最新刊期
卷 29 ， 期 6 ， 2008
- 摘要：Rare earth activated nanophosphors have attracted extensive attention because of their potential applications in lighting, display and fluorescence bio-label, and also of their elementary importance on under-standing of the 4fN electronic transition properties of rare earth ions in nanosized particles.In the latest ten years, a great number of improvements have been achieved in this field.In this review article, we mainly present some important research results on photo luminescence properties of rare earth doped oxide nanophos-phors.The contents concern exciton and charge transfer transitions, symmetry sites and local environmentssurrounding rare earth ions, radiative transition and nonradiative relaxation processses on 4fN states, tempra-ture-quenching and concentration-quenching of luminescence, energy transferamong rare earths, electron-pho-non coupling, ultravoilet irradiation induced spectral change andetc.Besides, the luminescence properties ofrare earth actived one-dimensional oxide nanowires(tubes, rods)and upconversion nanophosphors were intro-duced independently.It is expected thatmore universal conclusions relative to nanoparticle size and structureon the photolum inescence of rare earth actived nanoparticles can be drawn, however, it should be noted that some results introduced here might be still controversal, because some photolum inescence properties depend strongly on the preparation technique and detailed conditions.关键词：rare earth;nanocrystal;photoluminescence;surface effec;tenergy transfer152|64|9更新时间：2020-08-12
- 摘要：We configured reaction solution using zinc acetate [Mg(CH3COO)2·H2O] and methenamine (C6H12N4) with a certain percentage, magnesium acetate [Mg(CH3COO)2·H2O] was added appropriately in the reaction so-lution.High quality ZnO microrods were prepared on the silicon substrate at 90℃ for 24 h by hydro ther malmethod.Surfacemorphology and crystal structure of ZnO microrods are analyzed, using scanning electronmicroscopy (SEM)and X-ray diffraction (XRD).The results show the sample presents a rod-like shape with a hexagonal cross sectionsand typicalmorphology of wurtzite ZnO.The ratio of length and diameterof the ZnO rod is about10:1.And the ZnO microrods grow along [002] direction.Mg ions are not found in the sample, which probably played the role ofa cata-lyst.Photo luminescence (PL) spectrum of ZnO microrodswasmeasured.Room-temperature PL spectrum of the sam-ple shows an UV luminescence peak located at 384 nm, and the FWHM of the emission peak is only 13 nm, intensity of UV luminescence peak is stronger than thatofvisible luminescence peak, indicating the high quality of the sample.关键词：ZnO microrods;hydrothermalmethod;photoluminescence117|89|0更新时间：2020-08-12
- 摘要：The Sr3B2O6:Tb3+ Li+, green phosphor was synthesized by the general high temperature solid-state reaction and its luminescence properties were investigated.It shows four major emission peaks locating at 495,548,598 and 625 nm corresponding to the 5D4→7F6,5D4→7F5,5D4→7F4 and 5D4→7F3 typical transitions of Tb3+,respectively,and the strongest one appears at 548 nm.The excitation spectrum contains a broad band extending from 200 nm to 400 nm,which is coupled well with the emission of ultraviolet light-emitting diodes (UVLEDs).The influences of doped-Tb3+ concentration and charge compensation of Li+ on the emission intensity were also investigated.The Sr3B2O6:Tb3+ is a kind of potential green-emitting phosphor for white light emitting diode (w-LED).关键词：Sr3B2O6：Tb3+;Li+;luminescence95|54|7更新时间：2020-08-12
- 摘要：The novel 2D leaf-like zinc dendritic structures have been synthesized on ZnO buffer layer coated onto Si substrates.The growth process is described as free-catalyst,self-assembly and vapor-solid growth mode.The length of the Zn dendrite is about dozens of micrometers and its thickness is about 200 nm.The fastest growth direction of the dendrites is along the carrier gases downstream direction to release the latent heat of solidification.After the zinc dendrites have the thermal process in oxygen ambient,the slim and uniform ZnO nanowires are grown on the surface of Zn dendrites.The results of XRD analysis indicated that the ZnO nanowires are with a hexagonal wurtzite structure.The growth mechanisms of Zn/ZnO structures were investigated.The PL spectrum of Zn/ZnO dendritic structures shown that a weak UV near-band-edge emission is at 380 nm and a strong green emission is centered at 505 nm.The green emission is attributed to radiation transition of donor-acceptor pair.关键词：thermal evaporation;zinc oxide;microstructure;photoluminescence106|76|0更新时间：2020-08-12
- 摘要：Photophysical, electrochemical and optoelectronic properties of a conjugated polymer, poly (p-phenylene benzobisoxazole)(PBO) were investigated.Due to its delocalized π electrons in chemical structure, thematerial is low in solubility, excellent in thermo-oxidative stabilities and mechanical properties; it becomes increasingly important inmany applications.This work focused on the photophysicalproperties, in particular the luminescence property of PBO and its preliminary lightemitting device fabrication.The properties of thematerialwere investigated using absorption, and luminescence spectrometries, cyclic voltammetry.Photoluminescence from PBO solutionwere in the range of 430~500 nm.Concentration dependencewas observed.Photoluminescence of the film peaked at 500 nm.Itwas indicated that the emission shift from solutions is due to the intermolecular interaction.Through electro-chemical analysis of the polymer the highestlevel occupied molecular orbital (HOMO) is about EHOMO=5.69eV, through spectral analysis the lowestunoccupiedmolecularorbital energy (LUMO) is about ELUMO=2.99eV.Singlelayer and double-layer lightemitting deviceswere prepared, which have structures as follows: (a)ITO/PBO(60 nm)/Al for the single-layerdevice, and (b)ITO/CuPc(25 nm)/PBO(60 nm)/Al double-layer device.Their currentvoltage characteristicswere analyzed and compared.Although CuPc absorbed in visible, itshowed a transmittedwindow around green spectral range.This allows the light from the device through as it emitted in green around 520 nm.Brightness and stabilityweremuch improved in double-layerdevices.However a voltage-dependentcolour changewas observed for the doublelayerdevice.The electroluminescence intensity is increased as the voltage increase, which reaches amaximum at 21V.The red shift isobserved in the emission spectra as the driving voltage increased.It is predicted that thismay be related to excitation state of PBO at the different field strength, which requires further investigation in the future.关键词：PBO;conjugated polymer;electroluminescentdevice103|91|0更新时间：2020-08-12
