Preparation and surface modification of bismuth thin film, porous, and microelectrodes
Date
2010-05-21T13:10:54Z
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Abstract
Käesolevas töös konstrueeriti mitmesuguseid vismutil baseeruvaid elektroode ja mõõteseadmeid ning töötati välja vismuti pinna modifitseerimise meetodeid. Mõõtmiste käigus saadi ka uut informatsiooni vismuti elektrokeemiliste omaduste kohta. Kasutati peamiselt tsüklilise voltammeetria, elektrokeemilise impedantsi ja infrapuna spektroskoopia meetodeid ning pinna mikroskoopia tehnikaid.
Kõrge vesiniku ülepinge tõttu pakub vismut huvi elektrokeemilises analüüsis detektorelektroodina ja elektrilise kaksikkihi fundamentaaluuringutes. Konstrueeriti uueneva pinnaga vismuti mikroelektrood (BiCCE) koos mõõtesüsteemiga ning näidati, et BiCCE abil saab teostada raskmetalli jääkide analüüsi ja läbi viia uudseid adsorptsiooni ning elektrilise kaksikkihi alaseid uuringuid pinna uuenemise hetkel.
Teisest küljest on vismuti nanostruktuure väga põhjalikult uuritud, sest kvantefektide tõttu saab neid kasutada magnetiliste sensoritena ja teistes elektroonika rakendustes.
Leiti, et õhukest vismutkihti või nanoosakesi on lihtsasti võimalik räni pinnale sadestada vismutfluoriidi sisaldavast vesilahusest. Tekkinud vismutkihid on kollase läikega.
Poorse vismuti valmistamiseks kasutati kahte erinevat strateegiat. Bi pinda oksüdeeriti lahustumiseni ja seejärel redutseeriti kiiresti tagasi metalseks vismutiks. Tekkinud poorse struktuuri eripind on kuni on 220, selle mahtuvus ei sõltu mõõtesagedusest ning sel on 140 mV suurem vesiniku eraldumise ülepinge kui siledal Bi elektroodil. Teiseks hoiti Bi elektroodi väga katoodsetel potentsiaalidel ja leiti, et tekib gaasiline vismuthüdriid, mis seejärel laguneb Bi nanoosakesteks ning sadeneb tagasi elektroodi pinnale.
Selgus, et erinevalt tioolide monokihtidest kullal, tekib vismuti pinnale paksem vismuttiolaadi kiht. Tekkinud kihi tuvastamiseks sünteesiti ka uued ühendid tris(1-oktadetsüültio)vismutiin ja tris(1-detsüültio)vismutiin ning tõestati, et just need ained tekkisid ka Bi pinnal.
This work gives new information about electrochemical properties of bismuth as well as some new preparation methods for Bi electrodes and new compounds. The studies were mainly carried out using cyclic voltammetry, impedance spectroscopy, infrared spectroscopy, and surface imaging techniques. Because of high hydrogen overvoltage, bismuth is of interest in the field of electrochemical analysis and in electric double layer fundamental studies. Therefore, a new method for preparation of bismuth microelectrode with the renewable surface (BiCCE) and the corresponding measurement system has been worked out. BiCCE was shown to be suitable for the analysis of trace metal cations or organic compounds and enables to study the double layer formation properties at the moment of the electrode cleavage. On the other hand, bismuth nanostructures are thoroughly studied, because of quantum confinement effects, these can be used as magnetic sensors or in a variety of other electronic applications. It was shown that thin bismuth films or Bi nanoparticles can be deposited onto silicon wafer from bismuth(III)fluoride aqueous solution. The formed films have yellowish tinge. Two different strategies were used for in situ deposition of porous bismuth. Porous surface was prepared by anodic dissolution of bismuth electrode followed by fast electroreduction back to metallic Bi. Formed porous bismuth, with surface roughness factor up to 220, consists of Bi nanowires and has higher hydrogen evolution overvoltage than observed for smooth Bi electrodes. Secondly, it was established that gaseous bismuth hydride formation and decomposition into Bi nanoparticles takes place at high cathodic electrode potentials. It was found that, differently from self-assembled thiol monolayers on Au electrodes, bismuth is covered with a thick porous layer of bismuth thiolate compound. For the verification of formed thiolate layers, the new compounds tris(1-octadecylthio)bismuthine and tris(1-decylthio)bismuthine were also synthesised from bismuth(III)oxide and thiol in hexane solution.
This work gives new information about electrochemical properties of bismuth as well as some new preparation methods for Bi electrodes and new compounds. The studies were mainly carried out using cyclic voltammetry, impedance spectroscopy, infrared spectroscopy, and surface imaging techniques. Because of high hydrogen overvoltage, bismuth is of interest in the field of electrochemical analysis and in electric double layer fundamental studies. Therefore, a new method for preparation of bismuth microelectrode with the renewable surface (BiCCE) and the corresponding measurement system has been worked out. BiCCE was shown to be suitable for the analysis of trace metal cations or organic compounds and enables to study the double layer formation properties at the moment of the electrode cleavage. On the other hand, bismuth nanostructures are thoroughly studied, because of quantum confinement effects, these can be used as magnetic sensors or in a variety of other electronic applications. It was shown that thin bismuth films or Bi nanoparticles can be deposited onto silicon wafer from bismuth(III)fluoride aqueous solution. The formed films have yellowish tinge. Two different strategies were used for in situ deposition of porous bismuth. Porous surface was prepared by anodic dissolution of bismuth electrode followed by fast electroreduction back to metallic Bi. Formed porous bismuth, with surface roughness factor up to 220, consists of Bi nanowires and has higher hydrogen evolution overvoltage than observed for smooth Bi electrodes. Secondly, it was established that gaseous bismuth hydride formation and decomposition into Bi nanoparticles takes place at high cathodic electrode potentials. It was found that, differently from self-assembled thiol monolayers on Au electrodes, bismuth is covered with a thick porous layer of bismuth thiolate compound. For the verification of formed thiolate layers, the new compounds tris(1-octadecylthio)bismuthine and tris(1-decylthio)bismuthine were also synthesised from bismuth(III)oxide and thiol in hexane solution.
Description
Väitekirja elektroonilisest versioonist puuduvad publikatsioonid.