Selective Detection Of Pb2 Research Articles

A nanohybrid system based on covalently functionalized graphene quantum dots with dithienopyrrole derivative for the sensitive and selective fluorometric detection of Pb2+ ions.

Recently graphene quantum dot (GQD) based nanohybrid materials have received much attention. Herein, a highly fluorescent biocompatible GQD and N-functionalized dithienopyrrole (DTP-PPD) modified nanohybrid system was fabricated (DTP-PPD-fn-GQD) for the first time. Modification resulted in stable fluorescence with a quantum yield of approximately 22% and 36 nm redshift compared to unmodified GQD. The apparent bandgap tuning along with fluorescence property changes was investigated by cyclic voltammetry measurements and density functional theory studies. This water-soluble system was then applied for the sensitive and selective detection of Pb2+ ions. As a result of a specific interaction towards Pb2+ ions, the fluorescence intensity was quenched. The detection limit is found to be 1.02 nM within the linear range of 3 to 30 nM. Finally, the feasibility of the developed probe was tested with real samples of water. Chemically modified GQDs are already widely exploited for Pb2+ sensing, whereas GQD/thiophene-based nanohybrid systems are less utilized. This newly developed nanohybrid of GQD (DTP-PPD-fn-GQD) has excellent fluorescence properties and bandgap tunability. Moreover, effective fluorometric sensing of Pb2+ ions in an aqueous medium is well investigated. This gives more insight into developing GQD-based highly promising nanohybrid colorimetric as well as fluorescent sensors.

Lignin-mediated green synthesis of functionalized gold nanoparticles via pulsed laser technique for selective colorimetric detection of lead ions in aqueous media

A versatile green synthesis technique of pulsed laser irradiation and the sonochemical process was used for the production of functionalized gold nanoparticles (Au NPs) in the presence of lignin matrixes. In this study, the futuristic advantages of the lignin biopolymer were explored for the preparation of zero-valent Au NPs in the absence of any other reducing agents. The resulting lignin functionalized Au NPs (L-Auf NPs) were characterized via high-resolution transmission electron microscopy, X-ray diffraction, UV–vis spectroscopy, and Fourier-transform infrared spectroscopy. The optimum lignin concentration can generate uniformly dispersed crystalline L-Auf NPs. The optimized L-Auf (1–5) NPs permit the selective colorimetric detection of heavy metal ions; thus, the L-Auf (1–5) NPs demonstrated a highly selective colorimetric sensing tendency toward Pb2+ ions within a short time interval among the various metal ions (Pb2+, Fe3+, Cu2+, Cr6+, Co2+, Ag2+, Ca2+, Cd2+, Ba2+, and Hg2+). The prominent color change of L-Auf NPs from red wine to purple indicates the detection of Pb2+ ions. This robust characteristic nature of L-Auf (1–5) NPs can also detect very low concentrations of 1.8 μM in the linear range of 0.1–1 mM. Hence, the outcome of this study coincides with existing studies and indicates that L-Auf (1–5) NPs can also be used as effective sensors for the rapid and selective detection of Pb2+ ions via the colorimetric analysis using the real environmental samples.

Bifunctional single-labelled oligonucleotide probe for detection of trace Ag(I) and Pb(II) based on cytosine-Ag(I)-cytosine mismatches and G-quadruplex

A novel bifunctional oligonucleotide (OND) probe with single fluorescent group HEX labelled at 5′-end was designed for detecting trace Ag(I) and Pb(II) in real samples. In the presence of Ag(I), the hairpin structure originating from Ag(I) induced cytosine-Ag(I)-cytosine mismatches causes the proximity of the HEX to the consecutive guanine bases (G)4 at 3′-terminal, resulting in the fluorescence quenching of the HEX. While in the presence of Pb(II), the G-quadruplex structure originating from two G-quartet planes by the intramolecular hydrogen bond with Pb(II) also causes the HEX approaching the (G)4 terminal and consequently the fluorescence quenching. The results showed the quantitative detection of trace Ag(I) and Pb(II) both in the linear response ranges of 1.0–20.0 × 10−9 mol L−1 with no visible interferences of other 11 metal ions observed. And the detection limits were 82 × 10−12 mol L−1 for Ag(I), 92 × 10−12 mol L−1 for Pb(II), respectively. The fluorescence quenching mechanism of the (G)4 to HEX was verified to be the photoinduced electron transfer in the aspect of thermodynamics. This method provided a feasible application for sensitive and selective detection of Pb(II) and Ag(I) in water and Chinese traditional herbs with convenient operation.

