ZnO荧光粉中的紫外发射和绿色发射之间的关系

通过在低氧分压和真空中热处理ZnO粉末, 获得了ZnO荧光粉. ZnO荧光粉有两个发射谱带, 分别位于380 nm(紫外)和510 nm(绿色). 紫外谱带对应于ZnO中的激子发射, 是一个单中心发光过程；绿色谱带是一个复合发光过程, 与ZnO中的本征缺陷相关, 如氧空位、锌空位等. 实验表明, 高密度的激发条件有利于紫外发射, 而低氧分压下的热处理有利于提高绿色发射谱带的强度. 研究结果还表明, 与紫外发射相联系的激子可向与本征缺陷相联系的绿色发光中心传递能量, 这种传递可能是通过激子扩散实现的.     

SINGLET OXYGEN GENERATION FROM LIPOSOMES: A COMPARISON OF TIME-RESOLVED 1270 NM EMISSION WITH SINGLET-OXYGEN KINETICS CALCULATED FROM A ONE DIMENSIONAL MODEL OF SINGLET-OXYGEN DIFFUSION and QUENCHING

Abstract— Time-resolved measurements of 1270 nm singlet-oxygen emission following pulsed-laser excitation were made from unilamellar dimyristoyl 1-α-phosphatidylcholine liposomes labeled with zinc phthalocyanine. The effect of the hydrophobic quenchers, β-carotene and ethyl β-apo-8' trans carotenoate, and the hydrophilic quenchers, histidine and methionine, upon the kinetics of the 1270 nm singlet-oxygen emission was studied. Hydrophobic quenchers principally lowered the intensity of the 1270 nm emission and caused only modest changes in the lifetime of the 1270 nm emission. The decrease in 1270 nm emission caused by hydrophobic quenchers was related to the size of the liposomes. The larger the radius of the liposome, the greater the decrease in 1270 nm emission caused by a given concentration of hydrophobic quencher. In contrast, hydrophilic quenchers principally decreased the lifetime of the 1270 nm emission. The effect of hydrophilic quenchers was independent of the size of the liposomes.
There was good agreement between the experimental results and the kinetics of the singlet-oxygen emission calculated using a one dimensional model of singlet-oxygen quenching and diffusion. The kinetics of singlet-oxygen emission from liposomes without added hydrophobic quenchers closely approximated the theoretical kinetics of singlet oxygen in a homogeneous aqueous solution.     

Excited-state intermolecular proton transfer of firefly luciferin IV. Temperature and pH dependence

Time-resolved emission as well as steady-state UV-vis techniques were employed to study the photoprotolytic processes that d-luciferin, the natural substrate of the firefly luciferase, undergoes in both acidic aqueous solutions and ice. The emission spectrum of D-luciferin in a 20 mM HCl aqueous solution or higher has an additional emission band at 590 nm red-shifted with respect to the strongest emission band positioned at 530 nm of the deprotonated NRO(-*) form in a pH-neutral aqueous solution. We attribute this emission band to the zwitterion form designated as (+)HNRO(-). The time-resolved emission signals show that the NRO(-*) emission band at 530 nm and the zwitterion emission band at 590 are strongly quenched by a recombination process with a proton in an acidic solution and in ice. In ice, the quenching rate is 10 times faster than in the liquid state. We attribute the fast quenching rate to the high value of the proton diffusion constant in ice.     

Fluorescent Gold Nanoparticles: Synthesis of Composite Materials of Two‐Component Disulfide Gels and Gold Nanoparticles

Pseudoenantiomeric ethynylhelicene oligomers containing a disulfide group formed two‐component gels, which showed different solvent properties from gels without the disulfide group. The disulfide gels reacted with gold nanoparticles, and the resulting organic–inorganic composite materials exhibited fluorescence emission between 600–800 nm, along with emission from the oligomers at 450 nm. The disulfide gels and isolated gold nanoparticles loaded with the oligomers did not show the former emission. The 600–800 nm emission reversibly disappeared upon sol formation with heating, which was accompanied by an enhancement of the emission at 450 nm. The novel emission was also observed in the solid state.     

