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. 2019 Jan 4;5(1):eaau7555.
doi: 10.1126/sciadv.aau7555. eCollection 2019 Jan.

Rapid isotopic exchange in nanoparticles

Papri Chakraborty  1 , Abhijit Nag  1 , Ganapati Natarajan  1 , Nayanika Bandyopadhyay  1 , Ganesan Paramasivam  1 , Manoj Kumar Panwar  1 , Jaydeb Chakrabarti  2 , Thalappil Pradeep  1
Affiliations

Rapid isotopic exchange in nanoparticles

Papri Chakraborty et al. Sci Adv. .

Abstract

Rapid solution-state exchange dynamics in nanoscale pieces of matter is revealed, taking isotopically pure atomically precise clusters as examples. As two isotopically pure silver clusters made of 107Ag and 109Ag are mixed, an isotopically mixed cluster of the same entity results, similar to the formation of HDO, from H2O and D2O. This spontaneous process is driven by the entropy of mixing and involves events at multiple time scales.

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Figures

Fig. 1
Fig. 1. Mass spectra of the parent isotope clusters and the product of mixing.
(A) ESI MS of the as-synthesized isotopically pure clusters, (a) [107Ag25(DMBT)18]− and (b) [109Ag25(DMBT)18]−. (B) Mass spectral distribution of the product obtained by mixing the two isotopic clusters at 1:1 molar ratio. The spectrum was collected within 1 min after mixing the solutions of the clusters at room temperature. A representation of the clusters is shown. Comparison with the calculated mass spectrum is presented in figs. S1 and S2. Yellow, S; transparent gray, ligands.
Fig. 2
Fig. 2. Low-temperature reaction showing the intermediate steps of exchange.
Exchange between the two isotopic [Ag25(DMBT)18]− clusters at −20°C showing the intermediate stages of exchange (A) to (D) with mixing time (s). Distributions (i) and (ii) denote exchange at the [107Ag25(DMBT)18]− and [109Ag25(DMBT)18]− sides, respectively. Noise in the spectrum is due to the short acquisition time.
Fig. 3
Fig. 3. Kinetic study of isotopic exchange in [Ag29(BDT)12(TPP)4]3− clusters.
Plot of percentage of unexchanged parent isotopic cluster (Ct) versus time (min) of reaction at room temperature (25°C). Kinetics at 40° and 60°C are presented in the inset. Average of three kinetic measurements is plotted, and the error bar is indicated at each point. A schematic showing the different stages of isotopic exchange is also shown in the figure. Yellow, S; orange, P; transparent gray, ligands.
Fig. 4
Fig. 4. Molecular docking studies.
Force-field global minimum geometry (FFGMG) of two (A) [Ag25(DMBT)18]− and (B) [Ag29(BDT)12(TPP)4]3− clusters, lying in close proximity. Gray, Ag; yellow, S; orange, P. The overlapping Borromean rings are shown in blue, green, and red in (A); staple units are shown in green and blue in (B); and ligand shell is shown in transparent gray. Atomic diameters were reduced to show the bonding.
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