Aqueous-based synthesis of atomic gold clusters: Geometry and optical properties

Rath, S.; Nozaki, Shinji; Palagin, Dennis; Матулис, Вадим Э.; Ивашкевич, Олег А.; Maki, Shôjirô

doi:10.1063/1.3467261

Cited by 15 publications

(28 citation statements)

References 22 publications

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“…The most probable electronic transitions from the ground to excited states of A1, A2, and A3 were calculated to be 2.94, 3.26, and 3.01 eV, respectively, at the B3LYP/LANL2DZ level. [19] Overall, the calculated absorption energies were shifted to take into account the solvation effect and the Stokes shift together. To a first approximation, it was supposed that the solvation effect in the aqueous solution would be similar to that within the dendrimer in aqueous solution, because the interaction between gold nanoclusters and dendrimer is known to be weak in dendrimer-encapsulated gold clusters.…”

Section: Resultsmentioning

confidence: 99%

Blue Luminescence of Dendrimer‐Encapsulated Gold Nanoclusters

et al. 2014

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Direct evidence for the blue luminescence of gold nanoclusters encapsulated inside hydroxyl-terminated polyamidoamine (PAMAM) dendrimers was provided by spectroscopic studies as well as by theoretical calculations. Steady-state and time-resolved spectroscopic studies showed that the luminescence of the gold nanoclusters consisted largely of two electronic transitions. Theoretical calculations indicate that the two transitions are attributed to the different sizes of the gold nanoclusters (Au8 and Au13). The luminescence of the gold nanoclusters was clearly distinguished from that of the dendrimers.

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Section: Resultsmentioning

confidence: 99%

Blue Luminescence of Dendrimer‐Encapsulated Gold Nanoclusters

et al. 2014

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“…Finally, to compare the calculated absorption spectrum to the observed emission spectrum, the Stokes shift was taken into account. The Stokes shift depended on the geometries of the isomers, which were calculated in the range of 0.10–0.16 eV for the two‐dimensional Au 8 in the aqueous solution . On the other hand, the Stokes shift was observed as 0.50 eV in the three‐dimensional Au 8 encapsulated by dendrimers in the aqueous solution, suggesting that the Stokes shift was strongly affected by the geometries and solvation conditions.…”

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confidence: 96%

Electronic Transitions of Gold Nanoclusters

Sohn

Kim

Park

et al. 2015

Bulletin Korean Chem Soc

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Size-dependent luminescence is one of the most promising properties in semiconductor nanocrystals.1 -3 Such sizedependent luminescence is also found in various metal nanocrystals like the gold nanoclusters.4 -6 For example, blue luminescence was observed from Au 8 , which was stabilized and encapsulated by dendrimers. The color of the luminescence was extended to near-IR, as the size of the gold nanoclusters increased, 7,8 which was attributed to the confinement of the cluster sizes comparable to the Fermi wavelength of electrons (approximately 0.7 nm). 9 We recently studied the luminescence of the gold nanoclusters, especially the blue luminescence of Au 8 , 10 which provided a clue to the origin of luminescence in the gold nanoclusters. 11 -13 In this work, we examined the electronic transitions of Au 8 to elucidate the photoluminescence spectrum of the gold nanoclusters in more detail. The calculated geometries and energies of the isomers in Au 8 indicated that one isomer was more stable than the others, implying that a single isomer was the main contributor to the photoluminescence spectrum of Au 8 . The calculated spectrum of the most stable isomer agreed with the experimental spectrum, suggesting that several excited states of the single isomer contributed to the photoluminescence spectrum, whose shape was broad and asymmetric.The photoluminescence of the gold nanoclusters encapsulated by dendrimers was previously reported. 10 The emission maximum at 460 nm (2.7 eV) matched the emission energy of Au 8 (2.75 eV) in the spherical jellium approximation (Figure 1 (a)).8 On the other hand, the photoluminescence band was broad and asymmetric, which was ascribed to the spectral overlapping of emission bands.10 Indeed, the photoluminescence spectrum could be deconvoluted by two Gaussian functions. The low-energy band at 535 nm (2.32 eV) happened to agree with the emission energy of Au 13 (2.34 eV) in the spherical jellium model. 8 In this regard, another nanocluster was previously assigned as Au 13 , 10 because Au 13 was also the stable size of the gold nanoclusters. 8 For better understanding of the broad and asymmetric shape, the electronic transitions of Au 8 were calculated using the GAUSSIAN program.14 At first, the stable geometries and energies of Au 8 were obtained, by analytical gradients with full optimization using ab initio method such as the Møller-Plesset perturbation theory (MP2) and the density functional theory (DFT) such as Becke three-parameter Lee-Yang-Parr (B3LYP) and Perdew-Wang 1991 (B3PW91) gradient corrected exchange and correlation functional at two basis sets (CEP-4G and LANL2DZ). These levels of calculation have been frequently employed to obtain the stable geometries and energies of small gold nanoclusters. 15 -17 Since the emission energy of the dendrimer-encapsulated Au 8 matched the spherical jellium model, three-dimensional geometries were mainly examined, although the most stable geometry was known to be two-dimensional in the gas phase.15 -17 Among the optimized three-dimensio...

