Method Developed for Producing Chitosan Nanoparticles Using Nanoporous Membranes
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fibers compared to the nanoparticle films. As a result, transport of photoinjected electrons to the back contact was faster and recombination with the electrolyte slowed down significantly. To further
improve device efficiency, the researchers are interested in decreasing the diameter of the nanofibers to increase the roughness factor of the films. To enhance the durability of the DSSC devices, the group
also intends to employ ionic liquid electrolytes to obtain long-term stability at full sunlight intensity. MELISSA A. HARRISON
Functionalized Silsesquioxanes Show High Sensitivity and Stability for Next-Generation E-Beam Lithography Resists One of the most prevalent methods for creating submicron patterns is e-beam lithography (EBL). Electron optics can produce electron beams with a diameter of a few nanometers. The spatial resolution of EBL (typically ≈10s nm) is limited by scattering in the photoresist. Thus, it remains a challenge to create EBL resists which maintain high contrast below 20 nm. Hydrogen silsesquioxane (HSQ) has shown promise as a negative resist due to its ability to create sub-20 nm features with high contrast and fidelity. However, HSQ has low sensitivity and is not stable for long periods of time. J.H. Sim of Seoul National University, H.-J. Lee of the National Institute of Standards and Technology, and their colleagues propose a solution to these problems in the May 25 issue of Chemistry of Materials (DOI: 10.1021/cm9035456; p. 3021). Sim and coresearchers created two compositions of functionalized HSQ resists (shown in Scheme 1). Norbornene-modified HSQ is created by co-polymerizing triethoxysilane (TES) with norbornene ethyltrimethoxysilane (NETMS). Norbornene-co-chloromethylphenyl functionalized silsesquioxane is obtained by co-polymerizing p-chloromethylphenyl trimethoxysilane and norbornene ethyltrimethoxsilane.
Method Developed for Producing Chitosan Nanoparticles Using Nanoporous Membranes The drive to develop drug delivery systems that can be tailored for controlled release of pharmaceutical action continues to receive immense research, but the efficacy of many drugs is limited by their ability to reach the site of optimum therapeutic action. Recently, R.N. Zare of Stanford University and C.R. Martin of the University of Florida and their colleagues have developed a liquid–liquid separation approach using a nanoporous membrane
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Scheme 1. Schematic showing compounds used for creating norbornene-functionalized HSQ (top line) and norbornene-co-chloromethylphenyl functionalized silsesquioxane (bottom line). Reproduced with permission from Chemistry of Materials 22 (10) (2010) 3021; DOI:10.1021/cm9035456. © 2010 American Chemical Society.
Contrast curves demonstrate that the norbornene and norbornene-co-chloromethylphenyl resists become insoluble at 58% and 75% of the electron dose for standard HSQ, respectively. Scanning electron micrographs qualitatively show that these resists also maintained high-resolution patterning at low electron dosages. The norbornene-functionalized r
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