Application of single-walled carbon nanotube body to unique emitter: a first-principles study

The field emission characteristics of the body for single-walled carbon nanotubes (SWNTs) are investigated by use of the first-principles calculations. We find that field emission property, chemical stability and binding energy of the tube body with the practical diameter are less sensitive to the tube diameter, morphology, and conductive characteristic, and conclude the emission features of the body film: consistence in emission sites, uniformity in emission energy distribution, predictability in emission effects and high emission stability, which are similar to those of graphite sheet or diamond film. These unique features guarantee the tube body to be applicable to flat panel displays with the same picture quality, cylindrical cathode and linear emitter.     

Anatomic characterization of human ultra-weak photon emission with a moveable photomultiplier and CCD imaging

Ultra-weak photon emission of a living system has received scientific attention because of its potential for monitoring oxidative metabolism and oxidative damage to tissues. Heretofore, most studies have focused only on the emission from hands. The data regarding emission from other anatomic locations are limited. A previous multi-anatomic site recording of four subjects quantitatively demonstrated that the emission from several corresponding anatomic locations could differ by as much as a factor of 4. The data also suggested a "common" anatomic emission percentage distribution pattern. This information raised the question whether such a typical anatomic percentage emission exists. The objective of the present paper is to systematically replicate the emission from identical anatomic locations to document whether the anatomic percentage distribution pattern is generic. Part 1 includes the recording of ultra-weak photon emission from one sample subject over the torso, head and upper extremities with a highly sensitive charge-coupled device (CCD). Part 2 includes the analysis of that data to select a series of anatomic locations that were subsequently studied with a group of 20 subjects utilizing a highly sensitive, cooled and moveable (in three directions) photomultiplier system. Total sum emission of all recorded anatomic locations per subject fluctuates in this study almost 5-fold between subjects. However, the contribution of each anatomic location to the total emission from each subject was approximately the same percentage for each subject and similar to the sample CCD subject. The deviation of the anatomic percentage contribution for each subject was also established. The study presents evidence that there is a "common" anatomic percentage distribution pattern of ultra-weak photon emission for corresponding locations from each subject.     

Spectroscopic investigation of defect-state emission in CdSe quantum dots

CdSe quantum dots are the most studied Cd-based quantum dots with their high quantum yield, high photostability, narrow emission band, and easy synthesis procedure. They are frequently used to develop light emitting diode (LED) due to their unique photophysical properties; however, their narrow emission band causes a challenge to design white LEDs because white light emission requires emission in multiple wavelengths with broad emission bands. Here in this study, we developed CdSe quantum dots with a narrow band-edge emission band and broad defect-state emission band through a modified two-phase synthesis method. Our results revealed that defect-state emission is directly linked to the surface of quantum dots and can be excited through exciting surfactant around the quantum dot. The effect of surfactant on emission properties of CdSe quantum dots diminished upon growing a shell around CdSe quantum dots; as a result, surface-dependent defect-state emission cannot be observed in gradient heterogeneous alloyed CdS_xSe_1-x quantum dots.     

Year-long biophoton measurements: normalized frequency count analysis and seasonal dependency

Biophoton emissions from three healthy human subjects were measured for 52 weeks. The active nature of dorsal hands and personal discernable patterns in palmar hands were investigated through frequency count analysis of biophoton emission rates. Also, the seasonal dependency of biophoton emission rates from human hands was studied and we found that emission rates were lowest in autumn. There was a reversion of relative emission rates from the palms and the dorsa depending upon the season. The emission rates from the palms remain rather stable throughout the year, but those from the dorsa vary widely depending upon the season. These features of biophoton emission rates were considered in light of the diagnostic view of traditional Chinese medicine.     

