Electron transfer from the benzophenone triplet excited state directs the photochemical synthesis of gold nanoparticles

McTiernan, Christopher D.; Alarcon, Emilio I.; Hallett-Tapley, Geniece L.; Murillo-López, Juliana A.; Arratia‐Pérez, Ramiro; Netto‐Ferreira, José Carlos; Scaiano, Juan C.

doi:10.1039/c3pp50247c

Cited by 13 publications

(24 citation statements)

References 16 publications

(19 reference statements)

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“…In LFP experiments (laser excitation of BPND in acetonitrile at 355 nm), the observed transient (absorption spectrum centered at 520 nm, close to that of benzophenone itself; long lifetime: 41 µs and quenched by O 2 with a diffusion controlled reaction) can be ascribed to the BPND triplet state. The weak transient signals suggest, however, a rather limited intersystem crossing from the singlet to the triplet state.…”

Section: Resultsmentioning

confidence: 98%

A benzophenone‐naphthalimide derivative as versatile photoinitiator of polymerization under near UV and visible lights

Zhang

Zivic

Dumur

et al. 2014

J. Polym. Sci. Part A: Polym. Chem.

102

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A benzophenone-naphthalimide derivative (BPND) bearing tertiary amine groups has been developed as a highperformance photoinitiator in combination with 2,4,6-tris(trichloromethyl)-1,3,5-triazine or an iodonium salt for both the free radical polymerization (FRP) of acrylates and the cationic polymerization (CP) of epoxides upon exposure to near UV and visible LEDs (385-470 nm). BPND can even produce radicals without any added hydrogen donor. The photochemical mechanisms are studied by molecular orbital calculations, steady state photolysis, electron spin resonance spin trapping, fluorescence, cyclic voltammetry and laser flash photolysis techniques.These novel BPND based photoinitiating systems exhibit an efficiency higher than that of the well-known camphorquinonebased systems (FRP and CP) or comparable to that of bis(2,4, 6-trimethylbenzoyl)-phenylphosphineoxide (FRP at k 455 nm).

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Section: Resultsmentioning

confidence: 98%

A benzophenone‐naphthalimide derivative as versatile photoinitiator of polymerization under near UV and visible lights

Zhang

Zivic

Dumur

et al. 2014

J. Polym. Sci. Part A: Polym. Chem.

102

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“…− in the presence of a reductant, 25 or via an electron transfer process from excited benzophenone. 12 However, all of these mechanisms result in the loss of the absorbing chromophore, which therefore does not exhibit catalytic activity. In contrast, we find that when toluene is used as the organic phase, there is no degradation of 1 and that the toluene solution of 1 can be isolated and reused to prepare another batch of AuNP.…”

Section: Direct Excitation Of Auclmentioning

confidence: 99%

“…The photoinduced reduction of AuCl 3 by triplet benzophe none was recently investigated in detail by the group of Scaiano and shown to proceed via a diffusion limited photoinduced electron transfer to generate Au nanoparticles (AuNP) and benzophenone oxidation products. 12 We reasoned that a photosensitizer might be able to drive the photoreduction of a metal ion such as Au III either by pumping electrons from the solvent to the gold ions, or by exciting the gold ions via an energy transfer mechanism. Such a system would be very useful for providing a photochemical route toward low valent Au species using long wavelength light that is not absorbed by common small organic molecules, as well as providing an example of the use of an organic photocatalyst for the generation of an inorganic material.…”

Section: Introductionmentioning

confidence: 99%

Supramolecular Photocatalyst for the Reduction of Au(III) to Au(I) and High-Turnover Generation of Gold Nanocrystals

et al. 2014

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We report a photocatalyst composed of a diphenylan thracene core appended with two lipophilic thioether side chains that binds gold(III) chloride. Upon excitation using visible light, the Au III ions are smoothly reduced to Au I which, in the presence of water, lead to the formation of crystalline gold nanoparticles of 20−50 nm diameter that are devoid of sulfur containing capping agents. Ultrafast transient absorption spectroscopy shows that the anthracene excited state is quenched with a rate k = 3.5 × 10 10 s −1 , assigned to intramolecular energy transfer to the bound gold ions, which then oxidizes the solvent to produce an intermediate low valency gold(I) species. In the absence of water, the latter is stable and can be used as a homogeneous Au I catalyst. When employed in a biphasic reactor, the photocatalyst shows average turnover numbers of 150 atoms of Au III reduced to Au 0 per molecule of photocatalyst.

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“…[2][3][4][5] Its most known attribute is related to its electronic structure, and particularly to the featured long-lived lowest-lying triplet state that can be easily generated at long wavelengths (>320 nm). 6 This makes of BP an ideal photoinitiator, 7 as it was proven in photodynamic therapy: BP acts as a non-covalently bound photosensitizer, producing several photo-lesions to DNA. 4 Nevertheless, routine experimental characterization techniques found extreme difficulties to investigate BP/DNA binding modes, 8 and only recent theoretical works have shown the possibility of two stable interacting modes: the minor groove mode and the less common double insertion mode, characterized by the simultaneous displacement of a full nucleobase pair from the Watson-Crick pairing.…”

Section: Introductionmentioning

confidence: 99%

Resolving the Singlet Excited State Manifold of Benzophenone by First-Principles Simulations and Ultrafast Spectroscopy

Segarra‐Martí

Zvereva

Marazzi

et al. 2018

J. Chem. Theory Comput.

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Accurate characterization of the high-lying excited state manifolds of organic molecules is of fundamental importance for the interpretation of the rich response detected in time-resolved nonlinear electronic spectroscopies. Here, we have characterized the singlet excited state manifold of benzophenone (BP), a versatile organic photoinitiator and a well-known DNA photosensitizer. Benchmarks of various multiconfigurational/multireference (RASSCF/PT2) and time-dependent density functional theory (TD-DFT) approaches allowed assignments of experimental linear absorption signals of BP in the ultraviolet (UV) region, with unprecedented characterization of ground state absorptions in the far UV. Experimental transient absorption spectra obtained by UV-vis pump-probe spectroscopy at very short time delays are shown to be directly comparable to theoretical estimates of excited state absorptions (from the low-lying nπ* and ππ* singlet states) in the Franck-Condon region. Multireference computations provided reliable interpretation of the PP spectra, with TD-DFT results yielding a fair agreement as long as electronic transitions featuring double excitations contributions are not involved. These results lay the groundwork for further computational studies and interpretation of experimental nonlinear electronic spectra of benzophenone in more complex systems, such as BP/DNA adducts.

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Electron transfer from the benzophenone triplet excited state directs the photochemical synthesis of gold nanoparticles

Abstract: The rarely recognized electron donating ability of the benzophenone triplet excited state provides an unusual route for the photochemical synthesis of gold nanoparticles.

Cited by 13 publications

References 16 publications

A benzophenone‐naphthalimide derivative as versatile photoinitiator of polymerization under near UV and visible lights

A benzophenone‐naphthalimide derivative as versatile photoinitiator of polymerization under near UV and visible lights

Supramolecular Photocatalyst for the Reduction of Au(III) to Au(I) and High-Turnover Generation of Gold Nanocrystals

Resolving the Singlet Excited State Manifold of Benzophenone by First-Principles Simulations and Ultrafast Spectroscopy

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