Graphene oxide-fullerene nanocomposite laminates for efficient hydrogen purification.

Graphene oxide (GO) with its unique two-dimensional structure offers an emerging platform for designing advanced gas separation membranes that allow for highly selective transport of hydrogen molecules. Nevertheless, further tuning of the interlayer spacing of GO laminates and its effect on membrane separation efficiency remains to be explored. Here, positively charged fullerene C60 derivatives are electrostatically bonded to the surface of GO sheets in order to manipulate the interlayer spacing between GO nanolaminates. The as-prepared GO-C60 membranes have a high H2 permeance of 3370 GPU (gas permeance units) and an H2/CO2 selectivity of 59. The gas separation selectivity is almost twice that of flat GO membranes because of the role of fullerene.

Carbonic Anhydrase-Mimicking Supramolecular Nanoassemblies for Developing Carbon Capture Membranes.

As a ubiquitous family of enzymes with high performance in converting carbon dioxide (CO2) into bicarbonate, carbonic anhydrases (CAs) sparked enormous attention for carbon capture. Nevertheless, the high cost and operational instability of CAs hamper their practical relevance, and the utility of CAs is mainly limited to aqueous applications where CO2-to-bicarbonate conversion is possible. Taking advantage of the chemical motif that endows CA-like active sites (metal-coordinated histidine), here we introduce a new line of high-performance gas separation membranes with CO2-philic behavior. We first self-assembled a histidine-based bolaamphiphile (His-Bola) molecule in the aqueous phase and coordinated the resulting entities with divalent zinc. Optimizing the supramolecular synthesis conditions ensured that the resultant nanoparticles (His-NPs) exhibit high CO2 affinity and catalytic activity. We then exploited the His-NPs as nanofillers to enhance the separation performance of Pebax MH 1657. The hydrogen-bonding interactions allowed the dispersion of His-NPs within the polymer matrix uniformly, as confirmed by microscopic, spectroscopic, and thermal analyses. The imidazole and amine functionalities of His-NPs enhanced the solubility of CO2 molecules in the polymer matrix. The CA-mimic active sites of His-NPs nanozymes, on the other hand, catalyzed the reversible hydration of CO2 molecules in humid conditions, facilitating their transport across the membranes. The resulting nanocomposite membranes displayed excellent CO2 separation performance, with a high level of stability. At a filling ratio as low as 3 wt %, we achieved a CO2 permeability of >145 Barrer and a CO2/N2 selectivity of >95 with retained performance under humid continuous gas feeds. The bio-inspired approach presented in this work offers a promising platform for designing durable and highly selective CO2 capture membranes.

Structural colour enhanced microfluidics.

Advances in microfluidic technology towards flexibility, transparency, functionality, wearability, scale reduction or complexity enhancement are currently limited by choices in materials and assembly methods. Organized microfibrillation is a method for optically printing well-defined porosity into thin polymer films with ultrahigh resolution. Here we demonstrate this method to create self-enclosed microfluidic devices with a few simple steps, in a number of flexible and transparent formats. Structural colour, a property of organized microfibrillation, becomes an intrinsic feature of these microfluidic devices, enabling in-situ sensing capability. Since the system fluid dynamics are dependent on the internal pore size, capillary flow is shown to become characterized by structural colour, while independent of channel dimension, irrespective of whether devices are printed at the centimetre or micrometre scale. Moreover, the capability of generating and combining different internal porosities enables the OM microfluidics to be used for pore-size based applications, as demonstrated by separation of biomolecular mixtures.

Influence of microstructural variations on morphology and separation properties of polybutadiene-based polyurethanes.

Polybutadiene-based polyurethanes with different cis/trans/1,2-vinyl microstructure contents are synthesized. The phase morphology and physical properties of the polymers are investigated using spectroscopic analysis (FTIR and Raman), differential scanning calorimetry (DSC), X-ray scattering (WAXD and SAXS) and atomic force microscopy (AFM). In addition, their gas transport properties are determined for different gases at 4 bar and 25 °C. Thermodynamic incompatibility and steric hindrance of pendant groups are the dominant factors affecting the morphology and properties of the PUs. FTIR spectra, DSC, and SAXS analysis reveal a higher extent of phase mixing in high vinyl-content PUs. Moreover, the SAXS analysis and AFM phase images indicate smaller microdomains by increasing the vinyl content. Smaller permeable soft domains as well as the lower phase separation of the PUs with higher vinyl content create more tortuous pathways for gas molecules and deteriorate the gas permeability of the membranes.

