Fatih Buyukserin

Imprinted large-scale high density polymer nanopillars for organic solar cells

Nanoimprint with a large-scale nanoporous Si mold is developed to fabricate high density periodic nanopillars (∼1010∕cm2) in various functional polymers. A anodic alumina membrane is first obtained using electrochemical anodization. The membrane is used as a mask for a two-step plasma etching process to obtain a Si mold of 50–80nm wide and 100–900nm deep pores. The mold is used in nanoimprint lithography to fabricate ordered and high density polymer nanopillars and nanopores in SU-8, hydrogen silsesquixane, polymethylmethacrylate, poly(3-hexylthiophane) (P3HT), and phenyl-C61-butyric acid methyl ester (PCBM). Then, the imprinted P3HT nanopillars were used to make bulk heterojunction solar cells by depositing PCBM on top of the pillars. Imprinting provides a way to precisely control the interdigitized heterojunction morphology, leading to improved solar cell performance.

Size controlled synthesis of sub-100 nm monodisperse poly(methylmethacrylate) nanoparticles using surfactant-free emulsion polymerization.

Surfactant-free emulsion polymerization (SFEP) is a well-known technique for the production of polymeric nanoparticles that does not require post-synthetic cleaning steps. Obtaining hydrophobic particles at sub-100 nm scale, however, is quite challenging with this polymerization method. Here, we demonstrate a single step synthetic approach that yields poly(methylmethacrylate) (PMMA) nanoparticles with controlled sub-100 nm size and relatively high resultant solid content. Dynamic light scattering (DLS) was used for the particle characterization. Spherical and uniformly sized nanoparticles were confirmed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Acetone was used as a cosolvent in order to obtain monodisperse sub-100 nm diameter particles. Stable PMMA nanoparticle dispersions were obtained for all formulations where the persulfate initiator causes the negative charges on the particle surface. The effects of acetone, monomer and initiator concentration were studied to optimize average particle hydrodynamic diameter and polydispersity index of the final particles. Non-crosslinked monodisperse PMMA nanoparticles (polydispersity index less than 0.05) with diameters from 32 nm to 72 nm were synthesized by using this method.

Fabrication of Polymeric Nanorods Using Bilayer Nanoimprint Lithography

Polymeric nanoparticles are becoming increasingly important in a variety of biological applications, such as biomolecular sensing, diagnostic imaging, and therapeutic drug delivery. For these applications, the mass production of multifunctional nanocomposite materials with precise control of particle size, shape, and composition is a significant challenge. For instance, the use of conventional bottom-up strategies (e.g., emulsion polymerization) to fabricate polymeric nanostructures with nonspherical geometry and a uniform size distribution is difficult because these methods are typically driven by the minimization of interfacial free energy that yields spherical particles with a size variation. Moreover, the formation of nanocomposite materials is difficult due to the challenge in assembling multiple components from large volume fractions of solvent. On the other hand, in the field of microelectronics, polymers as resist can be precisely patterned to have arbitrary shapes using state-of-the-art photo-, e-beam, and X-ray lithographic technologies. They are limited either by high cost, poor accessibility, slow speed, or radiation damage to functional polymers. In the past decade, many lowcost nanopatterning techniques have been invented to pattern polymer structures, such as nanoimprint lithography (NIL) and soft lithography, among many others. These methods are capable of making nanostructures of desired shape and size. However, it is not straightforward to produce large quantities of biofunctional nanoparticles using them. Most of these nanopatterning approaches, either imprinting or soft lithography, result in a residual layer that connects the periodic structures on a surface. Furthermore, they are limited

Resistive-pulse detection of short dsDNAs using a chemically functionalized conical nanopore sensor

AIMS To develop nanopore resistive-pulse sensors for the detection of short (50 base-pair [bp] and 100 bp) DNAs. MATERIALS & METHODS Conically shaped nanopores were chemical etched into polyethylene terphthalate membranes. The as-etched membrane had anionic carboxylate sites on the pore walls. Neutral and hydrophilic ethanolamine functional groups were attached to these carboxylate sites using well-established EDC (1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride) chemistry. RESULTS & DISCUSSION The ethanolamine-functionalized pores were used to detect 50 and 100 bp DNAs via the resistive-pulse method. The resistive-pulse signature produced by the 50 bp DNA could be distinguished from that of the 100 bp DNA with these sensors. CONCLUSIONS Attachment of ethanolamine to the carboxylate groups on the pore wall lowered the anionic charge density on the wall. This mitigated the problem of electrostatic rejection of the anionic DNAs from the pore and enabled the detection of these DNA analytes.

Antibody-functionalized nano test tubes target breast cancer cells

AIM To develop nano test tubes that will deliver a biomedical payload to a specific cell type. METHODS The template-synthesis method was used to prepare silica nano test tubes. An antibody that is specific for breast cancer cells was attached to the outer tube surfaces. A fluorophore was attached to the inner surfaces of the nano test tubes. The tubes were incubated with the breast cancer cells and the extent of attachment to the cell surfaces was investigated by fluorescence microscopy. RESULTS Tubes modified on their outer surfaces with the target antibody showed enhanced attachment to breast-cancer cells, relative to tubes modified on their outer surfaces with a species and isotype-matched control antibody. CONCLUSIONS This work is a first step toward demonstrating that nano test tubes can be used as cell-specific delivery vehicles.

Novel antifouling oligo(ethylene glycol) methacrylate particles via surfactant-free emulsion polymerization.

The use of particle formulations with antifouling surface properties attracts increasing interest in several biotechnological applications. Majority of these studies utilize a poly(ethylene glycol) coating to render the corresponding surface nonrecognizable to biological macromolecules. Herein, we report a simple way to prepare novel antifouling colloids composed of oligo(ethylene glycol) backbones via surfactant-free emulsion polymerization. Monodisperse cross-linked poly(ethylene glycol) ethyl ether methacrylate particles were characterized by dynamic light scattering and transmission electron microscopy. The effects of monomer, cross-linker and initiator on particle characteristics were investigated. More importantly, a prominent blockage of bovine serum albumin adsorption was obtained for the poly(ethylene glycol)-based sub-micron (~200 nm) particles when compared with similar-sized poly(methyl methacrylate) counterparts.

Fabrication and modification of composite silica nano test tubes for targeted drug delivery

This work describes the use of template synthesis to fabricate multifunctional composite silica nano test tubes for targeted drug delivery. The tubular nanostructures were formed within nanoporous anodized alumina templates and their inner voids were filled with a drug-bearing gel matrix while the test tubes were embedded within the template. Upon template removal, the composite nanocarriers were biofunctionalized with a targeting moiety towards breast cancer cells. The results show that targeting is critical in inducing cell death and the targeted nanocarriers are extensively more cytotoxic towards cancer cells compared with healthy controls.