Measurement of the radiative lifetime of the cesium 5D5/2 level using pulsed excitation and delayed probe absorption

The 5D_5/2 level of cesium is populated by pulsed 540 nm photodissociation of Cs₂, and selectively detected via the 6P_3/2 population that results by radiative decay. It is monitored by absorption of a delayed probe pulse. Its time evolution yields a value of 1260±80 ns for the radiative lifetime of the Cs 5D_5/2 level, in good agreement with the calculation by Theodosiou [15].     

Report on the extremely low threshold for the CO2 laser induced multiple photon absorption and dissociation processes in chromyl chloride

We have studied the behaivior of the CrO₂Cl₂ molecule upon irradiation with an unfocused, low power (0.45 J/cm² pulsed CO₂ laser using a visible dye laser as a probe of the population changes in the vibrationless ground electronic state and various low-lying vibrational levels. Wavelength and time-resolved measurements indicate that the vibrationless ground state is depleted as a result of the CO₂ laser pumping and that the recovery of the ambient population does not take palce even after 5.0 milliseconds. Mass spectroscopic analysis of the CO₂ laser irradiated samples suggests an extremely low thereshold for dissociation in the case of CrO₂Cl₂.     

Vibrational population lifetimes of polyatomic molecules in liquids

CH-stretching modes were first excited by picosecond infrared pulses and the generated excess population was monitored by anti-Stokes scattering of subsequent ultrashort probe pulses. Experimental data are reported on five molecules: CHCl₃, CH₂Cl₂, CH₃CCl₃, CH₃CH₂OH, and CH₃I in the neat liquid and/or in solutions of CCl₄. The observed time constants vary between 1 and 100 ps depending upon the individual molecule and surrounding. Theoretical calculations show that rotational coupling, Fermi resonance, Coriolis coupling, and resonance energy transfer can strongly effect the vibrational population lifetime. The relevance of these processes is quite different for the various molecules investigated.     

A FRET-based fluorescent probe for imaging H2S in living cells

A FRET-based fluorescence probe was developed for selective detection of H₂S in aqueous buffer and inside living cells. For this probe, the FRET probe could be cleaved by H₂S, and the fluorescence of FRET donor is released. The probe is highly selective to H₂S over other biologically relevant species to give color change for naked eye observation. Confocal imaging indicated that the probe could monitor intracellular H₂S level changes.     

Assessment of Lewis-Acidic Surface Sites Using Tetrahydrofuran as a Suitable and Smart Probe Molecule

Measuring the Lewis-acidic surface sites in catalysis is problematic when the material‘s surface area is very low (S_BET ≤1 m² ⋅ g⁻¹). For the first time, a quantitative assessment of total acidic surface sites of very small surface area catalysts (MoO₃ as pure and mixed with 5–30 % CdO (wt/wt), as well as CdO for comparison) was performed using a smart new probe molecule, tetrahydrofuran (THF). The results were nearly identical compared to using another commonly used probe molecule, pyridine. This audition is based on the limited values of the surface area of these samples that likely require a relatively moderate basic molecule as THF with pK_b=16.08, rather than strong basic molecules such as NH₃ (pK_b=4.75) or pyridine (pK_b=8.77). We propose mechanisms for the interaction of vapour phase molecules of THF with the Lewis-cationic Mo and Cd atoms of these catalysts. Besides, dehydration of isopropyl alcohol was used as a probe reaction to investigate the catalytic activity of these catalysts to further support our findings in the case of THF in a temperature range of 175–300 °C. A good agreement between the obtained data of sample MoO₃-10 % CdO, which is characterised by the highest surface area value, the population of Lewis-acidic sites and % selectivity of propylene at all the applied reaction temperatures was found.     

