Optimum fluorescence emission around 1.8μm for LiYF_4 single crystals of various Tm^(3+)-doping concentrations

In this paper, optical spectra of LiYF4 single crystals doped with Tm3＋ ions of various concentrations are reported. The emission intensity at 1.8 ktm first increases with increasing Tm3＋ concentration, and reaches a maximum value when the concentration of Tm3＋ is about 1.28 mol%, then it decreases rapidly as the concentration of Tm3＋ further increases to 3.49 mol%. The emission lifetime at 1.8 p.m also shows a similar tendency to the emission intensity. The maximum lifetime of 1.8 μm is measured to be 17.68 ms for the sample doped with Tm3＋ of 1.28 mol%. The emission cross section of 3F4 level is calculated. The maximum reaches 3.76 × 10 -21 cm2 at 1909 nm. The cross relaxation （3H6, 3H4 →3 F4, 3F4） between Tm3＋ ions and the concentration quenching effect are mainly attributed to the change of emission with Tm3＋ concentration. The largest quantum efficiency between Tm3＋ ions is estimated to be ,-147% from the measured lifetime and calculated radiative lifetime. All the results suggest that the Tm3＋/LiYF4 single crystal may have potential applications in 2 μm mid-infrared lasers.

Fluorescence emission difference microscopy based on polarization modulation

In this paper,we propose a new fluorescence emission difference microscopy(FED)technique based on polarization modulation.An electro-optical modulator(EOM)is used to switch the excitation beam between the horizontal and vertical polarization states at a high frequency,which leads to solid-and donut-shaped beams after spatial light modulation.Experiment on the fluorescent nanoparticles demonstrates that the proposed method can achieve~λ=4 spatial resolution.Using the proposed system,the dynamic imaging of subcellular structures in living cells over time is achieved.

High carrier mobility and strong fluorescence emission: Toward highly sensitive single-crystal organic phototransistors

Organic single crystals(OSCs)offer a unique combination of both individual and collective properties of the employed molecules,but it remains highly challenging to achieve OSCs with both high mobilities and strong fluorescence emissions for their potential applications in multifunctional optoelectronics.Herein,we demonstrate the design and synthesis of two novel triphenylamine-functionalized thienoacenes-based organic semiconductors,4,8-distriphenylamineethynylbenzo[1,2-b:4,5-b′]dithiophene(4,8-DTEBDT)and 2,6-distriphenylamineethynylbenzo[1,2-b:4,5-b′]dithiophene(2,6-DTEBDT),with high-mobility and strong fluorescence emission.The two compounds show the maximum mobilities up to 0.25 and 0.06 cm^(2) V^(-1) s^(-1),the photoluminescence quantum yields(PLQYs)of 51% and 45%,and the small binding energies down to 55.13 and 58.79 meV.The excellent electrical and optical properties ensured the application of 4,8-DTEBDT and 2,6-DTEBDT single crystals in ultrasensitive UV phototransistors,achieving high photoresponsivity of 9.60×105 and 6.43×10^(4) AW^(-1),and detectivity exceeding 5.68×10^(17) and 2.99×10^(16) Jones.

Absorption and Fluorescence Emission Spectra of Molecules Containing Azo and/or Oxadiazole Units

The ground state structures of a series of organic molecules containing azo and/or oxadiazole units were obtained by means of density functional theory B3LYP/6-3IG（d） method. The first singlet excited state structures were optimized by virtue of singlet-excitation configuration interaction CIS/6-31G（d） method. The absorption and fluorescence emission spectra were then evaluated via the time-dependent density functional theory B3LYP and PBE1PBE methods with 6-31 l＋＋G（3df,2p） basis set. The calculation results show that compared with those of their parent molecules A-H, B-H, C-H, D-H, the absorption and emission wavelength values of all the derivatives show red shifts. The derivatives containing both the oxadiazole and methoxyl units are good candidates for longer absorption wavelength materials. The effects of azo, oxadiazole, and methoxyl units on the absorption and emission wavelength were discussed.

