Investigating temperature effects on extra virgin olive oil using fluorescence spectroscopy

NASA Astrophysics Data System (ADS)

Saleem, M.; Ahmad, Naveed; Ali, H.; Bilal, M.; Khan, Saranjam; Ullah, Rahat; Ahmed, M.; Mahmood, S.

2017-12-01

The potential of fluorescence spectroscopy has been utilized to study the heating effects on extra virgin olive oil (EVOO). Through a series of experiments, a temperature range from 140 °C  -  150 °C has been found where cooking with EVOO is possible without destroying its natural ingredients. Fluorescence emission spectra from all heated and non-heated EVOO samples were recorded using an excitation source at 350 nm, where emission bands in non-heated EVOO at 380, 440, 455, and 525 nm are labelled for vitamin E and a band at 673 nm is assigned for chlorophyll a. The emission band at 525 nm is also responsible for beta carotenoids (vitamin A). As a result of heating, prominent intensity variations have been observed in all spectral bands, but it is particularly affected at 525 nm, indicating the deterioration of vitamin E and beta carotenoids. However, if the temperature of oil can be maintained in the above defined range, then frying food with EVOO is possible by preserving its natural ingredients. The spectral variations resulting from the heating effects have been further highlighted by using principal component analysis for classification purposes.

Ultraviolet electroluminescence from zinc oxide nanorods/deoxyribonucleic acid hybrid bio light-emitting diode

NASA Astrophysics Data System (ADS)

Gupta, Rohini Bhardwaj; Nagpal, Swati; Arora, Swati; Bhatnagar, Pramod Kumar; Mathur, Parmatma Chandra

2011-01-01

Ultraviolet (UV) light-emitting diode using salmon deoxyribonucleic acid (sDNA)-cetyltrimethylammonium complex as an electron blocking layer and zinc oxide (ZnO) nanorods as emissive material was fabricated. UV emission, which was blue shifted up to 335 nm with respect to the band edge emission of 390 nm, was observed. This blue shift was caused due to accumulation of electrons in the conduction band of ZnO because of a high potential barrier existing at the sDNA/ZnO interface.

Supramolecular assembly of group 11 phosphorescent metal complexes for chemosensors of alcohol derivatives

NASA Astrophysics Data System (ADS)

Lintang, H. O.; Ghazalli, N. F.; Yuliati, L.

2018-04-01

We report on systematic study on vapochromic sensing of ethanol by using phosphorescent trinuclear metal pyrazolate complexes with supramolecular assembly of weak intermolecular metal-metal interactions using 4-(3,5-dimethoxybenzyl)-3,5-dimethyl pyrazole ligand (1) and group 11 metal ions (Cu(I), Ag(I), Au(I)). Upon excitation at 284, the resulting complexes showed emission bands with a peak centered at 616, 473 and 612 nm for 2(Cu), 2(Ag) and 2(Au), respectively. Chemosensor 2(Cu) showed positive response to ethanol vapors in 5 mins by blue-shifting its emission band from 616 to 555 nm and emitting bright orange to green. Otherwise 2(Au) gave shifting from its emission band centered at 612 to 587 nm with Δλ of 25 nm (41%) and color changes from red-orange to light green-orange while 2(Ag) showed quenching in its original emission intensity at 473 nm in 40% with color changes from dark green to less emissive. These results demonstrate that sensing capability of chemosensor 2(Cu) with suitable molecular design of ligand and metal ion in the complex is due to the formation of a weak intermolecular hydrogen bonding interaction of O atom at the methoxy of the benzyl ring with the OH of the vapors at the outside of the molecules.

New localized/delocalized emitting state of Eu 2+ in orange-emitting hexagonal EuAl 2O 4

DOE PAGES

Liu, Feng; Meltzer, Richard S.; Li, Xufan; ...

2014-11-18

Eu 2+-activated phosphors are being widely used in illuminations and displays. Some of these phosphors feature an extremely broad and red-shifted Eu 2+ emission band; however, convincing explanation of this phenomenon is lacking. Here we report a new localized/delocalized emitting state of Eu 2+ ions in a new hexagonal EuAl 2O 4 phosphor whose Eu 2+ luminescence exhibits a very large bandwidth and an extremely large Stokes shift. At 77 K, two luminescent sites responsible for 550 nm and 645 nm broadband emissions are recognized, while at room temperature only the 645 nm emission band emits. The 645 nm emissionmore » exhibits a typical radiative lifetime of 1.27 μs and an unusually large Stokes shift of 0.92 eV. We identify the 645 nm emission as originating from a new type of emitting state whose composition is predominantly that of localized 4f 65d character but which also contains a complementary component with delocalized conduction-band-like character. This investigation gives new insights into a unique type of Eu 2+ luminescence in solids whose emission exhibits both a very large bandwidth and an extremely large Stokes shift.« less

Intensity Variations of Narrow Bands of Solar UV Radiation during Descending Phases of SACs 21-23

NASA Astrophysics Data System (ADS)

Gigolashvili, M.; Kapanadze, N.

2014-12-01

The study of variations of four narrow bands of solar spectral irradiance (SSI) in the ultraviolet (UV) range for period 1981-2008 is presented. Observational data obtained by space-flight missions SORCE, UARS, SME and daily meanings of international sunspot number (ISN) have been used. The investigated data cover the decreasing phases of the solar activity cycles (SACs) 21, 22 and 23. We have revealed a peculiar behavior of intensity variability of some solar ultraviolet spectral lines originated in the solar chromospheres for period corresponding to the declining phase of the solar cycle 23. It is found that variability of emission of different solar spectral narrow bands (289.5 nm, 300.5 nm) does not agree equally well with ISN variability during decreasing phase of the solar activity cycle 23. The negative correlations between total solar irradiance and the solar spectral narrow bands of UV emission (298.5 nm, 300.5 nm) had been revealed. The existence of the negative correlation can be explained by the sensitivity of SSI of some emission lines to the solar global magnetic field.

Red Emission of SrAl2O4:Mn4+ Phosphor for Warm White Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Chi, N. T. K.; Tuan, N. T.; Lien, N. T. K.; Nguyen, D. H.

2018-05-01

In this work, SrAl2O4:Mn4+ phosphor is prepared by co-precipitation. The phase structure, morphology, composition and luminescent performance of the phosphor are investigated in detail with x-ray diffraction, field emission scanning electron microscopy, steady-state photoluminescence (PL) spectra, and temperature-dependent PL measurements. The phosphor shows a strong red emission peak at ˜ 690 nm, which is due to the transition between electronic levels and the electric dipole transition 2Eg to 4A2g of Mn4+ ions located at the sites with D3d local symmetry. The sample doped with 0.04 mol.% Mn4+ exhibits intense red emission with high thermal stability and appropriate International Commission on Illumination (CIE) coordinates (x = 0.6959, y = 0.2737). It is also found that the phosphor absorption in an extended band from 250 nm to 500 nm has three peaks at 320 nm, 405 nm, and 470 nm, which match well with the emission band of ultraviolet (UV) lighting emission diode (LED) or blue LED chips. These results demonstrate that SrAl2O4:Mn4+ phosphor can play the role of activator in narrow red-emitting phosphor, which is potentially useful in UV (˜ 320 nm) or blue (˜ 460 nm) LED.

Laser-induced optical breakdown spectroscopy of polymer materials based on evaluation of molecular emission bands

NASA Astrophysics Data System (ADS)

Trautner, Stefan; Jasik, Juraj; Parigger, Christian G.; Pedarnig, Johannes D.; Spendelhofer, Wolfgang; Lackner, Johannes; Veis, Pavel; Heitz, Johannes

2017-03-01

Laser-induced breakdown spectroscopy (LIBS) for composition analysis of polymer materials results in optical spectra containing atomic and ionic emission lines as well as molecular emission bands. In the present work, the molecular bands are analyzed to obtain spectroscopic information about the plasma state in an effort to quantify the content of different elements in the polymers. Polyethylene (PE) and a rubber material from tire production are investigated employing 157 nm F2 laser and 532 nm Nd:YAG laser ablation in nitrogen and argon gas background or in air. The optical detection reaches from ultraviolet (UV) over the visible (VIS) to the near infrared (NIR) spectral range. In the UV/VIS range, intense molecular emissions, C2 Swan and CN violet bands, are measured with an Echelle spectrometer equipped with an intensified CCD camera. The measured molecular emission spectra can be fitted by vibrational-rotational transitions by open access programs and data sets with good agreement between measured and fitted spectra. The fits allow determining vibrational-rotational temperatures. A comparison to electronic temperatures Te derived earlier from atomic carbon vacuum-UV (VUV) emission lines show differences, which can be related to different locations of the atomic and molecular species in the expanding plasma plume. In the NIR spectral region, we also observe the CN red bands with a conventional CDD Czerny Turner spectrometer. The emission of the three strong atomic sulfur lines between 920 and 925 nm is overlapped by these bands. Fitting of the CN red bands allows a separation of both spectral contributions. This makes a quantitative evaluation of sulfur contents in the start material in the order of 1 wt% feasible.

Upconversion emission study of Er{sup 3+} doped CaMoO{sub 4} phosphor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sinha, Shriya, E-mail: Shriya.sinha6@gmail.com; Mahata, Manoj Kumar; Kumar, Kaushal

2016-05-06

The infrared to visible upconversion emission in Er{sup 3+} doped CaMoO{sub 4} phosphor has been investigated upon 980 nm diode laser excitation. The X-ray diffraction analysis reveals well crystalline nature and tetragonal phase structure of the prepared phosphor annealed at 800 °C. The Er{sup 3+} doped CaMoO{sub 4} phosphor has shown intense green upconversion emission upon 980 nm didode laser excitation. The green emission bands at 530 nm and 552 nm corresponds to the {sup 2}H{sub 11/2}→{sup 4}I{sub 15/2} and {sup 4}S{sub 3/2}→{sup 4}I{sub 15/2} electronic transitions, respectively of Er{sup 3+} ion. The very weak red emission band around 656more » nm is assigned to the {sup 4}F{sub 9/2}→{sup 4}I{sub 15/2} transition of Er{sup 3+} ion. The CIE color coordinate exhibits the emission color in intense green region, indicating the use of present phosphor in display device applications.« less

Impact of firing temperature on multi-wavelength selective Stokes and anti-Stokes luminescent behavior by Gd2O2S:Er,Yb phosphor and its application in solar energy harvesting

NASA Astrophysics Data System (ADS)

Kataria, V.; Mehta, D. S.

2018-04-01

Erbium (Er3+)-ytterbium (Yb3+) doped gadolinium oxysulphide (Gd2O2S) phosphor has been developed via a facile method of solid-state flux fusion, and offers two-fold spectrum modification with highly intense Stokes and anti-Stokes shift. The effect of the firing cycle on the photoluminescent response and morphology of Gd2O2S:Er,Yb is scrutinized, wherein the firing temperature was varied (1000 °C-1250 °C), keeping firing time and all other parameters constant. Interestingly, the nanostructures fired below 1150 °C showed nanorods of diameter ~200 nm and length ~1-2 µm, whereas firing at 1150 °C and above rendered nanospheres with small diameter, ~350 nm. Highly bright upconversion (UC) emission was achieved even under an extremely low excitation power density of 800 µW cm-2 from a 980 nm laser, and was comfortably visible to the naked eye. The incident power dependent studies disclosed increase in UC-emission intensity with increasing excitation power and a quasi-linear dependence on excitation power density. Intense characteristic UC-emission of Er3+ excited states at 525 nm, 556 nm and 668 nm were observed, and the green emission band was found to be dominant over the red band in intensity. Concurrently, downconversion (DC) emission at 556 nm and 669 nm was also exhibited under ultraviolet excitation (285 nm and 380 nm), with the red band being more powerful than the green, unlike UC-emission. Firing temperature dependent studies divulged the dependence of luminescence intensity on the firing cycle of the luminophore and formation of the respective luminescent phase. The UC-emission intensity was found to be maximum for samples fired at 1150 °C, whereas samples fired at 1000 °C showed the highest DC-emission intensity. The excitation and emission profile of single Gd2O2S:Er,Yb phosphor lying in the desired spectral region and as a dual spectral converter marks its possible application for enhanced harvesting of sunlight.

21-nm-range wavelength-tunable L-band Er-doped fiber linear-cavity laser

NASA Astrophysics Data System (ADS)

Yang, Shiquan; Zhao, Chunliu; Li, Zhaohui; Ding, Lei; Yuan, Shuzhong; Dong, Xiaoyi

2001-10-01

A novel method, which utilizes amplified spontaneous emission (ASE) as a secondary pump source, is presented for implanting a linear cavity erbium-doped fiber laser operating in L-Band. The output wavelength tuned from 1566 nm to 1587 nm, about 21 nm tuning range, was obtained in the experiment and the stability of the laser is very good.

UV-visible-NIR light generation through frequency upconversion in Tm3+-doped low silica calcium aluminosilicate glasses using multiple excitation around 1.2 μm

NASA Astrophysics Data System (ADS)

Trindade, C. M.; Rego-Filho, F. G.; Astrath, N. G. C.; Jacinto, C.; Gouveia-Neto, A. S.

2018-04-01

Intense ultraviolet upconversion emission was produced in single Tm3+-doped OH--free low silica calcium aluminosilicate glasses. A new excitation route based upon multi-Stokes Raman emissions generated in an optical fiber pumped at 1.064 μm, and exploiting the absorption band around 1.2 μm by means of the 3H5 thulium excited state, was used. Furthermore, the other bands of the stimulated Raman scattering spectrum resonantly enhances all the upconversion processes, resulting in efficient ultraviolet (295 nm, 360 nm), blue (456 nm, 480 nm), red (650 nm, 667 nm), and near-infrared (800 nm) emissions. The population of the 1P0, 1D2, 1G4, 3F2 and 3H4 excited-state emitting levels was accomplished through stepwise multi-photon absorption. Results indicate competing cross-relaxation processes involving Tm3+ ion-pairs producing UV emission population quenching Simplified energy-level diagram of Tm3+- doped sample excited using multi-stokes emissions. The λp indication describes all excitation wavelengths, represented by a single arrow for the sake of simplicity.

TIMED/GUVI Observations of Aurora, Ionosphere, Thermosphere and Solar EUV Variations

NASA Astrophysics Data System (ADS)

Zhang, Y.; Paxton, L. J.; Schaefer, R. K.

2017-12-01

The FUV (100-200 nm) emissions from the ionosphere and thermosphere carry rich information of the density and composition of the IT system, aurora and solar EUV flux. The key emissions include atomic hydrogen line (121.6nm), atomic oxygen lines (e.g. 130.4, 135.6, 164.1 nm), atomic nitrogen lines (e.g. 120.0, 149.3, 174.3 nm), molecular nitrogen bands (LBH and VK bands) and nitric oxide ɛ bands. TIMED/GUVI data cover the nearly full FUV range and generate many space weather products (ionosphere, thermosphere, aurora and solar EUV) that extend the products from other missions (such as NASA GOLD and ICON) and help to solve some of MIT (Magnetosphere-Ionosphere-Thermosphere) science problems and serve as validation data sources for models.

Synthesis and spectroscopic study of CdS nanoparticles using hydrothermal method

NASA Astrophysics Data System (ADS)

AL-Mamoori, Mohammed H. K.; Mahdi, Dunia K.; Al-Shrefi, Saif M.

2018-05-01

In this work, cadmium sulfide nanoparticles (powder) with diameter 50.8 nm was prepared using hydrothermal method. The structural and optical properties of CdS nanoparticles was studied by X-ray diffraction, FESEM, EDS, FTIR, UV-Diffuse Reflectance spectroscopy and Photoluminance spectrum. X-ray diffraction reveal the formation the purity of prepared phase of CdS particles with hexagonal wurtzite structure with particle size 31.8nm by using sheerer equation. The energy dispersion scattering (EDS) examination explains that the sample is composed of a large amount of Cd and S which are exactly CdS nanoparticles and there is a very small trace of (Zn) and (O) element observed because of there is a small pollutions in the measurement place of samples. FESEM shows the spherical shape of nanoparticles with around 50.8 nm diameter. The optical absorption spectral study identified the red shift of the sample in comparison to bulk ZnO in three dimensions. Photoluminance spectrum (PL) at room temperature showed that there are two luminescence peaks at 433.14 nm and 518.21nm. Samples demonstrate a sharp emission band at around 433.18 nm, which is attributed to the typical exciton luminescence. The broad band at 518.21nm which were attributed to the trapped luminescence. The green emission band at 518.21 nm was associated with the emission due to electronic transition from the conduction band to an accepter level due to interstitial sulphur ion.

Density Measurements in Air by Optically Exciting the Cordes Bands of I2

NASA Technical Reports Server (NTRS)

Balla, R. Jeffrey; Exton, Reginald J.

2000-01-01

We describe an optical method based on laser-induced fluorescence for obtaining instantaneous measurements of density along a line in low-density air seeded with I2. The Cordes bands of I2 (D(sup 1)sigma(sup +, sub u)) left arrow X(sup 1)sigma(sup +, sub g)) are excited with a tunable ArF excimer laser. air densities in the range (0.1-6.5) x 10(exp 17) cm(exp -3) are measured over 295-583 K using the density-dependent emission ratio of two emission bands of I2; the 340 nm bands and the diffuse-structured McLennan bands near 320 nm.

E-band Nd 3+ amplifier based on wavelength selection in an all-solid micro-structured fiber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dawson, Jay W.; Kiani, Leily S.; Pax, Paul H.

Here, a Nd 3+ fiber amplifier with gain from 1376 nm to 1466 nm is demonstrated. This is enabled by a wavelength selective waveguide that suppresses amplified spontaneous emission between 850 nm and 1150 nm. It is shown that while excited state absorption (ESA) precludes net gain below 1375 nm with the exception of a small band from 1333 nm to 1350 nm, ESA diminishes steadily beyond 1375 nm allowing for the construction of an efficient fiber amplifier with a gain peak at 1400 nm and the potential for gain from 1375 nm to 1500 nm. A peak small signalmore » gain of 13.3 dB is measured at 1402 nm with a noise figure of 7.6 dB. Detailed measurements of the Nd 3+ emission and excited state absorption cross sections suggest the potential for better performance in improved fibers. Specifically, reduction of the fiber mode field diameter from 10.5 µm to 5.25 µm and reduction of the fiber background loss to <10 dB/km at 1400 nm should enable construction of an E-band fiber amplifier with a noise figure < 5 dB and a small signal gain > 20 dB over 30 nm of bandwidth. Such an amplifier would have a form factor and optical properties similar to current erbium fiber amplifiers, enabling modern fiber optic communication systems to operate in the E-band with amplifier technology similar to that employed in the C and L bands.« less

E-band Nd 3+ amplifier based on wavelength selection in an all-solid micro-structured fiber

DOE PAGES

Dawson, Jay W.; Kiani, Leily S.; Pax, Paul H.; ...

2017-03-13

Here, a Nd 3+ fiber amplifier with gain from 1376 nm to 1466 nm is demonstrated. This is enabled by a wavelength selective waveguide that suppresses amplified spontaneous emission between 850 nm and 1150 nm. It is shown that while excited state absorption (ESA) precludes net gain below 1375 nm with the exception of a small band from 1333 nm to 1350 nm, ESA diminishes steadily beyond 1375 nm allowing for the construction of an efficient fiber amplifier with a gain peak at 1400 nm and the potential for gain from 1375 nm to 1500 nm. A peak small signalmore » gain of 13.3 dB is measured at 1402 nm with a noise figure of 7.6 dB. Detailed measurements of the Nd 3+ emission and excited state absorption cross sections suggest the potential for better performance in improved fibers. Specifically, reduction of the fiber mode field diameter from 10.5 µm to 5.25 µm and reduction of the fiber background loss to <10 dB/km at 1400 nm should enable construction of an E-band fiber amplifier with a noise figure < 5 dB and a small signal gain > 20 dB over 30 nm of bandwidth. Such an amplifier would have a form factor and optical properties similar to current erbium fiber amplifiers, enabling modern fiber optic communication systems to operate in the E-band with amplifier technology similar to that employed in the C and L bands.« less

Investigation of optical properties and local structure of Gd3+ doped nano-crystalline GeSe2

NASA Astrophysics Data System (ADS)

Hantour, Hanan Hassan

2017-04-01

Pure and Gd-doped nano-crystalline GeSe2 were prepared by the melt-quenching technique. Structure analysis using Rietveld program suggests monoclinic structure for both virgin and doped samples with nano-particle size 41 nm for GeSe2 and 48 nm for Gd-doped sample. A wide optical band gap as estimated from absorbance measurements is 4.1 and 4.8 eV for pure and doped samples in accordance with the confinement effects. Raman spectra show two unresolved components at ˜202 cm-1 with broad line width. Also, well identified low intensity (υ < 145 cm-1) and high intensity (υ > 250 cm-1) bands are detected. For Gd-doped sample, the main band is shifted to lower energies and its full width at half maximum (FWHM) is reduced by ˜50% accompanied by an intensity increase of about ˜17 fold times. The photoluminescence analysis of the pure sample shows a main emission band at ˜604 nm. This band is split into two separated bands with higher intensity. The detected emission bands at wavelength >650 nm are assigned to transmission from 6GJ to the different 6PJ terms.

Thermal, optical and structural properties of Dy3+ doped sodium aluminophosphate glasses

NASA Astrophysics Data System (ADS)

Kaur, Manpreet; Singh, Anupinder; Thakur, Vanita; Singh, Lakhwant

2016-03-01

Trivalent Dysprosium doped sodium aluminophosphate glasses with composition 50P2O5-10Al2O3-(20-x)Na2O-20CaO-xDy2O3 (x varying from 0 to 5 mol%) were prepared by melt quench technique. The density of the prepared samples was measured using Archimedes principle and various physical properties like molar volume, rare earth ion concentration, polaron radius, inter nuclear distance and field strength were calculated using different formulae. The differential scanning calorimetry (DSC) was carried out to study the thermal stability of prepared glasses. The UV Visible absorption spectra of the dysprosium doped glasses were found to be comprised of ten absorption bands which correspond to transitions from ground state 6H15/2 to various excited states. The indirect optical band gap energy of the samples was calculated by Tauc's plot and the optical energy was found to be attenuated with Dy3+ ions. The photoluminescence spectrum revealed that Dy3+ doped aluminophosphate glasses have strong emission bands in the visible region. A blue emission band centred at 486 nm, a bright yellow band centred at 575 nm and a weak red band centred at 668 nm were observed in the emission spectrum due to excitation at 352 nm wavelength. Both FTIR and Raman spectra assert slight structural changes induced in the host glass network with Dy3+ ions.

UVB emitting LiSrBO3 phosphor for phototherapy lamp

NASA Astrophysics Data System (ADS)

Kunghatkar, R. G.; Hemne, P. S.; Dhoble, S. J.

2018-05-01

LiSrBO3 doped Gadolinium have been synthesized by sol gel technique. The formation of host was confirmed by XRD techniques. The incorporation of Gd3+ was confirmed by photoluminescence (PL) characterization. The UVB emission is observed at 316 nm when UV excited by 274 nm. The second order emission are also observed in PL emission spectra at 612 nm and 627 nm. Energy band gap is found to be 5.81 eV by using Kubelka - Munk function. The UVB emission at 316 nm of Gd3+ doped materials are used as phototherapy lamp phosphor.

Luminescence studies of CdS spherical particles via hydrothermal synthesis

NASA Astrophysics Data System (ADS)

Xu, Guo Qin; Liu, Bing; Xu, Shi Jie; Chew, Chwee Har; Chua, Soo Jin; Gana, Leong Ming

2000-06-01

The spherical particles of CdS consisting of nanoparticles (∼100 nm) were synthesized by a hydrothermal process. The particle formation and growth depend on the rate of sulfide-ion generation and diffusion-controlled aggregation of nanoparticles. As demonstrated in the profiles of powder X-ray diffraction, the crystalline phases are governed by the reaction temperature. Photoluminescence studies on CdS particles show two emission bands at the room temperature. The red emission at 680 nm is due to sulfur vacancies, and a new infrared red (IR) emission at 760 nm is attributed to self-activated centers. A red shift of IR band with the decrease of temperature was explained with a configurational coordinate model. The different saturation limits for the red and IR bands are discussed in terms of the formation of donor-acceptor pairs and exciton in CdS particles.

Optical properties of cytostatic drugs used in cancer treatment

NASA Astrophysics Data System (ADS)

Pascu, Mihail-Lucian; Mogos, Ioan; Enescu, Mironel; Staicu, Angela; Truica, Sorina; Voicu, Letitia; Gazdaru, Doina M.; Pascu, Mihaela O.; Radu, Alina

2001-10-01

A spectroscopical characterization of methotrexate, cytostatic drug used frequently in cancer therapy, was performed. The absorption, emission and excitation spectra were measured for methotrexate solutions in natural saline and sodium hydroxide at concentration in the range 10-5 M -10-6 M and pH 8.4. The absorption bands are noticed in the spectral range 250 nm - 450 nm. The fluorescence excitation was made at 340 nm and 370 nm; the fluorescence emission was detected in the spectral range 400 nm - 500 nm with a maximum at 450 nm. The behavior of absorption and fluorescence spectra of methotrexate solution exposed to uv-visible light was investigated. The irradiation was made using an Xe lamp (emission between 325 nm and 420 nm and power density of 11 mW/cm2). The exposure time was between 15 min. and 3 h. Major modifications on absorption bands for irradiation times longer than 1 hour were observed. Furthermore, the methotrexate solutions become strongly fluorescent after irradiation. The observed changes are not linear with the exposure time indicating complex photochemical processes which implies, at least, one intermediate product.

Synthesis and characterization of Mg2SiO4:Tb3+, Eu3+ phosphors for white light generation

NASA Astrophysics Data System (ADS)

Cho, Shinho

2016-09-01

The effect of Eu3+ codoping on the structural, morphological, and optical properties of Mg2SiO4:Tb3+ was investigated. The phosphor powders were synthesized by changing the molar concentration of Eu3+ at a fixed Tb3+ content of 5 mol% by using a conventional solid-state reaction. The X-ray diffraction patterns revealed that the crystal structure of all the phosphors, irrespective of the Eu3+ and the Tb3+ contents, showed an orthorhombic structure, and the surface morphology exhibited pebble-like crystalline grains. The emission spectra of Eu3+ and Tb3+-codoped Mg2SiO4 phosphors under an ultraviolet excitation of 252 nm consisted of one intense red band at 619 nm and five weak bands at 448, 488, 598, 658, and 707 nm originating from the transitions of Eu3+, in addition to the several emission bands located at 492, 552, 592, and 628 nm arising from the transitions of Tb3+. As the Eu3+ content was increased, the intensity of the main green emission band at 552 nm decreased markedly and disappeared at 10 mol% Eu3+, when complete energy transfer from Tb3+ to Eu3+ was observed. The results suggest that the emission wavelength and the luminescent intensity of the phosphors can be tuned by modulating the Eu3+ and the Tb3+ contents incorporated into the host matrix.

Photonic band edge assisted spontaneous emission enhancement from all Er3+ 1-D photonic band gap structure

NASA Astrophysics Data System (ADS)

Chiasera, A.; Meroni, C.; Varas, S.; Valligatla, S.; Scotognella, F.; Boucher, Y. G.; Lukowiak, A.; Zur, L.; Righini, G. C.; Ferrari, M.

2018-06-01

All Er3+ doped dielectric 1-D Photonic Band Gap Structure was fabricated by rf-sputtering technique. The structure was constituted by of twenty pairs of SiO2/TiO2 alternated layers doped with Er3+ ions. The scanning electron microscopy was used to check the morphology of the structure. Transmission measurements put in evidence the stop band in the range 1500 nm-1950 nm. The photoluminescence measurements were obtained by optically exciting the sample and detecting the emitted light in the 1.5 μm region at different detection angles. Luminescence spectra and luminescence decay curves put in evidence that the presence of the stop band modify the emission features of the Er3+ ions.

Broadband near-infrared downconversion luminescence in Yb3+-doped BaZn2(BO3)2

NASA Astrophysics Data System (ADS)

Yu, Hua; Deng, Degang; Su, Weitao; Li, Chenxia; Xu, Shiqing

2018-06-01

BaZn2(BO3)2 self-activated phosphors were prepared by the conventional high temperature solid-state method. The PL spectra of BaZn2(BO3)2 powders prepared under reductive and air atmosphere consist of a weak ultraviolet emission band (∼410 nm) and a broad emission band which were centered at ∼ 500 and 545 nm, respectively. According to the spectral analysis and EPR results, the green and yellow emissions may arise from the transitions of photo-generated electron close to the conduction band to the deeply trapped hole in single ionized oxygen vacancy (V+ o) centers and single negatively charged interstitial oxygen ion (O- i), respectively. An efficient broadband near-infrared (NIR) quantum cutting was demonstrated in Yb3+ doped BaZn2(BO3)2 phosphor. Upon excitation with an ultraviolet photon at 375 nm, the emissions of two NIR photons at 983 nm from Yb3+ ions were achieved. The dependences of the visible and NIR emissions, the decay lifetime, the energy transfer efficiency, and the quantum efficiency on the Yb3+ doping content were investigated in detail. The results indicated that the maximum energy transfer and the corresponding downconversion quantum efficiency could reach between 68.5% and 168.5%.

Photovoltaic Performance Enhancement of Silicon Solar Cells Based on Combined Ratios of Three Species of Europium-Doped Phosphors.

PubMed

Ho, Wen-Jeng; You, Bang-Jin; Liu, Jheng-Jie; Bai, Wen-Bin; Syu, Hong-Jhang; Lin, Ching-Fuh

2018-05-18

This paper presents a scheme for the enhancement of silicon solar cells in terms of luminescent emission band and photovoltaic performance. The proposed devices are coated with an luminescent down-shifting (LDS) layer comprising three species of europium (Eu)-doped phosphors mixed within a silicate film (SiO₂) using a spin-on film deposition. The three species of phosphor were mixed at ratios of 0.5:1:1.5, 1:1:1, or 1.5:1:0.5 in weight percentage (wt %). The total quantity of Eu-doped phosphors in the silicate solution was fixed at 3 wt %. The emission wavelengths of the Eu-doped phosphors were as follows: 518 nm (specie-A), 551 nm (specie-B), and 609 nm (specie-C). We examined the extended luminescent emission bands via photoluminescence measurements at room temperature. Closely matching the luminescent emission band to the high responsivity band of the silicon semiconductor resulted in good photovoltaic performance. Impressive improvements in efficiency were observed in all three samples: 0.5:1:1.5 (20.43%), 1:1:1 (19.67%), 1.5:1:0.5 (16.81%), compared to the control with a layer of pure SiO₂ (13.80%).

NIR dual luminescence from an extended porphyrin. Spectroscopy, photophysics and theory.

PubMed

Gourlaouen, Christophe; Daniel, Chantal; Durola, Fabien; Frey, Julien; Heitz, Valérie; Sauvage, Jean-Pierre; Ventura, Barbara; Flamigni, Lucia

2014-05-22

Spectroscopic and photophysical properties of an extended Zn porphyrin with fused bis(tetraazaanthracene) arms including a 2,9-diphenyl-1,10-phenanthroline incorporated in a polyether macrocycle are investigated in solvents of different polarity pointing to the presence of two emitting singlet excited states. The absorption and emission features are identified and ascribed, on the basis of solvent polarity dependence, to a π-π* and to a charge transfer (CT) state, respectively. Whereas the intraligand π-π* transition is assigned to the intense absorption observed at 442-455 nm, the CT states contribute to the bands at 521-525 nm and 472-481 nm. The theoretical analysis of the absorption spectrum confirms the presence of two strong bands centered at 536 and 437 nm corresponding to CT and π-π* states, respectively. Weak CT transitions are calculated at 657 and 486 nm. Two emission maxima are observed in toluene at 724 nm from a (1)π-π* state and at 800 nm from a (1)CT state, respectively. (1)CT bands shift bathochromically by increasing the solvent polarity whereas the energy of the (1)π-π band is less affected. Likewise, the emission yield and lifetime associated with the low energy (1)CT band are strongly affected by solvent polarity. This is rationalized by a (1)π-π* → (1)CT internal conversion driven by solvent polarity, this process being competitive with the (1)π-π* to ground state deactivation channel. Time resolved absorption spectra indicate the presence of two triplet states, a short-lived one (nanoseconds range) and a longer lived one (hundreds of microsecond range) ascribed to a (3)π-π* and a (3)CT, respectively. For them, a conversion mechanism similar to that of the singlet excited states is suggested.

The modification of spectral characteristics of cytostatics by optical beams

NASA Astrophysics Data System (ADS)

Pascu, Mihail Lucian; Brezeanu, Mihail; Carstocea, Benone D.; Voicu, Letitia; Gazdaru, Doina M.; Smarandache, Adriana A.

2004-10-01

Besides the biochemical action of methotrexate (MTX) and 5-fluorouracil (FU) their effect in destroying cancer tumours could be enhanced by exposure to light at different doses. Absorption, excitation and emission spectra of 10-4M - 10-5M MTX solutions in natural saline and sodium hydroxide at pH = 8.4 were measured, while their exposure to coherent and uncoherent light in the visible and near ultraviolet (UV) spectral ranges was made (Hg lamps and Nitrogen pulsed laser radiation were used). Absorption spectra exhibit spectral bands in the range 200 nm - 450 nm. The 200 - 450 nm excitation spectra were measured with emission centered on 470 nm; MTX fluorescence excitation was measured at 390 nm and the emission was detected between 400 nm and 600 nm showing a maximum at 470 nm. Spectra modifications, nonlinearly depending on exposure time (varying from 1 min to 20 min), evidenced MTX photo-dissociation to the fluorescent compound 2,4 diamino-formylpteridine. In the 5-FU case the absorption spectra exhibit bands between 200 nm and 450 nm. The emission fluorescence spectra were measured between 400 nm and 600 nm, with λex = 350 nm for UV Hg lamp and with λex = 360 nm for laser irradiated samples; at irradiation with N2 laser emitted radiation the excitation spectra were measured in the range of 200 nm - 400 nm, with λem = 440 nm. New vascularity rapid destruction was observed for conjunctive impregnated with 5-FU solution whilst exposed to incoherent UV and visible light.

Pressure-induced emission band separation of the hybridized local and charge transfer excited state in a TPE-based crystal.

PubMed

Liu, Xuedan; Li, Aisen; Xu, Weiqing; Ma, Zhiyong; Jia, Xinru

2018-05-08

We herein report a newly synthesized simple molecule, named TPE[double bond, length as m-dash]C4, with twisted D-A structure. TPE[double bond, length as m-dash]C4 showed two intrinsic emission bands ascribed to the locally excited (LE) state and the intramolecular charge transfer (ICT) state, respectively. In the crystal state, the LE emission band is usually observed. However, by applying hydrostatic pressure to the powder sample and the single crystal sample of TPE[double bond, length as m-dash]C4, dual-fluorescence (445 nm and 532 nm) was emerged under high pressure, owing to the pressure-induced emission band separation of the hybridized local and charge transfer excited state (HLCT). It is found that the emission of TPE[double bond, length as m-dash]C4 is generally determined by the ratio of the LE state to the ICT state. The ICT emission band is much more sensitive to the external pressure than the LE emission band. The HLCT state leads to a sample with different responsiveness to grinding and hydrostatic pressure. This study is of significance in the molecular design of such D-A type molecules and in the control of photoluminescence features by molecular structure. Such results are expected to pave a new way to further understand the relationship between the D-A molecular structure and stimuli-responsive properties.

Energy transfer dynamics of Er3+/Nd3+ embedded SiO2-Al2O3-Na2CO3-SrF2-CaF2 glasses for optical communications

NASA Astrophysics Data System (ADS)

Gelija, Devarajulu; Kadathala, Linganna; Borelli, Deva Prasad Raju

2018-04-01

The fluorescence and upconversion studies of Er3+ doped and Er3+/Nd3+ co-doped silicate based oxyfluoride glasses have been systematically analyzed. The broad band NIR emissions (830-1700 nm), includes optical bands like O, E, S, C and L were observed in the Er3+-Nd3+ co-doped glasses. The NIR emission intensity peaks centered at 876, 1057, 1329 and 1534 nm were observed for the Er3+-Nd3+ co-doped glasses. In the co-doped samples the strongest emission intensity at 1534 nm increased up to 0.5 mol % and then decreased to 3.0 mol % of Nd3+ ions under the excitation of 980 nm. The upconversion studies of the co-doped samples were recorded under the excitation of 980 and 808 nm and found the upconversion emission peaks centered at 524, 530, 547, 590 and 656 nm. The energy transfer processes between the relevant excitation levels of Er3+ and Nd3+ ions and energy transfer efficiency were discussed. The obtained results indicate that Nd3+ can be an efficient sensitizer for Er3+ to enhance upconversion emission at green laser transition for sensors and NIR emission at 1534 nm for optical communication applications.

Near band edge emission characteristics of sputtered nano-crystalline ZnO films

NASA Astrophysics Data System (ADS)

Kunj, Saurabh; Sreenivas, K.

2016-05-01

Sputtered zinc oxide (ZnO) thin films deposited on unheated glass substrate under different sputtering gas mixtures (Ar+O2) have been investigated using X-ray diffraction and photo luminescence spectroscopy. Earlier reported studies on ZnO films prepared by different techniques exhibit either a sharp/broad near band edge (NBE) emission peak depending on the crystalline quality of the film. In the present study zinc oxide films, grown on unheated substrates, are seen to possess a preferred (002) orientation with a microstructure consisting of clustered nano-sized crystallites. The splitting in the near band edge emission (NBE) into three characteristic peaks is attributed to quantum confinement effect, and is observed specifically under an excitation of 270 nm. Deep level emission (DLE) in the range 400 to 700 nm is not observed indicating absence of deep level radiative defects.

Tunable Emission Wavelength Stacked InAs/GaAs Quantum Dots by Chemical Beam Epitaxy for Optical Coherence Tomography

PubMed Central

Ilahi, Bouraoui; Zribi, Jihene; Guillotte, Maxime; Arès, Richard; Aimez, Vincent; Morris, Denis

2016-01-01

We report on Chemical Beam Epitaxy (CBE) growth of wavelength tunable InAs/GaAs quantum dots (QD) based superluminescent diode’s active layer suitable for Optical Coherence Tomography (OCT). The In-flush technique has been employed to fabricate QD with controllable heights, from 5 nm down to 2 nm, allowing a tunable emission band over 160 nm. The emission wavelength blueshift has been ensured by reducing both dots’ height and composition. A structure containing four vertically stacked height-engineered QDs have been fabricated, showing a room temperature broad emission band centered at 1.1 µm. The buried QD layers remain insensitive to the In-flush process of the subsequent layers, testifying the reliability of the process for broadband light sources required for high axial resolution OCT imaging. PMID:28773633

Development of transition metal dichalcogenide based quantum dots for light emitting diodes

NASA Astrophysics Data System (ADS)

Seth, Subhashree; Sharma, S. K.

2018-05-01

Photoluminescent quantum dots (QDs) were synthesized by facile colloidal chemical route. Its properties were characterized and analysed by utilizing Fluorescence, FTIR and UV-Vis spectrophotometers. The resultant MoS2 QD exhibits fluorescence at 470 nm for excitation wavelength 400 nm. The as prepared sample exhibits excitation dependent emission due to polydispersion of MoS2 in the dispersive medium which is the characteristics of colloidal synthesis. It is also observed that resultant MoS2 QDs show size tunable emission in the visible region. The FTIR spectrum confirms the attachment of oleic acid on the surface of MoS2. Absorption spectrum shows a band at 346 nm and a shoulder band at 400 nm. The band gap of quantum dots was obtained as 3.5 eV. CIE diagram indicates the shifting of colour coordinates towards green region with increasing excitation wavelength.

Enhancement of luminescence properties in Er3+ doped TeO2-Na2O-PbX (X=O and F) ternary glasses.

PubMed

Kumar, Kaushal; Rai, S B; Rai, D K

2007-04-01

An enhancement of luminescence properties in Er3+ doped ternary glasses is observed on the addition of PbO/PbF2. The infrared to visible upconversion emission bands are observed at 410, 525, 550 and 658 nm, due to the 2H9/2-->4I15/2, 2H11/2-->4I15/2, 4S3/2-->4I15/2, 4F9/2-->4I15/2 transitions respectively, on excitation with 797 nm laser line. A detailed study reveals that the 2H9/2-->4I15/2 transition arises due to three step upconversion process while other transitions arise due to two step absorption. On excitation with 532 nm radiation, ultraviolet and violet upconversion bands centered at 380, 404, 410 and 475 nm wavelengths are observed along with one photon luminescence bands at 525, 550, 658 and 843 nm wavelengths. These bands are found due to the 4G11/2-->4I15/2, 2P3/2-->4I13/2, 2H9/2-->4I15/2, 2P3/2-->4I11/2, 2H11/2-->4I15/2, 4S3/2-->4I15/2, 4F9/2-->4I15/2 and 4S3/2-->4I13/2 transitions, respectively. Though incorporation of PbO and PbF2 both enhances fluorescence intensities however, PbF2 content has an important influence on upconversion luminescence emission. The incorporation of PbF2 enhances the red emission (658 nm) intensity by 1.5 times and the violet emission (410 nm) intensity by 2.0 times. A concentration dependence study of fluorescence reveals the rapid increase in the red (4F9/2-->4I15/2) emission intensity relative to the green (4S3/2-->4I15/2) emission with increase in the Er3+ ion concentration. This behaviour has been explained in terms of an energy transfer by relaxation between excited ions.

Magneto-optical properties of α-Fe2O3@ZnO nanocomposites prepared by the high energy ball-milling technique

NASA Astrophysics Data System (ADS)

Chaudhury, Chandana Roy; Roychowdhury, Anirban; Das, Anusree; Das, Dipankar

2016-05-01

Magnetic-fluorescent nanocomposites (NCs) with 10 wt% of α-Fe2O3 in ZnO have been prepared by the high energy ball-milling. The crystallite sizes of α-Fe2O3 and ZnO in the NCs are found to vary from 65 nm to 20 nm and 47 nm to 15 nm respectively as milling time is increased from 2 to 30 h. XRD analysis confirms presence of α-Fe2O3 and ZnO in pure form in all the NCs. UV-vis study of the NCs shows a continuous blue-shift of the absorption peak and a steady increase of band gap of ZnO with increasing milling duration that are assigned to decreasing particle size of ZnO in the NCs. Photoluminescence (PL) spectra of the NCs reveal three weak emission bands in the visible region at 421, 445 and 485 nm along with the strong near band edge emission at 391 nm. These weak emission bands are attributed to different defect - related energy levels e.g. Zn-vacancy, Zn interstitial and oxygen vacancy. Dc and ac magnetization measurements show presence of weakly interacting superparamagnetic (SPM) α-Fe2O3 particles in the NCs. 57Fe-Mössbauer study confirms presence of SPM hematite in the sample milled for 30 h. Positron annihilation lifetime measurements indicate presence of cation vacancies in ZnO nanostructures confirming results of PL studies.

Thermally switchable photonic band-edge to random laser emission in dye-doped cholesteric liquid crystals

NASA Astrophysics Data System (ADS)

Ye, Lihua; Wang, Yan; Feng, Yangyang; Liu, Bo; Gu, Bing; Cui, Yiping; Lu, Yanqing

2018-03-01

By changing the doping concentration of the chiral agent to adjust the relative position of the reflection band of cholesteric liquid crystals and the fluorescence emission spectrum of the dye, photonic band-edge and random lasing were observed, respectively. The reflection band of the cholesteric phase liquid crystal can also be controlled by adjusting the temperature: the reflection band is blue-shifted with increasing temperature, and a reversible switch from photonic band-edge to random lasing is obtained. Furthermore, the laser line width can be thermally adjusted from 1.1 nm (at 27 °C) to 4.6 nm (at 32.1 °C). A thermally tunable polarization state of a random laser from dual cells was observed, broadening the field of application liquid crystal random lasers.

Surface temperature measurements from a stator vane doublet in a turbine afterburner flame using a YAG:Tm thermographic phosphor

NASA Astrophysics Data System (ADS)

Eldridge, Jeffrey I.; Allison, Stephen W.; Jenkins, Thomas P.; Gollub, Sarah L.; Hall, Carl A.; Walker, D. Greg

2016-12-01

Phosphor thermometry measurements in turbine engine environments can be difficult because of high background radiation levels. To address this challenge, luminescence lifetime-based phosphor thermometry measurements were obtained using thulium-doped Y3Al5O12 (YAG:Tm) to take advantage of the emission wavelengths at 365 nm (1D2  →  3H6 transition) and at 456 nm (1D2  →  3F4 transition). At these wavelengths, turbine engine radiation background is reduced compared with emission from longer wavelength phosphors. Temperature measurements of YAG:Tm coatings were demonstrated using decay of both the 365 and 456 nm emission bands in a furnace environment up to 1400 °C. To demonstrate that reliable surface temperatures based on short-wavelength YAG:Tm emission could be obtained from the surface of an actual engine component in a high gas velocity, highly radiative environment, measurements were obtained from a YAG:Tm-coated Honeywell stator vane doublet placed in the afterburner flame exhaust stream of the augmenter-equipped General Electric J85 turbojet test engine at the University of Tennessee Space Institute (UTSI). Using a probe designed for engine insertion, spot temperature measurements were obtained by measuring luminescence decay times over a range of steady state throttle settings as well as during an engine throttle acceleration. YAG:Tm phosphor thermometry measurements of the stator vane surface in the afterburner exhaust stream using the decay of the 456 nm emission band were successfully obtained at temperatures up to almost 1300 °C. Phosphor thermometry measurements acquired with the engine probe using the decay of the 365 nm emission band were not successful at usefully high temperatures because the probe design allowed transmission of intense unfiltered silica Raman scattering that produced photomultiplier tube saturation with extended recovery times. Recommendations are made for probe modifications that will enable temperature measurements using the 365 nm emission band decay, which will be beneficial in environments with strong reflections of combustor radiation.

Investigations on the effects of the Stark splitting on the fluorescence behaviors in Yb3+-doped silicate, tellurite, germanate, and phosphate glasses

NASA Astrophysics Data System (ADS)

Zhang, Liaolin; Xia, Yu; Shen, Xiao; Yang, Runlan; Wei, Wei

2018-01-01

In this work, we systematically studied the spectroscopic characteristics of Yb3+ doped germanate, phosphate, silicate, and tellurite glasses. The emission peak beyond 976 nm showed irregular shift from 1001 nm to 1023 nm when Yb3+ in different glass matrices. It was associated with the Stark splitting of 2F7/2 and the emission intensities ratio between the transition from the lowest Stark splitting energy level of 2F5/2 to the Stark splitting energy levels of 2F7/2, e to b and that of e to d. Larger Stark splitting of 2F7/2 results in the red-shift of the near infrared emission band at room temperature and larger ratio results in the blue-shift of emission band. The fluorescence lifetimes of Yb3+ doped germanate, phosphate, silicate, and tellurite glasses were measured to be 0.94, 0.82, 1.51, and 0.66 ms, respectively. The fluorescence lifetime was associated with the reabsorption of Yb3+, which larger absorption cross section at the emission band results in larger reabsorption, then leads to the shorter near infrared fluorescence lifetime.

Strong visible and near infrared photoluminescence from ZnO nanorods/nanowires grown on single layer graphene studied using sub-band gap excitation

NASA Astrophysics Data System (ADS)

Biroju, Ravi K.; Giri, P. K.

2017-07-01

Fabrication and optoelectronic applications of graphene based hybrid 2D-1D semiconductor nanostructures have gained tremendous research interest in recent times. Herein, we present a systematic study on the origin and evolution of strong broad band visible and near infrared (NIR) photoluminescence (PL) from vertical ZnO nanorods (NRs) and nanowires (NWs) grown on single layer graphene using both above band gap and sub-band gap optical excitations. High resolution field emission scanning electron microscopy and X-ray diffraction studies are carried out to reveal the morphology and crystalline quality of as-grown and annealed ZnO NRs/NWs on graphene. Room temperature PL studies reveal that besides the UV and visible PL bands, a new near-infrared (NIR) PL emission band appears in the range between 815 nm and 886 nm (1.40-1.52 eV). X-ray photoelectron spectroscopy studies revealed excess oxygen content and unreacted metallic Zn in the as-grown ZnO nanostructures, owing to the low temperature growth by a physical vapor deposition method. Post-growth annealing at 700 °C in the Ar gas ambient results in the enhanced intensity of both visible and NIR PL bands. On the other hand, subsequent high vacuum annealing at 700 °C results in a drastic reduction in the visible PL band and complete suppression of the NIR PL band. PL decay dynamics of green emission in Ar annealed samples show tri-exponential decay on the nanosecond timescale including a very slow decay component (time constant ˜604.5 ns). Based on these results, the NIR PL band comprising two peaks centered at ˜820 nm and ˜860 nm is tentatively assigned to neutral and negatively charged oxygen interstitial (Oi) defects in ZnO, detected experimentally for the first time. The evidence for oxygen induced trap states on the ZnO NW surface is further substantiated by the slow photocurrent response of graphene-ZnO NRs/NWs. These results are important for tunable light emission, photodetection, and other cutting edge applications of graphene-ZnO based 2D-1D hybrid nanostructures.

Photovoltaic Performance Enhancement of Silicon Solar Cells Based on Combined Ratios of Three Species of Europium-Doped Phosphors

PubMed Central

You, Bang-Jin; Liu, Jheng-Jie; Bai, Wen-Bin; Syu, Hong-Jhang; Lin, Ching-Fuh

2018-01-01

This paper presents a scheme for the enhancement of silicon solar cells in terms of luminescent emission band and photovoltaic performance. The proposed devices are coated with an luminescent down-shifting (LDS) layer comprising three species of europium (Eu)-doped phosphors mixed within a silicate film (SiO2) using a spin-on film deposition. The three species of phosphor were mixed at ratios of 0.5:1:1.5, 1:1:1, or 1.5:1:0.5 in weight percentage (wt %). The total quantity of Eu-doped phosphors in the silicate solution was fixed at 3 wt %. The emission wavelengths of the Eu-doped phosphors were as follows: 518 nm (specie-A), 551 nm (specie-B), and 609 nm (specie-C). We examined the extended luminescent emission bands via photoluminescence measurements at room temperature. Closely matching the luminescent emission band to the high responsivity band of the silicon semiconductor resulted in good photovoltaic performance. Impressive improvements in efficiency were observed in all three samples: 0.5:1:1.5 (20.43%), 1:1:1 (19.67%), 1.5:1:0.5 (16.81%), compared to the control with a layer of pure SiO2 (13.80%). PMID:29783716

High-performance field emission device utilizing vertically aligned carbon nanotubes-based pillar architectures

NASA Astrophysics Data System (ADS)

Gupta, Bipin Kumar; Kedawat, Garima; Gangwar, Amit Kumar; Nagpal, Kanika; Kashyap, Pradeep Kumar; Srivastava, Shubhda; Singh, Satbir; Kumar, Pawan; Suryawanshi, Sachin R.; Seo, Deok Min; Tripathi, Prashant; More, Mahendra A.; Srivastava, O. N.; Hahm, Myung Gwan; Late, Dattatray J.

2018-01-01

The vertical aligned carbon nanotubes (CNTs)-based pillar architectures were created on laminated silicon oxide/silicon (SiO2/Si) wafer substrate at 775 °C by using water-assisted chemical vapor deposition under low pressure process condition. The lamination was carried out by aluminum (Al, 10.0 nm thickness) as a barrier layer and iron (Fe, 1.5 nm thickness) as a catalyst precursor layer sequentially on a silicon wafer substrate. Scanning electron microscope (SEM) images show that synthesized CNTs are vertically aligned and uniformly distributed with a high density. The CNTs have approximately 2-30 walls with an inner diameter of 3-8 nm. Raman spectrum analysis shows G-band at 1580 cm-1 and D-band at 1340 cm-1. The G-band is higher than D-band, which indicates that CNTs are highly graphitized. The field emission analysis of the CNTs revealed high field emission current density (4mA/cm2 at 1.2V/μm), low turn-on field (0.6 V/μm) and field enhancement factor (6917) with better stability and longer lifetime. Emitter morphology resulting in improved promising field emission performances, which is a crucial factor for the fabrication of pillared shaped vertical aligned CNTs bundles as practical electron sources.

Electron impact excitation of higher energy states of molecular oxygen in the atmosphere of Europa

NASA Astrophysics Data System (ADS)

Campbell, L.; Tanaka, H.; Kato, H.; Jayaraman, S.; Brunger, M. J.

2012-01-01

Recent measurements of integral cross sections for electron impact excitation of the Schumann-Runge continuum, longest band and second band of molecular oxygen are applied to calculations of emissions from the atmosphere of Europa. Molecules excited to these bands predissociate, producing O(1D) (excited oxygen) atoms which subsequently decay to produce 630.0-nm radiation. Radiation of this wavelength is also produced by direct excitation of O atoms and by the recombination of O _2^+ + 2 with electrons, but these two processes also produce O(1S) atoms which then emit at 557.7 nm. It is shown by modeling that the ratio of 630.0-nm to 557.7-nm is sensitive to the relative importance of the three processes, suggesting that the ratio would be a useful remote sensing probe in the atmosphere of Europa. In particular, the excitation of the Schumann-Runge continuum, longest band and second band is produced by magnetospheric electrons while the recombination is produced by secondary electrons produced in the atmosphere. This difference raises the possibility of determination of the secondary electron spectrum by measurement of light emissions.

Design of a portable optical emission tomography system for microwave induced compact plasma for visible to near-infrared emission lines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rathore, Kavita, E-mail: kavira@iitk.ac.in, E-mail: pmunshi@iitk.ac.in, E-mail: sudeepb@iitk.ac.in; Munshi, Prabhat, E-mail: kavira@iitk.ac.in, E-mail: pmunshi@iitk.ac.in, E-mail: sudeepb@iitk.ac.in; Bhattacharjee, Sudeep, E-mail: kavira@iitk.ac.in, E-mail: pmunshi@iitk.ac.in, E-mail: sudeepb@iitk.ac.in

A new non-invasive diagnostic system is developed for Microwave Induced Plasma (MIP) to reconstruct tomographic images of a 2D emission profile. A compact MIP system has wide application in industry as well as research application such as thrusters for space propulsion, high current ion beams, and creation of negative ions for heating of fusion plasma. Emission profile depends on two crucial parameters, namely, the electron temperature and density (over the entire spatial extent) of the plasma system. Emission tomography provides basic understanding of plasmas and it is very useful to monitor internal structure of plasma phenomena without disturbing its actualmore » processes. This paper presents development of a compact, modular, and versatile Optical Emission Tomography (OET) tool for a cylindrical, magnetically confined MIP system. It has eight slit-hole cameras and each consisting of a complementary metal–oxide–semiconductor linear image sensor for light detection. The optical noise is reduced by using aspheric lens and interference band-pass filters in each camera. The entire cylindrical plasma can be scanned with automated sliding ring mechanism arranged in fan-beam data collection geometry. The design of the camera includes a unique possibility to incorporate different filters to get the particular wavelength light from the plasma. This OET system includes selected band-pass filters for particular argon emission 750 nm, 772 nm, and 811 nm lines and hydrogen emission H{sub α} (656 nm) and H{sub β} (486 nm) lines. Convolution back projection algorithm is used to obtain the tomographic images of plasma emission line. The paper mainly focuses on (a) design of OET system in detail and (b) study of emission profile for 750 nm argon emission lines to validate the system design.« less

Investigating the 3.3 micron infrared fluorescence from naphthalene following ultraviolet excitation

NASA Technical Reports Server (NTRS)

Williams, Richard M.; Leone, Stephen R.

1994-01-01

Polycyclic aromatic hydrocarbon (PAH) type molecules are proposed as the carriers of the unidentified infrared (UIR) bands. Detailed studies of the 3.3 micrometer infrared emission features from naphthalene, the simplest PAH, following ultraviolet laser excitation are used in the interpretation of the 3.29 micrometer (3040 cm(sup -1)) UIR band. A time-resolved Fourier transform spectrometer is used to record the infrared emission spectrum of gas-phase naphthalene subsequent to ultraviolet excitation facilitated by an excimer laser operated at either 193 nm or 248 nm. The emission spectra differ significantly from the absorption spectrum in the same spectral region. Following 193 nm excitation the maximum in the emission profile is red-shifted 45 cm(sup -1) relative to the absorption maximum; a 25 cm(sup -1) red-shift is observed after 248 nm excitation. The red-shifting of the emission spectrum is reduced as collisional and radiative relaxation removes energy from the highly vibrationally excited molecules. Coupling between the various vibrational modes is thought to account for the differences between absorption and emission spectra. Strong visible emission is also observed following ultraviolet excitation. Visible emission may play an important role in the rate of radiative relaxation, which according to the interstellar PAH hypothesis occurs only by the slow emission of infrared photons. Studying the visible emission properties of PAH type molecules may be useful in the interpretation of the DIB's observed in absorption.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Machado, Thales R.; QIO-UJI, Universitat Jaume I, 12071 Castellón; Sczancoski, Júlio C.

Defect-related photoluminescence (PL) in materials have attracted interest for applications including near ultraviolet (NUV) excitable light-emitting diodes and in biomedical field. In this paper, hydroxyapatite [Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}] nanorods with intense PL bands (bluish- and yellowish-white emissions) were obtained when excited under NUV radiation at room temperature. These nanoparticles were synthesized via chemical precipitation at 90 °C followed by distinct heat treatments temperatures (200–800 °C). Intense and broad emission profiles were achieved at 350 °C (380–750 nm) and 400 °C (380–800 nm). UV–Vis spectroscopy revealed band gap energies (5.58–5.78 eV) higher than the excitation energies (~3.54 and ~2.98more » eV at 350 and 415 nm, respectively), confirming the contribution of defect energy levels within the forbidden zone for PL emissions. The structural features were characterized by X-ray diffraction, Rietveld refinement, thermogravimetric analysis, and Fourier transform infrared spectroscopy. By means of these techniques, the relation between structural order-disorder induced by defects, chemical reactions at both lattice and surface of the materials as well as the PL, without activator centers, was discussed in details. - Graphical abstract: The self-activated photoluminescence emissions of chemically precipitated hydroxyapatite nanorods were improved by different heat treatment temperatures. - Highlights: • HA nanorods were synthesized with improved self-activated PL at room temperature. • PL profile and intensity dependents on the temperature of posterior heat treatments. • Bluish- and yellowish-white emissions under NUV excitation (350 and 415 nm). • Broad and intense profiles achieved at 350 °C (380–750 nm) and 400 °C (380–800 nm). • PL from the e′–h{sup •} recombination between defect energy levels within the band gap.« less

A double-stream Xe:He jet plasma emission in the vicinity of 6.7 nm

NASA Astrophysics Data System (ADS)

Chkhalo, N. I.; Garakhin, S. A.; Golubev, S. V.; Lopatin, A. Ya.; Nechay, A. N.; Pestov, A. E.; Salashchenko, N. N.; Toropov, M. N.; Tsybin, N. N.; Vodopyanov, A. V.; Yulin, S.

2018-05-01

We present the results of investigations of extreme ultraviolet (EUV) light emission in the range from 5 to 10 nm. The light source was a pulsed "double-stream" Xe:He gas jet target irradiated by a laser beam with a power density of ˜1011 W/cm2. The radiation spectra were measured with a Czerny-Turner monochromator with a plane diffraction grating. The conversion efficiency of the laser energy into EUV radiation caused by Xe+14…+16 ion emission in the range of 6-8 nm was measured using a calibrated power meter. The conversion efficiency of the laser radiation into EUV in the vicinity of 6.7 nm was (2.17 ± 0.13)% in a 1 nm spectral band. In the spectral band of the real optical system (0.7% for La/B multilayer mirrors) emitted into the half-space, it was (0.1 ± 0.006)%. The results of this study provide an impetus for further research on laser plasma sources for maskless EUV lithography at a wavelength of 6.7 nm.

Localized-Surface-Plasmon Enhanced the 357 nm Forward Emission from ZnMgO Films Capped by Pt Nanoparticles

PubMed Central

2009-01-01

The Pt nanoparticles (NPs), which posses the wider tunable localized-surface-plasmon (LSP) energy varying from deep ultraviolet to visible region depending on their morphology, were prepared by annealing Pt thin films with different initial mass-thicknesses. A sixfold enhancement of the 357 nm forward emission of ZnMgO was observed after capping with Pt NPs, which is due to the resonance coupling between the LSP of Pt NPs and the band-gap emission of ZnMgO. The other factors affecting the ultraviolet emission of ZnMgO, such as emission from Pt itself and light multi-scattering at the interface, were also discussed. These results indicate that Pt NPs can be used to enhance the ultraviolet emission through the LSP coupling for various wide band-gap semiconductors. PMID:20596433

Sensitive determination of rutin by spectrofluorimetry using carbon dots synthesized from a non-essential amino acid

NASA Astrophysics Data System (ADS)

Sinduja, B.; Abraham John, S.

2018-03-01

The present study describes the synthesis of carbon dots (CDs) using a non-essential amino acid, asparagine as a precursor. The HR-TEM image shows that the size of the prepared CDs was 2.9 ± 0.2 nm with a spherical morphology. The UV-visible spectrum of CDs exhibits a major band at 307 nm along with a shoulder band around 207 nm corresponding to n-π* and π-π* transitions, respectively. Further, the CDs show emission maximum at 441 nm when excited at 348 nm. The synthesized CDs were then exploited for the determination of rutin by spectrofluorimetry based on the decrease in emission intensity at 441 nm. It was found that emission intensity of CDs at 441 nm was decreased while adding 0.5 μM rutin to CDs. On the other hand, addition of other metal ions and anions including 5 mM Mg2 +, K+, Ca2 +, Na+, NO3- and oxalate, 2.5 mM Cu2 + and Fe3 + and 3 mM glycine, glucose, histidine, proline and cysteine does not affect the emission intensity at 441 nm. A good linearity was observed for the emission intensity against 0.5-15 μM rutin with a correlation coefficient of 0.997 and the limit of detection was found to be 1 × 10- 7 M (61 μg/L) (S/N = 3). The real sample analysis was done by determining rutin in a pharmaceutical sample.

A Multi-Instrument Measurement of a Mesospheric Bore at the Equator

NASA Technical Reports Server (NTRS)

Shiokawa, K.; Suzuki, S.; Otsuka, Y.; Ogawa, T.; Nakamura, T.; Mlynczak, M. G.; Russell, J. M., III

2005-01-01

We have made a comprehensive measurement of mesospheric bore phenomenon at the equator at Kototabang, Indonesia (0.2 deg S, 100.3 deg E), using an airglow imager, an airglow temperature photometer, a meteor radar, and the SABER instrument on board the TIMED satellite. The bore was detected in airglow images of both OH-band (peak emission altitude: 87 km) and 557.7-nm (96 km) emissions, as east-west front-like structure propagating northward with a velocity of 52-58 m/s. Wave trains with a horizontal wavelength of 30-70 km are observed behind the bore front. The airglow intensity decreases for all the mesospheric emissions of OI (557.7 nm), OH-band, O2-band (altitude: 94 km), and Na (589.3 nm) (90 km) after the bore passage. The rotational temperatures of both OH-band and O2-band also decrease approximately 10 K after the bore passage. An intense shear in northward wind velocity of 80m/s was observed at altitudes of 84-90 km by the meteor radar. Kinetic temperature profile at altitudes of 20-120 km was observed near Kototabang by TIMED/SABER. On the basis of these observations, we discuss generation and ducting of the observed mesospheric bore.

Areosynchronous weather imager

NASA Astrophysics Data System (ADS)

Puschell, Jeffery J.; Lock, Robert

2016-09-01

Mars is characterized by rapidly changing, poorly understood weather that is a concern for future human missions. Future Areosynchronous Mars Orbit (AMO) communication satellites offer possible platforms for Mars weather imagers similar to the geosynchronous Earth orbit (GEO) weather imagers that have been observing Earth since 1966. This paper describes an AReosynchronous Environmental Suite (ARES) that includes two imagers: one with two emissive infrared bands (10.8 μm and 12.0 μm) at 4 km resolution and the other with three VNIR bands (500 nm, 700 nm, 900 nm) at 1 km resolution. ARES stares at Mars and provides full disk coverage as fast as every 40 sec in the VNIR bands and every 2 min in the emissive bands with good sensitivity (SNR 200 in the VNIR for typical radiances and NEDT 0.2K at 180 K scene temperature in the emissive infrared). ARES size, mass, power and data rate characteristics are compatible with expectations for hosted payloads onboard future AMO communication satellites. Nevertheless, more work is needed to optimize ARES for future missions, especially in terms of trades between data rate, full disk coverage rate, sensitivity, number of spectral bands and spatial resolution and in study of approaches for maintaining accurate line of sight knowledge during data collection.

Growth and optical properties of Co,Nd:LaMgAl11O19

NASA Astrophysics Data System (ADS)

Xu, Peng; Xia, Changtai; Di, Juqing; Xu, Xiaodong; Sai, Qinglin; Wang, Lulu

2012-12-01

Nd,Co:LaMgAl11O19 (abbreviated as Co,Nd:LMA) was grown using the Czochralski method. The structure, polarized absorption spectrum, fluorescence spectrum, and fluorescence decay time were analyzed. The as-grown crystal had very wide absorption bands at 794 nm, which can be pumped by GaAs laser diode without temperature stabilization. Two strong emission bands were present at 1056 nm and 1082 nm with full-width at half-maximum (FWHM) of 6 and 8 nm, respectively. The large FWHM is due to the inhomogeneity of the Nd ion sites. The lifetimes of the 4F3/2 manifold of Co,Nd:LMA at room temperature monitored at 905 nm, 1056 nm, and 1344 nm were 292, 288, and 350 μs, respectively, which was caused by the different contribution of the three different sites with D3h and C2v symmetry. The absorption band of Co is from 1.3 μm to 1.6 μm, and Co,Nd:LMA still has a strong emission around the 1.38 μm, indicating that the Co,Nd:LMA can be applied as a potential self-Q-switched material operating at 1.3 μm.

Luminescence Mechanism of Carbon Dots by Tailoring Functional Groups for Sensing Fe3+ Ions

PubMed Central

Yu, Jingjing; Liu, Chang; Yuan, Kang; Lu, Zunming; Cheng, Yahui; Li, Lanlan; Jin, Peng; Meng, Fanbin; Liu, Hui

2018-01-01

In this paper, spherical carbon dots (CDs) with distinct compositions and surface states have been successfully synthesized by a facile microwave method. From the fluorescence spectra, several characteristic luminescence features have been observed: surface amino groups are dominant in the whole emission spectra centering at 445 nm, and the fingerprint emissions relevant to the impurity levels formed by some groups related to C and N elements, including C-C/C=C (intrinsic C), C-N (graphitic N), N-containing heterocycles (pyridine N) and C=O groups, are located around 305 nm, 355 nm, 410 nm, and 500 nm, respectively. Those fine luminescence features could be ascribed to the electron transition among various trapping states within the band structure caused by different chemical bonds in carbon cores, or functional groups attached to the CDs’ surfaces. According to the theoretical calculations and experimental results, a scheme of the band structure has been proposed to describe the positions of those trapping states within the band gap. Additionally, it has also been observed that the emission of CDs is sensitive to the concentration of Fe3+ ions with a linear relation in the range of Fe3+ concentration from 12.5 to 250 μM. PMID:29649110

Optical properties of Eu3+ & Tb3+ ions doped alkali oxide (Li2O/ Na2O/ K2O) modified boro phosphate glasses for red, green lasers and display device applications

NASA Astrophysics Data System (ADS)

Moulika, G.; Sailaja, S.; Reddy, B. Naveen Kumar; Reddy, V. Sahadeva; Dhoble, S. J.; Reddy, B. Sudhakar

2018-04-01

In this article we report on alkali oxide modified borophosphate glasses doped with Eu3+and Tb3+ ions, with the chemical composition of 69.5 B2O3+10P2O5 + 10CaF2 + 5 Li2O+ 5ZnO+ R+ 0.5 Eu2O3 [where R = 5 (LiO2/Na2O/K2O)] have been prepared by conventional melt quenching technique, and the spectroscopic properties of the prepared glasses have been studied by XRD, Optical absorption, excitation and emission spectral analysis. XRD spectrum of the glasses have shown the amorphous nature of the glasses. The red emission corresponding to 5D0 → 7F2 (613 nm) transition was observed under the excitation of 394 nm wavelength, corresponding to Eu3+ ions, for all the prepared glasses. For Eu3+ ion doped glasses, emission bands were observed, such as; 5D1→ 7F1 (538 nm), 5D0→ 7F0 (580 nm), 5D0→ 7F1 (592 nm), 5D0→ 7F2 (613 nm), 5D0→ 7F3 (613 nm) and 5D0→ 7F4 (702 nm) are identified. In the case of Tb3+ ion doped glasses, four emission lines were observed, such as 5D4→ (7F6, 7F5, 7F4), which are located at 489 nm, 545 nm and 585 nm, respectively, after the samples were excited with 376 nm ultraviolet source. The green emission corresponding to 5D4 → 7F5 (543 nm) transition was observed under excitation wavelength 376 nm of the Tb3+ ions for all the prepared glasses. For all these emission bands, the decay curves were recorded to evaluate the emission life times. The mechanism underlying the observed emission from the glasses was explained in terms of energy levels.

Comparative study of nondoped and Eu-doped SrI2 scintillator

NASA Astrophysics Data System (ADS)

Yanagida, Takayuki; Koshimizu, Masanori; Okada, Go; Kojima, Takahiro; Osada, Junya; Kawaguchi, Noriaki

2016-11-01

Optical and scintillation properties of nondoped and Eu 3% doped SrI2 crystals grown by the Vertical Bridgman method were investigated. Eu-doped crystal showed an intense single band emission at 430 nm due to the Eu2+ 5d-4f transitions in both photoluminescence and scintillation while the nondoped crystal had a complex spectral shape. The latter emission consists of mainly four bands: 360 nm, 540 nm, 410 nm and 430 nm. The origins of 360 nm and 540 nm were self-trapped exciton and unexpected impurity, respectively. The origins of 410 and 430 nm lines were ascribed to F center in different I sites. Under 137Cs γ-ray irradiations, both crystals showed a clear photoabsorption peak. The scintillation light yields of the nondoped and Eu-doped SrI2 resulted 33,000 ph/MeV and 82,000 ph/MeV, respectively. The energy resolution at 662 keV of Eu-doped was 4% while that of the non-doped SrI2 was 8%.

High precision low resolution spectrophotometry of Comets Giacobini-Zinner and Halley

NASA Technical Reports Server (NTRS)

Odell, C. R.; Tegler, Stephen C.

1986-01-01

Optical window (300 to 1000 nm) observations were made of Comet Halley during 12 to 14 Mar. 1986 by a scanning spectrometer. The results provide accurate spectrophotometric measurements of the principal molecular bands from the 308 nm OH through the 918 nm CN emissions. The observations can be used to tie space derived ultraviolet and groundbased infrared observations to the optical observations and to one another. Additional observations were made of comet Giacobini-Zinner on 30 September 1985 of the same OH band and the 388 nm band of CN. The Swan band sequence ratios are used to test the best models of C2, with different ratios favoring different models, calling into question the assumptions of these very complete models.

Combustion synthesis of MgO nanoparticles using plant extract: Structural characterization and photoluminescence studies

NASA Astrophysics Data System (ADS)

Kumar, Danith; Yadav, L. S. Reddy; Lingaraju, K.; Manjunath, K.; Suresh, D.; Prasad, Daruka; Nagabhushana, H.; Sharma, S. C.; Naika, H. Raja; Chikkahanumantharayappa, Nagaraju, G.

2015-06-01

Magnesium oxide nanoparticles (MgO Nps) have been successfully synthesized via solution combustion method using Parthenium plant extract as fuel for the first time. Powder X-ray diffraction (PXRD) pattern reveal that product belongs to the cubic phase (Periclase). FTIR spectrum shows the band at 822 cm-1 indicates the formation of cubic periclase MgO. The optical band gap of MgO Nps estimated from UV -Vis spectrum was found to be in the range 5.40-5.45 eV. SEM images showed that, the product is agglomerated and particle in nature. Photoluminescence (PL) studies shows violet emission at 390 nm, blue emission at 470 nm and green emission at 550 nm. MgO Nps shows good photocatalytic activity for the degradation of methylene blue (MB) dye under UV/Sun light irradiation.

Novel Galvanic Corrosion Inhibitors: Synthesis, Characterization, Fabrication and Testing

DTIC Science & Technology

2007-09-30

have attempted to develop methods based on chemical structural modification to prevent galvanically-induced composite corrosion. [9, 10-12] These...of the two metallopolymers 11 and 12 show characteristic MLCT (metal-to-ligand charge transfer) absorption band of tris(bipyridyl)Ru(II) unit at k...showed absorption band at 450 nm and emission band at 325 nm of tris(bipyridyl)Ru(II) units in its respective UV-vis and fluorescence spectra. Very

Dayglow emissions of the O2 Herzberg bands and the Rayleigh backscattered spectrum of the earth

NASA Technical Reports Server (NTRS)

Frederick, J. E.; Abrams, R. B.

1982-01-01

It is pointed out that numerous fluorescent emissions from the Herzberg bands of molecular oxygen lie in the spectral region 242-300 nm. This coincides with the wavelength range used by orbiting spectrometers that observe the Rayleigh backscattered spectrum of the earth for the purpose of monitoring the vertical distribution of stratospheric ozone. Model calculations suggest that Herzberg band emissions in the dayglow could provide significant contamination of the ozone measurements if the quenching rate of O2(A3Sigma) is sufficiently small. It is noted that this is especially true near 255 nm, where the most intense fluorescent emissions relative to the Rayleigh scattered signal are located and where past satellite measurements have shown a persistent excess radiance above that expected for a pure ozone absorbing and molecular scattering atmosphere. Very small quenching rates, however, are adequate to reduce the dayglow emission to negligible levels. Noting that available laboratory data have not definitely established the quenching on the rate of O2(A3Sigma) as a function of vibration level, it is emphasized that such information is required before the Herzberg band contributions can be evaluated with confidence.

N2 triplet band systems and atomic oxygen in the dayglow

NASA Astrophysics Data System (ADS)

Broadfoot, A. L.; Hatfield, D. B.; Anderson, E. R.; Stone, T. C.; Sandel, B. R.; Gardner, J. A.; Murad, E.; Knecht, D. J.; Pike, C. P.; Viereck, R. A.

1997-06-01

New spectrographic observations of the Earth's dayglow have been acquired by the Arizona Airglow Experiment (GLO) flown on the space shuttle. GLO is an imaging spectrograph that records simultaneous vertical profiles of prominent Earth limb emissions occurring at wavelengths between 115 and 900 nm. This study addresses the measured emissions from the N2 triplet states (first positive, second positive, and Vegard-Kaplan band systems) and their excitation by the local photoelectron flux. The triplet state population distributions modeled for aurora by Cartwright [1978] are modified for dayglow conditions by changing to a photoelectron-flux energy distribution and including resonance scattering by the first positive system. Modeled and observed intensities are in excellent agreement, in contrast to the well-studied auroral case. This work concentrates on dayglow conditions at 200 km altitude near the subsolar point. Parameters to infer the local photoelectron flux from the emission band intensities are provided. Several atomic oxygen dayglow emission features were analyzed to complement the N2 analysis. The photoelectron-excited O I(135.6, 777.4 nm) lines were found to be 3 to 4 times weaker than predicted while the O I(630.0, 844.6 nm) lines were in close agreement with the model prediction.

Emission dynamics of hybrid plasmonic gold/organic GaN nanorods

NASA Astrophysics Data System (ADS)

Mohammadi, F.; Schmitzer, H.; Kunert, G.; Hommel, D.; Ge, J.; Duscher, G.; Langbein, W.; Wagner, H. P.

2017-12-01

We studied the emission of bare and aluminum quinoline (Alq3)/gold coated wurtzite GaN nanorods by temperature- and intensity-dependent time-integrated and time-resolved photoluminescence (PL). The GaN nanorods of ˜1.5 μm length and ˜250 nm diameter were grown by plasma-assisted molecular beam epitaxy. Gold/Alq3 coated GaN nanorods were synthesized by organic molecular beam deposition. The near band-edge and donor-acceptor pair luminescence was investigated in bare GaN nanorods and compared with multilevel model calculations providing the dynamical parameters for electron-hole pairs, excitons, impurity bound excitons, donors and acceptors. Subsequently, the influence of a 10 nm gold coating without and with an Alq3 spacer layer was studied and the experimental results were analyzed with the multilevel model. Without a spacer layer, a significant PL quenching and lifetime reduction of the near band-edge emission is found. The behavior is attributed to surface band-bending and Förster energy transfer from excitons to surface plasmons in the gold layer. Inserting a 5 nm Alq3 spacer layer reduces the PL quenching and lifetime reduction which is consistent with a reduced band-bending and Förster energy transfer. Increasing the spacer layer to 30 nm results in lifetimes which are similar to uncoated structures, showing a significantly decreased influence of the gold coating on the excitonic dynamics.

Emission dynamics of hybrid plasmonic gold/organic GaN nanorods.

PubMed

Mohammadi, F; Schmitzer, H; Kunert, G; Hommel, D; Ge, J; Duscher, G; Langbein, W; Wagner, H P

2017-12-15

We studied the emission of bare and aluminum quinoline (Alq 3 )/gold coated wurtzite GaN nanorods by temperature- and intensity-dependent time-integrated and time-resolved photoluminescence (PL). The GaN nanorods of ∼1.5 μm length and ∼250 nm diameter were grown by plasma-assisted molecular beam epitaxy. Gold/Alq 3 coated GaN nanorods were synthesized by organic molecular beam deposition. The near band-edge and donor-acceptor pair luminescence was investigated in bare GaN nanorods and compared with multilevel model calculations providing the dynamical parameters for electron-hole pairs, excitons, impurity bound excitons, donors and acceptors. Subsequently, the influence of a 10 nm gold coating without and with an Alq 3 spacer layer was studied and the experimental results were analyzed with the multilevel model. Without a spacer layer, a significant PL quenching and lifetime reduction of the near band-edge emission is found. The behavior is attributed to surface band-bending and Förster energy transfer from excitons to surface plasmons in the gold layer. Inserting a 5 nm Alq 3 spacer layer reduces the PL quenching and lifetime reduction which is consistent with a reduced band-bending and Förster energy transfer. Increasing the spacer layer to 30 nm results in lifetimes which are similar to uncoated structures, showing a significantly decreased influence of the gold coating on the excitonic dynamics.

Concentration and size dependence of peak wavelength shift on quantum dots in colloidal suspension

NASA Astrophysics Data System (ADS)

Rinehart, Benjamin S.; Cao, Caroline G. L.

2016-08-01

Quantum dots (QDs) are semiconductor nanocrystals that have significant advantages over organic fluorophores, including their extremely narrow Gaussian emission bands and broad absorption bands. Thus, QDs have a wide range of potential applications, such as in quantum computing, photovoltaic cells, biological sensing, and electronics. For these applications, aliasing provides a detrimental effect on signal identification efficiency. This can be avoided through characterization of the QD fluorescence signals. Characterization of the emissivity of CdTe QDs as a function of concentration (1 to 10 mg/ml aqueous) was conducted on 12 commercially available CdTe QDs (emission peaks 550 to 730 nm). The samples were excited by a 50-mW 405-nm laser with emission collected via a free-space CCD spectrometer. All QDs showed a redshift effect as concentration increased. On average, the CdTe QDs exhibited a maximum shift of +35.6 nm at 10 mg/ml and a minimum shift of +27.24 nm at 1 mg/ml, indicating a concentration dependence for shift magnitude. The concentration-dependent redshift function can be used to predict emission response as QD concentration is changed in a complex system.

