Construction of a Graphene/Au-Nanoparticles/Cucurbit[7]uril-Based Sensor for Pb(2+) Sensing.

The development of highly sensitive and selective methods for the detection of lead ion (Pb(2+)) is of great scientific importance. In this work, we develop a new surface-enhanced Raman scattering (SERS)-based sensor for the selective trace measurement of Pb(2+). The SERS-based sensor is assembled from gold nanoparticles (AuNPs) and graphene using cucurbit[7]uril (CB[7]) as a precise molecular glue and a local SERS reporter. Upon the addition of Pb(2+), CB[7] forms stronger complexes with Pb(2+) and desorbs from AuNPs, resulting in a sensitive "turn-off" of SERS signals. This SERS-based assay shows a limit of detection (LOD) of 0.3 nm and a linear detection range from 1 nm to 0.3 µm for Pb(2+). The feasibility of the assay is further demonstrated by probing Pb(2+) in real water samples. This SERS-based analytical method is highly sensitive and selective, and therefore holds promising applications in environmental analysis.

In situ regulation nanoarchitecture of Au nanoparticles/reduced graphene oxide colloid for sensitive and selective SERS detection of lead ions.

In this work, the colloid of Au nanoparticles (AuNPs)/reduced graphene oxide (rGO) was synthesized by growth AuNPs on rGO via the reduction of HAuCl4 on graphene oxide (GO) nanosheets. The nanoarchitecture of the colloid could be controllably regulated through in-situ Pb(2+)-enhanced gold leaching reaction, which made the colloid be a flexible surface-enhanced Raman scattering (SERS) platform for Pb(2+) detection. Upon the addition of Pb(2+), the Raman signal of graphene underwent significant descent due to the decrease of the amount of the "hot spots", which was originated from Pb(2+)-accelerated dissolution of AuNPs on the graphene surface in the present of thiosulfate (S2O3(2-)). Based on the change of SERS signal through in situ regulation the nanoarchitecture of the colloid, a sensitive and selective strategy for Pb(2+) measurement was developed with a linear range from 5nM to 4µM as well as a low detection limit of 1nM. Furthermore, the SERS-based method was applied for the determination of Pb(2+) in water samples with satisfactory results.

A label-free colorimetric sensor for Pb2+ detection based on the acceleration of gold leaching by graphene oxide.

In this work, we developed a novel, label-free, colorimetric sensor for Pb(2+) detection based on the acceleration of gold leaching by graphene oxide (GO) at room temperature. Gold nanoparticles (AuNPs) can be dissolved in a thiosulfate (S2O3(2-)) aqueous environment in the presence of oxygen; however, the leaching rate is very slow due to the high activation energy (27.99 kJ mol(-1)). In order to enhance the reaction rate, some accelerators should be added. In comparison with the traditional accelerators (metal ions or middle ligands), we found that GO could efficiently accelerate the gold leaching reaction. Kinetic data demonstrate that the dissolution rate of gold in the Pb(2+)-S2O3(2-)-GO system is 5 times faster than that without GO at room temperature. In addition, the effects of surface modification and the nanoparticle size on the etching of AuNPs were investigated. Based on the GO-accelerated concentration-dependent colour changes of AuNPs, a colorimetric sensor for Pb(2+) detection was developed with a linear range from 0.1 to 20 µM and the limit of detection (LOD) was evaluated to be 0.05 µM. This colorimetric assay is simple, low-cost, label-free, and has numerous potential applications in the field of environmental chemistry.