Designing hybrid materials allows leveraging the properties of different material systems to achieve novel functions. Significant progress has been made in recent years to exploit the physicochemical properties of a new generation of hybrid materials for emerging biomedical applications. In Chapter 1, I review the recent advances in the field of dye-lanthanide hybrid materials, centring on the interface between organic dyes and inorganic lanthanide materials and investigating their photophysical and photochemical properties. Five representative dye-lanthanide hybrid material systems including lanthanide complex, dye-sensitised downshifting nanoparticles (DSNPs), dye-sensitised downconversion nanoparticles (DCNPs), dye-sensitised upconversion nanoparticles (UCNPs), and UCNPs-dye energy transfer systems have been thoroughly discussed. We highlight the key applications of dye-lanthanide hybrid materials in bioimaging, sensing, drug delivery, therapy, and cellular activity studies. In Chapter 2, I design and synthesize an ytterbium complex-based sensor for the detection of Hg2+ ions. The water-soluble ytterbium complex exhibits reversible off−on visible and NIR emission upon the binding with mercury ion. The fast response and 150 nM sensitivity of Hg2+ detection are based upon FRET and the lanthanide antenna effect. The reversible Hg2+ detection can be performed in vitro, and the binding mechanism is studied by NMR employing the motif structure in a La complex and by DFT calculations. In Chapter 3, I report a pair of stoichiometric terbium-europium dyads as molecular thermometers and study their energy transfer properties. A strategy for synthesizing hetero-dinuclear complexes that contain chemically similar lanthanides is developed. By this strategy, a pair of thermosensitive dinuclear complexes, cycTb-phEu and cycEu-phTb, was synthesized. Their structures were geometrically optimized with an internuclear distance of approximately 10.6 Å. The dinuclear complexes have sensitive temperature-dependent luminescent intensity ratios of europium and terbium emission, and temporal dimension responses over a wide temperature range (50 - 298 K and 10 - 200 K, respectively). This indicates that both dinuclear complexes are excellent self-referencing thermometers. In Chapter 4, I investigate spectral structure and intensity changes of a pair of dinuclear complexes with a europium ion on cyclen site and a lanthanum ion on phen site or vice verses (cycEu-phLa and cycLa-phEu). Though they have the same components and the same energy levels, they present different photophysical properties due to the different coordination environment. The band positions are different in the emission spectra. The emission of cycEu-phLa showed a stronger relative intensity of 5D0 7F2 transition whereas the relative intensity of 5D0 7F4 transition was weaker in comparison with cycLa-phEu. We found the cycEu-phLa have higher internal quantum efficiency while the cycEu-phLa have higher sensitizing efficiency, though they have similar external quantum yield. We determined the singlet-triplet intersystem crossing rate with values as ~108 s-1. In Chapter 5, I exploit a dye sensitised upconversion nanoparticle with highly enhanced upconversion emission. I designed and synthesized a new dye by connecting tetraphenylethene (TPE) with the cyanide NIR dye, IR783. The resultant compound (TPEO-IR783) has a quantum yield of 22.46% which is 3 times higher than that of reported UCNP sensitiser (IR806). The TPEO-IR783 exhibits a transparent window in a range of 400 nm to 600 nm, making it suitable sensitiser for upconversion nanoparticles by avoiding reabsorption. The TPEO-IR783 sensitised UCNPs show more than 200-fold upconversion emission than the reported IR806 sensitised UCNPs under the same condition. In Chapter 6, I develop an ytterbium nanoparticle-mediated upconversion system. The system enables the singlet energy transfer from sensitisers to acceptor triplet states without the requirement of intersystem crossing. I evaluate the hybrid upconversion design by IR808 and rubrene acid. While the mixture of IR808 and rubrene acid does not show any upconversion emission, the introduction of an intermediate ytterbium energy level by adding NaGdF4:Yb nanoparticles displays strongly enhanced upconversion emissions. This design bypasses the specific requirement of traditional sensitisers in TTA system, providing a wide range of opportunities in deep tissue applications. Chapter 7 is the experiment sections where details of materials, characterizations, and synthetic procedures in each chapter have been provided.

