Generation of combinatorial libraries has become an essential tool in synthetic organic chemistry, 1 but only recently have these methods been used for rapid screening of materials properties of inorganic substances. 2,3 The initial report described the use of vapor deposition and masking techniques to vary the composition of multi-metal superconducting materials; 2 more recently, a similar mask-driven approach to spatially-selective vapor deposition led to discovery of materials exhibiting colossal magnetoresistance. 3 Compared to traditional routes to property optimization in mixed-metal systems, e.g. preparation of separate samples with varying metal ratios, 4 combinatorial methods potentially offer significant advantages in speed and cost. We recently described a new approach to fabrication of macroscopic Au surfaces that is based on self-assembly of nanosized Au particles from solution. 5,6 Reductive deposition of Ag onto these substrates leads to Ag-clad colloidal Au arrays 7 that exhibit an increased enhancement factor (EF) for surface enhanced Raman scattering (SERS). 8 We describe herein a new, solution-based combinatorial strategy for synthesis of surfaces exhibiting nanometer-scale variation in mixed-metal composition and architecture. With this method, continuous or stepped gradients in the size and number density of surface features can be generated simultaneously over different regions of a single substrate. To demonstrate this approach, we have optimized the SERS response of a glass slide upon which the coverage of colloidal Au and the extent of Ag coating were varied. Over a 2 cm × 2 cm sample area, changes in EF spanning almost three orders of magnitude were realized, and the changes in nanostructure responsible for these effects were elucidated using atomic force microscopy (AFM). Our results show significant changes in SERS EFs over small alterations in surface morphology, demonstrating the power of solution-based combinatorial approaches for synthesis of mixed-metal materials.The general combinatorial assembly approach is described in Scheme 1. Prior work has shown that the number of colloidal Au particles bound to functionalized surfaces can be predicted from immersion times in colloidal solution using initial (time) 1/2 kinetics. 9 Thus, when a (3-mercaptopropyl)trimethoxysilane (MPTMS)-coated glass slide attached to a motorized translation stage is immersed at a fixed rate into a 17 nM aqueous solution of 12-nm diameter colloidal Au, a gradient in particle coverage is generated in the direction of immersion. After sample rotation by 90°, fixed-rate immersion into a Ag + -containing solution designed to specifically deposit Ag on Au 7b leads to a gradient in particle size over the new immersion direction. The resulting surface exhibits a continuous variation in nanometer scale morphologysas defined by particle coverage and particle sizesthat results from known, repeatable immersion conditions. 10 In our apparatus, a stepper motor with a 2°step yields a 3 µm translation. Over a 3 cm × 3 cm r...

Raman chemical imaging of lipid and protein distribution in breast is performed without the use of invasive contrast agents. Instead, tissue component discrimination is based on the unique vibrational spectra intrinsic to lipids and proteins. Component discrimination is possible using ratiometric image analysis techniques. However, chemical image contrast is enhanced when techniques are employed that use the entire Raman spectrum, including peak shift analysis and multivariate image analysis. Visualization of breast tissue components is an essential step in the development of a quantitative Raman ‘optical biopsy’ technique suitable for the non‐invasive detection and classification of breast cancer. A high spatial/spectral resolution Raman imaging microscope is used that employs a liquid crystal tunable filter (LCTF). The imaging performance of the Raman microscope is quantitated with the measurement of the imaging system’s contrast transfer function (CTF). A comparison between the theoretical (diffraction limited) CTF and the measured CTF establishes that the LCTF does not produce appreciable image degradation. © 1997 by John Wiley & Sons, Ltd.

We have studied reactions of thermalized, mass-selected boron oxide (B,?O,,,+, n = 1-3, m = 1-4) and hydrogenated boron oxide (HB,,O,,,+, n = 1, 2, m = 1-3) ions with HF. Cross sections are reported for each product channel for collision energies ranging from 0.1 to 10 eV (center of mass). On the basis of the observed collision energy dependence, product branching, and effects of hydrogenation, we propose a reaction mechanism where facile reaction occurs only at certain sites on the oxide, most likely at terminal -B=O groups. H atom addition greatly decreases reactivity, apparently by blocking the reactive sites. Our data also point out several significant uncertainties in the literature thermochemistry for B/O/F/H species, and we are able to give some limits on AHi for several molecules.

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