We alloyed Zn2+ into CsPbI3 perovskite nanocrystals
by partial substitution of Pb2+ with Zn2+, which
does not change their crystalline phase. The resulting alloyed CsPb0.64Zn0.36I3 nanocrystals exhibited an
improved, close-to-unity photoluminescence quantum yield of 98.5%
due to the increased radiative decay rate and the decreased non-radiative
decay rate. They also showed an enhanced stability, which correlated
with improved effective Goldschmidt tolerance factors, by the incorporation
of Zn2+ ions with a smaller radius than the Pb2+ ions. Simultaneously, the nanocrystals switched from n-type (for CsPbI3) to nearly ambipolar for the alloyed
nanoparticles. The hole injection barrier of electroluminescent LEDs
was effectively eliminated by using alloyed CsPb0.64Zn0.36I3 nanocrystals, and a high peak external quantum
efficiency of 15.1% has been achieved.
Ultrabroadband supercontinuum light expanding from ultraviolet to 6.28 μm is generated in a centimeter-long fluoride fiber pumped by a 1450 nm femtosecond laser. The spectral broadening in the fluoride fiber is caused by self-phase modulation, Raman scattering and four-wave mixing. The experimental and simulated results show that fluoride fiber is a promising candidate for generating the midinfrared supercontinuum light up to 8 μm.
Y 2 O 3 : Eu nanotubes were fabricated by a surfactant assembly mechanism. The tubular structure was characterized by transmission electron microscopy. Under an ultraviolet-light excitation, the nanotubes show a relatively intense emission peak at 618 nm besides the 610 nm peak, different from that of single Y2O3:Eu nanocrystallites. The results of laser-selective excitation indicate that the emission centers near the surface of nanotube walls exhibit inhomogenously broadened spectra without spectral structures while the two sites (sites B and C) inside the nanotube walls present legible spectral structures. It is concluded by the number and peak positions of Stark levels that the sites B and C possess different site symmetries.
Passive Q-switching was experimentally demonstrated in an erbium-doped fiber laser (EDFL) by using gold nanocrystals (GNCs). The GNCs were mixed with sodium carboxymethylcellulose (NaCMC) to form GNCs-NaCMC films. The films exhibited a broad absorption band in the range of 400–1750 nm. By placing the GNCs-NaCMC film in an EDFL cavity pumped by a 980 nm laser diode, stable passive Q-switching was achieved for a threshold pump power of ∼30 mW, and 3.2 μs pulses at 1560 nm with a repetition rate of 24.2 kHz were obtained for a pump power of ∼125 mW.
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