- 摘要：It is effectivemethod to enhance brightness and to change emission colorby doping fluorescentdye in active layer oforganic lightemitting diodes (OLEDs).The energy transfer in the blend films is significant information of the devices to understand the excited state process.In this paper, the luminescence properties of the PVK:DCJTB blend film was studied.The results show that the efficiency ofenergy transfer from PVK to DCJTB is increased as the concentration of DCJTB changed from 1% to 2%, but it is not complete yet.The emission of PVK was obviously reduced by the introduction of Alq3 layer to form doublelayer film PVK:DCJTB/Alq3.The layer of Alq3 plays a energy transfer "bridge" role in the double-layer film.It is obviously differentbetween EL and PL spectra of the devicewith the structure of ITO/PVK:DCJTB/Alq3/LiF/Al.The emission of Alq3 is relative strong in EL than that in PL, and the intensity of Alq3 emission is enhanced with the increase of drive voltage.It is because that the recombination probability of electrons and holes is increased in the Alq3 layerby increase of the numberof injected holes as the increase of electric field in the device.The result of this paper ismeaningful for the understanding of energy transfer in the blend films aswell as the recombination zone in the double-layer devices.关键词：energy transfer;organic electroluminescence;photoluminescence;doping107|95|0更新时间：2020-08-12
- 摘要：The performance of organic light emitting devices (OLEDs) is closely related to the electric field intensity and carrierdensity distribution in the organic layer.Based on the drift-diffusion theory for themotion of charge carriers, we considered the OLED structure consists of a single layerof luminescentor ganicmaterial sandwiched between twometallic electrodes, the contacts between themetallic electrodes and organicmaterial are ohmic.We adopted themethod of numerical calculation to study the potential, electric field intensity, carrier density and recombination rate in the organicmaterial.The results shown these:(1) when holes and electrons have the same mobility, the distribution of the potential, electric field, carrierdensity and recombination rate is symmetrical.This is because the in fluence of two differentcarriers injection is the same.Mostcarriers distribute near the electrodes and decrease very fast, the interface of metal/semiconductor contact is just like a carrier packet and the carrierdensity is very low in the middle of the device, so the electric fieldsnear the two contacts aremuch stronger than that in themiddle.(2)When themobility of holes and electronsdiffersgreatly, the highermobility carriers can notonly distribute near the injecting electrode butalso transmit to another electrode.However, the lowermobility carriers distri-butemainly near the injecting electrode.When themobility difference of electron and hole is small, the distri-bution of the carriers isbetween the above two cases.When the ratio of holemobility to electronmobility changes, the position of themaximum of the electric fieldmoves to the electrode from which the lowmobility carriers are in jected.关键词：organic electroluminescence;mobility;carrier distribution;numerical calculation133|96|1更新时间：2020-08-12
- 摘要：Indium-tin oxide (ITO) film on flexible polyethylene terephthalate (PET) substrateswere prepared by DC magnetron sputtering deposition method.The effects of substrate temperature, sputtering power and pressure on ITO film propertieswere investigated.The results shown that ITO filmswith a low square resistivity of 50Ω/□ and a high transmittance in visible region over 90% can be achieved ata DC power of 100W, working pressure of 2.66×10-1Pa and substrate temperature of 50℃.Using the fabricated flexible ITO substrate as the anode, the organic light-emitting device consisting of PET/ITO/NPB/Alq3/Mg:Ag is fabricated.The obtained FOLEDs have amaximum luminance of 2834 cd/m2 at 13 V.关键词：organic light-emitting devices (OELDs);flexible substrate;ITO thin films;DCmagnetron sputtering83|99|0更新时间：2020-08-12
- 摘要：Owing to its properties of high-luminescent efficiency, chemical stability and wetresistence,Zn2SiO4 exhibitsmore excellent performance than the sulfides as luminescent hostmaterial. Zn2SiO4:Mn2+ (willemite) is an efficient phosphor for plasma display, cathodoluminescent and electroluminecent displays.Over the past few decades, researchers have studied intensely about factors influencing on the photolumines-centproperties of Zn2SiO4:Mn2+, such as calcining temperatures, concentration of Mn2+, atmosphere of heat treatment, various preparationmethods.However, the pH value of the Zn2SiO4:Mn2+ precursor sol also plays an important role in its luminescent properties.Herein, we investigate the effects of pH value of the precursor sol, heating atmosphere (oxidizing, neutralprotecting and reducing) and calcining temperature on the photo-luminescent intensity of Zn2SiO4:Mn2+ phosphor powder.Zn2SiO4:Mn2+ phosphors have been prepared via a solgel route.DifferentpH values of the sol resulted in differentgeling time and the sol with pH value lower than 3 could notbe gelatinized.After preheating at 600℃, Zn2SiO4:Mn2+ precursorswere calcined in different atmosphere (air, N2 and mixture of 10% H2+90% N2) atheating temperature varing from 800℃ to 1100℃.The structure of Zn2SiO4:Mn2+ has been characterized by X-ray diffraction (XRD), which shows thatall the phase of phosphors is with α-Zn2SiO4phase.The phosphor prepared from the sol with pH of 4.34 has the best crystallinity.Scanning electronmicroscope (SEM) is used tomeasure the particle size of the Zn2SiO4:Mn2+ phosphors and the mean size of the phosphor obtained from the solwith pH value of 4.34 is about 100 nm, larger than the size of the phosphors obtained from sols with pH values of 5.32 and 6.53.The results of photoluminescent (PL) spectra indicate that the PL intensity of the phosphor increaseswith increasing the pH value ofprecursor sol, and themaximum was obtainedwhen the pH value of precursor sol is 4.34.Because the phosphor obtained from the sol with pH value of 4.34 has bestcrystallinity, and its particle size is larger, leading to smaller specific surface area.When the specific surface area is smaller, there are lower defects in the surface ofparticles and fewernonradiative transitions appear.Additionally, the hydrolysis and polyconden-sation reactions of the precursor solwith pH value of 4.34 have been carried throughly and properly, resulting in the well dispersion of the Mn ions.The emission intensity of Zn2SiO4:Mn2+ phosphors calcined in themixture of nitrogen and hydrogen is stronger than those of the phosphors calcined in the other heating at mosphere.Reducing atmosphere could easily split Mn-Mn pair and produce large number of is olated Mn ions.With H2 existing in the heating at mosphere, more Zn ions in cline to be volatilized and more Mn ionswould substitute for Zn ions.There fore, the PL intensity of Zn2SiO4:Mn2+ phosphors is the strongestwhen the pH value of the precursor sol is 4.34 and the phosphors are calcined in the mixture of N2 and H2 at 900℃.关键词：Zn2SiO4：Mn2+;solgel;pH value;calcining ambience;photoluminescent109|63|0更新时间：2020-08-12
- 摘要：Eu2+ doped BaAl12O19 phosphorswere prepared by using the sol gelmethod, and their structure and luminescence propertieswere characterized by X-ray diffraction(XRD) analysis and fluorescence spectrometry.The results showed thata single hexagonal BaAl12O19 crystal structurewas synthesized and the emission spectrum of BaAl12O19:Eu exhibited a broad asymmetric band, which was composed of three emission peaks at 438, 462, 511 nm, respectively.The position and intensity of emission band were affected by crystallization temperature, Eu2+ concentration and Al3+ content. With crystallization temperature increasing, the emission intensity of 438 nm significantly increaseed, but the emission intensity of 511 nm decreaseed.With Eu2+ concentration increasing, the emission peak shifted to longerwavelength.The optimum concentration of Eu2+ was 10%.The emission intensity increased effectively in blue light region and decreased in green light region by Al3+ content reducing.关键词：BaAl12O19：Eu2+;luminescence properties;lattice position91|58|0更新时间：2020-08-12
