High O2 Pressure Research Articles

Electrochemical hydrogenation and oxidation of organic species involving water.

Fossil fuel-driven thermochemical hydrogenation and oxidation using high-pressure H2 and O2 are still popular but energy-intensive CO2-emitting processes. At present, developing renewable energy-powered electrochemical technologies, especially those using clean, safe and easy-to-handle reducing agents and oxidants for organic hydrogenation and oxidation reactions, is urgently needed. Water is an ideal carrier of hydrogen and oxygen. Electrochemistry provides a powerful route to drive water splitting under ambient conditions. Thus, electrochemical hydrogenation and oxidation transformations involving water as the hydrogen source and oxidant, respectively, have been developed to be mild and efficient tools to synthesize organic hydrogenated and oxidized products. In this Review, we highlight the advances in water-participating electrochemical hydrogenation and oxidation reactions of representative organic molecules. Typical electrode materials, performance metrics and key characterization techniques are firstly introduced. General electrocatalyst design principles and controlling the microenvironment for promoting hydrogenation and oxygenation reactionsinvolving waterare summarized. Furthermore, paired hydrogenation and oxidation reactions are briefly introduced before finally discussing the challenges and future opportunities of this research field.

High-energy all-solid-state lithium batteries enabled by Co-free LiNiO2 cathodes with robust outside-in structures.

A critical current challenge in the development of all-solid-state lithium batteries (ASSLBs) is reducing the cost of fabrication without compromising the performance. Here we report a sulfide ASSLB based on a high-energy, Co-free LiNiO2 cathode with a robust outside-in structure. This promising cathode is enabled by the high-pressure O2 synthesis and subsequent atomic layer deposition of a unique ultrathin LixAlyZnzOδ protective layer comprising a LixAlyZnzOδ surface coating region and an Al and Zn near-surface doping region. This high-quality artificial interphase enhances the structural stability and interfacial dynamics of the cathode as it mitigates the contact loss and continuous side reactions at the cathode/solid electrolyte interface. As a result, our ASSLBs exhibit a high areal capacity (4.65 mAh cm-2), a high specific cathode capacity (203 mAh g-1), superior cycling stability (92% capacity retention after 200 cycles) and a good rate capability (93 mAh g-1 at 2C). This work also offers mechanistic insights into how to break through the limitation of using expensive cathodes (for example, Co-based) and coatings (for example, Nb-, Ta-, La- or Zr-based) while still achieving a high-energy ASSLB performance.

Catalytic aerobic oxidation of carbohydrates to formic acid over H5PV2Mo10O40: Rate relationships among catalyst reduction, catalyst re-oxidation and acid-catalyzed reactions and evidence for the Mars-van Krevelen mechanism

Catalytic aerobic oxidation of biomass-derived carbohydrates is a promising way to sustainably produce formic acid. Understanding the rate relationships among catalyst reduction, catalyst re-oxidation and acid-catalyzed reactions occurring in catalytic systems is significant for the revelation of catalytic mechanism and the selection of reaction conditions. Herein, the rate relationships among the multiple reactions over an excellent homogeneous catalyst, H5PV2Mo10O40 (HPA-2) were investigated. A rate matching relationship between catalyst reduction and catalyst re-oxidation was unveiled by the separate redox kinetics of catalyst, indicating that higher O2 pressures are required to maintain the activity of HPA-2 at higher temperatures. The consistency between the separate redox kinetics and the catalytic oxidation provided the first kinetic evidence of the Mars-van Krevelen mechanism for catalytic oxidation of carbohydrates. Furthermore, rate relationships among the multiple reactions at different conditions were discussed to clarify the correlation between product selectivity and reaction conditions.

Minimizing the Lag Phase of Cupriavidus necator Growth under Autotrophic, Heterotrophic, and Mixotrophic Conditions.

