Emission enhancement

In the emission spectra of coumarins 9a, 10a, 10c, and 9d in BSA/SDS mixture, the most pronounced bands revealed similar wavelengths to those in the presence of BSA. Observed Stokes shifts values for dyes 9a-d and lOa-d occurred between 8 and 102 nm. The fluorescence increase of the dye upon BSA/SDS addition varied from 2.5 times (9b) to 330 times (lOd), while the brightest complex resulted from dye 10a, its quantum yield being about 0.27. Despite the observed emission enhancement value, the fluorescence intensity of other coumarin dyes in the presence of BSA/SDS mixture was only low to moderate. 

From the results obtained, it was found that compound 10a showed very high fluorescence intensity in the presence of the BSA and BSA/SDS mixture ( F 0.27) together with a noticeable emission enhancement. The presence of dimethyl indo-lenyl increased the affinity of the dyes to both native and denatured proteins. The authors proposed compound 10a for further studies as fluorescent probes for protein detection. 

Thomas, L, Netzel, K. N. and Zhao, M. (1995). Base-content dependence of emission enhancements, quantum yields, and lifetimes for cyanine dyes bound to double-strand DNA Photophysical properties of monomeric and bichromophoric DNA stains. J. Phys. Chem. 99,17936-17947. 

X. Zhang and S.A. Jenekhe, Electroluminescence of multicomponent conjugated polymers. 1. Roles of polymer/polymer interfaces in emission enhancement and voltage-tunable multicolor emission in semiconducting polymer/polymer heterojunction, Macromolecules, 33 2069-2082, 2000. 

Sponge consolidation, in titanium manufacture, 24 854 Spontaneous emission, 14 848-850 Spontaneous emission enhancements, 14 855... 

Qian Y, Li S, Zhang G, Wang Q, Wang S, Xu H, Li C, Li Y, Yang G (2007) Aggregation-induced emission enhancement of 2-(2 -hydroxyphenyl)benzothiazole-based excited-state intramolecular proton-transfer compounds. J Phys Chem B 111 5861-5868... 

Figure 7. Difference in the spontaneous emission enhancement in a LED (a) and a microcavity laser (b) Density of electronic states in bulk semiconductor material and lowdimensional semiconductor heterostructures (c).

In some manufacturing process analysis applications the analyte requires sample preparation (dilution, derivatization, etc.) to afford a suitable analytical method. Derivatization, emission enhancement, and other extrinsic fluorescent approaches described previously are examples of such methods. On-line methods, in particular those requiring chemical reaction, are often reserved for unique cases where other PAT techniques (e.g., UV-vis, NIR, etc.) are insufficient (e.g., very low concentrations) and real-time process control is imperative. That is, there are several complexities to address with these types of on-line solutions to realize a robust process analysis method such as post reaction cleanup, filtering of reaction byproducts, etc. Nevertheless, real-time sample preparation is achieved via an on-line sample conditioning system. These systems can also address harsh process stream conditions (flow, pressure, temperature, etc.) that are either not appropriate for the desired measurement accuracy or precision or the mechanical limitations of the inline insertion probe or flow cell. This section summarizes some of the common LIF monitoring applications across various sectors. 

Demas et al.228 1 observed luminescence quenching of [Ru(bpy)2(CN)2] by aciuo lons of cobalt(II), nickel(II), and copper(II) as well as by a number of other complexes. However, Kinnaird and Whitten232) observed blue shifts in both absorbance and emission and substantial emission enhancement in a silver(I) adduct, [Ru(bpy)2(CN)(CNAg)]+,... 

In 1992, Barton reported the coupling of a ruthenium(II) dppz complex to the 5 -end of a 15-mer oligonucleotide to form a DNA probe (7) [36]. Since the complex binds to double-stranded DNA with a high affinity and shows substantial emission enhancement after the binding, the ruthenium(II) dppz oligonucleotide has been used as a probe for single-stranded DNA molecules... 

Another approach to increasing the emission enhancement factors is to identify a system that inherently shows very weak emission in aqueous buffer,... 

The considerable enhancement in fluorescence emission is evident. The transition involved is 5D4—7Fs transition. The enhancement of fluorescence also depends on the excitation wavelength. From the value of the excitation wavelength, Aexc giving rise to the maximum emission enhancement, the residue involved in the energy transfer can be usually identified. 

Figure 6 (a) UV-vis absorption changes of [Pt(terpy)(C=C-C=CH)]+ (concentration = 1.47 x 10 " M) in acetonitrile with increasing diethyl ether content. Inset Plot of absorbance vs. diethyl ether composition in acetonitrile at 615mn ( ) and in acetone at 610mn ( ). (b) Emission enhancement of [Pt(terpy)(C=C-C=CH)]+ (concentration = 1.47 x 10 " M) in acetone npon increasing diethyl ether content. Inset Plot of corrected emission intensity as a limction of diethyl ether composition (A). (Reprinted with permission from Ref. 65. 2002 American Chemical Society)... 

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