Surface-enhanced-Raman-spectroscopy (SERS) can be made an attractive approach for the identification of Raman-active compounds and biological materials (i.e., toxins, viruses, or intact bacterial cells or spores) through development of reproducible, spatially uniform SERS-active substrates. Recently, reproducible (from substrate to substrate), spatially homogeneous (over large areas) SERS-active substrates have been commercialized and are now available in the marketplace. Scanning electron microscopy and high-resolution, tapping-mode atomic force microscopy have been used to analyze these novel plasmonic surfaces for topographical consistency. Additionally, we have assessed, by wavelength-tunable microreflectance spectrometry, the spatial distribution of the localized surface plasmon resonance (LSPR) across a single substrate surface as well as the LSPR lambda(MAX) variance from substrate to substrate. These analyses reveal that these surfaces are topologically uniform with small LSPR variance from substrate to substrate. Further, we have utilized these patterned surfaces to acquire SERS spectral signatures of four intact, genetically distinct Bacillus spore species cultivated under identical growth conditions. Salient spectral signature features make it possible to discriminate among these genetically distinct spores. Additionally, partial least squares, a multivariate calibration method, has been used to develop personal-computer-borne algorithms useful for classification of unknown spore samples based solely on SERS spectral signatures. To our knowledge, this is the first report detailing application of these commercially available SERS-active substrates to identification of intact Bacillus spores.

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Lifetime measurements on single-chip, packaged 285 nm light-emitting diodes (LEDs) performed under constant current injection at 20 and 75 mA, were compared to the performance of unbiased LEDs baked at the equivalent operating junction temperatures. The thermally stressed devices showed a lesser degradation than those electrically stressed, indicating that elevated temperature alone does not cause degradation. Despite a decay to less than half of the initial power under current injection, time-resolved photoluminescence of the active region exhibits little change, while capacitance-voltage measurements imply that the reduced efficiency and power decay originate from the generation of point defects near the p-side of the p-n junction.

A novel methodology has been developed for the investigation of bacterial spores. Specifically, this method has been used to probe the spore coat composition of two different Bacillus stearothermophilus variants. This technique may be useful in many applications; most notably, development of novel detection schemes toward potentially harmful bacteria. This method would also be useful as an ancillary environmental monitoring system where sterility is of importance (i.e., food preparation areas as well as invasive and minimally invasive medical applications). This unique detection scheme is based on the near-infrared (NIR) surface-enhanced Raman scattering (SERS) from single, optically trapped, bacterial spores. The SERS spectra of bacterial spores in aqueous media have been measured using SERS substrates based on approximately 60-nm-diameter gold colloids bound to 3-aminopropyltriethoxysilane derivatized glass. The light from a 787-nm laser diode was used to trap and manipulate as well as simultaneously excite the SERS of an individual bacterial spore. The collected SERS spectra were examined for uniqueness and the applicability of this technique for the strain discrimination of Bacillus stearothermophilus spores. Comparison of normal Raman and SERS spectra reveals not only an enhancement of the normal Raman spectral features but also the appearance of spectral features absent in the normal Raman spectrum.

Surface-enhanced Raman spectroscopy (SERS) can be made an attractive approach for identification of Raman-active compounds and biological materials (i.e., toxins, viruses, or intact bacterial cells/spores) through development of reproducible, spatially uniform SERS-active substrates. Recently, reproducible (from substrate-to-substrate), spatially homogeneous (over large areas) SERS-active substrates have been commercialized and are now available in the marketplace. We have utilized these patterned surfaces to acquire SERS spectral signatures of intact bovine papular stomatitis, pseudocowpox, and Yaba monkey tumor viruses. Salient spectral signature features make it possible to discriminate among these genetically distinct Poxviridae-Chordopoxvirinae virions. In addition, partial least-squares, a multivariate calibration method, has been used to develop personal computer-borne algorithms useful for classification of unknown Parapoxvirus (e.g., bovine papular stomatitis virus and pseudocowpox virus) samples based solely on SERS spectral signatures. To our knowledge, this is the first report detailing application of these commercial-off-the-shelf (COTS) SERS-active substrates to identification of intact poxviruses.

A new method based on near-infrared (NIR) spectrometry and partial least-squares analysis has been developed for the noninvasive and nondestructive determination of the identity and sequences of amino acid residues in di- and tripeptides. The di- and tripeptides were synthesized from six amino acids with similar structures (Gly, Ala, Leu, Met, Phe, Val) on two different polymer beads (bead with and without a linker) using the solid-phase peptide synthetic method. The developed NIR method is capable of determining the identity of sequences of these di- and tripeptides (with and without the Fmoc protecting group) directly on the polymer beads. It can distinguish not only dipeptides from tripeptides but also peptides with very similar structures (e.g., bead-Gly-Ala-Ala, bead-Gly-Ala-Phe, bead-Gly-Ala-Leu, bead-Gly-Ala-Val, and bead-Gly-Ala-Met). More importantly, the method is capable of distinguishing di- and tripeptides with the same amino acid residues but different sequences (e.g., bead-Gly-Leu-Val from bead-Gly-Val-Leu).

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A new method based on the near-infrared (NIR) multispectral imaging technique has been developed for the noninvasive and nondestructive determination of the identity and sequences of amino acid residues in di- and tripeptides. The di- and tripeptides were synthesized on polymer beads (i.e., Rink) using the solid phase peptide synthetic method. The developed method is capable of determining the identity of sequences of the peptides (with and without the Fmoc protecting group) directly on the polymer beads. It can distinguish not only dipeptides from tri-peptides but also peptides with very similar structures (e.g., Rink-Gly-Ala-Ala, Rink-Gly-Ala-Phe, Rink-Gly-Ala-Leu, Rink-Gly-Ala-Val, and Rink-Gly-Ala-Met). More importantly, it is capable of distinguishing peptides with the same amino acid residues but different sequences (e.g., Rink-Gly-Leu-Val from Rink-Gly-Val-Leu).