Distribution of Nanoparticles in Photopolymer Controlled Holographically
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nanoshell bioconjugates can be used to effectively target and image human epidermal growth factor receptor 2 (HER2—a relevant biomarker that is prevalent in human breast carcinoma cells). The researchers chose nanoshells composed of a dielectric silica core surrounded by a thin metallic shell composed of gold whose optical properties can be adjusted by controlling their dimensions. Nanoshells have a strong optical resonance that can be tuned in wavelength across the visible and infrared spectrum, allowing the relative contributions of scattering and absorption at a given wavelength to be tuned by controlling the dimensions of the core and the shell. In this study, nanoshells with a 240-nm-diameter silica core and a 35–nmthick gold shell were used. By utilizing these nanoshells, it is possible to conjugate bio-relevant materials, in this case, proteins that facilitate in vivo imaging. The researchers attached a linker complex—either anti-HER2 or anti-IgG antibodies–PEG (poly ethylene glycol)—to the nanoshell surface. These conjugated nanoshells where exposed to HER2 expressing SKBr3 cells and studied by dark-field microscopy. A significant increase in optical contrast was observed in the HER2 positive cells targeted with anti-HER2-labeled nanoshells as compared to anti-IgG-labeled nanoshells or cells not exposed to the nanoshell conjugates. The researchers said that nanoshellbased conjugates offer the next generation to in vivo imaging due to their nearinfrared tunability, size flexibility, and systemic control of optical properties. LARKEN E. EULISS
Hybrid Photoelectrodes for Solar Water Splitting Efficient production of hydrogen from water using solar energy is a much-soughtafter research goal that has eluded scientists for many years. The wide-bandgap materials that are used in single-junction electrochemical devices to carry out water splitting processes typically absorb sunlight poorly, resulting in low solar-tohydrogen (STH) conversion efficiencies. Recently, E.L. Miller and colleagues from the Hawaii Natural Energy Institute at the University of Hawaii developed a prototype multijunction photoelectrode proposed to more effectively harness the sun’s energy for hydrogen production than has been previously possible. In the May issue of Electrochemical and Solid-State Letters (p. A247), the researchers reported on the performance characteristics of a prototype hybrid photoelectrode (HPE) device and discussed materials developments that will be necMRS BULLETIN • VOLUME 30 • JUNE 2005
essary to improve the STH efficiency. An HPE is a monolithic thin-film device that integrates photoelectrochemical (PEC) and photovoltaic (PV) components in a multiple-junction arrangement. In such a device, the efficiency of hydrogen production is ideally proportional to the photocurrent in the PEC semiconductor, and thus optimum performance is achieved by maximizing this photocurrent. The prototype HPE described and tested by the research group consists of an aSiGe/a-SiGe tandem structure coated with a sputtered WO3 thin film. Thi
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