A new dinuclear complex Europium(III) bis[(μ2-ethoxy)(benzoyl trifluoroacetonato)(nitrate) (1,10-phenanthroline) europium(III)]2 1,10-phenanthroline, here after [Eu(μ2-OC2H5)(btfa)(NO3)(phen)]2·phen)(1) (Figure 1a) and the mononuclear complex Eu(TTA)3(Ph3PO)2(2) (Figure 2a) were synthesized and characterized by photoluminescence (PL) spectroscopy. The PL emission spectra of the powder samples of the compounds were recorded in the temperature range 10.7 – 300 K. Both complexes show rare metal-centered luminescence in the energy range characteristic of the Eu3+ ion (580 – 710 nm) with emission bands according to ion selection rule. The emission bands in the PL are attributed to the internal 4f → 4f radiative transitions of the Eu3+ ion 5D0 → 7Fi (i = 0→4) and, in addition, to the splitting of each level caused by the influence of the electric field of the ligands of the complex. Due to the splittings, each level is divided into 2i+1 sublevels, which are well observed in the mononuclear compound 2 centered at 580, 595, 615, 650, and 698 nm. However, in the PL spectrum of the dinuclear compound, the splits show a double number of splits (2(2i + 1)), which indicates the presence of two positions of the Eu3+ ion in the molecule and which are not optically equivalent.
A series of coordination organic compounds based on the trivalent Eu3+ ion were synthesized and optimized: Eu(o- MBA)3phen, Eu(DBM)3(Ph3PO)1·H2O and Eu(TTA)3(Ph3PO)2. The efficiency of the photoluminescence (PL) emission of these coordination compounds depend on preparation technology, specifically on the optimal choice of the ligands. The photoluminescence spectrum measured in the range 500 – 750 nm exhibits a number of narrow (atomic-like) emission bands with the FWHM less than 10 nm. These PL emission bands are attributed to optical transitions5D0 → 7Fj , j 0...4 in the 4f orbital of the, ion. PL experimental results were analyzed in the framework of Judd-Ofelt theory and the characteristic luminescence parameters were obtained: PL lifetime constant, quantum yield, Ω coefficient, the probability Ai jfor electric dipole transitions, etc.
A new coordinate organic compound (COC) Eu(DBM)3(Ph3PO)1H2O was synthesized and investigated (DBM stands for 1,3-Diphenyl-1,3-propanedione and Ph3PO for triphenylphosphine oxide). The size of obtained Eu(DBM)3(Ph3PO)1H2O powder nanocrystals is around 50 nm. Under ultraviolet light excitation, the material exhibits an abundant and pure red color photoluminescence (PL). The PL spectrum measured in the range of 500 - 750 nm has a number of narrow (atomic) emission lines with FWHM less than 10 nm, which are assigned to the energy transitions 5D0→7Fi (i = 0,1,2,3,4) in the 4f – shell of the Eu3+ ion. PL experimental results and its kinetics were analyzed using the theory of Judd-Ofelt's parametric method and the characteristic parameters were obtained: the lifetime τ, quantum efficiency η, and transitions probability of electrical dipoles Aij.
Were obtained a new nanocomposite (NC) based on poly N-epoxy prolyl carbazol (PEPC) and the coordination compound luminophore Eu(o-MBA)3Phen, where o-MBA is o- methylbenzoic acid and Phen – phenanthroline. Nanocrystals of Eu(o-MBA)3Phen with the dimensions ~ 50 nm were uniformly incorporated into the PEPC polymer matrix with various concentrations. The absorption spectra of coordination compounds and thin layers of NC PEPC/Eu(o-MBA)3Phen revealed 1 intensive absorption bands at 2.02 eV. Photoluminescence (PL) spectra showed an intense red luminescence at 578 – 699 nm, which is assigned to the transitions 4D0→7Fi (i= 0,1,2 3 4) in the 4f-shell of the Eu3+ ion.
We present experimental results on preparation and characterization of colloidal CdSe quantum dots (QD) in organic solvent. CdSe QDs were synthesized following a modified literature method and have been characterized by UV-Vis absorption and photoluminescent (PL) spectroscopy, as well as by 2D Diffusion Ordered Spectroscopy (DOSY) NMR. The average CdSe particles size estimated from the UV-Vis absorption spectra was found to be in the range 2.28 - 2.92 nm, which correlates very well with the results obtained from NMR measurements. The PL spectrum for CdSe nanodots can be characterized by a narrow emission band with the peak maximum shifting from 508 to 566 nm in dependence of the CdSe nanoparticle size. The PL is dominated by a near-band-edge emission, accompanied by a weak broad band in the near IR, related to the surface shallow trap emission.