Designing hybrid materials allows leveraging the properties of different material systems to achieve novel functions. Significant progress has been made in recent years to exploit the physicochemical properties of a new generation of hybrid materials for emerging biomedical applications. In Chapter 1, I review the recent advances in the field of dye-lanthanide hybrid materials, centring on the interface between organic dyes and inorganic lanthanide materials and investigating their photophysical and photochemical properties. Five representative dye-lanthanide hybrid material systems including lanthanide complex, dye-sensitised downshifting nanoparticles (DSNPs), dye-sensitised downconversion nanoparticles (DCNPs), dye-sensitised upconversion nanoparticles (UCNPs), and UCNPs-dye energy transfer systems have been thoroughly discussed. We highlight the key applications of dye-lanthanide hybrid materials in bioimaging, sensing, drug delivery, therapy, and cellular activity studies. In Chapter 2, I design and synthesize an ytterbium complex-based sensor for the detection of Hg2+ ions. The water-soluble ytterbium complex exhibits reversible off−on visible and NIR emission upon the binding with mercury ion. The fast response and 150 nM sensitivity of Hg2+ detection are based upon FRET and the lanthanide antenna effect. The reversible Hg2+ detection can be performed in vitro, and the binding mechanism is studied by NMR employing the motif structure in a La complex and by DFT calculations. In Chapter 3, I report a pair of stoichiometric terbium-europium dyads as molecular thermometers and study their energy transfer properties. A strategy for synthesizing hetero-dinuclear complexes that contain chemically similar lanthanides is developed. By this strategy, a pair of thermosensitive dinuclear complexes, cycTb-phEu and cycEu-phTb, was synthesized. Their structures were geometrically optimized with an internuclear distance of approximately 10.6 Å. The dinuclear complexes have sensitive temperature-dependent luminescent intensity ratios of europium and terbium emission, and temporal dimension responses over a wide temperature range (50 - 298 K and 10 - 200 K, respectively). This indicates that both dinuclear complexes are excellent self-referencing thermometers. In Chapter 4, I investigate spectral structure and intensity changes of a pair of dinuclear complexes with a europium ion on cyclen site and a lanthanum ion on phen site or vice verses (cycEu-phLa and cycLa-phEu). Though they have the same components and the same energy levels, they present different photophysical properties due to the different coordination environment. The band positions are different in the emission spectra. The emission of cycEu-phLa showed a stronger relative intensity of 5D0 7F2 transition whereas the relative intensity of 5D0 7F4 transition was weaker in comparison with cycLa-phEu. We found the cycEu-phLa have higher internal quantum efficiency while the cycEu-phLa have higher sensitizing efficiency, though they have similar external quantum yield. We determined the singlet-triplet intersystem crossing rate with values as ~108 s-1. In Chapter 5, I exploit a dye sensitised upconversion nanoparticle with highly enhanced upconversion emission. I designed and synthesized a new dye by connecting tetraphenylethene (TPE) with the cyanide NIR dye, IR783. The resultant compound (TPEO-IR783) has a quantum yield of 22.46% which is 3 times higher than that of reported UCNP sensitiser (IR806). The TPEO-IR783 exhibits a transparent window in a range of 400 nm to 600 nm, making it suitable sensitiser for upconversion nanoparticles by avoiding reabsorption. The TPEO-IR783 sensitised UCNPs show more than 200-fold upconversion emission than the reported IR806 sensitised UCNPs under the same condition. In Chapter 6, I develop an ytterbium nanoparticle-mediated upconversion system. The system enables the singlet energy transfer from sensitisers to acceptor triplet states without the requirement of intersystem crossing. I evaluate the hybrid upconversion design by IR808 and rubrene acid. While the mixture of IR808 and rubrene acid does not show any upconversion emission, the introduction of an intermediate ytterbium energy level by adding NaGdF4:Yb nanoparticles displays strongly enhanced upconversion emissions. This design bypasses the specific requirement of traditional sensitisers in TTA system, providing a wide range of opportunities in deep tissue applications. Chapter 7 is the experiment sections where details of materials, characterizations, and synthetic procedures in each chapter have been provided.

