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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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The partial DOS of (a) Au20−nAgn clusters.
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f2-ijms-12-02972: The partial DOS of (a) Au20−nAgn clusters.

Mentions: Figure 2 shows the density of states (DOS) to reveal the electronic structure of Au20−nAgn clusters. The Au20 cluster shows the large HOMO-LUMO gap, which is in good agreement with the other computational results [10,21]. The exact band gap of Au20 is 1.47 eV, which is less than the experimental data of 1.78 eV (or 1.818 eV) due to the underestimation of electronic states by DFT [22]. Meanwhile, the Au d states are dominated in HOMO, and are located in the range of −6 and 0 eV. HOMO consists of Au s and d states; the Au d states are dominant. It is clearly seen that when n changes from 1 to 4, the DOS also changes. In general, the band gap of Au20−nAgn clusters is less than that of the pure Au20 cluster expect for Au16Ag4. It confirms that the Ag incorporation into Au20 can induce the obvious effect on gap, which is consistent with the previous results [19,23,24]. The exact band gaps of Au20−nAgn are 1.42, 1.34, 1.40, and 1.68 eV, which are corresponding to the different n values from 1 to 4. The variation of gap can be understood by electronic states. It can be seen that the LUMO of Au19Ag1, Au18Ag2, and Au17Ag3 is shifted to the low energy range compared with Au20, which can be clearly seen in Figure 2. This shift can lead to the obvious variation of electronic properties. As it is incorporated more and more, the p states in LUMO become stronger, which leads to the LUMO shift and band gap narrowing. However, the LUMO of Au16Ag4 shift to high energy range, and thus induce the increase of the gap, which should be related to improving structural stability and enclosing electronic configurations [25]. Meanwhile, the p and s states are obviously enhanced in the LUMO, and these electronic states can have effects on optical properties.


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)

The partial DOS of (a) Au20−nAgn clusters.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2-ijms-12-02972: The partial DOS of (a) Au20−nAgn clusters.
Mentions: Figure 2 shows the density of states (DOS) to reveal the electronic structure of Au20−nAgn clusters. The Au20 cluster shows the large HOMO-LUMO gap, which is in good agreement with the other computational results [10,21]. The exact band gap of Au20 is 1.47 eV, which is less than the experimental data of 1.78 eV (or 1.818 eV) due to the underestimation of electronic states by DFT [22]. Meanwhile, the Au d states are dominated in HOMO, and are located in the range of −6 and 0 eV. HOMO consists of Au s and d states; the Au d states are dominant. It is clearly seen that when n changes from 1 to 4, the DOS also changes. In general, the band gap of Au20−nAgn clusters is less than that of the pure Au20 cluster expect for Au16Ag4. It confirms that the Ag incorporation into Au20 can induce the obvious effect on gap, which is consistent with the previous results [19,23,24]. The exact band gaps of Au20−nAgn are 1.42, 1.34, 1.40, and 1.68 eV, which are corresponding to the different n values from 1 to 4. The variation of gap can be understood by electronic states. It can be seen that the LUMO of Au19Ag1, Au18Ag2, and Au17Ag3 is shifted to the low energy range compared with Au20, which can be clearly seen in Figure 2. This shift can lead to the obvious variation of electronic properties. As it is incorporated more and more, the p states in LUMO become stronger, which leads to the LUMO shift and band gap narrowing. However, the LUMO of Au16Ag4 shift to high energy range, and thus induce the increase of the gap, which should be related to improving structural stability and enclosing electronic configurations [25]. Meanwhile, the p and s states are obviously enhanced in the LUMO, and these electronic states can have effects on optical properties.

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