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
The effect of lanthanide and transition metal ions on the fluorescence spectra of theanticoagulation factor(ACF)of snake venom has been studied.It is postulated that the quenching oftryptophan residue fluorescence by ...The effect of lanthanide and transition metal ions on the fluorescence spectra of theanticoagulation factor(ACF)of snake venom has been studied.It is postulated that the quenching oftryptophan residue fluorescence by lanthanide and transition metal ions is caused by the metal ion-inducedconformation change of ACF.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
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 th...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
Fluorescence spectra of ladderlike polyphenylsilsesquioxane (LPPS) and ladderlike 1,4-phenylene-bridged polyvinylsiloxane (LPPVS) have been measured as a function of temperature (4-55℃), in dilute tetrahydrofuran sol...Fluorescence spectra of ladderlike polyphenylsilsesquioxane (LPPS) and ladderlike 1,4-phenylene-bridged polyvinylsiloxane (LPPVS) have been measured as a function of temperature (4-55℃), in dilute tetrahydrofuran solution.The excimer (IE) to monomer (IM) intensity ratio (IE/IM) of LPPS dilute solution shows a double linear Arrhenius plot with a break point ascribable to a transition temperature Tr. 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 ln(IE/IM) 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 structure around Ti<sup>4+</sup> in BaO-SiO<sub>2</sub>-B<sub>2</sub>O<sub>3</sub>-TiO<sub>2</sub> had been studied by X-ray fluorescence spectra. The re...The structure around Ti<sup>4+</sup> in BaO-SiO<sub>2</sub>-B<sub>2</sub>O<sub>3</sub>-TiO<sub>2</sub> had been studied by X-ray fluorescence spectra. The results show that the Ti<sup>4+</sup> mainly exists in the [TiO<sub>4</sub>] and enters the network of [SiO<sub>4</sub>]. [TiO<sub>4</sub>] has the tendency to change to [TiO<sub>6</sub>] with the increase of TiO<sub>2</sub> content. When the TiO<sub>2</sub> content increases to about 20mol% the tendency reaches its maximum.展开更多
The simple approach to acquire the fluorescence spectra of vitamin b1,b2 and b6 is proposed by direct illumination on solid powder sample.The experimentally acquired fluorescence spectra are in accordance with the pre...The simple approach to acquire the fluorescence spectra of vitamin b1,b2 and b6 is proposed by direct illumination on solid powder sample.The experimentally acquired fluorescence spectra are in accordance with the previous measurements on soluble samples.The fluorescence spectra for a mixture of vitamins b1,b2 and b6 with different concentrations have been investigated,and the fluorescence mechanism is explained on the basis of molecular structure.Possible reasons of the blue-shift of the fluorescence peak and enhancement of the peak power are explained as well.The advantages of solid powder method is analyzed and discussed.展开更多
Development of a prototype of a portable optical sensing system is presented for fast detecting of samples’fluorescence spectra.A compact configuration is achieved by integrating a small spectrometer,a microcontrolle...Development of a prototype of a portable optical sensing system is presented for fast detecting of samples’fluorescence spectra.A compact configuration is achieved by integrating a small spectrometer,a microcontroller,a Universal Serial Bus(USB)Host Shield,a network module,and a web server.The fluorescence spectra of a tested sample can be obtained.Then the test data are sent through network communication to our Cloud Server which can store the data for further analyses.With this configuration,test results can be revealed in a short time and downloaded by users to their laptops,tablets or cellphones anytime and anywhere.展开更多
In this work, a novel method was constructed to determine the enantiomeric composition of tryptophan (Trp) by bovine serum albumin (BSA) based on the fluorescence spectra of the receptor-ligand mixtures coupled with p...In this work, a novel method was constructed to determine the enantiomeric composition of tryptophan (Trp) by bovine serum albumin (BSA) based on the fluorescence spectra of the receptor-ligand mixtures coupled with partial least squares (PLS-1) analysis. As a result the enantiomeric composition of Trp was accurately determined.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）<sub>3</sub>Phen] （NO<sub>3</...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）<sub>3</sub>Phen] （NO<sub>3</sub>）<sub>3</sub> 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