Determination of Ion Frequencies in a Quadrupole Ion Trap By Using a Fast Direct Current Pulse as Pump and a Laser Probe

A new technique has been developed which allows the direct measurement of frequencies of ions trapped in a quadrupole ion trap mass spectrometer. This pump/probe method employs a fast direct current (DC) pulse (pump) to displace a kinetically cooled ion population from the center of the trap, and a laser (probe) which recognizes when ions reappear at the center of the trap by the formation of photodissociation fragments. The translationally excited ions undergo periodic motion within the confines of the ion trap, and this periodic motion can be followed by recording the intensity of the photodissociation fragment as a function of the delay time between the DC pump and the laser probe. The DC pulse has a rise time of 15 ns; data are taken 1 ms after its application to allow stable ion motion to be sampled. Sampling of the ion cloud is done at 50 ns intervals, and fast Fourier transformation of the time-based data yields the ion frequencies and their relative magnitudes. Data are reported for ions derived from acetophenone (m/z 105) and 1,4-cyclohexadiene (m/z 80) under various trapping conditions corresponding to different Mathieu q_z values. The measured fundamental secular frequencies, f_z and f_r, are found to agree well with those predicted. The presence of higher order multipole contributions to the trapping field is evident from such ion frequencies as the drive frequency, f_RF,. The ability to measure ion frequencies under operating conditions provides a new tool for comparing simulated and experimental data. Simulation data from the program ITSIM, modified to account for the effects of collisions, are shown to predict the major frequency components observed in the experimental data.     

A two-photon fluorescent probe with a large turn-on signal for imaging hydrogen sulfide in living tissues

A two-photon fluorescence turn-on H₂S probe GCTPOC–H₂S based on a two-photon platform with a large cross-section, GCTPOC, and a sensitive H₂S recognition site, dinitrophenyl ether was constructed. The probe GCTPOC–H₂S exhibits desirable properties such as high sensitivity, high selectivity, functioning well at physiological pH and low cytotoxicity. In particular, the probe shows a 120-fold enhancement in the presence of Na₂S (500 μM), which is larger than the reported two-photon fluorescent H₂S probes. The large fluorescence enhancement of the two-photon probe GCTPOC–H₂S renders it attractive for imaging H₂S in living tissues with deep tissue penetration. Significantly, we have demonstrated that the probe GCTPOC–H₂S is suitable for fluorescence imaging of H₂S in living tissues with deep penetration by using two-photon microscopy. The further application of the two-photon probe for the investigation of biological functions and pathological roles of H₂S in living systems is under progress.     

Quadrupole interactions in mixed-valency states of indium chloride

Quadrupole interaction parameters have been determined for InCl_1.5, InCl_1.8 and InCl₂ by using ¹¹¹In as a probe for perturbed λ-λ angular correlation measurements. For InCl_1.5 a broadened spectrum is obtained with estimated quadrupole interaction frequency ν_q ≈ 110 MHz. Three interactions, comprising one static and two time-dependent components, are required to fit the data for InCl_1.8 and InCl₂. In each case the interactions are identical, but with different population coefficients. The static interaction has a narrow width (δ = 4%) and frequency ν_q = 135.0 ± 1.1 MHz.     

A Golgi Apparatus-Targetable Probe Based on Lanthanide Complexes for Ratiometric Time-Gated Luminescence Detection of Hydrogen Sulfide

Development of bioanalytical methods for selective and accurate detection of H₂S in living samples is essential for understanding the pathological and physiological functions of this gasotransmitter in biological systems. Here we report a Golgi apparatus-targetable lanthanide complex-based luminescent probe, Golgi-ABTTA-Eu³⁺/Tb³⁺, that can be used for accurately determining H₂S in aqueous solution and living cells via the ratiometric time-gated luminescence (RM-TGL) technique. This probe is composed of 2,2′:6′,2′′-terpyridine-Eu³⁺/Tb³⁺ mixed complexes as the luminophore, 4-azidobenzyl-ether as the responsive moiety, and sulfanilamide as the Golgi apparatus-targeting moiety. Upon reaction with H₂S, accompanied by the cleavage of 4-azidobenzyl group from the probe molecule, the long-lived emission of Tb³⁺ complex at 540 nm is significantly enhanced, while that of Eu³⁺ complex at 610 nm is obviously reduced. It was noted that the I₅₄₀/I₆₁₀ ratio increased by 8.8 times after the probe was exposed to H₂S, which enabled H₂S to be detected with RM-TGL method. After being incubated with living cells, the probe molecules were selectively accumulated in the Golgi apparatus, which allowed H₂S in the Golgi apparatus to be successfully imaged in RM-TGL mode.     