Nanotechnology is a new frontier for the advancement of science and technology. Nanomaterials are playing a crucial role and that they will continue to do so is beyond doubt. They are being used in electronic, magnetic, optical and catalytic applications where the unique interactions of nanostructured materials with electromagnetic radiation is of great benefit. While significant progress in understanding fundamental nanoparticle - electromagnetic radiation interactions has been made, and has improved practical technology applications, there is plenty left to be fully understood. This dissertation aims to further probe nanoparticle - electromagnetic radiation interactions and unveil details previously not known. More specifically, this dissertation looks at how microwaves can aid in the synthesis of anisotropic magnetic nickel nanoparticles, how small sized nanoparticles can be used in tuning the dielectric properties of polymer-nanocomposites, and how core-shell nanoparticles can be used for high quenching of fluorescence red dyes. An overview of chapters section that provides a more detailed content summary for each chapter is found at the end of the introduction chapter. / A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester 2018. / July 13, 2018. / anisotropic, microwave, nanoparticle, nickel, polymer nanocomposite, surface energy transfer / Includes bibliographical references. / Geoffrey F. Strouse, Professor Directing Dissertation; Subramanian Ramakrishnan, University Representative; Joseph B. Schlenoff, Committee Member; Lei Zhu, Committee Member.

abstract: More recently there have been a tremendous advancement in theoretical studies showing remarkable properties that could be exploited from transition metal dichalcogenide (TMDC) Janus crystals through various applications. These Janus crystals are having a proven intrinsic electrical field due to breaking of out-of-plane inversion symmetry in a conventional TMDC when one of the chalcogenides atomic layer is being completely replaced by a layer of different chalcogen element. However, due to lack of accurate processing control at nanometer scales, key for creating a highly crystalline Janus structure has not yet been familiarized. Thus, experimental characterization and implication of these Janus crystals are still in a state of stagnation. This work presents a new advanced methodology that could prove to be highly efficient and effective for selective replacement of top layer atomic sites at room temperature conditions. This is specifically more focused on proving an easy repeatability for replacement of top atomic layer chalcogenide from a parent structure of already grown TMDC monolayer (via CVD) by a post plasma processing technique. Though this developed technique is not limited to only chalcogen atom replacement but can be extended to any type of surface functionalization requirements. Basic characterization has been performed on the Janus crystal of SeMoS and SeWS where, creation and characterization of SeWS has been done for the very first time, evidencing a repeatable nature of the developed methodology. / Dissertation/Thesis / Masters Thesis Materials Science and Engineering 2019

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The recent emergence of a new class of two dimensional layered materials (2DLMs) have not only opened up the potential for exciting new technological opportunities but also established a new platform to explore exciting new fundamental physics and chemistry at the limit of atomic thickness. Among several of these newly rediscovered 2DLMs, transition metal dichalcogenides (TMDCs) as well as other elemental combinations of Group III and Group VI represent a large family of 2D layered materials, which can be isolated into few atomic layers. These materials show remarkable promise for future electronic and opto-electronics applications. The scope of this dissertation, thus, broadly covers the electronic and opto-electronic properties of such few layered 2D materials. Extensive investigation of electronic and opto-electronic transport phenomena of charge carriers in few layer MoS2 synthesized using a variety of methods such as Chemical Vapor Deposition (CVD), liquid phase exfoliation and mechanical exfoliation as well as CVT grown mechanically exfoliated WSe2 and