Based on Fe and Ni prepared organic colloidal materials as efficient oxide nanozymes for chemiluminescence detection of GSH and Hg(II) ions.

Metal-organic gels (MOGs) are a type of metal-organic colloid material with a large specific surface area, loose porous structure, and open metal active sites. In this work, FeNi-MOGs were synthesized by the simple one-step static method, using Fe(III) and Ni(II) as the central metal ions and terephthalic acid as the organic ligand. The prepared FeNi-MOGs could effectively catalyze the chemiluminescence of luminol without the involvement of H2O2, which exhibited good catalytic activity. Then, the multifunctional detected platform was constructed for the detection of GSH and Hg2+, based on the antioxidant capacity of GSH, and the strong affinity between mercury ion (Hg2+) and GSH which inactivated the antioxidant capacity of GSH. The experimental limits of detection (LOD) for GSH and Hg2+ were 76 nM and 210 nM, and the detection ranges were 2-100 µM and 8-4000 µM, respectively. The as-proposed sensor had good performance in both detection limit and detection range of GSH and Hg2+, which fully met the needs of daily life. Surprisingly, the sensor had low detection limits and an extremely wide detection range for Hg2+, spanning five orders of magnitude. Furthermore, the detection of mercury ions in actual lake water and GSH in human serum showed good results, with recovery rates ranging from 90.10 % to 105.37 %, which proved that the method was accurate and reliable. The as-proposed sensor had great potential as the platform for GSH and Hg2+ detection applications.

Superparamagnetic photonic crystals with DNA probes for rapid visual detection of mercury.

A novel superparamagnetic photonic crystal DNA probe (Fe3O4@SiO2@amino@DNA SPC) was developed to enable rapid visual detection of Hg2+. This unique photonic crystal (PC) was synthesized by combining superparamagnetic nanospheres with DNA probes. The DNA probe, rich in thymine (T), detects mercury ions through base mismatch, resulting in the formation of T-Hg2+-T loop hairpin structures. With the binding of Hg2+ to the probe attached to superparamagnetic nanospheres, the PC structure assembled by these nanospheres, formed by the magnetic field, was changed. This change enhanced the reflection intensity; it could be quantified using a fiber optic spectrometer and was visible to the naked eye. The Fe3O4@SiO2@amino@DNA SPC, specific to Hg2+, exhibited a reflection peak at 679 nm, which intensified with increasing Hg2+ concentration. The reflection intensity increased by 132.58 a.u., and the PC color shifted from red to yellow as the Hg2+ concentration increased from 0.1 µg/L to 1 mg/L.

Highly sensitive turn-on electrochemical sensing of organophosphorus pesticides by integration of homogeneous reaction and heterogeneous catalytic signal amplification.

Enzyme-inhibited electrochemical sensor is a promising strategy for detecting organophosphorus pesticides (OPs). However, the poor stability of enzymes and the high oxidation potential of thiocholine signal probe limit their potential applications. To address this issue, an indirect strategy was proposed for highly sensitive and reliable detection of chlorpyrifos by integrating homogeneous reaction and heterogeneous catalysis. In the homogeneous reaction, Hg2+ with low oxidation potential was employed as signal probe for chlorpyrifos detection since its electroactivity can be inhibited by thiocholine, which was the hydrolysate of acetylthiocholine catalyzed by acetylcholinesterase. Additionally, Co,N-doped hollow porous carbon nanocage@carbon nanotubes (Co,N-HPNC@CNT) derived from ZIF-8@ZIF-67 was utilized as high-performance electrode material to amplify the stripping voltammetry signal of Hg2+. Thanks to their synergistic effect, the sensor exhibited outstanding sensing performance, excellent stability and good anti-interference ability. This strategy paves the way for the development of high-performance OP sensors and their application in food safety.

A dual responsive bis-thiophene affixed thiosemicarbazide based chemosensor for colorimetrically Hg2+ and fluorometrically Cu2+ ions and their applications in live cell imaging.

