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Two-dimensional perovskites that could be regarded as natural organic-inorganic hybrid quantum wells (HQWs) are promising for light-emitting diode (LED) applications. High photoluminescence quantum efficiencies (approaching 80%) and extremely narrow emission bandwidth (less than 20 nm) have been demonstrated in their single crystals; however, a reliable electrically driven LED device has not been realized owing to inefficient charge injection and extremely poor stability. Furthermore, the use of toxic lead raises concerns. Here, we report Sn(II)-based organic-perovskite HQWs employing molecularly tailored organic semiconducting barrier layers for efficient and stable LEDs. Utilizing femtosecond transient absorption spectroscopy, we demonstrate the energy transfer from organic barrier to inorganic perovskite emitter occurs faster than the intramolecular charge transfer in the organic layer. Consequently, this process allows efficient conversion of lower-energy emission associated with the organic layer into higher-energy emission from the perovskite layer. This greatly broadened the candidate pool for the organic layer. Incorporating a bulky small bandgap organic barrier in the HQW, charge transport is enhanced and ion migration is greatly suppressed. We demonstrate a HQW-LED device with pure red emission, a maximum luminance of 3466 cd m-2, a peak external quantum efficiency up to 3.33%, and an operational stability of over 150 h, which are significantly better than previously reported lead-free perovskite LEDs.

Silver nanoparticles were prepared under a microwave high-pressure condition using citric acid sodium as a reducer while the excess citrate was removed under high speed centrifugation. There is a resonance scattering (RS) peak at 470 nm for silver nanoparticles. In a pH 4.0 HAc-NaAc buffer solution, hydroxyl radicals from the Fenton reaction can oxidize silver nanoparticles to Ag+, resulting in the RS intensity decreasing. The decreased RS intensity at 470 nm (ΔI 470 nm) is linear with respect to the concentration of H2O2 (C) in the range of 0.27–7.56 μmol/L with a detection limit of 0.23 μmol/L. Its regression equation is ΔI 470 nm = 24.3 C + 13.8 with a correlation coefficient of 0.9959. This method was applied to screening the antioxidants with satisfactory results.

The experiments show that Pd(II) has a strong catalytic effect on the slowly decolored reaction between malachite green and NaH 2 PO 2 in acetate buffer solution (pH 4.4) at 100°C. The catalytic reaction system is investigated using high-performance liquid chromatography (HPLC) with ultraviolet detection at 625 nm. A novel HPLC method for the determination of 0.6-50 ng/mL Pd with a detection limit of 0.2 ng/mL is described. Palladium in real samples is analyzed using this catalytic HPLC method.

A highly sensitive and novel polarographic method has been developed for determination of ultratrace amounts of osmium, based on the catalysis of the cerium(IV)-arsenic(III) reaction by osmium(VIII). The reaction rate is monitored by measuring the arsenic(III) with a single-sweep oscillopolarograph. Osmium concentrations from 7.0 x 10(-11) to 5.0 x 10(-9)M can be determined by the initial rate method. The method has been applied to determination of osmium in refined ore and chlorination residues with satisfactory results.