Rice yellow mottle is considered the most destructive disease threatening rice production in Africa. Early detection of this infection in rice is essential to limit its expansion and proliferation. However, there is n...Rice yellow mottle is considered the most destructive disease threatening rice production in Africa. Early detection of this infection in rice is essential to limit its expansion and proliferation. However, there is no research devoted to the spectral detection of rice yellow mottle virus (RYMV) infection, especially in the asymptomatic or early stages. This work proposes the use of hyperspectral fluorescence and reflectance data at leaf level for the detection of this disease in asymptomatic stages. A greenhouse experiment was therefore conducted to collect hyperspectral fluorescence and reflectance data at different stages of infection. These data allowed to calculate nine vegetation indices: one from fluorescence spectra and eight from reflectance spectra. A t-test made it possible to identify, from the second day after infection, four relevant reflectance vegetation indices to discriminate healthy leaves from those infected: these are Photochemical Reflectance Index (PRI), Transformed Chlorophyll Absorption in Reflectance Index (TCARI), Structure Intensive Pigment Index (SIPI) and Simple Ratio Pigment Index (SRPI). The fluorescence index was less sensitive in detecting infection. The four significant vegetation indices for the detection of RYMV were then used to build and evaluate models for discriminating plants according to their health status by the supervised classification of support vector machine (SVM) at different stages of infection. The maximum overall accuracy is 92.5% six days after inoculation (6 DAI). The sixth day after inoculation would be the adequate day to detect RYMV. This plants discrimination was validated by the mean reflectance spectra and by the histograms showing the differences between the average reflectance vegetation indices values of the two types of plants. Our results demonstrate the feasibility of differentiating RYMV-infected samples. They suggest that support vector machine learning models could be developed to diagnose RYMV-infected plants based on vegetation indices derived from spectral profiles at early stages of disease development.展开更多
In the preparation of this precursor tetraethlortho silicate (TEOS), sodium tungstate, ethyl alcohol, HCl and RECl3(RE=Eu,Tb) were mixed and then heated at 800 ℃ for 2 h, leading to a luminescent compound. The struct...In the preparation of this precursor tetraethlortho silicate (TEOS), sodium tungstate, ethyl alcohol, HCl and RECl3(RE=Eu,Tb) were mixed and then heated at 800 ℃ for 2 h, leading to a luminescent compound. The structure of the materials was characterized by TG-DTA and IR analysis, and the results indicate that the materials were in SiO2 network structure. Three-dimensional fluorescence spectra was used to characterize the luminescent properties of the materials. The luminescence property of doped and un-doped Eu3+or Tb3+ and Na2WO4 in silica materials were prepared and measured. The results show that good energy transfer from WO2-4 to Eu3+ ion, sensitized the luminescence intensity of Eu3+ remarkably. Tb3+ ion incorporated silica materials expressed the inverse energy transition from Tb3+ to WO2-4, however, we got the materials with homogeneous green blue fluorescent light. Finally, the energy transfer of WO2-4 and Eu3+, WO2-4 and Tb3+ were explained by energy levels diagram.展开更多
Much attention is devoted to fluorescent dyes especially those with potential in versatile applications.Reactions under "click" conditions between nonfluorescent 3-azidocoumarins and terminal alkynes produce...Much attention is devoted to fluorescent dyes especially those with potential in versatile applications.Reactions under "click" conditions between nonfluorescent 3-azidocoumarins and terminal alkynes produced 3-(1,2,3-triazol-1-yl)coumarins,a novel type of fluorescent dyes with intense fluorescence.The structures of the new coumarins were characterized by 1H NMR,MS,and IR spectra.Fluorescence spectra measurement demonstrated excellent fluorescence performance of the triazolylcoumarins and this click reaction is a promising candidate for bioconjugation and bioimaging applications since both azide and alkynes are quite inert to biological systems.展开更多
