Search

The newly emerging Stimulated Raman Scattering (SRS) Microscopy has been proved to be a powerful tool in biomedical research. This advanced imaging platform offers high spatiotemporal resolution and chemical specificity, which greatly empowers the label-free biomedical imaging and small molecule metabolite tracing. Throughout the research introduced in this thesis, we focus on the exploration of more applications of SRS microscopy beyond aforementioned. Particularly, this new expedition involves more chemistry and answered two major questions: what SRS can do for chemistry and what chemistry can do for SRS. Chapter 1 introduces the basics of SRS microscopy, such as the physical fundamentals and start-of-art instrumentations. Besides, this chapter discusses the design principles of vibrational reporters through a chemistry view. Chapter 2 introduces one of the major progresses of SRS microscopy beyond biomedical study. We use SRS microscopy to study the ion transportation and concentration polarization phenomena in lithium metal batteries (LMBs), with a strong focus in solid-state polymer electrolyte. A self-induced phase separation process over lithium metal electrode is observed and correlated with local lithium ion concentrations, which inspires a protection mechanism for durable LMB design. Chapter 3 discusses the use of SRS microscopy for in-vivo drug tracing in mammalian cells. A novel alkyne tag is incorporated into bio-engineered natural depsi-peptides and serves as Raman reporter. The mode-of-action of the labeled drug is visualized with SRS microscopy. Chapter 4 heavily focuses on the development of synthetic molecular probes for super-multiplexed optical imaging. We systematically synthesize a library of molecular probes based on 9-cyanopyronin, and their Raman features are characterized to build a model that correlates photophysical properties with structures. The Raman shifts of probes can be tuned with high precision. The multiplexing capability of the new library is demonstrated in labeling fixed and living cell samples.

In this paper we investigated the calculation of the anodic limit of two anions of ionic liquids, largely used as electrolyte of lithium batteries. Starting from a model based on calculations performed on single ions at the MP2 level of theory, we showed that the matching between calculation and experiments decreases while using more expanded basis set with respect to 6-31G**, possibly because of the destabilization of the neutral species when larger basis sets are considered. Additionally, in order to decrease the computational time, the performances for the calculation of the anodic limit obtained by means of a series of DFT functionals with increasing level of complexity (from the Generalized Gradient Approximation to the Range Separated Hybrid meta-Generalized Gradient Approximation) were compared. Overall, the best performing functionals are BMK, ωB97M-V and MN12-SX, while acceptable results can be obtained by M06-2X, M11, M08-HX and M11-L. Some less computationally expensive functionals, like CAM-B3LYP and ωB97X-D, also provide reasonable values of the anodic limit.

The implementation of high potential materials as positive electrodes in high energy Li-ion batteries requires to develop scalable and smart synthetic routes. In the case of the LiNi0.5Mn1.5O4 (LNMO) spinel material, a successful preparation strategy must drive the phase formation in order to obtain structural, morphological and surface properties capable to boost performances in lithium cells and minimize the electrolyte degradation. Here we discuss a novel simple and easily scalable mechanochemical synthetic route, followed by a high temperature annealing in air, to prepare LMNO materials starting from oxides. A synergic doping with chromium and iron has been incorporated, resulting in the spontaneous segregation of a CrOx-rich surface layer. The effect of the annealing temperature on the physico-chemical properties of the LMNO material has been investigated as well as the effect on the performances in Li-cells. © 2017 Elsevier Ltd

Lithium samarium oxide has been prepared by solid-state reaction method and characterized by X-ray diffraction (XRD) and impedance spectroscopy. XRD pattern of the sample reveals the formation of the sample. The conductivity studies, dielectric studies, and modulus analysis of the samples have been carried out for different temperatures. The bulk conductivity of the sample has been found to be 1.21 x 10(-5) Scm(-1) at 420 A degrees C. The temperature variation of the direct current conductivity obeys the Arrhenius relation. The modulus analysis of the sample indicates the non-Debye nature of the sample which corresponds to long-time slow polarization and relaxation of hopping charges.