煤粉锅炉NOX排放特性及控制的研究

对电站煤粉锅炉NOx生成特性进行了详细的研究，获得锅炉负荷、过量空气系数、热风温度、制粉系统运行方式、燃烧器配风形式、煤种等与NOx生成的关系，并就降低NOx的措施与锅炉效率的关系进行了分析，在此基础上提出电站煤粉锅炉在不影响锅炉燃烧效率的前提下，进行低NOx优化运行的方法，通过燃烧调整来达到控制NOx排放的目的。     

煤燃烧过程中氟析出特性与生成机理

通过建立的固定床管式炉煤燃烧氟析出试验装置，研究了煤燃烧过程中气态氟的排放特性，并根据燃煤氟析出等温动力学实验建立了气态氟生成动力学模型。结果表明：氟析出率随燃烧温度的升高而逐渐增加，煤中氟在300 ℃～400 ℃开始析出，500 ℃～1 100 ℃为主要析出温度范围；氟析出率随煤在炉内停留时间的增加而增加，但前5 min为主要析出阶段；炉内还原性气氛对氟析出有一定的影响；氟析出率与煤中氟赋存形态和含氟量有关。燃煤过程中氟析出过程可用一级反应动力学描述，反应活化能E和频率因子A依赖于煤中氟的赋存形态和氟化物的热稳定性。不同煤种E为28.0 kJ·mol－1～65.1 kJ·mol－1，A为12.5 min－1～46.0 min－1。     

Role of conformational isomerism in solvent-mediated charge transfer in chiral (S) 1,2,3,4-tetrahydro-3-isoquinoline methanol (THIQM): condensed-phase to jet-cooled spectroscopic studies

Intramolecular charge-transfer reaction in chiral (S) 1,2,3,4-tetrahydro-3-isoquinoline methanol (THIQM) has been investigated in the condensed phase and in jet-cooled conditions by means of laser-induced fluorescence, dispersed emission, resonance-enhanced two-photon ionization, and IR-UV double resonance experiments, as well as quantum chemical calculations. In the condensed phase, THIQM only shows local emission in nonpolar and protic solvents and dual emission in aprotic polar solvents, where the solvent-polarity dependent Stokes shifted emission is ascribed to a state involving charge transfer from the nitrogen lone pair to the benzene π-cloud. Ab initio calculations reveal two low-energy conformers, which are observed in jet-cooled conditions. In the most stable conformer, THIQM(I), the CH(2)OH substituent acts as a hydrogen bond donor to the nitrogen lone pair in the equatorial position, while the second most stable conformer, THIQM(II), corresponds to the opposite NH···O hydrogen bond, with the nitrogen lone pair in the axial position. The two low-energy jet-cooled conformers of THIQM evidenced from the laser-induced fluorescence and dispersed emission spectra only show structured local emission. Complexes with usual solvents reproduce the condensed phase properties. The jet-cooled complex with aprotic polar solvent acetonitrile shows both local emission and charge transfer emission as observed in solution. The jet-cooled hydrate mainly shows local emission due to the unavailability of the nitrogen lone pair through intermolecular hydrogen bonding.     

Optical emission of a molecular nanoantenna pair

The optical emission from a pair of nanoantennas is investigated within the theoretical framework of quantum electrodynamics. The analysis of fluorescent emission from a pair of molecular antenna species in close proximity is prompted by experimental work on oriented semiconductor polymer nanostructures. Each physically different possibility for separation-dependent features in photon emission by any such pair is explored in detail, leading to the identification of three distinct mechanisms: emission from a pair-delocalized exciton state, emission that engages electrodynamic coupling through quantum interference, and correlated photon emission from the two components of the pair. Although each mechanism produces a damped oscillatory dependence on the pair separation, each of the corresponding results exhibits an analytically different form. Significant differences in the associated spatial frequencies enable an apparent ambiguity in the interpretation of experiments to be resolved. Other major differences are found in the requisite conditions, the associated selection rules, and the variation with angular disposition of the emitters, together offering grounds for experimental discrimination between the coupling mechanisms. The analysis paves the way for investigations of pair-wise coupling effects in the emission from nanoantenna arrays.     

