Tuning the Pore Size in Ionic Nanoparticle Networks

Highly promising hybrid materials consisting of silica, titania, or zirconia nanoparticles linked with ionic liquid-like imidazolium units have been developed. The nanoparticle networks are prepared by click-chemistry-like process through a nucleophilic substitution reaction. The type of metal oxide nanoparticles appears to play a key role regarding the pore size of the hybrid material.</jats:p

Photoluminescence as Complementary Evidence for Short-Range Order in Ionic Silica Nanoparticle Networks

Recently we published the synthesis of new hybrid materials, Ionic Silica Nanoparticles Networks (ISNN), made of silica nanoparticles covalently connected by organic bridging ligands containing imidazolium units owing to a "click chemistry-like" reaction. Among other techniques small-angle X-ray scattering (SAXS) experiments were carried out to get a better picture of the network extension. It turned out that the short range order in ISNN materials was strongly influenced by the rigidity of the bridging ligand, while the position of the short range order peaks confirmed the successful linking of the bridging ligands. The photoluminescence experiments reported in this communication revealed strongly enhanced emission in the hybrid material in comparison with neat imidazolium salts. Moreover the shift of the emission maximum towards longer wavelengths, obtained when varying the aromatic ring content of the bridging ligand, suggested the existence of strong π-π stacking in the hybrid material. Experiments revealed a stronger luminescence in those samples exhibiting the higher extent of short range order in SAXS

Neue Hybridmaterialien basierend auf der Chemie ionischer Flüssigkeiten

Im ersten Teil der Arbeit wurden zur Synthese eines 3-dimensionalen Netzwerkes, aufgebaut aus SiO2-Nanopartikel, drei Syntheserouten untersucht. Hierfür wurde für die ersten zwei Synthesewege eine ionische Flüssigkeit mit zwei Trialkoxygruppen, 1,3-Di(propyltrimethoxysilyl) imidazolium-Iodid, synthetisiert. Danach wurde dieses zur Verbrückung verwendete Molekül, um eine Kondensation hervorzurufen, entweder mit Tetraethylorthosilicat (TEOS) oder mit zuvor hergestellten SiO2-Nanopartikeln umgesetzt. Bei der Variante mit TEOS wurden die Partikel in situ hergestellt, wobei die ionische Flüssigkeit die Funktion als Co-Precursor inne hatte. Bei der dritten Methode wurden ebenfalls zuvor synthetisierte SiO2-Nanopartikel eingesetzt. Hier fand zuerst eine getrennte Modifikation entweder mit 3-Chloropropyltrimethoxysilan oder mit N-(Propyltrimethoxysilyl)imidazol. Danach erst fand eine Reaktion der beiden unterschiedlich funktionalisierten Nanopartikel statt. Bei allen drei Wegen wurden die erhaltenen Materialien mittels TGA, TEM, NMR, und DLS untersucht.Aufbauend auf diesen Ergebnissen wurden im zweiten Teil der Arbeit die beiden letzten Synthesewege weiter variiert, indem Verbrückungsmoleküle mit jeweils Diimidazoliumeinheiten synthetisiert wurden. Dies wurde durchgeführt, um die Verbrückungslänge bzw. -festigkeit zu steigern.Auch hier fand eine Charakterisierung mittels TGA und TEM statt.Im dritten Teil der Arbeit wurden zuerst ionische Flüssigkeiten synthetisiert; 1-Butyl-3-methylimidazolium-Nitrat und 1-Propyl-3-methylimidazolium-Chlorid. Danach wurde Silbernitrat, in Anwesenheit der synthetisierten Verbindungen, in wässriger Lösung zu elementarem Silber reduziert. Der Einschluss erfolgte in beiden Fällen und wurde mittels XRD, TGA, IR und NMR bestätigt. In dieser Arbeit wurde die Herstellung neuer Hybridmaterialien basierend auf der Chemie von ionischen Flüssigkeiten vorgestellt. Es wird gezeigt, dass es möglich ist die Morphologie von Metallen, bzw. Metalloxiden mittels des Einsatzes ionischer Flüssigkeiten, bzw. ionischen Flüssigkeiten ähnlichen Verbindungen, entscheidend zu beeinflussen.In the first part of this thesis three different approaches were investigated to obtain a 3-dimensional network based on SiO2-units. For the first two routes an ionic liquid like molecule, containing two trialkoxy-groups, was synthesised, 1,3-di(propyltrimethoxysilyl)imidazolium-iodid. Afterwards, to induce a condensation reaction, this bridging agent was either reacted with tetraethylorthosilcate (TEOS) or previously synthesised silica nanoparticles. With TEOS the particles were formed in situ and the ionic liquid acted like a co-precursor. The third method was also carried out with already synthesised nanoparticles. These particles were modified separately either with 3-chloropropyltrimethoxysilane or N-(propyltrimethoxysilyl)imidazol and then coupled through a nucleophilic substitution reaction, forming the desired network. In all three cases a powder was obtained, which were characterised via TGA, TEM, NMR and DLS. In the second part of this thesis the last two approaches of part one were varied. Here ionic liquid like molecules containing two imidazolium-groups were synthesised. Also the length and the appearance between these imidazolium-units were changed. Characterisation of the obtained material was also carried out through TGA and TEM. For the last part of this thesis two ionic liquids were synthesised; 1-butyl-3-methylimidazolium-nitrate und 1-propyl-3-methylimidazolium-chloride. Afterwards silvernitrate was reduced, in the presence of one of these ionic liquids, to yield the ionic liquid entrapped in silver. Characterisation was managed through XRD, TGA, IR and NMR.In this thesis it a new way of developing hybrid materials based on the chemistry of ionic liquids is shown. It was also proven, that it is possible to influence the morphology of metal- and metaloxides through the use of ionic liquids, respectively ionic liquid like molecules.<br /