The work documented in this thesis realizes a small-scale implementation of a Battery Management System (BMS) that has the charging, storage, and discharge capabilities to meet scaled down requirements of a pulsed power system. Further, this work establishes a flexible battery research and testing capability resident at the Naval Postgraduate School (NPS). The designed architecture will provide this flexibility by providing the capability to change charging methodologies and types of batteries with only a change of the FPGA software. The BMS design uses lithium-ion batteries as the energy storage medium and uses one charger per battery for maximum charging flexibility. In order to meet a pulsed power system's requirements, the BMS performs three functions: charging lithium-ion batteries, storing energy for the pulsed power application in lithium-ion batteries, and discharging the energy in pulses to simulate the requirements of a pulse power system. To perform these three functions the BMS has several elements to include the power source, the charger, the batteries, the FPGA controller, and the discharge mechanism. The design and construction of the BMS and these individual elements will be explored in detail in this thesis. http://archive.org/details/apulsedpowersyst109454443 US Marine Corps (USMC) author. Approved for public release; distribution is unlimited.

In this thesis, we investigate the advantages of modifying current military Unmanned Aerial Vehicles (UAV) with available thinfilm photovoltaic (PV) cells to increase their endurance, and/or capabilities. The approach taken was to explore available off-theshelf flexible solar technology and to integrate it in a proof-of-concept model for testing and analysis. A physically similar commercially available battery-powered plane was used to demonstrate the materials and methods by which the RQ-11B (Raven) Small Unmanned Aerial Vehicle (SUAV) could be modified. This research extends academic and private pursuit of solar flight to near-term improvement of military SUAV. Besides increasing on-station time of reconnaissance assets, this research also displays the additional advantage of enabling systems on the ground to "self-charge." This will enable tactical units to operate further afield, untethered from conventional power sources. Beyond the proof-of-concept, findings are extended to other potential military uses and greater improvement through new or modified UAV design. http://archive.org/details/applicationofcop109454539 US Navy (USN) author. Approved for public release; distribution is unlimited.

In this study it was proposed to investigate the use of 3D metal oxides (specifically titanium oxides) as potential electrode materials for lithium ion batteries. Three different approaches were taken: mesoporous materials to increase the surface area and improve the capacity; nanocrystalline materials to increase the surface area and to investigate any changes that may occur using nanocrystals; and microporous materials that are more open, allowing rapid diffusion of lithium and higher capacities. Of the three categories of materials studies, mesoporous TiO2 was the least promising with low reversible capacities (20 mAh·g-1) due to densification resulting in a loss of surface area. In nanocrystalline rutile an irreversible phase change occurred upon initial intercalation, however after this intercalation occurred reversibly in a single phase mechanism giving capacities of 100 mAh·g-1. A trend in intercalation potential was observed with crystallite size that was related to the ability of the structure to relax and accept lithium. Doping of rutile yielded no real improvement. Brookite gave only low capacities from a single phase intercalation mechanism. TiO2 films produced by a novel electrochemical technique showed that while amorphous films give greater capacities, more crystalline (anatase) films give greater reversibility. Overall, microporous titanosilicates showed the most promise with sitinakite giving a reversible capacity of 80 mAh·g-1 after twenty cycles or double this when dried. The intercalation was found to occur by two steps that generate large changes in crystallite size explaining the capacity fade witnessed. While doping did not improve the performance, cation exchange has proven beneficial. The remaining titanosilicates did not perform as well as sitinakite, however a trend was observed in the intercalation potentials with the wavenumber of the Ti-O Raman stretch. This was due to the covalent nature of the bonding. Upon reduction an electron is added to the bond meaning the energy of the bond determines intercalation potential. Overall, most promise was shown by the microporous titanosilicates. The capacities of sitinakite after drying, are comparable to those of the "zero strain" material Li4Ti5O12. Investigation of the titanosilicates and their ion-exchanged derivatives is a promising path for new lithium-ion battery electrode materials.