Dependence of tryptophan emission wavelength on conformation in cyclic hexapeptides

The wavelength of maximum emission of tryptophan depends on the local electrostatic environment of the indole chromophore. The time-resolved emission spectra of seven rigid cyclic hexapeptides containing a single tryptophan residue were measured. The emission maxima of the three decay-associated spectra for the seven peptides ranged from 341 to 359 nm, suggesting that different tryptophan rotamers have different emission maxima even in the case of solvent-exposed tryptophans. This conclusion is supported by quantum mechanical/molecular dynamics simulations of the six canonical side chain rotamers of tryptophan in solvated hexapeptides. The calculated range of emission maxima for the tryptophan rotamers of the seven peptides is 344-365 nm. The precision of the wavelength calculations and the peptide, water, and charged side chain contributions to the spectral shifts are examined. The results indicate that the emission maxima of decay-associated spectra can aid in the assignment of fluorescence lifetimes to tryptophan rotamers.     

2,3-Diarylbenzo[b]arsole: Structural Modification and Polymerization for Tuning of Photophysical Properties

2,3-Diarylbenzo[b]arsoles were synthesized from zirconacycles and diiodophenylarsine. The structural modification to the luminophore was attained through diarylacetylene precursors, Suzuki–Miyaura coupling, and oxidation of the arsenic atom. The emission properties were controlled according to these modifications. The 2,3-diarylbenzo[b]arsoles showed aggregation-induced emission enhancement; the stronger emission was observed in the solid states than in solutions. In addition, Suzuki–Miyaura polycondensation and olefin metathesis polymerization produced main- and side-chain polymers, respectively. The resultant polymers showed different emission behaviors such as aggregation caused quenching and aggregation induced emission enhancement.     

微孔晶体材料C12A7-Cl-的表面氯负离子发射性能和机理

利用飞行时间质谱(TOF-MS)观测到氯负离子从合成的微孔晶体材料C12A7-Cl-(11CaO·7Al2O3·CaCl2)表面发射出来, 详细研究了C12A7-Cl-的发射特性, 包括发射强度分支比、温度效应、电场效应和表观活化能. 在我们的检测范围内从C12A7-Cl-表面发射的离子中绝大部分是氯负离子(最大强度分支比为98%), 此外还有弱的氧负离子和电子发射. 各种离子的绝对发射电流强度都随着表面温度升高或引出电场强度的增加而显著增强, 随着引出电场强度从200增加到1200 V·cm-1, 氯负离子发射的表观活化能从180.9 kJ·mol-1减小到110.0 kJ·mol-1. 氯负离子和C12A7-Cl-表面之间的结合能大约是228 kJ·mol-1. 研究了氯负离子的发射稳定性, 并且应用一种电化学注入法, 以获得持续的氯负离子发射. 基于上述实验还讨论了氯负离子的形成和发射机理. 目前的方法可望被用于发展氯负离子储存/发生器.     

The impact of molecular emission in compositional depth profiling using Glow Discharge-Optical Emission Spectroscopy

The scope of this paper is to investigate and discuss how molecular emission can affect elemental analysis in glow discharge optical emission (GD-OES), particularly in compositional depth profiling (CDP) applications. Older work on molecular emission in glow discharges is briefly reviewed, and the nature of molecular emission spectra described. Work on the influence of hydrogen in the plasma, in particular elevated background due to a continuum spectrum, is discussed. More recent work from sputtering of polymers and other materials with a large content of light elements in a Grimm type source is reviewed, where substantial emission has been observed from several light diatomic molecules (CO, CH, OH, NH, C₂). It is discussed how the elevated backgrounds from such molecular emission can lead to significant analytical errors in the form of “false” depth profile signals of several atomic analytical lines. Results from a recent investigation of molecular emission spectra from mixed gases in a Grimm type glow discharge are presented. An important observation is that dissociation and subsequent recombination processes occur, leading to formation of molecular species not present in the original plasma gas. Experimental work on depth profiling of a polymer coating and a thin silicate film, using a spectrometer equipped with channels for molecular emission lines, is presented. The results confirm that molecular emission gives rise to apparent depth profiles of elements not present in the sample. The possibilities to make adequate corrections for such molecular emission in CDP of organic coatings and very thin films are discussed.     