Fluorescence spectra of ladderlike polyphenylsilsesquioxane (LPPS) and ladderlike 1,4-phenylene-bridged polyvinylsiloxane (LPPVS) have been measured as a function of temperature (4-55 degreesC), in dilute tetrahydrofu...Fluorescence spectra of ladderlike polyphenylsilsesquioxane (LPPS) and ladderlike 1,4-phenylene-bridged polyvinylsiloxane (LPPVS) have been measured as a function of temperature (4-55 degreesC), in dilute tetrahydrofuran solution. The excimer (IF) to monomer (I-M) intensity ratio (I-E/I-M) of LPPS dilute solution shows a double linear Arrhenius plot with a break point ascribable to a transition temperature Tt. This behavior has not been found for single chain polyorganosiloxanes. When In/(E) of LPPS was plotted against 1/T, it also gave a double linear plot with one break point, which was found in single chain polyorganosiloxanes. The different behaviors between LPPS and single chain polyorganosiloxanes may be mainly attributed to the relatively rigid double-chain macromolecular backbone of LPPS. However, the 1n(I-E/I-M) of dilute LPPVS solution versus 1/T shows a simple linear variation with a positive slope which confirms our proposition. The difference between the fluorescence results of LPPS and those of LPPVS may possibly derive from their structure differences and cooperative motion in backbone chain bonds.展开更多
The fluorescence spectra of the poly (N-vinylcarbazole) in solution obtained with chirally organic salts or acid as catalyst or initiator [ (-)Sp: (-)-Sparteine, (+)CSA: D- (+)Camphor-10-sulfonic acid)], respectively,...The fluorescence spectra of the poly (N-vinylcarbazole) in solution obtained with chirally organic salts or acid as catalyst or initiator [ (-)Sp: (-)-Sparteine, (+)CSA: D- (+)Camphor-10-sulfonic acid)], respectively, have been investigated. It is found that the two emission peaks at the longer wavelength (lambda max, ca, 415nm) and the shorter wavelength (lambda max, ca, 370nm) are assigned to the sandwich excimer and second excimer (partial overlap) fluorescence, respectively. The sandwich excimer and partially overlapped excimer are attributed to a fully overlapped structure of neighbouring carbazole chromophores in a totally elipsed conformation of the isotactic sequence, and partially overlapped structure of the syndiotactic sequence. The estimated values of I-415/I-370 and isotactic sequence content by using the fluorescence spectra are in the order: (-)Sp(+) (+)CSA(-)> (+)CSA(-)> (-)Sp(+)ClO(4)(-) (no peak at 415nm for AIBN).展开更多
We have found some fluorescence characteristics of fossil fuels based on the contour maps of the three dimensional fluorescence spectra of their non quenching samples. The common fluorescence characteristic is t...We have found some fluorescence characteristics of fossil fuels based on the contour maps of the three dimensional fluorescence spectra of their non quenching samples. The common fluorescence characteristic is that the main peaks of various fossil fuels are located in the vicinity of excitation/emission wavelength pair 228nm/340nm.The diversity of fluorescence characteristics can be represented with several indexes α,K,F and R ,and these indexes provide measurable parameters for division of fluorescence fingerprints of fossil fuels. The fluorescence fingerprints of fossil fuels can be divided into five models named O,B,Q,P and G that are corresponding to condensate oil, light oil, heavy oil, coal and natural gas, respectively. The technique has a potential application in study of environment pollution on crude oil and geochemical exploration of fossil fuels.展开更多
The structure around Ti^(4+) in Bao-SiO_2 -B_2O_3-TiO_2 had been studied by X-ray fluorescence spectra. The results show that the Ti^(4+) mainly exists in the [TiO_4] and enters the network of [SiO_4]. [TiO_4] has the...The structure around Ti^(4+) in Bao-SiO_2 -B_2O_3-TiO_2 had been studied by X-ray fluorescence spectra. The results show that the Ti^(4+) mainly exists in the [TiO_4] and enters the network of [SiO_4]. [TiO_4] has the tendency to change to [TiO_6] with the increase of TiO_2 con-tent. When the TiO_2 content increases to about 20mol% the tendency reaches its maximum.展开更多
Rare earth chelates of benzoyl urea derivatives were prepared in ethanol and fluorescence spectra of these chelates were studied in detail. A composition of [RE(BU)_3Phen] (NO_3)_3 was obtained. Correlation between ch...Rare earth chelates of benzoyl urea derivatives were prepared in ethanol and fluorescence spectra of these chelates were studied in detail. A composition of [RE(BU)_3Phen] (NO_3)_3 was obtained. Correlation between chemical properties of ligands, chelates and spectroscopy was discussed. Intramolecular energy transfer in rare earth chelates was explained.展开更多
