Chabal, Yves J.
Permanent URI for this collectionhttps://hdl.handle.net/10735.1/2471
Dr. Chabal holds the Texas Instruments Distinguished University Chair in Nanoelectronics. He serves as professor of Materials Science & Engineering and Physics and department head of Materials Science & Engineering Texas Instruments Distinguished University Chair in Nanoelectronics. His current interests are centered on surface chemical functionalization of semiconductor and oxide surfaces, atomic layer deposition, organic electronics, biosensors and H2 storage materials. For more information about Dr. Chabel visit his home page and his Research Explorer page.
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Item Biphenyl-Bridged Wrinkled Mesoporous Silica Nanoparticles for Radioactive Iodine Capture(Cambridge Univ Press, 2019-02-11) Brown, Alexander T.; Lin, Jason; Thomas, Milana C.; Chabal, Yves J.; Balkus, Kenneth J.; 0000-0003-0291-2081 (Brown, AT); Brown, Alexander T.; Lin, Jason; Thomas, Milana C.; Chabal, Yves J.; Balkus, Kenneth J.The capture of volatile radioactive iodine-129 is an important process for nuclear fission. Biphenyl-bridged wrinkled mesoporous silica shows similar performance for iodine sequestration to commercial Ag-mordenite and avoids the use of expensive silver The biphenyl-wrinkled mesoporous silica nanoparticles function as a scaffold for biphenyl groups and also as a fluorescent indicator for the loading of iodine. The nanoparticles have a surface area of 973 m²/g and the biphenyl molecules form an electron charge-transfer complex with iodine. Iodine was loaded into the biphenyl-bridged wrinkled mesoporous silica (BUMS) at 19 ± 0.2 % loading by mass.Item Capture of Organic Iodides from Nuclear Waste by Metal-Organic Framework-Based Molecular Traps(Nature Publishing Group) Li, Baiyan; Dong, Xinglong; Wang, Hao; Ma, Dingxuan; Tan, Kui; Jensen, Stephanie; Deibert, Benjamin J.; Butler, Joseph; Cure, Jeremy; Shi, Zhan; Thonhauser, Timo; Chabal, Yves J.; Han, Yu; Li, Jing; Tan, Kui; Butler, Joseph; Cure, Jeremy; Chabal, Yves J.Effective capture of radioactive organic iodides from nuclear waste remains a significant challenge due to the drawbacks of current adsorbents such as low uptake capacity, high cost, and non-recyclability. We report here a general approach to overcome this challenge by creating radioactive organic iodide molecular traps through functionalization of metal-organic framework materials with tertiary amine-binding sites. The molecular trap exhibits a high CH₃I saturation uptake capacity of 71 wt% at 150 ⁰C, which is more than 340% higher than the industrial adsorbent Ag⁰@MOR under identical conditions. These functionalized metal-organic frameworks also serve as good adsorbents at low temperatures. Furthermore, the resulting adsorbent can be recycled multiple times without loss of capacity, making recyclability a reality. In combination with its chemical and thermal stability, high capture efficiency and low cost, the adsorbent demonstrates promise for industrial radioactive organic iodides capture from nuclear waste. The capture mechanism was investigated by experimental and theoretical methods.Item Characterization of Ru Thin-Film Conductivity upon Atomic Layer Deposition on H-Passivated Si(111)Roodenko, Ecatherina (Katy); Park, S. K.; Kwon, Jinhee; Wielunski, L.; Chabal, Yves J.; 0000 0000 4239 3958 (Chabal, YJ); 89624105 (Chabal, YJ)The sheet resistance measured by a four-probe technique is compared to the resistivity data derived from the optical response of thin ruthenium films grown on hydrogen-passivated Si(111) surfaces by atomic-layer deposition using cyclopentadienyl ethylruthenium dicarbonyl, Ru(Cp)(CO)2Et and O 2 as gas reactant. The Drude-Landauer theory is applied to evaluate the spectroscopic ellipsometry response and the DC resistivity evaluated by 4-point probe measurements. Results indicate that thin Ru films (below ∼5nm) deposited on Si exhibit a higher sheet resistance than similarly grown Ru films on TiN. This is explained by an island-growth mechanism at the initial stages of Ru deposition that greatly diminishes the film conductivity before the formation of