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We demonstrate that the apparent emission colors of InGaN-based light-emitting diodes using microstructured multifacet quantum wells as active layers can externally be controlled over a wide spectral range that encompasses green to blue or white at a color temperature of 4000 K to blue along the Planckian locus. The controllability relies on facet-dependent polychromatic emissions. The pulsed current operation with the appropriate duties varied their relative intensities and the consequent apparent colors without seriously affecting the total number of emitted photons, particularly for the blue to green variation.

Monolithic polychromatic light-emitting diodes (LEDs) based on micro-structured InGaN/GaN quantum wells are demonstrated. The microstructure is created through regrowth on SiO2 mask stripes along the [1100] direction and consists of (0001) and {1122} facets. The LEDs exhibit polychromatic emission, including white, due to the additive color mixture of facet-dependent emission colors. Altering the growth conditions and mask geometry easily controls the apparent emission color. Furthermore, simulations predict high light extraction efficiencies due to their three-dimensional structures. Those observations suggest that the proposed phosphor-free LEDs may lead to highly efficient solid-state lighting in which the color spectra of light sources are synthesized to satisfy specific requirements for illuminations.

Fatty acids (FAs) are known to form vesicle structures, depending on the surrounding pH conditions. In this study, we prepared vesicles by mixing FAs and a cationic surfactant, and then investigated their physicochemical properties using fluorescence spectroscopy and dielectric dispersion analysis (DDA). The assemblies formed from oleic acid (OA) and linoleic acid (LA) were modified by adding didecyldimethylammonium bromide (DDAB). The phase state of FA/DDAB mixtures was investigated with pH titration curves and turbidity measurements. The trigonal diagram of FA/ionized FA/DDAB was successfully drawn to understand the phase behaviors of FA/DDAB systems. The analysis of fluidities in the interior of the membrane with use of 1,6-diphenyl-1,3,5-hexatriene (DPH) indicated that the membrane fluidities of OA/DDAB and LA/DDAB at pH 8.5 slightly decreased in proportion to the molar ratio of DDAB in FA/DDAB systems. The fluorescent probe 6-lauroyl-2-dimethylamino naphthalene (Laurdan) indicated that the LA vesicle possessed a dehydrated surface, while the OA vesicle surface was hydrated. Modification of LA vesicles with DDAB induced the hydration of membrane surfaces, whereas modification of OA vesicles by DDAB had the opposite effect. DDA analysis indicated that the membrane surfaces were hydrated in the presence of DDAB, suggesting that the surface properties of FA vesicles are tunable by DDAB modification.