Search

California Policy Options 2019. Annual volume of the UCLA Luskin School of Public Affairs

Most lead-free halide double perovskite materials display low photoluminescence quantum yield (PLQY) due to the indirect bandgap or forbidden transition. Doping is an effective strategy to tailor the optical properties of materials. Herein, efficient blue-emitting Sb3+-doped Cs2NaInCl6 nanocrystals (NCs) are selected as host, rare-earth (RE) ions (Sm3+, Eu3+, Tb3+, and Dy3+) are incorporated into the host, and excellent PLQY of 80.1% is obtained. Femtosecond transient absorption measurement found that RE ions not only served as the activator ions but also filled the deep vacancy defects. Anti-counterfeiting, optical thermometry, and white-light-emitting diodes (WLEDs) are exhibited using these RE ions-doped halide double perovskite NCs. For the optical thermometry based on Sm3+-doped Cs2NaInCl6:Sb3+ NCs, the maximum relative sensitivity is 0.753% K−1, which is higher than those of most temperature-sensing materials. Moreover, the WLED fabricated by Sm3+-doped Cs2NaInCl6:Sb3+ NCs@PMMA displays CIE color coordinates of (0.30, 0.28), a luminous efficiency of 37.5 lm W−1, a CCT of 8035 K, and a CRI over 80, which indicate that Sm3+-doped Cs2NaInCl6:Sb3+ NCs are promising single-component white-light-emitting phosphors for next-generation lighting and display technologies.

California Policy Options 2019. Annual volume of the UCLA Luskin School of Public Affairs

In one-dimensional (1D) systems, the definition of three common states of matter (solid, liquid, and gas) becomes obscure because it has been theoretically predicted that a 1D system has no phase transition. Due to technical difficulty in tracking 1D thermal evolution, hardly any experimental evidence has demonstrated whether there exist these three states. Here we report Raman experimental observation that 1D iodine molecular chains formed inside the nanosized channel undergo continuous transformation from chain structure to single molecules with increasing temperature, without having a sudden change as commonly observed in phase transition. At low temperatures, short-range order exists and manifests itself as long chains in structure, which gradually break into shorter chains with increasing temperature. The 1D system progressively gets more and more disordered, which is in agreement with the theoretical derivations. Our work may benefit the emerging molecular scale electronics. © 2017 American Chemical Society.

In one-dimensional (1D) systems, the definition of three common states of matter (solid, liquid, and gas) becomes obscure because it has been theoretically predicted that a 1D system has no phase transition. Due to technical difficulty in tracking 1D thermal evolution, hardly any experimental evidence has demonstrated whether there exist these three states. Here we report Raman experimental observation that 1D iodine molecular chains formed inside the nanosized channel undergo continuous transformation from chain structure to single molecules with increasing temperature, without having a sudden change as commonly observed in phase transition. At low temperatures, short-range order exists and manifests itself as long chains in structure, which gradually break into shorter chains with increasing temperature. The 1D system progressively gets more and more disordered, which is in agreement with the theoretical derivations. Our work may benefit the emerging molecular scale electronics. © 2017 American Chemical Society.

In one-dimensional (1D) systems, the definition of three common states of matter (solid, liquid, and gas) becomes obscure because it has been theoretically predicted that a 1D system has no phase transition. Due to technical difficulty in tracking 1D thermal evolution, hardly any experimental evidence has demonstrated whether there exist these three states. Here we report Raman experimental observation that 1D iodine molecular chains formed inside the nanosized channel undergo continuous transformation from chain structure to single molecules with increasing temperature, without having a sudden change as commonly observed in phase transition. At low temperatures, short-range order exists and manifests itself as long chains in structure, which gradually break into shorter chains with increasing temperature. The 1D system progressively gets more and more disordered, which is in agreement with the theoretical derivations. Our work may benefit the emerging molecular scale electronics. © 2017 American Chemical Society.

Resonant third-order nonlinear optical susceptibility and hyperpolarizability of CdSe nanocrystal quantum dots were revealed to be ~2.6 10(exp -20) 2.7 10(exp -19) sq m/V2 and ~2.2 10(exp -40) m5/V2 by using nanosecond degenerate four-wave mixing at 532 nm. The large nonlinearity of the CdSe nanocrystals is attributed to the resonant excitation and multiple nonlinear optical processes., Pres. at International Conference On New Phenomena In Mesoscopic Structures (7th) & International Conference On Surfaces And Interfaces Of Mesoscopic Devices (5th) held in Maui, Hawaii, USA on 27 November-2 December 2005. Pub. in Jnl. of Physics: Conference Series, v38 p91-94, 2006. Continuation of Contract W911NF-04-1-0393.