最新刊期
卷 27 ， 期 3 ， 2006
- 摘要：Chromophoric cyclic polyenes including 4H-pyrans,fulvenes,and siloles are designed and synthesized.Unlike "conventional" luminescent molecules,these polyenes are practically nonemissive when molecularly dissolved,but become highly luminescent with a dramatic increase in emission efficiency when aggregated(hence "aggregation-induced emission" or AIE).Upon exposure to solvent vapors,their emissions on TLC plates are quenched but become visible again when the vapors are removed.This process is reversible and can be repeated many times.Their emissions can also be tuned by changing their packing patterns such as from crystalline to amorphous state or from one crystal form to another crystal form.关键词：photolum inescence;aggregation-induced-emission;Silole;fulvene;pyran135|108|1更新时间：2020-08-11
- 摘要：The progresses of our group in combinatorial luminescent materials are reviewed.A combinatorial inkjet delivery system was developed to synthesize the powder phosphors libraries.The system consists of eight independent piezoelectric inkjet heads and an x-y stage that controlled by a computer via the driving circuit and motion controller.Thin-film deposition conjunction with a combinatorial masking strategy is used to(synthesize)high-density thin-film phosphors libraries.Photography using either film cameras or digital charge-coupled devices can be used to characterize the luminescent intensities and color coordinate of a phosphors library by taking the photoluminescent photograph of the library under UV or other high-energy excitations.For more quantitative analysis,an automatic scanning spectrometer system is used to measure the emission spectra of luminescent samples in the library.This system consists of a mercury lamp,a portable optical fiber spectrometer and an x-y stage.To implement the high throughput screening of VUV phosphor library,a parallel screening apparatus for VUV photoluminescence was developed,which consists of a cathode gas(Xe/He or Xe/Ne)discharge lamp and a vacuum characterization chamber.The photoluminescence of the phosphors library that excited by the VUV emission are photographed outside the chamber through an optical window.The luminescence enhancement effect of different kinds and contents of rare earth complexes(RE-(DBM)3phen,RE=Dy,La,Gd,Sm,Y,DBM=dibenzoylmethane,phen=1,10-phenanthroline)sensitized Eu(DBM)3phen doped in poly(methyl methacrylate)(PMMA)matrix was investigated using combinatorial method.The La(DBM)3phen shows the highest sensitization efficiency.At the optimal content of 5%(mass fraction)Eu(DBM)3phen and 350 kg/mol number average molecular weight(Mn)of PMMA,the maximum sensitization efficiency of La(DBM)3phen is about 20 times.Through the combinatorial method,a efficient VUV red phosphor GdSr(BxP2-x)O5.5~7.5:Eu0.1 was identified from a RE doped borophosphate phosphors libraries.It is believed that the dominant transition in GdSr(BxP2-x)O5~7:Eu0.1 is 5D0→7F0.The scale up experimental results show that the bulk GdSr(BxP2-x)O5.5~7.5:Eu0.1 sample prepared by conventional(methods)is brighter than that of the famous red commercial phosphor Y2O3:Eu under the same excitation(condition.)The combinatorial study of long persistence phosphor is in progress.关键词：combinatorial approach;advanced luminescent materials106|102|4更新时间：2020-08-11
- 摘要：The normal-mode coupling dispersive medium in a symmetric one-dimension photonic crystals(1D PCs)was studied.The frequency shift effect,homogeneous broadening effect,and the detuning effect of the normal coupled modes can be well controlled by adjusting the parameters of the dispersive medium.It is found that the separation between the two transmission peaks enlarges with increasing the dimensionless coupling strength.It implies that we can modulate the frequency shift of the dispersive defect by adjusting the parameter of the dispersive medium.The broadening effect of normal coupled modes is related to the reduced oscillator HWHM linewidth.Detuning effect of dispersive layer will make one peak rapidly drop and the other relatively much higher.It can be understood by Fabry-Pérot cavity analysis.关键词：optical response;normal-mode coupling;dispersive medium104|77|0更新时间：2020-08-11
- 摘要：With the development of several experimental techniques,for instance,metalorganic chemical vapour deposition,molecular beam epitaxy and electron beam lithography combined with reverse mesa etching,there has been of considerable interest in understanding of hydrogenic-impurity states in low-dimensional semiconductor heterostructures such as quantum wells,quantum wires and quantum dots.In recent years,there has been great interest in investigating the problem of a bound magnetopolaron in a parabolic quantum wires both theoretically and experimentally.And a lot of work has also been devoted to study the properties of the bound magnetopolaron in a parabolic quantum wires by kinds of methods.However,by using a linear combination operator and unitary transformation method to study it is seldom.The properties of the bound magnetopolaron in a parabolic quantum wires were studied by using a linear combination operator and unitary transformation method.The ground state energy,the vibration frequency and the mean number of optical phonons of both weak-coupling and strong-coupling bound magnetopolaron in a parabolic quantum wires calculated respectively.The influence of the electron-phonon coupling strength,the cyclotron frequency and the confinemend length of the quantum wires on the ground state energy,the vibration frequency and the mean number of optical phonons of the bound magnetopolaron in a parabolic quantum wires were discussed.More obviously the variational relation of the ground state energy,the vibration frequency and the mean number of optical phonons with the electron-phonon coupling strength,the cyclotron frequency and the confinemend length of the quantum wires were studied.Numerical calculations were performed for GaAs quantum wire,as an example,and the results illustrated that the ground state energy,the vibration frequency and the mean number of optical phonons in a parabolic quantum wires will increase with increasing the confinemend length of the quantum wires and the magnetic field,for both weak-coupling and strong-coupling bound(magnetopolaron)and they will increase with decreasing the Coulomb potential and the electron-phonon coupling strength.关键词：parabolic quantum wires;bound magnetopolaron;linear combination operator108|88|0更新时间：2020-08-11
