In demand for early and accurate diagnosis, plasmonic-based biosensors have emerged as an attractive solution that can achieve rapid, real-time, and label-free detection of various biomarkers. In this project, a portable system for fluorescence measurements based on plasmonic nanochip was demonstrated. I developed an image analysis program, which was used to perform image analysis to get the relationship between the fluorescence intensity of the image and the concentration of protein biomarkers. The project thus shows promising results in building a portable detecting system for medical diagnostics, which is highly sensitive, multiple tests, easy to use.

Thin films are nanoscale layers of material, with exotic properties useful in diverse areas, ranging from biomedicine to nanoelectronics and surface protection. Film properties are not only determined by their chemical composition, but also by their microstructure and roughness, features that depend crucially on the growth process due to the inherent out-of equilibrium nature of the film deposition techniques. This fact suggest that it is possible to control film growth, and in turn film properties, in a knowledge-based manner by tuning the deposition conditions. This requires a good understanding of the elementary film-forming processes, and the way by which they are affected by atomic-scale kinetics. The kinetic Monte Carlo (kMC) method is a simulation tool that can model film evolution over extended time scales, of the order of microseconds, and beyond, and thus constitutes a powerful complement to experimental research aiming to obtain an universal understanding of thin film formation and morphological evolution. In this work, kMC simulations, coupled with analytical modelling, are used to investigate the early stages of formation of metal films and nanostructures supported on weakly-interacting substrates. This starts with the formation and growth of faceted 3D islands, that relies first on facile adatom ascent at single-layer island steps and subsequently on facile adatom upward diffusion from the base to the top of the island across its facets. Interlayer mass transport is limited by the rate at which adatoms cross from the sidewall facets to the island top, a process that determines the final height of the islands and leads non-trivial growth dynamics, as increasing temperatures favour 3D growth as a result of the upward transport. These findings explain the high roughness observed experimentally in metallic films grown on weakly-interacting substrates at high temperatures. The second part of the study focus on the next logical step of film formation, when 3D islands come into contact and fuse into a single one, or coalesce. The research reveals that the faceted island structure governs the macroscopic process of coalescence as well as its dynamics, and that morphological changes depend on 2D nucleation on the II facets. In addition, deposition during coalescence is found to accelerate the process and modify its dynamics, by contributing to the nucleation of new facets. This study provides useful knowledge concerning metal growth on weakly-interacting substrates, and, in particular, identifies the key atomistic processes controlling the early stages of formation of thin films, which can be used to tailor deposition conditions in order to achieve films with unique properties and applications.

archives@tulane.edu / Enzymes are most powerful catalysts in Nature. Despite decades of research, there are still many open questions surrounding the mechanisms by which enzymes catalyze reactions. Supramolecular chemists have made lots of effort to designing a variety of host molecules to mimic enzymes over the last decade. They aim to understand the power of noncovalent forces and how local environment can be involved in enzymes’ catalytic functions. In our studies, two synthetic water-soluble deep cavity cavitands with different electrostatic potential (EP) that can provide well-defined nano-spaces and can be encapsulated with guests through hydrophobic effect were utilized to investigative the inner guests’ pKa shifts and reactions. First, pKa shifts of thiol guests in deep cavity cavitands have been examined. Here we utilize supramolecular capsules assembled via the hydrophobic effect to encapsulate guests and control their acidity. We found that the greatest impact on the acidity of the bound guests is the position of the acid group in the yotoliter space. Moreover, the nature of the electrostatic potential field (EPF) generated by charged solubilizing groups also plays an important role in acidity, as does the counter ion complexing to the outer surface of the capsule. In summary, these results suggest an electrostatic potential field (EPF) engendered by remote solubilizing groups can affect reactions inside of confined spaces. Second, macrocyclization reactions were investigated in two different electrostatic potential (EP) nano capsules. Here, we quantify these effects through acidity and cyclization rate by the size of the encapsulated guests, which confirmed primary role of Coulombic forces with a simple mathematical model approximating the capsules as Born spheres within a continuum dielectric. These results reveal the reaction rate accelerations possible under Coulombic control and highlight important design criteria for nanoreactors. / 1 / Xiaoyang Cai