Nanochannel-based sensor for the detection of lead ions in traditional Chinese medicine.

Lead ions (Pb2+) are used in the quality control of traditional Chinese medicine (TCM) preparations because they are highly toxic to human health. At present, sophisticated analytical instrumentation and complicated procedures for sample analysis are needed for the determination of Pb2+. Herein, a simple, fast, and sensitive peptide-modified nanochannel sensor to detect Pb2+ in TCM is reported, which is based on a Pb2+-specific peptide modified porous anodized aluminum membrane (PAAM). This peptide-based nanochannel clearly has the highest selectivity for Pb2+ when compared to other heavy metal ions, including As2+, Cd3+, Co2+, Cr2+, Cu2+, Fe3+, Hg2+, Mg2+, Mn2+, Ni2+, and Zn2+. Based on linear ranges from 0.01 to 0.16 μM and 10 to 100 μM, the detection limit was calculated to be 0.005 μM. Moreover, this peptide-based nanochannel sensor was successfully used to detect Pb2+ in complex TCM samples. In addition, when compared with the gold standard atomic absorption spectrophotometry (AAS) method, the recovery of the peptide-modified nanochannel sensor was between 87.7% and 116.8%. The experimental results prove that this new sensor is able to achieve accurate detection of Pb2+ in TCM samples. Thus, this sensor system could provide a simple assay for sensitive and selective detection of Pb2+ in TCM, thereby showing great potential in the practical application for the quality control of heavy metals in TCM.

Rigidified naphtho-aza-crown ethers: synthesis and ion selectivity on heavy metal ions

Crown ethers (CRs) are one of the generally used host molecules to increase selectivity of heavy metal ions (HMIs) in electrochemical analysis. To study the cavity size and geometry induced ions selectivity change in naphtho-aza-crown ethers (NACEs), three novel rigidified NACEs have been synthesized and characterized by 1H NMR, 13C NMR and high resolution mass spectra (HRMS). The optimized structures of three NACEs were calculated by using density functional theory. The ion selectivity of three NACEs modified glassy carbon electrode toward Pb(II), Cd(II), Co(II), Cu(II), Ni(II), Zn(II) were investigated in 0.1 M NaCl solution and NaAc-HAc solution by using square wave voltammetry (SWV). Three NACEs have the highest current response toward Pb(II) among the six metal ions in two kinds of supporting electrolytes. Meanwhile, NACE 1 and 3 showed relatively higher current response toward Cu(II) and Cd(II) in 0.1 M NaAc-HAc solution. The SWV response potential of each metal ion could be well separate from each other. In order to screen the superior ionophore for the selective detection of Pb(II) among three NACEs, the calibration curve and interference study of each NACE modified electrode toward detection of Pb(II) were investigated. The SWV peak currents have a good linear relationship with the concentration of Pb(II) in the range from 2 × 10–5 to 2 × 10–4 M for NACE 1, 2 systems and the range from 2 × 10–5 to 1.5 × 10–4 M for NACE 3 system. From the point of view of the interference study, NACE 3 is a optimal choice for selective detection of Pb(II).

Synthesis of bovine serum albumin capped boron-doped carbon dots for sensitive and selective detection of Pb(II) ion

Carbon dots have tremendous potential to be used for biochemical sensing and environmental testing due to its superior optical properties and excellent biocompatibility. The surface of carbon dots can be easily functionalized. In the present study boron doped carbon dots have been synthesized using one pot approach by microwave treatment method. The surface of boron doped carbon dots is capped with bovine serum albumin. The maximum fluorescence emission observed at 444 nm when excited upon 345 nm of wavelength. In the normal light, it is light green in colour but when exposed in long wavelength UV light it exhibited blue fluorescence. The carbon dots have an irregular shape with a diameter below 5 nm. The applicability of synthesized carbon dots as the fluorescent sensor has been checked using different metal ions. It is observed that Pb(II) ion shows appreciable and selective quenching. Linear relationship is exist between the decrease in fluorescence intensity and the concentrations of Pb(II) ion in the range from 1 ppb to 10 ppb concentration. Limit of detection is found to be 0.08 ppb. This study will be helpful in the development of new fluorescent nano-biosensors.

