RESUMEN
It has been reported that the scattering cross-sections of resonance Raman spectra strongly depend on the resonance between the laser's excitation energy and the electronic absorption band of pigments in solution. However, the actual collection of scattered photons is affected by diffuse scattering and self-absorption when studying painted colorants in artworks. Quantitative spectroscopic measurements are required to elucidate the apparent resonance Raman cross-sections in both solution and solid. In this study, we explored the excitation-dependent Raman scattering of natural and artificial Korean pigments painted on a wood block with six visible wavelengths. Our study shows that the Raman intensity profile agrees with the emission profile rather than with the absorption. We also assessed the validity of self-absorption and the outgoing resonance mechanism in the solid state for the results.
RESUMEN
In situ real-time and nondestructive identification of packaged chemicals is essential for applications such as homeland security and terrorism prevention. Although various Raman spectroscopic methods such as spatially offset Raman spectroscopy (SORS) and time-resolved Raman spectroscopy have been investigated for real-time detection, the background interference originating from packaging materials limits the accuracy of the analysis. In principle, the Raman background from the packaging cannot be removed completely. To overcome this limitation, we developed a SORS-based dual-offset optical probe (DOOP) system that offers real-time prediction of 20 chemicals concealed in various containers by completely removing the background signal. The DOOP system selectively acquires the Raman photons generated from both the outer packaging and the inner contents, whose intensities are dependent on the penetration depth of the laser. The Raman spectra obtained at two remote offsets are automatically subtracted after normalization. We demonstrate that the DOOP method provides the pure component spectra by completely removing background interference from three plastic containers for a total of 20 samples in three different containers. In addition, an artificial neural network (ANN) was applied to evaluate the accuracy of the real-time chemical identification system; our system led to drastic improvements of the ANN prediction accuracy.
RESUMEN
We fabricated hexagonal arrays of Co/Pt nanodots on Si surfaces by pulsed laser deposition (PLD) using cylindrically phase-separated polystyrene-b-poly(methylmethacrylate) (PS-b-PMMA) diblock copolymer thin films as templates after the removal of PMMA. The size and the separation of the nanodots were 23 and 40 nm, respectively, and the density of the nanodots was 1.5 x 10(11)/cm2. The magnetic properties of nanodot arrays measured by vibrating sample magnetometer were compared with those of PLD grown film. The films showed magnetic anisotropy with an easy axis in the in-plane direction, whereas no noticeable anisotropy was observed for nanodot arrays. In addition, the saturation magnetization (Ms) of both the Co/Pt nanodots and the film increased with the Pt content.