Cupriavidus necator has the unique metabolic capability to grow under heterotrophic, autotrophic, and mixotrophic conditions. In the current work, we examined the effect of growth conditions on the metabolic responses of C. necator. In our lab-scale experiments, autotrophic growth was rapid, with a short lag phase as the exponential growth stage was initiated in 6 to 12 h. The lag phase extended significantly (>22 h) at elevated O2 and CO2 partial pressures, while the duration of the lag phase was independent of the H2 or N2 partial pressure. Under heterotrophic conditions with acetate as the organic substrate, the lag phase length was short (<12 h), but it increased with increasing acetate concentrations. When glucose and glycerol were provided as the organic substrate, the lag phase was consistently long (>12 h) regardless of the examined substrate concentrations (up to 10.0 g/L). In the transition experiments, C. necator cells showed rapid transitions from autotrophic to heterotrophic growth in less than 12 h and vice versa. Our experimental results indicate that C. necator can rapidly grow with both autotrophic and heterotrophic substrates, while the lag time substantially increases with nonacetate organic substrates (e.g., glucose or glycerol), high acetate concentrations, and high O2 and CO2 partial pressures. IMPORTANCE The current work investigated the inhibition of organic and gaseous substrates on the microbial adaption of Cupriavidus necator under several metabolic conditions commonly employed for commercial polyhydroxyalkanoate production. We also proposed a two-stage cultivation system to minimize the lag time required to change over between the heterotrophic, autotrophic, and mixotrophic pathways.

Migration of weakly bonded oxygen atoms in a-IGZO thin films and the positive shift of threshold voltage in TFTs

Amorphous indium-gallium-zinc oxide (a-IGZO) thin films are prepared by pulsed laser deposition and fabricated into thin-film transistor (TFT) devices. In-situ x-ray photoelectron spectroscopy (XPS) illustrates that weakly bonded oxygen (O) atoms exist in a-IGZO thin films deposited at high O2 pressures, but these can be eliminated by vacuum annealing. The threshold voltage (V th) of the a-IGZO TFTs is shifted under positive gate bias, and the V th shift is positively related to the deposition pressure. A temperature variation experiment in the range of 20 K–300 K demonstrates that an activation energy of 144 meV is required for the V th shift, which is close to the activation energy required for the migration of weakly bonded O atoms in a-IGZO thin films. Accordingly, the V th shift is attributed to the acceptor-like states induced by the accumulation of weakly bonded O atoms at the a-IGZO/SiO2 interface under positive gate bias. These results provide an insight into the mechanism responsible for the V th shift of the a-IGZO TFTs and help in the production of reliable designs.

Tailoring pulsed laser deposition of phosphorus doped WOx films from (PO2)4(WO3)4 target by space-resolved optical emission spectroscopy.

Phosphorus doped WOx films were deposited on fused silica substrates from a target of monophosphate tungsten bronze (PO2)4(WO3)2 m with m = 2. Different conditions of O2 pressures and substrate temperature depositions were performed in parallel to plasma investigations during the depositions step. Changes were observed in the film stoichiometries affecting the film properties while the increase of the O2 pressure. Optical bandgap was shifted from 3.39 eV to 3.86 eV as a function of the deposition pressure from 7.5 Pa to 20 Pa. In situ optical emission spectroscopy was carried out in all the O2 atmosphere conditions. With an increase in the oxygen pressure to 5 Pa, a change in the spectral composition of the plasma with a deficit of the phosphorus lines was observed. A complex plasma containing atoms and multiple ionized ions attributed to each composing species was observed at high O2 pressures of deposition. The increase in O2 pressure led to strong thermalization of the plasma and strong scattering of the plasma particle which created a favourable environment for the WO3 formation.

