Fabrication of Nanopatterned Poly(ethylene glycol) Brushes by Molecular Transfer Printing from Poly(styrene-block-methyl methacrylate) Films to Generate Arrays of Au Nanoparticles

This article presents a soft lithographic approach using block copolymer (BCP) films to fabricate functional chemically patterned polymer brushes on the nanoscale. Hydroxyl-terminated poly(ethylene glycol) (PEG-OH) was transfer printed from the poly(methyl methacrylate) (PMMA) domains of self-assembled poly(styrene-block-methyl methacrylate) films to a substrate in conformal contact with the film to generate patterned PEG brushes mirroring the pattern of BCP domains. A key point in the study is that the chemistry of the functional transferred brushes is different from the chemistry of either block of the copolymer; PEG-OH is miscible only in the PMMA block and therefore transferred only from PMMA domains. The functionality of the PEG brushes was demonstrated by the selective immobilization of citrate-stabilized Au NPs (15 nm) and validated the generation of high-quality chemical patterns with sub-30-nm feature sizes

Superhydrophobic coatings made from biocompatible polydimethylsiloxane and natural wax

There is a strong need for mechanically robust superhydrophobic coatings that can be manufactured from ecofriendly and sustainable materials for a broad portfolio of applications. Here, we report the preparation of a composite suspension coating from biocompatible carnauba wax and polydimethylsiloxane, and demonstrate its superhydrophobicity and resistance to water impact. The superhydrophobicity and mechanical stability of the coated surfaces can be controlled by adjusting the concentrations of constituent materials. The composite suspension can be easily drop cast or spray-coated on common materials, such as glass and paper, wherein the coated surface exhibits excellent superhydrophobicity and self-cleaning property. Glass substrates spray-coated with the composite suspension demonstrate high levels of resistance against water impact, retaining superhydrophobicity even after the impact of 250,000 water droplets

Polymer nanofilm mediated photo-assisted growth of gold nanostructures for sensing of drugs

The growing interest in sensing systems based on surface-enhanced Raman scattering (SERS) motivates the development of versatile and eco-friendly methods for the fabrication of nanostructured metallic surfaces. In this study, we report photo-assisted growth of Au nanostructures (NSs) on a similar to 7 nm thick film that consists of endgrafted poly(2-vinyl pyridine). The nanofilm plays a key role in the photo-assisted growth of Au NSs with high SERS activity. The structure, crystallinity, and morphology of Au NSs were probed by different analytical techniques. The limit of detection under laser excitation of 532 nm for rhodamine 6 G was 10 nM with an enhancement factor of 6.4 x 10(5). The sensing of tamoxifen and sulfamethazine drugs was further performed on the Au NSs, showing the application potential of the presented SERS platform

Transferrable SERS Barcodes

The demand for encoded surfaces has increased significantly over the past decade driven by the rapid digitalization of the world. Surface-enhanced Raman scattering (SERS) offers unique capabilities in generation of encoded surfaces. The challenge is the limited versatility of SERS-based encoding systems in terms of the applicable surfaces. This study addresses this challenge by using a temporary tattoo approach together with simplified fabrication of SERS-active patterns by ink-jet printing of a particle-free reactive silver ink. Plasmonic silver nanostructures form on the tattoo paper upon ink-jet printing and a brief thermal annealing. The SERS activity is sufficient to detect taggant molecules of rhodamine 6G, methylene blue, and rhodamine B with a nanomolar level sensitivity. Raman-active taggants can be incorporated into the ink, for drop-on-demand patterning of multiple molecules in 1D and 2D barcode geometries. The SERS barcodes can be effectively transferred to a range of different substrates retaining high plasmonic activity and geometric integrity. The presented approach decouples the SERS-active pattern preparation from the final substrate and greatly improves the versatility of the barcodes

Highly Selective Immobilization of Au Nanoparticles onto Isolated and Dense Nanopatterns of Poly(2-viinyl pyridine) Brushes down to Single-Particle Resolution

Chemical patterns consisting of poly(2-vinyl pyridine) (P2VP) brushes in a background of a cross-linked polystyrene (PS) mat enabled the highly selective placement of citrate-stabilized Au nanoparticles (NPs) in arrays on surfaces. The cross-linked PS mat prevented the nonspecific binding of Au NPs, and the regions functionalized with P2VP brushes allowed the immobilization of the particles. Isolated chemical patterns of feature sizes from hundreds to tens of nanometers were prepared by standard lithographic techniques. The number of 13 nm Au NPs bound per feature increased linearly with increasing area of the patterns. This behavior is similar to previous reports using 40 nm particles or larger. Arrays of single NPs were obtained by reducing the dimensions of patterned P2VP brushes to below 20 nm. To generate dense (center-to-center distance = 80 nm) linear chemical patterns for the placement of rows of single NPs, a block-copolymer (BCP)assisted lithographic process was used. BCPs healed defects associated with the standard lithographic patterning of small dimensions at high densities and led to highly registered, linear, single NP arrays

