Enhanced luminescence

Luciferase-catalyzed luminescence of luciferin. Odontosyllis luciferin emits light in the presence of Mg2+, molecular oxygen and luciferase. The relationship between the luminescence intensity and the pH of the medium shows a broad optimum (Fig. 7.2.8). The luminescence reaction requires a divalent alkaline earth ion, of which Mg2+ is most effective (optimum concentration 30 mM). Monovalent cations such as Na+, K+, and NH have little effect, and many heavy metal ions, such as Hg2+, Cu2+, Co2+ and Zn2+, are generally inhibitory. The activity of crude preparations of luciferase progressively decreases by repeated dialysis and also by concentrating the solutions under reduced pressure. However, the decreased luciferase activity can be completely restored to the original activity by the addition of 1 mM HCN (added as KCN). The relationship between the concentration of HCN and the luciferase activity is shown in Fig. 7.2.9. Low concentrations of h and K3Fe(CN)6 also enhance luminescence, but their effects are only transient. 

Berger-Collaudin A., Blum L. J., Enhanced luminescent response of a fiberoptic sensor for H2O2 by a high-salt concentration medium, Sens. Actuators B 1997 38-39 189-194. 

Yin S, Peng Q, Shuai Z, Fang W, Wang Y-H, Luo Y (2006) Aggregation-enhanced luminescence and vibronic coupling of silole molecules from first principles. Phys Rev B 73 205409... 

Enhanced Luminescence of Lanthanides Determination of Europium by Enhanced Luminescence 184... 

Standard addition of Eu(lll) to pond water or tap water. [Data from A. L Jenkins and G. M. Murray, "Enhanced Luminescence of Lanthanides," J. Chem. Ed. 1998, 75, 227 ]... 

Whitehead, T. P, Thorpe, G. H G, Carter, T. J. N, Groucutt, C., and Kricka, L J. (1983) Enhanced luminescence procedure for sensitive determination of peroxidase-labeled conjugates in immunoassay. Nature 305, 158,159. 

The emission properties of lumophores change when included within the microenvironment of a supramolecule bucket. Nonradiative decay processes are generally curtailed within the confines of the bucket interior and luminescence intensity is therefore increased [138,208,209], Because CDs present a more protected microenvironment than calixarenes, the binary complexes of the former supramolecule have been examined most extensively. Spurred by Cramer s pioneering observation that the spectral properties of a lumophore are perturbed by complexation within a CD [210], a large body of work has sought to define the influence of CDs on the photophysics of bound lumophores. Different factors contribute to the enhanced luminescence of 1 1 CDilumophore complexes. These include the following. 

Figure 14 Modification of Scheme 1 to incorporate a PET mechanism for the detection of protons by 1. Proton binding to amine lone pair of electrons disrupts the PET quenching process to give rise to enhanced luminescence. Within the context of Scheme 1, the protonated diethylammonium bromonaphthyl is the luminescent analyte. 

Diamond and coworkers attribute an increase in fluorescence from the anthracene reporter sites of 44 to the increased rigidity induced by complexation of Li+, Na+, and K+ to the calixarene s tetraester cleft. The tetraamide derivative, 45, shows an especially selective response to Na+ ion [383], Restricted motion of the calix[4]arene is believed to lead to the enhanced luminescence response. This contention is supported by H NMR studies, which show metal ions to confer significant order on the calix[4]arene receptor. 

Hardcastle, A., W. Aherne, and V. Marks (1988). A sensitive enhanced luminescent immunoassay for the triazine pesticides atrazine and simazine. J. Biolumin. Chemilumin., 2 209. 

V12. Venditti, P., DiMeo, S., de Martino Rosaroll, P., and De Leo, T., Determination by enhanced luminescence technique of liver antioxidant capacity. Arch. Physiol. Biochem. 103, 484-491 (1995). 

Enhanced luminescence of SiC>2 Eu3+ by energy transfer from ZnO nanocrystals (3 nm) was recently reported (Bang et al., 2005). The defect-related green emission from ZnO nanocrystals was completely quenched when they were embedded in Si02 doped with Eu3+, indicating a very efficient energy transfer from the embedded ZnO to Eu3+. As a result, the f-f emissions fromEu3"1" were enhanced 5-10 times. 

Because of the higher sensitivity of Ndm ions towards deactivation through O-H oscillators, the complexes with this lanthanide have much lower quantum yields and lifetimes when compared to Ybm. The best photophysical properties are obtained with phthalexon S and since complexes with PS contain 4-5 water molecules, depending on the lanthanide ion, it is quite clear that exclusion of these water molecules from the first coordination sphere will lead to much enhanced luminescent properties. This is indeed demonstrated by bis(cyclen)-substituted PS, H736 (see fig. 36), which increases quantum yields to 0.23 and 1.45% in D2O for Ndm and Ybm, respectively (Korovin and Rusakova, 2002). 

Wang, H., Qian, G, Wang, M., et al. (2004) Enhanced luminescence of an erbium (III) ion-association ternary complex with a near-infrared dye. The Journal of Physical Chemistry B, 108, 8084-8088. 

In the previous sections we have discussed the historical development of enhanced fluorescence as well as giving a detailed theoretical basis for the phenomena. In this section we will highlight some of the experimental results that illustrate how LSPR supporting nanostructures have been used for enhanced luminescence. 

It is appropriate here to present a few examples of the various approaches that have successfully applied to the task of tailoring LSPR for enhanced luminescence. 

Plasmonic en neering provides the flmdamentals for nanostructure fabrication exploiting the unique optical propolies of certain metals (mainly silver and gold) and advancing the development and applications of plasmon enhanced luminescence. Nanostructures can not only be fabricated to provide enhancement throughout the UV-Vis spectrum but also for near infiared excitation and emissions. 

Kulakovich, O., Strekal, N., Yaroshevich, A., Maskevich, S., Gaponenko, S., Nabiev, I., Woggon, U. and Artemyev, M. (2002). Enhanced Luminescence of CdSe Quantum Dots on Gold Colloids. Nano Lett. 2 1449-1452. 

Zhang, J., Malicka, J., Gryczynski, I. and Lakowicz, J. R. (2004). Oligonucleotide-displaced organic monolayer-protected silver nanoparticles and enhanced luminescence of their salted aggregates. Anal. Biochem. 330 81-86. 

Sackrow M, Stanciu C, Lieb MA, Meixner AJ (2008) Imaging nanometre-sized hot spots on smooth Au Aims with high-resolution tip-enhanced luminescence and Raman near-fleld optical microscopy. Chemphyschem 9(2) 316-320 93. Berweger S, Raschke MB (2009) Polar phonon mode selection rules in tip-enhanced Raman scattering. J Raman Spectrosc 40(10) 1413-1419... 

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