Optical Sensing of Toxic Cyanide Anions Using Noble Metal Nanomaterials

Abstract

Water toxicity, one of the major concerns for ecosystems and the health of humanity, is usually attributed to inorganic anions-induced contamination. Particularly, cyanide ions are considered one of the most harmful elements required to be monitored in water. The need for cyanide sensing and monitoring has tempted the development of sensing technologies without highly sophisticated instruments or highly skilled operations for the objective of in-situ monitoring. Recent decades have witnessed the growth of noble metal nanomaterials-based sensors for detecting cyanide ions quantitatively as nanoscience and nanotechnologies advance to allow nanoscale-inherent physicochemical properties to be exploited for sensing performance. Particularly, noble metal nanostructure e-based optical sensors have permitted cyanide ions of nanomolar levels, or even lower, to be detectable. This capability lends itself to analytical application in the quantitative detection of harmful elements in environmental water samples. This review covers the noble metal nanomaterials-based sensors for cyanide ions detection developed in a variety of approaches, such as those based on colorimetry, fluorescence, Rayleigh scattering (RS), and surface-enhanced Raman scattering (SERS). Additionally, major challenges associated with these nano-platforms are also addressed, while future perspectives are given with directions towards resolving these issues.

Ultrasensitive Monitoring of Cyanide Concentrations in Water Using a Aucore–Agshell Hybrid-Coating-Based Fiber Optical Sensor

“…Sensors developed in recent years for CN – detection are mainly based on fluorescence on/off thanks to advantages such as high sensitivity, selectivity, and quick response. − However, the challenge of this method is choosing a luminous material and setting the procedures for monitoring changes in the fluorescence spectrum. Most organic fluorophores are toxic and are only soluble in organic solvents, thus causing limitations in the manufacturing process and practical applications . To overcome this limitation, metal nanoparticles have been used as fluorescence-based chemosensors but have not achieved high sensitivity efficiency …”

“…Moreover, Au and Ag are known to be low-toxicity, highly biocompatible, and thus user-friendly compared to the sensors based on fluorescence quenching: The sensors developed in recent years for high sensitivity CN – detection that were mainly based on fluorescence on/off switching. − faced challenge of inevitable use of organic solvent for given organic fluorophores. This aspect caused limitation in easy manufacturing process and environment-friendly practical applications . However, use of metal nanoparticles in fiber sensor format as presented above could overcome these difficulties …”

“…A minute change in the dielectric properties of an ambient medium causes a change in both the plasmonic absorbance and its spectral peaks. The LSPR effects have been demonstrated for a wide range of analytes such as CN – and biomolecules …”

“…Hajizadeh et al used colloidal Ag NPs for rapid detection of CN – in solution with the linear response range of the concentration from 16.7–133.3 μmol/L at around the wavelength of 394 nm, while the LOD was 1.8 μM . Au NP-based LSPR was also employed for colorimetric sensors that detected CN ions with the LOD at the nanomolar concentration level. ,− …”

Efficient cyanide sensing using plasmonic Ag/Fe3O4 nanoparticles

“…[21][22][23] H. Ju group have been reviewed optical sensing of cyanide anions by noble metal nanomaterials. 24 Metal NPs, especially silver and gold NPs, with the distinct optical and electronic properties have received signicant attention for the fabrication of plasmonic sensors. [25][26][27] The collective excitations of electrons in the conduction band in resonance with an electromagnetic eld of incoming light (coherent oscillation of the metal conduction and free electrons at the surface of metal nanoparticles, in the local enhanced electromagnetic eld called surface plasmon resonance, SPR 28 ) and consequently an intense excitation signal can enhance weak multi-photon processes leading to surface enhanced spectroscopy that improve the sensitivity dramatically.…”