- 摘要：The cerium-doped yttrium aluminum garnet(YAG:Ce) phosphor is commonly used in white LED as the luminescence converter.The thermal quenching property of YAG:Ce3+ phosphor has important effects on the luminous efficiency, photo-chromic parameters and reliability ofwhiteLED athigh temperature.In this paper, Y3-xCexAlO12(and Y2.93-yCe0.07MyAl5O12(M=Lu, Gd) phosphorswere prepared by the high tempe-rature solidstate reaction method.The temperature-dependent photoluminescence properties of these phos-phorswere investigated under the excitation of 460 nm blue light.It is observed that the temperature has great influences on the photoluminescence properties of YAG:Ce3+ phosphors.With the temperature increasing, the relative brightness is decreased and the emission band shifts toward the red.For Y2.93Al5O12:Ce0.07, the relative brightness at 150℃ is only 89% comparedwith thatat the room temperature, and the emission band shifts toward the red for about 10 nm.The Ce3+ concentration has no obvious effecton the thermalquenching properties of YAG:Ce3+.For Ludoped YAG:Ce3+ phosphors, the blue shift of the emission spectra is observed because of the introduction ofLu3+ion which has a smaller ion radius than that of Y3+ ion.The emission peak shifts to the blue for about 15 nm as the concentration ofLu increases from 0 to 2.5.It is also noted that the Lu3+ substitution for Y3+ has an improvementon the thermalquenching property of YAG:Ce3+ phosphor.The relative brightness of Y2.93-yCe0.07LuyAl5O12 phosphors with different y values retains above 94% at 150℃ compared with that at the room temperature.The relative brightness of Lu2.93Al5O12:Ce0.07 phosphor changes very little at elevated temperature, and falls only by 3% at 150℃ comparedwith its brightness at room temperature.TheGd substitution for Y3+ can shift the emission spectra of YAG:Ce3+ toward longerwavelength, at the expense ofdeteriorating the thermal quenching property.The red shiftof the emission peak with Gd-doped YAG:Ce3+ phosphorswasmeasured up to 35 nm with the concentration of Gd increasing from 0 to 2.5%.At the same time, the emission intensity is falling down rapidly.With the concentration of Gd increasing, the thermalquenching properties of Gd-doped YAG:Ce3+ phosphors are alsoworsened.At 150℃, the Y2.93-yGdyAl5O12:Ce0.07 phosphorwithy 0.5 only can retain 78% of its luminance atroom tempera-ture, lower than that of undoped YAG:Ce3++phosphor.The relative brightness of Y2.93-yCe0.07MyAl5O12:Ce0.07 phosphor withy 2.5 is below 90% when temperature is above 60℃, and drop to 30% at 150℃关键词：white LED;YAG：Ce3+ phosphors;thermal quenching151|81|12更新时间：2020-08-12
- 摘要：Phosphors Ba3MgSi2O8:Eu,Mn,Al in application of white light emitting diodes(WLEDs)have been synthesized by sol spray-microwave calcining process,as well as solid state reaction,respectively.Samples prepared by sol spray-microwave calcining method with higher purity and better crystallinity according to XRD results,show three emission bands locating at 437,500 and 608 nm,which give the expected white light with color coordinates x=0.3253,y=0.2134,correlated color temperature (CCT) 7391 K under rexcitation of 375 nm ultraviole.t Samples from solid state reaction, however, show only the former two peaks under the same excitation, and take on bluish greenwith color coordinates x=0.2210,y=0.3730.关键词：Ba3MgSi2O8：Eu;Mn;Al phosphor;microwave calcining synthesis;spray drying;energy transfer;white light emitting diodes101|73|4更新时间：2020-08-12
- 摘要：Over the past decades,there has been a significant interest in the production of new materials for multicolor displays.A new technique for solid-state color displays has been developed based upon infrared to visible frequency upconversion in lanthanide doped materials.The three primary colors red,green and blue can be obtained from upconversion luminescence of Er3+,Pr3+,Ho3+ and Tm3+ etc.However the relative intensities of the three primary colors are still required to control.Thus,it is necessary to develop novel mate-rials capable of multicolor upconversion and investigate their upconversion mechanisms of rare earth ions employed.Rare earth doped fluoride crystals is one of the most attractive materials for near-infrared to visible upconversion because its low phonon energies.In this work,we present intense multicolor upconversion luminescence in Er3+/Tm3+ codoped NaYbF4.The relation between upconversion intensity of three fundamental colors and the dopant concentration was discussed and the corresponding upconversion mechanism was proposed.The generation and control of the primary colors through upconversion of Tm3+ and Er3+ in NaYbF4 with single excitation(980 nm)were obtained.The hexagonal NaYbF4:Er3+,NaYbF4:Tm3+,NaYbF4:Er3+/Tm3+ upconverting phosphors have been prepared by hydrothermal method under 220℃ for 48 h.The crystal structure and luminescent properties were investigated by using powder X-ray diffraction,diffuse reflectance absorption spectra and fluorescent spectra.The result of powder XRD spectra reveals that Er3+ and Tm3+ ions can incorporate completely into hexagonal NaYbF4 lattice at any concentration by mild hydrothermal method.The diffuse reflectance absorption spectra shows that the absorption peak band centered at 957 nm corresponds to 2F7/2→2F5/2 transition of /Yb3+ ion for NaYbF4,and the absorption peaks of NaErF4 or NaTmF4 could be assigned to the transitions from ground state of Er3+(4I15/2)or Tm3+(3H6)to excited states.Under 980 nm excitation,hexagonal NaYbF4:Er3+ can emit strong green and,red emission,which correspond to(2H11/2,4S3/2)→4I15/2,4F9/2→4I15/2 transition of Er3+,respectively.NaYbF4:Tm3+ exhibit intense blue upconversion emission,which is attributed to 1D2→3F4 and 1G4→3H6 transition of Tm3+.The emission intensity of blue transitions(1G4→3H6,1D2→3F4)is enhanced considerably as increasing Yb3+ content and reach the optimum at NaYbF4:Tm3+.We agree with the view that the excitation is mobile within the NaYbF4 lattice,it could thus readily reach the Tm3+ traps,which cause the high relative intensity of the two blue emissions(1G4→3H6,1D2→3F4).Tm3+ and Er3+ ions can be easily codoped in NaYbF4 lattice through the mild hydrothermal route,and an energy transfer between Tm3+ and Er3+ exists under 980 nm laser excitation:1D2(Tm3+)+4I15/2(Er3+)→3F4(Tm3+)+4S3/2 or 2H11/2(Er3+),1G4(Tm3+)+4I15/2(Er3+)→3H6(Tm3+)+4S3/2 or 2H11/2(Er3+).The relative ratio of green,red and blue emission intensity can be tuned by defining Tm3+ and Er3+ ion concentration in the NaYbF4 lattice,and through which,a white light simulation could be obtained in the Tm3+ and Er3+ codoped NaYbF4.关键词：upconversion;white light;hydrothermal synthesis;luminescence;complex fluoride105|67|3更新时间：2020-08-12
