Naphtali O'Connor

A covalently linked phenanthridine–ruthenium(II) complex as a RNA probe

A phenanthridine derivative covalently linked to a ruthenium complex yields an imaging probe whose fluorescence intensity and lifetime change substantially in the presence of RNA.

Strategies for delivering porphyrinoid-based photosensitizers in therapeutic applications

Delivery strategies for porphyrinoid-based photosensitizers for use in therapeutic applications are based on a myriad of factors, which include porphyrinoid structure, solubility and cellular targets. These drug-delivery methods include encapsulation, hydrogels, protein carriers, nanoparticles and polymeric micelles among others. This article reviews the strategies for delivering porphyrinoids published to date and will focus on porphyrins, corroles, chlorins, bacteriochlorins, porphyrazines and phthalocyanines. Highlighted are the most recent and different strategies used for each of the corresponding porphyrinoid-based macrocycles.

High-Index Immersion Lithography : Preventing Lens Photocontamination and Identifying Optical Behavior of LuAG

A potential extension of water-based 193-nm immersion lithography involves transition to a higher refractive index organic immersion fluid coupled with a higher index last lens element. While considerable progress has been made in improving the photo-durability of the immersion fluid itself, photo-induced contamination of the last lens element caused by laser exposure in the presence of such organic fluids remains a major concern. In this work, we study remediation strategies for such contamination, which would be compatible with conventional lithographic production environments. In general, surface photocontamination layers were found to be highly graphitic in nature, where the first monolayer is strongly bound to the substrate. We have attempted to develop a surface passivation treatment for altering the monolayer chemistry and preventing large-scale contamination, but found such treatments to be unstable under laser irradiation. On the other hand, using hydrogen peroxide as a in-situ cleaning solution has been shown to be extremely effective. We also present first laser-based durability results of LuAG, which is a leading candidate material for high index last element to be used with high index fluids.

Development and Evaluation of a 193nm Immersion Generation-Three Fluid Candidates

The need to extend 193nm immersion lithography necessitates the development of a third generation (Gen-3) of high refractive index (RI) fluids that will enable approximately 1.7 numerical aperture (NA) imaging. A multi-pronged approach was taken to develop these materials. One approach investigated the highest-index organic thus far discovered. The second approach used a very high refractive index nanoparticle to make a nanocomposite fluid. This report will describe the chemistry of the best Gen-3 fluid candidates and the systematic approach to their identification and synthesis. Images obtained with the Gen-3 fluid candidates will also be presented for a NA ≥ 1.7.

Dextran hydrogels by crosslinking with amino acid diamines and their viscoelastic properties

Amine functionalized polysaccharide hydrogels such as those based on chitosan are widely examined as biomaterials. Here we set out to develop a facile procedure for developing such hydrogels by crosslinking dextran with amino acid diamines. The dextran-amino acid gels were formed by the addition of the amino acid diamines to a dextran and epichlorohydrin solution once it became homogeneous. This was demonstrated with three amino acid diamines, lysine, lysine methyl ester, and cystine dimethyl ester. Hydrogel networks with albumin entrapped were also demonstrated. These hydrogels were characterized by FTIR, SEM, rotational rheometry, swelling studies and cell biocompatibility analysis. These hydrogels showed the unexpected pH-responsive behavior of greater swelling at more basic pH, similar to that of an anionic hydrogel. This is uncharacteristic for amine functionalized gels as they typically exhibit cationic hydrogel behavior. All hydrogels showed similar biocompatibility to that of dextran crosslinked without amino acids.