Mesoporous silica-encapsulated Pt-Sn intermetallic nanoparticles (iNPs), synthesized by a novel ship-in-a-bottle approach, were recently demonstrated to be effective and robust catalysts for parahydrogen induced hyperpolarization (PHIP). Here it is shown that these iNPs are also effective for the production of long-lived hyperpolarized states on dimethyl maleate and fumarate in solution by pairwise addition of parahydrogen to dimethyl acetylene dicarboxylate in a slurry reactor. The transformation of the singlet state spin order into NMR-observable hyperpolarized longitudinal spin order is demonstrated by two different methods: (i) low-field level-anti crossing state mixing and (ii) Spin-Lock Induced Crossing (SLIC). The hyperpolarized proton singlet state lifetime in dimethyl maleate was measured to be 196 s, consistent with the published value, and more than an order of magnitude longer than the ordinary spin-lattice relaxation time.  Because the silica-encapsulated iNPs afford rapid, spontaneous separation of catalyst and product mixture, this advanced catalytic system has excellent potential for high-throughput continuous-flow production of long-lived hyperpolarized biomolecules for in vivo magnetic resonance imaging of metabolic processes on an extended time scale.

References

1. C. R. Bowers and D. P. Weitekamp, Phys. Rev. Lett., 1986, 57, 2645–2648.
2. C. R. Bowers and D. P. Weitekamp, J. Am. Chem. Soc., 1987, 109, 5541–5542.
3. Y. Zhang, K. Basu, J.W. Canary and A. Jerschow, Phys. Chem. Chem. Phys., 2015, 17, 24370-24375.
4. R.V. Maligal-Ganesh, C. Xiao, T.W. Goh, L.L. Wang, J. Gustafson, Y. Pei, Z. Qi, D.D. Johnson, S. Zhang, F. Tao, W. Huang, ACS Catal. 2016, 6, 1754-1763.
5. E.W. Zhao, R. Maligal-Ganesh, C. Xiao, T.-W. Goh, Z. Qi, Y. Pei, H.E. Hagelin-Weaver, W. Huang, and C.R. Bowers, 2017, 56, 3925-3929.

Rechargeable lithium-ion batteries (LIBs) are one of the leading technologies for energy storage. To overcome safety issues caused by traditional liquid electrolytes, non-flammable solid-state electrolytes are emerging as a promising solution for developing high-performance rechargeable batteries. Current ceramic, glass, and polymer electrolytes all show limitations for application because of their perspective drawbacks in ionic conductivity, chemical stability, or mechanical robustness. For example, ceramics are brittle, most glassy electrolytes are not stable against Li metal, and polymers exhibit low Li-ion conductivity at room temperature. Composite electrolytes offer a new path to create better electrolytes with both high ionic conductivity and good mechanical properties. To improve the ionic conductivity of composite electrolytes, fundamental understanding of the relevant factors, including charge carrier concentration, ion dynamics, and transport pathways is critical. NMR has been proven to be a powerful tool to study local structural environments, dynamics, and transport pathways of Li ions. In this study, high-resolution solid-state ^{6, 7}Li NMR was used to determine the local structural environments of Li ions in the polymer, the ceramic, and the interface of the Li₇La₃Zr₂O₁₂-polyethylene oxide (LiClO₄) composite electrolytes. Moreover, through isotope exchange technique, the trail of Li ions passing through the composite electrolyte was determined, revealing the mechanism of Li-ion transportation within the complex system.

Rechargeable lithium-ion batteries (LIBs) are the predominant power source in electronic devices and electric cars due to high-energy density and long cycling stability. However, liquid electrolytes using organic solvents found in commercial LIBs have safety issues such as flammability and leakage. Polymer-ceramic composite electrolytes have been investigated for the implementation in all solid-state lithium ion batteries with high perfomance. Polyethylene oxide (PEO) has been combined with Li7La3Zr2O12, a cubic-phase ceramic garnet, to create a thin-film, flexible composite electrolyte. Ionic conductivity needs to be improved to achieve high-performing all solid-state batteries. Small molecule additives, including TEGDME (tetraethylene glycol dimethyl ether) and succinonitrile, have been added to the LLZO-PEO composite electrolyte for enhancing the ionic conductivity. High-resolution solid state Li NMR was employed to understand Li ion pathways within the composite electrolyte in a symmetric battery cell, Li/LLZO-PEO/Li. This study provides guidance for the development of composite electrolytes with high ionic conductivity.