- 摘要：Upconversion of rare-earth ions has been paid more attention because of its application in visible laser and display area.Nd:KGW radiated yellow-orange luminescence under excitation of 808 nm diode laser,and the upconversion spectrum was measured.The upconversion emission peak wavelengths are at 657,631,610,596 and 540 nm.We analyzed the mechanism,and discussed the effect of upconversion on the infrared laser of Nd ions.The feasibility of Nd upconversion laser is also discussed.For comparison,the upconversion emission spectrum of Nd:YLF was also measured.The results indicated that the photon avalanche process was happened when high-doped Nd:KGW was excited by high power 808 nm LD,and yellow-green upconversion luminescence happened in the two materials doped with Nd ions.It's difficult to generate upconversion laser of Nd.关键词：upconversion emission;Nd：KGW;yellow-orange luminescence;energy transfer110|110|0更新时间：2020-08-12
- 摘要：Red Long lasting phosphorescent(LLP)materials β-Zn3(PO4)2:Mn0.152+ and β-Zn3(PO4)2:Mn0.152+,Bx3+ were prepared by high temperature solid-state method,respectively.The XRD results showed that the addition of HBO3 has no notable effects on the formation of Zn3(PO4)2 crystal structure.The excitation and emission spectra of series doped materials were studied.The materials show red long lasting phosphorescence and the highest emission peak is located at 616 nm.From the excitation and emission spectra results it could be observed that the doping of HBO3 didn't change the spectral shape and position of β-Zn3(PO4)2:Mn2+,but changed the luminescence intensities.When the doping concentration of B3+ is x=0.05,the luminescence intensity is the strongest.Furthermore,B3+ doping also improved the LLP properties.The optimized LLP performance could be obtained when the doping concentration of B3+ is x=0.10 with the LLP decay curves.It was due to more traps caused by the unequal doping of B3+.108|28|5更新时间：2020-08-12
- 摘要：Microwave assisted synthesis together with heat-treatment at a high temperature were employed to prepare the phosphor of terbium-aluminium garnet doped by Ce3+(TAG:Ce).The crystal form,particle topography and the photoluminescence properties of the powder were characterized by XRD,SEM and fluorescence spectrophotometer.SEM results show that the particles of the prepared samples are clear and smooth.Most particles have the size of less than 2 μm.The powder has slightly agglomeration.The excitation spectrum consists of two peaks with the highest intensity at 467 nm and the second at 330 nm,respectively,all corresponding to Ce3+ 4f-5d absorption.The third peak is at 375 nm,which corresponds to 7F6→5D3 absorption of Tb3+.Ce3+ 5d-4f transition is also observed clearly,the highest emission peak is at 550 nm.The reaction pathway has been analyzed,implying that the tracer diffusion coefficient of aluminum is bigger than that of terbium in Tb2O3-Al2O3 system.Compared with the traditional high-temperature solid-state synthesis,this route employed in this investigation has the advantages of easier synthesizing,energy saving and environmental protecting.关键词：rare earth;TAG：Ce;ceramic phosphor100|56|0更新时间：2020-08-12
- 摘要：Rare-earth doped fibers based on silica materials have been the subject of a tremendous research effort over a few decades for high power laser source applications.The main advantage of using a silica host is that it provides low propagation loss,high gain,large bandwidth and high chemical durability.It has been predicted that the fiber lasers have many advantages including very high conversion efficiency,immunity from thermal lensing effect due to large ratio of surface area to volume,no need of beam steering,simplicity of optical cavity construction,excellent beam quality,small volume and weight,low cost,and inherently fiber-coupled output.Thus fiber laser is now competing with conventional bulk solid-state lasers in applications such as micro-machining,welding and other material processing.It has been predicted that the fiber lasers will show good application prospect in the field of communication,printing,marking,medicine,and so on.A laser diode pumped all-fiber acousto-optic Q-switched Er/Yb co-doped double-cladding fiber laser was reported.The technical difficulties were resolved,including full fiber configuration,pump coupling,and enhance output power ulteriorly.Two laser diodes were employed as the pumping source,acousto-optical modulation with fiber was employed as Q-switched,Er3+//Yb3+ co-doped double-cladding fiber was employed as gain medium,fiber Bragg grating was employed as feedback device,in linear cavity the stable pulse train with wavelength of 1 549.47 nm and spectrum bandwidth of 0.499 nm was obtained.The repetition rate is adjustable from 1 kHz to 15 kHz.Single pulse energy up to 209 μJ,average output power of 209 mW,pulse width of 100 ns and peak power of 2 kW were obtained at the repetition rate of 1 kHz.Single pulse energy was calculated at repetition rate of 1 kHz theoretically.Single pulse energy and average output power were measured at different input pump power.At low pump power,pulse train with twice and thrice modulation period were observed.关键词：fiber lasers;acousto-optic Q-switched;erbium/ytterbium co-doped fiber149|78|1更新时间：2020-08-12
- 摘要：The study on the temperature dependence of photoluminescence(PL)is essentially important for clarifying the processes of energy relaxation and energy transfer in the self-assembled quantum dots(QDs).The unusual dependence on temperature of both the peak energy position and the width of the PL bands has been reported.The fast redshift of PL energy and the anomalous decrease of line-width with increasing tempe-rature have been attributed to thermally enhanced carrier relaxation between quantum dots due to carrier thermal emission and carrier transport through thewetting layer.The PL intensity quencheswith temperature due to carrier thermal escape from the dotground states to the states of thematrixmaterial and/ornonradiative recombination centers.In this paper, the temperature dependence of the PL of self-assembled bimodal QDs was simulated by using a steady-state rate equationmodel. The temperature dependence ofPL intensity ratio of two Q Dspopulationswas emphatically investigated.The results showed tha,t the intensity ratio remains constant at low temperature (<75K) and increases continuously at intermediate temperature(75K<T<150K); when the temperature is raised above 150 K, the intensity ratio has an abnormal decrease.关键词：self-assembled bimodal quantum dots;photoluminescence;thermal excitation102|81|0更新时间：2020-08-12
