- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Excitation-Emission Synchronization Mediated Directional Fluorescence: Insight into Plasmon Coupled Emission at the Vibrational Resolution
摘要： Light-matter interaction is always the fundamentally significant topic to attract much attentions. It is important to reveal fluorophore-plasmon interaction at the nanoscale. Although as a powerful investigative tool, fluorescence spectroscopy still suffers from the limited spectral resolution and its susceptibility to interfering substances. In this work, the excitation-emission synchronization mediated surface plasmon coupled emission (EES-SPCE) is proposed to break the bottleneck. By actively screening the energy transitions for observation, the improved spectral resolution has been achieved, which is advantageous to the investigation of the fluorophore-plasmon interactions under different coupling modes. The spectral information related to the plasmonic interactions through tuning vibrational energy levels are clearly distinguished at directional emission angles. EES-SPCE is demonstrated to selectively and efficiently extract the coupled emission with the vibrational resolution, which would open up the opportunities to improve the capability of spectral feature identification and signal collection for practical applications of plasmonic fluorescence spectroscopy.
关键词： synchronous fluorescence spectroscopy,energy difference,directional emission,surface plasmon coupled emission,spectral resolution
更新于2025-09-23 15:19:57
-
How quantum dots aggregation enhances F??rster??Resonant Energy Transfer
摘要： As luminescent quantum dots (QDs) are known to aggregate themselves through their chemical activation by carbodiimide chemistry and their functionalization with biotin molecules, we investigate both effects on the fluorescence properties of CdTe QDs and their impact on F?rster Resonant Energy Transfer (FRET) occurring with fluorescent streptavidin molecules (FA). First, the QDs fluorescence spectrum undergoes significant changes during the activation step which are explained thanks to an original analytical model based on QDs intra-aggregate screening and inter-QDs FRET. We also highlight the strong influence of biotin in solution on FRET efficiency, and define the experimental conditions maximizing the FRET. Finally, a free-QD-based system and an aggregated-QD-based system are studied in order to compare their detection threshold. The results show a minimum concentration limit of 80 nM in FA for the former while it is equal to 5 nM for the latter, favouring monitored aggregation in the design of QDs-based biosensors.
关键词： fluorescence spectroscopy,biosensors,FRET,quantum dots,Biochemical functionalization
更新于2025-09-23 15:19:57
-
Interaction of Zinc Oxide and Copper Oxide Nanoparticles with Chlorophyll: A Fluorescence Quenching Study
摘要： The present study aims to investigate the interactions of zinc oxide nanoparticles and copper oxide nanoparticles with the major photosynthetic pigment chlorophyll using ultraviolet-visible, steady state, and time resolved laser induced fluorescence spectroscopy. The steady state fluorescence measurements show that zinc oxide and copper oxide nanoparticles quench the fluorescence of chlorophyll in concentration-dependent manner. The Stern-Volmer plot for the chlorophyll-zinc oxide nanoparticles is linear, and the value of quenching constant has been observed to increase with temperature indicating the possibility of dynamic quenching. A decrease in the lifetime of chlorophyll with increase in the concentration of zinc oxide nanoparticles confirms the involvement of dynamic quenching in the chlorophyll–zinc oxide nanoparticle interaction. In the case of copper oxide nanoparticles, the Stern-Volmer plot deviates from linearity observed in the form of upward curvature depicting the presence of both static and dynamic quenching. In addition, the lifetime of chlorophyll decreases with increase in the concentration of copper oxide nanoparticles displaying the dominance of dynamic quenching in the chlorophyll-copper oxide nanoparticle interaction. The decrease observed in the value of binding constant with increasing temperature and negative values of change in enthalpy, entropy, and Gibb’s free energy indicates that van der Waal and hydrogen bonding are the prominent forces during the interaction of chlorophyll with both zinc oxide and copper oxide nanoparticles and that the process is spontaneous and exothermic. The interaction of zinc oxide and copper oxide nanoparticles with chlorophyll occurs through electron transfer mechanism. The obtained results are useful in understanding the sensitization processes involving chlorophyll and zinc oxide and copper oxide nanoparticles.