Noble metal nanoparticles exhibit unique surface plasmon resonance dependent optical properties.On this basis,gold nanoparticles(AuNPs)encapsulated in metal–organic frameworks(MOFs)can form AuNPs@MOFs composites to m...Noble metal nanoparticles exhibit unique surface plasmon resonance dependent optical properties.On this basis,gold nanoparticles(AuNPs)encapsulated in metal–organic frameworks(MOFs)can form AuNPs@MOFs composites to modulate the optical properties of fluorescent molecules,which is less reported.In this paper,based on the fluorescence enhancement effect of AuNPs on 2-(2-hydroxyphenyl)-1H-benzimidazole(HPBI)molecules,zeolitic imidazolate framework-8(ZIF-8)crystals with structural stability were introduced.AuNPs@ZIF-8 exhibited a significantly pronounced fluorescence enhancement of the HPBI molecules.In addition,by comparing the fluorescence characteristics of the HPBI molecules adsorbed on AuNPs@ZIF-8 and those captured in AuNPs@ZIF-8,we found that the ZIF-8 can act as a spacer layer with highly effective near-field enhancement.All our preliminary results shed light on future research on the composite structures of noble metal particles and MOFs for fluorescent probes and sensing applications.展开更多
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 s...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.展开更多
Wheat ( Triticum aestivum L.) plants were grown under ambient and doubled_CO 2(plus 350 μL/L) concentration in cylindrical open_top chamber to examine their effects on the ultrastructure, supramolecular architect...Wheat ( Triticum aestivum L.) plants were grown under ambient and doubled_CO 2(plus 350 μL/L) concentration in cylindrical open_top chamber to examine their effects on the ultrastructure, supramolecular architecture, absorption spectrum and low temperature (77 K) fluorescence emission spectrum of the chloroplasts from wheat leaves. The results were briefly summarized as follows: (1) The wheat leaves possessed normally developed chloroplasts with intact grana and stroma thylakoid membranes; The grana intertwined with stroma thylakoid membranes and increased slightly in stacking degree and the width of granum, in spite of more accumulated starch grains within the chloroplasts than those in control; (2) The particle density in the stacked region of the endoplasmic fracture face (EFs) and protoplasmic fracture face (PFs) and in the unstacked region the endoplasmic fracture face (EFu) and the protoplasmic fracture face (PFu) was significantly higher than that of control. Furthermore, in some cases many more particles on EFs faces of thylakoid membranes appeared as a paracrystalline particle array; (3) The variations in the structure of chloroplasts were consistent with the absorption spectra and the low temperature (77 K) fluorescence emission spectra of the chloroplasts developed under the doubled_CO 2 concentration. Results indicate that the capability of light energy absorption of chloroplasts and regulative capability of excitation energy distribution between PSⅡ and PSⅠ were raised by doubled_CO 2 concentration. This is very favorable for final productivity of wheat.展开更多
Dissolved organic matter(DOM) of municipal solid waste(MSW) consists of minerals, water, ash and humic substances, and is known to enhance plant growth. In this study, inoculating microbes(Z J, MS) were used in ...Dissolved organic matter(DOM) of municipal solid waste(MSW) consists of minerals, water, ash and humic substances, and is known to enhance plant growth. In this study, inoculating microbes(Z J, MS) were used in municipal solid wastes composting, and composting implemented a industrialized technology. During composting, dissolved organic matter was extracted from the compost and purified. The spectral characteristics of dissolved organic matter was determined by fluorescence emission, excitation, and synchronous spectroscopy. Fluorescence emission, excitation, and synchronous spectra characterized by different relative fluorescent intensities and peaks over time. Fluorescence spectra were similar to that of fulvic acid in sewage sludge, indicating the presence of dissolved organic matter with aromatic structures and a high degree of molecular polymerization. Compared with the controls with no microbial inoculation, the microbe-inoculated treatments exhibited the increase of aromatic polycondensation, in the following order: MS + ZJ 〉 ZJ 〉 MS 〉 CK.展开更多
Three new complexes TbL3dipy (H2O)2, TbL3phen (H2O) 2 and TbL2 (TPPO) 2NO3 were synthesized (L = phenylglyoxylate ion, dipy = 2, 2-dipyridine, phen = 1,10-phenanthmline, TPPO = Triphenyl phosphine oxide). Elem...Three new complexes TbL3dipy (H2O)2, TbL3phen (H2O) 2 and TbL2 (TPPO) 2NO3 were synthesized (L = phenylglyoxylate ion, dipy = 2, 2-dipyridine, phen = 1,10-phenanthmline, TPPO = Triphenyl phosphine oxide). Elemental analysis, conductivity, IR spectra, and ^1HNMR spectra studies were performed. IR spectra indicate that the carboxylate ion of phenylglyoxylate is coordinated to the Tb(Ⅲ) ion as an unidentate ligand. In ^1HNMR, the signals of different hydrogens in phenylglyoxylate ion shift upfield. The excitation and emission spectra of the three solid complexes were recorded at morn temperature, in which the optimum excitation wavelengths are, 361.0, 359.0 and 367.0 nm for these three complexes, respectively. Four emission bands due to the ^5D4-^7Fj(j = 6, 5, 4, 3) transitions were observed for TbL3dipy(H2O)2(489.0, 545.0, 584.0, 620.0 nm) and TbL3phen(H2O)2(490.0, 544.0, 583.0, 620.0 nm). Under the same conditions, only one emission band due to the ^5D4-^7F5 transition was observed for the complex TbL2(TPPO)2NO3. The emission intensity of TbL3dipy(H2O)2 is the strongest among the three complexes.展开更多
