Study Of Upconverting Nanomaterial And Boron-dipyrromethene Probe For Sensing And Biological Analysis

Lanthanide ions exhibit unique luminescent properties, including the ability to convert near infrared long-wavelength excitation radiation into shorter visible wavelength through a process known as photon upconversion. In recent years lanthanide-doped upconversion nanocrystals have been developed as a new class of luminescent optical labels that have become promising alternatives to organic fluorophores and quantum dots for applications in biological assays and medical imaging. These techniques offer low autofluorescence background, large anti-Stokes shifts, sharp emission bandwidths, high resistance to photobleaching, and high penetration depth and temporal resolution. Our research focuses on various synthetic approaches and possibilities for chemical tuning of upconversion properties, as well as biological applications of these luminescent nanocrystals. Carrier-based chemical sensors are conventional analysis methods in analytical chemistry field with well-defined theory and expected experiment results. However, there are still some drawbacks exposed during applications, such as low limit of detection, biological application and so on. Lots of works have been done:(1) We proposed a chloride selective optode incorporating NaYF4:Er, Yb upconverting nanorods and chromionophore ETH5294 together in hydrophobic polymer matrixes. Because the excitation source of 980 mn, as well as the emission wavelength lies in the near-infrared region, the background absorption and autofluorescence of the biological sample could be eliminated, and ensure the sensitivity and selectivity of the sensor.(2) Surface modification of lanthanide-doped nanocrystals not only improve photostability of the nanocrystals with desirable interfacial properties, but also provide a potential platform for attaching biological macromolecules for various biomedical applications. The luminescent probes are based on fluorescence resonance energy transfer (FRET) between upconverting material that serve as donor and rhodamine acceptors that are immobilized to the surface the nanocrystals. We can achieve the specificity analysis through change the linker between the upconverting nanocrystals and fluorescent dye.(3) Designed and prepared a solid-contact Pb2+-selective-electrodes with polymer-carbon nanotube composites. This electrode use the MMA-BA as the framework of the sensing membrane. The speciality of MMA-BA and polymer-carbon nanotube leads to excellent reproducibility of the electrode and makes an essential role to enhance the hydrophobicity of the membrane-conductor interface, which contributes to the more stable potential signal by elimination of undesirable water layer at the interface. The limit of detection in nanomolar range opens the possibility of their use for trace analysis of Pb2+ in environmental water samples.(4)We synthetize near-infrared fluorescent probe based on BODIPY fluorophore 8-nitrophenyl-3,5-dipiperidin-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (NPBDP). We characterize the fluorescent probe and find out the probe is of excellent characters. It has high quantum yield, low toxicity, great specifity and reproducibility. The NPBDP probe are used to detect and image the intracellular lipid droplets by fluorescence microscopy.