We present experimental results on copolymer-based nanocomposite made of styrene with butyl methacrylate (SBMA) (1:1) and inorganic semiconductor CdS. Thin film composite samples have been characterized by UV-Vis absorption and photoluminescent spectroscopy, as well as by transmission electron microscopy. Transmission electron microscope (TEM) examination confirms a relatively narrow distribution of CdS nanoclusters in the SBMA matrix, which covers the range 2-10 nm. On the other side, the average CdS particles size estimated from the position of first excitonic peak in the UV-Vis absorption spectrum was found to be 2.8 nm and 4.4 nm for two samples with different duration of thermal treatment, which is in good agreement with photoluminescence (PL) experimental data. The PL spectrum for CdS nanocrystals is dominated by near-band-edge emission. The relatively narrow line width (40-45 nm) of the main PL band suggests the nanoparticles having narrow size distribution. On the other side, relatively low PL emission from surface trap states at longer wavelengths were observed in the region 500-750 nm indicating on recombination on defects. Key words: nanocomposite, polymer matrix, photoluminescence,
We describe a new nanocomposite material based on the copolymer of styrene with butyl methacrylate (1:1) (SBMA), and coordinating compound of Europium(III) Eu(TTA)3(Ph3PO)2. The SBMA/Eu(TTA)3(Ph3PO)2 nanocomposite was prepared by a simple technology and can be obtained in the form of optical fibers, thin films and planar waveguides on various substrates with large area. Experimental results on optical transmission and photoluminescence spectroscopy are presented. The nanocomposite exhibits a strong photoluminescence emission in the range 560-750 nm, with the main photoluminescence band at 613 nm.
Thin films (1-10 μm thickness) of nanocomposites (NCs) based on coordinated compounds (CC)
Tb(TTA)2(Ph3PO)2NO3 (where TTA is thenoyltrifluoroacetonate (C8H5F3O2S), Ph3PO - triphenylphosphine oxide) and
polymer – polyvinylpyrrolidone (PVP) ((C6H9NO)n)) were obtained by chemical methods. NCs were characterized by measurements of optical transmission (T(λ)), and photoluminescence (PL) at different concentrations of CC in NCs.
Using the optical transmission spectra, the characteristic parameters of NCs such as threshold of absorbance and the
position of the absorption edge versus the concentration of the CC in NCs, etc., were determined. A slight displacement
of absorption threshold to infrared region was observed with increasing of concentration of coordinated material in NCs.
It was established that the excitation spectrum at which the photoluminescence (PL) in NCs take place covers the range
of wavelengths from 200 to 410 nm. The PL of nanocomposites was detected as specific for internal transitions 4f → 4f
of the Tb3+ ion 5D4 →7Fi (i = 6, 5, 4 and 3) centered at 488, 543, 589 and 614 nm, respectively at T=300 K. The dominant PL was observed at 543 nm and its halfwidth is less than 10 nm. The intensity of photoluminescence signal at 543 nm in the case of NCs films is 2 times higher than the intensity of PL of Tb(TTA)2(Ph3PO)2NO3powders at equal conditions of excitation. PL intensity of the NCs to 77 K is growing more than 20 times compared with that at 300 K.
New light-emitting layers of nanocomposites on polymer base have been obtained. As polymeric matrices the
copolymers of styrene and butilmetacrylate in the ratio (1:1) have been used. As organic luminophore compounds from
izotiocianatopropenone and propenone classes were utilized. Transparent composite layers were deposited by spin-coating
method on glass and quartz substrates. The morphological and optical properties of the obtained nanocomposites
have been investigated. An intensive photoluminescence signal has been identified in green area of the spectrum.
Nanocomposites are proposed for various practical applications.
Results of researches on technology of deposition of thin layers of mixed composition As2(SxSe1-x)3 (0 <x <1), obtained from chemical solutions of separate components As2S3 and As2Se3 are given, and some optical properties (transmittance and recording of holographic information) were studied. The photodarkening of layers and shift of edge of absorption in infra-red (IR) area were found at ultra-violet (UV) and actinic irradiations. The maximum efficiency of holographic writing of diffraction gratings (with Ar laser recording (λ=488 nm)) on thin layers is 2.5 % and after additional processing in the negative etching is 36 %.