The optical absorption spectrum ranging from 200 to 800 nm and fluorescence spectra ranging from 300 to 650 nm of GaP nanoparticles at room temperature were reported. From the optical absorption spectrum it is inferre...The optical absorption spectrum ranging from 200 to 800 nm and fluorescence spectra ranging from 300 to 650 nm of GaP nanoparticles at room temperature were reported. From the optical absorption spectrum it is inferred that the GaP nanoparticles exhibit a direct transition of about 410 nm (3.02 eV) and an indirect transition around 480 nm (2.58 eV). In addition, an absorption peak at about 308 nm (4.02 eV) corresponding to the direct transition at higher energy was observed. The absorption peak was attributed to the transition from the spin-orbit-split valence band to the lowest conduction band along the Λ direction. By observing the fluorescence of the GaP nanoparticles, it follows that multiple emission bands corresponding to the violet, blue, and yellow light are shown peaking at about 400.4?414.1 nm (3.097?2.994 eV), 450.1?466.8 nm (2.755?2.656 eV), and 582.4 nm (2.129 eV), respectively. The violet and blue light emissions are ascribed to the direct and indirect transitions from conduction band to valence band of the GaP nanoparticles. As to the weak yellow emission, it may be attributed to the radiative recombination from defect centers. The spin-orbit-splitting of the GaP nanoparticles is determined as about 100 meV.展开更多
Intrinsic fluorescence emission maxima of hemoglobin(Hb) was investigated in relation to peroxidase property of Hb. The peroxidase activity of Hb was based on its ca\| talytic activity for oxidation of o \|phenylenedi...Intrinsic fluorescence emission maxima of hemoglobin(Hb) was investigated in relation to peroxidase property of Hb. The peroxidase activity of Hb was based on its ca\| talytic activity for oxidation of o \|phenylenediamine by hydrogen peroxide. Hb was treated in the condition (temperature, ethanol and salt) that tetramer\|dimer equilibrium of Hb is shifted to the dimer state and its fluorescence spectrum was measured . When Hb treated in temperature (60\|70 ℃), ethanol concentration (60%\|70%) and NaCl concentration (2.5\|3.0 mol/L), the fluorescence emission maxima of Hb shifted towards red wavelength and its activity decreased quickly. Experimental results revealed that the activity and stability of Hb as mimetic peroxidase was closely relative to the hydrophobic environment of active center of Hb, and when Hb (Fe Ⅱ ) converted into met Hb (Fe Ⅲ ), its activity was 1.6 times as much as that of Hb.展开更多
In acid medium, rhodamine B（RhB）, rhodamine S（RhS）, rhodamine 6G（RhG） and butyl rhodamine B（b-RhB） have a fluorescence peak at 580, 549, 553 and 580 nm , respectively. BrO-3 oxidizes excess I- into I-3...In acid medium, rhodamine B（RhB）, rhodamine S（RhS）, rhodamine 6G（RhG） and butyl rhodamine B（b-RhB） have a fluorescence peak at 580, 549, 553 and 580 nm , respectively. BrO-3 oxidizes excess I- into I-3. Rhodamine dyes combine I-3 to form ion association nanoparticles, resulting in fluorescence quenching at 580, 549, 553 and 580 nm, respectively. The fluorescence quenching intensity is proportional to the concentration of BrO-3 in the range of 0.020 40.710 μg/mL for RhB, 0.0250.512 μg/mL for RhS, 0.0250.260 μg/mL for RhG, 0.0251.28 μg/mL for b-RhB, respectively. In the four systems, RhB system has good stability and high sensitivity. Thus, a simple, sensitive fluorescence method was proposed for the determination of BrO-3 in commercial bread additives and flours, with satisfactory results. The results of the fluorescence spectra and scan electron microscopy show that the formation of about 60 nm （RhB-I3）n association nanoparticles and the interface between the nanoparticles and solution are main factors that cause the fluorescence quenching.展开更多
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
Water stress early detection is essential for precision farming to improve crop productivity and product quality. The methods usually used are destructive, long and expensive. In this work, we used hyperspectral chlor...Water stress early detection is essential for precision farming to improve crop productivity and product quality. The methods usually used are destructive, long and expensive. In this work, we used hyperspectral chlorophyll fluorescence technology as a rapid, non-destructive approach to detect the water deficiency of eggplant plants using their spectral footprint. So, an experiment was made on 54 eggplant plants subjected to three water treatments: normal irrigation (T<sub>100</sub>), intermediate irrigation (T<sub>50</sub>) and no irrigation (T<sub>0</sub>). The fluorescence spectra were acquired in vivo and in situ using a USB4000 spectrometer from Ocean optics. For the classification of the plants subjected to three water treatments, we used three pretreatments of the raw hyperspectral data in order to suppress the non-informative variability present in these spectra and to obtain robust models. These are the Savitzky-Golay smoothing (SG), the standard normal variable (SNV) and the first derivative of Savitzky-Golay (SG-D1). The preprocessed data were then subjected to two partial least squares discriminant analyses (PLS-DA): Hard PLS-DA and Soft PLS-DA. These statistical approaches are suitable for large samples as it reduces the dimensionality of the data but improves the accuracy of the prediction. The SG-D1 combined with the Soft PLS-DA gave the best discrimination of plants with scores of sensitivity, specificity and total efficiency respectively of 97.33%, 94% and 95% for calibration, 6 days after hydric stress induction. For the plants used for the prediction, the scores are 86%, 91% and 90% respectively. This study shows that hyperspectral chlorophyll fluorescence spectroscopy is a fast and non-destructive technology allowing early detection of water stress in eggplant plants.展开更多
