Photoluminescence emission spectra

The polyoxadiazoles 14 were found to fluoresce purple-blue under ultraviolet irradiation (quantum efficiency of film 11%). The photoluminescence emission spectrum of the polymer 14b-l is shown in Figure 4. 

As depicted in Figure 5.5 PFs in film display an unstructured, long absorption maximum centered at 3.3 eV. The photoluminescence emission spectrum of PFs shows a vibronic fine structure with an energetic spacing of 180 meV (stretching vibration of the C = C-C = C structure of the polymer backbone) with the transition at 2.9 eV yielding a deep blue emission. In dilute solution the spectra are very similar to that of the solid state and only a small bathochromic shift of 20 meV is typically observed for both absorption and emission. 

Figure 4. Photoluminescence emission spectrum of octaphenylcyclotetrasiloxane solid, at liquid nitrogen temperature. Excitation wavelength 320 nm, spectral bandwidth ca. 8 nm.

The photoluminescence emission spectrum from the background (zero level) before the peak to the same background after the peak to give the total number of photons per second in the wavelength range of the peak, and therefore the number of emission photons that are emitted by the sample. P3... 

Figure 9-12. Absorption (Abs), photoluminescence excitation spectrum (PLCX), pholo-lumincscence (PL), and electroluminescence (EL) emission of mLPPP.

Figure 11.2. Nanowire electronic and optical properties, (a) Schematic of an NW-FET used to characterize electrical transport properties of individual NWs. (inset) SEM image of an NW-FET two metal electrodes, which correspond to source and drain, are visible at the left and right sides of the image, (b) Current versus voltage for an n-type InP NW-FET. The numbers inside the plot indicate the corresponding gate voltages (Vg). The inset shows current versus Vg for Fsd of 0.1 V. (c) Real-color photoluminescence image of various NWs shows different color emissions, (d) Spectra of individual NW photoluminescence. All NW materials show a clean band-edge emission spectrum with narrow FWHM around 20nm. (See color insert.)...

Because of the high sensitivity of Ti-containing luminescence centers to their local environments, photoluminescence spectroscopy can be applied to discriminate between various kinds of tetrahedral or near-tetrahedral titanium sites, such as perfectly closed Ti(OSi)4 and defective open Ti(OSi)3(OH) units. Lamberti et al. (49) reported an emission spectrum of TS-1 with a dominant band at 495 nm, with a shoulder at 430 nm when the sample was excited at 250 nm. When the excitation wavelength was 300 nm, the emission spectrum was characterized by a dominant band at 430 nm with a shoulder at 495 nm. These spectra and their dependence on the excitation wavelength clearly indicate the presence of two slightly different families of luminescent Ti species, which differ in their local environments, in agreement with EXAFS measurements carried out on the same samples. 

The emission spectrum of compound 8 exhibits in the solid state at room temperature an intense emission at 558 nm after excitation at 371 nm. According to the photoluminescent properties of Cu4I4 clusters, the emission band might be assigned to a combination of iodide-to-copper charge transfer (LMCT) and d-s transitions by Cu—Cu interaction within Cu3 clusters. 

The optical emission spectrum of uranium, while exceedingly rich in lines, cannot be depended upon in the detection and identification of this element. None of its lines is sufficiently persistent, and unless a comparatively large quantity of uranium is present in the zone of excitation, no spectral lines will be observed. On the other hand, it is possible to make use of a simple photoluminescence reaction which will enable the chemist to detect small traces of uranium. 

