Developments of techniques such as confocal microscopy are been of great interest for the petroleum industry. Confocal
images permits through of direct observation, obtain the acquisition and interpretation of in situ information of the
petroleum emulsions systems, without requirement of sample pretreatments and can be applied to samples of high
optical density as crude oils. This property of the confocal technique is of great utility for studies of the colloidal
structural evolution in dark samples as asphaltenes, and water in crude oils emulsions. In this work, the applicability of
a homemade confocal microscope is shown. Studies of stability of colloidal suspensions (asphaltenes and emulsions)
such as aggregation kinetic, flocculation dynamic, and characterization of colloidal system are showed by confocal
images. The aggregation process of flocculated asphaltenes for Furrial crude oils was showed through of high-resolution
micrographics image, and their colloidal structural evolution are described by an analysis of size distribution of
flocculated asphaltenes particles. Additional, the images of the dynamics in the drop size and drop size distributions
during the initial stage of the separation of water drops from Furrial crude oils were also reported. This technique
directly permitted for example, visualization of the coalescence of small droplets to form large ones from water-in-crude
oil emulsions and visualize the morphology of flocculated asphaltenes.
The antiphotooxidative properties of boldine and chloride berberine were studied by time-resolved thermal lensing technique. These compounds belong to isoquinoline alkaloids possessing interesting biological activity (e.g. antibacterial, antimalarial, antitumor). Antiphotooxidative properties of the alkaloids were studied by mechanism of energy transference between powerful oxidizing agents such as singlet oxygen. Singlet oxygen was produced by energy transfer from chlorophyll-sensitized photooxidation of oil by exposure of high light intensities like laser. The lifetimes of singlet oxygen in dimethylsulfoxide, methanol and water were determined to confirm the assignment of the singlet molecular oxygen O2 (1Δg) in the experiments. In order to understand the effect of the alkaloids on active oxygen species, we carried out in detail an analysis of the thermal lensing signal. It was shown that the alkaloids can act as quenchers of singlet oxygen. To demonstrate the ability of the alkaloids to act efficient singlet oxygen acceptors, we have measured the fluorescence spectra of the studied alkaloids in the presence and in the absence of singlet oxygen. The antiphotooxidative activity of boldine and chloride berberine can be explained by the ability to quench singlet oxygen.
In this work, a detail analysis of the flocculation kinetic of asphaltenes colloidal particles has been carried out usng confocal microscopy. The colloidal structural evolution of the asphaltene flocculated has had varies postulated; however, the aggregation process of asphaltene is still not fully understood. In a recent paper, using Confocal microscope (homemade), we reported high-resolution micrographic images of asphaltenes flocculated and the correlation between crude oil stability and flocculation process. This technique permitted visualizes directly the physical nature of asphaltene flocculated. In this work, a detail analysis of the flocculation kinetic of asphaltene colloidal particles has been carried out using confocal microscopy. The physical nature of asphaltene flocculated from different crude oils is showed through of high-resolution image micrographies and its colloidal structural evolution.
A led-fluorescence spectroscopy method determinate the inhibitory effects of probe compounds on MAO-B activity is described. In this assay, we demonstrate the possibility of determinate the activity of MAO-B efficiently and rapidly without the use of reference substrate. Measuring variations in fluorescence intensity of MAO-B enzyme during the reaction with inhibitors, L-deprenyl and berberine IC50 and KI values were obtained. For L-deprenyl (IC50 = 0.017 μM and KI = 0.019 μM) and berberine (IC50 = 90 μM and KI = 47 μM) were in agreement to the values obtained with a standard method and literature reported.
The asphaltenes flocculation process in heavy crude oils is a subject of great interest for the oil industry due to the negative effect of this process in the oil extraction. In this work we present the application of the Confocal Microscopy to the study of the aggregation process of asphaltene in crude oils. The advantages of the technique for study of the particles in surface and in the dispersed phase are shown. Confocal images of different shows changes in the behavior of the differents solutions. The results can be related with the stability and the prediction of asphaltene precipitation in crude oils.
The quenching of fluorescence due to the high values of the fluence of the excitation field is studied for three different samples of Rhodamine 6G: ethanol and glycerol solutions and a film of the dye deposited over a silica substrate. High level of quenching is reported for the ethanol solution, while the effect is barely observed for the glycerol solution. The film sample does not exhibit the quenching effect. We also report correlation between the presence of quenching of the fluorescence and the fluence dependence of the fluorescence decay. The results confirm the validity of a model, which suggests this dependence as an explanation of the quenching effect.
Molecular absorption and fluorescence studies of Asphaltenes in toluene solution and thin films absorbed onto glass plates were carried out. The fluorescence was induced by two different type of laser: a CW Ar+ and Nd-Yag laser. A red shifted was observed in both: fluorescence and absorption spectra, which can be attributed to asphaltenes aggregation. Experiments made with sample films in glass plate with the 532 nm Nd-Yag laser, shows a very narrow band at 566.1 nm (1126 cm-1) but with higher relative intensity compare to those obtained with CW laser, which is attributed to a Raman line. This signal can be employed to perform adsorption studies onto solid surfaces.
In this work we present an application of the forward-angle light scattering (FAST) for the flocculation point determination in asphaltene-toluene solutions. This technique allows to obtain an accurate and precise flocculation point determination compare to those obtained by traditional techniques. Estimations of flock dimensions based in the FAST measurements are presented.
In the present work an application of z-scan technique to the study of asphaltenes is presented in order to determine their nonlinear properties. For asphaltenes toluene solution a high value of nonlinear refraction index (n2 equals 6.04 X 10-12) it is obtained. Strong dependence of the two photon absorption coefficient ((beta) ) with the input intensity was observed for higher solutions concentration, which can be explained by molecular aggregation.
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