a continuous film. © 2012 American Institute of Physics.Item Chemical Modification Mechanisms in Hybrid Hafnium Oxo-Methacrylate Nanocluster Photoresists for Extreme Ultraviolet Patterning(American Chemical Society) Mattson, Eric C.; Cabrera, Yasiel; Rupich, Sara M.; Wang, Yuxuan; Oyekan, Kolade A.; Mustard, T. J.; Halls, M. D.; Bechtel, H. A.; Martin, M. C.; Chabal, Yves J.; Mattson, Eric C.; Cabrera, Yasiel; Rupich, Sara M.; Wang, Yuxuan; Oyekan, Kolade A.; Chabal, Yves J.The potential implementation of extreme ultraviolet (EUV) lithography into next generation device processing is bringing urgency to identify resist materials that optimize EUV lithographic performance. Inorganic/organic hybrid nanoparticles or clusters constitute a promising new class of materials, with high EUV sensitivity from the core and tunable chemistry through the coordinating ligands. Development of a thorough mechanistic understanding of the solubility switching reactions in these materials is an essential first step toward their implementation in patterning applications but remains challenging due to the complexity of their structures, limitations in EUV sources, and lack of rigorous in situ characterization. Here, we report a mechanistic investigation of the solubility switching reactions in hybrid clusters comprising a small HfOx core capped with a methacrylic acid ligand shell (HfMAA). We show that EUV-induced reactions can be studied by performing in situ infrared (IR) spectroscopy of electron-irradiated films using a variable energy electron gun. Combining additional ex situ metrology, we track the chemical evolution of the material at each stage of a typical resist processing sequence. For instance, we find that a cross-linking reaction initiated by decarboxylation of the methacrylate ligands under electron irradiation constitutes the main solubility switching mechanism, although there are also chemical changes imparted by a typical post application bake (PAB) step alone. Lastly, synchrotron-based IR microspectroscopy measurements of EUV-irradiated HfMAA films enable a comparison of reactions induced by EUV vs electron beam irradiation of the same resist material, yielding important insight into the use of electron beam irradiation as an experimental model for EUV exposure.Item Cobalt and Iron Segregation and Nitride Formation from Nitrogen Plasma Treatment of CoFeB Surfaces(American Institute of Physics Inc) Mattson, Eric C.; Michalak, D. J.; Veyan, Jean Francois; Chabal, Yves J.; 0000-0002-3743-5521 (Veyan, JF); 0000-0002-6435-0347 (Chabal, YJ); Mattson, Eric C.; Veyan, Jean Francois; Chabal, Yves J.Cobalt-iron-boron (CoFeB) thin films are the industry standard for ferromagnetic layers in magnetic tunnel junction devices and are closely related to the relevant surfaces of CoFe-based catalysts. Identifying and understanding the composition of their surfaces under relevant processing conditions is therefore critical. Here we report fundamental studies on the interaction of nitrogen plasma with CoFeB surfaces using infrared spectroscopy, x-ray photoemission spectroscopy, and low energy ion scattering. We find that, upon exposure to nitrogen plasma, clean CoFeB surfaces spontaneously reorganize to form an overlayer comprised of Fe2N3 and BN, with the Co atoms moved well below the surface through a chemically driven process. Subsequent annealing to 400 °C removes nitrogen, resulting in a Fe-rich termination of the surface region. © 2016 Author(s).Item Colored Porous Silicon as Support for Plasmonic NanoparticlesLublow, M.; Kubala, S.; Veyan, Jean-Francois; Chabal, Yves J.; 0000 0000 4239 3958 (Chabal, YJ); 89624105 (Chabal, YJ)Colored nanoporous silicon thin films were employed as dielectric spacing layers for the enhancement of localized surface plasmon (LSP) polaritons. Upon formation of Au nanoparticles (Au-NPs) on these layers, a visible color change is observed due to multiple LSP resonance excitations. Far-field effects were assessed by angle-resolved reflectometry. Resonance enhancements, particularly for s-polarized light, account for the observed color change and are discussed in terms of effective medium and Mie