Methionine-Capped Gold Nanoclusters as a Fluorescence-Enhanced Probe for Cadmium(II) Sensing

Abstract

Gold nanoclusters (Au NCs) have been considered as novel heavy metal ions sensors due to their ultrafine size, photo-stability and excellent fluorescent properties. In this study, a green and facile method was developed for the preparation of fluorescent water-soluble gold nanoclusters with methionine as a stabilizer. The nanoclusters emit orange fluorescence with excitation/emission peaks at 420/565 nm and a quantum yield of about 1.46%. The fluorescence of the Au NCs is selectively and sensitively enhanced by addition of Cd(II) ions attributed to the Cd(II) ion-induced aggregation of nanoclusters. This finding was further used to design a fluorometric method for the determination of Cd(II) ions, which had a linear response in the concentration range from 50 nM to 35 μM and a detection limit of 12.25 nM. The practicality of the nanoprobe was validated in various environmental water samples and milk powder samples, with a fairly satisfactory recovery percent.

Perspectives of different colour‐emissive nanomaterials in fluorescent ink, LEDs, cell imaging, and sensing of various analytes

“…Furthermore, different types of analytes [ 186–230 ] such as Zn 2+ ions, [ 186 ] ascorbic acid, [ 187 ] norfloxacin, [ 188 ] GSH, [ 189 ] PO 4 3− , [ 190 ] lysozyme, [ 191 ] Hg 2+ , [ 192 ] Cd 2+ , [ 193 ] Al 3+ , [ 194 ] metal ions (Hg 2+ , Ag + and Cd 2+ ), [ 195,196 ] quercetin, [ 197 ] Cr 6+ , [ 198 ] Hg 2+ ion, [ 199 ] melamine and Hg 2+ ion, [ 200 ] trinitrophenol, [ 201 ] H 2 S, [ 202 ] Pb 2+ , [ 203 ] Al 3+ ion, [ 204 ] Zn 2+ , [ 205 ] Hg 2+ ion, [ 206 ] MiR‐155, [ 207 ] melamine, [ 209 ] dopamine, [ 215 ] DNA, [ 216 ] 5‐hydroxytryptamine [ 218 ] and picric acid [ 230 ] have been recognized by using various ultra‐small nanostructure materials as probes in fluorescence spectrometry. Orange‐emissive Au NCs were prepared by using auric chloride and GSH as precursors and used as a sensor to detect Zn 2+ ions with a wider linear range from 4.68 to 2,240 μM.…”

Synthesis of Orange-Red Emissive Au-SG and AuAg-SG Nanoclusters and Their Turn-OFF vs. Turn-ON Metal Ion Sensing

“…In general the luminescence quenching phenomenon occurs through photo-induced electron transfer (PET) process via static or dynamic interaction between probe and the analyte [40][41][42][43][44][45][46][47][48]. However, the turn-on sensing is uncommon and the underlying mechanism may be very distinct for different probes [49][50][51]. The TCSPC measurement was performed to record the excited state lifetime values of AuAg cluster upon gradual addition of Cu 2+ , Fe 3+ , Hg 2+ and Cd 2+ (Fig.…”

“…The advantages of luminescence sensing of analytes includes very high sensitivity and selectivity, low cost, on the spot testing feasibility and fast response time [38] Luminescence quenching (Turn-OFF) is the most dominant pathway of sensing analytes demonstrated by various metal clusters and we may ascribe its origin through electron/energy transfer from metal cluster to analyte through a static or dynamic adduct formation mechanism [44][45][46][47][48]. Luminescence enhancement (Turn-ON) based sensing of analytes is more advantageous but is less common and it follows a distinct mechanism than the previous one [49][50][51]. In metal ion sensing, the ions may interact with surface ligands, or it may interact with surface metal atoms of the cluster and may also form a different alloy resulting a luminescence response.…”

Metal Nanostructures for Environmental Pollutant Detection Based on Fluorescence

“…For example, orange-emitting fluorescence AuNCs with methionine as a stabilizer, was synthesized to detect Cd(II) ions in water by a fluorescent enhancement mechanism with a LOD of 12.25 nM. In this case 10 cations and 11 anions were tested but only the presence of Cd(II) in solution causes the AuNCs aggregation due to the link between Cd(II) and Au via chelating bonds with a carboxyl group or an amino group in methionine adsorbed on the Au nanoclusters [ 83 ].…”