On heterogeneity in fluorescent few-atom silver nanoclusters

Area of Science:

• Materials Science
• Spectroscopy
• Nanotechnology

Background:

• Fluorescent silver (Ag) atom clusters are sub-nanometer fluorophores with desirable properties like high quantum yield and large Stokes shift.
• Formation of Ag clusters on polymeric scaffolds leads to spectral heterogeneities in excitation and emission.
• Understanding these spectral variations is crucial for optimizing their applications.

Purpose of the Study:

• To investigate the spectroscopic properties of Ag atom clusters formed on amphiphilic block copolymers.
• To elucidate the origins of spectral heterogeneities observed in these fluorophores.
• To develop a model explaining the observed excitation and emission spectral behaviors.

Main Methods:

• Photochemical reduction of silver salt on polystyrene-block-poly(methacrylic acid) in N,N-dimethylformamide.
• Detailed spectroscopic studies, including excitation and emission spectroscopy.
• Analysis of spectral dependences to identify emitter types and broadening mechanisms.

Main Results:

• Discrimination of three distinct types of emitters based on their excitation and emission bands.
• Observation of inhomogeneous broadening effects, evidenced by wavelength-dependent spectral shifts.
• Mirror-image relationship between excitation and emission spectra, with an exception for excitation at the second band.

Conclusions:

• The spectral heterogeneities in Ag atom clusters on polymer scaffolds can be attributed to inhomogeneous broadening.
• A qualitative model based on inhomogeneous broadening successfully explains the observed spectroscopic phenomena.
• These findings provide a deeper understanding of Ag cluster fluorophores for tailored applications.