Preparation And Fluorescent Labeling Of Molybdenum Oxide Quantum Dots

Transition metal oxide quantum dots?TMO QDs?have attracted great attention in basic scientific researches due to their unique electrical,optical,and mechanical properties.And molybdenum oxide quantum dots?MoO_x QDs?have relative high stability,low toxicity and better biocompatibility,special quantum size effect and surface effect characteristic.These characteristics make researchers pay more and more attention to the synthesis of MoO_x nanomaterials and to their potential applications in more and more fields.The electrical,optical,magnetic,and chemical properties of thus QDs are dependent greatly on the sizes and size distributions of the obtained nanocrystals,so better disperse MoO_x QDs with uniform sizes are of significant and challenging.In this paper,a reduction method was proposed to synthesize better disperse MoO_x QDs with stable fluorescence properties by using ethanol as reducing agent and surfactant of oleylamine as modified agent to explore the potential application of MoO_x QDs in the biological field.A one-pot method was proposed to synthesize MoO_x QDs by using molybdenum disulfide?Mo S₂?and hydrogen peroxide?H₂O₂?as precursor and oxidant.And the optimum experimental conditions were determined.MoO_x QDs with better dispersion were prepared by improving the synthesis process.A reduction method was proposed to synthesize better disperse MoO_x QDs with stable fluorescence properties by using ethanol as reducing agent and surfactant of oleylamine as modified agent.The composition and the structure between the components were characterized and detected by FTIR and X-ray diffraction?XRD?.The characteristic vibration bands of Mo₃-O,Mo-O-Mo and Mo-O were obtained from FTIR and the morphology of the prepared MoO_x QDs was characterized and detected by AFM and TEM.MoO_x QDs with better dispersity and uniform-sized morphology were obtained and MoO_x QDs displayed an average size of 1.96 nm.The height of MoO_x QDs was in the average values of about 2.8 nm.The QDs revealed its crystallization with a lattice spacing of 0.23 nm,which was associated with the?060?plane.The fluorescence properties of MoO_x QDs were characterized and detected by Fluorescence spectrometer.When excited with a 350 nm beam,the PL spectrum of MoO_x QDs gave a strong peak at 435 nm.MoO_x QDs emitted bright blue fluorescence under UV light?at 365 nm?,and the excellent stability of MoO_x QDs could be observed.Factors that influenced the syntheses of MoO_x QDs were discussed,and the highest value of fluorescence intensity could be gained under the adding amount of oleylamine of 5mL and the reaction time for 24 h.It caused the creation of the red shift of the emission wavelength and the increasing of the sizes of QDs.HeLa cells were selected as models and were incubated with the prepared MoO_x QDs.The fluorescence image of HeLa cells was observed through fluorescence microscope and the bright blue fluorescence could be observed within the incubated cells.In addition,the HeLa cells incubated with the MoO_x QDs did not weaken the cell activity,and could maintain their normal morphology.HeLa cells were incubated and the in vitro cytotoxicity testing by MTT assay with HeLa cells as a model were proceeded.The MTT testing results showed that no obvious cytotoxicity was observed for HeLa cells with the concentration of MoOx QDs ranging from 25 to 400?g/mL.The physiological stability of MoO_x QDs was investigated and the results showed that the prepared MoO_x QDs could remain the stable state in water,in high salt solution?PBS?and in cell medium for two weeks.Moreover,the characteristic UV-vis absorption at 234 nm showed negligible changes and there was no distinct precipitates,indicating the well stability of MoO_x QDs.