In this work, we developed a fast and straightforward colorimetric and photoluminescent chemosensor probe (P1), featuring bis-thiophene-thiosemicarbazide moieties as its signaling and binding unit. This probe exhibited rapid sensitivity to Hg2+ and Cu2+ ions in a semi-aqueous medium, resulting in distinct colorimetric and photoluminescent changes. In the presence of Cu2+, P1 displayed an impressive 50-fold increase in photoluminescence (PL) at 450 nm (with excitation at 365 nm). The probe P1 formed a 1:1 complex with Hg2+ and Cu2+ ions, featuring association constant values of 4.04 × 104 M-1 and 1.25 × 103 M-1, respectively. P1 has demonstrated its efficacy in the analysis of real samples, yielding promising results. Additionally, the probe successfully visualized copper ions on a mouse fibroblast cell line (NIH3T3), highlighting its potential as an intracellular probe for copper ion detection.

Simultaneous Hg2+ and Pb2+ detection in water samples using an electrochemical aptasensor with dual signal amplification by exonuclease III and metal-organic frameworks.

Heavy metal pollution in the environment has become a significant global concern due to its detrimental effects on human health and the environment. In this study, we report an electrochemical aptasensor for the simultaneous detection of Hg2+ and Pb2+. Gold nanoflower/polyethyleneimine-reduced graphene oxide (AuNFs/PEI-rGO) was introduced on the surface of a gold electrode to improve sensing performance. The aptasensor is based on the formation of a T-Hg2+-T mismatch structure and specific cleavage of the Pb2+-dependent DNAzyme, resulting in a dual signal generated by the Exo III specific digestion of methylene blue (MB) labeled at the 3' end of probe DNA-1 and the reduction of the substrate ascorbic acid (AA) catalyzed by the signal label. The decrease of MB signal and the increase of AA oxidation peak was used to indicate the content of Hg2+ and Pb2+, respectively, with detection limits of 0.11 pM (Hg2+) and 0.093 pM (Pb2+). The aptasensor was also used for detecting Hg2+ and Pb2+ in water samples with good recoveries. Overall, this electrochemical aptasensor shows promising potential for sensitive and selective detection of heavy metals in environmental samples.

A novel red-to-near-infrared AIE fluorescent probe for detection of Hg2+ with large Stokes shift in plant and living cells.

Due to the highly toxic nature of mercury ions to living organisms, accurately detecting Hg2+ in water samples and biological systems is of great significance. In this study, we designed and synthesized a novel red-to-near-infrared Aggregation-Induced Emission (AIE) fluorescent probe (named as DS) based Fluorene derivatives on specifically for Hg2+ detection. Probe DS can visually identify Hg2+ through an red-to-near-infrared fluorescence enhancement change, characterized by a large Stokes shift (130 nm) and AIE feature. This probe offers a fast response, high selectivity and sensitivity. The Hg2+-induced deprotection reaction of the thioketal mechanism was thoroughly investigated using nuclear magnetic resonance spectroscopy (NMR), mass spectrometry (MS) and density functional theory (DFT) calculation. Additionly, dynamic light scattering (DLS) results indicated that the aggregation states changes of the molecular play a crucial role in the AIE fluorescence response of probe DS toward Hg2+. The red-to-near-infrared response with AIE feature not only avoids the interference of auto-fluorescence signals in complex environments, but also reduces the fluorescence quenching caused by probe molecular aggregation. This makes probe DS highly suitable for high-quality imaging detection of Hg2+ in aqueous environments. Furthermore, probe DS demonstrates the capability for visual fluorescence detection of Hg2+ concentrations in water sample, plant roots and living cells.

Hg2+-enhanced oxidase-like activity of platinum nanoparticles immobilized on porphyrin-based porous organic polymer for the colorimetric detection and removal of Hg2.

Porphyrin-based porous organic polymer (POP) with uniformly immobilized platinum nanoparticles (Pt NPs) were designed and synthesized, and it was demonstrated that such nanocomposites (Pt/POP) have oxidase-like activity. Surprisingly, Hg2+ significantly enhanced the oxidase-like activity of Pt/POP. The enhancement was attributed to the capture of Hg2+ by the thioether group in Pt/POP and the subsequent redox reaction of Hg2+ with Pt NPs, accelerating the electron transfer. In the presence of Hg2+, Pt/POP catalyzed the colorless 3,3',5,5'-tetramethylbenzidine (TMB) to turn blue rapidly and changed its absorbance at 652 nm. Based on this, a fast-response colorimetric sensor was constructed for the sensitive detection of Hg2+ with a linear range of 0.2-50 µM and a detection limit of 36.5 nM. Importantly, Pt/POP can be used as an adsorbent for the efficient removal of Hg2+ with a removal efficiency as high as 99.4%. This work provides a valuable strategy for colorimetric detection and efficient removal of Hg2+.

