Generation of profluorescent isoindoline nitroxides using click chemistry

Novel profluorescent nitroxides bearing a triazole linker between the coumarin fluorophore and an isoindoline nitroxide were prepared in good yields using the copper-catalyzed azide-alkyne 1,3-dipolar cycloaddition reaction (CuAAC). Nitroxides containing 7-hydroxy and 7-diethylamino substitution on their coumarin rings displayed significant fluorescence suppression, and upon reaction with methyl radicals, normal fluorescence emission was returned. The fluorescence emission for the 7-hydroxycoumarin nitroxide and its diamagnetic analogue was found to be strongly influenced by pH with maximal fluorescence emission achieved in basic solution. Solvent polarity was also shown to affect fluorescence emission. The significant difference in fluorescence output between the nitroxides and their corresponding diamagnetic analogues makes these compounds ideal tools for monitoring processes involving free-radical species.     

Chemiluminescence accompanied by the reaction of gold nanoparticles with potassium permanganate

It was found that potassium permanganate (KMnO(4)) could react with gold nanoparticles in a strong acid medium to generate particle size-dependent chemiluminescence (CL). For gold nanoparticles with the size of 2.6 or 6.0 nm, the reaction was fast and could produce the excited state Mn(II) with light emission around 640 nm. For gold nanoparticles larger than 6.0 nm, no light emission was observed due to a much slower reaction rate. The CL intensity was found to increase linearly with the concentration of 2.6 nm gold nanoparticles. The effects of the acid medium, concentration of KMnO(4) and presence of N(2) and O(2) were investigated. UV-Vis absorption spectra and X-ray photoelectron spectra (XPS) measured before and after the CL reaction were analyzed. A CL mechanism has been proposed suggesting that the potassium permanganate was reduced by gold nanoparticles in the strong acid medium to the excited state Mn(II), yielding light emission. The results bestow new light on the size-dependent chemical reactivities of the gold nanoparticles and on nanoparticle-induced chemiluminescence. The CL reaction was considered to be of potential use for bioanalysis applications.     

Effect of pH on the reaction of tris(2,2'-bipyridyl)ruthenium(III) with amino-acids: Implications for their detection

A new technique for the detection of amino-acids is described, which is based on their chemiluminescence reaction with tris(2,2'-bipyridyl)ruthenium(III). The pH-dependence of this reaction has been investigated and found to be the key experimental parameter in application of this reaction as a detection technique. The chemiluminescence emission obtained is maximal at pH values higher than the N-terminal amino group pK(a) of the amino-acid. The background reaction between the ruthenium reagent and hydroxide ion does not occur with the same efficiency as the amino-acid reaction and the optimum signal to noise ratio is obtained at pH 10. A limit of detection of 30 picomole was found for valine and the response was shown to be linear over two orders of magnitude.     

Acoustic emission in solid-liquid decomposition reactions

The chemical acoustic emission method was used to study solid-liquid decomposition reactions for the example of the interaction of potassium carbonate pellets with solutions of hydrochloric acid (HCl). The reaction was shown to follow different mechanisms at different hydrochloric acid concentrations (the concentration was varied from 0.12 to 12 M). An increase in the concentration of HCl not always caused an increase in the rate of generation of acoustic emission signals and, therefore, the reaction rate. The generation of acoustic emission was studied at various reaction stages. The advantages of the chemical acoustic emission method include measurements in real time (this is of importance for fast reactions, the reaction studied took no more than 5 min) and the possibility of determining rates at separate reaction stages. An automated acoustic emission unit was tested. The unit showed high reproducibility of measurement results, reliability, and rich possibilities for studying chemical acoustic emission in solids.     

Mechanically Initiated Reaction of Aluminum with Alkyl Halides

Mechanochemical reactions of aluminum with alkyl halides were examined at room temperature. The reaction was initiated by mechanical activation of vibromilling without any activator. It was found that the initiation was not due to the temperature rise at mechanical contact but the active sources formed on aluminum surface by vibromilling. The reactivity of milled aluminum was well correlated with the intensity of exoelectron emission. Both the reactivity and the emission intensity increased sharply after 60 min of milling. The decaying characteristics by exposure of preactivated aluminum were observed for both the reactivity and the emission intensity. The role of exoelectron on the reaction was discussed.     