scattering theory. Enhancements of the electric field strengths in the near-field and of the absorption in the substrate were deduced from finite difference time domain calculations and exceed considerably those of the non-porous Au-NP/Si interface. First results of improved photoelectrocatalytic hydrogen evolution at these interfaces are discussed. Samples were prepared by varied procedures of metal assisted etching and dry etching with XeF2. Structural and chemical properties were investigated by scanning electron and atomic force microscopy as well as energy dispersive x-ray analysis.Item Diffusion of Small Molecules in Metal Organic Framework MaterialsCanepa, Pieremanuele; Nijem, Nour; Chabal, Yves J.; Thonhauser, T.; 0000 0000 4239 3958 (Chabal, YJ); 89624105 (Chabal, YJ)Ab initio simulations are combined with in situ infrared spectroscopy to unveil the molecular transport of H-2, CO2, and H2O in the metal organic framework MOF-74-Mg. Our study uncovers-at the atomistic level-the major factors governing the transport mechanism of these small molecules. In particular, we identify four key diffusion mechanisms and calculate the corresponding diffusion barriers, which are nicely confirmed by time-resolved infrared experiments. We also answer a long-standing question about the existence of secondary adsorption sites for the guest molecules, and we show how those sites affect the macroscopic diffusion properties. Our findings are important to gain a fundamental understanding of the diffusion processes in these nanoporous materials, with direct implications for the usability of MOFs in gas sequestration and storage applications. DOI: 10.1103/PhysRevLett.110.026102Item Effective Sensing of RDX via Instant and Selective Detection of Ketone VaporsHu, Zhichao; Tan, Kui; Lustig, William P.; Wang, Hao; Zhao, Yonggang; Zheng, Chong; Banerjee, Debasis; Emge, Thomas J.; Chabal, Yves J.; Li, Jing; 0000 0000 4239 3958 (Chabal, YJ); 89624105 (Chabal, YJ)Two new luminescent metal-organic frameworks (LMOFs) were synthesized and examined for use as sensory materials. Very fast and effective sensing of RDX was achieved by vapor detection of a cyclic ketone used as a solvent in the production of plastic explosives. The effects of porosity and electronic structure of the LMOFs on their sensing performance were evaluated. We demonstrate that the optimization of these two factors of an LMOF can significantly improve its sensitivity and selectivity. We also elucidate the importance of both electron and energy transfer processes on the fluorescence response of a sensory material.Item Energy Transfer from Colloidal Nanocrystals into Si Substrates Studied via Photoluminescence Photon Counts and Decay Kinetics(2013-08-16) Nguyen, H. M.; Seitz, Oliver; Gartstein, Yuri N.; Chabal, Yves J.; Malko, Anton V.; 0000 0001 2678 9765 (Malko, AV); Nguyen, H. M.; Seitz, Oliver; Gartstein, Yuri N.; Chabal, Yves J.; Malko, Anton V.We use time-resolved photoluminescence (PL) kinetics and PL intensity measurements to study the decay of photoexcitations in colloidal CdSe/ZnS nanocrystals grafted on SiO₂ - Si substrates with a wide range of the SiO₂ spacer layer thicknesses. The salient features of experimental observations are found to be in good agreement with theoretical expectations within the framework of modification of spontaneous decay of electric-dipole excitons by their environment. Analysis of the experimental data reveals that energy transfer (ET) from nanocrystals into Si is a major enabler of substantial variations in decay rates, where we quantitatively distinguish contributions from nonradiative and radiative ET channels. We demonstrate that time-resolved PL kinetics provides a more direct assessment of ET, while PL intensity measurements are also affected by the specifics of the generation and emission processes.Item Energy Transfer from Colloidal Nanocrystals to Strongly Absorbing Perovskites(Royal Society of Chemistry, 2018-06-01) Cabrera, Yasiel; Rupich, Sara M.; Shaw, Ryan; Anand, Benoy; Villa, Manuel de Anda; Rahman, Rezwanur; Dangerfield, Aaron; Gartstein, Yuri N.; Malko, Anton V.; Chabal, Yves J.; 0000-0002-6435-0347 (Chabal, YJ); Cabrera, Yasiel; Rupich, Sara M.; Shaw, Ryan; Anand, Benoy; Villa, Manuel de Anda; Rahman, Rezwanur; Dangerfield, Aaron; Gartstein, Yuri N.; Malko, Anton V.; Chabal, Yves J.Integration of colloidal nanocrystal quantum dots (NQDs) with strongly absorbing semiconductors offers the possibility of developing optoelectronic and photonic devices with new functionalities. We examine the process of energy transfer (ET) from photoactive CdSe/ZnS core/shell NQDs into lead-halide perovskite polycrystalline films as a function of distance from the perovskite surface using time-resolved photoluminescence (TRPL) spectroscopy. We demonstrate near-field electromagnetic coupling between vastly dissimilar excitation in two materials that can reach an efficiency of 99% at room temperature. Our experimental results, combined with electrodynamics modeling, reveal the leading role of non-radiative ET at close distances, augmented by the waveguide emission coupling and light reabsorption at separations >10 nm. These results open the way to combining materials with different dimensionalities to achieve novel nanoscale architectures with improved photovoltaic and light emitting functionalities.Item HIF-1α-PDK1 Axis-Induced Active Glycolysis Plays an Essential Role in Macrophage Migratory Capacity(American Physical Society) Anand, Benoy; Sampat, Siddharth; Danilov, E. O.; Peng, Weina; Rupich, Sara M.; Chabal, Yves J.; Gartstein, Yuri N.; Malko, Anton V.; 0000 0001 1969 6683 (Gartstein, YN); 0000 0001 2678 9765 (Malko, AV); 170647442 (Gartstein, YN); Anand, Benoy; Sampat, Siddharth; Peng, Weina; Rupich, Sara M.; Chabal, Yves J.; Gartstein, Yuri N.; Malko, Anton V.Ultrafast transient pump-probe measurements of thin CH₃NH₃PbI₃ perovskite films over a wide spectral range from 350 to 800 nm reveal a family of photoinduced bleach (PB) and absorption (PA) features unequivocally pointing to the fundamentally multiband character of the underlying electronic structure. Excitation pump-energy dependent kinetics of three long-lived PB peaks at 1.65, 2.55, and 3.15 eV along with a broad PA band shows the involvement of band-edge thermalized carriers in all transitions and at least four, possibly more, electronic bands. The evolution of the transient signatures is described in terms of the redistribution of the conserved oscillator strength of the whole system. The multiband perspective opens up different directions for understanding and controlling photoexcitations in hybrid perovskites.Item Influence of Growth Temperature on Bulk and Surface Defects in Hybrid Lead Halide Perovskite Films(Royal Society of Chemistry, 2015-12-14) Peng, Weina; Anand, Benoy; Liu, Lihong; Sampat, Siddharth; Bearden, Brandon E.; Malko, Anton V.; Chabal, Yves J.The rapid development of perovskite solar cells has focused its attention on defects in perovskites, which are gradually realized to strongly control the device performance. A fundamental understanding is therefore needed for further improvement in this field. Recent efforts have mainly focused on minimizing the surface defects and grain boundaries in thin films. Using time-resolved photoluminescence spectroscopy, we show that bulk defects in perovskite samples prepared using vapor assisted solution process (VASP) play a key role in addition to surface and grain boundary defects. The defect state density of samples prepared at 150 °C (~10¹⁷ cm⁻³) increases by 5 fold at 175 °C even though the average grains size increases slightly, ruling out grain boundary defects as the main mechanism for the observed differences in PL properties upon annealing. Upon surface passivation using water molecules, the PL intensity and lifetime of samples prepared at 200 °C are only partially improved, remaining significantly lower than those prepared at 150 °C. Thus, the present study indicates that the majority of these defect states observed at elevated growth temperatures originates from bulk defects and underscores the importance to control the formation of bulk defects together with grain boundary and surface defects to further improve the optoelectronic properties of perovskites.Item Interaction of Acid Gases SO₂ and NO₂ with