We are living in an age where the demand for energy is growing rapidly. This means that supplies to easily accessible oil and natural gas is unlikely to keep up with the demand as times goes on. The world will have to use energy more efficiently and increase its use of other sources of energy. This study is aiming at developing materials that will improve the power conversion efficiency of photovoltaic cells by using up and down-converting phosphor materials. ZnTiO3-Zn2TiO4 composite and ZnTiO3 phosphors doped with Er3+,Yb3+, Eu3+ and Al3+, which display up and down-converted luminescence were synthesized by a simple high temperature conventional solid state reaction method. The structure, particle morphology, absorption, photoluminescent properties and elemental distribution were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis-NIR absorption spectrometer, photoluminescence (PL) spectroscopy and time of flight secondary ion mass spectroscopy (TOF-SIMS), respectively. ZnTiO3-Zn2TiO4 composite doped with different concentration of Er3+ ions was synthesized via solid state chemical reaction method at 1100 ℃. The X-ray diffraction (XRD) confirmed the crystallization of both the hexagonal ZnTiO3 and cubic spinel Zn2TiO4 phases of the composite. The SEM images of ZnTiO3-Zn2TiO4:Er3+ composite showed that the particle morphology was made up of faceted hexagons. Furthermore, the ZnTiO3-Zn2TiO4:Er3+ phosphors were excited in the near-infrared (NIR) region using a laser diode with a wavelength of 980 nm and displayed both green and red up-conversion emission bands in the visible range at 543, 553, 650 – 670 nm. These emission bands correspond to 2H11/2, 4S1/2→ 4 I15/2 and 4F9/2→ 4 I15/2 transitions of Er3+ ions. However, the interaction mechanisms involved in the upconversion process of ZnTiO3-Zn2TiO4:Er3+ phosphor is discussed with the help of an energylevel schematic diagram and the number of the photons involved in the up-conversion luminescence process were of a double photon mechanism. The decay lifetimes were studied by fitting the luminescence decay curve with a single-component exponential decay. Er3+ and Yb3+ incorporated zinc titanate (ZnTiO3) phosphor powders were synthesized using conventional solid-state reaction method at 800 ℃. A ZnTiO3:Er3+,Yb3+ phosphor that resembled an ecandrewsite single phase with space group R-3 (148) was obtained, as proven by X-ray diffraction (XRD). The SEM image showed a surface morphology composed of agglomerated irregular shaped particles. The energy band gap of ZnTiO3 was engineered by incorporating different concentration of the dopant ions. After irradiating ZnTiO3:Er3+with a 980 nm laser beam, the phosphor up-converted the photon energy to display green and red emissions in the visible range that were positioned at 527, 545 and 665 nm. Enhancement of the luminescence intensity of ZnTiO3:Er3+ phosphor was achieved by variation of Er3+ concentration. Co-doping with Yb3+ ions proved to be effective in enhancing the luminescence intensity of the optimized Er3+ ion emission and new emission bands at 410 and 480 nm, through an energy transfer mechanism were observed. The enhancement of the lifetime of the up-conversion luminescence was also achieved by co-doping ZnTiO3:Er3+ phosphor with Yb3+ ion. The energy transfer mechanisms involved in Er3+ - Yb3+ co-doped ZnTiO3 phosphor was illustrated and discussed in detail. The ZnTiO3:Er3+, Yb3+ thin films were successfully deposited by pulsed laser deposition (PLD) by varying the silicon (100) substrate temperature. The distribution of the ions in the films was investigated and the TOF-SIMS showed that the ions were homogeneously distributed throughout the ZnTiO3 host lattice which indicated a successful incorporation of the Er3+ and Yb3+ ions. The optical response of the phosphors revealed that the reflectance percentages of the ZnTiO3:Er3+, Yb3+ vary with the silicon substrate temperature due to the differences in the thickness and morphological roughness of the thin films. The ZnTiO3:Er3+, Yb3+ thin films also exhibited up-conversion emission from Er3+ electronic transitions, with violet, blue, green and red emission lines at 410, 480, 525, 545 and 660 nm from 2H9/2 → 4 I15/2, 4F7/2 → 4 I15/2, 2H11/2 → 4 I15/2, 4S3/2 → 4 I15/2 and 4F9/2 → 4 I15/2 transitions, respectively. These up-conversion emissions were enhanced by increasing the silicon substrate temperature during the