the classical electrochemical cell using potassium dicyanoaurate-citrate electrolyte. Long, smooth and high purity nanowires were obtained using semi-immersed templates.publishersversionPeer reviewe

Elektrochemical impedance spectra analysis of airborne particulate matter

Darbā veikta elektroķīmiskās impedances spektru analīze Rīgas pilsētvides gaisa smalkajām un rupjajām aerosolu daļiņām, kas uzkrātas uz stikla šķiedras filtriem. Pēc aerosolu daļiņu paraugu priekšapstrādes tika uzņemtas cikliskās voltamperogrammas, impedances spektri un dubultslāņa kapacitātes spektri. Impedances spektru analīzei izmantota ekvivalento shēmu metode un statistiskā metode. Analizējot impedances un dubultslāņa kapacitātes spektrus, novērtēta aerosolu daļiņu izmēra, piesārņojuma, ogles un pārējo sastāvdaļu ietekme uz parauga virsmas raksturu.The current work is dedicated to electrochemical spectra analysis of fine and coarse airborne particulate matter sampled on the glass fibre filters in Riga city air. The cyclic voltammogram, impedance spectra and double-layer capacitance spectra of particulate matter were obtained after the sample pre-treatment. Equivalent circuit method and statistic method were used for impedance spectra analysis. Airborne particulate matter size, pollution, carbon and other components’ impact on the surface character was evaluated, analyzing impedance spectra and double-layer capacitance spectra

Chemical and electrochemical characteristics of solid particulate matter

Darbā ir pētītas cietas aerosolu daļiņas, ievāktas no Rīgas pilsētas atmosfēras un no dūmiem, kas rodas dedzinot dažādus kurināmos. Daļiņu ievākšana tika veikta ar dihotomo impaktoru un ar laboratorijā izveidoto slēgto dedzināšanas kameru. Furjē transformācijas infrasarkanie spektri un elektronu paramagnētiskās rezonanses spektri tika uzņemti pirms un pēc paraugu ķīmiskās apstrādes. Aerosolu daļiņu struktūra tika apskatīta skenējošā elektronu mikroskopā. Daļiņām tika mērīts ζ-potenciāls ar laboratorijā izveidoto aparātu.In this work solid particulate matter, collected from atmosphere of the city of Riga and from burning of various combustibles, was analyzed. Particulate matter was collected by dichotomous impactor and by closed burning chamber, laboratory built. Fourier transform infrared spectra and electron paramagnetic resonance spectra were obtained before and after chemical treatment of samples. The structure of particulate matter was analyzed by scanning electron microscope. ζ-potential of particulate matter was measured by the laboratory built apparatus

Fabrication of graphene containing layered nanostructures and investigation of their properties

Elektroniskā versija nesatur pielikumusPromocijas darbs ir veltīts jaunu, uz unikālā materiāla –grafēna(G)balstītu slāņainu nanomateriālu ar uzlabotu struktūru, optiskām un termoelektriskām īpašībām izveidošanai, to pārbaudei pielietojumam elektroniskās, termoelektriskās un fotojutīgāsierīcēs. Darbā izstrādātas metodikas termoelektriskā (TE) materiāla Bi2Se3atsevišķu nanostruktūru un nanostrukturēto pārklājumu sintēzei uz dažādām virsmām (stikls, kvarcs, G, ITO, AAO). Izveidots TEierīces prototips, balstīts uz Bi2Se3nanostrukturētā pārklājumu, ieslēgtu starp diviem Gslāņiem. Pirmo reizi ir izveidoti G/ZnOnanolamināti ar dažādu Gstarpslāņu skaitu un ZnOslāņu biezumu. Izpētītas šo struktūru kristāliskās un optiskās īpašības atkarībā no Gslāņu skaita un ZnOslāņu biezuma, kas ir svarīgi to perspektīviem pielietojumiem optiskos sensoros un optoelektroniskās ierīcēs. Uz Gpamatnēm ir izveidotas Bi2Se3/ZnOslāņainas heterostruktūras, izpētīta Gpamatnes ietekme uz ZnOkārtiņas struktūru un optiskām īpašībām. Ir izskaidroti lādiņu pārnešanas procesi, kas notiek Gsaturošās slāņainās nanostruktūrās un atbild par šo struktūru optisko un TEīpašību uzlabošanu.The doctoral thesis is dedicated to the fabrication ofnew layered nanomaterials with improved structure, optical and thermoelectric(TE)properties, and to testing of these nanomaterials for applications in electronic, TEand photosensitive devices. The fabricated nanomaterials are based on the uniquecarbon allotrope –graphene(G)–joined together with the well-known TEand/or optically active materials such as Bi2Se3and ZnO.In this work, methodologies for the synthesis of individual nanostructures and nanostructured coatings of Bi2Se3on different surfaces (glass, quartz, G, ITO, AAO) are developed. A prototype of a TEdevice based on Bi2Se3nanostructured coating enclosed between two Glayers is demonstrated. G/ZnOnanolaminates with a different number of Glayers and ZnOinterlayers with different thicknesses are fabricated for the first time. The crystalline and optical properties of these structures in relation to the number of Ginterlayers and thickness of ZnOlayers are investigated, which is important for their prospective applications in optical sensors and optoelectronic devices. Bi2Se3/ZnOlayered heterostructures on Gsubstrate are synthesized, the impact of the Gsubstrate on the structure and optical properties of the ZnOlayer is investigated. The charge transfer processes that occur in G-containing layered nanostructures and are responsible for the improvement of the optical and TEproperties of these structures are clarifie

