Applications of Raman-based techniques to on-site and in-vivo analysis

Raman-based technologies have proved to be excellent tools for on-site and in-vivo analysis, due to the non-invasive nature of their detection, their capability of providing structure information, their high tolerance to aqueous samples, the ultra-sensitivity of surface-enhanced Raman scattering (SERS) and resonance Raman scattering (RRS), the high spatial resolution of tip-enhanced Raman scattering (TERS), and the ultrashort spectra-acquisition time for coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS).In this review, we highlight the recent success of Raman-based technologies in various applications, including:

• (1) 

  on-site surface analysis and chemical-reaction monitoring;

• (2) 

  on-site identification of cultural objects, archeological studies and planetary science;

• (3) 

  in-vivo analysis of cells and microorganisms;

• (4) 

  in-vivo diagnosis inside human and animal bodies;

• (5) 

  in-vivo fast Raman imaging and mapping;

• (6) 

  the study of SERS processes; and,

• (7) 

  assessment of nanomaterial safety.

     

Shape-dependent local internal stress of α-Cr2O3 nanocrystal fabricated by pulsed laser ablation

The α-Cr₂O₃ single-crystal nanocondensates were fabricated by pulsed laser ablation in air and characterized by analytical electron microscopy regarding shape-dependent local internal stress of the anisotropic crystal. The nanocondensates formed predominantly as rhombohedra with well-developed surfaces and occasionally hexagonal plate with thin edges and blunt corners. Such nanocondensates showed Raman shift for the CrO₆ polyhedra, indicating a local compressive stress up to ca. 4 GPa on the average. Careful analysis of the lattice fringes revealed a local compressive stress (0.5% strain) at the thin edge of the hexagonal plates and a local tensile stress (0.3–1.0% strain) near the relaxed , , and (0 0 0 1) surfaces of truncated rhombohedra. The combined effects of nanosize, capillarity force at sharp edge, and specific surface relaxation account for the retention of a local internal compressive stress built up in an anisotropic crystal during a very rapid heating–cooling process.     

Vacuum ultraviolet-induced surface modification of cyclo-olefin polymer substrates for photochemical activation bonding

The surface of cyclo-olefin polymer (COP) was treated with vacuum ultraviolet (VUV) light at 172 nm wavelength to improve the wettability and adhesion properties. Through VUV treatment in air, the terminal groups of the COP surface were oxidized into oxygen functional groups, containing CO, CO, and COO components, making the COP surface hydrophilic. The extent of oxygenation was evaluated by XPS and FTIR-ATR spectra, and it was shown that the surface properties, hydrophilicity, and functionalization were dependent on both VUV irradiation distance and irradiation time, which have an effect on the concentration of oxygen functional groups. VUV-light treatment with a short irradiation distance was more effective in introducing oxygen functional groups.     

Polarized neutron reflectometer SUIREN at JRR-3

Recent status of the neutron reflectometer SUIREN is presented. Since its startup in 2006, SUIREN has been the only neutron reflectometer in Japan for magnetic samples with high magnetic field sample environment, and used for investigations of magnetic films, solid-liquid interfaces and other solid thin films. SUIREN provides monochromatic neutron beam of 3.93 Å for vertically placed sample surface. Polarized beam is also available together with a 1 T electromagnet for sample. Beam intensity at the sample position in the unpolarized mode is for beam collimation of Δθ=0.08. Reflectivity can be explored down to 10^-6.     

含左手材料光纤的表面模特性

在弱导条件下,利用Maxwell方程组,对纤芯是左手材料,包层是右手材料的光纤表面模进行了研究,得到了TE (TM)、 EH和 HE表面模的色散方程,.根据色散方程,画出了相应表面模和含左手材料光纤导模的色散曲线.比较这些色散曲线,发现了含左手材料光纤表面模一些新的特性.     

Effective interactions of colloids on nematic films

The elastic and capillary interactions between a pair of colloidal particles trapped on top of a nematic film are studied theoretically for large separations d. The elastic interaction is repulsive and of quadrupolar type, varying as d^-5. For macroscopically thick films, the capillary interaction is likewise repulsive and proportional to d^-5 as a consequence of mechanical isolation of the system comprised of the colloids and the interface. A finite film thickness introduces a nonvanishing force on the system (exerted by the substrate supporting the film) leading to logarithmically varying capillary attractions. However, their strength turns out to be too small to be of importance for the recently observed pattern formation of colloidal droplets on nematic films.     