关键词： chlorophyll and nanoparticles,molecular interaction,ultraviolet-visible spectroscopy,laser-induced fluorescence spectroscopy,Attenuated total reflectance–Fourier transform infrared spectroscopy,steady state and time resolved fluorescence,X-ray diffraction
更新于2025-09-19 17:15:36
-
Laser-induced fluorescence and dispersed-fluorescence spectroscopy of the ?2E?X?2A1 transition of jet-cooled calcium methoxide (CaOCH <sub/>3</sub> ) radicals
摘要： Laser-induced fluorescence (LIF) and dispersed fluorescence (DF) spectra of the ?A2E ? ?X2A1 electronic transition of the calcium methoxide (CaOCH3) radical have been obtained under jet-cooled conditions. Complete active space self-consistent field and coupled-cluster calculations on the free radical were performed to aid the assignment of vibronic transitions observed in the LIF/DF spectra. In addition to dominant spectral features that are well reproduced by vibrational frequencies and Franck-Condon (FC) factors calculated ab initio, the FC matrix for the ?A2E ? ?X2A1 electronic transition contains considerable off-diagonal elements that connect (i) the CaO-stretch (ν4) mode and non-CaO stretch modes and (ii) the asymmetric CaOC stretch (ν3) and the CaOC bending (ν8) modes. The Jahn-Teller and pseudo-Jahn-Teller interactions involving the ?2E state as well as the spin-orbit interaction induce additional vibronic transitions that are not allowed under the Born-Oppenheimer approximation. Additionally, anharmonic vibrational terms in the ground state induce transitions that are forbidden in the harmonic-oscillator approximation. Spin-orbit splitting has been observed for several vibrational levels of the ?2E state, and an essentially constant value was measured at all levels accessed in the LIF experiment. Implications of the present spectroscopic investigation to the proposed schemes of laser-cooling MOCH3 (M = alkaline earth metals) molecules and detection of time-reversal-symmetry-violating interactions are discussed.
关键词： calcium methoxide,laser cooling,spin-orbit interaction,Jahn-Teller effect,Franck-Condon factors,vibronic transitions,CaOCH3,Laser-induced fluorescence,pseudo-Jahn-Teller effect,dispersed-fluorescence spectroscopy
更新于2025-09-19 17:13:59
-
Analysis of the release kinetics of surface-bound proteins via laser-induced fluorescence
摘要： The drying and resolving processes of surface-bound proteins were analysed with a stereoscopic microscope combined with laser-induced fluorescence (LIF) with the aim to assist the advancement of a semi-automated point-of-care allergy diagnostic device. The results shown in this paper present the use of the LIF-method for concentration calibration and the analysis of drying and resolving dyed proteins. The method is established successfully and delivers precise results.
关键词： point-of-care testing (POCT),laser-induced fluorescence,spectroscopy,release kinetics
更新于2025-09-16 10:30:52
-
A Model for the Binding of Fluorescently Labeled Anti-Human CD4 Monoclonal Antibodies to CD4 Receptors on Human Lymphocytes
摘要： The CD4 glycoprotein is a component of the T cell receptor complex which plays an important role in the human immune response. This manuscript describes the measurement and modeling of the binding of fluorescently labeled anti-human CD4 monoclonal antibodies (mAb; SK3 clone) to CD4 receptors on the surface of human peripheral blood mononuclear cells (PBMC). CD4 mAb fluorescein isothiocyanate (FITC) and CD4 mAb allophycoerythrin (APC) conjugates were obtained from commercial sources. Four binding conditions were performed, each with the same PBMC sample and different CD4 mAb conjugate. Each binding condition consisted of the PBMC sample incubated for 30 min in labeling solutions containing progressively larger concentrations of the CD4 mAb-label conjugate. After the incubation period, the cells were re-suspended in PBS-based buffer and analyzed using a flow cytometer to measure the mean fluorescence intensity (MFI) of the labeled cell populations. A model was developed to estimate the equilibrium concentration of bound CD4 mAb-label conjugates to CD4 receptors on PBMC. A set of parameters was obtained from the best fit of the model to the measured MFI data and the known number of CD4 receptors on PBMC surface. Divalent and monovalent binding had to be invoked for the APC and FITC CD4 mAb conjugates, respectively. This suggests that the mAb binding depends on the size of the label, which has significant implications for quantitative flow cytometry. The study supports the National Institute of Standards and Technology program to develop quantitative flow cytometry measurements.