The /3-diketonate [Nd(dbm)3bath] (see figs. 41 and 117) has a photoluminescence quantum efficiency of 0.33% in dmso-7r, solution at a 1 mM concentration. It has been introduced as the active 20-nm thick layer into an OLED having an ITO electrode with a sheet resistance of 40 il cm-2, TPD as hole transporting layer with a thickness of 40 nm, and bathocuproine (BCP) (40 nm) as the electron injection and transporting layer (see fig. 117). The electroluminescence spectrum is identical to the photoluminescence emission the luminescence intensity at 1.07 pm versus current density curve deviates from linearity from approximately 10 mA cm-2 on, due to triplet-triplet annihilation. Near-IR electroluminescent efficiency <2el has been determined by comparison with [Eu(dbm)3bath] for which the total photoluminescence quantum yield in dmso-tig at a concentration of 1 mM is Dpi, = 6% upon ligand excitation, while its external electroluminescence efficiency is 0.14% (3.2 cdm-2 at 1 mAcm-2) ... 

Figure 1. Photoluminescence emission and excitation spectrum for benitoite showing Ti + luminescence.

Figure 5. Triboluminescence Spectrum of Uranyl Nitrate Hexa-hydrate. The photoluminescence excitation spectrum is shown for comparison the photoluminescence emission has been...

The photoluminescent behavior of a complex of the type Zn(diimine)(dtsq), where diimine = 2,2 -biquinoline, phen (44), or 4,7-diphenyl-2,9-dimethyl-phen (batho) and dtsq = dithiosquarate, have been reported by Gronlund et al (135). The phen and batho complexes display broad, featureless luminescence spectra in the solid state at room temperature. Upon cooling to 77 K, the emission spectrum of Zn(batho)(dtsq) resolves into three sharp peaks overlapping the broad emission feature these sharp peaks are assigned to a diimine localized ji-ji emission. The Zn(diimine)(dithiolate) solids degrade upon UV laser excitation, which has inhibited accurate lifetime measurements. 

Figure 26 Emission spectra (PL, EL) in PC at room temperature of 40 wt% TPD donor solution with a 40 wt% of PBD acceptor added. The photoluminescence (PL) spectrum excited at 360 nm, the electroluminescence (EL) spectra (I, II) originate from the recombination radiation in a 60 nm thick film, taken at two different voltages. Absorption (Abs) and PL spectra (excitation at 360 nm) of (75wt% TPD 25wt% PC) and (75wt% PBD 25wt% PC) spin-cast films are given for comparison. Molecular structures of the compounds used are given in the upper part of the figure TPD [N,Nf-diphenyl-A v/V/-bis(3-methylphenyl)-l,l -biphenyl-4,4 diamine PBD [2-(4-biphenyl)-5-(4- er .-butylphenyl)l,3,4-oxadiazole PC[bisphe-nol-A-polycarbonate]. Adapted from Ref. 112.

Photoluminescence is the radiation emitted by the recombination process and as such is a direct measure of the radiative transition. Information about non-radiative recombination can often be inferred from the luminescence intensity, which is reduced by the competing processes (Street 1981a). The most useful feature of the luminescence experiment is the ability to measure the emission spectrum to obtain information about the energy levels of the recombination centers. The transition rates are found by measuring the transient response of the luminescence intensity using a pulsed excitation source. Time resolution to about 10 s is relatively easy to obtain and is about the maximum radiative recombination rate. The actual recombination times of a-Si H extend over a wide range, from 10 s up to at least 10- s. 

It has been observed that the SWNTs suspended in a micellar solution exhibit a well-defined optical spectrum and show a bright photoluminescence in the near infrared region (Figme 22). The individual SWNT suspended in air at room temperature also shows a bright photoluminescence. The emission spectrum of the semiconducting SWNTs correlates well with the absorption spectrum in a micellar solution. The intensity of emission decreases dramatically when the isolated nanotubes start aggregating in a destabilized micellar solution. The decrease in the emission is attributed to the quenching of electrons by the metallic nanotubes when... 

Figure 2.20 Photoluminescence spectra of SrO recorded at 300K before and after pyridine (Py) adsorption, (a) emission spectrum of SrO (b) excitation spectrum of SrO (c) emission spectrum after Py adsorption (d) excitation spectrum after Py adsorption. Reprinted from ref [88], with permission from the Royal Society of Chemistry.

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