The structure–property correlation
of a series of silver
nanoclusters (NCs) is essential to understand the origin of photophysical
properties. Here, we report a series of face-centered cubic (fcc)-based
silver NCs by varying the halogen atom in the thiolate ligand to investigate
the influence of the halide atoms on the electronic structure. These
are {Ag14(FBT)12(PPh3)8·(solvent)
x
} (NC-1),
Ag14(CBT)12(PPh3)8 (NC-2), and Ag14(BBT)12(PPh3)8 (NC-3), where 4-fluorothiophenol (FBT),
4-chlorothiophenol (CBT), and 4-bromothiophenol (BBT) have been utilized
as thiolate ligands, respectively. Interestingly, the optical and
electrochemical bandgap values of these NCs nicely correlated with
the electronic effect of the halides, which is governed by the intracluster
and interclusters π–π interactions. These clusters
are emissive at room temperature and the luminescence intensity increases
with the lowering of temperature. The short lifetime data suggest
that the emission is predominantly originating due to the interband
relaxation (d → sp) of the Ag cores. Femtosecond transient
absorption (TA) spectra revealed similar types of decay profiles for NC-2 and NC-3 and longer decay time for NC-2. The relaxation dominates the decay profile to the surface
states and most of the excited-state energy dissipates via this process.
This supports the molecular-like dynamics of these series of NCs with
an fcc core. This overview shed light on an in-depth understanding
of ligand’s role in luminescence and transient absorption spectra.
In this work, we report the adsorption kinetics of electrochemically synthesized WS quantum dots (QDs) (ca. 3 nm) onto a polycrystalline gold electrode. The Langmuir adsorption isotherm approach was employed to explore the temperature and adsorbate concentration dependence of the experimentally calculated equilibrium constant of adsorption ( K) and the free energy for adsorption (Δ G). Subsequently, we extract other thermodynamic parameters, such as adsorption rate constant ( K), desorption rate constant ( K), the enthalpy of adsorption (Δ H), and the entropy of adsorption (Δ S). Our findings indicate that Δ G is temperature-dependent and ca. -7.64 ± 0.6 kJ/mol, Δ H = -43.72 ± 1.7 kJ/mol, and Δ S = -0.126 ± 0.017 kJ/(mol K). These investigations on the contribution of the enthalpic and entropic forces to the total free energy of this system underscore the role of entropic forces on the stability of the WS QDs monolayer and provide new thermodynamic insights into other transition-metal dichalcogenide quantum dot (TMDQD) monolayers as well.
Combined experimental and theoretical calculations shed light on the enhancement of conductivity through I2 incorporation in an indium metal–organic framework.
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