A facile colorimetric sensor for ultrasensitive and selective detection of Lead(II) in environmental and biological samples based on intrinsic peroxidase-mimic activity of WS2 nanosheets

Two-dimentional layered WS2 nanosheets with rich active edge exhibit intrinsic peroxidase-mimic activity, which make them an ideal material for sensor design. However, there is still lack of research on the catalysis and regulation mechanisms of the layered WS2 nanosheets as well as their application in the detection of hazardous substances. Herein, the regulatory effect of Pb(II) on the peroxidase-mimic activity of the layered WS2 nanosheets was firstly investigated, which enable us to construct a novel and facile colorimetric sensor for ultrasensitive and selective detection of Pb(II). To improve the performance of colorimetric sensor, some important parameters like buffer conditions, substrates and temperature have been investigated. Under the optimal conditions, the catalytic kinetics of layered WS2 nanosheets were extensively investigated. The peroxidase-mimic catalytic reaction was proved to be the “ping pong” mechanism, and the regulatory effect of Pb(II) on layered WS2 nanosheets was agreed with noncompetitive inhibition. The absorbance variation of colorimetric sensor is proportionally related to the concentration of heavy metals, which enable us to easily distinguish whether Pb(II) exceeds the permissible level in less than 20 min even by the naked eyes. The limit of detection (LOD) and the limit of quantification (LOQ) of the proposed colorimetric sensor for Pb(II) were determined as low as 4 μg L−1 and 13.3 μg L−1, and displays excellent selectivity against other competitive metal ions. Moreover, the further studies also validate the applicability of colorimetric sensor in several actual samples, indicating that our strategy may has prospective applications for Pb(II) detection in environment and biological samples.

Highly Sensitive and Selective Detection of Pb(II) by NH2−SiO2/Ru(bpy)32+−UiO66 based Solid‐state ECL Sensor

AbstractIn this study, a novel electrochemiluminescence (ECL) sensor for highly sensitive and selective detection of Pb(II) was developed based on Ru(bpy)32+ encapsulated UiO66 metal‐organic‐framework (Ru(bpy)32+−UiO66 MOF) and −NH2 group functionalized silica (NH2−SiO2). The NH2−SiO2 with large surface area provided an excellent platform for the ECL sensor. As numerous exposed carboxyl groups were present on UiO66 backbone, the Ru(bpy)32+−UiO66 could be steadily immobilized to NH2−SiO2 by forming amide bonds. Meanwhile, the introduced UiO66 MOF which used for the encapsulation of Ru(bpy)32+, significantly enhanced the ECL efficiency of the proposed sensor, as it possessed a large specific surface area and porosity for the loading of Ru(bpy)32+. Moreover, a high quenching effect on ECL intensity was obtained in the presence of Pb(II) in the electrolyte. Under the optimal conditions, the quenched ECL intensity showed a good linear relationship within Pb(II) concentration in the range from 1.0×10−6 to 1.0×102 μM, with a detection limit of 1.0×10−7 μM (S/N=3). The proposed sensor for Pb(II) detection was simple in operation, rapid in testing, stable in signal, and showed a good anti‐interference ability to some other metal ions. Besides, its application for detecting Pb(II) in a real sample was also investigated here. This work provides a potential platform for metal ions detection in environmental monitoring field.

Sensitive and selective detection of Pb (II) and Cu (II) using a metal-organic framework/polypyrrole nanocomposite functionalized electrode

An electrochemical sensor based on a NH2-MIL-53(Al)/polypyrrole (PPy) nanocomposite modified gold electrode for determination of ultra-trace Pb (II) and Cu (II) was developed. The PPy nanowires were synthesized through a chemical polymerization process, and the NH2-MIL-53(Al) was deposited on the PPy nanosubstrates by an in-situ electrochemical method. Field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) spectroscopy and attenuated total reflection infrared (ATR-IR) spectroscopy were used to study the structural features of the nanocomposite. The electrochemical behavior of the NH2-MIL-53(Al)/PPy nanocomposite toward Pb (II) and Cu (II) was investigated by differential pulse voltammetry (DPV) technique. Due to the synergistic effect of the PPy and NH2-MIL-53(Al), the nanocomposite modified electrode exhibited good sensing performance to Pb (II) and Cu (II) in the range of 1–400 μg L−1 with detection limit of 0.315 μg L−1 and 0.244 μg L−1, respectively. The limit of detection and the sensitivity of the NH2-MIL-53(Al)/PPy nanocomposite modified electrode were significantly enhanced than those of the individual modified electrodes. The effective electrochemical property of the nanomaterial for the Pb (II) and Cu (II) could provide a new direction for the heavy metal ions determination.