Materials from functionalised metal oxide surfaces : ionic nanoparticle networks and cellulose aerogels

Zsfassung in dt. SpracheIn dieser Arbeit wurde die Synthese neuer anorganisch-organischer Hybridmaterialien, basierend aufMetalloxid Nanopartikel und ionischer Bindeglieder untersucht. Hierfür wurden SiO2 Nanopartikel, mit Durchmessern von ca. 15 nm, mit Hilfe von Trialkoxysilanen, welche entweder Imidazol oder Chlorid Funktionalitäten besitzen, oberflächenfunktionalisiert. Der entscheidende Schritt, eine nukleophile Substitutionsreaktion, resultiert in einem Netzwerk aus SiO2 Nanopartikeln basierend auf Imidazolium als verbrückende Einheit.Mittels diverser spektroskopischer Methoden, wie etwa NMR und SAXS, konnte gezeigt werden, dass das erhaltene System eine Nahordnung besitzt, obwohl nicht alle Imidazol Funktionalitäten eine Verbindung eingehen.Weiters wurde der Einfluss der verschiedenen Komponenten, die Partikel, die Verbindungseinheiten und die Anionen, auf die Eigenschaften des Materials untersucht. Verschiedene Übergangsmetalloxid, in einem anderen Teil der Arbeit auch metallisches Silber, Nanopartikel wurden synthetisiert und funktionalisiert mit Phosphonsäurederivaten. Durch FTIR und TGA Methoden konnte ein Beweis über die Funktionalisierungen erbracht werden. Beispielhaft wurden TiO2 Nanopartikel Netzwerke synthetisiert, welche hohe spezi sche Oberflächen mit interpartikulärer Porösität aufweisen. Netzwerke mit zwei Imidazoliumeinheiten wurden mittels Dichlormolekülen hergestellt. Dabei führen exible Alkylketten zu schwächer geordneten Systemen, als gegenüber starren. Weiters wurden Austauschreaktionen, mit verschiedensten Anionen durchgeführt. Durch Elementaranalyse konnte gezeigt werden, dass die Chloridanionen nur teilweise ausgetauscht werden konnten. SAXS Untersuchungen wiesen auf eine Anordnung der Imidazoliumeinheiten hin. In einem weiteren Teil der Arbeit wurde die Herstellung von Mono- und Multischichten von TiO2 Nanopartikel auf Siliziumwafern gezeigt. Dabei zeigen die erhaltenen Schichten Widerstände gegenüber Scherkräften, im Bereich von kovalenten Bindungen. Weiters wurde der Sol-Gel Prozess, welcher verwendet wurde um die SiO2 Nanopartikel zu funtionalisieren, zur Oberflächenmodi zierung von Zelluloseaerogelen, mittels verschiedenen Verhältnissen von CPTMS und TEOS, benutzt. Mit Hilfe von N2-sorptionsmessungen bei 77K wurde gezeigt, dass durch bestimmte Kombinationen das poröse System der Aerogele erhalten werden konnte.In this work the synthesis of new inorganic-organic hybrid materials based on metal oxide nanoparticles and ionic connectors was investigated.Therefore, SiO2 nanoparticles, with sizes around 15 nm diameter, were surface functionalised using trialkoxysilanes bearing either imidazole or chloride end groups. The final step, a nucelophilic substitution reaction between these two functionalities, results in a SiO2 nanoparticle network based on imidazolium as bridging units. Through various spectroscopic methods, such as NMR and SAXS, it could be shown, that the system exhibits a short-range ordering, even though not every imidazole undergoes a reaction. Further, the influences of the different components, the nanoparticles, the ionic bridging unit and the anionic counterpart, on the properties of the system were investigated. First, diff erent transition metal oxide, and in another part also metallic silver, nanoparticles were synthesised, and functionalised with phosphonic acid, bearing chloro or imidazole end groups. FTIR and TGA measurements provided proof of the modi cations. Exemplary, TiO2 nanoparticle systems were synthesised, showing high surface areas, together with interparticle porosity. For the second alteration, di fferent dichloro compounds were used to bridge SiO2 nanoparticles.Thereby, flexible alkyl chains resulted in weaker ordered networks, than by using more rigid ones. Furthermore anion metathesis reactions with di fferent anions were carried out on the networks. Through elemental analyses it could be seen, that the chloride anions where only partially exchanged. SAXS investigations showed the evaluation of arrangement of the imidazolium units.In another part of the work the fabrication of these covalently connected nanoparticle networks was highlighted. Mono- and multilayers of TiO2 nanoparticles were deposited on silicon substrates. Thereby, the connections showed resistances against shearing forces, typical for covalent bonds.In the last part the sol-gel process, used for the functionalisation of SiO2 nanoparticles, was also used in order to surface functionalised cellulose aerogels, using di fferent ratios of CPTMS or TEOS. It was shown through nitrogen sorption measurements at 77K, that di fferent combinations of these led to the preservation of the porous systems.12