The problem of obtaining low cost but efficient luminescent materials is still actually. Data concerning fabrication and
luminescent properties of new composite materials on the base of thenoyltrifluoroacetone (TTA) of Europium(III)
(Eu(TTA)3) and chalcogenide glasses doped with rare earth ions and polymers are presented. The visible emission
spectra of the composites on the base of Eu(TTA)3 structured with phenantroline (Eu(TTA)3Phen) and copolymer from
styrene and butylmethacrylate (1:1)(SBMA) under the excitation with N2-laser (λ=337 nm) contain sharp emission bands
located at 354, 415, 580, 587, 590, 596, 611.4, 616.5, 621, 652, 690, 700, 713 nm. The nature of the observed emission
bands and the possible mechanisms of the radiative electron transition in the investigated composite materials are
discussed.
New composite and nanocomposite materials consisting from amorphous chalcogenide (As2S3, As2Se3) and polymers
such as polyvinylalcool (PVA) and polyvinylpyrrolidone (PVP) were prepared by inexpensive and easy coating
technique from chemical solution and were investigated. Composite retains many properties of the initial components
from which they are prepared. Morphology and optical properties of deposited materials in the form of films are
presented. The decreasing of the As2S3 component in the composite leads to the shift of the absorption edge to higher
energies and spheroid dimensions are decreased. For the samples As2S3:Pr3+/PVA an increasing of transparency in the
visible region with respect to pure As2S3 was observed. As a result of ultraviolet light irradiation of the composites
change of optical properties is observed. For example the refractive index may be change in value 0,1. This allows
utilizing these structures for holographic recording of diffraction gratings. The investigated new composites are
perspective for different photonic devices as well as for recording media with high resolution.
Electrophotographic spectroscopy, low-frequency capacity and photoconductivity methods were applied to investigate density of the located states in a mobility band of amorphous semiconductors layers As2S3 II As2Se3. Quasicontinuous and strictly localized states of donor and acceptor types are found. The explanation of this is offered on the basis of existence of metastable states, which are created under light, X-Ray and electron excitation. On the basis of the mentioned materials barriers structures are created and elaborated devices for record and reading of optical information in them.
The Me-Amorphous chalcogenide semiconductor (AChS)--dielectric- semiconductor (Me - As2Se3: Sn - SiO2 - Si) (MChDS) structure was obtained. There have been found that under the lighting in electric field the MChDS in dependence from applied external direction of electric field positive or negative are charged. There were found that quantity of accumulated charge from light intensity have been depended linear type Q equals Qmax ((alpha) + (beta) D), where D--is the dose of radiation (D equals I t, where I is the intensity and t duration of radiation). There were studied and developed three different type of signal recording: by measuring of the photoempf, displacement photocurrent and accumulated charge, which allow to propose two type of sensors of radiation. The dose measuring and the image writing and readout processes in the real time and accumulation of the small signals regimes. The space functional separation of the recording and readout allows to carry out understroing repetition readout of the image and other operations.
The A62Se3 - Si02 - Si structure with A62Ses for writing a.nd Si for readout :h.a.s been suggested ior Xra. y im.a.ge a.pplica.tion. In this structure th.e recording ha.ve been. ca.:rri.ed out under sim:ulta.n.eous projectioit oi a.n X-ray pa.ttern on the top semitransparent contact a.nd a.pplica.tion of the external volta.ge, but the erasing - under illumin.a.tion. of light from the ra.n.ge of th.e .4s2S es funda.men.tal a.bsorption. a.n.d a.pplica.tion. of th.e opposite pola.rity external voltage. Th.e cha.."ging kinetics was revealed to be described by exponential la.w with. saturation.. It was found th.at th.e charge is a.ccumu.la.ted at th.e deep tra.ps disposed a.t th.e As2Se3- Si02 interface. Th.is structure ma.ke it possible to work m the integration small signa.i regime but the space separation. of recording and read.out layers provides un.destromg repetition.al readout of image. It was established th.at th.e da.rk rela.xa.tion of a.ccumula.ted cha.rge ta.kes place due to th.e.rmo-:iield emission of holes from t:ra.ps according to Pool-Frenkel la.w.
Keywords: solid state detector, image device structure, X-ray, area meter, amorph.ous semiconductor
The Me-Chalcogenide glassy semiconductor-dielectric-semiconductor (Me-As2S3- SiO2-Si) structure was formed and the writing and readout processes of the optical image with high resolution were studied. The structures make the positive and negative images possible. The device works in both accumulation of the small signals and real time. The space functional separation of the recording and readout allows us to carry out repetition readout of the image and other operations.
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