重原子掺杂对碳量子点室温磷光性能的影响及其在防伪加密中的应用

Effect of heavy atom doping on the performance of phosphorescent carbon quantum dots and its application in anti-counterfeiting encryption

室温磷光(RTP)碳量子点(CQDs)因其在生物成像、光电器件、防伪加密等领域的广泛应用,而受到了研究者们的关注.由于单线态激子到三线态激子的自旋禁阻跃迁,系间窜跃(ISC)速率常数较低,使得CQDs很难观察到磷光,严重限制了其在实际中的应用.本文提出了一种通过"重原子效应"提高CQDs系间窜跃速率常数的新方法.以溴化苄为重原子掺杂剂,将其混入柠檬酸、丙烯酰胺、尿素的前驱体中,在200℃下采用水热法制备出了RTP碳量子点,并研究了溴化苄掺杂对CQDs光学性能的影响.实验结果表明,由于溴化苄的引入,使得CQDs的磷光寿命由112 ms提高到了493 ms,且肉眼可识别的时间长达7 s.随后,采用丝网印刷制备了基于BrNCDs的防伪印刷图片,展示了重原子掺杂RTP碳量子点在防伪印刷领域的潜在应用前景.

Room temperature phosphorescent(RTP)carbon quantum dots(CQDs)have attracted extensive attention due to their applications in biological imaging,optoelectronic devices,anti-counterfeiting encryption and other fields.Due to the spin-forbidden transition from singlet exciton to triplet exciton,the rate constant of intersystem crossing transition(ISC)is low,which makes it difficult to observe phosphor and severely limits the development of CQDs.Here,we propose a new method to increase the rate constant of carbon quantum dots ISC by the"heavy atom effect".In this study,RTP carbon quantum dots doped with heavy atoms were prepared by hydrothermal method at 200℃using benzyl bromide as reactant and mixed with the precursor of citric acid,acrylamide and urea.The effects of benzyl bromide doping on the optical properties of CQDs were studied.The experimental results show that the phosphorescence lifetime of CQDs is increased from 112 ms to 493 ms due to the introduction of benzyl bromide,and the visual recognition time is up to 7 s.Then,we further show the application prospect of RTP carbon quantum dots doped with heavy atoms in the field of anti-counterfeiting printing.