- 摘要：In the past few years advance in nanofabrication techniques have made it possible to make well-like compound semiconductor structures of low nanometer size.In these structures,the state of the electron in the direction perpendicular to the length of the well is quantized with sufficiently large separation in energy levels and the motion of the electron parallel to the length is that of a quasi-free electron.One of the most remarkable properties of these one-dimensional electron system is that the optical transitions between the size-quantized subbands are feasible.The result shows there is a large optical nonlinearities in asymmetric quantum wells.The problem of optical saturation of intersubband absorption has recently attracted considerable attention.The problem is very important to the development of superlattice devices such as fast infrared detectors and modulators because one needs to know the range of input optical intensities for which linear operation is possible.The analytical expression of the linear and the third-order nonlinear optical intersubband absorption coefficients are obtained in P schl-Teller wells using the density matrix formalism taking into account the intrasubband relaxation.Since there are two adjustable parameters κ and λ in P schl-Teller wells,the shapes of the wells will change with the change of the parameters κ and λ,accordingly the linear and the third-order nonlinear optical absorption coefficients will change with the parameters κ and λ.It is shown that the optical absorption coefficient depends on the parameter,and the optical intensity strongly.The absorption saturation will occur with I increase.Numerical results are presented for a typical AlGaAs/GaAs P schl-Teller well.关键词：P schl-Teller wells;nonlinear optical absorption;density matrix method124|76|0更新时间：2020-08-11
- 摘要：A computerized system used for measuring three dimensional emission spectra of thermoluminesence(TL)and optically stimulated luminescence(OSL)is introduced.The system is composed of heating system,optical stimulation sources,optic spectrometer,and computer system.The sample is coupled to the spectro-meter through a fiber optic cable.When the sample is stimulated by heating or light irradiation,the TL or OSL signal will be decomposed into spectrum by a diffraction grating,and the spectrum is collected by a charge coupled device(CCD)with high sensitivity,and then a high speed ADC converts the analog signal of spectrum image to digital signal which can directly be dealt with the computer.The wavelength range of the spectrometer is from 200 nm to 800 nm.All programming was done in VC++ 6.0.The man-machine interface is friendly and the operation is easy and efficient.As an example,the TL and OSL emission spectra of SrSO4:Eu(0.1%,mol fraction)and CaSO4:Eu(0.1%,mol fraction)were measured with satisfying results.Thermoluminescence(TL)and optical stimulated luminescence(OSL)emission spectra of SrSO4:Eu(0.1%)and CaSO4:Eu(0.1%)were measured.The results illuminate that the TL and OSL emission wavelengths of SrSO4:Eu are 375 nm,and those of CaSO4:Eu are 385 nm.The TL and OSL emission spectra also indicate that TL and OSL have the same luminescence centers,and the luminescence comes from transitions between energy levels of Eu2+.The luminescence of Eu3+ is observed in the TL emission spectrum of CaSO4:Eu as well.From the 3-dimensional spectra,more information about luminescence can be used to perform further studies on the kinetics of TL and OSL materials.关键词：optical stimulated luminescence;thermoluminescence;3D emission spectra172|57|5更新时间：2020-08-11
- 摘要：Two thermoluminescence(TL)materials MgB4O7:Dy and MgB4O7:Tb were synthesized under the condition of high temperature.The 3-dimensional(3D)TL spectra of two materials were measured by the 3D TL spectrometer made in the laboratory.From the 3D TL spectra of MgB4O7:Dy,we can conclude:there are two TL glow peaks at about 220 and 380℃ and the wavelengths of the TL emission spectra are 480,575,660 nm.The intensity ratio of glow peak at about 220℃ to that at 380℃ can be raised gradually by high temperature treatment.However,the temperature and wavelength of the glow peaks have no obvious change.From the 3D spectra of MgB4O7:Tb,we can conclude:there are three TL peaks at about 230,360 and 420℃ and the wavelengths of the TL emission spectra is 489,543,589,620 nm.Different sintered temperature affects not only the TL sensitivity of MgB4O7:Tb,but also the spectral shape of the 3D TL spectra.When the temperature is higher than 850℃,the spectral line of Tb3+ turns to the spectral band.By comparing the TL glow curve and emission spectra between MgB4O7:Dy and MgB4O7:Tb,we can conclude that in the TL material doped with trivalence rare earth ions,the temperature of the glow peak is mainly decided by the host and the emission wavelength of the glow peak is mainly due to the transition of the energy level of the rare earth ions.关键词：magnesium tetraborate;dysprosium;terbium;thermoluminescence117|73|2更新时间：2020-08-11
- 摘要：The Sr2MgSi2O7:Eu2+,Dy3+ is an excellent blue long afterglow phosphor.Its afterglow can last longer than 20 h.But the mechanism of the afterglow luminescence is not clear so far.In order to study the physical process of the afterglow luminescence,Eu2+,Dy3+ singly doped or co-doped silicate:Sr2MgSi2O7:Eu2+,Sr2MgSi2O7:Dy3+,Sr2MgSi2O7:Eu2+,Dy3+ and Sr2MgSi2O7 were prepared and their VUV-UV excitation properties and temperature dependence were studied with synchrotron radiation VUV light.In emission spectrum of Sr2MgSi2O7:Eu2+,Dy3+ under 300 nm excitation,a broad band emission around 465 nm due to(4f65d→4f7)transition of Eu2+.Its excitation band lied around 360 nm.But under excitation at 172 nm,(besides)the broad band emission of Eu2+,a relative low line emission peaked at 575 nm can also be seen.Compared with the emission spectrum of Sr2MgSi2O7:Dy3+,it could be assigned to 4f-4f transition of Dy3+.This implied that Dy3+ acted as not only traps,but luminescent centers also in the phosphor.In excitation spectra of Sr2MgSi2O7:Dy3+ and Sr2MgSi2O7 we could see that both host and Dy3+ excitation band were in VUV range.So when Sr2MgSi2O7:Eu2+,Dy3+ was excited in UV-Vis range,only Eu2+ emission 465 nm band can be recorded and no Dy3+ and host emission existed.The phosphor is excited by daylight in applications,thus only the useful Eu3+ emission can be observed.These results made the long afterglow phosphor Sr2MgSi2O7:Eu2+,Dy3+ very suitable for practical use.关键词：long afterglow phosphor;synchrotron radiation;Sr2MgSi2O7：Eu2+;Dy3+;VUV-UV excitation116|62|0更新时间：2020-08-11
