Colloidal CsPbX 3 (X = Br, Cl, and I) perovskite nanocrystals exhibit tunable bandgaps over the entire visible spectrum and high photoluminescence quantum yields in the green and red regions. However, the lack of highly efficient blue-emitting perovskite nanocrystals limits their development for optoelectronic applications. Herein, neodymium (III) (Nd 3+) doped CsPbBr 3 nanocrystals are prepared through the ligand-assisted reprecipitation method at room temperature with tunable photoemission from green to deep blue. A blue-emitting nanocrystal with a central wavelength at 459 nm, an exceptionally high photoluminescence quantum yield of 90%, and a spectral width of 19 nm is achieved. First principles calculations reveal that the increase in photoluminescence quantum yield upon doping is driven by an enhancement of the exciton binding energy due to increased electron and hole effective masses and an increase in oscillator strength due to shortening of the Pb-Br bond. Putting these results together, an all-perovskite white light-emitting diode is successfully fabricated, demonstrating that B-site composition engineering is a reliable strategy to further exploit the perovskite family for wider optoelectronic applications.

Surface-enhanced Raman scattering (SERS)based capillary system is a promising route toward fast, realtime, and in-situ detection using a facile sampling process. Here, we demonstrate for the first time resonance-tunable SERSactive capillaries with high sensitivity, reproducibility, and stability. The strong signal consistency independent of measurement spots or storage time supports the long-term storage and signal tracking of analytes in practical use. The capillaries were successfully applied to the in-situ detection of pesticide residues, and the sampling process provides operation conveniency compared to conventional methods. These results indicate that our SERS-active capillaries have great potentials in fast in-situ detection for many practical applications.

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ZnO nanophosphors with a diameter of 7 -50 nm have been fabricated under an oxygen gas atmosphere at room temperature by evaporating ZnO powder or Zn targets using pulsed laser ablation. The size and uniformity of ZnO nanophosphors strongly depend on oxygen gas pressure. Results of cathodoluminescence analysis show strong ultraviolet, blue, green, and greenyellow emissions from ZnO nanophosphors excited by a $150 eV low-energy electron beam emitted from carbon nanotubes, depending upon the target material and oxygen gas pressure. Ultraviolet, blue, green, and green-yellow emissions can be attributed to the transitions from the conduction band to the valence band, the Zn i level to the V Zn level or the valence band, the V O level to the valence band, and the Zn i level to the O i level, respectively.

A seed-mediated electroless deposition (SMED) approach for fabrication of large-area and uniform gold nanoparticle films as efficient and reproducible as surface-enhanced Raman scattering (SERS) substrates was presented. This approach involved a seeding pretreatment procedure and a subsequent growth step. The former referred to activation of polylysine-coated glass slides in gold seed solution, and the latter required a careful control of the reactant concentration and reaction time. With the aid of gold seeds and appropriate reaction conditions, a large-area and uniform nanofilm with evenly distributed gold nanoparticles (Au NPs) was formed on the surface of the substrates after adding a mixed solution containing ascorbic acid and trisodium citrate. The morphology of the Au nanofilm was examined by scanning electron microscopy. The size evolution of Au NPs on the surface of the substrates was analyzed in detail. The nanofilm substrate was prepared by reaction conditions of the seeded activation process: 10 mL ascorbic acid and trisodium citrate mixture and 30 min of soaking time, which exhibited an excellent uniformity and reproducibility of SERS enhancement with relative standard deviation (RSD) values of less than 8% (particularly, a RSD value of 3% can be reached for the optimized measurement). Compared to the common electroless deposition, the seed-mediated electroless deposition possessed inherent advantages in controllability, reproducibility, and economic benefit.