Precisely tailoring surface chemistry of layered materials is a growing need for fields ranging from electronics to biology. For many applications, the need for noncovalently adsorbed ligands to simultaneously control interactions with a nonpolar substrate and a polar solvent is a particular challenge. However, biology routinely addresses a similar challenge in the context of the lipid bilayer. While conventional standing phases of phospholipids (such as those found in a bilayer) would not provide spatially ordered interactions with the substrate, here we demonstrate formation of a sitting phase of polymerizable phospholipids, in which the two alkyl chains extend along the surface and the two ionizable functionalities (a phosphate and an amine) sit adjacent to the substrate and project into the solvent, respectively. Interfacial ordering and polymerization are assessed by high-resolution scanning probe measurements. Water contact angle titrations demonstrate interfacial pKa shifts for the lipid phosphate but not for the amine, supporting localization of the phosphate near the nonpolar graphite surface.

Innovative solid-phase sorbent technologies are needed to extract radionuclides from harsh media for environmental remediation and in order to close the nuclear fuel cycle. Highly porous inorganic materials with remarkable sorptive properties have been prepared by topotactic transformations of metal–organic frameworks (MOFs) using both basic and acidic solutions. Treatment of Ti and Zr nanoMOFs with NaOH, Na3PO4, and H3PO4 yields Ti and Zr oxides, oxyphosphates, and phosphates via sacrificial removal of the organic ligands. This controlled ligand extraction process results in porous inorganic materials, which preserve the original MOF morphologies and impart useful surface functionalities, but are devoid of organic linkers. Structural investigation by X-ray absorption spectroscopy reveals preservation of the coordination environment of the scattering metal. Changing the MOF template introduces different metal and structural possibilities, while application of different digest solutions allows preparation of metal oxides, metal oxyphosphates, and metal phosphates. The high stability and porosity of these novel materials makes them ideally suited as nanosorbents in severe environments. Their potential for several radionuclide separations is demonstrated, including decontamination of high level nuclear waste, extraction of lanthanides, and remediation of radionuclide-contaminated seawater.

Nanoscale coordination polymers (NCPs) containing a Pt(IV) cisplatin prodrug, disuccinatocisplatin, were formed by a surfactant-templated synthesis and were shown to have a prodrug loading of 8.2 wt% and a diameter of ~133 nm by dynamic light scattering. These NCPs were stabilized by coating with a DOPC/cholesterol/DSPE-Peg2K lipid layer; a release profile in phosphate buffered saline showed an initial drug release of ~25% within the first hour and no more release observed up to 192 h. The NCP was rendered target-specific for sigma receptors by addition of an AA-DSPE-Peg2K conjugate (AA = anisamide) in the lipid formulation. The AA-containing NCP showed a statistically significant decrease in IC50 (inhibitory concentration, 50%) compared to the non-targeted NCP. Enhanced uptake of the AA-containing NCP was further supported by confocal microscopy and competitive binding assays.

Orienting anisotropic nanostructures at interfaces during bottom-up device fabrication is a significant challenge. However, biology routinely orients complex nanostructures at cell surfaces, in part based on collective interactions with flexible phospholipid headgroups having large dipoles. We show that phospholipid striped phases, which expose polar heads and nonpolar tails in alternating stripes with pitches of 7 nm, order and orient gold nanowires with diameters < 2 nm and lengths of 1 mm. Assembly of the wires from nonpolar solvent is correlated with the presence of nanometer-wide water channels surrounding the phospholipid headgroups, suggesting that the minimal polar environments are important in regulating processes in the nonpolar surroundings.

Integrating functionalized 2D materials into multilayer device architectures increasingly requires understanding the behavior of noncovalently adsorbed ligands during solution processing. Here, we demonstrate that the headgroup dynamics of polymerized monolayers of functional alkanes can be controlled to modify surface wetting and environmental interactions. We find that headgroup dynamics are sensitive to the position of the polymerizable diyne group; thus, the polymerization process, typically used to stabilize the noncovalent monolayer, can also be used to selectively destabilize chain-chain interactions near the headgroups, making the headgroups more solvent-accessible and increasing surface hydrophilicity. Conversely, interactions with divalent ions can be used to tether headgroups in-plane, decreasing surface hydrophilicity. Together, these results suggest a strategy for the rational design of 2D chemical interfaces in which the polymerization step reconfigures the monolayer to promote the desired environmental interactions.