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First-principles investigation of Ag-doped gold nanoclusters.

Zhang XD, Guo ML, Wu D, Liu PX, Sun YM, Zhang LA, She Y, Liu QF, Fan FY - Int J Mol Sci (2011)

Bottom Line: The electronic structure of a stable Au(20) cluster can be modulated by incorporating Ag, and the HOMO-LUMO gap of Au(20-) (n)Ag(n) clusters is modulated due to the incorporation of Ag electronic states in the HOMO and LUMO.Furthermore, the results of the imaginary part of the dielectric function indicate that the optical transition of gold clusters is concentration-dependent and the optical transition between HOMO and LUMO shifts to the low energy range as the Ag atom increases.These calculated results are helpful for the design of gold cluster-based biomaterials, and will be of interest in the fields of radiation medicine, biophysics and nanoscience.

View Article: PubMed Central - PubMed

Affiliation: Tianjin Key Laboratory of Molecular Nuclear Medicine, Institute of Radiation Medicine, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin 300192, China; E-Mails: wudi521wan@163.com (D.W.); pharm8888@yahoo.com.cn (P.-X.L.); yuanmings1962@163.com (Y.-M.S.); zhangla43@yahoo.com.cn (L.-A.Z.); yi_she2005@yahoo.com.cn (Y.S.); qingfenliu@yahoo.com.cn (Q.-F.L.).

ABSTRACT
Gold nanoclusters have the tunable optical absorption property, and are promising for cancer cell imaging, photothermal therapy and radiotherapy. First-principle is a very powerful tool for design of novel materials. In the present work, structural properties, band gap engineering and tunable optical properties of Ag-doped gold clusters have been calculated using density functional theory. The electronic structure of a stable Au(20) cluster can be modulated by incorporating Ag, and the HOMO-LUMO gap of Au(20-) (n)Ag(n) clusters is modulated due to the incorporation of Ag electronic states in the HOMO and LUMO. Furthermore, the results of the imaginary part of the dielectric function indicate that the optical transition of gold clusters is concentration-dependent and the optical transition between HOMO and LUMO shifts to the low energy range as the Ag atom increases. These calculated results are helpful for the design of gold cluster-based biomaterials, and will be of interest in the fields of radiation medicine, biophysics and nanoscience.

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Optical absorption of Au20−nAgn clusters.
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f6-ijms-12-02972: Optical absorption of Au20−nAgn clusters.

Mentions: Figure 6 presents the optical absorption of Au20−nAgn clusters. The dominant absorption around 450–550 nm can be observed in all Au20−nAgn clusters. For Au20, the absorption band of 450 nm could be due to the optical transition of E2, while the 707 nm absorption band is related to the intrinsic optical transition of E1. The Ag incorporation induces the red-shift of absorption band (E2) from 478 nm (Au19Ag1) to 543 nm (Au16Ag4). We need to consider two possible effects on the optical absorption of these Au20−nAgn clusters. On the one hand, the HOMO-LUMO gap can be underestimated by the DFT. According to the available optical data of Au20 from the experiment, the gap of tetrahedral Au20 is about 1.7–1.8 eV, which is larger 0.23–0.33 eV than the calculated gap of 1.47 eV. Thus, the actual gap of Au20−nAgn is wider than that of present calculated results. On the other hand, the structure stability of Au20−nAgn should also be taken into account. In the geometry calculations, the binding energy of Au16Ag4 is higher than that of the pure Au20 cluster and the other AuAg clusters, which indicates the doping feasibility. Therefore, more Ag atom incorporation may be promising for further fabrication, NIR absorption and related applications. Zorriasatein et al. have proposed that Cu incorporation into Au clusters can modulate the band gap effectively, and the results showed that the introduction of Cu enhanced the binding energy per atom compared to Au clusters [25]. AuAg clusters also showed good structural stability and optical properties [23,26,27]. Thus, it can be expected that Ag incorporation is an effective strategy for modulating optical properties of Au clusters. Our results also clearly show that Ag incorporation can modify structural stability and modulate the optical properties of Au20 clusters. These methods also have potential applications in understanding the optical properties of metal nanoclusters and designing materials for photothermal therapy.