The 1,10 phenan throline aromatic carboxylic acid(benzoic acid and o phthalic acid) binary and ternary complexes of europium were synthesized.The fluorescence and FT IR spectroscopy,elemental analysis,UV spectroscopic...The 1,10 phenan throline aromatic carboxylic acid(benzoic acid and o phthalic acid) binary and ternary complexes of europium were synthesized.The fluorescence and FT IR spectroscopy,elemental analysis,UV spectroscopic studies on these complexes were also performed.These complexes can emit strong red fluorescence of Eu? excited by UV light.At the same excited wavelength,the fluorescence spectra of the complexes were also studied.The results indicated that the fluorescence intensities of ternary complexes are stronger than that of binary complexes.The reason is that phenanthroline has higher electron density and higher orbit scope in the conjugated system and consequently an easier energy transfer to the europium ion,which makes the fluorescence intensity of ternary complexes be stronger than that of binary complexes.展开更多
Octadecylamine was derivatized with dansyl chloride (5-dimethylaminonaphthalene-1-sulfonyl chloride) In order to simplify and understand the LB films of fluorescent probe labeling proteins. its monolayer and multilaye...Octadecylamine was derivatized with dansyl chloride (5-dimethylaminonaphthalene-1-sulfonyl chloride) In order to simplify and understand the LB films of fluorescent probe labeling proteins. its monolayer and multilayers in the absence and presence of stearic acid were deposited by LB technique. Fluorescence spectra and lifetimes of the fluorescent products were studied to elucidate the microenvironment of molecules in the LB films.展开更多
The crystal growth,x-ray diffraction pattern,absorption spectrum,emission spectrum,and fluorescence lifetime of a Tb:Lu2O3 single crystal were studied.Excited at 483 nm,the peak absorption cross-section was calculate...The crystal growth,x-ray diffraction pattern,absorption spectrum,emission spectrum,and fluorescence lifetime of a Tb:Lu2O3 single crystal were studied.Excited at 483 nm,the peak absorption cross-section was calculated to be 3.5×10(-22)cm2,and the full width at half maximum was found to be 2.85 nm.The Judd-Ofelt(J-O)intensity parameters 2,4,and 6 were computed to be 3.79×10(-20)cm2,1.30×10(-20)cm2,and 1.08×10(-20)cm2,with a spectroscopic quality factor 4/6 being 1.20.The emission cross-sections of green emission around 543 nm and yellow emission around 584 nm were calculated to be 9.43×10(-22)cm2 and 1.32×10(-22)cm2,respectively.The fluorescence lifetimeτexp of -5D4 was fitted to be 1.13 ms.The data suggest that the Tb:Lu2O3 crystal could be a potential candidate for green and yellow laser operation.展开更多
Three new complexes TbL3dipy (H2O)2, TbL3phen ( H2O )2 and TbL2 ( TPPO )2NO3 have been synthesized (L = phenylglyoxylate ion, dipy = 2, 2- dipyfidine, phen = 1,10-phenanthroline, TPPO = Triphenyl phosphine oxi...Three new complexes TbL3dipy (H2O)2, TbL3phen ( H2O )2 and TbL2 ( TPPO )2NO3 have been synthesized (L = phenylglyoxylate ion, dipy = 2, 2- dipyfidine, phen = 1,10-phenanthroline, TPPO = Triphenyl phosphine oxide ). Elemental analysis, conductivity, IR spectra and ^1HNMR spectra studies were performed on them. IR spectra indicate that carboxylate ions in the phenylglyoxylate are coordinated to Tb (Ⅲ) ions as unidentate ligands. In ^1HNMR, the signals of hydrogens in phenylglyoxylate shift upfield. The excitation and emission spectra of the three comolexes were recorded at room temoerature, the excitation spectra show that the optimum excitation wavelengths are 361.0, 359.0 and 367.0 nm, respectively. Four emission bands due to ^5D4-^7Fj (j = 6, 5, 4, 3 ) transitions were observed for TbLadipy ( H2O )2 (489.0, 545. 0, 584.0,620.0 nm) and TbL3phen (H2O)2 (490. , 544.0, 583.0, 620.0 nm). And under the same conditions, only one emission band due to ^5Da-^7F5 transition was observed for TbL2 (TPPO)ENO3. The emission intensity of TbLadipy (H2O)2 is the strongest among the three complexes.展开更多
By using 1-methyl-2-formyl-5 -Y-substituted pyrrole (4-nitrophenyl)hydrazones as a model for nitrogen-containing heterocyclic aromatic compounds, the emission wavelength [lambda(max(em))] values df their fluorescence ...By using 1-methyl-2-formyl-5 -Y-substituted pyrrole (4-nitrophenyl)hydrazones as a model for nitrogen-containing heterocyclic aromatic compounds, the emission wavelength [lambda(max(em))] values df their fluorescence spectra have been measured. Correlation results show that the Delta E-em values are mainly affected by polar effects, but spin-delocalizatin effects also exist.展开更多
