On the Synthesis, Morphology, and Applications of Engineered Aerosol Nanoparticles

Nanotechnology, the manipulation of matter at the scale of 1–100 nm, is present in everyday life and continues extending into new areas of application. Aerosol synthesis routes, the production of nanoparticles in the gas phase, are known to be continuous, highly controllable, and even suitable for fabricating different types of nanostructured metamaterials—materials with properties not found in nature. In this thesis, single and multicomponent engineered aerosol nanoparticles with different morphologies were synthesized for applications involving interactions between light and matter. The synthesized nanoparticles included spherical silver particles, titania-encapsulated iron oxide particles, silver-decorated silica particles, and silver–titania composite doublet particles. Furthermore, the studied applications for the nanoparticles were magnetically separable photocatalyst nanopowders and nanostructured metal–dielectric metamaterials with linear and nonlinear optical properties, more specifically, localized surface plasmon resonance and second-harmonic generation, respectively.The aerosol synthesis techniques utilized for the nanoparticle production in this thesis included particle size selection, sintering, encapsulation, and coating. The sintering of the size-selected silver agglomerates to spheres continued the trends found from the literature. In the simple encapsulation process, liquid precursor containing solid particles was sprayed into a tubular furnace where the precursor thermally decomposed on the surface of the solid particles, forming multicomponent particles. This approach was demonstrated by synthesizing titania-encapsulated iron oxide particles. As titania and iron oxide are known to be photocatalytic and magnetic, respectively, the produced nanopowder could find use as a magnetically separable photocatalyst. The silver coatings on the silica and titania carrier particles, accomplished by physical vapor condensation, were found to form different types of morphologies due to the migration of the silver on the carrier particles.The wavelength of the localized surface plasmon resonance of spherical silver particles deposited on glass substrates was tuned between 400–450 nm with the particle size. Due to the random deposition process, particle–particle contacts on the substrate caused broadening of the extinction spectrum with higher area fractions. On the other hand, the silver-decorated silica nanoparticles maintained the narrow plasmon resonance band even with high particle number densities. This enabled the fabrication of thicker bulk-type optical materials. The nonlinear optical properties of bulk-type multilayer nanostructures consisting of alternating layers of silver-decorated silica nanoparticles and pure silica were investigated. It was proposed that the porous particle layers were in a key role in the formation of the required non-centrosymmetric structure. Furthermore, both the silver particles and the multilayer structure were important for the second-harmonic generation, whose intensity increased with the number of layers. The fabricated structures could be further optimized in order to increase the conversion efficiency of the second-order nonlinear optical process

On the Synthesis, Morphology, and Applications of Engineered Aerosol Nanoparticles

Nanotechnology, the manipulation of matter at the scale of 1–100 nm, is present in everyday life and continues extending into new areas of application. Aerosol synthesis routes, the production of nanoparticles in the gas phase, are known to be continuous, highly controllable, and even suitable for fabricating different types of nanostructured metamaterials—materials with properties not found in nature. In this thesis, single and multicomponent engineered aerosol nanoparticles with different morphologies were synthesized for applications involving interactions between light and matter. The synthesized nanoparticles included spherical silver particles, titania-encapsulated iron oxide particles, silver-decorated silica particles, and silver–titania composite doublet particles. Furthermore, the studied applications for the nanoparticles were magnetically separable photocatalyst nanopowders and nanostructured metal–dielectric metamaterials with linear and nonlinear optical properties, more specifically, localized surface plasmon resonance and second-harmonic generation, respectively.The aerosol synthesis techniques utilized for the nanoparticle production in this thesis included particle size selection, sintering, encapsulation, and coating. The sintering of the size-selected silver agglomerates to spheres continued the trends found from the literature. In the simple encapsulation process, liquid precursor containing solid particles was sprayed into a tubular furnace where the precursor thermally decomposed on the surface of the solid particles, forming multicomponent particles. This approach was demonstrated by synthesizing titania-encapsulated iron oxide particles. As titania and iron oxide are known to be photocatalytic and magnetic, respectively, the produced nanopowder could find use as a magnetically separable photocatalyst. The silver coatings on the silica and titania carrier particles, accomplished by physical vapor condensation, were found to form different types of morphologies due to the migration of the silver on the carrier particles.The wavelength of the localized surface plasmon resonance of spherical silver particles deposited on glass substrates was tuned between 400–450 nm with the particle size. Due to the random deposition process, particle–particle contacts on the substrate caused broadening of the extinction spectrum with higher area fractions. On the other hand, the silver-decorated silica nanoparticles maintained the narrow plasmon resonance band even with high particle number densities. This enabled the fabrication of thicker bulk-type optical materials. The nonlinear optical properties of bulk-type multilayer nanostructures consisting of alternating layers of silver-decorated silica nanoparticles and pure silica were investigated. It was proposed that the porous particle layers were in a key role in the formation of the required non-centrosymmetric structure. Furthermore, both the silver particles and the multilayer structure were important for the second-harmonic generation, whose intensity increased with the number of layers. The fabricated structures could be further optimized in order to increase the conversion efficiency of the second-order nonlinear optical process

