Two‐photon excitation spectroscopy and excited state decay kinetics of isolated diphenylbutadiene

Micelle-Encapsulated Quantum Dot-Porphyrin Assemblies as in Vivo Two-Photon Oxygen Sensors

Micelles have been employed to encapsulate the supramolecular assembly of quantum dots with palladium(II) porphyrins for the quantification of O2 levels in aqueous media and in vivo. Förster resonance energy transfer from the quantum dot (QD) to the palladium porphyrin provides a means for signal transduction under both one- and two-photon excitation. The palladium porphyrins are sensitive to O2 concentrations in the range of 0-160 Torr. The micelle-encapsulated QD-porphyrin assemblies have been employed for in vivo multiphoton imaging and lifetime-based oxygen measurements in mice with chronic dorsal skinfold chambers or cranial windows. Our results establish the utility of the QD-micelle approach for in vivo biological sensing applications.

The vibrational structure of (E,E')-1,4-diphenyl-1,3-butadiene Linear dichroism FT-IR spectroscopy and quantum chemical calculations

The title compound (DPB) was investigated by FT-IR spectroscopy in liquid solutions and by FT-IR linear dichroism (LD) measurements on samples aligned in stretched polyethylene. The LD data provided experimental assignments of molecular transition moment directions and vibrational symmetries for more than 40 vibrational transitions. The observed IR wavenumbers, relative intensities, and polarization directions were generally well reproduced by the results of a harmonic analysis based on B3LYP/cc-pVTZ density functional theory (DFT). The combined experimental and theoretical results led to proposal of a nearly complete assignment of the IR active fundamentals of DPB, involving reassignment of a number of transitions. In addition, previously published Raman spectra of DPB were well predicted by the B3LYP/cc-pVTZ calculations.

Franck-Condon analysis of the absorption and fluorescence spectra of all trans α,ω-diphenylpolyenes with one to seven polyene double bonds

Fluorescence and absorption spectra have been measured for all-trans alpha,omega-diphenylpolyenes with one to seven polyene double bonds in room-temperature solution, along with the fluorescence spectra of those with one to six polyene double bonds in n-alkane matrices at 77 K. All the spectral data were fitted by sums of Gaussians to treat the Franck-Condon envelopes of the measured spectra quantitatively. The Franck-Condon analyses of the spectra in the harmonic limit revealed that the displacements of the C=C and C-C stretching vibrational modes in the 2 Ag state relative to those in the ground state, 1 1Ag(S0), increase, while those in the 1 1Bu state show a slight decrease with the increase of the polyene chain length. It is also shown that the bandwidths of the absorption and fluorescence spectra exhibit a monotonic decrease with the increase of the chain length.

TWO-PHOTON–INDUCED FLUORESCENCE

Nonresonant two-photon electronic spectroscopy of polyatomic molecules is reviewed for the period since 1979. Emphasis is placed on studies that expose patterns in the two-photon fluorescence (also ionization, optoacoustic) excitation spectra of aromatic hydrocarbons and the effect of vibrations and substitution, particularly within the framework of pseudoparity rules. A section is devoted to biological molecules and the emerging use of two-photon-induced fluorescence anisotropy. Relevant theoretical results are discussed, with emphasis on quantum chemical predictions of vibronic coupling and substituent effects on two-photon absorptivity and tensor properties of individual molecules. This chapter includes higher-order spectroscopy, and a limited number of three- and four-photon studies are discussed.

A Rotationally Resolved Fluorescence Excitation Spectrum of all-trans -1,4-Diphenyl-1,3-butadiene

Band 1 in the jet-cooled one-photon S(1) <-- S(0) fluorescence excitation spectrum of all-trans-1,4-diphenyl-1,3-butadiene has been rotationally resolved with a molecular beam laser spectrometer. Both the orientation of the optical transition moment and the rotational constants of the two vibronic levels have been measured. The molecule shows no evidence of being significantly distorted from a C(24) geometry when it is low in the vibrational manifolds of either of the two electronic states.