Fluorescence properties of Eu 3+ :Y 2SiO 5 have been investigated. Transitions between 5D and 7Fwere were studied with transmission spectra, fluorescence spectra, photoluminescence excitation ( or a...Fluorescence properties of Eu 3+ :Y 2SiO 5 have been investigated. Transitions between 5D and 7Fwere were studied with transmission spectra, fluorescence spectra, photoluminescence excitation ( or absorption ) spectra and site selective fluorescence spectra. The X ray powder diffraction pattern of Eu 3+ :Y 2SiO 5 shows that the crystal belong to monoclinic, and lattice's constants a, b, c and β are obtained by a simulation with the measured diffraction angles.展开更多
文摘Rice yellow mottle is considered the most destructive disease threatening rice production in Africa. Early detection of this infection in rice is essential to limit its expansion and proliferation. However, there is no research devoted to the spectral detection of rice yellow mottle virus (RYMV) infection, especially in the asymptomatic or early stages. This work proposes the use of hyperspectral fluorescence and reflectance data at leaf level for the detection of this disease in asymptomatic stages. A greenhouse experiment was therefore conducted to collect hyperspectral fluorescence and reflectance data at different stages of infection. These data allowed to calculate nine vegetation indices: one from fluorescence spectra and eight from reflectance spectra. A t-test made it possible to identify, from the second day after infection, four relevant reflectance vegetation indices to discriminate healthy leaves from those infected: these are Photochemical Reflectance Index (PRI), Transformed Chlorophyll Absorption in Reflectance Index (TCARI), Structure Intensive Pigment Index (SIPI) and Simple Ratio Pigment Index (SRPI). The fluorescence index was less sensitive in detecting infection. The four significant vegetation indices for the detection of RYMV were then used to build and evaluate models for discriminating plants according to their health status by the supervised classification of support vector machine (SVM) at different stages of infection. The maximum overall accuracy is 92.5% six days after inoculation (6 DAI). The sixth day after inoculation would be the adequate day to detect RYMV. This plants discrimination was validated by the mean reflectance spectra and by the histograms showing the differences between the average reflectance vegetation indices values of the two types of plants. Our results demonstrate the feasibility of differentiating RYMV-infected samples. They suggest that support vector machine learning models could be developed to diagnose RYMV-infected plants based on vegetation indices derived from spectral profiles at early stages of disease development.
基金Project supported by State Natural Science Foundation (20161001)Natural Science Foundation of Inner Mongolia Autonomous Region Science Commission (200508010206)
文摘In the preparation of this precursor tetraethlortho silicate (TEOS), sodium tungstate, ethyl alcohol, HCl and RECl3(RE=Eu,Tb) were mixed and then heated at 800 ℃ for 2 h, leading to a luminescent compound. The structure of the materials was characterized by TG-DTA and IR analysis, and the results indicate that the materials were in SiO2 network structure. Three-dimensional fluorescence spectra was used to characterize the luminescent properties of the materials. The luminescence property of doped and un-doped Eu3+or Tb3+ and Na2WO4 in silica materials were prepared and measured. The results show that good energy transfer from WO2-4 to Eu3+ ion, sensitized the luminescence intensity of Eu3+ remarkably. Tb3+ ion incorporated silica materials expressed the inverse energy transition from Tb3+ to WO2-4, however, we got the materials with homogeneous green blue fluorescent light. Finally, the energy transfer of WO2-4 and Eu3+, WO2-4 and Tb3+ were explained by energy levels diagram.
基金the Program for Changjiang Scholars and Innovative Research Teamin University(No.IRT0526)Shanghai Municipal Natural Science Foundation (No.06ZR14001)
文摘Much attention is devoted to fluorescent dyes especially those with potential in versatile applications.Reactions under "click" conditions between nonfluorescent 3-azidocoumarins and terminal alkynes produced 3-(1,2,3-triazol-1-yl)coumarins,a novel type of fluorescent dyes with intense fluorescence.The structures of the new coumarins were characterized by 1H NMR,MS,and IR spectra.Fluorescence spectra measurement demonstrated excellent fluorescence performance of the triazolylcoumarins and this click reaction is a promising candidate for bioconjugation and bioimaging applications since both azide and alkynes are quite inert to biological systems.