Self-powered photochemical cathode aptamer sensor based on ZnIn2S4 photoanode and Cu2O@Ag@Ag3PO4 photocathode for the sensitive detection of Hg2.

A self-powered photoelectrochemical (PEC) aptamer sensor based on ZnIn2S4 as the photoanode and Cu2O@Ag@Ag3PO4 as the sensing cathode is designed for the detection of Hg2+. An indium tin oxide (ITO) electrode modified with ZnIn2S4 was used instead of a platinum (Pt) counter electrode to provide an obviously stable photocurrent signal. The suitable band gap width of ZnIn2S4 can generate photogenerated electrons well. The unique hydrangea structure of ZnIn2S4 can enhance light absorption and accelerate the separation and transfer of photocarriers. At the same time, Cu2O@Ag@Ag3PO4 with excellent electrical conductivity further enhances the photocurrent provided by the ZnIn2S4 photoanode. Because the reducing substances in the biological medium can change the photoanode characteristics of the photoanode interface, the separation of the photoanode and the sensing bicathode is beneficial to improve the anti-interference ability of the sensor. Under optimized conditions, the PEC aptamer sensor realizes the detection of Hg2+ (1 mM-1 fM), and the detection limit is 0.4 fM. In addition, the constructed self-powered PEC sensor has good selectivity, repeatability, and stability, which provides a new idea for the design of the PEC aptamer sensor platform.

CRISPR-Hg: Rapid and visual detection of Hg2+ based on PCR coupled with CRISPR/Cas12a.

Mercury (Hg) is a notorious toxic heavy metal, causing neurotoxicity and liver damage, posing grave threats to human health and environmental safety. There is an urgent imperative for developing novel Hg2+ detection methods. In this work, we developed a CRISPR-based method for Hg2+ detection named CRISPR-Hg. A CRISPR/Cas12a system was employed and could be activated by the PCR product, generating fluorescence signals based on the trans-cleavage activity. CRISPR-Hg exhibited remarkable selectivity and specificity, achieving a detection limit of 10 pM and minimal interference with background signals. This approach has been successfully applied to detect Hg2+ in real samples, including water, soil, and mushroom. Ulteriorly, a portable device was devised to streamline the readout of fluorescence signals by a smartphone within 30 min. We offer an affordable, highly selective and visually interpretable method for Hg2+ detection, with the potential for broad application in Hg2+ monitoring for food safety and public health.

A dual-signaling surface-enhanced Raman spectroscopy ratiometric strategy for ultrasensitive Hg2+ detection based on Au@Ag/COF composites.

Heavy metal ion pollution poses significant risks to human health and ecological systems, and its monitoring is important. A sensitive and accurate surface-enhanced Raman spectroscopy (SERS) detection assay for Hg2+ was developed using Au@Ag/COF substrates and Y-shaped DNA labeled with two Raman reporters. The Au@Ag NPs in the COF produced robust and uniform E-fields, improving their detection reproducibility. The Y-shaped DNA design increased sensitivity with a low detection limit of 5.0 × 10-16 M by bringing the Raman reporter closer to the substrate surface. Additionally, the use of two Raman reporters allowed for a ratiometric method, improving detection accuracy by detecting both "signal-off" and "signal-on" signals. This selective sensor exhibited excellent recovery in river water, tap water, and milk samples, showcasing its robust biosensing capability for the detection of Hg2+ and its potential for sensing other heavy-metal ions in food and environmental applications.

Engineering "three-in-one" fluorescent nanozyme of Ce-Au NCs for on-site visual detection of Hg2.

Hg2+ contamination poses a serious threat to the environment and human health. Although gold nanoclusters (Au NCs) have been utilized as fluorescence probes or colorimetric nanozymes for performing Hg2+ assays by using a single method, designing multifunctional nanoclusters as fluorescent nanozyme remains challenging. Herein, Ce-aggregated gold nanoclusters (Ce-Au NCs) were reported with "three in one" functions to generate strong fluorescence, excellent peroxidase-like activity, and the highly specific recognition of Hg2+ via its metallophilic interaction. A portable fluorescence and colorimetric dual-mode sensing device based on Ce-Au NCs was developed for on-site visual analysis of Hg2+. In the presence of Hg2+, fluorescence was effectively quenched and the paper-based chips gradually darkened from green till they became completely absent, while peroxidase-like activity was significantly enhanced. Two independent signals were captured by one identification unit, which provided self-validation to improve reliability and accuracy. Therefore, this work presents a simple synthesis of a multifunctional fluorescent nanozyme, and the developed portable device for on-site visual detection has considerable potential for application in the rapid on-site analysis of heavy metal ions in the environment.

