Gas-Phase Fluorescence Excitation and Emission Spectroscopy of Three Xanthene Dyes (Rhodamine 575, Rhodamine 590 and Rhodamine 6G) in a Quadrupole Ion Trap Mass Spectrometer

Abstract

The gas-phase fluorescence excitation, emission and photodissociation characteristics of three xanthene dyes (rhodamine 575, rhodamine 590, and rhodamine 6G) have been investigated in a quadrupole ion trap mass spectrometer. Measured gas-phase excitation and dispersed emission spectra are compared with solution-phase spectra and computations. The excitation and emission maxima for all three protonated dyes lie at higher energy in the gas phase than in solution. The measured Stokes shifts are significantly smaller for the isolated gaseous ions than the solvated ions. Laser power-dependence measurements indicate that absorption of multiple photons is required for photodissociation. Redshifts and broadening of the dispersed fluorescence spectra at high excitation laser power provide evidence of gradual heating of the ion population, pointing to a mechanism of sequential multiple-photon activation through absorption/emission cycling. The relative brightness in the gas phase follows the order R575 (1.00)GR590(1.15)GR6G(1.29). Fluorescence emission from several mass-selected product ions has been measured.

Fluorescence lifetimes of rhodamine dyes in vacuo

“…Unfortunately, the low signal-to-noise in the fluorescence data obtained with their present set-up would make lifetime measurements extremely difficult. Recently, our laboratory has reported excitation and emission spectra of several cationic rhodamines in the gas phase, including R575, R590, R6G, R640 and rhodamine B (RB) [34,41,42,61]. Here, we extend this work and report the fluorescence lifetimes of these gaseous ions, formed by ESI, mass selected and stored in a quadrupole ion trap mass spectrometer.…”

Action-FRET: Probing the Molecular Conformation of Mass-Selected Gas-Phase Peptides with Förster Resonance Energy Transfer Detected by Acceptor-Specific Fragmentation

“…This is consistent with previous study of the photofragmentation of rhodamines, which shows the same quadratic dependence at low power. 39 For measurement of all spectra presented here, the average power at each wavelength is kept between 0.9 and 1.1 mW.…”

“…Rh575 was also used as the donor chromophore by Talbot et al 18 , and both the fluorescence excitation and emission spectra along with photofragmentation mass spectra have been previously studied in detail. 39 Both chromophores are designed to be functionalized onto primary amines, and thus peptides containing two primary amine groups only were chosen. For the initial study, the simple tripeptide N-alanine−alanine−lysine−OH (AAK) was chosen to ensure that the chromophores remain spatially close to each other in the doubly grafted species.…”

Long-lived and largely red-shifted photoluminescence of solid-state rhodamine dyes: Molecular exciton coupling and structural effect

“…Such studies have been the subject of many investigations over last 50 years [7][8][9][10][11][12][13][14][15][16][17][18]. Only recently literature on gas-phase rhodamine fluorescence became available [19][20][21][22][23][24]. The emission of isolated molecular rhodamine dyes in gas-phase reveals quite different properties from that in liquid-phase.…”