Deep-Ultraviolet Luminescence of Rocksalt-Structured Mg x Zn1-x O (x > 0.5) Films on MgO Substrates

NASA Astrophysics Data System (ADS)

Kaneko, Kentaro; Tsumura, Keiichi; Ishii, Kyohei; Onuma, Takayoshi; Honda, Tohru; Fujita, Shizuo

2018-04-01

Rocksalt-structured Mg x Zn1-x O films with Mg composition x of 0.47, 0.57, and 0.64 were grown on (100)-oriented MgO substrates using mist chemical vapor deposition. Cathodoluminescence measurements showed deep ultraviolet (DUV) emission peaking at 4.88 eV (254 nm), 5.15 eV (241 nm), and 5.21 eV (238 nm), respectively, at 12 K. The peak energies were lower than the band gap energies by ca. 1 eV, suggesting that the deep ultraviolet (DUV) emission may be recognized as near band edge luminescence but is associated with impurities, defects, or band fluctuations. The use of carbon-free precursors in the growth is suggested to eliminate carbon impurities and to improve the optical properties of Mg x Zn1-x O.

Enhancement of white light emission from novel Ca3Y2Si3O12:Dy3+ phosphors with Ce3+ ion codoping

NASA Astrophysics Data System (ADS)

Bandi, Vengala Rao; Nien, Yung-Tang; Chen, In-Gann

2010-07-01

The luminescent properties of the Ce3+ or Dy3+ singly doped and Ce3+/Dy3+ codoped in Ca3Y2Si3O12 novel phosphors were investigated, which are prepared by a sol-gel method. Ce3+ doped phosphor showed a brighter and broader violet-blue color emission band with a maximum peak centered at 389 nm, which is attributed to the parity and spin allowed 5d-4f transition. Photoluminescence spectra reveals that the white color emission is originated from the mixtures of two characteristic emission bands of Dy3+ ion, viz., the 473 nm blue emission (F49/2-H615/2) and the 580 nm yellow emission (F49/2-H613/2). codoping of Ce3+ has enhanced the luminescence of Dy3+ quite significantly upon the UV excitation wavelength (242 nm) and the optimized codopant concentration of Ce3+ is found to be 3 mol %. The mechanism involved in the energy transfer between Ce3+ and Dy3+ has been elucidated by an energy level diagram. The structure and morphology of the prepared samples have been analyzed by x-ray diffraction and transmission electron microscope.

Atmospheric dayglow diagnostics involving the O2(b-X) Atmospheric band emission: Global Oxygen and Temperature (GOAT) mapping

NASA Astrophysics Data System (ADS)

Slanger, T. G.; Pejaković, D. A.; Kostko, O.; Matsiev, D.; Kalogerakis, K. S.

2017-03-01

The terrestrial dayglow displays prominent emission features from the 0-0 and 1-1 bands of the O2 Atmospheric band system in the 760-780 nm region. We present an analysis of observations in this wavelength region recorded by the Space Shuttle during the Arizona Airglow Experiment. A major conclusion is that the dominant product of O(1D) + O2 energy transfer is O2(b, v = 1), a result that corroborates our previous laboratory studies. Moreover, critical to the interpretation of dayglow is the possible interference by N2 and N2+ bands in the 760-780 nm region, where the single-most important component is the N2 1PG 3-1 band that overlaps with the O2(b-X) 0-0 band. When present, this background must be accounted for to reveal the O2(b-X) 0-0 and 1-1 bands for altitudes at which the O2 and N2/N2+ emissions coincide. Finally, we exploit the very different collisional behavior of the two lowest O2(b) vibrational levels to outline a remote sensing technique that provides information on Atmospheric composition and temperature from space-based observations of the 0-0 and 1-1 O2 atmospheric bands.

Direct evidence of recombination between electrons in InGaN quantum discs and holes in p-type GaN.

PubMed

Sun, Xiaoxiao; Wang, Xinqiang; Wang, Ping; Wang, Tao; Sheng, Bowen; Zheng, Xiantong; Li, Mo; Zhang, Jian; Yang, Xuelin; Xu, Fujun; Ge, Weikun; Shen, Bo

2017-11-27

Intense emission from an InGaN quantum disc (QDisc) embedded in a GaN nanowire p-n junction is directly resolved by performing cathodoluminescence spectroscopy. The luminescence observed from the p-type GaN region is exclusively dominated by the emission at 380 nm, which has been usually reported as the emission from Mg induced impurity bands. Here, we confirm that the robust emission from 380 nm is actually not due to the Mg induced impurity bands, but rather due to being the recombination between electrons in the QDisc and holes in the p-type GaN. This identification helps to get a better understanding of the confused luminescence from nanowires with thin QDiscs embedded for fabricating electrically driven single photon emitters.

Near Infrared Multispectral Mapping of Venus Supports the Hypothesis that Tessera Plateau Material was Formed in the Presence of Surface Water

NASA Astrophysics Data System (ADS)

Mueller, N. T.; Tsang, C.; Nunes, D. C.; Helbert, J.; Dyar, M. D.; Smrekar, S. E.

2017-12-01

The VIRTIS instrument on Venus Express observed surface thermal emission from the surface. Studies of 1020nm data showed that tessera plateaus, intensely tectonically deformed highlands that predate most other terrains, have significantly lower thermal emission than other highlands. Lower thermal emission could be due either to lower surface emissivity, supporting the hypothesis that tessera are analogous to continental crust on Earth, or to a bias of Magellan altimetry, which does not fully resolve the topographic relief of tessera terrain. To eliminate this ambiguity, we additionally investigate the spectral windows at 1100 and 1180nm. Data are reduced to surface emissivity using an atmospheric radiative transfer model to account for atmospheric scattering and absorption/emission. Magellan altimetry was used to model atmospheric column height and surface temperature. The model uses a binary (collision-induced) absorption coefficient for each window. It fits absolute radiance and gradient with surface elevation reasonably well, although there are indications that the assumed adiabatic temperature lapse rate is not appropriate globally. The 1100nm band has a relatively low signal-to-noise ratio at the latitudes of the tessera plateaus, but Alpha Regio is visible in both the 1020 and the 1180nm band. The difference in emissivity between Alpha and the adjacent corona Eve, which has a similar elevation as Alpha, is 3.6% at 1020nm, but only 2% at 1180nm. The altimetry bias equivalent to the 1020nm deviation is 230 m, while the equivalent is only 70m at 1180nm. An altimetry bias therefore cannot fully explain the observations, and there must be a real difference in emissivity. The observations are consistent with the hypothesis that Alpha Regio has a more felsic composition. The emissivity spectra of granites at Venus temperatures are lower than those of basalt at 1020nm, but the difference decreases or vanishes towards the 1180nm window. The most plausible explanation for continent-sized felsic plateaus would be a formation analogous to Earth's continents, i.e. differentiation of basaltic crust in the presence of water.

Emission cross sections of excited fragments produced by electron impact on BCl3

NASA Astrophysics Data System (ADS)

Tokue, Ikuo; Kudo, Mikiko; Kusakabe, Masanobu; Honda, Tomohisa; Ito, Yoshio

1992-06-01

Emission spectra in the 190-600 nm region produced by electron impact on BCl3 have been studied up to 110 eV. Emission cross sections of the B(2s2p2 2D-2p 2P0) and B(3s 2S-2p 2P0) lines and the BCl(A 1Π-X 1Σ+) band are evaluated to be 4.9±1.0, 4.5±0.7, and (1.9±0.3)×10-18 cm2, respectively, at 100 eV. Formation cross sections of these species have been determined from the analysis of their fluorescence decaying curves. Two continuous emissions observed in the 230-380 and 400-580 nm regions are attributed to the BCl*2 band. The fluorescence lifetime of BCl*2 in the 300-342 nm region is obtained to be 1.65±0.2 μs, which is nearly independent of the wavelength.

The emission characteristics of uranium hexafluoride at high temperatures

NASA Technical Reports Server (NTRS)

Krascella, N. L.

1976-01-01

Relative emission measurements were made for UF6/Argon mixtures heated in a plasma torch over a range of temperatures from 800 to about 3600 K over a wavelength range from 80 to 600 nm. Total pressures were varied from 1 to approximately 1.7 atm. Similarly absorption measurements were carried out in the visible region from 420 to 580 nm over a temperature range from about 1000 to 1800 K. Total pressure for these measurements was 1.0 atm. The emission results exhibited relatively no emission at wavelengths below 250 nm over the range of temperatures investigated. At temperatures in excess of 1800 K an additional emission band centered at 310 nm appears and becomes more well defined at higher temperatures. Essentially no pressure effect was observed with respect to emission at pressures up to 1.7 atm.

Low-temperature growth and photoluminescence property of ZnS nanoribbons.

PubMed

Zhang, Zengxing; Wang, Jianxiong; Yuan, Huajun; Gao, Yan; Liu, Dongfang; Song, Li; Xiang, Yanjuan; Zhao, Xiaowei; Liu, Lifeng; Luo, Shudong; Dou, Xinyuan; Mou, Shicheng; Zhou, Weiya; Xie, Sishen

2005-10-06

At a low temperature of 450 degrees C, ZnS nanoribbons have been synthesized on Si and KCl substrates by a simple chemical vapor deposition (CVD) method with a two-temperature-zone furnace. Zinc and sulfur powders are used as sources in the different temperature zones. X-ray diffraction (XRD), selected area electron diffraction (SEAD), and transmission electron microscopy (TEM) analysis show that the ZnS nanoribbons are the wurtzite structure, and there are two types-single-crystal and bicrystal nanoribbons. Photoluminescence (PL) spectrum shows that the spectrum mainly includes two parts: a purple emission band centering at about 390 nm and a blue emission band centering at about 445 nm with a weak green shoulder around 510 nm.

UV-Vis spectroscopy and solvatochromism of the tyrosine kinase inhibitor AG-1478

NASA Astrophysics Data System (ADS)

Khattab, Muhammad; Wang, Feng; Clayton, Andrew H. A.

2016-07-01

The effect of twenty-one solvents on the UV-Vis spectrum of the tyrosine kinase inhibitor AG-1478 was investigated. The absorption spectrum in the range 300-360 nm consisted of two partially overlapping bands at approximately 340 nm and 330 nm. The higher energy absorption band was more sensitive to solvent and exhibited a peak position that varied from 327 nm to 336 nm, while the lower energy absorption band demonstrated a change in peak position from 340 nm to 346 nm in non-chlorinated solvents. The fluorescence spectrum of AG-1478 was particularly sensitive to solvent. The wavelength of peak intensity varied from 409 nm to 495 nm with the corresponding Stokes shift in the range of 64 nm to 155 nm (4536 cm- 1 to 9210 cm- 1). We used a number of methods to assess the relationship between spectroscopic properties and solvent properties. The detailed analysis revealed that for aprotic solvents, the peak position of the emission spectrum in wavenumber scale correlated with the polarity (dielectric constant or ET(30)) of the solvent. In protic solvents, a better correlation was observed between the hydrogen bonding power of the solvent and the position of the emission spectrum. Moreover, the fluorescence quantum yields were larger in aprotic solvents as compared to protic solvents. This analysis underscores the importance of polarity and hydrogen-bonding environment on the spectroscopic properties of AG-1478. These studies will assume relevance in understanding the interaction of AG-1478 in vitro and in vivo.

Scintillation properties of the silver doped lithium iodide single crystals at room and low temperature

NASA Astrophysics Data System (ADS)

Khan, Sajid; Kim, H. J.; Lee, M. H.

2016-06-01

This study presents luminescence and scintillation properties of Silver doped LiI crystals. Single crystals of LiI: x% Ag (x=0.02, 0.05, 0.1 and 0.5) were grown by using the Bridgman technique. X-ray induced luminescence spectra show emission bands spanning from 275 nm to 675 nm, dominated by Ag+ band having a peak at 300 nm. Under UV-luminescence, a similar emission band was observed with the peak excitation wavelength of 265 nm. Energy resolution, light yield and decay time profiles of the samples were measured under a 137Cs γ-ray irradiation. The LiI(0.1%Ag) showed the highest light yield and the best energy resolution among the samples. The light yield of LiI(0.1%Ag) is higher than commercially available LiI(Eu) crystal (15,000±1500 ph/MeV). The LiI(Ag) samples exhibit three exponential decay time components except the LiI(0.02%Ag), where the fitting found two decay time components. Temperature dependences of emission spectra, light yield and decay time were studied from 300 K to 10 K. The LiI(0.1%Ag) crystal showed an increase in the light yield and a shortening of decay time with a decrease in temperature..

Photoluminescence emission spectra of Makrofol® DE 1-1 upon irradiation with ultraviolet radiation

NASA Astrophysics Data System (ADS)

El Ghazaly, M.; Aydarous, Abdulkadir

Photoluminescence (PL) emission spectra of Makrofol® DE 1-1 (bisphenol-A based polycarbonate) upon irradiation with ultraviolet radiation of different wavelengths were investigated. The absorption-and attenuation coefficient measurements revealed that the Makrofol® DE 1-1 is characterized by high absorbance in the energy range 6.53-4.43 eV but for a lower energy than 4.43 eV, it is approximately transparent. Makrofol® DE 1-1 samples were irradiated with ultraviolet radiation of wavelength in the range from 250 (4.28 eV) to 400 (3.10 eV) nm in step of 10 nm and the corresponding photoluminescence (PL) emission spectra were measured with a spectrofluorometer. It is found that the integrated counts and the peak height of the photoluminescence emission (PL) bands are strongly correlated with the ultraviolet radiation wavelength. They are increased at the ultraviolet radiation wavelength 280 nm and have maximum at 290 nm, thereafter they decrease and diminish at 360 nm of ultraviolet wavelength. The position of the PL emission band peak was red shifted starting from 300 nm, which increased with the increase the ultraviolet radiation wavelength. The PL bandwidth increases linearly with the increase of the ultraviolet radiation wavelength. When Makrofol® DE 1-1 is irradiated with ultraviolet radiation of short wavelength (UVC), the photoluminescence emission spectra peaks also occur in the UVC but of a relatively longer wavelength. The current new findings should be considered carefully when using Makrofol® DE 1-1 in medical applications related to ultraviolet radiation.

Color Tunable and Upconversion Luminescence in Yb-Tm Co-Doped Yttrium Phosphate Inverse Opal Photonic Crystals.

PubMed

Wang, Siqin; Qiu, Jianbei; Wang, Qi; Zhou, Dacheng; Yang, Zhengwen

2016-04-01

For this paper, YPO4: Tm, Yb inverse opals with the photonic band gaps at 475 nm and 655 nm were prepared by polystyrene colloidal crystal templates. We investigated the influence of photonic band gaps on the Tm-Yb upconversion emission which was in the YPO4: Tm Yb inverse opal photonic crystals. Comparing with the reference sample, significant suppression of both the blue and red upconversion luminescence of Tm3+ ions were observed in the inverse opals. The color purity of the blue emission was improved in the inverse opal by the suppression of red upconversion emission. Additionally, mechanism of upconversion emission in the inverse opal was discussed. We believe that the present work will be valuable for not only the foundational study of upconversion emission modification but also the development of new optical devices in upconversion lighting and display.

Multimodal emissions from Tb{sup 3+}/Yb{sup 3+} co-doped lithium borate glass: Upconversion, downshifting and quantum cutting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bahadur, A.; Yadav, R.S.; Yadav, R.V.

This paper reports the optical properties of Tb{sup 3+}/Yb{sup 3+} co-doped lithium borate (LB) glass prepared by melt quench method. The absorption spectrum of the Yb{sup 3+} doped LB glass contains intense NIR band centered at 976 nm due to {sup 2}F{sub 7/2}→{sup 2}F{sub 5/2} transition. The emission spectra of the prepared glasses have been monitored on excitation with 266, 355 and 976 nm. The Yb{sup 3+} doped glass emits a broad NIR band centered at 976 nm whereas the Tb{sup 3+} doped glass gives off visible bands on excitations with 266 and 355 nm. When the Tb{sup 3+} andmore » Yb{sup 3+} ions are co-doped together, the emission intensity in the visible region decreases whereas it increases in the NIR region significantly. The increase in the emission intensity in the NIR region is due to efficient cooperative energy transfer (CET) from Tb{sup 3+} to Yb{sup 3+} ions. The quantum cutting efficiency for Tb{sup 3+}/Yb{sup 3+} co-doped glass has been calculated and compared for 266 and 355 nm excitations. The quantum cutting efficiency is larger for 355 nm excitation (137%). The Tb{sup 3+}/Yb{sup 3+} co-doped LB glass also emits upconverted visible bands on excitation with 976 nm. The mechanisms involved in the energy transfer have been discussed using schematic energy level diagram. The Tb{sup 3+}/Yb{sup 3+} co-doped LB glass may be used in the optical devices and in solar cell for solar spectral conversion and behaves as a multi-modal photo-luminescent material. - Graphical abstract: The Tb{sup 3+}/Yb{sup 3+} co-doped lithium borate (LB) glass prepared by melt quench method emits upconverted visible emissions through upconversion CET from Yb{sup 3+} to Tb{sup 3+} ions and quantum cutting emissions through downconversion CET from Tb{sup 3+} to Yb{sup 3+} ions. Therefore, the Tb{sup 3+}/Yb{sup 3+} co-doped LB glass may find applications in optical devices and solar cell and behaves as a multi-modal photo-luminescent material. - Highlights: • The Tb{sup 3+}/Yb{sup 3+} co-doped lithium borate (LB) glass prepared by melt quench method. • The Tb{sup 3+}/Yb{sup 3+} co-doped glass gives QC emissions upon 266 and 355 nm excitations. • The Tb{sup 3+}/Yb{sup 3+} co-doped glass also emits intense green color on excitation with 976 nm. • The quantum cutting efficiency is larger for 355 nm excitation (137%). • The Tb{sup 3+}/Yb{sup 3+} co-doped glass may be used in solar cell and display devices.« less

Laser action in chromium-activated forsterite for near infrared excitation

NASA Technical Reports Server (NTRS)

Petricevic, V.; Gayen, S. K.; Alfano, R. R.

1988-01-01

This paper reports on laser action in chromium-doped forsterite (Cr:Mg2SiO4) for 1064-nm excitation of the crystal's double-hump absorption band spanning the 850-1200-nm wavelength range. The cavity arrangement used for obtaining laser action in Cr:Mg2SiO2 was similar to that described by Petricevic et al. (1988). The fundamental and second harmonic emissions from a Q-switched Nd:YAG laser operating at a 10-Hz repetition rate were used for excitation of the NIR and visible bands, respectively. Pulsed laser action was readily observed for both the 1064-nm and 532-nm pumping at or above the respective thresholds. The laser parameters of the 532-nm and 1064-nm excitations were similar, indicating that the IR band is responsible for laser action for both excitations.

Investigation and characterization of ZnO single crystal microtubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Al-Naser, Qusay A.H.; Zhou, Jian, E-mail: jianzhou@whut.edu.cn; Liu, Guizhen

2016-04-15

Morphological, structural, and optical characterization of microwave synthesized ZnO single crystal microtubes were investigated in this work. The structure and morphology of the ZnO microtubes are characterized using X-ray diffraction (XRD), single crystal diffraction (SCD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The results reveal that the as-synthesized ZnO microtube has a highly regular hexagonal cross section and smooth surfaces with an average length of 650–700 μm, an average outer diameter of 50 μm and wall thickness of 1–3 μm, possessing a single crystal wurtzite hexagonal structure. Optical properties of ZnOmore » single crystal microtubes were investigated by photoluminescence (PL) and ultraviolet-visible (UV-vis) absorption techniques. Room-temperature PL spectrum of the microtube reveal a strong UV emission peak at around 375.89 nm and broad and a weak visible emission with a main peak identified at 577 nm, which was assigned to the nearest band-edge emission and the deep-level emission, respectively. The band gap energy of ZnO microtube was found to be 3.27 eV. - Highlights: • ZnO microtube length of 650–700 μm, diameter of 50 μm, wall thickness of 1–3 μm • ZnO microtube possesses a single crystal wurtzite hexagonal structure. • The crystal system is hexahedral oriented along a-axis with indices of (100). • A strong and sharp UV emission at 375.89 nm (3.29 eV) • One prominent absorption band around 378.88 nm (3.27 eV)« less

The nature of unusual luminescence in natural calcite, CaCO3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gaft, M.; Nagli, L.; Panczer, G.

2008-11-01

The unusual luminescence of particular varieties of natural pink calcite (CaCO{sub 3}) samples was studied by laser-induced time-resolved luminescence spectroscopy at different temperatures. The luminescence is characterized by intense blue emission under short-wave UV lamp excitation with an extremely long decay time, accompanied by pink-orange luminescence under long wave UV excitation. Our investigation included optical absorption, natural thermostimulated luminescence (NTL) and Laser-Induced Breakdown Spectroscopy (LIBS) studies. Two luminescence centers were detected: a narrow violet band, with {lambda}{sub max} = 412 nm, {Delta} = 45 nm, two decay components of {tau}{sub 1} = 5 ns and {tau}{sub 2} = 7.2 ms,more » accompanied by very long afterglow, and an orange emission band with {lambda}{sub max} = 595 nm, {Delta} = 90 nm and {tau} = 5 ns. Both luminescence centers are thermally unstable with the blue emission disappearing after heating at 500 C, and the orange emission disappearing after heating at different temperatures starting from 230 C, although sometimes it is stable up to 500 C in different samples. Both centers have spectral-kinetic properties very unusual for mineral luminescence, which in combination with extremely low impurity concentrations, prevent their identification with specific impurity related emission. The most likely explanation of these observations may be the presence of radiation-induced luminescence centers. The long violet afterglow is evidently connected with trapped charge carrier liberation, with their subsequent migration through the valence band and ultimate recombination with a radiation-induced center responsible for the unusual violet luminescence.« less

Modelling of N2 Vegard-Kaplan and LBH emissions in the planetary atmospheres

NASA Astrophysics Data System (ADS)

Jain, Sonal Kumar; Bhardwaj, Anil

The N_{2} triplet band emissions are common features in the dayglow of Earth. Recent discoveries of N _{2} Vegard-Kaplan (VK) band emissions on Mars by SPICAM/Mars-Express and N _{2} VK and LBH band emissions on Titan by Cassini's UVIS have led planetary scientists to look for the processes governing the N _{2} triplet and singlet band emissions in different planetary atmospheres. We have developed a model to calculate N _{2} triplet and Lyman-Birge-Hopefield (LBH) band emissions in the dayglow of Venus, Mars, Titan, and Pluto. The Steady state photoelectron fluxes and volume excitation rates have been calculated using the Analytical Yield Spectra (AYS) technique. Since interstate cascading is important for triplet and singlet states of N _{2}, the population of any given level of N _{2} triplet and singlet states is calculated under statistical equilibrium considering direct excitation, cascading, and quenching effects. Relative population of all vibrational levels of each triplet and singlet states is calculated in the model. Line of sight intensities and height-integrated overhead intensities have been calculated for VK ( A(3Sigma_u^+) - X(1Sigma^+_g) ), first positive ( B(3Pi_g) - A(3Sigma^+_u) ), second positive ( C(3Pi_u) - B(3Pi_g) ), Wu-Benesch (W(3Delta_u) - B(3Pi_g) ), B '-> B, E -> B, E-> C, E-> A, and LBH (a(1Pi_g) - X(1Sigma^+_g) ) bands of N _{2}. The N _{2} VK band span wavelength range from far ultraviolet to visible, and some transitions even originate at wavelength more than 1000 nm. Our calculations show that the overhead intensity of VK bands in the wavelength range 400-800, 300-190, 200-300, and 150-200 nm are 22%, 39%, 35%, and 4% of the total VK band emission. On Titan, the calculated intensities of N _{2} VK and LBH bands in 150-190 and 120-190 nm wavelength range, respectively, are in good agreement with the Cassini-UVIS observation. On Mars, calculated intensities of N _{2} VK bands are in agreement with the SPICAM observed limb profile of N _{2} VK (0-6) when the N _{2} density in Martian upper atmosphere is reduced by a factor of 3. Calculations are also carried out on Venus using this model. Calculated intensities on Venus are about factor of 10 higher than that on Mars. On Pluto, the predicted limb intensities of N _{2} VK and LBH bands for New Horizons flyby condition peak at radial distance of 2000 km with a value of about 5 and 9.5 R, respectively for solar zenith angle 60(°) . The results will presented and discussed.

Application of Cathodoluminescence to The Study of Feldspars: Imaging and Spectrometry

NASA Astrophysics Data System (ADS)

Fonseca, Rute; Couto, Helena

2017-12-01

Cathodoluminescence (CL) studies were carried out on polished thin sections of different feldspar samples (from migmatites, granites, aplite-pegmatites and granitic aggregates) using a hot cathode CL equipment HC3-LM coupled to an optical microscope and to a spectrometer (SpectraPro 2300i and a CCD Pixis 400B detector and the software Winspec32) from the Faculty of Sciences of University of Porto. The system was operated at 14kV and a filament current of 0.18 mA. The samples were coated with a thin gold film using a Cressington 108 Auto device. Luminescence images were acquired during the CL analysis with an adapted digital video-camera (KAPPA PS 40C-285 (DX) with dual stage Peltier cooling) and an acquisition time between 351ms and 3,52s. The CL study, including imaging and spectrometry, proved to be an important tool to complement the feldspar petrography as it contributes to the identification of features not observed under optical microscope. The application of the Cathodoluminescence to feldspar allows distinguishing between potassic feldspar and plagioclase, differentiating generations of feldspar and displaying internal zoning and growth areas, among other. The spectrometry complements the CL imaging. It allows obtaining a qualitative level of emission intensity, which permits the interpretation of the nature of this luminescence in each feldspar. Bands shown in the spectra are related to the existing activator elements. In the present study, it was found an association of each feldspar to different spectra and respective colour. The plagioclases exhibit yellow or green luminescence. The activator element is Mn2+, showing a broad emission band between 550 - 570 nm specially detected on this type of feldspars, due to the replacement of K+ for Mn2+. The potassium feldspars have more or less intense blue colour associated with various activators elements: the activator element is Cu2+ showing a broad emission band between 420±5 nm. This emission band can be detected either in potassium feldspar or in plagioclases, but when associated with the blue colour, it indicates that it is a potassium feldspar. Spectra with a wavelength of 460±10 nm, associated to the element activator/synthesizer Ti3+, which is initially deposited as Ti4+, replacing Al, as temperature rise. The emission band with a wavelength of 860 nm correspond to the activator element Pb+, and occurs specially in potassium feldspar like adularia and orthoclase. The activator element Al - O - Al, show a broad emission band between 450-480 nm. This emission in CL is caused by the replacement of Al3+ and Si4+ in feldspars.

Synthesis and luminescence properties of Ca3Ga2Si3O12:RE3+ (RE = Eu/Tb) powder phosphors.

PubMed

Reddy, M Bhushana; Sailaja, S; Raju, K Vemasevana; Raju, C Nageswara; Giridhar, P; Rao, B Vengala; Reddy, B Sudhakar

2011-01-01

Rare earth ions (Eu(3+) or Tb(3+) )-activated Ca(3) Ga(2) Si(3) O(12) (CaGaSi) phosphors were synthesized by using a sol-gel method. Photoluminescence spectra of Eu(3+):CaGaSi phosphors exhibited five emission bands at 578, 592, 612, 652 and 701 nm, which were assigned to the transitions ((5)D(0) → (7)F(0), (7)F(1,)(7)F(2), (7)F(3) and (7)F(4)), respectively, with an excitation wavelength of λ(exci) = 392 nm. Among these, the transition (5) D(0) → (7) F(2) (612 nm) displayed bright red emission. In the case of Tb(3+):CaGaSi phosphors, four emission bands were observed at 488 ((5)D(4) → (7)F(6)), 543 ((5)D(4) → (7)F(5)), 584 ((5)D(4) → (7)F(4)) and 614 nm ((5)D(4) → (7) F(3) ) from the measurement of PL spectra with λ(exci) = 376 nm. Among these, the transition (5)D(4) → (7) F(5) at 543 nm displayed bright green emission. The structure and morphology of the phosphors were studied from the measurements of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDAX) results. Copyright © 2011 John Wiley & Sons, Ltd.

Surface defect assisted broad spectra emission from CdSe quantum dots for white LED application

NASA Astrophysics Data System (ADS)

Samuel, Boni; Mathew, S.; Anand, V. R.; Correya, Adrine Antony; Nampoori, V. P. N.; Mujeeb, A.

2018-02-01

This paper reports, broadband photoluminescence from CdSe quantum dots (QDs) under the excitation of 403 nm using fluorimeter and 403 nm CW laser excitation. The broad spectrum obtained from the colloidal quantum dots was ranges from 450 nm to 800 nm. The broadness of the spectra was attributed to the merging of band edge and defect driven emissions from the QDs. Six different sizes of particles were prepared via kinetic growth method by using CdO and elemental Se as sources of Cd and Se respectively. The particle sizes were measured from TEM images. The size dependent effect on broad emission was also studied and the defect state emission was found to be predominant in very small QDs. The defect driven emission was also observed to be redshifted, similar to the band edge emission, due to quantum confinement effect. The emission corresponding to different laser power was also studied and a linear relation was obtained. In order to study the colour characteristics of the emission, CIE chromaticity coordinate, CRI and CCT of the prepared samples were measured. It is observed that, these values were tunable by the addition of suitable intensity of blue light from the excitation source to yield white light of various colour temperatures. The broad photoluminescence spectrum of the QDs, were compared with that of a commercially available white LED. It was found that the prepared QDs are good alternatives for the phosphor in phosphor converted white LEDs, to provide good spectral tunability.

Frequency upconversion in Er3+ doped tungsten tellurite glass containing Ag nanoparticles

NASA Astrophysics Data System (ADS)

Mahajan, S. K.; Parashar, J.

2018-05-01

The frequency upconversion emission in Er3+ doped TeO2-WO3-Li2O containing Ag nanoparticle (TWLEOAG) glasses at 980nm excitation is reported. The absorption spectra reveal not only the peaks due to Er3+ ions, but also the surface plasmon resonance band of silver NPs located around 525nm and 650 nm. The spherical AgNPs with average size ˜38 nm in the glassy matrix is evidenced from the TEM measurement. Under 980nm laser excitation upconversion emission spectra show two major emission at 550nm and 638nm originating from 4S3/2 and 4F9/2 energy levels of the Er3+ ions, respectively was observed. Upconversion emission enhancement factor 7 fold has been measured for sample heat treated during 40h. However for 18h heat treated TWLEOAG sample under 980 nm flash lamp excitation produced Intense green compare to red emission. Since the 980nm frequency is far from the AgNPs surface plasmon resonance frequency, visible emission ehancement is attributed to local field increase in proximity of the Ag NPs and not energy tranfer from NPs to emitters. Possible energy transfer upconversion mechanism has been also discussed.

Cathodoluminescent UV-radiation sources

NASA Astrophysics Data System (ADS)

Vereschagina, N. Y.; Danilkin, M. I.; Kazaryan, M. A.; Ozol, D. I.; Sheshin, E. P.; Spassky, D. A.

2018-04-01

Mercury-free UV-radiation sources are described. An electron beam similar to cathode-ray tubes (CRT) excites a luminescent material in a vacuum bulb. A high density of excitation requires the cathode and the luminescent material to be resistant for that and provide the extended lifetime of the UV-radiation source. Carbon fibre and nano-carbon based field-emission cathodes produce long lasting stable emission with a high current density (up to 0.3-0.5 A/cm2 ). Li2B4O7:Cu and Li2B4O7:Ag luminescent ceramics survive under high radiation doses and provide UV luminescence bands peaked at 360-370 nm and 270 nm, respectively. The luminescence band at 360-370 nm has a good overlap with the fundamental absorption edge of TiO2, which is known as a photo-catalyst in air and water cleaning systems. The luminescence band at 270 nm overlaps with DNA absorption and provides a direct disinfection effect. We suggest the structure of complex luminescence centres and energy transfer mechanisms. The electron structure of lithium tetraborate and the contribution of impurities are also discussed in paper.

Post-polymerization C-H Borylation of Donor-Acceptor Materials Gives Highly Efficient Solid State Near-Infrared Emitters for Near-IR-OLEDs and Effective Biological Imaging.

PubMed

Crossley, Daniel L; Urbano, Laura; Neumann, Robert; Bourke, Struan; Jones, Jennifer; Dailey, Lea Ann; Green, Mark; Humphries, Martin J; King, Simon M; Turner, Michael L; Ingleson, Michael J

2017-08-30

Post-polymerization modification of the donor-acceptor polymer, poly(9,9-dioctylfluorene-alt-benzothiadiazole), PF8-BT, by electrophilic C-H borylation is a simple method to introduce controllable quantities of near-infrared (near-IR) emitting chromophore units into the backbone of a conjugated polymer. The highly stable borylated unit possesses a significantly lower LUMO energy than the pristine polymer resulting in a reduction in the band gap of the polymer by up to 0.63 eV and a red shift in emission of more than 150 nm. Extensively borylated polymers absorb strongly in the deep red/near-IR and are highly emissive in the near-IR region of the spectrum in solution and solid state. Photoluminescence quantum yield (PLQY) values are extremely high in the solid state for materials with emission maxima ≥ 700 nm with PLQY values of 44% at 700 nm and 11% at 757 nm for PF8-BT with different borylation levels. This high brightness enables efficient solution processed near-IR emitting OLEDs to be fabricated and highly emissive borylated polymer loaded conjugated polymer nanoparticles (CPNPs) to be prepared. The latter are bright, photostable, low toxicity bioimaging agents that in phantom mouse studies show higher signal to background ratios for emission at 820 nm than the ubiquitous near-IR emissive bioimaging agent indocyanine green. This methodology represents a general approach for the post-polymerization functionalization of donor-acceptor polymers to reduce the band gap as confirmed by the C-H borylation of poly((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2c,2cc-diyl) (PF8TBT) resulting in a red shift in emission of >150 nm, thereby shifting the emission maximum to 810 nm.

Detection of boron nitride radicals by emission spectroscopy in a laser-induced plasma

NASA Astrophysics Data System (ADS)

Dutouquet, C.; Acquaviva, S.; Hermann, J.

2001-06-01

Several vibrational bands of boron nitride radicals have been observed in a plasma produced by pulsed-laser ablation of a boron nitride target in low-pressure nitrogen or argon atmospheres. Using time- and space-resolved emission spectroscopic measurements with a high dynamic range, the most abundant isotopic species B 11N have been detected. The emission bands in the spectral range from 340 to 380 nm belong to the Δυ =-1, 0, +1 sequences of the triplet system (transition A 3Π-X 3Π). For positive identification, the molecular emission bands have been compared with synthetic spectra obtained by computer simulations. Furthermore, B 10N emission bands have been reproduced by computer simulation using molecular constants which have been deduced from the B 11N constants. Nevertheless, the presence of the lower abundant isotopic radical B 10N was not proved due the noise level which masked the low emission intensity of the B 10N band heads.

Optical and electrical properties of copper-incorporated ZnS films applicable as solar cell absorbers

NASA Astrophysics Data System (ADS)

Mehrabian, M.; Esteki, Z.; Shokrvash, H.; Kavei, G.

2016-10-01

Un-doped and Cu-doped ZnS (ZnS:Cu) thin films were synthesized by Successive Ion Layer Absorption and Reaction (SILAR) method. The UV-visible absorption studies have been used to calculate the band gap values of the fabricated ZnS:Cu thin films. It was observed that by increasing the concentration of Cu2+ ions, the Fermi level moves toward the edge of the valence band of ZnS. Photoluminescence spectra of un-doped and Cu-doped ZnS thin films was recorded under 355 nm. The emission spectrum of samples has a blue emission band at 436 nm. The peak positions of the luminescence showed a red shift as the Cu2+ ion concentration was increased, which indicates that the acceptor level (of Cu2+) is getting close to the valence band of ZnS.

Exciplex electroluminescence and photoluminescence spectra of the new organic materials based on zinc complexes of sulphanylamino-substituted ligands.

PubMed

Kaplunov, Mikhail G; Krasnikova, Svetlana S; Nikitenko, Sergey L; Sermakasheva, Natalia L; Yakushchenko, Igor K

2012-04-03

We have investigated the electroluminescence spectra of the electroluminescent devices based on the new zinc complexes of amino-substituted benzothiazoles and quinolines containing the C-N-M-N chains in their chelate cycles. The spectra exhibit strong exciplex bands in the green to yellow region 540 to 590 nm due to interaction of the excited states of zinc complexes and triaryl molecules of the hole-transporting layer. For some devices, the intrinsic luminescence band of 460 nm in the blue region is also observed along with the exciplex band giving rise to an almost white color of the device emission. The exciplex band can be eliminated if the material of the hole-transporting layer is not a triarylamine derivative. We have also found the exciplex emission in the photoluminescence spectra of the films containing blends of zinc complex and triphenylamine material.

Exciplex electroluminescence and photoluminescence spectra of the new organic materials based on zinc complexes of sulphanylamino-substituted ligands

PubMed Central

2012-01-01

We have investigated the electroluminescence spectra of the electroluminescent devices based on the new zinc complexes of amino-substituted benzothiazoles and quinolines containing the C-N-M-N chains in their chelate cycles. The spectra exhibit strong exciplex bands in the green to yellow region 540 to 590 nm due to interaction of the excited states of zinc complexes and triaryl molecules of the hole-transporting layer. For some devices, the intrinsic luminescence band of 460 nm in the blue region is also observed along with the exciplex band giving rise to an almost white color of the device emission. The exciplex band can be eliminated if the material of the hole-transporting layer is not a triarylamine derivative. We have also found the exciplex emission in the photoluminescence spectra of the films containing blends of zinc complex and triphenylamine material. PMID:22471942

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, Mu-Tsun, E-mail: mttsai@ms23.hinet.net; Chang, Yee-Shin; Chou, You-Hsin

A blue-emitting phosphor of titanium-doped zinc spinel (ZnAl{sub 2}O{sub 4}:Ti; Ti=0–6.0 mol% in relation to Al) nanopowders was prepared by a simple sol–gel method. On annealing at 1000 °C, single-phase ZnAl{sub 2}O{sub 4}:Ti powders had primary particles of 25–30 nm in size and most Ti ions in the form of Ti{sup 4+}. Under UV excitation at 280 nm, a strong and broad blue emission centered at 435 nm was observed. The sources of the excitation and emission were assigned to the charge-transfer excitation and recombination between O{sup 2–}–Ti{sup 4+} and Ti{sup 3+}–O{sup –} ion pairs. Optimum brightness occurred at amore » doping of 2.0 mol% Ti. The decay lifetime of ZnAl{sub 2}O{sub 4}:2%Ti was calculated to be 3.0 ms for the blue emission with CIE coordinates of x=0.168 and y=0.153. The results suggest that ZnAl{sub 2}O{sub 4}:Ti is a promising candidate for application as a blue component phosphor for UV-converting white light-emitting diodes. - Graphical abstract: The absorption band around 270 nm is associated with the charge-transfer processes between octahedral Ti{sup 4+} and O{sup 2−} ions. The excitation band around 280 nm corresponds to the charge-transfer excitations from O{sup 2–}(2p){sup 6} electrons to Ti{sup 4+} (3d{sup 0}). Under 280 nm excitation, the PL spectrum shows a strong blue emission with a peak at around 435 nm. - Highlights: • Single-phase ZnAl{sub 2}O{sub 4}:Ti nanocrystals have been synthesized by a sol–gel process. • Under UV excitation at 280 nm, the blue emission centered at 435 nm is observed. • Blue emission is attributed to a charge-transfer transition involving the Ti{sup 4+} ions.« less

Photoluminescent properties of Eu-doped ZnLiNbO4

NASA Astrophysics Data System (ADS)

Huang, Meng-Hsi; Lin, Ming-Hong; Fang, Te-Hua; Chang, Chia-Wei

2018-04-01

In this study, fluorescent Eu3+-doped ZnLiNbO4 materials were prepared via a vibrating milled solid-state reaction method. The objective was to develop new fluorescent oxide materials and study their fluorescent properties. The ZnLiNbO4 tetragonal spinel structure was formed with a single phase at a sintering temperature of 800 °C and with a regular shape at 1000 °C. The main exciton band was at 466 nm (7F0 → 5D2), and the main emission band was at 615 nm (5D0 → 7F2), which was an orange–red light band. The emission intensity was approximately 5% when the doping concentration reached 7%. The decay time was 2.96 ms.

Modification of fluorescence and optical properties of Rhodamine B dye doped PVA/Chitosan polymer blend films

NASA Astrophysics Data System (ADS)

Padmakumari, R.; Ravindrachary, V.; Mahantesha, B. K.; Sagar, Rohan N.; Sahanakumari, R.; Bhajantri, R. F.

2018-05-01

Pure and Rhodamine B doped Poly (vinyl alcohol)/Chitosan composite films are prepared using solution casting method. Fourier transforms infrared spectra (FTIR), Ultraviolet-Visible (UV-Vis), fluorescence studies were used to characterize the prepared polymer films. The FT-IR results show that the appearance of new peaks along with shift in peak positions indicates the interaction of Rhodamine B with PVA-CS blend. Optical absorption edge, band gap and activation energy were determined from UV-Visible studies. The optical absorption edge increases, band gap decreases and activation energy increases with dopant concentration respectively. The corresponding emission spectra were studied using fluorescence spectroscopy. From the fluorescence study the quenching phenomena are observed in emission wavelength range of 607nm-613nm upon excitation with absorption maxima 443nm.

Resonant enhancement of Raman scattering in metamaterials with hybrid electromagnetic and plasmonic resonances

NASA Astrophysics Data System (ADS)

Guddala, Sriram; Narayana Rao, D.; Ramakrishna, S. Anantha

2016-06-01

A tri-layer metamaterial perfect absorber of light, consisting of (Al/ZnS/Al) films with the top aluminum layer patterned as an array of circular disk nanoantennas, is investigated for resonantly enhancing Raman scattering from C60 fullerene molecules deposited on the metamaterial. The metamaterial is designed to have resonant bands due to plasmonic and electromagnetic resonances at the Raman pump frequency (725 nm) as well as Stokes emission bands. The Raman scattering from C60 on the metamaterial with resonantly matched bands is measured to be enhanced by an order of magnitude more than C60 on metamaterials with off-resonant absorption bands peaking at 1090 nm. The Raman pump is significantly enhanced due to the resonance with a propagating surface plasmon band, while the highly impedance-matched electromagnetic resonance is expected to couple out the Raman emission efficiently. The nature and hybridization of the plasmonic and electromagnetic resonances to form compound resonances are investigated by numerical simulations.

Oxidized forms of polyene antibiotic amphotericin B

NASA Astrophysics Data System (ADS)

Gagoś, Mariusz; Czernel, Grzegorz

2014-04-01

Amphotericin B (AmB) is one of the most important drug for the medical treatment of internal fungal infections. In this work we study electronic absorption and fluorescence properties of AmB in aqueous solution upon adding strong oxidizing agent. Particularly, we focus on the origin of the emission band ˜470 nm, which has been previously assigned to either formation of AmB dimers or to tetraene and pentaenes impurities. We find clear correlation between appearance of this band and oxidation of AmB, therefore, we conclude that the emission with maximum ˜470 nm is mainly related to the oxidation of AmB chromophore.

Scintillation properties of phosphate-borate-fluoride glass doped with Tb3+/Pr3+

NASA Astrophysics Data System (ADS)

Valiev, D.; Stepanov, S.; Polisadova, E.; Yao, G.

2018-06-01

Scintillation glass doped with Tb3+ and Pr3+ ions with different concentrations were prepared by the melt-quenching method. Optical, photoluminescence and decay kinetic characteristics of the pulse cathodoluminescence (PCL) were investigated. It was shown that the absorption coefficient of the induced absorption in the visible range of the spectrum decreases significantly with the increase of the Pr2O3 content starting from 0.2 to 1 wt%. There was the difference in the luminescence spectra of the glass at a selective and non-selective type of excitation. The "green" emission (λem= 542 nm, 5D4→7F5 radiative transition of Tb3+ ions) was excited an electron beam. The "red" emission (λem= 600 nm, 3P0→3H6 radiative transition of Pr3+ ion) was observed under selective excitation action (λexc= 450 nm). It was demonstrated that decreasing of intensity the main bands of Tb3+ ions at 487, 544, 622 nm connected with increases of concentration Pr3+ ions. The luminescence decay time of terbium ions at 487, 544, 622 nm emission bands depend on Pr3+ concentration. The tendency of reducing the luminescence decay time in the main luminescence bands of Tb3+ ions at increasing the Pr3+ concentration was presented. The results showed that Tb3+/ Pr3+ co-doped phosphate-borate-fluoride glasses are promising non-crystalline scintillation materials.

Photodissociation of PbI2 in the ultraviolet: analysis of the A rightarrow X band of PbI

NASA Astrophysics Data System (ADS)

Rodriguez, G.; Herring, C. M.; Fraser, R. D.; Eden, J. G.

1996-07-01

Emission and absorption studies of lead moniodide (PbI) have been carried out by photodissociation of PbI2 vapor at one of several wavelengths (193, 248, 266, 308, and 351 nm) in the ultraviolet. Strong emission on the A \\rightarrow X2 Pi 1/2 band (14400-22800 cm -1 ; 440 \\similar-or-less lambda \\similar-or-less 695 nm) occurs when PbI2 is photodissociated at 248 or 266 nm. Also, absorption bands attributed to the B \\leftarrow X2 Pi 1/2,3/2 , D \\leftarrow X2 Pi 1/2,3/2 , and E \\leftarrow X2 Pi 1/2,3/2 transitions of the diatomic molecule have been observed at 290 and 380, 225 and 265, and 203 and 240 nm, respectively, as have emission bands peaking at 397.6, 531.6, 582.0, 595.1, 639.7, 685.9, and 707.9 nm that appear to arise from PbI2 itself. Analysis and computer simulations of the A \\rightarrow X2 Pi 1/2 emission spectra have resulted in identifications for virtually all (>120) of the observed vibrational bandheads. Several spectroscopic constants for the A and the X2 Pi 1/2 states of PbI have been determined to be Te(A)=20659+/-130 cm-1 , omega e\\prime =132.2+/-1.0cm -1 , omega e\\prime xe\\prime =1.91+/-0.06cm -1 , omega e\\prime \\prime=160.3+/-0.6cm-1 , and omega e\\prime \\primexe \\prime\\prime=0.24+/-0.03cm -1 . Also, the difference between the equilibrium internuclear separations for the X2 Pi 1/2 and the A states has been determined to be Delta Re=0.45+/-0.05 . The spontaneous-emission lifetime for the PbI(A) state and the rate constant for quenching of this state by PbI2 (in two-body collisions) have been measured to be (94.3+/-8.8) ns and (4.3+/-0.4) \\times 10-10 cm3s -1 , respectively.

Luminescence properties of Ca{sub 14}Mg{sub 2}(SiO{sub 4}){sub 8}:Eu{sup 2+} from various Eu{sup 2+} sites for white-light-emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jia, E-mail: zhangjia@hytc.edu.cn; Jiang, Cheng

2014-12-15

Ca{sub 14}Mg{sub 2}(SiO{sub 4}){sub 8}:Eu{sup 2+} phosphors were synthesized by solid-state reaction method, and their luminescence properties were investigated. In the emission spectra, several overlapping emission bands originating from various Eu{sup 2+} sites were found. Eu{sup 2+} in Ca{sub 14}Mg{sub 2}(SiO{sub 4}){sub 8} exhibits green emission around 506 nm, and the sample doped with 0.1 mol% Eu{sup 2+} shows the strongest brightness under 365 nm excitation with the quantum efficiency of 63.6%. In the excitation spectra, strong and broad excitation bands from 250 to 450 nm were observed, which could well match with the emission wavelength of the light-emitting diodemore » chip. The fabrication test on the InGaN chip indicates the Ca{sub 14}Mg{sub 2}(SiO{sub 4}){sub 8}:Eu{sup 2+} phosphor could be promising candidate for white light-emitting diodes.« less

UV-Vis spectroscopy and solvatochromism of the tyrosine kinase inhibitor AG-1478.

PubMed

Khattab, Muhammad; Wang, Feng; Clayton, Andrew H A

2016-07-05

The effect of twenty-one solvents on the UV-Vis spectrum of the tyrosine kinase inhibitor AG-1478 was investigated. The absorption spectrum in the range 300-360nm consisted of two partially overlapping bands at approximately 340nm and 330nm. The higher energy absorption band was more sensitive to solvent and exhibited a peak position that varied from 327nm to 336nm, while the lower energy absorption band demonstrated a change in peak position from 340nm to 346nm in non-chlorinated solvents. The fluorescence spectrum of AG-1478 was particularly sensitive to solvent. The wavelength of peak intensity varied from 409nm to 495nm with the corresponding Stokes shift in the range of 64nm to 155nm (4536cm(-1) to 9210cm(-1)). We used a number of methods to assess the relationship between spectroscopic properties and solvent properties. The detailed analysis revealed that for aprotic solvents, the peak position of the emission spectrum in wavenumber scale correlated with the polarity (dielectric constant or ET(30)) of the solvent. In protic solvents, a better correlation was observed between the hydrogen bonding power of the solvent and the position of the emission spectrum. Moreover, the fluorescence quantum yields were larger in aprotic solvents as compared to protic solvents. This analysis underscores the importance of polarity and hydrogen-bonding environment on the spectroscopic properties of AG-1478. These studies will assume relevance in understanding the interaction of AG-1478 in vitro and in vivo. Copyright © 2016 Elsevier B.V. All rights reserved.

Dominant transverse-electric polarized emission from 298 nm MBE-grown AlN-delta-GaN quantum well ultraviolet light-emitting diodes

NASA Astrophysics Data System (ADS)

Liu, Cheng; Ooi, Yu Kee; Islam, S. M.; Xing, Huili Grace; Jena, Debdeep; Zhang, Jing

2017-02-01

III-nitride based ultraviolet (UV) light emitting diodes (LEDs) are of considerable interest in replacing gas lasers and mercury lamps for numerous applications. Specifically, AlGaN quantum well (QW) based LEDs have been developed extensively but the external quantum efficiencies of which remain less than 10% for wavelengths <300 nm due to high dislocation density, difficult p-type doping and most importantly, the physics and band structure from the three degeneration valence subbands. One solution to address this issue at deep UV wavelengths is by the use of the AlGaN-delta-GaN QW where the insertion of the delta-GaN layer can ensure the dominant conduction band (C) - heavyhole (HH) transition, leading to large transverse-electric (TE) optical output. Here, we proposed and investigated the physics and polarization-dependent optical characterizations of AlN-delta- GaN QW UV LED at 300 nm. The LED structure is grown by Molecular Beam Epitaxy (MBE) where the delta-GaN layer is 3-4 monolayer (QW-like) sandwiched by 2.5-nm AlN sub-QW layers. The physics analysis shows that the use of AlN-delta-GaN QW ensures a larger separation between the top HH subband and lower-energy bands, and strongly localizes the electron and HH wave functions toward the QW center and hence resulting in 30-time enhancement in TEpolarized spontaneous emission rate, compared to that of a conventional Al0.35Ga0.65N QW. The polarization-dependent electroluminescence measurements confirm our theoretical analysis; a dominant TE-polarized emission was obtained at 298 nm with a minimum transverse-magnetic (TM) polarized emission, indicating the feasibility of high-efficiency TEpolarized UV emitters based on our proposed QW structure.

Spectroscopic properties of Sm3+ doped sodium-tellurite glasses: Judd-Ofelt analysis

NASA Astrophysics Data System (ADS)

Mawlud, Saman Q.; Ameen, Mudhafar M.; Sahar, Md. Rahim; Mahraz, Zahra Ashur Said; Ahmed, Kasim F.

2017-07-01

Modifying the optical response of rare earth doped inorganic glasses for diverse optical applications is the current challenge in materials science and technology. We report the enhancement of the visible emissions of the Sm3+ ions doped sodium-tellurite (TNS) glasses. The impacts of varying Sm3+ ions concentration on the spectroscopic properties of such glass samples are evaluated. Synthesized glass samples are characterized via emission and absorption measurements. The UV-Vis-NIR absorption spectra revealed nine absorption peaks which are assigned to the transitions from the ground level (6H5/2) to 6P3/2, 4I11/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2, 6H15/2 and 6F1/2 excited energy levels of Sm3+ ions. Emission spectra of the prepared glass under 404 nm excitation wavelength consisted of four bands centered at 561 nm, 598 nm, 643 nm and 704 nm which are originated from 4G5/2→6HJ (J = 5/2, 7/2, 9/2 and 11/2) transitions. The experimental oscillator strengths, fexp are calculated from the area under absorption bands. Using Judd-Ofelt theory and fit process of least square, the phenomenological intensity parameters Ωλ (λ = 2, 4, 6) are obtained. In order to evaluate potential applications of Sm3+ ions in telluride glasses, the spectroscopic parameters: radiative transition probability AR, branching ratio BR, radiative life time τr and stimulated emission cross section σλ for each band are calculated. These glass compositions could be a potential candidate for lasers.

Observation of radio-wave-induced red hydroxyl emission at low altitude in the ionosphere.

PubMed

Kagan, L M; Nicolls, M J; Kelley, M C; Carlson, H C; Belikovich, V V; Bakhmet'eva, N V; Komrakov, G P; Trondsen, T S; Donovan, E

2005-03-11

We report the discovery of radio-wave-induced red emission of OH Meinel rotation-vibrational bands at 629.79 nm. These are the first measurements of artificial aurora below 100 km. We believe that the 629.79-nm OH emission was due to radio-wave focusing by sporadic ionization clouds near 80-85 km altitude, thus giving a technique to visualize the low-altitude sporadic ionization and providing insight into ionospheric interactions at these low altitudes.

Enhance luminescence by introducing alkali metal ions (R+ = Li+, Na+ and K+) in SrAl2O4:Eu3+ phosphor by solid-state reaction method

NASA Astrophysics Data System (ADS)

Prasad Sahu, Ishwar

2016-05-01

In the present article, the role of charge compensator ions (R+ = Li+, Na+ and K+) in europium-doped strontium aluminate (SrAl2O4:Eu3+) phosphors was synthesized by the high-temperature, solid-state reaction method. The crystal structures of sintered phosphors were in a monoclinic phase with space group P21. The trap parameters which are mainly activation energy (E), frequency factor (s) and order of the kinetics (b) were evaluated by using the peak shape method. The calculated trap depths are in the range from 0.76 to 0.84 eV. Photoluminescence measurements showed that the phosphor exhibited emission peak with good intensity at 595 nm, corresponding to 5D0-7F1 (514 nm) orange emission and weak 5D0-7F2 (614 nm) red emission. The excitation spectra monitored at 595 nm show a broad band from 220 to 320 nm ascribed to O-Eu charge-transfer state transition and the other peaks in the range of 350-500 nm originated from f-f transitions of Eu3+ ions. The strongest band at 394 nm can be assigned to 7F0-5L6 transition of Eu3+ ions due to the typical f-f transitions within Eu3+ of 4f6 configuration. The latter lies in near ultraviolet (350-500 nm) emission of UV LED. CIE color chromaticity diagram and thermoluminescence spectra confirm that the synthesized phosphors would emit an orange-red color. Incorporating R+ = Li+, Na+ and K+ as the compensator charge, the emission intensity of SrAl2O4:Eu3+ phosphor can be obviously enhanced and the emission intensity of SrAl2O4:Eu3+ doping Li+ is higher than that of Na+ or K+ ions.

Hydrothermal synthesis infrared to visible upconversion luminescence of SrMoO4: Er3+/Yb3+ phosphor

NASA Astrophysics Data System (ADS)

Sinha, Shriya; Kumar, Kaushal

2018-04-01

The upconversion emission properties in Er3+/Yb3+ doped SrMoO4 phosphor synthesized via hydrothermal method is investigated upon 980 nm laser light excitation. The crystal structure and morphology of the synthesized phosphor are characterized by X-ray diffraction and field emission scanning electron microscopy. The X-ray diffraction pattern suggests that SrMoO4 phosphor has tetragonal phase structure. The phosphor emits strong green (525 and 552 nm) and red (665 nm) UC emissions along with weak blue (410 and 488 nm) and near infrared (798 nm) emission bands. The color emitted from the phosphor is shifted from yellow to green region with increasing the power density from 15 to 65 W/cm2. The result indicates that the present material is suitable for making infrared to visible up-converts and display devices.

Green Color Purification in Tb(3+) Ions through Silica Inverse Opal Heterostructure.

PubMed

Shrivastava, Vishnu Prasad; Sivakumar, Sri; Kumar, Jitendra

2015-06-10

The ordered SiO2:Tb(3+) inverse opal heterostructure films are fabricated through polystyrene spheres hetero-opal template using the convective self-assembly method to examine their potential for color purification. Their optical properties and photoluminescence have been investigated and compared with individual single inverse opals and reference (SiO2:Tb(3+) powder). The heterostructures are shown to possess two broad photonic stop bands separated by an effective pass band, causing suppression of blue, orange, and red emission bands corresponding to (5)D4 → (7)F(j); j = 6, 4, 3 transitions, respectively and an enhancement of green emission (i.e., (5)D4 → (7)F5). Although the suppression of various emission occurs because of its overlap with the photonic band gaps (PSBs), the enhancement of green radiation is observed because of its location matching with the pass band region. The Commission International de l'Eclairage (CIE) chromaticity coordinates of the emission spectrum of the heterostructure based on polystyrene sphere of 390 and 500 nm diameter are x = 0.2936, y = 0.6512 and lie closest to those of standard green color (wavelength 545 nm). In addition, a significant increase observed in luminescence lifetime for (5)D4 level of terbium in inverse opal heterostructures vis-à-vis reference (SiO2:Tb(3+) powder) is attributed to the change in the effective refractive index.

Thermal evaporation and condensation synthesis of metallic Zn layered polyhedral microparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, Waheed S.; Cao, Chuanbao, E-mail: cbcao@bit.edu.cn; Usman, Zahid

2011-12-15

Highlights: Black-Right-Pointing-Pointer Zn polyhedral microparticles prepared by thermal evaporation and condensation route. Black-Right-Pointing-Pointer Vapour-solid process based growth model governs the formation of Zn microparticles. Black-Right-Pointing-Pointer A strong PL emission band is observed at 369 nm in UV region. Black-Right-Pointing-Pointer Radiative recombination of electrons in the s, p conduction band and the holes in the d bands causes this emission. -- Abstract: Metallic zinc layered polyhedral microparticles have been fabricated by thermal evaporation and condensation technique using zinc as precursor at 750 Degree-Sign C for 120 min and NH{sub 3} as a carrier gas. The zinc polyhedral microparticles with oblate sphericalmore » shape are observed to be 2-9 {mu}m in diameter along major axes and 1-7 {mu}m in thickness along minor axes. The structural, compositional and morphological characterizations were performed by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). A vapour-solid (VS) mechanism based growth model has been proposed for the formation of Zn microparticles. Room temperature photoluminescence (PL) emission spectrum of the product exhibited a strong emission band at 369 nm attributed to the radiative recombination of electrons in the s, p conduction band near Fermi surface and the holes in the d bands generated by the optical excitation.« less

Effect of different surfactants on structural and optical properties of Ce3+ and Tb3+ co-doped BiPO4 nanostructures

NASA Astrophysics Data System (ADS)

Lakshminarayana, G.; Dao, T. D.; Chen, K.; Sharma, Manoj; Takeda, T.; Brik, M. G.; Kityk, I. V.; Singh, Sarabjot; Nagao, T.

2015-01-01

In this paper we report on the Ce3+ and Tb3+ ions co-doped bismuth phosphate (BiPO4) nanostructures that were synthesized by a simple precipitation method using different surfactants such as glycerol/H2O, glycerol/ethylene glycol, oleic acid, and ethylene glycol. The structural (X-ray diffraction, scanning electron microscopy, tunneling electron microscopy), functional groups analysis (Fourier transform infrared and Raman spectroscopy), thermal (thermogravimetry and differential thermal analysis), and optical (photoluminescence, photoluminescence-excitation) properties were investigated. The structural and morphological analysis confirms the pure hexagonal crystal structure of the synthesized nanostructures. From the measured Fourier transform infrared (FTIR) and Raman spectra various functional groups such as υ3 stretching vibration of the PO4 group, and δ(O-P-O) and υ4 (PO4) vibrations including the υ2 and υ1 bending modes of the PO4 units are identified. Based on the thermal analysis, for all the studied samples an exothermic peak between 680 °C and 700 °C was observed due to phase transition from hexagonal to high temperature monoclinic. The Ce3+and Tb3+ codoped samples show spectrally broad 5d → 4f luminescence in the blue (centered at 459 nm) wavelength region under the direct optical excitation of Ce3+ at 417 nm. Similarly, Tb3+ has revealed four main emission bands (5D4 → 7F6, 5, 4 and 3) at 490 nm, 545 nm, 585 nm and 621 nm with 378 nm (7F6 → 5G6) as the excitation wavelength, including three more weak emission bands at 647 nm, 669 nm, and 681 nm which could be assigned to 5D4 → 7F2, 1, 0 emission transitions. Among them, 545 nm (5D4 → 7F5) has shown bright green emission. The Ce3+ and Tb3+ codoped sample synthesized with pure oleic acid have shown relatively high green emission intensity for Tb3+, and relatively weak blue emission intensity for Ce3+ under their respective optical excitation wavelengths.

Differentiation of ocular fundus fluorophores by fluorescence lifetime imaging using multiple excitation and emission wavelengths

NASA Astrophysics Data System (ADS)

Hammer, M.; Schweitzer, D.; Schenke, S.; Becker, W.; Bergmann, A.

2006-10-01

Ocular fundus autofluorescence imaging has been introduced into clinical diagnostics recently. It is in use for the observation of the age pigment lipofuscin, a precursor of age - related macular degeneration (AMD). But other fluorophores may be of interest too: The redox pair FAD - FADH II provides information on the retinal energy metabolism, advanced glycation end products (AGE) indicate protein glycation associated with pathologic processes in diabetes as well as AMD, and alterations in the fluorescence of collagen and elastin in connective tissue give us the opportunity to observe fibrosis by fluorescence imaging. This, however, needs techniques able to differentiate particular fluorophores despite limited permissible ocular exposure as well as excitation wavelength (limited by the transmission of the human ocular lens to >400 nm). We present an ophthalmic laser scanning system (SLO), equipped with picosecond laser diodes (FWHM 100 ps, 446 nm or 468 nm respectively) and time correlated single photon counting (TCSPC) in two emission bands (500 - 560 nm and 560 - 700 nm). The decays were fitted by a bi-exponential model. Fluorescence spectra were measured by a fluorescence spectrometer fluorolog. Upon excitation at 446 nm, the fluorescence of AGE, FAD, and lipofuscin were found to peak at 503 nm, 525 nm, and 600 nm respectively. Accordingly, the statistical distribution of the fluorescence decay times was found to depend on the different excitation wavelengths and emission bands used. The use of multiple excitation and emission wavelengths in conjunction with fluorescence lifetime imaging allows us to discriminate between intrinsic fluorophores of the ocular fundus. Taken together with our knowledge on the anatomical structure of the fundus, these findings suggest an association of the short, middle and long fluorescence decay time to the retinal pigment epithelium, the retina, and connective tissue respectively.

Nanophosphor CaSO4:Eu2+ for photoluminescence liquid crystal display (PLLCD)

NASA Astrophysics Data System (ADS)

Patle, Anita; Patil, R. R.; Moharil, S. V.

2018-05-01

In this work PL enhancement of CaSO4:Eu2+ nanophosphor which was synthesized with 0.01M molarity by co-precipitation method is presented. Synthesized phosphor was characterized by XRD, SEM, TEM and PL measurements. Average particle size is found to be in the range 80-100nm with Hexagonal morphology and PL studies showed emission peaks at 380nm, when samples were excited by 254nm. The observed PL emission is characteristic emission of Eu2+ similar to that observed in bulk CaSO4:Eu2. However under identical condition it is observed that intensity of emission get enhanced for 0.01M size which is doubled to that of 0.1M with similar emission at 380nm. A phosphor with narrow emission band around 390 nm is desirable, since at this wavelength the transmission of standard glass, polarizing plastic, other coating and LCD material is at acceptable level. Strong Eu2+ emission is observed in CaSO4:Eu nanophosphor which finds applications for PLLCD (photoluminescent liquid crystal display).

Optical properties of Ni2+ and radiation defects in MgF sub 2 and MnF sub 2

NASA Astrophysics Data System (ADS)

Feuerhelm, L. N.

1980-03-01

The radiation defects in pure MgF2 were made by observating the polarized absorption, luminescence, and excitation spectra in electron-irradiated MgF2. Additionally, studies of the absorption, emission, excitation, and temperature dependence of the lifetimes of transitions in nickel-doped MgF2 and MnF2 were accomplished, as well as the observation of radiation effects on these crystals. The absorption band at about 320 nm in irradiated MgF2 is identified to be due to the F2(D2b) center, and to have an emission at about 450 nm. Analysis of the temperature dependence of this band indicates a dominant phonon mode of 255 cm(-1) for the excited state. The F2(C1) center is identified with an absorption of about 360 nm and an emission of 410 nm. An absorption peak at 300 nm, for which no corresponding emission was found, is tentatively identified to be the F3-center, and to have a dominant phonon mode of 255 cm(-1). The temperature dependence of the lifetimes of transitions in nickel-doped MgF2 is analyzed by the quantum mechanical single configuration coordinate model of Struck and Fonger, and a complete configuration coordinate model is made for this crystal. Similar studies are made in MnF2:Ni.

Mars, Venus, Earth and Titan UV Laboratory Aeronomy by Electron Impact

NASA Astrophysics Data System (ADS)

Malone, C. P.; Ajello, J. M.; McClintock, W. E.; Eastes, R.; Evans, J. S.; Holsclaw, G.; Schneider, N. M.; Jain, S.; Gerard, J. C. M. C.; Hoskins, A.

2017-12-01

The UV response of the Mars, Earth, Titan and Venus upper atmospheres to the solar radiation fields [solar wind and solar EUV] is the focus of the present generation of Mars, Earth, Titan and Venus missions. These missions are Mars Express (MEX), the Mars Atmosphere and Volatile Evolution Mission (MAVEN), Cassini at Titan, Global-scale Observations of the Limb and Disk (GOLD) mission for Earth and Venus Express (VEX). Each spacecraft is equipped with a UV spectrometer that senses far ultraviolet (FUV) emissions from 110-190 nm, whose dayglow intensities are proportional to three quantities:1) particle (electron, ion) fluxes, 2) the altitude distribution of species in the ionosphere: CO, CO2, O, N2 at Venus and Mars and N2, O and O2 at Titan and Earth and 3) the emission cross section for the interaction process. UV spectroscopy provides a benchmark to the present space environment and indicates pathways for removing upper atmosphere gas (e.g., water escape from Mars and Earth) or N2 escape at Titan over eons. We present a UV laboratory program that utilizes an instrument, unique in the world, at the University of Colorado that can measure excitation mechanisms by particle (electron, ion) impact and the resulting emission cross sections that include processes occurring in a planetary atmosphere, particularly the optically forbidden emissions presented by the Cameron bands, the Lyman Birge Hopfield bands and the OI 135.6 nm multiplet. There are presently uncertainties by a factor of two in the existing measurements of the emission cross section, affecting modeling of electron transport. We have utilized the MAVEN Imaging Ultraviolet Spectrograph (IUVS) engineering model which operates at moderate spectral resolution ( 0.5-1.0nm FWHM) to obtain the full vibrational spectra of the Cameron band system CO(a 3Π → X 1Σ+) from both CO direct excitation and CO2 dissociative excitation, and for the dipole-allowed Fourth Positive band system of CO, while for N2 we have studied molecular nitrogen (N2 LBH bands, a 1Πg → X 1Σg+). We have performed laboratory measurements using mono-energetic electrons in a large chamber to excite band systems by the same processes as occur at low densities in planetary atmospheres. We have ascertained vibrational structure and emission cross sections for the strongest band systems on solar system objects.

Tunable Narrow Band Emissions from Dye-Sensitized Core/Shell/Shell Nanocrystals in the Second Near-Infrared Biological Window

PubMed Central

Shao, Wei; Chen, Guanying; Kuzmin, Andrey; Kutscher, Hilliard L.; Pliss, Artem; Ohulchanskyy, Tymish Y.; Prasad, Paras N.

2017-01-01

We introduce a hybrid organic–inorganic system consisting of epitaxial NaYF4:Yb3+/X3+@NaYbF4@NaYF4:Nd3+ (X = null, Er, Ho, Tm, or Pr) core/shell/shell (CSS) nanocrystal with organic dye, indocyanine green (ICG) on the nanocrystal surface. This system is able to produce a set of narrow band emissions with a large Stokes-shift (>200 nm) in the second biological window of optical transparency (NIR-II, 1000–1700 nm), by directional energy transfer from light-harvesting surface ICG, via lanthanide ions in the shells, to the emitter X3+ in the core. Surface ICG not only increases the NIR-II emission intensity of inorganic CSS nanocrystals by ~4-fold but also provides a broadly excitable spectral range (700–860 nm) that facilitates their use in bioapplications. We show that the NIR-II emission from ICG-sensitized Er3+-doped CSS nanocrystals allows clear observation of a sharp image through 9 mm thick chicken breast tissue, and emission signal detection through 22 mm thick tissue yielding a better imaging profile than from typically used Yb/Tm-codoped upconverting nanocrystals imaged in the NIR-I region (700–950 nm). Our result on in vivo imaging suggests that these ICG-sensitized CSS nanocrystals are suitable for deep optical imaging in the NIR-II region. PMID:27935695

On the controlled isotropic shrinkage induced fine-tuning of photo-luminescence in terbium ions embedded silica inverse opal films

NASA Astrophysics Data System (ADS)

Shrivastava, Vishnu Prasad; Kumar, Jitendra; Sivakumar, Sri

2017-12-01

Tb3+ embedded silica inverse opal structures with different photonic stop bands have been fabricated by annealing the SiO2-polystyrene spheres (diameter 390 nm) opal template at 320-650 oC. The PSB tuning realized in the wavelength range 498 - 600 nm is shown to depend on annealing temperature and impending isotropic shrinkage of silica matrix. The impact of wide PSB shift on four Tb3+ ion emission bands (blue, green, yellow, and red at 486, 545, 580, and 620 nm, respectively) corresponding to 5D4→7Fj (j = 6,5,4,3) transitions have been investigated. The effect amounts to significant suppression of emission bands at 586, 545 and 486 nm in inverse opals, obtained by annealing opal template at 350, 400, and 650 oC, respectively. Further, luminescence lifetime of Tb3+ ion 5D4 state increases with shrinkage induced in inverse opal progressively and get enhanced up to 2.3 times vis-à-vis reference silica. The changes in refractive index caused by thermal annealing of opal template is found to be responsible for the observed improvement in 5D4 state lifetime.

Violet-green excitation for NIR luminescence of Yb3+ ions in Bi2O3-B2O3-SiO2-Ga2O3 glasses.

PubMed

Li, Weiwei; Cheng, Jimeng; Zhao, Guoying; Chen, Wei; Hu, Lili; Guzik, Malgorzata; Boulon, Georges

2014-04-21

60Bi(2)O(3)-20B(2)O(3)-10SiO(2)-10Ga(2)O(3) glasses doped with 1-9 mol% Yb(2)O(3) were prepared and investigated mainly on their violet-green excitation for the typical NIR emission of Yb(3+), generally excited in the NIR. Two violet excitation bands at 365 nm and 405 nm are related to Yb(2+) and Bi(3+). 465 nm excitation band and 480 nm absorption band in the blue-green are assigned to Bi(0) metal nanoparticles/grains. Yb-content-dependence of the excitation and absorption means that Bi(0) is the reduced product of Bi(3+), but greatly competed by the redox reaction of Yb(2+) ↔ Yb(3+). It is proved that the violet-green excitations result in the NIR emission of Yb(3+). On the energy transfer, the virtual level of Yb(3+)-Yb(3+) as well as Bi(0) dimers probably plays an important role. An effective and controllable way is suggested to achieve nano-optical applications by Bi(0) metal nanoparticles/grains and Yb(3+).

Experimental and theoretical investigations on spectroscopic properties of the imidazole-fused phenanthroline and its derivatives

NASA Astrophysics Data System (ADS)

Zhong, Rongfeng; Xu, Shengxian; Wang, Jinglan; Zhao, Feng; Xia, Hongying; Wang, Yibo

2016-05-01

Two phenanthroline derivatives, 1H-imidazo[4,5-f][1,10]phenanthroline (imPhen) and 2-(9H-fluoren-2-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (Flu-imPhen), have been synthesized and characterized and the corresponding absorption and emission spectroscopic properties have been studied in CH2Cl2 solution. The imPhen exhibits the main two absorption bands at 282 nm and 229 nm and these bands are assigned as the typical π → π*(Phen) state. In addition, the weak absorption bands at 313 nm associated with a shoulder near 302 nm were assigned to the π → π*(Phen) state with partial charge transfer (CT) character. A similar absorption spectra are observed in the case of the Flu-imPhen in the region of 200-300 nm, while the region of 300-400 nm of the spectra are dominated by the characteristic π → π* transition of the fluorene moiety. imPhen shows the typical ligand-centered 1π → π* emission, while Flu-imPhen emits from the mixed 1π → π*/CT states. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) were employed to rationalize the photophysical properties of these ligands studied. The theoretical data confirm the assignment of the experimental absorption spectra and the nature of the emitting states.

Synthesis and Crystal Structure of Highly Strained [4]Cyclofluorene: Green-Emitting Fluorophore.

PubMed

Liu, Yu-Yu; Lin, Jin-Yi; Bo, Yi-Fan; Xie, Ling-Hai; Yi, Ming-Dong; Zhang, Xin-Wen; Zhang, Hong-Mei; Loh, Teck-Peng; Huang, Wei

2016-01-15

[4]Cyclo-9,9-dipropyl-2,7-fluorene ([4]CF) with the strain energy of 79.8 kcal/mol is synthesized in high quantum yield. Impressively, hoop-shaped [4]CF exhibits a green fluorescence emission around 512 nm offering a new explanation for the green band (g-band) in polyfluorenes. The solution-processed [4]CF-based organic light emitting diode (OLED) has also been fabricated with the a stronger green band emission. Strained semiconductors offer a promising approach to fabricating multifunctional optoelectronic materials in organic electronics and biomedicine.

Simultaneous retrieval of daytime O(3P) and O3 concentrations in the altitude interval 80 - 100 km.

NASA Astrophysics Data System (ADS)

Yankovsky, Valentine; Manuilova, Rada; Koval, Andrey

2017-04-01

We propose methods of simultaneously independent retrievals of the key components of Mesosphere and Lower Thermosphere (MLT) [O3] and [O(3P)]. The altitude profile of ozone concentration, [O3], can be measured by direct method of the measurement of absorbing radiation from the Sun or the stars in the UV range of the spectrum. However, this method is most often realized in twilight. Retrieval of daytime [O3] depends on a prior information about the O(3P) altitude profile. Vice versa, atomic oxygen concentration, [O(3P)], is usually retrieved from the measured values of [O3]. The problem of independent and simultaneous retrieval of [O3] and [O(3P)] can be solved by using individual proxy for each of the target component. Using a sensitivity study and uncertainty analysis of the contemporary model of O3 and O2 photolysis in the MLT, YM2011, we determined that populations of three excited electronic-vibrational levels O2(b1, v = 0, 1, 2) and of metastable O(1D) atom depend on [O(3P)] and [O3] concentrations. For [O(3P)] retrieval the following transitions should be used: O2(b1, v') -> O2(X3, v") which produce emissions: (a) at 780.4 nm in the band (v' = 2, v" = 2) and at 697.0 nm in the band (2, 1) with the uncertainty of retrieval smaller than 30% for the whole altitude range 80 - 100 km; (b) at 771.0 nm in the band (1, 1), 688.4 nm in the band (1, 0) and at 874.4 nm in the band (1, 2) with the uncertainty of retrieval about 30% above 90 km. For [O3] retrieval the following transitions should be used: O2(b1, v') -> O2(X3, v") which produce emissions: (c) at 762.1 nm in the band (0, 0) and at 864.7 nm in the band (0, 1) with the uncertainty of retrieval 20 - 25% for the altitude range 80 - 85 km and smaller than 20% in the interval 85 - 95 km; (d) in the line of O(1D) 630.0 nm with the uncertainty of retrieval 10 - 15% in the interval 80 - 95 km. Above 95 km the uncertainty of [O3] retrieval grows and reaches up to 80% at 100 km for all suggested proxies. For simultaneously [O3] and [O(3P)] retrievals the observations of above mentioned emissions (a) or (b) and (c) or (d) could be used.

Different sensing modes of fluoride and acetate based on a calix[4]arene with 25,27-bistriazolylmethylpyrenylacetamides.

PubMed

Hung, Hao-Chih; Chang, Yung-Yu; Luo, Liyang; Hung, Chen-Hsiung; Diau, Eric Wei-Guang; Chung, Wen-Sheng

2014-02-01

25,27-Bis{1'-N-(1-pyrenyl)-aminocarbonylmethyl-1H-[1',2',3']tri-azolyl-4'-methoxy}-26,28-dihydroxycalix[4]arene, 4, is synthesized as a fluorescent chemosensor for the selective detection of both anions and ion pairs in MeCN. Sensor 4 uses bis-triazoles as ligands to bind a metal ion, bis-amides and bis-triazoles as the sites to recognize anions, and pyrenes as fluorophores. Among eight anions screened, chemosensor 4 showed a marked fluorescence change toward F(-), H2PO4(-) and AcO(-), but 4 responded to each anion in a distinct way. In the presence of F(-) at low concentrations, the dynamic excimer emission of compound 4 at λ(max) 482 nm was quenched, but an emission at λ(max) 472 nm appeared at large doses of F(-). A control compound 6 showed very similar red shifts in the UV-vis and excitation spectra as 4 did, and its 472 nm emission band grew as the fluoride doses increased. Thus, the growth of the 472 nm emission of 4 and 6 in the presence of excess F(-) may be because strong H-bonding interactions of amido protons with F(-) favoured the formation of pyrene dimers in the ground state with charge transfer characteristics. The addition of H2PO4(-), unlike F(-), to a solution of 4 showed an enhanced monomer emission but a decreased excimer emission (λ(max) 482 nm). Adding AcO(-) to 4 produced a systematic change from a dynamic excimer (λ(max) 482 nm) to λ(max) 472 nm but with very little change in the UV-vis spectrum. Time-resolved fluorescence measurements on compound 6 with F(-) and AcO(-) confirmed that the 472 nm emission band mainly came from static excimers for the former, but was partly from a dynamic excimer for the latter because it contained a growth component in the fluorescence decay traces. Without pre-treatment with an anion, chemosensor 4 showed recognition of only metal ions Cu(2+), Hg(2+) and Cr(3+), but it became sensitive to Ag(+) when it was pretreated with fluoride.

Assessment of growth and spectral properties of Cr3+-doped La0.83Y0.29Sc2.88(BO3)4 crystal

NASA Astrophysics Data System (ADS)

Huang, Yisheng; Sun, Shijia; Lin, Zhoubin; Zhang, Lizhen; Wang, Guofu

2017-10-01

This paper reports the spectral characteristic of Cr3+-doped La0.83Y0.29 Sc2.88 (BO3)4 crystal. Cr3+-doped La0.83Y0.29Sc2.88 (BO3)4 crystal was grown from a flux of Li6B4O9 by the top seeded Solution growth method. Cr3+:La0.83Y0.29 Sc2.88 (BO3)4 crystal exhibits broad absorption and emission bands of Cr3+ ions. The absorption cross-section σa is 3.38 × 10-20 cm2 at 467 nm and 4.40 × 10-20 cm2 at 656 nm for E//c, respectively. The emission band with a peak at 906 nm has a full width at half maximum (FWHM) of 188 nm for E//c. The emission cross-section σe at 906 nm is 2.35 × 10-20 cm2 for E//c axis and 2.03 × 10-20 cm2 for E⊥c axis. The fluorescence lifetime of 4T2 → 4A2 transition is 37.7 μs. The investigated result indicates that it may be considered as a potential CW tunable laser crystal material.