Electrochemical Characteristics of Particulate Matter

The current work is dedicated to electrochemical impedance spectra analysis of the fine and coarse airborne particulate matter sampled on the glass fibre filters in Riga city air. The cyclic voltammograms, impedance spectra and double layer capacitance spectra of particulate matter were obtained after the pre-treatment of samples. The equivalent circuit method and the statistical method were used for impedance spectra analysis. Analyzing the impedance spectra, it was concluded that the impedance of both – fine and coarse particles heated in N2 flow does not change by aerosol mass concentration variations. On the other hand, the impedance of particulate matter heated in O2 flow increases, by increasing PM10 mass concentration. Describing the spectra of double layer capacitance, it was observed that the double layer capacitance of aerosols heated in N2 flow did not change, by mass concentration and size variations. However, by increasing mass concentration of coarse aerosols heated in O2 flow, the double layer capacitance reduced

Fabrication and characterization of ZnO/Graphene layered structures

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Influence of ZnO/graphene nanolaminate periodicity on their structural and mechanical properties

International audienceStructural, electronic and mechanical properties of ZnO/Graphene (ZnO/G) nanolaminates fabricated by low temperature atomic layer deposition (ALD) and chemical vapor deposition (CVD) were investigated. We performed scanning and transmission electron microscopy (SEM/TEM), X-ray diffraction (XRD), electron energy loss spectroscopy (EELS), Raman spectroscopy, X-Ray photoelectron spectroscopy (XPS) and nanoindentation to characterize the ZnO/G nanolaminates. The main structural and mechanical parameters of ZnO/G nanolaminates were calculated. The obtained results were analyzed and interpreted taking into account mechanical interaction and charge effects occurring at the G-ZnO interface. The influence of graphene sublayers number on the mechanical behavior of the ZnO/G nanolaminates was studied. By reducing the bilayer thickness, the mechanical parameters of the films can be tuned (Young's modulus 100-200 GPa, hardness 3-9 GPa). The softer response of the multilayers as compared to the single layers of ZnO and graphene was attributed to the structural changes in the ZnO layer and the interfaces. This study shows the mechanical behavior of ZnO/G nanolaminates and their influence on the development of novel electro-optical devices based on these structures. (C) 2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology

Surface structure promoted high-yield growth and magnetotransport properties of Bi2Se3 nanoribbons

International audienceIn the present work, a catalyst-free physical vapour deposition method is used to synthesize high yield of Bi2Se3 nanoribbons. By replacing standard glass or quartz substrates with aluminium covered with ultrathin porous anodized aluminium oxide (AAO), the number of synthesized nanoribbons per unit area can be increased by 20-100 times. The mechanisms of formation and yield of the nanoribbons synthesized on AAO substrates having different arrangement and size of pores are analysed and discussed. It is shown that the yield and average length of the nanoribbons can base tuned by adjustment of the synthesis parameters. Analysis of magnetotransport measurements for the individual Bi2Se3 nanoribbons transferred on a Si/SiO2 substrate show the presence of three different populations of charge carriers, originating from the Dirac surface states, bulk carriers and carriers from a trivial 2DEG from an accumulation layer at the Bi2Se3 nanoribbon interface with the substrate

Improved Crystalline Structure and Enhanced Photoluminescence of ZnO Nanolayers in Bi2Se3/ZnO Heterostructures

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