Innovaatiopolkupilotti : Toimintamalli innovaatio- ja yrittäjyysosaamisen vahvistamiseksi korkeakoulun TKI-toiminnassa

Ammattikorkeakoulujen tehtävänä on tukea opiskelijoita kohti innovatiivista ja yrittäjämäistä ammattilaisuutta. Tässä julkaisussa esitellään tähän tarkoitukseen käyttökelpoinen innovaatiopolkumalli, joka on syntynyt keväällä 2018 toteutuneessa palveluasumisen innovaatiopolkupilotissa. Pilotti tarjosi innovatiivisia yhteisopintoja sosiaali- ja terveysalan, kiinteistö- ja talorakennusalan sekä ICT-alan yhteyspinnoille, mutta innovaatiopolkumalli on hyödynnettävissä myös muille aloille. Innovaatiopolun kehittäminen lähti liikkeelle tarpeesta kehittää opiskelijoille mielekäs oppimisympäristö innovaatiokyvykkyyden ja innovaatioiden testaamiseksi ja kaupallistamiseksi. Kehittämisen taustalla on Metropolian kaikille opiskelijoille pakollisista innovaatio-opinnoista (Minno) saadut kokemukset. Lisäksi kehittämistä on ohjannut tieto siitä, että Minnoissa tuotettuja ideoita ja potentiaalisia tuotteita on jäänyt hyödyntämättä. Innovaatiopolulla haluttiin tarjota opiskelijoille valmennusta, joka auttaa jatkamaan ideoiden kehittämistä joko osana olemassa olevia yrityksiä tai ryhtymällä yrittäjiksi start up -toiminnan tai omistajanvaihdosten kautta. Julkaisu on tarkoitettu innovaatiotoiminnan kehittämisestä kiinnostuneille asiantuntijoille sekä korkeakoulujen opettajille ja tki-suunnittelijoille. Innovaatiopolkumallia voidaan jatkossa testata ja jatkokehittää esimerkiksi hanketoiminnassa sekä korkeakouluyhteistyössä

Liquid flame spray—a hydrogen-oxygen flame based method for nanoparticle synthesis and functional nanocoatings

In this review article, a specific flame spray pyrolysis method, Liquid Flame Spray (LFS), is introduced to produce nanoparticles using a coflow type hydrogen-oxygen flame utilizing pneumatically sprayed liquid precursor. This method has been widely used in several applications due to its characteristic features, from producing nanopowders and nanostructured functional coatings to colouring of art glass and generating test aerosols. These special characteristics will be described via the example applications where the LFS has been applied in the past 20 years.publishedVersionPeer reviewe

Second-harmonic response of multilayer nanocomposites of silver-decorated nanoparticles and silica

We perform a detailed characterisation of the second-order nonlinear optical response of nanocomposites consisting of alternating layers of silver-decorated silica glass nanoparticles and pure silica glass. The samples are fabricated using aerosol techniques and electron-beam dielectric coating, resulting in a bulk-like material with symmetry-breaking induced by the porosity of the alternating layers. The second-order nonlinear response increases with the number of layers. Further, by determining the components of the second-order susceptibility tensor of the samples, we show that the structural properties of the samples are well maintained as the sample thickness is increased. Our results form an important baseline for any further optimization of these types of structures, which can be fabricated using very straightforward methods.Peer reviewe

Surface-Enhanced Impulsive Coherent Vibrational Spectroscopy

Surface-enhanced Raman spectroscopy (SERS) has attracted a lot of attention in molecular sensing because of the remarkable ability of plasmonic metal nanostructures to enhance the weak Raman scattering process. On the other hand, coherent vibrational spectroscopy triggered by impulsive excitation using ultrafast laser pulses provides complete information about the temporal evolution of molecular vibrations, allowing dynamical processes in molecular systems to be followed in "real time". Here, we combine these two concepts and demonstrate surface-enhanced impulsive vibrational spectroscopy. The vibrational modes of the ground and excited states of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), spin-coated on a substrate covered with monodisperse silver nanoparticles, are impulsively excited with a sub-10 fs pump pulse and characterized with a delayed broad-band probe pulse. The maximum enhancement in the spectrally and temporally resolved vibrational signatures averaged over the whole sample is about 4.6, while the real-time information about the instantaneous vibrational amplitude together with the initial vibrational phase is preserved. The phase is essential to determine the vibrational contributions from the ground and excited states.publishedVersionPeer reviewe

Ordered multilayer silica-metal nanocomposites for second-order nonlinear optics

We use aerosol synthesis to fabricate ordered metal-silica nanocomposites consisting of alternating layers of pure silica and silica nanoparticles decorated with silver nanodots. These multilayer structures preserve the narrow plasmon resonance of the nanodots even for high optical densities and allow second-harmonic generation due to spontaneous symmetry breaking arising from the interfaces between silica and nanoparticle layers. Our concept opens up perspectives for complex structures for advanced optical applications.Peer reviewe