A BLUE FLUORESCENT PROTEIN FROM A YELLOW-EMITTING LUMINOUS BACTERIUM

Vibrio fischeri strain Y1 emits yellow light in vivo due to the participation of a yellow fluorescent protein (YFP) in the luciferase reaction. In this study it was found that the organism also produces a protein (referred to as Y1-BFP) emitting strong blue fluorescence. Its molecular weight, about 25 kDa, is the same as or very close to that of YFP. The fluorescence excitation and emission maxima of the purified Y1-BFP are at 416 and 461 nm, respectively, and the fluorescence lifetime is 12.5 ns at 2 degrees C. The molar extinction coefficient of Y1-BFP at 416 nm was estimated to be approx. 9500. With the homologous luciferase, Y1-BFP decreases the intensity and rate of decay in the in vitro reaction but has no effect on its emission spectrum (in contrast to YFP, which has a striking effect on the spectrum). With luciferase isolated from Vibrio harveyi, however, Y1-BFP causes a small blue-shift (approximately 10 nm) in the emission of the enzyme catalyzed reaction, whereas YFP has no effect on the emission spectrum.     

Very fast peroxyoxalate chemiluminescence

Peroxyoxalate chemiluminescence (PO-CL) detection offers an advantage in chromatographic detection, by the virtue of its multiple unique selectivities and high sensitivity. However, many of the analytical separation techniques available today require observation times in the millisecond range to preserve the band resolution, and as the reaction kinetics of the PO-CL reaction is considerably slower, extra flow elements are needed to observe the reaction in a time window at maximum emission intensity. Since these flow elements increase the complexity of the system and contribute to band-broadening, the rational way to adapt PO-CL detection to miniaturised separation systems is to speed up the reaction, so that it emits an initial burst of light within the acceptable detection time-frame. Although this may result in a lower overall quantum yield, the actual detection sensitivity could be equal to, or better than slower PO-CL systems. By making careful selections of oxalic reagent and catalyst(s) the reaction can be fine-tuned to maximise the intensity. In this work, the time-dependent light emission from the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) was studied under the catalytic influence of imidazole, 1,2,4-triazole, 4-dimethylaminopyridine (DMAP), and 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) in acetonitrile. Both DMAP and DBU accelerated the reaction substantially, but the best combination of reaction speed and intensity was found for a mixture of 0.5 mM DBU and 5 mM 1,2,4-triazole, which reached its maximum emission after only 40 ms and had an emission intensity comparable to that seen with 5 mM imidazole as catalyst.     

Background reactivity in smog chambers

Data from several smog chamber reaction vessels have been analyzed in an attempt to elucidate the chemical species which are responsible for chamber specific background phenomena, and the nature of the processes which determine the heterogeneous interactions of those species. There is good evidence for the emission of a compound which yields both NO_x, and free radicals (probably HONO) and emissions of reactive organics (e.g. HCHO) may also be deduced. Total integrated chamber emission of these compounds may be as high as 20 to 60 ppb during a typical smog chamber experiment. In addition to the direct emission of these contaminants, the surface reaction of NO2 and H2O to HONO is examined. In some cases this reaction may have as great an effect on a smog chamber experiment as the emission of trace contaminants. Overall chamber perturbations to gas phase chemistry have been estimated for several experiments and were found to be less than 20 percent in the majority of cases, although higher perturbations were found in experiments involving compounds of low reactivity such as butane.     

Electroplex emission from a blend of poly(N-vinylcarbazole) and 2,9-dimethyl-4,7-diphenyl-1, 10-phenanthroline

The PL and EL spectra of poly(N-vinylcarbazole) (PVK) : 2,9-dimethyl-4,7-diphenyl-1, 10-phenanthroline (BCP) (1:1 w/w) film were found completely different. The PL spectrum is a single peak at 415 nm that originates from excitons emission from PVK, and the tail of the spectrum is suggested to be excimer emission from BCP molecules. However, a new emission at 595 nm was found in the EL spectra of devices ITO/PEDOT:PSS(50 nm)/PVK:BCP(1:1)(100 nm)/Al. After aggregate, exciplex and product of electrochemical reaction were ruled out, the new emission was proposed to be electroplex emission that occurred between PVK and BCP molecules. Under high voltage, only electroplex emission can be observed in the EL spectra.     