Production of N2 Vegard-Kaplan and Lyman-Birge-Hopfield emissions on Pluto

NASA Astrophysics Data System (ADS)

Jain, Sonal Kumar; Bhardwaj, Anil

2015-01-01

We have developed a model to calculate the emission intensities of various vibrational transitions of N2 triplet band and Lyman-Birge-Hopfield (LBH) band emissions in the dayglow of Pluto for solar minimum, moderate, and maximum conditions. The calculated overhead intensities of Vegard-Kaplan (A3Σu+ -X1 Σg+) , First Positive (B3Πg -A3 Σu+), Second Positive (C3Πu -B3Πg) , Wu-Benesch (W3Δu -B3Πg) , Reverse First Positive, and LBH (a1Πg -X1 Σg+) bands of N2 are 17 (74), 14.8 (64), 2.4 (10.8), 2.9 (12.7), 2.9 (12.5), and 2.3 (10) R, respectively, for solar minimum (maximum) condition. We have predicted the overhead and limb intensities of VK (150-190 nm) and LBH (120-190 nm) bands of N2 on Pluto for the New Horizons (NH) flyby condition that can be observed by ALICE: the ultraviolet imaging spectrograph also know as P-ALICE. The predicted limb intensities of VK and LBH bands peak at radial distance of ∼2000 km with the value of about 5 (13) and 9.5 (22) R for solar zenith angle 60° (0°), respectively. We have also calculated overhead and limb intensities of few prominent transition of CO Fourth Positive bands for NH flyby condition.

Preparation of electrospun pyrochlore-structure KGdTa2O7:Eu3+ phosphor: the optical and structural properties for white light emitting diode applications.

PubMed

Yim, Chul Jin; Unithrattil, Sanjith; Chung, Woon Jin; Im, Won Bin

2013-12-01

Red emitting nanofibers, KGdTa2O7:Eu3+ were synthesized by electrospinning technique followed by heat treatment. As-prepared uniform fiber precursor with diameter ranging from about 700 nm to about 900 nm were calcined after removing organic species by calcination. The fiber surface become rough and diameter decreased to about 250-340 nm range due to decomposition of organic species and formation of inorganic phase. Morphology, structural and photoluminescent properties of fibers were analyzed using thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL). TG-DTA analysis indicates that KGdTa2O7:Eu3+ began to crystalize at 520 degrees C. Fibers annealed at 900 degrees C formed well crystallized uniform fibers. Under ultraviolet excitation KGdTa2O7:Eu3+ exhibits red emission due to transitions in 4f states of Eu3+. The excitation band is dominated by the Eu(3+)--O2-charge transfer band peaked at 289 nm. The emission peak is in the region that is ideal for red light emission.

Synthesis and Luminescence Properties of Blue Na(Sr0.97-xCa(x))PO4:0.03Eu2+ Phosphors for White Light Emitting Diode Applications.

PubMed

Hakeem, D A; Park, K

2015-07-01

The crystal structure and luminescence properties of Na(Sr0.97-xCax)PO4:0.03Eu2+ (0 < x < 1.0) phosphors were studied, depending on the Ca2+ concentration. All the Na(Sr0.97-xCax)PO4:0.03Eu2+ phosphors had a hexagonal crystal structure. The excitation spectra of the prepared phosphors showed a broad band ranging from 250 to 420 nm, which arises due to the 4f-5d transitions of Eu2+ ions. Upon the excitation of 334 nm wavelength, the emission spectra showed a broad blue band ranging from 400 to 700 nm peaking at 450 nm. Among the prepared phosphors, the Na(Sr0.72Ca0.25)PO4:0.03Eu2+ showed the strongest emission intensity and could be applied as a blue emitting phosphor for UV-based w-LEDs.

Characterization of fluorescence in heat-treated silver-exchanged zeolites.

PubMed

De Cremer, Gert; Coutiño-Gonzalez, Eduardo; Roeffaers, Maarten B J; Moens, Bart; Ollevier, Jeroen; Van der Auweraer, Mark; Schoonheydt, Robert; Jacobs, Pierre A; De Schryver, Frans C; Hofkens, Johan; De Vos, Dirk E; Sels, Bert F; Vosch, Tom

2009-03-04

Thermal treatment of Ag(+)-exchanged zeolites yields discrete highly photostable luminescent clusters without formation of metallic nanoparticles. Different types of emitters with characteristic luminescence colors are observed, depending on the nature of the cocation, the amount of exchanged silver, and the host topology. The dominant emission bands in LTA samples are situated around 550 and 690 nm for the samples with, respectively, low and high silver content, while in FAU-type materials only a broad band around 550 nm is observed, regardless of the degree of exchange. Analysis of the fluorescent properties in combination with ESR spectroscopy suggests that a Ag(6)(+) cluster with doublet electronic ground state is associated with the appearance of the 690-nm emitter, having a decay of a few hundred microseconds. Tentatively, the nanosecond-decaying 550-nm emitter is assigned to the Ag(3)(+) cluster. This new class of photostable luminescent particles with tunable emission colors offers interesting perspectives for various applications such as biocompatible labels for intracellular imaging.

Enhanced 630nm equatorial airglow emission observed by Limb Viewing Hyper Spectral Imager (LiVHySI) onboard YOUTHSAT-1

NASA Astrophysics Data System (ADS)

Bisht, R. S.; Thapa, N.; Babu, P. N.

2016-04-01

The Earth's airglow layer, when observed in the limb view mode, appears to be a double layer. LiVHySI onboard YOUTHSAT (inclination 98.730, apogee 817 km, launched by Indian Space Research Organization in April, 2011) is an Earth's limb viewing camera measuring airglow emissions in the spectral window of 550-900 nm. Total altitude coverage is about 500 km with command selectable lowest altitude. During few of the orbits we have observed the double layer structure and obtained absolute spectral intensity and altitude profile for 630 nm airglow emission. Our night time observations of upper atmosphere above dip equator carried out on 3rd May, 2011 show a prominent 630 nm double layer structure. The upper airglow layer consists of the 630 nm atomic oxygen O(1D) emission line and lower layer consists of OH(9-3) meinel band emission at 630 nm. The volume emission rate as a function of altitude is simulated for our observational epoch and the modeled limb intensity distribution is compared with the observations. The observations are in good agreement with the simulated intensity distribution.

AURORA on MEGSAT 1: a photon counting observatory for the Earth UV night-sky background and Aurora emission

NASA Astrophysics Data System (ADS)

Monfardini, A.; Trampus, P.; Stalio, R.; Mahne, N.; Battiston, R.; Menichelli, M.; Mazzinghi, P.

2001-08-01

A low-mass, low-cost photon-counting scientific payload has been developed and launched on a commercial microsatellite in order to study the near-UV night-sky background emission with a telescope nicknamed ``Notte'' and the Aurora emission with ``Alba''. AURORA, this is the name of the experiment, will determine, with the ``Notte'' channel, the overall night-side photon background in the 300-400nm spectral range, together with a particular 2+N2 line (λc=337nm). The ``Alba'' channel, on the other hand, will study the Aurora emissions in four different spectral bands (FWHM=8.4-9.6nm) centered on: 367nm (continuum evaluation), 391nm (1-N+2), 535nm (continuum evaluation), 560nm (OI). The instrument has been launched on the 26 September, 2000 from the Baikonur cosmodrome on a modified SS18 Dnepr-1 ``Satan'' rocket. The satellite orbit is nearly circular (hapogee=648km, /e=0.0022), and the inclination of the orbital plane is 64.56°. An overview of the techniques adopted is given in this paper.

Microwave Synthesis, Characterization, and Photoluminescence Properties of Nanocrystalline Zirconia

PubMed Central

Singh, A. K.; Nakate, Umesh T.

2014-01-01

We report synthesis of ZrO2 nanoparticles (NPs) using microwave assisted chemical method at 80°C temperature. Synthesized ZrO2 NPs were calcinated at 400°C under air atmosphere and characterized using FTIR, XRD, SEM, TEM, BET, and EDS for their formation, structure, morphology, size, and elemental composition. XRD results revealed the formation of mixed phase monoclinic and tetragonal ZrO2 phases having crystallite size of the order 8.8 nm from most intense XRD peak as obtained using Scherrer formula. Electron microscope analysis shows that the NPs were less than 10 nm and highly uniform in size having spherical morphology. BET surface area of ZrO2 NPs was found to be 65.85 m2/g with corresponding particle size of 16 nm. The band gap of synthesized NPs was found to be 2.49 eV and PL spectra of ZrO2 synthesized NPs showed strong peak at 414 nm, which corresponds to near band edge emission (UV emission) and a relatively weak peak at 475 and 562 nm. PMID:24578628

Fourier transform emission spectroscopy of the TiF radical in the 407 nm region

NASA Astrophysics Data System (ADS)

Imajo, Takashi; Kobayashi, Yuki; Nakashima, Yoshihiro; Tanaka, Keiichi; Tanaka, Takehiko

2005-04-01

Ultraviolet emission spectra of the TiF radical in the 407 nm region have been observed at a resolution of 0.04 cm -1 using a Fourier transform spectrometer. A new electronic assignment of 4Γ- X4Φ has been proposed. Rotational analysis has been obtained for the 0-0 and 1-1 vibrational bands of the 4Γ 5/2- X4Φ 3/2, 4Γ 9/2- X4Φ 7/2, and 4Γ 11/2- X4Φ 9/2 subbands and the 0-0 band of 4Γ 7/2- X4Φ 5/2. The lower state rotational and centrifugal distortion constants are consistent with the previous results [J. Mol. Spectrosc. 184 (1997) 186; J. Chem. Phys. 119 (2003) 9496], to the conformation that the lower state of the 407 nm band is the 4Φ ground electronic state. Rough estimates of the vibrational interval Δ G(1/2) and the spin-orbit coupling constant A in the 4Γ state were also obtained.

UV- Vis- NIR and luminescent characterization of PZCdO:Tm laser oxide glasses

NASA Astrophysics Data System (ADS)

Al-Assiri, M. S.; Algarni, H.; Reben, M.; Yousef, E.; Hegazy, H. H.; AbouDeif, Y. M.; Umar, Ahmad

2017-11-01

The luminescent oxide glasses with composition 50P2O5- 30ZnO- 20CdO (PZCdO pure) and 50P2O5- 30ZnO- 20CdO- 30000 ppm Tm2O3 (PZCdO:Tm) were synthesized by using melt- quenching technique. The optical energy gap and Urbach energy of these glasses were calculated by using UV-Vis-NIR spectroscopy. Judd- Ofelt parameters Ω2, Ω4 and Ω6, branching ratio, βR, and radiative lifetimes, τR, of Tm3+ ions doped PZCdO glasses were estimated. The spectroscopic results showed that the present glasses has the effective emission cross section bandwidth (Δλeff = 90 nm) and high stimulated emission cross-section (σem = 1.5 × 10-21 cm2). The blue up conversion emissions sharp band at 458 nm corresponding to transition 1D2 → 3F6 and weak emission band in NIR region assigned to 1G4→3H4 for the glasses PZCdO:Tm with UV- excited at 354 nm region were obtained. From result we can suggest that the present glasses can be used for blue light emitting diodes BLED chip.

A novel approach to obtain highly intense self-activated photoluminescence emissions in hydroxyapatite nanoparticles

NASA Astrophysics Data System (ADS)

Machado, Thales R.; Sczancoski, Júlio C.; Beltrán-Mir, Héctor; Nogueira, Içamira C.; Li, Máximo S.; Andrés, Juan; Cordoncillo, Eloisa; Longo, Elson

2017-05-01

Defect-related photoluminescence (PL) in materials have attracted interest for applications including near ultraviolet (NUV) excitable light-emitting diodes and in biomedical field. In this paper, hydroxyapatite [Ca10(PO4)6(OH)2] nanorods with intense PL bands (bluish- and yellowish-white emissions) were obtained when excited under NUV radiation at room temperature. These nanoparticles were synthesized via chemical precipitation at 90 °C followed by distinct heat treatments temperatures (200-800 °C). Intense and broad emission profiles were achieved at 350 °C (380-750 nm) and 400 °C (380-800 nm). UV-Vis spectroscopy revealed band gap energies (5.58-5.78 eV) higher than the excitation energies ( 3.54 and 2.98 eV at 350 and 415 nm, respectively), confirming the contribution of defect energy levels within the forbidden zone for PL emissions. The structural features were characterized by X-ray diffraction, Rietveld refinement, thermogravimetric analysis, and Fourier transform infrared spectroscopy. By means of these techniques, the relation between structural order-disorder induced by defects, chemical reactions at both lattice and surface of the materials as well as the PL, without activator centers, was discussed in details.

Optical Studies of Nd-doped benzil, a potential luminescent and laser material

NASA Astrophysics Data System (ADS)

Noginov, M. A.; Curley, M.; Noginova, N.; Wang, W. S.; Aggarwal, M. D.

1998-08-01

Neodymium-doped benzil crystals have been synthesized and characterized for their absorption, emission, and kinetics properties. From Judd Ofelt analysis, the radiative decay time of Nd emission (peaking at 1055 nm) is estimated to be equal to 441 s. The experimental Nd lifetime (under Ar laser excitation) is equal to 19 s. The broad emission band centered at approximately 700 nm ( decay 15 ns) and the Raman scattering with characteristic frequency shift of 1600 cm 1 have been observed at excitation of benzil with 532-nm Q -switched laser pulses. We show that rare-earth-doped benzil can be considered as a potential candidate for luminescent and solid-state laser material.

Optical Studies of Nd-doped benzil, a potential luminescent and laser material.

PubMed

Noginov, M A; Curley, M; Noginova, N; Wang, W S; Aggarwal, M D

1998-08-20

Neodymium-doped benzil crystals have been synthesized and characterized for their absorption, emission, and kinetics properties. From Judd-Ofelt analysis, the radiative decay time of Nd emission (peaking at 1055 nm) is estimated to be equal to 441 mus. The experimental Nd lifetime (under Ar+ laser excitation) is equal to 19 mus. The broad emission band centered at approximately 700 nm (tau(decay) approximately 15 ns) and the Raman scattering with characteristic frequency shift of 1600 cm(-1) have been observed at excitation of benzil with 532-nm Q-switched laser pulses. We show that rare-earth-doped benzil can be considered as a potential candidate for luminescent and solid-state laser material.

Synthesis and photoluminescence of ultra-pure germanium nanoparticles

NASA Astrophysics Data System (ADS)

Chivas, R.; Yerci, S.; Li, R.; Dal Negro, L.; Morse, T. F.

2011-09-01

We have used aerosol deposition to synthesize defect and micro-strain free, ultra-pure germanium nanoparticles. Transmission electron microscopy images show a core-shell configuration with highly crystalline core material. Powder X-ray diffraction measurements verify the presence of highly pure, nano-scale germanium with average crystallite size of 30 nm and micro-strain of 0.058%. X-ray photoelectron spectroscopy demonstrates that GeO x ( x ⩽ 2) shells cover the surfaces of the nanoparticles. Under optical excitation, these nanoparticles exhibit two separate emission bands at room temperature: a visible emission at 500 nm with 0.5-1 ns decay times and an intense near-infrared emission at 1575 nm with up to ˜20 μs lifetime.

Combustion synthesis of MgO nanoparticles using plant extract: Structural characterization and photoluminescence studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Danith; Chikkahanumantharayappa; Yadav, L. S. Reddy

Magnesium oxide nanoparticles (MgO Nps) have been successfully synthesized via solution combustion method using Parthenium plant extract as fuel for the first time. Powder X-ray diffraction (PXRD) pattern reveal that product belongs to the cubic phase (Periclase). FTIR spectrum shows the band at 822 cm{sup −1} indicates the formation of cubic periclase MgO. The optical band gap of MgO Nps estimated from UV –Vis spectrum was found to be in the range 5.40–5.45 eV. SEM images showed that, the product is agglomerated and particle in nature. Photoluminescence (PL) studies shows violet emission at 390 nm, blue emission at 470 nm and green emissionmore » at 550 nm. MgO Nps shows good photocatalytic activity for the degradation of methylene blue (MB) dye under UV/Sun light irradiation.« less

Hyperspectral Image Analysis for Skin Tumor Detection

NASA Astrophysics Data System (ADS)

Kong, Seong G.; Park, Lae-Jeong

This chapter presents hyperspectral imaging of fluorescence for nonin-vasive detection of tumorous tissue on mouse skin. Hyperspectral imaging sensors collect two-dimensional (2D) image data of an object in a number of narrow, adjacent spectral bands. This high-resolution measurement of spectral information reveals a continuous emission spectrum for each image pixel useful for skin tumor detection. The hyperspectral image data used in this study are fluorescence intensities of a mouse sample consisting of 21 spectral bands in the visible spectrum of wavelengths ranging from 440 to 640 nm. Fluorescence signals are measured using a laser excitation source with the center wavelength of 337 nm. An acousto-optic tunable filter is used to capture individual spectral band images at a 10-nm resolution. All spectral band images are spatially registered with the reference band image at 490 nm to obtain exact pixel correspondences by compensating the offsets caused during the image capture procedure. The support vector machines with polynomial kernel functions provide decision boundaries with a maximum separation margin to classify malignant tumor and normal tissue from the observed fluorescence spectral signatures for skin tumor detection.

Optical absorption and photoluminescence study of nanocrystalline Zn0.92M0.08O (M: Li & Gd)

NASA Astrophysics Data System (ADS)

Punia, Khushboo; Lal, Ganesh; Kumar, Sudhish

2018-05-01

Nanocrystalline samples of Zn0.92Li0.08O and Zn0.92Gd0.08O have been synthesized using citrate sol-gel route without post synthesis annealing and characterized using powder X-ray diffraction (XRD), UV-Vis-NIR and Photoluminescence spectroscopic measurements. Analysis of XRD pattern and PL spectra revealed single phase formation of the nanocrystalline Zn0.92Li0.08O and Zn0.92Gd0.08O in the wurtzite type hexagonal structure with intrinsic crystal and surface defects. UV-Vis-NIR optical absorption measurements show that the maximum photo absorption occurs below 600nm in the UV& visible band. The estimated values of band gap energy were found to be 2.53eV and 2.73eV for Zn0.92Li0.08O and Zn0.92Gd0.08O respectively. The photoluminescence spectra excited at the wavelength 325nm displays two broad peaks in the UV and visible bands centered at ˜416 nm & ˜602 nm for Zn0.92Gd0.08O and ˜406nm & ˜598nm for Zn0.92Li0.08O. Both Gd and Li doping in ZnO leads to considerable decrease in the optical band gap energy and red shifting of the UV emission band towards the visible band.

A dense plasma ultraviolet source

NASA Technical Reports Server (NTRS)

Lee, J. H.; Mcfarland, D. R.

1978-01-01

The intense ultraviolet emission from the NASA Hypocycloidal-Pinch (HCP) plasma is investigated. The HCP consists of three disk electrodes whose cross section has a configuration similar to the cross section of a Mather-type plasma focus. Plasma foci were produced in deuterium, helium, xenon, and krypton gases in order to compare their emission characteristics. Time-integrated spectra in the wavelength range from 200 nm to 350 nm and temporal variations of the uv emission were obtained with a uv spectrometer and a photomultiplier system. Modifications to enhance uv emission in the iodine-laser pump band (250 to 290 nm) and preliminary results produced by these modifications are presented. Finally, the advantages of the HCP as a uv over use of conventional xenon lamps with respect to power output limit, spectral range, and lifetime are discussed.

Potential of solar-induced chlorophyll fluorescence to estimate transpiration in a temperate forest

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Xiaoliang; Liu, Zhunqiao; An, Shuqing

By utilizing continuous measurements of water fluxes and solar-induced chlorophyll fluorescence (SIF) over the entire growing season, we exploit the potential of broadband SIF in predicting plant transpiration (T) in a temperate forest. After reconstructing the full SIF spectrum from the selected absorption lines and simulations from the SCOPE (Soil Canopy Observation Photochemistry and Energy fluxes) model, linear regression (LR) and Gaussian processes regression (GPR) models are used to analyze the relation between T and combinations of different SIF bands. We find that SIF emissions in the near-infrared spectrum (at 720 nm, 740 nm and 760 nm) are more sensitivemore » to T than SIF emissions in the red spectrum (at 685 nm and 687 nm). While conditions such as light and heat stress decouple the relationship between single-band SIF and T, the combination of different SIF bands allows the retrieval of reliable T estimates even in these conditions. Overall, we find that the use of SIF as a proxy for T yields estimates that are at least as accurate as those from traditional transpiration models such as the Penman-Monteith equation, which are input demanding and complex to apply to in situ and satellite data. Specifically, we find that (1) the SIF-T relationship deteriorates when Photosynthetically Active Radiation (PAR), vapor pressure deficit and air temperature exceed biological optimal thresholds; (2) a high leaf area index exerts a negative impact on the SIF-T correlation due to increasing scattering and (re)absorption of the SIF signal; (3) the SIF-T relationship does not change depending on the observation time during the day; and (4) temporal aggregation to days further enhanced the SIF-T correlations. Altogether, our results provide the first ground-based evidence that SIF emission has potential to be a close predictor of plant transpiration, especially when a combination of different SIF bands is considered.« less

[Multiply upconversion emission in oxyfluoride ceramics].

PubMed

Xiao, Si-guo; Yang, Xiao-liang; Liu, Zhen-wei

2003-02-01

Oxyfluoride ceramics with the host composition of SiO2 and PbF2 have been prepared. X-ray diffraction analysis of the ceramics revealed that fluoride type beta-PbF2 solid solution regions are precipitated in the glass matrix. Rare earth ions in the beta-PbF2 solid solution show highly efficient upconversion performance due to the very small multi-phonon relaxation rates. Eight upconversion emission bands whose central wavelength are 846, 803, 665, 549, 523, 487, 456 and 411 nm have been observed when the sample was excited with 930 nm diode light. Four possible energy transfer processes between Er3+ and Yb3+ cause the electronic population of high energy level of Er3+ and realize the abound upconversion luminescence bands.

Pure ultraviolet emission from ZnO quantum dots-based/GaN heterojunction diodes by MgO interlayer

NASA Astrophysics Data System (ADS)

Chen, Cheng; Liang, Renli; Chen, Jingwen; Zhang, Jun; Wang, Shuai; Zhao, Chong; Zhang, Wei; Dai, Jiangnan; Chen, Changqing

2017-07-01

We demonstrate the fabrication and characterization of ZnO/GaN-based heterojunction light-emitting diodes (LEDs) by using air-stable and solution-processable ZnO quantum dots (QDs) with a thin MgO interlayer acting as an electron blocking layer (EBL). The ZnO QDs/MgO/ p-GaN heterojunction can only display electroluminescence (EL) characteristic in reverse bias regime. Under sufficient reverse bias, a fairly pure ultraviolet EL emission located at 370 nm deriving from near band edge of ZnO with a full width at half maximum (FWHM) of 8.3 nm had been obtained, while the deep-level emission had been almost totally suppressed. The EL origination and corresponding carrier transport mechanisms were investigated qualitatively in terms of photoluminescence (PL) results and energy band diagram.[Figure not available: see fulltext.

An analysis of dissolved organic matter from freshwater Karelian Lakes using reversed-phase high-performance liquid chromatography with online absorbance and fluorescence analysis

NASA Astrophysics Data System (ADS)

Khundzhua, D. A.; Patsaeva, S. V.; Trubetskoj, O. A.; Trubetskaya, O. E.

2017-01-01

The spectral and optical properties of the fractionated components of dissolved organic matter (DOM) of three freshwater lakes in Karelia were studied using reversed-phase high-performance liquid chromatography (RP-HPLC) with online detection of fluorescence and absorption spectra. It is shown that the DOM fractions are qualitatively similar, but differ quantitatively in the ratio of components and consist of at least three types of fluorophores: (1) hydrophilic "humic-like" fluorophore(s) with the emission maximum in the region of 420 nm and an absorption band at 260-270 nm; (2) hydrophobic "humic-like" fluorophore(s) with the emission maximum at approximately 450 nm that has no characteristic absorption maxima in the region from 220 to 400 nm; and (3) a "protein-like" fluorophore with the emission maximum in the region of 340-350 nm, which is typical of proteins and peptides containing tryptophan.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu Changle; Qiao Xueliang; Luo Langli

Flower-like ZnO nano/microstructures have been synthesized by thermal treatment of Zn(NH{sub 3}){sub 4}{sup 2+} precursor in aqueous solvent, using ammonia as the structure directing agent. A number of techniques, including X-ray diffraction (XRD), field emission scan electron microscopy (FESEM), transmission electron microscopy (TEM), thermal analysis, and photoluminescence (PL) were used to characterize the obtained ZnO structures. The photoluminescence (PL) measurements indicated that the as-synthesized ZnO structures showed UV ({approx}375 nm), blue ({approx}465 nm), and yellow ({approx}585 nm) emission bands when they were excited by a He-Gd laser using 320 nm as the excitation source. Furthermore, it has been interestingly foundmore » that the intensity of light emission at {approx}585 nm remarkably decreased when the obtained ZnO nanocrystals were annealed at 600 deg. C for 3 h in air. The reason might be the possible oxygen vacancies and interstitials in the sample decreased at high temperature.« less

Excitation of sensitized fluorescence of europium and curium in an aqueous solution of thenoyltrifluoroacetone by a nitrogen laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dem'yanova, T.A.; Stepanov, A.V.; Babaev, A.S.

1987-03-01

The fluorescence spectrum of trivalent europium in aqueous solutions of thenoyltrifluoroacetone, excited by a nitrogen laser with emission wavelength 337 nm, exhibits bands at 582, 593, 616, 650, and 695 nm. Two bands appear in the fluorescence spectrum of trivalent curium under the same conditions - at 598 and 607 nm. The times of quenching of the fluorescence of the ions of these elements were measured, both in H/sub 2/O medium and in D/sub 2/O. A linear relationship was found between the fluorescence intensity of europium and curium and their concentration in TTA solution. The limit of determination of europiummore » and curium by the fluorescent method with laser excitation using the bands at 615 and 607 nm proved equal to 0.3 and 0.07 ng/ml, respectively.« less

Studies on cytostatics used as photosensitizing material in photodynamic therapy

NASA Astrophysics Data System (ADS)

Pascu, Mihail-Lucian; Danaila, Leon; Carstocea, Benone D.; Staicu, Angela; Truica, Sorina; Gazdaru, Doina M.

2002-10-01

Introduction of the photosensitizer properties of cytostatics drus was made, pointing out that the fact that besides the biochemical action of the cytostatics their effects could be enhanced by the exposure to light at different doses. A spectroscopical characterisation of methotrexate and fluorouracil, cytostatic drugs used frequently in cancer therpy was performed. The absorption, emission and excitation spectra were measured for methotrexate solutions in natural saline and sodium hydroxide at concentration in the range 10-5 -10-6M and pH 8.4. The absorption, emission and excitation spectra were measured for fluorouracil solutions in natural saline at concentration in the range 10-4 -10-5M. The absorption spectrum exhibits spectral bands in the range 250nm -450nm for both drugs. The fluorescence excitatioan for methotrexate was made at 340nm and 370nm, the fluorescence emission was detected in the spectral range 400nm - 500nm with a maximum at 470nm. The fluorescence excitation was measured in teh range 200nm-500nm with the emission centred on 530nm, for Xe lamp irradiation, and 300nm for Hg lamp and laser irradiation. The fluorescence emission spectra was monitored in the spectral range 400nm - 600nm. The effects of irradiation on spectroscopic characteristics of methrotrexate and fluorouracil were investigated. The irraditaion was made using a UV classic lamp with Xe, for the first experimental part and for the second one it was used both a class Hg lamp and a nytorgen pulsed laser.

One-pot and ultrafast synthesis of nitrogen and phosphorus co-doped carbon dots possessing bright dual wavelength fluorescence emission

NASA Astrophysics Data System (ADS)

Sun, Xiangcheng; Brückner, Christian; Lei, Yu

2015-10-01

Very brief microwave heating of aniline, ethylene diamine, and phosphoric acid in water at ambient pressure generated nitrogen and phosphorus co-doped carbon dots (N,P-CDs) that exhibit bright dual blue (centred at 450 nm; 51% quantum yield) and green (centred at 510 nm, 38% quantum yield) fluorescence emission bands. The N,P-CDs were characterized using TEM, XRD, XPS, IR, UV-vis, and fluorescence spectroscopy, demonstrating their partially crystalline carbon, partially amorphous structures, and the incorporation of O, N, and P into the carbogenic scaffold. The N,P-CDs demonstrated excitation-dependent and nearly pH-independent emission properties. The unique dual emission properties lay the foundation for the use of N,P-CDs in ratiometric sensing applications.Very brief microwave heating of aniline, ethylene diamine, and phosphoric acid in water at ambient pressure generated nitrogen and phosphorus co-doped carbon dots (N,P-CDs) that exhibit bright dual blue (centred at 450 nm; 51% quantum yield) and green (centred at 510 nm, 38% quantum yield) fluorescence emission bands. The N,P-CDs were characterized using TEM, XRD, XPS, IR, UV-vis, and fluorescence spectroscopy, demonstrating their partially crystalline carbon, partially amorphous structures, and the incorporation of O, N, and P into the carbogenic scaffold. The N,P-CDs demonstrated excitation-dependent and nearly pH-independent emission properties. The unique dual emission properties lay the foundation for the use of N,P-CDs in ratiometric sensing applications. Electronic supplementary information (ESI) available: Detailed experimental section, XRD, FTIR, explosive sensing and the applications results. See DOI: 10.1039/c5nr05549k

Spatial modulation of above-the-gap cathodoluminescence in InP nanowires

NASA Astrophysics Data System (ADS)

Tizei, L. H. G.; Zagonel, L. F.; Tencé, M.; Stéphan, O.; Kociak, M.; Chiaramonte, T.; Ugarte, D.; Cotta, M. A.

2013-12-01

We report the observation of light emission on wurtzite InP nanowires excited by fast electrons. The experiments were performed in a scanning transmission electron microscope using an in-house-built cathodoluminescence detector. Besides the exciton emission, at 850 nm, emission above the band gap from 400 to 800 nm was observed. In particular, this broad emission presented systematic periodic modulations indicating variations in the local excitation probability. The physical origin of the detected emission is not clear. Measurements of the spatial variation of the above-the-gap emission points to the formation of leaky cavity modes of a plasmonic nature along the nanowire length, indicating the wave nature of the excitation. We propose a phenomenological model, which fits closely the observed spatial variations.

Analysis of Sr{sub 5{minus}x}Ba{sub x}(PO{sub 4}){sub 3}F:Yb{sup 3+} crystals for improved laser performance with diode-pumping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schaffers, K.I.; Bayramian, A.J.; Marshall, C.D.

Crystals of Yb{sup 3+}:Sr{sub 1-x}Ba{sub x}(PO{sub 4}){sub 3}F (0 < x < 5) have been investigated as a means to obtain broader absorption bands than are currently available with Yb{sup 3+}:S-FAP [Yb{sup 3+}: Sr{sub 5}(PO{sub 4}){sub 3}F], thereby improving diode-pumping efficiency for high peak power applications. Large diode-arrays have a FWHM pump band of >5 nm while the FWHM of the 900 nm absorption band for Yb:S-FAP is 5.5 nm; therefore, a significant amount of pump power can be wasted due to the nonideal overlap. Spectroscopic analysis of Yb:Sr{sub 5-x}Ba{sub x}-FAP crystals indicates that adding barium to the lattice increasesmore » the pump band to 13-16 run which more than compensates for the diode-array pump source without a detrimental reduction in absorption cross section. However, the emission cross section decreases by approximately half with relatively no effect on the emission lifetime. The small signal gain has also been measured and compared to the parent material Yb:S-FAP and emission cross sections have been determined by the method of reciprocity, the Filchtbauer-Ladenburg method, and small signal gain. Overall, Yb{sup 3+}:Sr{sub 5-x}Ba{sub x}(PO{sub 4}){sub 3}F crystals appear to achieve the goal of nearly matching the favorable thermal and laser performance properties of Yb:S-FAP while having a broader absorption band to better accommodate diode pumping.« less

Direct Band Gap Wurtzite Gallium Phosphide Nanowires

PubMed Central

2013-01-01

The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency. Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong photoluminescence at a wavelength of 594 nm with short lifetime, typical for a direct band gap. Furthermore, by incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555–690 nm). This approach of crystal structure engineering enables new pathways to tailor materials properties enhancing the functionality. PMID:23464761

Effect of tin ions on enhancing the intensity of narrow luminescence line at 311 nm of Gd3+ ions in Li2Osbnd PbOsbnd P2O5 glass system

NASA Astrophysics Data System (ADS)

Gandhi, Y.; Rajanikanth, P.; Sundara Rao, M.; Ravi Kumar, V.; Veeraiah, N.; Piasecki, M.

2016-07-01

This study is mainly focused on enriching the UVB 311 narrow emission band of Gd3+ ions in Li2Osbnd PbOsbnd P2O5 glasses doped with 1.0 mol% of Gd2O3 and mixed with different concentrations of SnO2 (0-7.0 mol%). The emission spectra SnO2 free glasses exhibited intense narrow UVB band at 311 nm due to 6P7/2 → 8S7/2 transition of Gd3+ ions when excited at 273 nm. The intensity of this band is found to be enhanced nearly four times when the glasses are mixed with 3.0 mol% of SnO2. The reasons for this enhancement have been explored in the light of energy transfer from Sn4+ to Gd3+ ions with the help of rate equations. The declustering of Gd3+ ions (that reduce cross relaxation losses) by tin ions is also found to the other reason for such enrichment. The 311 nm radiation is an efficient in the treatment of various skin diseases and currently it is one of the most desirable and commonly utilised UVB in the construction of phototherapy devices.

UV excited downconversion luminescence properties of Eu3+: NaZnPO4 phosphors

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Lakshmi; Rai, Vineet Kumar

2018-05-01

The structural and optical properties of Eu3+: NaZnPO4 phosphors prepared by chemical coprecipitation method have been studied. The phase formation and morphology of the phosphors have been confirmed by the X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM) analysis. The downconversion emission spectra upon 392 nm excitation exhibit five emission bands centred at ˜ 575 nm, ˜ 590 nm, ˜ 612 nm, ˜ 660 nm and ˜ 702 nm corresponding to the 5D0→7F0, 5D0→7F1, 5D0→7F2, 5D0→7F3 and 5D0→7F4 transitions of Eu3+ ions respectively. The observed downconversion emission peaks can be explained with the help of suitable energy level diagram. The CIE chromaticity diagram shows the purity of the emitted colour from the prepared phosphors. The present phosphors emit in intense red region which shows the applicability of the phosphors in red light emitting display devices.

Aqueous based synthesis of N-acetyl-L-cysteine capped ZnSe nanocrystals with intense blue emission

NASA Astrophysics Data System (ADS)

Soheyli, Ehsan; Sahraei, Reza; Nabiyouni, Gholamreza

2016-10-01

In this work a very simple reflux route for preparation of ZnSe nanocrystals with minor modification and faster preparation over conventional ones is introduced. X-ray diffraction analysis indicated that the ZnSe nanocrystals have a cubic structure. The complete disappearance of the S-H band in FT-IR spectrum of N-acetyl-L-cysteine capped ZnSe nanocrystals was an indication over formation of Zn-thiol covalent bonds at the surface of the nanocrystals which results in passivation of small nanocrystals. The strong size-quantization regime was responsible of significant blue shift in absorption/emission spectra. Using the well-known calculations, band gap and Urbach energy of the ZnSe nanocrystals were measured and their average size was estimated optically to be around 4.6 nm along with the TEM image. A dark blue emission with higher relative intensity of excitonic to trap emissions (compared to conventional method), very narrow excitonic emission peak of about 16 nm and remarkable stability was obtained from the ZnSe nanocrystals.

Photoactive platinum(ii) β-diketonates as dual action anticancer agents.

PubMed

Raza, Md Kausar; Mitra, Koushambi; Shettar, Abhijith; Basu, Uttara; Kondaiah, Paturu; Chakravarty, Akhil R

2016-08-16

Platinum(ii) complexes, viz. [Pt(L)(cur)] (1), [Pt(L)(py-acac)] (2) and [Pt(L)(an-acac)] (3), where HL is 4,4'-bis-dimethoxyazobenzene, Hcur is curcumin, Hpy-acac and Han-acac are pyrenyl and anthracenyl appended acetylacetone, were prepared, characterized and their anticancer activities were studied. Complex [Pt(L)(acac)] (4) was used as a control. Complex 1 showed an absorption band at 430 nm (ε = 8.8 × 10(4) M(-1) cm(-1)). The anthracenyl and pyrenyl complexes displayed bands near 390 nm (ε = 3.7 × 10(4) for 3 and 4.4 × 10(4) M(-1) cm(-1) for 2). Complex 1 showed an emission band at 525 nm (Φ = 0.017) in 10% DMSO-DPBS (pH, 7.2), while 2 and 3 were blue emissive (λem = 440 and 435, Φ = 0.058 and 0.045). There was an enhancement in emission intensity on glutathione (GSH) addition indicating diketonate release. The platinum(ii) species thus formed acted as a transcription inhibitor. The released β-diketonate base showed photo-chemotherapeutic activity. The complexes photocleaved plasmid DNA under blue light of 457 nm forming ∼75% nicked circular (NC) DNA with hydroxyl radicals and singlet oxygen as the ROS. Complexes 1-3 were photocytotoxic in skin keratinocyte HaCaT cells giving IC50 of 8-14 μM under visible light (400-700 nm, 10 J cm(-2)), while being non-toxic in the dark (IC50: ∼60 μM). Complex 4 was inactive. Complexes 1-3 generating cellular ROS caused apoptotic cell death under visible light as evidenced from DCFDA and annexin-V/FITC-PI assays. This work presents a novel way to deliver an active platinum(ii) species and a phototoxic β-diketone species to the cancer cells.

Eu2+-Doped Sr2B2-2xSi2+3xAl2-xN8+x: A Boron-Containing Orange-Emitting Nitridosilicate with Interesting Composition-Dependent Photoluminescence Properties.

PubMed

Ten Kate, Otmar M; Xie, Rong-Jun; Wang, Chun-Yun; Funahashi, Shiro; Hirosaki, Naoto

2016-11-07

Novel Sr 2-y Eu y B 2-2x Si 2+3x Al 2-x N 8+x phosphors were investigated as a function of the boron and aluminum over silicon ratio and as a function of the Eu 2+ concentration. Samples were prepared via solid-state reaction synthesis by carefully controlling the synthesis conditions and composition. At high boron and aluminum content, that is, x = 0, a Eu 2+ 5d-4f emission is observed of which the maximum shifts from 595 nm for low Eu concentrations (y = 0.005) toward 623 nm for high Eu concentrations (y = 0.5). The samples can be excited by UV or blue light up to ∼475 nm. Substitution of [B 2 Al] 9+ units by [Si 3 N] 9+ units, increasing x up to 0.15, greatly improves the luminescence efficiency up to 46% and shows a very large redshift of the excitation bands with ∼100 nm, while the emission band shifts with ∼10 nm. The shifts are attributed to the lowering of the 5d level as a result of the decreased Eu-N distance upon substitution. Temperature-dependent measurements show that the Eu 2+ 5d-4f emission is largely thermally quenched at room temperature for x = 0 due to thermal ionization toward the conduction band, explaining the low luminescence efficiency. The lowering of the 5d level at larger values of x reduces the thermal ionization and consequently increases the thermal stability and quantum efficiency, resulting in strongly luminescent blue-to-orange conversion phosphors that are interesting for light-emitting diode applications.

Optical Properties of ZnCdS:I Orange and ZnSTe:I White Thin Film Phosphor for High Ra White LED

NASA Astrophysics Data System (ADS)

Fujii, Satoshi; Tasaki, Norio; Shinomura, Naohiko; Kurai, Satoshi; Yamada, Yoichi; Taguchi, Tsunemasa

In order to develop visible thin film phosphors, we have for the first time prepared ZnCdS and ZnSTe doped with Iodine (I) using low-pressure MOCVD method. ZnCdS:I, of which Cd composition was calibrated to match the lattice constant to that of substrate and the band gap to absorption peak, showed a orange broad emission consist of yellow near band edge emission and red SA emission. Isoelectronic Te in ZnS indicates strong blue-green emissions, whilst I donor impurity in ZnS shows strong red SA emissions. A typical ZnSTe:I thin film shows two broad emission bands locating at around 500 and 680 nm, respectively, indicating Ra˜90. It was shown that high Ra thin film phosphor can be realized by single material (ZnSTe:I), and that MOCVD method is capable for controlling the thickness and doping profile to obtain uniform white emission pattern.

Experimental and theoretical study on emission spectra of a nitrogen photoionized plasma induced by intense EUV pulses

NASA Astrophysics Data System (ADS)

Saber, Ismail; Bartnik, Andrzej; Skrzeczanowski, Wojciech; Wachulak, Przemyslaw; Jarocki, Roman; Fiedorowicz, Henryk; Limpouch, Jiri

2018-01-01

Spectral lines of low-temperature nitrogen photoionized plasma were investigated. The photoionized plasma was created in the result of irradiation N2 gas using laser plasma EUV radiation pulses. The source was based on a 10J/10ns Nd:YAG (λ = 1064 nm) laser system and a gas puff target. The EUV radiation pulses were collected and focused using a grazing incidence multifoil EUV collector. The emission spectra were measured in the ultraviolet and visible (UV/Vis) range. It was found that the plasma emission lines in the lower region of the UV range are relativley weak. Nonetheless, a part of the spectra contains strong molecular band in the 300 - 430 nm originated from second positive and first negative systems band transitions of nitrogen. These molecular band transitions were identified using a code for study the diatomic molecules, LIFBASE. The vibrational band of Δv = 0 and ±1 transitions were significantly populated than of that with Δv = ±2 and 3 transitions. A comparison of the calculated and measured spectrum is presented. With an assumption of a local thermodynamic equilibrium (LTE), the vibrational temperature was determined from the integrated band intensities with the help of the Boltzmann plot method and compared to the temperature predicted by SPECAIR and LIFBASE simulations. A summary of the results and the variations in the vibrational temperatures was discussed.

Response of the upper atmosphere to variations in the solar soft x-ray irradiance. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Bailey, Scott Martin

1995-01-01

Terrestrial far ultraviolet (FUV) airglow emissions have been suggested as a means for remote sensing the structure of the upper atmosphere. The energy which leads to the excitation of FUV airglow emissions is solar irradiance at extreme ultraviolet (EUV) and soft x-ray wavelengths. Solar irradiance at these wavelengths is known to be highly variable; studies of nitric oxide (NO) in the lower thermosphere have suggested a variability of more than an order of magnitude in the solar soft x-ray irradiance. To properly interpret the FUV airflow, the magnitude of the solar energy deposition must be known. Previous analyses have used the electron impact excited Lyman-Birge-Hopfield (LBH) bands of N2 to infer the flux of photoelectrons in the atmosphere and thus to infer the magnitude of the solar irradiance. This dissertation presents the first simultaneous measurements of the FUV airglow, the major atmospheric constituent densities, and the solar EUV and soft x-ray irradiances. The measurements were made on three flights of an identical sounding rocket payload at different levels of solar activity. The linear response in brightness of the LBH bands to variations in solar irradiance is demonstrated. In addition to the N2 LBH bands, atomic oxygen lines at 135.6 and 130.4 nm are also studied. Unlike the LBH bands, these emissions undergo radiative transfer effects in the atmosphere. The OI emission at 135.6 nm is found to be well modeled using a radiative transfer calculation and the known excitation processes. Unfortunately, the assumed processes leading to OI 130.4 nm excitation are found to be insufficient to reproduce the observed variability of this emission. Production of NO in the atmosphere is examined; it is shown that a lower than previously reported variability in the solar soft x-ray irradiance is required to explain the variability of NO.

Hα Monitoring of Early-Type Emission Line Stars

NASA Astrophysics Data System (ADS)

Souza, Steven P.; Boettcher, E.; Wilson, S.; Hosek, M.

2011-05-01

We have begun a narrowband imaging program to monitor Hα emission in early-type stars in young open clusters and associations. A minority of early-type stars, particularly Be stars, show Hα in emission due to extended atmospheres and non-equilibrium conditions. Emission features commonly vary irregularly over a range of timescales (Porter, J.M. & Rivinus, T., P.A.S.P. 115:1153-1170, 2003). Some of the brightest such stars, e.g. γ Cas, have been spectroscopically monitored for Hα variability to help constrain models of the unstable disk, but there is relatively little ongoing monitoring in samples including fainter stars (Peters, G., Be Star Newsletter 39:3, 2009). Our program uses matched 5nm-wide on-band (656nm) and off-band (645nm) filters, in conjunction with the Hopkins Observatory 0.6-m telescope and CCD camera. Aperture photometry is done on all early-type stars in each frame, and results expressed as on-band to off-band ratios. Though wavelength-dependent information is lost compared with spectroscopy, imaging allows us to observe much fainter (and therefore many more) objects. Observing young clusters, rather than individual target stars, allows us to record multiple known and candidate emission line stars per frame, and provides multiple "normal" reference stars of similar spectral type. Observations began in the summer of 2010. This project has the potential to produce significant amounts of raw data, so a semi-automated data reduction process has been developed, including astrometric and photometric tasks. Early results, including some preliminary light curves and recovery of known Be stars at least as faint as R=13.9, are presented. We gratefully acknowledge support for student research through an REU grant to the Keck Northeast Astronomy Consortium from the National Science Foundation, and from the Division III Research Funding Committee of Williams College.

Broad emission band of Yb3+ in the nonlinear Nb:RbTiOPO4 crystal: origin and applications.

PubMed

Carvajal, J J; Ciatto, G; Mateos, X; Schmidt, A; Griebner, U; Petrov, V; Boulon, G; Brenier, A; Peña, A; Pujol, M C; Aguiló, M; Díaz, F

2010-03-29

By means of micro-structural and optical characterization of the Yb:Nb:RbTiOPO(4) crystal, we demonstrated that the broad emission band of Yb(3+) in these crystals is due to the large splitting of the ytterbium ground state only, and not to a complex multisite occupation by the ytterbium ions in the crystals. We used this broad emission band to demonstrate wide laser tuning range and generation of femtosecond laser pulses. Passive mode-locked laser operation has been realized by using a semiconductor saturable absorber mirror, generating ultra short laser pulses of 155 fs, which were very stable in time, under Ti:sapphire laser pumping at 1053 nm.

Ho3+-Yb3+ codoped tellurite based glasses in visible lasers and optical devices: Judd-Ofelt analysis and frequency upconversion

NASA Astrophysics Data System (ADS)

Azam, Mohd; Rai, Vineet Kumar

2017-04-01

The optical absorption and frequency upconversion emission in the Ho3+/Yb3+ codoped TeO2-ZnO (TZ), TeO2-ZnO-WO3 (TZW) and TeO2-ZnO-WO3-TiO2 (TZWTi) glasses prepared by melting and quenching method has been studied. Judd-Ofelt theory has been used to calculate the Judd-Ofelt intensity parameters (Ω2, Ω4 and Ω6), transition probabilities, radiative lifetimes, absorption cross sections and the branching ratios. Upconversion (UC) emission bands centered at ∼ 549 nm, ∼658 nm and ∼754 nm are observed upon 980 nm excitation. On codoping with the Yb3+ ions at 3.0 mol% the upconversion emission intensity enhancement of about ∼57 times, ∼342 times and ∼480 times for the green band whereas for the red band arising from the Ho3+ ions it is about ∼71 times, ∼438 times and ∼707 times respectively have been observed. The enhancement observed in the UC emission intensity is explained on the basis of efficient energy transfer from Yb3+ to Ho3+, larger absorption cross section, larger oscillator strengths and increase in the local field corrections factor. The spectroscopic quality factor Ω4/Ω6 has been calculated to get the information about the developed materials for laser applications. The upconversion emission cross section determined on the basis of Judd-Ofelt analysis is found to be maximum for Ho-Yb-TZWTi glass. The nephelauxetic ratio, bonding and covalency parameters have been calculated to know the nature of bonding between the rare earth ions and neighbouring oxygen atoms. The high color purity 83.8% has been reported in the codoped glasses at ∼81.2 W/cm2 pump power density.

Preparation of Cu-doped nickel oxide thin films and their properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gowthami, V.; Meenakshi, M.; Anandhan, N.

2014-04-24

Copper doped Nickel oxide film was preferred on glass substrate by simple nebulizer technique keeping the substrate temperature at 350°C and characterized by X-ray diffraction (XRD), Photoluminescence (PL) and Four probe resistivity measurements. XRD studies indicated cubic structure and the crystallites are preferentially oriented along the [111] direction. Interesting results have been obtained from the study of PL spectra. A peak corresponding to 376nm in the emission spectra for 0%, 5% and 10% copper doped samples. The samples show sharp and strong UV emission corresponding to the near band edge emission under excitation of 275nm.

Spectroscopy of high index contrast Yb:Ta2O5 waveguides for lasing applications

NASA Astrophysics Data System (ADS)

Aghajani, A.; Murugan, G. S.; Sessions, N. P.; Apostolopoulos, V.; Wilkinson, J. S.

2015-06-01

Ytterbium-doped waveguides are required for compact integrated lasers and Yb- doped Ta2O5 is a promising candidate material. The design, fabrication and spectroscopic characterisation of Yb:Ta2O5 rib waveguides are described. The peak absorption cross-section was measured to be 2.75×10-20 cm2 at 975 nm. The emission spectrum was found to have a fluorescence emission peak at a wavelength of 976 nm with a peak cross-section of 2.9×10-20 cm2 and a second broad fluorescence band spanning from 990 nm to 1090 nm. The excited- state life time was measured to be 260 μs.

Synthesis, Structural Characterization and Up-Conversion Luminescence Properties of NaYF4:Er3+,Yb3+@MOFs Nanocomposites

NASA Astrophysics Data System (ADS)

Giang, Lam Thi Kieu; Marciniak, Lukasz; Huy, Tran Quang; Vu, Nguyen; Le, Ngo Thi Hong; Binh, Nguyen Thanh; Lam, Tran Dai; Minh, Le Quoc

2017-10-01

This paper describes a facile synthesis of NaYF4:Er3+,Yb3+ nanoparticles embraced in metal-organic frameworks (MOFs), known as NaYF4:Er3+, Yb3+@MOFs core/shell nanostructures, by using iron(III) carboxylate (MIL-100) and zeolitic imidazolate frameworks (ZIF-8). Morphological, structural and optical characterization of these nanostructures were investigated by field emission-scanning electron microscopy, Fourier transform infrared spectroscopy, x-ray diffraction, and up-conversion luminescence measurements. Results showed that spherical-shaped NaYF4:Er3+,Yb3+@MIL-100 nanocomposites with diameters of 150-250 nm, and rod-shaped NaYF4:Er3+,Yb3+@ZIF-8 nanocomposites with lengths of 300-550 nm, were successfully synthesized. Under a 980-nm laser excitation at room temperature, the NaYF4:Er3+,Yb3+@MOFs nanocomposites exhibited strong up-conversion luminescence with two emission bands in the green part of spectrum at 520 nm and 540 nm corresponding to the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions of Er3+ ions, respectively, and a red emission band at 655 nm corresponding to the 4F9/2 → 4I15/2 transition of Er3+ ions. The above properties of NaYF4:Er3+,Yb3+@MOFs make them promising candidates for applications in biotechnology.

Synthesis, crystal structure, photoluminescence and electrochemical properties of a sandwiched Ni2Ce complex

NASA Astrophysics Data System (ADS)

Güngör, Seyit Ali; Kose, Muhammet

2017-12-01

In this study, a Ni2Ce complex [(NiL)2Ce(NO3)2](NO3) was synthesized and characterized by spectroscopic and analytical methods. The structure of the complex was determined by single crystal X-ray diffraction study. In the structure of the complex, a Ce(III) ion is sandwiched between the two NiL units, which are virtually parallel to each other. The Ce(III) center is 12-coordinate, surrounded by 12 oxygen atoms; four are from phenolic groups, four from methoxy groups, and four from two bidentate nitrate ligands. Hirshfeld surface analysis was used to evaluate the inter-molecular interactions within the crystal packing. The complex molecules are linked by H⋯ONO2 interactions. The largest contribution is H⋯O/O⋯H with 41.6% contribution and followed by H⋯H contacts with 39.1%. The complex showed an excitation band in the range of 510-580 nm. A band in the range of 520-580 nm observed in the emission spectrum almost completely overlapped. This suggests that the band in the emission spectrum of the complex is not the actual fluorescence emission and is assigned to the Rayleigh scattering band. Electrochemical and thermal behaviours of the complex were also investigated.

Leaf Level Chlorophyll Fluorescence Emission Spectra: Narrow Band versus Full 650-800 nm Retrievals

NASA Astrophysics Data System (ADS)

Middleton, E.; Zhang, Q.; Campbell, P. K.; Huemmrich, K. F.; Corp, L.; Cheng, Y.

2012-12-01

Recently, chlorophyll fluorescence (ChlF) retrievals in narrow spectral regions (< 1 nm, between 750-770 nm) of the near infrared (NIR) region of Earth's reflected radiation have been achieved from satellites, including the Japanese GOSAT and the European Space Agency's Sciamachy/Envisat. However, these retrievals sample the total full-spectrum ChlF and are made at non-optimal wavelengths since they are not located at the peak fluorescence emission features. We wish to estimate the total full-spectrum ChlF based on emissions obtained at selected wavelengths. For this, we drew upon leaf emission spectra measured on corn leaves obtained from a USDA experimental cornfield in MD (USA). These emission spectra were determined for the adaxial and abaxial (i.e., top and underside) surfaces of leaves measured throughout the 2008 and 2011 growing seasons (n>400) using a laboratory instrument (Fluorolog-3, Horiba Scientific, USA), recorded in either 1 nm or 5 nm increments with monochromatic excitation wavelengths of either 532 or 420 nm. The total ChlF signal was computed as the area under the continuous spectral emission curves, summing the emission intensities (counts per second) per waveband. The individual narrow (1 or 5 nm) waveband emission intensities were linearly related to full emission values, with variable success across the spectrum. Equations were developed to estimate total ChlF from these individual wavebands. Here, we report the results for the average adaxial/abaxial emissions. Very strong relationships were achieved for the relatively high fluorescence intensities at the red chlorophyll peak, centered at 685 nm (r2= 0.98, RMSE = 5.53 x 107 photons/s) and in the nearby O2-B atmospheric absorption feature centered at 688 nm (r2 = 0.94, RMSE = 4.04 x 107), as well as in the far-red peak centered at 740 nm (r2=0.94, RMSE = 5.98 x107). Very good retrieval success occurred for the O2-A atmospheric absorption feature on the declining NIR shoulder centered at 760 nm (r2 = 0.88, RMSE = 7.54 x 107). When perfect retrievals were assumed (0% noise), retrievals remained good in the low emission regions on either side of the peaks-- those associated with the H alpha line at 655 nm (r2 = 0.83, RMSE =8.87 x 107) and the far-NIR wavelengths recently utilized for satellite retrievals: a K line at 770 nm (r2 = 0.85, RMSE = 8.36 x 107) and the 750-770 nm interval (r2 = 0.88, RMSE = 6.92 x 107). However, the atmosphere and satellite observations are expected to add noise to retrievals. Adding 5% random error to these relationships did not seriously impair the retrieval successes in the red and far-red peaks (r2 ~ 0.85, RMSEs = 6.31 x 107). A greater impact occurred (reducing retrieval success by ~10%) when adding 5% noise for the far-NIR narrow band at 770 nm (r2 ~ 0.70, RMSE ~ 8.5 x 107). When a 10% random error was added, the retrieval successes fell to ~68 ± 7% for all retrieval wavebands, and RMSEs increased by a factor of 10. This laboratory approach will be critical to calibrate space borne retrievals, but additional information across plant species is needed. Furthermore, this experiment indicates that ChlF retrievals from space should include information from the red and far-red peak emission regions, since the true total fluorescence signal is the desired parameter for Earth carbon and energy budgets.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xinmin, E-mail: zhxmuga@163.com; Pan, Qi; Kim, Sun Il

Graphical abstract: - Highlights: • Emission spectrum at 20 K confirms that Eu{sup 2+} ions occupy three sites. • Decay curves of three types of Eu{sup 2+} reflect the characteristics of energy transfer. • The Eu(I) emission is thermally quenched at 323 K. • Ca{sub 3}Mg{sub 3}(PO{sub 4}){sub 4}:Eu{sup 2+} has good thermal stability. • Ca{sub 3}Mg{sub 3}(PO{sub 4}){sub 4}:Eu{sup 2+} is a promising phosphor for near UV excited white LEDs. - Abstract: A blue-emitting phosphor Ca{sub 3}Mg{sub 3}(PO{sub 4}){sub 4}:Eu{sup 2+} peaking at 450 nm was synthesized by a solid state reaction. The XRD patterns, luminescence properties, decay curvesmore » of samples as well as their thermal quenching and comparing the luminescence properties with that of commercial material were investigated. At 20 K, the emission spectrum exhibiting two distinct bands peaking at 437 and 473 nm with a shoulder peak at 510 nm can be attributed to the overlap of Eu(I), Eu(II) and Eu(III) emission bands. At 423 K the PL intensity decreases to 80% of the value at room temperature, and the emission wavelength shifts toward high energy. The derived activation energy indicates that the lowest energy level of the Eu{sup 2+} 4f{sup 6}5d{sup 1} state is well isolated from the host lattice conduction band. The PL spectra and chromaticity coordinates are close to those of BAM. Ca{sub 3}Mg{sub 3}(PO{sub 4}){sub 4}:Eu{sup 2+} could be a potential candidate for near-UV excited white LEDs.« less

Tunable optical properties of some rare earth elements-doped mayenite Ca12Al14O33 nanopowders elaborated by oxalate precursor route

NASA Astrophysics Data System (ADS)

Rashad, Mohamed M.; Mostafa, Ahmed G.; Mwakikunga, Bonex W.; Rayan, Diaa A.

2017-01-01

Rare earth (RE) ions-doped mayenite Ca12Al14- x RE x O33 nanopowders (where RE = La and Gd and x = 0-1.0) were synthesized using the oxalate precursor technique. The as-prepared precursors were calcined at 800 °C for 2 h. Obviously, all RE-doped Ca12Al14- x RE x O33 possessed a well-crystalline cubic mayenite phase till RE content of 0.8. The crystallo-chemical aspects including crystallite size, lattice parameters, theoretical X-ray density and bulk density were robustly on RE nature and ratio. The microstructure and the average grain size were significantly influenced by the RE kind and content. The high transparency of Ca12Al14- x RE x O33 over 80% was found to be evinced in the visible wavelength range of 400-800 nm. Besides, the incorporation of RE cation minimized the direct band gap energy from 4.42 eV for pure mayenite to 3.85 and 3.59 eV with x value 1.0 of La3+ and Gd3+ ions. The photoluminescence spectra of pure mayenite nanoparticles showed that the band edge emission ( λ exc = 248 nm) with an intense visible emission band at 360 nm was detected. Otherwise, the band edge emission showed a slight shift toward short wavelength due to the substitution Al3+ by RE3+ ions. Such results open a new avenue for application of mayenite as a good candidate for transparent low-temperature electron conductor for optoelectronics applications.

Tuning the photoluminescence of graphene quantum dots through the charge transfer effect of functional groups.

PubMed

Jin, Sung Hwan; Kim, Da Hye; Jun, Gwang Hoon; Hong, Soon Hyung; Jeon, Seokwoo

2013-02-26

The band gap properties of graphene quantum dots (GQDs) arise from quantum confinement effects and differ from those in semimetallic graphene sheets. Tailoring the size of the band gap and understanding the band gap tuning mechanism are essential for the applications of GQDs in opto-electronics. In this study, we observe that the photoluminescence (PL) of the GQDs shifts due to charge transfers between functional groups and GQDs. GQDs that are functionalized with amine groups and are 1-3 layers thick and less than 5 nm in diameter were successfully fabricated using a two-step cutting process from graphene oxides (GOs). The functionalized GQDs exhibit a redshift of PL emission (ca. 30 nm) compared to the unfunctionalized GQDs. Furthermore, the PL emissions of the GQDs and the amine-functionalized GQDs were also shifted by changes in the pH due to the protonation or deprotonation of the functional groups. The PL shifts resulted from charge transfers between the functional groups and GQDs, which can tune the band gap of the GQDs. Calculations from density functional theory (DFT) are in good agreement with our proposed mechanism for band gap tuning in the GQDs through the use of functionalization.

Luminescence properties of Sr2Mg3P4O15:Mn2+ phosphor and the improvement by co-doping Bi3+

NASA Astrophysics Data System (ADS)

Cao, Renping; Wang, Wudi; Zhang, Jinlong; Ye, Yujiao; Chen, Ting; Guo, Siling; Xiao, Fen; Luo, Zhiyang

2018-05-01

Sr2Mg3P4O15:R (R = Bi3+, Mn2+, and Bi3+/Mn2+) phosphors are synthesized by a solid-state reaction method in air. Sr2Mg3P4O15:Bi3+ phosphor with excitation 380 nm shows blue light and its emission band peaking at ∼445 nm is observed. Under excitation at 355 and 416 nm, Sr2Mg3P4O15:Mn2+ phosphor shows red emission with a single broad emission band peaking at ∼630 nm in the range of 500-800 nm owing to the 4T1(G) → 6A1 transition of the Mn2+ ion. The optimal Mn2+ ion content in Sr2Mg3P4O15:Mn2+ phosphor is ∼0.05 and the lifetime of Sr2Mg2.95P4O15:0.05Mn2+ phosphor is ∼6.17 ms. After Bi3+ ion is co-doped, emission intensity of Sr2Mg3P4O15:Mn2+ phosphor can be enhanced obviously due to energy transfer (ET) from Bi3+ to Mn2+, which is confirmed by the luminescence properties and lifetimes of Sr2Mg3-xP4O15:Bi3+, Mn2+ phosphor. Luminous mechanism and ET process of Sr2Mg3-xP4O15:Bi3+, Mn2+ phosphor are explained by the simple energy level diagram of Bi3+ and Mn2+ ions.

Compositional dependence of broadband near-infrared downconversion and upconversion of Yb3+-doped multi-component glasses

NASA Astrophysics Data System (ADS)

Zhang, Liaolin; Xia, Yu; Shen, Xiao; Wei, Wei

2017-07-01

Yb3+ single-doped glasses show a strong excitation band in the 300-400 nm region, and efficiently emit photons with wavelengths of 920-1150 nm, and have potential applications in solar cells operating in an extraterrestrial situation. In this work, we systematically study the broadband near-infrared downconversion and upconversion of Yb3+-doped silicate, germanate, phosphate, tellurite and tungsten tellurite glasses. All samples show a broad excitation band in the 300-400 nm range, which is attributed to the charge transfer of the Yb3+-O2- couple. The position of the charge transfer band (CTB) shifts from 300 nm to longer wavelengths around 350 nm when the length of the R-O(Si, P, Ge, Te) increases. The longer R-O gives rise to a smaller central void for Yb3+, thus resulting in a small proportion of Yb3+ ions, thus leading to the blue-shift of the CTB. A smaller proportion of Yb3+ in silicate glasses causes in the strongest upconversion emission at 500 nm.

Nd3+/Yb3+ cascade-sensitized single-band red upconversion emission in active-core/active-shell nanocrystals.

PubMed

Ding, M Y; Hou, J J; Yuan, Y J; Bai, W F; Lu, C H; Xi, J H; Ji, Z G; Chen, D Q

2018-08-24

Lanthanide-doped upconversion nanomaterials (UCNMs) have promoted extensive interest for its biological research and biomedical applications, benefiting from low autofluorescence background, deep light penetration depth, and minimal photo-damage to biological tissues. However, owing to the 980 nm laser-induced overheating issue and the attenuation effect associated with conventional multi-peak emissions, the usage of UCNMs as fluorescent bioprobes is still limited. To address these issues, an effective strategy has been proposed to tune both the excitation and emission peaks of UCNMs into the first biological window (650 ∼ 900 nm), where the light absorption by water and hemoglobin in biological tissues is minimal. Based on the Nd 3+ /Yb 3+ cascade-sensitized upconversion process and efficient exchange-energy transfer between Mn 2+ and Er 3+ in conjunction with the active-core@active-shell nanostructured design, we have developed a new class of upconversion nanoparticles (UCNPs) that exhibit strong single-band red emission upon excitation of an 808 nm near-infrared laser. Hopefully, the well-designed KMnF 3 :Yb/Er/Nd@ KMnF 3 :Yb/Nd core-shell nanocrystals will be considered a promising alternative to conventionally used UCNPs for biolabeling applications without the concern of the overheating issue and the attenuation constraints.

Exploring high power, extreme wavelength operating potential of rare-earth-doped silica fiber

NASA Astrophysics Data System (ADS)

Zhou, Pu; Li, Ruixian; Xiao, Hu; Huang, Long; Zhang, Hanwei; Leng, Jinyong; Chen, Zilun; Xu, Jiangmin; Wu, Jian; Wang, Xiong

2017-08-01

Ytterbium-doped fiber laser (YDFL) and Thulium doped fiber laser (TDFL) have been two kinds of the most widely studied fiber laser in recent years. Although both silica-based Ytterbium-doped fiber and Thulium doped fiber have wide emission spectrum band (more than 200 nm and 400 nm, respectively), the operation spectrum region of previously demonstrated high power YDFL and TDFL fall into 1060-1100 nm and 1900-2050nm. Power scaling of YDFL and TDFL operates at short-wavelength or long-wavelength band, especially for extreme wavelength operation, although is highly required in a large variety of application fields, is quite challenging due to small net gain and strong amplified spontaneous emission (ASE). In this paper, we will present study on extreme wavelength operation of high power YDFL and TDFL in our group. Comprehensive mathematical models are built to investigate the feasibility of high power operation and propose effective technical methods to achieve high power operation. We have achieved (1) Diodepumped 1150nm long wavelength YDFL with 120-watt level output power (2) Diode-pumped 1178nm long wavelength YDFL operates at high temperature with 30-watt level output power (3) Random laser pumped 2153nm long wavelength TDFL with 20-watt level output power (4) Diode-pumped 1018nm short wavelength YDFL with a record 2 kilowatt output power is achieved by using home-made fiber combiner.

Enhanced photoemission from glancing angle deposited SiOx-TiO2 axial heterostructure nanowire arrays

NASA Astrophysics Data System (ADS)

Dhar, J. C.; Mondal, A.; Singh, N. K.; Chattopadhyay, K. K.

2013-05-01

The glancing angle deposition technique has been employed to synthesize SiOx-TiO2 heterostructure nanowire (NW) arrays on indium tin oxide (ITO) coated glass substrate. A field emission gun scanning electron microscopic image shows that the average diameter of the NWs is ˜50 nm. Transmission electron microscopy images show the formation of heterostructure NWs, which consist of ˜180 nm SiOx and ˜210 nm long TiO2. The selected-area electron diffraction shows the amorphous nature of the synthesized NWs, which was also confirmed by X-ray diffraction method. The main band absorption edges at 3.5 eV were found for both the SiOx-TiO2 and TiO2 NW arrays on ITO coated glass plate from optical absorption measurement. Ti3+ defect related sub-band gap transition at 2.5 eV was observed for TiO2 NWs, whereas heterostructure NWs revealed the SiOx optical band gap related transition at ˜2.2 eV. Two fold improved photon absorption as well as five times photoluminescence emission enhancement were observed for the SiOx-TiO2 multilayer NWs compared to TiO2 NWs.

First Look at the 3-channel Photometer Data from RENU2

NASA Astrophysics Data System (ADS)

Hecht, J. H.; Brinkman, D. G.; Clemmons, J. H.; Walterscheid, R. L.; Evans, J. S.; Fritz, B.; Lessard, M.

2016-12-01

The Rocket Experiment for Neutral Upwelling-2 (RENU2) rocket launched north towards the cusp region from Andoya, Norway at 735 UT on December 12th 2015. It included a 3-channel forward looking photometer which included narrow-band interference filters at the following wavelengths: (1) 391.4 nm to measure the relatively bright N2+(0,0) band, primarily excited in cusp aurora via resonant scattering of solar light, (2) 557.7 nm, the auroral green line, which is seen in both dayglow emission (very weakly) and when auroral precipitation is present, and (3) 630.0 nm, the auroral redline, which is also excited in the dayglow and by low energy auroral electrons typically present in the cusp. Averaging over the 2 seconds, to minimize out the rocket spin modulation, revealed a volume emission rate profile as a function of altitude that showed dayglow and resonant scattering emission from all three features on the up leg before the cusp aurora region was entered, and a combination of this and auroral emission on the down leg. Noteworthy on the down leg was a sudden increase in the 391.4 nm emission strongly suggestive of an increase in N2+ ions above the rocket. The data are compared to results of AURIC and B3C model runs where electron data from the EPLAS instrument were used to provide the electron spectra. This comparison revealed information not only about the N2+ ion and atomic oxygen density but also showed, via the effects of the different lifetime of the red and green emissions, that there were many short timescale bursts of precipitation lasting much less than 1 second.

Space- and Ground-based Coronal Spectro-Polarimetry

NASA Astrophysics Data System (ADS)

Fineschi, Silvano; Bemporad, Alessandro; Rybak, Jan; Capobianco, Gerardo

This presentation gives an overview of the near-future perspectives of ultraviolet and visible-light spectro-polarimetric instrumentation for probing coronal magnetism from space-based and ground-based observatories. Spectro-polarimetric imaging of coronal emission-lines in the visible-light wavelength-band provides an important diagnostics tool of the coronal magnetism. The interpretation in terms of Hanle and Zeeman effect of the line-polarization in forbidden emission-lines yields information on the direction and strength of the coronal magnetic field. As study case, this presentation will describe the Torino Coronal Magnetograph (CorMag) for the spectro-polarimetric observation of the FeXIV, 530.3 nm, forbidden emission-line. CorMag - consisting of a Liquid Crystal (LC) Lyot filter and a LC linear polarimeter - has been recently installed on the Lomnicky Peak Observatory 20cm Zeiss coronagraph. The preliminary results from CorMag will be presented. The linear polarization by resonance scattering of coronal permitted line-emission in the ultraviolet (UV)can be modified by magnetic fields through the Hanle effect. Space-based UV spectro-polarimeters would provide an additional tool for the disgnostics of coronal magnetism. As a case study of space-borne UV spectro-polarimeters, this presentation will describe the future upgrade of the Sounding-rocket Coronagraphic Experiment (SCORE) to include the capability of imaging polarimetry of the HI Lyman-alpha, 121.6 nm. SCORE is a multi-wavelength imager for the emission-lines, HeII 30.4 nm and HI 121.6 nm, and visible-light broad-band emission of the polarized K-corona. SCORE has flown successfully in 2009. This presentation will describe how in future re-flights SCORE could observe the expected Hanle effect in corona with a HI Lyman-alpha polarimeter.

The UV photochemistry of C2N2

NASA Technical Reports Server (NTRS)

Halpern, Joshua B.; Barts, Samuel A.

1989-01-01

The absorption, emission, and photodissociation yield spectra of C2N2 were measured in the 220 and 210 nm region near the 4(0)1 and 1(0)1 4(0)1 bands of the A 1 sigma + from the X 1 sigma + system. The emission spectrum showed very few lines which appeared in the absorption spectrum. Moreover, the emission had 660 ns lifetime and, at 210 nm a very large electronic emission quenching rate. Laser induced fluorescence was used to measure the relative yield of CN radicals as a function of photolysis wavelength. This spectrum seemed to follow the absorption spectrum below the dissociation threshold. Energy in the CN fragments appeared to be statistically distributed.

Ho:YAG Single Crystal Fiber: Fabrication and Optical Characterization

DTIC Science & Technology

2014-06-16

between the 5I8 and 5I7 energy levels. The results verified the absorption peaks suitable for in- band direct pumping at 1908 nm and 1932 nm with the...Efficient high-power Ho:YAG laser directly in- band pumped by a GaSb -based laser diode stack at 1.9 μm,” Appl. Phys. B 106(2), 315–319 (2012). 21. M...characterized for its optical absorption and emission properties involving transitions between the 5I8 and 5I7 energy levels. The results verified

Experimental determination of the absorption cross-section and molar extinction coefficient of CdSe and CdTe nanowires.

PubMed

Protasenko, Vladimir; Bacinello, Daniel; Kuno, Masaru

2006-12-21

Absorption cross-sections and corresponding molar extinction coefficients of solution-based CdSe and CdTe nanowires (NWs) are determined. Chemically grown semiconductor NWs are made via a recently developed solution-liquid-solid (SLS) synthesis, employing low melting Au/Bi bimetallic nanoparticle "catalysts" to induce one-dimensional (1D) growth. Resulting wires are highly crystalline and have diameters between 5 and 12 nm as well as lengths exceeding 10 microm. Narrow diameters, below twice the corresponding bulk exciton Bohr radius of each material, place CdSe and CdTe NWs within their respective intermediate to weak confinement regimes. Supporting this are solution linear absorption spectra of NW ensembles showing blue shifts relative to the bulk band gap as well as structure at higher energies. In the case of CdSe, the wires exhibit band edge emission as well as strong absorption/emission polarization anisotropies at the ensemble and single-wire levels. Analogous photocurrent polarization anisotropies have been measured in recently developed CdSe NW photodetectors. To further support fundamental NW optical/electrical studies as well as to promote their use in device applications, experimental absorption cross-sections are determined using correlated transmission electron microscopy, UV/visible extinction spectroscopy, and inductively coupled plasma atomic emission spectroscopy. Measured CdSe NW cross-sections for 1 microm long wires (diameters, 6-42 nm) range from 6.93 x 10(-13) to 3.91 x 10(-11) cm2 at the band edge (692-715 nm, 1.73-1.79 eV) and between 3.38 x 10(-12) and 5.50 x 10(-11) cm2 at 488 nm (2.54 eV). Similar values are obtained for 1 microm long CdTe NWs (diameters, 7.5-11.5 nm) ranging from 4.32 x 10(-13) to 5.10 x 10(-12) cm2 at the band edge (689-752 nm, 1.65-1.80 eV) and between 1.80 x 10(-12) and 1.99 x 10(-11) cm2 at 2.54 eV. These numbers compare well with previous theoretical estimates of CdSe/CdTe NW cross-sections far to the blue of the band edge, having order of magnitude values of 1.0 x 10(-11) cm2 at 488 nm. In all cases, experimental NW absorption cross-sections are 4-5 orders of magnitude larger than those for corresponding colloidal CdSe and CdTe quantum dots. Even when volume differences are accounted for, band edge NW cross-sections are larger by up to a factor of 8. When considered along with their intrinsic polarization sensitivity, obtained NW cross-sections illustrate fundamental and potentially exploitable differences between 0D and 1D materials.

Near-infrared fluorescence amplified organic nanoparticles with aggregation-induced emission characteristics for in vivo imaging

NASA Astrophysics Data System (ADS)

Geng, Junlong; Zhu, Zhenshu; Qin, Wei; Ma, Lin; Hu, Yong; Gurzadyan, Gagik G.; Tang, Ben Zhong; Liu, Bin

2013-12-01

Near-infrared (NIR) fluorescence signals are highly desirable to achieve high resolution in biological imaging. To obtain NIR emission with high brightness, fluorescent nanoparticles (NPs) are synthesized by co-encapsulation of 2,3-bis(4-(phenyl(4-(1,2,2-triphenylvinyl)phenylamino)phenyl)fumaronitrile (TPETPAFN), a luminogen with aggregation-induced emission (AIE) characteristics, and a NIR fluorogen of silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) (NIR775) using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] as the encapsulation matrix. The good spectral overlap between the emission of TPETPAFN and the absorption of NIR775 leads to efficient energy transfer, resulting in a 47-fold enhancement of the NIR775 emission intensity upon excitation of TPETPAFN at 510 nm as compared to that upon direct excitation of NIR775 at 760 nm. The obtained fluorescent NPs show sharp NIR emission with a band width of 20 nm, a large Stokes shift of 275 nm, good photostability and low cytotoxicity. In vivo imaging study reveals that the synthesized NPs are able to provide high fluorescence contrast in live animals. The Förster resonance energy transfer strategy overcomes the intrinsic limitation of broad emission spectra for AIE NPs, which opens new opportunities to synthesize organic NPs with high brightness and narrow emission for potential applications in multiplex sensing and imaging.Near-infrared (NIR) fluorescence signals are highly desirable to achieve high resolution in biological imaging. To obtain NIR emission with high brightness, fluorescent nanoparticles (NPs) are synthesized by co-encapsulation of 2,3-bis(4-(phenyl(4-(1,2,2-triphenylvinyl)phenylamino)phenyl)fumaronitrile (TPETPAFN), a luminogen with aggregation-induced emission (AIE) characteristics, and a NIR fluorogen of silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) (NIR775) using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] as the encapsulation matrix. The good spectral overlap between the emission of TPETPAFN and the absorption of NIR775 leads to efficient energy transfer, resulting in a 47-fold enhancement of the NIR775 emission intensity upon excitation of TPETPAFN at 510 nm as compared to that upon direct excitation of NIR775 at 760 nm. The obtained fluorescent NPs show sharp NIR emission with a band width of 20 nm, a large Stokes shift of 275 nm, good photostability and low cytotoxicity. In vivo imaging study reveals that the synthesized NPs are able to provide high fluorescence contrast in live animals. The Förster resonance energy transfer strategy overcomes the intrinsic limitation of broad emission spectra for AIE NPs, which opens new opportunities to synthesize organic NPs with high brightness and narrow emission for potential applications in multiplex sensing and imaging. Electronic supplementary information (ESI) available: Characterization of AIE properties of TPETPAFN, UV-vis spectra of NPs, PL spectra comparison upon excitation at the donor and receptor absorbance maxima, ex vivo fluorescence imaging of mice organs. See DOI: 10.1039/c3nr04243j

Ce3+ luminescent centers of different symmetries in KMgF3 single crystals

NASA Astrophysics Data System (ADS)

Francini, R.; Grassano, U. M.; Landi, L.; Scacco, A.; D'elena, M.; Nikl, M.; Cechova, N.; Zema, N.

1997-12-01

Absorption, emission, and excitation spectra of KMgF3 doped with Ce3+ have been measured in the near ultraviolet up to 180 nm. In this fluoroperovskite lattice, absorption of the Ce3+ impurity is found at energies higher than 4.4 eV. Broad-band emissions are measured at 350 nm and 275 nm which are identified as the 5d-->4f radiative recombination at two different Ce3+ centers. The same substitutional site is proposed for both centers, with the unperturbed site rapidly saturating with an increasing concentration of Ce3+ in favor of a site perturbed by two K+-ion vacancies.

Photoluminescence of transparent glass-ceramics based on ZnO nanocrystals and co-doped with Eu3+, Yb3+ ions

NASA Astrophysics Data System (ADS)

Arzumanyan, Grigory M.; Kuznetsov, Evgeny A.; Zhilin, Aleksandr A.; Dymshits, Olga S.; Shemchuk, Daria V.; Alekseeva, Irina P.; Mudryi, Alexandr V.; Zhivulko, Vadim D.; Borodavchenko, Olga M.

2016-12-01

Glasses of the K2Osbnd ZnOsbnd Al2O3sbnd SiO2 system co-doped with Eu2O3 and Yb2O3 were prepared by the melt-quenching technique. Transparent zincite (ZnO) glass-ceramics were obtained by secondary heat-treatments at 680-860 °C. At 860 °C, traces of Eu oxyapatite appeared in addition to ZnO nanocrystals. The average crystal size obtained from the X-ray diffraction data was found to range between 14 and 35 nm. Absorption spectra of the initial glasses are composed of an absorption edge and absorption bands due to electronic transitions of Eu3+ ions. With heat-treatment, the absorption edge pronouncedly shifts to the visible spectral range. The luminescence properties of the glass and glass-ceramics were studied by measuring their excitation and emission spectra at 300, 78, and 4.2 K. Strong red emission of Eu3+ ions dominated by the 5D0-7F2 (612 nm) electric dipole transition was detected. Changes in the luminescence properties of the Eu3+-related excitation and emission bands were observed after heat-treatments at 680 °C and 860 °C. The ZnO nanocrystals showed both broad luminescence (400-850 nm) and free-exciton emission near 3.3 eV at room temperature. The upconversion luminescence spectrum of the initial glass was obtained under excitation of the 976 nm laser source.

Tunable violet-blue emission from 3 C-SiC nanowires

NASA Astrophysics Data System (ADS)

Zhu, J.; Wu, H.; Chen, H. T.; Wu, X. L.; Xiong, X.