A pH‐Triggered Synthesis of Blue‐Emitting Au Nanoclusters and Their Luminescence Enhancement in a Metallohydrogel: Selective Detection of Pb2+ through Luminescence Quenching

AbstractThe synthesis and stabilization of blue‐emitting nanoclusters (Au, Cu or Ag) are very challenging. We have developed a facile, acid‐induced protocol to synthesize blue‐emitting Au NCs (B‐NCs) in aqueous medium at room temperature from green‐emitting ones (G‐NCs). The rapid quenching of the blue emission was successfully arrested, and in fact enhanced, by the incorporation of the NCs in a bile acid derived metallohydrogel, demonstrating the special effect of the gel medium. The NCs in both solution and gel were characterized in detail using microscopic and photophysical techniques, including a detailed analysis of the excited state relaxation pathway. We have demonstrated that this NC can be switched back to G‐NCs reversibly upon the reaction with a base. We have also shown that the B‐NC can be efficiently applied towards detection of Pb2+. This simple approach towards B‐NC synthesis and its stabilization can contribute to application of this material in LEDs, bioimaging, and energy transfer.

An aptamer-based colorimetric lead(II) assay based on the use of gold nanoparticles modified with dsDNA and exonuclease I.

The authors describe a colorimetric method for the sensitive and selective detection of Pb(II). It is based on the use exonuclease I (Exo I), a Pb(II)-binding aptamer bound to gold nanoparticles (AuNPs), and a DNA strand that complementary to the aptamer. In the absence of Pb(II), the dsDNA on the AuNPs prevents aggregation of the AuNPs in the presence of NaCl. In the presence of Pb(II), however, the aptamer binds Pb(II) and complementary strand is released and digested by Exo I. As a result, the solution of AuNPs undergoes a color change from red to purple if salt is added to the sample. The assay is selective for Pb(II) and has a limit of detection as low as 2.4nM. It was successfully applied to the determination of Pb(II) in spiked tap water. Graphical abstract Schematic presentation of theaptamer based method for Pb2+ detection via salt-induced aggregation of gold nanoparticlesandcolorimetric quantitation.

Highly sensitive and selective detection of Pb2+ using a turn-on fluorescent aptamer DNA silver nanoclusters sensor

A novel turn-on fluorescent biosensor has been constructed using C-PS2.M-DNA-templated silver nanoclusters (Ag NCs) with an average diameter of about 1 nm. The proposed approach presents a low-toxic, simple, sensitive, and selective detection for Pb2+. The fluorescence intensity of C-PS2.M-DNA-Ag NCs enhances significantly in the presence of Pb2+, which is attributed to the special interaction between Pb2+ and its aptamer DNA PS2.M. Pb2+ induces the aptamer to form G-quadruplex and makes two darkish DNA/Ag NCs located at the 3′ and 5′ terminus close, resulting in the fluorescence light-up. Moreover, Pb2+ can be detected as low as 3.0 nM within a good linear range from 5 to 50 nM (R = 0.9862). Furthermore, the application for detection of Pb2+ in real water samples further demonstrates the reliability of the sensor. Thus, this sensor system shows a potential application for monitoring Pb2+ in environmental samples.

Logic Catalytic Interconversion of G-Molecular Hydrogel.

By incorporating hemin into G-quadruplex (G4) during cation-templated self-assembly between guanosine and KB(OH)4, we have constructed an artificial enzyme hydrogel (AEH)-based system for the highly sensitive and selective detection of Pb2+. The sensing strategy is based on a Pb2+-induced decrease in AEH activity. Because of the higher efficiency of Pb2+ for stabilizing G4 compared with K+, the Pb2+ ions substitute K+ and trigger hemin release from G4, thus giving rise to a conformational interconversion accompanied by the loss of enzyme activity. The Pb2+-induced catalytic interconversion endows the AEH-based system with high sensitivity and selectivity for detecting Pb2+. As a result, the AEH-based system shows an excellent response for Pb2+ in the range from 1 pM to 50 nM with a limit of detection of ∼0.32 pM, which is much lower than that of the previously reported G4-DNAzyme. We also demonstrate that this AEH-based system exhibits high selectivity toward Pb2+ over other metal ions. Furthermore, two two-input INHIBIT logic gates have been constructed via switching of the catalytic interconversion induced by K+ and Pb2+ or K+ and pH. Given its versatility, this AEH-based system provides a novel platform for sensing and biomolecular computation.

The selective capture of Pb2+ in rice phloem sap using glutathione-functionalized gold nanoparticles/multi-walled carbon nanotubes: enhancing anti-interference electrochemical detection

Selective detection of Pb2+ in rice phloem sap by a simple and effective method.

Ratiometric Fluorescent Detection of Pb2+ by FRET-Based Phthalocyanine-Porphyrin Dyads.