First-principles investigation of Ag-doped gold nanoclusters.

Zhang XD, Guo ML, Wu D, Liu PX, Sun YM, Zhang LA, She Y, Liu QF, Fan FY - Int J Mol Sci (2011)

Optical absorption of Au20−nAgn clusters.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3116168&req=5

f6-ijms-12-02972: Optical absorption of Au20−nAgn clusters.
Mentions: Figure 6 presents the optical absorption of Au20−nAgn clusters. The dominant absorption around 450–550 nm can be observed in all Au20−nAgn clusters. For Au20, the absorption band of 450 nm could be due to the optical transition of E2, while the 707 nm absorption band is related to the intrinsic optical transition of E1. The Ag incorporation induces the red-shift of absorption band (E2) from 478 nm (Au19Ag1) to 543 nm (Au16Ag4). We need to consider two possible effects on the optical absorption of these Au20−nAgn clusters. On the one hand, the HOMO-LUMO gap can be underestimated by the DFT. According to the available optical data of Au20 from the experiment, the gap of tetrahedral Au20 is about 1.7–1.8 eV, which is larger 0.23–0.33 eV than the calculated gap of 1.47 eV. Thus, the actual gap of Au20−nAgn is wider than that of present calculated results. On the other hand, the structure stability of Au20−nAgn should also be taken into account. In the geometry calculations, the binding energy of Au16Ag4 is higher than that of the pure Au20 cluster and the other AuAg clusters, which indicates the doping feasibility. Therefore, more Ag atom incorporation may be promising for further fabrication, NIR absorption and related applications. Zorriasatein et al. have proposed that Cu incorporation into Au clusters can modulate the band gap effectively, and the results showed that the introduction of Cu enhanced the binding energy per atom compared to Au clusters [25]. AuAg clusters also showed good structural stability and optical properties [23,26,27]. Thus, it can be expected that Ag incorporation is an effective strategy for modulating optical properties of Au clusters. Our results also clearly show that Ag incorporation can modify structural stability and modulate the optical properties of Au20 clusters. These methods also have potential applications in understanding the optical properties of metal nanoclusters and designing materials for photothermal therapy.

Bottom Line: The electronic structure of a stable Au(20) cluster can be modulated by incorporating Ag, and the HOMO-LUMO gap of Au(20-) (n)Ag(n) clusters is modulated due to the incorporation of Ag electronic states in the HOMO and LUMO.Furthermore, the results of the imaginary part of the dielectric function indicate that the optical transition of gold clusters is concentration-dependent and the optical transition between HOMO and LUMO shifts to the low energy range as the Ag atom increases.These calculated results are helpful for the design of gold cluster-based biomaterials, and will be of interest in the fields of radiation medicine, biophysics and nanoscience.

View Article: PubMed Central - PubMed

Affiliation: Tianjin Key Laboratory of Molecular Nuclear Medicine, Institute of Radiation Medicine, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin 300192, China; E-Mails: wudi521wan@163.com (D.W.); pharm8888@yahoo.com.cn (P.-X.L.); yuanmings1962@163.com (Y.-M.S.); zhangla43@yahoo.com.cn (L.-A.Z.); yi_she2005@yahoo.com.cn (Y.S.); qingfenliu@yahoo.com.cn (Q.-F.L.).

ABSTRACT
Gold nanoclusters have the tunable optical absorption property, and are promising for cancer cell imaging, photothermal therapy and radiotherapy. First-principle is a very powerful tool for design of novel materials. In the present work, structural properties, band gap engineering and tunable optical properties of Ag-doped gold clusters have been calculated using density functional theory. The electronic structure of a stable Au(20) cluster can be modulated by incorporating Ag, and the HOMO-LUMO gap of Au(20-) (n)Ag(n) clusters is modulated due to the incorporation of Ag electronic states in the HOMO and LUMO. Furthermore, the results of the imaginary part of the dielectric function indicate that the optical transition of gold clusters is concentration-dependent and the optical transition between HOMO and LUMO shifts to the low energy range as the Ag atom increases. These calculated results are helpful for the design of gold cluster-based biomaterials, and will be of interest in the fields of radiation medicine, biophysics and nanoscience.

Show MeSH
Related in: MedlinePlus