2009-04-01

Bulk quantities of straight and curled cubic silicon carbide nanowires (3 C-SiC NWs) are synthesized from the mixture of ZnS, Si, and C powders. The 3 C-SiC NWs are wrapped by amorphous SiO 2 shells with very thin thicknesses of less than 2.0 nm. The deionized water suspension of the as-made NWs shows a photoluminescence (PL) band centered at 548 nm, and a tunable violet-blue photoluminescence is observed as the excitation wavelength increases from 300 to 375 nm after the SiO 2 shell is removed. The PL band at 548 nm relates to the SiO 2 shell. Careful microstructural observation suggests that the tunable PL originates from the quantum confinement effect of 3 C-SiC nanocrystallites with sizes of several nm at the turning of the curled NWs.

A potential single-phased emission-tunable silicate phosphor Ca3Si2O7:Ce3+,Eu2+ excited by ultraviolet light for white light emitting diodes

NASA Astrophysics Data System (ADS)

Lv, Wenzhen; Guo, Ning; Jia, Yongchao; Zhao, Qi; You, Hongpeng

2013-03-01

Single-phased Ca3Si2O7:Ce3+,Eu2+ phosphor has been successfully prepared by the high temperature solid-state method. The phosphor shows efficient excitation bands from 200 to 400 nm and adjustable emission bands through the energy transfer from the Ce3+ to Eu2+ ions. The color hues can change from blue towards white ultimately to orange by adjusting the percentage content of doping ions. The investigation reveals that an electric dipole-dipole reaction mechanism should be responsible for the energy transfer from the Ce3+ to Eu2+ ions. The critical distance was obtained from the spectral overlap in terms of Dexter's theory. The developed phosphor Ca3Si2O7:Ce3+,Eu2+ exhibits two bands at 440 and 625 nm, respectively, which reveling that it has a great potentiality to be an UV-convertible phosphor for white-light emitting diodes with low color temperature.

Ocular fundus auto-fluorescence observations at different wavelengths in patients with age-related macular degeneration and diabetic retinopathy.

PubMed

Hammer, Martin; Königsdörffer, Ekkehart; Liebermann, Christiane; Framme, Carsten; Schuch, Günter; Schweitzer, Dietrich; Strobel, Jürgen

2008-01-01

Post-translational protein modification by lipid peroxidation products or glycation is a feature of aging as well as pathologic processes in postmitotic cells at the ocular fundus exposed to an oxidative environment. The accumulation of modified proteins such as those found in lipofuscin and advanced glycation end products (AGEs) contribute greatly to the fundus auto-fluorescence. The distinct fluorescence spectra of lipofuscin and AGE enable their differentiation in multispectral fundus fluorescence imaging. A dual-centre consecutive case series of 78 pseudo-phacic patients is reported. Digital colour fundus photographs as well as auto-fluorescence images were taken from 33 patients with age related macular degeneration (AMD), 13 patients with diabetic retinopathy (RD), or from 32 cases without pathologic findings (controls). Fluorescence was excited at 475-515 nm or 476-604 nm and recorded in the emission bands 530-675 nm or 675-715 nm, respectively. Fluorescence images excited at 475-515 nm were taken by a colour CCD-camera (colour-fluorescence imaging) enabling the separate recording of green and red fluorescence. The ratio of green versus red fluorescence was calculated within a representative region of each image. The 530-675 nm auto-fluorescence in AMD patients was dominated by the red emission (green vs. red ratio, g/r = 0.861). In comparison, the fluorescence of the diabetics was green-shifted (g/r = 0.946; controls: g/r = 0.869). Atrophic areas (geographic atrophy, laser scars) showed massive hypo-fluorescence in both emission bands. Hyper-fluorescent drusen and exudates, unobtrusive in the colour fundus images as well as in the fluorescence images with emission >667 nm, showed an impressive green-shift in the colour-fluorescence image. Lipofuscin is the dominant fluorophore at long wavelengths (>675 nm or red channel of the colour fluorescence image). In the green spectral region, we found an additional emission of collagen and elastin (optic disc, sclera) as well as deposits in drusen and exudates. The green shift of the auto-fluorescence in RD may be a hint of increased AGE concentrations.

Long persistent phosphorescence of V3+ centers in MgAl2O4:Ce3+

NASA Astrophysics Data System (ADS)

Jia, Dongdong; William, Yen

2002-03-01

: Ceramic samples of Ce3+ doped and undoped MgAl2O4 have been prepared and studied. Long persistent phosphorescence was observed at 520nm in Ce3+ doped sample. The persistence time of the 520nm afterglow is longer than 10 hours. The long persistent 520nm afterglow is due to the V3+ centers in MgAl2O4. The V3+ emission is coming from a recombination of the electron from conduction band and the hole of the V3+ center. The hole level of the V3+ center is about 2.4eV below the conduction band. Thermoluminescence spectra of the two samples have been studied. There two hole traps in the MgAl2O4 are found at 41 and 238oC . Doping of Ce3+ also produces two F center like electron traps at 14 and 131oC. Doping of Ce3+ greatly enhanced the afterglow emission of the V3+ center.

ZnO nanoparticles obtained by ball milling technique: Structural, micro-structure, optical and photo-catalytic properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balamurugan, S., E-mail: scandium.chemistry@gmail.com; Joy, Josny; Godwin, M. Anto

The ZnO nanoparticles were obtained by ball milling of commercial grade ZnO powder at 250 rpm for 20 h and studied their structural, micro-structure, optical and photo-catalytic properties. Due to ball milling significant decrease in lattice parameters and average crystalline size is noticed for the as-milled ZnO nano powder. The HRSEM images of the as-milled powder consist of agglomerated fine spherical nanoparticles in the range of ~10-20 nm. The room temperature PL spectrum of as-milled ZnO nano powder excited under 320 nm reveals two emission bands at ~406 nm (violet emission) and ~639 nm (green emission). Interestingly about 98 % of photo degradation of methylene (MB)more » by the ZnO catalyst is achieved at 100 minutes of solar light irradiation.« less

Band gap enhancement of glancing angle deposited TiO2 nanowire array

NASA Astrophysics Data System (ADS)

Chinnamuthu, P.; Mondal, A.; Singh, N. K.; Dhar, J. C.; Chattopadhyay, K. K.; Bhattacharya, Sekhar

2012-09-01

Vertically oriented TiO2 nanowire (NW) arrays were fabricated by glancing angle deposition technique. Field emission-scanning electron microscopy shows the formation of two different diameters ˜80 nm and ˜40 nm TiO2 NW for 120 and 460 rpm azimuthal rotation of the substrate. The x-ray diffraction and Raman scattering depicted the presence of rutile and anatase phase TiO2. The overall Raman scattering intensity decreased with nanowire diameter. The role of phonon confinement in anatase and rutile peaks has been discussed. The red (7.9 cm-1 of anatase Eg) and blue (7.4 cm-1 of rutile Eg, 7.8 cm-1 of rutile A1g) shifts of Raman frequencies were observed. UV-vis absorption measurements show the main band absorption at 3.42 eV, 3.48 eV, and ˜3.51 eV for thin film and NW prepared at 120 and 460 rpm, respectively. Three fold enhance photon absorption and intense light emission were observed for NW assembly. The photoluminescence emission from the NW assembly revealed blue shift in main band transition due to quantum confinement in NW structures.

Structural and optical properties of lithium sodium borate glasses doped with Sm3+ ions

NASA Astrophysics Data System (ADS)

Dawaud, R. S. E. S.; Hashim, S.; Alajerami, Y. S. M.; Mhareb, M. H. A.; Maqableh, M. M.; Tamchek, N.

2014-07-01

Absorption and emission spectra of Sm3+ doped lithium sodium borate (LNB) have been reported. The samples were prepared by the melt-quenching technique and characterized by X-ray diffraction (XRD), diffraction thermal analysis (DTA), Fourier transforms infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FESEM). From the thermo-grams spectrum, glass transition (Tg), crystallization (Tc) and melting temperatures (Tm) have been evaluated. Direct and indirect optical band gaps have been calculated based on the glasses UV absorption spectra. These glasses have shown strong nine absorption bands with hypersensitive transition at 1221 nm (6H5/2→4H3/2) and five emission bands for the transition at 4I7/2→6H13/2 (green color), 4I7/2→6H7/2 (orange color), 4I7/2→6H9/2 (orange color), 4I7/2→6H11/2 (red color) and 4I7/2→6H13/2 (red color) with performing an excitation of 400 nm. The oscillator strengths, refractive index, ions concentration, polaron radius and other parameters have been calculated for each dopant.

Spatial and Temporal Stability of Airglow Measured in the Meinel Band Window at 1191.3 nm

NASA Astrophysics Data System (ADS)

Nguyen, Hien T.; Zemcov, Michael; Battle, John; Bock, James J.; Hristov, Viktor; Korngut, Phillip; Meek, Andrew

2016-09-01

We report on the temporal and spatial fluctuations in the atmospheric brightness in the narrow band between Meinel emission lines at 1191.3 nm using a λ/Δλ = 320 near-infrared instrument. We present the instrument design and implementation, followed by a detailed analysis of data taken over the course of a night from Table Mountain Observatory. At low airmasses, the absolute sky brightness at this wavelength is found to be 5330 ± 30 nW m-2 sr-1, consistent with previous measurements of the inter-band airglow at these wavelengths. This amplitude is larger than simple models of the continuum component of the airglow emission at these wavelengths, confirming that an extra emissive or scattering component is required to explain the observations. We perform a detailed investigation of the noise properties of the data and find no evidence for a noise component associated with temporal instability in the inter-line continuum. This result demonstrates that in several hours of ˜100 s integrations the noise performance of the instrument does not appear to significantly degrade from expectations, giving a proof of concept that near-infrared line intensity mapping may be feasible from ground-based sites.

Optical characterization of Eu3+ and Tb3+ ions doped zinc lead borate glasses.

PubMed

Thulasiramudu, A; Buddhudu, S

2007-02-01

This paper reports on the spectral analysis of Eu3+ or Tb3+ ions (0.5 mol%) doped heavy metal oxide (HMO) based zinc lead borate glasses from the measurement of their absorption, emission spectra and also different physical properties. From the XRD, DSC profiles, the glass nature and glass thermal properties have been studied. The measured emission spectrum of Eu3+ glass has revealed five transitions (5D0-->7F0, 7F1, 7F2, 7F3 and 7F4) at 578, 591, 613, 654 and 702 nm, respectively, with lambdaexci=392 nm (7F0-->5L6). In the case of Tb3+:ZLB glass, four emission transitions such as (5D4-->7F6, 7F5, 7F4 and 7F3) that are located at 489, 542, 585 and 622 nm, respectively, have been measured with lambdaexci=374 nm. For all these emission bands decay curves have been plotted to evaluate their lifetimes and the emission processes that arise in the glasses have been explained in terms of energy level schemes.

Narrow-band generation in random distributed feedback fiber laser.

PubMed

Sugavanam, Srikanth; Tarasov, Nikita; Shu, Xuewen; Churkin, Dmitry V

2013-07-15

Narrow-band emission of spectral width down to ~0.05 nm line-width is achieved in the random distributed feedback fiber laser employing narrow-band fiber Bragg grating or fiber Fabry-Perot interferometer filters. The observed line-width is ~10 times less than line-width of other demonstrated up to date random distributed feedback fiber lasers. The random DFB laser with Fabry-Perot interferometer filter provides simultaneously multi-wavelength and narrow-band (within each line) generation with possibility of further wavelength tuning.

Cathodoluminescence, laser ablasion inductively coupled plasma mass spectrometry, electron probe microanalysis and electron paramagnetic resonance analyses of natural sphalerite

USGS Publications Warehouse

Karakus, M.; Hagni, R.D.; Koenig, A.; Ciftc, E.

2008-01-01

Natural sphalerite associated with copper, silver, lead-zinc, tin and tungsten deposits from various world-famous mineral deposits have been studied by cathodoluminescence (CL), laser ablasion inductively coupled plasma mass spectrometry (LA-ICP-MS), electron probe microanalysis (EPMA) and electron paramagnetic resonance (EPR) to determine the relationship between trace element type and content and the CL properties of sphalerite. In general, sphalerite produces a spectrum of CL colour under electron bombardment that includes deep blue, turquoise, lime green, yellow-orange, orange-red and dull dark red depending on the type and concentration of trace quantities of activator ions. Sphalerite from most deposits shows a bright yellow-orange CL colour with ??max centred at 585 nm due to Mn2+ ion, and the intensity of CL is strongly dependent primarily on Fe2+ concentration. The blue emission band with ??max centred at 470-490 nm correlates with Ga and Ag at the Tsumeb, Horn Silver, Balmat and Kankoy mines. Colloform sphalerite from older well-known European lead-zinc deposits and late Cretaceous Kuroko-type VMS deposits of Turkey shows intense yellowish CL colour and their CL spectra are characterised by extremely broad emission bands ranging from 450 to 750 nm. These samples are characterised by low Mn (<10 ppm) and Ag (<1 ppm), and they are enriched in Tl (1-30 ppm) and Pb (80-1500 ppm). Strong green CL is produced by sphalerite from the Balmat-Edwards district. Amber, lime-green and red-orange sphalerite produced weak orange-red CL at room temperatures, with several emission bands centred at 490, 580, 630, 680, 745, with ??max at 630 nm being the strongest. These emission bands are well correlated with trace quantities of Sn, In, Cu and Mn activators. Sphalerite from the famous Ogdensburg and Franklin mines exhibited brilliant deep blue and orange CL colours and the blue CL may be related to Se. Cathodoluminescence behaviour of sphalerite serves to characterise ore types and help detect technologically important trace elements.

Cathodoluminescence microscopy and spectroscopy of forsterite from Kaba meteorite: An application to the study of hydrothermal alteration of parent body

NASA Astrophysics Data System (ADS)

Gucsik, Arnold; Endo, Taro; Nishido, Hirotsugu; Ninagawa, Kiyotaka; Kayama, Masahiro; Bérczi, Szaniszló; Nagy, Szabolcs; Ábrahám, Péter; Kimura, Yuki; Miura, Hitoshi; Gyollai, Ildikó; Simonia, Irakli; Rózsa, Péter; Posta, József; Apai, Dániel; Mihályi, Krisztián; Nagy, Mihály; Ott, Ulrich

2013-12-01

Highly forsteritic olivine (Fo: 99.2-99.7) in the Kaba meteorite emits bright cathodoluminescence (CL). CL spectra of red luminescent forsterite grains have two broad emission bands at approximately 630 nm (impurity center of divalent Mn ions) in the red region and above 700 nm (trivalent Cr ions) in the red-IR region. The cores of the grains show CL blue luminescence giving a characteristic broad band emission at 400 nm, also associated with minor red emissions related to Mn and Cr ions. CL color variation of Kaba forsterite is attributed to structural defects. Electron probe microanalyzer (EPMA) analysis shows concentrations of Ca, Al, and Ti in the center of the forsterite grain. The migration of diffusible ions of Mn, Cr, and Fe to the rim of the Kaba meteoritic forsterite was controlled by the hydrothermal alteration at relatively low temperature (estimated at about 250 °C), while Ca and Al ions might still lie in the core. A very unusual phase of FeO (wüstite) was also observed, which may be a terrestrial alteration product of FeNi-metal.

Diode-pumped continuous-wave eye-safe Nd:YAG laser at 1415 nm.

PubMed

Lee, Hee Chul; Byeon, Sung Ug; Lukashev, Alexei

2012-04-01

We describe the output performance of the 1415 nm emission in Nd:YAG in a plane-concave cavity under traditional pumping into the 4F5/2 level (808 nm) and direct in-band pumping into the 4F3/2 level (885 nm). An end-pumped Nd:YAG laser yielded maximum cw output power of 6.3 W and 4.2 W at 885 nm and 808 nm laser diode (LD) pumping, respectively. To the best of our knowledge, this is the highest output power of a LD-pumped 1415 nm laser.

Amplified stimulated emission in the NaK(D-X) band by high power copper vapor laser pumping

NASA Astrophysics Data System (ADS)

Dinev, S. G.; Hadjicristov, G. B.; Marazov, O.

1991-04-01

Using a 10 W copper vapor laser we have studied a stimulated emission at 520-570 nm in the D-X electronic transition of the NaK heteronuclear molecule. The influence of the cavity configuration on the bound-bound stimulated lines is considered.

Amplified stimulated emission in the NaK( D→ X) band by high power copper vapor laser pumping

NASA Astrophysics Data System (ADS)

Dinev, S. G.; Hadjichristov, G. B.; Marazov, O.

1991-04-01

Using a 10 W copper vapor laser we have studied a stimulated emission at 520 570 nm in the D→ X electronic transition of the NaK heteronuclear molecule. The influence of the cavity configuration on the bound-bound stimulated lines is considered.

Preparation of poly(N-vinylpyrrolidone)-stabilized ZnO colloid nanoparticles

PubMed Central

Gutul, Tatyana; Condur, Nadejda; Ursaki, Veaceslav; Goncearenco, Evgenii; Vlazan, Paulina

2014-01-01

Summary We propose a method for the synthesis of a colloidal ZnO solution with poly(N-vinylpyrrolidone) (PVP) as stabilizer. Stable colloidal solutions with good luminescence properties are obtained by using PVP as stabilizer in the synthesis of ZnO nanoparticles by a sol–gel method assisted by ultrasound. Nanoparticles with sizes of 30–40 nm in a PVP matrix are produced as a solid product. The colloidal ZnO/PVP/methanol solution, apart from the most intense PL band at 356 nm coming from the PVP, exhibits a strong PL band at 376 nm (3.30 eV) which corresponds to the emission of the free exciton recombination in ZnO nanoparticles. PMID:24778966

Chlorophyll as a biomarker for early disease diagnosis

NASA Astrophysics Data System (ADS)

Manzoor Atta, Babar; Saleem, M.; Ali, Hina; Arshad, Hafiz Muhammad Imran; Ahmed, M.

2018-06-01

The current study was designed to identify the stage for the diagnosis of disease before visible symptoms appeared. Fluorescence spectroscopy has been employed to identify disease signatures for its early diagnosis in rice plant leaves. Bacterial leaf blight (BLB) diseased and healthy leaf samples were collected from the rice fields in September, 2017 which were then used to record spectra using an excitation wavelength at 410 nm. The spectral range of emission was set from 420 to 800 nm which covers the blue–green and the chlorophyll bands. It was found that diseased leaves have a narrower ‘chlorophyll a’ band than healthy ones, and furthermore, that the emission band at 730 nm was either declined or depleted in the sample with high infection symptoms. In contrast, the blue–green region was observed to increase due to the emergence of disease. As the band intensity of chlorophyll decreases during infection, this decrease in chlorophyll content and increase in the blue–green spectral region could provide a new approach for predicting BLB at an early stage. The important finding was that the chlorophyll degradation and rise in the blue–green region take place in leaves with BLB or during BLB infection. Principal component analysis has been applied to spectral data which successfully separated diseased samples from healthy ones even with very small spectral variations.

Design and analysis of InN - In0.25Ga0.75N single quantum well laser for short distance communication wavelength

NASA Astrophysics Data System (ADS)

Polash, Md. Mobarak Hossain; Alam, M. Shah; Biswas, Saumya

2018-03-01

A single quantum well semiconductor laser based on wurtzite-nitride is designed and analyzed for short distance communication wavelength (at around 1300 nm). The laser structure has 12 Å well layer of InN, 15 Å barrier layer of In0.25Ga0.75N, and 54 Å separate confinement heterostructure layer of GaN. To calculate the electronic characteristics of the structure, a self-consistent method is used where Hamiltonian with effective mass approximation is solved for conduction band while six-bands Hamiltonian matrix with k · p formalism including the polarization effect, valence-band mixing effect, and strain effect is solved for valence band. The interband optical transition elements, optical gain, differential gain, radiative current density, spontaneous emission rate, and threshold characteristics have been calculated. The wave function overlap integral is found to be 45.93% for TE-polarized structure. Also, the spontaneous emission rate is found to be 6.57 × 1027 s - 1 cm - 3 eV - 1 at 1288.21 nm with the carrier density of 5 × 1019 cm - 3. Furthermore, the radiative current density and the radiative recombination rate are found to be 121.92 A cm - 2 and 6.35 × 1027 s - 1 cm - 3, respectively, while the TE-polarized optical gain of the structure is 3872.1 cm - 1 at 1301.7 nm.

Diameter Control and Photoluminescence of ZnO Nanorods from Trialkylamines

DOE PAGES

Andelman, Tamar; Gong, Yinyan; Neumark, Gertrude; ...

2007-01-01

A novel solution method to control the diameter of ZnO nanorods is reported. Small diameter (2-3 nm) nanorods were synthesized from trihexylamine, and large diameter (50–80 nm) nanorods were synthesized by increasing the alkyl chain length to tridodecylamine. The defect (green) emission of the photoluminescence (PL) spectra of the nanorods varies with diameter, and can thus be controlled by the diameter control. The small ZnO nanorods have strong green emission, while the large diameter nanorods exhibit a remarkably suppressed green band. We show that this observation supports surface oxygen vacancies as the defect that gives rise to the green emission.

Extreme Ultraviolet Emission Spectrum of CO_2 Induced by Electron Impact at 200 eV

NASA Technical Reports Server (NTRS)

Kanik, I.; Ajello, J. M.; James, G. K.

1993-01-01

We present the extreme ultraviolet (EUV) emission spectrum of CO_2 induced by electronimpact at 200 eV. There are 36 spectral features which are identified with a resolution of 0.5 nmover the wavelength range of 40 to 125 nm. Absolute emission cross sections were obtained for eachof these features. The EUV emission spectrum induced by electron impact consist of atomicmultiplets of CI,II and OI,II,III as well as CO and CO^+ molecular band systems produced bydissociative excitation. The CI (119.4 nm) multiplet is the strongest feature of CI with a peak crosssection of 3.61 x 10^(-19) cm^2 at 200 eV. The strongest feature of OI in the EUV spectrum is theOI (99.0 nm) multiplet with a peak cross section of 3.59 x 10^(-19) cm^2 at 200 eV.

Optical characterization of CdS nanorods capped with starch

NASA Astrophysics Data System (ADS)

Roy, J. S.; Pal Majumder, T.; Schick, C.

2015-05-01

Well crystalline uniform CdS nanorods were grown by changing the concentration of maize starch. The highly polymeric (branched) structure of starch enhances the growth of CdS nanorods. The average diameter of the nanorods is 20-25 nm while length is of 500-600 nm as verified from SEM and XRD observations. The optical band gaps of the CdS nanorods are varying from 2.66 eV to 2.52 eV depending on concentration of maize starch. The photoluminescence (PL) emission bands are shifted from 526 nm to 529 nm with concentration of maize starch. We have also observed the enhanced PL intensity in CdS nanorods capped with starch. The Fourier transform infrared (FTIR) spectroscopy shows the significant effect of starch on CdS nanorods.

Optical waveguide and room temperature high-quality nanolasers from tin-catalyzed CdSSe nanostructures

NASA Astrophysics Data System (ADS)

Guo, Pengfei; Shen, Xia; Zhang, Baolong; Sun, Haibin; Zou, Zhijun; Yang, Wenchao; Gong, Ke; Luo, Yongsong

2018-05-01

A simple two-step CVD method is developed to realize the growth of high-quality tin-catalyzed CdSSe alloy nanowires. Microstructural characterizations demonstrate that these wires are high-quality crystalline nanostructures. Local photoluminescence investigation of these nanostructures shows a typical band edge emission at 656 nm with a full-width at half-maximum of 22.3 nm. Optical waveguide measurement along an individual nanowire indicates that the output signal of the guided light has a rapid linear decrease accompanied with maximum red-shift about 109 meV after the transmission of 102 μm. This obvious red-shift is caused by the intensive band-tail absorption during the optical transmission process. Moreover, optically pumped nanolasers are successfully realized at room temperature based on these unique wires, further demonstrating the achievement of stimulated emission from spontaneous emission, promoted by the pump power intensity. This work may find a simple route to the manufacture of superior nanowires for applications in waveguide and integrated photonic devices.

Optical waveguide and room temperature high-quality nanolasers from tin-catalyzed CdSSe nanostructures.

PubMed

Guo, Pengfei; Shen, Xia; Zhang, Baolong; Sun, Haibin; Zou, Zhijun; Yang, Wenchao; Gong, Ke; Luo, Yongsong

2018-05-04

A simple two-step CVD method is developed to realize the growth of high-quality tin-catalyzed CdSSe alloy nanowires. Microstructural characterizations demonstrate that these wires are high-quality crystalline nanostructures. Local photoluminescence investigation of these nanostructures shows a typical band edge emission at 656 nm with a full-width at half-maximum of 22.3 nm. Optical waveguide measurement along an individual nanowire indicates that the output signal of the guided light has a rapid linear decrease accompanied with maximum red-shift about 109 meV after the transmission of 102 μm. This obvious red-shift is caused by the intensive band-tail absorption during the optical transmission process. Moreover, optically pumped nanolasers are successfully realized at room temperature based on these unique wires, further demonstrating the achievement of stimulated emission from spontaneous emission, promoted by the pump power intensity. This work may find a simple route to the manufacture of superior nanowires for applications in waveguide and integrated photonic devices.

Luminescence and Site Occupancy of Eu2+ in Ba2 Ca(BO3)2

NASA Astrophysics Data System (ADS)

Li, Pan-Lai; Wang, Zhi-Jun; Yang, Zhi-Ping; Guo, Qing-Lin

2011-01-01

A green phosphor Ba2Ca(BO3)2:Eu2+ was synthesized by a high temperature solid-state reaction method under a reductive atmosphere. The luminescence and site occupancy of Eu2+ in Ba2Ca(BO3)2 are investigated. Ba2Ca(BO3)2:Eu2+ shows one green band (537 nm) under 400 nm near ultraviolet excitation which is suitable for UV LED. Ca2+ and Ba2+ ions in Ba2Ca(BO3)2 are replaced by Eu2+ ions, the Ba2Ca(BO3)2:Eu2+ shows a dissymmetrical emission band. The influence of Eu2+ doping concentrations on the emission intensity of Ba2Ca(BO3)2:Eu2+ is studied. It is found that the emission intensity is influenced by the Eu2+ concentration and reaches the maximum value at 2% Eu2+. According to the Dexter theory, the concentration quenching mechanisms of Eu2+ in Ba2Ca(BO3)2 are the d-dinteraction.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Bo; Zhang, Xiaosong, E-mail: zhangxiaosong@tjut.edu.cn; Li, Lan

Trap-rich CdS nanocrystals were synthesized by employing CdSt{sub 2} and sulfur as precursors via thermal decomposition. Furthermore, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), absorption and photoluminescence (PL) spectra were used to characterize structure, morphology and luminescence properties of CdS nanocrystals (NCs). CdS NCs have a broad emission across 500–700 nm under the excitation of blue light with 460 nm, consequently, white light can be produced by mixing broad emission from CdS NCs excited by blue light, with the remaining blue light. In addition, the broad emission generation is closely and inseparably related to surface defects. Moreover, LaMer modelmore » was used to explain the phenomenon that the intensity of the trap emission gradually decreases as the reaction time increases in contrast with that of the band-edge emission. - Graphical abstract: Trap-rich CdS nanocrystals were synthesized. Furthermore, white light is produced by mixing broad emission across 500–700 nm from CdS NCs excited by blue light, in combination with the remaining blue light. - Highlights: • Trap-rich CdS nanocrystals were synthesized. • CdS NCs have a broad emission across 500–700 nm under the excitation of blue light. • White light can be produced by mixing broad emission with the remaining blue light.« less

EPR, optical absorption and luminescence studies of Cr3+-doped antimony phosphate glasses

NASA Astrophysics Data System (ADS)

De Vicente, F. S.; Santos, F. A.; Simões, B. S.; Dias, S. T.; Siu Li, M.

2014-12-01

Antimony phosphate glasses (SbPO) doped with 3 and 6 mol% of Cr3+ were studied by Electron Paramagnetic Resonance (EPR), UV-VIS optical absorption and luminescence spectroscopy. The EPR spectra of Cr3+-doped glasses showed two principal resonance signals with effective g values at g = 5.11 and g = 1.97. UV-VIS optical absorption spectra of SbPO:Cr3+ presented four characteristics bands at 457, 641, 675, and 705 nm related to the transitions from 4A2(F) to 4T1(F), 4T2(F), 2T1(G), and 2E(G), respectively, of Cr3+ ions in octahedral symmetry. Optical absorption spectra of SbPO:Cr3+ allowed evaluating the crystalline field Dq, Racah parameters (B and C) and Dq/B. The calculated value of Dq/B = 2.48 indicates that Cr3+ ions in SbPO glasses are in strong ligand field sites. The optical band gap for SbPO and SbPO:Cr3+ were evaluated from the UV optical absorption edges. Luminescence measurements of pure and Cr3+-doped glasses excited with 350 nm revealed weak emission bands from 400 to 600 nm due to the 3P1 → 1S0 electronic transition from Sb3+ ions. Cr3+-doped glasses excited with 415 nm presented Cr3+ characteristic luminescence spectra composed by two broad bands, one band centered at 645 nm (2E → 4A2) and another intense band from 700 to 850 nm (4T2 → 4A2).

Structural and optical investigation in Er3+ doped Y2MoO6 phosphors

NASA Astrophysics Data System (ADS)

Mondal, Manisha; Rai, Vineet Kumar

2018-05-01

The Er3+ doped Y2MoO6 phosphors have been structurally and optically characterized by X-ray Diffraction (XRD), Field emission scanning electron microscopy (FESEM), UV-Vis absorption spectroscopy and frequency upconversion (UC) emission studies. The crystal and the particles size are found to be ˜ 85 nm and ˜ 200 nm from XRD and FESEM analysis. The intense peak at ˜ 206 nm in the UV-Vis absorption spectroscopy is attributed due to the charge transfer transition between the Mo6+ and the O2- ions in the MoO4 group in the host molybdate. The frequency UC emission studies of the prepared phosphors under 980 nm diode laser excitation shows the intense UC emission in the 0.3 mol% concentrations for the Er3+ ions. In the UC emission spectra, the emission peaks at green (˜ 525 nm and ˜ 546 nm) and red (˜ 656 nm) bands are corresponding to the 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ ions. The mechanisms involved in the UC process have been explored with the help of energy level diagram. Moreover, the CIE point (0.31, 0.60) lie in the green colour region which indicates that the developed phosphor have suitable applications in NIR to visible upconverter and in making green light display devices.

Study of white light emission from ZnS/PS composite system

NASA Astrophysics Data System (ADS)

Wang, Caifeng; Li, Qingshan; Lu, Lei; Zhang, Lichun; Qi, Hongxia

2007-09-01

ZnS films were deposited by pulsed laser deposition (PLD) on porous silicon (PS) substrates formed by electrochemical anodization of p-type (100) silicon wafer. The photoluminescence (PL) spectra of ZnS/PS composites were measured at room temperature. Under different excitation wavelengths, the relative integrated intensities of the red light emission from PS layers and the blue-green emission from ZnS films had different values. After samples were annealed in vacuum at different temperatures (200, 300, and 400 Celsius degree) for 30 min respectively, a new green emission located at around 550 nm appeared in the PL spectra of all ZnS/PS samples, and all of the ZnS/PS composites had a broad PL band (450-700 nm) in the visible region, exhibiting intensively white light emission.

Studies of Gravity Waves Using Michelson Interferometer Measurements of OH (3-1) Bands

NASA Astrophysics Data System (ADS)

Won, Young-In; Cho, Young-Min; Lee, Bang Yong; Kim, J.

2001-06-01

As part of a long-term program for polar upper atmospheric studies, temperatures and intensities of the OH (3-1) bands were derived from spectrometric observations of airglow emissions over King Sejong station (62.22o S, 301.25o E). These measurements were made with a Michelson interferometer to cover wavelength regions between 1000 nm and 2000 nm. A spectral analysis was performed to individual nights of data to acquire information on the waves in the upper mesosphere/lower thermosphere. It is assumed that the measured fluctuations in the intensity and temperature of the OH (3-1) airglow were caused by gravity waves propagating through the emission layer. Correlation of intensity and temperature variation revealed oscillations with periods ranging from 2 to 9 hours. We also calculated Krassovsky's parameter and compared with published values.

Structural and luminescence properties of self-yellow emitting undoped and (Ca, Ba, Sr)-doped Zn2V2O7 phosphors synthesized by combustion method

NASA Astrophysics Data System (ADS)

Foka, Kewele E.; Dejene, Birhanu F.; Koao, Lehlohonolo F.; Swart, Hendrik C.

2018-04-01

A self-activated yellow emitting Zn2V2O7 was synthesized by combustion method. The influence of the processing parameters such as synthesis temperature and dopants concentration on the structure, morphology and luminescence properties was investigated. The X-ray diffraction (XRD) analysis confirmed that the samples have a tetragonal structure and no significant structural change was observed in varying both the synthesis temperature and the dopants concentration. The estimated average crystallite size was 78 nm for the undoped samples synthesized at different temperatures and 77 nm for the doped samples. Scanning electron microscope (SEM) images showed agglomerated hexagonal-shaped particles with straight edges at low temperatures and the shape of the particles changed to cylindrical structures at moderate temperatures. At higher temperatures, the morphology changed completely. However, the morphologies of the doped samples looked alike. The photoluminescence (PL) of the product exhibited broad emission bands ranging from 400 to 800 nm. The best luminescence intensity was observed for the undoped Zn2V2O7 samples and those synthesized at 600 ℃ . Any further increase in synthesis temperature, type and concentration of dopants led to a decrease in the luminescence intensity. The broad band emission peak of Zn2V2O7 consisted of two broad bands corresponding to emissions from the Em1 (3T2→1A1) and Em2 (3T1→1A1) transitions.

Influence of Li+ charge compensator ion on the energy transfer from Pr3 + to Gd3 + ions in Ca9Mg(PO4)6F2:Gd3 +, Pr3 +, Li+ phosphor

NASA Astrophysics Data System (ADS)

Tamboli, Sumedha; Dhoble, S. J.

2017-09-01

Phototherapy is a renowned treatment for curing skin diseases since ancient times. Phototherapeutic treatment for psoriasis and many other diseases require narrow band ultra violet-B (NB-UVB) light with peak intensity at 313 nm to be exposed to the affected part of body. In this paper, we report combustion synthesis of NB-UVB - 313 nm emitting Ca9Mg(PO4)6F2 phosphors doped with Gd3 +, Pr3 + and Li+ ions. The phase formation was confirmed by obtaining X-ray diffraction (XRD) pattern and morphology was studied with the Scanning electron microscopy (SEM) images. Photoluminescence (PL) emission spectra show intense narrow band emission at 313 nm under 274 nm excitation wavelengths. Emission intensity was enhanced when Ca9Mg(PO4)6F2 compound is co-doped with Pr3 + ions. Excitation spectra of Ca9Mg(PO4)6F2:Gd3 +, Pr3 + doped samples shows broad excitation in ultra violet C (UVC) region. Diffuse reflectance spectra (DRS), obtained by UV-visible spectrophotometer, measures the absorption properties of the material. By applying Kubelka Munk function on the diffuse reflectance spectra, band gap of the material is determined. PL decay curves were examined which indicates efficient energy transfer between Pr3 + and Gd3 + ions. Charge compensation effect was also studied by co-doping Li+ ion in host. Emission intensity was found to increase with the addition of charge compensator. The prepared phosphor has potential to convert UVC light into NB-UVB. The luminescence intensity of Gd3 + shows remarkable increase when it is sensitized with Pr3 +, and an addition of charge compensator in the form of Li+, show even better results. This phosphor surely has the potential to be used as phototherapy lamp phosphor.

System and method for controlling depth of imaging in tissues using fluorescence microscopy under ultraviolet excitation following staining with fluorescing agents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levenson, Richard; Demos, Stavros

A method is disclosed for analyzing a thin tissue sample and adapted to be supported on a slide. The tissue sample may be placed on a slide and exposed to one or more different exogenous fluorophores excitable in a range of about 300 nm-200 nm, and having a useful emission band from about 350 nm-900 nm, and including one or more fluorescent dyes or fluorescently labeled molecular probes that accumulate in tissue or cellular components. The fluorophores may be excited with a first wavelength of UV light between about 200 nm-290 nm. An optical system collects emissions from the fluorophoresmore » at a second wavelength, different from the first wavelength, which are generated in response to the first wavelength of UV light, to produce an image for analysis.« less

New challenges and insights in the detection and spectral identification of organic explosives by laser induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Lucena, P.; Doña, A.; Tobaria, L. M.; Laserna, J. J.

2011-01-01

With the objective of detection and identification of explosives, different organic compounds, including aromatic nitrocompounds, RDX, anthracene, 2,4-diaminotoluene (DAT), 4-methyl-3-nitroaniline (MNA) and pentaerythritol (PENT) have been analyzed by laser induced breakdown spectroscopy (LIBS). To avoid the secondary ionization and to discriminate between the spectral contribution due to air from that of the compound in the plasma generated in air, the emission signatures from atomic lines (C at 247.9 nm, H at 656.3 nm, N at 746.8 nm and O at 777.2 nm) and molecular bands (CN at 388.3 nm and C 2 at 516.5 nm) have been investigated in plasmas generated in air and in helium. The different possible pathways leading to the observation of molecular emissions have been studied, together with a discussion of the most useful tools for the explosives discrimination. Moreover, the effect of the laser fluence on the atomic and molecular emissions and their relationship with the oxygen balance of an organic explosive is presented.

Lasing characteristics of gas mixtures involving UFG: Application to nuclear pumping of lasers

NASA Technical Reports Server (NTRS)

Verdeyen, J. T.; Eden, J. G.

1980-01-01

Intense blue-green fluorescence from a structured band centered at lambda approximately 484 nm was observed from Ar, CF3I and NF3 gas mixtures excited by an electron beam. This emission was tentatively assigned to the E yields A transition of the iodine monofluoride (IF) molecule. The fluorescence efficiency of the IF(E yields A) band and the IF (E) state radiative lifetime were estimated to be approximately 6% and 15 ns, respectively. The emission band structure, the short IF(E) radiative lifetime and the Franck-Condon shift between the E and A states suggest that IF is an attractive candidate for a blue-green laser.

Impact of Antibody Bioconjugation on Emission and Energy Band Profile of CdSeTe/ZnS Quantum Dots

NASA Astrophysics Data System (ADS)

Torchynska, T. V.; Gomez, J. A. Jaramillo; Polupan, G.; Macotela, L. G. Vega

2018-03-01

The variation of the photoluminescence (PL) and Raman scattering spectra of CdSeTe/ZnS quantum dots (QDs) on conjugation to an antibody has been investigated. Two types of CdSeTe/ZnS QD with different emission wavelength (705 nm and 800 nm) were studied comparatively before and after conjugation to anti-pseudorabies virus antibody (AB). Nonconjugated QDs were characterized by Gaussian-type PL bands. PL shifts to higher energy and asymmetric shape of PL bands was detected in PL spectra of bioconjugated QDs. The surface-enhanced Raman scattering effect was exhibited by the bioconjugated CdSeTe/ZnS QDs, indicating that the excitation light used in the Raman study generated electric dipoles in the AB molecules. The optical bandgap of the CdSeTe core was calculated numerically as a function of its radius based on an effective mass approximation model. The energy band diagrams for non- and bioconjugated CdSeTe/ZnS QDs were obtained, revealing a type II quantum well in the CdSeTe core. The calculations show that AB dipoles, excited in the bioconjugated QDs, stimulate a change in the energy band diagram of the QDs that alters the PL spectrum. These results could be useful for improving the sensitivity of QD biosensors.

Quantum effect on the energy levels of Eu2+ doped K2Ca2(SO4)3 nanoparticles.

PubMed

Salah, Numan; Habib, Sami S; Khan, Zishan H

2010-09-01

Quantum confinement effect on the energy levels of Eu(2+) doped K(2)Ca(2)(SO(4))(3) nanoparticles has been observed. The broad photoluminescence (PL) emission band of Eu(2+) doped K(2)Ca(2)(SO(4))(3) microcrystalline sample observed at ∼436 nm is found to split into two narrow well resolved bands, located at 422 and 445 nm in the nanostructure form of this material. This has been attributed to the reduction in the crystal field strength of the nanomaterials, which results in widening the energy band gap and splitting the broad 4f(6)5d energy level of Eu(2+). Energy band gap values of the micro and nanocrystalline K(2)Ca(2)(SO(4))(3) samples were also determined by measuring the UV-visible absorption spectra. These values are 3.34 and 3.44 eV for the micro and nanocrystalline samples, respectively. These remarkable results suggest that activators having wide emission bands might be subjected to weak crystal strength via nanostructure materials to modify their electronic transitions. This might prove a powerful technique for producing new-advanced materials for use in the fields of solid state lasers and optoelectronic devises.

Emission Analysis Of Pr{sup 3+}: PVP And Nd{sup 3+}: PVP Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sivaiah, K.; Buddhudu, S.

Here we report on the results concerning the absorption and emission spectra of RE{sup 3+} (Pr{sup 3+} or Nd{sup 3+}) doped PVP polymer films. The absorption spectrum of Pr{sup 3+}: PVP polymer film has shown three absorption bands at 444 nm ({sup 3}H{sub 4{yields}}{sup 3}P{sub 2}), 469nm ({sup 3}H{sub 4{yields}}{sup 3}P{sub 1}) and 481nm ({sup 3}H{sub 4{yields}}{sup 3}P{sub 0}). From the Pr{sup 3+}: PVP polymer film, an emission at 603 nm ({sup 1}D{sub 2{yields}}{sup 3}H{sub 4}) has been observed with an excitation at 443 nm ({sup 3}H{sub 4{yields}}{sup 3}P{sub 2}). The absorption spectrum of Nd{sup 3+}: PVP polymer film hasmore » exhibited eleven absorption bands at 324 nm, 383 nm, 432 nm, 462 nm, 511 nm, 526 nm, 580 nm, 686 nm, 746 nm, 799 nm, and 869 nm which are assigned to the electronic transitions of {sup 4}I{sub 9/2{yields}}{sup 4}D{sub 7/2}, {sup 4}I{sub 9/2{yields}}{sup 2}D{sub 3/2}, {sup 4}I{sub 9/2{yields}}{sup 4}P{sub 1/2}, {sup 4}I{sub 9/2{yields}}{sup 4}G{sub 11/2}, {sup 4}I{sub 9/2{yields}}{sup 4}G{sub 9/2}, {sup 4}I{sub 9/2{yields}}{sup 4}G{sub 7/2}, {sup 4}I{sub 9/2{yields}}{sup 4}G{sub 5/2}, {sup 4}I{sub 9/2{yields}}{sup 2}F{sub 9/2}, {sup 4}I{sub 9/2{yields}}{sup 2}F{sub 7/2}, {sup 4}I{sub 9/2{yields}}{sup 2}H{sub 9/2} and {sup 4}I{sub 9/2{yields}}{sup 4}F{sub 3/2} respectively. From the Nd{sup 3+}: PVP polymer film, an emission transition has been measured at 1055 nm ({sup 4}F{sub 3/2{yields}}{sup 4}I{sub 11/2}) with an excitation at 324 nm ({sup 4}I{sub 9/2{yields}}{sup 4}D{sub 7/2}). For the host polymer film, structural properties have been studied from the measurement of XRD, FTIR, Raman spectra. For this film thermal properties have also been investigated from the measured profiles of TGA-DTA.« less

Thermal stability and Judd-Ofelt analysis of optical properties of Sm3+-doped sodium tellurite glasses

NASA Astrophysics Data System (ADS)

Mawlud, Saman Q.; Ameena, Mudhafar M.; Sahar, Md. Rahim; Mahraz, Zahra A. Said; Ahmed, Kasim Fawzy

2017-09-01

Series of glasses based on (70-x) TeO2 - 20Na2O - xSm2O3 (x=0, 0.3, 0.6, 1, 1.2, 1.5 mol%) have been prepared using melt-quenching technique. The nature of the glass has been confirmed using X-ray diffraction; it is found that the glass samples are amorphous in nature. The thermal stability of the glass has been determined by means of Differential Thermal Analysis (DTA). From the DTA curve, the glass transition temperature (Tg), crystallization temperature (Tc) and melting temperature (Tm) have been identified and thermal stability is also calculated. The absorption properties of these samples are obtained by using UV-Visible-NIR spectrometer, the recorded absorption spectra exhibit nine absorption transition bands peaks corresponding to the transitions from ground level 6H5/2→6P3/2, 4I11/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2, 6H15/2 and 6F1/2. The emission characteristic of this glass is characterized using Photoluminescence (PL) spectroscopy at excited wavelength 404 nm, the emission spectra consisted of four emission bands at 561.95 nm, 598.69 nm, 643.77 nm and 704.56 nm which were assigned as a transition 4G5/2→6H5/2, 6H7/2, 6H9/2 and 6H11/2 respectively. From f-f intensity model the experimental oscillator strengths, fexp and theoretical oscillator strength fcal were calculated. Using Judd-Ofelt theory and fit process of least square, the phenomenological intensity parameters Ωλ (λ=2,4,6) were obtained, In order to evaluate potential applications of Sm3+ ions in telluride glasses, the spectroscopic parameters: transition probability AR, branching ratio Br, radiative life time τr, emission pick cross section σλ for each band were calculated. The comparative studies with other Sm3+ doped different glasses showed that present glasses could be a potential candidate for lasers.

The enhanced and broadband near-infrared emission in Pr3+/Nd3+ co-doped tellurite glass

NASA Astrophysics Data System (ADS)

Zhou, Zizhong; Zhou, Yaxun; Cheng, Pan; Zhou, Minghan; Su, Xiue; Li, Jun

2017-11-01

This paper reports an enhanced and broadband near-infrared fluorescence emission in the Pr3+/Nd3+ co-doped tellurite glass, which was prepared using melt-quenching technique. Under the excitation of 488 nm laser diode (LD), three near-infrared emission bands at around 0.9, 1.04 and 1.30 μm from 3P1,0 → 1G4, 1G4→3H4 and 1G4→3H5 radiative transitions respectively were observed in the Pr3+ single-doped glass, and the fluorescence intensities increased further with the introduction of Nd3+ ions, which is mainly attributed to the energy transfers from Nd3+ to Pr3+ emissions. Meanwhile, the spectral overlapping of Pr3+:1G4→3H4 and Nd3+:4F3/2 → 4I11/2 radiative transitions resulted in a broadband emission ranging from 1000 to 1100 nm, whose full-width at half-maximum (FWHM) reached about 66 nm. Additionally, the spectroscopic properties of Nd3+ and Pr3+ ions were analyzed using Judd-Ofelt theory and the thermal stability property of prepared glass was characterized by the differential scanning calorimeter (DSC) measurement, and larger than 134 °C for the difference ΔT(=Tx -Tg) was observed, which indicates its feasibility for later fiber drawing. The enhanced fluorescence and broadband emission indicate that Pr3+/Nd3+ co-doped tellurite glass can be applied in the near-infrared band tunable lasers and broadband optical amplifiers.

Radical Beam Gettering Epitaxy of Zno and Gan

NASA Astrophysics Data System (ADS)

Georgobiani, A. N.; Demin, V. I.; Vorobiev, M. O.; Gruzintsev, A. N.; Hodos, I. I.; Kotljarevsky, M. B.; Kidalov, V. V.; Rogozin, I. V.

2002-11-01

P-type ZnO layers with a hole mobility about 23 cm2/(V s), and a hole concentration about 1015 cm-3 were grown by means of radical-beam gettering epitaxy (the annealing of n-ZnO single crystals in atomic oxygen flux). The effect of native defects on the photoluminescence spectra of the layers was studied. The dominant bands in the spectra peaked at 370.2 and 400 nm. These bands were attributed to the annihilation of exciton localised on neutral Vzn and to electron transitions from the conduction band to singly positively charged Vzn correspondingly. The effect of annealing in atomic nitrogen flux of p-CaN:Mg films on their photoluminescence spectra and on the value of their conductivity were studied. Such annealing leads to appearance of a number of emission bands that peaked at 404.9, 390.8 and 378.9 nm and increases hole concentration from 5 × 1015 to 5 × 1016 cm-3, and the hole mobility from 120 to 150 cm2/(V s). The n-ZnO - p-GaN:Mg electroluminescence heterostructures were obtained. Their spectrum contains bands in the excitonic region of GaN at the wavelength 360.2 nm and in the edge region at wavelengths 378.9 and 390.8 nm.

Influence of thermally induced structural and morphological changes, and UV irradiation on photoluminescence and optical absorption behavior of CdS nanoparticles

NASA Astrophysics Data System (ADS)

Osman, M. A.; El-Said, Waleed A.; Othman, A. A.; Abd-Elrahim, A. G.

2016-04-01

Polycrystalline cubic CdS nanoparticles (NPs) with a crystallite size ({{D}\\text{Sch}} ) ~3 nm were synthesized by chemical precipitation method at room temperature. Thermal induced structural and morphological changes have been investigated using x-ray diffraction, high-resolution transmission electron microscope, x-ray fluorescence, Fourier transform infrared and Raman spectroscopy. The influence of these changes on optical absorption and photoluminescence (PL) characteristics have been studied. It was found that increasing annealing temperature (T a), results in structural phase transitions at 300 and 700 °C, increasing {{D}\\text{Sch}} and red shift of the optical band gap (E\\text{g}\\text{opt} ) due to the improvement in crystallinity. The photoluminescence emission spectrum of nonstoichiometric CdS (Cd-rich) nanopowder reveals emission bands at 365, 397, and 434 nm. Furthermore, PL spectrum of colloidal solution exhibits additional green and red emission bands at 535, 570 and 622 nm. To explain the mechanism of PL emission in CdS NPs, trapping and radiative recombination levels have been identified and the corresponding energy band diagrams are suggested. Annealing process results in an overall enhancement in PL intensity due to the improvement in crystallinity associated with the reduction of nonradiative surface state defects. Irradiation of CdS NPs colloidal solution at UV irradiation dose  <13 J cm-2 leads to the enhancement of PL quantum efficiency and blue shift of E\\text{g}\\text{opt} (i.e. photo-brightening) due to the decrease in the particle size deduced from Brus equation ≤ft({{D}\\text{Brus}}\\right) , This behavior is due to UV irradiation effects such as photopolymerization, the formation of CdSO4 passivation layers due to photooxidation and the reduction in {{D}\\text{Brus}} by photocorrosion process. At UV irradiation dose  <13 J cm-2, PL emission intensity continuously enhances without any change in both E\\text{g}\\text{opt} and {{D}\\text{Brus}} . This behavior is discussed in terms of electron filling model. Boltzmann curve fitting successfully describes the dependence of both {{D}\\text{Brus}} and E\\text{g}\\text{opt} on UV irradiation dose.

Tuning the optical properties of ZnO nanorods by variation of precursor concentration through hydrothermal method

NASA Astrophysics Data System (ADS)

Kumari, Lakshmi; Kar, Asit Kumar

2018-05-01

ZnO nanorods with varying precursor concentration have been successfully synthesized by the hydrothermal method. The effect of the precursor concentration on the structural, morphological and optical properties of the resulting nanorods was investigated by means of X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), UV-Vis spectroscopy and photoluminescence (PL) spectroscopy. The crystalline structural characterization demonstrated that the synthesized materials crystallize in pure ZnO wurtzite structure without any other secondary phase. SEM micrographs demonstrate nanorod type features in all the samples. In addition, they show that increase of precursor concentration changes the length and diameter of nanorods. The UV-Vis studies show a strong absorption band in UV region at 373 nm attributed to the band-edge absorption of wurtzite hexagonal ZnO, blue shifted relative to its bulk form (380 nm). The PL spectra of obtained nanorods excited at 360 nm present broad visible emission. Moreover, as the visible region (from 510 to 550 nm) is concerned, it is speculated that the increase of the precursor concentration affects strongly the kind of interstitial defects (Oi, Zni and Vo) formed in ZnO nanorods. The luminescence intensity decreases with the increase of precursor concentration.

Enhanced frequency upconversion study in Er3+/Yb3+ doped/codoped TWTi glasses

NASA Astrophysics Data System (ADS)

Azam, Mohd; Rai, Vineet Kumar

2018-04-01

Er3+/Yb3+ doped/codoped TeO2-WO3-TiO2 (TWTi) glasses have been prepared by using the melt-quenching technique. The upconversion (UC) emission spectra of the developed glasses have been recorded upon 980 nm laser excitation. Three intense UC emission bands have been observed within the green and red region centered at ˜532 nm, ˜553 nm and ˜669 nm corresponding to the 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions respectively in the singly Er3+ doped glass. On introducing Yb3+ ions in the singly Er3+ doped glass, an enhancement of about ˜ 12 times and ˜50 times in the green and red bands respectively have been observed even at low pump power ˜ 364 mW followed by two photon absorption process. Colour tunability from yellowish green to pure green colour region has been observed on varying the pump power. The prepared glass can be used to produce NIR to green upconverter and colour tunable display devices.

Detection and evaluation of normal and malignant cells using laser-induced fluorescence spectroscopy.

PubMed

Khosroshahi, Mohamad E; Rahmani, Mahya

2012-01-01

The aim of this research is to study the normalized fluorescence spectra (intensity variations and area under the fluorescence signal), relative quantum yield, extinction coefficient and intracellular properties of normal and malignant human bone cells. Using Laser-Induced Fluorescence Spectroscopy (LIFS) upon excitation of 405 nm, the comparison of emission spectra of bone cells revealed that fluorescence intensity and the area under the spectra of malignant bone cells was less than that of normal. In addition, the area ratio and shape factor were changed. We obtained two emission bands in spectra of normal cells centered at about 486 and 575 nm and for malignant cells about 482 and 586 nm respectively, which are most likely attributed to NADH and riboflavins. Using fluorescein sodium emission spectrum, the relative quantum yield of bone cells is numerically determined.

Luminescence characteristics of nanoporous anodic alumina annealed at different temperatures

NASA Astrophysics Data System (ADS)

Ilin, D. O.; Vokhmintsev, A. S.; Weinstein, I. A.

2016-09-01

Anodic aluminum oxide (AAO) membranes with 100 µm thickness were synthesized in oxalic acid solution under constant current density. Grown samples were annealed in 500-1250 °C range for 5 h in air. Average pore diameter was evaluated using quantitative analysis of SEM images and appeared to be within 78-86 nm diapason. It was found there was a broad emission band in the 350-620 nm region of photoluminescence (PL) spectra in amorphous membranes which is attributed to F-type oxygen deficient centers or oxalic ions. It was shown that intensive red emission caused by Cr3+ (696 nm) and Mn4+ (680 nm) impurities dominates in PL of AAO samples with crystalline α- and δ-phases after annealing at 1100-1250 °C temperatures.

Investigation of optical properties of nickel oxide nanostructures using photoluminescence and diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Siddique, M. Naseem; Ahmed, Ateeq; Ali, T.; Tripathi, P.

2018-05-01

Nickel oxide (NiO) nanoparticles with a crystal size of around 16.26 nm have been synthesized via sol-gel method. The synthesized precursor was calcined at 600 °C for 4 hours to obtain the nickel oxide nanoparticles. The XRD analysis result indicated that the calcined sample has a cubic structure without any impurity phases. The FTIR analysis result confirmed the formation of NiO. The NiO nanoparticle exhibited absorption band edge at 277.27 nm and the optical band gap have been estimated approximately 4.47 eV using diffuse reflectance spectroscopy and photoluminescence emission spectrum of our as-synthesized sample showed strong peak at 3.65 eV attributed to the band edge transition.

Characterization of photoluminescence spectra from poly allyl diglycol carbonate (CR-39) upon excitation with the ultraviolet radiation of various wavelengths

NASA Astrophysics Data System (ADS)

El Ghazaly, M.; Al-Thomali, Talal A.

2013-04-01

The induced photoluminescence (PL) from the π-conjugated polymer poly allyl diglycol carbonate (PADC) (CR-39) upon excitation with the ultraviolet radiation of different wavelengths was investigated. The absorption and attenuation coefficients of PADC (CR-39) were recorded using a UV-visible spectrometer. It was found that the absorption and attenuation coefficients of the PADC (CR-39) exhibit a strong dependence on the wavelength of ultraviolet radiation. The PL spectra were measured with a Flormax-4 spectrofluorometer (Horiba). PADC (CR-39) samples were excited by ultraviolet radiation with wavelengths in the range from 260 to 420 nm and the corresponding PL emission bands were recorded. The obtained results show a strong correlation between the PL and the excitation wavelength of ultraviolet radiation. The position of the fluorescence emission band peak was red shifted starting from 300 nm, which was increased with the increase in the excitation wavelength. The PL yield and its band peak height were increased with the increase in the excitation wavelength till 290 nm, thereafter they decreased exponentially with the increase in the ultraviolet radiation wavelength. These new findings should be considered carefully during the use of the PADC (CR-39) in the scientific applications and in using PADC (CR-39) in eyeglasses.

Ultrasound assisted sonochemical synthesis of samarium doped Y2O3 nanostructures for display applications

NASA Astrophysics Data System (ADS)

Venkatachalaiah, K. N.; Nagabhushana, H.; Basavaraj, R. B.; Venkataravanappa, M.; Suresh, C.

2018-04-01

Sm3+ doped (1-11 mol %) cubic Y2O3 nanoflowers were fabricated by simple low temperature Sonochemical method using Aloe Vera gel as fuel. The product was characterized by PXRD, SEM, TEM, DRS, PL etc. The powder X-ray diffraction (PXRD) profiles of nanophosphors showed cubic phase structure. The particle size was further confirmed by transmission electron microscope (TEM) and it was found to be in the range of 17-25 nm. The PL emission results reveal that the phosphor nanoparticles (NPs) emit an intensive yellowish light under 367 nm excitation. The excitation spectrum of Y2O3: Sm3+ (5 mol %) obtained by monitoring the emission of the 4f - 4f (4G5/2→6H7/2) transition of Sm3+ at 612 nm As can be seen that the excitation spectrum consists of strong band at 332 nm and a broad band centered at 367 nm which corresponds to host absorption, confirming the effective energy transfer from Y2O3 host to Sm3+ ions. In the present study, CIE and CCT were estimated and found to be (0.45688, 0.51727) and the CCT of Y2O3: Sm3+ at 367 nm excitation was found to be 3357 K which was within the range of vertical daylight. Thus it can be useful for artificial production of illumination devices.

Spectral Selectivity of Plasmonic Interactions between Individual Up-Converting Nanocrystals and Spherical Gold Nanoparticles.

PubMed

Piątkowski, Dawid; Schmidt, Mikołaj K; Twardowska, Magdalena; Nyk, Marcin; Aizpurua, Javier; Maćkowski, Sebastian

2017-08-04

We experimentally demonstrate strong spectral selectivity of plasmonic interaction that occurs between α-NaYF₄:Er 3+ /Yb 3+ nanocrystals, which feature two emission bands, and spherical gold nanoparticles, with plasmon frequency resonant with one of the emission bands. Spatially-resolved luminescence intensity maps acquired for individual nanocrystals, together with microsecond luminescence lifetime images, show two qualitatively different effects that result from the coupling between plasmon excitations in metallic nanoparticles and emitting states of the nanocrystals. On the one hand, we observe nanocrystals, whose emission intensity is strongly enhanced for both resonant and non-resonant bands with respect to the plasmon resonance. Importantly, this increase is accompanied with shortening of luminescence decays times. In contrast, a significant number of nanocrystals exhibits almost complete quenching of the emission resonant with the plasmon resonance of gold nanoparticles. Theoretical analysis indicates that such an effect can occur for emitters placed at distances of about 5 nm from gold nanoparticles. While under these conditions, both transitions experience significant increases of the radiative emission rates due to the Purcell effect, the non-radiative energy transfer between resonant bands results in strong quenching, which in that situation nullifies the enhancement.

Photoluminescence and cathodoluminescence of Mn doped zinc silicate nanophosphors for green and yellow field emissions displays

NASA Astrophysics Data System (ADS)

Omri, K.; Alyamani, A.; Mir, L. El

2018-02-01

Mn2+-doped Zn2SiO4 (ZSM2+) was synthesized by a facile sol-gel technique. The obtained samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, photoluminescence (PL) and cathodoluminescence (CL) techniques. Under UV excitation, spectra showed that the α-ZSM2+ phosphor exhibited a strong green emission around 525 nm and reached the highest luminescence intensity with the Mn doping concentration of 5 at.%. However, for the β-ZSM2+ phase, an interesting yellow emission band centered at 575 nm of Mn2+ at the Zn2+ tetrahedral sites was observed. In addition, an unusual red shift with increasing Mn2+ content was also found and attributed to an exchange interaction between Mn2+. Both PL and CL spectra exhibit an intense green and yellow emission centered at 525 and 573 nm, respectively, due to the 4T1 (4G)-6A1 (6S) transition of Mn2+. Furthermore, these results indicated that the Mn2+-doped zinc silicate phosphors may have potential applications in green and yellow emissions displays like field emission displays (FEDs).

Structure and photoluminescence properties of TeO2-core/TiO2-shell nanowires

NASA Astrophysics Data System (ADS)

Park, Sunghoon; An, Soyeon; Lee, Chongmu

2013-12-01

TeO2-core/TiO2-shell nanowires were fabricated by thermal evaporation of Te powders and MOCVD of TiO2. The as-synthesized TeO2 nanowires showed a weak broad violet band centered at approximately 430 nm. The emission peak was shifted to a bluish violet region (∼455 nm) by the encapsulation of the nanowires with a TiO2 thin film. The intensity of the major emission from the core-shell nanowires showed strong dependence on the shell layer thickness. The strongest emission was obtained for the shell layer thickness of ∼15 nm and its intensity was approximately 80 times higher than that of the violet emission from the as-synthesized TeO2 nanowires. This enhancement in emission intensity is attributed to the subwavelength optical resonant cavity formation in the shell layer. The major emission intensity was enhanced further and blue-shifted by annealing, which might be attributed to the increase in the Ti interstitial and O vacancy concentrations in the TeO2 cores during annealing.

Fluorescence spectroscopy in the visible range for the assessment of UVB radiation effects in hairless mice skin.

PubMed

de Paula Campos, Carolina; de Paula D'Almeida, Camila; Nogueira, Marcelo Saito; Moriyama, Lilian Tan; Pratavieira, Sebastião; Kurachi, Cristina

2017-12-01

Ultraviolet (UV) radiation may induce skin alterations as observed in photoaging. Some recognized modifications are epidermal hyperplasia, amorphous deposition of degraded elastic fibers and reduction in the number of collagen fibers. They alter the tissue biochemical properties that can be interrogated by steady state fluorescence spectroscopy (SSFS). In this study, we monitored the changes in endogenous fluorescence emission from hairless mice skin during a protocol of photoaging using UVB irradiation. To perform the fluorescence spectroscopy, it was used a violet laser (408nm) to induce the native fluorescence that is emitted in the visible range. Under 408nm excitation, the emission spectrum showed bands with peaks centered around 510, 633 and 668nm for irradiated and control groups. A relative increase of the fluorescence at 633nm emission on the flank was observed with time when compared to the ventral skin at the same animal and the non-irradiated control group. We correlated the emission at 633nm with protoporphyrin IX (PpIX), and our hypothesis is that the PpIX metabolism in the photoaged and aged skin are different. PpIX fluorescence intensity in the photoaged skin is higher and more heterogeneous than in the aged skin. Notwithstanding, more spectroscopic and biochemistry studies investigating the 510 and 633nm emission are needed to confirm this hypothesis. Copyright © 2017 Elsevier B.V. All rights reserved.

Deep-UV emission at 219 nm from ultrathin MBE GaN/AlN quantum heterostructures

NASA Astrophysics Data System (ADS)

Islam, S. M.; Protasenko, Vladimir; Lee, Kevin; Rouvimov, Sergei; Verma, Jai; Xing, Huili Grace; Jena, Debdeep

2017-08-01

Deep ultraviolet (UV) optical emission below 250 nm (˜5 eV) in semiconductors is traditionally obtained from high aluminum containing AlGaN alloy quantum wells. It is shown here that high-quality epitaxial ultrathin binary GaN quantum disks embedded in an AlN matrix can produce efficient optical emission in the 219-235 nm (˜5.7-5.3 eV) spectral range, far above the bulk bandgap (3.4 eV) of GaN. The quantum confinement energy in these heterostructures is larger than the bandgaps of traditional semiconductors, made possible by the large band offsets. These molecular beam epitaxy-grown extreme quantum-confinement GaN/AlN heterostructures exhibit an internal quantum efficiency of 40% at wavelengths as short as 219 nm. These observations together with the ability to engineer the interband optical matrix elements to control the direction of photon emission in such binary quantum disk active regions offer unique advantages over alloy AlGaN quantum well counterparts for the realization of deep-UV light-emitting diodes and lasers.

Eu2+ -induced enhancement of defect luminescence of ZnS.

PubMed

Xiao-Bo, Zhang; Fu-Xiang, Wei

2016-12-01

The Eu 2 + -induced enhancement of defect luminescence of ZnS was studied in this work. While photoluminescence (PL) spectra exhibited 460 nm and 520 nm emissions in both ZnS and ZnS:Eu nanophosphors, different excitation characteristics were shown in their photoluminescence excitation (PLE) spectra. In ZnS nanophosphors, there was no excitation signal in the PLE spectra at the excitation wavelength λ ex  > 337 nm (the bandgap energy 3.68 eV of ZnS); while in ZnS:Eu nanophosphors, two excitation bands appeared that were centered at 365 nm and 410 nm. Compared with ZnS nanophosphors, the 520 nm emission in the PL spectra was relatively enhanced in ZnS:Eu nanophosphors and, furthermore, in ZnS:Eu nanophosphors the 460 nm and 520 nm emissions increased more than 10 times in intensity. The reasons for these differences were analyzed. It is believed that the absorption of Eu 2 + intra-ion transition and subsequent energy transfer to sulfur vacancy, led to the relative enhancement of the 520 nm emission in ZnS:Eu nanophosphors. In addition, more importantly, Eu 2 + acceptor-bound excitons are formed in ZnS:Eu nanophosphors and their excited levels serve as the intermediate state of electronic relaxation, which decreases non-radiative electronic relaxation and thus increases the intensity of the 460 nm and 520 nm emission dramatically. In summary, the results in this work indicate a new mechanism for the enhancement of defect luminescence of ZnS in Eu 2 + -doped ZnS nanophosphors. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Luminescence investigation and thermal stability of blue-greenish emission generated from Ca3MgSi2O8: Eu2+ phosphor

NASA Astrophysics Data System (ADS)

Stefańska, D.; Dereń, P. J.

2018-06-01

Europium-doped silicate Ca3MgSi2O8 has been successfully obtained using solid-state reaction at 1400 °C in a vacuum atmosphere. The photoluminescence study of Eu2+ in investigated host showed broad emission band with a maximum at 480 nm attributed to the allowed 5d → 4f electron transition of Eu2+ located in two different crystallographic sites. The excitation, emission spectra as well as the luminescence decays were analyzed. Thermal quenching process begins at 240 K, however, the emission stability of investigated compound is quite good, and emission intensity reached to 70% of its initial value at 100 °C. The QE of Ca3MgSi2O8: 0.5% Eu2+ excited at 365 nm equal to 47%.

Aligned silica nanowires on the inner wall of bubble-like silica film: the growth mechanism and photoluminescence.

PubMed

Chen, Yiqing; Zhou, Qingtao; Jiang, Haifeng; Su, Yong; Xiao, Haihua; Zhu, Li-Ang; Xu, Liang

2006-02-28

Large area, aligned amorphous silica nanowires grow on the inner wall of bubble-like silica film, which is prepared by thermal evaporation of a molten gallium-silicon alloy in a flow of ammonia. These nanowires are 10-20 nm in diameter and 0.5-1.5 µm in length. The bubble-like silica film functions as a substrate, guiding the growth of silica nanowires by a vapour-solid process. This work helps us to clearly elucidate the growth mechanism of aligned amorphous silica nanowires, ruling out the possibility of liquid gallium acting as a nucleation substrate for the growth of the aligned silica nanowires. A broad emission band from 290 to 600 nm is observed in the photoluminescence (PL) spectrum of these nanowires. There are seven PL peaks: two blue emission peaks at 430 nm (2.88 eV) and 475 nm (2.61 eV); and five ultraviolet emission peaks at 325 nm (3.82 eV), 350 nm (3.54 eV), 365 nm (3.40 eV), 385 nm (3.22 eV) and 390 nm (3.18 eV), which may be related to various oxygen defects.

Spectroscopic properties of the 1.4 microm emission of Tm3+ ions in TeO2-WO3-PbO glasses.

PubMed

Balda, R; Lacha, L M; Fernández, J; Arriandiaga, M A; Fernández-Navarro, J M; Muñoz-Martin, D

2008-08-04

In this work, we report the spectroscopic properties of the infrared 3H4-->3F4 emission of Tm3+ ions in two different compositions of glasses based on TeO2, WO3, and PbO for three Tm2O3 concentrations (0.1,0.5, and 1 wt%). Judd-Ofelt intensity parameters have been determined and used to calculate the radiative transition probabilities and radiative lifetimes. The infrared emission at around 1490 nm corresponding to the 3H4-->F4 transition has two noticeable features if compared to fluoride glasses used for S-band amplifiers. On one hand, it is broader by nearly 30 nm, and on the other, the stimulated emission cross section is twice the value for fluoride glasses. Both the relative intensity ratio of the 1490 nm emission to 1820 nm and the measured lifetime of the 3H4 level decrease as concentration increases, due to the existence of energy transfer via cross-relaxation among Tm3+ ions. The analysis of the decays from the 3H4 level with increasing concentration indicates the presence of a dipole-dipole quenching process assisted by energy migration.

Modeling of N2 and O optical emissions for ionosphere HF powerful heating experiments

NASA Astrophysics Data System (ADS)

Sergienko, T.; Gustavsson, B.

Analyses of experiments of F region ionosphere modification by HF powerful radio waves show that optical observations are very useful tools for diagnosing of the interaction of the probing radio wave with the ionospheric plasma Hitherto the emissions usually measured in the heating experiment have been the 630 0 nm and the 557 7 nm lines of atomic oxygen Other emissions for instance O 844 8 nm and N2 427 8 nm have been measured episodically in only a few experiments although the very rich optical spectrum of molecular nitrogen potentially involves important information about ionospheric plasma in the heated region This study addresses the modeling of optical emissions from the O and the N2 triplet states first positive second positive Vegard-Kaplan infrared afterglow and Wu-Benesch band systems excited under a condition of the ionosphere heating experiment The auroral triplet state population distribution model was modified for the ionosphere heating conditions by using the different electron distribution functions suggested by Mishin et al 2000 2003 and Gustavsson at al 2004 2005 Modeling results are discussed from the point of view of efficiency of measurements of the N2 emissions in future experiments

A room-temperature-operated Si LED with β-FeSi2 nanocrystals in the active layer: μW emission power at 1.5 μm

NASA Astrophysics Data System (ADS)

Shevlyagin, A. V.; Goroshko, D. L.; Chusovitin, E. A.; Balagan, S. A.; Dotsenko, S. A.; Galkin, K. N.; Galkin, N. G.; Shamirzaev, T. S.; Gutakovskii, A. K.; Latyshev, A. V.; Iinuma, M.; Terai, Y.

2017-03-01

This article describes the development of an Si-based light-emitting diode with β-FeSi2 nanocrystals embedded in the active layer. Favorable epitaxial conditions allow us to obtain a direct band gap type-I band alignment Si/β-FeSi2 nanocrystals/Si heterostructure with optical transition at a wavelength range of 1500-1550 nm at room temperature. Transmission electron microscopy data reveal strained, defect-free β-FeSi2 nanocrystals of diameter 6 and 25 nm embedded in the Si matrix. Intense electroluminescence was observed at a pumping current density as low as 0.7 A/cm2. The device reached an optical emission power of up to 25 μW at 9 A/cm2 with an external quantum efficiency of 0.009%. Watt-Ampere characteristic linearity suggests that the optical power margin of the light-emitting diode has not been exhausted. Band structure calculations explain the luminescence as being mainly due to radiative recombination in the large β-FeSi2 nanocrystals resulting from the realization of an indirect-to-direct band gap electronic configuration transformation arising from a favorable deformation of nanocrystals. The direct band gap structure and the measured short decay time of the luminescence of several tens of ns give rise to a fast operation speed for the device. Thus a method for developing a silicon-based photonic integrated circuit, combining complementary metal-oxide-semiconductor technology functionality and near-infrared light emission, is reported here.

Optical Properties of Nickel(ii) and Radiation Defects in Magnesium-Fluoride and Manganese-Fluoride

NASA Astrophysics Data System (ADS)

Feuerhelm, Leonard Norman

1980-12-01

Scope and Method of Study. A study has been made of the radiation defects in pure MgF(,2) by observating the polarized absorption, luminescence, and excitation spectra in electron-irradiated MgF(,2). Additionally, studies of the absorption, emission, excitation, and temperature dependence of the lifetimes of transitions in nickel-doped MgF(,2) and MnF(,2) have been accomplished, as well as the observation of radiation effects on these crystals. Findings and Conclusions. The absorption band at about 320 nm in irradiated MgF(,2) is identified to be due to the F(,2)(D(,2h)) center, and to have an emission at about 450 nm. Analysis of the temperature dependence of this band indicates a dominant phonon mode of 255 cm(' -1) for the excited state. The F(,2)(C(,1)) center is identified with an absorption of about 360 nm and an emission of 410 nm. An absorption peak at 300 nm, for which no corresponding emission has been found, is tentatively identified to be the F(,3)-center, and to have a dominant phonon mode of 255 cm('-1). The temperature dependence of the lifetimes of transitions in nickel-doped MgF(,2) have been analyzed by the quantum mechanical single configuration coordinate model of Struck and Fonger, and a complete configuration coordinate model has been made for this crystal. Similar studies have been made in MnF(,2):Ni, but energy transfer between Mn('2+) ions and Ni('2+) ions prevents completion of the complete model. Energy transfer in this crystal was studied, with the finding that a gain of about 2 in luminescence output was possible for excitation in the visible region (400-600 nm) as compared with MgF(,2):Ni. The effects of radiation upon the Ni('2+) transitions in these crystals were studied with the finding that no observable change occurred in the Ni('2+) transitions with radiation, although other radiation effects were noted in the crystal.

Spectral dependence of irreversible light-induced fluorescence quenching: Chlorophyll forms with maximal emission at 700-702 and 705-710nm as spectroscopic markers of conformational changes in the core complex.

PubMed

Nematov, Sherzod; Casazza, Anna Paola; Remelli, William; Khuvondikov, Vakhobjon; Santabarbara, Stefano

2017-07-01

The spectral dependence of the irreversible non-photochemical fluorescence quenching associated with photoinhibition in vitro has been comparatively investigated in thylakoid membranes, PSII enriched particles and PSII core complexes isolated from spinach. The analysis of the fluorescence emission spectra of dark-adapted and quenched samples as a function of the detection temperature in the 280-80K interval, indicates that Chlorophyll spectral forms having maximal emission in the 700-702nm and 705-710nm ranges gain relative intensity in concomitance with the establishment of irreversible light-induced quenching, acting thereby as spectroscopic markers. The relative enhancement of the 700-702nm and 705-710nm forms emission could be due either to an increase of their stoichiometric abundance or to their intrinsically low fluorescence quantum yields. These two factors, that can also coexist, need to be promoted by light-induced alterations in chromophore-protein as well as chromophore-chromophore interactions. The bands centred at about 701 and 706nm are also observed in the PSII core complex, suggesting their, at least partial, localisation in proximity to the reaction centre, and the occurrence of light-induced conformational changes in the core subunits. Copyright © 2017 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Ren-Chun; Zhang, You-Juan; Yuan, Bai-Qing

A new three-dimensional framework iodide, (DabcoH){sub 2}[(Dabco){sub 2}Ag{sub 14}I{sub 16}] (1), was solvothermal synthesized by transformation of dense AgI using p-methylthiophenol as mineralizer, and characterized by elemental analysis, single-crystal and powder X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry analysis, UV–vis diffuse reflectance spectroscopy and fluorescence spectroscopy. Compound 1 crystallizes in the trigonal space group R-3c, a=13.4452(2) Å, c=63.725(2) Å, V=9976.5(4) Å{sup 3}, Z=6. It features a 3D silver-rich [(Dabco){sub 2}Ag{sub 14}I{sub 16}]{sup 2−} anionic framework built up from corner-sharing of hybrid [(Dabco){sub 2}Ag{sub 14}I{sub 19}]{sup 5−} clusters, with protonated DabcoH{sup +} as counterions residing in the channels. UV–vis reflectance spectroscopymore » reveals the band gap of 1 is 3.3 eV. Compound 1 exhibits a strong photoluminescent emission band at 567 nm upon excitation at 489 nm. - Graphical abstract: A new 3-D iodoargentate was synthesized by transformation of dense AgI in I{sup −}-deficient system using thiophenol as mineralizer. - Highlights: • We have developed a new method to synthesize iodide using thiophenol as mineralizer. • A new 3D iodide, (DabcoH){sub 2}[(Dabco){sub 2}Ag{sub 14}I{sub 16}], was synthesized by transformation of dense AgI under solvothermal condition. • The compound features a 3D Ag–I framework with highest Ag/I ratio. • Compound 1 is a semiconductor with the band gap of 3.3 eV. • Compound 1 exhibits a strong photoluminescent emission band at 567 nm upon excitation at 489 nm.« less

A new silver metaniobate semiconductor of Ag0.5La0.5Nb2O6 with defect-perovskite structure

NASA Astrophysics Data System (ADS)

Mi, Longqing; Feng, Yongyi; Cao, Lei; Xue, Mingqiang; Huang, Yanlin; Qin, Lin; Seo, Hyo Jin

2018-03-01

Silver-containing lanthanum metaniobate Ag0.5La0.5Nb2O6 nanoparticles were synthesized by sol-gel polymerized complex method. A typical defect-perovskite structure was confirmed by XRD Rietveld refinements. The surface characteristics of the sample were tested by SEM, TEM and EDS measurements. SEM and TEM show that the sample presents ball-like particles with the diameters of 100 nm to 400 nm. The sample shows both self-activated luminescence and photocatalytic activities. Ag0.5La0.5Nb2O6 has a direct transition with band energy of 2.85 eV. The Ag4d-O2p hybridization in the valence band contributes to the narrowed band gap. The luminescence properties of Ag0.5La0.5Nb2O6 have been investigated for the first time. The luminescence is characterized by two emission centers with maximum wavelength near 460 and 530 nm. The emission and excitation spectra, decay curves and the thermal quenching mechanism were discussed. Ag0.5La0.5Nb2O6 shows the efficient photocatalytic activities and the photodegradation rate for methylene blue dye (MB) can reach about 95% under visible light (> 420 nm) irradiation in 5 h. The trapped experiments for the active species were tested and discussed, which verified that rad OH radicals could be the major active species in photocatalysis.

Spectrofluorimetric assessment of hydrochlorothiazide using optical sensor nano-composite terbium ion doped in sol-gel matrix.

PubMed

Youssef, A O

2012-05-01

A new, simple, sensitive and selective spectrofluorimetric method for the determination of Hydrochlorothiazide was developed in acetonitrile at pH 6.2. The Hydrochlorothiazide can remarkably enhance the luminescence intensity of the Tb(3+) ion doped in sol-gel matrix at λ(ex) = 370 nm. The intensity of the emission band of Tb(3+) ion doped in sol-gel matrix was increased due to the energy transfer from the triplet excited state of Hydrochlorothiazide to ((5)D(4)) excited energy state of Tb(3) ion. The enhancement of the emission band of Tb(3+) ion doped in sol-gel matrix at ((5)D(4)→(7)F(5)) 545 nm was directly proportion to the concentration of Hydrochlorothiazide with a dynamic ranges of 5.0 × 10(-10)-5.0 × 10(-6) mol L(-1) and detection limit of 2.2 × 10(-11) mol L(-1).

Highly sensitive and selective spectrofluorimetric determination of metoclopramide hydrochloride in pharmaceutical tablets and serum samples using Eu3+ ion doped in sol-gel matrix.

