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On electrophoretic NMR. Exploring high conductivity samples
KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.ORCID-id: 0000-0002-0231-3970
2014 (Engelska)Ingår i: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 243, s. 17-24Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The performance of a new electrophoretic NMR (eNMR) method that uses a Carr-Purcell-Meiboom-Gill echo train with repeated electric field reversal is investigated. We show that this pulse sequence, with acronym CPMGER, yields strongly reduced artifacts from convective flow effects caused by the simultaneous presence of electroosmotic and thermal driving forces. We demonstrate the achieved improvements in various aqueous solutions. Ultimately, the method can be used for obtaining electrophoretic mobilities by eNMR without relying on uncharged reference molecules, otherwise a significant limitation for electrophoretic experiments performed with nuclei other than 1H.

Ort, förlag, år, upplaga, sidor
2014. Vol. 243, s. 17-24
Nyckelord [en]
CPMG, Double stimulated echo, Electroosmosis, eNMR, Sample cell, Thermal convection
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
URN: urn:nbn:se:kth:diva-145393DOI: 10.1016/j.jmr.2014.03.005ISI: 000337121300003Scopus ID: 2-s2.0-84898065953OAI: oai:DiVA.org:kth-145393DiVA, id: diva2:718065
Forskningsfinansiär
Vetenskapsrådet
Anmärkning

QC 20140519

Tillgänglig från: 2014-05-19 Skapad: 2014-05-19 Senast uppdaterad: 2017-12-05Bibliografiskt granskad
Ingår i avhandling
1. Characterizing ions in solution by NMR methods
Öppna denna publikation i ny flik eller fönster >>Characterizing ions in solution by NMR methods
2014 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

NMR experiments performed under the effect of electric fields, either continuous or pulsed, can provide quantitative parameters related to ion association and ion transport in solution.  Electrophoretic NMR (eNMR) is based on a diffusion pulse-sequence with electric fields applied in the form of pulses. Magnetic field gradients enable the measurement of the electrophoretic mobility of charged species, a parameter that can be related to ionic association.

The effective charge of the tetramethylammonium cation ion in water, dimethylsulphoxide (DMSO), acetonitrile, methanol and ethanol was estimated by eNMR and diffusion measurements and compared to the value predicted by the Debye-Hückel-Onsager limiting law. The difference between the predicted and measured effective charge was attributed to ion pairing which was found to be especially significant in ethanol.

The association of a large set of cations to polyethylene oxide (PEO) in methanol, through the ion-dipole interaction, was quantified by eNMR. The trends found were in good agreement with the scarce data from other methods. Significant association was found for cations that have a surface charge density below a critical value. For short PEO chains, the charge per monomer was found to be significantly higher than for longer PEO chains when binding to the same cations. This was attributed to the high entropy cost required to rearrange a long chain in order to optimize the ion-dipole interactions with the cations. Moreover, it was suggested that short PEO chains may exhibit distinct binding modes in the presence of different cations, as supported by diffusion measurements, relaxation measurements and chemical shift data.

The protonation state of a uranium (VI)-adenosine monophosphate (AMP) complex in aqueous solution was measured by eNMR in the alkaline pH range. The question whether or not specific oxygens in the ligand were protonated was resolved by considering the possible association of other species present in the solution to the complex.

The methodology of eNMR was developed through the introduction of a new pulse-sequence which suppresses artifactual flow effects in highly conductive samples.

In another experimental setup, using NMR imaging, a constant current was applied to a lithium ion (Li ion) battery model. Here, 7Li spin-echo imaging was used to probe the spin density in the electrolyte and thus visualize the development of Li+ concentration gradients. The Li+ transport number and salt diffusivity were obtained within an electrochemical transport model. The parameters obtained were in good agreement with data for similar electrolytes. The use of an alternative imaging method based on CTI (Constant Time Imaging) was explored and implemented.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2014. s. xii, 58
Serie
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:29
Nyckelord
electrophoretic NMR, diffusion NMR, NMR imaging, ion pairing, ion association, polyethylene oxide, metal-ion complex, Li ion batteries, electrolyte characterization
Nationell ämneskategori
Naturvetenskap
Forskningsämne
Kemi
Identifikatorer
urn:nbn:se:kth:diva-149552 (URN)978-91-7595-208-6 (ISBN)
Disputation
2014-09-12, F3, Lindstedtsvägen 26, KTH, Stockholm, 14:00 (Engelska)
Opponent
Handledare
Forskningsfinansiär
VetenskapsrådetKnut och Alice Wallenbergs Stiftelse
Anmärkning

QC 20140825

Tillgänglig från: 2014-08-25 Skapad: 2014-08-22 Senast uppdaterad: 2014-08-25Bibliografiskt granskad

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