Assembly-Induced Emission in Mercaptosuccinic Acid-Templated Silver Nanoclusters: Metal Ion Selectivity and pH Sensitivity

Abstract

The phenomenon of aggregation-induced emission (AIE) is an emerging strategy used to tune the optical properties of luminescent metal nanoclusters (MNCs). Various external factors such as cations, hydrophobicity, and solvents provide impetus for AIE in MNCs. Our present investigations delineate the remarkable tuning of the photophysical properties of weakly luminescent mercaptosuccinic acid (MSA)-templated silver nanoclusters (AgNCs). Upon AIE of AgNCs through the introduction of Zn2+ ions, the emission maximum of AgNCs was shifted from ∼465 to ∼670 nm with an unusual augmentation in photoluminescence intensities (∼3000 times). The minimization of energy dissipation due to the formation of the Zn2+-induced rigid assembly mainly accounts for these unprecedented optical signatures. As a consequence of this, the otherwise weakly emissive AgNC system (quantum yield, QY ∼ 0.1%) gets converted to a highly luminescent red-emitting Zn2+-induced AgNC assembly (Zn–AgNCs, QY ∼ 2%). Our MSA-templated AgNCs demonstrated the selectivity toward Zn2+ ions in forming the Zn–AgNC assemblies, which in turn were highly sensitive toward the pH of the medium in the pH range of 5–8.

Solvent‐Induced Modulation in the Optical Properties of Copper Nanoclusters and Revealing the Isomeric Effect of Templates

“…Excitation-dependent emission spectra (Figure 2c) illustrate that the emission maximum of CuNCs remains unaltered at different excitation wavelengths, thereby indicating the fixed HOMO-LUMO energy gap of the CuNCs investigated herein. [18] The excited-state lifetime of the B-CuNCs was found to be 15.46 ns (Figure 2d and Table S1). To evaluate the most probable composition of the CuNCs, ESImass analysis was performed which displays the most intense peak centered at m/z = 712.9, corresponding to the composition [Cu 4 (p-MBA) 3 ] + (Figure S5).…”

“…As a consequence, more comprehensive investigations are indeed required to have a molecular‐level understanding toward this direction. The variable reaction parameters like solvents, [16] pH, [17] cations, [18] and intra‐ and inter‐ligand interactions [19] (hydrophobic, and/or electrostatic) can also regulate the arrangement of the metallic kernel of the MNCs. These in turn control the spatial distribution of the ligand shell and consequently influence their optical signatures.…”

Fluorescence Resonance Energy Transfer in a Supramolecular Assembly of Luminescent Silver Nanoclusters and a Cucurbit[8]uril-Based Host–Guest System

“…Noble metal NCs serve as a bridge between bulk metals and nanomaterials and behave like “molecular species.” They are characterized by a size domain comparable to the Fermi wavelength of conduction electrons and possess discrete electronic states, which in turn results in their photoluminescent properties . As a consequence of their excellent photostability, better biocompatibility, and low cytotoxicity, they serve as excellent fluorophores that can be used in biomedical research, light energy conversion, sensing, and cellular imaging. − Thus, another objective of this work was to prepare blue-emitting metal NCs using both large and small ligands as a template and thereafter explore FRET between AgNCs (donor) and EtBr-CB[8]­system (acceptor). In FRET, the rate of the energy transfer is influenced by many aspects, which include the extent of spectral overlap between the donor emission and acceptor absorption spectrum, dipole–dipole interaction, and, most importantly, the distance between the donor and acceptor molecules. , Apart from these, herein, we have also tried to decipher the effect of ligands on the FRET efficiency between organic supramolecular complex and biologically useful luminescent noble metal NCs.…”

In Vivo Aggregation of Clearable Bimetallic Nanoparticles with Interlocked Surface Motifs for Cancer Therapeutics Amplification

“…15,16 Unlike the stable AuNPs, unstable silver nanoparticles (AgNPs) usually exhibited high killing ability but suffered the loss of selectivity, which caused indiscriminate damage to normal tissue and inhibited their biological applications. 17,18 Alloy metal NPs normally feature improved physicochemical properties (e.g., better luminescence, catalysis activity, and stability), 19−23 which results from the diverse anchoring sites on the surface of NPs. However, until now, their ROS production was insignificant for efficient PDT therapy of cancer.…”

“…Great effort has been expended to enhance ROS generation. For molecular probes, the effective suppression of intra-/intermolecular motion could largely promote a nonradiative intersystem crossing process. − For metal NPs, surface regulation strategies (e.g., to regulate surface charge or surface coverage) have been utilized to investigate the ROS production; however, stable gold NPs (AuNPs) typically showed a low ROS quantum yield. , Unlike the stable AuNPs, unstable silver nanoparticles (AgNPs) usually exhibited high killing ability but suffered the loss of selectivity, which caused indiscriminate damage to normal tissue and inhibited their biological applications. , Alloy metal NPs normally feature improved physicochemical properties (e.g., better luminescence, catalysis activity, and stability), − which results from the diverse anchoring sites on the surface of NPs. However, until now, their ROS production was insignificant for efficient PDT therapy of cancer. , Therefore, directly using these facile strategies for PDT usually gave low photodynamic efficacy.…”