Self-assembled monolayer of 2-(((5-mercapto-1,3,4-thiadiazol-2-yl)imino)methyl)phenol (MTP) on gold surface: A platform for impedimetric and potentiometric sensing of mercury(II).

2-(((5-mercapto-1,3,4-thiadiazol-2-yl)imino)methyl)phenol (MTP) was synthesized, self-assembled on the surface of gold (Au) electrode (Au-MTP) followed by characterization using Cyclic voltammetry (CV) and Electrochemical impedance spectroscopy (EIS). CV and EIS confirmed the formation of well-organized Au-MTP SAM free from defects and pinholes. Au-MTP was further utilized as a platform for sensing of Hg2+ using EIS. The results showed sensitive and selective response of Au-MTP towards Hg2+ in the linear concentration range from 1.0 × 10-10 M to 1.0 × 10-4 M with limit of detection (LoD) of 5.6 × 10-11 M. Furthermore, MTP was self-assembled on gold nanoparticles (AuNPs) and MTP bound gold nanoparticles (MTP-AuNPs) so obtained were used as modifier for construction of carbon paste electrode (CPE). Hg2+-CPE exhibited Nernstian response towards Hg2+ with slope of 28.3 mV/decade in the concentration range from 1.0 × 10-5 M to 1.0 × 10-1 M with LoD of 6.3 × 10-6 M. Both the Au-MTP EIS sensor and Hg2+-CPE were successfully applied for estimation of Hg2+ content in tap water samples.

pH-responsive dual-emission carbon dots for the ratiometric detection of organophosphorus pesticides in Brassica chinensis and Hg2+ in water.

Accurate and rapid monitoring of organophosphorus pesticides (OPs) residues is crucial for regulating food safety. Herein, dual-emission carbon dots (de-CDs) were fabricated for the ratiometric detection of OPs and Hg2+. The de-CDs exhibited two emission peaks at 678 and 485 nm when excited with visible light. Interestingly, the fluorescence at 678 nm was significantly quenched by Hg2+ mainly because of the static quenching effect, whereas that at 485 nm exhibited a slight change. More significantly, the quenched fluorescence of the de-CDs recovered remarkably after introducing omethoate, diazinon and malathion. Accordingly, the ratiometric detection of the three OPs and Hg2+ was achieved with high selectivity and robust performance. In addition, the OPs residues assay in Brassica chinensis was successfully performed with satisfactory results. This study not only provides an attractive tool for the simple and rapid assay of OPs but also offers new insights into the fabrication of multi-functional carbon dots.

Heavy metal ions interactions with G-quadruplex-prone DNA sequences.

The industrial world exposes living organisms to a variety of metal pollutants. Here we investigated whether such elements affect G-rich sequences susceptible to fold into G-quadruplex (GQ) structures. Thermal stability and conformation of these oligoncleotides was studied at various molar ratios of a variety of heavy metal salts using thermal FRET, transition-FRET (t-FRET) and circular dichroism. Metal ions affected the thermal stability of the GQs to different extents; some metals had no effect on Tm while other metals caused small to moderate changes in Tm at 1:1 or 1:10 molar ratio. While most of the metals had no major effect, Al3+, Cd2+, Pb2+, Hg2+ and Zn2+ altered the thermal stability and structural features of the GQs. Some metals such as Pb2+ and Hg2+ exhibit differential interactions with telomere, c-myc and c-kit GQs. Overall, toxic heavy metals affect G-quadruplex stability in a sequence and topology dependent manner. This study provides new insight into how heavy metal exposure may affect gene expression and cellular responses.

A highly sensitive and selective fluorescent "on-off-on" peptide-based probe for sequential detection of Hg2+ and S2- ions: Applications in living cells and zebrafish imaging.

