Abstract
Development of gold nanoparticles (GNPs) for metal-ion sensing is an active research because of their high extinction coefficients and distance-dependent optical absorbance. The aims of this study are to improve the the analytical performance and to design new sensing strategies for GNP-based sensors. To improve the sensitivity of the GNP sensors with the dispersive-to-aggregated transformation, the minimization of electrostatic repulsion is suggested as well as the increase of the sensing moieties on the GNPs. For the model system, the recognition of K+ by 15c5-C4-/TA-GNPs, the adjustments of pH and ionic strength were carried out to reduce electrostatic repulsion and the optimizd sensing performance was achieved. Different from the dispersion-to-aggregation transformation, a novel sensing strategy that the aggregated GNPs recognize analytes followed by forming dispersion is also reported. The interparticle hydrogen bonds are introduced to trigger GNP aggregation. The recognition events break the hydrogen bonds and make the GNPs dispersive. The proof-of-concept study is the recognition of Pb2+ by using 15c5-C4-/TA-GNPs in the methanol solution. A visual sensing phenomenon with phase segregation is provided for the circumstances without instrumental assistance. An example demonstrated here is the detection of Cu2+ via the cysteine-copper chemistry. The fluffy flocculates resulting from the reaction of Cu2+ with cysteine are applied to recognize Cu2+ concentration range.