Light Function Nanomaterials In The Photoelectric Conversion And Biological Detection Applications

This thesis is composed of two parts.One part is dye-sensitized solar cells(DSSCs) and another is rare-earth nanophosphors.â… .Optoelectronic nanomaterials for dye-sensitized solar cells.DSSCs have been currently attracting widespread scientific and technological interest.To promote conversion efficiencies and thermostability of quasi-solid/solid state DSSCs,in this study,we prepared two kinds of highly conductive-thermostable gel electrolytes and novel nanocrystalline TiO₂ films with the channels for DSSCs.1).Nanocomposite gel electrolyte:By introducing the hydrogen bond(O-H…F) network upon addition of silica nanoparticles and ionic liquid containing F atom,two kinds of highly conductive-thermostable gel electrolytes can be prepared with succinonitrile or another ionic liquid as the solvent.Both kinds of DSSCs with the gel electrolytes show high solar-to-electric energy conversion efficiencies(5-6%).Importantly,these DSSCs can work well over a wide temperature range(20-80℃),and have excellent long-time durability,making the device viable for practical outdoor application.2) Novel nanocrystalline TiO₂ films with the textural channelsNovel nanocrystalline TiO₂ films with the textural channels are obtained for DSSCs. The textural channels consisting of the cracks on the surface and the nanopores with average diameter of about 41 nm are produced by packaging ZnO nanowires with diameter of 30-50 nm into TiO₂ films and subsequently etching ZnO nanowires by hydrochloric acid.When several quasi-solid/solid state electrolytes are used,the energy conversion efficiencies of DSSCs from novel TiO₂ films are improved by 15～30%compared to that from traditional TiO₂ films.The introduction of the textural channels facilitates better penetration of quasi-solid/solid state electrolytes into the nanopores of novel TiO₂ films and thus results in better interfacial/electrical contact and faster interfacial reaction.â…¡.Rare-earth nanophosphors for biological applicationsDue to their attractive chemical and optical features,rare-earth nanophosphors (RENPs) have great potential as a new kind of biological luminescent label.A prerequisite for their biological applications is to gain access to water-soluble nanoparticles bearing appropriate functional groups(such as -COOH,-NH₂ or -SH) on their surface.In this study,we have developed some simple and versatile synthesis strategies for the desired RENPs.1) Versatile oxidization strategy for carboxylic acid-functionalized RENPs:By directly oxidizing oleic acid ligands to azelaic acids(HOOC(CH₂)₇COOH) ligands with the Lemieux-von Rudloff reagent,a simple and versatile strategy has been developed for converting hydrophobic up-converting rare-earth nanophosphors (UC-RENPs) into water-soluble and carboxylic acid-functionalized analogues.This oxidation process has no obvious adverse effects on the morphologies,phases, compositions and luminescent capabilities of UC-RENPs.In addition,the presence of free carboxylic acid groups on UC-RENPs surface not only confers high solubility in water,but also allows further conjugation with biomolecules such as streptavidin.A highly sensitive DNA sensor based on streptavidin-coupled UC-RENPs has been prepared,and the demonstrated results suggest that these UC-RENPs have great superiority as luminescent labels for biological applications.2) Hydrothermal microemulsion-directed synthesis of amine-functionalized RENPs:We present the one-step preparation of amine-functionalized UC-RENPs by a modified hydrothermal microemulsion synthesis strategy.A ternary water-in-oil microemulsion,consisting of an anionic surfactant(sodium bis(2-ethyihexyi) sulfosuccinate:known as APT),n-heptane and water,is used,and 6-aminohexanoic acid as a suitable chelating agent is added into water core.Amine-functionalized UC-RENPs can be obtained after hydrothermai treatment,and the content of free amine moieties is found to be(9.5±0.8)×10^-5 mol/g.Importantly,these UC-RENPs can be used as the label for laser scanning up-conversion luminescence imaging of Cells.3) Room temperature synthesis of carboxylic acid-functionalized nanophosphors by reverse microemulsion route.Quaternary water-in-oil microemulsion,consisting of a cationic surfactant (Cetyltrimethylammonium bromide:CTAB),n-butanol,n-heptane and water,is used to prepare nanomaterials.By mixing two reverse micelle containing different ions or compound,and subsequently combining with another reverse micelle containing aqueous soluteion of sodium glutarate as surface ligands,carboxylic acid-functionalized RENPs and other nanocrystals can be prepared at room termperature.