PubMed

Attia, M S; Aboaly, M M

2010-06-30

A simple, sensitive and selective spectrofluorimetric method for the determination of Metoclopramide hydrochloride (MCP) is developed. The MCP can remarkably enhances the luminescence intensity of the Eu(3+) ion doped in sol-gel matrix at lambda(ex)=380 nm in DMSO at pH 8.7. The intensity of the emission band of Eu(3+) ion doped in sol-gel matrix increases due to energy transfer from MCP to Eu(3+) in the excited state. The enhancement of the emission band of Eu(3+) ion doped in sol-gel matrix at 617 nm was found to be directly proportional to the concentration of MCP with a dynamic range of 5 x 10(-9) - 1.0 x 10(-6) mol L(-1) and detection limit of 2.2 x10(-11) mol L(-1). Copyright 2010 Elsevier B.V. All rights reserved.

Room temperature three-photon pumped CH3NH3PbBr3 perovskite microlasers.

PubMed

Gao, Yisheng; Wang, Shuai; Huang, Can; Yi, Ningbo; Wang, Kaiyang; Xiao, Shumin; Song, Qinghai

2017-03-28

Hybrid lead halide perovskites have made great strides in next-generation light-harvesting and light emitting devices. Recently, they have also shown great potentials in nonlinear optical materials. Two-photon absorption and two-photon light emission have been thoroughly studied in past two years. However, the three-photon processes are rarely explored, especially for the laser emissions. Here we synthesized high quality CH 3 NH 3 PbBr 3 perovskite microstructures with solution processed precipitation method and studied their optical properties. When the microstructures are pumped with intense 1240 nm lasers, we have observed clear optical limit effect and the band-to-band photoluminescence at 540 nm. By increasing the pumping density, whispering-gallery-mode based microlasers have been achieved from CH 3 NH 3 PbBr 3 perovskite microplate and microrod for the first time. This work demonstrates the potentials of hybrid lead halide perovskites in nonlinear photonic devices.

Room temperature three-photon pumped CH3NH3PbBr3 perovskite microlasers

NASA Astrophysics Data System (ADS)

Gao, Yisheng; Wang, Shuai; Huang, Can; Yi, Ningbo; Wang, Kaiyang; Xiao, Shumin; Song, Qinghai

2017-03-01

Hybrid lead halide perovskites have made great strides in next-generation light-harvesting and light emitting devices. Recently, they have also shown great potentials in nonlinear optical materials. Two-photon absorption and two-photon light emission have been thoroughly studied in past two years. However, the three-photon processes are rarely explored, especially for the laser emissions. Here we synthesized high quality CH3NH3PbBr3 perovskite microstructures with solution processed precipitation method and studied their optical properties. When the microstructures are pumped with intense 1240 nm lasers, we have observed clear optical limit effect and the band-to-band photoluminescence at 540 nm. By increasing the pumping density, whispering-gallery-mode based microlasers have been achieved from CH3NH3PbBr3 perovskite microplate and microrod for the first time. This work demonstrates the potentials of hybrid lead halide perovskites in nonlinear photonic devices.

Dissociative Excitation of Acetylene Induced by Electron Impact: Excitation-emission Cross-sections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Országh, Juraj; Danko, Marián; Čechvala, Peter

The optical emission spectrum of acetylene excited by monoenergetic electrons was studied in the range of 190–660 nm. The dissociative excitation and dissociative ionization associated with excitation of the ions initiated by electron impact were dominant processes contributing to the spectrum. The spectrum was dominated by the atomic lines (hydrogen Balmer series, carbon) and molecular bands (CH(A–X), CH(B–X), CH{sup +}(B–A), and C{sub 2}). Besides the discrete transitions, we have detected the continuum emission radiation of ethynyl radical C{sub 2}H(A–X). For most important lines and bands of the spectrum we have measured absolute excitation-emission cross sections and determined the energy thresholdsmore » of the particular dissociative channels.« less

Crystal structure and luminescent properties of Sr2SiO4:Eu2+ phosphor prepared by sol-gel method.

PubMed

Pan, Heng; Li, Xu; Zhang, Jinping; Guan, Li; Su, Hongxin; Yang, Zhiping; Teng, Feng

2016-07-04

A series of Eu2+ (0.0025≤ × ≤0.025) activated Sr2SiO4:xEu2+ (SSO:xEu2+) phosphors were synthesized via a sol-gel method. The phosphors were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. The differences between α' and β phase of SSO in the density of states and energy band gap were investigated. The energy gap of α'-SSO and β-SSO are 4.489 and 4.106 eV, respectively. While, two samples showed similar total and partial densities of states. Under the excitation by the ultra violet (UV) light (365 nm), the SSO:xEu2+ phosphor exhibited a green emission band from 400 to 700 nm, which was corresponding to the transition of 5d → 4f of Eu2+ ions. Two emission peaks at 464 and 532 nm could be obtained through Gauss fitting curves. The ratio of the blue to green emission peak decreased with the Eu2+ concentration and the peaks shifted regularly with it. The thermal quenching property was investigated and its activation energy was calculated. The results indicated that this phosphor could be a candidate of green phosphor for UV-based light-emitting diodes (LEDs).

Effect of AgCl NPs: Physical, thermal, absorption and luminescence properties

NASA Astrophysics Data System (ADS)

Nurhafizah, H.; Rohani, M. S.

2017-06-01

Silver nanoparticles (AgCl NPs) are embedded in Er3+/Nd3+ co-doped lithium niobate tellurite glasses of the form (68-x)TeO2-15Li2CO3-15Nb2O5-1Er2O3-1Nd2O3-(x)AgCl with x = 1,2 and 3 mol% via conventional melt-quenching technique. The physical properties such as density, ionic packing density, refractive index and electronic polarizability are computed utilizing the usual method. The existence of AgCl NPs with an average size of 3.7 nm is confirmed using TEM analysis. Moreover, the thermal stability and Hruby criterion of the glass decreases as the AgCl NPs content increases. The direct optical band gap are found decrease as the AgCl NPs content increase, but both indirect optical band gap and Urbach energy are found increases as AgCl NPs content increases. The luminescence spectra shows two strong emission which is the purple emission at 436 nm and red emission at 724 nm which also been observed has strong quenching due to the AgCl NPs, Er3+/Nd3+ dopant and modifier, lithium niobate which possessed magnetic penetration. These glass compositions may be potential for various applications such as solid state devices including laser.

Giant Enhancement of Defect-Bound Exciton Luminescence and Suppression of Band-Edge Luminescence in Monolayer WSe2-Ag Plasmonic Hybrid Structures.

PubMed

Johnson, Alex D; Cheng, Fei; Tsai, Yutsung; Shih, Chih-Kang

2017-07-12

We have investigated how the photoluminescence (PL) of WSe 2 is modified when coupled to Ag plasmonic structures at low temperature. Chemical vapor deposition (CVD) grown monolayer WSe 2 flakes were transferred onto a Ag film and a Ag nanotriangle array that had a 1.5 nm Al 2 O 3 capping layer. Using low-temperature (7.5 K) micro-PL mapping, we simultaneously observed enhancement of the defect-bound exciton emission and quenching of the band edge exciton emission when the WSe 2 was on a plasmonic structure. The enhancement of the defect-bound exciton emission was significant with enhancement factors of up to ∼200 for WSe 2 on the nanotriangle array when compared to WSe 2 on a 1.5 nm Al 2 O 3 capped Si substrate with a 300 nm SiO 2 layer. The giant enhancement of the luminescence from the defect-bound excitons is understood in terms of the Purcell effect and increased light absorption. In contrast, the surprising result of luminescence quenching of the bright exciton state on the same plasmonic nanostructure is due to a rather unique electronic structure of WSe 2 : the existence of a dark state below the bright exciton state.

Structural and optical characterizations of Ca2Al2SiO7:Ce3+, Mn2+ nanoparticles produced via a hybrid route

NASA Astrophysics Data System (ADS)

Teixeira, V. C.; Montes, P. J. R.; Valerio, M. E. G.

2014-07-01

Pure, Ce3+ doped and Ce3+ and Mn2+ co-doped Ca2Al2SiO7 ceramic powders were prepared by two different methodologies which are the proteic sol-gel process and a new hybrid route combining the proteic sol-gel with solid state reaction processes. The second one is an eco-friendly method because it uses natural raw materials in replacement of the metal alkoxides used in the traditional sol-gel routes. X-ray diffraction showed that Ca2Al2SiO7 crystalline phase was obtained for both preparations. Differential thermal analysis indicated that the exothermic event around 850 °C, for sample produced by proteic sol-gel method, and around 927 °C, for ceramics prepared by hybrid synthesis, can be associated to crystallization of Ca2Al2SiO7. Transmission electron microscope indicates that regular and spherical nanoparticles were obtained with average sizes of about 12 nm. The Scherrer's method was used to determine the average crystallite sizes and it was shown that nanometric crystallites were obtained of about 74 nm for samples produced via hybrid route. For all the single phase samples, the crystallite sizes are about the same and that agrees with TEM results. Diffuse optical reflectance measurements were used to estimate the Ca2Al2SiO7 optical band gap and the obtained value is about 6 eV, photoluminescence (PL) spectra presented typical emissions of Ce3+ and Mn2+ ions. Upon excitation at 352 nm the emission spectra showed a broad band centered at 415 nm due to the Ce3+ 4f1 → 5d1 typical transition. This emission is resonant with Mn2+ excitation and it transfers energy to Mn ions generating a second broad emission band centered at 620 nm due to the Mn2+. The PL results were used to obtain, as a fist approach, the Ce3+ energy levels diagram and, using the Tanabe-Sugano diagrams, the transitions due to the Mn2+ were calculated. X-ray excited optical luminescence measurements showed the same emission spectra as the PL emission spectra. Luminescence lifetime decay constants were measured for Ce and Mn co-doped and for Ce doped samples and the results indicate Ca2Al2SiO7:Ce3+, Mn2+ showed quite fast responses with main time constants below 30 ns.

Efficient Green Emission from Wurtzite Al xIn1- xP Nanowires.

PubMed

Gagliano, L; Kruijsse, M; Schefold, J D D; Belabbes, A; Verheijen, M A; Meuret, S; Koelling, S; Polman, A; Bechstedt, F; Haverkort, J E M; Bakkers, E P A M

2018-06-13

Direct band gap III-V semiconductors, emitting efficiently in the amber-green region of the visible spectrum, are still missing, causing loss in efficiency in light emitting diodes operating in this region, a phenomenon known as the "green gap". Novel geometries and crystal symmetries however show strong promise in overcoming this limit. Here we develop a novel material system, consisting of wurtzite Al x In 1- x P nanowires, which is predicted to have a direct band gap in the green region. The nanowires are grown with selective area metalorganic vapor phase epitaxy and show wurtzite crystal purity from transmission electron microscopy. We show strong light emission at room temperature between the near-infrared 875 nm (1.42 eV) and the "pure green" 555 nm (2.23 eV). We investigate the band structure of wurtzite Al x In 1- x P using time-resolved and temperature-dependent photoluminescence measurements and compare the experimental results with density functional theory simulations, obtaining excellent agreement. Our work paves the way for high-efficiency green light emitting diodes based on wurtzite III-phosphide nanowires.

Chromium doped nano-phase separated yttria-alumina-silica glass based optical fiber preform: fabrication and characterization

NASA Astrophysics Data System (ADS)

Dutta, Debjit; Dhar, Anirban; Das, Shyamal; Bysakh, Sandip; Kir'yanov, Alexandar; Paul, Mukul Chandra

2015-06-01

Transition metal (TM) doping in silica core optical fiber is one of the research area which has been studied for long time and Chromium (Cr) doping specially attracts a lot of research interest due to their broad emission band covering U, C and L band with many potential application such as saturable absorber or broadband amplifier etc. This paper present fabrication of Cr doped nano-phase separated silica fiber within yttria-alumina-silica core glass through conventional Modified Chemical Vapor Deposition (MCVD) process coupled with solution doping technique along with different material and optical characterization. For the first time scanning electron microscope (SEM) / energy dispersive X-ray (EDX) analysis of porous soot sample and final preform has been utilized to investigate incorporation mechanism of Crions with special emphasis on Cr-species evaporation at different stages of fabrication. We also report that optimized annealing condition of our fabricated preform exhibited enhanced fluorescence emission and a broad band within 550- 800 nm wavelength region under pumping at 532 nm wavelength due to nano-phase restructuration.

Intense blue upconversion emission and intrinsic optical bistability in Tm3+/Yb3+/Zn2+ tridoped YVO4 phosphors

NASA Astrophysics Data System (ADS)

Yadav, Manglesh; Mondal, Manisha; Mukhopadhyay, Lakshmi; Rai, Vineet Kumar

2018-04-01

Tm3+/Yb3+/Zn2+:yttrium metavanadate (YVO4) phosphors prepared through chemical coprecipitation and the solid state reaction method have been structurally characterized by an x-ray diffraction (XRD) study. Photoluminescence study of the developed phosphors under ultraviolet (UV) and near infrared (NIR) excitation has been performed. The excitation spectrum of the tetragonal zircon type YVO4 phosphors corresponding to the emission at ˜476 nm exhibits a broad excitation peak in the 250-350 nm region, which is due to charge distribution in the {{{{VO}}}4}3- group. Under 980 nm CW diode laser excitation, enhancements of about ˜3000 times and ˜40 times have been observed for the blue band in the tridoped Tm3+Yb3+Zn2+:YVO4 phosphors compared to those of the Tm3+:YVO4 singly and Tm3+/Yb3+:YVO4 codoped phosphors, respectively. A downconversion (DC) emission study shows an enhancement of about ˜50 times for the blue band in the tridoped phosphors compared to that of the singly doped phosphors. Optical bistability (OB) behavior of the developed phosphors has been also investigated upon 980 nm excitation. The calculated Commission Internationale de l’Éclairage (CIE) color coordinates lie in the blue region with 96.5% color purity under 980 nm excitation, having a color temperature of ˜3400 K. Our observations show that the developed phosphors may be suitably used in dual mode luminescence spectroscopy, display devices, and UV LED chips.

Intense blue upconversion emission and intrinsic optical bistability in Tm3+/Yb3+/Zn2+ tridoped YVO4 phosphors.

PubMed

Yadav, Manglesh; Mondal, Manisha; Mukhopadhyay, Lakshmi; Rai, Vineet Kumar

2018-01-22

Tm 3+ /Yb 3+ /Zn 2+ :yttrium metavanadate (YVO 4 ) phosphors prepared through chemical coprecipitation and the solid state reaction method have been structurally characterized by an x-ray diffraction (XRD) study. Photoluminescence study of the developed phosphors under ultraviolet (UV) and near infrared (NIR) excitation has been performed. The excitation spectrum of the tetragonal zircon type YVO 4 phosphors corresponding to the emission at ∼476 nm exhibits a broad excitation peak in the 250-350 nm region, which is due to charge distribution in the [Formula: see text] group. Under 980 nm CW diode laser excitation, enhancements of about ∼3000 times and ∼40 times have been observed for the blue band in the tridoped Tm 3+ Yb 3+ Zn 2+ :YVO 4 phosphors compared to those of the Tm 3+ :YVO 4 singly and Tm 3+ /Yb 3+ :YVO 4 codoped phosphors, respectively. A downconversion (DC) emission study shows an enhancement of about ∼50 times for the blue band in the tridoped phosphors compared to that of the singly doped phosphors. Optical bistability (OB) behavior of the developed phosphors has been also investigated upon 980 nm excitation. The calculated Commission Internationale de l'Éclairage (CIE) color coordinates lie in the blue region with 96.5% color purity under 980 nm excitation, having a color temperature of ∼3400 K. Our observations show that the developed phosphors may be suitably used in dual mode luminescence spectroscopy, display devices, and UV LED chips.

Excitonic lasing of strain-free InP(As) quantum dots in AlInAs microdisk

NASA Astrophysics Data System (ADS)

Lebedev, D. V.; Kulagina, M. M.; Troshkov, S. I.; Vlasov, A. S.; Davydov, V. Y.; Smirnov, A. N.; Bogdanov, A. A.; Merz, J. L.; Kapaldo, J.; Gocalinska, A.; Juska, G.; Moroni, S. T.; Pelucchi, E.; Barettin, D.; Rouvimov, S.; Mintairov, A. M.

2017-03-01

Formation, emission, and lasing properties of strain-free InP(As)/AlInAs quantum dots (QDs) embedded in AlInAs microdisk (MD) cavity were investigated using transmission electron microscopy and photoluminescence (PL) techniques. In MD structures, the QDs have the nano-pan-cake shape with the height of ˜2 nm, the lateral size of 20-50 nm, and the density of ˜5 × 109 cm-2. Their emission observed at ˜940 nm revealed strong temperature quenching, which points to exciton decomposition. It also showed unexpected type-I character, indicating In-As intermixing as confirmed by band structure calculations. We observed lasing of InP(As) QD excitons into whispering gallery modes in MD having the diameter of ˜3.2 μm and providing a free spectral range of ˜27 nm and quality factors up to Q˜13 000. Threshold of ˜50 W/cm2 and spontaneous emission coupling coefficient of ˜0.2 were measured for this MD-QD system.

CdZnO coated film: A material for photovoltaic applications

NASA Astrophysics Data System (ADS)

Zargar, R. A.; Bhat, M. A.; Reshi, H. A.; Khan, S. D.

2018-06-01

The present study reports structural and optical parameters of wide band gap oxide thick film prepared by screen-printing followed by sintering route. Characterization of the samples was carried out with UV-spectroscopy, XRD, SEM, and Photoluminous study. The XRD and SEM studies reveal that the film deposited is polycrystalline, double phase, and porous with unsymmetrical grain distributions. Optical diffused reflection spectroscopy and Pl measurements give optical band gap of 2.87 eV and near band edge emission at 430 nm.

A fluorescence approach to the unfolding thermodynamics of horseradish peroxidase based on heme degradation by hydrogen peroxide

NASA Astrophysics Data System (ADS)

Ke, Zhigang; Ma, Shanshan; Li, Lamei; Huang, Qing

2016-07-01

Horseradish peroxidase (HRP) is a classical heme-containing protein which has been applied in many fields. The prosthetic group heme in HRP, especially in unfolded state, can react with hydrogen peroxide (H2O2) to produce a fluorescent product with the maximum emission wavelength at 450 nm. Utilizing this emission band as a fluorescence probe, the unfolding process of HRP in urea can be assessed quantitatively, and the calculated thermodynamic parameters are consistent with those determined by circular dichroism (CD) at 222 nm and steady-state tryptophan (Trp) fluorescence methods.

Development Status of Optical and Electromagnetic Instruments onboard JEM-GLIMS

NASA Astrophysics Data System (ADS)

Sato, Mitsuteru; Ushio, Tomoo; Morimoto, Takeshi; Suzuki, Makoto; Yamazaki, Atsushi; Ishida, Ryohei; Takahashi, Yukihiro; Hobara, Yasuhide; Sakamoto, Yuji; Yoshita, Kengo

In order to study the generation mechanism of Transient Luminous Events (TLEs), global oc-currence rates and distributions of lightning and TLEs, and the relationship between lightning, TLEs and Terrestrial Gamma-ray Flashes (TGFs), we will carry out the lightning and TLE observation at Exposed Facility of Japanese Experiment Module (JEM-EF) of International Space Station (ISS). In this mission named JEM-GLIMS (Global Lightning and sprIte Mea-surementS on JEM-EF) two kinds of optical instruments and two sets of radio receivers will be integrated into the Multi mission Consolidated Equipment (MCE) which is the bus system and will be installed at JEM-EF. The optical instruments consist of two wide FOV CMOS cameras and six wide FOV photometers, and all these optical instruments are pointed to the nadir direction. CMOS cameras named LSI (Lightning and Sprite Imager) use the STAR-250 device as a detector, which has 512x512 pixels and 25x25 µm pixel size, and have 28.3x28.3 deg. FOV. One CMOS camera with a wide band filter (730-830 nm) mainly measures lightning emission, while another camera with a narrowband filter (766+/-6 nm) mainly measures TLE emission. Five of six photometers named as PH have 42.7 deg. FOV and use photomultiplier tube (PMT) as a photon detector. They equip band-pass filters (150-280 nm, 316+/-5 nm, 337+/-5 nm, 392+/-5 nm, and 762+/-5 nm) for the absolute intensity measurement of the TLE emission. One of six photometers equips a wide-band filter (600-900 nm) to detect light-ning occurring within 86.8 deg. FOV. These output signals will be recorded with the sampling frequency of 20 kHz with a 12-bit resolution. One of two electromagnetic instruments is a VLF receiver (VLFR), which measures electromagnetic waves in the frequency range of 1-40 kHz with 16-bit resolution. Another instrument is VHF interferometer (VITF), which measures VHF pulses generated lightning discharge in the frequency range of 70-100 MHz. JEM-GIMS will be launched in 2011. We have passed the critical design review (CDR) on January and February and have started the fabrication of the proto-flight model. We will present the devel-opment status of the JEM-GLISM optical instruments and discuss the scientific outputs derived from this mission more in detail.

Emirates Mars Ultraviolet Spectrometer (EMUS) Overview from the Emirates Mars Mission

NASA Astrophysics Data System (ADS)

Lootah, F. H.; Almatroushi, H. R.; AlMheiri, S.; Holsclaw, G.; Deighan, J.; Chaffin, M.; Reed, H.; Lillis, R. J.; Fillingim, M. O.; England, S.

2017-12-01

The Emirates Mars Ultraviolet Spectrometer (EMUS) instrument is one of three science instruments on board the "Hope Probe" of the Emirates Mars Mission (EMM). EMM is a United Arab Emirates' (UAE) mission to Mars, launching in 2020, to explore the global dynamics of the Martian atmosphere, while sampling on both diurnal and seasonal timescales. The EMUS instrument is a far-ultraviolet imaging spectrograph that measures emissions in the spectral range 100-170 nm. Using a combination of its one-dimensional imaging and spacecraft motion, it will build up two-dimensional far-ultraviolet images of the Martian disk and near-space environment at several important wavelengths: the Lyman beta atomic hydrogen emission (102.6 nm), the Lyman alpha atomic hydrogen emission (121.6 nm), two atomic oxygen emissions (130.4 nm and 135.6 nm), and the carbon monoxide fourth positive group band emission (140 nm-170 nm). Radiances at these wavelengths will be used to derive the column abundance of atomic oxygen, and carbon monoxide in the Martian thermosphere, and the density of atomic oxygen and atomic hydrogen in the Martian exosphere both with spatial and sub-seasonal variability. The EMUS instrument consists of a single telescope mirror feeding a Rowland circle imaging spectrograph with selectable spectral resolution (1.3 nm, 1.8 nm, or 5 nm), and a photon-counting and locating detector (provided by the Space Sciences Laboratory at the University of California, Berkeley). The EMUS spatial resolution of less than 300 km on the disk is sufficient to characterize spatial variability in the Martian thermosphere (100-200 km altitude) and exosphere (>200 km altitude). The instrument is jointly developed by the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder and Mohammed Bin Rashid Space Centre (MBRSC) in Dubai, UAE.

Emirates Mars Ultraviolet Spectrometer (EMUS) Overview from the Emirates Mars Mission

NASA Astrophysics Data System (ADS)

Almatroushi, Hessa; Lootah, Fatma; Holsclaw, Greg; Deighan, Justin; Chaffin, Michael; Lillis, Robert; Fillingim, Matthew; England, Scott; AlMheiri, Suhail; Reed, Heather

2017-04-01

The Emirates Mars Ultraviolet Spectrometer (EMUS) instrument is one of three science instruments to be carried on board the Emirate Mars Mission (EMM), the "Hope Probe". EMM is a United Arab Emirates' (UAE) mission to Mars launching in 2020 to explore the dynamics in the Martian atmosphere globally, while sampling on both diurnal and seasonal timescales. The EMUS instrument is a far-ultraviolet imaging spectrograph that measures emissions in the spectral range 100-170 nm. Using spacecraft motion, it will build up two-dimensional far-ultraviolet images of the Martian disk and near-space environment at several important wavelengths: Lyman beta atomic hydrogen emission (102.6 nm), Lyman alpha atomic hydrogen emission (121.6 nm), atomic oxygen emission (130.4 nm and 135.6 nm), and carbon monoxide fourth positive group band emission (140 nm-170 nm). Radiances at these wavelengths will be used to derive the column abundance of atomic oxygen, and carbon monoxide in the Martian thermosphere, and the density of atomic oxygen and atomic hydrogen in the Martian exosphere both with spatial and sub-seasonal variability. EMUS consists of a single telescope mirror feeding a Rowland circle imaging spectrograph capable of selectable spectral resolution (1.3 nm, 1.8 nm, or 5 nm) with a photon-counting and locating detector (provided by the Space Sciences Laboratory at the University of California, Berkeley). The EMUS spatial resolution of less than 300km on the disk is sufficient to characterize spatial variability in the Martian thermosphere (100-200 km altitude) and exosphere (>200 km altitude). The instrument is jointly developed by the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder and Mohammed Bin Rashid Space Centre (MBRSC) in Dubai, UAE

The influence of the pressure and temperature on the light emission of the ZnO

NASA Astrophysics Data System (ADS)

Dantas, N. O.; Couto dos Santos, M. A.; Cunha, F.; Macêdo, M. A.

2007-09-01

A new route for the preparation of zinc oxide powder is described along with its characterization. A proteic sol was prepared dissolving zinc nitrate in filtered coconut water. After calcination at 1000 °C, the powder was compressed to 1.3×10 8 Pa and ZnO pellets were obtained. The emission spectra were recorded under UV excitation at 325 and 400 nm. The powder showed no spectroscopic response, whereas one peak around 396 nm was observed for the pressed powder (pellet with no heat treatment). The pellets were then annealed for 24 h at 500, 800 and 1000 °C. In the first case, bands at 396 and 440 nm and a structure of narrow peaks around 480 nm (oxygen vacancies) were observed. Increasing the annealing temperature led to a decrease in the intensity of the emissions at 440 and 480 nm. We propose that the high pressure induces a red-shift in the UV region of the ZnO nanopowder emission peaks to 396 nm. This is an indication that the ZnO nanopowder treated under pressure and sintering temperature exhibits the spectroscopic behavior characteristic of the ZnO single crystal. The disappearance of the 440 and 480 nm lines indicate the reduction of oxygen vacancies. The atomic force micrographs suggest a coalescence thermal point.

The effect of ASE reinjection configuration through FBGs on the gain and noise figure performance of L-Band EDFA

NASA Astrophysics Data System (ADS)

Durak, Fırat Ertaç; Altuncu, Ahmet

2017-03-01

In this study, we present the gain and noise figure performance improvement in L-band erbium-doped fiber amplifier (L-EDFA) provided by amplified spontaneous emission (ASE) reinjection through different configurations of 1533 nm band FBGs. The experimental results are compared with a single-stage bidirectionally pumped conventional L-EDFA design. It is shown that when the forward and/or the backward ASE noise is partly reinjected to L-EDFA using a double/single 1533 nm fiber Bragg gratings (FBG), the gain and noise figure performance of L-EDFA increases depending on the FBG configuration. The best gain and NF performance in our L-EDFA was achieved by reinjection of forward and backward ASE through FBG1 and FBG2 leading to an 4.5 dB increase in gain and 1 dB decrease in NF at 1585 nm and -30 dBm input signal power. The results show that both FBGs must be used at the same time to improve gain and NF performance in L-band EDFAs.

Tuning sputtered gold thickness to enhance absorption and emission in core-shell type erbium doped upconversion nanoparticles

NASA Astrophysics Data System (ADS)

Manurung, R. V.; Wu, C. T.; Chattopadhyay, S.

2018-03-01

Upconversion nanoparticles (UCNPs) converts near-infrared excitation to visible emission with advantages e.g. photostable, non-blinking, and background-free probes for bioimaging and biosensor. However, low quantum yield and low efficiency (∼1%) as drawback need to be enhanced. A plasmonic gold nano-structured surface was designed and fabricated to couple with the 980 nm radiation and produce plasmonic enhancement of the upconversion luminescence. The synthesis of the UCNPs was done by thermal decomposition and SiO2 coating prepared by the reverse microemulsion process. Here, we report a novel tunable plasmon-enhanced fluorescence by modulating the thickness and surface roughness of gold island film on Si. The localized surface plasmon resonance (LSPR) at 980 nm was obtained, matched with the native excitation of UCNPs resulting in maximum enhancement of 10-fold of green emission band at 540 nm for the Er-doped UCNPs.

Influence of the CdSe quantum dots concentration on the amplified spontaneous emission from the conjugated polymer (MEH-PPV) in solution

NASA Astrophysics Data System (ADS)

Ibnaouf, K. H.

2015-04-01

The spectral properties of a conjugated polymer poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV) in benzene have been studied intensively. The fluorescence spectra for MEH-PPV, under low concentrations, have shown two peaks around 560 nm and 600 nm, which could be attributed to the monomer and excimer states respectively. In our earlier communication, we had shown that MEH-PPV alone could produce amplified spontaneous emission (ASE) only in its excimeric state (600 nm). The spectral properties of 5 nm size of CdSe (core) quantum dots have been investigated. The fluorescence spectra of CdSe core in benzene showed only one band at 590 nm. Mixtures made of MEH-PPV and CdSe (core) quantum dots have been utilized for studying the amplified spontaneous emission characteristics (ASE) in an organic solution under laser excitation. When the mixture was pumped by the third harmonic of Nd:YAG (355 nm), we observed two ASE peaks; one at 575 nm and another at 595 nm. These ASE peaks could arise from the monomer and excimer states of MEH-PPV. This is perhaps the first report on the influence of quantum dots on the laser from the conjugated polymer MEH-PPV, in liquid solution.

Ultraviolet emission enhancement in ZnO thin films modified by nanocrystalline TiO2

NASA Astrophysics Data System (ADS)

Zheng, Gaige; Lu, Xi; Qian, Liming; Xian, Fenglin

2017-05-01

In this study, nanocrystalline TiO2 modified ZnO thin films were prepared by electron beam evaporation. The structural, morphological and optical properties of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV-visible spectroscopy, fluorescence spectroscopy, respectively. The composition of the films was examined by energy dispersive X-ray spectroscopy (EDX). The photoluminescent spectrum shows that the pure ZnO thin film exhibits an ultraviolet (UV) emission peak and a strong green emission band. Surface analysis indicates that the ZnO thin film contains many oxygen vacancy defects on the surface. After the ZnO thin film is modified by the nanocrystalline TiO2 layer, the UV emission of ZnO is largely enhanced and the green emission is greatly suppressed, which suggests that the surface defects such as oxygen vacancies are passivated by the TiO2 capping layer. As for the UV emission enhancement of the ZnO thin film, the optimized thickness of the TiO2 capping layer is ∼16 nm. When the thickness is larger than 16 nm, the UV emission of the ZnO thin film will decrease because the TiO2 capping layer absorbs most of the excitation energy. The UV emission enhancement in the nanocrystalline TiO2 modified ZnO thin film can be attributed to surface passivation and flat band effect.

The visible spectrum of manganese hydride: Rotational analyses of the 480- and 450-nm systems

NASA Astrophysics Data System (ADS)

Balfour, W. J.; Lindgren, B.; Launila, O.; O'Connor, S.; Cusack, E. J.

1992-07-01

Two visible systems in MnH near 480 and 450 nm, and the 480-nm system in MnD have been recorded photographically both in absorption and in emission. The 480-nm system is shown to be the spectrum of the d5Π i- a5Σ + transition, while the 450-nm system reprsents the e5Σ +- a5Σ + transition, where the upper state is heavily perturbed. The numbers of identified branches in the (0,0), (1,1), and (2,2) bands of the 480-nm system of MnH are 35, 20, and 10, respectively. In the MnD 480-nm system, only the (0,0) band was assigned; the number of assigned branches here was 23. In the 450-nm system of MnH, all the 10 main branches were identified in the (0,0) system, while only the five P branches were found in the (1,1) system. Molecular parameters have been derived for all three states involved. Observed perturbations in the 450-nm system of MnH and in the 480-nm system of MnD have been discussed.

A high resolution ultraviolet Shuttle glow spectrograph

NASA Technical Reports Server (NTRS)

Carruthers, George R.

1993-01-01

The High Resolution Shuttle Glow Spectrograph-B (HRSGS-B) is a small payload being developed by the Naval Research Laboratory. It is intended for study of shuttle surface glow in the 180-400 nm near- and middle-ultraviolet wavelength range, with a spectral resolution of 0.2 nm. It will search for, among other possible features, the band systems of excited NO which result from surface-catalyzed combination of N and O. It may also detect O2 Hertzberg bands and N2 Vegard-Kaplan bands resulting from surface recombination. This wavelength range also includes possible N2+ and OH emissions. The HRSGS-B will be housed in a Get Away Special canister, mounted in the shuttle orbiter payload bay, and will observe the glow on the tail of the orbiter.

Optical properties of Dy3+ and Eu3+ -Codoped SrWO4 phosphors for white light-emitting diodes

NASA Astrophysics Data System (ADS)

Cho, Shinho

2018-01-01

Dy3+ - and Eu3+ -codoped SrWO4 phosphor powders were prepared using a solid-state reaction technique by changing the molar concentration of Eu3+ within the range of 0 to 15 mol% at a fixed Dy3+ concentration of 5 mol%. The effects of Dy3+ and Eu3+ doping on the structural, morphological, and optical properties of SrWO4:Dy3+, Eu3+ phosphors were investigated via Xray diffraction, scanning electron microscopy, and photoluminescence spectrophotometry, respectively. Irrespective of the concentrations of Dy3+ and Eu3+ ions, the crystal structures of all the phosphors were tetragonal, and the grains exhibited a tendency to agglomerate. The emission spectra of Sr0.925WO4:5 mol% Dy3+ contained an intense yellow band at 573 nm arising from the 4 F 9/2 → 6 H 13/2 electric dipole transition of Dy3+, as well as three weak emission lines. When the Eu3+ ions were incorporated into the SrWO4:Dy3+ phosphors, a strong red emission peak at 615 nm originating from the 5D0 → 7F2 transition of Eu3+ appeared in addition to the four emission bands centered at 481, 573, 662, and 750 nm, which result from the 4 f-4 f transitions of Dy3+. The emission intensity decreased as the Eu3+ concentration increased up to 15 mol% due to concentration quenching, which resulted from dipole-dipole interactions. The results suggest that the color emissions and intensities of SrWO4:Dy3+, Eu3+ phosphors can be tuned from yellow to white to red by varying the types of ions used and the ratio of Dy3+ to Eu3+ ions.

Photoluminescence Properties of Red-Emitting Ca3Sr3-x(PO4)4:xEu3+ Phosphors for White Light-Emitting Diodes.

PubMed

Hakeem, D A; Park, K

2015-07-01

The photoluminescent properties of the Eu(3+)-activated Ca3Sr3(PO4)4 phosphors prepared by a solution combustion method were investigated. The excitation spectra of Ca3Sr3-x(PO4)4:xEu3+ (0.05 ≤ x ≤ 0.6) phosphors under 614 nm wavelength showed a broad band centered at 266 nm along with other peaks at 320, 362, 381, 394, 414, 464, and 534 nm. The emission spectra observed in the range of 450 to 750 nm under excitation at 394 nm were ascribed to the 5D0-7F1-4 transitions of Eu3+ ions. The Ca3Sr3-x(PO4)4:xEu3+ phosphors showed the strongest red emission at 614 nm due to the electric dipole 5DO -->7F2 transition of Eu3+. The strongest emission intensity was obtained for the Eu3+ ions of x = 0.5. The prepared Ca3Sr3-x(PO4)4:xEu3+ can be used as an efficient red phosphor for UV-based white LEDs.

Optical properties of P ion implanted ZnO

NASA Astrophysics Data System (ADS)

Pong, Bao-Jen; Chou, Bo-Wei; Pan, Ching-Jen; Tsao, Fu-Chun; Chi, Gou-Chung

2006-02-01

Red and green emissions are observed from P ion implanted ZnO. Red emission at ~680 nm (1.82 eV) is associated with the donor-acceptor pair (DAP) transition, where the corresponding donor and acceptor are interstitial zinc (Zn i) and interstitial oxygen (O i), respectively. Green emission at ~ 516 nm (2.40 eV) is associated with the transition between the conduction band and antisite oxygen (O Zn). Green emission at ~516nm (2.403 eV) was observed for ZnO annealed at 800 oC under ambient oxygen, whereas, it was not visible when it was annealed in ambient nitrogen. Hence, the green emission is most likely not related to oxygen vacancies on ZnO sample, which might be related to the cleanliness of ZnO surface, a detailed study is in progress. The observed micro-strain is larger for N ion implanted ZnO than that for P ion implanted ZnO. It is attributed to the larger straggle of N ion implanted ZnO than that of P ion implanted ZnO. Similar phenomenon is also observed in Be and Mg ion implanted GaN.

Structural and optical characterization of terbium doped ZnGa{sub 2}O{sub 4} thin films deposited by RF magnetron sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Somasundaram, K.; Department of Physics, Nallamuthu Gounder Mahalingam College, Pollachi-642001; Girija, K. G., E-mail: kgirija@barc.gov.in

2016-05-23

Tb{sup 3+} doped ZnGa{sub 2}O{sub 4} nanophosphor (21 nm) has been synthesized via low temperature polyol route and subsequently thin films of the same were deposited on glass and ITO substrates by RF magnetron sputtering. The films were characterized by X-ray Diffraction and luminescence measurements. The XRD pattern showed that Tb{sup 3+} doped ZnGa{sub 2}O{sub 4} nanophosphor has a cubic spinel phase. Luminescence behavior of the nanophosphor and as deposited sputtered film was investigated. The PL emission spectra of nanophosphor gave a broad ZnGa{sub 2}O{sub 4} host emission band along with a strong terbium emission and the thin films showedmore » only broad host emission band and there was no terbium ion emission.« less

Broad visible emission from GaN nanowires grown on n-Si (1 1 1) substrate by PVD for solar cell application

NASA Astrophysics Data System (ADS)

Saron, K. M. A.; Hashim, M. R.

2013-04-01

Nanostructured gallium nitrides (GaNs) were grown on a catalyst-free Si (1 1 1) substrates using physical vapor deposition via thermal evaporation of GaN powder at 1150 °C in the absence of NH3 gas for different deposition time. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometer (EDX) results indicated that the growth of GaN nanostructure varies with deposition time. Both X-ray diffraction (XRD) patterns and Raman spectra reveals a hexagonal GaN with wurtzite structure. Photoluminescence (PL) showed that the UV emission was suppressed, and the visible band emission was enhanced with increasing deposition time. Enhancement of visible band emission from the GaN NWs is due to the increasement of deep level states, which was resulted from growth process. Current-voltage (IV) characteristics of GaN/Si heterostructure were measured and good rectifying behavior was observed for this photodiode (PD). The forward current under illumination was almost three times than that in the dark current at +5 V. Responsivity of the photodetector was 10.5 A/W at range from 350 nm to 500 nm, which rapidly increased to 13.6 A/W at 700 nm. We found that the fabricated photodiode PD has an infra-red (IR) photoresponse behavior. The analysis of optical and electrical properties indications that the grown GaN in the absent of NH3 is a promising optical material and has potential applications in photo voltage solar cell.

Shock-layer-induced ultraviolet emissions measured by rocket payloads

NASA Astrophysics Data System (ADS)

Caveny, Leonard H.; Mann, David M.

1991-08-01

Hypervelocity missiles in the continuum and near-continuum atmosphere produce high temperature shocklayers (i.e., greater than 4000 K at 3.5 km/s and 9000 K at 5.5 km/s). Atmospheric oxygen and nitrogen react and the products are excited to produce nitrogen oxide gamma-band radiation. Analyses and shock tube experiments explored the reaction chemistry and the emissions. Two rocket experiments were conducted to obtain ultraviolet (UV) data under flight conditions using innovative onboard instruments. The first (Bow Shock 1) flew onboard a Terrier-Malemute in April 1990; the second (Bow Shock 2) flew aboard a Strypi XI (Castor 1/Antares IIa/Star 27) in February 1991. The principal instruments were: (1) scanning UV spectrometers, from 190 to 400 nm, (2) quartz fiber-optic coupled photometers to measure selected spectral features, and (3) atomic oxygen (130.4 nm) and hydrogen Lyman-alpha (121.6 nm) detectors. Bow Shock 1 acquired new data on the spectral intensity from UV emissions at 3.5 km/s between 40 and 70 km. For example, at 55 km, the observations included well-defined spectra of nitrogen oxide gamma-band UV emitters with signal strengths more than 10 times stronger than recent theory predicted. Significant signal strength persisted to 70 km, 20 km higher than anticipated. Bow Shock 2 extended the velocity to 5 km/s. An additional scanning spectrometer and 8 photometers observed the downstream shock structures and shock plume interactions. Initial data interpretations indicate that aerodynamic interactions significantly enhance plume emissions.

Foliar Reflectance and Fluorescence Responses for Plants Under Nitrogen Stress Determined with Active and Passive Systems

NASA Technical Reports Server (NTRS)

Middleton, E. M.; McMurtrey, J. E.; Campbell, P. K. Entcheva; Corp, L. A.; Butcher, L. M.; Chappelle, E. W.

2003-01-01

Vegetation productivity is driven by nitrogen (N) availability in soils. Both excessive and low soil N induce physiological changes in plant foliage. In 2001, we examined the use of spectral fluorescence and reflectance measurements to discriminate among plants provided different N fertilizer application rates: 20%, 50%, 100% and 150% of optimal N levels. A suite of optical, fluorescence, and biophysical measurements were collected on leaves from field grown corn (Zea mays L.) and soybean plants (Glycine max L.) grown in pots (greenhouse + ambient sunlight daily). Three types of steady state laser-induced fluorescence measurements were made on adaxial and abaxial surfaces: 1) fluorescence images in four 10 nm bands (blue, green, red, far-red) resulting from broad irradiance excitation; 2) emission spectra (5 nm resolution) produced by excitation at single wavelengths (280,380 or 360, and 532 nm); and 3) excitation spectra (2 nm resolution), with emission wavelengths fixed at wavelengths centered on selected solar Fraunhofer lines (532,607,677 and 745 nm). Two complementary sets of high resolution (less than 2 nm) optical spectra were acquired for both adaxial and abaxial leaf surfaces: 1) optical properties (350-2500 nm) for reflectance, transmittance, and absorptance; and 2) reflectance spectra (500-1000 nm) acquired with and without a short pass filter at 665 nm to determine the fluorescence contribution to apparent reflectance in the 650-750 spectrum, especially at the 685 and 740 nm chlorophyll fluorescence (ChIF) peaks. The strongest relationships between foliar chemistry and optical properties were demonstrated for C/N content and two optical parameters associated with the red edge inflection point. Select optical properties and ChIF parameters were highly correlated for both species. A significant contribution of ChIF to apparent reflectance was observed, averaging 10-25% at 685 nm and 2 - 6% at 740 nm over all N treatments. Discrimination of N treatment groups was possible with specific fluorescence band ratios (e.g., F740/F525 obtained with 380EX). From all measurements assessing fluorescence, higher ChIF and blue/green emissions were measured from the abaxial leaf surfaces; Abaxial surfaces also produced higher reflectances in the 400-800 nm spectrum. Fluorescence information collected in Fraunhofer regions located on the shoulders of ChIF features compared favorably with peak emissions. This supports the potential capability of a future space-born interferometer sensor to capture plant canopy fluorescence.

Temperature dependent luminescence and energy transfer properties of Na2SrMg(PO4)2:Eu2+, Mn2+ phosphors.

PubMed

Geng, Dongling; Shang, Mengmeng; Zhang, Yang; Lian, Hongzhou; Lin, Jun

2013-11-21

Eu(2+) singly and Eu(2+)/Mn(2+) co-doped Na2SrMg(PO4)2 (NSMP) phosphors have been prepared via a high-temperature solid-state reaction process. Upon UV excitation of 260-360 nm, the NSMP:xEu(2+) phosphors exhibit a violet band located at 399 nm and a blue band centered at 445 nm, which originate from Eu(2+) ions occupying two different crystallographic sites: Eu(2+)(I) and Eu(2+)(II), respectively. Excitation wavelengths longer than 380 nm can selectively excite Eu(2+)(II) to emit blue light. Energy transfer processes in the Eu(2+)(I)-Eu(2+)(II) and Eu(2+)-Mn(2+) pairs have been observed and investigated by luminescence spectra and decay curves. The emission color of as-prepared samples can be tuned by changing the relative concentrations of Eu(2+) and Mn(2+) ions and adjusting the excitation wavelength. Under UV excitation of 323 nm, the absolute quantum yield of NSMP:0.005Eu(2+) is 91%, which is higher than most of the other Eu(2+)-doped phosphors reported previously. The temperature dependent luminescence properties and decay curves (4.3-450 K) of NSMP:Eu(2+) and NSMP:Eu(2+), Mn(2+) phosphors have been studied in detail. Thermal quenching of Eu(2+) has been observed while the emission band of Mn(2+) shows a blue-shift and an abnormal increase of intensity with increasing temperature. The unusual thermal quenching behavior indicates that the NSMP compound can serve as a good lattice host for Mn(2+) ions which can be used as a red-emitting phosphor. Additionally, the lifetimes for Eu(2+)(I) and Eu(2+)(II) increase with increasing temperatures.

MODIS In-flight Calibration Methodologies

NASA Technical Reports Server (NTRS)

Xiong, X.; Barnes, W.

2004-01-01

MODIS is a key instrument for the NASA's Earth Observing System (EOS) currently operating on the Terra spacecraft launched in December 1999 and Aqua spacecraft launched in May 2002. It is a cross-track scanning radiometer, making measurements over a wide field of view in 36 spectral bands with wavelengths from 0.41 to 14.5 micrometers and providing calibrated data products for science and research communities in their studies of the Earth s system of land, oceans, and atmosphere. A complete suite of on-board calibrators (OBC) have been designed for the instruments in-flight calibration and characterization, including a solar diffuser (SD) and solar diffuser stability monitor (SDSM) system for the radiometric calibration of the 20 reflective solar bands (RSB), a blackbody (BB) for the radiometric calibration of the 16 thermal emissive bands (TEB), and a spectro-radiometric calibration assembly (SRCA) for the spatial (all bands) and spectral (RSB only) characterization. This paper discusses MODIS in-flight Cali bration methodologies of using its on-board calibrators. Challenging issues and examples of tracking and correcting instrument on-orbit response changes are presented, including SD degradation (20% at 412nm, 12% at 466nm, and 7% at 530nm over four and a half years) and response versus scan angle changes (10%, 4%, and 1% differences between beginning of the scan and end of the scan at 412nm, 466nm, and 530nm) in the VIS spectral region. Current instrument performance and lessons learned are also provided.

Study of upconversion fluorescence property of novel Er3+/Yb3+ co-doped tellurite glasses.

PubMed

Xu, Tie-Feng; Li, Guang-Po; Nie, Qiu-Hua; Shen, Xiang

2006-06-01

Er3+/Yb3+ co-doped TeO2-B2O3-Nb2O5-ZnO (TBN) glasses were prepared. The absorption spectra and upconversion luminescence spectra of TBN glasses were measured and analyzed. The upconversion emission bands centered at 530, 546 and 658 nm were observed under the excitation at 975 nm, corresponding to the transitions of 2H11/2-->4I15/2, 4S3/2-->4I15/2 and 4F9/2-->4I15/2 respectively. The ratio of red emission to green emission increases with an increasing of Yb3+ ions concentration. According to the quadratic dependence on excitation power, the possible upconversion mechanisms and processes were discussed.

Ultraviolet/blue light-emitting diodes based on single horizontal ZnO microrod/GaN heterojunction.

PubMed

Du, Chia-Fong; Lee, Chen-Hui; Cheng, Chao-Tsung; Lin, Kai-Hsiang; Sheu, Jin-Kong; Hsu, Hsu-Cheng

2014-01-01

We report electroluminescence (EL) from single horizontal ZnO microrod (MR) and p-GaN heterojunction light-emitting diodes under forward and reverse bias. EL spectra were composed of two blue emissions centered at 431 and 490 nm under forward biases, but were dominated by a ultraviolet (UV) emission located at 380 nm from n-ZnO MR under high reverse biases. Light-output-current characteristic of the UV emission reveals that the rate of radiative recombination is faster than that of the nonradiative recombination. Highly efficient ZnO excitonic recombination at reverse bias is caused by electrons tunneling from deep-level states near the n-ZnO/p-GaN interface to the conduction band in n-ZnO.

Bright Single InAsP Quantum Dots at Telecom Wavelengths in Position-Controlled InP Nanowires: The Role of the Photonic Waveguide

NASA Astrophysics Data System (ADS)

Haffouz, Sofiane; Zeuner, Katharina D.; Dalacu, Dan; Poole, Philip J.; Lapointe, Jean; Poitras, Daniel; Mnaymneh, Khaled; Wu, Xiaohua; Couillard, Martin; Korkusinski, Marek; Schöll, Eva; Jöns, Klaus D.; Zwiller, Valery; Williams, Robin L.

2018-05-01

We report on the site-selected growth of bright single InAsP quantum dots embedded within InP photonic nanowire waveguides emitting at telecom wavelengths. We demonstrate a dramatic dependence of the emission rate on both the emission wavelength and the nanowire diameter. With an appropriately designed waveguide, tailored to the emission wavelength of the dot, an increase in count rate by nearly two orders of magnitude (0.4kcps to 35kcps) is obtained for quantum dots emitting in the telecom O-band. Using emission-wavelength-optimised waveguides, we demonstrate bright, narrow linewidth emission from single InAsP quantum dots with an unprecedented tuning range from 880nm to 1550nm. These results pave the way towards efficient single photon sources at telecom wavelengths using deterministically grown InAsP/InP nanowire quantum dots.

How to make hypericin water-soluble.

PubMed

Kubin, A; Loew, H G; Burner, U; Jessner, G; Kolbabek, H; Wierrani, F

2008-04-01

Hypericin, isolated from Hypericum perforatum, is an effective photodynamic substance as demonstrated by various studies. Practical forms of applications of hypericin solutions for systemic use and introduction into body cavities are, however, lacking. We developed an aqueous solution of hypericin non-covalently bound to polyvinylpyrrolidone (PVP). PVP is a poly-N-vinylamide of various degrees of polymerization and forms of intermolecular crosslinks suitable for diagnostic and therapeutic applications. We used PVP (molecular weights of PVP between 10 kD and 40 kD) as a complex forming agent to prepare hypericin for photodynamic therapy and diagnostics. In pure water, hypericin forms aggregates which are non-soluble and non-fluorescent. The hypericin-PVP complex binds more than 1000 mg of hypericin in presence of 100 g PVP or less and is soluble in 1 liter of pure water. Aqueous complex solutions of hypericin-PVP display a characteristic absorption spectrum and fluorescence emission band around 600 nm wavelength. Varying concentrations of hypericin do not cause a blue- or red-shift in the absorption maximum at 595 nm. Excitation at 200 nm to 500 nm leads to emission at 590 nm; a property conducive to diagnostic investigations both in vitro and in vivo. Furthermore, hypericin-PVP exhibits high photostability in the presence of oxygen and broad band light which ensures reproducible photodynamic therapy and diagnosis. Hypericin forms liquid molecular chromophore complexes in water when bound to PVP thus allowing investigations in biological media.

Optical Band Gap Alteration of Graphene Oxide via Ozone Treatment.

PubMed

Hasan, Md Tanvir; Senger, Brian J; Ryan, Conor; Culp, Marais; Gonzalez-Rodriguez, Roberto; Coffer, Jeffery L; Naumov, Anton V

2017-07-25

Graphene oxide (GO) is a graphene derivative that emits fluorescence, which makes GO an attractive material for optoelectronics and biotechnology. In this work, we utilize ozone treatment to controllably tune the band gap of GO, which can significantly enhance its applications. Ozone treatment in aqueous GO suspensions yields the addition/rearrangement of oxygen-containing functional groups suggested by the increase in vibrational transitions of C-O and C=O moieties. Concomitantly it leads to an initial increase in GO fluorescence intensity and significant (100 nm) blue shifts in emission maxima. Based on the model of GO fluorescence originating from sp 2 graphitic islands confined by oxygenated addends, we propose that ozone-induced functionalization decreases the size of graphitic islands affecting the GO band gap and emission energies. TEM analyses of GO flakes confirm the size decrease of ordered sp 2 domains with ozone treatment, whereas semi-empirical PM3 calculations on model addend-confined graphitic clusters predict the inverse dependence of the band gap energies on sp 2 cluster size. This model explains ozone-induced increase in emission energies yielding fluorescence blue shifts and helps develop an understanding of the origins of GO fluorescence emission. Furthermore, ozone treatment provides a versatile approach to controllably alter GO band gap for optoelectronics and bio-sensing applications.

Observation of Quartz Cathode-Luminescence in a Low Pressure Plasma Discharge

NASA Technical Reports Server (NTRS)

Foster, John E.

2004-01-01

Intense, steady-state cathode-luminescence has been observed from exposure of quartz powder to a low pressure rf-excited argon plasma discharge. The emission spectra (400 to 850 nm) associated with the powder luminescence were documented as a function of bias voltage using a spectrometer. The emission was broad-band, essentially washing out the line spectra features of the argon plasma discharge.

Reflective Filters Design for Self-Filtering Narrowband Ultraviolet Imaging Experiment Wide-Field Surveys (NUVIEWS) Project

NASA Technical Reports Server (NTRS)

Park, Jung- Ho; Kim, Jongmin; Zukic, Muamer; Torr, Douglas G.

1994-01-01

We report the design of multilayer reflective filters for the self-filtering cameras of the NUVIEWS project. Wide angle self-filtering cameras were designed to image the C IV (154.9 nm) line emission, and H2 Lyman band fluorescence (centered at 161 nm) over a 20 deg x 30 deg field of view. A key element of the filter design includes the development of pi-multilayers optimized to provide maximum reflectance at 154.9 nm and 161 nm for the respective cameras without significant spectral sensitivity to the large cone angle of the incident radiation. We applied self-filtering concepts to design NUVIEWS telescope filters that are composed of three reflective mirrors and one folding mirror. The filters with narrowband widths of 6 and 8 rim at 154.9 and 161 nm, respectively, have net throughputs of more than 50 % with average blocking of out-of-band wavelengths better than 3 x 10(exp -4)%.

Interfacial exciplex formation in bilayers of conjugated polymers

NASA Astrophysics Data System (ADS)

Nobuyasu, R. S.; Araujo, K. A. S.; Cury, L. A.; Jarrosson, T.; Serein-Spirau, F.; Lère-Porte, J.-P.; Dias, F. B.; Monkman, A. P.

2013-10-01

The donor-acceptor interactions in sequential bilayer and blend films are investigated. Steady-state and time-resolved photoluminescence (PL) were measured to characterize the samples at different geometries of photoluminescence collection. At standard excitation, with the laser incidence at 45° of the normal direction of the sample surface, a band related to the aggregate states of donor molecules appears for both blend and bilayer at around 540 nm. For the PL spectra acquired from the edge of the bilayer, with the laser incidence made at normal direction of the sample surface (90° geometry), a new featureless band emission, red-shifted from donor and acceptor emission regions was observed and assigned as the emission from interfacial exciplex states. The conformational complexity coming from donor/acceptor interactions at the heterojunction interface of the bilayer is at the origin of this interfacial exciplex emission.

1.7  μm band narrow-linewidth tunable Raman fiber lasers pumped by spectrum-sliced amplified spontaneous emission.

PubMed

Zhang, Peng; Wu, Di; Du, Quanli; Li, Xiaoyan; Han, Kexuan; Zhang, Lizhong; Wang, Tianshu; Jiang, Huilin

2017-12-10

A 1.7 μm band tunable narrow-linewidth Raman fiber laser based on spectrally sliced amplified spontaneous emission (SS-ASE) and multiple filter structures is proposed and experimentally demonstrated. In this scheme, an SS-ASE source is employed as a pump source in order to avoid stimulated Brillouin scattering. The ring configuration includes a 500 m long high nonlinear optical fiber and a 10 km long dispersion shifted fiber as the gain medium. A segment of un-pumped polarization-maintaining erbium-doped fiber is used to modify the shape of the spectrum. Furthermore, a nonlinear polarization rotation scheme is applied as the wavelength selector to generate lasers. A high-finesse ring filter and a ring filter are used to narrow the linewidth of the laser, respectively. We demonstrate tuning capabilities of a single laser over 28 nm between 1652 nm and 1680 nm by adjusting the polarization controller (PC) and tunable filter. The tunable laser has a 0.023 nm effective linewidth with the high-finesse ring filter. The stable multi-wavelength laser operation of up to four wavelengths can be obtained by adjusting the PC carefully when the pump power increases.

Synthesis, Structural, Thermal, and Electronic Properties of Palmierite-Related Double Molybdate α-Cs2Pb(MoO4)2.

PubMed

Solodovnikov, Sergey F; Atuchin, Victor V; Solodovnikova, Zoya A; Khyzhun, Oleg Y; Danylenko, Mykola I; Pishchur, Denis P; Plyusnin, Pavel E; Pugachev, Alexey M; Gavrilova, Tatiana A; Yelisseyev, Alexander P; Reshak, Ali H; Alahmed, Zeyad A; Habubi, Nadir F

2017-03-20

Cs 2 Pb(MoO 4 ) 2 crystals were prepared by crystallization from their own melt, and the crystal structure has been studied in detail. At 296 K, the molybdate crystallizes in the low-temperature α-form and has a monoclinic palmierite-related superstructure (space group C2/m, a = 2.13755(13) nm, b = 1.23123(8) nm, c = 1.68024(10) nm, β = 115.037(2)°, Z = 16) possessing the largest unit cell volume, 4.0066(4) nm 3 , among lead-containing palmierites. The compound undergoes a distortive phase transition at 635 K and incongruently melts at 943 K. The electronic structure of α-Cs 2 Pb(MoO 4 ) 2 was explored by using X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy methods. For α-Cs 2 Pb(MoO 4 ) 2 , the photoelectron core-level and valence-band spectra and the XES band representing the energy distribution of Mo 4d and O 2p states were recorded. Our results allow one to conclude that the Mo 4d and O 2p states contribute mainly to the central part and at the top of the valence band, respectively, with also significant contributions throughout the whole valence-band region of the molybdate under consideration.

The origin of the red emission in n-ZnO nanotubes/p-GaN white light emitting diodes

PubMed Central

2011-01-01

In this article, the electroluminescence (EL) spectra of zinc oxide (ZnO) nanotubes/p-GaN light emitting diodes (LEDs) annealed in different ambients (argon, air, oxygen, and nitrogen) have been investigated. The ZnO nanotubes by aqueous chemical growth (ACG) technique on p-GaN substrates were obtained. The as-grown ZnO nanotubes were annealed in different ambients at 600°C for 30 min. The EL investigations showed that air, oxygen, and nitrogen annealing ambients have strongly affected the deep level emission bands in ZnO. It was concluded from the EL investigation that more than one deep level defect is involved in the red emission appearing between 620 and 750 nm and that the red emission in ZnO can be attributed to oxygen interstitials (Oi) appearing in the range from 620 nm (1.99 eV) to 690 nm (1.79 eV), and to oxygen vacancies (Vo) appearing in the range from 690 nm (1.79 eV) to 750 nm (1.65 eV). The annealing ambients, especially the nitrogen ambient, were also found to greatly influence the color-rendering properties and increase the CRI of the as - grown LEDs from 87 to 96. PMID:21711671

The origin of the red emission in n-ZnO nanotubes/p-GaN white light emitting diodes.

PubMed

Alvi, N H; Ul Hasan, Kamran; Nur, Omer; Willander, Magnus

2011-02-10

In this article, the electroluminescence (EL) spectra of zinc oxide (ZnO) nanotubes/p-GaN light emitting diodes (LEDs) annealed in different ambients (argon, air, oxygen, and nitrogen) have been investigated. The ZnO nanotubes by aqueous chemical growth (ACG) technique on p-GaN substrates were obtained. The as-grown ZnO nanotubes were annealed in different ambients at 600°C for 30 min. The EL investigations showed that air, oxygen, and nitrogen annealing ambients have strongly affected the deep level emission bands in ZnO. It was concluded from the EL investigation that more than one deep level defect is involved in the red emission appearing between 620 and 750 nm and that the red emission in ZnO can be attributed to oxygen interstitials (Oi) appearing in the range from 620 nm (1.99 eV) to 690 nm (1.79 eV), and to oxygen vacancies (Vo) appearing in the range from 690 nm (1.79 eV) to 750 nm (1.65 eV). The annealing ambients, especially the nitrogen ambient, were also found to greatly influence the color-rendering properties and increase the CRI of the as - grown LEDs from 87 to 96.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romero, V.H.; De la Rosa, E., E-mail: elder@cio.mx; Salas, P.

In this paper, we report the obtained strong broadband blue photoluminescence (PL) emission centered at 427 nm for undoped BaZrO{sub 3} observed after 266 nm excitation of submicron crystals prepared by hydrothermal/calcinations method. This emission is enhanced with the introduction of Tm{sup 3+} ions and is stronger than the characteristic PL blue emission of such lanthanide. The proposed mechanism of relaxation for host lattice emission is based on the presence of oxygen vacancies produced during the synthesis process and the charge compensation due to the difference in the electron valence between dopant and substituted ion in the host. Brilliant whitemore » light emission with a color coordinate of (x=0.29, y=0.32) was observed by combining the blue PL emission from the host with the green and red PL emission from Tb{sup 3+} and Eu{sup 3+} ions, respectively. The color coordinate can be tuned by changing the ratio between blue, green and red band by changing the concentration of lanthanides. - Graphical abstract: Strong blue emission from undoped BaZrO{sub 3} phosphor and white light emission by doping with Tb{sup 3+} (green) and Eu{sup 3+} (red) after 266 nm excitation. Highlights: Black-Right-Pointing-Pointer Blue emission from BaZrO{sub 3} phosphor. Black-Right-Pointing-Pointer Blue emission enhanced with Tm{sup 3+}. Black-Right-Pointing-Pointer White light from BaZrO{sup 3+} phosphor.« less

Enhanced photoluminescence property and broad color emission of ZnGa2O4 phosphor due to the synergistic role of Eu3+ and carbon dots

NASA Astrophysics Data System (ADS)

Huo, Qiuyue; Tu, Weixia; Guo, Lin

2017-10-01

ZnGa2O4 phosphors co-composited with nanoscale carbon dots (CDs) and Eu3+ were presented for the tunable color emission. Novel single phase CDs or/and Eu3+ composited ZnGa2O4 phosphors were synthesized by microwave hydrothermal method and their optical properties were investigated. The ZnGa2O4 phosphors composited with CDs exhibited an intense broad blue light emission at 421 nm and a more enhanced photoluminescence intensity than those without CDs. The Eu3+ composited ZnGa2O4 phosphors gave an ideal red color emission. The CDs/Eu3+ co-composited ZnGa2O4 phosphors exhibited a wide emission band peak at 450 nm and narrow emission peak at 618 nm. Furthermore, the tunable color emissions of CDs/Eu3+ co-composited ZnGa2O4 phosphors from blue to the white light region, and then to red were obtained with the increasing Eu3+ concentration, which can be a promising single phased phosphor candidate in light emitting diodes. Broadly tunable emission single phased phosphor is tuned firstly through the synergistic role of the non-metal element and the rare earth metal ions.

Modified InGaN/GaN quantum wells with dual-wavelength green-yellow emission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Z. L., E-mail: zhilaifang@hotmail.com; Li, Q. F.; Shen, X. Y.

2014-01-28

Energy band engineering by indium pretreatment of the bottom GaN barriers and control of the growth temperature profile for the InGaN active layers were employed to improve the green-yellow emitting InGaN/GaN quantum well (QW). The modified InGaN/GaN QWs were investigated by various characterization techniques and demonstrated to be of good interface abruptness and well-defined indium concentration profile, composed of 0.52 nm In{sub 0.35}Ga{sub 0.65}N “wetting layer,” 1.56 nm In{sub 0.35-0.22}Ga{sub 0.65-0.78}N graded layers, and 1.56 nm In{sub 0.22}Ga{sub 0.78}N layer along the growth direction. Broad-band dual-wavelength green-yellow emission at about 497 and 568 nm was observed and attributed to the major contribution of enhancedmore » interband transitions from the first and second quantized electron states “e1” and “e2” to the first quantized hole state “h1.” With the modified QW structure, electron overflow loss would be suppressed by filling of the excited electron state with electrons at high carrier injection density and reduction in polarization-induced band bending. APSYS simulation shows efficiency and droop improvements due to the enhanced overlapping of electron and hole wave functions inside the modified InGaN active layers, and the enhanced interband transitions involving the excited electron state.« less

Tunable blue-green emission and energy transfer properties in β-Ca3(PO4)2:Eu(2+), Tb(3+) phosphors with high quantum efficiencies for UV-LEDs.

PubMed

Li, Kai; Zhang, Yang; Li, Xuejiao; Shang, Mengmeng; Lian, Hongzhou; Lin, Jun

2015-03-14

A series of Eu(2+) and Tb(3+) singly-doped and co-doped β-Ca3(PO4)2 phosphors have been synthesized via the high-temperature solid-state reaction method. Thermogravimetric (TG) analysis, fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD) patterns and Rietveld refinements, photoluminescence (PL) spectra including temperature-dependent PL and quantum efficiency, and fluorescence decay lifetimes have been used to characterise the as-prepared samples. Under UV excitation, β-Ca3(PO4)2:Eu(2+) presents a broad emission band centered at 415 nm, which can be decomposed into five symmetrical bands peaking at 390, 408, 421, 435 and 511 nm based on the substitution of five kinds of Ca(2+) sites by Eu(2+) ions. β-Ca3(PO4)2:Tb(3+) shows characteristic emission lines under Tb(3+) 4f-5d transition excitation around 223 nm. In β-Ca3(PO4)2:Eu(2+), Tb(3+) phosphors, similar excitation spectra monitored at 415 and 547 nm have been observed, which illustrates the possibility of energy transfer from Eu(2+) to Tb(3+) ions. The variations in the emission spectra and decay lifetimes further demonstrate the existence of energy transfer from Eu(2+) to Tb(3+) ions under UV excitation. The energy transfer mechanism has been confirmed to be dipole-quadrupole, which can be validated via the agreement of critical distances obtained from the concentration quenching (12.11 Å) and spectrum overlap methods (9.9-13.2 Å). The best quantum efficiency can reach 90% for the β-Ca3(PO4)2:0.01Eu(2+), 0.15Tb(3+) sample under 280 nm excitation. These results show that the developed phosphors may possess potential applications in UV-pumped white light-emitting diodes.

Measurement of fluorescence in a rhodamine-123 doped self-assembled "giant" mesostructured silica sphere using a smartphone as optical hardware.

PubMed

Canning, John; Lau, Angelica; Naqshbandi, Masood; Petermann, Ingemar; Crossley, Maxwell J

2011-01-01

The blue OLED emission from a mobile phone was characterised, revealing a sharp emission band centred at λ = 445 nm with a 3dB bandwidth Δλ ∼ 20 nm. It was used to excite Rhodamine 123 doped within a "giant" mesostructured silica sphere during fabrication through evaporative self-assembly of silica nanoparticles. Fluorescence was able to be detected using a standard optical microscope fitted with a green transmission pass filter and cooled CCD and with 1 ms exposure time demonstrating the potential of mobile platforms as the basis for portable diagnostics in the field.

Bridgman growth and luminescence properties of dysprosium doped lead potassium niobate crystal

NASA Astrophysics Data System (ADS)

Liu, Wenbin; Tian, Tian; Yang, Bobo; Xu, Jiayue; Liu, Hongde

2017-06-01

Dy-doped lead potassium niobate (Pb2KNb5O15, PKN) single crystal was grown by the modified vertical Bridgman method through spontaneous nucleation. The crystal was brownish, transparent and inclusion free. Five excitation peaks of Dy3+ ions were clearly seen from near ultraviolet region to blue range. It was unique that the excitation peaks in blue range were more intense, especially the one centered at 455 nm. The emission bands consisted of blue, yellow and red emissions, which were at about 487 nm, 573 nm and 662 nm respectively. The CIE chromaticity diagram of PKN:Dy indicated that white light and yellow light could be emitted when the crystal was excited under near ultraviolet light and blue light, respectively. Thus PKN:Dy crystal is a candidate material whose emitting light could be tunable through changing the excited light wavelength.

Pressure Study of Photoluminescence in GaN/InGaN/ AlGaN Quantum Wells

NASA Astrophysics Data System (ADS)

Perlin, Piotr; Iota, V.; Weinstein, B. A.; Wisniewski, P.; Osinski, M.; Eliseev, P. G.

1997-03-01

We have studied the photoluminescence (PL) from two commercial high brightness single quantum well light emitting diodes (Nichia Chem. Industs.) with In_xGa_1-x N (x=0.45 and 0.2) as the active layers under hydrostatic pressures up to 7 GPa. These diodes are the best existing light emitters at short wavelengths, having the emission wavelengths of 430 nm and 530 nm depending on the content of indium in the 30 Åthick quantum wells. Although these devices show a remarkable quality and efficiency (luminosity as high as 12 cd), the mechanism of recombination remains obscure. We discovered that the pressure coefficient for each of the observed PL peaks is dramatically (2-3 times) lower than that of the energy gap of its InGaN active layer. These observations, in conjunction with the fact that the observed emission occurs below the energy gap of the quantum well material, and also considering the anomalous temperature behavior of the emission (peak energy increasing with temperature) suggest the involvement of localized states and exclude a simple band-to-band recombination picture. These localized states may be tentatively attributed to the presence of band tails in the gap which stem from composition fluctuations in the InGaN alloy. (figures)

Luminescent silver(I) tert-butylethynide compounds with nicotinic/isonicotinic acid as ligands

NASA Astrophysics Data System (ADS)

Xie, Yi-Ming; Fan, Yue-Yue; Lin, Fu-Lin; Hu, Ting; Liu, Jia; Lu, Can-Zhong

2017-12-01

Solvothermal reaction of tBuC≡CAg, AgBF4 and nicotinic/isonicotinic acid in acetonitrile afforded two new silver(I) tert-butylethynide double salts, namely [(tBuC≡CAg)(AgL1)3] (HL1 = nicotinic acid) (1) and [(tBuC≡CAg)(AgL1)2] (HL2 = isonicotinic acid) (2). These compounds have been characterized by elemental analysis, infrared spectra, single-crystal X-ray analysis, X-ray powder diffraction, thermogravimetric analysis, UV-visible absorption spectra, and luminescent measurement. 1 exhibits a two-dimensional coordination network, and 2 features a three-dimensional coordination architecture. Luminescence measurements indicate that 1 shows a fluorescent emission band centered at 568 nm, and 2 exhibits an intense emission maximum at 550 nm and a shoulder peak at 436 nm.

Yttrium orthoaluminate nanoperovskite doped with Tm3+ ions as upconversion optical temperature sensor in the near-infrared region.

PubMed

Hernández-Rodriguez, M A; Lozano-Gorrín, A D; Lavín, V; Rodríguez-Mendoza, U R; Martín, I R

2017-10-30

The thermal sensing capability of the Tm 3+ -doped yttrium orthoaluminate nanoperovskite in the infrared range, synthetized by a sol-gel method, was studied. The temperature dependence of the infrared upconverted emission bands located at around 705 nm ( 3 F 2,3 → 3 H 6 ) and 800 nm ( 3 H 4 → 3 H 6 ) of YAP: Tm 3+ nanoperovskite under excitation at 1210 nm was analyzed from RT up to 425 K. Calibration of the optical sensor has been made using the fluorescence intensity ratio technique, showing a high sensitivity in the near-infrared compared to other trivalent rare-earth based optical sensors working in the same range. In addition, a second calibration procedure of the YAP: Tm 3+ optical sensor was performed by using the FIR technique on the emission band associated to the 3 H 4 → 3 H 6 transition in the physiological temperature range (293-333 K), showing a very high relative sensitivity compared with other rare-earth based optical temperature sensors working in the physiological range. Moreover, the main advantage compared with other optical sensors is that the excitation source and the upconverted emissions do not overlap, since they lie in different biological windows, thus allowing its potential use as an optical temperature probe in the near-infrared range for biological applications.

Summary of Quantitative Interpretation of Image Far Ultraviolet Auroral Data

NASA Technical Reports Server (NTRS)

Frey, H. U.; Immel, T. J.; Mende, S. B.; Gerard, J.-C.; Hubert, B.; Habraken, S.; Span, J.; Gladstone, G. R.; Bisikalo, D. V.; Shematovich, V. I.;

ISUAL-Observed Blue Luminous Events: The Associated Sferics

NASA Astrophysics Data System (ADS)

Chou, Jung-Kuang; Hsu, Rue-Ron; Su, Han-Tzong; Chen, Alfred Bing-Chih; Kuo, Cheng-Ling; Huang, Sung-Ming; Chang, Shu-Chun; Peng, Kang-Ming; Wu, Yen-Jung

2018-04-01

The blue luminous events (BLEs) recorded by ISUAL (Imager of Sprites and Upper Atmospheric Lightning) radiate unambiguous middle ultraviolet to blue emissions (230-450 nm) but contain dim red emissions (623-754 nm). The BLE appears to be dot-like on one ISUAL image with an integration time of 29 ms. A few BLEs develop upward into blue jets/starters or type II gigantic jets (GJs). The associated sferics of the BLEs in the extremely low frequency to very low frequency band and in the low-frequency band exhibit similar patterns to the narrow bipolar events (NBEs) identified in the very low frequency and low-frequency band. The ISUAL BLEs are conjectured to be the accompanied light emissions of the NBEs. Both upward and downward propagating current obtained from the associated sferics of the BLEs have been found. The source heights of the six BLEs related to negative NBEs are estimated in the range of 16.2-17.8 km. These six events are suggested to occur between the upper positive charge layer and the negative screen charge layer on the top of the normally electrified thunderstorm. The six blue starters, one blue jet, and one type II GJ are inferred to be positive upward discharges from their associated sferics in the extremely low frequency to very low frequency band. Based on the simultaneous radio and optical observations, a NBE is conjectured to be the initiation discharge with rapidly flowing current within the thunderstorm, while a blue jet/starter or a type II GJ is suggested to be the ensuing discharge with slowly varying current propagating upward from the thunderstorm.

Nanostructured GdxZn1-xO thin films by nebulizer spray pyrolysis technique: Role of doping concentration on the structural and optical properties

NASA Astrophysics Data System (ADS)

Mariappan, R.; Ponnuswamy, V.; Suresh, P.; Suresh, R.; Ragavendar, M.

2013-07-01

Nanostructured GdxZn1-xO thin films with different Gd concentration from 0% to 10% deposited at 400 °C using the NSP technique. The films were characterized by structural, surface and optical properties, respectively. X-ray diffraction analysis shows that the Gd doped ZnO films have lattice parameters a = 3.2497 Å and c = 5.2018 Å with hexagonal structure and preferential orientation along (0 0 2) plane. The estimated values compare well with the standard values. When film thickness increases from 222 to 240 nm a high visible region transmittance (>70%) is observed. The optical band gap energy, optical constants (n and k), complex dielectric constants (ɛr and ɛi) and optical conductivities (σr and σi) were calculated from optical transmittance data. The optical band gap energy is 3.2 eV for pure ZnO film and 3.6 eV for Gd0.1Zn0.9O film. The PL studies confirm the presence of a strong UV emission peak at 399 nm. Besides, the UV emission of ZnO films decreases with the increase of Gd doping concentration correspondingly the ultra-violet emission is replaced by blue and green emissions.

VIIRS Reflective Solar Band Radiometric and Stability Evaluation Using Deep Convective Clouds

NASA Technical Reports Server (NTRS)

Chang, Tiejun; Xiong, Xiaoxiong; Mu, Qiaozhen

2016-01-01

This work takes advantage of the stable distribution of deep convective cloud (DCC) reflectance measurements to assess the calibration stability and detector difference in Visible Infrared Imaging Radiometer Suite (VIIRS) reflective bands. VIIRS Sensor Data Records (SDRs) from February 2012 to June 2015 are utilized to analyze the long-term trending, detector difference, and half angle mirror (HAM) side difference. VIIRS has two thermal emissive bands with coverage crossing 11 microns for DCC pixel identification. The comparison of the results of these two processing bands is one of the indicators of analysis reliability. The long-term stability analysis shows downward trends (up to approximately 0.4 per year) for the visible and near-infrared bands and upward trends (up to 0.5per year) for the short- and mid-wave infrared bands. The detector difference for each band is calculated as the difference relative to the average reflectance overall detectors. Except for the slightly greater than 1 difference in the two bands at 1610 nm, the detector difference is less than1 for other solar reflective bands. The detector differences show increasing trends for some short-wave bands with center wavelengths from 400 to 600 nm and remain unchanged for the bands with longer center wavelengths. The HAM side difference is insignificant and stable. Those short-wave bands from 400 to 600 nm also have relatively larger HAM side difference, up to 0.25.Comparing the striped images from SDR and the smooth images after the correction validates the analyses of detector difference and HAM side difference. These analyses are very helpful for VIIRS calibration improvement and thus enhance product quality

Laser Measurements of the H Atom + Ozone Rate Constant at Atmospheric Temperatures

NASA Astrophysics Data System (ADS)

Liu, Y.; Smith, G. P.; Peng, J.; Reppert, K. J.; Callahan, S. L.

2015-12-01

The exothermic H + O3 reaction produces OH(v) Meinel band emissions, used to derive mesospheric H concentrations and chemical heating rates. We have remeasured its rate constant to reduce resulting uncertainties and the measurement extend to lower mesospheric temperatures using modern laser techniques. H atoms are produced by pulsed ultraviolet laser trace photolysis of O3, followed by reaction of O(D) with added H2. A second, delayed, frequency-mixed dye laser measures the reaction decay rate with the remaining ozone by laser induced fluorescence. We monitor either the H atom decay by 2 photon excitation at 205 nm and detection of red fluorescence, or the OH(v=9) product time evolution with excitation of the B-X (0,9) band at 237 nm and emission in blue B-A bands. By cooling the enclosed low pressure flow cell we obtained measurements from 146-305 K. Small kinetic modeling corrections are made for secondary regeneration of H atoms. The results fully confirm the current NASA JPL recommendation for this rate constant, and establish its extrapolation down to the lower temperatures of the mesosphere. This work was supported by the NSF Aeronomy Program and an NSF Physics summer REU student grant.

Properties of Cathodoluminescence for Cryogenic Applications of SiO2-based Space Observatory Optics and Coatings

NASA Technical Reports Server (NTRS)

Evans, Amberly; Dennison, J.R.; Wilson, Gregory; Dekany, Justin; Bowers Charles W.; Meloy, Robert; Heaney, James B.

2013-01-01

Disordered thin film SiO2SiOx coatings undergoing electron-beam bombardment exhibit cathodoluminescence, which can produce deleterious stray background light in cryogenic space-based astronomical observatories exposed to high-energy electron fluxes from space plasmas. As future observatory missions push the envelope into more extreme environments and more complex and sensitive detection, a fundamental understanding of the dependencies of this cathodoluminescence becomes critical to meet performance objectives of these advanced space-based observatories. Measurements of absolute radiance and emission spectra as functions of incident electron energy, flux, and power typical of space environments are presented for thin (60-200 nm) SiO2SiOx optical coatings on reflective metal substrates over a range of sample temperatures (40-400 K) and emission wavelengths (260-5000 nm). Luminescent intensity and peak wavelengths of four distinct bands were observed in UVVISNIR emission spectra, ranging from 300 nm to 1000 nm. A simple model is proposed that describes the dependence of cathodoluminescence on irradiation time, incident flux and energy, sample thickness, and temperature.

Widely tunable 1.94-μm Tm:BaY2F8 laser

NASA Astrophysics Data System (ADS)

Galzerano, Gianluca; Cornacchia, Francesco; Parisi, Daniela; Toncelli, Alessandra; Tonelli, Mauro; Laporta, Paolo

2005-04-01

A novel BaY2F8 crystal doped with thulium ions is grown and extensively investigated. Owing to the large number of vibronic levels and to a favorable electron-phonon coupling, extremely wide absorption and emission bands around 1.9 μm are observed. A room-temperature Tm:BaY2F8 laser tunable over a 210-nm interval, from 1849 to 2059 nm, is demonstrated.

Concentration dependence of luminescence efficiency of Dy3+ ions in strontium zinc phosphate glasses mixed with Pb3 O4.