- 摘要：In recent years,ultraviolet(UV)photodetector has drawn a great deal of interest,due to their potential application such as solar astronomy,fire alarm and combustion monitoring,missile plume detection,space-to-space transmission.Zinc oxide(ZnO)has large exciton binding energy(60 meV)at room temperature,and a large band gap at room temperature(3.37 eV),and low power threshold for optical pumping at room temperature,high electromechanical coupling factor and high stability under hard conditions,ZnO is recognized as promising material in the ultraviolet(UV)detectors.High quality ZnO films can be obtained by various deposition techniques such as radio frequency(rf)magnetron sputtering technique,pulsed laser deposition(PLD),metalorganic chemical vapor deposition(MOCVD),and also molecular beam epitaxy(MBE).Among these techniques,the operation of radio frequency magnetron sputtering technique is simply and lower cost.ZnO thin flms were grown on quartz substrates using radio frequency(rf)magnetron sputtering technique.Before sputtering,the quartz substrates were cleaned in an ultrasonic bath with acetone,ethanol and deionized water at room temperature and the zinc(99.999%)target was etched with diluted nitric acid to remove the contamination.The base pressure of sputtering chamber was evacuated to be below 5×10-4 Pa,and then filled to 1.0 Pa with mixed gases of 99.99% pure Ar and O2,which were introduced into the sputtering chamber though a set of mass flow controllers with the rates of 60 and 20 sccm(standard cubic centimeter perminute),respectively.The target-substrate distance was maintained at 50 mm and the substrate temperature was controlled at 400℃.The rate of deposition was adjusted so as to have a film thickness of nearly 400 nm during the film growth.The MSM structure with interdigitated configuration on the ZnO thin films was obtained by lithography and wet etching.It consists of 12 fingers at each electrode 5 μm wide and 500 μm long and have an interelectrode spacing of 5 μm.The θ-2θ XRD patterns of the ZnO films indicated that the highly c-axis oriented film was grown.The PL spectrum of the ZnO thin film taken at room temperature shows a luminescence peak at 3.3 eV.With the applied bias below 3 V,the dark current of the ZnO MSM UV detector is below 250 nA.The typical responsivity peaked at around 370 nm,and had values of 0.34 A/W.In addition,the UV(360 nm)to visible(420 nm)rejection ratio of around four orders can be extracted from the spectra response.Furthermore,the transient response measurement revealed its fast photoresponse with a rise time of 20 ns.关键词：ZnO thin films;MSM;photoconductive UV detector;radio frequency magnetron sputtering116|92|1更新时间：2020-08-12
- 摘要：Spintronics is a multidisciplinary field whose central theme is the active manipulation of spin degrees of freedom in electron devices.Compared with conventional semiconductor devices,due to adding the spin degree of freedom to conventional charge-based electronic devices has the potential merits of nonvolatility,increased data processing speed,reduced electric power consumption,and added integration densities.Seeking right magnetic materials is also very important.ZnO has been recognized as a promising material for optoelectronic devices,such as ultraviolet light-emitting diodes,laser diodes,and photodetectors,owing to its wide band gap and large exciton binding energy at room temperature.Diluted magnetic semiconductors are attracting considerable attention because they are anticipated to be used in the spintronic devices.For the realization of spintronic devices,the ferromagnetic semiconductors with Curie temperature above room temperature are highly expected.At present oxide-diluted magnetic semiconductors have being a focus especially based on ZnO material.First-principle's study has already broadly been applied to the material calculation.So far,much of work has concentrated on Co-or Mn-doped ZnO and characterization of their structural,magnetic,and optical properties.However,little attention was paid to(Mn,Co)-codoped ZnO system.In this paper,the geometrical structure of pure ZnO,Co doped and(Co,Mn)-codoped 32-atom supercell of ZnO was optimized by using the ultra-soft pseudopotential method of total-energy plane wave based on the density functional theory(DFT).Density of states and band structure were calculated and discussed in detail.The results revealed that Co doped ZnO and(Co,Mn)-codoped ZnO showed ferromagnetism,however,ferromagnetism of(Co,Mn)-codoped ZnO was weaken because of Mn doping.These results will provide very good references for the experiment studies.关键词：ZnO;first-principles;ferromagnetism117|69|0更新时间：2020-08-12
- 摘要：ZnO is an interesting wide direct band gap Ⅱ-Ⅵ semiconductor with wurtzite structure.The high quality ZnO thin film is one of most potential membranous materials at present.Zinc oxide with high stability and a direct band gap of 3.37 eV has attracted tremendous attention because of its high potential for application as short wavelength optical devices.In recent studies,it is found that doping of other elements can broad the band gap of ZnO films.This will be beneficial to the development of optical devices.There are many methods to prepare ZnO films,such as pulsed laser deposition,reactive thermal evaporation,reactive magnetron sputtering,electrodeposition,sol-gel and so on.Sol-gel method has many advantages,may prepare big area semiconductor thin film,fit for industry production,and so on.In order to prepare ultraviolet optical device,study on how to broad the band gap of ZnO is very important.In this paper,in order to study the effect of Mg concentration and annealing temperature on the microstructure and band gap of Zn1-xMgxO films,the Zn1-xMgxO(x=0.1,0.2,0.3,0.4,0.5,0.6,0.7)thin films were prepared on glass substrate by the method of sol-gel.The grown films were characterized by means of X-ray diffraction,photoluminescence spectroscopy and transmission spectrum.The XRD results show that when the value of x is between 0.1 and 0.3,the thin film remains the structure of hexagonal wurtzite and the angle of diffraction peak becomes bigger with increasing x,MgO impurity phase segregated at x≥0.4.According to PL spectra,the thin films show an intensive UV emission peak due to the near band-edge emission and a weak UV emission peak around 403 nm between 340 nm and 520 nm at room temperature,and the intensive UV emission peak have the blue shift with the content of Mg increasing from 0.1 to 0.3.It indicates that the band gap of ZnO was broaden with increasing Mg-doping concentration from 0.1 to 0.3.According to the transmission spectrum of Zn1-xMgxO(x=0.3,0.4,0.5,0.6,0.7)films,it is found that absorption edges are formed when incident wavelength λ<350 nm and blue shifted with increase in Mg content.It also indicates more doping Mg may broad the band gap of Zn1-xMgxO.Meantime,annealing temperature also can broad the band gap obviously,but the band gap decreases when annealing temperature is above 590℃.Though the doping of Mg can broad the band gap,but high Mg doping can result in precipitation of MgO.Therefore,we must control Mg content and annealing temperature strictly when an optical device is prepared.关键词：ZnO films;structure;band gap;photoluminescence99|54|3更新时间：2020-08-12
- 摘要：Water-soluble CdS nanoparticles have been prepared by femtosecond laser(100 fs,800 nm,FL)ablation of a bulk CdS target in water.Being performed in a controllable contamination-free environment,this method makes possible the production of nanomaterials without impurities.The morphology and the optical characteristics were studied through transmission electronic microscopic,UV-Vis optical absorption,and room temperature photoluminescence.The results indicated that the obtained water soluble CdS quantum dots fabricated by femtosecond laser ablation have small size and narrow size distribution.As well,these quantum dots were found to be exceptionally stable in air for at least 6 months.In addition,under the excitation of 300 nm,the photoluminescence of the CdS quantum dots ablated in water shows a band-edge emission peaked at 420 nm with FWHM of 62 nm.The above-mentioned characteristics make these CdS nanoparticles of great attraction for potential application in biological labeling.This work demonstrates that the FL ablation is a simple but effective method for preparation of high quality quantum dots.关键词：femtosecond laser;ablation;CdS;quantum dots;water-solubility101|99|1更新时间：2020-08-12
