Femtosecond to nanosecond dynamics in fullerenes: Implications for excitedstate optical nonlinearities

Klimov, Victor I.; Smilowitz, Laura; Wang, H.; Grigorova, M.; Robinson, Jeanne M.; Koskelo, Aaron C.; Mattes, Benjamin R.; Wudl, Fred; McBranch, D.

doi:10.1163/156856797x00024

Cited by 25 publications

(6 citation statements)

References 17 publications

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“…Many authors have reported on the photophysical properties of molecular solutions of C 60 . [12][13][14][15][16][17][18][19][20] Likewise, many authors have studied the photophysical and structural properties of solid films of C 60 . [21][22][23][24][25][26][27][28][29][30][31][32][33][34] Under certain conditions, C 60 forms stable colloidal assemblies in solvents.…”

Section: Introductionmentioning

confidence: 99%

Photophysical Properties of C₆₀ Colloids Suspended in Water with Triton X-100 Surfactant: Excited-State Properties with Femtosecond Resolution

et al. 2009

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We examine the photophysics of a colloidal suspension of C 60 particles in a micellar solution of Triton X-100 and water, prepared via a new synthesis which allows high-concentration suspensions. The particle sizes are characterized by transmission electron microscopy and dynamic light scattering and found to be somewhat polydisperse in the range of 10-100 nm. The suspension is characterized optically by UV-vis spectroscopy, femtosecond transient absorption spectroscopy, laser flash photolysis, and z-scan. The ground-state absorbance spectrum shows a broad absorbance feature centered near 450 nm which is indicative of colloidal C 60 . The transient absorption dynamics, presented for the first time with femtosecond resolution, are very similar to that of thin films of C 60 and indicate a strong quenching of the singlet excited state on short time scales and evidence of little intersystem crossing to a triplet excited state. Laser flash photolysis reveals that a triplet excited-state absorption spectrum, which is essentially identical in shape to that of molecular C 60 solutions, does indeed arise, but with much lower magnitude and somewhat shorter lifetime. Z-scan analysis confirms that the optical response of this material is dominated by nonlinear scattering. IntroductionSince its discovery, 1 the uniquely symmetrical C 60 molecule has been widely studied, and many applications for it and its derivatives have been proposed, notably lubricants, 2 superconductors, 3 sensors, 4-7 solar cells, 8 and biomedical applications [9][10][11] such as drug delivery and photodynamic therapy. In particular, the photophysical properties of the C 60 molecule have been the subject of intense study. Many authors have reported on the photophysical properties of molecular solutions of C 60 . [12][13][14][15][16][17][18][19][20] Likewise, many authors have studied the photophysical and structural properties of solid films of C 60 . [21][22][23][24][25][26][27][28][29][30][31][32][33][34] Under certain conditions, C 60 forms stable colloidal assemblies in solvents. [35][36][37][38][39][40][41][42][43][44] Colloidal suspensions of C 60 particles can also be formed in binary solvent mixtures, in which one is a good solvent and the other is a poor solvent for C 60 . [45][46][47][48][49] Aqueous suspensions of colloidal C 60 particles are also formed by a number of methods, [50][51][52][53][54][55][56][57][58][59][60][61][62][63][64] including solubilization in micellar solutions. 55,61,[65][66][67][68][69] Some studies have been done of the photophysical properties of these colloidal fullerene suspensions. 67,68,70,71 The photochemical properties, and in particular the generation of reactive oxygen species (ROS) via intersystem crossing to the triplet state, have been of interest both for potential exploitation for photodynamic therapy 9 and regarding concerns about their potential environmental impact, because there have been reports of significant cytotoxicity effects. [50][51][52][53] This work reports on the excited-state dynamics o...

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Section: Introductionmentioning

confidence: 99%

Photophysical Properties of C₆₀ Colloids Suspended in Water with Triton X-100 Surfactant: Excited-State Properties with Femtosecond Resolution

et al. 2009

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“…Photoexcited fullerenes have been the subject of much interest in recent years, both fundamental and applied. 1 Relaxation of laser excited C 60 thin films [2][3][4][5][6] and toluene suspensions of C 60 , [7][8][9][10][11] C 70 , 7 and C 76 and C 84 ͑Ref. 12͒ yielded relaxation times on the order of 40 ps with all of the authors attributing the relaxation to a decay or transport property of the electronic system.…”

