Graphene Oxide Enhanced Terbium Luminescence To Determine Dopamine

Dopamine (DA), as a kind of catecholamine neurotransmitters, plays an important role in regulating muscles, emotion and memory. The abnormal concentration of DA in human body is related to the neurological disorders such as Parkinson’s disease, attention deficit hyperactivity disorder, schizophreniaand so on.The article reported new methods of determining DA based on the fluorescence enhancement effect of graphene oxide (GO) on the Tb3+-DA system. By introducing co-luminescence ions and subligand into the system, the fluorescence of Tb3+ was improved, a sensitive method to determine DA was established and the interaction mechanism of the systems was studied. The article is divided into four parts.In the first part of the article, we reviewed the researches on the aspects of the application of GO in the analysis of DA, the fluorescence analysis of DA and the applications of rare earth ions luminescence.In the second part of the article, we established the new dual mode method of determining DA based on the fluorescence enhancement of GO on the Tb3+ luminescence and the anti-stokes luminescence. We found that under the pH 7.0, there is a linear ship between the enhanced Tb3+fluorescence and the concentration of DA. The linear range is 9.0 nM-180 nM, the detection limit (LOD) is 2.7 nM (S/N=3) and the correlation coefficient is 0.990. Under the same condition, there is a linear ship between the enhanced antistokes fluorescence of system and the concentration of DA in 3.0 nM-1000 nM. The LOD and the correlation coefficient are 2.6 nM (S/N=3) and 0.998, respectively. The two methods had been successfully applied in the detection of DA in real human serum. Compared with the Tb3+ luminescence method, this method owns wider linear range, lower detection limit, higher anti-interferences abilities and lower demand of diluted real sample. The interaction mechanism showed that the enrichment effect of GO on DA could promote the intramolecular energy transfer in the Tb3+-DA system. The coordination of GO with Tb3+ could increase the rigidity of the complex, the asymmetry of the ligand field, the probability of the electric dipole transition and effective absorption cross section of the complex and limit the free motion of complex resulting in the increase of fluorescence lifetime of the Tb3+-DA system and the enhancement of the Tb3+ fluorescence.In the third part of the article, we enhanced the fluorescence of Tb3+ by introducing the co-luminescence ion Y3+ and the subligand Ac" to further improve the sensitivity of the methods. It was found that under the optimal condition, there was a linear ship between the enhanced fluorescence of system and the concentration of DA. The linear range was 5.0 nM-50 nM and the detection limit was 1.8 nM (S/N=3). This method had been successfully applied in the detection of DA in real human serum. Compared with other analytical methods of DA, this method analyzed much more rapidly and sensitively. The mechanism studies showed that the introduction of Ac" decrease the asymmetry of the ligand field and the probability of the electric dipole transition resulting in the decrease of the Tb3+ characteristic fluorescence at 547 nm which effectively reduce the background signal. The Ac- coordinated with terbium ion by double coordination can decrease the energy loss of the excited complex. The enrichment of GO on DA could result in the promotion of the energy transfer by intramolecular and intermolecular of the system. What is more, GO could increase the rigidity of the rare earth complex and further enhance the fluorescence of the Y3+-Tb3+-GO-DA-NaAc system.In the fourth part of the article, we made conclusion and outlook of the above studies.The key feature of the thesis:1. We studied the enhancement effect of GO on the Tb3+-DA system and established a new dual mode method of detecting DA which was successfully applied in the analysis of real human serum. We found that the method based on the anti-stokes fluorescence enhancement effect of GO owns wider linear range, higher sensitivity, higher anti-interferences abilities and much more suitable for the lower diluted real sample.2. By introducing into the co-luminescent ions and subligand, and combining the enrichment effect and coordination effect of GO and the synergistic coordination effect of Ac-, the sensitivity of the method was further improved.