Excimer–monomer fluorescence changes by supramolecular disassembly for protein sensing and quantification

A binding-induced supramolecular dissociation strategy is developed with the ratio of monomer and excimer fluorescence as the tool for protein sensing and quantification, exhibiting excellent selectivity.

Imaging of gasoline-like sprays with planar laser-induced exciplex fluorescence using a stereoscopic imaging system

The role of the fuel injection systems in direct injected gasoline engines is to achieve a suitable fuel vapordistribution, homogeneous or with some degree of stratification, while avoiding unwanted effects such as wall wetting. Planar laser-induced exciplex fluorescence (PLIEF) is a method suitable for the characterization of such sprays since it enables separate imaging of both vapor and liquid phase of fuel simultaneously. In this study a hollow-cone spray generated with an outwards-opening piezo-actuated injector is investigated, with the injector mounted in a constant volume, constant pressure spray chamber with quartz windows, providing a controlled steady test environment. N-hexane is used as surrogate fuel of gasoline, together with exciplex-forming fluorescence tracers - fluorobenzene and diethylmethylamine. Fluorescence excitation is carried out with a parallel laser sheet from the fourth harmonic light of a Nd:YAG-laser (266 nm) running at 10 Hz. Exciplex fluorescence images from liquid phase and monomer fluorescence spray images from vapor phase can be acquired by a single UV-sensitive CMOS camera equipped with a stereoscope having filters selectively transmitting monomer fluorescence at 295 nm and exciplex fluorescence at 355 nm. Since the fluorescence is strongly quenched by oxygen, most of the experiments were carried out in a nitrogen atmosphere.Images were recorded during the injection and at various time steps after the end of the injection, and typical spray development for this type of injector was observed, i.e. the fuel forms an expanding cone, the sheet breaks up to form a vortex structure and the vortices continue to expand after the end of the injection. Fuel vapor is firstly observed at the same locations as the liquid drops, and is then accumulated into the center of the vortices. In addition, penetration of liquid phase and vapor phase are found to be very similar. Various injection pressures have been tested, which shows that increasing the fuel pressure from 10 to 20 MPa results in a larger vortex structure. The fuel evaporation can be followed by studying the evolution of the monomer and exciplex fluorescence as a function of time. At room temperature the vaporization is found to be very slow, but above 40°C there is a noticeablepresence of vapor at the end of the injection, and at higher temperatures, the vaporization goes even faster.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.5023

Effects of added phthalate plasticizers on photodegradation of irradiated poly (α-methylstyrene) films

The effects of UV irradiation and blending on the stability of poly (α-methylstyrene) (PαMS) in solid films were studied at different intervals of irradiation time in the presence of air, by absorption, emission and Fourier transform infrared (FT-IR) spectroscopy. The increase in irradiation time caused an increase in the intensity of the absorption band of the polymer, and an increase in the intensity of absorption of a new broad band at a longer wavelength, thus indicating the possibility of photodegradation of polymeric chains. The influence of added plasticizers, dimethyl terephthalate (DMT), diethyl terephthalate (DET), dibutyl phthalate (DBP), dioctyl phthalate (DOP) and dioctyl terephthalate (DOT) on photoquenching of the polymer fluorescence band was also investigated, and found to increase the photoquenching processes with increase in the amount of added plasticizers. By contrast, the intensity of excimer and monomer fluorescence bands was also found to decrease with increase in irradiation times. These changes may be attributed to the formation of new photoproducts which resulted from the photodegradation and photooxidation of irradiated polymeric chains. In addition, the observed increase in the intensities of the carbonyl and hydroxyl regions of the FT-IR spectra provides evidence for the photooxidation of polymeric chains. The increase in the intensity of some bands and the disappearance of new bands indicate the photodegradation of polymeric chains.

Irradiation Effect on Stability of Plasticized Poly(Fluorostyrene) Isomers in Solution

The UV irradiation and blending effects on stability of Poly(Fluorostyrene) isomers in solution were studied at different intervals of irradiation time in presence of air. The increase in irradiation time of these isomers caused an increase in the intensity of the absorption band and an increase in the intensity of the absorption of new broad band at longer wavelength, thus indicating a possibility of photodegradation of polymeric chains. The influence of added dioctyl phthalate and dioctyl terephthalate plasticizers on photooxidative degradation was also investigated and was found to increase the photodegradation processes in polymeric chains. On the other hand, the intensity of excimer and monomer fluorescence bands maxima was also found to decrease with increase in irradiation times. These changes may be attributed to the formation of new photoproducts resulted from the photodegradation of irradiated polymeric chains. The decrease in polarity of used solvents caused a considerable enhancement to the intensity of the polymer fluorescence band and accelerated photodegradation. A proposed mechanism is suggested to account for the effects of added plasticizers, the increase in irradiation time, and polarity of solvents on photodegradation and photooxidation processes in polymeric chains.

Detection of Membrane Fluidity in Submitochondrial Particles of Platelets and Erythrocyte Membranes from Mexican Patients with Alzheimer Disease by Intramolecular Excimer Formation of 1,3 Dipyrenylpropane

It has been suggested that mitochondrial dysfunction and defects in membrane structure could be implied in AD pathogenesis. The aim of the present work was the study of membrane fluidity in submitochondrial platelet particles and erythrocyte membranes from Mexican patients. Blood samples were obtained from 30 patients with Alzheimer disease and 30 aged-matched control subjects. Membrane fluidity determinations were done using a very low concentration of the fluorescent dipyrenylpropane probe incorporated in both types of membranes. This probe is able to give excimer and monomer fluorescence, therefore it can be used to monitor fluidity changes in biological membranes.The data obtained showed that in submitochondrial particles from AD patients, the excimer to monomer fluorescent intensity ratio was lower (0.231 ± 0.008) than aged-matched control subjects (0.363 ± 0.014). Therefore, membrane fluidity was lower in AD samples. On the other hand, we found similar membrane fluidity in erythrocytes from AD patients and aged-matched controls: the fluorescent intensity ratios were 0.312 ± 0.03 and 0.305 ± 0.033, respectively. In addition, lipid peroxidation in submitochondrial particles and erythrocyte membranes was higher in AD samples than in aged-matched controls. These data suggest that submitochondrial platelet particles are more sensitive to oxidative stress than erythrocyte membranes.

Synthesis of Fluorescent Molecular Sensory System for Endocrine Disruptors Based on Dansylthiacalix[6]arenes

Flexible fluorescent hosts, mono-, di- and tridansyl-modified tert-butylthiacalix[6]arenes (TC[6]A-1, TC[6]A-2 and TC[6]A-3, respectively) and didansyl-tert-butylcalix[6]arene (C[6]A-2) have been synthesized in order to investigate their fluorescent chemosensor functionality, which detects endocrine disruptors. The hosts, TC[6]A-1, TC[6]A-2, TC[6]A-3 and C[6]A-2 exhibit pure monomer fluorescence spectra, of which the spectra shows a decrease fluorescence intensity in the presence of guests. The extent of fluorescence variation of TC[6]A-1, TC[6]A-2, TC[6]A-3 and C[6]A-2 upon a guest addition was recognized as the manifestation of sensing ability of the hosts. A sensing parameter (∆I/I0) was used to describe the sensing ability of four hosts. Host TC[6]A-2 was able to detect 2,4-dichlorophenoxyacetic acid with high sensitivity. The guest-induced variations in the fluorescence intensities and MM2-minimized structures of the hosts suggest that the appended moieties of the hosts act as a hydrophobic cap and a probe showing the host to form a 1:1 host- guest complex.