Heavy metal-contained wastewater in China: Discharge, management and treatment

The present work describes, for the first time, in
situ electrochemical preparation of dendrimer-encapsulated
Cu nanoparticles using a self-assembled monolayer of fourthgeneration
amine-terminated polyamidoamine (PAMAM)
dendrimer as the template. Atomic force microscopy (AFM)
and X-ray photoelectron spectroscopy (XPS) studies of the
modified surface confirmed the presence of Cu nanoparticles
entrapped in dendrimer film. Au electrode modified with a
monolayer of the dendrimer enables preconcentration and
subsequent voltammetric detection of Cu2+ at picomolar
concentrations. Further, Cu nanoparticles in the dendrimer
monolayer could be electrochemically derivatised to Cu
hexacyanoferrate, which exhibits specific crystal planes,
unlike the random distribution of crystal planes in bulkformed
Cu hexacyanoferrate, which is another catalytically
active material for sensor applications.

Electrochemical preparation of copper–dendrimernanocomposites: picomolar detection of Cu2+ ions

FRET-based innovative assays for precise detection of the residual heavy metals in food and agriculture-related matrices

Heavy metal ions are highly toxic, carcinogens, and non-biodegradable in nature and pollute most water resources that lead to severe health-related issues. It is essential to develop highly sensitive, selective, rapid, and accurate approaches for their detection in water. Semiconducting devices and materials with micro and nanostructures have been featured with fast response time, low power, high sensitivity, low detection limit. This review concisely introduces the recent trends in heavy metal ion sensing with semiconductor devices, including ion-sensitive field-effect transistors (ISFETs) and AlGaN/GaN high electron mobility transistors (HEMTs) and semiconductor materials like graphene, two-dimensional metal dichalcogenides, decorated with different nanoparticles with appropriate functionalization.

Development of semiconductor based heavy metal ion sensors for water analysis: A review

A Disposable Electrochemical Biosensor Based on Screen-Printed Carbon Electrodes Modified with Silver Nanowires/HPMC/Chitosan/Urease for the Detection of Mercury (II) in Water.

We have demonstrated a highly sensitive novel platform for real-time detection of Mercury (Hg2+) ions after successfully making silver nanowires (AgNWs)-MoS2 nanocomposite and functionalizing it over ungated AlGaN/GaN high electron mobility transistor (HEMT) The AlGaN/GaN HEMT structures were grown over the sapphire substrate using Molecular Beam Epitaxy AgNWs-MoS2 nanocomposites were optimized for the device functionalization and 1:4 ratio was found highly sensitive for Hg2+ ions The sensor exhibits high sensitivity towards Hg2+ ions of 1604 mA/ppb and calculated its Limit of Detection (LoD) up to the range of 20 ppt The observed sensitivity is highest among previously reported AlGaN/GaN fabricated HEMT based sensors for Mercury (Hg2+) ions detection and is well below the standard permissible limits as set by World Health Organization (WHO) and Environmental Protection Agency (EPA) The enhancement in sensitivity is due to the enhanced surface to volume ratio of AgNW-MoS2 nanocomposite and the highly conductive nature of silver nanowires incorporated in MoS2 Moreover, we also performed sensing on real water samples of tap water and lake water Further, we showed the smart sensing capability of our developed sensor by illustrating the Internet of Things (IoT) enabled system for next-generation heavy metal ion sensing

Mercury (II) Ion Detection using AgNWs-MoS2 Nanocomposite on GaN HEMT for IoT Enabled Smart Water Quality Analysis

In this work, the MoS2 functionalized AlGaN/GaN high-electron mobility transistor (HEMT) was utilized for the first time to detect toxic mercury (Hg2+) ions under ultraviolet (UV) illumination. The AlGaN/GaN HEMT was fabricated on the sapphire substrate, and corresponding structural and electrical properties were investigated. Subsequently, the optimization of MoS2 concentration for device functionalization was carried out by performing sensing analysis of Hg2+ ions on three devices, and it was observed that the 20 mg/mL concentration of MoS2 is optimum for the detection of Hg2+ ions. Furthermore, the detection of Hg2+ ions was performed under UV exposure, where the developed sensor showed much-improved sensitivity of $548.07~\mu \text{A}$ /ppb compared with normal light. The comparative analysis indicates the increase of three orders of magnitude in sensitivity under UV irradiation, and it is the highest sensitivity ever observed by the AlGaN/GaN HEMT sensor for Hg2+ ion detection. Moreover, the sensor also exhibits the limit of detection (LoD) of 6.14 parts per trillion (ppt) that is much lower than the World Health Organization (WHO) standard limit for Hg2+ ions in drinking water. Due to the photoexcitation process, the generation of electron–hole pairs provides more binding sites on the MoS2 surface, which results in the ultrasensitive detection of the Hg2+ ions at trace and ultratrace levels.

Nipun Sharma

Papers

Development of semiconductor based heavy metal ion sensors for water analysis: A review

Mercury (II) Ion Detection using AgNWs-MoS2 Nanocomposite on GaN HEMT for IoT Enabled Smart Water Quality Analysis

Ultrasensitive Detection of Mercury Ions Under UV Illumination of MoS 2 Functionalized AlGaN/GaN Transistor