Understanding the stability of zeolitic imidazolate framework-8 (ZIF-8) under physiological conditions is critical in biotechnology and biomedicine for biosensing, biocatalysis, and drug delivery.

The tribological properties of poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG)-coated oxide interfaces have been investigated with atomic force microscopy (AFM) as a function of the molecular structure. Polymer-bearing surfaces were obtained via spontaneous adsorption of the polymer onto the oxide substrate from a buffered solution of physiological pH. Interfacial friction of these PLL-g-PEG-coated surfaces was found to be highly dependent on the duration of deposition and the architecture of PLL-g-PEG. In terms of the architecture, the PEG chain length and the grafting ratio (i.e., the molar ratio of L-lysine monomer to PEG side chain) of adsorbed PLL-g-PEG significantly influence the interfacial friction; specifically, friction is reduced as the PEG chain length increases and as the molar ratio of L-lysine monomer to PEG side chain decreases. The characteristics of the polymer deposition time and the influence of the lysine/PEG grafting ratio are rationalized in terms of spatial packing density considerations.

γ-Graphyne is the most symmetric sp 2 /sp 1 allotrope of carbon, which can be viewed as graphene uniformly expanded through the insertion of two-carbon acetylenic units between all the aromatic rings. To date, synthesis of bulk γ-graphyne has remained a challenge. We here report the synthesis of multilayer γ-graphyne through crystallization-assisted irreversible cross-coupling polymerization. A comprehensive characterization of this new carbon phase is described, including synchrotron powder X-ray diffraction, electron diffraction, lateral force microscopy, Raman spectroscopy, infrared spectroscopy, and cyclic voltammetry. Experiments indicate that γ-graphyne is a 0.48 eV band gap semiconductor, with a hexagonal a-axis spacing of 6.88 Å and an interlayer spacing of 3.48 Å, which is consistent with theoretical predictions. The observed crystal structure has an aperiodic sheet stacking. The material is thermally stable up to 240 °C but undergoes transformation at higher temperatures. While conventional 2D polymerization and reticular chemistry rely on error correction through reversibility, we demonstrate that a periodic covalent lattice can be synthesized under purely kinetic control. The reported methodology is scalable and inspires extension to other allotropes of the graphyne family.

Aniline-catalyzed hydrazone ligation between surface immobilized hydrazines and aldehyde-modified antibodies is shown to be an efficient method for attaching protein capture agents to model oxide-coated biosensor substrates. Silicon photonic microring resonators are used to directly evaluate the efficiency of this surface bioconjugate reaction at various pHs and in the presence or absence of aniline as a nucleophilic catalyst. It is found that aniline significantly increases the net antibody loading for surfaces functionalized over a pH range from 4.5 to 7.4, allowing derivatization of substrates with reduced incubation time and sample consumption. This increase in antibody loading directly results in more sensitive antigen detection when functionalized microrings are employed in a label-free immunoassay. Furthermore, these experiments also reveal an interesting pH dependent non-covalent binding trend that plays an important role in dictating the amount of antibody attached onto the substrate, highlighting the competing contributions of the bioconjugate reaction rate and the dynamic interactions that control opportunities for a solution-phase biomolecule to react with a substrate-bound reagent.