含均二苯乙烯荧光探针的合成及其对金属离子的识别研究

通过Wittig-Horner反应合成了两个含有均二苯乙烯发色团, 一端为N,N-双(2-乙酰氧乙基)氨基受体, 另一端分别为N,N-二甲氨基(DMDE)或N,N-二苯氨基(DPDE)的荧光探针分子. 进行了NMR和MS表征. 测试了加入不同金属离子时探针分子的吸收和荧光光谱变化. 加入Ag+和Zn2+, DMDE在420 nm处出现强的荧光峰, 在600 nm的荧光峰先增强后减弱, 认为发生了分子间的荧光共振能量转移. 而DPDE在加入Ag+和Zn2+, 420 nm处无荧光发射, 600 nm处的荧光红移并减弱.     

The reaction products of the 193 nm photolysis of vinyl bromide and vinyl chloride studied by time-resolved Fourier transform infrared emission spectroscopy

Time-resolved Fourier transform infrared (TRFTIR) emission spectroscopy has been used to study the 193 nm photolysis of vinyl bromide (C(2)H(3)Br) and vinyl chloride (C(2)H(3)Cl). Time-resolved IR emission was analysed to obtain nascent vibrational state populations of two primary photolysis products: HBr (v = 1-7) and HCl (v = 1-6). In both cases the nascent vibrational state populations monotonically decrease with increasing v and are in excellent agreement with previously published data. Time-resolved populations were analysed to yield rate constants for vibrational relaxation of HBr (v = 1-3) and HCl (v = 1-4) by parent vinyl bromide and vinyl chloride, respectively. In both cases the rate constants were found to increase with increasing vibrational quantum number, in agreement with a single quantum de-excitation via vibrational to vibrational energy transfer. Butadiene (C(4)H(6)) was identified as a secondary product of the photolysis of both vinyl halides, and shown to be formed from the reaction of parent vinyl halide with the vinyl radical. The presence of a buffer gas was found to produce a strong emission feature centred at 2,200 cm(-1), the intensity of which was dependent on the pressure of the buffer gas used, and whose kinetics are indicative of a secondary reaction product. We propose that this emission is from the vibrational progression of the electronic transition A(0, v, 1) --> X(0, v, 2) in the secondary reaction product C(2)H, whose formation route is favoured by the presence of buffer gas.     

CORRELATION BETWEEN DELAYED LIGHT EMISSION AND FLUORESCENCE OF CHLOROPHYLL a IN SYSTEM II PARTICLES DERIVED FROM SPINACH CHLOROPLASTS

Abstract— The induction transient of delayed light of chlorophyll a, excited by repetitive flashes (0.5 ms in duration) and emitted 0.1 - 1.2 ms after the flashes, was measured in system II particles derived from spinach chloroplasts. An uncoupler, gramicidin S, was always added to the particles in order to eliminate the influence of the phosphorylation system on the delayed light and to isolate a direct relationship between the delayed light emission and the primary photochemical reaction, except for the experiments described in the next paragraph. The yield of delayed light emission from the system II particles was found to be about three–times higher than that of chloroplasts on a chlorophyll content basis. System I particles, on the other hand, emitted much weaker delayed light than chloroplasts. Upon intermittent illumination, induction of delayed light in system II particles showed a decrease from the initial rise level to the steady-state level. The initial rise level was the maximum. The fluorescence induction, on the other hand, exhibited an increase from the initial rise level to the maximum steady-state level. The induction of both delayed light emission and fluorescence arrived at their final steady-state levels after the same period of illumination. Induction of delayed light emission was measured under various conditions that changed the oxidation-reduction state of the primary electron acceptor, X, of photoreaction II: by adding an electron acceptor and an inhibitor of electron transport, and by changing the light intensity. The state of A'was monitored by measuring the fluorescence yield. The yield of delayed light emission excited by each flash was found to depend on the amount of oxidized form of X present before the flash. To examine the role of the primary electron donor Y of photoreaction II in delayed light emission, effects of electron donors of photoreaction II such as Mn²⁺, hydroquinone and p-phenylenediamine were investigated. These agents were found to markedly decrease the yield of delayed light emission without altering the pattern of its induction. They had little effect on the induction of fluorescence. These findings are interpreted by a mechanism in which transformation of the reaction center from the form (X^-Y⁺) into (X Y) produces a singlet excitation of chlorophyll a that is the source of millisecond delayed light emission. This reaction is probably non–physiological and must be very slow if compared to the transformation of (X^-Y⁺) into (X^-Y). Since the form (X^-Y⁺) is produced when the excitation is transferred to the reaction center in the form (XY), it is expected in this scheme that the yield of delayed light emission should depend on the amount of the form (X Y) present before the excitation flashes. Electron donors stimulate transformation of the reaction center from (X^-Y⁺) into (X^-Y). Since this reaction competes with the process of delayed light emission, electron donors are expected to suppress delayed light emission.     