Section: Introductionmentioning

confidence: 99%

Role of attached polymer chains on the vibrational relaxation of aC60fullerene in aqueous solution

et al. 2005

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We have investigated the vibrational relaxation of a bare C 60 fullerene and C 60 fullerenes with covalently attached poly ͑ethylene oxide͒ ͑PEO͒ chains in aqueous solution using classical molecular dynamics simulations. The rate of transfer of vibrational energy from the excited fullerene to the surrounding water was found to be slow for the bare fullerene, with a vibrational relaxation time of approaching 200 ps. Attachment of a single short PEO chain ͑M W = 250͒, yielding C 60-PEO, was found to decrease the vibrational relaxation time by about a factor 5, while the vibrational relaxation time for a fullerene with six attached PEO chains, or C 60-͑PEO͒ 6 , exhibited approximately 25 times faster vibrational relaxation than the bare fullerene. The temperature of the attached PEO chain͑s͒ was found to increase during the vibrational relaxation of the fullerene, but remained well below that of the fullerene, indicating that the rate limiting step in vibrational relaxation of C 60-PEO is energy transfer from the fullerene to the attached PEO.

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“…The initial peak is the excitation of fullerene electrons due to absorption of the pump pulse. Electrons equilibrate among themselves in the first few picoseconds (note, this is not recombination, as recombination rates are on the order of nanoseconds or longer). − The following vibrational relaxation (cooling) is the dominating effect observed as the decay of the TDTT signal for the next few hundred picoseconds. This thermal relaxation rate has been measured experimentally and computationally for higher order fullerenes and ranges from ∼10 to 200 ps with a strong dependence on functionalization. − …”

Section: Resultsmentioning

confidence: 99%

Molecular Tuning of the Vibrational Thermal Transport Mechanisms in Fullerene Derivative Solutions

Szwejkowski¹,

Giri²,

Warzoha

et al. 2017

ACS Nano

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Control over the thermal conductance from excited molecules into an external environment is essential for the development of customized photothermal therapies and chemical processes. This control could be achieved through molecule tuning of the chemical moieties in fullerene derivatives. For example, the thermal transport properties in the fullerene derivatives indene-C monoadduct (ICMA), indene-C bisadduct (ICBA), [6,6]-phenyl C butyric acid methyl ester (PCBM), [6,6]-phenyl C butyric acid butyl ester (PCBB), and [6,6]-phenyl C butyric acid octyl ester (PCBO) could be tuned by choosing a functional group such that its intrinsic vibrational density of states bridge that of the parent molecule and a liquid. However, this effect has never been experimentally realized for molecular interfaces in liquid suspensions. Using the pump-probe technique time domain thermotransmittance, we measure the vibrational relaxation times of photoexcited fullerene derivatives in solutions and calculate an effective thermal boundary conductance from the opto-thermally excited molecule into the liquid. We relate the thermal boundary conductance to the vibrational modes of the functional groups using density of states calculations from molecular dynamics. Our findings indicate that the attachment of an ester group to a C molecule, such as in PCBM, PCBB, and PCBO, provides low-frequency modes which facilitate thermal coupling with the liquid. This offers a channel for heat flow in addition to direct coupling between the buckyball and the liquid. In contrast, the attachment of indene rings to C does not supply the same low-frequency modes and, thus, does not generate the same enhancement in thermal boundary conductance. Understanding how chemical functionalization of C affects the vibrational thermal transport in molecule/liquid systems allows the thermal boundary conductance to be manipulated and adapted for medical and chemical applications.

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Femtosecond to nanosecond dynamics in fullerenes: Implications for excitedstate optical nonlinearities

Cited by 25 publications

References 17 publications

Photophysical Properties of C₆₀ Colloids Suspended in Water with Triton X-100 Surfactant: Excited-State Properties with Femtosecond Resolution

Photophysical Properties of C₆₀ Colloids Suspended in Water with Triton X-100 Surfactant: Excited-State Properties with Femtosecond Resolution

Role of attached polymer chains on the vibrational relaxation of aC60fullerene in aqueous solution

Molecular Tuning of the Vibrational Thermal Transport Mechanisms in Fullerene Derivative Solutions

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Femtosecond to nanosecond dynamics in fullerenes: Implications for excitedstate optical nonlinearities

Cited by 25 publications

References 17 publications

Photophysical Properties of C60 Colloids Suspended in Water with Triton X-100 Surfactant: Excited-State Properties with Femtosecond Resolution

Photophysical Properties of C60 Colloids Suspended in Water with Triton X-100 Surfactant: Excited-State Properties with Femtosecond Resolution

Role of attached polymer chains on the vibrational relaxation of aC60fullerene in aqueous solution

Molecular Tuning of the Vibrational Thermal Transport Mechanisms in Fullerene Derivative Solutions

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Photophysical Properties of C₆₀ Colloids Suspended in Water with Triton X-100 Surfactant: Excited-State Properties with Femtosecond Resolution

Photophysical Properties of C₆₀ Colloids Suspended in Water with Triton X-100 Surfactant: Excited-State Properties with Femtosecond Resolution