Fluorescent atomically precise Ag38(11-azido-2-ol-undecane-thiolate)24 nanoclusters have been successfully synthesized using sodium ascorbate as a green and mild reducing agent. This method enables the preservation of sensitive functional groups, particularly the terminal azido moiety, which is crucial for subsequent “click” chemistry applications. The nanoclusters were extensively characterized through elemental analysis, ATR-FTIR spectroscopy, X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), UV-vis absorption, and fluorescence spectroscopy. The combination of atomic precision, strong fluorescence, and the presence of reactive azido groups makes these nanoclusters ideal candidates for biosensing, molecular recognition, biomedicine, and catalytic applications.
The synthesis begins with the preparation of the 11-azido-2-ol-undecanethiolate ligand via a substitution reaction between 11-azido-1-bromoundecan-2-ol and sodium thiosulfate. The resulting ligand is then reacted with silver nitrate to form a polymeric silver thiolate complex. Upon addition of sodium ascorbate, partial reduction of Ag⁺ ions occurs, leading to the formation of the Ag₃₈ core surrounded by a protective shell of thiolate ligands. The use of sodium ascorbate ensures a controlled reduction process, avoiding over-reduction and preserving the integrity of the azido group—a significant advantage over conventional reductants like NaBH₄.
ATR-FTIR analysis confirms the presence of characteristic vibrational modes corresponding to C–H stretching at 2917 and 2854 cm⁻¹, N≡N≡N azido stretching at 2095 cm⁻¹, OH bending at 1352 cm⁻¹, C–N stretching at 1258 cm⁻¹, and C–O stretching at 1077 cm⁻¹. These data validate the chemical structure of the ligand and confirm that the azido group remains intact. TEM images reveal an average diameter of approximately 3 nm, consistent with the expected size of an Ag₃₈ nanocluster.
UV-vis absorption spectra display two distinct peaks at 290 nm and 370 nm, typical of silver nanoclusters, with no evidence of free silver nanoparticles in the 420–460 nm range. Fluorescence measurements show dual emission: one peak at ~450 nm in the visible region and another at ~630 nm in the near-infrared (NIR), indicating multiple excited states. Time-resolved fluorescence studies indicate multi-exponential decay with lifetimes of 0.8 ns, 5.1 ns, and 0.01 ns, suggesting complex radiative relaxation pathways. The quantum yield of 0.21 relative to Rhodamine 6G is notably high, enabling efficient detection under low-light conditions.
X-ray scattering techniques provide insight into the supramolecular organization of the nanoclusters. WAXS patterns reveal sharp diffraction spots on concentric rings, indicating the presence of crystalline domains with nanoscale order. SAXS profiles exhibit quasi-Bragg peaks at q ≈ 0.6 nm⁻¹ and higher, signaling the formation of paracrystalline lamellar (dL = 3.4 nm) and hexagonal (dH = 3.0 nm) phases. At lower q-values, a Porod-like behavior suggests the aggregation of larger particles with a network of correlated nanoregion defects. Electron density maps derived from the SAXS data confirm the assembly of NCs into lamellar and hexagonal superstructures, with defect regions permeating the ordered phases.Bacithrocin A References
Computational modeling supports experimental findings.WNT1 Antibody Autophagy Global optimization using the Basin Hopping algorithm identifies a stable structure closely resembling the known Au₃₈(SR)₂₄ cluster, with a D₃h symmetric Ag₂₃ core and six dimeric Ag₂S₃ and three monomeric AgS₂ staples.PMID:35020093 TDDFT simulations reproduce the experimentally observed absorption spectrum, confirming the electronic transitions responsible for the optical response. Molecular dynamics simulations of interacting clusters reveal that unfolded conformations—where alkyl chains are extended—favor interdigitation and stronger van der Waals interactions, explaining the preference for disordered, self-assembled structures over tightly folded ones.
In summary, this work presents a scalable, environmentally friendly route to fluorescent Ag₃₈(SRN3)₂₄ nanoclusters with unique structural and functional properties. The integration of atomically precise design, robust fluorescence, and click-ready functionality opens new avenues for advanced applications in bioimaging, targeted drug delivery, asymmetric catalysis, and nanoscale device engineering.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