Red Dye Concentration Research Articles

Improvement of Device Efficiency by Phosphorescent Materials in Polymers Bulk Heterojunction Solar Cells

To improve the performance of organic solar cells, various methods have been used to increase the light absorbance and electron transfer efficiency or decrease the internal resistance of the device. In this article, red dyes of phosphorescent materials are used to improve the performance of bulk heterojunction organic solar cells based on MDMO-PPV and PCBM. Solar cell devices doped with different red dyes showed higher performances in terms of current, voltage and conversion efficiency than those without red dyes. The efficiency was maximized in the devices with a 10% concentration of red dye 2, which was attributed to the longer exciton lifetimes that were induced by the triplet spin state of the red dyes allowing them to reach the p-n junction and thereby generate more photocurrent.

Laboratory-Scale Thermal Stability Experiments on RP-1 and RP-2

The thermal stability of kerosene-based rocket propellants enables successful regenerative cooling of liquid rocket engines. This work experimentally investigates the effect of sulfur level and red dye concentrations on the thermal stability of RP-1 and RP-2 rocket fuels. A high Reynolds number thermal stability test unit evaluated various compositions of the fuels. The experiment consisted of an electrically heated, stainless steel capillary tube with controlled fuel outlet temperature. As deposits built up inside the capillary tube, an optical pyrometer monitored external temperature profiles. Multiple runs at individual test sites provided results on measurement repeatability. Testing at two facilities provided results on measurement reproducibility. The technique is able to distinguish between RP-1 and RP-2 rocket fuels which mainly differ in their sulfur concentrations. Red dye is shown to have a measurable negative impact on thermal stability. Carbon burn-off analysis of residue in the capillary tubes correlates with the external temperature results.

Prediction of emulsion color from droplet characteristics: dilute monodisperse oil-in-water emulsions

The influence of droplet characteristics on the transmission of light through dilute monodisperse oil-in-water emulsions was investigated in the presence and absence of dye. The turbidity spectra and tristimulus color coordinates ( L*, a*, b*) of a series of n-hexadecane oil-in-water emulsions with different disperse phase volume fractions ( φ=0–0.02 wt%), mean droplet radii ( r=0.1–1 μm) and red dye concentration (0 and 0.002 wt%) were measured. The dependence of the optical properties of colored and non-colored emulsions on droplet size and concentration could be qualitatively described by light scattering theory. Nevertheless, there was relatively poor quantitative agreement between theory and experiment because of the influence of the measurement system on the optical properties of emulsions. The information presented in this paper will facilitate the formulation of dilute food and beverage emulsions with specific optical characteristics.

Theoretical and Experimental Study of Spectral Reflectance and Color of Concentrated Oil-in-Water Emulsions

The influence of droplet and dye concentration on the optical properties of oil-in-water emulsions has been investigated. The spectral reflectance and tristimulus color coordinates (L, a, b) of a series of n-hexadecane oil-in-water emulsions with the same median droplet diameters (∼0.3 μm), but different droplet concentrations (0.25 to 38.3 wt%) and red dye concentrations (0 to 0.2 wt%), were measured. Spectral reflectances decreased with increasing dye concentration and decreasing droplet concentration and had troughs at the same wavelengths as the peaks in the absorption spectra of the dyes. Emulsion L-values (“lightness”) decreased and a- and b-values (“chromacity measures”) increased as the dye concentration increased or the droplet concentration decreased. There was good qualitative agreement between the measured spectral reflectance of the emulsions and that predicted by the Kubelka–Munk theory of diffuse reflectance. Excellent agreement between theory and experiment could be obtained using an empirically determined correction-factor that accounts for cuvette effects.

AN RTD DETERMINATION METHOD FOR EXTRUSION COOKING

The residence time distribution (RTD) in an APV Baker twin-screw extruder was studied by injecting a red color during extrusion of rice flour. the redness color value from a Hunter Colorimeter and the red dye concentration of the ground extrudate were used to determine the RTD of rice flour and RTD spread. the redness color values significantly overestimated the mean residence times and RTD spreads (p < 0.0001). the redness color values cannot replace the red dye concentrations to determine the residence time distribution in a twin-screw extrusion cooking system.