We report a facile and sensitive analytical method for the detection of pathogenic bacteria. Salmonella bacteria in milk were captured by antibody-conjugated magnetic nanoparticles (MNPs) and separated from analyte samples by applying an external magnetic field. The MNP–Salmonella complexes were re-dispersed in a buffer solution then exposed to antibody-immobilized TiO₂ nanocrystals (TNs), which absorb UV light. After magnetically separating the MNP–Salmonella–TN complexes from solution, the UV-Vis absorption spectrum of the unbound TN solution was obtained. Because the light absorption intensity was reversely proportional to the Salmonella concentration, the assay exhibited high sensitivity toward low concentrations of Salmonella bacteria. The detection limit of Salmonella in milk was found to be more than 100 cfu mL⁻¹.

Nanoporous anodic aluminum oxide (AAO) microcantilevers are fabricated and MIL-53 (Al) metal-organic framework (MOF) layers are directly synthesized on each cantilever surface by using the aluminum oxide as the metal ion source. Exposure of the MIL53-AAO cantilevers to various concentrations of CO₂, N₂, CO and Ar induces changes in their deflections and resonance frequencies. The results of the resonance frequency measurements for the different adsorbed gas molecules are almost identical when the frequency changes are normalized by the molecular weights of the gases. In contrast, the deflection measurements show that only CO₂ adsorption induces substantial bending of the MIL53-AAO cantilevers. This selective deflection of the cantilevers is attributed to the strong interactions between CO₂ and the hydroxyl groups in MIL-53, which induce structural changes in the MIL-53 layers. Simultaneous measurements of the resonance frequency and the deflection are performed to show that the diffusion of CO₂ into the nanoporous MIL-53 layers occurs very rapidly, whereas the binding of CO₂ to hydroxyl groups occurs relatively slowly, which indicates that the adsorption of CO₂ onto the MIL-53 layers and the desorption of CO₂ from the MIL-53 layers are reaction limited.