Time-Resolved Single Photon Counting Study of the Quenching of Fluorescent Probes by Petroleum: Probing the Energy Distribution of the Nonaliphatic Components

Nicodem, David E.; Cunha, Maria Fernanda V. da; Guedes, Carmen Luı́sa Barbosa

doi:10.1366/0003702001951129

Cited by 9 publications

(9 citation statements)

References 9 publications

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“…This 'curved' wavelength dependence had been noted in previous studies and is due to the complex interplay between collisional energy transfer and quenching processes. 17,19 Brie y, at short emission wavelengths the uorophores have large bandgaps and can readily undergo collisional energy transfer with larger, aromatic, sm all bandgap molecules. The rate of energy transfer is dependent on the bandgap between the two populations, and so the value of relative to the maximum lifetime ( max ) is shortened t t the m ost at short emission wavelengths where the bandgap is greatest.…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, as the bandgaps of the excited uorophores decrease there is an increased rate of internal conversion, which also contributes to a reduction in the average lifetime. 4,17,19,20 There are a number of disadvantages to using steady state uorescence spectroscopy for quantitative measurements, in particular the dif culty in determining the absolute uorescence intensity of the sample and the broad nature of the bands. Fluorescence lifetime m easurements, on the other hand, are insensitive to uorescence intensity changes, sample turbidity, and to photobleaching.…”

Section: Introductionmentioning

confidence: 99%

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Quantitative Analysis of Crude Oils by Fluorescence Lifetime and Steady State Measurements Using 380-nm Excitation

Ryder

2002

Appl Spectrosc

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Fluorescence emission and lifetime spectroscopy using 380-nm excitation have been successfully applied to the determination of API gravity and aromatic concentration of crude petroleum oils. Twelve crude oils from the North Sea with American Petroleum Institute (API) gravities of between 20 and 50 were analyzed; emission spectra were obtained with a standard fluorometer and the lifetime data with a pulsed ultraviolet light-emitting diode (UV-LED) coupled to a fluorescence lifetime system assembled in-house. A strong correlation between API gravity and the ratio of the fluorescence intensities recorded at 650 nm and 450 nm yielded a partial least-squares (PLS) regression model with an accurcy of ±4.6 °API; using the fluorescence intensity ratio at 650 nm and 550 nm gave an accuracy of ±5.8 °API. The average fluorescence lifetimes (τ̄) of the oils ranged from 1.9 to 18.6 ns, with τ̄ first increasing and then decreasing as the emission wavelength increased. These effects are due to the interplay between energy transfer and the quenching processes, which are governed by oil composition. A strong linear correlation was found between the ratio of the fluorescence lifetime measured at 650 nm and 550 nm and the aromatic concentration. A PLS regression model using this ratio had an accuracy of ±4% for aromatic concentration. Combining the fluorescence intensity with the lifetime measurements at 550 nm and 650 nm provides a rapid, quantitative, non-contact, nondestructive method of oil characterization.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Quantitative Analysis of Crude Oils by Fluorescence Lifetime and Steady State Measurements Using 380-nm Excitation

Ryder

2002

Appl Spectrosc

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“…Longer wavelength excitation also results in a shortening of the observed fluorescence lifetimes. 6,7,8 The use of fluorescence based methods for the characterisation of petroleum products has been widely demonstrated. Steady state fluorescence emission spectroscopy has been used to characterize bulk petroleum materials from liquid oils, both crude and refined, 9 to solid asphaltenes, 10 bitumens, 11 and kerogens.…”

Section: Introductionmentioning

confidence: 99%

Influence of chemical composition on the fluorescence lifetimes of crude petroleum oils

2003

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Fluorescence based methods are increasingly being used for the analysis of crude oils because they offer high speed, low cost, non-contact, and non-destructive testing options. The fluorescence of crude oils is due to the presence of a wide range of cyclic aromatic compounds, with the intensity and temporal behaviour of this fluorescence being directly related to chemical composition. In particular, we have found that the Fluorescence Lifetime (FL) measured at a range of different emission wavelengths is correlated with the concentrations of the aromatic and polar fractions of petroleum oils, and the density (API gravity).We have analysed 22 different crude oils from around the world with API gravities of between 10 to 50. The fluorescence steady-state emission spectra and fluorescence lifetimes at a range of emission wavelengths were measured for 380 nm excitation. It was found that the correlations between the chemical and physical characteristics of the crude oils and the measured fluorescence parameters are highly non-linear. Furthermore, there is a wide degree of scatter in the observed data for medium oils, which have similar physical properties but widely varying chemical compositions. We discuss these findings in the context of developing quantitative methods of analysis for crude petroleum oils based on fluorescence lifetime measurements.