荧光光谱法研究β-环糊精与齐墩果酸生成的包合物

在磷酸、硼酸及乙酸组成的缓冲介质中,齐墩果酸与β-环糊精反应生成包合络合物,其包合摩尔比为1比1。包合物的激发波长及发射波长的峰分别位于355nm及404nm处,在25℃条件下的结合常数为71L.mol-1,还测定了反应的热力学参数。测得ΔH0与ΔS0均大于0,说明此包合反应为吸热反应。测得ΔG0值小于0,且随反应温度升高而变得更负,说明此反应在试验条件下能自发进行,而随反应温度的升高,反应的自发性增强。     

MOLECULAR DESIGN OF LIGHT EMITTING POLYMERS

Fluorene-based alternating and statistical copolymers were synthesized by employing reaction methods of Wittig,Heck and Suzuki. The copolymers were classified into three groups with the photoluminescence (PL) emission maxima at420, 475 and 500 nm, respectively. Statistical copolymers with two chromophores having PL emission maxima at 420 and475 nm emitted light with the emission maximum at 475 nm on photoexcitation at 365 nm and improved the quantumefficiency by the energy transfer. However, the intramolecular energy transfer was inefficient compared to the intermolecularenergy transfer when the two chromophores were apart from each other in the range of the Forster critical distance. Fluorene-pyridinedivinylene alternating copolymer was synthesized by the Wittig reaction and found to have physical, electronic andelectrochemical properties of the individual units intact. The double-layered light emitting diode (LED) with the statisticalcopolymer as an emitting layer and the pyridine-containing copolymer as an electron transporting-hole blocking layer, whichwere sandwiched between ITO and Al, displayed a quantum efficiency of 0.1%.     

CHEMILUMINESCENCE FROM CARBENE OXIDATION

Abstract— The chemiluminescent reaction between carbenes and O₂ in Freon 113 at and above 77 K was investigated. The reaction was found to be general for phenylated carbenes and independent of precursor. Spectra obtained by optical multichannel analyzer (OMA) are consistent with the emission being from the excited ketone formed. Kinetics studies at 77 K indicate that the decay of the chemi-luminescence is significantly faster than the decay of the carbene as monitored by fluorescence and electron paramagnetic resonance.     

Mechano- and Photoresponsive Behavior of a Bis(cyanostyryl)benzene Fluorophore

The mechanoresponsive behavior and photochemical response of a new bis(cyanostyryl)benzene fluorophore (CSB-5) were investigated. Green fluorescence with λ_em,max of 507 nm was found for CSB-5 in chloroform solution, mirroring the behavior of a previously reported similar dye (CSB-6). Alternatively, crystalline samples of CSB-5 exhibited orange fluorescence with λ_em,max of 620 nm, attributable to excimer emission. Although the emission color change was not clearly noticeable by naked eye, CSB-5 exhibited mechanochromic luminescence, due to transformation into the amorphous state upon grinding the crystalline powder. Interestingly, rubbed films of CSB-5 prepared on glass substrates exhibited a pronounced emission color change from orange to green when exposed to UV light. This response is the result of a photochemical reaction that occurs in the amorphous state and which causes a decrease of the excimer emission sites so that the emission color changes from excimer to monomer. The crystalline material did not display such a photoinduced emission color change and the difference in photochemical reactivity between crystalline and amorphous states was exploited to pattern the emission color of rubbed films.     

橙红色荧光粉BaZnP2O7∶Eu3+的制备与发光特性

采用高温固相法合成了BaZnP2O7∶Eu3+荧光粉, 并对其发光性质进行了研究.     

