Stepwise Molding, Etching, and Imprinting to Form Libraries of Nanopatterned Substrates

Herein, we describe a novel colloidal lithographic strategy for the stepwise patterning of planar substrates with numerous complex and unique designs. In conjunction with colloidal self-assembly, imprint molding, and capillary force lithography, reactive ion etching was used to create complex libraries of nanoscale features. This combinatorial strategy affords the ability to develop an exponentially increasing number of two-dimensional nanoscale patterns with each sequential step in the process. Specifically, dots, triangles, circles, and lines could be assembled on the surface separately and in combination with each other. Numerous architectures are obtained for the first time with high uniformity and reproducibility. These hexagonal arrays were made from polystyrene and gold features, whereby each surface element could be tuned from the micrometer size scale down to line widths of ∼35 nm. The patterned area could be 1 cm² or even larger. The techniques described herein can be combined with further steps to make even larger libraries. Moreover, these polymer and metal features may prove useful in optical, sensing, and electronic applications

Tunable Micro/Nanomaterial Encapsulation in Porous Melamine Sponges by Rotational Vortexing: Implications for Functional Nanomaterial Recycling

A fully tunable encapsulation of functional micro/nanomaterials inside three-dimensional (3D) porous structures by the unique rotational vortexing operation is reported. The constantly swirling liquid flow through a porous matrix induces efficient particle stacking onto the supporting substrate fiber surface via van der Waals interaction. Homogeneous or gradient distributions of functional nanomaterials inside porous structure are achievable, depending on the relative dimensions between filling material and matrix pore size, while the vortexing duration and precursor concentration affect the total captured particle quantity. This unique stereo control over particle packing relies on gradient accumulations of colloidal particles from the exterior edge to the center by three pairs of directional filtration from two opposite faces of a cubic sponge. This material filling approach overcomes conventional obstacles such as process complexity, expensive equipment necessity, and material distribution uncertainty, which should inspire the development of filling technology for diverse stereo-architecture-related applications

Multicolor Functional Carbon Dots via One-Step Refluxing Synthesis

Carbon dots are admirable fluorescent nanomaterials due to their low cost, high photostability, excellent biocompatibility, and environmental friendliness. Most conventional carbon dot fabrication approaches produce single-colored fluorescent material in the preparation process; different methods are therefore required to synthesize distinct carbon dots for specific optical applications. In this study, carbon dots carrying different emission colors are prepared through a one-step refluxing process. The emission of these materials can be well-tuned by sodium hydroxide content in the precursor solution. The carbon dots produced are used as sensing probes based on the spectrofluorometric inner filter effect for target molecule detection. Three sensing categories that combine carbon dots and inner filter effect are demonstrated, including direct, metal nanoparticle-assisted, and enzymatic reaction-supported detection. Caffeine, melamine, and fenitrothion are selected as targets to demonstrate the strategies, respectively. These multifunctional carbon dot-based sensors achieve comparable sensitivity toward analytes with a much more convenient preparation route

Small-Molecule Arrays for Sorting G‑Protein-Coupled Receptors

Precise self-assembled monolayer chemistries and microfluidic technology are combined to create small-molecule biorecognition arrays. Small-molecule neurotransmitters or precursors are spatially encoded on monolayer-modified substrates. This platform enables multiplexed screening of G-protein-coupled receptors (GPCRs) from complex media via protein–ligand interactions. Preserving access to all epitopes of small molecules is critical for GPCR recognition. The ability to address multiple small molecules on solid substrates and to sort protein mixtures based on specific affinities is a critical step in creating biochips for proteomic applications

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