ternary alloy of CuIn7Se11 is reported. Specifically, it is shown that in case of MoS2, the ac conductance (σ(ω); measured in the range of 10mHz < ω < 0.1 MHz) of atomically thin 2D layers of chemical vapor deposited (CVD) Molybdenum Disulphide (MoS2) as well as thin films of exfoliated flakes of MoS2, show "universal" power law behavior (with σ(ω) ~ ωs). The temperature dependence of 's' indicate that the mechanism of ac transport in CVD MoS2 is due to electron hopping by quantum mechanical tunneling (QMT) process whereas the ac transport in exfoliated MoS2 films is due to correlated barrier hoping (CBH) mechanism. The ac conductivity also show scaling behavior, manifested by collapse of the ac conductivity data for both the samples at various temperatures to one single master curve. The T-γ dependence of the d.c conductance suggests that in case of the CVD – grown and mechanically exfoliated MoS2, γ=1/3 which corresponds to the Mott’s variable range hopping (VRH) transport where as in case of liquid phase exfoliated MoS2, γ=1 which relates to thermally activated Arrhenius type transport mechanism. Opto-electronic measurements were also performed in a variety of 2DLM samples. From the field effect transport measurements on the mechanically exfoliated samples of few layers of MoS2, WSe2 and CuIn7Se11, we found at room temperature the charge carrier mobility is ~ 47 cm2/V.s, 80 cm2/V.s and 37 cm2/V.s for MoS2, WSe2 and CuIn7Se11 respectively. The photoconductivity measurements performed on these samples show that it is possible to achieve photo-responsivities values~50 μA/W, 0.2 A/W, 1 A/W and 51 A/W at room temperature for liquid exfoliated MoS2, mechanically exfoliated MoS2, WSe2 and CuIn7Se11 based devices respectively. Mechanisms of photoconduction in these materials were explained on the basis of intensity dependent photo-current measurements. From the intensity dependent photo-current along with the low temperature photoconduction measurements we found that in case of liquid phase exfoliated MoS2 thin film devices the trap states are continuously distributed within the mobility gap in these thin film of MoS2, and play a vital role in influencing the overall photo response. On the other hand for CVT grown mechanically exfoliated WSe2 based devices bimolecular recombination mechanism is the most dominant process for photoconduction. The result obtained are discussed and compared with the available literature on the subject.

After the completion and failure of 44 phase III clinical trials, Traumatic Brain Injury (TBI) continues to be a leading cause of disability, morbidity, and mortality amongst military personnel and civilians of all age groups. TBI is characterized by primary and secondary injury processes of which the secondary injury is defined by oxidative stress, increased energy demands, mitochondrial dysfunction, neuroinflammation, and more; characteristics which are also shared with neurodegenerative diseases. Creatine (Cr) is one of the most abundantly used and studied supplements in the fitness industry which, when in the form of Phosphoryl-Creatine (PCr), directly aids in the conversion of ADP to ATP, particularly in metabolically stressed conditions where oxygen is unavailable, and hypothesized to be a JAK2 inhibitor. Similarly, Tannic Acid (TA) is a polyphenol naturally available in teas and nuts that provides neuroprotective effects against TBI through the PGC-1?/Nrf2/HO-1 pathway. However, bioavailability of these compounds in the brain is limited through oral supplementation. Therefore, increasing the local concentration of these compounds in the brain parenchyma may provide therapeutic benefits after cerebral injury. In this study, efficiently loaded, TA-based Creatine nanoparticles (NPs) were synthesized as a potential therapeutic for secondary TBI and related neuroinflammatory conditions. This nanosystem demonstrates surface chemistry augmentation, high loading efficiency, and biodegradation with 24 hours. Purified NPs had an average hydrodynamic diameter of 200 nm, an average surface charge of -44mV, and a polydispersity index (PDI) of 0.171. Purified particles also demonstrate long shelf life and stability over many months, suggesting this inexpensive formulation could be utilized as a cheap therapeutic in underserved, low-income areas.