Journal: The journal of physical chemistry. C, Nanomaterials and interfaces

Article Title: Mechanisms of Gadographene-Mediated Proton Spin Relaxation

doi: 10.1021/jp406909b

Figure Lengend Snippet: (A) Relaxivity (r1 and r2) at 60 MHz as a function of sonication dose for Gd(III) Graphene 2%PL and 2%SC. The trend is opposite for the two surfactants. (B) Sonication results in thinner graphene stacks, as measured by DLS and AFM height, but no clear positive correlation between relaxivity and graphene size is detected. Symbols and shades in (B) indicate surfactant choice and sonication dose as in (A). More pristine gadographenes possess larger r2/r1 ratios than more damaged gadographenes (A) and materials based on graphene oxide (C) for both GdCl3 and Gd(III)-complexes (Gd(III)-DO3A-NH2 and Gd(III)-DTPA-NH2). Where available, error bars represent standard error.

Article Snippet: Briefly, sodium cholate (SC)-dispersed graphene was prepared by ultrasonication of graphite (3061 grade, Asbury Graphite Mills) at 40 – 70 W for 45 min – 16 h and purified by removal of large particles via centrifugation (~4,620 g for 30 min), followed by repeated washing and centrifugation in DI water.

Techniques: Sonication

Journal: The journal of physical chemistry. C, Nanomaterials and interfaces

Article Title: Mechanisms of Gadographene-Mediated Proton Spin Relaxation

doi: 10.1021/jp406909b

Figure Lengend Snippet: Mechanism of Gd(III) Graphene Oxide-induced proton relaxation. Gd(III) was found to experience local mobility based on analysis of the NMRD profiles at 298 and 310K; better fits were obtained when the modified Florence model (A) incorporated the Lipari-Szabo order parameter S2 (B). The observed high relaxivity is derived from a q of 5 and a τR ≥ 1000 ns while fast local motions (τfast and S2) and a τM < 10 ns act as limiting factors. The fitted parameters accurately predicted the transverse relaxivity (r2) measured at 60 MHz, 310K. q = hydration number, µeff = effective magnetic moment, µB = Bohr magneton, r = Gd(III)-proton distance, d = distance of closest approach, Ddiff = diffusion coefficient, τR = rotational correlation time, S2 = order paramter, τfast = fast motion correlation time, τM = mean water residence time, T1e = longitudinal electronic relaxation time.

Article Snippet: Briefly, sodium cholate (SC)-dispersed graphene was prepared by ultrasonication of graphite (3061 grade, Asbury Graphite Mills) at 40 – 70 W for 45 min – 16 h and purified by removal of large particles via centrifugation (~4,620 g for 30 min), followed by repeated washing and centrifugation in DI water.

Techniques: Modification, Derivative Assay, Diffusion-based Assay

Journal: The journal of physical chemistry. C, Nanomaterials and interfaces

Article Title: Mechanisms of Gadographene-Mediated Proton Spin Relaxation

doi: 10.1021/jp406909b

Figure Lengend Snippet: Mechanism of Gd(III) Graphene-induced proton relaxation. Similar to Gd(III) GO, local motions were found to be an important feature of Gd(III) Graphene. Their NMRD profiles were analyzed by the modified Florence model incorporating the Lipari-Szabo approach. The relaxivity of Gd(III) Graphene depended on the choice of surfactant (SC or PL) and was reduced compared to Gd(III) GO. Possible explanations include 1) decreased q by transient surfactant coordination to Gd(III), 2) a difference in Gd(III) microenvironments that resulted in different local motions and S2, 3) reduced water access due to a surfactant-posed diffusion barrier, or some combination of the three factors. The plausibility of the first two explanations were supported by NMRD fitting in (A) and (B), respectively. Theory consistently underestimated the r2 of Gd(III) Graphene, as shown by the r2 prediction accuracy.

Article Snippet: Briefly, sodium cholate (SC)-dispersed graphene was prepared by ultrasonication of graphite (3061 grade, Asbury Graphite Mills) at 40 – 70 W for 45 min – 16 h and purified by removal of large particles via centrifugation (~4,620 g for 30 min), followed by repeated washing and centrifugation in DI water.

Techniques: Modification, Diffusion-based Assay

Journal: The journal of physical chemistry. C, Nanomaterials and interfaces

Article Title: Mechanisms of Gadographene-Mediated Proton Spin Relaxation

doi: 10.1021/jp406909b

Figure Lengend Snippet: Mechanism of Gd(III)-Complex Graphene Oxide-induced proton relaxation. Gd(III)-DO3A-NH2 (q=2) or Gd(III)-DTPA-NH2 (q=1) was conjugated to either GO or reduced GO (rGO). Analysis of the NMRD profiles shows that these agents have higher relaxivities per q compared to Gd(III) GO as a result of their more optimized τM and slower local motion. The near-zero values of S2 suggest isotropic tumbling of Gd(III)-complexes on the GO surface. Consistent with the findings in Gd(III) Graphene, r2 prediction (r2,predicted / r2,measured ) using the fitted parameters is more accurate for Gd(III)-DO3A-GO than for its rGO counterpart. τM and q of the complexes were obtained from literature37 and assumed to remain unchanged post-conjugation.

Article Snippet: Briefly, sodium cholate (SC)-dispersed graphene was prepared by ultrasonication of graphite (3061 grade, Asbury Graphite Mills) at 40 – 70 W for 45 min – 16 h and purified by removal of large particles via centrifugation (~4,620 g for 30 min), followed by repeated washing and centrifugation in DI water.

Techniques: Conjugation Assay