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  1. Abstract

    Polymer‐derived amorphous SiCN has excellent high‐temperature stability and properties. To reduce the shrinkage during pyrolysis and to improve the high‐temperature oxidation resistance, Y2O3was added as a filler. In this study, polymer‐derived SiCN–Y2O3composites were fabricated by mixing a polymeric precursor of SiCN with Y2O3submicron powders in different ratios. The mixtures were cross‐linked and pyrolyzed in argon. SiCN–Y2O3composites were processed using field‐assisted sintering technology at 1350°C for 5 min under vacuum. Dense SiCN–Y2O3composite pellets were successfully made with relative density higher than 98% and homogeneous microstructure. Due to low temperature and short time of the heat‐treatment, the grain growth of Y2O3was substantially inhibited. The Y2O3grain size was ∼1 μm after sintering. The composites’ heat capacity, thermal diffusivity, and thermal expansion coefficients were characterized as a function of temperature. The thermal conductivity of the composites ceramics decreased as the amount of amorphous SiCN increased and the coefficient of thermal expansion (CTE) of the composites increased with Y2O3content. However, the thermal conductivity and CTE did not follow the rule of mixture. This is likely due to the partial oxidation of SiCN and the resultant impurity phases such as Y2SiO5, Y2Si2O7, and Y4.67(SiO4)3O.

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  2. Abstract

    In this study, we demonstrate a novel environmental barrier coating processed from polymer‐derived ceramics (PDCs) with homogeneously distributed sub‐micrometer Y2O3as the filler. Under suitable conditions, dense and crack‐free coatings can be achieved for all the designed compositions with the volumetric content of Y2O3varied from 45 to 93 vol%. To process the PDC SiC–Y2O3composite coatings, Y2O3particles and SiC liquid precursor were uniformly dispersed in hexane and then dip‐coated on SiC substrates. After cross‐linking at 250°C and heat‐treated at 900°C in argon, dense and crack‐free PDC SiC–Y2O3composite coatings were formed. The effect of coating thickness and heat‐treatment temperature on the formation of cracks due to constrained pyrolysis was studied. The critical thickness for realizing crack‐free coatings of three compositions (i.e., 93, 77, and 45 vol% Y2O3) was studied for heat treatment from 1000 to 1300°C using atomic force microscope and scanning electron microscopy. As heat‐treatment temperature increases, the critical coating thickness decreases for the same coating compositions due to enhanced shrinkage at higher temperature. With higher Y2O3content, the critical thickness of the coating increased. The inert Y2O3particles reduce the amount of polymer leading to reduction in the overall constrained shrinkage of the coating during heat treatment.

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  3. Abstract

    Biofilm formation is a major cause of hospital‐acquired infections. Research into biofilm‐resistant materials is therefore critical to reduce the frequency of these events. Polymer microarrays offer a high‐throughput approach to enable the efficient discovery of novel biofilm‐resistant polymers. Herein, bacterial attachment and surface chemistry are studied for a polymer microarray to improve the understanding ofPseudomonas aeruginosabiofilm formation on a diverse set of polymeric surfaces. The relationships between time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) data and biofilm formation are analyzed using linear multivariate analysis (partial least squares [PLS] regression) and a nonlinear self‐organizing map (SOM). The SOM models revealed several combinations of fragment ions that are positively or negatively associated with bacterial biofilm formation, which are not identified by PLS. With these insights, a second PLS model is calculated, in which interactions between key fragments (identified by the SOM) are explicitly considered. Inclusion of these terms improved the PLS model performance and shows that, without such terms, certain key fragment ions correlated with bacterial attachment may not be identified. The chemical insights provided by the combination of PLS regression and SOM will be useful for the design of materials that support negligible pathogen attachment.

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  4. Abstract

    Bacterial natural product biosynthetic genes, canonically clustered, have been increasingly found to rely on hidden enzymes encoded elsewhere in the genome for completion of biosynthesis. The study and application of lanthipeptides are frequently hindered by unclustered protease genes required for final maturation. Here, we establish a global correlation network bridging the gap between lanthipeptide precursors and hidden proteases. Applying our analysis to 161,954 bacterial genomes, we establish 5209 correlations between precursors and hidden proteases, with 91 prioritized. We use network predictions and co-expression analysis to reveal a previously missing protease for the maturation of class I lanthipeptide paenilan. We further discover widely distributed bacterial M16B metallopeptidases of previously unclear biological function as a new family of lanthipeptide proteases. We show the involvement of a pair of bifunctional M16B proteases in the production of previously unreported class III lanthipeptides with high substrate specificity. Together, these results demonstrate the strength of our correlational networking approach to the discovery of hidden lanthipeptide proteases and potentially other missing enzymes for natural products biosynthesis.

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  5. Abstract

    Self‐assembling peptides are a popular vector for therapeutic cargo delivery due to their versatility, tunability, and biocompatibility. Accurately predicting secondary and supramolecular structures of self‐assembling peptides is essential for de novo peptide design. However, computational modeling of such assemblies is not yet able to accurately predict structure formation for many peptide sequences. This review identifies patterns in literature between secondary and supramolecular structures, primary sequences, and applications to provide a guide for informed peptide design. An overview of peptide structures, their applications as nanocarriers, and analytical methods for characterizing secondary and supramolecular structure is examined. A top‐down approach is then used to identify trends between peptide sequence and assembly structure from the current literature, including an analysis of the drivers at work, such as local and nonlocal sequence effects and solution conditions.

