Bhowmik Sagar, Paria Shashikana, Tater Ishika, Maity Prasenjit
School of Engineering and Technology, National Forensic Sciences University - Gandhinagar, Sector-09, Gandhinagar, 382007, India.
School of Forensic Science, National Forensic Sciences University - Tripura, Radhanagar, Agartala, 799001, India.
J Fluoresc. 2022 Nov;32(6):2271-2280. doi: 10.1007/s10895-022-03017-x. Epub 2022 Sep 7.
Synthesis of luminescent metal cluster for selective sensing of specific analyte with detail mechanistic understanding is very important for real world applications as well as for developing new emissive materials. In the present work, we have synthesized L-glutathione stabilized gold (Au-SG) and gold-silver bimetallic (AuAg-SG) clusters under identical experimental conditions with orange red emissive characteristics for both. Detail photo physical analysis reveals that both clusters are phosphorescent in nature with moderate quantum yield of 7% and 19% for Au-SG and AuAg-SG respectively and their excited state lifetime values are in the range of 1-2 μs. While Au-SG cluster showed luminescence quenching response (turn-off) in presence of Fe and Hg ions, AuAg-SG cluster showed turn-off response for Cu, Fe and Hg, but luminescent enhancement (turn-on) response for Cd ions. The highest detection limit obtained for Cu ion by AuAg-SG cluster is 20 nM while for Cd ion it is 75 nM. From Time Correlated Single Photo Counting (TCSPC) and Dynamic Light Scattering (DLS) measurements we postulated that except Cd, all other metal ions cause aggregation of clusters through ligation with SG ligands while Cd ion does not induce any cluster aggregation but binds to cluster surface atoms. The near constant life time values of both clusters during gradual addition of respective metal ions confirms static quenching/enhancement process through formation of stable ground state adducts.
合成用于选择性传感特定分析物并具有详细机理理解的发光金属簇，对于实际应用以及开发新型发光材料都非常重要。在本工作中，我们在相同实验条件下合成了L-谷胱甘肽稳定的金（Au-SG）和金-银双金属（AuAg-SG）簇，二者均具有橙红色发光特性。详细的光物理分析表明，两种簇本质上都是磷光的，Au-SG和AuAg-SG的量子产率分别为7%和19%，且它们的激发态寿命值在1-2微秒范围内。虽然Au-SG簇在铁离子和汞离子存在下表现出发光猝灭响应（关闭），但AuAg-SG簇对铜离子、铁离子和汞离子表现出关闭响应，而对镉离子表现出发光增强（开启）响应。AuAg-SG簇对铜离子获得的最高检测限为20 nM，对镉离子则为75 nM。通过时间相关单光子计数（TCSPC）和动态光散射（DLS）测量，我们推测除镉离子外，所有其他金属离子通过与SG配体配位导致簇聚集，而镉离子不会诱导任何簇聚集，但会与簇表面原子结合。在逐渐添加各自金属离子过程中，两种簇的寿命值近乎恒定，这证实了通过形成稳定基态加合物的静态猝灭/增强过程。
