A comprehensive review of atomically precise metal nanoclusters with emergent photophysical properties towards diverse applications.

Atomically precise metal nanoclusters (MNCs) composed of a few to hundreds of metal atoms represent an emerging class of nanomaterials with a precise composition. With the size approaching the Fermi wavelength of electrons, their energy levels are well-separated, leading to molecule-like properties, like discrete single electronic transitions, tunable photoluminescence (PL), inherent structural anisotropy, and distinct redox behavior. Extensive synthetic efforts and electronic structure revelation have expanded applicability of MNCs in catalysis, optoelectronics, and biology.

Power-dependent and ultrafast spectroscopic studies of Ag ion-doped colloidal CdSe nanoplatelets.

Atomically precise two-dimensional (2D) semiconductor nanoplatelets (NPLs) are found to be promising materials for next-generation optoelectronic devices due to their excellent optical properties. However, energy loss through phonon emission significantly causes problems in achieving efficient performance. Power-dependent steady-state spectroscopy and ultrafast spectroscopic studies have been performed to understand the influence of Ag ions on ultrafast carrier dynamics and thermalization processes in colloidal CdSe NPLs.

The impact of ligand chain length on the HER performance of atomically precise Pt(SR) nanoclusters.

Atomically precise metal cluster-based electrocatalysts have been paid significant attention for an efficient hydrogen evolution reaction (HER). Herein, we have synthesized atomically precise Pt(SR) nanoclusters using 3-mercaptopropionic acid (MPA), 6-mercaptohexanoic acid (MHA), 8-mercaptooctanoic acid (MOA), and 11-mercaptoundecanoic acid (MUA) thiol ligands in aqueous media at room temperature to understand the impact of ligand chain length on the HER performance. The composition of Pt(SR) metal clusters was confirmed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry.

Synthesis of atomically precise Ag nanoclusters and investigating solvent-dependent ultrafast relaxation dynamics.

In this article, the main focus is to employ a new synthetic strategy to prepare atomically precise Ag nanoclusters (NCs) and unveil the critical role played by the solvents in the excited state dynamics of Ag NCs. The compositional analysis confirms the formula of the nanoclusters as Ag(PDT)(PPh) (Ag-PDT NCs). These NCs showed a sharp absorption band at 525 nm and a comparatively broad absorption band at 633 nm.

Chirality of CsPbBr Nanocrystals with Varying Dimensions in the Presence of Chiral Molecules.

Chiral lead halide perovskite (LHP) nanocrystals (NCs) have been attracting considerable interest for circularly polarized luminescence (CPL)-based optoelectronic applications. This study combined experimental and computational analyses to investigate how the dimensionality of 3D (cubic) to 0D (quantum dots) influences the tunable chiral emission of CsPbBr LHP NCs. The circular dichroism (CD) spectra have a significant blue shift from 508 to 406 nm.

Evidence of Energy and Hole Transfer between 2D CdSeTe Alloy NPLs with Porphyrin Molecules.

Colloidal two-dimensional (2D) nanoplatelets (NPLs) have been extensively studied owing to promising potential in optoelectronic applications. Here, we have reported the preparation of 2D CdSeTe alloy NPLs and investigated their energy and charge transfer with porphyrin molecules. The red shifting in the optical properties suggests the change in the band gaps.

Introducing Ag Dopants into CdSe Nanoplatelets (NPLs) Leads to Effective Charge Separation for Better Photodetector Performance.

Solution-processed colloidal cadmium chalcogenide nanoplatelets (NPLs)-based photodetectors (PD) are promising materials for next-generation optoelectronic devices due to their excellent optical properties. Here, we report on ultrafast carrier relaxation dynamics of four monolayer (4 ML) Ag-doped CdSe (Ag: CdSe) NPLs using ultrafast transient absorption spectroscopy and their photodetectors applications. A broad dopant emission is observed at around 650 nm with a large FWHM of ~431 meV and band edge emission at 515 nm.

Insights of the efficient hydrogen evolution reaction performance in bimetallic AuCu nanoclusters.

The design of efficient electrocatalysts for improving hydrogen evolution reaction (HER) performance using atomically precise metal nanoclusters (NCs) is an emerging area of research. Here, we have studied the HER electrocatalytic performance of monometallic Cu and Au nanoclusters and bimetallic AuCu nanoclusters. A bimetallic AuCu/MoS composite exhibits excellent HER catalytic activity with an overpotential () of 155 mV reversible hydrogen electrode observed at 10 mA cm current density.

