Small-angle and wide-angle X-ray scattering experiments reveal the complex supramolecular organization of Ag₃₈(11-azido-2-ol-undecanethiolate)₂₄ nanoclusters in the solid state. Synchrotron-based WAXS measurements on the XRD1 beamline at ELETTRA show diffraction spots arranged on weak concentric rings, indicating a polycrystalline sample composed of differently oriented nanocrystals. The presence of sharp peaks at low q-values suggests long-range nanoscale order, while broad features arise from amorphous components or anisotropic crystal shapes such as elongated rods or platelets. Notably, no reflections match known crystalline phases in the JCPDS database, confirming the unique nature of this nanomaterial.
SAXS analysis provides deeper insight into the hierarchical assembly. At low momentum transfer (q < 0.2 nm⁻¹), the I(q) profile follows a Porod law (I ∝ q⁻⁴), indicating the formation of large aggregates with sharp interfaces—consistent with particle coalescence during self-assembly. At higher q-values (q > 1.2 nm⁻¹), distinct quasi-Bragg peaks emerge, revealing two dominant ordered phases: a lamellar phase (L) with interlayer spacing dL = 3.4 nm and a planar hexagonal phase (H) with dH = 3.0 nm. The lamellar phase is indexed up to order n = 7, yielding a coherent domain size of approximately 130 nm via the Debye-Scherrer formula. The hexagonal phase is confirmed by three characteristic peaks corresponding to (1,0), (1,1), and (2,0) reflections, with no out-of-plane contributions observed, suggesting spatial separation between the two phases.
Electron density maps calculated from the SAXS data confirm the structural arrangement. In both phases, the red regions represent the dense metal cores, while the surrounding lower-density areas correspond to the extended alkyl chains. The lamellar structure shows alternating layers of core-rich and ligand-rich regions, whereas the hexagonal phase exhibits a close-packed arrangement of NCs with directional ordering. A network of correlated nanoregion defects permeates both phases, visible as a prominent peak near q ≈ 0.6 nm⁻¹ in the SAXS profile. This defect pattern arises during aggregation and reflects dynamic disorder at the nanoscale.SOX10 Antibody site
A theoretical model based on interacting hard spheres with radius R and center-to-center distance 2RHS successfully fits the experimental data. The fitted hard-sphere diameter RHS ≈ 5 nm aligns well with the estimated particle size, supporting a pure hard-sphere model for defect formation. These defects disrupt perfect crystallinity but may enhance functional properties such as charge transport or catalytic accessibility.
Molecular dynamics simulations further elucidate the origin of this structural diversity. Starting from the DFT-predicted global minimum structure, annealing procedures were performed using classical force fields. Two configurations were compared: a folded isomer with ligands compactly wrapped around the core and an unfolded isomer with extended chains.Ataxin-1 Antibody Technical Information The folded structure has a smaller gyration radius (Rg ≈ 10.PMID:34266968 1 Å), while the unfolded one expands significantly (Rg ≈ 11.5 Å). The energy difference between them is ~20 kcal/mol, favoring the folded form due to stronger van der Waals interactions among adjacent carbon backbones.
However, when considering pairwise interactions, the unfolded configuration leads to much stronger binding energies (~80 kcal/mol more favorable) due to efficient interdigitation of long alkyl chains and azido groups. The equilibrium distance between centers of mass is 1.6 nm for folded clusters but increases to 2.6 nm for unfolded ones—closer to the experimentally observed dH = 3.0 nm. This discrepancy highlights that thermodynamic stability at the single-cluster level does not dictate packing in bulk; instead, cooperative intermolecular forces dominate the final architecture.
The results demonstrate that the self-assembly behavior of Ag₃₈(SRN₃)₂₄ is governed by a balance between intramolecular stability and intermolecular interactions. While the folded conformation minimizes internal energy, the unfolded state maximizes intercluster cohesion through dispersion forces and chain entanglement. This explains the prevalence of disordered crystalline domains and multiple phases observed experimentally. The presence of nanoscale defects introduces flexibility and heterogeneity, which may be beneficial for applications requiring tunable porosity, enhanced surface reactivity, or adaptive mechanical properties.
In conclusion, the supramolecular architecture of these nanoclusters is not pre-defined but emerges dynamically during aggregation. The interplay between ligand conformation, intermolecular forces, and kinetic factors leads to a rich variety of nanostructures, including lamellar and hexagonal phases interspersed with defect networks. Understanding these principles enables rational design of functional nanomaterials where controlled self-assembly can be harnessed for advanced technologies in sensing, catalysis, and nanoelectronics.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com