Electrical detection of humanized Immunoglobulin G and single stranded DNA having different mismatched contents is presented in this thesis. For electrical detection a simple method relying on streaming current measurement in a functionalized silica capillary was used. Immobilization of the DNA capture probe on a capillary surface was done by standard chemical functionalization technique. The interaction of the immobilized DNA capture probes and their complimentary ssDNA having different mutations was studied for different concentration of target probes. The specificity and the reproducibility of the interactions were investigated by a number of control measurements and repeated measurements. For IgG detection, Z domain, an IgG binding partner, was immobilized by traditional chemical functionalization strategy as well as a novel recombinant silk-based technique. The silk-based approach allows a fast and high-density capture probe immobilization with a simple one-step coating. The specific interaction of IgG with its binding partner was investigated for different concentrations of IgG. A comparison of the two functionalization techniques is presented in addition to the degree of non-specific interaction in both cases.

Different semiconductor nanocrystals exhibit size dependent properties due to confinement effect. Light emission from these nanocrystals may turn ON and OFF seemingly at random, an effect known as blinking. In this work blinking studies have been done to monitor the effect of X-ray exposure and to investigate the radiation hardness of CdSe/ZnS QD’s. Correct parameters to dilute and spin-coat the obtained sample were found to get access to individual single dots. Blinking of these dots was analyzed using Image J and MATLAB plug-in, where ON and OFF-times distribution power exponents Mon and Moff have been extracted to see the change in emission intermittency after a total cumulative dose of ~1026 Gy (absorbed by SiO2) in steps. It was observed that blinking was quenched and consequently the QD’s went permanently to off state as a result of X-ray exposure.

The increasing mandate to transition power generation from fossil fuels to renewable energy sources, combined with the growing electrification, has significantly boosted the demand for advanced energy storage. Lithium-ion battery (LIB) has dominated the market in a full spectrum of applications since its breakthrough in commercialization by Sony in 199. Nonetheless, LIB’s cost, safety, and somewhat limited energy density and material sources make it necessary to develop battery materials that use more abundant elements such as sodium, potassium, aluminum, silicon, and calcium. Yet, the realization of such alternative technologies is challenging to meet using conventional carbon materials. In this thesis, state-of-the-art energy storage devices based on three-dimensional porous carbon materials, namely laser-scribed graphene (LSG), are developed. The proposed strategies involve optimizing the synthesis process and properties of 3D carbon nanomaterials by laser irradiation due to its multifunctionality, cost-effectiveness and simplicity. We have innovatively developed doped and composite nanomaterials for sodium-ion batteries, lithium-sulfur batteries, and silicon-based lithium-ion batteries. This type of 3D graphitic carbon offers several advantages, including (1) binder-free self-supported electrode configuration, (2) high electrical and ionic conductivity, (3) hierarchical porosity, and (4) controllable composition upon laser exposure. Finally, we conclude by giving future perspectives and outlooks for developing this class of carbon materials to advance the field of batteries beyond conventional LIB technology.

