Controlled DNA Patterning by Chemical Lift-Off Lithography: Matrix Matters

Nucleotide arrays require controlled surface densities and minimal nucleotide–substrate interactions to enable highly specific and efficient recognition by corresponding targets. We investigated chemical lift-off lithography with hydroxyl- and oligo(ethylene glycol)-terminated alkanethiol self-assembled monolayers as a means to produce substrates optimized for tethered DNA insertion into post-lift-off regions. Residual alkanethiols in the patterned regions after lift-off lithography enabled the formation of patterned DNA monolayers that favored hybridization with target DNA. Nucleotide densities were tunable by altering surface chemistries and alkanethiol ratios prior to lift-off. Lithography-induced conformational changes in oligo(ethylene glycol)-terminated monolayers hindered nucleotide insertion but could be used to advantage <i>via</i> mixed monolayers or double-lift-off lithography. Compared to thiolated DNA self-assembly alone or with alkanethiol backfilling, preparation of functional nucleotide arrays by chemical lift-off lithography enables superior hybridization efficiency and tunability

Advancing Biocapture Substrates via Chemical Lift-Off Lithography

Creating small-molecule-functionalized platforms for high-throughput screening or biosensing applications requires precise placement of probes on solid substrates and the ability to capture and to sort targets from multicomponent samples. Here, chemical lift-off lithography was used to fabricate large-area, high-fidelity patterns of small-molecule probes. Lift-off lithography enables biotin–streptavidin patterned recognition with feature sizes ranging from micrometers to below 30 nm. Subtractive patterning via lift-off facilitated insertion of a different type of molecule and, thus, multiplexed side-by-side placement of small-molecule probes such that binding partners were directed to cognate probes from solution. Small molecules mimicking endogenous neurotransmitters were patterned using lift-off lithography to capture native membrane-associated receptors. We characterized patterning of alkanethiols that self-assemble on Au having different terminal functional groups to expand the library of molecules amenable to lift-off lithography enabling a wide range of functionalization chemistries for use with this simple and versatile patterning method

Na₂Ti₃O₇ Nanoplatelets and Nanosheets Derived from a Modified Exfoliation Process for Use as a High-Capacity Sodium-Ion Negative Electrode

The increasing interest in Na-ion batteries (NIBs) can be traced to sodium abundance, its low cost compared to lithium, and its intercalation chemistry being similar to that of lithium. We report that the electrochemical properties of a promising negative electrode material, Na₂Ti₃O₇, are improved by exfoliating its layered structure and forming 2D nanoscale morphologies, nanoplatelets, and nanosheets. Exfoliation of Na₂Ti₃O₇ was carried out by controlling the amount of proton exchange for Na⁺ and then proceeding with the intercalation of larger cations such as methylammonium and propylammonium. An optimized mixture of nanoplatelets and nanosheets exhibited the best electrochemical performance in terms of high capacities in the range of 100–150 mA h g^–1 at high rates with stable cycling over several hundred cycles. These properties far exceed those of the corresponding bulk material, which is characterized by slow charge-storage kinetics and poor long-term stability. The results reported in this study demonstrate that charge-storage processes directed at 2D morphologies of surfaces and few layers of sheets are an exciting direction for improving the energy and power density of electrode materials for NIBs

Defect-Tolerant Aligned Dipoles within Two-Dimensional Plastic Lattices

Carboranethiol molecules self-assemble into upright molecular monolayers on Au{111} with aligned dipoles in two dimensions. The positions and offsets of each molecule’s geometric apex and local dipole moment are measured and correlated with sub-Ångström precision. Juxtaposing simultaneously acquired images, we observe monodirectional offsets between the molecular apexes and dipole extrema. We determine dipole orientations using efficient new image analysis techniques and find aligned dipoles to be highly defect tolerant, crossing molecular domain boundaries and substrate step edges. The alignment observed, consistent with Monte Carlo simulations, forms through favorable intermolecular dipole–dipole interactions