Coordinatively Unsaturated Metal Organic Frameworks: M-MOF-74 (M = Zn, Mg, Ni, Co)(Amer Chemical Soc, 2017-05-01) Tan, Kui; Zuluaga, Sebastian; Wang, Hao; Canepa, Pieremanuele; Soliman, Karim; Cure, Jeremy; Li, Jing; Thonhauser, Timo; Chabal, Yves J.; 0000-0002-5167-7295 (Tan, K); 0000-0002-6435-0347 (Chabal, YJ); Tan, Kui; Cure, Jeremy; Chabal, Yves J.In situ infrared spectroscopy and ab initio density functional theory (DFT) calculations are combined to study the interaction of the corrosive gases SO₂ and NO₂ with metal organic frameworks M-MOF-74 (M = Zn, Mg, Ni, Co). We find that NO₂ dissociatively adsorbs into MOF-74 compounds, forming NO and NO₃̅. The mechanism is unraveled by considering the Zn-MOF-74 system, for which DFT calculations show that a strong NO₂-Zn bonding interaction induces a significant weakening of the N-O bond, facilitating the decomposition of the NO₂ molecules. In contrast, SO₂ is only molecularly adsorbed into MOF-74 with high binding energy (>90 kJ/mol for Mg-MOF-74 and >70 for Zn-MOF-74). This work gives insight into poisoning issues by minor components of flue gases in metal organic frameworks materials.Item Investigation of LiAlH 4-THF Formation by Direct Hydrogenation of Catalyzed Al and LiHLacina, D.; Yang, L.; Chopra, Irinder; Muckerman, J.; Chabal, Yves J.; Graetz, J.; 0000 0000 4239 3958 (Chabal, YJ); 89624105 (Chabal, YJ)The formation of LiAlH 4-THF by direct hydrogenation of Al and LiH in tetrahydrofuran (THF) was investigated using spectroscopic and computational methods. The molecular structures and free energies of the various possible adducts (THF-AlH 3, THF-LiH and THF-LiAlH 4) present in a LiAlH 4/THF solution were calculated and the dominant species were determined to be contact ion pairs where three THF molecules coordinate the lithium. Raman and X-ray absorption spectroscopy were used to investigate the effect of different Ti precursors on the formation of Al-H species and LiAlH 4-THF and determine the optimal reaction conditions. A unique sample stage was developed from a microfluidic cell to evaluate the catalysts in situ. The effectiveness of two types of catalysts, titanium chloride (TiCl 3) and titanium butoxide (Ti(C 4H 9O) 4), and the catalyst concentration were evaluated under similar reaction conditions. Both catalysts were effective at facilitating hydrogenation, although TiCl 3 was more effective over the first few cycles with the greatest kinetic enhancement achieved with a low concentration of around 0.15 mol%. These results were qualitatively supported by infrared spectroscopy, which indicated that although a small amount of Ti is necessary for disassociating H 2, excess surface Ti (>0.1 ML) hinders the formation of Al-H species. © the Owner Societies 2012.Item Lowering the Density of Electronic Defects on Organic-Functionalized Si(100) Surfaces(Amer Inst Physics) Peng, Weina; DeBenedetti, William J. I.; Kim, Seonjae; Hines, Melissa A.; Chabal, Yves J.; 0000 0000 4239 3958 (Chabal, YJ); 89624105 (Chabal, YJ)The electrical quality of functionalized, oxide-free silicon surfaces is critical for chemical sensing, photovoltaics, and molecular electronics applications. In contrast to Si/SiO₂ interfaces, the density of interface states (D-it) cannot be reduced by high temperature annealing because organic layers decompose above 300⁰C. While a reasonable D-it is achieved on functionalized atomically flat Si(111) surfaces, it has been challenging to develop successful chemical treatments for the technologically relevant Si(100) surfaces. We demonstrate here that recent advances in the chemical preparation of quasi-atomically-flat, H-terminated Si(100) surfaces lead to a marked suppression of electronic states of functionalized surfaces. Using a non-invasive conductance-voltage method to study functionalized Si(100) surfaces with varying roughness, a D-it as low as 2.5 x 10¹¹ cm⁻² eV⁻¹ is obtained for the quasi-atomically-flat surfaces, in contrast to > 7 x 10¹¹ cm⁻² eV⁻¹ on atomically rough Si(100) surfaces. The interfacial quality of the organic/quasi-atomically-flat Si(100) interface is very close to that obtained on organic/atomically flat