deposition. ZnTiO3 host co-doped with Eu3+ and Al3+ was synthesized by solid state reaction to convert the UV photons to visible photons. Charge compensation effects of Al3+ incorporated ZnTiO3:Eu3+ as a co-dopant ion was reported in detail. The structural and morphological characterization show that the addition of Eu3+ and Al3+ does not affect the phase formation and the surface morphology of the host. The visible emission intensity of Eu3+ ions for an optimal concentration of 2 mol% under 395 nm excitation, was enhanced by incorporating Al3+. The energy level diagram showing the charge compensation mechanism was proposed for the co-doped system. / College of Engineering, Science and Technology

Un-doped, Tb3+ as well as Yb3+ doped ZnO nanocrystals with different concentrations of RE3+ (Tb3+, Yb3+) ions were successfully synthesized via sol-gel method to produce rare earth activated zinc oxide nanophosphors. The phosphor powders were produced by drying the precursor gels at 200˚C in ambient air. Based on the X-ray diffraction results, it was found that the pure and RE3+ doped ZnO nanophosphors were highly polycrystalline in nature regardless of the incorporation of Tb3+ or Yb3+ ions. Moreover, the diffraction patterns were all indexed to the ZnO Hexagonal wurtzite structure and belong to P63mc symmetry group. The Raman spectroscopy confirmed the wurtzitic structure of the prepared samples. Elemental mapping conducted on the as prepared samples using Scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer (EDX) revealed homogeneous distribution of Zn, O, and RE3+ ions. The high resolution transmission electron microscope (HR-TEM) analyses indicated that the un-doped and RE3+ doped samples were composed of hexagonal homogeneously dispersed particles of high crystallinity with an average size ranging from 4 to 7 nm in diameter, which was in agreement with X-ray diffraction (XRD) analyses. ZnO:Tb3+ PL study showed that among different Tb3+ concentrations, 0.5 mol% Tb3+ doped ZnO nanoparticles showed clear emission from the dopant originating from the 4f-4f intra-ionic transitions of Tb3+ while the broad defects emission was dominating in the 0.15 and 1 mol% Tb3+doped ZnO. Optical band-gap was extrapolated from the Ultraviolet Visible spectroscopy (UV-Vis) absorption spectra using TAUC‟s method and the widening of the optical band-gap for the doped samples as compared to the un-doped sample was observed. The PL study of ZnO:Yb3+ samples was studied using a 325 nm He-Cd laser line. It was observed that the ZnO exciton peak was enhanced as Yb3+ions were incorporated in ZnO matrix. Furthermore, UV-VIS absorption spectroscopic study revealed the widening of the band-gap in Tb3+ doped ZnO and a narrowing in the case of Yb3+ doped ZnO system. X-ray photoelectron spectroscopy demonstrated that the dopant was present in the doped samples and the result was found to be consistent with PL data from which an energy transfer was evidenced. Energy transfer mechanism was evidenced between RE3+ and ZnO nanocrystals and was discussed in detail. / Physics / M.Sc. (Physics)

Title: Development of novel photoactive cationic zirconocene complexes Author: Bc. David Dunlop Department: Department of inorganic chemistry Supervisor: RNDr. Martin Lamač Ph.D. Advisor: prof. RNDr. Petr Štěpnička, Ph.D., DSc. Abstract: Environmental concerns have brought about an unprecedented demand for sustainable energy sources among which electromagnetic radiation, light, currently dominates. Development of novel light- harvesting compounds and materials is at the forefront of current science, as it is essential to further our technological progress. This thesis contributes to the field by development of novel photoactive cationic group 4 metallocene complexes stabilized by pendant imine and pyridinyl donor groups, or N,O-donor aromatic ligands, as crystalline [B(C6F5)4]− salts. The complexes are prepared either by protonation of the intramolecularly bound imine moiety by PhNMe2H[B(C6F5)4] or by chloride ligand abstraction, by Li[B(C6F5)4]·2.5Et2O or in situ generated Et3Si[B(C6F5)4]. Prepared compounds were characterized by NMR spectroscopy. Solid state structures of the compounds were determined by X-ray diffraction analysis. The cationic complexes of Zr and Hf exhibited significantly enhanced luminescence which originates from triplet ligand-to-metal (3 LMCT) excited states with lifetimes of up to...

