16 research outputs found

    Impact of Proteins on Aggregation Kinetics and Adsorption Ability of Hematite Nanoparticles in Aqueous Dispersions

    No full text
    The initial aggregation kinetics of hematite nanoparticles (NPs) that were conjugated with two model globular proteinscytochrome c from bovine heart (Cyt) and bovine serum albumin (BSA)were investigated over a range of monovalent (NaCl) and divalent (CaCl<sub>2</sub>) electrolyte concentrations at pH 5.7 and 9. The aggregation behavior of Cyt-NP conjugates was similar to that of bare hematite NPs, but the additional electrosteric repulsion increased the critical coagulation concentration (CCC) values from 69 mM to 113 mM in NaCl at pH 5.7. An unsaturated layer of BSA, a protein larger than Cyt, on hematite NPs resulted in fast aggregation at low salt concentrations and pH 5.7, due to the strong attractive patch-charge interaction. However, the BSA-NP conjugates could be stabilized simply by elevating salt concentrations, owing to the screening of the attractive patch-charge force and the increasing contribution from steric force. This study showed that the aggregation state of protein-conjugated NPs is proved to be completely switchable via ionic strength, pH, protein size, and protein coverage. Macroscopic Cu­(II) sorption experiments further established that reducing aggregation of hematite NPs via tailoring ionic strength and protein conjugation could promote the metal uptake by hematite NPs under harsh conditions

    Energy Consumption and Exergy Analysis of MEA-Based and Hydrate-Based CO<sub>2</sub> Separation

    No full text
    Carbon capture and storage (CCS) is regarded as the most efficient approach in handling the global warming crisis. MEA-based CO<sub>2</sub> capture is a well-developed chemical absorption method with a long period of industrial application. A novel hydrate-based gas separation (HBGS) method, with a wide range of advantages, has recently received special attention from researchers. In this study, two different CO<sub>2</sub> separation processes were simulated utilizing Aspen Plus software. The feasibility of both processes was validated, and the process energy consumption and exergy loss were also compared at the same flue gas condition. Some efforts have also been made to investigate the effects of different operation parameters on the process energy efficiency. Results show that the first law efficiency of the MEA-based CO<sub>2</sub> separation system is 88.19% and the second law efficiency of the system is 38.32%, while the corresponding values of the hydrate-based separation system are 74.15% and 38.85%, respectively. Cooling of the lean amine solution and the regeneration process occupy the largest portion of exergy loss in the MEA separation system. In the hydration separation, the flue gas compression and cooling are the major causes for exergy loss

    σ Phase Formed in Conformationally Asymmetric AB-Type Block Copolymers

    No full text
    The stability of various spherical phases formed in conformationally asymmetric AB diblock and architecture asymmetric AB<sub><i>m</i></sub> miktoarm block copolymers is investigated using self-consistent field theory. Both the conformational and architecture asymmetries are unified into a parameter of conformationally asymmetric degree, ε. We find that a complex spherical phase, the σ phase, becomes stable and its phase region expands between bcc and hexagonal phases as increasing ε. Only for large conformational asymmetry, for example, ε = 9 (or <i>m</i> = 3), the A15 phase becomes stable in the region between the σ phase and the hexagonal phase and its phase region terminates at the intermediate segregation region. Compared with the σ phase, the A15 phase has more favorable interfacial energy by enabling the formation of larger spherical domains, and therefore, it becomes more stable in the region of more symmetric volume fraction and stronger segregation

    Perfectly Ordered Patterns via Corner-Induced Heterogeneous Nucleation of Self-Assembling Block Copolymers Confined in Hexagonal Potential Wells

    No full text
    The ordering dynamics of cylinder-forming diblock copolymer/homopolymer blends confined in hexagonal potential wells is systematically investigated using time-dependent Ginzburg–Landau (TDGL) theory. It is demonstrated that a high-efficient method to obtain large-scale ordered hexagonal patterns is to utilize corner-induced heterogeneous nucleation processes, in which nucleation events with controlled positions and orientations are triggered exclusively at the six corners of the confining hexagonal wells. Subsequent growth of the six domains originated from the corners leads to the formation of perfectly ordered patterns occupying the entire hexagonal well. The heterogeneous nucleation rate is regulated by the homopolymer concentration as well as the surface potential of the confining walls. Defect-free hexagonal patterns are obtained in hexagons with a diagonal size containing up to 61 cylinders (about 2 μm). The robustness of the method is examined by studying the tolerance window of the size-commensurability of the confining wells. The results indicate that controlled heterogeneous nucleation provides an efficient method for the fabrication of large-scale ordered patterns using graphoepitaxy of block copolymer self-assembly

    Modular Design of Poly(norbornenes) for Organelle-Specific Imaging in Tumor Cells

    No full text
    Through modular ROMP (ring-opening metathesis polymerization) directly from monomeric norbornenes of bioactive peptides, rhodamine B chromophore, and PEG solubilizer, we designed and synthesized a series of water-soluble poly­(norbornenes) with organelle-specific imaging capability in tumor cells. For the selection of F<sub><i>x</i></sub>rF<sub><i>x</i></sub>K, TAT, and SV40 peptide sequences, these fluorescence probes exhibited different targeting specificity toward mitochondria, lysosome, and nucleolus, respectively, based on the same poly­(norbornene) backbonds. More importantly, the ROMP strategy enables selective combination from various monomers and allows programmable biofunctionalization via peptide sequence permutations, which would greatly extend the biomedical applications such as imaging, diagnosis, and therapy for these synthetic polymers

