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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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Calculated ground state geometries of Au20−nAgn.
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f1-ijms-12-02972: Calculated ground state geometries of Au20−nAgn.

Mentions: Figure 1 gives the calculated ground state geometries of Au20−nAgn. The stability of gold nanostructure is very important for its electronic and optical properties. Thus, the binding energy per atom Eb(n) of gold clusters is calculated to evaluate the stability of gold clusters, which are defined by the following formula:(1)Eb(n)=E(Ag)+nE(Au)−nE(AunAg)n+1where E(Ag), E(Au), and E(AunAg) represent the total energies of the most stable Ag, Au, and AuAg clusters, respectively. It is worth pointing out that all of the clusters are found to prefer the lowest spin state. We find that the binding energy of Au20 is 2.40 eV, which is very close to the previous investigation of gold clusters [21]. It has been demonstrated that the binding energy increases with an increase in the size of gold clusters [11]. Increasing binding energy means increasing stability due to enhanced core electron configurations. After Ag doping, the binding energy of Au19Ag1, Au18Ag2, Au17Ag3, and Au16Ag4 are 2.68, 2.68, 2.68, and 2.69 eV, respectively. The increasing doping atom induces a tiny effect on the binding energy. It is worth noting that the binding energy of AuAg alloy is higher than the Au20. It shows that Ag atom incorporation can enhance the structural stability. Indeed, the Au–Ag bond is stronger than the Au–Au bond and gives an extra σ-bonding interaction by the overlap between the vacant Ag 4p and valence Au 6s (5d) orbital, which is very similar to the previous Ag-doped gold clusters [20].


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)

Calculated ground state geometries of Au20−nAgn.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1-ijms-12-02972: Calculated ground state geometries of Au20−nAgn.
Mentions: Figure 1 gives the calculated ground state geometries of Au20−nAgn. The stability of gold nanostructure is very important for its electronic and optical properties. Thus, the binding energy per atom Eb(n) of gold clusters is calculated to evaluate the stability of gold clusters, which are defined by the following formula:(1)Eb(n)=E(Ag)+nE(Au)−nE(AunAg)n+1where E(Ag), E(Au), and E(AunAg) represent the total energies of the most stable Ag, Au, and AuAg clusters, respectively. It is worth pointing out that all of the clusters are found to prefer the lowest spin state. We find that the binding energy of Au20 is 2.40 eV, which is very close to the previous investigation of gold clusters [21]. It has been demonstrated that the binding energy increases with an increase in the size of gold clusters [11]. Increasing binding energy means increasing stability due to enhanced core electron configurations. After Ag doping, the binding energy of Au19Ag1, Au18Ag2, Au17Ag3, and Au16Ag4 are 2.68, 2.68, 2.68, and 2.69 eV, respectively. The increasing doping atom induces a tiny effect on the binding energy. It is worth noting that the binding energy of AuAg alloy is higher than the Au20. It shows that Ag atom incorporation can enhance the structural stability. Indeed, the Au–Ag bond is stronger than the Au–Au bond and gives an extra σ-bonding interaction by the overlap between the vacant Ag 4p and valence Au 6s (5d) orbital, which is very similar to the previous Ag-doped gold clusters [20].

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