Synthesis And Sensing Application Of Several Fluorescent Nanomaterials

Compared to the conventional fluorescent molecules,fluorescent(phosphorescent)nanomaterials display lots of advantages of easy regulation of morphology and particle size,good photostability,as well as multi-functionalization.The application of fluorescent(phosphorescent)nanomaterials as optical sensors has become a research hotspot in many fields such as biomedicine,chemistry and optics.In this paper,some novel fluorescent and phosphorescent nanomaterials with good properties were synthesized including gold nanoparticals(Au NPs),carbon dots(CDs)and N-acetyl-L-cysteine(NAC)capped Mn-doped ZnS quantum dots(NAC-Mn:ZnS QDs),and based on the fluorescence(phosphorescence)quenching or enhancemence to establish new sensing platforms,achieving the determination of GSH,Cu2+,L-His and ATP.Chapter 1:The study progress in synthesis,characters and applications of fluorescent(phosphorescent)nanomaterials are reviewed.Including gold nanoparticals(Au NPs),carbon dots(CDs)and N-acetyl-L-cysteine(NAC)capped Mn-doped ZnS quantum dots(NAC-Mn:ZnS QDs).Thus we proposed the relevant design ideas.Chapter 2:Fluorescence resonance energy transfer(FRET)is a kind of energy transfer mechanism depending on the distance between donor and acceptor,which exhibited potential application in biosensors.In this study,an efficient fluorescence"turn-on" strategy for the detection of glutathione(GSH)has been established based on FRET between nitrogen and sulphur dual-doped carbon dots(N,S-CDs)and gold nanoparticles(Au NPs).A novel N,S-CDs was synthesized by a one-pot hydrothermal treatment of 3-aminothiophenol,which possessed excellent fluorescence property with the maximum emission wavelength of 530 nm.Then,the as-prepared N,S-CDs served as energy donor to transfer energy to Au NPs via FRET process,resulting in fluorescence quenching of N,S-CDs.However,the fluorescence of N,S-CDs was recovered efficiently by adding GSH into the mixture solution of N,S-CDs and Au NPs.Therefore,the FRET assembly of N,S-CDs and Au NPs was used as a fluorescence probe for the“turn-on”sensing GSH with the linear range from 3.8 to 415.1 ?M and the detection limit of 21 nM.This nanosensor platform was employed to monitor GSH in serum samples with satisfying results.Chapter 3:In the present study,a far-red fluorescence "off-on" sensing strategy has been constructed for sequential ratiometric determination of Cu2+ and L-histidine(L-His)based on fluorescence resonance energy transfer(FRET)system.N,S,P co-doped carbon dots(N,S,P-CDs)and N-acetyl-L-cysteine functionalized gold nanoclusters(NAC-AuNCs)are used in the FRET system,which serve as energy donor and acceptor,respectively.After adding NAC-AuNCs into the solution of N,S,P-CDs,the fluorescence of N,S,P-CDs is effectively quenched,while the far-red fluorescence of NAC-AuNCs appears.Cu2+ can decrease fluorescence of NAC-AuNCs,and then L-His can effectively recover the fluorescence of NAC-AuNCs.The possible reason is that the stronger affinity between Cu2+ and L-His can pull Cu2+ away from the surface of NAC-AuNCs.Through it all,the emission intensity of N,S,P-CDs remains nearly constant,so the ratio of fluorescence intensities at 485 and 625 nm exhibits a linear correlation to the Cu2+ and L-His concentration,respectively.The sensing platform shows a good selectively towards Cu2+and L-His with a linear range of 0.65-26.58 ?M and 3.13-56.25 ?M and the determination limit of 0.50 ?M and 0.374 ?M,respectively.The proposed method has been successfully used for Cu2+ and L-His determination in real samples with satisfying results.Chapter 4:In this paper,N-acetyl-L-cysteine-modified Mn-doped ZnS quantum dots(NAC-Mn:ZnS QDs)were successfully prepared and functionalized by single-stranded DNA 1 and DNA 2 to obtain QDs 1 and QDs 2 respectively.sDNA-NAC-Mn:ZnS QDs was obtained by mixing QDs 1 and QDs 2 equally.The aforementioned quantum dot materials have excellent room temperature phosphorescence properties,which are combined with the specific recognition properties of nucleic acid aptamers to construct an phosphorescence“off-on”sensor for the determination of ATP.The principle of detection is as follows:firstly,when the ends of the designed DNA 1 and DNA 2 chain are connected,they can just form complementary bases with ATP aptamers.Therefore,when ATP aptamers are added to the solution of sDNA-NAC-Mn:ZnS QDs,the luminescent sites of the quantum dots are blocked due to the base complementarity,resulting in the room temperature phosphorescence quenching(turn-off);After the addition of ATP,the ATP nucleic acid aptamer is preferentially bound to ATP,which makes the previously formed complementary chain open and release free QDs 1 and QDs 2,thus enhancing the room temperature phosphorescence signal(turn-on).Therefore,the detection of target molecule ATP can be realized based on this principle,with the linear range and detection limit of 0.2-60 ?M and 10.5 nM respectively.The phosphorescent sensor does not require complex pretreatment,can effectively eliminate the interference of spontaneous fluorescence and scattered light,and improve the sensitivity and selectivity of detectionChapter 5:We summarized the research results about the gold nanoparticals(Au NPs),carbon dots(CDs)and N-acetyl-L-cysteine(NAC)capped Mn-doped ZnS quantum dots(NAC-Mn:ZnS QDs)as original fluorescence(phosphorescence)sensors for applications in ions and small molecules determination.And the future experimental work is prospected.