Anomalous green emission and energy transfer in the n,n-dimethylformamide/hydrochloric acid/europium chloride system

The unusual green photoluminescence (PL) of N,N-dimethylformamide (DMF)/hydrochloric acid (HCl)/europium chloride (EuCl3) solutions discovered earlier was investigated in more detail to clarify the emission mechanism. It was revealed that the DMF/HCl pair alone can yield a green PL band under UV excitation, and the emission has features of that of excimers. The addition of EuCl3 salt to the solution further stimulates the green emission. The quantum yield of the line emission of Eu3+ ions at 592 and 612 nm is also affected by the presence of HCl in the solution. Both the green emission band and Eu3+ emission lines possess a common channel of excitation at approximately 280 nm. This channel is the only source for the green emission band and an additional source for the Eu3+ emission lines, which can also be stimulated through a conventional Eu3+ excitation channel at 394 nm. The common excitation channel was found to be time-dependent, and its excitation maximum gradually shifts to longer wavelengths. Changes in the PL profiles of europium ions were also observed depending on the presence of HCl and the solution aging.     

Radiation-induced emission from golden hamster embryo cells

Emission from high-energy-electron-irradiated golden hamster embryo (GHE) cells has been studied over the temperature range 12–300 K both by a one-shot-single-photon-counting method and by photocurrent measurements with an oscilloscope. Emission from the irradiated phosphate buffered saline (PBS) also has been studied. The emission spectra from PBS at 12 and 77 K show a maximum around 330 and 380 nm, respectively, which are the same spectra as those from irradiated pure H₂O. The emission from irradiated GHE consists of the new band at 480 nm in addition to the emission from H₂O. The 480 nm emission is observed at the temperature range of 12–300 K, though the emission at 300 K is much lower than that at low temperature. The 480 nm emission is ascribed to the transition from excited organic substances in GHE cells. The intensity of 480 nm emission at 300 K increases linearly with increasing irradiation-dose in the range of 11–600 Gy.     

The effects of oxygen on the detection of mercury using laser-induced breakdown spectroscopy

A systematic study of the processes associated with mercury atomic emission in a laser-induced plasma and the interactions of mercury with oxygen species is presented. At early plasma decay times, on the order of 5–10 μs, no significant variation in mercury atomic emission was observed with the addition of oxygen-containing species. At intermediate and long decay times (10–100 μs), a significant reduction in the 253.7-nm mercury emission intensity was recorded with the introduction of oxygen-containing species. The decrease in mercury emission was temporally coincident with the recombination of atomic oxygen, as measured by the O(I) emission. The decreased mercury emission was not due to thermal effects, based on plasma temperature measurements, and was independent of the molecular source of oxygen, for similar concentrations of oxygen as air, carbon dioxide, and carbon monoxide. Analysis of additional mercury atomic emission lines revealed that the reduction in mercury emission in the presence of oxygen species is limited primarily to the 253.7-nm transition. In concert, the data lead to the conclusion that the 253.7-nm mercury emission line is selectively quenched by oxygen species, primarily O₂ and NO, that are formed during the plasma recombination process. Implications for laser-induced breakdown spectroscopy-based emissions monitoring of mercury species are discussed.     

A comparative study of the enhancement of molecular emission in a spatially confined plume through optical emission spectroscopy and probe beam deflection measurements

The spatial confinement effects of shock wave on the expansion of a carbon plume induced by pulsed laser ablation of graphite in air and the enhancement of the plume emission were studied by optical emission spectroscopy and probe beam deflection measurements. A metal disk was set in the way of the ablation-generated shock wave to block and reflect the supersonically propagating shock wave. The reflected shock wave propagated backwards and confined the expanding plume. The optical emission of CN molecules was enhanced in contrast to the case without the block disk and the emission enhancement was dependent on the position of the disk. Based on the results of time-integrated and -resolved optical emission spectroscopy, and the time- and space-resolved probe beam deflection measurements, the processes occurring in the plume were discussed and the mechanisms responsible for the enhancement of molecular emission in the spatially confined plume were investigated.