- 摘要：In order to study preparation process recipes and nonlinear optical properties of Si/SiNx superla-ttice,Si/SiNx superlattice has been fabricated by RF magnetron sputtering technique and thermal annealing.The superlattice has been characterized by absorption measurement,and X-ray diffraction.Nonlinear optical properties of Si/SiNx superlattice was probed by a Z-scan technique at λ=1064 nm.The experimental results show that the nonlinear refractive index of the sample is a negative value and the nonlinear absorption is two-photon absorption.The real and imaginary parts of χ(3) have been found to be 1.27×10-7(esu)and 1.51×10-8(esu)according to the experimental data of Z-scan curve.The value of Si/SiNx superlattice is larger 5 scales than that of bulk silicon.The nonlinear mechanism of the material was discussed.The enhancement of non-linear refractive index is mainly attributed to intensive quantum confinement.The results indicate that such Si/SiNx superlattice material could be applied to the optoelectronics and microelectronics industry since it is compatible with Si technology.关键词：Si/SiNx superlattice;third-order nonlinear polarizability;Z-scanning;RF magnetron reaction sputtering108|65|2更新时间：2020-08-12
- 摘要：Many strategies have been developed to improve silicon's and germanium's light emission efficiency,such as band gap engineering and quantum confinement in low-dimensional structures.Porous silicon,silicon nanocrystals and germanium nanocrystals in the SiO2 layer are being investigated actively as some means of improving the light-emission properties of silicon and germanium.Many physical mechanisms have been proposed to explain the photoluminescence(PL)in low-dimensional nanostructures.In this paper,some kinds of low-dimensional nanostructures were formed by etching with laser irradiation on Si1-xGex sample.Dot structure and line structure was formed,respectively,on the SiGe film after anodizing and irradiating for 5 min and 10 min;after 15 min,nano-strap pieces structure was formed when the SiGe layer was dug up.Due to the impaction of ion and the irradiation of laser,after etching with laser irradiation for 30 min,the Si1-xGex layer was almost peeled,then porous structure was formed on the substrate.After anodizing and irradiation,the porous structure samples were oxided by annealing treatment in the furnace at 800℃ for different time.We studied the evolution of photoluminescence with annealing time.It was found that the PL peak at 724 nm increases obviously on the porous structure where the Si nanocrystals/SiO2,Ge nanocrystals/GeO2 system exists before annealing treatment.After annealing for 20 min,the PL intensity reduces obviously.However,the PL intensity incresases again after annealing for 30 min,and that PL emission shows blue-shift obviously to 683 nm.When annealing time was longer than 90 min,the PL spectra vanishes.The change of PL emission of SiGe sample cannot be explained by quantum confinement(QC)or quantum confinement-luminescence center(QCLC)model.According to the QC and QCLC model,a new model of quantum confinement-the trap states of the interface between some oxides of silicon and nanocrystal was proposed for interpreting the change of PL emission in Si1-xGex alloys.Through this model,we hope to solve the problem of "critical size" in QC and QCLC models.In this model,the photoexcitation occurs in Si nanoclusters and Ge nanoclusters embedded in the oxide layer,where the band gap opens by quantum confinement.The enhancing photoemission occurs in the interface states of the Si oxide adjacent to the nanocrystals only when the level of the excitation states opened by QC is higher than that of the interface states,so that the interface states can trap the electrons photoexcited.It is clear that after deeper oxidation on SiGe,the level of the excitation states opened is lower than that of the interface states due to higher level of oxide states where the PL band is weaker.The wavelength of intensive PL peaks is also determined by the level position of the trap states in the crystal-oxide interface due to oxidation conditions in laser irradiation and annealing.We think that the energy state distribution is various in different crystals and different oxide interface states which play an important role for explaining the change of frequency and intensity of PL.关键词：photoluminescence;low-dimensional nanostructure;porous SiGe;interface state93|92|0更新时间：2020-08-12
- 摘要：SrMoO4:Yb,Er nano-sized up-conversion luminescent powder was prepared by sol-gel method in the presence of citric acid.The impact of different proportion of /Yb3+ to Er3+ on the up-conversion luminescent intensity was discussed.The experiment showed that when the proportion of /Yb3+ to Er3+ is 7:1,the up-conversion luminescent intensity is the strongest.The sample was characterized via XRD,TME and emission spectrum.The results showed that SrMoO4:Yb,Er belongs to pyramidal system;the grain size of SrMoO4:Yb,Er is under 100 nm,and belongs to polycrystals.Under 980 nm laser diode(LD) excitation,two strong green emissions and a wake red emission,which centered around 526,558,652 nm,respectively,are observed at room temperature.They correspond to 2H11/2→4I15/2,4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3+ ion,respectively.According to the relationship between pump power and luminescent intensity,it was concluded that the both the green and the red emission all are dominated by two-photon process.关键词：sol-gel;upconversion emission;nanopowder121|73|1更新时间：2020-08-12
- 摘要：The optical properties of Gd2O3:Eu3+ nanoparticles immersed in different solvent were investigated.The 4f intraconfigurational transition peaks are nearly not changed by the surrounding media.The spontaneous emission lifetime of 5D0 of Eu3+ in Gd2O3 nanocrystalline is significantly affected by the surrounding media,mainly due to the refractive index of the media and the filling factor of the nanocrystalline.Different models predict substantially different dependences of radiative lifetime on the surrounding media.There are some measurements intended to discriminate these models have been given,and most experimental results tend to agree with the real-cavity model.Especially,recent measurements on the radiative lifetime of Eu3+ ion embedded in glass with varying refractive index also tend to agree with the real-cavity model in contrary to the general belief that the virtual-cavity model should be more relevant.With states of opposite parity,depends strongly on the environment and does not serve as a good examination of the real-and virtual models.To overcome the problem in 4f→4f transitions,Duan and Reid analyzed the lifetimes of 5d→4f transitions of Ce3+ ions in hosts with different refractive indices and the results maintained the textbook virtual-cavity model.However,there was no intention to answer the questions why most other experimental results agree with the real-cavity model,and which model should be used for a given situation.The two models that describe the radiative lifetime:virtual cavity and real-cavity model,are with respect to "interstitial" and "substitutional" impurities,respectively.In our experiment,the real-cavity model is more reliable.关键词：Gd2O3：Eu3+ nanocrystals;localfield;refractive index;spontaneous emission lifetime111|47|0更新时间：2020-08-12
