Inorganic Nanocrystals Synthesis And Their Sensor Applications

Fluorescence detection techniques have been widely applied in modern chemistry, biology research and medical diagnosis. For the analytes with trace levels, organic fluoreophores are most commonly used for signal transduction. Although these fluorophores are versatile and convenient to use, there are drawbacks that limit their applications limitations for further study.In most cases, there are only one or a few fluorophores that can signal a certain biomolecular recognition event and be attached to a biomolecule without interfering with its binding specificity or causing precipitate. Consequently, trace levels of biological analytes analysis can be particularly difficult, additional operation will be required to amplify the signals which can be time-consuming and hinder quantitative analysis. Furthermore, organic fluorephores are not very stable when exposed to a continuous light source. The biological and physiological environment is complex, which can lead to the degradation and phototbleaching of organic fluorophores. These factors can result in false signals and affect prolonged cell monitoring and imaging. Although most organic fluorophores can be conjugated with biomolecules, such as DNA and proteins, it is usually much more difficult, time-consuming, and expensive compared to routine applications.The rapid development of nanoscience and nanotechnology has illuminated a promising direction for new biomarkers. Nanoparticles with unique optical properties, high surface-to-volume ratio, and other size-dependent qualities have been used in bioimaging, labeling and sensing. By tuning the composition and surface modification, we could obtain the nanoparticle probes with enhanced fluorescence signal, increased sensitivity and prolonged detection time to generate better reproducibility.Lanthanides doped NaYF4 nanoparticles have unique upconversion luminescent properties that enable the conversion of low-energy photons (near infrared photons) into high-energy photons (visible to ultraviolet photons) via the multiphoton processes. This feature makes them ideal bioimaging materials with excellent advantages such as no autofluorescence from biotissues and a large penetration depth. By incorporating advanced features, the applications of upconversion nanoparticles can be expanded to biomedical fields such as specific targeting, multimodality imaging and therapeutic delivery.We synthesized a chemsensor based on BODIPY-functionalised silica nanoparticles to detect copper ions in ethanol-aqueous solution with high selectivity and sensitivity. Silica NPs are materials with high transparency, hydrophilic and biocompatible properties. They are usually stable in biological environment with little toxicity on living cells. BODIPY dye was conjugated with silica NPs to stabilize them in the solution and to improve the biocompatibility of the probe. Confocal fluorescence microscopy was employed for the detection of copper ions in living cells.NaYF4:Yb3+, Er3+ upconversion nanoparticles with pure hexagonal-phase, appropriate shape and size were produced (20-50 nm). Upon excitation at 980nm, the intensity ratio of the green fluorescence bands of the Er3+ dopant ions changes with temperature. A colloidal solution of NaYF4:Yb3+, Er3+ nanoparticles in water was heated and we got the thermal profiles. Then rhodamine B isothiocyanate was functionlized on the surface of UCNPs. Their temperature dependent UCL spectra were also investigated.