Probing the Regioselectivity with Encapsulated H2: Diels–Alder Reaction of an Open-Cage C60 Derivative with Anthracene

The regioselectivity in the Diels–Alder reaction of an unsymmetrical open-cage C₆₀ derivative with anthracene was studied. By using an encapsulated H₂ molecule as a magnetic probe, the product population was successfully evaluated in detail, indicating the formation of approximately ten compounds as major components. The nucleus-independent chemical shift (NICS) calculations showed a close resemblance to the observed ¹H NMR spectrum, which allowed for a facile characterization of the products. Theoretical studies on the formation of all 29 possible anthracene adducts were also performed. The results indicated that the regioselectivity is strongly governed by steric factors, values of the frontier orbital coefficients, and thermodynamic stabilities. Single-crystal X-ray analysis of the dominant compound revealed the supramolecular architecture between the anthracene moiety and the π-sphere of a neighboring molecule.     

An ultrasensitive fluorescent probe for hydrazine detection and its application in water samples and living cells

Hydrazine, as a strong reducing agent, has been extensively used in many industrial manufactures. However, it is a potential human carcinogen and an environmental contaminant due to its high toxicity. Therefore, developing an ultrasensitive method for determining hydrazine in real water and biosystems is of great significance. Herein, based on coumarin dye, a turn-on fluorescent probe Cou-1-N₂H₄, which contains an acetyl group as the trigger unit and the fluorescence quencher, is developed. The probe can achieve a rapid (3min) and colorimetric sensing detection for hydrazine with an extremely low limit detection (11.9?nM or 0.38?ppb). More importantly, the practical utilities of probe have been successfully proved through quantitative N₂H₄ detection in environmental water samples and bioimaging of N₂H₄ in living cells.     

A Golgi Apparatus-Targeting,Naphthalimide-Based Fluorescent Molecular Probe for the Selective Sensing of Formaldehyde

Formaldehyde (FA) is a colorless, flammable, foul-smelling chemical used in building materials and in the production of numerous household chemical goods. Herein, a fluorescent chemosensor for FA is designed and prepared using a selective organ-targeting probe containing naphthalimide as a fluorophore and hydrazine as a FA-binding site. The amine group of the hydrazine reacts with FA to form a double bond and this condensation reaction is accompanied by a shift in the absorption band of the probe from 438 nm to 443 nm upon the addition of FA. Further, the addition of FA is shown to enhance the emission band at 532 nm relative to the very weak fluorescent emission of the probe itself. Moreover, a high specificity is demonstrated towards FA over other competing analytes such as the calcium ion (Ca²⁺), magnesium ion (Mg²⁺), acetaldehyde, benzaldehyde, salicylaldehyde, glucose, glutathione, sodium sulfide (Na₂S), sodium hydrosulfide (NaHS), hydrogen peroxide (H₂O₂), and the tert-butylhydroperoxide radical. A typical two-photon dye incorporated into the probe provides intense fluorescence upon excitation at 800 nm, thus demonstrating potential application as a two-photon fluorescent probe for FA sensing. Furthermore, the probe is shown to exhibit a fast response time for the sensing of FA at room temperature and to facilitate intense fluorescence imaging of breast cancer cells upon exposure to FA, thus demonstrating its potential application for the monitoring of FA in living cells. Moreover, the presence of the phenylsulfonamide group allows the probe to visualize dynamic changes in the targeted Golgi apparatus. Hence, the as-designed probe is expected to open up new possibilities for unique interactions with organ-specific biological molecules with potential application in early cancer cell diagnosis.     

Measurement of kinetic processes in photoexcited stilbene solutions

The kinetics of photophysical processes has been measured in stilbene solutions in the temperature range between ?40°C and 20°C. The population of the S₁ level excited by two-photon absorption (TPA) and of secondary populated levels has been investigated using a probe beam method. It was found an energy barrier ΔE = 5 × 10² cm^?1 of the thermically activated transition S₁ → 1′. The rate parameter of this transition is determined to be k^?1_11′, ≈ 2 ps at very high temperatures.     