- 摘要：The Er3+ doped tellurite up-conversion laser materials have been attracted much attention due to the applications in areas such as optoelectronics,optic-communication,and color display.The up-conversion emission efficiency of tellurite glasses is low,because of the multi-phonon relaxation.A simpler way of removing the OH-from the glass during melting is to add a metal-fluoride to the batch and the fluoride will liberate hydrogen species from the melt.However,this process is effective in the dry air.In the humid atmosphere,water in the air can be reacted with fluoride to make the oxyfluoride tellutite glass with the residual OH-.So the oxyfluoride tellurite glasses prepared in different air have different OH-concentration.The oxyfluoride tellurite glasses with different OH-concentration were prepared in dry air and in humid atmosphere.The Judd-Ofelt intensity parameters and the total spontaneous emissions probabilities Aij,(branching)ratios βij and radiative lifetimes of the major emitting states of the Er3+ ion were determined from the absorption spectrum and Judd-Ofelt theory.The OH-concentration of oxyfluoride tellurite glasses was studied by the Fourier transform infrared(FTIR)absorption spectra.The effect of OH-on green up-conversion luminescence in the Er3+-doped oxyfluoride tellurite glasses was studied by fluorescence decay curves and up-conversion luminescence spectra.The OH-concentration of oxyfluoride tellurite glass prepared in dry air is 0.017×10-20 cm-3,15 times lower than that of glass prepared in humid atmosphere(0.25×10-20 cm-3).The Er3+ ion 4S3/2 level lifetime of glass with lower OH-concentration is 60 μs increasing 40% than that of glass with(higher)OH-concentration,and the 543 nm emission intensity increases 2.4 times.The up-conversion luminescence of Er3+ doped oxyfluoride tellurite glasses prepared in removing the OH-process has a great improvement.关键词：upconversion;Er3+-doped;OH-106|67|3更新时间：2020-08-11
- 摘要：Effects of Dy3+ ions on red long afterglow of Mg2SiO4:Dy3+,Mn2+ are investigated,which will help to discover the long lasting phosphorescent mechanism of this material.Red long afterglow phosphor,Mg2SiO4 doped with Dy3+ and Mn2+was prepared by solid-state reaction(SS)at 1300℃.The samples show a red(emission)peaked at 660 nm under UV excitation,which can be assigned as 4T1(4G)→6A1(6S)transition of Mn2+.The excitation and emission spectra of single-doped series were measured,and the energy levels of Mn2+ and Dy3+ in Mg2SiO4 were also assigned.In the excitation spectra of Mn2+ 650 nm emission of Mg2SiO4,there are several intense bands in the visible region corresponding to the transitions of 6A1(6S)→4T1(4G)(542 nm),6A1(6S)→4T2(4G)(459 nm,429 nm),6A1(6S)→4E(4G)/4A1(4G)(413 nm).It is a main advantage of this material.In the co-doped series,energy transfer from Dy3+ to Mn2+ was analyzed.When the concentration of Dy3+ was less than 5%,the emission intensity of Mn2+ increased with increasing Dy3+ concentration.After irradiated by low-pressure mercury lamp,the afterglow time of Mn2+ doped and co-doped with Dy3+ samples is 6 and 17 min,respectively.In the thermoluminescence curves of co-doped series,Dy3+ induced a new thermoluminescence peak at 70℃,showing its effect for extending the afterglow of Mn2+ luminescence.关键词：Mg2SiO4：Dy3+;Mn2+;long afterglow phosphor;energy transfer116|108|7更新时间：2020-08-11
- 摘要：The luminescence of Pr3+ or Mn2+ singly doped as well as Pr3+ and Mn2+ codoped SrB4O7 powder microcrystalline samples were investigated using synchrotron radiation.The photon cascade emission originating from the 1S0 level was observed in the SrB4O7:Pr3+(0.1%,mol fraction)sample upon 206 nm excitation.There are desirable spectral overlaps in the region of 330430 nm between the emission spectra of the SrB4O7:Pr3+ sample and the excitation spectra of the SrB4O7:Mn2+ sample monitoring the Mn2+ luminescence at 640 nm.The wavelengths corresponding to transitions 1S0→1I6,3P2,1,0(405 nm)and 1S0→1D2(340 nm)of Pr3+ coincide very well with those corresponding to transitions 6A1g→4Eg-4A1g(410 nm)and 6A1g→4T2g(350 nm)of Mn2+,respectively.These spectral overlaps are in favor of the energy transfer from Pr3+ to Mn2+,converting the first step photon from Pr3+:1S0 in the unpractical ultraviolet or near-ultraviolet regions into the red Mn2+ emission.A comparison of the room temperature emission spectra of the SrB4O7:Pr3+,Mn2+ sample with that of the SrB4O7:Pr3+ sample revealed the existence of the proposed energy transfer between Pr3+ and Mn2+.This conclusion about Pr→Mn energy transfer was also supported by the evidences from the low temperature(10 K)spectra and decay curves of 405 nm emission from Pr3+ singly doped and Pr3+,Mn2+ codoped samples.The efficiency of the energy transfer was estimated to be 43% by a simple equation based on the comparison of the emission spectra of the SrB4O7:Pr3+,Mn2+ sample with that of the SrB4O7:Pr3+ sample,thus a 143% quantum efficiency was achieved,suggesting an promising VUV phosphor based on Pr3+ and Mn2+ combination.关键词：vacuum ultraviolet(VUV);quantum cutting;photon cascade emission;energy transfer;phosphor109|28|1更新时间：2020-08-11
- 摘要：The Eu3+-doped glasses are well known as technologically important material and have been used widely in laser,luminescent material,and optical data storage.The glass doped with rare earth(RE)with wide emission band is very important for their application in wide band communication and other fields.The wide emission band of RE-doped in Bi-based glass is expected due to the high reflective index of Bi.The(60-x)Bi2O3xPbO30B2O310ZnO(x=0,10,30,mol fraction)glasses doped with Eu3+ in 1% were fabricated by melting method.The emission situation of other rare earth ions can be reflected from that of Eu3+ in the glass due to the similar size of ionic diameter and chemical properties.The DTA curves,absorption,phonon side-band,emission and excitation spectra of the glasses were measured.The Ω2 and Ω4 parameters of Eu3+ for optical transition were calculated from their emission spectra in terms of reduced matrix Uλ(λ=2,4,6)character for optical transitions.The results indicated that the intensity parameters Ω2 and Ω4 decrease slightly as the increase of PbO contents.It suggests that the symmetry becomes higher,the band of Eu and O atoms becomes weaker and the covalency decreases slightly.The difference between glass transition temperature(Tg)and the crystallization onset temperature decreases as increase of PbO content,indicating that the thermal stability of the glass becomes worse.The electron-phonon coupling becomes weaker as increase of PbO content.关键词：Eu3+ ion;Bi2O3-PbO-B2O3-ZnO glass;intensity parameters;thermal stability;spectra102|66|0更新时间：2020-08-11