PubMed

Kumar, Valluri Ravi; Giridhar, G; Veeraiah, N

2017-02-01

In this work we synthesized SrO-ZnO-P 2 O 5 glasses mixed with Pb 3 O 4 (heavy metal oxide) and doped with different amounts of Dy 2 O 3 (0.1 to 1.0 mol%). Subsequently their emission and decay characteristics were investigated as a function of Dy 2 O 3 concentration. The emission spectra exhibited three principal emission bands in the visible region corresponding to 4 F 9 /2  →  6 H 15 /2 (482 nm), 6 H 13 /2 (574 nm) and 6 H 11 /2 (663 nm) transitions. With increase in the concentration of Dy 2 O 3 (upto 0.8 mol%) a considerable increase in the intensity of these bands was observed and, for further increase, quenching of photoluminescence (PL) output was observed. Using emission spectra, various radiative parameters were evaluated and all these parameters were found to increase with increase in Dy 2 O 3 concentration. The Y/B integral emission intensity ratio of Dy 3 + ions evaluated from these spectra exhibited a decreasing trend with increase in the Dy 2 O 3 concentration up to 0.8 mol%. Quenching of luminescence observed in the case of the glasses doped with 1.0 mol% is attributed to clustering of Dy 3 + ions. The quantitative analysis of these results together with infra-red (IR) spectral studies indicated that 0.8 mol% is the optimum concentration of Dy 3 + ions needed to achieve maximum luminescence efficiency. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Emirates Mars Ultraviolet Spectrometer's (EMUS) Prediction of Oxygen OI 135.6 nm and CO 4PG Emissions in the Martian Atmosphere

NASA Astrophysics Data System (ADS)

Almatroushi, H. R.; Lootah, F. H.; Deighan, J.; Fillingim, M. O.; Jain, S.; Bougher, S. W.; England, S.; Schneider, N. M.

2017-12-01

This research focuses on developing empirical and theoretical models for OI 135.6 nm and CO 4PG band system FUV dayglow emissions in the Martian thermosphere as predicted to be seen from the Emirates Mars Ultraviolet Spectrometer (EMUS), one of the three scientific instruments aboard the Emirates Mars Mission (EMM) to be launched in 2020. These models will aid in simulating accurate disk radiances which will be utilized as an input to an EMUS instrument simulator. The developed zonally averaged empirical models are based on FUV data from the IUVS instrument onboard the MAVEN mission, while the theoretical models are based on a basic Chapman profile. The models calculate the brightness (B) of those emissions taking into consideration observation geometry parameters such as emission angle (EA), solar zenith angle (SZA) and planet distance from the sun (Ds). Specifically, the empirical models takes a general form of Bn=A*cos(SZA)n/cos(EA)m , where Bn is the normalized brightness value of an emission feature, and A, n, and m are positive constant values. The model form shows that the brightness has a positive correlation with EA and a negative correlation with SZA. A comparison of both models are explained in this research while examining full Mars and half Mars disk images generated using geometry code specially developed for the EMUS instrument. Sensitivity analyses have also been conducted for the theoretical modeling to observe the contributions of electron impact on atomic oxygen and CO2 to the brightness of OI 135.6nm, in addition to the effect of electron temperature on the CO2± dissociative recombination contribution to the CO 4PG band system.

Ultra-narrow band perfect absorbers based on Fano resonance in MIM metamaterials

NASA Astrophysics Data System (ADS)

Zhang, Ming; Fang, Jiawen; Zhang, Fei; Chen, Junyan; Yu, Honglin

2017-12-01

Metallic nanostructures have attracted numerous attentions in the past decades due to their attractive plasmonic properties. Resonant plasmonic perfect absorbers have promising applications in a wide range of technologies including photothermal therapy, thermophotovoltaics, heat-assisted magnetic recording and biosensing. However, it remains to be a great challenge to achieve ultra-narrow band in near-infrared band with plasmonic materials due to the large optical losses in metals. In this letter, we introduced Fano resonance in MIM metamaterials composed of an asymmetry double elliptic cylinders (ADEC), which can achieve ultra-narrow band perfect absorbers. In theoretical calculations, we observed an ultranarrow band resonant absorption peak with the full width at half maximum (FWHM) of 8 nm and absorption amplitude exceeding 99% at 930 nm. Moreover, we demonstrate that the absorption increases with the increase of asymmetry and the absorption resonant wavelength can be tuned by changing the size and arrangement of the unit cell. The asymmetry metallic nanostructure also exhibit a higher refractive sensitivity as large as 503 nm/RIU with high figure of merit of 63, which is promising for high sensitive sensors. Results of this work are desirable for various potential applications in micro-technological structures such as biological sensors, narrowband emission, photodetectors and solar thermophotovoltaic (STPV) cells.

Structure and luminescence of nanocrystalline gallium nitride synthesized by a novel polymer pyrolysis route

NASA Astrophysics Data System (ADS)

Garcia, Rafael; Hirata, Gustavo A.; Thomas, Alan C.; Ponce, Fernando A.

2006-10-01

Thermal decomposition in a horizontal quartz tube reactor of a polymer [-(CH 6N 4O) 3Ga(NO 3) 3-] in a nitrogen atmosphere, yield directly nano-structured gallium nitride (GaN) powder. The polymer was obtained by the reaction between high purity gallium nitrate (Ga(NO 3) 3) dissolved in toluene and carbohydrazide as an azotic ligand. The powder synthesized by this method showed a yellow color and elemental analysis suggested that the color is due to some carbon and oxygen impurities in the as-synthesized powder. Electron microscopy showed that the as-synthesized powders consist of a mixture of various porous particles containing nanowires and nano-sized platelets. The size of the crystallites can be controlled by annealing processes under ammonia. Photoluminescence analysis at 10 K on as-synthesized powders showed a broad red luminescence around 668 nm under UV laser excitation (He-Cd laser, 325 nm). However after annealing process the red luminescence disappears and the typical band edge emission of GaN around 357 nm (3.47 eV) and the UV band were the dominant emissions in the PL spectra.

Investigations on surface chemical analysis using X-ray photoelectron spectroscopy and optical properties of Dy3+-doped LiNa3P2O7 phosphor

NASA Astrophysics Data System (ADS)

Munirathnam, K.; Dillip, G. R.; Chaurasia, Shivanand; Joo, S. W.; Deva Prasad Raju, B.; John Sushma, N.

2016-08-01

Near white-light emitting LiNa3P2O7:Dy3+ phosphors were prepared by a conventional solid-state reaction method. The orthorhombic crystal structure of the phosphors was confirmed using X-ray diffraction (XRD), and the valence states of the surface elements were determined from the binding energies of Li 1s, O 1s, Na 1s, P 2p, and Dy 3d by X-ray photoelectron spectroscopy (XPS). Attenuated total reflectance (ATR) - Fourier transform infrared (FT-IR) spectroscopy was employed to identify the pyrophosphate groups in the phosphors. Diffuse reflectance spectra (DRS) show the absorption bands of the Dy3+ ions in the host material. Intense blue (481 nm) and yellow (575 nm) emissions were obtained at an excitation wavelength of 351 nm and are attributed to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions, respectively. The combination of these two intense bands generates light emission in the near-white region of the chromaticity diagram.

Annealing effects on cathodoluminescence of zircon

NASA Astrophysics Data System (ADS)

Tsuchiya, Y.; Nishido, H.; Noumi, Y.

2011-12-01

U-Pb zircon dating (e. g., SHRIMP) is an important tool to interpret a history of the minerals at a micrometer-scale, where cathodoluminescence (CL) imaging allows us to recognize internal zones and domains with different chemical compositions and structural disorder at high spatial resolution. The CL of zircon is attributed by various types of emission centers, which are extrinsic ones such as REE impurities and intrinsic ones such as structural defects. Metamictization resulted from radiation damage to the lattice by alpha particles from the decay of U and Th mostly causes an effect on the CL features of zircon as a defect center. However, slightly radiation-damaged zircon, which is almost nondetectable by XRD, has not been characterized using CL method. In this study, annealing effects on CL of zircon has been investigated to clarify a recovery process of the damaged lattice at low radiation dose. A single crystal of zircon from Malawi was selected for CL measurements. It contains HfO2: 2.30 w.t %, U: 241 ppm and Th: 177 ppm. Two plate samples perpendicular to c and a axes were prepared for annealing experiments during 12 hours from room temperature to 1400 degree C. Color CL images were captured using a cold-cathode microscope (Luminoscope: Nuclide ELM-3R). CL spectral measurements were conducted using an SEM (JEOL: JSM-5410) combined with a grating monochromator (Oxford: Mono CL2) to measure CL spectra ranging from 300 to 800 nm in 1 nm steps with a temperature controlled stage. The dispersed CL was collected by a photoncounting method using a photomultiplier tube (Hamamatsu: R2228) and converted to digital data. All CL spectra were corrected for the total instrumental response. Spectral analysis reveals an anisotropy of the CL emission bands related to intrinsic defect center in blue region, radiation-induced defect center from 500 to 700 nm, and trivalent Dy impurity center at 480 and 580 nm, but their relative intensities are almost constant. CL on the surface perpendicular to c-axis, at which direction its intensity is maximum, was characterized in this study. Color CL imaging indicates yellow emission below 300 degree C, white to pale blue between 400 ~ 800 degree C and blue above 900 degree C. The broad band emission assigned to radiation-induced defect center in metamict state decreases in an increase of annealed temperature and disappeared above 700 degree C, whereas any change in XRD patterns was not detected. The blue CL emission caused by intrinsic defect center gradually increases in heating due to a recovery of its crystal field. Furthermore, the emission bands of trace amounts of trivalent Gd at 320 nm and Er at 400nm become to be appeared in response to a recrystallization by annealing. Therefore, CL analysis provides useful information on characteristics of the nature of metamict zircon rather than other conventional methods.

Effects of the ZnO layer on the structure and white light emission properties of a ZnS:Mn/GaN nanocomposite system.

PubMed

Wang, Cai-Feng; Hu, Bo

2017-10-01

ZnO films were inserted between the ZnS:Mn films and GaN substrates by pulsed laser deposition (PLD). The structure, morphology, and optical properties of the ZnS:Mn/ZnO/GaN nanocomposite systems have been investigated. X-ray diffraction results show that there are three diffraction peaks located at 28.4°, 34.4°, and 34.1°, which correspond to the β-ZnS(111), ZnO(002), and GaN(002) planes, respectively. Due to the insertion of ZnO films, the diffraction peak intensity of ZnS:Mn in ZnS:Mn/ZnO/GaN is stronger than that of ZnS:Mn in ZnS:Mn/GaN, and the full width at half-maximum is smaller. Though the transmittance of ZnS:Mn/ZnO films is slightly lower than that of ZnS:Mn films, the transmittance is still higher than 80%. Compared with ZnS:Mn/GaN, an ultraviolet (UV) emission at 387 nm (originated from the near-band emission of ZnO) and a green light emission at about 520 nm appeared in the photoluminescence (PL) spectra of ZnS:Mn/ZnO/GaN, in addition to the blue emission at 435 nm and the orange-red emission at 580 nm. The emission at 520 nm may be related to the deep-level emission from ZnO and the interface of ZnS:Mn/ZnO. The PL spectrum of ZnS:Mn/ZnO/GaN covers the visible region from the blue light to the red light (400-700 nm), and its color coordinate and color temperature are (0.3103,0.3063) and 6869 K, respectively, presenting strong white light emission.

CdS quantum dots in a novel glass with a very low activation energy and its variation of diffusivity with temperature

NASA Astrophysics Data System (ADS)

Nagpal, Swati

2011-07-01

CdS quantum dots of different average sizes in the range 2 to 3.8 nm were grown by diffusion-limited growth process in indigenously made silicate glass. The absorption spectra showed a strong quantum confinement effect with a blue shift of the order of 500 meV depending on the average size. Critical radius of quantum dots was found to be 1.8 nm. The size dispersion decreased from 15.2 to 12.5% with a 20% increase in the particle size. The activation energy for diffusion was found to be very low i.e. 193 kJ mol-1 and the diffusion coefficient increased by 60% for 10 K rise in temperature. The PL emission spectra showed the presence of only deep traps around 600 nm with a red shift of 200 nm. No shallow traps or band edge emission was observed. The PL peak position changed from 560 to 640 nm with a 35 K increase in annealing temperature.

White/blue-emitting, water-dispersible CdSe quantum dots prepared by counter ion-induced polymer collapse

NASA Astrophysics Data System (ADS)

Wang, Jing; Goh, Jane Betty; Goh, M. Cynthia; Giri, Neeraj Kumar; Paige, Matthew F.

2015-09-01

The synthesis and characterization of water-dispersible, luminescent CdSe/ZnS semiconductor quantum dots that exhibit nominal "white" fluorescence emission and have potential applications in solid-state lighting is described. The nanomaterials, prepared through counter ion-induced collapse and UV cross-linking of high-molecular weight polyacrylic acid in the presence of appropriate aqueous inorganic ions, were of ∼2-3 nm diameter and could be prepared in gram quantities. The quantum dots exhibited strong luminescence emission in two bands, the first in the blue-region (band edge) of the optical spectrum and the second, a broad emission in the red-region (attributed to deep trap states) of the optical spectrum. Because of the relative strength of emission of the band edge and deep trap state luminescence, it was possible to achieve visible white luminescence from the quantum dots in aqueous solution and in dried, solid films. The optical spectroscopic properties of the nanomaterials, including ensemble and single-molecule spectroscopy, was performed, with results compared to other white-emitting quantum dot systems described previously in the literature.

Synthesis and optoelectronic properties of dodecyl substituted diphenylamine and pyridine based conjugated molecule

NASA Astrophysics Data System (ADS)

Priyanka, V.; Vijai Anand, A. S.; Mahesh, K.; Karpagam, S.

2017-11-01

The new donor-acceptor type conjugated moiety, namely 3-([4-(2-Cyano-2pyridine-2yl-vinyl)-phenyl]-dodecyl-amino)-phenyl)-2-pyridine-2-yl-acrylonitrile (DPA-PA) has been synthesized according to the Knoevenagel condensation. Here dodecyloxy diphenylamine moiety acts as an electron donor and cyano-pyridyl moiety acts as an electron acceptor. These moieties are recently showing great interest in optoelectronic applications. The structure of the DPA-PA was confirmed by FT-IR, 1H NMR. The final product showed great solubility in common organic solvents such as toluene, tetrahydrofuran, ethyl acetate, dichloromethane, chloroform etc due to the dodecyl chain. The absorption maximum of DPA-PA appeared at 433 nm in chloroform solution. The optical band gap is 2.2 eV calculated from thin film absorption edge (550 nm). The photoluminescence spectra exhibited a maximum peak at 513 nm with greenish fluorescence in chloroform solution and at 541 nm as the thin film state. The emission spectra of thin film state are 28 nm red shifted with broadening peak. The lower electrochemical band gap 1.55 eV was observed by cyclic voltammetry. This type of low band gap materials has much attention for their various potential applications in optoelectronic devices.

Ultraviolet/blue light-emitting diodes based on single horizontal ZnO microrod/GaN heterojunction

PubMed Central

2014-01-01

We report electroluminescence (EL) from single horizontal ZnO microrod (MR) and p-GaN heterojunction light-emitting diodes under forward and reverse bias. EL spectra were composed of two blue emissions centered at 431 and 490 nm under forward biases, but were dominated by a ultraviolet (UV) emission located at 380 nm from n-ZnO MR under high reverse biases. Light-output-current characteristic of the UV emission reveals that the rate of radiative recombination is faster than that of the nonradiative recombination. Highly efficient ZnO excitonic recombination at reverse bias is caused by electrons tunneling from deep-level states near the n-ZnO/p-GaN interface to the conduction band in n-ZnO. PMID:25232299

Thin-walled boron nitride microtubes exhibiting intense band-edge UV emission at room temperature.

PubMed

Huang, Yang; Bando, Yoshio; Tang, Chengchun; Zhi, Chunyi; Terao, Takeshi; Dierre, Benjamin; Sekiguchi, Takashi; Golberg, Dmitri

2009-02-25

Boron nitride (BN) microtubes were synthesized in a vertical induction furnace using Li(2)CO(3) and B reactants. Their structures and morphologies were investigated using x-ray diffraction, scanning and transmission electron microscopy, and energy-dispersive x-ray spectroscopy. The microtubes have diameters of 1-3 microm, lengths of up to hundreds of micrometers, and well-structured ultrathin walls only approximately 50 nm thick. A mechanism combining the vapor-liquid-solid (VLS) and template self-sacrificing processes is proposed to explain the formation of these novel one-dimensional microstructures, in which the Li(2)O-B(2)O(3) eutectic reaction plays an important role. Cathodoluminescence studies show that even at room temperature the thin-walled BN microtubes can possess an intense band-edge emission at approximately 216.5 nm, which is distinct compared with other BN nanostructures. The study suggests that the thin-walled BN microtubes should be promising for constructing compact deep UV devices and find potential applications in microreactors and microfluidic and drug delivery systems.

Improvement for the performance of solar-blind photodetector based on β-Ga2O3 thin films by doping Zn

NASA Astrophysics Data System (ADS)

Zhao, Xiaolong; Wu, Zhenping; Zhi, Yusong; An, Yuehua; Cui, Wei; Li, Linghong; Tang, Weihua

2017-03-01

Highly oriented (\\bar{2} 0 1 ) Ga2-x Zn x O3 thin films with different doping concentrations were grown on (0 0 0 1) sapphire substrates by laser molecular beam epitaxy technology. The expansion of lattice and the shrinkage of band gap with increasing doping level confirms the chemical substitution of Zn2+ ions into the Ga2O3 crystal lattice. The emission intensity of blue-violet emission bands enhanced with the increase of (ZnGa)‧ under 254 nm ultraviolet excitation, and the maximum was obtained at x  =  0.8. A metal-semiconductor-metal structured solar-blind photodetector based on Ga2-x Zn x O3 (x  =  0, 0.8) was made, the increasing responsivity and diminishing relaxation time constants for β-Ga2-x Zn x O3 (x  =  0.8) photodetector were observed with 254 nm ultraviolet illumination.

Interfacial exciplex formation in bilayers of conjugated polymers.

PubMed

Nobuyasu, R S; Araujo, K A S; Cury, L A; Jarrosson, T; Serein-Spirau, F; Lère-Porte, J-P; Dias, F B; Monkman, A P

2013-10-28

The donor-acceptor interactions in sequential bilayer and blend films are investigated. Steady-state and time-resolved photoluminescence (PL) were measured to characterize the samples at different geometries of photoluminescence collection. At standard excitation, with the laser incidence at 45° of the normal direction of the sample surface, a band related to the aggregate states of donor molecules appears for both blend and bilayer at around 540 nm. For the PL spectra acquired from the edge of the bilayer, with the laser incidence made at normal direction of the sample surface (90° geometry), a new featureless band emission, red-shifted from donor and acceptor emission regions was observed and assigned as the emission from interfacial exciplex states. The conformational complexity coming from donor/acceptor interactions at the heterojunction interface of the bilayer is at the origin of this interfacial exciplex emission.

Controlled synthesis and novel photoluminescence properties of BaTiO{sub 3}:Eu{sup 3+}/Eu{sup 2+} nanocrystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Li; Li, Ying; Wang, Guofeng, E-mail: wanggf75@gmail.com

2015-01-15

Highlights: • Tetragonal phase BaTiO{sub 3}:Eu nanocrystals were successfully synthesized using a hydrothermal method. • Under 398 nm excitation, the emissions from Eu{sup 2+} and Eu{sup 3+} ions were observed. • The emission band of Eu{sup 2+} from BaTiO{sub 3}:Eu was observed to broaden with increasing Eu concentration. - Abstract: Tetragonal phase BaTiO{sub 3}:Eu nanocrystals were successfully synthesized using a hydrothermal method and a subsequent calcination treatment. The structures and morphologies of nanocrystals were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and scanning electron microscopy. The photoluminescence properties of BaTiO{sub 3}:Eu were investigated in detail. Under 398 nmmore » excitation, the emissions from Eu{sup 2+} and Eu{sup 3+} ions were observed, indicating that Eu{sup 2+} and Eu{sup 3+} ions coexisted in BaTiO{sub 3}:Eu nanocrystals. Especially, the emission band of Eu{sup 2+} from BaTiO{sub 3}:Eu was observed to broaden with increasing Eu concentration. When the Eu concentration was 0.5 mol%, the {sup 5}D{sub 0} → {sup 7}F{sub 0} and {sup 5}D{sub 1} → {sup 7}F{sub 0} emissions were observed. In addition, under 537 nm excitation, the emission intensity increased with increasing Eu concentration.« less

High pressure luminescence spectra of CaMoO4:Ln3+ (Ln = Pr, Tb)

NASA Astrophysics Data System (ADS)

Mahlik, S.; Behrendt, M.; Grinberg, M.; Cavalli, E.; Bettinelli, M.

2013-03-01

Photoluminescence spectra and luminescence kinetics of pure CaMoO4 and CaMoO4 doped with Ln3+ (Ln = Pr or Tb) are presented. The spectra were obtained at high hydrostatic pressure up to 240 kbar applied in a diamond anvil cell. At ambient pressure undoped and doped samples exhibit a broad band emission extending between 380 and 700 nm with a maximum at 520 nm attributed to the {{MoO}}_{4}^{2-} luminescence. CaMoO4 doped with Pr3+ or Tb3+ additionally yields narrow emission lines related to f-f transitions. The undoped CaMoO4 crystal was characterized by a strong MoO{}_{4}^{2-} emission up to 240 kbar. In the cases of CaMoO4:Pr3+ and CaMoO4:Tb3+, high hydrostatic pressure caused quenching of Pr3+ and Tb3+ emission, and this effect was accompanied by a strong shortening of the luminescence lifetime. In doped samples, CaMoO4:Pr3+ and CaMoO4:Tb3+, quenching of the emission band attributed to {{MoO}}_{4}^{2-} was also observed, and at pressure above 130 kbar this luminescence was totally quenched. The effects mentioned above were related to the influence of the praseodymium (terbium) trapped exciton PTE (ITE—impurity trapped exciton) on the efficiency of the Pr3+ (Tb3+) and {{MoO}}_{4}^{2-} emissions.

Effect of thickness on surface morphology, optical and humidity sensing properties of RF magnetron sputtered CCTO thin films

NASA Astrophysics Data System (ADS)

Ahmadipour, Mohsen; Ain, Mohd Fadzil; Ahmad, Zainal Arifin

2016-11-01

In this study, calcium copper titanate (CCTO) thin films were deposited on ITO substrates successfully by radio frequency (RF) magnetron sputtering method in argon atmosphere. The CCTO thin films present a polycrystalline, uniform and porous structure. The surface morphology, optical and humidity sensing properties of the synthesized CCTO thin films have been studied by X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), UV-vis spectrophotometer and current-voltage (I-V) analysis. XRD and AFM confirmed that the intensity of peaks and pore size of CCTO thin films were enhanced by increasing the thin films. Tauc plot method was adopted to estimate the optical band gaps. The surface structure and energy band gaps of the deposited films were affected by film thickness. Energy band gap of the layers were 3.76 eV, 3.68 eV and 3.5 eV for 200 nm, 400 nm, and 600 nm CCTO thin films layer, respectively. The humidity sensing properties were measured by using direct current (DC) analysis method. The response times were 12 s, 22 s, and 35 s while the recovery times were 500 s, 600 s, and 650 s for 200 nm, 400 nm, and 600 nm CCTO thin films, respectively at humidity range of 30-90% relative humidity (RH).

Near-infrared photocatalysts of BiVO4/CaF2:Er3+, Tm3+, Yb3+ with enhanced upconversion properties

NASA Astrophysics Data System (ADS)

Huang, Shouqiang; Zhu, Nanwen; Lou, Ziyang; Gu, Lin; Miao, Chen; Yuan, Haiping; Shan, Aidang

2014-01-01

Upconversion photocatalysts have the potential to absorb the near-infrared (NIR) light in solar energy and improve the photocatalytic performance. A hierarchical upconversion photocatalyst of BiVO4 (BVO)/CaF2:Er3+, Tm3+, Yb3+ (CF) combined with the narrow-band semiconductor of BVO and the luminescence agent of CF to enhance upconversion properties was synthesized via the hydrothermal method. The CF particles were deposited homogeneously on the surface of the BVO/CF composite with regular dendritic structure, which led to efficient upconversion emissions. The upconversion emission intensity of the BVO/CF composite was 8 times higher than that of pure CF, through tailoring the crystal symmetry of lanthanide ions by Bi3+ ions. The upconverted ultraviolet (361 and 379 nm), violet (408 nm), and blue (485 nm) light was able to excite BVO for photocatalysis in BVO/CF under NIR irradiation, which improved the degradation rate of methyl orange (MO).Upconversion photocatalysts have the potential to absorb the near-infrared (NIR) light in solar energy and improve the photocatalytic performance. A hierarchical upconversion photocatalyst of BiVO4 (BVO)/CaF2:Er3+, Tm3+, Yb3+ (CF) combined with the narrow-band semiconductor of BVO and the luminescence agent of CF to enhance upconversion properties was synthesized via the hydrothermal method. The CF particles were deposited homogeneously on the surface of the BVO/CF composite with regular dendritic structure, which led to efficient upconversion emissions. The upconversion emission intensity of the BVO/CF composite was 8 times higher than that of pure CF, through tailoring the crystal symmetry of lanthanide ions by Bi3+ ions. The upconverted ultraviolet (361 and 379 nm), violet (408 nm), and blue (485 nm) light was able to excite BVO for photocatalysis in BVO/CF under NIR irradiation, which improved the degradation rate of methyl orange (MO). Electronic supplementary information (ESI) available: Additional tables and figures. See DOI: 10.1039/c3nr05266d

A spectrally tunable all-graphene-based flexible field-effect light-emitting device

NASA Astrophysics Data System (ADS)

Wang, Xiaomu; Tian, He; Mohammad, Mohammad Ali; Li, Cheng; Wu, Can; Yang, Yi; Ren, Tian-Ling

2015-07-01

The continuous tuning of the emission spectrum of a single light-emitting diode (LED) by an external electrical bias is of great technological significance as a crucial property in high-quality displays, yet this capability has not been demonstrated in existing LEDs. Graphene, a tunable optical platform, is a promising medium to achieve this goal. Here we demonstrate a bright spectrally tunable electroluminescence from blue (~450 nm) to red (~750 nm) at the graphene oxide/reduced-graphene oxide interface. We explain the electroluminescence results from the recombination of Poole-Frenkel emission ionized electrons at the localized energy levels arising from semi-reduced graphene oxide, and holes from the top of the π band. Tuning of the emission wavelength is achieved by gate modulation of the participating localized energy levels. Our demonstration of current-driven tunable LEDs not only represents a method for emission wavelength tuning but also may find applications in high-quality displays.

Synthesis and luminescence studies of Eu (III) doped Sr2P2O7 phosphor for white LED applications

NASA Astrophysics Data System (ADS)

Khan, Z. S.; Ingale, N. B.; Omanwar, S. K.

2018-05-01

Europium (III) doped distrontium diphosphate (Sr2P2O7) is synthesized by slow vaporization method and its luminescence properties are carried out. Using X-Ray diffraction, the crystal structure of this material was confirmed. Photoluminescence (PL) measurement make clear the phosphor exhibited intense emission at 593 nm (yellow) and 612 nm (orange) respectively corresponding to 5D0→7F1 and 5D0→7F2 transitions of Eu3+ on excitation with most favourable 394 nm wavelengths. The remaining excitation peaks at 381 nm and 465 nm with broad band 200-310 nm are also witness in the excitation spectra. The particle morphology using SEM images shows micro level particles for this phosphor. The effect of concentration of Eu3+ ions on the PL intensity has also been investigated. It has been observed that the powder sample exhibits highest PL emission intensity for Eu3+ concentration of about 0.02 moles. The emission spectra exhibit orange performance (CIE chromaticity coordinates: X = 0.672, Y = 0.328), which is due to the 5D0→7F2 transitions of Eu3+ ions. This phosphor is very good for white LED applications.

Synthesis and photoluminescence of EuII in barium zinc orthosilicate: a novel green color emitting phosphor for white-LEDs.

PubMed

Kasturi, S; Sivakumar, V; Varadaraju, U V

2017-05-01

A series of Eu 2+ -activated barium orthosilicates (BaZnSiO 4 ) were synthesized using a high-temperature solid-state reaction. A photoluminescence excitation study of Eu 2 + shows a broad absorption band in the range of 270-450 nm, with multiple absorption peak maxima (310, 350 and 400 nm) due to 4f-5d electronic transition. The emission spectra of all the compositions show green color emission (in the spectral region 450-550 nm with a peak maximum at 502 nm and a shoulder at ~ 490 nm) with appropriate Comission Internationale de l'Eclairage (CIE) color coordinates. The two emission peaks are due to the presence of Eu 2 + in two different Ba sites in the BaZnSiO 4 host lattice. The energy transfers between the Eu 2 + ions in BaZnSiO 4 host are elucidated from the critical concentration quenching data based on the electronic multipolar interaction. All Eu 2 + -activated BaZnSiO 4 phosphor materials can be efficiently excited in the ultraviolet (UV) to near UV-region (270-420 nm), making them attractive candidate as a green phosphor for solid state lighting-white light-emitting diodes. Copyright © 2016 John Wiley & Sons, Ltd.

Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+}: A novel blue emitting phosphor for white LEDs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Panlai, E-mail: li_panlai@126.com; Wang, Zhijun, E-mail: wangzj1998@126.com; Yang, Zhiping

2014-12-15

Graphical abstract: Under the 350 nm radiation excitation, Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} has a broad blue emission band. When the temperature turned up to 150 °C, the emission intensity of Ba{sub 1.97}B{sub 2}O{sub 5}:0.03Ce{sup 3+} is 63.4% of the initial value at room temperature. The activation energy ΔE is calculated to be 0.25 eV, which prove the good thermal stability of Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+}. All the properties indicate that Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} may have potential application in white LEDs. - Highlights: • Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} has a broad blue emission band under themore » 350 nm radiation excitation. • Emission intensity of Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} is 63.4% (150 °C) of the initial value (30 °C). • The activation energy ΔE for thermal quenching is 0.25 eV. - Abstract: A novel blue emitting phosphor Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} is synthesized by a high temperature solid state method. The luminescent property and the thermal stability of Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} are investigated. Under the 350 nm radiation excitation, Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} has a broad blue emission band, and the peak locates at 417 nm which is assigned to the 5d{sup 1}–4f{sup 1} transition of Ce{sup 3+}. It is further proved that the dipole–dipole interaction results in the concentration quenching of Ce{sup 3+} in Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+}. When the temperature turned up to 150 °C, the emission intensity of Ba{sub 1.97}B{sub 2}O{sub 5}:0.03Ce{sup 3+} is 63.4% of the initial value at room temperature. The activation energy ΔE is calculated to be 0.25 eV, which prove the good thermal stability of Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+}. All the properties indicate that Ba{sub 2}B{sub 2}O{sub 5}:Ce{sup 3+} may have potential application in white LEDs.« less

Nd3+-doped TeO2-Bi2O3-ZnO transparent glass ceramics for laser application at 1.06 μm

NASA Astrophysics Data System (ADS)

Hu, Xiaolin; Luo, Zhiwei; Liu, Taoyong; Lu, Anxian

2017-04-01

The high crystallinity transparent glass ceramics based on Nd3+-doped 70TeO2-15Bi2O3-15ZnO (TBZ) compositions were successfully prepared by two-step heat treatment process. The effects of Nd2O3 content on the thermal, structural, mechanical, and optical properties of TBZ glass ceramics were studied. The incorporation of Nd2O3 enhanced the crystallization tendency in the matrix glass composition. The crystal phase and morphology of Bi2Te4O11 in the glass ceramics were confirmed by X-ray diffraction and field emission scanning electron microscopy. Due to precipitate more crystal phase, the hardness values increased from 3.21 to 3.66 GPa. Eight absorption peaks were observed from 400 to 900 nm and three emission bands appeared in the range of 850-1400 nm. With the increasing of Nd2O3 content from 0.5 to 2.5 wt%, the intensity of absorption peaks enhanced and the emission intensity increased up to 1.0 wt% and then fell down for further dopant concentration. The fluorescence decay lifetime decreased rapidly starting from 1.5 wt% Nd2O3 content due to the obvious energy migration among Nd3+. According to the extreme strong emission band around 1062 nm and the optimum Nd2O3 content (1.0 wt%), N10 glass ceramic was considered as a potential material for 1.06 μm laser applications.

Demonstration of transverse-magnetic deep-ultraviolet stimulated emission from AlGaN multiple-quantum-well lasers grown on a sapphire substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xiao-Hang, E-mail: xli@gatech.edu, E-mail: dupuis@gatech.edu; Kao, Tsung-Ting; Satter, Md. Mahbub

2015-01-26

We demonstrate transverse-magnetic (TM) dominant deep-ultraviolet (DUV) stimulated emission from photo-pumped AlGaN multiple-quantum-well lasers grown pseudomorphically on an AlN/sapphire template by means of photoluminescence at room temperature. The TM-dominant stimulated emission was observed at wavelengths of 239, 242, and 243 nm with low thresholds of 280, 250, and 290 kW/cm{sup 2}, respectively. In particular, the lasing wavelength of 239 nm is shorter compared to other reports for AlGaN lasers grown on foreign substrates including sapphire and SiC. The peak wavelength difference between the transverse-electric (TE)-polarized emission and TM-polarized emission was approximately zero for the lasers in this study, indicating the crossover of crystal-fieldmore » split-off hole and heavy-hole valence bands. The rapid variation of polarization between TE- and TM-dominance versus the change in lasing wavelength from 243 to 249 nm can be attributed to a dramatic change in the TE-to-TM gain coefficient ratio for the sapphire-based DUV lasers in the vicinity of TE-TM switch.« less

Solvatochromism and linear solvation energy relationship of the kinase inhibitor SKF86002

NASA Astrophysics Data System (ADS)

Khattab, Muhammad; Van Dongen, Madeline; Wang, Feng; Clayton, Andrew H. A.

2017-01-01

We studied the spectroscopic characteristics of SKF86002, an anti-inflammatory and tyrosine kinase inhibitor drug candidate. Two conformers SKF86002A and SKF86002B are separated by energy barriers of 19.68 kJ·mol- 1 and 6.65 kJ·mol- 1 due to H-bonds, and produce the three major UV-Vis absorption bands at 325 nm, 260 nm and 210 nm in cyclohexane solutions. This environment-sensitive fluorophore exhibited emission in the 400-500 nm range with a marked response to changes in environment polarity. By using twenty-two solvents for the solvatochromism study, it was noticed that solvent polarity, represented by dielectric constant, was well correlated with the emission wavelength maxima of SKF86002. Thus, the SKF86002 fluorescence peak red shifted in aprotic solvents from 397.5 nm in cyclohexane to 436 nm in DMSO. While the emission maximum in hydrogen donating solvents ranged from 420 nm in t-butanol to 446 nm in N-methylformamide. Employing Lippert-Mataga, Bakhshiev and Kawski models, we found that one linear correlation provided a satisfactory description of polarity effect of 18 solvents on the spectral changes of SKF86002 with R2 values 0.78, 0.80 and 0.80, respectively. Additionally, the multicomponent linear regression analysis of Kamlet-Taft (R2 = 0.94) revealed that solvent acidity, basicity and polarity accounted for 31%, 24% and 45% of solvent effects on SKF86002 emission, respectively. While Catalán correlation (R2 = 0.92) revealed that solvatochromic change of SKF86002 emission was attributed to changes in solvent dipolarity (71%), solvent polarity (12%), solvent acidity (11%) and solvent basicity (6%). Plot of Reichardt transition energies and emission energies of SKF86002 in 18 solvents showed also a linear correlation with R2 = 0.90. The dipole moment difference between excited and ground state was calculated to be 3.4-3.5 debye.

Solvatochromism and linear solvation energy relationship of the kinase inhibitor SKF86002.

PubMed

Khattab, Muhammad; Van Dongen, Madeline; Wang, Feng; Clayton, Andrew H A

2017-01-05

We studied the spectroscopic characteristics of SKF86002, an anti-inflammatory and tyrosine kinase inhibitor drug candidate. Two conformers SKF86002A and SKF86002B are separated by energy barriers of 19.68kJ·mol(-1) and 6.65kJ·mol(-1) due to H-bonds, and produce the three major UV-Vis absorption bands at 325nm, 260nm and 210nm in cyclohexane solutions. This environment-sensitive fluorophore exhibited emission in the 400-500nm range with a marked response to changes in environment polarity. By using twenty-two solvents for the solvatochromism study, it was noticed that solvent polarity, represented by dielectric constant, was well correlated with the emission wavelength maxima of SKF86002. Thus, the SKF86002 fluorescence peak red shifted in aprotic solvents from 397.5nm in cyclohexane to 436nm in DMSO. While the emission maximum in hydrogen donating solvents ranged from 420nm in t-butanol to 446nm in N-methylformamide. Employing Lippert-Mataga, Bakhshiev and Kawski models, we found that one linear correlation provided a satisfactory description of polarity effect of 18 solvents on the spectral changes of SKF86002 with R(2) values 0.78, 0.80 and 0.80, respectively. Additionally, the multicomponent linear regression analysis of Kamlet-Taft (R(2)=0.94) revealed that solvent acidity, basicity and polarity accounted for 31%, 24% and 45% of solvent effects on SKF86002 emission, respectively. While Catalán correlation (R(2)=0.92) revealed that solvatochromic change of SKF86002 emission was attributed to changes in solvent dipolarity (71%), solvent polarity (12%), solvent acidity (11%) and solvent basicity (6%). Plot of Reichardt transition energies and emission energies of SKF86002 in 18 solvents showed also a linear correlation with R(2)=0.90. The dipole moment difference between excited and ground state was calculated to be 3.4-3.5debye. Copyright © 2016 Elsevier B.V. All rights reserved.

Sintering time optimization on red photoluminescence properties of manganese-doped boron carbon oxynitride (BCNO:Mn) phosphor

NASA Astrophysics Data System (ADS)

Wahid Nuryadin, Bebeh; Suryani, Yayu; Yuliani, Yuli; Setiadji, Soni; Yeti Nuryantini, Ade; Iskandar, Ferry

2018-04-01

The effect of sintering time to the transient nature and optimization of red photoluminescence manganese-doped boron carbon oxynitride (BCNO:Mn) phosphor was investigated. The BCNO:Mn samples were synthesized using a facile urea-assisted combustion route involving boric acid, citric acid, manganese salt and urea. The optimized intensity of the dual peak emission at 420 nm (blue emission) and 630 nm (red emission) in the photoluminescence (PL) spectrum could be achieved by controlling the sintering time of the BCNO:Mn. The BCNO:Mn samples in high-crystalline form was found to be in a cubic and hexagonal structure. Based on the PL analysis, it is suggested that the BCNO:Mn symmetric band at 630 nm can be attributed to the 4T1(4G)—6A1(6S) transition absorption of Mn2+ ions into the hexagonal structure. Microstructure analysis showed an irregular and agglomerated shape of the BCNO:Mn sample.

Using phosphorescence as a fingerprint for the Hope and other blue diamonds

NASA Astrophysics Data System (ADS)

Eaton-Magaña, Sally; Post, Jeffrey E.; Heaney, Peter J.; Freitas, Jaime; Klein, Paul; Walters, Roy; Butler, James E.

2008-01-01

Sixty-seven natural blue diamonds, including the two largestsuch gemstones known (the Hope and the Blue Heart), were probedby ultraviolet radiation, and their luminescence was analyzedusing a novel spectrometer system. Prior to this study, thefiery red phosphorescence of the Hope Diamond was regarded asquite rare compared to greenish-blue phosphorescence. However,our results demonstrated that virtually all blue diamonds phosphoresceat 660 nm (orange-red) but that this emission often is obscuredby a concomitant luminescence at 500 nm (green-blue). Althoughboth bands were nearly always present, the relative intensitiesof these emissions and their decay kinetics varied dramatically.Consequently, phosphorescence analysis provides a method todiscriminate among individual blue diamonds. Treated and syntheticblue diamonds showed behavior distinct from natural stones.Temperature-dependent phosphorescence revealed that the 660nm emission has an activation energy of 0.4 eV, close to the0.37 eV acceptor energy for boron, suggesting that the phosphorescenceis caused by donor-acceptor pair recombination.

Effects of multiple organic ligands on size uniformity and optical properties of ZnSe quantum dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Archana, J., E-mail: archana.jayaram@yahoo.com; Navaneethan, M.; Hayakawa, Y.

2012-08-15

Highlights: ► Highly monodispersed ZnSe quantum dots have been synthesized by wet chemical route. ► Strong quantum confinement effect have been observed in ∼ 4 nm ZnSe quantum dots. ► Enhanced ultraviolet near band emission have been obtained using long chain polymer. -- Abstract: The effects of multi-ligands on the formation and optical transitions of ZnSe quantum dots have been investigated. The dots are synthesized using 3-mercapto-1,2-propanediol and polyvinylpyrrolidone ligands, and have been characterized by X-ray diffraction, transmission electron microscopy (TEM), UV–visible absorption spectroscopy, photoluminescence spectroscopy, and Fourier transform infrared spectroscopy. TEM reveals high monodispersion with an average size ofmore » 4 nm. Polymer-stabilized, organic ligand-passivated ZnSe quantum dots exhibit strong UV emission at 326 nm and strong quantum confinement in the UV–visible absorption spectrum. Uniform size and suppressed surface trap emission are observed when the polymer ligand is used. The possible growth mechanism is discussed.« less

Characteristics of a nanosecond-barrier-discharge-pumped multiwave UV – VUV lamp on a mixture of argon, krypton and vapours of freon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shuaibov, A K; Minya, A I; Hrytsak, R V

2015-02-28

We present the results of investigation of the characteristics of a nanosecond-barrier-discharge-pumped multiwave lamp based on a gas mixture of Ar – Kr – CCl{sub 4}, which emits in the spectral range of 170 – 260 nm. The main emission bands in the lamp spectrum are ArCl (B → X) near 175 nm, KrCl (B → X) near 222 nm and Cl{sub 2} (D' → A') near 258 nm. The lamp intensity with respect to pressure, working mixture composition and pump regime is optimised. (uv - vuv emitters)

Optical and electrical properties of sol-gel spin coated titanium dioxide thin films

NASA Astrophysics Data System (ADS)

Sahoo, Anusuya; Jayakrishnan, A. R.; Kamakshi, K.; Silva, J. P. B.; Sekhar, K. C.; Gomes, M. J. M.

2017-08-01

In this work; TiO2 thin films were deposited on glass and stainless steel substrates by sol-gel spin coating method. The films deposited on glass were annealed at different temperatures (Ta) in the range of 200 to 500 0C and that are deposited on steel substrate were annealed at 800 0C. The optical properties of TiO2 thin films were studied by using UV-VIS spectroscopy and photoluminescence (PL) spectroscopy. The transmittance on the average was found to ≥ 80 % and is found to sensitive to Ta. The PL spectra exhibited the strong emission band associated with band- to- band transition around 390 nm and the two weak bands at 480 and 510 nm associated to the oxygen defects and surface defects respectively. The current-voltage (I-V) characteristics of the Al/TiO2/steel capacitors were studied and analysed with application of various current mechanisms. Analysis reveals that the conduction in Al/TiO2/steel capacitors is governed by Poole-Frenkel mechanism.

Formation of 238U16O and 238U18O observed by time-resolved emission spectroscopy subsequent to laser ablation

NASA Astrophysics Data System (ADS)

Weisz, David G.; Crowhurst, Jonathan C.; Siekhaus, Wigbert J.; Rose, Timothy P.; Koroglu, Batikan; Radousky, Harry B.; Zaug, Joseph M.; Armstrong, Michael R.; Isselhardt, Brett H.; Savina, Michael R.; Azer, Magdi; Finko, Mikhail S.; Curreli, Davide

2017-07-01

We have measured vibronic emission spectra of an oxide of uranium formed after laser ablation of the metal in gaseous oxygen. Specifically, we have measured the time-dependent relative intensity of a band located at approximately 593.6 nm in 16O2. This band grew in intensity relative to neighboring atomic features as a function time in an oxygen environment but was relatively invariant with time in argon. In addition, we have measured the spectral shift of this band in an 18O2 atmosphere. Based on this shift, and by comparison with earlier results obtained from free-jet expansion and laser excitation, we can confirm that the oxide in question is UO, consistent with recent reports based on laser ablation in 16O2 only.

Target-specific nanoparticles containing a broad band emissive NIR dye for the sensitive detection and characterization of tumor development.

PubMed

Behnke, Thomas; Mathejczyk, Julia E; Brehm, Robert; Würth, Christian; Gomes, Fernanda Ramos; Dullin, Christian; Napp, Joanna; Alves, Frauke; Resch-Genger, Ute

2013-01-01

Current optical probes including engineered nanoparticles (NPs) are constructed from near infrared (NIR)-emissive organic dyes with narrow absorption and emission bands and small Stokes shifts prone to aggregation-induced self-quenching. Here, we present the new asymmetric cyanine Itrybe with broad, almost environment-insensitive absorption and emission bands in the diagnostic window, offering a unique flexibility of the choice of excitation and detection wavelengths compared to common NIR dyes. This strongly emissive dye was spectroscopically studied in different solvents and encapsulated into differently sized (15, 25, 100 nm) amino-modified polystyrene NPs (PSNPs) via a one-step staining procedure. As proof-of-concept for its potential for pre-/clinical imaging applications, Itrybe-loaded NPs were surface-functionalized with polyethylene glycol (PEG) and the tumor-targeting antibody Herceptin and their binding specificity to the tumor-specific biomarker HER2 was systematically assessed. Itrybe-loaded NPs display strong fluorescence signals in vitro and in vivo and Herceptin-conjugated NPs bind specifically to HER2 as demonstrated in immunoassays as well as on tumor cells and sections from mouse tumor xenografts in vitro. This demonstrates that our design strategy exploiting broad band-absorbing and -emitting dyes yields versatile and bright NIR probes with a high potential for e.g. the sensitive detection and characterization of tumor development and progression. Copyright © 2012 Elsevier Ltd. All rights reserved.

Electro-Optical Properties of Polymer Blends: Lasing, Electroluminescence and Photophysics

DTIC Science & Technology

2007-02-01

34- Phenylenevinylene" (Cirpan/Rathnayake/Lahti/Karasz) 16. Chem. Mater.: "Single-Molecule and Bulk Luminescence Studies of the Green Emission Band in 2,7- Bis...providing emission from the triplet state with a 100% theoretical yield. These electronic transitions of lanthanides result from different electronic...referred to above. Luminescence spectra and luminescence decays were recorded with a Thermo Laser Science pulsed nitrogen laser ( Aem =3 3 7 .1 nm; < 4 ns

Spectral enhancement of leucocrystal violet treated footwear impression evidence in blood.

PubMed

Spence, Lindsay; Asmussen, Gary

2003-03-27

The results presented demonstrate the capacity for spectral enhancement to substantially improve the forensic examination of footwear impressions in blood treated with leucocrystal violet (LCV). The UV-Vis absorption spectra were generated of (i) an aqueous solution of leucocrystal violet, (ii) leucocrystal violet in 3% H(2)O(2), (iii) LCV working solution and (iv) whole blood added to LCV working solution. The resultant fluorescence emission spectra were subsequently generated (lambda(ex)=630nm, lambda(em)=661-900nm). The results indicate that the UV-Vis absorption spectra of an unbuffered solution of whole blood with LCV working solution produces a strong absorbance curve with a maxima at 630nm. Subsequent excitation at this wavelength and generation of the emission spectrum in the fluorescence mode indicates that a solution of whole blood added to LCV working solution is an extremely weak fluorophore. Therefore, to enable an adequate and timely enhancement of blood impression evidence treated with LCV utilising either visible fluorescence or infrared luminescence requires (i) selection of the most appropriate excitation wavelength (lambda(ex)) and emission wavelength (lambda(em)) with extremely narrow band pass filters, which in the absence of substrate matrix interference is excitation at 630nm producing the emission maxima at 665nm and (ii) a visual enhancement system such as a CCD colour IR video camera with image integration.

Tunable room-temperature single-photon emission at telecom wavelengths from sp 3 defects in carbon nanotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Xiaowei; Hartmann, Nicolai F.; Ma, Xuedan

Generating quantum light emitters that operate at room temperature and at telecom wavelengths remains a significant materials challenge. To achieve this goal requires light sources that emit in the near-infrared wavelength region and that, ideally, are tunable to allow desired output wavelengths to be accessed in a controllable manner. Here, we show that exciton localization at covalently introduced aryl sp 3 defect sites in single-walled carbon nanotubes provides a route to room-temperature single-photon emission with ultrahigh single-photon purity (99%) and enhanced emission stability approaching the shot-noise limit. Moreover, we demonstrate that the inherent optical tunability of single-walled carbon nanotubes, presentmore » in their structural diversity, allows us to generate room-temperature single-photon emission spanning the entire telecom band. Furthermore, single-photon emission deep into the centre of the telecom C band (1.55 um) is achieved at the largest nanotube diameters we explore (0.936 nm).« less

Tunable room-temperature single-photon emission at telecom wavelengths from sp 3 defects in carbon nanotubes

DOE PAGES

He, Xiaowei; Hartmann, Nicolai F.; Ma, Xuedan; ...

2017-07-31

Generating quantum light emitters that operate at room temperature and at telecom wavelengths remains a significant materials challenge. To achieve this goal requires light sources that emit in the near-infrared wavelength region and that, ideally, are tunable to allow desired output wavelengths to be accessed in a controllable manner. Here, we show that exciton localization at covalently introduced aryl sp 3 defect sites in single-walled carbon nanotubes provides a route to room-temperature single-photon emission with ultrahigh single-photon purity (99%) and enhanced emission stability approaching the shot-noise limit. Moreover, we demonstrate that the inherent optical tunability of single-walled carbon nanotubes, presentmore » in their structural diversity, allows us to generate room-temperature single-photon emission spanning the entire telecom band. Furthermore, single-photon emission deep into the centre of the telecom C band (1.55 um) is achieved at the largest nanotube diameters we explore (0.936 nm).« less

Use of the fluorescence quantum yield for the determination of the number-average molecular weight of polymers of epicatechin with 4β→8 interflavin bonds

Treesearch

D. Cho; W.L. Mattice; L.J. Porter; Richard W. Hemingway

1989-01-01

Excitation at 280 nm produces a structureless emission band with a maximum at 321-324 nm for dilute solutions of catechin, epicatechin, and their oligomers in l,4-dioxane or water. The fluorescence quantum yield, Q, has been measured in these two solvents for five dimers, a trimer, a tetramer, a pentamer, a hexamer, and a polymer in which the monomer...

Nanostructures of Indium Gallium Nitride Crystals Grown on Carbon Nanotubes.

PubMed

Park, Ji-Yeon; Man Song, Keun; Min, Yo-Sep; Choi, Chel-Jong; Seok Kim, Yoon; Lee, Sung-Nam

2015-11-16

Nanostructure (NS) InGaN crystals were grown on carbon nanotubes (CNTs) using metalorganic chemical vapor deposition. The NS-InGaN crystals, grown on a ~5-μm-long CNT/Si template, were estimated to be ~100-270 nm in size. Transmission electron microscope examinations revealed that single-crystalline InGaN NSs were formed with different crystal facets. The observed green (~500 nm) cathodoluminescence (CL) emission was consistent with the surface image of the NS-InGaN crystallites, indicating excellent optical properties of the InGaN NSs on CNTs. Moreover, the CL spectrum of InGaN NSs showed a broad emission band from 490 to 600 nm. Based on these results, we believe that InGaN NSs grown on CNTs could aid in overcoming the green gap in LED technologies.

Maximizing Tensile Strain in Germanium Nanomembranes for Enhanced Optoelectronic Properties

NASA Astrophysics Data System (ADS)

Sanchez Perez, Jose Roberto

Silicon, germanium, and their alloys, which provide the leading materials platform of microelectronics, are extremely inefficient light emitters because of their indirect fundamental energy band gap. This basic materials property has so far hindered the development of group-IV photonic-active devices, including light emitters and diode lasers, thereby significantly limiting our ability to integrate electronic and photonic functionalities at the chip level. Theoretical studies have predicted that tensile strain in Ge lowers the direct energy band gap relative to the indirect one, and that, with sufficient strain, Ge becomes direct-band gap, thus enabling facile interband light emission and the fabrication of Group IV lasers. It has, however, not been possible to impart sufficient strain to Ge to reach the direct-band gap goal, because bulk Ge fractures at much lower strains. Here it is shown that very thin sheets of Ge(001), called nanomembranes (NMs), can be used to overcome this materials limitation. Germanium nanomembranes (NMs) in the range of thicknesses from 20nm to 100nm were fabricated and then transferred and mounted to a flexible substrate [a polyimide (PI) sheet]. An apparatus was developed to stress the PI/NM combination and provide for in-situ Raman measurements of the strain as a function of applied stress. This arrangement allowed for the introduction of sufficient biaxial tensile strain (>1.7%) to transform Ge to a direct-band gap material, as determined by photoluminescence (PL) measurements and theory. Appropriate shifts in the emission spectrum and increases in PL intensities were observed. The advance in this work was nanomembrane fabrication technology; i.e., making thin enough Ge sheets to accept sufficiently high levels of strain without fracture. It was of interest to determine if the strain at which fracture ultimately does occur can be raised, by evaluating factors that initiate fracture. Attempts to assess the effect of free edges (enchant access holes) on the NM were made and an increase of 35% in the strain to at which crack first formed was found on NMs that lack etchant access holes. Ge NMs were used as a platform to investigate the relationships between surface passivation / functionalization and the physical properties of the material.

Origin of luminescence from ZnO/CdS core/shell nanowire arrays

NASA Astrophysics Data System (ADS)

Wang, Zhiqiang; Wang, Jian; Sham, Tsun-Kong; Yang, Shaoguang

2014-07-01

Chemical imaging, electronic structure and optical properties of ZnO/CdS nano-composites have been investigated using scanning transmission X-ray microscopy (STXM), X-ray absorption near-edge structure (XANES) and X-ray excited optical luminescence (XEOL) spectroscopy. STXM and XANES results confirm that the as-prepared product is ZnO/CdS core/shell nanowires (NWs), and further indicate that ZnS was formed on the surface of ZnO NWs as the interface between ZnO and CdS. The XEOL from ZnO/CdS NW arrays exhibits one weak ultraviolet (UV) emission at 375 nm, one strong green emission at 512 nm, and two broad infrared (IR) emissions at 750 and 900 nm. Combining XANES and XEOL, it is concluded that the UV luminescence is the near band gap emission (BGE) of ZnO; the green luminescence comes from both the BGE of CdS and defect emission (DE, zinc vacancies) of ZnO; the IR luminescence is attributed to the DE (bulk defect related to the S site) of CdS; ZnS contributes little to the luminescence of the ZnO/CdS NW arrays. Interestingly, the BGE and DE from oxygen vacancies of ZnO in the ZnO/CdS nano-composites are almost entirely quenched, while DE from zinc vacancies changes little.Chemical imaging, electronic structure and optical properties of ZnO/CdS nano-composites have been investigated using scanning transmission X-ray microscopy (STXM), X-ray absorption near-edge structure (XANES) and X-ray excited optical luminescence (XEOL) spectroscopy. STXM and XANES results confirm that the as-prepared product is ZnO/CdS core/shell nanowires (NWs), and further indicate that ZnS was formed on the surface of ZnO NWs as the interface between ZnO and CdS. The XEOL from ZnO/CdS NW arrays exhibits one weak ultraviolet (UV) emission at 375 nm, one strong green emission at 512 nm, and two broad infrared (IR) emissions at 750 and 900 nm. Combining XANES and XEOL, it is concluded that the UV luminescence is the near band gap emission (BGE) of ZnO; the green luminescence comes from both the BGE of CdS and defect emission (DE, zinc vacancies) of ZnO; the IR luminescence is attributed to the DE (bulk defect related to the S site) of CdS; ZnS contributes little to the luminescence of the ZnO/CdS NW arrays. Interestingly, the BGE and DE from oxygen vacancies of ZnO in the ZnO/CdS nano-composites are almost entirely quenched, while DE from zinc vacancies changes little. Electronic supplementary information (ESI) available: PL spectra of the ZnO NW arrays before/after CdS coating. S K-edge XANES spectra of the ZnO/CdS core/shell NW arrays. See DOI: 10.1039/c4nr02231a

Measurement of Fluorescence in a Rhodamine-123 Doped Self-Assembled “Giant” Mesostructured Silica Sphere Using a Smartphone as Optical Hardware

PubMed Central

Canning, John; Lau, Angelica; Naqshbandi, Masood; Petermann, Ingemar; Crossley, Maxwell J.

2011-01-01

The blue OLED emission from a mobile phone was characterised, revealing a sharp emission band centred at λ = 445 nm with a 3dB bandwidth Δλ ∼ 20 nm. It was used to excite Rhodamine 123 doped within a “giant” mesostructured silica sphere during fabrication through evaporative self-assembly of silica nanoparticles. Fluorescence was able to be detected using a standard optical microscope fitted with a green transmission pass filter and cooled CCD and with 1 ms exposure time demonstrating the potential of mobile platforms as the basis for portable diagnostics in the field. PMID:22164002

The spectroscopy of MnH

NASA Astrophysics Data System (ADS)

Langhoff, Stephen R.; Bauschlicher, Charles W.; Rendell, Alistair P.

1989-11-01

The low-lying quintet and septet states of MnH have been studied using the state-averaged {CASSCF}/{MRCI} method. Our study focuses on the A7Π- X7Σ +, c5Σ +- a5Σ +, and b5Π- a5Σ + band systems, which almost certainly correspond to the 566-, 847-, and 939-nm band systems observed in emission. The radiative lifetimes for the v' = 0 level of the A7Π, b5Π, and c5Σ + states are 96.6 ns and 3.2 and 0.39 μs, respectively. Although the CASSCF calculations are not inconsistent with the assignment of the 480-nm band system to a 5Π- a5Σ + transition, they indicate the existence of a stronger 5Σ +- a5Σ + transition in the same energy region. The calculations also show that the quintet spectrum above 20 000 cm -1 is very complicated.

Preparation and characterization of PVP-PVA–ZnO blend polymer nano composite films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Divya, S., E-mail: divi.fysics@gmail.com; Saipriya, G.; Hemalatha, J., E-mail: hemalatha@nitt.edu

Flexible self-standing films of PVP-PVA blend composites are prepared by using ZnO as a nano filler at different concentrations. The structural, compositional, morphological and optical studies made with the help of X-ray diffraction (XRD), Fourier Transform Infra-Red spectroscopy (FTIR), Scanning electron microscope (SEM), Atomic Force Microscopy (AFM), Ultraviolet-visible spectroscopy (UV-vis) and Photoluminescence (PL) spectra are presented in this paper. The results of XRD indicate that ZnO nanoparticles are formed with hexagonal phase in the polymeric matrix. SEM images show the dispersion of ZnO nano filler in the polymer matrix. UV–vis spectra reveal that the absorption peak is centered around 235more » nm and 370 nm for the nano composite films. The blue shift is observed with decrease in the concentration of the nano filler. PL spectra shows the excitation wavelength is given at 320 nm.The emission peaks were observed at 383 nm ascribing to the electronic transitions between valence band and conduction band and the peak at 430 nm.« less

Optoelectronic and Electrochemical Properties of Vanadium Pentoxide Nanowires Synthesized by Vapor-Solid Process

PubMed Central

Pan, Ko-Ying; Wei, Da-Hua

2016-01-01

Substantial synthetic vanadium pentoxide (V2O5) nanowires were successfully produced by a vapor-solid (VS) method of thermal evaporation without using precursors as nucleation sites for single crystalline V2O5 nanowires with a (110) growth plane. The micromorphology and microstructure of V2O5 nanowires were analyzed by scanning electron microscope (SEM), energy-dispersive X-ray spectroscope (EDS), transmission electron microscope (TEM) and X-ray diffraction (XRD). The spiral growth mechanism of V2O5 nanowires in the VS process is proved by a TEM image. The photo-luminescence (PL) spectrum of V2O5 nanowires shows intrinsic (410 nm and 560 nm) and defect-related (710 nm) emissions, which are ascribable to the bound of inter-band transitions (V 3d conduction band to O 2p valence band). The electrical resistivity could be evaluated as 64.62 Ω·cm via four-point probe method. The potential differences between oxidation peak and reduction peak are 0.861 V and 0.470 V for the first and 10th cycle, respectively. PMID:28335268

Narrowband NanoSat Scale Photometry for VUV Planetary and Heliophysics missions

NASA Astrophysics Data System (ADS)

Noto, J.; Doe, R. A.; Frey, H. U.

2015-12-01

Remote vacuum ultraviolet (VUV) soundings to support Explorer-class atmospheric research are typically enabled by large aperture, wideband spectrographs carefully pointed to measure a planet's disk and limb regions (i.e. TIMED/GUVI and MAVEN/UVS). An alternate measurement paradigm is to identify key aeronomical emission targets (i.e HI 121.6-nm, OI 135.6-nm, N2 Lyman-Birge-Hopfield band 135 - 155 nm) and create a series of narrowband photometers each with greater in-band sensitivity (relative to a spectrograph) due to enhanced out-of-band rejection and absence of a dispersive element. Recent advances in narrowband VUV coating and PMT miniaturization have enabled design of a dual-channel nanosatellite-scale VUV photometer with flight heritage significantly leveraged from the NASA POLAR UVI imager the Air Force CubeSat Tiny Ionospheric Photometer (CTIP). Herein we present further modeled sensitivity studies and current build status of the dual-channel thermosphere/ionosphere photometer (DTIP) and address notional missions including dayside O/N2 composition, auroral energetics, nightside plasma structuring and peak layer characterization, and hydrogen geocoronal tomographic imaging.

Visible luminescence of Al2O3 nanoparticles embedded in silica glass host matrix

NASA Astrophysics Data System (ADS)

El Mir, L.; Amlouk, A.; Barthou, C.

2006-11-01

This paper deals with the sol gel elaboration and defects photoluminescence (PL) examination of Al2O3 nanocrystallites (size ˜30 nm) confined in glass based on silica aerogel. Aluminium oxide aerogels were synthesized using esterification reaction for hydrolysis of the precursor and supercritical conditions of ethyl alcohol for drying. The obtained nanopowder was incorporated in SiO2 host matrix. After heating under natural atmosphere at 1150 °C for 2 h, the composite Al2O3/SiO2 (AS) exhibited a strong PL bands at 400 600 and 700 900 nm in 78 300 K temperature range. PL excitation (PLE) measurements show different origins of the emission. It was suggested that OH-related radiative centres and non-bridging oxygen hole centres (NBOHCs) were responsible for the bands at 400 600 and 700 900 nm, respectively.

Optical and electrical properties of mechanochemically synthesized nanocrystalline delafossite CuAlO2.

PubMed

Prakash, T; Prasad, K Padma; Ramasamy, S; Murty, B S

2008-08-01

Nanocrystalline p-type semiconductor copper aluminum oxide (CuAlO2) has been synthesized by mechanical alloying using freshly prepared Cu2O and alpha-AlO2O3 nanocrystals in toluene medium. A study on structural property performed with different alloying and post annealing durations, by X-ray diffraction (XRD) reveals the formation of single phase with average crystallite size approximately 45 nm. Optical absorbance onset at 364.5 nm confirms its wide band gap nature (E(g) = 3.4 eV) and the fluorescence emission behaviour (390 nm) confirms its direct band type transition. The activation energy for electrical conduction has been calculated by Arrhenius plots using impedance measurement. Both grain and grain boundary conductivity takes place with almost equal activation energies of approximately 0.45 eV. The paper discusses synthesis, structural, optical and electrical properties of delafossite CuAlO2 in detail.

Spectroscopic properties and energy transfer parameters of Er3+-doped fluorozirconate and oxyfluoroaluminate glasses.

PubMed

Huang, Feifei; Liu, Xueqiang; Hu, Lili; Chen, Danping

2014-05-23

Er3+-doped fluorozirconate (ZrF4-BaF2-YF3-AlF3) and oxyfluoroaluminate glasses are successfully prepared here. These glasses exhibit significant superiority compared with traditional fluorozirconate glass (ZrF4-BaF2-LaF3-AlF3-NaF) because of their higher temperature of glass transition and better resistance to water corrosion. Judd-Ofelt (J-O) intensity parameters are evaluated and used to compute the radiative properties based on the VIS-NIR absorption spectra. Broad emission bands located at 1535 and 2708 nm are observed, and large calculated emission sections are obtained. The intensity of 2708 nm emission closely relates to the phonon energy of host glass. A lower phonon energy leads to a more intensive 2708 nm emission. The energy transfer processes of Er3+ ions are discussed and lifetime of Er3+:4I13/2 is measured. It is the first time to observe that a longer lifetime of the 4I13/2 level leads to a less intensive 1535 nm emission, because the lifetime is long enough to generate excited state absorption (ESA) and energy transfer (ET) processes. These results indicate that the novel glasses possess better chemical and thermal properties as well as excellent optical properties compared with ZBLAN glass. These Er3+-doped ZBYA and oxyfluoroaluminate glasses have potential applications as laser materials.

Tm3+/Yb3+ co-doped tellurite glass with silver nanoparticles for 1.85 μm band laser material

NASA Astrophysics Data System (ADS)

Huang, Bo; Zhou, Yaxun; Cheng, Pan; Zhou, Zizhong; Li, Jun; Jin, Wei

2016-10-01

Tm3+/Yb3+ co-doped tellurite glasses with different silver nanoparticles (Ag NPs) concentrations were prepared using the conventional melt-quenching technique and characterized by the UV/Vis/NIR absorption spectra, 1.85 μm band fluorescence emission spectra, transmission electron microscopy (TEM) images, differential scanning calorimeter (DSC) curves and X-ray diffraction (XRD) patterns to investigate the effects of Ag NPs on the 1.85 μm band spectroscopic properties of Tm3+ ions, thermal stability and structural nature of glass hosts. Under the excitation of 980 nm laser diode (LD), the 1.85 μm band fluorescence emission of Tm3+ ions enhances significantly in the presence of Ag NPs with average diameter of ∼8 nm and local surface Plasmon resonance (LSPR) band of ∼590 nm, which is mainly attributed to the increased local electric field induced by Ag NPs at the proximity of doped rare-earth ions on the basis of energy transfer from Yb3+ to Tm3+ ions. An improvement by about 110% of fluorescence intensity is observed in the Tm3+/Yb3+ co-doped tellurite glass containing 0.5 mol% amount of AgNO3 while the prepared glass samples possess good thermal stability and amorphous structural nature. Meanwhile, the Judd-Ofelt intensity parameters Ωt (t = 2,4,6), spontaneous radiative transition probabilities, fluorescence branching ratios and radiative lifetimes of relevant excited levels of Tm3+ ions were determined based on the Judd-Ofelt theory to reveal the enhanced effects of Ag NPs on the 1.85 μm band spectroscopic properties, and the energy transfer micro-parameters and phonon contribution ratios were calculated based on the non-resonant energy transfer theory to elucidate the energy transfer mechanism between Yb3+ and Tm3+ ions. The present results indicate that the prepared Tm3+/Yb3+ co-doped tellurite glass with an appropriate amount of Ag NPs is a promising lasing media applied for 1.85 μm band solid-state lasers and amplifiers.

Optical measurement of acidification of human dental plaque in vitro

NASA Astrophysics Data System (ADS)

Graham, Jasmine Y.; Nelson, Leonard Y.; Seibel, Eric J.

2018-02-01

A pH measurement of oral biofilms is helpful for monitoring the impact of acidogenic bacteria in the caries process. Demineralization of dental enamel is closely related to the time dependent pH of human plaque. Therefore, providing a means to easily measure the local pH of biofilms is a useful clinical diagnostic in the arsenal of caries prevention tools. Optical measurement methods of plaque metabolism can use intrinsic fluorescence or extrinsic fluorescence from added dyes. Autofluorescence spectral features of human oral biofilms at green (500 nm) and red (634 nm) fluorescence wavelengths using 405 nm excitation did not demonstrate a spectral or intensity shift between neutral and acidic conditions. Chlorin e6, an ingredient in chlorophyllin food supplement, exhibited a spectral and intensity shift of fluorescence emission in buffered solutions, but this quantitative pH-dependence was not transferable to a human plaque environment. Finally, a ratiometric quantitative pH measure was achieved by exciting (405 nm laser) a mixture of two dyes, fluorescein and rhodamine B. This two-dye mixture produced two strong fluorescent bands centered at 515 nm (fluorescein) and 580 nm (rhodamine B), where the 515 nm band was pH sensitive and the 580 nm band served as a pH insensitive reference. This dual-dye fluorescence ratio exhibited a linear response over pH 7 to 5 in human oral biofilms during a sugar challenge. We have explored methods to use non-contact, optical measures of local acidity levels in difficult to access dental locations such as occlusal fissures using various pH sensitive fluorescent dye systems.

Optical Properties of CdSe/ZnS Nanocrystals

PubMed Central

Gaigalas, Adolfas K; DeRose, Paul; Wang, Lili; Zhang, Yu-Zhong

2014-01-01

Measurements are presented of the absorbance, fluorescence emission, fluorescence quantum yield, and fluorescence lifetime of CdSe/ZnS nanocrystals, also known as quantum dots (QDs). The study included three groups of nanocrystals whose surfaces were either passivated with organic molecules, modified further with carboxyl groups, or conjugated with CD14 mouse anti-human antibodies. The surface modifications had observable effects on the optical properties of the nanocrystals. The oscillator strength (OS) of the band edge transition was about 1.0 for the nanocrystals emitting at 565 nm, 605 nm, and 655 nm. The OS could not be determined for QDs with emission at 700 nm and 800 nm. The fluorescence lifetimes varied from 26 ns for nanocrystals emitting near 600 nm to 150 ns for nanocrystals emitting near 800 nm. The quantum yield ranged between 0.4 and 0.9 for the nanocrystals in this study. A brightness index (BI) was used to evaluate the suitability of the nanocrystal labels for flow cytometer measurements. Most QD labels are at least as bright as fluorescein for applications in flow cytometer assays with 488 nm excitation. For optimal brightness the QDs should be excited with 405 nm light. We observed a strong dependence of the QD absorbance at 250 nm on the surface modification of the QD. PMID:26601047

[The Emission Spectroscopy of Nitrogen Discharge under Low Voltage at Room Temperature].

PubMed

Shen, Li-hua; Yu, Chun-xia; Yan, Bei; Zhang, Cheng-xiao

2015-03-01

A set of direct current (DC) discharge device of N2 plasma was developed, carbon nanotubes (CNT) modified ITO electrode was used as anode, aluminum plate as cathode, with -80 μm separation between them. Nitrogen emission spectra was observed at room temperature and low DC voltage (less than 150 V), and the emission spectrometry was used to diagnose the active species of the process of nitrogen discharge. Under DC discharge, the strongest energy band N2 (C3π(u)), the weak Gaydon's Green system N2 (H3 -Φ(u)-G3 Δ(g)) and the emission line of nitrogen atoms (4 p-4 p0) at 820 nm were observed. Found that metastable state of nitrogen molecules were the main factors leading to a series of excited state nitrogen atoms and nitrogen ionization. Compared the emission spectra under DC with that under alternating current (AC) (1.1 kV), and it can be seen that under DC the spectra band of nitrogen atoms can be obviously observed, and there was a molecular band in the range of 500 - 800 nm. The effect of oxygen and hydrogen on the emission spectra of nitrogen was investigated. The results showed that the oxygen inhibited the luminescence intensity of nitrogen, but the shape of spectra unchanged. All of the second positive system, Gaydon's Green system and atomic lines of nitrogen can be observed. The second positive system and Gaydon's Green system of nitrogen will be greatly affected when the volume ratio of nitrogen and hydrogen greatly affected is 1 : 1, which was due to the hydrogen. The hydrogen can depresse nitrogen plasma activation, and make the Gaydon's Green System disappeared. CNT modified ITO electrode can reduce the breakdown voltage, and the optical signal generated by the weakly ionized gas can be observed by the photo-multiplier tube at low voltage of 10 V.

Studies on nickel-tungsten oxide thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Usha, K. S.; Sivakumar, R., E-mail: krsivakumar1979@yahoo.com; Sanjeeviraja, C.

2014-10-15

Nickel-Tungsten oxide (95:5) thin films were prepared by rf sputtering at 200W rf power with various substrate temperatures. X-ray diffraction study reveals the amorphous nature of films. The substrate temperature induced decrease in energy band gap with a maximum transmittance of 71%1 was observed. The Micro-Raman study shows broad peaks at 560 cm{sup −1} and 1100 cm{sup −1} correspond to Ni-O vibration and the peak at 860 cm{sup −1} can be assigned to the vibration of W-O-W bond. Photoluminescence spectra show two peaks centered on 420 nm and 485 nm corresponding to the band edge emission and vacancies created duemore » to the addition of tungsten, respectively.« less

Shuttle-based measurements: GLO ultraviolet earthlimb view

NASA Astrophysics Data System (ADS)

Gardner, James A.; Murad, Edmond; Viereck, Rodney A.; Knecht, David J.; Pike, Charles P.; Broadfoot, A. Lyle

1996-11-01

The GLO experiment is an on-going shuttle-based spectrograph/imager project that has returned ultraviolet (100 - 400 nm) limb views. High spectral (0.35 nm FWHM) and temporal (4 s) resolution spectra include simultaneous altitude profiles (in the range of 80 - 400 km tangent height with 10 km resolution) of dayglow and nightglow features. Measured emissions include the NO gamma, N2 Vegard-Kaplan and second positive, N2+ first negative, and O2 Herzberg I band systems and both atomic and cation lines of N, O, and Mg. This data represents a low solar activity benchmark for future observations. We report on the status of the GLO project, which included three space flights in 1995, and present spectral data on important ultraviolet band systems.

Effect of concentration variation on 2.0 µm emission of Ho3+-doped SiO2-Al2O3-Na2CO3-SrF2-CaF2 oxyfluorosilicate glasses

NASA Astrophysics Data System (ADS)

Gelija, Devarajulu; Borelli, Deva Prasad Raju

2018-02-01

The concentration variation of Ho3+ ion-doped SiO2-Al2O3-Na2CO3-SrF2-CaF2 glasses has been prepared by conventional melt quenching method. The thermal stability of 1 mol % of Ho3+-doped oxyfluorosilicate glass has been calculated using the differential thermal analysis (DTA) spectra. The phenomenological Judd-Ofelt intensity parameters Ωλ ( λ = 2, 4 and 6) were calculated for all concentrations of Ho3+ ions. The luminescence spectra in visible region of Ho3+ ion-doped glasses were recorded under the excitation wavelength of 452 nm. The spectra consists of several intense emission bands (5F4, 5S2) → 5I8 (547 nm), 5F3 → 5I8 (647 nm), 5F5 → 5I7 (660 nm) and (5F4, 5S2) → 5I7 (750 nm) in the range 500-780 nm. The fluorescence emission at ˜2.0 µm (5I7 → 5I8) was observed under the excitation of 488 nm Ar-ion laser. The stimulated emission cross section for 5I7 → 5I8 transition (˜2.0 µm) varies from 8.46 to 9.52 × 10-21 cm2, as calculated by the Fuchtbauer-Ladenburg (FL) theory. However, Mc-Cumber theory was used to calculate emission cross section values about 4.24-5.75 × 10-21 cm2 for the 5I7 → 5I8 transition in all concentrations of Ho3+-doped oxyfluorosilicate glasses. Therefore, these results reveal that the 0.5 mol % of Ho3+-doped oxyfluorosilicate glasses, exhibiting higher emission cross section, has potentially been used for laser applications at ˜ 2.0 µm.

Structural, optical and photovoltaic properties of P3HT and Mn-doped CdS quantum dots based bulk hetrojunction hybrid layers

NASA Astrophysics Data System (ADS)

Jabeen, Uzma; Adhikari, Tham; Pathak, Dinesh; Shah, Syed Mujtaba; Nunzi, Jean-Michel

2018-04-01

Cadmium sulphide (CdS) and Mn-doped CdS nanocrystals were synthesized by co-precipitation method. The nanocrystals were characterized by Fluorescence, Fourier Transformed Infra-red Spectrometer (FTIR), UV-Visible, X-ray diffraction (XRD), X-ray photoelectron spectrometer (XPS), Field Emission Scanning Electron Microscope (FESEM), and High Resolution Transmission Electron Microscope (HRTEM). A considerable blue shift of absorption band with respect to the cadmium sulphide was observed by the Mn concentration (0.5 M) in the doped sample with decreasing the size of nanocrystals. Other reason for this may be Mn doping. Subsequently the band gap was altered from 2.11 to 2.21 eV due to quantum confinement effect. Scanning electron microscope supplemented with EDAX was operated to find grain size and chemical composition of the synthesized nanomaterials. The PL spectrum of Mn-doped CdS nanocrystals displays three PL bands the first one, within the range of 500 nm and the second band at 537 nm, and the third one around 713 nm is labelled red band emission due to attributed to a 4T1→6A1 transition within the 3d shell of divalent manganese. XRD analysis showed that the material was in cubic crystalline state. A comparative study of surfaces of un-doped and metal doped CdS nanocrystals were investigated using X-ray Photoelectron Spectroscopy (XPS). The synthesized nanomaterial in combination with polymer, poly (3-hexyl thiophene) was operated in the construction of photovoltaic cells. The photovoltaic devices with CdS nanocrystals exhibited power conversion efficiency of 0.34% without annealing and 0.38% with annealing. However, the power conversion efficiency was enhanced by a factor of 0.35 without annealing and 0.42 with annealing with corporation of Mn impurity in CdS lattice. Atomic Force Microscopy was employed for morphology and packing behavior of blend of nanocrystals with organic polymer.

Quantifying Industrial Methane Emissions from Space with the GHGSat-D Satellite

NASA Astrophysics Data System (ADS)

Germain, S.; Durak, B.; Gains, D.; Jervis, D.; McKeever, J.; Sloan, J. J.

2017-12-01

In June 2016, GHGSat, Inc. launched GHGSat-D, or "Claire", the world's first satellite capable of measuring greenhouse gas emissions from targeted industrial facilities around the world. The high-level objective of this mission is to demonstrate that a single measurement approach can quantify methane emission rates from selected industrial sources with greater precision, higher frequency, and lower cost than ground-based alternatives, across a wide range of industries. Providing industrial operators and regulators with frequent, cost-effective emission measurements can help identify super-emitters and monitor the progress of mitigation efforts. The GHGSat measurement platform is a 15 kg satellite that measures methane column densities using a novel wide-angle imaging Fabry-Perot spectrometer tuned to the 1600-1700 nm SWIR band. During each measurement sequence, a series of closely overlapping 2D images are taken so that each ground location samples a portion of the SWIR band with 0.1 nm spectral resolution. The data processing algorithm is able to co-register each image and, by comparison with a detailed forward model, perform a retrieval on each of the <50 m GSD over the entire 12 x 12 km2 field of view. Methane emission rates are then estimated using a dispersion model coupled with locally measured wind fields. We will present the economic rationale for satellite-based sensing of methane from industrial sources, introduce the GHGSat measurement concept, report on recent measurement results obtained by Claire, and describe performance upgrades planned for future missions.

