Sensitive Detection Of Heavy Metal Ions Research Articles

A Sulfur-Containing Capsule-Based Metal-Organic electrochemical sensor for Super-Sensitive capture and detection of multiple Heavy-Metal ions

Development of an effective way for super-sensitive capture and sensing of heavy metal ions (HMIs) is a great challenge because they are extremely toxic to public health and environment. Herein, a new sulfur-containing nano-capsule-based electrochemical metal–organic framework (MOF) sensor [Co2(TMC4R)(1,4-BDC)2(μ2-H2O)]·3DMF·CH3OH·5CH3CN·H2O (Co-TMC4R-BDC) was designed for capture and detection of HMIs in aqueous solutions (TMC4R = tetra(4-mercaptopyridine)calix[4]resorcinarene, 1,4-BDC = 1,4-benzenedicarboxylic acid and DMF = N,N’-dimethylformamide). Remarkably, the designed MOF sensors exhibited excellent capture and detection performances for HMIs under the optimal experimental condition. The wide linear ranges of 0.05–12.0, 0.05–13.0, 0.1–17.0 and 0.75–18.0 μM are obtained for Cu2+, Pb2+, Cd2+ and Hg2+, respectively. The corresponding limit of detection (LOD) values are 13, 11, 26, and 18 nM, respectively. Particularly, the LOD values for Cu2+, Pb2+ and Cd2+ are lower than the standard drinking water ones from the World Health Organization. X-ray photoelectron spectroscopy (XPS) confirmed that the exposed S atoms of the nano-capsule units effectively captured HMIs through the complexation between S atoms and HMIs. Further, density functional theory (DFT) calculations indicated the presence of cation···π interactions between phenyl rings and HMIs. Thereby, the synergistic effects accomplished the effective capture and sensitive detection of HMIs. This work provides a feasible strategy for the capture and electrochemical detection of HMIs in an aqueous solution with the sulfur-containing MOF sensors.

Monolayer g-C3N4 Fluorescent Sensor for Sensitive and Selective Colorimetric Detection of Silver ion from Aqueous Samples.

Rapid and sensitive detection of heavy-metal ions in natural water environments worldwide is urgently needed because of their severe threats to human health. In the present work, monolayer graphite-like flake C3N4 (g-C3N4) materials were applied as a new fluorescent sensor for the detection of trace silver ion in aqueous solution. The thickness of synthesized g-C3N4 was 0.45nm and obtained by exfoliating twice with ultrasonic. With the presence of ethylene diamine tetraacetic acid as a screening agent, the highly sensitive sensor reached a low detection limit of 52.3nmol/L for silver (I) ion and there was no disturbance when silver (I) ion coexisted with other metal ions in water samples. Under the optimal conditions, the monolayer g-C3N4 was successfully used to detect trace silver (I) ion in different environmental water and drinking water samples.

Detection of heavy-metal ions using liquid crystal droplet patterns modulated by interaction between negatively charged carboxylate and heavy-metal cations

Herein, we demonstrated a simple, sensitive, and rapid label-free detection method for heavy-metal (HM) ions using liquid crystal (LC) droplet patterns on a solid surface. Stearic-acid-doped LC droplet patterns were spontaneously generated on an n-octyltrichlorosilane (OTS)-treated glass substrate by evaporating a solution of the nematic LC, 4-cyano-4′-pentylbiphenyl (5CB), dissolved in heptane. The optical appearance of the droplet patterns was a dark crossed texture when in contact with air, which represents the homeotropic orientation of the LC. This was caused by the steric interaction between the LC molecules and the alkyl chains of the OTS-treated surface. The dark crossed appearance of the acid-doped LC patterns was maintained after the addition of phosphate buffered saline (PBS) solution (pH 8.1 at 25°C). The deprotonated stearic-acid molecules self-assembled through the LC/aqueous interface, thereby supporting the homeotropic anchoring of 5CB. However, the optical image of the acid-doped LC droplet patterns incubated with PBS containing HM ions appeared bright, indicating a planar orientation of 5CB at the aqueous/LC droplet interface. This dark to bright transition of the LC patterns was caused by HM ions attached to the deprotonated carboxylate moiety, followed by the sequential interruption of the self-assembly of the stearic acid at the LC/aqueous interface. The results showed that the acid-doped LC pattern system not only enabled the highly sensitive detection of HM ions at a sub-nanomolar concentration but it also facilitated rapid detection (<10min) with simple procedures.