Solution NMR Spectroscopy as a Useful Tool to Investigate Colloidal Nanocrystal Dispersions from the Capping Ligand's Point of View

AbstractColloidal semiconductor nanocrystals or quantum dots are an important building block in bottom-up nanotechnology. They consist of an inorganic, crystalline core surrounded by a monolayer of organic ligands. As these ligands can be modified or exchanged for others, they provide a convenient way to give the quantum dots functionality. Here, we show that solution NMR techniques, including diffusion pulsed field gradient spectroscopy, is a very useful tool to investigate the ligands of colloidal nanocrystals. This is demonstrated using InP quantum dots with trioctylphospine oxide ligands as an example. Combining 1H-13C HSQC spectroscopy with pulsed field gradient diffusion NMR, an unequivocal identification of the resonances of the bound ligands is possible. This leads to the determination of the diffusion coefficient of the nanocrystals in solution and allows to verify capping exchange procedures. By calibrating the surface area of the NMR resonances using a solute of known concentration, the density of ligands at the nanocrystal surface can be quantified. We could demonstrate that a dynamic equilibrium exists between bound and free ligands. Analysis of the corresponding adsorption isotherm - determined using 1H NMR - leads to an estimation of the free energy of adsorption and the free energy of ligand-ligand interaction at the nanocrystals surface. Similar investigations are in progress on capped PbSe and ZnO2 nanoparticles. Preliminary results strongly support the generic nature of the approach described for the case of TOPO capped InP nanocrystals.

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Pulsed Field Gradient NMR Studies of Polymer Adsorption on Colloidal CdSe Quantum Dots

The Journal of Physical Chemistry B ◽

10.1021/jp0768975 ◽

2008 ◽

Vol 112 (6) ◽

pp. 1626-1633 ◽

Cited By ~ 27

Author(s):

Lei Shen ◽

Ronald Soong ◽

Mingfeng Wang ◽

Anna Lee ◽

Chi Wu ◽

...

Keyword(s):

Quantum Dots ◽

Field Gradient ◽

Polymer Adsorption ◽

Cdse Quantum Dots ◽

Nmr Studies ◽

Pulsed Field Gradient Nmr ◽

Pulsed Field

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Controlling Gas Selectivity in Molecular Porous Liquids by Tuning the Cage Window Size

10.26434/chemrxiv.10247528.v1 ◽

2019 ◽

Author(s):

Benjamin Egleston ◽

Konstantin V. Luzyanin ◽

Michael C. Brand ◽

Rob Clowes ◽

Michael E. Briggs ◽

...

Keyword(s):

Nmr Spectroscopy ◽

Chemical Synthesis ◽

Field Gradient ◽

Window Size ◽

Standard Approach ◽

Porous Solids ◽

Pulsed Field Gradient Nmr ◽

Pulsed Field ◽

Cage Molecules ◽

Gas Selectivity

Control of pore window size is the standard approach for tuning gas selectivity in porous solids. Here, we present the first example where this is translated into a molecular porous liquid formed from organic cage molecules. Reduction of the cage window size by chemical synthesis switches the selectivity from Xe-selective to CH4-selective, which is understood using 129Xe, 1H, and pulsed-field gradient NMR spectroscopy.

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Controlling Gas Selectivity in Molecular Porous Liquids by Tuning the Cage Window Size

10.26434/chemrxiv.10247528 ◽

2019 ◽

Author(s):

Benjamin Egleston ◽

Konstantin V. Luzyanin ◽

Michael C. Brand ◽

Rob Clowes ◽

Michael E. Briggs ◽

...

Keyword(s):

Nmr Spectroscopy ◽

Chemical Synthesis ◽

Field Gradient ◽

Window Size ◽

Standard Approach ◽

Porous Solids ◽

Pulsed Field Gradient Nmr ◽

Pulsed Field ◽

Cage Molecules ◽

Gas Selectivity

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Phase-field gradient theory

Zeitschrift für angewandte Mathematik und Physik ◽

10.1007/s00033-020-01441-2 ◽

2021 ◽

Vol 72 (2) ◽

Author(s):

Luis Espath ◽

Victor Calo

Keyword(s):