Excited state intramolecular charge transfer reaction in binary mixtures of water and tertiary butanol (TBA): alcohol mole fraction dependence

The excited state intramolecular charge transfer reaction of 4-(1-azetidinyl)benzonitrile (P4C) has been studied in water-tertiary butanol (TBA) mixtures at different alcohol mole fractions by using steady state and time-resolved fluorescence spectroscopy. The ratio between the areas under the locally excited (LE) and charge transferred (CT) emission bands is found to exhibit a sharp rise at alcohol mole fraction approximately 0.04, a value at which several thermodynamic properties of this mixture is known to show anomalous change due to the enhancement of H-bonding network. The radiative rate associated with the LE emission also shows a maximum at this TBA mole fraction. Although the structural transition from the water-like tetrahedral network to the alcohol-like chain is reflected in the red shift of the absorption spectrum up to TBA mole fraction approximately 0.10, the emission bands (both LE and CT) show the typical nonideal alcohol mole fraction dependence at all TBA mole fractions. Quantum yield, CT radiative rate as well as transition moments also exhibit a nonideal alcohol mole fraction dependence. The time-resolved emission decay of P4C has been found to be biexponential at all TBA mole fractions, regardless of emission collection around either the LE or the CT bands. The time constant associated with the slow component (tau(slow)) shows a minimum at TBA mole fraction approximately 0.04, whereas such a minimum for the fast time constant, tau(fast) (representing the rate of LE --> CT conversion reaction) is not observed. The nonobservation of the minimum in tau(fast) might be due to the limited time resolution employed in our experiments.     

Chemiluminescence of Ce(IV) and surfactant Tween 20

It was found that cerium(IV) reacted with surfactant Tween 20 in acidic medium to generate green chemiluminescence. The maximum emission wavelength was about 478 nm. The enhancement and inhibition of the CL reaction by some polyphenols and anilines was studied and the possibility of analytical application was explored.     

Scanning electrochemical microscopy study of ion annihilation electrogenerated chemiluminescence of rubrene and [Ru(bpy)3]2+

Scanning electrochemical microscopy (SECM) was used for the study of electrogenerated chemiluminescence (ECL) in the radical annihilation mode. The concurrent steady-state generation of radical ions in the microgap formed between a SECM probe and a transparent microsubstrate provides a distance-dependent ECL signal that can provide information about the kinetics, stability, and mechanism of the light emission process. In the present study, the ECL emission from rubrene and [Ru(bpy)(3)](2+) was used to model the system by carrying out experiments with the SECM and light-detecting apparatus inside an inert atmosphere box. We studied the influence of the distance between the two electrodes, d, and the annihilation kinetics on the ECL light emission profiles under steady-state conditions, as well as the ECL profiles when carrying out cyclic voltammetry (CV) at a fixed d. Experimental results are compared to simulated results obtained through commercial finite element method software. The light produced by annihilation of the ions was a function of d; stronger light was observed at smaller d. The distance dependence of the ECL emission allows the construction of light approach curves in a similar fashion as with the tip currents in the feedback mode of SECM. These ECL approach curves provide an additional channel to describe the reaction kinetics that lead to ECL; good agreement was found between the ECL approach curve emission profile and the simulated results for a fast, diffusion-limited second-order annihilation process (k(ann) > 10(7) M(-1) s(-1)). In the CV mode at fixed distance, the ECL emission of rubrene showed two distinct signals at different potentials when fixing the substrate to generate the radical cation and scanning the tip to generate the radical anion. The first signal (pre-emission) corresponded to an emission well before reaching the generation of the radical anion and was more intense on Au than on Pt. The second ECL signal showed the expected steady-state behavior from the second-order annihilation reaction and agreed well with the simulation. A comparison of the emission obtained with rubrene and [Ru(bpy)(3)](2+) to test the direct formation of lower energy triplets directly at the electrode showed that triplets are not the cause of the pre-emission observed. Wavelength selection experiments for the rubrene system showed that the pre-emission ECL signal also appeared slightly red-shifted with respect to the main luminophore emission; a possible explanation for this phenomenon is inverse photoemission, where the injection of highly energetic holes by the oxidized species into the negatively biased tip electrode causes emission of states in the metal that appear at a different wavelength than the singlet emission from the ECL luminophore.