Gold Nanoclusters as a Fluorescent Probe for the Sensitive Determination of Morin and Sensing of Temperature

Abstract

The fluorescence detection has attracted extensive attentions because of its selective and sensitive determining characteristics for a series of analytes. In this detection system, a fluorescence method was first developed for the analysis of morin (MR) based on gold nanoclusters, which was prepared using tryptophan as the stabilizer and reducing agent. The assynthesized gold nanoclusters (Trp-Au NCs) showed maximum excitation wavelength and emission wavelength at 368 and 449 nm, respectively. When MR was added, the fluorescence intensity at 449 nm was significantly quenched, which might be attributed to the inner filter effect (IFE) and static quenching. The ln(F 0 /F) value of Trp-Au NCs displayed excellent linearity for sensing MR in the range of 0.5-90 μM (R 2 = 0.9958) with a lower detection limit of 0.063 μM. This proposed sensor could be used for the sensing of temperature. Moreover, this fluorescence detecting strategy was successfully used in real samples, which indicated its great potential value for MR sensing in actual samples.

Tryptophanhydroxamic Acid-Stabilized Ultrasmall Gold Nanoclusters: Tuning the Selectivity for Metal Ion Sensing

“…Based on these requirements, in the last 10 years, several production processes have emerged, where only one smaller or larger molecule like proteins [ 8 , 9 ], peptides [ 10 ] and simple amino acids [ 11 , 12 , 13 ] are used for the reduction of metal ions (e.g., [AuCl 4 ] − , Ag + or Cu 2+ ), which in addition play a dominant role in the stabilization and functionalization of the metallic surface as well. In the case of amino acids, several articles can be found for tryptophan (Trp) [ 12 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ], tyrosine (Tyr) [ 21 , 22 ], histidine (His) [ 12 , 13 , 23 ], arginine (Arg) [ 24 ], or amino acids containing S donors like cysteine (Cys) or methionine (Met) [ 11 , 13 ]. Among these amino acids for Trp, it was confirmed that Au- [ 12 , 15 , 16 , 18 , 20 ], Ag- [ 14 , 19 ], and Cu-based [ 18 ] NCs can also be produced via a direct reduction of the metal ions with Trp without the application of any other agents.…”

“…In the case of amino acids, several articles can be found for tryptophan (Trp) [ 12 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ], tyrosine (Tyr) [ 21 , 22 ], histidine (His) [ 12 , 13 , 23 ], arginine (Arg) [ 24 ], or amino acids containing S donors like cysteine (Cys) or methionine (Met) [ 11 , 13 ]. Among these amino acids for Trp, it was confirmed that Au- [ 12 , 15 , 16 , 18 , 20 ], Ag- [ 14 , 19 ], and Cu-based [ 18 ] NCs can also be produced via a direct reduction of the metal ions with Trp without the application of any other agents. By comparing the experimental conditions optimized in these publications, it can be stated that predominantly the use of ligand excess (depending on the metal ions, these are in the range of a 2:1–20:0 molar ratio, 100–120 °C temperature, and basic conditions (pH = 11–12)) can be generally used to produce blue-emitting Trp-coated NCs.…”