Recently,an article on ^(1)H solid-state NMR spectra was published,in which the authors proposed a deep learning approach to infer the pure isotropic proton NMR spectra obtained at an infinite magic angle spinning(MAS...Recently,an article on ^(1)H solid-state NMR spectra was published,in which the authors proposed a deep learning approach to infer the pure isotropic proton NMR spectra obtained at an infinite magic angle spinning(MAS)rate.This approach even allowed to obtain,by far,the best resolved ^(1)H spectra of molecular solids[1](https://doi.org/10.1002/anie.202216607).Deep learning based artificial intelligence is developing rapidly,and its application is deepening.Currently,there are many applications of deep learning in the field of magnetic resonance,such as the reconstruction of the under-sampled multidimensional spectra[2-4],the deconvolution of two-dimensional NMR spectra[5]and noise suppression and weak peak retrial[6],etc.展开更多
We delve into the phenomenon of high-order harmonic generation within a helium atom under the influence of a plasmon-assisted shaping pulse.Our findings reveal an intriguing manipulation of the frequency peak position...We delve into the phenomenon of high-order harmonic generation within a helium atom under the influence of a plasmon-assisted shaping pulse.Our findings reveal an intriguing manipulation of the frequency peak position in the harmonic emission by adjusting the absolute phase parameter within the frequency domain of the shaping pulse.This phenomenon holds potential significance for experimental setups necessitating precisely tuned single harmonics.Notably,we observe a modulated shift in the created harmonic photon energy,spanning an impressive range of 1.2 eV.This frequency peak shift is rooted in the asymmetry exhibited by the rising and falling edges of the laser pulse,directly influencing the position of the peak frequency emission.Our study quantifies the dependence of this tuning range and the asymmetry of the laser pulse,offering valuable insights into the underlying mechanisms driving this phenomenon.Furthermore,our investigation uncovers the emergence of semi-integer order harmonics as the phase parameter is altered.We attribute this discovery to the intricate interference between harmonics generated by the primary and secondary return cores.This observation introduces an innovative approach for generating semi-integer order harmonics,thus expanding our understanding of high-order harmonic generation.Ultimately,our work contributes to the broader comprehension of complex phenomena in laser-matter interactions and provides a foundation for harnessing these effects in various applications,particularly those involving precise spectral control and the generation of unique harmonic patterns.展开更多
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Project supported by the National Natural Science Foundation of China
文摘The effect of lanthanide and transition metal ions on the fluorescence spectra of theanticoagulation factor(ACF)of snake venom has been studied.It is postulated that the quenching oftryptophan residue fluorescence by lanthanide and transition metal ions is caused by the metal ion-inducedconformation change of ACF.
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.
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.
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℃), in dilute tetrahydrofuran solution.The excimer (IE) to monomer (IM) intensity ratio (IE/IM) of LPPS dilute solution shows a double linear Arrhenius plot with a break point ascribable to a transition temperature Tr. 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 ln(IE/IM) 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 structure around Ti<sup>4+</sup> in BaO-SiO<sub>2</sub>-B<sub>2</sub>O<sub>3</sub>-TiO<sub>2</sub> had been studied by X-ray fluorescence spectra. The results show that the Ti<sup>4+</sup> mainly exists in the [TiO<sub>4</sub>] and enters the network of [SiO<sub>4</sub>]. [TiO<sub>4</sub>] has the tendency to change to [TiO<sub>6</sub>] with the increase of TiO<sub>2</sub> content. When the TiO<sub>2</sub> content increases to about 20mol% the tendency reaches its maximum.
