Charge-transfer optical absorption mechanism of DNA:Ag-nanocluster complexes

Area of Science:

• Computational Chemistry
• Materials Science
• Biophysics

Background:

• DNA:silver nanocluster complexes exhibit useful optical properties in various scientific fields.
• The underlying mechanisms responsible for their optical activity are not fully understood.

Purpose of the Study:

• To investigate the optical absorption mechanisms of DNA:Ag4 complexes using theoretical calculations.
• To elucidate the origin of new absorption peaks in the visible spectrum of these complexes.

Main Methods:

• Time-dependent density functional theory (TD-DFT) calculations were employed.
• The study analyzed 23 different DNA:Ag4 complexes.
• The influence of different exchange-correlation functionals (PBE and CAM-B3LYP) was examined.

Main Results:

• New absorption peaks in the visible region were identified for DNA:Ag4 complexes, absent in isolated components.
• Red-to-green absorption is primarily due to Ag4-to-DNA charge transfer; blue-violet absorption involves mixed DNA-Ag4 or intracluster orbitals.
• The choice of functional significantly impacts calculated spectra, with PBE showing larger errors for purine-bound complexes.

Conclusions:

• The study provides a theoretical framework for understanding the optical activity of DNA:Ag nanocluster complexes.
• Accurate spectral characterization requires including complementary base pairs and the sugar-phosphate backbone.
• This research contributes to the rational design of novel nanomaterials for optical applications.