Polyanion-type materials, like lithium iron phosphate, are one of the recent great success in the research field of applied electrochemistry. Within this family, LiFePO4 (LFP) is a now mature material and its properties have been largely optimized thus opening the door to its commercial exploitation as cathode material in lithium-ion cells for power tools. In recent years the attention of the scientific community is focusing the great advantage of the substitution in the LFP lattice of Fe with Mn, Co or Ni. In fact the Mn3+/Mn2+, Co3+/Co2+ and Ni3+/Ni2+ couples show increasing redox potentials, all higher than the Fe3+/Fe2+, thus opening the door to large improvements in the energy performances. Among them LiCoPO4(LCP) is the best compromise: it shows in lithium cells an higher working potential compared to LFP, still within the working limits of the carbonate-based liquid electrolytes. However many fundamental aspects of the LCP properties and reaction mechanisms in lithium cells are not completely understood. Owing to this, large room for improvements in the performances in Li-cells of LCP is expected by assessing the synthesis route, the coatings, the doping/substitution and the electrolyte additives. The aim of this communication is to present our recent results concerning the study of one of the most detrimental phenomenon observed in the use of LCP in lithium-ion cells: self-discharge. Upon charge in lithium cells LCP undergoes to the following reversible two step oxidation: LiCoPO4 → Li0.7CoPO4+0.3Li++0.3e- → CoPO4+ Li+ + e- At the end of charge, in absence of flowing current, the self-relaxation of the charged LCP electrode is accompanied by a change in the OCV very similar to the discharge curve at constant current. Apparently prolonged OCV relaxation leads to the re-incorporation of lithium ions into the electrode that can be newly electrochemically charged. Self-discharge is a spontaneous phenomenon and has big technological consequences as it limits the use of LCP in commercial electrodes. Here we discuss the results of our study of LCP self-discharged electrodes by ex-situ synchrotron powder diffraction, synchrotron infrared spectroscopy and transmission electron microscopy. Self-discharge apparently occurs by the following spontaneous reactions in OCV conditions: CoPO4 + 0.7 Li++electrolyte (reduced form) → Li0.7CoPO4 + electrolyte (oxidized form) Li0.7CoPO4 + 0.3 Li++electrolyte (reduced form) → LiCoPO4 + electrolyte (oxidized form) The two self-discharge steps are accompained by accumulation of electrolyte decomposition by-products on the electrode surfaces.

The oxidation potentials, E ox , of several solutions of interest for nonaqueous Li cells have been measured by linear sweep voltammetric experiments. A correlation is found between E ox and the basicity of the solvents, expressed by their donor numbers (DN). Esters and sulfones have higher resistance to oxidation than ethers, which possess the highest DN values. All solutions have E ox > 4 V vs Li/Li + . However, some reactivity between positive electrodes and solutions has been observed below this potential.

Clearly there is nowadays an increasing use of portable electric devices (mobile phones, laptops, electric cars, sensor networks ...). These devices use batteries as a power source. Therefore, it is increasingly important to have a good knowledge of the remaining battery power, to exactly know at what point should be recharged. Moreover its wear out must also be known in order to replace it when necessary. Li-ion batteries have provided many advantages over their predecessors. They provide a higher voltage, they are lighter and the energy density with respect to their weight and volume is much higher. This project aims to estimate the actual remaining battery charge through temperature variations that occur inside the battery both during charging and discharging. The aim is to find a simple and cheap solution, which does not require external elements. For this reason, temperature measurements are carried out using a thermistor that is already present in lithium batteries. At present, its purpose is to avoid overheating. A Li-ion battery with 740mAh capacity provided by VARTA Microbattery was used. From measurements of current, voltage and temperature we calculated the internal resistance, the heat flow inside the battery and the thermal impedance. It has been shown that it is possible to relate temperature variations, current and voltage to the heat generated in the battery. Thus, it is possible to estimate the state of charge of the battery (SoC) from temperature fluctuations. In addition, consecutive charge and discharge cycles were carried out. Injected and extracted charge was calculated for each of them. Then, it was related to SoH. Finally, new definitions of SoC and SoH which consider their relationships are proposed.