Comparison of the emission wavelengths by a single fluorescent dye on in vivo 3-photon imaging of mouse brains

Multiphoton microscopy(MPM)is a powerful imaging technology for brain research.The imaging depth in MPM is partly determined by emission wavelength of fluorescent labels.It has been demonstrated that a longer emission wavelength is favorable for signal detection as imaging depth increases.However,there has been no comparison with near-infrared(NIR)emission.In order to quantitatively analyze the effect of emission wavelength on 3-photon imaging of mouse brains in vivo,we utilize the same excitation wavelength to excite a single fluorescent dye and simultaneously collect NIR and orange-red emission fluorescence at 828 nm and 620 nm,respectively.Both experimental and simulation results show that as the imaging depth increases,NIR emission decays less than orange-red fluorescent emission.These results show that it is preferable to shift the emission wavelength to NIR to enable more e±cient signal collection deep in the brain.

Elemental composition x-ray fluorescence analysis with a TES-based high-resolution x-ray spectrometer

The accurate analysis of the elemental composition plays a crucial role in the research of functional materials.The emitting characteristic x-ray fluorescence(XRF)photons can be used for precisely discriminating the specified element.The detection accuracy of conventional XRF methodology using semiconductor detector is limited by the energy resolution,thus posing a challenge in accurately scaling the actual energy of each XRF photon.We adopt a novel high-resolution x-ray spectrometer based on the superconducting transition-edge sensor(TES)for the XRF spectroscopy measurement of different elements.Properties including high energy resolution,high detection efficiency and precise linearity of the new spectrometer will bring significant benefits in analyzing elemental composition via XRF.In this paper,we study the Ledge emission line profiles of three adjacent rare earth elements with the evenly mixed sample of their oxide components:terbium,dysprosium and holmium.Two orders of magnitude better energy resolution are obtained compared to a commercial silicon drift detector.With this TES-based spectrometer,the spectral lines overlapped or interfered by background can be clearly distinguished,thus making the chemical component analysis more accurate and quantitative.A database of coefficient values for the line strength of the spectrum can then be constructed thereafter.Equipped with the novel XRF spectrometer and an established coefficient database,a direct analysis of the composition proportion of a certain element in an unknown sample can be achieved with high accuracy.

Factors affecting improvement of fluorescence intensity of quartet and doublet state of NO diatomic molecule excited by glow discharge

We report on the observation of new fluorescence emission spectral transitions obtained from NO diatomic molecule in the region from ultraviolet （UV） to near infrared （NIR） in a low power glow discharge system. This glow discharge electronic excitation populates different quartet and doublet states of NO in its proximity such as the A2Z （/9 = 2）, b4∑- （υ= 3）, B2М （1） = 4）, and X2Л （u= 33-32） states. Due to inter-system crossing, emission lines originating from these levels to lower lying states are recorded and spectral line assignments are performed. The observed systems include b4∑- a4∏, B21∏-a4∏, a4∏-X2I∏, A2∑X2∏, X2∏-X2∏ （33-15）, X2∏-X2∏ （33-17）, X2∏-X2∏ （33-20）, and X2∏-X2∏ （33- 18）. This new information will conduce to the better understanding of the interesting features of NO molecule. Such parameters that affect the recording of low density of NO molecules are also discussed In addition to the factors such as the time evolution, argon gas concentration relative to NO mixture, the percentage of NO molecular gas concentration, discharge electric current signals and discharge applied voltage are studied. Those factors would enhance the fluorescence signal intensity of NO molecules. The recent results might be significant as reference data for optimizing the glow discharge spectrometer and diagnostics of NO gas.

Fluorescence Behavior and Emission Mechanisms of Poly(ethylene succinamide)and Its Applications in Fe^(3+)Detection and Data Encryption

Conventional fluorescent polymers are featured by large conjugation structures.In contrast,a new class of fluorescent polymers without any conjugations is gaining great interest in immerging applications.Polyamide is a typical member of the conjugation-free fluorescent polymers.However,studies on their electrophotonic property are hardly available,although widely used in many fields.Herein,poly(ethylene succinamide),PA24,is synthesized;its chemical structure confirmed through multiple techniques(NMR,FTIR,XRD,etc.).PA24 is highly emissive as solid and in its solution at room temperature,and the emission is excitation and concentration dependant,with an unusual blue shift under excitation from 270 nm to 320 nm,a hardly observed phenomenon for all fluorescent polymers.Quite similar emission behavior is also observed under cryogenic condition at 77 K.Its emission behavior is thoroughly studied;the ephemeral emission blue-shift is interpreted through Förster resonance energy transfer.Based on its structures,the emission mechanism is ascribed to cluster-triggered emission,elucidated from multianalyses(NMR,FTIR,UV absorbance and DLS).In presence of a dozen of competitive metal ions,PA24 emission at 450 nm is selectively quenched by Fe^(3+).PA24 is used as probe for Fe^(3+)and H_(2)O_(2) detections and in data encryption.Therefore,this work provides a novel face of polyamide with great potential applications as sensors in different fields.

