Table 2 Recent developments in nanosensors for the detection of heavy metals
From: A Review on Biosensors and Nanosensors Application in Agroecosystems
Nanosensor type | Used nanomaterial | Detected heavy metal | Limit of detection | Method of nanosensor formulation | Sensing mechanism | Observation | References |
|---|---|---|---|---|---|---|---|
ICTS Nanosensor | Au | Cadmium | 0.35 µg/L | The Cd(II)-EDTA-BSA antigen and goat anti-mouse IgG were dispersed on the Nitrocellulose (NC) membrane followed by the addition of concentrated colloidal gold probe on glass fiber membrane | Decline in color intensity with the increase in the concentration of Cd(II) | A highly sensitive sensor specific for the detection of cadmium | [178] |
ICTS Nanosensor | Au | Lead | 0.19 ng/mL | Au nanoparticle conjugates were prepared using anti-Pb(II)-ITCBE monoclonal antibody and colloidal gold solution. The lateral flow assay strip for detecting lead ions was constructed using an NC membrane, absorbent pad, and two conjugate pads | Decline in color intensity with the increase in the concentration of Pb(II) | The detection method could be accomplished within 15 min | [179] |
Optical | Nanohybrid CdSe QDs | Cadmium | 25 nM | Amino capped CdTe@SiO2 core–shell structured fluorescent silica NPs synthesized using a modified reverse microemulsion method. The green-emitting dual-stabilizers capped CdSe QDs were covalently linked to the silica surface to form CdTe@SiO2@CdSe ratiometric probes | On the cadmium introduction the green photoluminescence got gradually restored | An alternative sensing approach for highly sensitive and selective detection | [117] |
Colorimetric nanosensor | Mesoporous silica nanoparticles (MSN) | Mercury | 60 pM | The nanodevice was fabricated by implanting new dithiocetal-grounded stimulus receptive molecular gates on MSN loaded with a reporter dye | Hg(II) has high affinity for sulfur, and can disrupt the linear dithioacetal linkages upon interaction with solid S2, yielding new Hg(S-R)2 leading to subsequent cargo release | The nanosensor displays a sensitivity of 29.9 a.u/μM | [180] |
Colorimetric nanosensor | Au | Pd(II) | 4.23 µM | Gold nanoparticles were stabilized by cationic 1-(3-(acetylthio)propyl)pyrazin-1-iumligand to detect Pd(II) | Pd(II) selectively induced the aggregation of APP-AuNPs as compared to other metals, resulting into the complete significant disappearance of surface plasmon resonane | The nanosensors warrants naked eye detection | [181] |
Colorimetric nanosensor | Silver-coated gold nanobipyramids | Mercury | 0.8 µM | The Au NBs were synthesized as per the seed-mediated growth method and later Au NBs@Ag nanoparticles were synthesized by adding different volumes of AgNO3 to Au NBs colloidal solution | Hg2+ detection is achieved by etching silver-coated gold nanobipyramids which brings a color change | The method is devoid of tedious procedures and is time-saving | [182] |
Multimodal nanosensor | Superparamagnetic Fe2O3 nanoparticles | Mercury | 0.49 nM | Fe2O3 nanoparticles prepared by the chemical coprecipitation method were coated by silica and later electrostatically attached with the cysteamine capped CdTe QDs | Fluorescence quenching with increasing concentrations of Hg2+ | The detected analyte can be removed with the use of an external bar magnet leaving no residual pollution | [124] |
Surface plasmon resonance | Epicatechin coated silver nanoparticles (ECAgNPs) | Lead | 1.52 μM | The ECAgNPs, were prepared by mixing various ratios of AgNO3 and epicatechin followed by magnetic stirring and was later used for lead detection | The metal exhibited hyperchromic shift upon binding with epicatechin based silver nanoparticles | ECAgNPs can selectively detect Pb2+ even in the presence of other interfering metal ions | [126] |
Electrochemical sensor | Nano sheets of Fc-NH2-UiO-66, and thermally reduced graphene oxide (trGNO) | Cadmium, Lead and Copper | 8.5 nM for Cd2+, 0.6 nM for Pb2+ and 0.8 nM for Cu2+, respectively | NH2-UiO-66 was synthesized by hydrothermal method whereas N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) were used as crosslinking agents to prepare Fc-NH2-UiO-66 followed by the dispersion of Fc-NH 2—UiO-66 on the trGNO nanosheets | The peak current increases with the increasing concentrations of heavy metal | A very good platform for simultaneous detection of multiple heavy metal ions | [183] |
Magnetic-fluorescent based nanosensor | Carboxymethyl chitosan-functionalized magnetic-fluorescent nanocomposites | Mercury | 9.1 × 10−8 mol/L | Carboxymethyl chitosan was used as encapsulation agent to package Fe3O4 nanoparticles and QDs, resulting in the multifunctional magnetic-fluorescent nanoparticle which were later used as nanosensors | Quenching of nanosensor’s fluorescence | The nanosensor shows a superior selectivity and sensitivity for Hg2+ ions | [128] |