Det finns många biotekniska analys- och detekteringsmetoder. Metoderna används för identifiering och kvantifiering av biomarkörer. Denna studie har analyserat detekteringsmetoder i de fall där två hjärtspecifika biomarkörer används, troponin och kreatinkinas. Studien avsåg att först identifiera tillämpningsfrekvensen av detekteringsmetoder i Sverige samt internationellt. Vidare identifieras sambandet mellan avgörande parametrar i val av detekteringsmetod. Metoden gick ut på att först bestämma den mest frekventa detekteringsmetoden i Sverige med hjälp av en enkät som skickades till olika laboratorier, sedan studerades tidigare studier publicerade på olika internationella databaser. Studierna som tillämpades var på hjärtspecifika troponin och kreatinkinas för att identifiera val av detekteringsmetod, detekteringskaraktäristika och användarvänlighetsparametrar. Studiens resultat visade att nationellt finns det tre detekteringsmetoder som är de mest använda för identifiering av kreatinkinas: masspektrometri, elektrokemisk luminescence och spektrometri. Internationellt är den dominerande metoden däremot elektrokemisk luminescence. För troponin är den dominerande metoden nationellt: elektrokemisk luminescence och flödescytometri, medan internationellt: elektrokemisk luminescence. Elektrokemisk luminescence är i många fall en stark vinnare i tillämpningen. Ytterligare iakttogs korrelationskoefficienter mellan parametern för att identifiera det starkaste respektive svagaste sambandet. Avgörande parametrar i val av elektrokemisk luminescence, visar på flera samband. Elektrokemisk luminescence och kreatinkinas tilldelas en korrelationskoefficient nära ett för parametrar som volym och känslighet och en korrelationskoefficient nära minus ett för linjärt mätområde och volym, samt kostnad och minimummängd. Medan för troponin och elektrokemisk luminescence erhålls en korrelationskoefficient nära ett för parametrar som känslighet och kostnad och en koefficient nära minus ett för kostnad och tid. / There are many biotechnological analysis- and detection methods. The methods are used for identification and quantification of biomarkers. This study has analyzed detection methods incases where two heart-specific biomarkers are used, troponin and creatine kinase. The study was intended to first identify the application frequency of detection methods in Sweden and internationally. Then identify the relationship between crucial parameters in the choice of detection method. The method consisted of first determining the most frequent detection method in Sweden with the help of a questionnaire that was sent to different laboratories, then previous studies published on various international databases were observed. The studies applied were on topics regarding cardiac-specific troponin and creatine kinase to identify choice of detection method, detection characteristics, and ease of use parameters. The results of the study showed that nationally, the detection methods most used for creatine kinase are mass spectrometry, electrochemical luminescence, and spectrometry. Internationally, however, the dominant method is electrochemical luminescence. For troponin, on a national level the dominant methods are electrochemical luminescence and flow cytometry, while internationally: electrochemical luminescence. Electrochemical luminescence is in many cases a strong winner in application. In addition, correlation coefficients are observed between the decisive parameters for a detection method, to identify the strongest and weakest relationships. Electrochemical luminescence and creatine kinase are assigned a correlation coefficient close to one for parameters such as volume and sensitivity and a correlation coefficient when minus one for measurement range and volume, as well as cost and minimum amount. While for troponin and electrochemical luminescence, a correlation coefficient close to one is obtained for parameters such as sensitivity and cost and a coefficient close to minus one for cost and time.