- 摘要：When preparing phosphor yttrium aluminum garnet Y3Al5O12(YAG)activated with cerium(Ce3+)by solid-state reactions,the fluxes addition has great influence on the ion diffusions,crystallization process as well as on the formation of YAG matrix with good crystallinity.As a result,the crystallite size distribution and luminous efficacy of the phosphor as well as the hardness of the product are closely relative to the flux applied.It is known that the YAG:Ce phosphor prepared by solid-state reaction using H3BO3 as a flux often exhibited high hardness,causing many troubles in post-treatment.In this paper,YAG:Ce phosphors with the same Y/Al atomic ratio and the same atomic fraction of Ce were synthesized using different fluxes including a series of fluorides fluxes(such as MgF2,CaF2,SrF2,BaF2,AlF3)and mixed fluxes of fluorides with H3BO3.Effect of types and concentrations of the flux on the morphology,crystallite and luminescent properties of YAG:Ce were studied.It was found that the phosphors prepared with the fluxes studied in this work exhibited typical crystal structure of garnet and no impurity phase was detected.The excitation and emission spectra of the phosphors with different fluxes were roughly same.The main differences of the phosphors prepared with different fluxes were the hardness and luminescent brightness of the products.The luminescent brightness was higher while the hardness was lower for the YAG: Ce phosphor prepared with BaF2,AlF3,SrF2 and their mixture with H3BO3 compared with that using H3BO3 as flux alone.It is supposed that from the practical application point of view,BaF2,AlF3,SrF2 and their mixture with H3BO3 were the better fluxes for YAG:Ce among all fluxes investigated.关键词：YAG：Ce;phosphor;flux106|113|16更新时间：2020-08-11
- 摘要：Up-converting phosphors material(UPM)is the material that exhibits two-photon anti-Stokes luminescence by up-converting infrared to visible light.The material we used is a kind of UCM that emits green light when excited by 980 nm light.In fluorescent labels,UPM have many advantages:1.Permanent,strong,anti-Stokes emission of discrete wavelengths;2.unmatched contrast in biological specimens due to the absence of autofluorescence upon excitation with IR light;3.simultaneous detection of multiple target analytes;4.low-cost microscope modifications.Recently there is growing interest in studying UPM because of their most promising use as fluorescent labels for the sensitive detection of cell and tissue antigens.But the up-converting phosphors materials unmodified are easy to reunite and deposit,so they can't directly apply to fluorescent labels reporters.To enlarge the usages of up-converting phosphors material(UPM)in fluorescent labels and biological check,we prepared a kind of UPM with surface coated by silica and then signified this kind of material.The particle size of the product is very uniform and the particle shape of product keeps spherical.The thickness of silica is about 10 nm and the luminescence intensity has greatly increased.The paper also did a lot of research about the conditions of up-conversion phosphors material cladding by silicon dioxide,and found out the best conditions.We selected n-butyl alcohol as solvent and used ammonia water as dispersing agent.The volume of solvent is 100 mL.The mole ratio is 1:1 between tetraethylorthosilicate and water,and reaction time is 40 min.After the surface coated,the up-conversion phosphors material's dispersibility on aqueous solutions is better than before,and the stability is strengthened.This paper is the first step to modify the UPM,then we will modify the UPM with amino-group.We expect that the new material has better application foreground in biochip field.关键词：silicon dioxide;up-converting phosphor;coating102|68|5更新时间：2020-08-11
- 摘要：Seven solid p-tert-butylcalix [8] arene(LH8)-DMF coordination compounds of rare earth(Sm3+,Eu3+,Tb3+,Dy3+)and Tb3+ nitrates doped with Ln3+(La3+,Gd3+,Y3+)have been synthesized.Their elemental analysis,rare earth complexometric titration,molar conductive,IR spectra,UV spectra and TG-DTA have been studied.The results suggest that the composition of the complexes are [RE(LH6)(NO3)(DMF)4]-3DMF and [Ln0.5Tb0.5(LH6)(NO3)(DMF)4]3DMF,respectively.In these complexes,the rare earth ions coordinate to the oxygen atoms of p-tert-butylcalix[8]arene(LH8)and DMF,NO-3 group coordinate to the rare earth ions as the bidentate form.The fluorescence spectra of the complexes are determined at room temperature.The results suggest that the fluorescence emission intensity data are very different for the complexes,the data of terbium complex is higher,but other complexes are weaker.The fluorescence intensity of terbium complex is determined by the optimum excitation wavelength 322 nm(the exbandpass and embandpass are all 3 nm).As seen from Fig.2,terbium complex and its doped with La3+,Gd3+and Y3+complexes have characteristic luminescence and its fluorescence intensity is enhanced after doping with La3+,Gd3+,Y3+.These show that the lowest excitation state energy level of Tb3+ ion with the triplet state energy level of the ligands match well each other.The absorbing energy of the ligands are effectively transferred to Tb3+ ion.The energy transferred process may be(LH6)2-→[(LH6)2-]* Ln3+→[(LH6)2-]* Tb3+→5D4(Tb3+)(Ln=La,Gd,Y).The fluorescence intensity of terbium complex is enhanced after doping with La3+,Gd3+,and Y3+ ions.The radius of Y3+ is the smallest,Gd3+ is middle,and La3+ is the biggest,so their coordination compounds.The distance is the shortest of Y3+ coordination compound with Tb3+ coordination compound,Gd3+coordination compound is middle,and La3+ coordination compound is the longest,for this reason,the sensitization actions from La3+,Gd3+,and Y3+ to Tb3+ ion are Y3+>Gd3+>La3+.关键词：terbium complex;rare earth nitrate;calix [8] arene;N;N-dimethylformamide115|18|2更新时间：2020-08-11
