A gold nanorod-based plasmonic platform for multi-logic operation and detection

Sequential colorimetric sensing of cupric and mercuric ions by regulating the etching process of triangular gold nanoplates

A triangular gold nanoplate (AuNPL)-based colorimetric assay is presented for ultrasensitive determination of cupric ions (Cu²⁺⁾ and mercuric ions (Hg²⁺) in sequence. AuNPLs were found to be etched efficiently when producing triiodide ions (I₃^-) by a redox reaction between Cu²⁺ and iodide ions (I^-), leading to a change of the shape of AuNPLs from triangular to sphere along with a color change from blue to pink. In the presence of Hg²⁺ the etching of AuNPLs was suppressed due to the consumption of I^- by the formation of HgI₂. With an increase of the concentration of the Hg²⁺ a transformation from sphere to triangular in the shape of AuNPLs occurred with a color change from pink to blue. The evolution of AuNPLs from etching to anti-etching state by sequential addition of Cu²⁺ and Hg²⁺ was accompanied with color variations and band shifts of localized surface plasmon resonance (LSPR), allowing for visual and spectroscopic determination of Cu²⁺ and Hg²⁺ successively within 15 min. In the range 0.01-1.5 μM for Cu²⁺ and 0.02-3.0 μM for Hg²⁺, the linear relationship between the band shift values and the target ions concentration was found good (R² > 0.996). The limit of detections (3S/k) was 19 nM for Cu²⁺ and 9 nM for Hg²⁺, respectively. The lowest visual estimation concentration was 80 nM for both Cu²⁺ and Hg²⁺ through the distinguishable color changes. This system exhibited desirable selectivity for Cu²⁺ and Hg²⁺ over other common ions tested. The method has been successfully applied to sequential determination of Cu²⁺ and Hg²⁺ in real water and food samples. Graphical abstract Scheme 1 Schematic illustration for sequential detection of Cu²⁺ and Hg²⁺ based on etching of AuNPLs.

Fabrication of prime number checkers based on colorimetric responses of gold nanoparticles

In this work, we demonstrated the fabrication of molecular prime number checkers based on the concentration- and sequence-dependent colorimetric responses of citrate-capped gold nanoparticles (Au NPs) to two simple model chemicals, i.e. cysteine (Cys) and Hg²⁺ ions.