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The discovery of ferroelectricity in hafnium oxide has revived the interest in ferroelectric memories as a viable option for low power non-volatile memories. However, due to the high coercive field of ferroelectric hafnium oxide, instabilities in the field cycling process are commonly observed and explained by the defect movement, defect generation and field induced phase transitions. In this work, the optical and transport experiments are combined with ab-initio simulations and transport modeling to validate that the defects which act as charge traps in ferroelectric active layers are oxygen vacancies. A new oxygen vacancy generation leads to a fast growth of leakage currents and a consequent degradation of the ferroelectric response in Hf₀.₅Zr₀.₅O₂ films. Two possible pathways of the Hf₀.₅Zr₀.₅O₂ ferroelectric property degradation are discussed.

Metallic nanostructures supporting surface plasmon modes can concentrate optical fields, and enhance luminescence processes from the metal surface at plasmonic hotspots. Such nanoplasmonic metal luminescence contributes to the spectral background in surface-enhanced Raman spectroscopy (SERS) measurements and is helpful in bioimaging, nano-thermometry, and chemical reaction monitoring applications. Despite increasing interest in nanoplasmonic metal luminescence, little attention has been paid to investigating its dependence on voltage modulation. Also, the hyphenated electrochemical surface-enhanced Raman spectroscopy (EC-SERS) technique typically ignores voltage-dependent spectral background information associated with nanoplasmonic metal luminescence due to limited mechanistic understanding and poor measurement reproducibility. In this thesis, we combine the experimental observations and theoretical study on dynamic Faradaic & non-Faradaic modulated nanoplasmonic metallic luminescence and molecular vibrational Raman from hotspots at the electrode-electrolyte interfaces using multiple novel nano-optoelectrodes. Our work represents a critical step toward the general application of nanoplasmonic metal luminescence signals in optical voltage biosensing, hybrid optical-electrical signal transduction, and interfacial electrochemical monitoring. / Master of Science / Understanding the non-Faradaic and Faradaic process pathway is crucial for unraveling reaction mechanisms, developing efficient catalysts, designing bionsensing methodology, energy conversion and cellular stimulator (1-7). Advances in spectroscopic techniques( 8, 9) and computational models (3, 10) have facilitated the investigation of the non-Faradic and Faradaic processes. Unlike bulk reactions, interfacial electrochemical reactions occur in nanometer-thin layers (3, 11), necessitating highly sensitive detection methods. A significant challenge is background interference from bulk electrolytes and electrodes, often obscuring weak signals from the interfacial region – traditional spectroelectrochemistry struggles to match the high temporal resolution requirement due to noise (12, 13). Surface plasmons have become a promising solution for enhancing the sensitivity of spectroelectrochemical techniques (14, 15). Surface plasmons are collective oscillations of electrons at the metal-dielectric interface, which can focus and intensify optical fields at the nanoscale (16), boosting diverse nonlinear emission signals, including fluorescence, Raman scattering, and harmonic generation (17-23). By utilizing surface plasmons, spectroelectrochemistry techniques have shown promise in detecting interfacial activities with high sensitivity. In this thesis, we introduce a pioneering dual-channel in situ EC-SERS methodology, which harnesses the synergy between plasmon-enhanced vibrational Raman scattering (PE-VRS) and plasmon-enhanced electronic Raman scattering (PE-ERS) interfacial signals to monitor and analyze the Faradaic and non-Faradaic process at the electrode-electrolyte interfaces.

The presented dissertation encompasses three distinct investigations into novel complexes with diverse applications. Firstly, a Europium-based complex, K[Eu(hfa)4], exhibits remarkable potential for detecting dissolved CO2 in an ethylene glycol medium, offering a low limit of detection, rapid response times, and high signal-to-noise ratios. This complex demonstrates promise for quantifying CO2 concentrations and finds utility in sugar fermentation monitoring. Secondly, an innovative ratiometric optical sensor, Eu(tta)3([4,4'-(t-bu)2-2,2'-bpy)], showcases exceptional sensitivity and selectivity in detecting aluminum ions, making it suitable for environmental and biological applications. It exhibits reliable quantification in both methanol and aqueous samples, with remarkable accuracy validated by ICP-OES. Lastly, modifications to the Au3Pz3 complex synthesis enable the development of a silver ion sensor, paving the way for detecting silver ion leaching in real-life scenarios, such as silver nanoparticle-embedded bandages. The research extends to the synthesis of silver nanoparticles using various methods and foresees expanded in vitro and in vivo studies. These investigations collectively offer insights into the development of advanced sensing technologies with significant implications for a wide range of practical applications.

