The Luminescence Mechanism Of Water-soluble QDS And Their Fundamental Application Research Forphotoelectric Sensor

Recently, QDs become a new generation of ideal photoelectric sensor for the unique photoelectricity properties, QDs attract wide attention in the field of biological/chemical sensing. The study about QDs-based photoelectric sensor had abundent research achievements, which includes all kinds of QDs-based photoelectric sensing mechanism, sensor design and construction. For the filed of sensing analysis, the introduction of QDs provides infinite imaginary space for the development of new photoelectric sensor, so they provided a new approach for the photoelectric sensor research, and made a lot of innovative achievements. The QDs-based photoelectric sensor has widely used in the intersection of multiple disciplines, such as physics, chemistry, material science and biology, so the QDs-based photoelectric sensor opened up a new direction of nano materials in the filed of sensing and analysis. This dissertation based on the outstanding photoelectric properties of QDs, studies the sensing mechanism of QDs in different photoelectric analysis system, then designs and builds the corresponding photoelectric sensors. The main research content of this paper is as follows:We demonstrate that CdTe QDs with different sizes and stabilizers evidently exhibited different ECL behavior in aqueous solution. The ECL of CdTe QDs stabilized by3-mercaptopropionic acid (MPA) displays two waves at a potential of about+1.17V and+1.74V vs. Ag/AgCl, respectively. ECL spectra confirm that ECL of QDs is attributed to their band gap luminescence, in which the peak positions are changed with QD sizes. The ECL mechanism of CdTe QDs involves in superoxide radical generated by reduction of dissolved oxygen at lower potential or the water splitting at higher potential. Direct evidence for superoxide radical in this medium was obtained via electron spin resonance (ESR) experiments. As comparison, the2-mercaptoethylamine (MEA)-capped CdTe QDs did not exhibit any ECL in air-saturated pH7.4PBS. Both ESR and X-ray photon spectroscopy (XPS) experiments revealed that amine groups in MEA-capped QDs were responsible for absence of ECL. The reaction of amine group with superoxide radical leads to the quenching of ECL. The ECL quenching of MPA-capped CdTe QDs was further used to detect melamine. Under the optimum conditions, the ECL intensity of the constructed photoelectric sensors was linear with the logarithm of concentration of melamine within the concentrations range of10-9to10-5M and the detection limit was found to be6.74×10-10M.Both electrochemiluminescence (ECL) and photoluminescence (PL) properties of the hybrid system of tris(2,2′-bipyridyl)ruthenium(II)([Ru(bpy)3]2+)/2-(dibutylamino) ethanol (DBAE) and QD have been investigated, respectively. Unexpectedly, we explore that ECL of the Ru(bpy)3]2+/DBAE system can be efficiently quenched by various types of QDs. In addition, ECL quenching of the [Ru(bpy)3]2+/DBAE system is independent on the core size and the surface charge of QDs, indicating that the quenching effect does not originate from resonance energy transfer between the [Ru(bpy)3]2+/DBAE system and QDs. Photoluminescence properties of the hybrid system under electrochemical control and electron spin resonance (ESR) measurements further reveal that a charge transfer between QDs and the radical-state DBAE is responsible for the ECL quenching of the [Ru(bpy)3]2+/DBAE system. Through this mechanism, we constructed the dissolved oxygen and hydrogen peroxide photoelectric sensors, detection limit reached44.43μM and8.79μM, respectively. We further demonstrate that such electron transfer could be switched to energy transfer by controlling the distance between [Ru(bpy)3]2+/DBAE ECL and QDs. And the energy/electron transfer process between the [Ru(bpy)3]2+/DBAE ECL and QDs is implemented to develop a novel platform for immune sensing. We used the ECL signal of [Ru(bpy)3]2+/DBAE and ECL-RET signal as sensor response signal to construct two IgG sensor, the detection limit is0.06ng/mL and0.91ng/mL, respectively.We investigate chiral supraparticle assemblies formed in a facile process driven by electrostatic attraction between positively charged NRs and negatively charged chiral CdTe NPs. Different types of assemblies were observed depending on the molar NR/NP ratios. When the NRs/NPs ratio was1:15, the (Side-by-Side)SBS SP assembly of the gold NRs formed, this bisignated plamonic CD signal induced by the chiral NPs absorbed on the side of NRs, and enhanced by the hotspots of two different hybrid modes. When NRs/NPs ratio was1:60, large assembly were appeared and strange CD response were obtained; when the NRs/NPs ratio was1:180, the majority of NRs were scattered among some small sheets randomly and minority of NRs went into solution separately, the origin of this plasmonic CD is also from the chiral NPs around the NRs, approximately only a fifteenth of SP1. This new chiral SP assemblies combine NRs with chiral semiconductor NPs should have a great potential in chiral sensing.We developed a new fim sensor consisted with QDs with different PL color and stabilizer by using Layer-by-Layer (LBL) assembly method, this sensor use the ratio of the two PL colour as optical signal response, set up a rapid, visualization, wide detection range of TNT sensors. For the two QDs with different PL colour had different complexing power with TNT, so when the concentration of TNT was lower, only the outside QDs with red color has been quenched by TNT, so the PL color of the sensor changed from red to green with the concentration of TNT increased, and then when the concentration of TNT was high, not only the outside QDs with red color has been quenched, the inside QDs with green color has also been quenched by redundant TNT, so the PL color of the sensor continuely changed from green to red with the concentration of TNT increased, and at last the whole PL intensity was quenched by TNT. And although the color was almost same, but the intensity was obviously different. And for accurately detection of the TNT concentration, we establishes two standard curve, the ratio of two color intensity of the constructed photoelectric sensors was linear with the logarithm of concentration of TNT, suitable for low concentration and high concentration of TNT respectively, also has a good sensitivity. And last, we describe a new micro-assay sensor by Bio-dot robot, which has same construction with the LBL film sensor, could visually detect TNT in differet concentration at the same time.