Silicon nanoparticles (Si-NPs) are useful phosphor materials for light emitting devices because of their multicolor luminescence, low production cost, and abundance. The luminescence properties of Si-NPs strongly depend on their surface condition. To improve their luminance and luminance stability, Si-NPs are combined with an alkyl group. We used ultraviolet irradiation to couple the surface of Si-NPs with an organic layer consisting of an alkyl group. The surface-modified Si-NPs demonstrated bright and stable luminance in air. Our findings suggest that alkyl-passivation of Si-NPs has future practical applications for light emitting devices and displays.
The aim of this study was to clarify how the characteristics of a lighting environment at nightinfluence psychological impressions. We carried out an experiment in which participants observed images of outdoor scenes at night and evaluated their psychological impressions of the scenes. Results showed that the impression of anxiety was highly correlated with five impressions: brightness, clarity, activity, comfort, and preference.The fact that the impression of brightness had a strong influence on anxiety suggests that brightness is a major factor dominatingthe psychological impression of an outdoor space at night.Analysis of the luminance distribution on the images showed that the impression of brightness was closely correlated with the statistical values representing the intermediate range of luminance distribution on road surfaces but not with the statistics computed from the luminance distribution over the entire area of the images. These results indicate that the impression of the brightness of an outdoor space at night may be determined by the luminance levels covering the wide area of the ground surface.
Recently, research has been done from various directions to evaluate the brightness of spaces. However, no studies have been conducted regarding quantitative measurements of the brightness at different positions in a visual field. That is, a model for evaluating the brightness of spaces and lighting design techniques have not been considered much regarding the brightness at different positions in the visual field. Therefore, in this study, the sensitivity to brightness at different positions in the visual field was investigated in order to quantify brightness perception throughout the entire visual field. The experimental results show the tendency for Lm/Lt rises as the visual angle increases. Moreover, they show the Lm/Lt in the vertical lower direction is higher than that in other directions, especially at 20 degrees or more.
Museum lighting environments are carefully controlled so as not to cause any damage or deterioration to artwork. However, no method currently exists for calculating the change in color rendering properties when illuminance is changed. The purposes of this study were to clarify color rendering properties at low illuminance and to develop a new method for calculating color rendering values while taking illuminance in to account. The results showed that subjective color feelings of color samples were influenced by illuminance as well as by hue in the samples, especially by red. We defined“color quality indices”called Rx and Rxi to evaluate the new color rendering properties expressing illuminance effects and hue effects. The new indices Rx and Rxi were found to correlate significantly with the subjective results.