Nanoscale Helical Optical Force for Determining Crystal Chirality.

The deterministic control of material chirality has been a sought-after goal. As light possesses intrinsic chirality, light-matter interactions offer promising avenues for achieving non-contact, enantioselective optical induction, assembly, or sorting of chiral entities. However, experimental validations are confined to the microscale due to the limited strength of asymmetrical interactions within sub-diffraction limit ranges. In this study, a novel approach is presented to facilitate chirality modulation through chiral crystallization using a helical optical force field originating from localized nanogap surface plasmon resonance. The force field emerges near a gold trimer nanogap and is propelled by linear and angular momentum transfer from the incident light to the resonant nanogap plasmon. By employing Gaussian and Laguerre-Gaussian incident laser beams, notable enantioselectivity is achieved through low-power plasmon-induced chiral crystallization of an organic compound-ethylenediamine sulfate. The findings provide new insights into chirality transmission orchestrated by the exchange of linear and angular momentum between light and nanomaterials.

Natal colony influences age-specific movement patterns of the Yellow-legged gull (Larus michahellis).

BACKGROUND: As for other life history traits, variation occurs in movement patterns with important impacts on population demography and community interactions. Individuals can show variation in the extent of seasonal movement (or migration) or can change migratory routes among years. Internal factors, such as age or body condition, may strongly influence changes in movement patterns. Indeed, young individuals often tend to move across larger spatial scales compared to adults, but relatively few studies have investigated the proximate and ultimate factors driving such variation. This is particularly the case for seabirds in which the sub-adult period is long and difficult to follow. Here, we examine migration variation and the factors that affect it in a common Mediterranean seabird, the Yellow-legged gull (Larus michahellis). METHODS: The data include the encounter histories of 5158 birds marked as fledglings between 1999 and 2004 at 14 different colonies in southern France and resighted over 10 years. Using a multi-event mark-recapture modeling framework, we use these data to estimate the probability of movement and survival, taking into account recapture heterogeneity and age. RESULTS: In accordance with previous studies, we find that young individuals have greater mobility than older individuals. However, the spatial extent of juvenile movements depends on natal colony location, with a strong difference in the proportion of sedentary individuals among colonies less than 50 km apart. Colony quality or local population dynamics may explain these differences. Indeed, young birds from colonies with strong juvenile survival probabilities (~ 0.75) appear to be more sedentary than those from colonies with low survival probabilities (~ 0.36). CONCLUSIONS: This study shows the importance of studying individuals of different ages and from different colonies when trying to understand seabird movement strategies. Local breeding success and the availability of food resources may explain part of the among colony differences we observe and require explicit testing. We discuss our results with respect to the feedback loop that may occur between breeding success and mobility, and its potential implications for population demography and the dissemination of avian disease at different spatial scales.

Efficacy of created and restored nesting sites for the conservation of colonial Laridae in the South of France.

By rapidly modifying key habitat components, habitat restoration is at risk of producing attractive cues for animals without providing habitats of sufficient quality. As such, individual fitness components, such as reproduction, could be reduced and restored habitats could become ecological traps. This risk notably appears by using artificial constructions in restoration projects, yet few studies have evaluated their efficacy in a robust way. We investigated this by analyzing 154 islets that were created or restored to improve the conservation status of 7 colonial Laridae species in the South of France. From 2007 to 2016, we compared occupancy dynamics and breeding parameters of these species between the restored sites and 846 unmanaged nesting sites. We also explored species' preference for different nesting site characteristics and their respective effect on breeding parameters. Restored nesting sites were 2-9 times as attractive as unmanaged sites for all species except the Black-headed Gull (Chroicocephalus ridibundus). Colonization probability was up to 100 times higher in sites already used by other species the previous year and increased with distance to the shore until >0.2 when distance was over 250 m. Abandonment probability was 29-70% lower when breeding was successful the previous year in all species except the Sandwich Tern (Thalasseus sandvicensis). Productivity and breeding success probability were 2 times higher on managed sites. Distance from the shore was an important attractive characteristic of artificial nesting sites in all species. Other nesting site characteristics had species-specific effects on colonization, abandonment, and breeding success. Our results indicate that managed nesting sites are successful conservation tools for colonial Laridae in the Mediterranean and do not act as ecological traps. Our study showed that testing the ecological trap hypothesis is a robust way to evaluate the success of restoration projects of breeding habitats.