关键词： fluorescence spectroscopy,PBMC,FITC,antibody binding,CD4 monoclonal antibody,flow cytometry,APC,cooperative binding
更新于2025-09-12 10:27:22
-
Study of Hydrolysis Kinetic of New Laser Material [anti-B18H22]
摘要： [anti-B18H22] is a potential blue laser material. In order to study the stability of [anti-B18H22] in aqueous solution, the hydrolytic reaction kinetic of [anti-B18H22] at various pH values and temperatures was studied by fluorescence spectroscopy. The results showed that [anti-B18H22] hydrolysis rate was accelerated by increasing temperature, and the trend showed that [anti-B18H22] hydrolyzed faster in low pH than in high pH solutions at the same temperature. The hydrolysis of [anti-B18H22] solution is second-order reaction at lower temperature (300.15–323.15 K), the activation energy is 52.37 kJ mol–1 and pre-exponential factor (A) is 7.9 × 1010. The work described here is significant for future studies of the properties of [anti-B18H22] in aqueous solution.
关键词： fluorescence spectroscopy,hydrolysis kinetics,borane,second-order reaction,[anti-B18H22]
更新于2025-09-12 10:27:22
-
Uma montagem experimental para a medida de fluorescência
摘要： In this work we present a simple and illustrative arrangement using materials available in research and teaching laboratories to measure fluorescence. The developed fluorimeter is basically composed of a dual LED lighting to excite the samples and produce their emission. Then, a converging lens focuses the emitted light in the entrance of a monochromator and a chopper is used to modulate this signal with a known frequency measured by an optical coupler. After that, the light enters the monochromator that is responsible for its spectral decomposition into components that are finally detected by an amplified photodiode. Since the intensity of the emitted light is very low, a lock-in amplifier is used for filtering this signal by the reference signal provided by the optical coupler. This fluorimeter was tested using an acridine orange fluorescence sample and the results were very similar to those expected by a commercial fluorimeter.
关键词： fluorescence measurement,fluorescence spectroscopy,fluorimeter,fluorescence
更新于2025-09-11 14:15:04
-
Laser-Induced Fluorescence and Dispersed Fluorescence Spectroscopy of Jet-Cooled Isopentoxy Radicals
摘要： The B?-X? laser-induced fluorescence (LIF) and dispersed fluorescence (DF) spectra of jet-cooled isopentoxy radicals have been obtained. The LIF spectrum of isopentoxy lacks strong transitions to the CO-stretch levels that are typical for alkoxy radicals. Instead, it contains two low-frequency vibrational progressions due to large-amplitude motions of the GG’ and GG conformers involving torsion of the C1C2C3H dihedral angle. Other vibronic bands observed in the LIF spectrum are attributed to the TG conformer. Molecular carriers of the vibronic transitions in the LIF spectrum are identified by comparing the experimentally obtained spectrum and the simulated one. DF spectra of the GG and TG conformers are dominated by strong vibrational progressions of the CO-stretch mode when the origin or the CO-stretch band is pumped. When non-CO-stretch bands are pumped, the DF spectra are dominated by combination bands of the CO-stretch and the pumped mode. ?-X? separations of the GG, and TG conformers were also determined from the DF spectra.
关键词： Isopentoxy Radicals,Conformers,Laser-Induced Fluorescence,Vibrational Progressions,Jet-Cooled,Dispersed Fluorescence Spectroscopy
更新于2025-09-11 14:15:04
-
Aggregation States of Organic Dye Molecules in Organic – Inorganic Hybrid Films Studied by Near-Field and Far-Field Fluorescence Spectroscopy
摘要： Near-field fluorescence spectroscopy in conjunction with far-field fluorescence and Raman spectroscopy has been applied to investigate the aggregation states of cyanine dye of 2-[5-(1,3-Dihydro-3,3-dimethyl-1-octadecyl-2H-indol-2-ylidene)-1,3-pentadienyl]-3,3-dimethyl-1-octadecyl-3H-indolium perchlorate (NK3175) molecules in the depth direction, from the nanometer-scale top surface to the bulk, in the hybrid films consisted of NK3175 and a clay compound (SWN). The far-field Raman spectra reveal that these hybrid films contained both NK3175 molecules which did not take part in the adsorption and those adsorbed on SWN. The near-field photoluminescence (PL) spectra in the outermost surface within ca. 30 nm exhibit a significant blue shift for the hybrid films as compared to their respective PL spectra in the bulk, implying that the top surface of these hybrid films becomes more polar and/or rigid in terms of the microenvironment around NK3175 molecules compared to the bulk of them, in contrast to the case for the other hybrid film which was prepared by the alternative method. These results provide new information on the aggregation states of organic dye molecules not only in the bulk but in the nanometer-scale top surface of organic-inorganic hybrid systems.
关键词： far-field fluorescence,Raman spectroscopy,organic-inorganic hybrid films,aggregation states,Near-field fluorescence spectroscopy,cyanine dye
更新于2025-09-10 09:29:36