Beyond the farm: Making edible protein from CO2 via hybrid bioinorganic electrosynthesis

Beyond the farm: Making edible protein from CO2 via hybrid bioinorganic electrosynthesis

High-Pressure O2 Annealing Enhances the Crystallinity of Ultrawide-Band-Gap Sesquioxides Combined with Graphene for Vacuum-Ultraviolet Photovoltaic Detection

(AlxGa1-x)2O3 is emerging as a promising wide-band-gap sesquioxide for vacuum-ultraviolet (VUV, 10-200 nm) photodetectors and high-power field-effect transistors. However, how the key parameters such as the band gap and crystalline phase of the (AlxGa1-x)2O3-based device vary with stoichiometry has not been explicitly defined, which is due to the unclear underlying mechanism of the Al local coordination environment. In this work, a high-pressure O2 (20 atm) annealing (HPOA) strategy that can significantly improve the crystallinity of β-(AlxGa1-x)2O3 and achieve a tunable optical band gap was proposed, facilitating the revelation of the local structure of Al3+ varying with Al content and the kinetic mechanism of Al3+ diffusion. By combining the as-HPOA-treated single-crystalline β-(Al0.69Ga0.31)2O3 films with p-type graphene (p-Gr), which serves as a transparent conductor, a VUV photovoltaic detector is fabricated, showing an improved photovoltage (0.80 V) and fast temporal response (2.1 μs). All of these findings provide a rewarding and important strategy for enhancing the band-gap tunability of sesquioxides, as well as the flexibility of zero-power-consumption photodetectors.

Hydroxyl-terminated carbon dots for efficient conversion of cyclohexane to adipic acid

Adipic acid (HOOC(CH2)4COOH, AA) is a crucial chemical in industrial manufactures and mainly produced by the oxidation of cyclohexane with air and nitric acid via a homogeneous two step path in industry. However, the conventional industrial method inevitably results in the generation of nitrous oxide (N2O, etc.), which is the main cause of the greenhouse effect and ozone depletion. Herein, we engineered five kinds of carbon dots (CDs) with different oxygen-containing functional groups on their surfaces, which were directly used as catalysts over the selective catalytic oxidation of cyclohexane. Among the five CDs, the hydroxyl-terminated CDs show the best catalytic activity with the conversion of cyclohexane ~ 29.43% and selectivity to AA ~ 95.89% under 130 °C, 20 atm with oxygen as oxidant. With the CDs directly as catalyst, the one-step efficient catalytic oxidation reaction for cyclohexane to AA was realized to replace the two-step routes. In addition, the density functional theory (DFT) computational results were performed to further prove that the more quantity of hydroxyl on CDs and the higher O2 pressure can boost the higher catalytic activity of CDs over oxidation of cyclohexane.

Effect of Using High-Pressure Gas Atmosphere with UV Photocatalysis on the CMP Characteristics of a 4H-SiC Substrate

The objective of this study was to realize high-efficiency and high-quality chemical mechanical polishing (CMP) of a silicon carbide (SiC) substrate. Consequently, the effect of a gas atmosphere on the CMP characteristics of a SiC substrate was investigated. The experimental results show that increasing the partial pressure of oxygen (O2) in the atmosphere to 300 kPa led to an over 2-fold increase in the material removal rates (MRRs) of the Si and carbon (C) faces compared to an open-air atmosphere. White light interference microscopy, energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) were used to analyze the face morphology and surface elements after processing. Si face atoms were more difficult to oxidize than C face atoms, resulting in a low MRR of the Si face after CMP. The MRR of the Si face was improved by using an ultraviolet (UV) photocatalysis reaction in the high-pressure O2 atmosphere. Excitation of O2 molecules in the slurry into HO 2 • with a stronger oxidation capability promoted the chemical reaction at the solid-liquid interface. The processing mechanism was elucidated.

Measurements and Modeling of High-Pressure O2 and CO2 Solubility in Brine (H2O + NaCl) between 303 and 373 K and Pressures up to 36 MPa

