Massively Parallel Patterning of Complex 2D and 3D Functional Polymer Brushes by Polymer Pen Lithography

We report the first demonstration of centimeter-area serial patterning of complex 2D and 3D functional polymer brushes by high-throughput polymer pen lithography. Arbitrary 2D and 3D structures of poly­(glycidyl methacrylate) (PGMA) brushes are fabricated over areas as large as 2 cm × 1 cm, with a remarkable throughput being 3 orders of magnitudes higher than the state-of-the-arts. Patterned PGMA brushes are further employed as resist for fabricating Au micro/nanostructures and hard molds for the subsequent replica molding of soft stamps. On the other hand, these 2D and 3D PGMA brushes are also utilized as robust and versatile platforms for the immobilization of bioactive molecules to form 2D and 3D patterned DNA oligonucleotide and protein chips. Therefore, this low-cost, yet high-throughput “bench-top” serial fabrication method can be readily applied to a wide range of fields including micro/nanofabrication, optics and electronics, smart surfaces, and biorelated studies

The methylation profile of the long CpG island in the b<i>Boule</i> 5' flanking region.

<p>(A) Schematic diagram of the long CGI within the b<i>Boule</i> promoter. (B) Schematic depiction of the CpG sites for methylation analysis. Nucleotide numbering is relative to +1 at the initiating ATG codon. The short vertical bars represent the CpG dinucleotides. (C) Methylation status of the b<i>Boule</i> promoter in the testes of cattle and cattle-yak hybrids. Each line represents an individual bacterial clone that was sequenced. Open circles indicate unmethylated CpG sites. Black circles indicate methylated CpG sites.</p

<i>In vitro</i> methylation assay of the b<i>Boule</i> promoter.

<p>The b<i>Boule</i> core promoter construct pbBoule-107 was treated with M.SssI methylase, and then methylated (mpbBoule-107) or unmethylated (pbBoule-107) plasmids were transiently transfected into GC-1 and COS-7 cell lines. Normalized luciferase activities are expressed as mean ± SEM of at least three independent experiments. The bar above the histogram indicates the SEM. ^** indicate a significant difference (P < 0.01).</p

The predicated TFBS of differentially methylated CpG sites within the b<i>Boule</i> promoter.

<p>Arrows indicate differentially methylated CpG sites. The TFBS is underlined.</p

mRNA expression of b<i>Boule</i> in BMECs treated with 5-Aza-dC.

<p>mRNA expression was detected in treated cells but not in untreated cells by qRT-PCR. All experiments were performed three times. The bar above the histogram indicates the SEM. Different uppercase letters denote significant differences between different groups with a significance level of P < 0.01. Different lowercase letters denote significant differences between different groups with a significance level of P < 0.05.</p

The methylation profile of the short CpG island in the b<i>Boule</i> gene body.

<p>(A) Schematic diagram of the short CGI within the b<i>Boule</i> gene body. (B) Schematic depiction of the CpG sites for methylation analysis. Nucleotide numbering is relative to +1 at the initiating ATG codon. The short vertical bars represent the CpG dinucleotides. (C) Methylation statuses of b<i>Boule</i> in testes of cattle and cattle-yak hybrids. Each line represents an individual bacterial clone that was sequenced. Open circles indicate unmethylated CpG sites. Black circles indicate methylated CpG sites.</p

Identification of the core promoter in the b<i>Boule</i> gene.

<p>Left panel, functional deletion constructs of the b<i>Boule</i> 5' flanking region. Right panel, the luciferase activity of each deletion construct of the b<i>Boule</i> 5' flanking region. The deletion constructs were transiently transfected into GC-1 and COS-7 cell lines. Normalized luciferase activities are expressed as mean ± SEM of duplicates for a minimum of three experiments. All data were compared with the control group (pGL3-basic). ^** indicates a significant difference (P < 0.01).</p

Windowless Observation of Evaporation-Induced Coarsening of Au–Pt Nanoparticles in Polymer Nanoreactors