Anisotropy in Third-Order Nonlinear Optical Susceptibility of a Squarylium Dye in a Nematic Liquid Crystal

A squarylium dye is dissolved in 4-cyano-4＇-pentylbiphenyl （SCB） and oriented by sandwiching mixtures between two pieces of rubbed glass plates. The optical absorption spectra of the oriented squarylium dye-5CB layers exhibit high anisotropy. The third-order nonlinear optical responses and susceptibilities X^（3）e of squarylium dye in 5CB are measured with light polarizations parallel and perpendicular to the orientational direction by the resonant femtosecond degenerate four-wave mixing （DFWM） technique. Temporal profiles of the DFWM signal of the oriented squarylium dye-5CB layers with light polarizations parallel and perpendicular to the orientational direction are measured with a time resolution of 0.3ps （FWHM）, and are found to consist of two components, i.e., the coherent instantaneous nonlinear response and slow response due to the formation of excited molecules. A high anisotropic ratio of x^（3）e, 10.8 ：k 1.2, is observed for the oriented layers.

Photosynthetic Characteristics of Flag Leaves in Rice White Stripe Mutant 6001 During Senescence Process

Physiological, biochemical and electron microscopy analyses were used to investigate the photosynthetic performance of flag leaves in rice white stripe mutant 6001 during the senescence process. Results showed that the chlorophyll content at the heading and milk-ripe stages in rice mutant 6001 were about 34.78% and 3.00% less than those in wild type 6028, respectively. However, the chlorophyll content at the fully-ripe stage in rice mutant 6001 was higher than that in wild type 6028. At the heading stage, the net photosynthetic rate （Pn） in rice mutant 6001 was lower than that in wild type 6028. Rice mutant 6001 also exhibited a significantly slower decrease rate of Pn than wild type 6028 during the senescence progress, especially at the later stage. Furthermore, Ca2^-ATPase, Mg~^-ATPase and photophosphorylation activities exhibited the similar trends as the Po. During the senescence process, the 68 kDa polypeptide concentrations in the thylakoid membrane proteins exhibited a significant change, which was one of the critical factors that contributed to the observed change in photosynthesis. We also observed that the chloroplasts of rice mutant 6001 exhibited higher integrity than those of wild type 6028, and the chloroplast membrane of rice mutant 6001 disintegrated more slow during the senescence process. In general, rice mutant 6001 had a relatively slower senescence rate than wild type 6028, and exhibited anti-senescence properties.

Electrical and Optical Properties of Nano Aluminum Film/Particle Structure

The electrical and optical effects of particles on the nano aluminum film deposited by thermal evaporation was investigated. From the characterization results of scanning electron microscope（SEM）, the accumulation in tens of nanometers had been observed. The current-voltage（I-V） curve of the sample indicates its nonlinear electrical characters expecting the corresponding nonlinear optical properties. By the theoretical calculation, nonlinear conduction of the carrier transportation may result from the barrier-well-barrier structure, where negative resistance and Coulomb blockade effect appears. The simulation results are approximately matched with the experimental results. By testing the fluorescence emission spectrum of the sample, peaks were found to be located at 420 and 440 nm. In addition, the full width at half maximum（FWHM） had been obviously broadened by means of adding 2, 5-diphenyloxazole（DPO）. Therefore, discrete energy levels could be estimated inside those particles.

Spectroscopic study of local thermal effect in transparent glass ceramics containing nanoparticles

Local thermal effect influencing the fluorescence of triply ionized rare earth ions doped in nanocrystals is studied with laser spectroscopy and theory of thermal transportation for transparent oxyfluoride glass ceramics containing nanocrystals. The result shows that the local temperature of the nanocrystals embedded in glass matrices is much higher than the environmental temperature of the sample. It is suggested that the tempera,ture-dependent thermal energy induced by the light absorption must be considered when the theory of thermal transportation is applied to the study of local thermal effect.