Knowledge of the solubility of oxygen in natural water, which is generally saline, is important for several scientific and engineering fields. Applications such as geological storage of gas (containing O2, e.g., flue gas) or energy (compressed air energy storage) operate at high pressure. However, to date, there is no high-pressure O2 solubility data in brine, which has led researchers to develop models to predict this important property. To overcome the lack of data, solubility of O2 in brine has been measured using two different techniques, at molalities between 0.5 and 4 mol/kgw (NaCl), temperatures between 303 and 373 K, and pressures up to 36 MPa. In order to validate the experimental methods, measurements of the solubility of CO2 in a highly concentrated brine (6 mol/kgw of NaCl) at temperatures between 303 and 373 K and pressures up to 39.5 MPa were performed also in this work. These measurements allowed the evaluation of existing models such as the well-known Geng and Duan model and the model recently developed by Zheng and Mao (ZM). The e-PR-CPA, Søreide–Whitson, and geochemical models used in our previous work were also used to process the new data. These last three models have been parameterized on measured and reported literature O2 solubility data, and new optimized parameters of the ZM model have been proposed. These models reproduce the effect of temperature, pressure, and NaCl concentration on solubility with an average absolute deviation less than 5% from the measured data.

(Invited) Separation and Hydrogenation of Ions By Micro-Scale Capacitive-Faradaic Adsorbing Fuel Cells

Capacitive deionization processes are aimed at separation of ions from water and wastewater. Since late 1960-s, when the CDI concept was proposed, the technique was improved via incorporation of ion exchange membranes (MCDI), utilization of slurry electrodes (FCDI) and introduction of one or two battery electrode(s) into the process to enhance the salt adsorption capacity of the cell and to reduce the energy demand of the process. In all these processes the monopolar electrodes must be physically connected to the DC power supply via wires, and cathodes and anodes should be separated to prevent short-circuiting. These and other requirements of CDI processes result in serious drawbacks, limitations and sophisticated design of water treatment reactors.A novel CDI-based method for separation of ions from water and wastewater using micro-scale (10µm – 5 mm) fuel cells is proposed1. The fuel cells comprise activated carbon particles loaded with bi-functional catalyst for hydrogen oxidation and oxygen reduction reactions. Within the proposed process of ions removal, the particles act as the micro-scale capacitive-faradaic adsorbing fuel cells (MS-CF-AFC) which require oxygen and hydrogen gases for adsorption of ions during the water treatment step and desorption of ions in brine production.Within the O2-induced adsorption of anions, thereduction of oxygen on Pt (faradaic electrode of the MS-CF-AFC) results in depletion of electrons from the carbonaceous part (i.e. the capacitive electrode) of the micro-scale fuel cell, which leads to adsorption of anions in the electrical double layer of carbon. The hydrogen oxidation that occurs during the regeneration of the anions-loaded MS-CF-AFCs results in accumulation of electrons in the capacitive electrode and in repulsion of perchlorate ions into the regenerant solution. This way the chemical energy of H2 and O2 is converted by the MS-CF-AFCs into the electrical energy which is utilized for separation of ions. For the separation of cations, the MS-CF-AFCs are powered by the H2 gas during the cationsadsorption step and by the O2 gas in brine production.The O2-induced adsorption of anions (and desorption of cations) results in pH increase in the treated water. Consequently, within the MS-CF-AFC treatment the separated anions are “exchanges” with OH- ions. The rate of the process is faster at lower pH values in the treated water. Higher anions adsorption capacity is achieved at higher O2 pressure. The H2-induced desorption of anions (and adsorption of cations) is accompanied by decrease in the pH. Thus, the cations removal process can be regarded as an exchange of separated cations with the H+ ions. The H2-induced step of the MS-CF-AFC processes is faster at higher pHs, and higher cations removal capacity is obtained at higher H2 pressure. To enhance the salt adsorption capacity of MS-CF-AFCs for anions and cations the activated carbon in the cells can be decorated with appropriate surface groups, e.g., carboxylic and amine groups (respectively).The process was proved for the removal of perchlorate, copper and nitrate ions using pure solutions of NaClO4, KNO3 and CuCl2 salts in deionized water and in groundwater, using batch and packed-bed reactors for two types of platinum loaded (5wt%) MS-CF-AFCs prepared from Lewatit AF5 microporous carbon and a powdered activated charcoal.The main disadvantage of the process described above is its inability to “deactivate” toxic NO3 - and ClO4 - ions as the process only concentrates the pollutant (similarly to the well-known ion-exchange). It was shown that Pt-Cu MS-CF-AFCs are capable to adsorb nitrate ions from water and to reduce them into the N2 gas during the H2-induced step of anions desorption from the MS-CF-AFCs.The proposed MS-CF-AFCs can be performed in batch, continuous stirred (CSTR), fixed-bed and other types of reactors normally applied in adsorptive water treatment processes.Potential advantages of the MS-CF-AFCs process are: (1) the process can be utilized for separation of all types of anions and cations (appropriate carbon modification might be required); (2) the process can be performed in any type of adsorption reactors; (3) desalinating hybrid capacitive-faradaic micro-scale fuel cells do not require any wiring as opposite to CDI, previously proposed desalinating fuel cells and battery electrode desalination processes; (4) the regeneration of the MS-CF-AFCs does not require any concentrated solutions of acids, bases or salts; and (5) the hydrogen required for the process can be produced on-site using hydrogen generators and air can be utilized as the oxygen source.[1] Gendel, Y., Amikam, G., Nativ, P., 2020. Separation of Anions and Cations from Water and Wastewater Using Micro-Scale Capacitive-Faradaic or Pseudocapacitive-Faradaic Adsorbing Fuel Cells. US Provisional Patent Application 62/983,689. Figure 1