SiO₂ units networking through ionic liquid-like bridges

Hybrid organic-inorganic silica-based materials containing bridging ionic liquid-like entities have been prepared, from 1,3-di(3-trimethoxysilylpropyl)imidazolium iodide and tetraethoxysilane. The final material is characterized by a high thermal stability. TEM micrographs of the obtained hybrid material allow its comparison with silica nanoparticles bridged through ionic liquid-like links

Porous Titania Nanoparticle Networks Connected Through Ionic Linkers

Recently an original method was developed to synthesize ionic silica nanoparticle networks based on imidazolium units These entities were produced through a nucleophilic substitution reaction between imidazole and halide functional ligands which were covalently bonded to the surface of nanoparticles. In the case of silica nanoparticles, trialkoxysilanes served as anchoring groups for the functional ligands. The synthesis pathway to form ionic nanoparticle networks was adapted to other metal oxide nanoparticle based networks. This communication will present ionic nanoparticle networks obtained with titania nanoparticles. The titania nanoparticles were produced through a bottom-up approach and posses a diameter of around 4 nm. Since Ti-O-Si bonds are known to be unstable towards hydrolysis,[2] the functional groups for the networking reaction were introduced through the modification of the nanoparticles with functional phosphonic acid groups. The formation of the imidazolium based titania nanoparticle networks was investigated by the means of CP MAS 15N NMR spectroscopy. The porous characteristic of the obtained hybrid material was investigated through nitrogen sorption, proving the existence of an inter-particle spacing. Furthermore, small angle X-ray scattering (SAXS) measurements provided an insight on the networks on a lager scale

Nanoparticles connected through an ionic linker

The 2D or 3D linking of metal or metal oxide nanoparticles is still a challenge, as well as research concerning the association of ionic species with nanoparticles. The originality of presented work lies in the combination of nanoparticles organization and concomitantly the introduction of ionic species. The two synthesis methods reported are related to the nucleophilic substitution taking place during the synthesis of imidazolium-based ionic liquids. The first approach utilized bis(trialkoxysilyl)-substituted imidazolium iodide to link the silica nanoparticles. In the second approach, the silica nanoparticles were first modified either by 3-chloropropyltrimethoxysilane or N-(3-trimethoxysilylpropyl)imidazol and then coupled through nucleophilic substitution. A comparison of both approaches shows that the second approach results in a more efficient linkage of nanoparticles. Furthermore, it is a new and original method for letting modified nanoparticles react with one another. This will result in covalently linking nanoparticles by means of an ionic linker and is characterized by using TGA, solid state NMR and TEM

Silica nanoparticles connected through ionic linkers

To obtain networks build up by silica nanoparticles, connected through ionic linkers, two different synthetic approaches were investigated. First, a bissilylated functional ionic compound was synthesized and afterwards linked to silica nanoparticles. In the second approach, silica nanoparticles were modified with either 3-chloropropyltrimethoxysilane or N-(3-trimethoxysilylpropyl)imidazol before being connected via nucleophilic substitution. Both strategies are compared in order to determine the most efficient method to get large networks

Ionic liquid entrapped in metallic silver

Ionic liquids (IL) are a relatively new class of compounds, which attracts intensive interest in many different applications as presenting very uncommon properties in terms of polarity, solubility, electrochemistry etc. Especially IL based on imidazolium salts drove the attention of the electrochemistry community.1 One of the numerous features of IL is their suitability for electrochemical deposition; they are an environmentally friendly alternative for silver electrodeposition.2 This is directly linked to the synergetic effect consecutive to the association of ionic liquids with metals.3,4 Consequently a challenge concerns the study of the possible formation of a metal-ionic liquid composite adapting the method developed by Avnir and co-workers5,6 for organic molecules entrapment within metal matrixes. This could be a unique way to investigate further the formation mechanism of the metal-organic compounds as well as it could be a new door to many other applications linked to the ionic liquids characteristics