- 摘要：Capping ZnO nanoparticles doped with 2% Zn,Fe,Mn and Co ions,respectivety,were grown by separately decomposing the mixtures of Zn and Fe,Mn,Co cupferrates in organic solvent at 200℃ under protection of N2.The nanoparticle structure,morphology,optical and magnetic properties were characterized by X-ray diffraction,transmission electron microscope,absorption spectroscopy,photoluminescence spectroscopy and superconducting quantum interference device magnetometer.The concentration of doped ions was measured by electron dispersion spectroscopy and the measured concentration was consistent very well with that in the mixed precursors.Both pure and Fe,Mn or Co doped ZnO nanoparticles are spherical.The average sizes of pure ZnO nanoparticles is 8.5 nm,Mn dope ZnO nanoparticles 12 nm,Fe doped ZnO nanoparticles 14nm and Co doped ZnO nanoparticles 15 nm.Two kinds of precursors were introduced and heterogeneous nucleation occurred during formation of doped ZnO nanoparticles.Enlargement of the doped ZnO nanoparticle sizes indicated that Mn-O,Fe-O and Co-O produced by precursor decomposing actes as crystal nucleus during heterogeneous nucleation.Only sharp diffraction of wurtzite ZnO phase was observed in Fe,Mn or Co doped nanoparticles.The doped nanoparticles has a good crystal structure.Exciton absorption of ZnO at 3.47 eV and a broadened band of transitional metal d-d absorption at lower energy were observed.The photoluminescence of nanocrystals doped with Mn and Fe ions is similar.The luminescence is consistent of sharp emission of exciton at 3.30 eV,broaden emission of near band at 3.18 eV and emission related with defects at 2.94 eV.The nanoparticles doped with Co ions has strong near band emission at 3.14 eV and very weak defect emission at 2.73 eV.All nanoparticles show strong ultraviolet emission.The field-cooled and zero-field-cooled magnetization of Mn,Fe doped ZnO taken at 1.19×103 H show no deviation when the temperature is higher than 40 K and the deviation temperature is 43 K in Co doped ZnO nanoparticle.The magnetization of Co doped nanoparticles is larger than that of Fe and Mn doped nanoparticle.All doped nanoparticls show paramagnetic behavior at room temperature.关键词：diluted magnetic nanoparticles;optical properties;paramagnetic behavior108|86|0更新时间：2020-08-12
- 摘要：Halas and her co-workers reported the gold nanoshells,with strong surface plasma resonance(SPR)absorption band in near-infrared(NIR)region of 800~1200 nm,the transparent window of biological tissues.This kind of gold nanoshells was successfully used in thermal ablative therapy for cancer by NIR photo-thermal conversion.The noble metal nanomaterials with strong NIR absorption are also an ideal candidate for diffuse optical tomography,which is a promising imaging modality for early detection of diseases.Silver nanomatertials,as the metal with the highest electrical and thermal conductivity,if their SPR absorption were extended to NIR region,should have more excellent photothermal conversion property.One-dimensional silver nanomaterials,such as silver nanowires or wire-like nanostructures,have both transverse and longitudinal SPR absorption modes.The absorption location for the transverse SPR mode is fixed at ~400 nm,while that of the longitudinal SPR mode varies depending on the ratio of length to width of the nanostructures.Therefore,if the ratios of length to width of the silver nanowires are modified,then the longitudinal SPR absorption should be broaden inhomogeneously and may extended to NIR region.In this work,cross-sectional Ag nanochains with diameters of 10~30 nm were prepared using the method of water/oil emulsion.This kind of Ag nanochains demonstrated strong and super-wide SPR absorption extending from 400 to 1 200 nm.It exhibited better photothermal conversion property than that of the well-known gold nanoshells,and thus is more suitable to be used in biomedicine as the photothermal converters and in diffuses optical tomography as the contrast agent.关键词：Ag nanochains;SPR absorption;photothermal conversion122|88|3更新时间：2020-08-12
- 摘要：GaN-based blue light-emitting diodes(LEDs)has been energy saving,commercial solid state lighting devices.But the research on GaN-based white-lighting LEDs has been expected to further study before commercialization.One kind of white LEDs consists of GaN-based LEDs and luminant phosphors,but conventional phosphors for GaN-based LEDs are undesirable,for example,phosphors matching GaN-based LEDs can hardly be found.Furthermore,losses caused by self-absorption or scattering of secondary photons in the phosphor medium itself contributes to a large part.In this study,CdTe nanocrystals as nanophosphor for GaN-based blue LEDs are discussed.CdTe NCs were prepared in aqueous solution employing thioglycolic acid(TGA)as stabilizer,the corresponding PL peak position of the NCs excited by 470 nm is 566 nm with full width at half maximum(FWHM)of 30 nm,indicating of monodisperse distribution.The large Stokes shift between its absorption and PL spectra would alleviate self-absorption loss.The InGaN/GaN multiple quantum wells(MQWs)epitaxial wafers were grown at(0001)plane sapphire substrate by the metalorganic chemical-vapor deposition systems(MOCVD),and flip-chip blue LEDs were fabricated with the standard procedure,blue light from MQWs was extracted from polished sapphire plane.A hybrid structure integrating flip-chip LEDs and nanocrystals was reported.CdTe NCs were deposited directly on transparent sapphire layer,which avoids the light emitted by CdTe NCs traped in high-index GaN cavity.And another advantage of the flip-chip structure for CdTe NCs reduces the losses from quenching of the luminescence,a behavior that has been well documented with NCs attaching to smooth metallic electrodes.Blue light part from InGaN LEDs in the hybrid structure provides blue element,and also acts as a pumping resource to excite CdTe nanocrystals to emit yellow light.From photoluminescence excitation(PLE)spectrum of CdTe NCs and electroluminescence(EL)of GaN-based LEDs,the absorption peak around 480 nm in the PLE spectrum match emission peak from InGaN blue LED,which indicates CdTe NCS can be efficiently excited by GaN blue light.The hybrid light of the structure was characterized by the room-temperature electroluminescence(EL)spectra,and CIE chromaticity coordinates corresponding to the EL spectra were obtained.With the hybrid structure,a hybrid white light has been achieved by combining blue component and photoluminescence of CdTe nanocrystals.Chromaticity coordinate of(x=0.29,y=0.30)was obtained at 10 mA driving current,and already lies in the white area.The experiment also conducted EL spectra with different forward driving current.It was demonstrated that the chromaticity coordinate of the hybrid device hardly varies with injection current,within 20 mA current level,the fluctuation of chromaticity coordinate lies about 5%.This is a favorable property of the hybrid LED as the color of the device is constant and independent of the injection current.关键词：GaN;white light;LED;CdTe;nanocrystals;nanophosphor107|65|0更新时间：2020-08-12