- 摘要：Polycyclic aromatic compounds are the important compounds in scientific research and practical(applications.)Generally speaking,they have a bigger conjugate system.Almost atoms of them are in one plane.So they are good electroluminescence materials.The study of spectra for these substances has become a(focus)in recent scientific researches.A theoretical study on fluorescence spectra of four polycyclic aromatic(compounds)is given.Their geometric configurations have been optimized by semi-empirical method RHF/PM3.The structure analysis indicates that double C=C bond length in four compounds is longer than normal double bond and shorter than normal C—C bond,which shows that their electrons partly shift.From the analysis of the torsion angles,it is found that all benzene cycles of four compounds are in one plane,which,to some extent,enhances the compounds' stability.For all optimal configurations,we have calculated the IR spectra and there is no imaginary frequency in vibrational analyses,which indicates that the opitimized geometries are basically reasonable.On this basis,the electronic spectra have been calculated by CIS method.All calculated results are basically consistent with experimental values.关键词：polycyclic aromatic hydrocarbons;fluorescence spectra;quantum chemistry;CIS126|93|2更新时间：2020-08-11
- 摘要：Synthesis of blue organic light-emitting materials is very important for practical applications of organic light-emitting diodes(OLEDs).Organometallic complex lithium tetra-(8-hydroxy-quinolinato)boron(LiBq4)was synthesized,purified and used as light-emitting material.Blue ITO/PVK:TPD/LiBq4/Alq3/Al OLED was fabricated adopting spin and vacuum deposition,and the electroluminescence spectrum was measured at different operation volta】ge.At the same time,the influence of thickness of Alq3,CuPc and LiF on the luminescence properties of blue OLEDs was studied.Results indicated that,the peak wavelength of fluorescence spectrum for LiBq4 is about 452 nm under excitation of 350 nm.The peak wavelength of electroluminescence spectrum for blue OLED ITO/PVK:TPD/LiBq4/Alq3/Al device locates at 475 nm,and one weak shoulder peak appears at about 500 nm,this is resulted from excitation of Alq3.The luminance of this blue OLED can reach 430 cd/m2 at 25 V operate voltage.As electron transfer material,the thickness of Alq3 film has distinct influence on the electroluminescence spectra and luminance of blue OLEDs.Through adjusting the thickness of Alq3 layer,the recombination region of holes and electrons can be restricted in LiBq4,and the shoulder peak will weaken and disappear.The optimal thickness of Alq3 film is about 10 nm.Although the addition of CuPc between ITO and PVK:TPD could enhance the injection ability of holes,simultaneously induces the imbalance injection of charge carriers,and deteriorates the properties of blue OLED.The addition of LiF thin film between Alq3 and Al cathode could enhance the injection ability of electrons,and makes the injection of electrons reach equilibrium with holes.So the recombination probability of holes and electrons was improved and the luminance of blue OLED was improved evidently.These results were explained with the schematic energy level structure of the blue OLEDs.关键词：LiBq4;blue OLED;synthesis;luminescence properties121|89|0更新时间：2020-08-11
- 摘要：In order to study regularity of fluorescence of complexes about rare earth with different benzoic acid,we have prepared much of BA-compiexes,RC6H4COOH(R=o-NH2,H,p-NH2,o-OH,m-Cl,o-COOH,m-COOH,p-COOH,p-OH,m-NO2,3,5-Dinitro,p-Br,o-I,2-OH-5-SO3H.They can be synthesized complexes with Sm3+,Eu3+,Tb3+,Gd3+.Under UV-excitation the complexes with Eu3+,Tb3+ have higher emitting intensity than complexes with Sm3+,Gd3+.There are some science bases about study a new luminophor.Spectra analyses of the complexes of europium with benzoic acid and its derivatives are discussed.The binary complexes of europium with benzoic acid and its derivatives benzene carbonic acid,phthalic acid,isophthahc acid,salicylic acid,o-aminobenzoic acid sulfosalicylic acid have been synthesized.They were characterized by elemental analysis,UV-Vis,IR,H NMR,fluorescence spectra and molar conductance.The UV spectra showed that the complexes' ultraviolet absorption were from the ligands(220-350 nm),so that it could transfer energy to rare earth.The measurement results of the emission spectra of the complexes indicated as follows the emission of Eu(BA)3,Eu(m-Phth)3·3H2O and Eu(o-Phth)3·3H2O consisted of three peaks at 582,596,and 618 nm which were caused from 5D0→7FJ(J=0,1,2)transition of Eu3+ respectively.Among these peaks the emission from 5D0→7F2 is the shrongest.But the emission of Eu o-aminobenzoic acid consisted(of three)peaks at 399,452,547 nm,and that of sulfosalicylic acid-Eu only one peak at 407 nm,which(were caused)from ligands.Fluorescence spectra show that there aren't red-characteristic emission of Eu in Eu(o-Amino)3 and Eu(Ssal)3.关键词：rare earth;europium;benzoic acid;fluorescence;complexes125|78|6更新时间：2020-08-11
- 摘要：Quinacridone was widely used as organic pigment for the applications of high-sensitivity photo-sensors or photoreceptors required for electro-photography,solar cells.Meanwhile,quinacridone was used often as a fluorescent guest in organic LED although it has no strong emission property in the solid state.In order to looking for derivatives of quinacridone with strong emission property in the solid state,4-tetrahydroquinolone as its derivative was designed and synthesized.The structure was also characterized by 1H NMR and IR.4-tetrahydroquinolone exists fluorescence in the solid state.Both the absorption and emission spectra in solvents with different polarities and with different concentrations were determined.It was found that extinction effect exists with increase in concentration,it means 4-tetrahydroquinolone is a fluorescent derivative of quinacridone and the extinction effect may be caused by non-radiative process or by reabsorption in high concentrations.It was also found that both the absorption band in absorption spectra and the emission band in emission spectra exhibit red shifts with increase of the solvents polarity.The relationship between the Stoke's shifts and the polarity of non protonic solvents was depicted by Lippert equation and the relative coefficient is 0.999 8.It is concluded that the fluorescence come from the photo-induced intramolecular charge transfer in the excited state.The Stoke's shifts in methanol is much greater than that in non protonic solvents and is not suitable to Lippert equation.It means the change of dipole moment from the ground state to the excited state is larger in protonic solvent and hydrogen bond may exist between 4tetrahydroquinolone and methanol.In a word,4-tetrahydroquinolone is a new photo-induced intramolecular charge transfer fluorescent compound with emission property in the solid state,it may be used in electroluminescent device as a emitting compound.关键词：4-tetrahydroquinolone;intramolecular charge transfer;fluorescence109|121|1更新时间：2020-08-11