基金supported by the Tianjin Natural Science Foundation(No.06YFJZJC00300)the Natural Science Foundation of China(Nos.10674075,10774077,10674074,50802044 and 60736039)
文摘The simple approach to acquire the fluorescence spectra of vitamin b1,b2 and b6 is proposed by direct illumination on solid powder sample.The experimentally acquired fluorescence spectra are in accordance with the previous measurements on soluble samples.The fluorescence spectra for a mixture of vitamins b1,b2 and b6 with different concentrations have been investigated,and the fluorescence mechanism is explained on the basis of molecular structure.Possible reasons of the blue-shift of the fluorescence peak and enhancement of the peak power are explained as well.The advantages of solid powder method is analyzed and discussed.
基金supported by the National Key Development Program (2016YFB1102704)Natural Science Foundation of Liaoning Province (2015020115)+1 种基金National Natural Science Foundation of China (U1609209)National Science Fund for Distinguished Youth Scholars (51625504)
文摘Development of a prototype of a portable optical sensing system is presented for fast detecting of samples’fluorescence spectra.A compact configuration is achieved by integrating a small spectrometer,a microcontroller,a Universal Serial Bus(USB)Host Shield,a network module,and a web server.The fluorescence spectra of a tested sample can be obtained.Then the test data are sent through network communication to our Cloud Server which can store the data for further analyses.With this configuration,test results can be revealed in a short time and downloaded by users to their laptops,tablets or cellphones anytime and anywhere.
文摘In this work, a novel method was constructed to determine the enantiomeric composition of tryptophan (Trp) by bovine serum albumin (BSA) based on the fluorescence spectra of the receptor-ligand mixtures coupled with partial least squares (PLS-1) analysis. As a result the enantiomeric composition of Trp was accurately determined.
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）<sub>3</sub>Phen] （NO<sub>3</sub>）<sub>3</sub> was obtained. Correlation between chemical properties of ligands, chelates and spectroscopy was discussed. Intramolecular energy transfer in rare earth chelates was explained.
文摘The optical absorption spectrum ranging from 200 to 800 nm and fluorescence spectra ranging from 300 to 650 nm of GaP nanoparticles at room temperature were reported. From the optical absorption spectrum it is inferred that the GaP nanoparticles exhibit a direct transition of about 410 nm (3.02 eV) and an indirect transition around 480 nm (2.58 eV). In addition, an absorption peak at about 308 nm (4.02 eV) corresponding to the direct transition at higher energy was observed. The absorption peak was attributed to the transition from the spin-orbit-split valence band to the lowest conduction band along the Λ direction. By observing the fluorescence of the GaP nanoparticles, it follows that multiple emission bands corresponding to the violet, blue, and yellow light are shown peaking at about 400.4?414.1 nm (3.097?2.994 eV), 450.1?466.8 nm (2.755?2.656 eV), and 582.4 nm (2.129 eV), respectively. The violet and blue light emissions are ascribed to the direct and indirect transitions from conduction band to valence band of the GaP nanoparticles. As to the weak yellow emission, it may be attributed to the radiative recombination from defect centers. The spin-orbit-splitting of the GaP nanoparticles is determined as about 100 meV.
文摘Intrinsic fluorescence emission maxima of hemoglobin(Hb) was investigated in relation to peroxidase property of Hb. The peroxidase activity of Hb was based on its ca\| talytic activity for oxidation of o \|phenylenediamine by hydrogen peroxide. Hb was treated in the condition (temperature, ethanol and salt) that tetramer\|dimer equilibrium of Hb is shifted to the dimer state and its fluorescence spectrum was measured . When Hb treated in temperature (60\|70 ℃), ethanol concentration (60%\|70%) and NaCl concentration (2.5\|3.0 mol/L), the fluorescence emission maxima of Hb shifted towards red wavelength and its activity decreased quickly. Experimental results revealed that the activity and stability of Hb as mimetic peroxidase was closely relative to the hydrophobic environment of active center of Hb, and when Hb (Fe Ⅱ ) converted into met Hb (Fe Ⅲ ), its activity was 1.6 times as much as that of Hb.
文摘In acid medium, rhodamine B（RhB）, rhodamine S（RhS）, rhodamine 6G（RhG） and butyl rhodamine B（b-RhB） have a fluorescence peak at 580, 549, 553 and 580 nm , respectively. BrO-3 oxidizes excess I- into I-3. Rhodamine dyes combine I-3 to form ion association nanoparticles, resulting in fluorescence quenching at 580, 549, 553 and 580 nm, respectively. The fluorescence quenching intensity is proportional to the concentration of BrO-3 in the range of 0.020 40.710 μg/mL for RhB, 0.0250.512 μg/mL for RhS, 0.0250.260 μg/mL for RhG, 0.0251.28 μg/mL for b-RhB, respectively. In the four systems, RhB system has good stability and high sensitivity. Thus, a simple, sensitive fluorescence method was proposed for the determination of BrO-3 in commercial bread additives and flours, with satisfactory results. The results of the fluorescence spectra and scan electron microscopy show that the formation of about 60 nm （RhB-I3）n association nanoparticles and the interface between the nanoparticles and solution are main factors that cause the fluorescence quenching.