Eficiencia de los sitios de anidación creados y restaurados para la conservación de láridos coloniales en el sur de Francia Resumen Con la rápida modificación de los componentes clave de un hábitat, la restauración corre el riesgo de producir entradas atractivas para los animales sin proporcionar hábitats con la suficiente calidad. Como tal, los elementos individuales de la aptitud, como la reproducción, podrían ser reducidos y los hábitats restaurados podrían convertirse en trampas ecológicas. Aunque este riesgo aparece especialmente cuando se usan construcciones artificiales en los proyectos de restauración, son pocos los estudios que han evaluado su efectividad de manera firme. Investigamos lo anterior con el análisis de 154 islotes que fueron creados o restaurados para mejorar el estado de conservación de siete especies de láridos coloniales en el sur de Francia. Comparamos las dinámicas de ocupación y los parámetros de reproducción de estas especies entre 2007 y 2016 en los sitios restaurados y en 846 sitios de anidación no administrados. También exploramos la preferencia de las especies por diferentes características en los sitios de anidación y su respectivo efecto sobre los parámetros de reproducción. Los sitios de anidación restaurados fueron de 2 a 9 veces más atractivos para todas las especies, excepto la gaviota de cabeza negra (Croicocephalus ridibundus), que los sitios no administrados. La probabilidad de colonización fue hasta 100 veces mayor en los sitios usados por otras especies el año previo e incrementó con la distancia a la costa hasta >0.2, cuando la distancia fue mayor a los 250 metros. La probabilidad de abandono fue de 29 a 70% más baja para todas las especies, excepto el charrán de Sándwich (Thalasseus sandvicensis), cuando la reproducción fue exitosa el año anterior. La probabilidad de la productividad y el éxito de reproducción fueron dos veces mayores en los sitios administrados. La distancia a la costa fue una característica atractiva importante de los sitios artificiales de anidación para todas las especies. Otras características de los sitios de anidación tuvieron efectos específicos por especie sobre la colonización, el abandono y el éxito de la reproducción. Nuestros resultados indican que los sitios de anidación administrados son herramientas exitosas de conservación para los láridos coloniales en el Mediterráneo y no funcionan como trampas ecológicas. Nuestro estudio demuestra que analizar la hipótesis de la trampa ecológica es una manera sólida de evaluar el éxito de la restauración en los proyectos de hábitats para la reproducción.

Spin-Orbit Angular-Momentum Transfer from a Nanogap Surface Plasmon to a Trapped Nanodiamond.

The ability to control the motion of single nanoparticles or molecules is currently one of the major scientific and technological challenges. Despite tremendous progress in the field of plasmonic nanotweezers, controlled nanoscale manipulation of nanoparticles trapped by a plasmonic nanogap antenna has not been reported yet. Here, we demonstrate the controlled orbital rotation of a single fluorescent nanodiamond trapped by a gold trimer nanoantenna irradiated by a rotating linearly polarized light or circularly polarized light. Remarkably, the rotation direction is opposite to the light's polarization rotation. We numerically show that this inversion comes from sequential excitation of individual nanotriangles in the reverse order when the linear polarization is rotated, whereas using a circular polarization, light-nanoparticle angular momentum transfer occurs via the generation of a Poynting vector vortex of reversed handedness. This work provides a new path for the control of light-matter angular momentum transfer using plasmonic nanogap antennas.

Localized ZnO Growth on a Gold Nanoantenna by Plasmon-Assisted Hydrothermal Synthesis.

The excitation of localized surface plasmon resonances (LSPRs) in metal nanostructures enables subwavelength photon localization and large electric field enhancement, which can be advantageously used to strongly enhance light-matter interactions at the nanoscale. For this purpose, efficient methods for deterministically handling and arranging nanomaterials at the exact position of the localized electric field are required. In this Letter, we propose a novel method based on a hydrothermal synthesis reaction to locally and selectively synthesize zinc oxide in a plasmonic nanoantenna. We first make evident the role of LSPR for achieving efficient heating of gold nanostructures. Then, by selectively addressing one of the LSPRs of a gold antenna, we demonstrate that localized zinc oxide formation at the targeted location of the antenna can be achieved due to the nanoscale confinement of the heat production.

Trapping and Deposition of Dye-Molecule Nanoparticles in the Nanogap of a Plasmonic Antenna.

Plasmonic nanostructures, which allow light focusing at the deep subwavelength scale, and colloidal nanoparticles with unique optoelectronic properties are nowadays fabricated with nanometer precision. However, to fully control and exploit nanoscale light-matter interactions in hybrid plasmonic-nanophotonic devices, both materials must be assembled in heterostructures with similar precision. Near-field optical forces have recently attracted much attention, as they can precisely trap and position nanoparticles at plasmonic hotspots. However, long-range attraction and the surface bonding of nanoparticles usually require other specific techniques, such as electrothermal heating and surface chemical treatments. This Letter reports on the optical trapping and deposition of dye-molecule nanoparticles in the nanogap of a gold antenna. The nanoparticles are captured by focusing a near-infrared laser beam on a targeted plasmonic antenna. This single-step deposition process requires only a few seconds under 1.4-1.8 MW·cm-2 continuous-wave illumination and shows a polarization dependence smaller than expected. Fluorescence and electronic microscopy observations suggest that nanoparticle deposition arises from a trade-off between optical and thermal effects.

Integrated plasmonic nanotweezers for nanoparticle manipulation.

We numerically demonstrate that short gold nanoparticle chains coupled to traditional SOI waveguides allow conceiving surface plasmon-based nanotweezers. This configuration provides for jumpless control of the trapping position of a nano-object as a function of the excitation wavelength, allowing for linear repositioning. This novel feature can be captivating for the conception of compact integrated optomechanical nanoactuators.