- 摘要：Group Ⅱ-Ⅵ semiconductor CdS with a direct band gap of 2.4 eV at room temperature has attractive photonic properties,which is suitable for window layer and buffer layer material of solar cells.CdS nanocrystalline films were grown on glass substrates by means of chemical bath deposition technique with CdCl2 as the Cd ions and(NH2)2CS as the S ions source.The concentration of Cd ions,deposition temperature,deposition time and pH value have effects on quality of CdS nanocrystalline films.UV-Vis absorption spectra and PL spectra indicate that the change of concentration of Cd ions,deposition temperature,deposition time and pH may adjust the band-gap of CdS nanocrystalline films.关键词：CdS nanocrystalline films;chemical bath deposition;UV-Vis absorption spectra120|73|1更新时间：2020-08-12
- 摘要：Tb(Asprin)3Phen/SiO2 nanospheres were synthesized by a microemulsion method.They have a uniform diameter of ~ 40 nm,and show the characteristic fluorescence of Tb3+ ions.TEM imaging indicated that the hybrid nanospheres are core/shell structure with fine spherical surfaces and Tb(Asprin)3Phen has been successfully enveloped in the SiO2 spheres as chromophores cores.IR absorption spectra and photoluminescence spectra propose that the hybrid nanoparticles are promising materials for biological application.关键词：rare earth;microemulsion;core/shell structure;acetylsalicylic acid96|60|0更新时间：2020-08-12
- 摘要：The complexes of samarium,europium and different proportion(Eu:Gd)with 4,4,4-trifluoro-1-(2-furyl)-1,3-butanedione and 1,10-phenanthroline were synthesized in anhydrous alcohol solution.The pure or doped solid complexes of Eu(FTFA)3Phen,Sm(FTFA)3Phen and EuxGd1-x(FTFA)3Phen(x=0.1,0.3,0.4,0.7,0.9)were characterized by elemental analysis,IR spectra,EDTA titration and molar conductivity.The molar conductivity indicated that all the complexes are nonelectrolyte;IR spectra showed that the ligand coordinate(double-tooth)with RE3+ ions is through the oxygen negative ion of enolic form of FTFA and the two nitrogen atoms of 1,10-phenanthroline.The fluorescence properties of these complexes were studied in this article,the excitation spectra showed that energy absorb is higher for the ligands and the energy transfer is efficient from the ligands to the RE3+.The fluorescence emission intensity of Eu(FTFA)3Phen is much higher than that of Sm(FTFA)3Phen at the fixed experimental condition.It showed that the triplet state energy of the two ligands are higher than the excitation energy of Eu3+ ion,thus it is possible that energy transfers from 4,4,4-trifluoro-1-(2-furyl)-1,3-butanedione and o-phenanthroline to Eu3+ through-COO-Eu-OOC-and-N-Eu-N-bonds are more efficient.Fluorescence emission intensity of 5D0→7F2 transitions is the strongest among the emission spectra of the europium ion complexes,so we choose this energy transition as the research object.The results showed that the emission intensity of Eu3+ ion can be enhanced when Eu3+ ion is substituted by Gd3+ ion.But the mole fraction of Gd3+ ion influence on the fluorescence emission intensity of the rare earth complexes differently.By changing the mole fraction of Gd3+ ion,we found that if the mole fraction of Gd3+ ion is between 0.1 to 0.6,the complexes can get higher fluorescence intensity than that of the pure Eu3+ system.When the mole fraction of Gd3+ was fixed at 0.3,we got the best fluorescence intensity.This doping method can not only decrease the cost of materials,but also enhance the fluorescence intensity,so it has a bright future in practical application.关键词：β-diketone;phenanthroline;europium complex;dopping102|60|2更新时间：2020-08-12
- 摘要：(E)-N'-(quinolin-2-ylmethylene)-3-[(E)-quinolin-2-ylmethyleneamino]-benzohydrazide(QQB),as a chelating fluorophore,can detect Zn2+ selectively by shifting emission peak from 405 nm to 510 nm upon Zn2+ addition.Zinc binding not only makes the emission band red-shifts,but also enhances the fluorescence intensity.The probe is highly selective for Zn2+ over biologically relevant alkali metals,alkaline earth metals and the first row transition metals such as Mn2+,Co2+ and Ni2+.Spectrophotometric titration and ESI-MS spectra indicate the formation of a 1:1 complex of Zn2+ with QQB.关键词：fluorescent probe;Zn2+;quinoline;chemosensor93|54|0更新时间：2020-08-12
- 摘要：Microchannel plate(MCP)is a key component in the low-level-light image intensifier.When the intensifier is working,positive ion feedback will be produced in front of the output surface of MCP.On the one hand,the ion feedback destroy the linear operation characteristics of the MCP;on the other hand,electron emission produced by these feedback ions results in the appearance of ion spots on the screen;furthermore,these positive ions can bombard the photo-electrical cathode and shorten the operating life of the cathode.At present,the effective method for minimizing the ion feedback phenomenon is to fabricate a super-thin Al2O3 or SiO2 thin film on the input surface of MCP.This thin film allows some electrons with certain energy and stop effectively positive ions to pass though it,thus the cathode can avoid the bombard from the feedback ions and prolong the operation life of image tube.In this paper,the silicon thin film with the thickness of 0.5~1 μm was firstly formed on an organic self-sustaining thin film using radio-frequency magnetron sputtering method.Next,the silicon thin film was attached on the MCP by discharging oxygen gas under a vacuum of 4~6 Pa.At the same time,silicon thin film was oxidized and the organic film was discomposed in this process.Finally a thin layer of SiO2 ion-preventive feedback thin film satisfied the requirement was formed on the input surface of MCP.This fabrication method is very stable,and with a good reproducibility,the yield of this method is well above 90%.The technological parameters in the fabrication of sputtered Si thin film on the self-sustaining organic thin film were also reported in this paper.The structure and operating method of vacuum-discharge attaching was introduced and the advantage of ion-preventive feedback thin film fabricated by this method was shown.After the measurement,the electron transmittance characteristics though the ion-preventive feedback thin film for unfilmed and filmed MCPs were shown.The relationship between the thickness of the ion-preventive feedback thin film and the dead-voltage(characterize the electron transmittance propertied through the film)was given.The electron transmittance characteristics for SiO2 ion-preventive feedback thin film was compared with that for Al2O3 thin film.The electron transmittance characteristic of SiO2 ion-preventive feedback thin film is better than that of Al2O3 film(the dead-voltage is 220 V for SiO2 thin film and 255 V for Al2O3 film with the same film's thickness of 5 nm).At the end,it was pointed out that the emphasis of this project should be placed on the measurement of ion transmittance characteristics.关键词：microchannel plate;silicon oxide;ion-preventive feedback thin film;electron transmission characteristic88|99|1更新时间：2020-08-12
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