First Report on the Plasmidome From a High-Altitude Lake of the Andean Puna

Mobile genetic elements, including plasmids, drive the evolution of prokaryotic genomes through the horizontal transfer of genes allowing genetic exchange between bacteria. Moreover, plasmids carry accessory genes, which encode functions that may offer an advantage to the host. Thus, it is expected that in a certain ecological niche, plasmids are enriched in accessory functions, which are important for their hosts to proliferate in that niche. Puquio de Campo Naranja is a high-altitude lake from the Andean Puna exposed to multiple extreme conditions, including high UV radiation, alkalinity, high concentrations of arsenic, heavy metals, dissolved salts, high thermal amplitude and low O2 pressure. Microorganisms living in this lake need to develop efficient mechanisms and strategies to cope under these conditions. The aim of this study was to characterize the plasmidome of microbialites from Puquio de Campo Naranja, and identify potential hosts and encoded functions using a deep-sequencing approach. The potential ecological impact of the plasmidome, including plasmids from cultivable and non-cultivable microorganisms, is described for the first time in a lake representing an extreme environment of the Puna. This study showed that the recovered genetic information for the plasmidome was novel in comparison to the metagenome derived from the same environment. The study of the total plasmid population allowed the identification of genetic features typically encoded by plasmids, such as resistance and virulence factors. The resistance genes comprised resistances to heavy metals, antibiotics and stress factors. These results highlight the key role of plasmids for their hosts and impact of extrachromosomal elements to thrive in a certain ecological niche.

Electrical characterization of mixed conducting SCY-YDC composite electrolyte

SrCe0.9Y0.1O3-δ-Ce0.9Y0.1O2-δ (SCY-YDC, 1:1 mole ratio), as a novel composite electrolyte, was successfully synthesized and characterized. X-ray diffraction patterns showed that SCY-YDC composite electrolyte is a mixture of SCY and YDC. Besides, no impurity phase emerged after sintering at 1550 °C for 10 h. AC impedance spectroscopy was used to determine the electrical properties of SCY-YDC at 500–800 °C in various atmospheres. Partial conductivities of oxygen vacancies, protons, and electrons (p-type) were calculated using the defect structure model. Results showed that SCY-YDC is a mixed (hole, proton, and oxygen-ion) conductor. Moreover, the contribution of holes is minor at 650–800 °C in high pressure (1 atm) or low pressure (10−4 atm) O2 atmospheres. Dominant carrier switched from protons to oxygen ions as temperature increased at vapor pressure in air of 0.038 atm. Total conductivity for SCY-YDC is 6.19 × 10−3 S cm−1 at 800 °C under pO2 = 1 atm and pH2O = 6 × 10−3 atm, which is higher than that of SCY (2.47 × 10−3 S cm−1). Results also showed that SCY-YDC composite material exhibits higher ionic conductivity and lower electron-hole conductivity than SCY. Electron-hole transference number for SCY-YDC is 0.049 at 800 °C in pO2 = 0.21 atm and pH2O = 0.038 atm. Ultraviolet–visible spectrophotometry results provided evidence that SCY-YDC can suppress electron conduction.