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“…Up to now, many theoretical and experimental studies have been carried out to synthesize the smallest possible MCs and characterize their structure and physical properties 7, 8 . For example, in the case of metallic gold clusters, the Au8 (eight atoms gold cluster) is one of the smallest possible MCs (atomicity < 10) that maintains a stable solid phase 9 . There are only a few studies on such small Au clusters 10 .…”

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“…Details of the sample preparation and identification of the Au8 MCs are described elsewhere 9 . First, the Au ions in gold chloride tetrahydrate were allowed to interact with L-cysteine methyl ester (LCME) hydrochloride for complex formation in an aqueous solution, and then reduced in the presence of an ice-cold solution of sodium borohydride (NaBH4).…”

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“…Similar sharp Raman modes were observed in the metal (Au andAg) atomic clusters by other researchers28, 29 . Therefore, to assign the above modes, the geometry optimization of the bare star shape, the h-Au8 and six-ligand passivated h-Au8 (Au8-(SR)6) cluster9,30 were carried out using the B3LYP (Becke three parameter Lee-Yang-Parr) functional with LANL2DZ (Los Alamos National Laboratory 2-double Zeta) basis set for the singlet state. Therefore, to assign the above modes, the geometry optimization of the bare star shape, the h-Au8 and six-ligand passivated h-Au8 (Au8-(SR)6) cluster9,30 were carried out using the B3LYP (Becke three parameter Lee-Yang-Parr) functional with LANL2DZ (Los Alamos National Laboratory 2-double Zeta) basis set for the singlet state.…”

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Raman modes, dipole moment and chirality in periodically positioned Au₈clusters

et al. 2015

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This study reports the solution-based assembly of hexagonal+1 shaped Au8 clusters surrounded by six ligands into a local periodic structure (LPS) of periodicity 1.47 nm, which was confirmed by experimental and theoretical Raman scattering analyses as well as transmission electron microscopy, x-ray diffraction and small angle x-ray scattering measurements. The enhancement of the net electric dipole moment to 21.17 Debye is due to the rearrangement of the charge distribution in the electronic states of the LPS. This results in exciton-exciton coupling through dipole interactions, which was evidenced by the splitting of the excitonic states in the circular dichroism (CD) spectra. The strong negativity of the CD index at the longer wavelength confirms the negative chirality of the LPS-Au8.

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Aqueous-based synthesis of atomic gold clusters: Geometry and optical properties

Cited by 15 publications

References 22 publications

Blue Luminescence of Dendrimer‐Encapsulated Gold Nanoclusters

Blue Luminescence of Dendrimer‐Encapsulated Gold Nanoclusters

Electronic Transitions of Gold Nanoclusters

Raman modes, dipole moment and chirality in periodically positioned Au₈clusters

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Aqueous-based synthesis of atomic gold clusters: Geometry and optical properties

Cited by 15 publications

References 22 publications

Blue Luminescence of Dendrimer‐Encapsulated Gold Nanoclusters

Blue Luminescence of Dendrimer‐Encapsulated Gold Nanoclusters

Electronic Transitions of Gold Nanoclusters

Raman modes, dipole moment and chirality in periodically positioned Au8clusters

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Raman modes, dipole moment and chirality in periodically positioned Au₈clusters