Synthesis And Application Of Metal Ion Probe Based On Fluorescent Functionalized Mesoporous Silica Nanoparticles

It is known that the mesoporous silica nanoparticles(MSNs) have unique characteristics such as high specific surface area, stable fluorescence characteristics, excellent solvent dispersibility, and abundant hydroxyl groups on their inner and outer surfaces easy to be modified. Therefore, MSNs were widely used in drug delivery, cell imaging and ion detection. We choose the conjugated polymer functionalized fluorescent MSNs as the host material to detect metal ions through fluorescence resonance energy transfer(FRET). The concrete work is as follows:1. The conjugated polymer-poly(p-phenylenevinylene)(PPV) functionalized fluorescent hybrid MSNs(PPV@MSN) with green-light-emission were fabricated. Then red-light Cd Te quantum dots(QDs) were absorbed onto the MSNs by electrostatic interaction using branched polyethyleneimine(PEI) as the polyelectrolyte. The resulted PPV@MSN@Cd Te hybrid nanoparticles had excellent water dispersion and showed the dual-emission centered at 500 nm and 717 nm in aqueous solution, which is necessary to detect Cu2+. Upon addition of Cu2+, Cu2+ can be captured by the amino groups of the polyethyleneimine to form an absorbent complex with a broad absorption bands from 450 to 800 nm, resulting in a strong quenching of red-emission at 717 nm from Cd Te QDs on the surface of nanoparticles via fluorescence resonance energy transfer(FRET). However, the green-emission at 500 nm of poly(p-phenylenevinylene) can be remained, so the fluorescence detection for Cu2+ can be carried out. The addition of Cu2+ induced the fluorescent evolution of the nanoprobe from red to green emission. The quenching fluorescence of PPV@MSN@Cd Te exhibited a distinct linear response to this equation toward Cu2+ in the concentration range of 3×10-8~1.6×10-7 M. The nanoprobe provided an efficient platform for the sensing of Cu2+ with a detection limit of 31.2 n M. Compared with pure QDs, the nanoprobe had excellent selectivity for Cu2+ and anti-interference ability of other metal ions.2. The PPV@MSN@PGMA NPs were first prepared by grafting poly(glycidyl methacrylate)(PGMA) brushes onto the fluorescent MSNs via RAFT polymerization. Then β-Cyclodextrin(CD) was modified onto the surface of these nanoparticles by ring-opening the epoxy groups with CD-NH2. Moreover, mercury ion-recognition element, adamantine modified spirolactam rhodamine amine(SRh B)(AD-SRh B), which is known for its capability to form stable host-guest inclusion complexes with β-CD derivatives, was anchored inside the cyclodextrin cavity to form a new type of ratiometric metal ion probe(PPV@MSN@PGMA@CD@AD-SRh B) based on the fluorescent MSNs as the detecting platform. In the absence of Hg2+, the synthetic probe NPs showed strong green fluorescence of PPV(496 nm). Upon the addition of Hg2+, the rhodamine spirocyclic ring opened, and the fluorescence(578 nm) of rhodamine was observed. Moreover, the fluorescent intensity at 578 nm was enhanced by FRET. Thus, the prepared fluorescent probe exhibited the ratiometric response to quantitatively detect Hg2+ with a detection limit of 4.2 μM. On the other hand, compared with pure AD-SRh B as probe, the novel ion probe fabricated by us can selectively detect Hg2+ from other correlative metal ions especially Fe3+ and Al3+.