Surface morphology and composition of c-, a- and m-sapphire surfaces in O2 and H2 environments

This paper reports that monitoring the composition of the c(0 0 0 1), a(11–20) and m(10–10) sapphire surfaces is essential for a proper interpretation of the surface morphologies obtained after annealing at 1253 and 1473 K in ArH₂ or ArO₂ atmospheres. Our experimental investigations, which have used Auger electron spectroscopy (AES) and atomic force microscopy (AFM) on the surfaces of 99.99% pure sapphire wafers, have led to the following original conclusions: (i) Calcium segregates at the c-surface of sapphire both under ArO₂ and ArH₂. (ii) Potassium adsorption enhances the kinetics of step-bunching on the c-surface under ArO₂. (iii) The step edges on the a-surface may develop a comb-like morphology made of parallel strips along the [10–10] direction. (iv) At 1253 K, clean m-surfaces may be stable. (v) Under ArH₂, alumina surface diffusion is much slower than under ArO₂ for all surface orientations, the surface concentration of impurities is low, and the Al–O ratio of the AES signals at the surface is significantly larger.     

Structural properties of Cu clusters on Si(1 1 1):Cu2Si magic family

Basing on the results of the scanning tunneling microscopy (STM) observations and density functional theory (DFT) calculations, the structural model for the Cu magic clusters formed on Si(1 1 1)7 × 7 surface has been proposed. Using STM, composition of the Cu magic clusters has been evaluated from the quantitative analysis of the Cu and Si mass transport occurring during magic cluster converting into the Si(1 1 1)‘5.5 × 5.5’-Cu reconstruction upon annealing. Evaluation yields that Cu magic cluster accommodates 20 Cu atoms with 20 Si atoms being expelled from the corresponding 7 × 7 half unit cell (HUC). In order to fit these values, it has been suggested that the Cu magic clusters resemble fragments of the Cu₂Si-silicide monolayer incorporated into the rest-atom layer of the Si(1 1 1)7 × 7 HUCs. Using DFT calculations, stability of the nineteen models has been tested of which five models appeared to have formation energies lower than that of the original Si(1 1 1)7 × 7 surface. The three of five models having the lowest formation energies have been concluded to be the most plausible ones. They resemble well the evaluated composition and their counterparts are found in the experimental STM images.     

Coarsening of mass-selected Au clusters on amorphous carbon at room temperature

Low-energy cluster beam deposition was used to deposit mass-selected Au_n clusters (n = 4, 6, 13 and 20) on amorphous carbon (a-C) substrates. The resulting samples were stored at room temperature under ambient conditions for time periods up to 32 months to analyze the coarsening behaviour of the clusters. Cluster-size distributions were measured in regular time intervals by transmission electron microscopy (TEM). The TEM experiments show a significant increase of the average cluster size with time analogous to classical surface Ostwald ripening (OR). The coarsening of Au clusters can be well described by steady-state diffusion-limited kinetics. The derived surface mass-transport diffusion coefficients at room temperature range between 1.1 and 3.8·10⁻²⁵ m² s⁻¹ for our samples. A detailed analysis of values suggests that, the rate of the surface OR for mass-selected Au_n clusters increases with the cluster size in the sequence: Au₄ ≈ Au₆ < Au₁₃ < Au₂₀ for the investigated range of Au clusters. Given that the initial, on-surface cluster-size distributions are nominally monodisperse, classical OR with cluster coarsening based only on the Gibbs-Thomson effect cannot explain the observed coarsening. The activation of the coarsening process is rationalized by initial variations of the cluster sizes due to the deposition process itself and/or the interaction of the clusters with the substrate. Moreover, the presence of initial deposited Au clusters as different isomers with slightly different chemical potential on the substrate, may also initiate the coarsening by surface OR. Furthermore, we find that the coarsening is most pronounced for the paucidispersed sample with Au_m (10 ? m ? 20) clusters. A possible explanation of this behaviour is the presence of an initial distribution of different cluster sizes directly after deposition.