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

Artificial nanoenzymes based on metal nanoclusters have received great attention for multienzyme activities nowadays. In this work, pepsin-capped copper NCs (Cu-Pep NCs) are used as oxidase, ascorbic acid oxidase (AAO), and peroxidase mimics, and their activities are enhanced by the introduction of imidazole. The oxidase activity increased almost 7.

Impacts of Exciton Binding Energy and Dielectric Confinement of Layered Lead Halide Perovskites on Carrier Relaxation and Exciton Phonon Interactions.

This work highlights the significance of dielectric confinements and exciton binding energy of hybrid layered perovskites (LPs) in controlling the carrier relaxation dynamics of LPs for designing efficient optoelectronic devices. The polarizability of organic spacer cations in LPs modulates the carrier-phonon and carrier-carrier interactions, which eventually control the carrier relaxation dynamics. Here, we have varied the alkyl-ammonium chain length in the LPs to change the dielectric confinement, and the first-principles calculations reveal that the long-chain organic spacer experiences stronger dielectric confinement in comparison to short-chain organic spacer cation-based LPs.

Probing the Fluorescence Intermittency of Bimetallic Nanoclusters using Single-Molecule Fluorescence Spectroscopy.

Single-molecule spectroscopy (SMS) is a unique and competent technique to study molecule dynamics and sense biomolecules precisely. The design of an ultrahigh-stability single fluorophore probe with excellent photostability and long-lived dark transient states for single-molecule fluorescence microscopy is challenging. Here, we found that the photostability of bimetallic AuAg nanoclusters is better than monometallic Ag nanoclusters.

Transition Metal Ions Influence the Performance of Photodetector of Two-Dimensional CdS Nanoplatelets.

Transition metal-doped two-dimensional (2D) semiconductor nanoplatelets (NPLs) with atomically precise thickness have attracted much research interest due to their inherent photo-physical properties. In this work, we have synthesized 2D Cu-doped CdS NPLs, investigated the charge transfer dynamics using ultrafast transient absorption spectroscopy, and fabricated an efficient photodetector device. A large Stoke's shifted emission at ~685 nm with an average lifetime of about ~1.

Electron Transfer Dynamics from CsPbBr Nanocrystals to Au Clusters.

Lead halide perovskite nanocrystals have received significant attention as an absorber material for designing efficient optoelectronic devices. The fundamental understanding of the hot carrier (HC) dynamics as well as its extraction in hybrid systems is essential to further boost the performance of solar cells. Herein, we have explored the electron transfer dynamics in the CsPbBr-Au cluster hybrid using ultrafast transient absorption spectroscopy.

Experimental and computational insights into luminescence in atomically precise bimetallic AuCu(MPA) ( = 0-2) clusters.

Bimetallic nanoclusters (NCs) have emerged as a new class of luminescent materials for potential applications in sensing, bio-imaging, and light-emitting diodes (LEDs). Here, we have synthesized gold-copper bimetallic nanoclusters (AuCu NCs) using a one-step co-reduction method and tuned the emission wavelength from 520 nm to 620 nm by changing the [Cu]/[Au] molar ratio. The quantum yield (QY) increases from 6% to 13% upon incorporation of the Cu atom in the Au NCs.

Self-assembly of copper nanoclusters: isomeric ligand effect on morphological evolution.

Tailoring the hierarchical self-assembly of metal nanoclusters (NCs) is an emergent area of research owing to their precise structure and flexible surface environment. Herein, the morphological evolution from rods to platelets to ribbon-like structures through self-assembly of Cu NCs is dictated by the positional isomerism of the surface capping ligand, dimethylbenzenethiol (DMBT). Besides cuprophilic interaction, the interplay between π-π stacking and agostic interaction (Cu⋯H-C) directs the inter-NC organization into different ordered architectures.

Unraveling the Effect of Single Atom Doping on the Carrier Relaxation Dynamics of MAg Nanoclusters.

Precisely doped metal nanoclusters (NCs) are currently emerging nanomaterials for their unique photophysical properties. Here, we report the influence of single atom doping on the excited state relaxation dynamics of a series of MAg(2,4-MePhS) NCs where M is Ag, Au, Pd, and Pt. The NCs with a group 11 metal (Ag and Au) as central atoms exhibit dual emission at NIR and visible range, whereas it shows only NIR emission for group 10 metal (Pd and Pt) doped NCs.