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  6. Abstract

    Cytochrome P450 OleT is a fatty acid decarboxylase that catalyzes the production of olefins with biofuel and synthetic applications. However, the relatively sluggish catalytic efficiency of the enzyme limits its applications. Here, we report the application of a novel class of benzene containing small molecules to improve the OleT activity. The UV‐Vis spectroscopy study and molecular docking results confirmed the high proximity of the small molecules to the heme group of OleT. Up to 6‐fold increase of product yield has been achieved in the small molecule‐modulated enzymatic reactions. Our work thus sheds the light to the application of small molecules to increase the OleT catalytic efficiency, which could be potentially used for future olefin productions.

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  7. Abstract

    To produce multi-dopant ferrite nanoparticles, the ‘Extended LaMer’ and seed-mediated growth techniques were combined by first utilizing traditional thermal decomposition of metal acetylacetonates to produce seed particles, followed by a continuous injection of metal oleate precursors to increase the volume of the seed particles. With the choice of precursors for the seeding and dripping stage, we successfully synthesized particles with manganese precursor for seeding and cobalt precursor for dripping (Mn0.18Co1.04Fe1.78O4, 17.6 ± 3.3 nm), and particles with cobalt precursors for seeding and manganese precursors for dripping (Mn0.31Co0.74Fe1.95O4, 19.0 ± 1.9 nm). Combining transmission electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction, and vibrating sample magnetometry, we conclude that the seed-mediated drip method is a viable method to produce multi-dopant ferrite nanoparticles, and the size of the particles was mostly determined by the seeding stage, while the magnetic properties were more affected by the dripping stage.

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  8. Abstract

    Although dipolar forces between copolymer chains are relatively weak, they result in ubiquitous inter‐ and/or intramolecular interactions which are particularly critical in achieving the mechanical integrity of polymeric materials. In this study, a route is developed to obtain self‐healable properties in thermoplastic copolymers that rely on noncovalent dipolar interactions present in essentially all macromolecules and particularly fluorine‐containing copolymers. The combination of dipolar interactions between C─F and C═O bonds as well as CH2/CH3entities facilitates self‐healing without external intervention. The presence of dipole‐dipole, dipole‐induced dipole, and induced‐dipole induced dipole interactions leads to a viscoelastic response that controls macroscopic autonomous multicycle self‐healing of fluorinated copolymers under ambient conditions. Energetically favorable dipolar forces attributed to monomer sequence and monomer molar ratios induces desirable copolymer tacticities, enabling entropic energy recovery stored during mechanical damage. The use of dipolar forces instead of chemical or physical modifications not only eliminates additional alternations enabling multiple damage‐repair cycles but also provides further opportunity for designing self‐healable commodity thermoplastics. These materials may offer numerous applications, ranging from the use in electronics, ion batteries, H2fuel dispense hoses to self‐healable pet toys, packaging, paints and coatings, and many others.

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  9. Abstract

    Known for their adaptability to surroundings, capability of transport control of molecules, or the ability of converting one type of energy to another as a result of external or internal stimuli, responsive polymers play a significant role in advancing scientific discoveries that may lead to an array of diverge applications. This review outlines recent advances in the developments of selected commodity polymers equipped with stimuli‐responsiveness to temperature, pH, ionic strength, enzyme or glucose levels, carbon dioxide, water, redox agents, electromagnetic radiation, or electric and magnetic fields. Utilized diverse applications ranging from drug delivery to biosensing, dynamic structural components to color‐changing coatings, this review focuses on commodity acrylics, epoxies, esters, carbonates, urethanes, and siloxane‐based polymers containing responsive elements built into their architecture. In the context of stimuli‐responsive chemistries, current technological advances as well as a critical outline of future opportunities and applications are also tackled.

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  10. Abstract

    A non‐volatile conjugated polymer‐based electrochemical memristor (cPECM), derived from sodium 4‐[(2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐2‐yl)methoxy]butane‐2‐sulfonate (S‐EDOT), is fabricated through roll‐to‐roll printing and exhibited neuromorphic properties. The 3‐terminal device employed a “read” channel where conductivity of the water‐soluble, self‐doped S‐PEDOT is equated to synaptic weight and was electrically decoupled from the programming electrode. For the model system, a +2500 mV programming pulse of 100 ms duration resulted in a 0.136 μS resolution in conductivity change, giving over 1000 distinct conductivity states for one cycle. The minimum programming power requirements of the cPECM was 0.31 pJ mm−2and with advanced printing techniques, a 0.1 fJ requirement for a 20 μm device is achievable. The mathematical operations of addition, subtraction, multiplication, and division are demonstrated with a single cPECM, as well as the logic gates AND, OR, NAND, and NOR. This demonstration of a printed cPECM is the first step toward the implementation of a mass produced electrochemical memristor that combines information storage and processing and may allow for the realization of printable artificial neural networks.

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