Sensing lymphoma cells based on a cell-penetrating/apoptosis-inducing/electron-transfer peptide probe

To electrochemically sense lymphoma cells (U937), we fabricated a multifunctional peptide probe that consists of cell-penetrating/apoptosis-inducing/electron-transfer peptides. Electron-transfer peptides derive from cysteine residue combined with the C-terminals of four tyrosine residues (Y₄). A peptide whereby Y₄C is bound to the C-terminals of protegrin 1 (RGGRLCYCRRRFCVCVGR-NH₂) is known to be an apoptosis-inducing agent against U937 cells, and is referred to as a peptide-1 probe. An oxidation response of the peptide-1 probe has been observed due to a phenolic hydroxyl group, and this response is decreased by the uptake of the peptide probe into the cells. To improve the cell membrane permeability against U937 cells, the RGGR at the N-terminals of the peptide-1 probe was replaced by RRRR (peptide-2 probe). In contrast, RNRCKGTDVQAWY₄C (peptide-3 probe), which recognizes ovalbumin, was constructed as a control. Compared with the other probes, the change in the peak current of the peptide-2 probe was the greatest at low concentrations and occurred in a short amount of time. Therefore, the cell membrane permeability of the peptide-2 probe was increased based on the arginine residues and the apoptosis-inducing peptides. The peak current was linear and ranged from 100 to 1000 cells/ml. The relative standard deviation of 600 cells/ml was 5.0% (n = 5). Furthermore, the membrane permeability of the peptide probes was confirmed using fluorescent dye.     

Langmuir probe measurements during plasma-activated chemical vapor deposition in the system argon/oxygen/Aluminum isopropoxide

A Langmuir probe investigation of Ar/O₂/Al(OPr¹)₃ plasmas is described. The probe contamination depends on the probe position and the flow of tine carrier gases. Whereus far from the working gas inlet characteristics without any hysteresis were obtained, near to the inlet undisturbed characteristics were recorded only for small gas flows or a low vapor pressure of the precursor. Condensation of the precursor ai the probe surface prior to the plasma excitation was the main source of probe contamination. A decrease ire the plasma potential with respect to the ground observed during experiments was attributed to the formation of a dielectric film on the rf electrode. This resulted in a self-bias responsible for the decrease in plasma potential.     

Iridium(III) Complex-Based Activatable Probe for Phosphorescent/Time-Gated Luminescent Sensing and Imaging of Cysteine in Mitochondria of Live Cells and Animals

This study reports an activatable iridium(III) complex probe for phosphorescence/time-gated luminescence detection of cysteine (Cys) in vitro and in vivo. The probe, [Ir(ppy)₂(NTY-bpy)](PF₆) [ppy: 2-phenylpyridine; NTY-bpy: 4-methyl-4′-(2-nitrovinyl)-2,2′-bipyridine], is developed by incorporating a strong electron-withdrawing group, nitroolefin, into a bipyridine ligand of the Ir^III complex. The luminescence of the probe is quenched owing to the intramolecular charge transfer (ICT) process, but switched on by a specific recognition reaction between the probe and Cys. [Ir(ppy)₂(NTY-bpy)](PF₆) shows high sensitivity and selectivity for Cys detection and good biocompatibility. The long-lived emission of [Ir(ppy)₂(NTY-bpy)](PF₆) allows time-gated luminescence analysis of Cys in cells and human sera. These properties make it convenient for the phosphorescence and time-gated luminescence imaging and flow cytometry analysis of Cys in live samples. The Cys images in cancer cells and inflamed macrophage cells reveal that [Ir(ppy)₂(NTY-bpy)](PF₆) is distributed in mitochondria after cellular internalization. Visualizations and flow cytometry analysis of mitochondrial Cys levels and Cys-mediated redox activities of live cells are achieved. By using [Ir(ppy)₂(NTY-bpy)](PF₆) as a probe, in vivo sensing and imaging of Cys in D. magna, zebrafish, and mice are then demonstrated.     