Sensitive probing of exoplanetary oxygen via mid-infrared collisional absorption

The collision-induced fundamental vibration-rotation band at 6.4 um is the most significant absorption feature from O2 in the infrared (Timofeyev and Tonkov, 1978; Rinslandet al., 1982, 1989), yet it has not been previously incorporated into exoplanet spectral analyses for several reasons. Either CIAs were not included or incomplete/obsolete CIA databases were used. Also, the current version of HITRAN does not include CIAs at 6.4 um with other collision partners (O2-X). We include O2-X CIA features in our transmission spectroscopy simulations by parameterizing the 6.4 um O2-N2 CIA based on Rinsland et al.(1989) and the O2-CO2 CIA based on Baranov et al. (2004). Here we report that the O2-X CIA may be the most detectable O2 feature for transit observations. For a potentialTRAPPIST-1e analogue system within 5 pc of the Sun, it could be the only O2 detectable signature with JWST (using MIRI LRS) for a modern Earth-like cloudy atmosphere with biological quantities of O2. Also, we show that the 6.4 um O2-X CIA would be prominent for O2-rich desiccated atmospheres (Luger and Barnes, 2015) and could be detectable with JWST in just a few transits. For systems beyond 5 pc, this feature could therefore be a powerful discriminator of uninhabited planets with non-biological "false positive" O2 in their atmospheres - as they would only be detectable at those higher O2 pressures.

Water Enables Efficient CO2 Capture from Natural Gas Flue Emissions in an Oxidation-Resistant Diamine-Appended Metal-Organic Framework.

Supported by increasingly available reserves, natural gas is achieving greater adoption as a cleaner-burning alternative to coal in the power sector. As a result, carbon capture and sequestration from natural gas-fired power plants is an attractive strategy to mitigate global anthropogenic CO2 emissions. However, the separation of CO2 from other components in the flue streams of gas-fired power plants is particularly challenging due to the low CO2 partial pressure (∼40 mbar), which necessitates that candidate separation materials bind CO2 strongly at low partial pressures (≤4 mbar) to capture ≥90% of the emitted CO2. High partial pressures of O2 (120 mbar) and water (80 mbar) in these flue streams have also presented significant barriers to the deployment of new technologies for CO2 capture from gas-fired power plants. Here, we demonstrate that functionalization of the metal-organic framework Mg2(dobpdc) (dobpdc4- = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate) with the cyclic diamine 2-(aminomethyl)piperidine (2-ampd) produces an adsorbent that is capable of ≥90% CO2 capture from a humid natural gas flue emission stream, as confirmed by breakthrough measurements. This material captures CO2 by a cooperative mechanism that enables access to a large CO2 cycling capacity with a small temperature swing (2.4 mmol CO2/g with ΔT = 100 °C). Significantly, multicomponent adsorption experiments, infrared spectroscopy, magic angle spinning solid-state NMR spectroscopy, and van der Waals-corrected density functional theory studies suggest that water enhances CO2 capture in 2-ampd-Mg2(dobpdc) through hydrogen-bonding interactions with the carbamate groups of the ammonium carbamate chains formed upon CO2 adsorption, thereby increasing the thermodynamic driving force for CO2 binding. In light of the exceptional thermal and oxidative stability of 2-ampd-Mg2(dobpdc), its high CO2 adsorption capacity, and its high CO2 capture rate from a simulated natural gas flue emission stream, this material is one of the most promising adsorbents to date for this important separation.