Si(111) surfaces, opening the door to applications previously thought to be restricted to Si(111).Item Mechanistic Study of the Atomic Layer Deposition of Scandium Oxide Films Using Sc(MeCp)₂(Me₂pz) and Ozone(A V S Amer Inst Physics, 2019-01-02) Rahman, Rezwanur; Klesko, Joseph P.; Dangerfield, Aaron; Fang, Ming; Lehn, Jean-Sebastien M.; Dezelah, Charles L.; Kanjolia, Ravindra K.; Chabal, Yves J.; 0000-0002-6435-0347 (Chabal, YJ); 0000-0003-3989-8009 (Klesko, JP); Rahman, Rezwanur; Klesko, Joseph P.; Dangerfield, Aaron; Chabal, Yves J.The atomic layer deposition (ALD) of scandium oxide (Sc₂O₃) thin films is investigated using Sc(MeCp)₂(Me₂pz) (1, MeCp = methylcyclopentadienyl, Me₂pz = 3,5-dimethylpyrazolate) and ozone on hydroxyl-terminated oxidized Si(111) substrates at 225 and 275 °C. In situ Fourier transform infrared spectroscopy reveals that 1 not only reacts with surface hydroxyl groups at 275 °C, as expected but also with the SiO₂ layer, as evidenced by losses in the SiO₂ longitudinal optical and transverse optical phonon modes, resulting in the partial transformation of near-surface SiO₂ to an ScSixOy interface layer. Ozone then combusts the MeCp groups of the O-Sc(MeCp)₂ chemisorbed species, yielding surface carbonates, and oxidizes some of the underlying silicon, evidenced by gains in the SiO₂ phonon modes. The Me₂pz group from the next pulse of 1 reacts with these surface carbonates, leading to Sc-O-Sc bond formation (Sc₂O₃ deposition) and the restoration of an O-Sc(MeCp)₂ surface. The reaction of the SiO₂ substrate with 1 and the oxidation of silicon by ozone are temperature-dependent processes that occur during the initial cycles of film growth and directly impact the changes in the intensities of the SiO₂ phonon modes. For instance, the intensity of the net gains in the phonon modes following ozone exposure is greater at 275 °C than at 225 °C. As the ALD cycle is repeated, the formation of an ScSiₓOᵧ interface layer and deposition of an Sc₂O₃ film result in the gradual attenuation of the reaction of the SiO₂ substrate with 1 and the oxidation of the underlying silicon by ozone. In addition to the ALD process, characterized by ligand exchange and self-limiting reactions, there are gas-phase reactions between 1 and residual water vapor near the substrate surface that lead to deposition of additional Sc₂O₃ and surface carbonates, the extent of which are also dependent on the temperature of the substrate. After 20 cycles of 1/ozone, the film thicknesses derived from ex situ X-ray photoelectron spectroscopy measurements are 2.18 nm (225 °C) and 3.88 nm (275 °C). This work constitutes the first mechanistic study of an Sc₂O₃ ALD process using ozone as the oxidant and emphasizes the significance of atypical reactions between the substrate and the reactants that influence the growth rate and near-surface stoichiometry during the initial cycles of film deposition. Published by the AVS.Item Morphology and Chemical Termination of HF-Etched Si₃N₄ Surfaces(American Institute of Physics Inc.) Liu, Li-Hong; Debenedetti, William J. I.; Peixoto, Tatiana; Gokalp, Sumeyra; Shafiq, Natis; Veyan, Jean-François; Michalak, D. J.; Hourani, R.; Chabal, Yves J.Several reports on the chemical termination of silicon nitride films after HF etching, an important process in the microelectronics industry, are inconsistent claiming N-Hx, Si-H, or fluorine termination. An investigation combining infrared and x-ray photoelectron spectroscopies with atomic force and scanning electron microscopy imaging reveals that under some processing conditions, salt microcrystals are formed and stabilized on the surface, resulting from products of Si₃N₄ etching. Rinsing in deionized water immediately after HF etching for at least 30s avoids such deposition and yields a smooth surface without evidence of Si-H termination. Instead, fluorine and oxygen are found to terminate a sizeable fraction of the surface in the form of Si-F and possibly Si-OH bonds. The fluorine termination is remarkably stable in air and water vapor in ambient conditions, with clear implications on further surface chemical functionalization.Item Nanocast Carbon Microsphere Flowers from