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.
文摘Water stress early detection is essential for precision farming to improve crop productivity and product quality. The methods usually used are destructive, long and expensive. In this work, we used hyperspectral chlorophyll fluorescence technology as a rapid, non-destructive approach to detect the water deficiency of eggplant plants using their spectral footprint. So, an experiment was made on 54 eggplant plants subjected to three water treatments: normal irrigation (T<sub>100</sub>), intermediate irrigation (T<sub>50</sub>) and no irrigation (T<sub>0</sub>). The fluorescence spectra were acquired in vivo and in situ using a USB4000 spectrometer from Ocean optics. For the classification of the plants subjected to three water treatments, we used three pretreatments of the raw hyperspectral data in order to suppress the non-informative variability present in these spectra and to obtain robust models. These are the Savitzky-Golay smoothing (SG), the standard normal variable (SNV) and the first derivative of Savitzky-Golay (SG-D1). The preprocessed data were then subjected to two partial least squares discriminant analyses (PLS-DA): Hard PLS-DA and Soft PLS-DA. These statistical approaches are suitable for large samples as it reduces the dimensionality of the data but improves the accuracy of the prediction. The SG-D1 combined with the Soft PLS-DA gave the best discrimination of plants with scores of sensitivity, specificity and total efficiency respectively of 97.33%, 94% and 95% for calibration, 6 days after hydric stress induction. For the plants used for the prediction, the scores are 86%, 91% and 90% respectively. This study shows that hyperspectral chlorophyll fluorescence spectroscopy is a fast and non-destructive technology allowing early detection of water stress in eggplant plants.
基金This work was partially supported by the National Natural Science Foundation of China(Grants 22174118 and 22374124).
文摘Recently,an article on ^(1)H solid-state NMR spectra was published,in which the authors proposed a deep learning approach to infer the pure isotropic proton NMR spectra obtained at an infinite magic angle spinning(MAS)rate.This approach even allowed to obtain,by far,the best resolved ^(1)H spectra of molecular solids[1](https://doi.org/10.1002/anie.202216607).Deep learning based artificial intelligence is developing rapidly,and its application is deepening.Currently,there are many applications of deep learning in the field of magnetic resonance,such as the reconstruction of the under-sampled multidimensional spectra[2-4],the deconvolution of two-dimensional NMR spectra[5]and noise suppression and weak peak retrial[6],etc.
基金This project was supported by the National Key Research and Development Program of China(Grant Nos.2022YFE134200 and 2019YFA0307700)the National Natural Science Foundation of China(Grant Nos.11604119,12104177,11904192,12074145,and 11704147)the Fundamental Research Funds for the Central Universities(Grant Nos.GK202207012 and QCYRCXM-2022-241).
文摘We delve into the phenomenon of high-order harmonic generation within a helium atom under the influence of a plasmon-assisted shaping pulse.Our findings reveal an intriguing manipulation of the frequency peak position in the harmonic emission by adjusting the absolute phase parameter within the frequency domain of the shaping pulse.This phenomenon holds potential significance for experimental setups necessitating precisely tuned single harmonics.Notably,we observe a modulated shift in the created harmonic photon energy,spanning an impressive range of 1.2 eV.This frequency peak shift is rooted in the asymmetry exhibited by the rising and falling edges of the laser pulse,directly influencing the position of the peak frequency emission.Our study quantifies the dependence of this tuning range and the asymmetry of the laser pulse,offering valuable insights into the underlying mechanisms driving this phenomenon.Furthermore,our investigation uncovers the emergence of semi-integer order harmonics as the phase parameter is altered.We attribute this discovery to the intricate interference between harmonics generated by the primary and secondary return cores.This observation introduces an innovative approach for generating semi-integer order harmonics,thus expanding our understanding of high-order harmonic generation.Ultimately,our work contributes to the broader comprehension of complex phenomena in laser-matter interactions and provides a foundation for harnessing these effects in various applications,particularly those involving precise spectral control and the generation of unique harmonic patterns.
