Construction And Properties Of Electrochemiluminescence Sensor Based On CdS-polyamidoamine Quantum Dots Film

Electrochemiluminescence （ECL） combined the electrochemical and luminescenttechniques has been a very active research hotspot in electroanalysis chemistry. ECL hassome remarkable features such as high sensitivity, wide linear range, simplified opticalsetup, versatility, fast detection, good temporal, spatial control and so on. In recent years,quantum dots has drawn a lot of attention for its’ specific merits of optics,electrochemistry and electrochemiluminescence. But using quantum dots to constructECL sensor might be one of the most important application fields. The QDs-based ECLhas many good characteristics such as high response sensitivity, quick detection, fineselectivity etc. The ECL intensity and stability of the QDs-based ECL sensor areinfluenced by the quality of the QDs and the construction methods. Therefore, efficientmethods taken to enhance and stable ECL signal for the semiconductor QDs-based ECLsensor are crucial. In this paper, well-distributed CdS/PAMAM QDs was prepared withPAMAM as a template. The numerous reactive groups on the surface of dendrimers canrender the CdS/PAMAM QDs to assemble firmly onto the electrodeposited goldnanoparticles film to configurate CdS-PAMAM/GNPs/Au electrode. The ECL propertywas investigated after modified with GNPs、CNTs and PAMAM. The major work andresult are as followed:In the first part of this paper, the synthesis of CdS/PAMAM QDs. Stable、watersoluble and well-dispersed CdS/PAMAM QDs was successfully synthesized withPAMAM as a template. We charactered the obtained CdS/PAMAM QDs by TEM,UV-vis spectroscopy and FL spectroscopy. The result indicated that the synthesizedCdS/PAMAM QDs under the optimizing conditions was stable, well-dispersed, goodoptics performance and its particle size was about4.0nm. In the synthesized process ofthe CdS-PAMAM QDs, PAMAM can retard the growth of QDs by its highly branchedstructure and inner cavities. The numerous reactive groups on the surface of dendrimers can be used to passive the surface dangling bond of the QDs and eliminate the surfacedefects, so the luminescent intensity of the QDs could be increased dramatically and theemission peak was symmetrical and blue shift. Moreover, the reactive groups on thesurface of dendrimers also can be used to render the composites soluble in essentiallyany solvent and biocompatibility to favorable the composites’ practical application.In the second part of this paper, the construction of the CdS-PAMAM/GNPs ECLsensor and its performance. First, gold nanoparticles was modified onto the Auelectrode by direct electrodeposited technique. Then the quality CdS-PAMAM QDs wasassembled to configurate the QDs-based ECL sensor. The film electrode wascharacterized by SEM and CV techniques etc. The ECL performance of theCdS-PAMAM/GNPs and the optimized conditions were investigated in the coreactantK₂S₂O₈PBS solution. The result indicating that the electrodeposited GNPs cooperatedwith PAMAM can promote the electron transfer on the electrode, facilitate the reactionof the QDs and coreactant K₂S₂O₈so that the ECL of the CdS-PAMAM/GNPs filmelectrode enhanced dramatically. The electrodeposited GNPs cooperated with PAMAMcan also simplify the construction steps and improve the ECL stability of the filmelectrode. The proposed ECL sensor demonstrated good selectivity, high responsesensitivity, wide linear rang from0.05¹0μM and low detection limit0.012μM todopamine. This film electrode sensor was used to detect actual samples and the satisfiedresult was obtained.In the third part of this paper, ECL sensor based on the CdS-PAMAM-CNTs/GNPsfilm and its ECL enhanced role. The CNTs has good chemical stability, strongconductivity etc. The CNTs can be used in the ECL to reduce the ECL potential barrierand increase the ECL intensity. So the CNTs was applied to promote the ECLperformance of the CdS-PAMAM/GNPs/Au electrode. The CNTs was used to furthermodify CdS-PAMAM QDs and the CdS-PAMAM-CNTs QDs was gained. Then, theCdS-PAMAM-CNTs QDs was applied to configurate the based-QDs ECL sensor. TheECL performance of the CdS-PAMAM-CNTs/GNPs/Au and the ECL enhancement ofthe CNTs to the CdS-PAMAM-CNTs/GNPs/Au was investigated. The study resultedthat, the ECL intensity of CdS-PAMAM-CNTs/GNPs/Au was much higher than that ofCdS-PAMAM/GNPs/Au and the ECL potential also positive shifted. All these suggestedthat the CNTs could increase the specific surface area effectively, promote the electron transfer, reduce the ECL potential barrier and facilitate the ECL reaction, so that thehigher ECL intensity of the the CdS-PAMAM-CNTs/GNPs/Au was generated. TheCdS-PAMAM-CNTs/GNPs/Au ECL sensor demonstrated higher response sensitivity,wider linear rang from0.04¹50μM and lower detection limit0.008μM to dopamine.Hence, the quality CdS-PAMAM QDs can be synthesized with PAMAM as atemplate. The CdS-PAMAM QDs-based ECL sensor showed excellent ECLperformance. With the synergy of GNPs、CNTs and PAMAM, the ECL property ofCdS-PAMAM QDs-based ECL sensor was further improved. This highly enhancedECL from the CdS-PAMAM/GNPs film sensor may open a newavenue to construct QDs-based ECL sensor.