Molten Salt-Derived RuO2 Nanocrystals and Nanowires: Unveiling Correlations of Morphology, Microstructure, and Electrocatalytic Performance.

Ruthenium oxide (RuO2), due to its comparable binding energy with *H and cost-effectiveness against Pt, has emerged as a pivotal electrocatalyst for oxygen evolution reaction (OER). In the present study, RuO2 nanocrystals (NCs) and nanowires (NWs) were obtained by a molten salt process and the morphology, crystal structure, and local bonding features were examined by using electron microscopy and X-ray absorption spectroscopy. From the electrochemical measurement, both RuO2 NCs and NWs exhibit favorable stability and activity toward oxygen evolution reaction in an alkali medium, althought NCs exhibit higher activity, which is likely attributed to the larger surface area and the high local structural disorder. The theoretical calculation reveals that RuO2 NWs with a primary (110) orientation show a higher overpotential due to its d-band center's proximity to the Fermi level versus (101). The present work suggests that the molten salt process could be an efficient method for producing metal oxide catalysts with tailorable geometry and performances.

Synthesis and structure of metal-TCPE (metal = Th, Ce) metal-organic frameworks based on 1,2,4,5-tetrakis(4-carboxyphenyl) ethylene.

Two new metal-organic frameworks (MOFs) (Th/ Ce -TCPE) based on 1,2,4,5-tetrakis(4-carboxyphenyl)ethylene were obtained using a straightforward reaction under moderate conditions. Th and Ce formed the central units of this MOF in the mononuclear and in the unusual trinuclear cluster configurations, respectively. The resulting MOFs were analysed by fluorescence spectroscopy to understand their luminescence. The obtained data revealed that benzene's electron cloud density and torsion angle on the ligand were affected by the acetic acid molecule and Th(IV), which caused Th-TCPE to irradiate stronger blue emission, but Ce-TCPE showed no fluorescence due to the self-quenching. Such a unique luminescence property could be used for fluorescence or radiopharmaceutical sensing.

Synthesis of luminescent thorium-based metal-organic frameworks with 1,2,4,5-tetrakis(4-carboxyphenyl)benzene.

Three new thorium-based MOFs based on 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (H4TCPB) were obtained under a similar reaction system (metal salt, ligand, solvent, and acid are the same). Th(iv) forms the central unit of the MOFs in mononuclear and binuclear clusters, respectively. All the MOFs show blue ligand-based luminescence under an ultraviolet environment. This is the first time that multiple thorium-based MOFs with luminescence have been found with the same ligand.

Broadband conversion of visible light to near-infrared emission by Ce3+, Yb3+-codoped yttrium aluminum garnet.

We show that Ce(3+) can be an efficient sensitizer for Yb(3+) in the host lattice of yttrium aluminum garnet (YAG). With blue-light excitation to induce the 4f-->5d transition of Ce(3+), characteristic near-IR emission of Yb(3+) due to transition of (2)F(5/2)-->(2)F(7/2) peaking at 1030 nm is generated as a result of energy transfer from Ce(3+) to Yb(3+). The result of spectral evolution with temperature indicates that the efficiency of energy transfer is enhanced owing to thermal effect. This evidence implies that the phonon-assisted process participates in the downconversion of YAG: Ce(3+), Yb(3+).

Facile synthetic strategy for efficient and multi-color fluorescent BCNO nanocrystals.

A facile strategy based on the reaction of urea and boric acid is developed for the synthesis of toxicity-free BCNO nanocrystals containing carbon impurities and which exhibit efficient multi-color fluorescence under both single-photon and two-photon excitation.

Optical gain at 1550 nm from colloidal solution of Er3+-Yb3+ codoped NaYF4 nanocubes.

We demonstrated optical amplification at 1550 nm with a carbon tetrachloride solution of Er(3+)-Yb(3+) codoped NaYF(4) nanocubes synthesized with solvo-thermal route. Upon excitation with a 980 nm laser diode, the nanocube solution exhibited strong near-infrared emission by the (4)I(13/2)-->(4)I(15/2) transition of Er(3+) ions due to energy transfer from Yb(3+) ions. We obtained the highest optical gain coefficient at 1550 nm of 0.58 cm(-1) for the solution with the pumping power of 200 mW. This colloidal solution might be a promising candidate as a liquid medium for optical amplifier and laser at the optical communication wavelength.

Transparent colloid containing upconverting nanocrystals: an alternative medium for three-dimensional volumetric display.

We report an alternative medium of transparent upconverting colloid containing lanthanide ion doped NaYF(4) nanocrystals for three-dimensional (3D) volumetric display. The colloids exhibit tunable upconversion luminescence with a wide spectrum of colors by adjusting the doping concentrations of the nanocrystals and the compositions of the colloids. Our preliminary experimental result indicates that an upconverting colloid-based 3D volumetric display using a convergent near infrared laser beam to induce a localized luminescent spot near the focus is technically feasible. Therefore arbitrary 3D objects can be created inside the upconverting colloid by use of computer controlled 3D scanning systems.

Cooperative downconversion in Yb3+/-RE3+ (RE=Tm or Pr) codoped lanthanum borogermanate glasses.

We report on cooperative downconversion in Yb(3+)-RE(3+) (RE=Tm or Pr) codoped lanthanum borogermanate glasses (LBG), which are capable of splitting a visible photon absorbed by Tm(3+) or Pr(3+) ions into two near-infrared photons. The results indicate that Pr(3+)-Yb(3+) is a more efficient ion couple than Tm(3+)-Yb(3+) in terms of cooperative downconversion. We have obtained a highest quantum yield of 165% and 138% for Pr(3+)-Yb(3+) and Tm(3+)-Yb(3+) codoped LBG glasses under 468 nm excitation, respectively. However, ultraviolet light excitation to the charge transfer band of Yb(3+) does not result in quantum splitting as rapid relaxation from the charge transfer band to 4f(13) levels of Yb(3+) dominates.

Enhanced broadband near-infrared luminescence from transparent Yb3+/Ni2+ codoped silicate glass ceramics.

The near-infrared emission intensity of Ni(2+) in Yb(3+)/Ni(2+) codoped transparent MgO-Al(2)O(3)-Ga(2)O(3)-SiO(2)-TiO(2) glass ceramics could be enhanced up to 4.4 times via energy transfer from Yb(3+) to Ni(2+) in nanocrystals. The best Yb(2)O(3) concentration was about 1.00 mol%. For the Yb(3+)/Ni(2+) codoped glass ceramic with 1.00 mol% Yb(2)O(3), a broadband near-infrared emission centered at 1265 nm with full width at half maximum of about 300 nm and lifetime of about 220 mus was observed. The energy transfer mechanism was also discussed.

Energy transfer between Cr3+ and Ni2+ in transparent silicate glass ceramics containing Cr3+/Ni2+ co-doped ZnAl2O4 nanocrystals.

The emission intensity of Ni(2+) at 1200 nm in transparent ZnO-Al(2)O(3)-SiO2 glass ceramics containing ZnAl(2)O(4) nanocrystals is improved approximately 8 times by Cr(3+) codoping with 532 nm excitation. This enhanced emission could be attributed to an efficient energy transfer from Cr(3+) to Ni(2+), which is confirmed by time-resolved emission spectra. The energy transfer efficiency is estimated to be 57% and the energy transfer mechanism is also discussed.