Fluorescence properties of Tb{sup 3+} and Sm{sup 3+} activated novel LiAl{sub 7}B{sub 4}O{sub 17} host via solution combustion synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palaspagar, R.S., E-mail: rspalaspagar@gmail.com; Gawande, A.B., E-mail: gawandeab@gmail.com; Sonekar, R.P., E-mail: sonekar_rp@yahoo.com

2015-12-15

Graphical abstract: - Highlights: • New LiAl{sub 7}B{sub 4}O{sub 17}:Tb{sup 3+}, Sm{sup 3+} phosphors were synthesized first time by solution combustion method. • The LiAl{sub 7}B{sub 4}O{sub 17}:Tb{sup 3+} emissions; 489, 544, 586 and 623 nm (λ{sub ex} = 234 nm). • Also for LiAl{sub 7}B{sub 4}O{sub 17}:Sm{sup 3+}; 564, 601 and 649 nm (λ{sub ex} = 403 nm). • Synthesized materials were characterized by powder XRD, FE-SEM. • Concentration quenching mechanism and critical transfer distance of Tb{sup 3+} and Sm{sup 3+} in the prepared sample has been investigated. - Abstract: Novel LiAl{sub 7}B{sub 4}O{sub 17} (LABO) phosphor activated withmore » trivalent rare earth ions (RE = Tb, Sm) was synthesized by using solution combustion synthesis. The powder X-ray diffraction (XRD), field emission-scanning electron microscope (FE-SEM), photoluminescence (PL), critical transfer distance (R{sub c}) and quenching mechanism studies were employed to characterize the samples. Under ultraviolet irradiation of the LiAl{sub 7}B{sub 4}O{sub 17}: Tb{sup 3+}, Sm{sup 3+} phosphors exhibit the typical green ({sup 5}D{sub 4} → {sup 7}F{sub j} = 6, 5, 4 and 3) emission band of the Tb{sup 3+} ions, as well as an orange-red and red ({sup 4}G{sub 5/2} → {sup 6}H{sub J=5/2,} {sub 7/2,} {sub 9/2}) emission bands of the Sm{sup 3+} ions. These results suggest that Tb{sup 3+} and Sm{sup 3+} activated LABO phosphor could be promising in vision of the necessity for solid state lighting applications.« less

Reddish-orange, neutral and warm white emissions in Eu3+, Dy3+ and Dy3+/Eu3+ doped CdO-GeO2-TeO2 glasses

NASA Astrophysics Data System (ADS)

Rodríguez-Carvajal, David A.; Meza-Rocha, A. N.; Caldiño, U.; Lozada-Morales, R.; Álvarez, E.; Zayas, Ma. E.

2016-11-01

Eu3+, Dy3+ and Dy3+/Eu3+ doped CdO-GeO2-TeO2 glasses were prepared using the melt-quenching process and analyzed by X-diffraction, Raman spectroscopy, excitation and emission spectra, and emission decay time profiles. The lack of X ray diffraction peaks revealed that all samples are amorphous. Vibrational modes associated with Tesbnd Osbnd Te and Gesbnd Osbnd Ge related bonds and molecular oxygen were detected by Raman spectroscopy. The luminescence characteristics were studied upon excitations that correspond with the emission of InGaN (370-420 nm) based LEDs. The Eu3+ singly doped glass displayed reddish-orange global emission, with x = 0.601 and y = 0.349 CIE1931 chromaticity coordinates, upon 393 nm excitation. Neutral emission with x = 0.373 and y = 0.412 CIE1931 chromaticity coordinates and correlated color temperature (CCT) of 4400 K, was achieved in the Dy3+ singly doped glass excited at 388 nm. The Dy3+/Eu3+ co-doped glass exhibited warm, neutral and soft warm white emissions with CCT values of 3435, 4153 and 2740 K, under excitations at 382, 388 and 393 nm, respectively, depending mainly on the Dy3+ and Eu3+ relative excitation. The Dy3+ excitation bands observed in the Dy3+/Eu3+ glass by monitoring the 611 nm Eu3+ emission, suggest that Dy3+ → Eu3+ energy transfer takes place, despite the fact that the Dy3+ emission decays in the Dy3+ and Dy3+/Eu3+ doped glass, remain without changes. The shortening of Eu3+ decay in presence of Dy3+ was attributed to an Eu3+ → Dy3+ non-radiative energy transfer process, which according with the Inokuti-Hirayama model might be dominated through an electric quadrupole-quadrupole interaction, with efficiency and probability of 5.5% and 51.6 s-1, respectively.

Zirconia based Ho3+-Yb3+ codoped upconverting nanophosphors for green light emitting devices applications

NASA Astrophysics Data System (ADS)

Dutta, Joydip; Rai, Vineet Kumar

2018-04-01

Photoluminescence study of the Ho3+-Yb3+ codoped ZrO, AlZrO and YZrO nanophosphors, synthesized by chemical co-precipitation method, upon excitation at 450 and 980 nm radiations have been performed. An improvement of about ˜4.5 times in the downconversion emission intensity of green band corresponding to the 5F4, 5S2 → 5I8 transition for codoped YZrO nanophosphors compared to ZrO codoped nanophosphors has been observed. On varying the pump power density upon 980 nm excitation the colour tunability in the codoped YZrO nanophosphors has been observed. UC emission intensity of the green band arising from the Ho3+ ion in the codoped YZrO nanophosphors is enhanced about ˜22 times compared to that of the codoped ZrO nanophosphors. The absorption and UC emission study for the codoped YZrO nanophosphors dispersed in different biologically compatible solvents viz. water, methanol, ethanol and dimethyl sulfoxide (DMSO) has been performed. The green UC emission intensity of about ˜1.3 and ˜1.7 times for the efficient codoped YZrO nanophosphors dispersed in methanol compared to that dispersed in water and DMSO respectively has been observed. The absorption spectra of an efficient upconverting YZrO nanophosphors dispersed in methanol exhibit no change with the passage of time.

Blue-green upconversion laser

DOEpatents

Nguyen, D.C.; Faulkner, G.E.

1990-08-14

A blue-green laser (450--550 nm) uses a host crystal doped with Tm[sup 3+]. The Tm[sup 3+] is excited through upconversion by a red pumping laser and an IR pumping laser to a state which transitions to a relatively lower energy level through emissions in the blue-green band, e.g., 450.20 nm at 75 K. The exciting laser may be tunable dye lasers or may be solid-state semiconductor laser, e.g., GaAlAs and InGaAlP. 3 figs.

Blue-green upconversion laser

DOEpatents

Nguyen, Dinh C.; Faulkner, George E.

1990-01-01

A blue-green laser (450-550 nm) uses a host crystal doped with Tm.sup.3+. The Tm.sup.+ is excited through upconversion by a red pumping laser and an IR pumping laser to a state which transitions to a relatively lower energy level through emissions in the blue-green band, e.g., 450.20 nm at 75 K. The exciting laser may be tunable dye lasers or may be solid-state semiconductor laser, e.g., GaAlAs and InGaAlP.

Advances in Fluorescence Sensing Systems for the Remote Assessment of Nitrogen Supply in Field Corn

NASA Technical Reports Server (NTRS)

Corp, L. A.; Chappelle, E. W.; McMurtrey, J. E.; Daughtry, C. S. T.; Kim, M. S.

2000-01-01

The studies described herein were conducted to better define changes in fluorescence properties of leaves from field grown corn (Zea mays L.) as they relate to varying levels of nitrogen (N) fertilization. This research was directed toward: 1) providing a remote non-destructive sensing technique to aid in the determination of optimal rates of N fertilization in corn crops and, 2) defining parameters for further development of fluorescence instrumentation to be operated remotely at field canopy levels. Fluorescence imaging bands centered in the blue (450 nm), green (525 nm), red (680 nm), and far-red (740 nm) and ratios of these bands were compared with the following plant parameters: rates of photosynthesis, N:C ratio, pigment concentrations, and grain yields. Both the fluorescence and physiological measures exhibited similar curvilinear responses to N fertilization level while significant linear correlations were obtained among fluorescence bands and band ratios to certain physiological measures of plant productivity. The red / blue, red / green, far-red / blue, far-red /green fluorescence ratios are well suited for remote observation and provided high correlations to grain yield, LAI, N:C, and chlorophyll contents. The results from this investigation indicate that fluorescence technology could aid in the determination of N fertilization requirements for corn. This discussion will also address design concepts and preliminary field trials of a mobile field-based Laser Induced Fluorescence Imaging System (LIFIS) capable of simultaneously acquiring images of four fluorescence emission bands from areas of plant canopies equaling 1 sq m and greater without interference of ambient solar radiation.

Energy transfer and optical gain properties of P{sub 2}O{sub 5}-ZnO-LiF: (Yb{sup 3+}, Er{sup 3+}) glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, C. Parthasaradhi, E-mail: cgparthasaradhi@gmail.com, E-mail: ktrkreddy@gmail.com; Naresh, V.; Reddy, K. T. Ramakrishna, E-mail: cgparthasaradhi@gmail.com, E-mail: ktrkreddy@gmail.com

2015-06-24

The present paper reports on the results pertaining to the emission properties of 0.5 mol% Er{sup 3+} and together (0.5 Yb{sup 3+} /0.5 Er{sup 3+}) doped PZL (P{sub 2}O{sub 5}-ZnO-LiF) glasses prepared by a melt quenching method. From the optical absorption data, absorption and stimulated emission cross-sections have been evaluated using McCumber’s theory and further cross-sectional gain has also been computed for Yb{sup 3+}/Er{sup 3+} doped glass. On exciting the single (Er{sup 3+}) and dual rare earth ions (Yb{sup 3+}/Er{sup 3+}) doped glass sample at λ{sub exci} = 379 nm, three emission bands in the visible region {sup 2}H{sub 11/2}→{sup 4}I{sub 15/2}more » (526 nm), {sup 4}S{sub 3/2}→{sup 4}I{sub 15/2} (549 nm) and {sup 4}F{sub 9/2}→{sup 4}I{sub 15/2} (664 nm) are observed and while at λ{sub exci} = 980 nm (Laser Diode) excitation a broad emission at 1530 nm attributed to {sup 4}H{sub 13/2}→{sup 4}I{sub 15/2} is observed in the NIR region. The enhancement in visible and NIR emission intensities with the addition of Yb{sup 3+} to Er{sup 3+} due to an energy transfer process from Yb{sup 3+} to Er{sup 3+} has been explained in terms of an energy level diagram.« less

Outstanding features of Cu-doped ZnS nanoclusters

NASA Astrophysics Data System (ADS)

Tawfik, Wael Z.; Farghali, A. A.; Moneim, Ahmed; Imam, N. G.; El-Dek, S. I.

2018-05-01

ZnS and their Cu-doped nanoclusters (NCs) were synthesized successfully using the wet chemical route with different Cu content. The crystalline structure was investigated using x-ray powder diffraction which assured the single-phase formation in cubic symmetry. High-resolution transmission electron microscope indicated the microstructure of NCs with a size ranging from 2–4 nm. A butterfly hysteresis (M-H) loop was observed at room temperature with large values of coercivity for the Cu content of x = 0.05. Photoluminescence emission spectra were recorded from 500–615 nm for pure and Cu-doped ZnS NCs at a 350 nm excitation wavelength. The sample exhibited green fluorescence bands peaking at 535, 544, 552.5, 558.2, and 560.6 nm, which confirmed the characteristic feature of Zn2+ as luminescent centers in the lattice. The additional yellow and orange emissions are due to defect levels or/and impurity centers. The dielectric constant as well as the conductivity values increased with increasing Cu content.

Down- and up-conversion emissions in Er-doped transparent fluorotellurite glass-ceramics

NASA Astrophysics Data System (ADS)

Miguel, A.; Morea, R.; Gonzalo, J.; Fernandez, J.; Balda, R.

2015-03-01

In this work, we report the near infrared and upconversion emissions of Er3+-doped transparent fluorotellurite glassceramics obtained by heat treatment of the precursor Er-doped TeO2-ZnO-ZnF2 glass. Structural analysis shows that ErF3 nanocrystals nucleated in the glass-ceramic sample are homogeneously distributed in the glass matrix with a typical size of 45±10 nm. The comparison of the fluorescence properties of Er3+-doped precursor glass and glass-ceramic confirms the successful incorporation of the rare-earth into the nanocrystals. An enhancement of the red upconversion emission due to 4F9/2→4I15/2 transition together with weak emission bands due to transitions from 2H9/2, 4F3/2,5/2, and 4F7/2 levels to the ground state are observed under excitation at 801 nm in the glass-ceramic sample. The temporal evolution of the red emission together with the excitation upconversion spectrum suggest that energy transfer processes are responsible for the enhancement of the red emission.

Formation of 238U 16O and 238U 18O observed by time-resolved emission spectroscopy subsequent to laser ablation

DOE PAGES

Weisz, David G.; Crowhurst, Jonathan C.; Siekhaus, Wigbert J.; ...

2017-07-17

Here, we have measured vibronic emission spectra of an oxide of uranium formed after laser ablation of the metal in gaseous oxygen. Specifically, we have measured the time-dependent relative intensity of a band located at approximately 593.6 nm in 16O 2. This band grew in intensity relative to neighboring atomic features as a function time in an oxygen environment but was relatively invariant with time in argon. In addition, we have measured the spectral shift of this band in an 18O 2 atmosphere. Based on this shift, and by comparison with earlier results obtained from free-jet expansion and laser excitation,more » we can confirm that the oxide in question is UO, consistent with recent reports based on laser ablation in 16O 2 only.« less

Formation of 238U 16O and 238U 18O observed by time-resolved emission spectroscopy subsequent to laser ablation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weisz, David G.; Crowhurst, Jonathan C.; Siekhaus, Wigbert J.

Here, we have measured vibronic emission spectra of an oxide of uranium formed after laser ablation of the metal in gaseous oxygen. Specifically, we have measured the time-dependent relative intensity of a band located at approximately 593.6 nm in 16O 2. This band grew in intensity relative to neighboring atomic features as a function time in an oxygen environment but was relatively invariant with time in argon. In addition, we have measured the spectral shift of this band in an 18O 2 atmosphere. Based on this shift, and by comparison with earlier results obtained from free-jet expansion and laser excitation,more » we can confirm that the oxide in question is UO, consistent with recent reports based on laser ablation in 16O 2 only.« less

The luminescence of nanoscale Y2Si2O7:Eu3+ materials.

PubMed

Lu, Shaozhe; Zhang, Jishen; Zhang, Jiahua

2010-03-01

The Y2Si2O7:Eu3+ sample was prepared with the sol-gel method. The Y2O3:EU3 was dispersed in SiO2, and the complex Y2Si2O7:Eu3+ particles were synthesized at high annealing temperature. The sample consisted of nearly spherical particles with an average size about 60 nm. The ultraviolet excitation spectra and emission spectra were measured. The sample excited by short ultraviolet light showed strongly red luminescence and fine monochromaticity. The luminescence was strongest from the 5D0 --> 7F2 electric dipole transition located at 611 nm. The excitation spectra of Y2Si2O7:Eu3+ excited with ultraviolet lights showed that the peak of the Eu(3+)-O2- charge transition band located at about 240 nm. During monitoring of different emission peaks of 5D0 --> 7F2, the charge transition band in the excitation spectra shifted, and the relative intensity of emission spectra changed obviously under the excitation of different ultraviolet wavelengths. These results confirmed that the Eu3+ could be excited with ultraviolet radiation of different wavelengths. At low temperature, using Eu3+ ions as fluorescence probes, we monitored the emission peaks of 5D0 --> 7F1 and 5D0 --> 7F2 transitions and measured the excitation spectra of 7F0 --> 5D0, 5D0 --> 7F1, and 5D0 --> 7F2 site-selective excitation spectra. These results indicated that Eu3+ ions are located in different local environments in the Y2Si2O7 host.

Fabrication and luminescent properties of (Y0.99Eu0.01)2O3 transparent nanostructured ceramics

NASA Astrophysics Data System (ADS)

Yavetskiy, R. P.; Dobrotvorskaya, M. V.; Doroshenko, A. G.; Tolmachev, A. V.; Petrusha, I. A.; Turkevich, V. Z.; Tomala, R.; Hreniak, D.; Strek, W.; Baumer, V. N.

2018-04-01

(Y0.99Eu0.01)2O3 nanoceramics have been produced by sintering of stable cubic nanopowders under 8 GPa at temperature in the range of 25-500 °C with the use of Low Temperature High Pressure (LTHP) technique. During consolidation step irreversible phase transition from cubic to monoclinic yttria occurs resulting in two-phase nanoceramics with a grain size in the 10-40 nm range. It has been demonstrated that composite nanoceramics possess a high transmittance in the visible and mid IR ranges due to small light scattering on the nanoscale pores and low birefringence due to extremely small grain size. It has been shown that Eu3+ ions act as a luminescent probe in composite (Y0.99Eu0.01)2O3 nanoceramics since their 4f-4f luminescence strongly depends on the crystallographic environment. The luminescence spectra excited in the charge transfer band (CTB) are presented by superposition of emission from europium ions in cubic and monoclinic yttria. A new wide emission band of (Y0.99Eu0.01)2O3 ceramics in the λ = 500-650 nm wavelengths range (λex. = 307 nm) were attributed to luminescence of Eu3+ ions located in perturbed sites at grain boundaries or interfaces.

Modeling 13.3nm Fe XXIII Flare Emissions Using the GOES-R EXIS Instrument

NASA Astrophysics Data System (ADS)

Rook, H.; Thiemann, E.

2017-12-01

The solar EUV spectrum is dominated by atomic transitions in ionized atoms in the solar atmosphere. As solar flares evolve, plasma temperatures and densities change, influencing abundances of various ions, changing intensities of different EUV wavelengths observed from the sun. Quantifying solar flare spectral irradiance is important for constraining models of Earth's atmosphere, improving communications quality, and controlling satellite navigation. However, high time cadence measurements of flare irradiance across the entire EUV spectrum were not available prior to the launch of SDO. The EVE MEGS-A instrument aboard SDO collected 0.1nm EUV spectrum data from 2010 until 2014, when the instrument failed. No current or future instrument is capable of similar high resolution and time cadence EUV observation. This necessitates a full EUV spectrum model to study EUV phenomena at Earth. It has been recently demonstrated that one hot flare EUV line, such as the 13.3nm Fe XXIII line, can be used to model cooler flare EUV line emissions, filling the role of MEGS-A. Since unblended measurements of Fe XXIII are typically unavailable, a proxy for the Fe XXIII line must be found. In this study, we construct two models of this line, first using the GOES 0.1-0.8nm soft x-ray (SXR) channel as the Fe XXIII proxy, and second using a physics-based model dependent on GOES emission measure and temperature data. We determine that the more sophisticated physics-based model shows better agreement with Fe XXIII measurements, although the simple proxy model also performs well. We also conclude that the high correlation between Fe XXIII emissions and the GOES 0.1-0.8nm band is because both emissions tend to peak near the GOES emission measure peak despite large differences in their contribution functions.

Optical properties of Sm3+ -doped TeO2sbnd WO3sbnd GeO2 glasses for solid state lasers

NASA Astrophysics Data System (ADS)

Subrahmanyam, T.; Gopal, K. Rama; Suvarna, R. Padma; Jamalaiah, B. Chinna; Rao, Ch Srinivasa

2018-03-01

Sm3+ -doped oxyfluoride tellurite-tungsten (TWGSm) glasses were prepared by conventional melt quenching method. The optical properties were investigated through photoluminescence excitation, emission and luminescence decay analysis. The optical band gap energy was determined as ∼3.425 eV for 1.0 mol% of Sm3+ -doped TWGSm glass. Upon 404 nm excitation, the TWGSm glasses emit luminescence through 4G5/2 → 6H5/2 (563 nm), 4G5/2 → 6H7/2 (600 nm), 4G5/2 → 6H9/2 (645 nm) and 4G5/2 → 6H11/2 (705 nm) transitions. The Judd-Ofelt analysis was performed using absorption spectrum and obtained radiative parameters were used to estimate the laser characteristics of present glasses. The concentration of Sm3+ has been optimized as 1.0 mol% for efficient luminescence. The luminescence decay of 4G5/2 emission level was studied by monitoring the emission and excitation wavelengths at 600 and 404 nm, respectively. The experimental lifetime of 4G5/2 level was decrease with increase of Sm3+ concentration. The 1.0 mol% of Sm3+ -doped TWGSm glass could be the best choice for solid state visible lasers to emit orange luminescence.

Exciton Emission from Bare and Alq3/Gold Coated GaN Nanorods

NASA Astrophysics Data System (ADS)

Mohammadi, Fatemesadat; Kuhnert, Gerd; Hommel, Detlef; Schmitzer, Heidrun; Wagner, Hans-Peter

We study the excitonic and impurity related emission in bare and aluminum quinoline (Alq3)/gold coated wurtzite GaN nanorods by temperature-dependent time-integrated (TI) and time-resolved (TR) photoluminescence (PL). The GaN nanorods were grown by molecular beam epitaxy. Alq3 as well as Alq3/gold covered nanorods were synthesized by organic molecular beam deposition. In the near-band edge region a donor-bound-exciton (D0X) emission is observed at 3.473 eV. Another emission band at 3.275 eV reveals LO-phonon replica and is attributed to a donor-acceptor-pair (DAP) luminescence. TR PL traces at 20 K show a nearly biexponential decay for the D0X with lifetimes of approximately 180 and 800 ps for both bare and Alq3 coated nanorods. In GaN nanorods which were coated with an Alq3 film and subsequently with a 10 nm thick gold layer we observe a PL quenching of D0X and DAP band and the lifetimes of the D0X transition shorten. The quenching behaviour is partially attributed to the energy-transfer from free excitons and donor-bound-excitons to plasmon oscillations in the gold layer.

Achieving deep-red-to-near-infrared emissions in Sn-doped Cu-In-S/ZnS quantum dots for red-enhanced white LEDs and near-infrared LEDs.

PubMed

Chen, Jixin; Li, Ye; Wang, Le; Zhou, Tianliang; Xie, Rong-Jun

2018-05-16

Semiconductor quantum dots (QDs) are promising luminescent materials for use in lighting, display and bio-imaging, and the color tuning is a necessity for such applications. In this work, we report tunable colors and deep-red or near infrared (NIR) emissions in Cu-In-S and Cu-In-S/ZnS QDs by incorporating Sn. These QDs (with a size of 5 nm) with varying Sn concentrations and/or Cu/In ratios were synthesized by a non-injection method, and characterized by a variety of analytical techniques (i.e., XRD, TEM, XPS, absorption, photoluminescence, decay time, etc.). The Cu-Sn-In-S and Cu-Sn-In-S/ZnS QDs with Cu/In = 1/2 show the emission maximum in the ranges of 701-894 nm and 628-785 nm, respectively. The red-shift in emission is ascribed to the decrease of the band gap with the Sn doping. The highest quantum yield of 75% is achieved in Cu-Sn-In-S/ZnS with 0.1 mmol Sn and Cu/In = 1/2. Both the white and NIR LEDs were fabricated by using Cu-Sn-In-S/ZnS QDs and a 365 nm LED chip. The white LED exhibits superhigh color rendering indices of Ra = 97.2 and R9 = 91 and a warm color temperature of 2700 K. And the NIR LED shows an interesting broadband near-infrared emission centered at 741 nm, allowing for applications in optical communication, sensing and medical devices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Peican; Zhou, Liya, E-mail: zhouliyatf@163.com; Mo, Fuwang

Graphical abstract: - Highlights: • Novel Eu{sup 2+} doped Sr{sub 6}Ca{sub 4}(PO{sub 4}){sub 6}F{sub 2} phosphors was synthesized for the first time. • The Sr{sub 6}Ca{sub 4}(PO{sub 4}){sub 6}F{sub 2}:Eu{sup 2+} phosphors produced blue light when irradiated at 368 nm. • The emission band of the sample could be decomposed into two Gaussian profiles. - Abstract: For the first time, a series of novel blue light-emitting phosphors Sr{sub 6}Ca{sub 4}(PO{sub 4}){sub 6}F{sub 2}:Eu{sup 2+} were synthesized by a traditional solid-state reaction. The phosphors exhibited a broad and intense excitation band that could be pumped by near ultraviolet to exhibit amore » broad photoluminescence band ranging from 400 nm to 530 nm peaking at 452 nm. Quenching concentration was 0.05 mol. Furthermore, the mechanism of concentration quenching involving SCPF:Eu{sup 2+} was demonstrated to be a dipole–dipole interaction with critical distance of 27.95 Å. Decay time curves were also measured to validate energy transfer, and quantum efficiency is investigated. The chromaticity diagram of Commission Internationale de l’Eclairage indicated that SCPF:Eu{sup 2+} may be used as a blue-emitting component for white light-emitting diode applications.« less

Photoluminescence properties of anodic aluminum oxide formed in a mixture of ammonium fluoride and oxalic acid

NASA Astrophysics Data System (ADS)

Li, Shou-Yi; Wang, Jian; Li, Yan

2017-06-01

Highly ordered anodic aluminum oxide (AAO) membranes are fabricated electrochemically in an electrolyte mixture with various concentrations of C2H2O4 or NH4F. Photoluminescence (PL) properties of AAO membranes have been investigated before and after annealing in the range from 300°C to 650°C. X-ray diffraction reveals the amorphous nature of AAO membranes. Energy dispersive spectroscopy indicates the presence of fluorine species incorporated in oxide membranes during the anodizing. PL measurements show a strong PL band in the wavelength range of 350 to 550 nm. With the increase of the concentration of the NH4F or C2H2O4 in the electrolyte mixture, the peak positions of the PL bands have a blueshift or redshift and the intensities have a maximum value. As indicated by the PL excitation spectra, there are two excitation peaks of 285 and 330 nm, which can account for the PL emission band. We have proposed that the PL originates from optical transitions in two kinds of centers that are related to oxygen vacancies, F+ (285 nm) and F (330 nm). This work is not only beneficial to further understanding of the light-emitting property of AAO membranes but also enlarges the application scope.

Compositional Dependence of Optical and Structural Properties of Nanogranular Mixed ZrO2/ZnO/SnO2 Thin Film

NASA Astrophysics Data System (ADS)

Salari, S.; Ghodsi, F. E.

2018-06-01

A study on the optical properties and photoluminescence (PL) spectra of ternary oxide nanogranular thin films comprising Zr, Zn, and Sn revealed that the change in component ratio could direct the roadmap to improve characteristics of the films. Grazing angle X-ray diffraction analysis showed that incorporation of Sn atoms into the tetragonal structure of Zn/Zr thin film resulted in an amorphous structure. The band gap of film was tunable by precisely controlling the concentration of components. The widening of band gap could correlate to the quantum confinement effect. PL spectra of the composite thin films under excitation at 365 nm showed a sharp red emission with relatively Gaussian line shape, which was intensified in the optimum percentage ratio of 50/30/20. This nearly red emission is attributed to the radiative emission of electrons captured at low-energy traps located near the valence band. An optimum red emission is strongly desirable for use in white LEDs. The comparative study on FTIR spectra of unary, binary, and ternary thin films confirmed successful composition of three different metal oxides in ternary thin films. Detailed investigation on FTIR spectra of ternary compounds revealed that the quenching in PL emission at higher percentage of Sn was originally due to the hydroxyl group.

Efficient color-tunable multiexcitonic dual wavelength emission from Type II semiconductor tetrapods.

PubMed

Wu, Wen-Ya; Li, Mingjie; Lian, Jie; Wu, Xiangyang; Yeow, Edwin K L; Jhon, Mark H; Chan, Yinthai

2014-09-23

We synthesized colloidal InP/ZnS seeded CdS tetrapods by harnessing the structural stability of the InP/ZnS seed nanocrystals at the high reaction temperatures needed to grow the CdS arms. Because of an unexpected Type II band alignment at the interface of the InP/ZnS core and CdS arms that enhanced the occurrence of radiative excitonic recombination in CdS, these tetrapods were found to be capable of exhibiting highly efficient multiexcitonic dual wavelength emission of equal intensity at spectrally distinct wavelengths of ∼485 and ∼675 nm. Additionally, the Type II InP/ZnS seeded CdS tetrapods displayed a wider range of pump-dependent emission color-tunability (from red to white to blue) within the context of a CIE 1931 chromaticity diagram and possessed higher photostability due to suppressed multiexcitonic Auger recombination when compared to conventional Type I CdSe seeded CdS tetrapods. By employing time-resolved spectroscopy measurements, we were able to attribute the wide emission color-tunability to the large valence band offset between InP and CdS. This work highlights the importance of band alignment in the synthetic design of semiconductor nanoheterostructures, which can exhibit color-tunable multiwavelength emission with high efficiency and photostability.

Energy transfer from Pr3+ to Gd3+ ions in BaB8O13 phosphor for phototherapy lamps

NASA Astrophysics Data System (ADS)

Tamboli, Sumedha; Nair, Govind B.; Dhoble, S. J.; Burghate, D. K.

2018-04-01

A series of BaB8O13 phosphors doped with different concentrations of Gd3+ ions and co-doped with Pr3+ ions were synthesized by solid state synthesis method. X-ray powder diffraction (XRD) analysis confirmed the formation of the compound in a crystalline and homogeneous form. Scanning Electron Microscopy (SEM) was performed to study the surface morphology of the compound and Fourier Transform Infrared (FT-IR) spectroscopy measurements determined the nature of bonding between elements of the compounds. The photoluminescence (PL) excitation spectra of BaB8O13:Gd3+ phosphor showed excitation peaks at 246 nm, 252 nm and 274 nm. The prominent emission peak was observed at 313 nm which is in narrow band ultraviolet B (NB-UVB) range. Energy transfer was achieved by co-doping Pr3+ ions with Gd3+ ions. PL decay time was also measured for BaB8O13: Gd3+, Pr3+ phosphor. Emission at 313 nm can be used for the treatment of skin diseases.

Bluish-green color emitting Ba2Si3O8:Eu2+ ceramic phosphors for white light-emitting diodes.

PubMed

Xiao, F; Xue, Y N; Zhang, Q Y

2009-10-15

This paper reports on the structural and optical properties of Eu(2+) activated Ba(2)Si(3)O(8) ceramic phosphors synthesized by a sol-gel method. The ceramic phosphors have been characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and fluorescence measurements. The structural characterization results suggest that the as-prepared phosphors are of single phase monoclinic Ba(2)Si(3)O(8) with rod-like morphology. A broad excitation band ranging from 300 to 410 nm matches well with the ultraviolet (UV) radiation of light-emitting diodes (LEDs). Upon 380 nm UV light excitation, these phosphors emit bluish-green emission centered at 500 nm with color coordination (x=0.25, y=0.40). All the obtained results indicate that the Ba(2)Si(3)O(8):Eu(2+) ceramic phosphors are promising bluish-green candidates for the phosphor-converted white LEDs.

The photochemical trapping rate from red spectral states in PSI-LHCI is determined by thermal activation of energy transfer to bulk chlorophylls.

PubMed

Jennings, Robert C; Zucchelli, Giuseppe; Croce, Roberta; Garlaschi, Flavio M

2003-03-06

The average fluorescence decay lifetimes, due to reaction centre photochemical trapping, were calculated for wavelengths in the 690- to 770-nm interval from the published fluorescence decay-associated emission spectra for Photosystem I (PSI)-light-harvesting complex of Photosystem I (LHCI) [Biochemistry 39 (2000) 6341] at 280 and 170 K. For 280 K, the overall trapping time at 690 nm is 81 ps and increases with wavelength to reach 103 ps at 770 nm. For 170 K, the 690-nm value is 115 ps, increasing to 458 ps at 770 nm. This underlines the presence of kinetically limiting processes in the PSI antenna (diffusion limited). The explanation of these nonconstant values for the overall trapping time band is sought in terms of thermally activated transfer from the red absorbing states to the "bulk" acceptor chlorophyll (chl) states in the framework of the Arrhenius-Eyring theory. It is shown that the wavelength-dependent "activation energies" come out in the range between 1.35 and 2.7 kcal mol(-1), increasing with the emission wavelength within the interval 710-770 nm. These values are in good agreement with the Arrhenius activation energy determined for the steady-state fluorescence yield over the range 130-280 K for PSI-LHCI. We conclude that the variable trapping time in PSI-LHCI can be accounted for entirely by thermally activated transfer from the low-energy chl states to the bulk acceptor states and therefore that the position of the various red states in the PSI antenna seems not to be of significant importance. The analysis shows that the bulk antenna acceptor states are on the low-energy side of the bulk antenna absorption band.

Synthesis and luminescent properties of Sm3+ doped zinc aluminate phosphor

NASA Astrophysics Data System (ADS)

Mahajan, Rubby; Kumar, Sandeep; Prakash, Ram; Kumar, Vinay

2018-05-01

Zinc Aluminate (ZnAl2O4) is a well-known wide band gap oxide that belongs to a class of mixed-metal oxides knows as spinels (AB2O4) where A and B are divalent and trivalent cations. Herein, the structural and photoluminescence properties of Sm3+ ion doped with ZnAl2O4 phosphors are reported. The nanophosphors were synthesized via solution combustion synthesis route at temperature 570 °C. The synthesized samples were characterized by X-ray powder diffraction (XRD), Photoluminescence (PL) spectroscopy, and Ultraviolet-visible spectroscopy. The XRD pattern confirms the cubic phase of phosphor. The calculated lattice parameter were found as a = b = c = 8.0517Å and V = 521.85Å3. The crystallite size of the phosphor was calculated using the Debye-Scherrer formula and found to be ˜19 nm. The emission spectrum at excitation wavelength of 401 nm gave the emission peaks at 563 nm, 601 nm, 648 nm, 697 nm corresponding to the transitions 4G5/2→ 6H5/2, 4G5/2→6H7/2, 4G5/2→6H9/2, 4G5/2 → 6H11/2 of Sm3+ ions, respectively. The diffuse reflectance spectrum was used to calculate the band gap of material and found to be 5.12 eV. The CIE coordinates were found to be (x = 0.56, y = 0.40) that falls in the orange red region of the color gamut. The present phosphor may have potential applications as phosphor for near UV WLED for solid state lighting.

Association of phycoerythrin and phycocyanin: in vitro formation of a functional energy transferring phycobilisome complex of Porphyridium sordidum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lipschultz, C.A.; Gantt, E.

1981-01-01

Functional in vitro association and dissociation of a phycobiliprotein complex, isolated from phycobilisomes of the red alga Porphyridium sordidum, were studied. The complex contained large bangiophyceaen phycoerythrin and cyanophytan phycocyanin in an equimolar ratio and had absorption maxima at 625, 567, and 550 nm and a shoulder at 495 nm. Emission at 655 nm (with excitation at 545 nm) from phycocyanin indicated functional coupling. The complex was stable over a wide buffer concentration range, and, notably, it was maximally stable in low phosphate, <0.01 M, unlike the phycobilisomes, which dissociate at this concentration. Its molecular weight was estimated to bemore » ca. 510 000, and by electron microscopy it was seen to consist of two units of similar size. The complex in 0.1 M phosphate was separated on a sucrose gradient into a homogeneous phycoerythrin band and a spectrally heterogeneous phycocyanin band. In vitro association of phycoerythrin and phycocyanin resulted in a complex with the same absorbance, emission, sedimentation, and molar pigment ratio as those of the native complex. The spectrally heterogeneous phycocyanin fractions from the dissociation gradient varied in the degree of association with phycoerythrin. Phycocyanin fractions absorbing from 622 to 633 nm exhibited high associability (>70%), whereas those with maxima at 617-620 nm had low associability (<30%). The presence of a 30 000 molecular weight polypeptide accompanied high associability, where it was ca. 2-fold more prominent. It is suggested that this polypeptide is involved in complex formation and could serve either in the stabilization of the conformational state of cyanophytan phycocyanin or as a direct linker between phycobiliproteins.« less

A novel approach to dual excitation ratiometric optical mapping of cardiac action potentials with di-4-ANEPPS using pulsed LED excitation.

PubMed

Bachtel, Andrew D; Gray, Richard A; Stohlman, Jayna M; Bourgeois, Elliot B; Pollard, Andrew E; Rogers, Jack M

2011-07-01

We developed a new method for ratiometric optical mapping of transmembrane potential (V(m)) in cardiac preparations stained with di-4-ANEPPS. V(m)-dependent shifts of excitation and emission spectra establish two excitation bands (<481 and >481 nm) that produce fluorescence changes of opposite polarity within a single emission band (575-620 nm). The ratio of these positive and negative fluorescence signals (excitation ratiometry) increases V(m) sensitivity and removes artifacts common to both signals. We pulsed blue (450 ± 10 nm) and cyan (505 ± 15 nm) light emitting diodes (LEDs) at 375 Hz in alternating phase synchronized to a camera (750 frames-per-second). Fluorescence was bandpass filtered (585 ± 20 nm). This produced signals with upright (blue) and inverted (cyan) action potentials (APs) interleaved in sequential frames. In four whole swine hearts with motion chemically arrested, fractional fluorescence for blue, cyan, and ratio signals was 1.2 ± 0.3%, 1.2 ± 0.3%, and 2.4 ± 0.6%, respectively. Signal-to-noise ratios were 4.3 ± 1.4, 4.0 ± 1.2, and 5.8 ± 1.9, respectively. After washing out the electromechanical uncoupling agent, we characterized motion artifact by cross-correlating blue, cyan, and ratio signals with a signal with normal AP morphology. Ratiometry improved cross-correlation coefficients from 0.50 ± 0.48 to 0.81 ± 0.25, but did not cancel all motion artifacts. These findings demonstrate the feasibility of pulsed LED excitation ratiometry in myocardium. © 2011 IEEE

A Novel Approach to Dual Excitation Ratiometric Optical Mapping of Cardiac Action Potentials with Di-4-ANEPPS using Pulsed LED Excitation

PubMed Central

Bachtel, Andrew D.; Gray, Richard A.; Stohlman, Jayna M.; Bourgeois, Elliot B.; Pollard, Andrew E.

2011-01-01

We developed a new method for ratiometric optical mapping of transmembrane potential (Vm) in cardiac preparations stained with di-4-ANEPPS. Vm-dependent shifts of excitation and emission spectra establish two excitation bands (<481 and >481 nm) that produce fluorescence changes of opposite polarity within a single emission band (575–620 nm). The ratio of these positive and negative fluorescence signals (excitation ratiometry) increases Vm sensitivity and removes artifacts common to both signals. We pulsed blue (450±10 nm) and cyan (505±15 nm) light emitting diodes (LEDs) at 375 Hz in alternating phase synchronized to a camera (750 frames-per-second). Fluorescence was bandpass filtered (585±20 nm). This produced signals with upright (blue) and inverted (cyan) action potentials (APs) interleaved in sequential frames. In 4 whole swine hearts with motion chemically arrested, fractional fluorescence for blue, cyan, and ratio signals was 1.2±0.3%, 1.2±0.3%, and 2.4±0.6%, respectively. Signal-to-noise ratios were 4.3±1.4, 4.0±1.2, and 5.8±1.9, respectively. After washing out the electromechanical uncoupling agent, we characterized motion artifact by cross-correlating blue, cyan, and ratio signals with a signal with normal AP morphology. Ratiometry improved cross-correlation coefficients from 0.50±0.48 to 0.81±0.25, but did not cancel all motion artifacts. These findings demonstrate the feasibility of pulsed LED excitation ratiometry in myocardium. PMID:21536528

Global-scale Observations of the Limb and Disk (GOLD): Science Implementation

NASA Astrophysics Data System (ADS)

Solomon, S. C.; McClintock, W. E.; Eastes, R.; Anderson, D. N.; Andersson, L.; Burns, A. G.; Codrescu, M.; Daniell, R. E.; England, S.; Eparvier, F. G.; Evans, J. S.; Krywonos, A.; Lumpe, J. D.; Richmond, A. D.; Rusch, D. W.; Siegmund, O.; Woods, T. N.

2017-12-01

The Global-scale Observations of the Limb and Disk (GOLD) is a NASA mission of opportunity that will image the Earth's thermosphere and ionosphere from geostationary orbit. GOLD will investigate how the thermosphere-ionosphere (T-I) system responds to geomagnetic storms, solar radiation, and upward propagating tides and how the structure of the equatorial ionosphere influences the formation and evolution of equatorial plasma density irregularities. GOLD consists of a pair of identical imaging spectrographs that will measure airglow emissions at far-ultraviolet wavelengths from 132 to 162 nm. On the disk, temperature and composition will be determined during the day using emissions from molecular nitrogen Lyman-Birge-Hopfield (LBH) band and atomic oxygen 135.6 nm, and electron density will be derived at night from 135.6 nm emission. On the limb, exospheric temperature will be derived from LBH emission profiles, and molecular oxygen density will be measured using stellar occultations. This presentation describes the GOLD mission science implementation including the as-built instrument performance and the planned observing scenario. It also describes the results of simulations performed by the GOLD team to validate that the measured instrument performance and observing plan will return adequate data to address the science objectives of the mission.

NaK 22Σ+ → 11Σ+ band optically pumped laser near 1.02 μm

NASA Astrophysics Data System (ADS)

Clark, B. K.; Luh, W. T.; Huennekens, J.

1989-08-01

Optically pumped laser emission has been observed on the NaK 2( A)1Σ+ → 1( X)1Σ+ electronic state transition. The emission occurs between 1.015 and 1.035 μm when a sodium-potassium heat-pipe oven is pumped with 695 745 nm pulsed dye laser radiation. The laser emission occurs on many ro-vibrational transitions without the use of cavity mirrors. However, the addition of a simple cavity increases both the number of observed lasing transitions and the amplitude of the emission on each line. We report our results for the dependence of the emission intensity on pump laser power, oven temperature, and buffer gas pressure.

Plasmonic distributed feedback lasers at telecommunications wavelengths.

PubMed

Marell, Milan J H; Smalbrugge, Barry; Geluk, Erik Jan; van Veldhoven, Peter J; Barcones, Beatrix; Koopmans, Bert; Nötzel, Richard; Smit, Meint K; Hill, Martin T

2011-08-01

We investigate electrically pumped, distributed feedback (DFB) lasers, based on gap-plasmon mode metallic waveguides. The waveguides have nano-scale widths below the diffraction limit and incorporate vertical groove Bragg gratings. These metallic Bragg gratings provide a broad bandwidth stop band (~500 nm) with grating coupling coefficients of over 5000/cm. A strong suppression of spontaneous emission occurs in these Bragg grating cavities, over the stop band frequencies. This strong suppression manifests itself in our experimental results as a near absence of spontaneous emission and significantly reduced lasing thresholds when compared to similar length Fabry-Pérot waveguide cavities. Furthermore, the reduced threshold pumping requirements permits us to show strong line narrowing and super linear light current curves for these plasmon mode devices even at room temperature.

ZnO-nanorods: A possible white LED phosphor

NASA Astrophysics Data System (ADS)

Sarangi, Sachindra Nath; T., Arun; Ray, Dinseh K.; Sahoo, Pratap Kumar; Nozaki, Shinji; Sugiyama, Noriyuki; Uchida, Kazuo

2017-05-01

The white light-emitting diodes (LEDs) have drawn much attention to replace conventional lighting sources because of low energy consumption, high light efficiency and long lifetime. Although the most common approach to produce white light is to combine a blue LED chip and a yellow phosphor, such a white LED cannot be used for a general lighting application, which requires a broad luminescence spectrum in the visible wavelength range. We have successfully chemically synthesized the ZnO nanorods showing intense broad luminescence in the visible wavelength range and made a white LED using the ZnO nanorods as phosphor excited with a blue LED. Their lengths and diameters were 2 - 10 μm and 200 - 800 nm, respectively. The wurtzite structure was confirmed by the x-ray diffraction measurement. The PL spectrum obtained by exciting the ZnO nanorods with the He-Cd laser has two peaks, one associated with the near band-edge recombination and the other with recombination via defects. The peak intensity of the near band-edge luminescence at 388 nm is much weaker than that of the defect-related luminescence. The latter luminescence peak ranges from 450 to 850 nm and broad enough to be used as a phosphor for a white LED. A white LED has been fabricated using a blue LED with 450 nm emission and ZnO nanorod powders. The LED performances show a white light emission and the electroluminescence measurement shows a stiff increase in white light intensity with increasing blue LED current. The Commission International de1'Eclairage (CIE) chromaticity colour coordinates of 450 nm LED pumped white emission shows a coordinate of (0.31, 0.32) for white LED at 350 mA. These results indicate that ZnO nanorods provides an alternate and effective approach to achieve high-performance white LEDs and also other optoelectronic devices.

Structural and optical properties of glancing angle deposited TiO2 nanowires array.

PubMed

Chinnamuthu, P; Mondal, A; Singh, N K; Dhar, J C; Das, S K; Chattopadhyay, K K

2012-08-01

TiO2 nanowires (NWs) have been synthesized by glancing angle deposition technique using e-beam evaporator. The average length 490 nm and diameter 80 nm of NWs were examined by field emission-scanning electron microscopy. Transmission electron microscopy emphasized that the NWs were widely dispersed at the top. X-ray diffraction has been carried out on the TiO2 thin film (TF) and NW array. A small blue shift of 0.03 eV was observed in Photoluminescence (PL) main band emission for TiO2 NW as compared to TiO2 TF. The high temperature annealing at 980 degrees C partially removed the oxygen vacancy from the sample, which was investigated by PL and optical absorption measurements.

Terahertz excitation spectra of InP single crystals

NASA Astrophysics Data System (ADS)

Norkus, R.; Arlauskas, A.; Krotkus, A.

2018-07-01

Investigation of terahertz (THz) pulse generation from semi-insulating and n-type InP crystals surfaces is presented in this letter. In order to determine energy separation between the main and subsidiary conduction band valleys, THz pulse amplitude dependences on the photoexcitation wavelength (in a range of 410–950 nm) were measured. These dependences had a clear maximum at ∼540 nm, from which the inter-valley energy separation in the conduction band of InP as equal to 0.75 eV was determined. Moreover, THz generation mechanisms at laser excited surfaces of InP were investigated by additionally analyzing the azimuthal angle dependences of the emitted THz signal amplitude and power. It has been shown that the main physical mechanism of the surface THz emission in this material is the spatial separation of photoexcited electrons and holes, which can also lead to a symmetry similar to the second order optical nonlinearity. Photocurrent surge in the surface electric field can also contribute to the THz emission from a semi-insulating crystal illuminated by optical pulses with the wavelengths close to the absorption edge.

Controlled synthesis of AlN/GaN multiple quantum well nanowire structures and their optical properties.

PubMed

Qian, Fang; Brewster, Megan; Lim, Sung K; Ling, Yichuan; Greene, Christopher; Laboutin, Oleg; Johnson, Jerry W; Gradečak, Silvija; Cao, Yu; Li, Yat

2012-06-13

We report the controlled synthesis of AlN/GaN multi-quantum well (MQW) radial nanowire heterostructures by metal-organic chemical vapor deposition. The structure consists of a single-crystal GaN nanowire core and an epitaxially grown (AlN/GaN)(m) (m = 3, 13) MQW shell. Optical excitation of individual MQW nanowires yielded strong, blue-shifted photoluminescence in the range 340-360 nm, with respect to the GaN near band-edge emission at 368.8 nm. Cathodoluminescence analysis on the cross-sectional MQW nanowire samples showed that the blue-shifted ultraviolet luminescence originated from the GaN quantum wells, while the defect-associated yellow luminescence was emitted from the GaN core. Computational simulation provided a quantitative analysis of the mini-band energies in the AlN/GaN superlattices and suggested the observed blue-shifted emission corresponds to the interband transitions between the second subbands of GaN, as a result of quantum confinement and strain effect in these AlN/GaN MQW nanowire structures.

Biogenic synthesis of SnO2 nanoparticles: Evaluation of antibacterial and antioxidant activities

NASA Astrophysics Data System (ADS)

Vidhu, V. K.; Philip, Daizy

2015-01-01

Nanostructured semiconductors have been of special interest to scientific community due to their peculiar properties. The quantum size effect results in spectacular variation in the optical and vibrational characteristics of nanostructured materials compared to their bulk counterparts. The present work emphasizes an unexploited, cost effective, and environmentally benign method of synthesizing bioactive tin oxide nanoparticles of size from 2.1 nm to 4.1 nm using Saraca indica flower. The XRD pattern and HRTEM images of the samples revealed an increase in particle size with annealing temperature. Fine tuning band gap could be attained as evidenced by the shift of absorption band edge and photoluminescence emission. It is found that oxygen vacancies play an important role on PL emission. The synthesized nanoparticles exhibit antibacterial activity against gram negative bacteria Escherichia coli. The antioxidant activity is evaluated by scavenging free radicals of 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH). The efficiency of biogenic SnO2 nanoparticles as a promising antibacterial agent as well as an antioxidant for pharmaceutical applications is suggested.

Multiple emissions of benzil at room temperature and 77 K and their assignments from ab initio quantum chemical calculations

NASA Astrophysics Data System (ADS)

Bhattacharya, Bhaswati; Jana, Barnali; Bose, Debosreeta; Chattopadhyay, Nitin

2011-01-01

Multiple emissions have been observed from benzil under different conditions in solutions at room temperature as well as in low temperature glass matrices at 77 K. Low temperature emission has been monitored in rigid matrices frozen under different conditions of illumination. Steady state and time-resolved results together with the ab initio quantum chemical calculations provide, for the first time, the assignments of the different fluorescence bands to the different geometries and/or electronic states of the fluorophore molecule. It is revealed that the skew form of benzil emits from the first (S1) as well as the second excited singlet (S2) states depending on the excitation wavelength, while the relaxed transplanar conformer fluoresces only from the S1 state. The yet unexplored emission band peaking at around 360 nm has been assigned to originate from the S2 state. Ab initio calculations using the density functional theory at B3LYP/6-31G** level corroborate well with the experimental observations.

Multiple emissions of benzil at room temperature and 77 K and their assignments from ab initio quantum chemical calculations.

PubMed

Bhattacharya, Bhaswati; Jana, Barnali; Bose, Debosreeta; Chattopadhyay, Nitin

2011-01-28

Multiple emissions have been observed from benzil under different conditions in solutions at room temperature as well as in low temperature glass matrices at 77 K. Low temperature emission has been monitored in rigid matrices frozen under different conditions of illumination. Steady state and time-resolved results together with the ab initio quantum chemical calculations provide, for the first time, the assignments of the different fluorescence bands to the different geometries and∕or electronic states of the fluorophore molecule. It is revealed that the skew form of benzil emits from the first (S(1)) as well as the second excited singlet (S(2)) states depending on the excitation wavelength, while the relaxed transplanar conformer fluoresces only from the S(1) state. The yet unexplored emission band peaking at around 360 nm has been assigned to originate from the S(2) state. Ab initio calculations using the density functional theory at B3LYP∕6-31G∗∗ level corroborate well with the experimental observations.

Tunable long persistent luminescence in the second near-infrared window via crystal field control.

PubMed

Nie, Jianmin; Li, Yang; Liu, Shanshan; Chen, Qiuqun; Xu, Qi; Qiu, Jianrong

2017-09-29

Construction of an active composite as a biomarker with deeper tissue penetration and higher signal-to-noise ratio (SNR) is of great importance for the application in bioimaging. Here, we report a strategy for tuning the emission bandwidth and intensity via crystal field control in long persistent phosphors (LPPs). Ni 2+ -doped Zn 1+y Sn y Ga 2-x-2y O 4 phosphors, with a tunable emission band peaking from 1270 to 1430 nm in the second near-infrared (NIR) window, have been successfully prepared. Such featured materials have the advantages of low absorption and scattering as well as more efficient tissue penetration. The emission spectra can be controlled by tailoring the local crystal field around the activator precisely via substitution of Zn and Sn for Ga. Moreover, with high resolution and weak light disturbance, these developed multi-band afterglow phosphors exhibit great application potential in advanced optical imaging.

YAG:Er3+, CaF2:Er3+, and Er2O3 Emission Spectra Under Laser and Laser Thermal Excitation

NASA Astrophysics Data System (ADS)

Marchenko, V. M.

2018-05-01

Experimental luminescence and selective-emission (SE) spectra of YAG:Er3+ (10 at.%) and CaF2:Er3+ (1 at.%) single crystals and Er2O3 polycrystal under laser and laser thermal excitation of the Er3+-ion multiplets are compared. Luminescence spectra under resonant excitation are determined by multiplet population relaxation with the corresponding radiative and nonradiative probabilities. The form of the SE spectra is determined by the thermal population of the multiplets and the probabilities of only radiative transitions. The SE band at 800 nm (4I9/2 → 4I15/2) is an indicator of high-temperature thermal emission of Er3+ ions. The absence of this band in luminescence spectra is explained by the short lifetime of the τ(4I9/2) level of 53 ns at T = 300 K.

Microstructure and optical properties of nanocrystalline Cu2O thin films prepared by electrodeposition.

PubMed

Jiang, Xishun; Zhang, Miao; Shi, Shiwei; He, Gang; Song, Xueping; Sun, Zhaoqi

2014-01-01

Cuprous oxide (Cu2O) thin films were prepared by using electrodeposition technique at different applied potentials (-0.1, -0.3, -0.5, -0.7, and -0.9 V) and were annealed in vacuum at a temperature of 100°C for 1 h. Microstructure and optical properties of these films have been investigated by X-ray diffractometer (XRD), field-emission scanning electron microscope (SEM), UV-visible (vis) spectrophotometer, and fluorescence spectrophotometer. The morphology of these films varies obviously at different applied potentials. Analyses from these characterizations have confirmed that these films are composed of regular, well-faceted, polyhedral crystallites. UV-vis absorption spectra measurements have shown apparent shift in optical band gap from 1.69 to 2.03 eV as the applied potential becomes more cathodic. The emission of FL spectra at 603 nm may be assigned as the near band-edge emission.

Time-resolved photoluminescence characterization of oxygen-related defect centers in AlN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Genji, Kumihiro; Uchino, Takashi, E-mail: uchino@kobe-u.ac.jp

2016-07-11

Time-resolved photoluminescence (PL) spectroscopy has been employed to investigate the emission characteristics of oxygen-related defects in AlN in the temperature region from 77 to 500 K. Two PL components with different decay constants are observed in the near-ultraviolet to visible regions. One is the PL component with decay time of <10 ns and its peak position shifts to longer wavelengths from ∼350 to ∼500 nm with increasing temperature up to 500 K. This PL component is attributed to the radiative relaxation of photoexcited electrons from the band-edge states to the ground state of the oxygen-related emission centers. In the time region from tens tomore » hundreds of nanoseconds, the second PL component emerges in the wavelength region from 300 to 400 nm. The spectral shape and the decay profiles are hardly dependent on temperature. This temperature-independent PL component most likely results from the transfer of photoexcited electrons from the band-edge states to the localized excited state of the oxygen-related emission centers. These results provide a detailed insight into the radiative relaxation processes of the oxygen-related defect centers in AlN immediately after the photoexcitation process.« less

Hydrothermally Grown In-doped ZnO Nanorods on p-GaN Films for Color-tunable Heterojunction Light-emitting-diodes

PubMed Central

Park, Geun Chul; Hwang, Soo Min; Lee, Seung Muk; Choi, Jun Hyuk; Song, Keun Man; Kim, Hyun You; Kim, Hyun-Suk; Eum, Sung-Jin; Jung, Seung-Boo; Lim, Jun Hyung; Joo, Jinho

2015-01-01

The incorporation of doping elements in ZnO nanostructures plays an important role in adjusting the optical and electrical properties in optoelectronic devices. In the present study, we fabricated 1-D ZnO nanorods (NRs) doped with different In contents (0% ~ 5%) on p-GaN films using a facile hydrothermal method, and investigated the effect of the In doping on the morphology and electronic structure of the NRs and the electrical and optical performances of the n-ZnO NRs/p-GaN heterojunction light emitting diodes (LEDs). As the In content increased, the size (diameter and length) of the NRs increased, and the electrical performance of the LEDs improved. From the electroluminescence (EL) spectra, it was found that the broad green-yellow-orange emission band significantly increased with increasing In content due to the increased defect states (oxygen vacancies) in the ZnO NRs, and consequently, the superposition of the emission bands centered at 415 nm and 570 nm led to the generation of white-light. These results suggest that In doping is an effective way to tailor the morphology and the optical, electronic, and electrical properties of ZnO NRs, as well as the EL emission property of heterojunction LEDs. PMID:25988846

Characterisation and luminescence studies of Tm and Na doped magnesium borate phosphors.

PubMed

Ekdal, E; Garcia Guinea, J; Karabulut, Y; Canimoglu, A; Harmansah, C; Jorge, A; Karali, T; Can, N

2015-09-01

In this study, structural and luminescence properties of magnesium borate of the form MgB4O7 doped with Tm and Na were investigated by X-ray diffraction (XRD), Raman spectroscopy and cathodoluminescence (CL). The morphologies of the synthetised compounds exhibit clustered granules and road-like materials. As doping trivalent ions into a host with divalent cations requires charge compensation, this effect is discussed. The CL spectra of undoped MgB4O7 shows a broad band emission centred around 350 nm which is postulated to be produced by self-trapped excitons and some other defects. From the CL emission spectrum, main emission bands centred at 360, 455, 475 nm due to the respective transitions of (1)D2→(3)H6,(1)D2→(3)F4 and (1)G4→(3)H6 suggest the presence of Tm(3+) ion in MgB4O7 lattice site. CL mechanism was proposed to explain the observed phenomena which are valuable in possibility of the developing new luminescent materials for different applications. In addition, the experimental Raman spectrum of doped and undoped MgB4O7 were reported and discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

Hydrothermally Grown In-doped ZnO Nanorods on p-GaN Films for Color-tunable Heterojunction Light-emitting-diodes.

PubMed

Park, Geun Chul; Hwang, Soo Min; Lee, Seung Muk; Choi, Jun Hyuk; Song, Keun Man; Kim, Hyun You; Kim, Hyun-Suk; Eum, Sung-Jin; Jung, Seung-Boo; Lim, Jun Hyung; Joo, Jinho

2015-05-19

The incorporation of doping elements in ZnO nanostructures plays an important role in adjusting the optical and electrical properties in optoelectronic devices. In the present study, we fabricated 1-D ZnO nanorods (NRs) doped with different In contents (0% ~ 5%) on p-GaN films using a facile hydrothermal method, and investigated the effect of the In doping on the morphology and electronic structure of the NRs and the electrical and optical performances of the n-ZnO NRs/p-GaN heterojunction light emitting diodes (LEDs). As the In content increased, the size (diameter and length) of the NRs increased, and the electrical performance of the LEDs improved. From the electroluminescence (EL) spectra, it was found that the broad green-yellow-orange emission band significantly increased with increasing In content due to the increased defect states (oxygen vacancies) in the ZnO NRs, and consequently, the superposition of the emission bands centered at 415 nm and 570 nm led to the generation of white-light. These results suggest that In doping is an effective way to tailor the morphology and the optical, electronic, and electrical properties of ZnO NRs, as well as the EL emission property of heterojunction LEDs.

A spectrally tunable all-graphene-based flexible field-effect light-emitting device

PubMed Central

Wang, Xiaomu; Tian, He; Mohammad, Mohammad Ali; Li, Cheng; Wu, Can; Yang, Yi; Ren, Tian-Ling

2015-01-01

The continuous tuning of the emission spectrum of a single light-emitting diode (LED) by an external electrical bias is of great technological significance as a crucial property in high-quality displays, yet this capability has not been demonstrated in existing LEDs. Graphene, a tunable optical platform, is a promising medium to achieve this goal. Here we demonstrate a bright spectrally tunable electroluminescence from blue (∼450 nm) to red (∼750 nm) at the graphene oxide/reduced-graphene oxide interface. We explain the electroluminescence results from the recombination of Poole–Frenkel emission ionized electrons at the localized energy levels arising from semi-reduced graphene oxide, and holes from the top of the π band. Tuning of the emission wavelength is achieved by gate modulation of the participating localized energy levels. Our demonstration of current-driven tunable LEDs not only represents a method for emission wavelength tuning but also may find applications in high-quality displays. PMID:26178323

Infrared Organic Light-Emitting Diodes with Carbon Nanotube Emitters.

PubMed

Graf, Arko; Murawski, Caroline; Zakharko, Yuriy; Zaumseil, Jana; Gather, Malte C

2018-03-01

While organic light-emitting diodes (OLEDs) covering all colors of the visible spectrum are widespread, suitable organic emitter materials in the near-infrared (nIR) beyond 800 nm are still lacking. Here, the first OLED based on single-walled carbon nanotubes (SWCNTs) as the emitter is demonstrated. By using a multilayer stacked architecture with matching charge blocking and charge-transport layers, narrow-band electroluminescence at wavelengths between 1000 and 1200 nm is achieved, with spectral features characteristic of excitonic and trionic emission of the employed (6,5) SWCNTs. Here, the OLED performance is investigated in detail and it is found that local conduction hot-spots lead to pronounced trion emission. Analysis of the emissive dipole orientation shows a strong horizontal alignment of the SWCNTs with an average inclination angle of 12.9° with respect to the plane, leading to an exceptionally high outcoupling efficiency of 49%. The SWCNT-based OLEDs represent a highly attractive platform for emission across the entire nIR. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surprising luminescent properties of the polyphosphates Ln(PO3)3:Eu (Ln = Y, Gd, Lu).

PubMed

Höppe, Henning A; Kazmierczak, Karolina; Kacprzak, Sylwia; Schellenberg, Inga; Pöttgen, Rainer

2011-10-21

The optical emission properties of the lanthanoid catena-polyphosphates Ln(PO(3))(3) (Ln = Y, Gd, Lu) doped with europium were investigated. Incommensurately modulated β-Y(PO(3))(3):Eu (super space group Cc (0|0.364|0)0) and Gd(PO(3))(3):Eu (space group I2/a) show the usual emission characteristics of Eu(3+), while in Lu(PO(3))(3):Eu (space group Cc) the europium is unprecedentedly partially reduced to the divalent state, as proven by both a broad emission band at 406 nm excited at 279 nm and an EPR spectroscopic investigation. (151)Eu-Mössbauer spectroscopy showed that only a very small part of the europium is reduced in Lu(PO(3))(3):Eu. An explanation for this unusual behaviour is given. This journal is © The Royal Society of Chemistry 2011

Study of Mn laser ablation in methane atmosphere

NASA Astrophysics Data System (ADS)

Krstulović, N.; Labazan, I.; Milošević, S.

2006-02-01

Laser ablation of Mn target in vacuum and in the presence of CH4 was studied under 308 nm laser irradiation. Time-resolved emission using gated detection and scanning monochromator and absorption using the cavity ring-down spectroscopy were used to study vaporized plume. In the CH4 atmosphere we observed transitions identified as C2 and MnH bands, while these spectral features were not detected in emission spectra. This is a clear evidence of importance in combining both spectroscopic techniques in laser vaporized plume study.

Spectroscopic properties and energy transfer parameters of Er3+- doped fluorozirconate and oxyfluoroaluminate glasses

PubMed Central

Huang, Feifei; Liu, Xueqiang; Hu, Lili; Chen, Danping

2014-01-01

Er3+- doped fluorozirconate (ZrF4-BaF2-YF3-AlF3) and oxyfluoroaluminate glasses are successfully prepared here. These glasses exhibit significant superiority compared with traditional fluorozirconate glass (ZrF4-BaF2-LaF3-AlF3-NaF) because of their higher temperature of glass transition and better resistance to water corrosion. Judd-Ofelt (J-O) intensity parameters are evaluated and used to compute the radiative properties based on the VIS-NIR absorption spectra. Broad emission bands located at 1535 and 2708 nm are observed, and large calculated emission sections are obtained. The intensity of 2708 nm emission closely relates to the phonon energy of host glass. A lower phonon energy leads to a more intensive 2708 nm emission. The energy transfer processes of Er3+ ions are discussed and lifetime of Er3+: 4I13/2 is measured. It is the first time to observe that a longer lifetime of the 4I13/2 level leads to a less intensive 1535 nm emission, because the lifetime is long enough to generate excited state absorption (ESA) and energy transfer (ET) processes. These results indicate that the novel glasses possess better chemical and thermal properties as well as excellent optical properties compared with ZBLAN glass. These Er3+- doped ZBYA and oxyfluoroaluminate glasses have potential applications as laser materials. PMID:24852112

Enhanced broadband near-infrared luminescence from Pr3+-doped tellurite glass with silver nanoparticles

NASA Astrophysics Data System (ADS)

Cheng, Pan; Zhou, Yaxun; Zhou, Minghan; Su, Xiue; Zhou, Zizhong; Yang, Gaobo

2017-11-01

Pr3+-doped tellurite glasses containing metallic silver NPs were synthesized by the conventional melt-quenching technique. Structural, thermal and optical properties of the synthesized glass samples were characterized by X-Ray diffraction (XRD) curves, Raman spectra, differential scanning calorimeter (DSC) curves, transmission electron microscopy (TEM) images, UV/Vis/NIR absorption and near-infrared fluorescence emission spectra. The XRD curves confirmed the amorphous structural nature of the synthesized glasses, the Raman spectra identified the presence of different vibrational groups, the DSC curves verified the good thermal stability, and the TEM images revealed the nucleated silver NPs with average diameter about 10 nm dispersed in the glass matrix and its surface Plasmon resonance (SPR) absorption band was located at around 510 nm. Besides, Judd-Ofelt intensity parameters Ωt (t = 2, 4, 6) and other important spectroscopic parameters like transition probability, radiative lifetime, branching ratio were calculated to evaluate the radiative properties of Pr3+ levels from the measured optical absorption spectra. It was found that Pr3+-doped tellurite glasses could emit an ultra-broadband fluorescence extending from 1250 to 1650 nm under the 488 nm excitation, and this fluorescence emission increased further with the introduction of silver NPs. The enhanced fluorescence was mainly attributed to the increased local electric field around Pr3+ induced by silver NPs. The present results demonstrate that Pr3+-Ag codoped tellurite glass is a promising candidate for the near-infrared band ultra-broadband fiber amplifiers covering the expanded low-loss communication window.

SEMICONDUCTOR MATERIALS: White light photoluminescence from ZnS films on porous Si substrates

NASA Astrophysics Data System (ADS)

Caifeng, Wang; Qingshan, Li; Bo, Hu; Weibing, Li

2010-03-01

ZnS films were deposited on porous Si (PS) substrates using a pulsed laser deposition (PLD) technique. White light emission is observed in photoluminescence (PL) spectra, and the white light is the combination of blue and green emission from ZnS and red emission from PS. The white PL spectra are broad, intense in a visible band ranging from 450 to 700 nm. The effects of the excitation wavelength, growth temperature of ZnS films, PS porosity and annealing temperature on the PL spectra of ZnS/PS were also investigated.

Crystal growth and scintillation properties of strontium iodide scintillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Loef, Edgar; Wilson, Cody; Cherepy, Nerine

2009-06-01

Single crystals of SrI{sub 2}:Eu and SrI{sub 2}:Ce/Na were grown from anhydrous iodides by the vertical Bridgman technique in evacuated silica ampoules. Growth rates were of the order of 5-30 mm/day. Radioluminescence spectra of SrI{sub 2}:Eu and SrI{sub 2}:Ce/Na exhibit a broad band due to Eu{sup 2+} and Ce{sup 3+} emission, respectively. The maximum in the luminescence spectrum of SrI{sub 2}:Eu is found at 435 nm. The spectrum of SrI{sub 2}:Ce/Na exhibits a doublet peaking at 404 and 435 nm attributed to Ce{sup 3+} emission, while additional impurity - or defected - related emission is present at approximately 525 nm.more » The strontium iodide scintillators show very high light yields of up to 120,000 photons/MeV, have energy resolutions down to 3% at 662 keV (Full Width Half Maximum) and exhibit excellent light yield proportionality with a standard deviation of less than 5% between 6 and 460 keV.« less

Thermoluminescent properties of nanocrystalline ZnTe thin films: Structural and morphological studies

NASA Astrophysics Data System (ADS)

Rajpal, Shashikant; Kumar, S. R.

2018-04-01

Zinc Telluride (ZnTe) is a binary II-VI direct band gap semiconducting material with cubic structure and having potential applications in different opto-electronic devices. Here we investigated the effects of annealing on the thermoluminescence (TL) of ZnTe thin films. A nanocrystalline ZnTe thin film was successfully electrodeposited on nickel substrate and the effect of annealing on structural, morphological, and optical properties were studied. The TL emission spectrum of as deposited sample is weakly emissive in UV region at ∼328 nm. The variation in the annealing temperature results into sharp increase in emission intensity at ∼328 nm along with appearance of a new peak at ∼437 nm in visible region. Thus, the deposited nanocrystalline ZnTe thin films exhibited excellent thermoluminescent properties upon annealing. Furthermore, the influence of annealing (annealed at 400 °C) on the solid state of ZnTe were also studied by XRD, SEM, EDS, AFM. It is observed that ZnTe thin film annealed at 400 °C after deposition provide a smooth and flat texture suited for optoelectronic applications.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Planar excilamp on rare gas chlorides pumped by a transverse self-sustained discharge

NASA Astrophysics Data System (ADS)

Panchenko, Aleksei N.; Tarasenko, Viktor F.

2006-02-01

The design and parameters of a UV—VUV spontaneous radiation source — an excilamp operating on chlorides of rare gases ArCl*, KrCl* and XeCl* in the wavelength range 175—308 nm are presented. The Ne—Xe(Kr, Ar)—HCl mixtures were excited by a high-pressure self-sustained discharge with spark preionisation. It is shown that upon pumping mixtures of rare gases and halogens by a transverse discharge, the intensities of the B—X emission band of molecules ArCl*, KrCl* and XeCl* are comparable and up to 90% of the emission energy of excilamps can be concentrated in the UV region. The peak UV power density at 222 and 308 nm on the output window of the excilamp was ~2 kW cm-2 for the pulse energy up to ~ 3 mJ. The output emission energy of the excilamp at 175 nm achieved ~0.6 mJ and the peak power density was ~0.4 kW cm-2.

High resolution measurements of solar induced chlorophyll fluorescence in the Fraunhofer oxigen bands

NASA Astrophysics Data System (ADS)

Mazzoni, M.; Agati, G.; Cecchi, G.; Toci, G.; Mazzinghi, P.

2017-11-01

Spectra of solar radiance reflected by leaves close to the Fraunhofer bands show the net contribution of chlorophyll fluorescence emission which adds to the reflected solar spectra. In a laboratory experiment, a low stray light, high resolution, 0.85 m double monochromator was used to filter radiation living leaves still attached to the plant in correspondence of the 687 nm and 760 nm O2 absorption bands. Reference spectra from a non fluorescent white reference were also acquired. Acquisition was performed by a Microchannel plate (MCP) intensified diode array with 512 elements. A fit of the spectral data outside the absorption lines allowed to retrieve the spectral base-line as a function of wavelength for the reference panel and the leaf. Reflectance functions were determined extending the Plascyck equation system to all the resolved lines of the oxygen absorption bands and using the base-lines for the continuum values. Fluorescence was deduced from the same equation system, using both the measured leaf and reference radiance spectra and the leaf reflectance fitting function.

Laser-emission imaging of nuclear biomarkers for high-contrast cancer screening and immunodiagnosis

PubMed Central

Chen, Yu-Cheng; Tan, Xiaotian; Sun, Qihan; Chen, Qiushu; Wang, Wenjie; Fan, Xudong

2017-01-01

Detection of nuclear biomarkers such as nucleic acids and nuclear proteins is critical for early-stage cancer diagnosis and prognosis. Conventional methods relying on morphological assessment of cell nuclei in histopathology slides may be subjective, whereas colorimetric immunohistochemical and fluorescence-based imaging are limited by strong light absorption, broad-emission bands and low contrast. Here, we describe the development and use of a scanning laser-emission-based microscope that maps lasing emissions from nuclear biomarkers in human tissues. 41 tissue samples from 35 patients labelled with site-specific and biomarker-specific antibody-conjugated dyes were sandwiched in a Fabry-Pérot microcavity while an excitation laser beam built a laser-emission image. We observed multiple sub-cellular lasing emissions from cancer cell nuclei, with a threshold of tens of μJ/mm2, sub-micron resolution (<700 nm), and a lasing band in the few-nanometre range. Different lasing thresholds of nuclei in cancer and normal tissues enabled the identification and multiplexed detection of nuclear proteomic biomarkers, with a high sensitivity for early-stage cancer diagnosis. Laser-emission-based cancer screening and immunodiagnosis might find use in precision medicine and facilitate research in cell biology. PMID:29204310

15 years of VLT/UVES OH intensities and temperatures in comparison with TIMED/SABER data

NASA Astrophysics Data System (ADS)

Noll, Stefan; Kimeswenger, Stefan; Proxauf, Bastian; Unterguggenberger, Stefanie; Kausch, Wolfgang; Jones, Amy M.

2017-10-01

The high-resolution echelle spectrograph UVES of the Very Large Telescope at Cerro Paranal in Chile has been regularly operated since April 2000. Thus, UVES archival data originally taken for astronomical projects but also including sky emission can be used to study airglow variations on a time scale longer than a solar cycle. Focusing on OH emission and observations until March 2015, we considered about 3000 high-quality spectra from two instrumental set-ups centred on 760 and 860 nm, which cover about 380 nm each. These data allowed us to measure line intensities for several OH bands in order to derive band intensities and rotational temperatures for different upper vibrational levels as a function of solar activity and observing date. The results were compared with those derived from emission and temperature profile data of the radiometer SABER on the TIMED satellite taken in the Cerro Paranal area between 2002 and 2015. In agreement with the SABER data, the long-term variations in OH intensity and temperature derived from the UVES data are dominated by the solar cycle, whereas secular trends appear to be negligible. Combining the UVES and SABER results, the solar cycle effects for the OH intensity and temperature are about 12-17% and 4-5 K per 100 sfu and do not significantly depend on the selected OH band. The data also reveal that variations of the effective OH emission layer height and air density can cause significant changes in the OH rotational temperatures due to a varying ratio of OH thermalising collisions by air molecules and OH radiation, deactivation, and destruction processes which impede the rotational relaxation. However, this effect appears to be of minor importance for the explanation of the rotational temperature variations related to the solar activity cycle, which causes only small changes in the OH emission profile.

Retrieval of O2(1Σ) and O2(1Δ) volume emission rates in the mesosphere and lower thermosphere using SCIAMACHY MLT limb scans

NASA Astrophysics Data System (ADS)

Zarboo, Amirmahdi; Bender, Stefan; Burrows, John P.; Orphal, Johannes; Sinnhuber, Miriam

2018-01-01

We present the retrieved volume emission rates (VERs) from the airglow of both the daytime and twilight O2(1Σ) band and O2(1Δ) band emissions in the mesosphere and lower thermosphere (MLT). The SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) onboard the European Space Agency Envisat satellite observes upwelling radiances in limb-viewing geometry during its special MLT mode over the range 50-150 km. In this study we use the limb observations in the visible (595-811 nm) and near-infrared (1200-1360 nm) bands. We have investigated the daily mean latitudinal distributions and the time series of the retrieved VER in the altitude range from 53 to 149 km. The maximal observed VERs of O2(1Δ) during daytime are typically 1 to 2 orders of magnitude larger than those of O2(1Σ). The latter peaks at around 90 km, whereas the O2(1Δ) emissivity decreases with altitude, with the largest values at the lower edge of the observations (about 53 km). The VER values in the upper mesosphere (above 80 km) are found to depend on the position of the sun, with pronounced high values occurring during summer for O2(1Δ). O2(1Σ) emissions show additional high values at polar latitudes during winter and spring. These additional high values are presumably related to the downwelling of atomic oxygen after large sudden stratospheric warmings (SSWs). Accurate measurements of the O2(1Σ) and O2(1Δ) airglow, provided that the mechanism of their production is understood, yield valuable information about both the chemistry and dynamics in the MLT. For example, they can be used to infer the amounts and distribution of ozone, solar heating rates, and temperature in the MLT.

Synthesis and photoluminescence study in Eu3+:Y2WO6 phosphors

NASA Astrophysics Data System (ADS)

Sonali, Mondal, Manisha; Rai, Vineet Kumar

2018-05-01

Eu3+ doped Y2WO6 phosphors were synthesized by solid state reaction method. The photoluminescence properties of the Eu3+:Y2WO6 phosphors were studied for different concentration of Eu3+ ions. The luminescence intensity is found maximum at 0.3 mol% of Eu3+ ions. The excitation spectra monitored at ˜617 nm lies in the 220 - 350 nm region occurs due to charge transfer state (CTS) band of the europium-oxygen interactions, which is caused by an electron transfer from oxygen 2p orbital to an empty 4f shell of europium ions. The phosphors effectively excited by ˜393 nm near-ultraviolet (NUV) light gives efficient red emission band (˜ 617 nm) corresponding to 5D0 → 7F2 transition. The concentration dependence photoluminescence study and the mechanisms behind the photoluminescence properties have been explored with the help of suitable energy level diagram. Moreover, the CIE colour coordinate lie in the near white region so the prepared phosphors can be suitably use in making visible downconverter and in making visible light display devices.

Microwave-Assisted Synthesis Cd Metal Hexagonal Nanosheets

NASA Astrophysics Data System (ADS)

Sun, Yidong; She, Houde; Bai, Wencai; Li, Liangshan; Zhou, Hua

2018-07-01

Sodium borohydride (NaBH4) as reducing agent, oleic acid (OA) as surfactant, deionized water as the dispersant, reducing cadmium nitrate (Cd(NO3)2 · 4H2O) can get Cd nanosheets by microwave method. Room temperature photoluminescence (PL) spectrum for Cd nanosheets recorded under xenon light wavelength of 325 nm exhibited obviously emission bands at 331, 379, and 390 nm. By analyzing the results of XRD and TEM, the nanosheets are thought as hexagonal phase and the size is about 20 nm. This synthesis performs in a lower temperature. Moreover our method is quite simple and the cost of the experiment is relatively lower.

Pulsed, atmospheric pressure plasma source for emission spectrometry

DOEpatents

Duan, Yixiang; Jin, Zhe; Su, Yongxuan

2004-05-11

A low-power, plasma source-based, portable molecular light emission generator/detector employing an atmospheric pressure pulsed-plasma for molecular fragmentation and excitation is described. The average power required for the operation of the plasma is between 0.02 W and 5 W. The features of the optical emission spectra obtained with the pulsed plasma source are significantly different from those obtained with direct current (dc) discharge higher power; for example, strong CH emission at 431.2 nm which is only weakly observed with dc plasma sources was observed, and the intense CN emission observed at 383-388 nm using dc plasma sources was weak in most cases. Strong CN emission was only observed using the present apparatus when compounds containing nitrogen, such as aniline were employed as samples. The present apparatus detects dimethylsulfoxide at 200 ppb using helium as the plasma gas by observing the emission band of the CH radical. When coupled with a gas chromatograph for separating components present in a sample to be analyzed, the present invention provides an apparatus for detecting the arrival of a particular component in the sample at the end of the chromatographic column and the identity thereof.

Pre and post annealed low cost ZnO nanorods on seeded substrate

NASA Astrophysics Data System (ADS)

Nordin, M. N.; Kamil, Wan Maryam Wan Ahmad

2017-05-01

We wish to report the photonic band gap (where light is confined) in low cost ZnO nanorods created by two-step chemical bath deposition (CBD) method where the glass substrates were pre-treated with two different seeding thicknesses, 100 nm (sample a) and 150 nm (sample b), of ZnO using radio frequency magnetron sputtering. Then the samples were annealed at 600°C for 1 hour in air before and after immersed into the chemical solution for CBD process. To observe the presence of photonic band gap on the sample, UV-Visible-NIR spectrophotometer was utilized and showed that sample a and sample b both achieved wide band gap between 240 nm and 380 nm, within the UV range for typical ZnO, however sample b provided a better light confinement that may be attributed by the difference in average nanorods size. Field Emission Scanning Electron Microscope (FESEM) of the samples revealed better oriented nanorods uniformly scattered across the surface when substrates were coated with 100 nm of seeding layer whilst the 150 nm seeding sample showed a poor distribution of nanorods probably due to defects in the sample. Finally, the crystal structure of the ZnO crystallite is revealed by employing X-ray diffraction and both samples showed polycrystalline with hexagonal wurtzite structure that matched with JCPDS No. 36-1451. The 100 nm pre-seeded samples was recognized to have bigger average crystallite size, however sample b was suggested as having a higher crystalline quality. In conclusion, the sample b is recognized as a better candidate for future photonic applications due to its more apparent of photonic band gap and this may be contributed by more random distribution of the nanorods as observed in FESEM images as well as higher crystalline quality as suggested from XRD measurements.

VizieR Online Data Catalog: Halpha measurements in Abell 2465 (Wegner+, 2015)

NASA Astrophysics Data System (ADS)

Wegner, G. A.; Chu, D. S.; Hwang, H. S.

2015-07-01

The wavelength of the Hα line at the redshift of Abell 2465 is near 817nm in a clear spectral region between the many telluric emission lines. A custom narrow-band filter for observing Hα was obtained from the Andover Corp. It has a peak transmission at 817.7nm (m817) and a full width at half-maximum (FWHM) of 8.77nm. The wide filter was a Gunn i (ig) filter with nearly the same central wavelength of 820nm and a FWHM of 185nm, and was manufactured by Custom Scientific. Hα observations of Abell 2465 were obtained 2012 September 19-23 using the 2.4m Hiltner telescope at the MDM Observatory on Kitt Peak. The 'Nellie' CCD was used. (1 data file).

