Electronegativity of the Substituent on Surface Motifs Influences the Ultrafast Relaxation Dynamics of Ag₄₄(SR)₃₀^4– Nanoclusters

Abstract

This work presents the influence of the substituent groups of surface staple motifs on the ultrafast relaxation dynamics of atomically precise Ag 44 (SR) 30 4− nanoclusters (NCs). A series of Ag 44 NCs, with Ag 32 core and Ag 12 (SR) 30 staple motifs, have been studied, where thiophenol (TP), 4-fluorothiophenol (FTP), and 4chlorothiophenol (CTP) are chosen as protecting ligands. This work reveals that the electronegativity and polarization of the surface ligand control the electron−phonon interaction, which ultimately influences the population transfer from the core state to the surface state of the Ag 44 NCs upon photoexcitation. Global analysis of the transient absorption spectroscopic data reveals the slower relaxation from the core state to the surface state, depending on electronegativity. The ligand-protected Ag 44 NCs show a fast internal conversion (∼2 ps), core-to-surface relaxation (900−1000 ps), and slower electron−hole recombination (>8 ns). The analysis of Ag 44 NCs and the closely bare system Ag 32 NCs reveals the impact of surface states on this threestate relaxation process. This study provides insights into the origin of the excited-state decay times and is expected to stimulate future work on Ag NCs.

Cumulative Impact of Ligands on the Optical Properties of Ag21 Nanoclusters: Insights into the Relaxation Dynamics

“…In our previous study, we observed that Ag 44 NCs having different surface ligands possess different coupling strengths and distinct average phonon frequencies . A comparative core–shell electron–phonon interaction of Ag 44 (TP) 30 , Ag 44 (FTP) 30 , and Ag 44 (CTP) 30 NCs was observed due to surface motifs.…”

“…The interaction can be the cooperative effect of the −CH/π hydrogen bond, or the axially oriented −CH bonds can interact with the π-face of the DPPB ligand . The primary ligand has no π-bond, making it different from other studied systems. , Although no benzene ring exists in the primary ligand, the stabilization comes from the secondary ligand, DPPB, and allows the NCs to remain stable. Based on the current observations and analysis, we can state that the temperature-dependent absorption study followed by the fs-TAS of the NCs strengthens the fundamental understanding of the physical properties.…”

“…48 In one of our recent studies, we have elucidated how the electronegativity of surface staple motifs modifies the electron−phonon vibration coupling of Ag 44 NCs employing temperature-dependent spectroscopic measurements and global analysis of ultrafast spectroscopy. 49 Utilizing global and target analysis, our group investigated the role of dopant atoms (Ag, Au, Pd, and Pt) in MAg 24 n-NCs with dual emission at NIR and visible regions in a different study. 50 Zhu et al explained that the effect of the Au doping site has a significant impact on the assembling of Au 12 Ag 60 NCs, which in turn affects their excited-state relaxation dynamics.…”

Effect of Silver Alloying on the Vibrational Dynamics of Rod-Shaped Gold Nanoclusters

“…Previous work reported that single-atom doping on the Au 25 (SR) 18 NCs can change the excited-state lifetimes by 3 orders of magnitude. , Quantum beat in fluorescence dynamics in Au 25 (SR) 18 NCs was also reported, which originated from coherence between singlet and triplet states . The effect of doping on the excited-state lifetimes of Au 13 , Au 38 , Ag 44 , and Au 144 has also been reported recently. ,− Nevertheless, the effect of doping and alloying on coherent vibrations remains largely unknown. Molecular vibrations in metal NCs have been investigated by low-frequency Raman spectroscopy, , while ultrafast spectroscopy can provide additional information on the coherent vibrations .…”

Copper Nanoclusters as Multienzymes Mimic Activities of Oxidase and Ascorbic Acid Oxidase in the Presence of Imidazole

“…Natural enzymes are mainly composed of proteins and modulate biological reactions through substrate specificity and high catalytic activity under mild conditions. − Various natural enzymes such as peroxidase, oxidase, catalase, ascorbic acid oxidase (AAO), etc. assist their specific substrates and convert them into products by generating reactive oxygen species (ROS). , Recently, research on nanomaterial-based artificial enzymes (nanoenzymes or nanozymes) has received significant attention for biosensing, biocatalysis, and nanomedical applications such as therapeutic treatments is developing. − The functionality of metal nanoclusters (MNCs) as nanoenzymes is intriguing due to their better stability, biocompatibility, ease of fabrication technique, etc. − These MNCs promote an intermediate state of molecules and metal nanoparticles (MNPs) and possess several intriguing properties. − The high surface area to volume ratio makes them advantageous catalytically active materials and useful for enzyme activities. − Yan et al first demonstrated Fe 3 O 4 nanoparticles (NPs) as artificial nanozymes that exhibit intrinsic peroxidase-like activity . They also discovered that this enzymatic activity of Fe 3 O 4 NPs is accelerated by a single amino acid, i.e.…”