- 摘要：In recent years,nanocrystals(NCs)of semiconductor materials have been attracting considerable interest due to their size-tunable optical and electronic properties,and they have already been used as sensors,laser materials,thin film light-emitting devices(LEDs),and biological labels.However,because of the high surface-to-volume ratio of nanoparticles,the surface properties have significant effects on their electronic and optical properties.It is for this reason that surface modification of these particles has been the subject of extensive investigation.In this report a simple one-pot synthetic route to prepare highly luminescent CdSe/ZnSe core-shell nanocrystals was presented.A ZnSe shell around a CdSe nanoparticles was formed by the reaction of selenium-richness on the surfaces of CdSe nanopaticles with Zn2+ from the injected zinc stearate precursor.The core-shell structure was verified by X-ray diffraction(XRD),X-ray photoelectron spectra(XPS),transmission electron microscopy(TEM),UV-vis absorption spectroscopy and photoluminescence(PL)spectro-scopy,respectively.The CdSe nanoparticles capped with wider band-gap ZnSe show successful passivation to remove surface defects.The X-ray diffraction patterns of the CdSe/ZnSe core-shell nanoparticles comparing with those of the bare CdSe cores shift to a higher angle.The X-ray photoelectron spectra analysis also clearly indicated the characteristic peaks such as Zn 2p3/2,Zn 2p1/2,and the Zn 2p signal detectable on the CdSe/ZnSe nanocrystals,indicating that Zn2+ was strongly bound to the nanocrystal's surface.The transmission electron microscopy micrographs of the core-shell nanoparticles show well-defined spherical particles with larger diameters than those of the particles of the parent material.Consequently photoluminescence efficiencies improved observably.关键词：core-shell nanoparticles;passivate;surface defect;photolum inescence104|99|2更新时间：2020-08-11
- 摘要：Surface effect is probably the most important factor that makes the spectral properties of rear earth doped nanosized materials different from that of bulk.In many cases,surface acts as a quenching center,that increases nonradiative transition rates of the dopant.Besides,the surface diversifies the local environments of the dopantions,thus the emission spectra of nanosized materials may shift,split or get broadening.In Eu3+ doped nanoparticles,such a site inequivalency was studied widely with selective excitation.In this report,we show that the temperature dependent emission spectra are also a result of this effect.5D0→7F2 emission spectra of Eu3+ in nanocrystalline YVO4 at different temperatures were measured with non-selective excitation.At low temperature,the spectrum is a broad band,superposed by a number of spectral lines,while at room temperature,it consists chiefly of two lines similar to that observed in bulk.Referring to the results of selective excitation in YVO4:Eu3+ nanoparticles,we decomposed the emission spectra into two parts:that(IC)from the Eu3+ ions located near the particle center with the emission similar to that in bulk;and that(IS)from Eu3+ ions close to the surface with the emission wavelengths extended wider.As the temperature decreases,the relative intensity of IS/IC approaches to a constant 2.3 in our sample with average radius of 27 nm.That gives an estimation of the surface layer thickness,4.5 nm,in which the spectral properties of the Eu3+ ions are disturbed by the surface.The temperature dependence of IS/IC can be fitted by either an energy transfer process with energy mismatch of 900 cm-1 or an electron transfer process from the Eu ions to the surface traps across a 900 cm-1 barrier.The variation of the emission spectra originates from the temperature dependent quenching via surface quenching centers.关键词：nanoparticles;YVO4：Eu3+;temperature dependence of emission spectrum;surface effect104|73|3更新时间：2020-08-11
- 摘要：In an effort to prepare efficient and uniform biolabels,we have developed a novel fluorophore doped silica nanoparticles via water-in-oil(W/O)microemulsion method.The controlled hydrolysis of tetraethyl orthosilicate(TEOS)in W/O microemulsion leads to the formation of monodisperse fluorophore doped silica nanoparticles.By synthesizing of monomer dansyl-Cl(DNS-Cl)silica precursor,we have successfully prepared fluorescent hybrid silica nanoparticles of DNS-Cl.The fluorophores are well protected from the environment when they were doped inside the silica network.The transmission electron microscope(TEM)photograph showed that the particles are very uniform,they are spherical and monodispersed with a diameter of about 40 nm.The excitation maximum and emission maximum,compared with the monomer precursor,have a blue-shift.The fluorescence intensity of the fluorophore doped silica nanoparticles passed through a maximum with increasing monomer precursor concentration,the optimal loading is 100 μL of monomer precursor.The effect of pH on monomer precursor is very distinct,both the fluorescence intensity and the excitation wavelength have changed a lot,but the fluorophore doped silica nanoparticles are nearly insusceptible,which indicates that core-shell structure reduces the effect of the environment on fluorophores.The method significantly reduces fluorescent dye leaching from the nanoparticles too,since there is a firm chemical bond between DNS-Cl and APTEOS,the particles are potential of good biocompatibility,since they have a pure silica surface and can thus be modified easily with many biomolecules for added biochemical functionality.The particles can be accepted as an effective biological labels.关键词：fluorescent nanoparticles;microemulsion;DNS-Cl103|85|0更新时间：2020-08-11
- 摘要：Recently,the study of nanometric luminescent materials has become of great interest.First,the microstructural characteristics of the phosphors,such as the size or the surface properties of the grains,play an important role in the efficiency of luminescent devices.Second,new developments such as electroluminescent devices,or biological labels imply the developments of new phosphors whose properties can be managed at the nanometric scale.So it is very exigent to develop a process that can produce particles having controlled characteristics such as morphology,composition and size for good luminescent characteristics.The choice of lanthanum phosphate was made because of the excellent luminescent properties of the bulk matrix when doped with Eu3+.A new gel-network precipitation method was presented to synthesize the precursor of LaPO4:Eu nanoparticles,based on the use of lanthanide salts and(NH4)2HPO4 in water along with gelatin used as the disperser.Then products with nicer luminescence were