Luminescence Properties of Ca(NbO_3)_2∶Dy^(3+)

On the base of the luminescence properties of the Dy (3+) activated Ⅱ-Ⅴ group complex oxide,the luminescence properties of Ca(NbO_3)_2∶Dy (3+) and compensation effect by Na + for the Ca(NbO_3)_2∶Dy (3+) were introducted. The Dy (3+) concentrations in the phosphor powder of Ca(NbO_3)_2∶Dy (3+) and Ca(NbO_3)_2Na +∶Dy (3+) are different. The excitation spectrum,the emission spectrum and the blue-yellow ratios are obtained,and the spectrum law and the luminescence mechanism are also discussed.

Synthesis,Crystal Structure and Fluorescent Property of a Lanthanum(Ⅲ) Complex Coordinated with Quinolinyloxy Acetamide Ligand

A novel lanthanum（III） complex, [LaL2（NO3）3].H2O （1） based on L （L = N-（na- phthalene-l-yl）-2-（quinolin-8-yloxy）acetamide）, was synthesized and characterized by X-ray diffraction. The crystal of I belongs to the monoclinic system, space group C2c with Mr= 1017.69, a = 25.1438（17）, b = 13.5950（9）, c = 18.2349（12） A, β= 132.4980（10）° V= 4595.8（5） A3, Z= 4, Dc = 1.471 Mg/m3, F（000） = 2056,μ= 1.004 mm-1, R = 0,0588 and wR = 0.1402. The central La（lI1） ion is coordinated to four oxygen atoms, two nitrogen atoms from two independent acetarnide ligands and six oxygen atoms from three nitrate anions, possessing a distorted icosahedron coordination geometry. In the crystal of 1, intermolecular N-H……O hydrogen bonds linked the molecules into chains along the c axis. In solid state and CH3CN solution, complex 1 exhibits stronger fluorescent emission than the ligand L.

Chemical properties of colored dissolved organic matter in the sea-surface microlayer and subsurface water of Jiaozhou Bay, China in autumn and winter

The distribution and chemical properties of chromophoric dissolved organic matter （CDOM） in the Jiaozhou Bay, China were examined during four cruises in 2010-2011. The influence of freshwater and industrial and municipal sewage along the eastern coast of the bay was clearly evident as CDOM level- s （defined as a30s）, and dissolved organic carbon （DOC） concentrations were well correlated with salinity during all the cruises. Moreover, DOC concentrations were significantly correlated with chlorophyll a con- centrations in the surface microlayer as well as in the subsurface water. The concentrations of DOC and CDOM displayed a gradually decreasing trend from the northwestern and eastern coast to the central hay, and the values and gradients of their concentrations on the eastern coast were generally higher than those on the western coast. In addition, CDOM and DOC levels were generally higher in the surface microlayer than in the subsurface water. In comparison with DOC, CDOM exhibited a greater extent of enrichment in the microlayer in each cruise, with average enrichment factor （EF） values of 1.38 and 1.84, respectively. Four fluorescent components were identified from the surface microlayer and subsurface water samples and could be distinguished as peak A, peak T, peak B and peak M. For all the cruises, peak A levels were higher in the surface microlayer than in the subsurface water. This pattern of variation might be attributed to the terrestrial input.

Rapid and simple analysis of amphetamine-type illegal drugs using excitation–emission matrix fluorescence coupled with parallel factor analysis

Nowadays,the abuse of illegal drugs has been an increasingly grim problem in the world.Excitation–emission matrix fluorescence combined with parallel factor analysis was used to make a quantitative analysis of the simulated amphetamine-type illegal drugs.Satisfactory results were achieved for simultaneous determination of methamphetamine(MAM)and 3,4-methylenedioxymethamphetamine(MDMA)in the presence of adulterants.The average recoveries were(99.8±0.6)%and(101.6±5.7)%for MAM and MDMA,respectively.Figures of merit including root-mean-square error of calibration and prediction,sensitivity and selectivity were investigated to evaluate the performance of the proposed method.The limits of detection were 0.054 and 0.0021 g/mL for MAM and MDMA,respectively.