Applying a current through a synthetic membrane is used to enhance the delivery rate of ionic drugs. However, a precise quantification of the amount of drug delivered requires knowing what fraction of that current is carried by the drug ion. We have developed a device to electrochemically induce membrane drug delivery through an ion selective membrane. This device was used to transport a surrogate drug anion, nitrate, to a receiver solution while applying a voltage across the membrane. The delivery rate scaled with the voltage applied across the membrane and dissipated when an equilibrium state was reached. At equilibrium, we have shown that a precisely quantifiable amount of drug can be delivered. We also have shown experimentally, and proven theoretically, that our membrane drug delivery prototype turns itself off when a predetermined amount of drug has been delivered. This suggests that dosage-controlled and selective drug delivery can be obtained using our proposed device.

The structural identification of unknown metabolites via MS/MS is constrained by the standards included in MS/MS databases.¹ Infrared (IR) ion spectroscopy provides detailed chemical information based on the vibrational modes of an analyte. Room temperature methods of IR spectroscopy, such as infrared multiple photon dissociation (IRMPD) spectroscopy, is relatively easy to implement in commercial mass spectrometers, however, it suffers from limited resolution.^2,3  In contrast, cryogenic techniques, such as infrared predissociation (IRPD) spectroscopy, offer enhanced resolution, but there are considerable challenges in both instrumentation and methodology to overcome before the technique becomes analytically useful. ^4,5  Experimental strategies to overcome sensitivity constraints, poor overall duty cycle, and extensive acquisition time of the experiment are intimately tied to the development of a mass-selective cryogenic trap. Here, we discuss the construction and operation of a cryogenic linear ion trap (LIT) in terms of performing IR predissociation spectroscopy.

(1)          J. Chromatogr. A. 2014, 1353, 99-105.

(2)          Int. Rev. Phys. Chem. 2009, 28, 481-515.

(3)          Chem. Soc. Rev. 2011, 40, 2211-2221.

(4)          J. Am. Chem. Soc. 2011, 133, 6440-6448.

(5)          J. Am. Soc. Spectrom. 2016, 27, 757-766.

Sensors employing split aptamers that reassemble in the presence of a target can achieve excellent specificity, but the accompanying reduction of target affinity mitigates any overall gains in sensitivity. We have generated a split cocaine-binding aptamer that incorporates two binding domains, such that target binding at one domain greatly increases the affinity of the second domain. We for the first time have developed a split aptamer that achieves enhanced target-binding affinity through cooperative target binding. We experimentally demonstrate that the resulting cooperative-binding split aptamer (CBSA) exhibits higher target binding affinity and is far more responsive in terms of target-induced aptamer assembly compared to the single-domain parent split aptamer (PSA) from which it was derived. Using this CBSA, we achieved specific, ultra-sensitive, one-step fluorescent detection of cocaine within fifteen minutes at concentrations as low as 50 nM in 10% saliva without signal amplification. To achieve an ultra-sensitive detection of small-molecule targets, we employed Exonuclease-assisted target recycling (EATR) strategy along with fluorophore/quencher modified, or AuNP-conjugated CBSA fragments to amplify CBSA-target binding events. Our results showed that by in simply introducing EATR into CBSA binding assay, the sensitivity of fluorescence assay has been enhanced by 50 folds in urine samples, or a clear red-to-blue color change was clearly observed in the saliva samples containg 2 μM of cocaine after 20 minutes. It is clear that the CBSA-based assays represent a robust and sensitive means for detection of small-molecule targets in actual clinical samples.