Metabolic effects of vitamin B12 on physiology, stress resistance, growth rate and biomass productivity of Cyanobacterium stanieri planktonic and biofilm cultures

Although synthesized only by bacteria and archaea, cobalamin (vitamin B12) is essential for virtually all living cells. One major function is its role in methionine synthesis, as a co-factor for the B12-dependent methionine synthase MetH. However, a large number of microbes avoid requirements for B12 by encoding cobalamin-independent enzymes, such as the B12-independent methionine synthase MetE. Interestingly, many such microbes retain transporters for exogenous B12, produced by neighboring microbes. We hypothesize that selection for retention of B12 transport suggests preservation of unrevealed but critical roles for cobalamin in photoautotroph fitness. To identify the impacts of B12 on photoautotrophic metabolism, we studied the physiological and transcriptional adaptation of Cyanobacterium stanieri HL-69 to varying irradiance and oxidative stress in the presence and absence of B12. The metabolic flexibility of C. stanieri, which possesses both MetH and MetE, allows comparative analysis of cobalamin impacts on its global metabolism. As anticipated, B12 availability governed transcription of cobalamin transporter btuB, metH and a number of genes involved in the methionine-folate cycle. Surprisingly, however, B12 impacted the cell integrity, growth rate and biomass productivity of C. stanieri under conditions of likely oxidative stress due to biofilm growth or under high partial pressures of O2. Furthermore, C. stanieri response to B12 globally rewired cellular metabolic networks, including nitrogen metabolism, energy metabolism, redox homeostasis and oxidative stress response. These findings demonstrate previously-unappreciated roles for B12 metabolism beyond methionine synthesis and reveal how interactions with cobalamin-producing heterotrophs may affect phytoplankton function and dynamics in natural microbial communities. Further comprehension and mastering of the natural oxidative stress resistance mechanisms modulated by cobalamin could be used for the design and implementation of more robust algal bioprocesses retaining high biomass productivities especially under stress conditions.

Biocompatible MOFs for Storage and Separation of O2: A Molecular Simulation Study

Metal organic frameworks (MOFs) are great candidates for capturing O2 due to their highly porous structures and tunable physical and chemical properties. In this study, we assessed the performance of 1525 biocompatible MOFs which have endogenous linkers and nontoxic metal centers for adsorption-based and membrane-based O2 separation and also for high-pressure O2 storage. We initially computed Henry’s constants of O2 and N2 at zero coverage and 298 K by performing Grand Canonical Monte Carlo (GCMC) simulations and estimated infinite dilution adsorption selectivities for O2/N2 mixture. We performed binary mixture GCMC simulations for the top 15 candidates at various pressures and 298 K and compared mixture adsorption selectivities with those obtained from infinite dilution. We then estimated O2 working capacities of 315 biocompatible MOFs obtained at 298 K and 140 bar for storage and 5 bar for release pressures. Our results showed that 15 biocompatible MOFs outperform gravimetric O2 working capacities of the traditional adsorbent materials such as activated carbon and NaX and some common MOFs such as NU-125 and UMCM-152 at 298 K. We finally calculated O2 and N2 permeabilities and membrane selectivities of 45 promising MOF candidates for O2/N2 separation. Seventeen biocompatible MOF membranes were identified to exceed the Robeson’s upper bound established for polymers. This computational study will be useful to identify the promising biocompatible MOFs for storage and separation of O2. The bio-MOF library constructed in this study will also guide both experimental and computational studies for design and development of biocompatible MOFs for various medical applications.

Effects of Changes in Gas Type and Partial Pressure on Chemical Mechanical Polishing Property of Si Substrate

As a critical link of efficient and high-quality semiconductor substrate chemical mechanical polishing process, this paper focuses on the effects of the changes of the atmosphere to be processed on the CMP property of Si substrate. The experiment results showed that O2 existing in the processing atmosphere played an active role in facilitating material removal, and when the partial pressure of O2 in the processing atmosphere increased to 500kPa, the Si MRR of CMP reached 905nm/min. The Si material surface dissolutions in different atmospheres were analyzed respectively using SEM, EDS and light interference microscope. It was found that when O2 was sufficient, an extremely thin and tight oxide film was formed on the Si substrate surface, which prevented the furtherance of oxidation reaction, and compared with the Si-Si bonds, the Si-O bonds generated during this process were more inclined to undergo hydrolysis reaction; on the other hand, the O2 atmosphere caused the polishing pad, polishing particles and Si substrate to contact closely, increasing the mechanical friction and thus significantly improving the MRR. Based on the results of experiment and analysis, the Mechanisms of Si substrate polishing in high-pressure O2 atmosphere were summarized and a material removal model was built.