基金The authors gratefully thank the National Natural Science Foundation of China (No. 29874034, 29992530, 29873060) and Dow Corning Corporation for their financial support.
文摘Fluorescence spectra of ladderlike polyphenylsilsesquioxane (LPPS) and ladderlike 1,4-phenylene-bridged polyvinylsiloxane (LPPVS) have been measured as a function of temperature (4-55 degreesC), in dilute tetrahydrofuran solution. The excimer (IF) to monomer (I-M) intensity ratio (I-E/I-M) of LPPS dilute solution shows a double linear Arrhenius plot with a break point ascribable to a transition temperature Tt. This behavior has not been found for single chain polyorganosiloxanes. When In/(E) of LPPS was plotted against 1/T, it also gave a double linear plot with one break point, which was found in single chain polyorganosiloxanes. The different behaviors between LPPS and single chain polyorganosiloxanes may be mainly attributed to the relatively rigid double-chain macromolecular backbone of LPPS. However, the 1n(I-E/I-M) of dilute LPPVS solution versus 1/T shows a simple linear variation with a positive slope which confirms our proposition. The difference between the fluorescence results of LPPS and those of LPPVS may possibly derive from their structure differences and cooperative motion in backbone chain bonds.
文摘The fluorescence spectra of the poly (N-vinylcarbazole) in solution obtained with chirally organic salts or acid as catalyst or initiator [ (-)Sp: (-)-Sparteine, (+)CSA: D- (+)Camphor-10-sulfonic acid)], respectively, have been investigated. It is found that the two emission peaks at the longer wavelength (lambda max, ca, 415nm) and the shorter wavelength (lambda max, ca, 370nm) are assigned to the sandwich excimer and second excimer (partial overlap) fluorescence, respectively. The sandwich excimer and partially overlapped excimer are attributed to a fully overlapped structure of neighbouring carbazole chromophores in a totally elipsed conformation of the isotactic sequence, and partially overlapped structure of the syndiotactic sequence. The estimated values of I-415/I-370 and isotactic sequence content by using the fluorescence spectra are in the order: (-)Sp(+) (+)CSA(-)> (+)CSA(-)> (-)Sp(+)ClO(4)(-) (no peak at 415nm for AIBN).
文摘We have found some fluorescence characteristics of fossil fuels based on the contour maps of the three dimensional fluorescence spectra of their non quenching samples. The common fluorescence characteristic is that the main peaks of various fossil fuels are located in the vicinity of excitation/emission wavelength pair 228nm/340nm.The diversity of fluorescence characteristics can be represented with several indexes α,K,F and R ,and these indexes provide measurable parameters for division of fluorescence fingerprints of fossil fuels. The fluorescence fingerprints of fossil fuels can be divided into five models named O,B,Q,P and G that are corresponding to condensate oil, light oil, heavy oil, coal and natural gas, respectively. The technique has a potential application in study of environment pollution on crude oil and geochemical exploration of fossil fuels.
文摘The structure around Ti^(4+) in Bao-SiO_2 -B_2O_3-TiO_2 had been studied by X-ray fluorescence spectra. The results show that the Ti^(4+) mainly exists in the [TiO_4] and enters the network of [SiO_4]. [TiO_4] has the tendency to change to [TiO_6] with the increase of TiO_2 con-tent. When the TiO_2 content increases to about 20mol% the tendency reaches its maximum.
文摘Rare earth chelates of benzoyl urea derivatives were prepared in ethanol and fluorescence spectra of these chelates were studied in detail. A composition of [RE(BU)_3Phen] (NO_3)_3 was obtained. Correlation between chemical properties of ligands, chelates and spectroscopy was discussed. Intramolecular energy transfer in rare earth chelates was explained.
文摘Noble metal nanoparticles exhibit unique surface plasmon resonance dependent optical properties.On this basis,gold nanoparticles(AuNPs)encapsulated in metal–organic frameworks(MOFs)can form AuNPs@MOFs composites to modulate the optical properties of fluorescent molecules,which is less reported.In this paper,based on the fluorescence enhancement effect of AuNPs on 2-(2-hydroxyphenyl)-1H-benzimidazole(HPBI)molecules,zeolitic imidazolate framework-8(ZIF-8)crystals with structural stability were introduced.AuNPs@ZIF-8 exhibited a significantly pronounced fluorescence enhancement of the HPBI molecules.In addition,by comparing the fluorescence characteristics of the HPBI molecules adsorbed on AuNPs@ZIF-8 and those captured in AuNPs@ZIF-8,we found that the ZIF-8 can act as a spacer layer with highly effective near-field enhancement.All our preliminary results shed light on future research on the composite structures of noble metal particles and MOFs for fluorescent probes and sensing applications.
