Fig. 8: Password decoding from a single sample with z-resolved NMR.

A Physical realization of a single NMR sample containing 5 different mixtures of M¹M²-TP1 compounds encoded with Tb³⁺/Dy³⁺/Ho³⁺/Yb³⁺ ions. Aqueous solutions (in MOPS/NaOH buffer, pH = 7) of the mixtures (layers 1–5) are separated by layers of CCl₄. The capillary is submerged in D₂O. B Z-resolved ¹⁹F NMR spectrum (470 MHz, T = 298.1 K) of the sample from panel A shows signals of the M¹M²-TP1 compounds and internal standard (TFA, trifluoroacetic acid) resolved for the layers along the z-axis. Shifts from different layers are not perfectly aligned due to bulk magnetic susceptibility (BMS) effects that varied for each layer. C Evaluation of the signals from panel B by comparison with an independently obtained 1D NMR spectrum of a mixture containing all 16 M¹M²-TP1 compounds. Note that peaks of DyDy and YbTb are close but distinguished in the 1D spectrum. Black dots mark shifts from the z-resolved spectrum after correcting for BMS effects in each layer (referencing to TFA). Good match is achieved between expected shifts (vertical lines) and determined shifts (black dots). D Binary representation of the information from C. E Final table of the binary codes for 10 ASCII (American Standard Code for Information Interchange) characters encoded in the sample. Relative to D, the binary codes are rearranged to start at the position of DyDy (green shading), which is not used to avoid confusion with YbTb. F ASCII characters obtained by conversion from the binary codes in E with indication of their order in a password. G The final decoded 10-character password.