Anisotropically Enhanced Nonlinear Optical Properties of Ensembles of Gold Nanorods Electrospun in Polymer Nanofiber Film

Polymeric nanofibers containing gold nanorods (GNRs) are aligned in a uniform orientation through electrospinning. The dispersive and absorptive parts of the third-order optical nonlinear optical refractive index of the composite film measured by polarization dependent <i>z</i>-scan method are demonstrated to be anisotropically enhanced. Anisotropic optical response of the aligned GNRs and its connection with the ultrafast electron dynamics are discussed in light of the results of resonant femtosecond pump–probe experiments. The significant appearance of anisotropic nonlinear optical properties of ensembles of GNRs is attributed to the sensitive excitation of longitudinal surface plasmon resonance (LSPR) of highly aligned GNRs. For the macroscopic applications of ensembles of GNRs, such as passive mode-locking and all-optical switching, the experimental results demonstrate that the alignment of GNRs through electrospinning should be very high efficient, and economic

Luffa-Sponge-Like Glass–TiO₂ Composite Fibers as Efficient Photocatalysts for Environmental Remediation

Structural design of photocatalysts is of great technological importance for practical applications. A rational design of architecture can not only promote the synthetic performance of photocatalysts but also bring convenience in their application procedure. Nanofibers have been established as one of the most ideal architectures of photocatalysts. However, simultaneous optimization of the photocatalytic efficiency, mechanical strength, and thermal/chemical tolerance of nanofibrous photocatalysts remains a big challenge. Here, we demonstrate a novel design of TiO₂–SiO₂ composite fiber as an efficient photocatalyst with excellent synthetic performance. Core–shell mesoporous SiO₂ fiber with high flexibility was employed as the backbone for supporting ultrasmall TiO₂ nanowhiskers of the anatase phase, constructing core@double-shell fiber with luffa-sponge-like appearance. Benefitting from their continuously long fibrous morphology, highly porous structure, and completely inorganic nature, the TiO₂–SiO₂ composite fibers simultaneously possess high photocatalytic reactivity, good flexibility, and excellent thermal and chemical stability. This novel architecture of TiO₂–SiO₂ glass composite fiber may find extensive use in the environment remediation applications

Improved Up-Conversion Luminescence from Er³⁺:LaF₃ Nanocrystals Embedded in Oxyfluoride Glass Ceramics via Simultaneous Triwavelength Excitation

Up-conversion (UC), harvesting near-infrared (NIR) sunlight, is highly desirable for photovoltaic (PV) cells. In regard to this concept, most of the reported experiments on UC materials and their applications, however, were conventionally studied on a monochromatic laser with a narrow excitation band, which is difficult to meet the requirement of solar spectrum conversion. Given the practical applications in PV cells, investigations for UC materials upon simultaneous multiwavelengths even broadband near-infrared (NIR) sunlight excitation are much more meaningful. Herein, we studied the UC luminescence properties of germanate oxyfluoride glass ceramics (GCs) containing LaF₃:Er³⁺ nanocrystals with lower phonon energy upon simultaneous triwavelength excitation. The UC emission intensities upon simultaneous triwavelength excitation were drastically enhanced in comparison with the case of that by monochromatic excitation. The UC luminescence mechanisms were interpreted in-depth in terms of synergetic UC effect owing to the perturbation in the excited states established by different excitation wavelengths. We demonstrated the application of the simultaneous triwavelength excited GC by adding it to the rear face of thin-film hydrogenated amorphous silicon (a-Si:H) solar cells. The photoactive current generated by the reflected UC light upon simultaneous triwavelength excitation was dramatically enhanced in contrast to the case of that upon monochromatic excitation. This Er³⁺-doped germanate oxyfluoride GC, harvesting broader NIR sunlight photons via simultaneous multiwavelength excitation, has colossal potential to improve the power conversion efficiency in PV cells in the near future