Free Energy ◽

Field Equation ◽

Field Gradient ◽

Phase Field ◽

Constitutive Relations ◽

The Body ◽

Second Grade ◽

Gradient Theory ◽

Boundary Edge ◽

Field Equations

AbstractWe propose a phase-field theory for enriched continua. To generalize classical phase-field models, we derive the phase-field gradient theory based on balances of microforces, microtorques, and mass. We focus on materials where second gradients of the phase field describe long-range interactions. By considering a nontrivial interaction inside the body, described by a boundary-edge microtraction, we characterize the existence of a hypermicrotraction field, a central aspect of this theory. On surfaces, we define the surface microtraction and the surface-couple microtraction emerging from internal surface interactions. We explicitly account for the lack of smoothness along a curve on surfaces enclosing arbitrary parts of the domain. In these rough areas, internal-edge microtractions appear. We begin our theory by characterizing these tractions. Next, in balancing microforces and microtorques, we arrive at the field equations. Subject to thermodynamic constraints, we develop a general set of constitutive relations for a phase-field model where its free-energy density depends on second gradients of the phase field. A priori, the balance equations are general and independent of constitutive equations, where the thermodynamics constrain the constitutive relations through the free-energy imbalance. To exemplify the usefulness of our theory, we generalize two commonly used phase-field equations. We propose a ‘generalized Swift–Hohenberg equation’—a second-grade phase-field equation—and its conserved version, the ‘generalized phase-field crystal equation’—a conserved second-grade phase-field equation. Furthermore, we derive the configurational fields arising in this theory. We conclude with the presentation of a comprehensive, thermodynamically consistent set of boundary conditions.

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Lithium-ion diffusivity in complex hydrides: Pulsed-field-gradient NMR studies of LiLa(BH4)3Cl, Li3(NH2)2I and Li-1-CB9H10

Solid State Ionics ◽

10.1016/j.ssi.2021.115585 ◽

2021 ◽

Vol 362 ◽

pp. 115585

Author(s):

A.V. Skripov ◽

G. Majer ◽

O.A. Babanova ◽

R.V. Skoryunov ◽

A.V. Soloninin ◽

...

Keyword(s):

Field Gradient ◽

Lithium Ion ◽

Nmr Studies ◽

Pulsed Field Gradient Nmr ◽

Pulsed Field ◽

Complex Hydrides

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Measurement of the diffusion of multiple nuclei in restricted spaces by pulsed field gradient NMR

Journal of Magnetic Resonance ◽

10.1016/j.jmr.2021.106958 ◽

2021 ◽

pp. 106958

Author(s):

Reiji Takekawa ◽

Junichi Kawamura

Keyword(s):

Field Gradient ◽

Pulsed Field Gradient Nmr ◽

Pulsed Field

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Nuclear Magnetic Resonance Metabolomics with Double Pulsed-Field-Gradient Echo and Automatized Solvent Suppression Spectroscopy for Multivariate Data Matrix Applied in Novel Wine and Juice Discriminant Analysis

Molecules ◽

10.3390/molecules26144146 ◽

2021 ◽

Vol 26 (14) ◽

pp. 4146

Author(s):

José Enrique Herbert-Pucheta ◽

José Daniel Lozada-Ramírez ◽

Ana E. Ortega-Regules ◽

Luis Ricardo Hernández ◽

Cecilia Anaya de Parrodi

Keyword(s):

Statistical Analysis ◽

Discriminant Analysis ◽

Field Gradient ◽

Multivariate Statistical Analysis ◽

Data Matrix ◽

Cabernet Sauvignon ◽

Gradient Echo ◽

Multivariate Statistical ◽

Orthogonal Projections ◽

Pulsed Field

The quality of foods has led researchers to use various analytical methods to determine the amounts of principal food constituents; some of them are the NMR techniques with a multivariate statistical analysis (NMR-MSA). The present work introduces a set of NMR-MSA novelties. First, the use of a double pulsed-field-gradient echo (DPFGE) experiment with a refocusing band-selective uniform response pure-phase selective pulse for the selective excitation of a 5–10-ppm range of wine samples reveals novel broad 1H resonances. Second, an NMR-MSA foodomics approach to discriminate between wine samples produced from the same Cabernet Sauvignon variety fermented with different yeast strains proposed for large-scale alcohol reductions. Third a comparative study between a nonsupervised Principal Component Analysis (PCA), supervised standard partial (PLS-DA), and sparse (sPLS-DA) least squares discriminant analysis, as well as orthogonal projections to a latent structures discriminant analysis (OPLS-DA), for obtaining holistic fingerprints. The MSA discriminated between different Cabernet Sauvignon fermentation schemes and juice varieties (apple, apricot, and orange) or juice authentications (puree, nectar, concentrated, and commercial juice fruit drinks). The new pulse sequence DPFGE demonstrated an enhanced sensitivity in the aromatic zone of wine samples, allowing a better application of different unsupervised and supervised multivariate statistical analysis approaches.

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