successfully obtained under mild calcining conditions.TEM images showed that the nanoparticles are basically monodisperse,and have good homogeneity with an average diameter of 50 nm.The Eu3+-doped LaPO4 phosphor was characterized by powder X-ray diffraction.According to our measurements with XRD,the products belong to monoclinic monazite type,it is consistent with space group P21/n.The excitation and emission spectra were measured.Under 396 nm radiation excitation,the emission spectra of LaPO4:Eu consists of the sharp line emissions in the range of 500～720 nm from the transitions of electrons in 4f shell of Eu3+.The main peak at 592 nm can be attributed to the 5D0→7F1 transition of Eu3+.The excitation spectra of Eu3+ 5D0→7F2 transition emission have two parts,the wide band at 264 nm and the sharp line at 396 nm.The wide band includes both charge transfer excitation of PO3-4 and charge transfer excitation of Eu3+,while the sharp line originate from Eu3+ f-f electron transitions,which indicate that there is energy transfer from host lattice to activator in the process of luminescence.The luminescence data indicate the optimum condition for heat-treatment of the precursor was at 850℃ for 0.5 h.The effects of different content of Eu3+ on the luminescence of LaPO4:Eu nanoparticles were also investigated,and the(results)show that luminescence intensity is enhanced with the increasing of Eu3+ content.关键词：LaPO4：Eu;nanoparticles;gel-network precipitation;luminescence properties112|45|2更新时间：2020-08-11
- 摘要：The special physicochemical environment caused by sonic-vacating provides an important outlet for the preparation of highly efficient luminescent porous silicon(PS)films.Experiment results show that sonic-chemical treatment is an effective technology for the improvement of the microstructure of porous silicon,the luminescent efficiency and stability thereof.Luminescent porous silicon films,prepared by ultrasonic-enhanced anode electrochemical etching,display better qualities than the samples prepared by conventional methods widely used at present.This ultrasonic-chemical effect roots in sonic-vacating,i.e.the generation,formation and rapid collapse of bubbles in the etching solution.In the process of the PS being etched,the escape rate and caving-in of hydrogen bubbles in the pores is increased as a result of the work of the ultrasonic wave which is helpful to the vertical etching of the pores.It made full width at half maximum of porous silicon photoluminescence peak compress to 3.8 nm.In summary,we have presented an ultrasonic anodic etching method for fabricating light-emitting porous silicon material.Surface and cross-sectional SEM investigations reveal that when other etch parameters are constant,the ultrasonic etching creates a thicker and more uniform porous silicon layer,with smaller silicon pores than that of PS prepared by DC etching or pulsed etching.AFM observations further confirm the improved structural properties,which can be explained by the porous silicon formation mechanics especially by ultrasonic cavitation.The studies of both porous silicon single layer and porous silicon microcavity(PSM)show that ultrasonic etching optimizes the sample's optical characteristics.The best quality sample has been acquired by combining the ultrasonic etching with pulsed etching.This new etching method is an efficient technique to fabricate porous silicon materials,especially PSM,and opens a feasible way to realizing the application of porous silicon materials.关键词：porous silicon;photoluminescence;ultrasonic sonic-vacating113|79|0更新时间：2020-08-11
- 摘要：Three methods,namely Voltage-Method,Pin-Method and Spectra-Method,for determining the junction temperature of GaN-based white LEDs were studied.In the Voltage-Method,we show that the forward voltage depends on the junction temperature linearly with uniform current.In the Spectra-Method,we show that the ratio R=W/B is strongly linear with the junction temperature as changing the ambient temperature or changing the forward current,where W and B are the entire and the blue part radiant power of the LED′s emission,respectively.The physical mechanism of Spectra-Method and the factors of controlling the junction temperature were also discussed.Increasing either the ambient temperature or the forward current can lead to the rise of junction temperature and the shift of emission peak wavelength of GaN-based LED chips.These two factors can cause the decrease of excitation and emission efficiency of phosphor much greater than that of LED chips.To lower the junction temperature of white-LEDs,we need to consider the contact and series resistance,the emission efficiency,the thermal conductivity of encapsulation material,the design of reflector cup and pins,and the cooling surface area.关键词：GaN-based white LED;junction temperature;forward voltage;pin temperature;electro-luminescent spectra98|94|13更新时间：2020-08-11
- 摘要：Wavelength division multiplexing technology can extend the potentiality of the fiber.Arrayed waveguide grating(AWG)which is based on a phased arrayed of bent optical waveguide,is one of the key devices of dense wavelength division multiplexing(DWDM)optical systems,because it offers multi-channel operation,design flexibility and suitability for mass production.This text described the fabrication of AWG in detail.Using the polymer materials to manufacture AWG,the refracting rate is apt to adjust,the fabrication process is simple and the price is cheap.For the moment,the technology of making waveguide with polymer materials conclude photo bleaching technology,laser scribe technology,ion implantation technology and reactive ion etching technology.The reactive ion etching technology don't depend on the material of waveguide.But there is high ion bombardment resulting in high physical damage and poor mask resistance.So the combined layer masks were used in the fabrication of the AWG to compensate the damage of the resist so that the shape and the size of waveguide is probably the same as the design.The combined layer masks are aluminium mask and photo resist.The aluminium is vaporised on the material of the core layer.And then the photo resist is formed by spin-coating.The rotate speed is 4 000 r/s for photo resist.The experiment was carried on mainly using MD-300B vacuum evaporation machine,JKG-3A photolithography machine and ME-2A ion etching machine.It gave the result that 100 nm is the best thickness for aluminium mask.The surface of waveguide became rough after RIE.It's not good for waveguide lose to change the parameters during RIE process.So the steam remelting technology is used to modify the scatter lose which is due to the roughness of the surface of the waveguide.The root-mean-square roughness of surface of waveguide was reduced from 41.307 nm to 24.564 nm.The samples of AWG was tested,and the one with combined layer masks has the better property.关键词：polymer AWG;the combined layer masks;steam remelting115|71|2更新时间：2020-08-11