Localization of Multiple DNA Sequences on Nanopatterns

DNA oligonucleotides of different sequences were patterned at the nanoscale. Areas of positive charge were generated by exposure of Insulating substrates, spin-on hydrogen silsesquioxane or vapor-deposited SiO2 on 51, with ionizing radiation sources used In electron beam and extreme ultraviolet lithography. Au nanoparticles (NPs) with a diameter of 15 nm, carrying covalently bound negatively charged single-stranded DNA Oligonucleotides, were site specifically immobilized directly on the exposed regions and presented oligonucleotides for subsequent hybridization. Repeated exposure and deposition of NPs allowed for patterning multiple DNA sequences. Patterns with dimensions as small as 15 nm were fabricated using electron beam lithography. The use of DNA-functionalized NPs rather than Just DNA facilitates metrology in scanning electron microscopy and Improves the hybridization efficiency of the oligonucleotides on the surface

Chemical Funneling of Colloidal Gold Nanoparticles on Printed Arrays of End-Grafted Polymers for Plasmonic Applications

Spatially defined assembly of colloidal metallic nanoparticles is necessary for fabrication of plasmonic devices. In this study, we demonstrate high-resolution additive jet printing of end-functional polymers to serve as templates for directed self-assembly of nanoparticles into architectures with substantial plasmonic activity. The intriguing aspect of this work is the ability to form patterns of end-grafted poly(ethylene glycol) through printing on a hydrophobic layer that consists of fluoroalkylsilanes. The simultaneous dewetting of the underlying hydrophobic layer together with grafting of the printed polymer during thermal annealing enables fabrication of spatially defined binding sites for assembly of nanoparticles. The employment of electrohydrodynamic jet printing and aqueous inks together with reduction of the feature size during thermal annealing are critically important in achieving high chemical contrast patterns as small as similar to 250 nm. Gold nanospheres of varying diameters selectively bind and assemble into nanostructures with reduced interparticle distances on the hydrophilic patterns of poly(ethylene glycol) surrounded with a hydrophobic background. The resulting plasmonic arrays exhibit intense and pattern-specific signals in surface-enhanced Raman scattering (SERS) spectroscopy. The localized seed-mediated growth of metallic nanostructures over the patterned gold nanospheres presents further routes for expanding the composition of the plasmonic arrays. A representative application in SERS-based surface encoding is demonstrated through large-area patterning of plasmonic structures and multiplex deposition of taggant molecules, all enabled by printing

Disintegration and Machine-Learning-Assisted Identification of Bacteria on Antimicrobial and Plasmonic Ag-CuxO Nanostructures

Bacteria cause many common infections and are the culprit of many outbreaks throughout history that have led to the loss of millions of lives. Contamination of inanimate surfaces in clinics, the food chain, and the environment poses a significant threat to humanity, with the increase in antimicrobial resistance exacerbating the issue. Two key strategies to address this issue are antibacterial coatings and effective detection of bacterial contamination. In this study, we present the formation of antimicrobial and plasmonic surfaces based on Ag-CuxO nanostructures using green synthesis methods and low-cost paper substrates. The fabricated nanostructured surfaces exhibit excellent bactericidal efficiency and high surface-enhanced Raman scattering (SERS) activity. The CuxO ensures outstanding and rapid antibacterial activity within 30 min, with a rate of >99.99% against typical Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. The plasmonic Ag nanoparticles facilitate the electromagnetic enhancement of Raman scattering and enables rapid, label-free, and sensitive identification of bacteria at a concentration as low as 103 cfu/mL. The detection of different strains at this low concentration is attributed to the leaching of the intracellular components of the bacteria caused by the nanostructures. Additionally, SERS is coupled with machine learning algorithms for the automated identification of bacteria with an accuracy that exceeds 96%. The proposed strategy achieves effective prevention of bacterial contamination and accurate identification of the bacteria on the same material platform by using sustainable and low-cost materials

Sustainable and Practical Superhydrophobic Surfaces via Mechanochemical Grafting

Abstract The broad adoption of superhydrophobic surfaces in practical applications is hindered by limitations of existing methods in terms of excessive usage of solvents, the need for tedious and lengthy chemical processes, insufficient biocompatibility, and the high cost of materials. Herein, a mechanochemical approach for practical and solvent‐free manufacturing of superhydrophobic surfaces is reported. This approach enables solvent‐free and ultra‐rapid preparation of superhydrophobic surfaces in a single‐step without the need for any washing, separation, and drying steps. The hydrolytic rupture of siloxane bonds and generation of free radicals induced by mechanochemical pathways play a key role in covalent grafting of silicone to the surface of nanoparticles that leads to superhydrophobic surfaces with a water contact angle of >165° and a sliding angle of <2°. The direct use of industrially available and non‐functional silicone materials together with demonstrated applicability to inorganic nanoparticles of varied composition greatly contribute to the scalability of the presented approach. The resulting superhydrophobic surfaces are highly biocompatible as demonstrated by fibroblast cells using two different assays. Monolith materials fabricated from silicone‐grafted nanoparticles exhibit bulk and durable superhydrophobicity. The presented approach offers tremendous potential with sustainability, scalability, cost‐effectiveness, simplicity, biocompatibility, and universality