The Preparation Of Fluorescent Noble Metal Nanoclusters And Its Research On Detection

Metal nanoclusters(MNCs) have developed rapidly as a new type of fluorescent nanomaterials,especially,their unique optical properties and practicality have attracted the attention of numerous researchers.The energy level close to the Fermi wavelength endows MNCs the unique spatial structure and fluorescence properties,which are potential research and development targets in the field of fluorescent nanomaterials.Compared with typically semiconductor quantum dots(QDs)and fluorescent dyes,MNCs are generally possessed the advantages of low toxicity,good biocompatibility and high stability,gradually applying to biologiccell imaging and chemical sensing,etc.In this paper,Cu nanoclusters(Cu NCs),Ag nanoclusters(Ag NCs)and Au nanoclusters(Au NCs)were synthesized respectively using (?)-histidine(His),folic acid(FA)and thioctic acid(TA)as precursors,and,the sensing process for pollutants(explosive DNP and heavy metal ions Hg²⁺/Ag⁺)in real water were explored in this paper based on the fluorescence quenching/enhancement process.In addition,the fundamental application of MNCs for in situ detection of contaminants in the water on a portable smartphone platform based on fluorescent test strips were also explored.Herein,we have reported a facile one-pot strategy to synthesize fluorescent Cu nanclusters(Cu NCs)by using (?)-histidine as stabilizer,and ascorbic acid as reducing agent.Cu NCs are stable,water-dispersible,and emit bright cyan emission with a quantum yield 26.08%.The Cu NCs can be employed as colorimetric and fluorimetric dual-mode detector,exhibiting excellent selectivity and sensitivity for detecting DNP,specifically.Notably,the concentration of DNP showed an excrllent linear relationship with the fluorescence intensity ratio I₀/I of Cu NCs in the interval of 0.01-0.15 m M,and the limit of detection(LOD)was as low as 3.96?M.The intrinsic mechanism of DNP detection by Cu NCs was analyzed by UV-vis absorption spectroscopy,fluorescence decay spectra and fluorescence spectra,which confirmed that the"turn-off"response is caused by the inner filter effect(IFE)and static quenching effect(SQE).In addition,this experiment demonstrated that Cu NCs have great potential for DNP detection in the field of practical water sample analysis.FA(folic acid)-stabilized silver nanoclusters(Ag NCs)are synthesized,and the in situ detection of Hg²⁺was alreadt achieved by the fluorescence method and sensing platform of the cell phone.The fluorescent species of Ag NCs with"turn-off"sensing strategy consisted of Ag L,Ag₂L,Ag₅L₄,Ag₆L₅and Ag₁₇L.Based on the process of the inner filter effect(IFE)and static quenching effect(SQE),the Ag NCs had sensitive detection performance for Hg²⁺recognition with a minimum detection limit of 1 n M.In addition,the Ag NCs probe can be applied to test paper sensing of Hg²⁺detection through the integrated cell phone software RGB sensing platform,fast,sensitively,intuitively and portably.It has been verified that both methods have ideal recoveries for the detection of Hg²⁺in real water samples.A novel TA-NAC Au NCs was synthesized using lipoic acid(TA)as protective agent.In the presence of the secondary reducing agent N-acetyl-L-cysteine(NAC),the prepared TA-NAC Au NCs emitted intense red fluorescence at 625 nm with a quantum yield of 15.7%.And,the synthesized TA-NAC Au NCs had superior stability.Moreover,the TA-NAC Au NCs exhibited high specific selectivity and sensitivity to Ag⁺due to the increased red fluorescence of TA-NAC Au NCs,thus realizing the sensitive detection process of TA-NAC Au NCs for Ag⁺with a LOD of 8.7 n M.The formation of Au-S bond gave the unique stability of TA-NAC Au NCs,and the addition of Ag⁺caused the newly generated Ag-S increasing the water solubility and fluorescence intensity of TA-NAC Au NCs,thus achieving selective detection.The TA-NAC Au NCs as fluorescent sensors provided a new idea and detection strategy for the identification of Ag⁺.