Emission wavelength maxima

Dramatic advances in modem fluorophore technology have been achieved with the introduction of Alexa Fluor dyes by Molecular Probes (Alexa Fluor is a registered trademark of Molecular Probes). Alexa Fluor dyes are available in a broad range of fluorescence excitation and emission wavelength maxima, ranging from the ultraviolet and deep blue to the near-infrared regions. Because of the large... 

Furthermore, above the CMC of SDS aqueous solution, the excitation and emission wavelength maxima are reached at 370 nm and 500 nm, respectively. 

TABLE 5.2. Absorption and Emission Wavelength Maxima of Some Useful Fluorochromes0... 

SAMSA-fluorescein is an orange solid compound. Dissolved in buffer at pH 9.0, its maximal wavelength of absorption or excitation is at 495 nm, while its emission wavelength maximum is 520 nm. The reagent and all solutions and derivatives made from it are light sensitive and should be stored in the dark. SAMSA-fluorescein is soluble in aqueous solutions above pH 6.0, but it can be dissolved in DMF to prepare a concentrated stock solution prior to adding a small amount to a buffered reaction mixture. 

Siano and coworkers [14] report the use of 8-anilino-l-naphthalenesulfonic acid (ANS) as a probe of environment polarity in polyacrylamides containing 1 mole percent n-dodecylacrylamide (estimated from feed ratio) in 2 wt% NaCl. ANS, an amphoteric probe is selectively solubilized at the water-hydrophobe interface. The fluorescence emission maximum is shifted from 520 nm, in aqueous environments to approximately 462 nm in hydrophobic environments [18]. Studies of the polymer described above and a homopolymer of acrylamide were accomplished by varying polymer concentration up to 5000 ppm at constant ANS concentration. In Fig. 2.10 a, a plot of the emission wavelength maximum of ANS vs polymer concentration indicated an increasingly hydro-phobic environment with increasing copolymer concentration. Above approximately 1000 ppm, emission wavelength remained constant, indicating that ANS... 

Direct-reading polychromators (Figure 3b) have a number of exit slits and photomultiplier tube detectors, which allows one to view emission from many lines simultaneously. More than 40 elements can be determined in less than one minute. The choice of emission lines in the polychromator must be made before the instrument is purchased. The polychromator can be used to monitor transient signals (if the appropriate electronics and software are available) because unlike slew-scan systems it can be set stably to the peak emission wavelength. Background emission cannot be measured simultaneously at a wavelength close to the line for each element of interest. For maximum speed and flexibility both a direct-reading polychromator and a slew-scan monochromator can be used to view emission from the plasma simultaneously. 

R ( ) Fluorescence Quantum. Yield, (t> Molar Absorptivity, e X 10 Wavelength Maximum Ahsorhance, A max (nm) Emission, em... 

In this case, the maximum enhancement is achieved when A,rcs is equal to the peak emission wavelength of the fluorophore. This enhancement is far more significant for fluorophores of low QE than for those of higher QE. An additional effect namely, a metal-fluorophore quenching can also occur for very small NP-fluorophore separations, typically within 5nm. This has important implications for the fabrication of an enhanced sensor chip, as will be seen in the following section. 

The fluorescent properties of FITC include an absorbance maximum at about 495 nm and an emission wavelength of 520 nm. Fluorescent quenching of the molecule is possible. Under... 

AMCA-hydrazide has a maximal excitation wavelength of 345 nm and a maximum emission wavelength in the range of 440-460 nm. A solution of AMCA in PBS at a concentration of 16.7ng/ml (71.61 nmoles/ml) gives an absorbance at 345 nm of about 1.28. This translates into a molar extinction coefficient at this wavelength of about 13,900M em-1. Different solvents and conditions may alter this value somewhat. 

The native fluorescence of aspirin, in contrast to salicylic acid, is a weak one and has been studied only recently.22 Excitation wavelength maximum is at 280 nm and emission maximum is at 335 nm. Maxima for salicylic acid are at 308 and 450 nm respectively. 

The emission wavelength of PF-PPV copolymer can be red-shifted and the band gap reduced by introducing alkoxy substituents, as demonstrated for compounds 344 [421], Consequently, the transport of both holes and electrons is facilitated and the PLED built in the configuration ITO/PEDOT/344/A1 produces an orange-red color (AEL = 574-592 nm) with a maximum brightness for 344b of 13 50 cd/m2 and a luminous efficiency of 0.51 cd/A, at a rather low turn-on voltage of 2.5 V (Chart 2.87.)... 

SCHEME 3.25 Chemical structures and optical properties of Alq3 derivatives (maximum emission wavelength, photoluminescent quantum efficiency in CH2C12 and the band gap are listed). 

Fig. 2. Parameters affecting the efficiency of energy transfer. (A) Overlay of FITC emission spectrum and PE absorbance spectrum normalized to maximum fluorescence intensity and maximum optical density, respectively. FITC fluorescence intensity was measured as a function of emissions wavelength using a fluorimeter with an excitation wavelength of 488 nm. PE optical density was measured as a function of wavelength using a spectrophotometer. (B) Schematic representation of energy absorption and the possible pathways for the subsequent energy release (abbreviations as in the text).

Lucigenin (10,10 -dimethyl-9,9 -biacridinium or bis-Af-methylacridinium (38)), in the presence of hydrogen peroxide in alkaline media, exhibits chemiluminescence with a maximum emission wavelength at 445 nm. Lucigenin chemiluminescence was first reported in 1935 by Glen and Petsch, and the 1,2-dioxetane 39 was postulated as a key intermediate. Nevertheless, the mechanism of lucigenin chemiluminescence was only elucidated by McCapra and Richardson, who also proposed the thermal decomposition... 

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