Energy transfer and colour tunability in UV light induced Tm3 +/Tb3 +/Eu3 +: ZnB glasses generating white light emission

NASA Astrophysics Data System (ADS)

Naresh, V.; Gupta, Kiran; Parthasaradhi Reddy, C.; Ham, Byoung S.

2017-03-01

A promising energy transfer (Tm3 + → Tb3 + → Eu3 +) approach is brought forward to generate white light emission under ultraviolet (UV) light excitation for solid state lightening. Tm3 +/Tb3 +/Eu3 + ions are combinedly doped in zinc borate glass system in view of understanding energy transfer process resulting in white light emission. Zinc borate (host) glass displayed optical and luminescence properties due to formation of Zn(II)x-[O(- II)]y centres in the ZnB glass matrix. At 360 nm (UV) excitation, triply doped Tm3 +/Tb3 +/Eu3 +: ZnB glasses simultaneously shown their characteristic emission bands in blue (454 nm: 1D2 → 3F4), green (547 nm: 5D4 → 7F5) and red (616 nm: 5D0 → 7F2) regions. In triple ions doped glasses, energy transfer dynamics is discussed in terms of Forster-Dexter theory, excitation & emission profiles, lifetime curves and from partial energy level diagram of three ions. The role of Tb3 + in ET from Tm3 + → Eu3 + was discussed using branch model. From emission decay analysis, energy transfer probability (P) and efficiency (η) were evaluated. Colour tunability from blue to white on varying (Tb3 +, Eu3 +) content is demonstrated from Commission Internationale de L'Eclairage (CIE) chromaticity coordinates. Based on chromaticity coordinates, other colour related parameters like correlated colour temperature (CCT) and colour purity are also computed for the studied glass samples. An appropriate blending of such combination of rare earth ions could show better suitability as potential candidates in achieving multi-colour and warm/cold white light emission for white LEDs application in the field of solid state lightening.

Physical and optical properties of lithium borosilicate glasses doped with Dy3+ ions

NASA Astrophysics Data System (ADS)

Ramteke, D. D.; Gedam, R. S.; Swart, H. C.

2018-04-01

The borosilicate glasses with Dy3+ ions were prepared by the melt quench technique with varying concentration of Dy2O3. The glasses were characterized by the density calculation, absorbance and photoluminescence (PL) spectroscopy measurements. Density and molar volume of the glasses increases with increase in Dy3+ ions in the glass matrix. This behavior is correlated with the higher molecular weight and larger ionic radius of Dy3+ ion compared to the other constituents of glass matrix. Emission of Dy3+ doped glasses showed three bands at 482, 573 and at 665 nm which correspond to 6H15/2 (blue), 6H13/2 (yellow) and 6H11/2 (red) transitions. The emission spectra of glasses with different concentration of Dy3+ ions shows that, glasses with 0.5 mol% of Dy2O3 shows highest emission and decreases with further doping. CIE 1931 chromaticity diagram showed that the emission of these glasses was in the white region. Photographs of these glasses under 349 nm Light emitting diode excitation also confirmed the white light emission from these glasses.

Intense infrared emission of Er(3+) in Ca(8)Mg(SiO(4))(4)Cl(2) phosphor from energy transfer of Eu(2+) by broadband down-conversion.

PubMed

Zhou, Jiajia; Teng, Yu; Liu, Xiaofeng; Ye, Song; Xu, Xiaoqiu; Ma, Zhijun; Qiu, Jianrong

2010-10-11

We report on conversion of near-ultraviolet and visible radiation ranging from 250 to 500 nm into near-infrared emission by a Ca(8)Mg(SiO(4))(4)Cl(2): Eu(2+), Er(3+) phosphor. Efficient 1530-1560 nm Er(3+) emission ((4)I(13/2)-->(4)I(15/2)) was detected under the excitation of Eu(2+) (4f?5d) absorption band as a result of energy transfer from Eu(2+) to Er(3+), which is confirmed by both steady state and time-resolved emission spectra. The laser power dependent emission intensity changes were investigated to analysis the energy transfer mechanism. Energy transfer from Eu(2+) to Er(3+) followed by a multi-photon quantum cutting of Er(3+) is proposed. The result indicates that the phosphor has potential application in enhancement of conversion efficient of germanium solar cells because the energy difference of Er(3+): (4)I(13/2)-->(4)I(15/2) transition matches well with the bandgap of Ge (Eg~0.785 eV).

Tuning extreme ultraviolet emission for optimum coupling with multilayer mirrors for future lithography through control of ionic charge states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ohashi, Hayato, E-mail: ohashi@cc.utsunomiya-u.ac.jp; Higashiguchi, Takeshi, E-mail: higashi@cc.utsunomiya-u.ac.jp; Suzuki, Yuhei

2014-01-21

We report on the identification of the optimum plasma conditions for a laser-produced plasma source for efficient coupling with multilayer mirrors at 6.x nm for beyond extreme ultraviolet lithography. A small shift to lower energies of the peak emission for Nd:YAG laser-produced gadolinium plasmas was observed with increasing laser power density. Charge-defined emission spectra were observed in electron beam ion trap (EBIT) studies and the charge states responsible identified by use of the flexible atomic code (FAC). The EBIT spectra displayed a larger systematic shift of the peak wavelength of intense emission at 6.x nm to longer wavelengths with increasingmore » ionic charge. This combination of spectra enabled the key ion stage to be confirmed as Gd{sup 18+}, over a range of laser power densities, with contributions from Gd{sup 17+} and Gd{sup 19+} responsible for the slight shift to longer wavelengths in the laser-plasma spectra. The FAC calculation also identified the origin of observed out-of-band emission and the charge states responsible.« less

Combustion synthesis and luminescence properties of yellow-emitting phosphors Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xia, Zhiguo, E-mail: xiazg426@yahoo.com.cn; Liao, Libing, E-mail: lbliao@cugb.edu.cn; Zhang, Zepeng

2012-02-15

Graphical abstract: A yellow-emitting phosphor Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} was firstly synthesized by the solution-combustion method. The photoluminescence excitation and emission spectra, temperature dependence of luminescence intensity, and luminescence lifetime of the phosphor were investigated. Highlights: Black-Right-Pointing-Pointer Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} phosphor was synthesized by a solution-combustion method. Black-Right-Pointing-Pointer Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} showed an intense yellow emission band centered at 569 nm with the CIE coordinate of (0.453, 0.526). Black-Right-Pointing-Pointer The temperature dependent luminescence property and mechanism of Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} were studied. -- Abstract: Yellow-emitting phosphor Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} was synthesized by a solution-combustion method. Themore » phase structure and microstructure were determined by the X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis, respectively. The as-prepared Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} phosphor absorbed near ultraviolet and blue light of 320-500 nm, and showed an intense yellow emission band centered at 569 nm with the CIE coordinate of (0.453, 0.526). The lifetime of Eu{sup 2+} ions in Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} phosphor was measured, furthermore the temperature dependent luminescence property and mechanism were studied, which also testified that the present phosphor had a promising potential for white light-emitting diodes.« less

Stimulated emission from aluminium anode oxide films doped with rhodamine 6G

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ibrayev, N Kh; Zeinidenov, A K; Aimukhanov, A K

The spectral and luminescent properties of the rhodamine 6G dye in a porous matrix of aluminium anode oxide are studied. The films with a highly-ordered porous structure are produced using the method of two-stage anodic oxidation. By means of raster electron microscopy it is found that the diameter of the pores amounts to nearly 50 nm and the separation between the adjacent channels is almost 105 nm. The thickness of the films is equal to 55 μm, and the specific surface area measured using the method of nitrogen capillary condensation is 15.3 m{sup 2} g{sup -1}. Fluorescence and absorption spectramore » of rhodamine 6G molecules injected into the pores of the aluminium anode oxide are measured. It is found that under the excitation of samples with the surface dye concentration 0.3 × 10{sup 14} molecules m{sup -2} by the second harmonic of the Nd : YAG laser in the longitudinal scheme with the pumping intensity 0.4 MW cm{sup -2}, a narrow band of stimulated emission with the intensity maximum at the wavelength 572 nm appears against the background of the laser-induced fluorescence spectrum. A further increase in the pumping radiation intensity leads to the narrowing of the stimulated emission band and an increase in its intensity. The obtained results demonstrate the potential possibility of using the porous films of aluminium anode oxide, doped with laser dyes, in developing active elements for quantum electronics. (laser applications and other topics in quantum electronics)« less

Future space missions and ground observatory for measurements of coronal magnetic fields

NASA Astrophysics Data System (ADS)

Fineschi, Silvano; Gibson, Sarah; Bemporad, Alessandro; Zhukov, Andrei; Damé, Luc; Susino, Roberto; Larruquert, Juan

2016-07-01

This presentation gives an overview of the near-future perspectives for probing coronal magnetism from space missions (i.e., SCORE and ASPIICS) and ground-based observatory (ESCAPE). Spectro-polarimetric imaging of coronal emission-lines in the visible-light wavelength-band provides an important diagnostics tool of the coronal magnetism. The interpretation in terms of Hanle and Zeeman effect of the line-polarization in forbidden emission-lines yields information on the direction and strength of the coronal magnetic field. As study case, this presentation will describe the Torino Coronal Magnetograph (CorMag) for the spectro-polarimetric observation of the FeXIV, 530.3 nm, forbidden emission-line. CorMag - consisting of a Liquid Crystal (LC) Lyot filter and a LC linear polarimeter. The CorMag filter is part of the ESCAPE experiment to be based at the French-Italian Concordia base in Antarctica. The linear polarization by resonance scattering of coronal permitted line-emission in the ultraviolet (UV)can be modified by magnetic fields through the Hanle effect. Space-based UV spectro-polarimeters would provide an additional tool for the disgnostics of coronal magnetism. As a case study of space-borne UV spectro-polarimeters, this presentation will describe the future upgrade of the Sounding-rocket Coronagraphic Experiment (SCORE) to include new generation, high-efficiency UV polarizer with the capability of imaging polarimetry of the HI Lyman-α, 121.6 nm. SCORE is a multi-wavelength imager for the emission-lines, HeII 30.4 nm and HI 121.6 nm, and visible-light broad-band emission of the polarized K-corona. SCORE has flown successfully in 2009. The second lauch is scheduled in 2016. Proba-3 is the other future solar mission that would provide the opportunity of diagnosing the coronal magnetic field. Proba-3 is the first precision formation-flying mission to launched in 2019). A pair of satellites will fly together maintaining a fixed configuration as a 'large rigid structure' in space. The paired satellites will together form a 150-m long solar coronagraph (ASPIICS) to study the Sun's faint corona closer to the solar limb than has ever before been achieved. High-resolution imaging in polarized visible-light of shock waves generated by Coronal Mass Ejections would provide a diagnostics of the magnetic field in the pre-shock ambient corona.

Detailed Observation of Multiphoton Emission Enhancement from a Single Colloidal Quantum Dot Using a Silver-Coated AFM Tip.

PubMed

Takata, Hiroki; Naiki, Hiroyuki; Wang, Li; Fujiwara, Hideki; Sasaki, Keiji; Tamai, Naoto; Masuo, Sadahiro

2016-09-14

The enhancement of multiphoton emission from a single colloidal nanocrystal quantum dot (NQD) interacting with a plasmonic nanostructure was investigated using a silver-coated atomic force microscopy tip (AgTip) as the plasmonic nanostructure. Using the AgTip, which exhibited a well-defined localized surface plasmon (LSP) resonance band, we controlled the spectral overlap and the distance between the single NQD and the AgTip. The emission behavior of the single NQD when approaching the AgTip at the nanometer scale was measured using off-resonance (405 nm) and resonance (465 nm) excitation of the LSP. We directly observed the conversion of the single-photon emission from a single NQD to multiphoton emission with reduction of the emission lifetime at both excitation wavelengths as the NQD-AgTip distance decreased, whereas a decrease and increase in the emission intensity were observed at 405 and 465 nm excitation, respectively. By combining theoretical analysis and the numerical simulation of the AgTip, we deduced that the enhancement of the multiphoton emission was caused by the quenching of the single-exciton state due to the energy transfer from the NQD to the AgTip and that the emission intensity was increased by enhancement of the excitation rate due to the electric field of the LSP on the AgTip. These results provide evidence that the photon statistics and the photon flux from the single NQD can be manipulated by the plasmonic nanostructure through control of the spectral overlap and the distance.

Na3Tb(PO4)2: Synthesis, crystal structure and greenish emitting properties

NASA Astrophysics Data System (ADS)

Zhao, Dan; Ma, Zhao; Liu, Bao-Zhong; Zhang, Rui-Juan; Wu, Zhi-Qiang; Wang, Jian; Duan, Pei-Gao

2018-03-01

A anhydrous orthoborate Na3Tb(PO4)2 has been prepared and its crystal structure was determined by X-Ray diffraction of a non-merohedral twinned single crystal. The results show that the compound crystallizes in monoclinic space group C2/c and the structure features a 3D framework containing PO4, NaO6, NaO7, NaO8 and TbO8 polyhedra. Under near-UV excitation (370 nm), Na3Tb(PO4)2 shows intense characteristic emission bands of Tb3+ (490 nm, 543 nm, 585 nm and 620 nm) with the CIE coordinate of (0.3062, 0.5901), corresponding to greenish color. The excitation spectrum covers a wide range from 340 nm to 390 nm, which indicates that phosphor Na3Tb(PO4)2 can be efficiently activated by near-UV LED ship.

Dynamic tissue analysis using time- and wavelength-resolved fluorescence spectroscopy for atherosclerosis diagnosis

PubMed Central

Sun, Yinghua; Sun, Yang; Stephens, Douglas; Xie, Hongtao; Phipps, Jennifer; Saroufeem, Ramez; Southard, Jeffrey; Elson, Daniel S.; Marcu, Laura

2011-01-01

Simultaneous time- and wavelength-resolved fluorescence spectroscopy (STWRFS) was developed and tested for the dynamic characterization of atherosclerotic tissue ex vivo and arterial vessels in vivo. Autofluorescence, induced by a 337 nm, 700 ps pulsed laser, was split to three wavelength sub-bands using dichroic filters, with each sub-band coupled into a different length of optical fiber for temporal separation. STWRFS allows for fast recording/analysis (few microseconds) of time-resolved fluorescence emission in these sub-bands and rapid scanning. Distinct compositions of excised human atherosclerotic aorta were clearly discriminated over scanning lengths of several centimeters based on fluorescence lifetime and the intensity ratio between 390 and 452 nm. Operation of STWRFS blood flow was further validated in pig femoral arteries in vivo using a single-fiber probe integrated with an ultrasound imaging catheter. Current results demonstrate the potential of STWRFS as a tool for real-time optical characterization of arterial tissue composition and for atherosclerosis research and diagnosis. PMID:21369214

Structural, morphological, and optical properties of tin(IV) oxide nanoparticles synthesized using Camellia sinensis extract: a green approach

NASA Astrophysics Data System (ADS)

Selvakumari, J. Celina; Ahila, M.; Malligavathy, M.; Padiyan, D. Pathinettam

2017-09-01

Tin oxide (SnO2) nanoparticles were cost-effectively synthesized using nontoxic chemicals and green tea ( Camellia sinensis) extract via a green synthesis method. The structural properties of the obtained nanoparticles were studied using X-ray diffraction, which indicated that the crystallite size was less than 20 nm. The particle size and morphology of the nanoparticles were analyzed using scanning electron microscopy and transmission electron microscopy. The morphological analysis revealed agglomerated spherical nanoparticles with sizes varying from 5 to 30 nm. The optical properties of the nanoparticles' band gap were characterized using diffuse reflectance spectroscopy. The band gap was found to decrease with increasing annealing temperature. The O vacancy defects were analyzed using photoluminescence spectroscopy. The increase in the crystallite size, decreasing band gap, and the increasing intensities of the UV and visible emission peaks indicated that the green-synthesized SnO2 may play future important roles in catalysis and optoelectronic devices.

Photoluminescence and thermoluminescence properties of BaGa2O4

NASA Astrophysics Data System (ADS)

Noto, L. L.; Poelman, D.; Orante-Barrón, V. R.; Swart, H. C.; Mathevula, L. E.; Nyenge, R.; Chithambo, M.; Mothudi, B. M.; Dhlamini, M. S.

2018-04-01

Rare-Earth free luminescent materials are fast becoming important as the cost of rare earth ions gradually increases. In this work, a Rare-Earth free BaGa2O4 luminescent compound was prepared by solid state chemical reaction, which was confirmed to have a single phase by X-ray Diffraction. The Backscattered Electron image and Energy Dispersive X-ray spectroscopy maps confirmed irregular particle and homogeneous compound formation, respectively. The Photoluminescence spectrum displayed broad emission between 350 to 650 nm, which was deconvoluted into two components. The photoluminescence excitation peak was positioned at 254 nm, which corresponds with the band-to-band position observed from the diffuse reflectance spectrum. The band gap was extrapolated to 4.65 ± 0.02 eV using the Kubelka-Munk model. The preliminary thermoluminescence results indicated that the kinetics involved were neither of first nor second order. Additionally, the activation energy of the electrons within the trap centres was approximated to 0.61 ± 0.01 eV using the Initial Rise model.

Effect of gadolinium incorporation on the structure and luminescence properties of niobium-based materials

NASA Astrophysics Data System (ADS)

Resende Oliveira, Lidia; Bonamin Moscardini, Susane; Ferreira Molina, Eduardo; José Nassar, Eduardo; Verelst, Marc; Alonso Rocha, Lucas

2018-06-01

In this work, we have investigated how the concentration of Gd3+ ions affects the structural and luminescent properties of niobium oxide-based matrices doped with Eu3+ ions obtained by the adapted non-hydrolytic sol–gel route. X-ray diffractograms revealed that increasing the concentration of Gd3+ ions favored the onset of the Gd2O3 structure decreasing the GdNbO4 phase. The excitation spectra (λ em = 613 nm) presented bands corresponding to the 7F0 → 5LJ transitions (L = D, G, and L, where J = 0–7), attributed to the Eu3+ ions, and a broad band at 270 nm, assigned to the charge transfer of the {{{{NbO}}}4}3- group. The emission spectra contained bands refer to the 5D0 → 7FJ internal configuration transitions (J = 0, 1, 2, 3, and 4). Finally, the CIE chromaticity coordinates met the standard for the color red established by the National Television Standard Committee (NTSC).

Multi-wavelength laser emission in dye-doped photonic liquid crystals.

PubMed

Wang, Chun-Ta; Lin, Tsung-Hsien

2008-10-27

Multi-wavelength lasing in a dye-doped cholesteric liquid crystal (CLC) cell is demonstrated. By adding oversaturated chiral dopant, the multi-photonic band CLC structure can be obtained with non-uniform chiral solubility. Under appropriate excitation, multi-wavelength lasing can be achieved with a multi-photonic band edge CLC structure. The number of lasing wavelengths can be controlled under various temperature processes. Nine wavelength CLC lasings were observed simultaneously. The wavelength range covers around 600-675nm. Furthermore, reversible tuning of multi-wavelength lasing was achieved by controlling CLC device temperature.

Absorption and Emission Spectroscopic Investigation of Thermal Dynamics and Photo-Dynamics of the Rhodopsin Domain of the Rhodopsin-Guanylyl Cyclase from the Nematophagous Fungus Catenaria anguillulae

PubMed Central

Penzkofer, Alfons; Scheib, Ulrike; Stehfest, Katja; Hegemann, Peter

2017-01-01

The rhodopsin-guanylyl cyclase from the nematophagous fungus Catenaria anguillulae belongs to a recently discovered class of enzymerhodopsins and may find application as a tool in optogenetics. Here the rhodopsin domain CaRh of the rhodopsin-guanylyl cyclase from Catenaria anguillulae was studied by absorption and emission spectroscopic methods. The absorption cross-section spectrum and excitation wavelength dependent fluorescence quantum distributions of CaRh samples were determined (first absorption band in the green spectral region). The thermal stability of CaRh was studied by long-time attenuation measurements at room temperature (20.5 °C) and refrigerator temperature of 3.5 °C. The apparent melting temperature of CaRh was determined by stepwise sample heating up and cooling down (obtained apparent melting temperature: 62 ± 2 °C). The photocycle dynamics of CaRh was investigated by sample excitation to the first inhomogeneous absorption band of the CaRhda dark-adapted state around 590 nm (long-wavelength tail), 530 nm (central region) and 470 nm (short-wavelength tail) and following the absorption spectra development during exposure and after exposure (time resolution 0.0125 s). The original protonated retinal Schiff base PRSBall-trans in CaRhda photo-converted reversibly to protonated retinal Schiff base PRSBall-trans,la1 with restructured surroundings (CaRhla1 light-adapted state, slightly blue-shifted and broadened first absorption band, recovery to CaRhda with time constant of 0.8 s) and deprotonated retinal Schiff base RSB13-cis (CaRhla2 light-adapted state, first absorption band in violet to near ultraviolet spectral region, recovery to CaRhda with time constant of 0.35 s). Long-time light exposure of light-adapted CaRhla1 around 590, 530 and 470 nm caused low-efficient irreversible degradation to photoproducts CaRhprod. Schemes of the primary photocycle dynamics of CaRhda and the secondary photocycle dynamics of CaRhla1 are developed. PMID:28981475

Influence of functional groups on the photophysical properties of dimethylamino chalcones as laser dyes

NASA Astrophysics Data System (ADS)

Ibnaouf, K. H.; Elzupir, A. O.; AlSalhi, M. S.; Alaamer, Abdulaziz S.

2018-02-01

In this report, a series of 3-(4-(Dimethylamino) phenyl)-1-(4,3 di-substituted phenyl)-(2E) - propen -1-one chalcones was synthesised and examined as optical materials. The influence of functional groups (FG) and solvents on their photophysical properties was investigated. These include absorption, fluorescence, Stokes shift, and amplified spontaneous emission (ASE). The absorption spectra of all compounds showed a wavelength band in the range 404-429 nm, whereas the fluorescence spectra exhibited a band at 470-535 nm. We found that the fluorescence intensity was inversely proportional to the concentration of chalcones. The FGs and solvents had an amazing effect on the photophysical properties of the synthesised materials. Unexpectedly, the electron withdrawing group showed a highly red shift, whereas the electron donating group exhibited a blue shift. Further, these compounds showed large Stokes shifts (up to 5800 cm-1). ASE was observed under pump pulse laser excitation, and the wavelengths were tuned from 509 to 566 nm.

Bluish-green BMes2-functionalized Pt(II) complexes for high efficiency PhOLEDs: impact of the BMes2 location on emission color.

PubMed

Rao, Ying-Li; Schoenmakers, Dylan; Chang, Yi-Lu; Lu, Jia-Sheng; Lu, Zheng-Hong; Kang, Youngjin; Wang, Suning

2012-09-03

New phosphorescent Pt(II) compounds based on dimesitylboron (BMes(2))-functionalized 2-phenylpyridyl (ppy) N,C-chelate ligands and an acetylacetonato ancillary ligand have been achieved. We have found that BMes(2) substitution at the 4'-position of the phenyl ring can blue-shift the phosphorescent emission energy of the Pt(II) compound by approximately 50 nm, compared to the 5'-BMes(2) substituted analogue, without substantial loss of luminescent quantum efficiencies. The emission color of the 4'-BMes(2) substituted Pt(II) compound, Pt(Bppy)(acac) (1) can be further tuned by the introduction of a substituent group at the 3'-position of the phenyl ring. A methyl substituent red-shifts the emission energy of 1 by approximately 10 nm whereas a fluoro substituent blue-shifts the emission energy by about 6 nm. Using this strategy, three bright blue-green phosphorescent Pt(II) compounds 1, 2 and 3 with emission energy at 481, 492, and 475 nm and Φ(PL)=0.43, 0.26 and 0.25, respectively, have been achieved. In addition, we have examined the impact of BMes(2) substitution on 3,5-dipyridylbenzene (dpb) N,C,N-chelate Pt(II) compounds by synthesizing compound 4, Pt(Bdpb)Cl, which has a BMes(2) group at the 4'-position of the benzene ring. Compound 4 has a phosphorescent emission band at 485 nm and Φ(PL)=0.70. Highly efficient blue-green electroluminescent (EL) devices with a double-layer structure and compounds 1, 3 or 4 as the phosphorescent dopant have been fabricated. At 100 cd m(-2) luminance, EL devices based on 1, 3 and 4 with an external quantum efficiency of 4.7, 6.5 and 13.4%, respectively, have been achieved. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhancement of luminescence emission from GdVO{sub 4}:Er{sup 3+}/Yb{sup 3+} phosphor by Li{sup +} co-doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gavrilović, Tamara V.; Jovanović, Dragana J., E-mail: draganaj@vinca.rs; Lojpur, Vesna M.

2014-09-15

This paper demonstrates the effects of Li{sup +} co-doping on the structure, morphology, and luminescence properties of GdVO{sub 4}:Er{sup 3+}/Yb{sup 3+} phosphor prepared using a high-temperature solid-state chemistry method. The GdVO{sub 4}:Er{sup 3+}/Yb{sup 3+} powders synthesized with the Li{sup +} co-dopant (in concentrations of 0, 5, 10, and 15 mol%) are characterized by X-ray powder diffraction, scanning electron microscopy, and photoluminescence spectroscopy. Structural analysis showed that powders co-doped with Li{sup +} have larger crystallite sizes and slightly smaller crystal lattice parameters than powders prepared without Li{sup +} ions. Photoluminescence down-conversion (345-nm excitation) and up-conversion (980-nm excitation) spectra show characteristic Er{supmore » 3+} emissions, with the most intense bands peaking at 525 nm ({sup 2}H{sub 11/2}→{sup 4}I{sub 15/2} transition) and 552 nm ({sup 4}S{sub 3/2}→{sup 4}I{sub 15/2}). The intensity of up-conversion emission from GdVO{sub 4}:Er{sup 3+}/Yb{sup 3+} is enhanced (by a factor of four) by co-doping with 5 mol% of Li{sup +} ions. The mechanisms responsible for this emission enhancement are discussed. - Graphical abstract: UC emission spectra for GdVO{sub 4}:1.5-mol% Er{sup 3+}/20-mol% Yb{sup 3+} powders co-doped with different concentrations of Li{sup +} ions, recorded under 980-nm excitation. - Highlights: • 5-mol% Li{sup +} co-doped powders have 400% enhanced up-conversion emission intensity. • 15-mol% Li{sup +} co-doping produces 40% higher emission in down-conversion. • Li{sup +} co-doped powders have larger crystallite size and smaller lattice parameters.« less

Red emission enhancement from CaMoO4:Eu3+ by co-doping of Bi3+ for near UV/blue LED pumped white pcLEDs: Energy transfer studies

NASA Astrophysics Data System (ADS)

Wangkhem, Ranjoy; Yaba, Takhe; Shanta Singh, N.; Ningthoujam, R. S.

2018-03-01

CaMoO4:Eu3+ (3 at. %)/Bi3+ (x at. %) nanophosphors were synthesized hydrothermally. All the samples can be excited by 280, 320, 393, and 464 nm (blue) wavelengths for generation of red color emission. Enhancement in 5D0 → 7F2 (615 nm) emission (f-f transition) of Eu3+ is observed when Bi3+ is incorporated in CaMoO4:Eu3+. This is due to the efficient energy transfer from Bi3+ to Eu3+ ions. Introduction of Bi3+ in the system does not lead to the change of emission wavelength of Eu3+. However, Bi3+ incorporation in the system induces a shift in Mo-O charge transfer band absorption from 295 to 270 nm. This may be due to the increase in electronegativity between Mo and O bond in the presence of Bi3+ leading to change in crystal field environment of Mo6+ in MoO42-. At the optimal concentration of Bi3+, an enhancement in emission by a factor of ˜10 and 4.2 in the respective excitation at 393 (7F0 → 5L6) and 464 nm (7F0 → 5D2) is observed. The energy transfer efficiency from Bi3+ to Eu3+ increases from 75% to 96%. The energy transfer is observed to occur mainly via dipole-dipole interactions. Maximum quantum yield value of 55% is observed from annealed CaMoO4:Eu3+ (3 at. %) when sensitized with Bi3+ (15 at. %) under 464 nm excitation. From Commission International de I'Eclairage chromaticity coordinates, the color (red) saturation is observed to be nearly 100%.

Single particle size and fluorescence spectra from emissions of burning materials in a tube furnace to simulate burn pits

NASA Astrophysics Data System (ADS)

Pan, Yong-Le; Houck, Joshua D. T.; Clark, Pamela A.; Pinnick, Ronald G.

2013-08-01

A single-particle fluorescence spectrometer (SPFS) and an aerodynamic particle sizer were used to measure the fluorescence spectra and particle size distribution from the particulate emissions of 12 different burning materials in a tube furnace to simulate open-air burning of garbage. Although the particulate emissions are likely dominated by particles <1 μm diameter, only the spectra of supermicron particles were measured here. The overall fluorescence spectral profiles exhibit either one or two broad bands peaked around 300-450 nm within the 280-650 nm spectral range, when the particles are illuminated with a 263-nm laser. Different burning materials have different profiles, some of them (cigarette, hair, uniform, paper, and plastics) show small changes during the burning process, and while others (beef, bread, carrot, Styrofoam, and wood) show big variations, which initially exhibit a single UV peak (around 310-340 nm) and a long shoulder in visible, and then gradually evolve into a bimodal spectrum with another visible peak (around 430-450 nm) having increasing intensity during the burning process. These spectral profiles could mainly derive from polycyclic aromatic hydrocarbons with the combinations of tyrosine-like, tryptophan-like, and other humic-like substances. About 68 % of these single-particle fluorescence spectra can be grouped into 10 clustered spectral templates that are derived from the spectra of millions of atmospheric aerosol particles observed in three locations; while the others, particularly these bimodal spectra, do not fall into any of the 10 templates. Therefore, the spectra from particulate emissions of burning materials can be easily discriminated from that of common atmospheric aerosol particles. The SFFS technology could be a good tool for monitoring burning pit emissions and possibly for distinguishing them from atmospheric aerosol particles.

Label-Free Carbon-Dots-Based Ratiometric Fluorescence pH Nanoprobes for Intracellular pH Sensing.

PubMed

Shangguan, Jingfang; He, Dinggeng; He, Xiaoxiao; Wang, Kemin; Xu, Fengzhou; Liu, Jinquan; Tang, Jinlu; Yang, Xue; Huang, Jin

2016-08-02

Measuring pH in living cells is of great importance for better understanding cellular functions as well as providing pivotal assistance for early diagnosis of diseases. In this work, we report the first use of a novel kind of label-free carbon dots for intracellular ratiometric fluorescence pH sensing. By simple one-pot hydrothermal treatment of citric acid and basic fuchsin, the carbon dots showing dual emission bands at 475 and 545 nm under single-wavelength excitation were synthesized. It is demonstrated that the fluorescence intensities of the as-synthesized carbon dots at the two emissions are pH-sensitive simultaneously. The intensity ratio (I475 nm/I545 nm) is linear against pH values from 5.2 to 8.8 in buffer solution, affording the capability as ratiometric probes for intracellular pH sensing. It also displays that the carbon dots show excellent reversibility and photostability in pH measurements. With this nanoprobe, quantitative fluorescence imaging using the ratio of two emissions (I475 nm/I545 nm) for the detection of intracellular pH were successfully applied in HeLa cells. In contrast to most of the reported nanomaterials-based ratiometric pH sensors which rely on the attachment of additional dyes, these carbon-dots-based ratiometric probes are low in toxicity, easy to synthesize, and free from labels.

Narrow-band double-pass superluminescent diodes emitting at 1060 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lobintsov, A A; Perevozchikov, M V; Shramenko, M V

2009-09-30

Experimental data are presented which show that double-pass superluminescent diodes (SLDs) with fibre Bragg grating (FBG) based spectrally selective external reflectors offer emission linewidths in the range 0.1-1.0 nm, i.e., one to two orders of magnitude narrower in comparison with conventional SLDs and considerably broader in comparison with single-frequency semiconductor lasers. Their optical power at the single-mode fibre output reaches 5.0-8.0 mW, and can be raised to 50 mW using a semiconductor optical amplifier. (lasers)

Study of surface and bulk electronic structure of II-VI semiconductor nanocrystals using Cu as a nanosensor.

PubMed

Grandhi, G Krishnamurthy; Tomar, Renu; Viswanatha, Ranjani

2012-11-27

Efficiency of the quantum dots based solar cells relies on charge transfer at the interface and hence on the relative alignment of the energy levels between materials. Despite a high demand to obtain size specific band offsets, very few studies exist where meticulous methods like photoelectron spectroscopy are used. However, semiconductor charging during measurements could result in indirect and possibly inaccurate measurements due to shift in valence and conduction band position. Here, in this report, we devise a novel method to study the band offsets by associating an atomic like state with the conduction band and hence obtaining an internal standard. This is achieved by doping copper in semiconductor nanocrystals, leading to the development of a characteristic intragap Cu-related emission feature assigned to the transition from the conduction band to the atomic-like Cu d state. Using this transition we determine the relative band alignment of II-VI semiconductor nanocrystals as a function of size in the below 10 nm size regime. The results are in excellent agreement with the available photoelectron spectroscopy data as well as the theoretical data. We further use this technique to study the excitonic band edge variation as a function of temperature in CdSe nanocrystals. Additionally, surface electronic structure of CdSe nanocrystals have been studied using quantitative measurements of absolute quantum yield and PL decay studies of the Cu related emission and the excitonic emission. The role of TOP and oleic acid as surface passivating ligand molecules has been studied for the first time.

Emission coefficients for the OH Meinel band system; calculations and nightglow comparisons

NASA Astrophysics Data System (ADS)

Slanger, T. G.

2016-12-01

The OH Meinel band system is an extensive series of bands that are transitions between the vibrational levels of the X2Π ground-state of the molecule. The exothermicity of the source reaction is sufficient to populate up to OH(v = 9), and in fact the nascent reaction puts most of the product into that level. Subsequently, relaxation of the population to lower levels takes place via collisions with the ambient atmosphere and radiation within the OH(v) manifold. Considerable effort has been spent in determining the emission coefficients of the OH Meinel band system. This emission is a prominent feature of the terrestrial nightglow, and because it is relatively intense, there have been numerous investigations, generally based on ground-based instrumentation. The very exothermic source reaction, H + O3 → OH(v) + O2, results in the production of vibrationally and rotationally hot OH(v), and leads to a great number of OH emission lines, covering a wide spectral range, 500-2000 nm. The full range of energy-accessible OH vibrational levels, up to v = 9, is produced in the reaction, and in this presentation we make the case that it is essential to simultaneously measure as many OH bands as possible, to retrieve the maximum amount of spectroscopic and dynamic information. In order to do so, we must agree on the emission coefficients (A-factors) associated with the individual OH bands, and this determination has presented problems in the past. A major advance in the study of atmospheric OH Meinel band emission took place when astronomical sky spectra were utilized to record all accessible OH bands simultaneously, from Mauna Kea [Cosby and Slanger, 2007]. Subsequently, similar studies were undertaken at the VLT [Noll et al. 2015 a,b], and at the GIANO-TNG [Oliva et al., 2015]. With these intensity-calibrated spectra, it becomes possible to compare the OH optical data with sets of A-factor calculations that have been presented over the years [Mies, 1974; Turnbull and Lowe, 1989; Langhoff et al., 1986; Goldman et al., 1998; Pendleton and Taylor, 2002; van der Loo and Groenenboom, 2007; Brooke et al., 2016] and others. We conclude that the most recent determinations provide the best representation of the Meinel band A-factors. AcknowledgementsThis work has been supported by NSF Aeronomy grants, with the participation of Dr. Philip Cosby.

Structure and photoluminescence studies of CeO2·CuAlO2 mixed metal oxide fabricated by co-precipitation method.

PubMed

Subhan, Md Abdus; Ahmed, Tanzir; Awal, M R; Kim, B Moon

2015-01-25

A novel mixed metal oxide, CeO2·CuAlO2 was fabricated by co-precipitation method in aqueous medium. CeO2·CuAlO2 was characterized by XRD, SEM, EDS, TEM, FTIR and PL spectra. The optical properties of the nanoparticles were studied by photoluminescence (PL) spectra. PL spectra at different excitations were recorded. The composite showed emission in UV, visible and NIR region depending on the excitation wavelength. The special spectral feature observed for this composite is that it showed six emission bands at 364, 409, 434, 448, 465 and 481 nm when excited at 298 nm. The green and red emissions observed at 512 and 669 nm are originated from cubic CeO2 phase when excited at 450 nm. The PL spectra were found to be dependent on excitation wavelength violating Kasha's rule. The X-ray diffraction reveals a cubic CeO2 phase and hexagonal CuAlO2 phase. EDS spectra revealed the presence of cerium (Ce), copper (Cu), aluminum (Al) and oxygen (O) elements. The particle size of the CeO2·CuAlO2 mixed oxide was estimated using Scherrer's formula, which was found to be in the range of 17.2-34.2 nm. The TEM image showed particles are almost uniform size of approximately 15-50 nm with spherical morphology. Copyright © 2014 Elsevier B.V. All rights reserved.

Structure and photoluminescence studies of CeO2·CuAlO2 mixed metal oxide fabricated by co-precipitation method

NASA Astrophysics Data System (ADS)

Subhan, Md Abdus; Ahmed, Tanzir; Awal, M. R.; Kim, B. Moon

2015-01-01

A novel mixed metal oxide, CeO2·CuAlO2 was fabricated by co-precipitation method in aqueous medium. CeO2·CuAlO2 was characterized by XRD, SEM, EDS, TEM, FTIR and PL spectra. The optical properties of the nanoparticles were studied by photoluminescence (PL) spectra. PL spectra at different excitations were recorded. The composite showed emission in UV, visible and NIR region depending on the excitation wavelength. The special spectral feature observed for this composite is that it showed six emission bands at 364, 409, 434, 448, 465 and 481 nm when excited at 298 nm. The green and red emissions observed at 512 and 669 nm are originated from cubic CeO2 phase when excited at 450 nm. The PL spectra were found to be dependent on excitation wavelength violating Kasha's rule. The X-ray diffraction reveals a cubic CeO2 phase and hexagonal CuAlO2 phase. EDS spectra revealed the presence of cerium (Ce), copper (Cu), aluminum (Al) and oxygen (O) elements. The particle size of the CeO2·CuAlO2 mixed oxide was estimated using Scherrer's formula, which was found to be in the range of 17.2-34.2 nm. The TEM image showed particles are almost uniform size of approximately 15-50 nm with spherical morphology.

Optical properties of cerium doped oxyfluoroborate glass.

PubMed

Bahadur, A; Dwivedi, Y; Rai, S B

2013-06-01

Cerium doped oxyfluoroborate glasses have been prepared and its spectroscopic properties have been discussed. It is found that the absorption edge shifts towards the lower energy side for the higher concentration of cerium dopant. Optical band gap for these glasses have been calculated and it is found that the number of non-bridging oxygen increases with cerium content. The emission spectra of these glasses have been recorded using UV laser radiations (266 and 355 nm) and it is observed that these glasses show bright blue emission. On the basis of excitation and emission spectra we have reported the existence of at least two different emission centers of Ce(3+)ions. Copyright © 2013 Elsevier B.V. All rights reserved.

Optical Properties of CdS Nanobelts and Nanosaws Synthesized by Thermal Evaporation Method

NASA Astrophysics Data System (ADS)

Peng, Zhi-wei; Zou, Bing-suo

2012-04-01

By a simple one-step H2-assisted thermal evaporation method, high quality CdS nanostructures have been successfully fabricated on Au coated Si substrates in large scale. The as-synthesized CdS nanostructures consisted of sword-like nanobelts and toothed nanosaws with a single-crystal hexagonal wurtzite structure. The deposition temperature played an important role in determining the size and morphology of the CdS nanostructures. A combination of vapor-liquid-solid and vapor-solid growth mechanisms were proposed to interpret the formation of CdS nanostructures. Photoluminescence measurement indicated that the nanobelts and nanosaws have a prominent green emission at about 512 nm, which is the band-to-band emission of CdS. The waveguide characteristics of both types of CdS nanostructures were observed and discussed.

Spectroscopic identification of rare earth elements in phosphate glass

NASA Astrophysics Data System (ADS)

Devangad, Praveen; Tamboli, Maktum; Muhammed Shameem, K. M.; Nayak, Rajesh; Patil, Ajeetkumar; Unnikrishnan, V. K.; Santhosh, C.; Kumar, G. A.

2018-01-01

In this work, rare earth-doped phosphate glasses were synthesized and characterized using three different spectroscopic techniques. The absorption spectra of the prepared praseodymium (Pr) and samarium (Sm) doped glasses, recorded by a UV-VIS-NIR spectrophotometer, show the characteristic absorption bands of these elements. To confirm this inference, laser-induced fluorescence spectra of Pr and Sm were obtained at a laser excitation of 442 nm. Their emission bands are reported here. The elemental analysis of these samples was carried out using a laser-induced breakdown spectroscopy (LIBS) system. Characteristic emission lines of Pr and Sm have been identified and reported by the recorded LIBS spectra of glass samples. Results prove that using these three complimentary spectroscopic techniques (absorption, fluorescence and LIBS), we can meaningfully characterize rare earth-doped glass samples.

Biologically inspired band-edge laser action from semiconductor with dipole-forbidden band-gap transition.

PubMed

Wang, Cih-Su; Liau, Chi-Shung; Sun, Tzu-Ming; Chen, Yu-Chia; Lin, Tai-Yuan; Chen, Yang-Fang

2015-03-11

A new approach is proposed to light up band-edge stimulated emission arising from a semiconductor with dipole-forbidden band-gap transition. To illustrate our working principle, here we demonstrate the feasibility on the composite of SnO2 nanowires (NWs) and chicken albumen. SnO2 NWs, which merely emit visible defect emission, are observed to generate a strong ultraviolet fluorescence centered at 387 nm assisted by chicken albumen at room temperature. In addition, a stunning laser action is further discovered in the albumen/SnO2 NWs composite system. The underlying mechanism is interpreted in terms of the fluorescence resonance energy transfer (FRET) from the chicken albumen protein to SnO2 NWs. More importantly, the giant oscillator strength of shallow defect states, which is served orders of magnitude larger than that of the free exciton, plays a decisive role. Our approach therefore shows that bio-materials exhibit a great potential in applications for novel light emitters, which may open up a new avenue for the development of bio-inspired optoelectronic devices.

Optical and dielectric properties of isothermally crystallized nano-KNbO3 in Er3+-doped K2O-Nb2O5-SiO2 glasses.

PubMed

Chaliha, Reenamoni Saikia; Annapurna, K; Tarafder, Anal; Tiwari, V S; Gupta, P K; Karmakar, Basudeb

2010-01-01

Precursor glass of composition 25K(2)O-25Nb(2)O(5)-50SiO(2) (mol%) doped with Er(2)O(3) (0.5 wt% in excess) was isothermally crystallized at 800 degrees C for 0-100 h to obtain transparent KNbO(3) nanostructured glass-ceramics. XRD, FESEM, TEM, FTIRRS, dielectric constant, refractive index, absorption and fluorescence measurements were carried out to analyze the morphology, dielectric, structure and optical properties of the glass-ceramics. The crystallite size of KNbO(3) estimated from XRD and TEM is found to vary in the range 7-23 nm. A steep rise in the dielectric constant of glass-ceramics with heat-treatment time reveals the formation of ferroelectric nanocrystalline KNbO(3) phase. The measured visible photoluminescence spectra have exhibited green emission transitions of (2)H(11/2), (4)S(3/2)-->(4)I(15/2) upon excitation at 377 nm ((4)I(15/2)-->(4)G(11/2)) absorption band of Er(3+) ions. The near infrared (NIR) emission transition (4)I(13/2)-->(4)I(15/2) is detected around 1550 nm on excitation at 980 nm ((4)I(15/2)-->(4)I(11/2)) of absorption bands of Er(3+) ions. It is observed that photoluminescent intensity at 526 nm ((2)H(11/2)-->(4)I(15/2)), 550 nm ((4)S(3/2)-->(4)I(15/2)) and 1550 nm ((4)I(13/2)-->(4)I(15/2)) initially decrease and then gradually increase with increase in heat-treatment time. The measured lifetime (tau(f)) of the (4)I(13/2)-->(4)I(15/2) transition also possesses a similar trend. The measured absorption and fluorescence spectra reveal that the Er(3+) ions gradually enter into the KNbO(3) nanocrystals. Copyright 2009 Elsevier B.V. All rights reserved.

Search for the OH (X(2)Pi) Meinel band emission in meteors as a tracer of mineral water in comets: detection of N(2)(+) (A-X)

NASA Technical Reports Server (NTRS)

Jenniskens, Peter; Laux, Christophe O.

2004-01-01

We report the discovery of the N(2)(+) A-X Meinel band in the 780-840 nm meteor emission from two Leonid meteoroids that were ejected less than 1000 years ago by comet 55P/Tempel-Tuttle. Our analysis indicates that the N(2)(+) molecule is at least an order of magnitude less abundant than expected, possibly as a result of charge transfer reactions with meteoric metal atoms. This new band was found while searching for rovibrational transitions in the X(2)Pi electronic ground state of OH (the OH Meinel band), a potential tracer of water bound to minerals in cometary matter. The electronic A-X transition of OH has been identified in other Leonid meteors. We did not detect this OH Meinel band, which implies that the excited A state is not populated by thermal excitation but by a mechanism that directly produces OH in low vibrational levels of the excited A(2)Sigma state. Ultraviolet dissociation of atmospheric or meteoric water vapor is such a mechanism, as is the possible combustion of meteoric organics.

Tuning from green to red the upconversion emission of Y2O3:Er3+-Yb3+ nanophosphors

NASA Astrophysics Data System (ADS)

Diaz-Torres, L. A.; Salas, P.; Oliva, J.; Resendiz-L, E.; Rodriguez-Gonzalez, C.; Meza, O.

2017-01-01

In this work, the structural, morphological and luminescent properties of Y2O3 nanophosphors doped with Er3+ (1 mol%) and different Yb3+ concentrations (2-12 mol%) have been studied. Those nanophosphors were synthesized using a simple hydrothermal method. XRD analysis indicates that all the samples presented a pure cubic phase even for Yb concentrations as high as 12 mol%. In addition, SEM images show nanoparticles with quasi-spherical shapes with average sizes in the range of 300-340 nm. Photoluminescence measurements obtained after excitation at 967 nm revealed that our samples have strong green (563 nm) and red emissions (660 nm) corresponding to 2H11/2 + 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ ions, respectively. We also observed that the green band is quenched and the red emission enhanced as the Yb concentration increases. In consequence, the CIE coordinates changed from (0.35, 0.64) in the green region to (0.59, 0.39) in the red region. Thus, the tuning properties of Y2O3 nanophosphors suggest that they are good candidates for applications in lighting.

Fluorescence of silicon nanoparticles prepared by nanosecond pulsed laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Chunyang, E-mail: chunyangliu@126.com; Sui, Xin; Yang, Fang

2014-03-15

A pulsed laser fabrication method is used to prepare fluorescent microstructures on silicon substrates in this paper. A 355 nm nanosecond pulsed laser micromachining system was designed, and the performance was verified and optimized. Fluorescence microscopy was used to analyze the photoluminescence of the microstructures which were formed using the pulsed laser processing technique. Photoluminescence spectra of the microstructure reveal a peak emission around 500 nm, from 370 nm laser irradiation. The light intensity also shows an exponential decay with irradiation time, which is similar to attenuation processes seen in porous silicon. The surface morphology and chemical composition of themore » microstructure in the fabricated region was also analyzed with multifunction scanning electron microscopy. Spherical particles are produced with diameters around 100 nm. The structure is compared with porous silicon. It is likely that these nanoparticles act as luminescence recombination centers on the silicon surface. The small diameter of the particles modifies the band gap of silicon by quantum confinement effects. Electron-hole pairs recombine and the fluorescence emission shifts into the visible range. The chemical elements of the processed region are also changed during the interaction between laser and silicon. Oxidation and carbonization play an important role in the enhancement of fluorescence emission.« less

Studies on 405nm blue-violet diode laser with external grating cavity

NASA Astrophysics Data System (ADS)

Li, Bin; Gao, Jun; Zhao, Jun; Yu, Anlan; Luo, Shiwen; Xiong, Dongsheng; Wang, Xinbing; Zuo, Duluo

2016-03-01

Spectroscopy applications of free-running laser diodes (LD) are greatly restricted as its broad band spectral emission. And the power of a single blue-violet LD is around several hundred milliwatts by far, it is of great importance to obtain stable and narrow line-width laser diodes with high efficiency. In this paper, a high efficiency external cavity diode laser (ECDL) with high output power and narrow band emission at 405 nm is presented. The ECDL is based on a commercially available LD with nominal output power of 110 mW at an injection current of 100 mA. The spectral width of the free-running LD is about 1 nm (FWHM). A reflective holographic grating which is installed on a home-made compact adjustable stage is utilized for optical feedback in Littrow configuration. In this configuration, narrow line-width operation is realized and the effects of grating groove density as well as the groove direction related to the beam polarization on the performances of the ECDL are experimentally investigated. In the case of grating with groove density of 3600 g/mm, the threshold is reduced from 21 mA to 18.3 mA or 15.6 mA and the tuning range is 3.95 nm or 6.01 nm respectively when the grating is orientated in TE or TM polarization. In addition, an output beam with a line-width of 30 pm and output power of 92.7 mW is achieved in TE polarization. With these narrow line-width and high efficiency, the ECDL is capable to serve as a light source for spectroscopy application such as Raman scattering and laser induced fluorescence.

Multispectral Observations and Analysis of the Rosette Nebula

NASA Astrophysics Data System (ADS)

Huber, Jeremy

The Rosette nebula is a large, ring-shaped emission nebula with a distinctive central cavity excavated by its central cluster of OB stars. Toward understanding the three dimensional structure and fundamental physical processes of this object, we have acquired ux-calibrated, 4-degree field, deep exposures of the Rosette region through 3 nm bandwidth Halpha (656.3 nm) as well as Hbeta (486.1nm), [OIII] (500.7 nm) and [SII] (671.6 nm) filters with 4.5 nm bandwidth. The 4 arcsec/pixel images are supplemented with 4 degree field slit spectra and combined with archival data from the Galactic Evolution Explorer satellite (GALEX), Akari, the Infrared Astronomical Satellite (IRAS), the Midcourse Space Experiment (MSX), the Wide-field Infrared Survey Explorer (WISE), the Wilkinson Microwave Anisotropy Probe (WMAP) and the Planck mission, along with published single dish radio data of the hydrogen continuum at 1410, 2700, and 4750 MHz. These disparate sources have been converted to the same flux and spatial scale as our own wide field data to create a multispectral data cube which allows comparative analysis across the electromagnetic spectrum. Using ratios of data cube slices, spatial maps of extinction and ionization have been constructed to explore the spatial variation of these parameters across the nebula. Comparison of emission in different wavelengths across the data cube allows generation of a spectral energy distribution (SED) to probe dust temperature and geometry. A radial profile analysis of emission from the Rosette in each band supports a spherical shell model of three dimensional structure, and visual representations of this model have been generated in both Python and Javascript/GLSL. An investigation of anomalous dust emission in the center of the nebula via supplemental spectroscopy, conducted on the Anglo-Australian Telescope, is also presented.

Orbital Stability Results for Soliton Solutions to Nonlinear Schrodinger Equations with External Potentials

NASA Astrophysics Data System (ADS)

Lindgren, Joseph B.

The Rosette nebula is a large, ring-shaped emission nebula with a distinctive central cavity excavated by its central cluster of OB stars. Toward understanding the three dimensional structure and fundamental physical processes of this object, we have acquired ux-calibrated, 4-degree field, deep exposures of the Rosette region through 3 nm bandwidth Halpha (656.3 nm) as well as Hbeta (486.1nm), [OIII] (500.7 nm) and [SII] (671.6 nm) filters with 4.5 nm bandwidth. The 4 arcsec/pixel images are supplemented with 4 degree field slit spectra and combined with archival data from the Galactic Evolution Explorer satellite (GALEX), Akari, the Infrared Astronomical Satellite (IRAS), the Midcourse Space Experiment (MSX), the Wide-field Infrared Survey Explorer (WISE), the Wilkinson Microwave Anisotropy Probe (WMAP) and the Planck mission, along with published single dish radio data of the hydrogen continuum at 1410, 2700, and 4750 MHz. These disparate sources have been converted to the same flux and spatial scale as our own wide field data to create a multispectral data cube which allows comparative analysis across the electromagnetic spectrum. Using ratios of data cube slices, spatial maps of extinction and ionization have been constructed to explore the spatial variation of these parameters across the nebula. Comparison of emission in different wavelengths across the data cube allows generation of a spectral energy distribution (SED) to probe dust temperature and geometry. A radial profile analysis of emission from the Rosette in each band supports a spherical shell model of three dimensional structure, and visual representations of this model have been generated in both Python and Javascript/GLSL. An investigation of anomalous dust emission in the center of the nebula via supplemental spectroscopy, conducted on the Anglo-Australian Telescope, is also presented.

A Study on Atomically Thin Ultra Short Conducting Channels, Breakdown, and Environmental Effects

NASA Astrophysics Data System (ADS)

Sundararajan, Abhishek

The Rosette nebula is a large, ring-shaped emission nebula with a distinctive central cavity excavated by its central cluster of OB stars. Toward understanding the three dimensional structure and fundamental physical processes of this object, we have acquired ux-calibrated, 4-degree field, deep exposures of the Rosette region through 3 nm bandwidth Halpha (656.3 nm) as well as Hbeta (486.1nm), [OIII] (500.7 nm) and [SII] (671.6 nm) filters with 4.5 nm bandwidth. The 4 arcsec/pixel images are supplemented with 4 degree field slit spectra and combined with archival data from the Galactic Evolution Explorer satellite (GALEX), Akari, the Infrared Astronomical Satellite (IRAS), the Midcourse Space Experiment (MSX), the Wide-field Infrared Survey Explorer (WISE), the Wilkinson Microwave Anisotropy Probe (WMAP) and the Planck mission, along with published single dish radio data of the hydrogen continuum at 1410, 2700, and 4750 MHz. These disparate sources have been converted to the same flux and spatial scale as our own wide field data to create a multispectral data cube which allows comparative analysis across the electromagnetic spectrum. Using ratios of data cube slices, spatial maps of extinction and ionization have been constructed to explore the spatial variation of these parameters across the nebula. Comparison of emission in different wavelengths across the data cube allows generation of a spectral energy distribution (SED) to probe dust temperature and geometry. A radial profile analysis of emission from the Rosette in each band supports a spherical shell model of three dimensional structure, and visual representations of this model have been generated in both Python and Javascript/GLSL. An investigation of anomalous dust emission in the center of the nebula via supplemental spectroscopy, conducted on the Anglo-Australian Telescope, is also presented.

OH Fluorescence and Prompt Emission in comet 103P/Hartley 2 observed by EPOXI mission and expected results for comet 67P/Churyumov-Gerasimenko observed by Rosetta/OSIRIS WAC camera

NASA Astrophysics Data System (ADS)

La Forgia, F.; A'Hearn, M. F.; Lazzarin, M.; Magrin, S.; Bodewits, D.; Bertini, I.; Pajola, M.; Barbier, C.; Sierks, H.

2014-04-01

The OH radical, observed in cometary comae, is the direct dissociation product of water. Given the strong A2∑ - X2II (0, 0) emission band in the near-UV at 308.5 nm due to resonance fluorescence, the OH radical has been used, for years, as a tracer of the water parent molecule. Specifically, the OH fluorescence band provides an immediate tool to monitor the water production rate and its variations with the comet's heliocentric distance, rotational period and possible activity changes. Photolysis of water in cometary comae gives rise, with a non negligible branching ratio, to OH fragments in the first electronically excited state (OH*). This state is very unstable, with a lifetime of about 10-6s (Becker and Haaks, 1973), therefore OH* molecules promptly decay to the ground state. This process, generally referred to as prompt emission (PE), is responsible for an emission band in the near-UV ranging approximatelly from 306 to 325 nm. Original studies and tentative detections of OH PE have been put forth by Bertaux (1986), Budzien and Feldman (1991), Bonev et al. (2004), A'Hearn et al. (2007) using ground and space observations. Both from the above mentioned works together with our analysis, this process is expected to be prominent at short distances from the nucleus, where there is high density of water molecules, requiring the need of spacecraft observations to reach the necessary resolution. The hyperactive Jupiter family comet 103P/Hartley 2 has been visited by EPOXI spacecraft on 4 November 2010 at a minimum distance of 694 km, when it was at 1.064 AU from the Sun (A'Hearn et al. 2011). We present the analysis of photometric observations in OH filter acquired by MRI camera onboard EPOXI used to investigate the spatial distribution of OH in the coma of Hartley 2. The data revealed a radial OH structure within 35 km from the nucleus, appearing to be coming directly from the nucleus, in the region of the central waist. A theoretical computation evidencing a strong possibility that this OH structure could be partially associated with OH PE has been performed. This is strongly supported by the agreement of the OH spatial distribution with the water spatial distribution derived from HRI IR spectrometer observations (A'Hearn et al. 2011). Given the results on comet Hartley 2, we present our expectations and preliminary analysis of OH fluorescence and prompt emission mechanisms in the coma of 67P/Churyumov-Gerasimenko, target of the Rosetta mission. The OSIRIS WAC camera on board Rosetta is equipped with 7 narrowband filters centered on molecular emission bands, including the OH gas filter. This will enable us to investigate OH fluorescence and PE at increasing resolution as Rosetta will approach the comet. This analysis, supported by accompanying observations acquired by OSIRIS WAC camera in the forbidden OI band at 630 nm, will help in further constrain the water photochemistry and the fluorescence and PE processes occurring in the cometary comae.

Amplified luminescence of heavily doped AlxGa1-xN structures under optical pumping

NASA Astrophysics Data System (ADS)

Bokhan, P. A.; Zhuravlev, K. S.; Zakrevskii, D. E.; Malin, T. V.; Osinnykh, I. V.; Fateev, N. V.

2018-03-01

Spectral, temporal, and polarisation characteristics of luminescence of heavily doped AlxGa1-xN films on a sapphire substrate are studied under pulsed pumping at the wavelength λ = 266 m. Spectra of spontaneous emission related to donor – acceptor transitions are inhomogeneously broadened with the FWHM of above 0.5 eV and cover the entire visible range. Spectra of radiation emitted from an edge of investigated structure comprise several narrow-band equidistant components, each of them being split to TE and TM modes with mutually orthogonal polarisations. This is related to plane waves propagating inside a plane waveguide along a zigzag path in the conditions of total internal reflection from waveguide surfaces. The optical gains measured for Al0.5Ga0.5N/AlN at λ ≈ 510 nm, Al0.74Ga0.26N/AlN at λ ≈ 468 nm, and AlN/Al0.6Ga0.4N/AlN/Al2O3 at λ ≈ 480 nm were, respectively, ~70, 20, and 44 cm-1. The luminescence quantum efficiencies measured for Al0.74Ga0.26N, Al0.65Ga0.35N, and Al0.5Ga0.5N films are, respectively, 0.79, 0.49, and 0.14; the transition cross sections calculated at emission band centres are ~10-18 cm2.

Emission Behavior of Fluorescently Labeled Silver Nanoshell: Enhanced Self-Quenching by Metal Nanostructure.

PubMed

Zhang, Jian; Fu, Yi; Lakowicz, Joseph R

2007-02-08

Labeled silica beads with an average diameter of 100 nm were synthesized by incorporating with 20-600 μM Ru(bpy)(3) (2+) complexes. Silver shells were deposited on the beads layer-by-layer with the shell thickness of 5-50 nm. The emission band became narrower and the intensity was enhanced depending on the shell thickness. Self-quenching of the probe was observed at high concentration. Poisson statistics were employed to analyze self-quenching of the fluorophores. The estimated quenching distance was extended from 6 to 16 nm with shell growth from 0 to 50 nm. Moreover, the silver shells were also labeled with Rhodamine 6G. Fluorescence enhancement and reduced lifetime were also observed for silver-silica shell containing R6G. We found that by adjustment of probe concentration and silver shell thickness, a Ru(bpy)(3) (2+)-labeled particle could be 600 times brighter than an isolated Ru(bpy)(3) (2+) molecule. We expect labeled metal core-shell structures can become useful probes for high sensitivity and/or single particle assay.

Search for Organic Matter in Leonid Meteoroids

NASA Technical Reports Server (NTRS)

Rairden, Richard L.; Jenniskens, Peter; Laux, Christophe O.; DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

Near-ultraviolet 300-410 nm spectra of Leonid meteors were obtained in an effort to measure the strong B to X emission band of the radical CN in Leonid meteor spectra at 387 nm. CN is an expected product of ablation of nitrogen containing organic carbon in the meteoroids as well as a possible product of the aerothermochemistry induced by the kinetic energy of the meteor. A slitless spectrograph with objective grating was deployed on FISTA during the 1999 Leonid Multi-Instrument Aircraft Campaign. Fifteen first-order UV spectra were captured near the 02:00 UT meteor storm peak on November 18. It is found that neutral iron lines dominate the spectrum, with no clear sign of the CN band. The meteor plasma contains less than one CN molecule per three Fe atoms at the observed altitude of about 100 km.

Fabrication et caracterisation de cristaux photoniques pour exaltation de fluorescence

NASA Astrophysics Data System (ADS)

Gascon, Annabelle

2011-12-01

In today's world, there is a pressing need for point-of-care molecular analysis that is fast, inexpensive and transportable. Lab-on-a- chips are designed to fulfill that need. They are micro-electromechanical systems (MEMS), fabricated with microelectronic techniques, that use the analytes physical properties to detect their presence in liquid samples. This detection can be performed by attaching the analyte to quantum dots. These quantum dots are semiconducting nanoparticles with narrow fluorescence band. In our project, we use a tuneable system with a two-slab photonic crystal that serves as a tuneable optical filter, detecting the presence and wavelength of these quantum dots. Photonic crystals are dielectrics with a variable refractive index, with a period near the visible light wavelength. They are called photonic crystals because they have a photonic band gap just as atomic crystals, periodic structure of atoms, have an electronic band gap. They are photonic because photons instead of electrons propagate through them. They can also enhance fluorescence from quantum dots at the photonic crystals guided resonance wavelength. My project objectives are to: (1) Fabricate two-slab photonic crystal, (2) Characterize photonic crystals, (3) Place quantum dots on photonic crystals, (4) Measure fluorescence enhancement. The device made during this project consists of a silicon wafer on which were deposited a 200 nm silicon nitride layer, then a 200 nm silicon dioxide layer and finally another 200 nm silicon nitride layer. An electron-beam lithography defines the photonic crystals and the MEMS. The photonic crystals are square lattices of holes 180 nm in diameter, at a period of 460 nm, etched through the two silicon nitride slabs. The two slabs are etched in a single step of Reactive Ion Etching (RIE). Then, the silicon under the photonic crystal is etched from the backside up to the nitride by deep-RIE. Finally, the oxide layer is removed in order to completely suspend the two-slab photonic crystal. The M EMS can change the gap between the two slabs in order to tune the guided resonance wavelength. An optical set-up is used to trace the photonic crystals transmission and reflection spectrum, in order to know the guided resonance position. A supercontinuum source illuminates the device at a normal incidence angle for wavelength between 400 nm and 800 nm. High-resolution spectra are obtained with a CCD camera spectrometer. Different types of one-slab photonic crystals are analyzed with this approach: we observe guided resonance peaks near 550 nm, 615 nm and 700 nm. Finally, a quantum dots microdrop is placed on the photonic crystal. The quantum dots emission wavelength matches with the photonic crystal guided resonance. A hyperspectral fluorescence microscope excites quantum dots between 436 nm and 483 nm, detects emission greater than 500 nm and plots a fluorescence wavelength spectrum. This set-up measures and compares the fluorescence of the quantum dots placed on and next to the photonic crystals. Our results show that the fluorescence is 30 times higher on the photonic crystals, but the fluorescence wavelength corresponds neither to the quantum dots emission nor to the photonic crystal guided resonance. In conclusion, this master thesis project demonstrates that it is possible to fabricate two-slab photonic crystals in silicon nitride and to plot their transmission and reflection spectra in order to find their guided resonance position. A fluorescence enhancement is visible, but at a different wavelength than of the quantum dots.

The effect of citric acid on morphology and photoluminescence properties of white light emitting ZnO-SiO2 nanocomposites

NASA Astrophysics Data System (ADS)

Sivakami, R.; Thiyagarajan, P.

2016-07-01

The white light emitting ZnO-SiO2 nanocomposites were synthesized by sol-gel combustion method using zinc nitrate, citric acid and tetraethoxysilane. To analyze the effect of fuel content on the photoluminescence properties of ZnO-SiO2 nanocomposites, the citric acid content was varied as 1, 5, and 10 moles with respect to one mole of zinc. The SEM images of the nanocomposites revealed the spherical, flower and platelet like morphology with variation in citric acid content and annealing temperatures. The ZnO-SiO2 nanocomposites prepared with various Zn:CA ratio excited at UV (280 nm), near UV (365 nm), violet (405 nm) and blue (465 nm) wavelength showed blue and greenish-yellow emission. Among all ratios, the ZnO-SiO2 nanocomposites with Zn:CA - 1:1 ratio showed the intense broad band emission compared to Zn:CA - 1:5 and 1:10 values. This particular composition of sample excited under violet (405 nm) LED source shows white light, as confirmed by the CIE chromaticity coordinates (x = 0.342, y = 0.318).

Synthesis and luminescence properties of CaSnO3 :Bi3+ blue phosphor and the emission improvement by Li+ ion.

PubMed

Cao, Renping; Zhang, Jinlong; Wang, Wudi; Hu, Qianglin; Li, Wensheng; Ruan, Wen; Ao, Hui

2017-09-01

CaSnO 3 :Bi 3+ blue-emitting phosphor was synthesized using a high-temperature solid-state reaction method in air. The crystal structures and luminescence properties were investigated. A broad emission band peaking at ~448 nm upon excitation at 262 and 308 nm was observed in the range 330-680 nm at room temperature due to 3 P 1  →  1 S 0 transition of the Bi 3+ ion. The chromaticity coordinate was (0.1786, 0.1665). The optimal Bi 3+ ion concentration was ~0.6 mol% in CaSnO 3 :Bi 3+ phosphor. The emission spectrum of CaSnO 3 :Bi 3+ phosphor showed a blue-shift with increasing temperature from 50 to 300 K due to the influence of temperature on the electron transition of the Bi 3+ ion. The emission intensity of CaSnO 3 :Bi 3+ phosphor may be increased ~1.45 times by co-doping Li + ions as a charge compensator and fluxing agent. The luminescence mechanism is explained by a configurational coordinate diagram of Bi 3+ ion in CaSnO 3 :Bi 3+ phosphor. Copyright © 2017 John Wiley & Sons, Ltd.

Emission intensity of the λ = 1.54 μm line in ZnO films grown by magnetron sputtering, diffusion doped with Ce, Yb, Er

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mezdrogina, M. M., E-mail: margeret.m@mail.ioffe.ru; Eremenko, M. V.; Smirnov, A. N.

2015-08-15

The effect of the Er{sup 3+}-ion excitation type on the photoluminescence spectra of crystalline ZnO(ZnO〈Ce, Yb, Er〉) films is determined in the cases of resonant (λ = 532 nm, Er{sup 3+}-ion transition from {sup 4}S{sub 3/2}, {sup 2}H{sub 11/2} levels to {sup 4}I{sub 15/2}) and non-resonant (λ = 325 nm, in the region near the ZnO band-edge emission) excitation. It is shown that resonant excitation gives rise to lines with various emission intensities, characteristic of the Er{sup 3+}-ion intracenter 4f transition with λ = 1535 nm when doping crystalline ZnO films with three rare-earth ions (REIs, Ce, Yb, Er) ormore » with two impurities (Ce, Er) or (Er, Yb), independently of the measurement temperature (T = 83 and 300 K). The doping of crystalline ZnO films with rare-earth impurities (Ce, Yb, Er) leads to the efficient transfer of energy to REIs, a consequence of which is the intense emission of an Er{sup 3+} ion in the IR spectral region at λ{sub max} = 1535 nm. The kick-out diffusion mechanism is used upon the sequential introduction of impurities into semiconductor matrices and during the postgrowth annealing of the ZnO films under study. The crystalline ZnO films doped with Ce, Yb, Er also exhibit intense emission in the visible spectral region at room temperature, which makes them promising materials for optoelectronics.« less

High luminescent L-cysteine capped CdTe quantum dots prepared at different reaction times

NASA Astrophysics Data System (ADS)

Kiprotich, Sharon; Onani, Martin O.; Dejene, Francis B.

2018-04-01

This paper reports a facile synthesis route of high luminescent L-cysteine capped CdTe quantum dots (QDs). The effect of reaction time on the growth mechanism, optical and physical properties of the CdTe QDs was investigated in order to find the suitability of them towards optical and medical applications. The representative high-resolution transmission microscopy (HRTEM) analysis showed that the as-obtained CdTe QDs appeared as spherical particles with excellent monodispersity. The images exhibited clear lattice fringes which are indicative of good crystallinity. The X-ray diffraction (XRD) pattern displayed polycrystalline nature of the QDs which correspond well to zinc blende phase of bulk CdTe. The crystallite sizes calculated from the Scherrer equation were less than 10 nm for different reaction times which were in close agreement with the values estimated from HRTEM. An increase in reaction time improved crystallinity of the sample as explained by highest peak intensity of the XRD supported by the photoluminescence emission spectra which showed high intensity at a longer growth time. It was observed that for prolonged growth time the emission bands were red shifted from about 517-557 nm for 5-180 min of reaction time due to increase in particle sizes. Ultraviolet and visible analysis displayed well-resolved absorption bands which were red shifted upon an increase in reaction time. There was an inverse relation between the band gap and reaction time. Optical band gap decreases from 3.98 to 2.59 eV with the increase in reaction time from 15 to 180 min.

Optical absorption and emission bands of Tm 3+ ions in calcium niobium gallium garnet crystal

NASA Astrophysics Data System (ADS)

Tsuboi, Taiju; Tanigawa, Masayuki; Shimamura, Kiyoshi

2000-12-01

Absorption spectra of Tm 3+ ions in Ca 3Nb 1.6875Ga 3.1875O 12 (CNGG) crystal have been investigated at various temperatures between 15 and 296 K. Luminescence spectra in a spectral region of 400-1750 nm are investigated under excitation into various excited states of Tm 3+ and the conduction band of CNGG at room temperature. The absorption and emission bands of Tm 3+ in CNGG are observed to be broader than those observed in other Tm 3+-doped crystals such as LiNbO 3. This is due to the disordered structure of CNGG. From the temperature dependence of absorption spectra, five Stark levels are derived for the 3H 6 ground state. The highest Stark level is found to be 351 cm -1 above the ground level. It is suggested that the low efficiency of the 2.02 μm lasing at room temperature is due to the narrow splitting of the Stark levels.

Sampling modulation technique in radio-frequency helium glow discharge emission source by use of pulsed laser ablation.

PubMed

Naeem, Tariq Mahmood; Matsuta, Hideyuki; Wagatsuma, Kazuaki

2004-05-01

An emission excitation source comprising a high-frequency diode-pumped Q-switched Nd:YAG laser and a radio-frequency powered glow discharge lamp is proposed. In this system sample atoms ablated by the laser irradiation are introduced into the lamp chamber and subsequently excited by the helium glow discharge plasma. The pulsed operation of the laser can produce a cyclic variation in the emission intensities of the sample atoms whereas the plasma gas species emit the radiation continuously. The salient feature of the proposed technique is the selective detection of the laser modulation signal from the rest of the continuous background emissions, which can be achieved with the phase sensitive detection of the lock-in amplifier. The arrangement may be used to estimate the emission intensity of the laser ablated atom, free from the interference of other species present in the plasma. The experiments were conducted with a 13.56 MHz radio-frequency (rf) generator operated at 80 W power to produce plasma and the laser at a wavelength of 1064 nm (pulse duration:34 ns, repetition rate:7 kHz and average pulse energy of about 0.36 mJ) was employed for sample ablation. The measurements resulted in almost complete removal of nitrogen molecular bands (N(2)(+) 391.44 nm). Considerable reduction (about 75%) in the emission intensity of a carbon atomic line (C I 193.03 nm) was also observed.

Detection of low-concentration ammonia using differential laser-induced fluorescence on vapochromic coordination polymers

NASA Astrophysics Data System (ADS)

Yin, Dawei; Chapman, Glenn H.; Stevens, David; Gray, Bonnie; Leznoff, Daniel

2018-02-01

The detection of ammonia in parts per millions range has been challenging in sensors research, and is of great importance for industrial applications. In previous literature, Vapochromic Coordination Polymers (VCP) were developed to achieve luminescence upon a targeted gas exposures. We investigate a specific VCP, Zn[Au(CN)2]2,as an ammonia sensing material. Upon high concentration ammonia exposure, the fluorescent peak under near-UV stimulation undergoes a spectral shift from 460nm to 520nm, while the intensity increases by 3 4X. However, at ammonia concentrations < 50ppm, the spectral shift becomes hidden within the overall changing fluorescent spectrum shape. Then simple methods, such as detecting the peak wavelength or subtracting post-exposure from pre-exposure spectrums do not work. We developed further excitation and data processing techniques to detect ammonia at lower concentrations. A low-cost 405nm blue-ray DVD laser diode was used as the excitation source, providing a narrow band-width (4nm) stimulation that is separated from the emission peak. We measured the emission using a portable spectrometer (Photon Control SPM-002), and processed the data by separating the spectrum into two regions; (A) from 425 nm to 460 nm and (B) from 460nm to 500nm. Next, the integrated emissions under both regions were computed, and the value of shorter wavelength region (A) was subtracted from the longer wavelength one (B). When exposed to ammonia, region (A) reduces overall intensity while region (B) increases, resulting a signal starting from negative value and gradually increases to positive values, enabling the detection of 5ppm ammonia in less than 30 seconds gas exposure.

Transformation of plastids in soil-shaded lowermost hypocotyl segments of bean (Phaseolus vulgaris) during a 60-day cultivation period.

PubMed

Kakuszi, Andrea; Solymosi, Katalin; Böddi, Béla

2017-04-01

The maintenance but substantial transformation of plastids was found in lowermost hypocotyl segments of soil-grown bean plants (Phaseolus vulgaris cv. Magnum) during a 60-day cultivation period. Although the plants were grown under natural light-dark cycles, this hypocotyl segment was under full coverage of the soil in 5-7 cm depth, thus it was never exposed to light. The 4-day-old plants were fully etiolated: amyloplasts, occasionally prolamellar bodies, protochlorophyllide (Pchlide) and protochlorophyll (Pchl) were found in the hypocotyls of these young seedlings. The 633 and 654 nm bands in the 77 K fluorescence emission spectra indicated the presence of Pchlide and Pchl pigments. During aging, both the Pchlide and Pchl contents increased, however, the Pchl to Pchlide ratio gradually increased. In parallel, the contribution of the 654 nm form decreased and in the spectra of the 60-day-old samples, the main band shifted to 631 nm, and a new form appeared with an emission maximum at 641 nm. The photoactivity had been lost; bleaching took place at continuous illumination. The inner membranes of the plastids disappeared, the amount of starch storing amyloplasts decreased. These data may indicate the general importance of plastids for plant cell metabolism, which can be the reason for their maintenance. Also the general heterogeneity of plastid forms can be concluded: in tissues not exposed to light, Pchl accumulating plastids develop and are maintained even for a long period. © 2016 Scandinavian Plant Physiology Society.

Research on up- and down-conversion emissions of Er3+/Yb3+ co-doped phosphate glass ceramic

NASA Astrophysics Data System (ADS)

Ming, Chengguo; Song, Feng; An, Liqun; Ren, Xiaobin; Yuan, Yize; Cao, Yang; Wang, Gangzhi

2012-12-01

By high-temperature melting method and thermal treatment technology, Er3+/Yb3+ co-doped phosphate glass and glass ceramic samples were prepared. The luminescence spectra of the glass and glass ceramic samples were studied under 975 nm excitation. In visible and near-infrared bands, the emission intensity of the glass ceramic is stronger than that of the glass. The glass ceramic can comprehensively improve the luminous characters of the precursor glass. The phosphate glass ceramic will be valuable luminescence materials.

Syntheses of nanocrystalline BaTiO3 and their optical properties

NASA Astrophysics Data System (ADS)

Yu, J.; Chu, J.; Zhang, M.

Stoichiometric and titanium-excess nanocrystalline barium titanates were synthesized using a hydrothermal process at various hydrothermal temperatures and with further heat treatment at 500 °C and 900 °C. Owing to the different process conditions, the excess titanium exists in different states and configurations within the nanocrystalline BaTiO3 matrix; this was demonstrated by X-ray diffraction, Raman scattering, and photoluminescence. In these nanocrystalline BaTiO3, the 590, 571, 543 and 694 nm light emission bands were observed; mechanisms leading to such emissions were also discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, J.; Yang, D. L.; Gong, H.

Conventional visible and novel infrared (IR) emissions of Sm{sup 3+} in heavy-metal-gallate glasses (Li{sub 2}O-K{sub 2}O-BaO-PbO-Bi{sub 2}O{sub 3}-Ga{sub 2}O{sub 3}, LKBPBG for short) with low phonon energy have been observed. Judd-Ofelt parameters {Omega}{sub 2} (3.00x10{sup -20} cm{sup 2}), {Omega}{sub 4} (5.19x10{sup -20} cm{sup 2}), and {Omega}{sub 6} (1.69x10{sup -20} cm{sup 2}) indicate a higher asymmetry and stronger covalent environment in the optical glasses. For the visible fluorescence bands peaked at 564, 601, 648, and 710 nm, the maximum stimulated emission cross-sections ({sigma}{sub e}) were derived to be 1.35x10{sup -22}, 9.21x10{sup -22}, 9.58x10{sup -22}, and 3.91x10{sup -22} cm{sup 2}, respectively, themore » values are larger than those in phosphate, oxyfluoroborate, tellurite, and calibo glasses obviously. The observed 1185 nm IR emission lies in the low-loss window of telecommunication system, and the maximum value of {sigma}{sub e} for this band was obtained to be 6.09x10{sup -23} cm{sup 2}. The characterization of multichannel radiative transitions of Sm{sup 3+} in LKBPBG glasses is beneficial in exposing its potential applications in visible and IR optoelectronic devices.« less

Role of Ni2+(d8) ions in electrical, optical and magnetic properties of CdS nanowires for optoelectronic and spintronic applications

NASA Astrophysics Data System (ADS)

Arshad Kamran, Muhammad

2018-06-01

For the first time, 1D Ni ion doped CdS nanowires (NWs) were synthesized via chemical vapour deposition (CVD). The synthesized Cd0.886Ni0.114S NWs were single crystalline. We have reported here the investigation of optical, electrical and magnetic properties of prepared NWs for optoelectronic and spintronic applications. Successful incorporation of Ni ions in an individual CdS NW has been confirmed through several characterization tools: significantly higher angle and phonon mode shift were observed in the XRD and Raman spectra. SEM-EDX and XPS analysis also confirmed the presence of Ni2+ ions. Room temperature photoluminescence (RT-PL) showed multiple peaks: two emission peaks in the visible region centered at 517.1 nm (green), 579.2 nm (orange), and a broad-band near infra-red (NIR) emission centered at 759.9 nm. The first peak showed 5 nm red shift upon Ni2+ doping, hinting at the formation of exciton magnetic polarons (EMPs), and broad NIR emission was observed in both chlorides and bromides, which was assigned to d‑d transition of Ni ions whose energy levels lying at 749.51 nm (13 342 cm–1) and 750.98 nm (13 316 cm–1) are very close to NIR emission. Orange emission not only remained at same peak position—its PL intensity was also significantly enhanced at 78 K; this was assigned to d‑d transition (3A2g → 1Eg) of Ni2+ ions. It was observed that 11.4% Ni2+ ion doping enhanced the conductivity of our sample around 20 times, and saturation magnetization (Ms) increased from 7.2 × 10‑5 Am2/Kg to 1.17 × 10‑4 Am2/Kg, which shows promise for optoelectronic and spintronic applications.