Die Ramanspektroskopie (RS) ist eine analytische Technik, die in Folge einer optischen Anregung eines Stoffes materialspezifische Informationen über dessen molekulare Schwingungen und Kristallstruktur liefert. Da sowohl Minerale als auch biologische Materialien untersucht werden können, ist die RS in der Weltraumforschung von besonderem Interesse. So werden im Jahr 2020 gleich zwei Marsrover (ExoMars und Mars 2020) Ramanspektrometer mitführen, deren Aufgabe unter anderem die Detektion von Spuren von vergangenem oder gegenwärtigem extraterrestrischen Leben sein wird. Die Charakterisierung von stark lumineszierenden biologischen Proben und Mineralen stellt eine der größten Herausforderungen in der konventionellen RS dar. Daher beschäftigt sich diese Dissertation mit dem Problem der Lumineszenz in der RS. Dazu wird das Potenzial von fünf verschiedenen ramanspektroskopischen Techniken zur Handhabung der Lumineszenz evaluiert. Diese Techniken beinhalten (i) die Auswahl von verschiedenen Anregungswellenlängen (325 nm, 532 nm, 785 nm, 1064 nm), welche auf dem Konzept der spektralen Trennung des Lumineszenz- und Ramansignals basiert. (ii) Eine Alternative ist das Photobleichen, wobei die Lumineszenz durch eine lange Belichtungszeit unterdrückt wird. (iii) Eine weitere Methode für die spektrale Separation von Raman- und Lumineszenzphotonen ist die anti-Stokes RS. (iv) Bei der SERDS Technik werden zwei leicht verschobene Anregungswellenlängen verwendet. (v) Abschließend erfolgt die Untersuchung der Streu- und Emissionsstrahlung in der Zeitdomäne. Die Ergebnisse dieser Arbeit zeigen, dass es keine universelle Lösung gibt um das Problem der Lumineszenz in der RS zu überwinden. Allerdings weist die Verwendung unterschiedlicher Laserwellenlängen großes Potenzial für die erfolgreiche Handhabung der Lumineszenz in der RS auf. In Kombination mit SERDS und/oder Photobleichen steigt die Wahrscheinlichkeit verwertbare Spektren für die Probencharakterisierung zu erhalten. / Raman spectroscopy (RS) is an analytical technique conveying material-specific information about a material’s molecular vibrations and crystal structure in succession of an optical excitation of the material. Due to the fact that mineralogical as well as biological material can be examined, RS is of special interest for space research. For instance, two Mars rovers (ExoMars and Mars 2020) will each carry along a Raman spectrometer in the year 2020, with the aim of detecting inter alia traces of extant or extinct extraterrestrial life. One of the biggest challenges in conventional RS is the characterization of strongly luminescent biological or mineralogical material; therefore, the dissertation at hand deals with the problem of luminescence in RS. For this purpose, the potential of five different Raman spectroscopic techniques for the handling of luminescence will be evaluated. These techniques include (i) the selection of different excitation wavelengths (325 nm, 532 nm, 785 nm and 1064 nm), which is based on the concept of the spectral separation of the luminescence signals as well as Raman signals. (ii) Photobleaching provides an alternative whereby the luminescence is suppressed by long exposure. (iii) A further method for the spectral separation of Raman photons as well as luminescence photons is provided by the anti-Stokes RS. (iv) The SERDS technique uses two slightly shifted excitation wavelengths. (v) Finally the examination of inelastic scattering and emission takes place in the time domain. The results of this dissertation show that there is no universal solution to overcome the problem of luminescence in RS. However, the usage of different excitation wavelengths offers great potential for handling luminescence in RS successfully. In combination with SERDS and/or photobleaching the probability to obtain exploitable spectra for sample characterization increases