Light Element Doping Induced Phase Change of Strongly Correlated Semiconductor SmNiO3

Introduction Correlated oxide semiconductors offer a unique relation between local structure and electrical properties because small amount of impurity atoms allow for significant changes in the band structure1,2. Electron doping of strongly correlated nickelates such as SmNiO3 (SNO) by small ion incorporation has been observed to change resistivity up to ten orders of magnitude – manifesting a quantum mechanical driven phase transition via ~3eV band gap opening3. During this process, cations with small atomic radii intercalate, reducing the Ni valence in of the SNO. Nevertheless, it is difficult to directly characterize the small amounts of such light elements within the structure. This study focuses on the band gap opening of the correlated oxide SmNiO3 upon charge doping as well as structural changes introduced by the dopants during this phase transition. The correlation among doping level – structural changes – electrical properties of SNO will be established. Experimental SNO thin films are grown by physical vapor deposition (PVD) from Sm and Ni targets in an Ar/O2 atmosphere and subsequent high pressure O2 annealing. LaAlO3 and Si/SiO2 substrates were used to create epitaxial and polycrystalline samples respectively. Films were then subjected to electrochemical treatment in a liquid environment to dope light elements into the lattice. Characterization of the changes in film resistance was used in conjunction to determine dopant distribution overall effect on SNO thin film properties. Synchrotron x-ray and neutron scattering will be used to investigate the structural evolution with doping of SNO. Results and Discussion Figure 1 shows resistivity changes as a function of temperature as the sample is doped with lightweight elements. It can be readily observed that this non-volatile doping process significantly changes not only the resistivity of the film, but also the characteristic metal-insulator transition observed in a number of pristine nickelates. This doping process is non-volatile due to resistivity remaining stable at ambient conditions. Notably, there is no change to the film resistance without further bias application. To better understand the structural implications of the doping process, X-ray diffraction was used to explore the effects on the SNO lattice with the incorporation of these impurity ions. Epitaxial SNO on LAO substrates before and after light element doping show a clear shift of the diffraction peaks of SNO to lower angle. This observation is consistent in that the lattice expands to accommodate the dopant ions. Additional investigations on the electrochemical doping process are also explored through cyclic voltammetry and will be discussed during the presentation. Summary SNO thin films show a large change in resistivity when doped with light elements via charge transfer to the Ni orbitals. To better understand the phase transition as it relates to this doping process, we highlight the association between the changing structure and properties as the light elements are intercalated into the lattice. A better understanding of the carrier density modulation and distribution are correlated with structural changes imparted with the electrochemical treatment. Ultimately, new insights into this highly sensitive wide gap semiconductor may be useful for future sensing applications. References Rondinelli, J.M., May, S.J. and Freeland, J.W., 2012. Control of octahedral connectivity in perovskite oxide heterostructures: An emerging route to multifunctional materials discovery.MRS bulletin, 37(03), pp.261-270.Middey, S., Chakhalian, J., Mahadevan, P., Freeland, J.W., Millis, A.J. and Sarma, D.D., 2016. Physics of Ultrathin Films and Heterostructures of Rare-Earth Nickelates.Annual Review of Materials Research, 46, pp.305-334.Shi, J., Zhou, Y. and Ramanathan, S., 2014. Colossal resistance switching and band gap modulation in a perovskite nickelate by electron doping. Nature communications, 5, 4860. Figure 1. Doping of SmNiO3 changing the resistance as a function of temperature and derivative. Figure 1