Fabrication of high-performance non-doped OLEDs by combining aggregation-induced emission and thermally activated delayed fluorescence

Undoubtedly,the realization of"one stone and two birds"is ideal,which is also applicable to the molecular design in the pursuit of excellent performance.Recently,this standpoint has been confirmed again by an interesting story written from the lab of Zujin Zhao,Shi-Jian Su,and BenZhong Tang,at South China University of Technology and the Hong Kong University of Science and Technology,in the design of DBT-BZ-DMAC(Figure 1)[1].Despite its simple structure,DBT-BZ-DMAC exhibits wonderful characteristics,

On the road towards the global analysis of human synapses

Synapses are essential units for the flow of information in the brain.Over the last 70 years,synapses have been widely studied in multiple animal models including worms,fruit flies,and rodents.In comparison,the study of human synapses has evolved significantly slower,mainly because of technical limitations.However,three novel methods allowing the analysis of molecular,morphological,and functional properties of human synapses may expand our knowledge of the human brain.Here,we briefly describe these methods,and evaluate how the information provided by each unique approach may contribute to the functional and anatomical analysis of the synaptic component of human brain circuitries.In particular,using tissue from cryopreserved human brains,synaptic plasticity can be studied in isolated synaptosomes by fluorescence analysis of single-synapse long-term potentiation（FASS-LTP）,and subpopulations of synapses can be thoroughly assessed in the ribbons of brain tissue by array tomography（AT）.Currently,it is also possible to quantify synaptic density in the living human brain by positron emission tomography（PET）,using a novel synaptic radio-ligand.Overall,data provided by FASS-LTP,AT,and PET may significantly contribute to the global understanding of synaptic structure and function in both healthy and diseased human brains,thus directly impacting translational research.

Unconventional Fluorescent and Multi-responsive Polyethyleneimine with LCST and UCST Behavior:Synthesis,Characterization and Biological Applications

Non-aromatic fluorescent and multi-responsive materials,exhibiting inherent fluorescence emission and controlled phase change,have garnered significant attention in recent years.However,the underlying interaction between their fluorescent properties and phase transition remains unclear.In this study,we synthesized a series of catalyst-free aza-Michael addition-based polyethyleneimine(RFPEI)materials by reacting polyethyleneimine(PEI)with N-isopropyl acrylamide(NIPAM).The resulting RFPEI was comprehensively characterized,and demonstrated dual-phase transition behavior(LCST and UCST)in water,which could be finely tuned by adjusting its composition or external factors such as pH.Notably,upon UV irradiation(365 nm),RFPEI exhibited strong fluorescence emission.We further investigated the effects of NIPAM grafting percentage to PEI,polymer concentration,and pH on the LCST/UCST and fluorescent properties of RFPEI aqueous solutions.Moreover,we showcased the great potential of RFPEI as a versatile tool for physiological cell imaging,trace detection,and controlled release of doxorubicin.Our study presents a novel class of stimuli-responsive fluorescent materials with promising applications in the field of biomedicine.

Effects of Chlorophyll Availability on Fluorescence Components of Photosystems in the ORF_469-Deletion Mutant of Cyanobacterium

PCR amplified ORF 469 fragment from Synechocystis sp . PCC 6803 was cloned into pUC118 and a construct was made in which part of ORF 469 was deleted and replaced by erythromycin resistance cassette. Transformation of wild type strain of Synechocystis sp . PCC 6803 with this construct yielded a mutant in which ORF 469 was deleted. In the resulting mutant, the light independent pathway of chlorophyll biosynthesis was inactivated and availability of chlorophyll was fully dependent on light. When propagated the mutant in dark, the chlorophyll was non detectable and protochlorophyllide with 645?nm fluorescence emission peak was accumulated. Meanwhile, the fluorescence emission peaks (excited at 435?nm) of thylakoids at 685?nm, 695?nm and 725?nm, which represented relative chlorophyll\|binding proteins, disappeared. Upon return of dark\|grown ORF 469 mutant to the light, greening occurred and chlorophyll was synthesized to assembly fluorescence emission components in photosystems. Newly synthesized chlorophyll combined the fluorescence component of 685?nm at first, then 725?nm and 695?nm at last, which indicates a pecking order for biogenesis of chlorophyll binding proteins when availability of chlorophyll is limited. The mutant lacking ORF 469 in Synechocystis sp . PCC 6803 was suggested as an excellent cyanobacterial system for studies on the interactions between chlorophyll and chlorophyll binding proteins in photosystems.