基金the National Major Scientific Research Instrument Development Project(Grant No.11927805)the National Key Research and Development Program of China(Grant No.2022YFF0608303)+2 种基金the NSFC Young Scientists Fund(Grant No.12005134)the Shanghai-XFEL Beamline Project(SBP)(Grant No.31011505505885920161A2101001)the Shanghai Municipal Science and Technology Major Project(Grant No.2017SHZDZX02)。
文摘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.
文摘Wheat ( Triticum aestivum L.) plants were grown under ambient and doubled_CO 2(plus 350 μL/L) concentration in cylindrical open_top chamber to examine their effects on the ultrastructure, supramolecular architecture, absorption spectrum and low temperature (77 K) fluorescence emission spectrum of the chloroplasts from wheat leaves. The results were briefly summarized as follows: (1) The wheat leaves possessed normally developed chloroplasts with intact grana and stroma thylakoid membranes; The grana intertwined with stroma thylakoid membranes and increased slightly in stacking degree and the width of granum, in spite of more accumulated starch grains within the chloroplasts than those in control; (2) The particle density in the stacked region of the endoplasmic fracture face (EFs) and protoplasmic fracture face (PFs) and in the unstacked region the endoplasmic fracture face (EFu) and the protoplasmic fracture face (PFu) was significantly higher than that of control. Furthermore, in some cases many more particles on EFs faces of thylakoid membranes appeared as a paracrystalline particle array; (3) The variations in the structure of chloroplasts were consistent with the absorption spectra and the low temperature (77 K) fluorescence emission spectra of the chloroplasts developed under the doubled_CO 2 concentration. Results indicate that the capability of light energy absorption of chloroplasts and regulative capability of excitation energy distribution between PSⅡ and PSⅠ were raised by doubled_CO 2 concentration. This is very favorable for final productivity of wheat.
文摘Dissolved organic matter(DOM) of municipal solid waste(MSW) consists of minerals, water, ash and humic substances, and is known to enhance plant growth. In this study, inoculating microbes(Z J, MS) were used in municipal solid wastes composting, and composting implemented a industrialized technology. During composting, dissolved organic matter was extracted from the compost and purified. The spectral characteristics of dissolved organic matter was determined by fluorescence emission, excitation, and synchronous spectroscopy. Fluorescence emission, excitation, and synchronous spectra characterized by different relative fluorescent intensities and peaks over time. Fluorescence spectra were similar to that of fulvic acid in sewage sludge, indicating the presence of dissolved organic matter with aromatic structures and a high degree of molecular polymerization. Compared with the controls with no microbial inoculation, the microbe-inoculated treatments exhibited the increase of aromatic polycondensation, in the following order: MS + ZJ 〉 ZJ 〉 MS 〉 CK.
文摘Three new complexes TbL3dipy (H2O)2, TbL3phen (H2O) 2 and TbL2 (TPPO) 2NO3 were synthesized (L = phenylglyoxylate ion, dipy = 2, 2-dipyridine, phen = 1,10-phenanthmline, TPPO = Triphenyl phosphine oxide). Elemental analysis, conductivity, IR spectra, and ^1HNMR spectra studies were performed. IR spectra indicate that the carboxylate ion of phenylglyoxylate is coordinated to the Tb(Ⅲ) ion as an unidentate ligand. In ^1HNMR, the signals of different hydrogens in phenylglyoxylate ion shift upfield. The excitation and emission spectra of the three solid complexes were recorded at morn temperature, in which the optimum excitation wavelengths are, 361.0, 359.0 and 367.0 nm for these three complexes, respectively. Four emission bands due to the ^5D4-^7Fj(j = 6, 5, 4, 3) transitions were observed for TbL3dipy(H2O)2(489.0, 545.0, 584.0, 620.0 nm) and TbL3phen(H2O)2(490.0, 544.0, 583.0, 620.0 nm). Under the same conditions, only one emission band due to the ^5D4-^7F5 transition was observed for the complex TbL2(TPPO)2NO3. The emission intensity of TbL3dipy(H2O)2 is the strongest among the three complexes.
