Tuning of Silver Cluster Emission from Blue to Red Using a Bio-Active Peptide in Water

Abstract

Blue, green, and red emitting silver quantum clusters have been prepared through green chemical approach by using a bio-active peptide glutathione (reduced) in a 50 mM phosphate buffer at pH 7.46. This study describes fluorescence emission tuning of the silver clusters by making different sized Ag clusters using slightly different reaction conditions keeping the same stabilizing ligand, reducing agent, solvent system, and silver salt precursor. The preparation procedure of these silver quantum clusters is new and highly reproducible. Each of these clusters shows very interesting fluorescence properties with large stokes shifts, and the quantum yields of blue, green, and red clusters are 2.08%, 0.125%, and 1.39%, respectively. These silver quantum clusters have been characterized by using different techniques including fluorescence spectroscopy, UV-vis spectroscopy, field-emission gun transmission electron microscopic (FEG-TEM) imaging and MALDI-TOF MS analyses. MALDI-TOF MS analyses show that the size of these blue, green and red emitting silver clusters are Ag5 (NC1, nanoclusters 1), Ag8 (NC2, nanoclusters 2) and Ag13 (NC3, nanoclusters 3), respectively, by using 2,5-dihydroxybenzoic acid as a matrix. These clusters are stable in broad ranges of pH. The NC3 (red emitting) has been successfully utilized for selective and sensitive detection of toxic Hg(II) ions in water by using even naked eyes, fluorometric, and calorimetric studies. The lower limit of detection of Hg(II) ions in water has been estimated to be 126 and 245 nM from fluorometric and UV-vis analyses, respectively. Enthalpy change (ΔH) during this Hg(II) sensing process is 2508 KJ mol(-1).

π‐Expanded α,β‐Unsaturated Ketones: Synthesis, Optical Properties, and Two‐Photon‐Induced Polymerization

“…Among the three AgNCs, the yellow emitting one had a QY over 60 % and was used for cancer cell imaging. The AgNCs‐GSH with different emissions could also be made by tuning the ratios of AgNO 3 to GSH and the reaction temperature 68. When Ag + was preloaded within polyacrylamide gel, sunlight could induce the in situ formation of AgNC 69…”

Preparation of multi-coloured different sized fluorescent gold clusters from blue to NIR, structural analysis of the blue emitting Au7cluster, and cell-imaging by the NIR gold cluster

“…Ultra-small noble metal quantum clusters [10][11][12][13][14][15][16][17][18][19][20][21][22] with a few number of metal atoms possess a missing link between single metal atom and relatively large sized nanocrystals. [10][11][12][13][14][15][16][17][18][19][20][21][22] Small size of these noble metal quantum clusters with very low toxicity and lack of blinking property than semiconducting nanocrystals make them attractive candidates for biological imaging, [23][24][25][26] chemical sensing [27][28] and other purposes. They show unique moleculelike properties, such as quantized charging and luminescence.…”

“…For the synthesis of gold quantum clusters, the bottom-up approach has been applied by using complexation of gold salt precursor with some suitable capping ligand followed by chemical, sonochemical or microwave reduction. These tuneable, emissive gold clusters have been characterized as Au 7 , Au 16 , Au 19 , Au 21 and Au 22 using MALDI-TOF MS. A structural organisation of Au atoms and ligands in blue emitting Au 7 cluster has been performed by using computational (density functional theory) and Raman spectroscopic studies. Proper choice of ligands, reducing agents and reaction conditions are important factors for the synthesis of gold quantum clusters.…”

The Application of Silver Nanoclusters to Sensing, Cell Imaging and Construction of Molecular Logic Gates

“…This makes that class of compound as efficient material for development of versatile sensor. Till now, several soft template methods have been developed to prepare stable water‐soluble fluorescent AgNCs under mild conditions such as DNA, proteins, aptamers, peptides and amino acids etc …”