Blue LED

Star-shaped molecules with oligophenyl arms derived from 9,9-spirobifluorene as the central unit have been synthesized by Tour et al. [58] and Salbeck et al. [59] and have been suggested as potential emitter materials for blue LEDs. 

From the perspective of the strategies aimed at fabrication of efficient blue LEDs, the results outlined above regarding yellow LPPP light emitting diodes are, nevertheless, unsatisfactory. In order to prepare blue LEDs from LPPP materials, it is necessary to efficiently mask out or suppress the dominant yellow aggregate emission. 

The crystal quality of the InGaN QWs becomes poor mainly due to the lattice-constant mismatch and the difference of the thermal expansion coefficient between InN and GaN with increasing the In composition [4,5]. Therefore, in order to improve the external quantum efficiency (i/ext) of the InGaN-based LEDs and LDs, it is important to elucidate and optimize the effects of the various growth conditions for the InGaN active layer on the structural and optical properties. Recently, we reported a fabrication of efficient blue LEDs with InGaN/GaN triangular shaped QWs and obtained a substantial improvement of electrical and optical properties of the devices [6,7]. 

In order to verify the enhancement provided by the cones, a sol-gel layer doped with a fluorescent ruthenium complex was deposited onto a chip in a configuration similar to that shown in Figure 15. Blue LED excitation of the fluorescent sol-gel layers was employed. The resultant fluorescence was recorded using a CMOS camera and the resultant image is shown in Figure 16. 

Borisov SM, Klimant I (2008) Blue LED excitable temperature sensors based on a new europium(III) chelate. J Fluoresc 18 581-589... 

In the case of the low-output blue LED, a photomultiplier tube (PMT) detector was used (Figure 13.7). 

Color-changi ng metJi urn Indium tin oxide - Blue LED Catnode... 

Astatination of the diazonium salt of 4-amino-methylene blue led to only 10% yield of 4-astato-methylene blue (VI). Alternatively, 4-astato-methylene blue was rapidly synthesized by heterogeneous nucleophilic isotopic exchange in the presence of 18-crown-6 ether at 80° C, with 4-iodo-methylene blue. The product was separated and identified by TLC yields ranged from 50 to 65% 41). Additionally, 2-astato-8-iodo-methylene blue (VII) has similarly been prepared in 60% yield from 2,8-diiodo-methylene blue 41). 

The industrial application of SiC began with the blue light emitting diode (LED), which was very weak due to the indirect bandgap of SiC but was the only commercial blue electroluminescent light source at the time (the late 1980s). The SiC blue LED was soon surpassed in intensity by the gallium nitride (GaN)-based... 

The LED has also been used as the excitation source for fluorescent detection. For instance, two LEDs (red and blue) were used to detect FTTC-labeled amino acids on a PMMA chip. The blue LED was used for excitation and the red LED for background noise compensation, leading to a four-fold S/N enhancement [681], Moreover, blue LEDs (470 nm) were used to detect various dyes, such as... 

APTS (for sugar isomers) [560], RNA molecular beacon probes [337], and YOPRO-1 (for dsDNA) [613]. In one report, a ring of 24 blue LEDs (470 nm) has been used for flood illumination [321]. 

In one report, the detection optical fiber (coupled to a blue LED light source) and the microavalanche photodiode were both embedded in a PDMS chip to detect proteins [692]. 

FIGURE 12 shows the dependence of output power for MQW blue LEDs on forward current. The output power increases linearly with forward current. This output power is about 1.5 times higher than that for conventional blue LEDs. The luminous intensity was 3 cd at 20 mA. 

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