    Perfectly Ordered Patterns via Corner-Induced Heterogeneous Nucleation of Self-Assembling Block Copolymers Confined in Hexagonal Potential Wells

    No full text
    The ordering dynamics of cylinder-forming diblock copolymer/homopolymer blends confined in hexagonal potential wells is systematically investigated using time-dependent Ginzburg–Landau (TDGL) theory. It is demonstrated that a high-efficient method to obtain large-scale ordered hexagonal patterns is to utilize corner-induced heterogeneous nucleation processes, in which nucleation events with controlled positions and orientations are triggered exclusively at the six corners of the confining hexagonal wells. Subsequent growth of the six domains originated from the corners leads to the formation of perfectly ordered patterns occupying the entire hexagonal well. The heterogeneous nucleation rate is regulated by the homopolymer concentration as well as the surface potential of the confining walls. Defect-free hexagonal patterns are obtained in hexagons with a diagonal size containing up to 61 cylinders (about 2 μm). The robustness of the method is examined by studying the tolerance window of the size-commensurability of the confining wells. The results indicate that controlled heterogeneous nucleation provides an efficient method for the fabrication of large-scale ordered patterns using graphoepitaxy of block copolymer self-assembly

    Microphase Separation and Crystallization in All-Conjugated Poly(3-alkylthiophene) Diblock Copolymers

    No full text
    The microphase separation and crystallization of all-conjugated poly­(3-butylthiophene)-<i>b</i>-poly­(3-dodecylthiophene) (P3BDDT) diblock copolymers were systematically investigated by temperature-resolved wide-angle X-ray diffraction (WAXD), Fourier transform infrared (FTIR), and synchrotron small-angle X-ray scattering (SAXS) in a step-by-step cooling process. The WAXD, FTIR, and SAXS results revealed that the crystallization of poly­(3-butylthiophene) (P3BT) blocks with shorter alkyl side-chains in high temperature region led to the formation of microphase-separated lamellar structure consisting of P3BT crystalline domains and P3BT/poly­(3-dodecylthiophene) (P3DDT) amorphous domains, followed by a rapid crystallization of P3DDT blocks in relatively low temperature region, which occurred in the amorphous domains between P3BT crystalline domains. Analysis of the one-dimensional (1D) correlation function derived from SAXS data suggested that the previously crystallized P3BT segments could confine the size of P3DDT crystalline subdomains and possibly contribute to the rapid increase in the P3DDT crystallinity

    Luminescence-Tunable Polynorbornenes for Simultaneous Multicolor Imaging in Subcellular Organelles

    No full text
    Through modular ROMP (ring-opening metathesis polymerization), biofunctional polynorbornenes are designed and fabricated from panchromatic fluorophores, bioactive peptides, and polyethylene glycol solubilizer for organelle-specific multicolor imaging. Attributed to the free permutation and combination of highly fluorescent red rhodamine B, green dichlorofluorescein and blue 9,10-diphenylanthracene fluorophores as well as signaling peptide sequences of F<sub><i>x</i></sub>rF<sub><i>x</i></sub>K and TAT, we successfully realize simultaneous multicolor imaging toward lysosomes and mitochondria in living cells first utilizing polymeric scaffolds. If more biofunctions could be incorporated, modularly designed copolymer would provide a promising opportunity to facilitate multitasking application to monitoring intracellular alterations and elucidating complex biological processes

    Reversible Light-Triggered Transition of Amphiphilic Random Copolymers

    No full text
    A new set of amphiphilic random copolymers has been constructed directly by hydrophilic, hydrophobic, and functional spiropyran monomers in one-pot ROMP. The resulting copolymers are able to self-assemble in water to polymeric micelles, which exhibit reversible disruption and regeneration characteristics upon ultraviolet (UV) and visible-light irradiation. When hydrophobic dyes Nile red, which served as a model for drug delivery, are encapsulated within the core of polymeric micelle, their releasing and reloading have been realized by exposure to UV and visible light, respectively, in the aqueous solution

    Solvothermally Synthesized Co(CoO)/Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>/TiO<sub>2</sub> Nanocomposites for Enhanced Microwave Absorption

    No full text
    Ti3C2Tx MXene has already been studied as an appealing microwave absorption material, benefiting from its fascinating laminated structure. Nevertheless, the single absorption mechanism of pure Ti3C2Tx MXene results in poor impedance matching. In this paper, magnetic Co nanoparticles were introduced on Ti3C2Tx MXene by using a simple solvothermal method. By introducing different contents of Co nanoparticles, the impedance matching and magnetic properties of the Co(CoO)/Ti3C2Tx/TiO2 nanocomposites could be optimized. It is demonstrated that the effective absorption bandwidth of Co(CoO)/Ti3C2Tx/TiO2 nanocomposites is 5.84 GHz (6.88–12.72 GHz), while the minimum reflection loss is −61.02 dB. Comparatively, our Co(CoO)/Ti3C2Tx/TiO2 nanocomposites exhibited better satisfied microwave absorption performance. The potential mechanism of microwave absorption was fully explored. Our report provides a simple and safe method to design high-efficiency absorbers which rely on Ti3C2Tx
    corecore