Synthesis of Fluorescent Ag Nanoclusters for Sensing and Imaging Applications

Abstract

Metal nanoparticles have attracted more and more attention in the last years due to their unique chemical and physical properties which are very different from the metal bulk material. In particular, when the size of nanoparticles decreases below two nm, nanoparticles can be described as nanoclusters (NCs), and they present peculiar optical properties. The excited electrons in addition to specific absorption bands show also a bright luminescence related to the quantum size effect which produce discrete energy levels. Optical properties (absorption and fluorescence) of these NCs are widely used in many different applications in science and engineering, such as chemical sensors, fluorescent probes for bio imaging or in environmental issues. In the present study, we report on the synthesis of silver nanoclusters (AgNCs) in aqueous phase using silver nitrate as precursor salt and L-Glutathione (GSH) as stabilizer. AgNCs were characterized using absorption and fluorescence spectroscopy, and transmission electron microscopy (TEM). The strong absorption and luminescence shown by these NCs are very promising for a possible exploitation both as label for bioimaging and for optical sensors for heavy metal ions.

Silver Nanoparticles as Colorimetric Sensors for Water Pollutants

“…In the last ten years nanotechnology has enabled the enhancement of low dimensional materials properties proponing their use in several application fields, such as sensors [1][2][3][4][5][6][7][8][9][10][11][12], optics [13][14][15][16][17][18][19][20][21][22], energy [23][24][25][26], catalysis [27,28] and biotechnology [29][30][31][32][33][34]. Among others the noble metal nanomaterials were developed by bottom up approach with various morphologies such as spheres, cubes, stars, flowers and wires, showing significant chemical-physical properties that allow to unique interactions with the environment [35][36][37][38][39][40][41][42].…”

Metal Nanostructures for Environmental Pollutant Detection Based on Fluorescence

“…Fluorescent nanomaterials such as inorganic quantum dots (QDs) [ 19 , 20 , 21 ] perovskite quantum dots (PQDs) [ 22 , 23 , 24 ], graphene quantum dots (GQDs) [ 25 , 26 , 27 , 28 ] are employed as nanosensors for environmental monitoring. Moreover, other nanostructures are used as fluorescent probes for pollutant detection such as noble metal nanoclusters (MNCs) [ 29 , 30 , 31 , 32 ] or functionalized nanoparticles [ 33 , 34 , 35 ]. In the case of noble metal nanoclusters, the fluorescence is an intrinsic property of the material itself and it is connected with the small dimensions that induce a quantization of the energy levels; in other cases and with specific functionalization, luminescent species or molecules are bond directly to the nanoparticles that do not show intrinsic fluorescence [ 36 , 37 , 38 ].…”

X‐ray and UV photoelectron spectroscopy of Ag nanoclusters

“…However, the reduced size (d ≤ 100 nm) of Ag NPs allows the phenomenon of localized surface plasmon resonance (LSPR) 19 or quantum effects, like photoluminescence (PL), if the size approaches the dimension of 2 nm. 20 In X-ray photoelectron spectroscopy (XPS), the metallic Ag 3D 5/2 peak lies at a binding energy (BE) of 368.2 eV and has a very small chemical shift; therefore, the identification of oxidation state in bulk Ag compounds is difficult. An interesting question on this regard is: could this property change if the NPs dimensions decrease?…”

“…It is well known that bulk Ag is a good electrical and thermal conductor and has a highly reflective surface. However, the reduced size ( d ≤ 100 nm) of Ag NPs allows the phenomenon of localized surface plasmon resonance (LSPR) 19 or quantum effects, like photoluminescence (PL), if the size approaches the dimension of 2 nm 20 …”