a Lanthanum-Based Template(Elsevier Science B.V., 2018-09-11) Brown, Alexander T.; Thomas, Milana C.; Chabal, Yves J.; Balkus, Kenneth J.; 0000-0001-5926-0200 (Fischetti, MV); 0000-0003-1142-3837 (Balkus, KJ); Brown, Alexander T.; Thomas, Milana C.; Chabal, Yves J.; Balkus, Kenneth J.Hollow carbon microsphere flowers were nanocast from glucose, acrylamide, and acetylene sources. Carbon growth was catalyzed by a lanthanum graft copolymer template using wet acetylene. The resulting spherical shape is beneficial for 3-D porosity, and has a highly graphitic content as indicated by raman spectroscopy (I_{D} :I_{G} = 0.99). The carbon has a high surface area of 1000 m²/g, as well as strong π-π stacking of aromatic carbons.Item Non-Dispersive Infrared (NDIR) Sensor for Real-Time Nitrate Monitoring in Wastewater Treatment(SPIE, 2019-02-27) Roodenko, K.; Hinojos, D.; Hodges, Kimari L.; Veyan, Jean-Francois; Chabal, Yves J.; Clark, K. P.; Katzir, A.; Robbins, D.; Hodges, Kimari L.; Veyan, Jean-Francois; Chabal, Yves J.Nitrate is a frequent water pollutant that results from human activities such as fertilizer over-Application and agricultural runoff and improper disposal of human and animals waste. Excess levels of nitrate in watersheds can trigger harmful algal blooms (HABs) and biodiversity loss with consequences that affect the economy and pose a threat to human health. Municipal drinking water and wastewater treatment plants are therefore required to control nitrogen levels to ensure the safety of drinking water and the proper discharge of effluent. Nitrate exhibits distinct absorption bands in the infrared spectral range. While infrared radiation is strongly attenuated in water, implementation of fiber optic evanescent wave spectroscopy (FEWS) enables monitoring of water contaminants in real-Time with high sensitivity. This work outlines the development of a non-dispersive infrared (NDIR) detector for the real-Time monitoring of nitrate, nitrite and ammonia concentrations targeting implementation at municipal wastewater treatment plants (WWTPs) and onsite wastewater treatment systems (OWTS). ©2019 SPIE. Downloading of the abstract is permitted for personal use only.Item Novel Binder-Free Electrode Materials for Supercapacitors Utilizing High Surface Area Carbon Nanofibers Derived from Immiscible Polymer Blends of PBI/6FDA-DAM:DABA(Royal Society of Chemistry, 2018-06-01) Abeykoon, Nimali C.; Garcia, Velia; Jayawickramage, Rangana A.; Perera, Wijayantha; Cure, Jeremy; Chabal, Yves J.; Balkus, Kenneth J.; Ferraris, John P.; 0000 0000 4239 3958 (Chabal, YJ); 0000-0002-3225-0093 (Ferraris, JP); Abeykoon, Nimali C.; Garcia, Velia; Jayawickramage, Rangana A.; Perera, Wijayantha; Cure, Jeremy; Chabal, Yves J.; Balkus, Kenneth J.; Ferraris, John P.Carbon nanofibers with high surface area have become promising electrode materials for supercapacitors because of their importance in increasing energy density. In this study, a high free volume polymer, 6FDA-DAM:DABA (6FDD) was blended with polybenzimidazole (PBI) in different ratios to obtain different compositions of PBI/6FDD immiscible polymer blends. Freestanding nanofiber mats were obtained via electrospinning using blend precursors dissolved in N,N-dimethylacetamide (DMAc). Subsequently, carbonization, followed by CO₂ activation at 1000 °C was applied to convert the fiber mats into porous carbon nanofibers (CNFs). The addition of 6FDD shows significant effects on the microstructure and enhancement of the surface area of the CNFs. The obtained CNFs show specific surface area as high as 3010 m² g⁻¹ with pore sizes comparable to those of the electrolyte ions (PYR₁₄TFSI). This provides good electrolyte accessibility to the pore of the carbon materials resulting in enhanced energy density compared to the CNFs obtained from pure PBI. Electrodes derived from PBI:6FDD (70 : 30) exhibited outstanding supercapacitor performance in coin cells with a specific capacitance of 142 F g⁻¹ at the scan rate of 10 mV s⁻¹ and energy density of 67.5 W h kg⁻¹ at 1 A g⁻¹ (58 W h kg⁻¹ at 10 A g⁻¹) thus demonstrating promising electrochemical performance for high performance energy storage system.