Artificial superlattices with their exceptional properties have been popular in a broad range of applications such as electronic, magnetic, optical, and hard coating. Another potential application for single crystal artificial superlattices is highly efficient interference neutron optics, owing to an ultimate interface width of just ±½ atomic layer. Moreover, studies of superlattices have been instrumental in understanding the hardening mechanisms in transition metal nitrides and carbides while such studies on transition metal diborides is lacking, despite extensive studies on monolithic transition metal diboride thin films. This work is an initiative to grow CrB2/TiB2 (0001) diboride superlattices epitaxially onto Al2O3 (0001) substrates by direct current magnetron sputter epitaxy implementing two different approaches; compound diboride targets, and co-sputtering of a metal target with a compound target. Effects of substrate temperature, B stoichiometry (B/TM ratio), modulation period Λ = DCrB2 + DTiB2, layer thickness ratio <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Ctiny%5CGamma%20=%20%5Cfrac%7BD_%7BTiB2%7D%7D%7BD_%7BCrB2+%7D%20D_%7BTiB2%7D%7D" data-classname="equation" />, and relative applied power to magnetrons on the structural and interface quality of superlattices are studied and discussed. Using compound targets, superlattices with thickness ratio Γ = 0.3 and modulation periods Λ between 1 and 10 nm, and with Λ = 6 nm and thickness ratios between 0.2 to 0.8 were synthesized at the optimum sputter gas pressure of pAr = 4 mTorr and a substrate temperature of 600 °C. It is found that superlattices with Λ = 6 nm and Γ in the range of 0.2-0.4 exhibit the highest structural quality. However, B segregation in the over-stoichiometric TiBy layers (y &gt; 2), grown from TiB2 compound target, results in narrow epitaxial superlattice columnar growth with structurally distorted B-rich boundaries. By co-sputtering from Ti and TiB2 targets, y could be reduced from 3.3 to 0.9 in TiBy layers through controlling the relative applied target power. Co-sputtered TiBy single layers and superlattices were grown at substrate temperatures between 600 and 900 °C. 300-nm-thick TiB2.3 single layers grown at 750 °C exhibited epitaxial domains about 10x larger than non-co-sputtered films.A significant enhancement for close-tostoichiometry CrB1.7/TiB2.3 superlattices with modulation periods Λ = 6 nm was achieved at 750 °C. X-ray diffraction, time of flight elastic recoil detection analysis, scanning transmission electron microscopy, electron energy loss spectroscopy, selected area electron diffraction, and nano-indentation are used for characterization. / <p>Funding agencies: The Swedish National Graduate School in Neutron Scattering (SwedNess) through the grant by the Swedish Foundation for Strategic Research (SSF) GSn15 - 0008, Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials (AFM) at Linköping University (Faculty Grant SFO Mat LiU No. 2009 00971), student grants from the center in Nanoscience and Technology at LiTH CeNano 2021 and 2022, ÅForsk 2022, Lars Hiertas Minne 2022, and scholarship from Society of Vacuum Coaters Foundation (SVCF) 2023</p>

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This thesis presents SiGe(C)/Si(C) multi quantum well (MQW) layers individually or in combination with Si(C) Schottky diodes as material structures to detect infrared (IR) radiation. The performance of devices was investigated in terms of SiGe/Si periodicity and quality of SiGe/Si interface. The structures were grown by chemical vapour deposition using GeH4 and SiH4 sources at 650 °C and processed into pixel arrays with sizes of 25×25, 100×100 and 200×200 μm2. The device response to thermal variations was expressed by temperature coefficient of resistance (TCR) and the signal-to-noise-ratio was evaluated by noise measurements. The strain relaxation in SiGe layers was investigated by implementing oxygen at the interface of SiGe/Si or during SiGe growth. A minor amount of 10 ppb oxygen at the interface can be detected by noise measurements while the material characterizations could reveal defects for significantly higher defect density. Oxygen and water contaminations should be accounted for in low temperature epitaxy (350-650 °C) of the layers. Furthermore, an empirical model was developed to describe the kinetics of the SiGe growth using Si2H6 and Ge2H6 as precursors at low temperature. The model takes into account the energy for dissociation of gas molecules, diffusion of the molecules from the gas boundaries toward the substrate and the incorporation of absorbed molecules. A good consistency was observed between the experimental and calculated data. / <p>QC 20150211</p>

Quantum dots exhibit a range of interesting and useful properties linked to their elemental composition, crystal structure, size and shape. Two such properties is the work function and blinking frequency. Tests on several different quantum dot types have shown that x-ray radiation will alter these factors; with increasing doses "bleaching" the dots and making them permanently dark. There are several competing theories to explain this behavior and a lot of materials systems that have not been investigated yet. One such unexplored material is oxidized silicon NCs. This work found no consistent change in work function or blinking frequency after an X-ray dose of ~272 000 Gy absorbed by the SiO2. Individual dots changed between PL measurements but as a whole the sample remained statistically unchanged.