- 摘要：Gallium oxide(Ga2O3),a wide direct-gap semiconductor(Eg≈4.9 eV),has recently attracted interests as a new material for a gas sensor,transparent conductor,luminescent phosphors,solar cells,electronic and optoeclectonic applications.For Ga2O3 films growth,numerous deposition techniques including sputtering,electron-beam evaporation,molecular beam epitaxy(MBE),pulse-laser deposition(PLD),and metal organic chemical vapor deposition(MOCVD)have been employed.Among these techniques,MOCVD has many advantages for volume production and it has been proved to be excellent growth technique for Ⅲ-Ⅴs especially for the nitrides.Ga2O3 films used in this study were grown by a home-built vertical atmospheric pressure MOCVD system.Deionized water and trimethylgallium(TMGa)were used as the O and Ga sources,respectively,using nitrogen as the carrier gas.Typical growth conditions were as follows:chamber pressure was 103.3 kPa.The thickness of buffer layer is about 15 nm,growth temperature was 500℃,epilayer growth temperature was 700℃,and a total carrier gas flow rate was about 15000 sccm.The thickness of the Ga2O3 layer was about 2 μm.Ga2O3 epilayer characteristics were investigated by AFM,X-ray diffraction(XRD)and secondary ion mass spectroscopy(SIMS).The results of AFM indicated the Ga2O3 films grew up with columniation shape and the structure was relatively compact.The root mean square(RMS)roughness as determined by AFM(30 μm×30 μm)of the film surface was about 40 nm.The Ga2O3 grain size was about 30～40 nm determined by AFM.X-ray diffraction spectrum showed that the FWHM of(102)diffraction peak was 0.25°,which indicated the good quality of βGa2O3 film.The Ga2O3 grain size was calculated about 32 nm by Scherrer's formula,which was consistent with the result of AFM.The results of SIMS showed that the Ga2O3 epitaxial films had good purity.关键词：MOCVD;Ga2O3;AFM;XRD;SIMS129|61|4更新时间：2020-08-11
- 摘要：Microchannel plate(MCP)is a kind of vacuum electron-multiplier with beehive structure,which is invented in the late sixties of the last century.It is a two-dimension array,consisting of single channel electron-multiplier.As MCP has the characteristics of high gain,low noise,high resolution,low power,long life and the self-saturation effect,it is applied in charge particles,short-wave optical quantum and other detection devices and systems.A method of traditional Reduced Lead Silicate-Glass Microchannel Plate(RLSG-MCP),its characteristics and the recent development are summarized briefly.The characteristics of secondary electron emitting of the materials are introduced,the structure characteristic and form technology of film continuous dynode of traditional MCP are given out.The method,that the new generation of film continuous dynode of twodimension electron-multiplier fabricated by semiconductor technology—Advanced Technology Microchannel Plate(AT-MCP)facture technology,is demonstrated emphatically.The detailed technology and experimental results are presented.Adopting UV-optoelectronic method,the MCP sample having a diameter of 25 mm is measured.When the working voltage is 400 V and the input current is 3×10-11 A,the electron gain is 110.The coefficient of secondary electron emitting is calculated to be 1.8 accordingly.The electron microscope(picture)and the experimental curves are also shown.Finally,the advantage and development foreground of the new technology are pointed out.The materials of continuous dynode of the new technology are flexible and not restricted to the materials of basic body.The fabrication technology of the dynode is independent of the formation technology of the basic body.As the film continuous dynode of AT-MCP fabricated by semiconductor technology is concerned,the LPCVD and thermal oxidation technology is the optimal choice at present.The principle is right and the technology is feasible.Especially,the conductibility of continuous dynode fabricated by the new technology can be satisfied for the requirement easily,but the traditional technology can not exceed.关键词：micro-channel-plate;continuous dynode;low-pressure chemical vapor deposition;secondary electron emitting129|117|0更新时间：2020-08-11
- 摘要：ZnO is a direct wide-band-gap(3.37 eV)semiconductor.It has attracted considerable attention as a potential candidate material for gas sensors,transparent electrode and surface acoustic wave deices,especially for ultraviolet light-emitting diodes(LEDs)and laser diodes(LDs).However,for ultimately fabricating ZnO-based optoelectronic devices,the performance of the contacts to ZnO is attracting more and more attention.This is because a good ohmic contact allows lower operating voltage and minimizes dissipation of power,while a poor ohmic property leads to poor device performance and eventually device failure.Compared with that to n-type ZnO,the fabrication of ohmic contacts to p-type ZnO is more difficult since the work function of p-type ZnO is higher than that of single metal.The contact properties of Au,In,Ni/Au to N-doped p-type ZnO films grown by MBE method were reported.The zinc(Zn)source was supplied by evaporating metal zinc with 99.999 9% through a Knudsen effusion cell.NO gas activated by an Oxford Applied Research r.f.(13.56 MHz)plasma source with a power of 300 W was used as both N and O source.Compared with Au and In contacts,Ni/Au contact is more suitable to form stable ohmic contact to p-type ZnO.The contacts behavior of Ni/Au after annealing under N2 and O2 ambient were given.It was found Ni/Au contact gave a degenerative behavior after rapid thermal annealing(RTA)under O2 ambient at the temperature of 300℃ for 150 s,while an improved contact behavior was obtained after RTA under N2 in the same temperature for 150 s.The dependence of Ni/Au contact on the annealing temperature under N2 gas ambient was investigated.With the increase of the annealing temperature,the resistances of Ni/Au contacts decrease firstly and then increase.In this experiment,after RTA at 400℃ under N2 for 150 s,the Ni/Au contact gives a better ohmic characteristic,and the contact resistivity is about 0.8 Ω·cm2.关键词：p-ZnO;Ni/Au;ohmic contact;annealing123|80|1更新时间：2020-08-11
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