Influence of Confined Water on the Photophysics of Dissolved Solutes in Reverse Micelles

The photophysical parameters of two probes with largely different hydrophobic character, namely, coumarin 1 and coumarin 343, are investigated in sodium bis‐(2‐ethylhexyl)sulfosuccinate (AOT)/hexane/water reverse micelles at various water/AOT molar ratio w₀. Correlation of photophysical parameters such as fluorescence quantum yield, fluorescence lifetime, and emission maxima with w₀ indicate distinctly different trends below and above w₀≈7 for both probes. The variation of the average rotational correlation times obtained from fluorescence anisotropy decays for both probes in reverse micelles further corroborate the above observation. Similar studies were also performed in nonaqueous reverse micelles with acetonitrile as polar solvent. Similar to aqueous reverse micelles, breaks in the photophysical parameters with increasing acetonitrile/AOT molar ratios w′₀ were also observed in these cases, although at a much lower w′₀ value of 3. The present results indicate that around w₀≈7 for aqueous reverse micelles (and around w′₀≈3 for nonaqueous reverse micelles) a distinct change occurs in the probe microenvironment, which is rationalized on the basis of the relative populations of interfacial and core water. We propose that until the ionic head groups and counterions are fully solvated by polar solvents, that is, up to w₀≈7 (or w′₀≈3), the interfacial water population dominates. Above these molar ratios coalescence of excess water molecules with each other to form truncated H‐bonded water clusters leads to a sizable population of core water. This is further substantiated by changes in the IR absorption spectra for the O? D stretching mode of diluted D₂O in reverse micelles with varying w₀. Critical comparison of the present results with relevant literature reports provide clear support for the proposals made on water structure in reverse micelles. The role of relative size of the probe and the reverse micelles for differences in polar solvent to AOT ratios (w₀=7 and w′₀=3) in the observed breaks in the two types of reverse micelles is also discussed.     

A Highly Efficient Chemiluminescence Probe for the Detection of Singlet Oxygen in Living Cells

Singlet oxygen is among the reactive oxygen species (ROS) with the shortest life‐times in aqueous media because of its extremely high reactivity. Therefore, designing sensors for detection of ¹O₂ is perhaps one of the most challenging tasks in the field of molecular probes. Herein, we report a highly selective and sensitive chemiluminescence probe ( SOCL‐CPP ) for the detection of ¹O₂ in living cells. The probe reacts with ¹O₂ to form a dioxetane that spontaneously decomposes under physiological conditions through a chemiexcitation pathway to emit green light with extraordinary intensity. SOCL‐CPP demonstrated promising ability to detect and image intracellular ¹O₂ produced by a photosensitizer in HeLa cells during photodynamic therapy (PDT) mode of action. Our findings make SOCL‐CPP the most effective known chemiluminescence probe for the detection of ¹O₂. We anticipate that our chemiluminescence probe for ¹O₂ imaging would be useful in PDT‐related applications and for monitoring ¹O₂ endogenously generated by cells in response to different stimuli.     

Two-photon fluorescent probe for hydrogen sulfide based on a red-emitting benzocoumarin dye

Hydrogen sulfide (H₂S) is an endogenous gasotransmitter and plays intriguing biological roles. To study the biological role of H₂S, efficient fluorescent probes are in great demand. For imaging of H₂S in deep-tissue, a two-photon probe that emits in the red wavelength region is of choice to avoid the autofluorescence from intrinsic biomolecules. Here, we disclose such a probe, which, developed based on an acetyl benzocoumarin fluorophore, can be excited at 900?nm under two-photon excitation and emit in the red region. The probe shows high reactivity, selectivity, and sensitivity in in vitro assays. Two-photon microscopic imaging of H₂S in HeLa cells aided by the probe demonstrates that it is potentially useful to study H₂S level changes in cells and tissues influenced by external stimuli.     

掺铒联吡啶钌为探针分子压敏漆的制备及氧猝灭特性

以2,2′-联吡啶,三氯化钌(RuCl3),氯化铒(ErCl3)为原料合成了铒掺杂的探针分子。将探针分子加入到铕掺杂的硅溶胶基质中获得了铕、铒共掺杂的压敏漆样品。采用IR,SEM,EDS及荧光发射光谱对探针分子和压敏漆进行了表征。红外光谱结果表明,探针分子中联吡啶的结构没有被破坏。扫描电镜观察发现探针分子呈片状,EDS测试发现探针分子表面含有Er,Ru等元素。紫外吸收光谱表明压敏漆的最佳吸收波段位于200~500 nm处,选择410 nm作为激发光源,压敏漆在590 nm处有很强的荧光发射,并且随着空气压力的增大(即氧分子浓度的增加),压敏漆的荧光发射强度降低,说明压敏漆具有较好的氧猝灭特性。