文摘The 1,10 phenan throline aromatic carboxylic acid(benzoic acid and o phthalic acid) binary and ternary complexes of europium were synthesized.The fluorescence and FT IR spectroscopy,elemental analysis,UV spectroscopic studies on these complexes were also performed.These complexes can emit strong red fluorescence of Eu? excited by UV light.At the same excited wavelength,the fluorescence spectra of the complexes were also studied.The results indicated that the fluorescence intensities of ternary complexes are stronger than that of binary complexes.The reason is that phenanthroline has higher electron density and higher orbit scope in the conjugated system and consequently an easier energy transfer to the europium ion,which makes the fluorescence intensity of ternary complexes be stronger than that of binary complexes.
基金the National Natural Science Foundation of China (296333010) and The President Science Foundation of the Chinese Academy of Scie
文摘Octadecylamine was derivatized with dansyl chloride (5-dimethylaminonaphthalene-1-sulfonyl chloride) In order to simplify and understand the LB films of fluorescent probe labeling proteins. its monolayer and multilayers in the absence and presence of stearic acid were deposited by LB technique. Fluorescence spectra and lifetimes of the fluorescent products were studied to elucidate the microenvironment of molecules in the LB films.
基金Project supported by the National Natural Science Foundation of China(Grant No.61621001)the National Key Research and Development Program of China(Grant Nos.2016YFB1102202 and 2016YFB0701002)+1 种基金the Fundamental Research Funds for the Central Universities,Chinathe help of MOE Key Laboratory of Advanced Micro-Structured Materials and School of Physical Science and Technology,Guangxi University
文摘The crystal growth,x-ray diffraction pattern,absorption spectrum,emission spectrum,and fluorescence lifetime of a Tb:Lu2O3 single crystal were studied.Excited at 483 nm,the peak absorption cross-section was calculated to be 3.5×10(-22)cm2,and the full width at half maximum was found to be 2.85 nm.The Judd-Ofelt(J-O)intensity parameters 2,4,and 6 were computed to be 3.79×10(-20)cm2,1.30×10(-20)cm2,and 1.08×10(-20)cm2,with a spectroscopic quality factor 4/6 being 1.20.The emission cross-sections of green emission around 543 nm and yellow emission around 584 nm were calculated to be 9.43×10(-22)cm2 and 1.32×10(-22)cm2,respectively.The fluorescence lifetimeτexp of -5D4 was fitted to be 1.13 ms.The data suggest that the Tb:Lu2O3 crystal could be a potential candidate for green and yellow laser operation.
文摘Three new complexes TbL3dipy (H2O)2, TbL3phen ( H2O )2 and TbL2 ( TPPO )2NO3 have been synthesized (L = phenylglyoxylate ion, dipy = 2, 2- dipyfidine, phen = 1,10-phenanthroline, TPPO = Triphenyl phosphine oxide ). Elemental analysis, conductivity, IR spectra and ^1HNMR spectra studies were performed on them. IR spectra indicate that carboxylate ions in the phenylglyoxylate are coordinated to Tb (Ⅲ) ions as unidentate ligands. In ^1HNMR, the signals of hydrogens in phenylglyoxylate shift upfield. The excitation and emission spectra of the three comolexes were recorded at room temoerature, the excitation spectra show that the optimum excitation wavelengths are 361.0, 359.0 and 367.0 nm, respectively. Four emission bands due to ^5D4-^7Fj (j = 6, 5, 4, 3 ) transitions were observed for TbLadipy ( H2O )2 (489.0, 545. 0, 584.0,620.0 nm) and TbL3phen (H2O)2 (490. , 544.0, 583.0, 620.0 nm). And under the same conditions, only one emission band due to ^5Da-^7F5 transition was observed for TbL2 (TPPO)ENO3. The emission intensity of TbLadipy (H2O)2 is the strongest among the three complexes.
文摘By using 1-methyl-2-formyl-5 -Y-substituted pyrrole (4-nitrophenyl)hydrazones as a model for nitrogen-containing heterocyclic aromatic compounds, the emission wavelength [lambda(max(em))] values df their fluorescence spectra have been measured. Correlation results show that the Delta E-em values are mainly affected by polar effects, but spin-delocalizatin effects also exist.
文摘Fluorescence properties of Eu 3+ :Y 2SiO 5 have been investigated. Transitions between 5D and 7Fwere were studied with transmission spectra, fluorescence spectra, photoluminescence excitation ( or absorption ) spectra and site selective fluorescence spectra. The X ray powder diffraction pattern of Eu 3+ :Y 2SiO 5 shows that the crystal belong to monoclinic, and lattice's constants a, b, c and β are obtained by a simulation with the measured diffraction angles.