Mercury ions (Hg2+) and sulfur ions (S2-), have caused serious harm to the ecological environment and human health as two kinds of highly toxic pollutants widely used. Therefore, the visual quantitative determination of Hg2+ and S2- is of great significance in the field of environmental monitoring and medical therapy. In this study, a novel fluorescent "on-off-on" peptide-based probe DNC was designed and synthesized using dipeptide (Asn-Cys-NH2) as the raw material via solid phase peptide synthesis (SPPS) technology with Fmoc chemistry. DNC displayed high selectivity in the recognition of Hg2+, and formed non-fluorescence complex (DNC-Hg2+) through 2:1 binding mode. Notably, DNC-Hg2+ complex generated in situ was used as relay response probe for highly selective sequential detection of S2- through reversible formation-separation. DNC achieved highly sensitive detection of Hg2+ and S2- with the detection limits (LODs) of 8.4 nM and 5.5 nM, respectively. Meanwhile, DNC demonstrated feasibility for Hg2+ and S2- detections in two water samples, and the considerable recovery rate was obtained. More importantly, DNC showed excellent water solubility and low toxicity, and was successfully used for consecutive discerning Hg2+ and S2- in test strips, living cells and zebrafish larvae. As an effective visual analysis method in the field, smartphone RGB Color Picker APP realized semi-quantitative detections of Hg2+ and S2- without the need for complicated device.

A colorimetric and electrochemical dual-mode Hg2+ sensor utilizing oxidase-like activity arising from the combination of Hg2+ and palladium metal-organic framework@graphene.

Developing convenient and reliable methods for Hg2+ monitoring is highly important. Some precious metal nanomaterials with intriguing peroxidase-like activity have been used for highly sensitive Hg2+ detection. However, H2O2 must be added during these detections, which impedes practical applications of Hg2+ sensors due to its susceptible decomposition by environmental factors. Herein, we discovered that the combination of Hg2+ and palladium metal-organic framework@graphene (Pd-MOF@GNs) exhibits oxidase-like activity (OXD). In the absence of H2O2, this activity not only catalyzes the oxidation of chromogenic substrates such as 3,3',5,5'-tetramethylbenzidine (TMB) or o-phenylenediamine (OPD) to produce a color change but also enhances the electrical signals during OPD oxidation. Based on these properties, an effective and convenient dual-mode colorimetric and electrochemical sensor for Hg2+ has been developed. The colorimetric and amperometric linear relationships for Hg2+ were 0.045 µM-0.25 mM and 0.020 µM-2.0 mM, respectively. The proposed strategy shows good recovery in real sample tests, indicating promising prospects for multiple environmental sample detection of Hg2+ without relying on H2O2. The colorimetric and electrochemical dual-mode Hg2+ sensor is expected to hold great potentials in applications such as environmental monitoring, rapid field detection, and integration into smartphone detection of Hg2+.

MOF derivatization of multifunctional nanozyme: Peroxidase-like catalytic activity combined with magnetic solid phase extraction for colorimetric detection of Hg2.

Nanozyme-based colorimetric sensing has drawn immense attention due to the rapid development of nanozyme in recent years. However, the selectivity of nanozyme-based colorimetric sensing greatly limits its subsequent practical application. It is well known that sample pretreatment can not only improve selectivity by eliminating the sample matrix interference, but also improve sensitivity by enriching trace targets. Based on the easy facile surface modification properties of nanozyme, we rationally designed nanozyme combined with sample pretreatment for colorimetric biosensing, through separation and enrichment, thereby improving the selectivity and sensitivity of the nanozyme colorimetric biosensing. As a proof of concept, the detection of Hg2+ by nanozyme-based colorimetric sensing was used as an example. Magnetic peroxidase-like nanozyme Fe3S4 was designed and synthesized. The selectivity is improved by the specific adsorption of S-Hg bond and the interference elimination after magnetic separation. In addition, the sensitivity is improved by magnetic solid-phase extraction enrichment. Our established colorimetric sensing based on Fe3S4 nanozyme integrated sample pretreatment with an enrichment factor of 100 and the limit of detection (LOD) is 26 nM. In addition, this strategy was successfully applied to detect Hg2+ in environmental water samples. Overall, the strategy showed good selectivity and sensitivity, providing a new practical method for the application of nanozyme-based biosensing in sample pretreatment.

Simple synthesis of flower-like ZnO@Pt composites for dual-mode colorimetric detecting Hg2+ with smartphone and UV-vis.