The interactions between nanoparticles and solvents play a critical role in the formation of complex, metastable nanostructures. However, direct observation of such interactions with high spatial and temporal resolution is challenging with conventional liquid-cell transmission electron microscopy (TEM) experiments. Here, a windowless system consisting of polymer nanoreactors deposited via scanning probe block copolymer lithography (SPBCL) on an amorphous carbon film is used to investigate the coarsening of ultrafine (1–3 nm) Au–Pt bimetallic nanoparticles as a function of solvent evaporation. In such reactors, homogeneous Au–Pt nanoparticles are synthesized from metal-ion precursors in situ under electron irradiation. The nonuniform evaporation of the thin polymer film not only concentrates the nanoparticles but also accelerates the coalescence kinetics at the receding polymer edges. Qualitative analysis of the particle forces influencing coalescence suggests that capillary dragging by the polymer edges plays a significant role in accelerating this process. Taken together, this work (1) provides fundamental insight into the role of solvents in the chemistry and coarsening behavior of nanoparticles during the synthesis of polyelemental nanostructures, (2) provides insight into how particles form via the SPBCL process, and (3) shows how SPBCL-generated domes, instead of liquid cells, can be used to study nanoparticle formation. More generally, it shows why conventional models of particle coarsening, which do not take into account solvent evaporation, cannot be used to describe what is occurring in thin film, liquid-based syntheses of nanostructures

Windowless Observation of Evaporation-Induced Coarsening of Au–Pt Nanoparticles in Polymer Nanoreactors

The interactions between nanoparticles and solvents play a critical role in the formation of complex, metastable nanostructures. However, direct observation of such interactions with high spatial and temporal resolution is challenging with conventional liquid-cell transmission electron microscopy (TEM) experiments. Here, a windowless system consisting of polymer nanoreactors deposited via scanning probe block copolymer lithography (SPBCL) on an amorphous carbon film is used to investigate the coarsening of ultrafine (1–3 nm) Au–Pt bimetallic nanoparticles as a function of solvent evaporation. In such reactors, homogeneous Au–Pt nanoparticles are synthesized from metal-ion precursors in situ under electron irradiation. The nonuniform evaporation of the thin polymer film not only concentrates the nanoparticles but also accelerates the coalescence kinetics at the receding polymer edges. Qualitative analysis of the particle forces influencing coalescence suggests that capillary dragging by the polymer edges plays a significant role in accelerating this process. Taken together, this work (1) provides fundamental insight into the role of solvents in the chemistry and coarsening behavior of nanoparticles during the synthesis of polyelemental nanostructures, (2) provides insight into how particles form via the SPBCL process, and (3) shows how SPBCL-generated domes, instead of liquid cells, can be used to study nanoparticle formation. More generally, it shows why conventional models of particle coarsening, which do not take into account solvent evaporation, cannot be used to describe what is occurring in thin film, liquid-based syntheses of nanostructures

Windowless Observation of Evaporation-Induced Coarsening of Au–Pt Nanoparticles in Polymer Nanoreactors

The interactions between nanoparticles and solvents play a critical role in the formation of complex, metastable nanostructures. However, direct observation of such interactions with high spatial and temporal resolution is challenging with conventional liquid-cell transmission electron microscopy (TEM) experiments. Here, a windowless system consisting of polymer nanoreactors deposited via scanning probe block copolymer lithography (SPBCL) on an amorphous carbon film is used to investigate the coarsening of ultrafine (1–3 nm) Au–Pt bimetallic nanoparticles as a function of solvent evaporation. In such reactors, homogeneous Au–Pt nanoparticles are synthesized from metal-ion precursors in situ under electron irradiation. The nonuniform evaporation of the thin polymer film not only concentrates the nanoparticles but also accelerates the coalescence kinetics at the receding polymer edges. Qualitative analysis of the particle forces influencing coalescence suggests that capillary dragging by the polymer edges plays a significant role in accelerating this process. Taken together, this work (1) provides fundamental insight into the role of solvents in the chemistry and coarsening behavior of nanoparticles during the synthesis of polyelemental nanostructures, (2) provides insight into how particles form via the SPBCL process, and (3) shows how SPBCL-generated domes, instead of liquid cells, can be used to study nanoparticle formation. More generally, it shows why conventional models of particle coarsening, which do not take into account solvent evaporation, cannot be used to describe what is occurring in thin film, liquid-based syntheses of nanostructures