Fragmentation patterns of DNA-stabilized silver nanoclusters under mass spectrometry

Area of Science:

• Nanomaterials Science
• Biophysical Chemistry
• Spectroscopy

Background:

• DNA-stabilized silver nanoclusters (Ag_N-DNAs) exhibit tunable optical properties.
• Understanding the degradation pathways of Ag_N-DNAs is crucial for their applications.
• Limited knowledge exists regarding the chemical transformations and stability of Ag_N-DNAs.

Purpose of the Study:

• To investigate the fragmentation products and degradation mechanisms of red and NIR Ag_N-DNAs.
• To elucidate the relationship between DNA template sequence, cluster structure, and fragmentation behavior.
• To explore the stability of Ag_N-DNAs based on their electron counts.

Main Methods:

• Analysis of fragmentation products using negative ion mode electrospray ionization mass spectrometry (ESI-MS).
• Investigation of 21 different red and NIR Ag_N-DNAs.
• Molecular dynamics simulations with density functional theory (DFT) calculations for fragmentation analysis.

Main Results:

• Ag_N-DNAs lose Ag⁺ under ESI-MS conditions, leading to transitions in effective valence electron counts (N₀).
• Only even values of N₀ were observed in mass spectra, suggesting instability of odd N₀ clusters in solution.
• Ag_N-DNAs with three DNA strands fragmented more than those with two strands.
• Fragmentation patterns were highly dependent on the DNA template sequence.
• Simulations confirmed fragmentation of Ag₁₆Cl₂ into Ag₁₀ and Ag₆, preserving electron-pairing rules.

Conclusions:

• The study reveals that Ag_N-DNAs preferentially fragment into stable even-electron clusters.
• DNA sequence and the number of stabilizing strands significantly influence Ag_N-DNA fragmentation and stability.
• Findings provide critical insights into Ag_N-DNA degradation mechanisms, relevant for sensing and biomedical applications.