Synthesis Of Naphthalimide-Rhodamine Fluorescent Probes And Application Researches

Reactive fluorescent probes is based on the specific chemical reaction between the probes and analytes,resulting in fluorescence signal changes to achieve the purpose of detection.With the ever-increasing demands on the probe's high sensitivity and selectivity for analytes,reaction-type probes based on specific chemical reactions(reversible or irreversible)have emerged.The ratiometric fluorescent probe based on fluorescence resonance(trans-bond)energy transfer has become a research.In this paper,based on the scaffolds of ratiometric fluorescent probe and the specific recognition of reaction sites to analytes,three ratiometric naphthalimide-rhodamine fluorescent probes RHSDN,CyRSN and RHDN were designed and synthesized,in which 1,8-naphthalimide fluorophores with good stability and easy modification and rhodamine B fluorophore with sensitive "off-on" process as a signal reporter group,and two novel naphthalimide dendrons PAN and PADN were synthesized while 4-bromo-1,8-naphthalic anhydride was the raw material,characterized by 1HNMR,13C NMR and HRMS techniques.We investigated three ratiometric naphthyimide-rhodamine fluorescent probes toward the specific recognition of the analytes HCIO,Hg2+,and Fe3+ with their application to hypochlorous acid cell imaging and the actual detection of heavy metal ions respectively.Meanwhile,the experiment also measured the aggregation induced fluorescence properties of the naphthalimide dendrimer PAN and PADN,and prepared silica nanoparticles loaded dyes,and studied their spectral properties.The details are as follows:1.Hypochlorous acid,as strong oxidant,plays a decisive role both in daily life and organism.A new ratiometric naphthalimide-rhodamine two-photon fluorescent turn-on probe RHSDN with a "naked-eye" recognition capability for hypochlorous acid has been rationally designed,in which rhodamine-thiosemicarbazide and pyridine-naphthalimide were connected by phenyl spacer.In presence of HClO,RHSDN exhibits high sensitivity,selectivity,acid-alkali resistance and fast response time with the detection limit of 9.6 � 10-8 M toward HClO based on hypochlorous acid-triggered intramolecular desulfurization-cyclization and fluorescence resonance energy transfer mechanism.Under the Ti:sapphire pulsed laser's 800 nm irradiation,rhodamine spirolactam closed-ring of RHSDN toward hypochlorous acid affords an OFF-ON signal response with an appearance and drastic enhancement of fluorescence emission peak at 600 nm accompanied by a dramatic color change from colorless to brightly pink.RHSDN has been employed for the imaging of artificially loaded HClO with satisfying results,which further displayed its valuable applications in biological systems.Besides,the probe also has a specific recognition of Hg2+with the detection limit of 9.2�10-8 M,and the response is not disturbed by other metal ions interference with the fluorescence resonance energy transfer efficiency of 73%.2.A smart two-photon fluorescent platform based on desulfurization-cyclization was developed by attaching rhodamine to the cyanine skeleton through Knoevenagel reaction.Based on the platform,probe CyRSN rationally designed and synthesized,in which morpholinyl naphthalimide and modified rhodamine thiohydrazide were linked to form a structure of monothio-bishydrazide.It exhibits excellent two-photon properties toward Hg2+under the Ti:sapphire pulsed laser's 800 nm irradiation,allowing the naked-eye and fluorescence "turn-on" signal at 746 nm to distinguish obviously.The addition of Hg2+ to probe ensured that naphthalimide donor and modified rhodamine acceptor were connected with electronically conjugated bonds(1,2,4-oxadiazole).Hence,a typical TBET process took place,resulting in the increase of modified rhodamine NIR emission at 746 nm by about 34-fold.The chemodosimeter exhibits a stable response for Hg2+ over other metal ions with a detection limit of 1.91 � 10-7 M and high sensitivity,a rapid response time and pH independent in medium condition(pH 6.0-10.0).In addition,probe CyRSN was successfully applied in the detection and quantification of Hg2+ in water samples with satisfactory recovery results.3.The selective recognition for Hg2+,Fe3+ and behavious of response to H+ of RHDN in the mixture ethanol and water solution were studied.The probe REPN exhibited typical FRET signal from pyridine-naphthalimide moiety to rhodamine moiety which was induced by Hg2+ with fluorescence resonance energy transfer of 82%and a detection limit of 2.72�10-6 M.the probe REPN performed segmented and ratiometric detection behavior via PET process combined with the classical ring-opening sensor system in the presence of Fe3+,the detection limit was 2.3�10-7 M.In the acidic solution,the color of the solution were all changed from colorless to pink,the characteristic peak of rhodamine moiety and naphthalimide moiety were all enhanced with the increased acidity.4.Aggregation induces fluorescence effect of naphthalimide dendrons PAN and PADN was studied and the silica nanoparticles loaded fluorescent molecules PAN and PADN were prepared and their fluorescence properties were studied.According to TEM imaging,the nanoparticles were dispersed in aqueous solution,the silica nanoparticles PAN/SiO2 and PADN/SiO2 not only maintain the fluorescent properties of the dye,but also have good stability and biocompatibility,and expand the application of naphthalimide fluorescent molecules in nanoparticle materials.Additionally,dye PADN was successfully applied for cell imaging,getting clear green-field photograph,which indicated a better uptake by lung cancer cells A-549 and suggested its promising application for biosensors.