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We report on the disparity in the assembly behavior of four types of nano-sized macroions induced by isotopic substitution of protium (H) to deuterium (D) in solvents. Macroions with modest charge density can self-assemble into single-layer, hollow, spherical "blackberry"-type structures, with larger assembly sizes representing stronger attractions among the macroions. Kinetically, all assembly processes become slower in D 2 O than in H 2 O. Thermodynamically, the polyoxometalate {SrPd 12 }, the uranium cage {U 60 } with alkali metal counterions, and the metal-organic cationic cage {Pd 12 L 24 } demonstrate similar assembly sizes in both H 2 O and D 2 O, whereas the metal oxide cluster {Mo 72 Fe 30 } as a weak acid shows an unusually large assembly size in H 2 O-suggesting a stronger contribution from the hydrogen bonding in the last case., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An interesting phenomenon is reported when uranyl peroxide nanoclusters U 60 (Li 48+m K 12 (OH) m [UO 2 (O 2 )(OH)] 60 (H 2 O) n , m≈20 and n≈310) interact with a small number of cationic surfactant molecules. Cationic surfactant molecules do not distribute evenly around the U 60 clusters during the interaction as expected. Instead, a small fraction of U 60 clusters attract almost all the surfactant molecules, leading to the self-assembly into supramolecular structures by using surfactant-U 60 complexes as building locks, and later further aggregate and precipitate based on hydrophobic interaction, whereas the rest of the clusters remained unbounded soluble macroions in bulk dispersion. This phenomenon nicely demonstrates a unique feature of macroion solutions. Considering that Debye-Hückel approximation is no longer valid in such solutions, the competition between the local electrostatic interaction and hydrophobic interaction becomes important to regulate the solution behaviors of macroions., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The Schulze-Hardy rule is a well-established observation in colloid science (can be derived from the DLVO theory) that demonstrates the relationship between the critical coagulation concentration (CCC) of colloids and the valence of extra counterionic electrolytes (z), with a simple mathematical relationship of CCC≈z -6 . Here the Schulze-Hardy Rule is expanded to much smaller, nano-scaled soluble macroions in aqueous solution, by examining the stability of the macroions in the presence of additional electrolytes. The CCC values of the macroions follow the general trend of CCC≈z -n but the n value is significantly dependent on the surface charge density of the macroions, ranging from n=2 at very low surface charge density to n=6 at a high surface charge density. In addition, different cations with the same valence showed clear different impacts on the CCC values, with an interesting trend being connected to the Hofmeister series originally discovered in protein solutions., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A transition between two isomeric clusters involving the change of the main skeleton structure of a well-defined, rigid molecular cluster [(UO 2 ) 24 (O 2 ) 24 (P 2 O 7 ) 12 ] 48- , {U 24 Pp 12 }, is achieved by simply introducing proper alkali cations into its dilute aqueous solution. While the unique structural transition can be triggered by introducing any of the Na + /K + /Rb + /Cs + alkali ions, the two isomers, Li/Na-{U 24 Pp 12 } and Na/K-{U 24 Pp 12 }, as typical macroions, can accurately choose among different alkali counter-cations based on their hydrated sizes, and the ion selectivity process clearly showed endothermic features. The preferred K + and Rb + ions have suitable sizes to be incorporated into the proper windows on {U 24 Pp 12 } nanocapsules, as supported by the transition points in both ITC studies and IR measurements., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The precise guidance to different ions across the biological channels is essential for many biological processes. An artificial nanopore system will facilitate the study of the ion-transport mechanism through nanosized channels and offer new views for designing nanodevices. Herein we reveal that a 2.5 nm-sized, fullerene-shaped molecular cluster Li48+m K12(OH)m [UO2(O2)(OH)]60-(H2O)n (m ≈ 20 and n ≈ 310) (U60) shows selective permeability to different alkali ions. The subnanometer pores on the water-ligand-rich surface of U60 are able to block Rb(+) and Cs(+) ions from passing through, while allowing Na(+) and K(+) ions, which possess larger hydrated sizes, to enter the interior space of U60. An interestingly high entropy gain during the binding process between U60 and alkali ions suggests that the hydration shells of Na(+)/K(+) and U60 are damaged during the interaction. The ion selectivity of U60 is greatly influenced by both the morphologies of the surface nanopores and the dynamics of the hydration shells., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The behavior in dilute solution of phosphate-functionalized γ-cyclodextrin macroanions with eight charges on the rim was explored. The hydrophilic macroions in mixed solvents show strong attraction between each other, mediated by the counterions, and consequently self-assemble into blackberry-type hollow spherical structures. Time-resolved laser light scattering (LLS) measurements at high temperature ruled out the possibility of hydrogen bonding as the main driving force in the self-assembly and indicated the good thermodynamic stability of assemblies regulated by the charge. The transition from single macroions to blackberries can be tuned by adjusting the content of organic solvent. The sizes of blackberries vary with the charge density of γ-cyclodextrin by adjusting pH. It is the first report that pure cyclodextrins can generate supramolecular structures by themselves in dilute solution. The unique solution behavior of macroions provides a new opportunity to assemble cyclodextrin into functional materials and devices., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The solution behavior of the two polyoxo-13-palladates(II) ([Pd(II) 13 As(V) 8 O34 (OH)6 ](8-) and [Pd(II) 13 (As(V) Ph)8 O32 ](6-) ) was studied in detail. We discovered that the countercation-mediated attraction is the driving force for their self-assembly into larger architectures. However, the presence of phenyl groups in the periphery of [Pd(II) 13 (As(V) Ph)8 O32 ](6-) results in an enhanced attraction among these polyanions through hydrophobic interactions, which leads to completely different trends of assembly size for these two very similar clusters when decreasing solvent polarity. An increase of assembly size with increasing solvent polarity was observed for [Pd(II) 13 (As(V) Ph)8 O32 ](6-) , whereas for [Pd(II) 13 As (V) 8 O34 (OH)6 ](8-) it was the opposite, due to the absence of hydrophobic interactions., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)