Continuous resonance Rayleigh scattering determination of titanium and iron ions using an Fe₃O₄@MIP nanoprobe

A novel magnetic nanostructured molecularly imprinted polymer probe (Fe₃O_{4 50nm}@MIP) was developed for the continuous detection of Ti⁴⁺/Fe³⁺. The synthesis employed 50 nm Fe₃O₄ nanoparticles as the core matrix, with Ti⁴⁺ and Fe³⁺ serving as template molecules. Functional monomers α-methylacrylic acid (MAA) and acrylamide (AM) were used, along with ethylene glycol dimethacrylate (EGDMA) as the crosslinking agent and 2,2'-azobisisobutyronitrile (AIBN) as the polymerization initiator, utilizing a microwave-assisted procedure. The nanomaterials were analyzed using molecular spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis, vibrating sample magnetometry, and scanning electron microscopy (SEM). The nanoprobe showed a strong resonance Rayleigh scattering (RRS) peak at 380 nm. The RRS signal decreased as the concentrations of Ti⁴⁺ and Fe³⁺ increased in the presence of tiron (Tir), respectively. Upon the addition of NaF, Fe³⁺ was effectively masked, and the enhancement of the RRS signal intensity was attributed to Ti⁴⁺. The linear ranges for Ti⁴⁺ and Fe³⁺ were found to be 0.5-3.5 nmol L^-1, with detection limits of 0.39 nmol L^-1 for Ti⁴⁺ and 0.37 nmol L^-1 for Fe³⁺. Due to the magnetic properties of Fe₃O₄@MIP, the nanomaterials were enriched by magnetic separation, resulting in a lower detection limit (LOD) of 5 pmol L^-1 for Ti⁴⁺ and Fe³⁺. The method was successfully applied to determination of Ti⁴⁺/Fe³⁺ in real water samples, yielding a relative standard deviation (RSD) between 2.68% and 9.78% and recoveries ranging from 91.7% to 108.2%.