Sensitivity of Localized Surface Plasmon Resonance and Acoustic Vibrations to Edge Rounding in Silver Nanocubes.

Precise knowledge of the dependence of nano-object properties on their structural characteristics such as their size, shape, composition, or crystallinity, in turn, enables them to be finely characterized using appropriate techniques. Spectrophotometry and inelastic light scattering spectroscopy are noninvasive techniques that are proving highly robust and efficient for characterizing the optical response and vibrational properties of metal nano-objects. Here, we investigate the optical and vibrational properties of monodomain silver nanocubes synthesized by the chemical route, with edge length ranging from around 20 to 58 nm. The synthesized nanocrystals are not perfectly cubic and exhibit rounded edges and corners. This rounding was quantitatively taken into account by assimilating the shape of the nanocubes to superellipsoids. The effect of rounding on their optical response was clearly evidenced by localized surface plasmon resonance spectroscopy and supported by calculations based on the discrete dipole approximation method. The study of their acoustic vibrations by high-resolution low-frequency Raman scattering revealed a substructure of the T2g band, which was analyzed as a function of rounding. The measured frequencies are consistent with the existence of an anticrossing pattern of the two T2g branches. Such an avoided crossing in the T2g modes is clearly evidenced by calculating the vibrational frequencies of silver nanocubes using the Rayleigh-Ritz variational method that accounts for both their real size, shape, and cubic elasticity. These results show that it is possible to assess the rounding of nanocubes, including by means of ensemble spectroscopic measurements on well-calibrated particles.

Metal Core-Shell Nanoparticle Supercrystals: From Photoactivation of Hydrogen Evolution to Photocorrosion.

Gas nanobubbles are directly linked to many important chemical reactions. While they can be detrimental to operational devices, they also reflect the local activity at the nanoscale. Here, supercrystals made of highly monodisperse Ag@Pt core-shell nanoparticles are first grown onto a solid support and fully characterized by electron microscopies and X-ray scattering. Supercrystals are then used as a plasmonic photocatalytic platform for triggering the hydrogen evolution reaction. The catalytic activity is measured operando at the single supercrystal level by high-resolution optical microscopy, which allows gas nanobubble nucleation to be probed at the early stage with high temporal resolution and the amount of gas molecules trapped inside them to be quantified. Finally, a correlative microscopy approach and high-resolution electron energy loss spectroscopy help to decipher the mechanisms at the origin of the local degradation of the supercrystals during catalysis, namely nanoscale erosion and corrosion.

Randomized controlled trial of mindfulness-based stress reduction (MBSR) on posttraumatic growth of Chinese breast cancer survivors.

Breast cancer (BC) patients in China suffered from a variety of psychology stress such as perceived stress and anxiety, posttraumatic growth (PTG) as a positive factor could promote their psychology health and quality of life. This study aimed to investigate the efficacy of mindfulness-based stress reduction (MBSR) on promoting PTG, decreasing perceived stress and anxiety of Chinese BC patients. A randomized controlled trial of 60 BC patients (Stages I-III) was conducted. They were randomly divided to the 8-week MBSR group or usual care (UC) group. PTG inventory, Perceived Stress Scale of Chinese version (CPSS) and State Trait Anxiety Inventory (STAI) evaluated the PTG level, perceived stress and anxiety at three times(before intervention-T1, after intervention-T2 and follow up at 3 months-T3). A repeated-measures analysis of variance model was used to compare each outcome measure of two groups at the three times. There was one patient discontinued the intervention and one lose to follow up in MBSR group, finally 58 BC patients completed the research. There was no difference between two groups before the intervention. The results showed significant improvements in MBSR group comparing with the UC group that PTG level was much higher after the 8-week intervention and the follow up (F = 34.73, p < .00). At the same time, CPSS (F = 14.41, p < .00) and STAI (F = 15.24, p < .00) scores were significant decreased at T2 and T3. The results showed that MBSR promoted the level of PTG and decreased perceived stress and anxiety state of Chinese BC patients, and the results persisted at three months after intervention. The research preliminary proved that MBSR was suitable to Chinese BC patients. MBSR should be recommending to BC survivors in China.