Light scattering photoluminescence

Fig. 10.2. Comparison of optical and hydrodynamic properties of CdTe quantum dots (2.5 nm) solubilized in water with an amphiphilic polymer (octylamine-modified polyacrylic acid) or a multidentate polymer ligand, (a) Absorption (blue curves) and fluorescence emission red curves) spectra of CdTe quantum dots with amphiphilic polymer upper) or multidentate polymer lower) coatings, (b) Dynamic light scattering size data of quantum dots with amphiphilic polymer blue curve) and multidentate polymer green curve) coatings. PL Photoluminescence, AU Arbitrary units. All samples were dissolved in phosphate buffered saline...

The physical chemistry of the anhydride and acid form of the 1 1 MA-hexene-1 copolymer have received some study, using viscosity, diffusion, and light-scattering measurements in solvents of varying polarities. In addition, the photoluminescence spectra of the copolymer have received some study, using uranyl (UOj) ions at 77 The acid copolymer takes on the confor-... 

Compared to photoluminescence processes, no external light source is required, which offers some advantages such as the absence of scattering or background photoluminescence signals, the absence of problems related to instability of the external source, reduction of interferences due to a nonselective excitation process, and simple instrumentation. 

Experimental technique used during these investigations is usual for Raman scattering and photoluminescence spectroscopy. For luminescence excitation He-Cd, He-Ne, and Ar+ ion lasers were used. The exciting light power not exceeds 25 mW in all experiments. 

Figure 4.11 Photoluminescence of quantum dots near Ag nanoprisms with a series of excitation wavelengths. (A) Schematic diagram of sample preparation Ag nanoprisms (NP) are attached to a 3-aminopropyItrimethoxysilane-treated glass coverslip and overcoated with a layer of quantum dot-doped PMMA (B) Darkfleld image showing locations of Ag nanoprism (C) scattering spectra of each of the labeled nanoprisms in (B). Correlated quantum dot photoluminescence images excited with (D) 410 nm, (E) 440 nm, (F) 470 nm, (G) 490 nm, (H) 570 nm, and (I) 590 nm light. Adapted from reference 43.

When the sample is stimulated hy application of an external electromagnetic radiation source, several processes are possible. For example, the radiation can be scattered or reflected. What is important to us is that some of the incident radiation can be absorbed and thus promote some of the analyte species to an excited state, as shown in Figure 24-5. In absorption spectroscopy, we measure the amount of light absorbed as a function of wavelength. This can give both qualitative and quantitative information about the sample. In photoluminescence spectroscopy (Figure 24-6), the emission of photons is measured after absorption. The most important forms of photoluminescence for analytical purposes are fluorescence and phosphorescence spectroscopy. 

Over the last several decades photonic band-gap materials attracted considerable interest due to the possibility of inhibition of the spontaneous emission and light propagation [1-3]. Mesoporous structures like three-dimensional artificial opals and two-dimensional PAA are considered as photonic band gap materials, demonstrating the photonic stop-band in transmission and reflection spectra [4,5] and anisotropy of photonic density of states (DOS) on scattering indicatrices [6]. An influence of photonic band-gap materials on photoluminescence and spontaneous emission rate of the embedded inclusions have been reported and discussed [7-9]. 

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