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“…22,23 The second effect observed is a red shift in the emission upon going from lighter to heavier crude oils, which can be more readily seen when the spectra are normalized at their emission maxima (inset of Figure 1), which may indicate the presence of quenching or energy-transfer processes. 24 Charge-transfer absorption and/ or quenching processes are implicitly assumed to be unimportant in crude oils. 25 Measurements of the fluorescence quantum yield of crude oils can potentially provide valuable information about quenching and energy-transfer processes.…”

Section: Articlementioning

confidence: 99%

Prediction of Crude Oil Properties and Chemical Composition by Means of Steady-State and Time-Resolved Fluorescence

et al. 2011

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Steady-state and time-resolved fluorescence measurements are reported for several crude oils and their saturates, aromatics, resins, and asphaltenes (SARA) fractions (saturates, aromatics and resins), isolated from maltene after pentane precipitation of the asphaltenes. There is a clear relationship between the American Petroleum Institute (API) grade of the crude oils and their fluorescence emission intensity and maxima. Dilution of the crude oil samples with cyclohexane results in a significant increase of emission intensity and a blue shift, which is a clear indication of the presence of energy-transfer processes between the emissive chromophores present in the crude oil. Both the fluorescence spectra and the mean fluorescence lifetimes of the three SARA fractions and their mixtures indicate that the aromatics and resins are the major contributors to the emission of crude oils. Total synchronous fluorescence scan (TSFS) spectral maps are preferable to steady-state fluorescence spectra for discriminating between the fractions, making TSFS maps a particularly interesting choice for the development of fluorescence-based methods for the characterization and classification of crude oils. More detailed studies, using a much wider range of excitation and emission wavelengths, are necessary to determine the utility of time-resolved fluorescence (TRF) data for this purpose. Preliminary models constructed using TSFS spectra from 21 crude oil samples show a very good correlation (R 2 > 0.88) between the calculated and measured values of API and the SARA fraction concentrations. The use of models based on a fast fluorescence measurement may thus be an alternative to tedious and time-consuming chemical analysis in refineries. ' INTRODUCTIONOnline remote characterization and real-time classification of crude petroleum are the most important current challenges faced by the petrochemical industry and environmental agencies. A rapid and inexpensive method for the remote analysis and classification of petroleum prior to distillation of the crude would provide chemical information of great importance for real-time adjustment of the critical operational parameters of a refinery, permitting an optimization of the process and resulting in economic and environmental benefits.A variety of spectroscopic techniques have been used over the last few decades for the analysis, characterization, and classification of crude oil in drilling fields, for the analysis of petroleum products, and for the detection of oil spills. The advantages of using such techniques include rapid response, the requirement of minimal sample preparation, and relatively inexpensive equipment costs. Of all of the optical spectroscopic techniques employed, vibrational [infrared (IR) and Raman] 1,2 and electronic [ultravioletÀvisible (UVÀvis) and fluorescence] spectroscopies have shown the highest potential in the field. Fluorescence is a more complex phenomenon than absorption (UVÀvis or IR), and effects such as quenching and energy transfer have to be considered. 3,...

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Time-Resolved Single Photon Counting Study of the Quenching of Fluorescent Probes by Petroleum: Probing the Energy Distribution of the Nonaliphatic Components

Abstract: Index Headings: Petroleum; Fluorescence; Time-resolved single photon counting; TRSPC; Quenching.

Cited by 9 publications

References 9 publications

Quantitative Analysis of Crude Oils by Fluorescence Lifetime and Steady State Measurements Using 380-nm Excitation

Quantitative Analysis of Crude Oils by Fluorescence Lifetime and Steady State Measurements Using 380-nm Excitation

Influence of chemical composition on the fluorescence lifetimes of crude petroleum oils

Prediction of Crude Oil Properties and Chemical Composition by Means of Steady-State and Time-Resolved Fluorescence

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