Discovery of Isomerization Intermediates in CdS Magic-Size Clusters

Area of Science:

• Nanoscale Chemistry
• Materials Science
• Physical Chemistry

Background:

• Isomerization is a known organic chemistry phenomenon, but its observation in inorganic nanoclusters is recent.
• Cadmium sulfide (CdS) nanoclusters previously isomerized between two phases (α and β) via hydroxyl groups, with no intermediates observed.
• The absence of intermediate states during CdS nanocluster isomerization posed significant structural and pathway questions.

Purpose of the Study:

• To investigate the stabilization of intermediate phases during CdS nanocluster isomerization.
• To understand the role of amide functional groups in mediating CdS nanocluster transformations.
• To elucidate the structural and electronic properties of these intermediate phases.

Main Methods:

• Treatment of CdS nanoclusters with amide functional groups in organic solvents.
• Spectroscopic analysis including Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.
• Pair distribution function analysis and density functional theory calculations.

Main Results:

• Amides facilitate isomerization and stabilize three distinct intermediate phases: β340-phase, β350-phase, and β367-phase.
• These intermediates structurally resemble the β-phase but exhibit significant differences in band gap energy (up to 583 meV).
• Kinetic studies reveal a thermodynamic stability progression: β340/β350 < α < β367 < β.
• Solvent identity and polarity are crucial for kinetically arresting these intermediates.
• Amides form amphoteric surface binding motifs, altering carboxylic acid binding modes from chelating to bridging, initiating isomerization.

Conclusions:

• Amide functional groups are effective in stabilizing intermediate phases of CdS nanocluster isomerization.
• The multifunctional nature of amides, particularly the carbonyl group, drives the isomerization mechanism.
• This study provides fundamental insights into the nanoscale chemistry and physics of isomerization in inorganic nanoclusters.