White light emitting diodes (LEDs) have been realized using the active packaging (AP) method. The starting materials were bare InGaN LED chips and CdSe/ZnS core-shell quantum dots (QDs) dispersed in photosensitive epoxy resins. Such hybrid LED devices were fabricated using QD mixtures with one ('single'), two ('dual') or four ('multi') emission wavelengths. The AP method allows for convenient adjustment of multiple parameters such as the CIE-1931 coordinate (x, y), color temperature, and color rending index (CRI). All samples show good white balance, and under a 20 mA working current the luminous efficacies of the single, dual, and multi hybrid devices were 8.1 lm W(-1), 5.1 lm W(-1), and 6.4 lm W(-1), respectively. The corresponding quantum efficiencies were 4.1%, 3.1%, and 3.1%; the CRIs were 21.46, 43.76, and 66.20; and the color temperatures were 12 000, 8190, and 7740 K. This shows that the CRI of the samples can be enhanced by broadening the QD emission band, as is exemplified by the 21.46 CRI of the single hybrid LED compared to the 66.20 value for the multi hybrid LED. In addition, we were able to increase the CRI of the single hybrid LED from 15.31 to 32.50 by increasing the working currents from 1 to 50 mA.

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Influence of buffer layer and growth temperature on the properties of an undoped GaN layer grown on sapphire substrate by metalorganic chemical vapor deposition This study examines the influence of the growth mode on defect formation and strain relaxation in GaN thin films grown on cone-shaped patterned sapphire ͑CSPS͒ substrates by metal-organic chemical vapor deposition. A dramatic reduction in the luminescence dark spot density and a red-shifted excitonic emission were found for GaN on CSPS compared to GaN on planar sapphire substrates. The results also show that both the crystal quality and optical properties are improved in GaN on CSPS with a strong spatial correlation between the dark spots and local structural properties due to the induced-lateral overgrowth on the cone-shaped patterns.

Residues of the polar pesticide pymetrozine were compared using two methods: hydromatrix and liquid–liquid extraction (LLE). The biological half-life and the final residue level were investigated using Aster scaber over a 10-days cultivation period. The respective biological half-lives of the pesticide were 4.2 and 3.5 days at the recommended and double dose. The final residue levels were 1.28 and 1.98 mg kg−1, respectively, at the same application rate of pymetrozine according to the GAP standard of the United Kingdom. Average recovery was higher with LLE than with the hydromatrix method. Dissipation curves of pymetrozine were influenced by the application amount and growth rate of A. scaber. The final residue level of pymetrozine could be predicted to be lower than the UK maximum residue limit for lettuce applying the GAP standard.

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