BACKGROUND: Mercury is one of the most toxic heavy metal contaminants that can be harmful to human health through the food chain. Recently, the colorimetric detection of heavy metals based on nanozyme catalytic activity has received extensive interest due to the simplicity, signal visibility and suitability for in situ detection. However, the majority of these nanozymes that can be utilized for detecting mercury with high synthesis temperature and complicated synthesis methods, which limited their practical application. RESULTS: In this work, flower-like ZnO@Pt composites were simply synthesized at room temperature, the flower-like structure and the high electron mobility of ZnO endow ZnO@Pt with stronger peroxidase-like activity. Consequently, dual-mode (UV-vis and smartphone) colorimetric sensors were designed to detect Hg2+. In UV-vis mode, the Hg2+ concentration linear range was 10-400 nM, and the limit of detection (LOD) was 0.54 nM. In smartphone mode, the Hg2+ concentration linear range was 50-1250 nM, and the LOD was 29.8 nM. A parallel analysis in 3 real water samples was confirmed by ICP-MS, the results showed good correlations (R2 > 0.98), indicating the practical reliability of these sensors. SIGNIFICANCE: The novel flower-like ZnO@Pt composites with high stability, catalytic activity and Hg2+ response were simply synthesized at room temperature, simplifying the synthesis steps and reducing costs. The sensitivity of the developed colorimetric sensor in UV-vis mode was 3-145 times higher than that of the similar methods. The colorimetric sensor in smartphone mode broadened the detection range and improved the portability of Hg2+ detection. Thus, the dual-mode (UV-vis and smartphone) colorimetric sensors providing new detection modes for rapid monitoring of Hg2+ in environmental water.

Coumarin derivative-functionalized nanoporous silica as an on-off fluorescent sensor for detecting Fe3+ and Hg2+ ions: a circuit logic gate.

A highly efficient fluorescent sensor (S-DAC) was easily created by functionalizing the SBA-15 surface with N-(2-Aminoethyl)-3-Aminopropyltrimethoxysilane followed by the covalent attachment of 7-diethylamino 3-acetyl coumarin (DAC). This chemosensor (S-DAC) demonstrates selective and sensitive recognition of Fe3+ and Hg2+ in water-based solutions, with detection limits of 0.28 × 10-9 M and 0.2 × 10-9 M for Hg2+ and Fe3+, respectively. The sensor's fluorescence characteristics were examined in the presence of various metal ions, revealing a decrease in fluorescence intensity upon adding Fe3+ or Hg2+ ions at an emission wavelength of 400 nm. This sensor was also able to detect ferric and mercury ions in spinach and tuna fish. The quenching mechanism of S-DAC was investigated using UV-vis spectroscopy, which confirmed a static-type mechanism for fluorescence quenching. Moreovre, the decrease in fluorescence intensity caused by mercury and ferric ions can be reversed using trisodium citrate dihydrate and EDTA as masking agents, respectively. As a result, a circuit logic gate was designed using Hg2+, Fe3+, trisodium citrate dihydrate, and EDTA as inputs and the quenched fluorescence emission as the output.

A novel colormetric and light-up fluorescent sensor from flavonol derivative grafted cellulose for rapid and sensitive detection of Hg2+ and its applications in biological and environmental system.

Mercury ion (Hg2+) is one of harmful heavy metal ions that can accumulate inside the human organism and cause some health problems. In the article, a highly effective fluorescent probe named EC-T-PCBM was prepared by grafting flavonol derivatives onto ethyl cellulose for the specific recognition of Hg2+. EC-T-PCBM exhibited a remarkable fluorescence light-up response toward Hg2+ with excellent sensitivity. EC-T-PCBM possessed several prominent sensing properties for Hg2+, such as low detection limit (43.9 nM), short response time (5 min), and wide detection pH range (6-9). The response mechanism of EC-T-PCBM to Hg2+ has been verified through 1H NMR titration and DFT computation. Additionally, EC-T-PCBM not only can be used for accurately determining trace amount of Hg2+ in actual environmental water samples, but also can serve as a portable and rapid device by loading it on test strips for sensitive and selective visualization of Hg2+. More importantly, the confocal fluorescence imaging of onion cells suggested the favorable cell membrane permeability of EC-T-PCBM and its prominent ability to continuously monitor the enrichment from Hg2+ within fresh plant tissues.