Modulating the Carrier Relaxation Dynamics in Heterovalently (Bi) Doped CsPbBr Nanocrystals.

Manipulation of intrinsic carrier relaxation is crucial for designing efficient lead halide perovskite nanocrystal (NC) based optoelectronic devices. The influence of heterovalent Bi doping on the ultrafast carrier dynamics and hot carrier (HC) cooling relaxation of CsPbBr NCs has been studied using femtosecond transient absorption spectroscopy and first-principles calculations. The initial HC temperature and LO phonon decay time point to a faster HC relaxation rate in the Bi-doped CsPbBr NCs.

Self-Assembled Metal Nanoclusters: Driving Forces and Structural Correlation with Optical Properties.

Studies on self-assembly of metal nanoclusters (MNCs) are an emerging field of research owing to their significant optical properties and potential applications in many areas. Fabricating the desired self-assembly structure for specific implementation has always been challenging in nanotechnology. The building blocks organize themselves into a hierarchical structure with a high order of directional control in the self-assembly process.

Role of Ligand on Photophysical Properties of Nanoclusters with fcc Kernel: A Case Study of Ag(SCHX)(PPh) (X = F, Cl, Br).

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 {Ag(FBT)(PPh)·(solvent)} (), Ag(CBT)(PPh) (), and Ag(BBT)(PPh) (), where 4-fluorothiophenol (FBT), 4-chlorothiophenol (CBT), and 4-bromothiophenol (BBT) have been utilized as thiolate ligands, respectively.

Deciphering the Relaxation Mechanism of Red-Emitting Carbon Dots Using Ultrafast Spectroscopy and Global Target Analysis.

Red-emitting carbon dots (C-dots) have tremendous potential for bioimaging and optoelectronic applications. Here, we investigated the structural modification of red-emitting C-dots due to boron doping and their ultrafast relaxation dynamics. It is evident from the X-ray photoelectron spectroscopy study that the relative percentage of pyrridinic nitrogen is increased at the expense of amino nitrogen and graphitic nitrogen in B-doped C-dots.

Implications of relaxation dynamics of collapsed conjugated polymeric nanoparticles for light-harvesting applications.

Conjugated polymer-based nanostructures have been explored extensively from energy harvesting to healthcare applications due to their unique photophysical properties. This perspective includes the mechanism of the formation of polymer nanoparticles from linear chain polymers by utilizing experimental and theoretical studies. Conjugated polymer nanoparticles lead to changes in excitonic absorption bands, photoluminescence (PL) bands, and relaxation kinetics due to the inter-chain interactions between the chromophoric sub-units and the formation of the low-lying delocalized collective state.

The Impact of Aggregation of Quaterthiophenes on the Excited State Dynamics.

Oligothiophenes and their aggregates play a dominant role in optoelectronic and light-harvesting applications. Here, we controlled the degree of aggregation of 2,2':5',2″:5'',2‴-quaterthiophene (QTH) to shed light on the impact of the aggregation on the excited state dynamics. QTH aggregation realized the control over the Intersystem Crossing (ISC) rates and, in turn, the formation of triplet excited states via the simple addition of water to QTH solutions in THF.

One-Dimensional Silver-Thiolate Cluster-Assembly: Effect of Argentophilic Interactions on Excited-State Dynamics.

We report the synthesis, crystal structure, and electronic structure calculations of a one-dimensional silver-thiolate cluster-assembled and its ultrafast spectroscopic investigation. Experiments and theory find the material to have a significant gap as the HOMO-LUMO absorption corresponds to 2.69 eV, and the defect-free structure is calculated to have a gap of 2.

Investigation of Morphology-Controlled Ultrafast Relaxation Processes of Aggregated Porphyrin.

Here, we have synthesized rod and flake shaped morphology of porphyrin aggregates from 5, 10, 15, 20-tetra (4-n-octyloxyphenyl) porphyrin (4-opTPP) molecule which are evident from scanning electron microscopy (SEM). The formation of J-type aggregation is evident from steady state and time-resolved fluorescence spectroscopic studies. Ultrafast transient absorption spectroscopic studies reveal that the excited state lifetime is controlled by the morphology and the time constant for S→S relaxation changes from 3.