Jana Jayasmita, Aditya Teresa, Ganguly Mainak, Mehetor Shyamal Kumar, Pal Tarasankar
Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India.
Department of Chemistry, Furman University, Greenville, SC 29613, United States.
Spectrochim Acta A Mol Biomol Spectrosc. 2018 Jan 5;188:551-560. doi: 10.1016/j.saa.2017.07.045. Epub 2017 Jul 24.
Metal enhanced fluorescence of carbon dots has been reported in aqueous solution. Moderately fluorescing carbon dots (λ=360nm and λ=440nm) of 6-8nm diameters (CDA) have been synthesized from freshly prepared aqueous ascorbic acid solution under modified hydrothermal treatment. The CDA fluorescence is quenched at the close proximity with gold nanoparticles (AuNPs). Here, a substrate specific near-field electric field distribution is pronounced. Anticipating distance dependent fluorescence enhancement phenomenon, long-chain aliphatic thiol capped AuNPs are introduced to improve fluorescence of moderately fluorescing CDAs. The long-chain aliphatic thiols act as spacers between CDA and AuNP. Interestingly, the fluorescence of CDA is observed to be enhanced successively as the chain lengths of aliphatic thiols are increased. Fluorescing CDA, upon excitation, transfers energy to the nearby AuNP and a plasmon is induced. This plasmon radiates in the far-field resulting in fluorescence enhancement of CDAs. Such an interesting enhancement in emission with metallic gold is termed as gold enhanced fluorescence. This far-field effect for fluorescence enhancement of CDA particles becomes a general consensus in solution with varied long-chain aliphatic amine ligand capped silver nanoparticles (AgNPs). Finally, consequence of far-field effect of fluorescence enhancement has been observed while derivatized AuNP and AgNP are introduced into the CDA solution simultaneously which is described as reinforced fluorescence enhancement due to coupled plasmonic radiation.
已报道在水溶液中碳点的金属增强荧光现象。通过在改良水热处理条件下，由新制备的抗坏血酸水溶液合成了直径为6 - 8nm的中等荧光碳点（λ = 360nm和λ = 440nm）（CDA）。CDA的荧光在与金纳米颗粒（AuNP）紧密接近时会淬灭。在此，底物特异性近场电场分布很明显。预期存在距离依赖性荧光增强现象，引入了长链脂肪族硫醇封端的AuNP以改善中等荧光CDA的荧光。长链脂肪族硫醇充当CDA和AuNP之间的间隔物。有趣的是，随着脂肪族硫醇链长度的增加，观察到CDA的荧光依次增强。激发后的荧光CDA将能量转移到附近的AuNP并诱导产生等离子体激元。这种等离子体激元在远场辐射，导致CDA的荧光增强。这种与金属金相关的有趣的发射增强被称为金增强荧光。对于CDA颗粒荧光增强的这种远场效应在含有各种长链脂肪族胺配体封端的银纳米颗粒（AgNP）的溶液中已成为普遍共识。最后，当将衍生化的AuNP和AgNP同时引入CDA溶液中时，观察到了荧光增强远场效应的结果，这被描述为由于耦合等离子体激元辐射导致的增强荧光增强。