Structural colour using organized microfibrillation in glassy polymer films.

The formation of microscopic cavities and microfibrils at stress hotspots in polymers is typically undesirable and is a contributor to material failure. This type of stress crazing is accelerated by solvents that are typically weak enough not to dissolve the polymer substantially, but which permeate and plasticize the polymer to facilitate the cavity and microfibril formation process1-3. Here we show that microfibril and cavity formation in polymer films can be controlled and harnessed using standing-wave optics to design a periodic stress field within the film4. We can then develop the periodic stress field with a weak solvent to create alternating layers of cavity and microfibril-filled polymers, in a process that we call organized stress microfibrillation. These multi-layered porous structures show structural colour across the full visible spectrum, and the colour can be tuned by varying the temperature and solvent conditions under which the films are developed. By further use of standard lithographic and masking tools, the organized stress microfibrillation process becomes an inkless, large-scale colour printing process generating images at resolutions of up to 14,000 dots per inch on a number of flexible and transparent formats5,6.

Asymmetric autocatalysis induced by meteoritic amino acids with hydrogen isotope chirality.

Achiral meteoritic amino acids, glycine and alpha-methylalanine, with hydrogen isotope (D/H) chirality, acted as the source of chirality in asymmetric autocatalysis with amplification of ee to afford highly enantioenriched 5-pyrimidyl alkanols.

Asymmetric autocatalysis triggered by carbon isotope (13C/12C) chirality.

Many apparently achiral organic molecules on Earth may be chiral because of random substitution of the 1.11% naturally abundant 13C for 12C in an enantiotopic moiety within the structure. However, chirality from this source is experimentally difficult to discern because of the very small difference between 13C and 12C. We have demonstrated that this small difference can be amplified to an easily seen experimental outcome using asymmetric autocatalysis. In the reaction between pyrimidine-5-carbaldehyde and diisopropylzinc, addition of chiral molecules in large enantiomeric excess that are, however, chiral only by virtue of isotope substitution causes a slight enantiomeric excess in the zinc alkoxide of the produced pyrimidyl alkanol. Asymmetric autocatalysis then leads to pyrimidyl alcohol with a large enantiomeric excess. The sense of enantiomeric excess of the product alcohol varies consistently with the sense of the excess enantiomer of the carbon isotopically chiral compound.

Single probe nucleic acid immobilization on chemically modified single protein by controlling ionic strength and pH.

In an effort toward determining the feasibility of single molecule analysis, we describe a case whereby the binding of one biotinylated DNA to one streptavidin molecule via electrostatic interactions was controlled by altering in pH 4.0-9.0 and 0.16 of the ion strength. The quantitative analysis of immobilized probe ssDNA was realized in real-time via a quartz crystal microbalance (QCM) and electrochemical (EC) measurement in the range 100 pM to 50 microM of probe oligonucleotide concentration. The variation amount of biotinylated ssDNA immobilized on the streptavidin-modified surface at pH 7.5 was about 0.16 pmol, giving a ratio of streptavidin to biotinylated ssDNA of about 1:1.1. On the other hand, at pH 4.9, it was immobilized about 0.29 pmol. From the shape of the Langmuir plot and QCM, the immobilization efficiency of biotinylated DNA via streptavidin at pH 4.9 was approximately twofold that at pH 7.5. In view points of the reaction velocity, it was increased with decreasing buffer solution pH, indicating a strong interaction of negatively charged probe DNA with the positively charged streptavidin. And also the EC response value of deltaI/I(streptavidin) for the immobilized biotinylated ssDNA in pH 4.9 was about 49%, while the corresponding value for the pH 7.5 was approximately 34%. As DNA molecules possess negative charges, electrostatic repulsion occurred between streptavidin and biotinylated ssDNA at pH 7.5. At pH 4.9, the attraction between the biotinylated ssDNA and streptavidin resulted in increased adsorption which has an isoelectric point of about 5.9. It was deduced that the binding of biotinylated ssDNA to one or two of the four binding sites of streptavidin can be controlled by adjusting the pH-controlled electrostatic interaction.