Sensitive and selective detection of Pb2+ is a very worthwhile endeavor in terms of both human health and environmental protection, as the heavy metal is fairly ubiquitous and highly toxic. In this study, we designed phthalocyanine-porphyrin (Pc-Por) heterodyads, namely, H2Pc-α-ZnPor (1) and H2Pc-β-ZnPor (2), by connecting a zinc(II) porphyrin moiety to the nonperipheral (α) or peripheral (β) position of a metal-free phthalocyanine moiety. Upon excitation at the porphyrin Soret region (420 nm), both of the dyads exhibited not only a porphyrin emission (605 nm) but also a phthalocyanine emission (ca. 700 nm), indicating the occurrence of intramolecular fluorescence resonance energy transfer (FRET) processes from the porphyrin donor to the phthalocyanine acceptor. The dyads can selectively bind Pb2+ in the phthalocyanine core leading to a red shift of the phthalocyanine absorption and thus a decrease of spectral overlap between the porphyrin emission and phthalocyanine absorption, which in turn suppresses the intramolecular FRET. In addition, the binding of Pb2+ can highly quench the emission of phthalocyanine by heavy-metal ion effects. The synergistic coupled functions endow the dyads with remarkable ratiometric fluorescent responses at two distinct wavelengths (F605/F703 for 1 and F605/F700 for 2). The emission intensity ratio increased as a linear function to the concentration of Pb2+ in the range of 0-4.0 μM, whereas the detection limits were determined to be 3.4 × 10-9 and 2.2 × 10-8 M for 1 and 2, respectively. Furthermore, by comparative study of 1 and 2, the effects of distance and relative orientation between Pc and ZnPor fluorophores on the FRET efficiency and sensing performance were highlighted, which is helpful for further optimizing such FRET systems.

A label–free GR–5DNAzyme sensor for lead ions detection based on nanoporous gold and anionic intercalator

A label–free electrochemical sensor, based on a classic lead ions (Pb2+)–dependent GR–5DNAzyme as the catalytic unit, disodium–anthraquinone–2,6–disulfonate (AQDS) as DNA intercalator, and nanoporous gold (NPG) for signal amplification, was designed for sensitive and selective detection of Pb2+. Firstly, NPG modified electrode surface were employed as a platform for the immobilization of thiolated probe DNA, and then, hybridized with DNAzyme catalytic beacons. The Pb2+–induced catalytic reaction makes the substrate strand break at the cleavage sitGe irreversibly, which disturbs the formation of DNA strands. AQDS served as an indicator that intercalated into the base–pairing regions of DNAzyme, resulting in a strong electrochemical signal. In the presence of Pb2+, the complementary regions were reduced, due to the fracture of the DNA strand, resulting in the release of AQDS. And a decreased current was obtained, corresponding to Pb2+ concentration. Taking advantage of the amplification effect of NPG electrode for increasing the reaction sites of thiol modified capture probe, the proposed electrochemical biosensor could detect Pb2+ quantitatively, in the range of 1–120nM, with a limit of detection as low as 0.02nM, which is much lower than the maximum contamination level for Pb2+ in drinking water defined by the U.S. Environmental Protection Agency. The electrochemical sensor was also used to detect Pb2+ from real water samples, and the results showed excellent agreement with the values determined by inductively coupled plasma mass spectroscopy. This biosensor showed a promising potential for on–site detecting Pb2+ in aqueous environment.

Synthesis and application of novel ion-imprinted polymer coated magnetic multi-walled carbon nanotubes for selective solid phase extraction of lead(II) ions

In this study, novel magnetic ion-imprinted polymer (MIIP) nanoparticles were utilized for the sensitive and selective detection of Pb(II) ions by graphite furnace atomic absorption spectrometry (GFAAS). The Pb(II)-imprinted polymer was synthesized by using 4-vinylpyridine (4VP) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, 2,3,5,6-tetra(2-pyridyl) pyrazine (TPPZ) as the chelating agent and magnetic multi-walled carbon nanotubes (MMWCNTs) as the carrier. The synthesized MIIP materials were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM). Various analytical parameters such as extraction and desorption time, eluent type and concentration, pH and sample volume were systematically examined. The selectivity of MIIP sorbent for Pb(II) ions in the presence of some cations was also evaluated. The limit of detection (LOD, 3Sb) and the relative standard deviation (RSD, n=8, c=25ngL−1) were found to be 2.4ngL−1 and 5.6%, respectively. The maximum sorption capacity of the MIIP for Pb(II) was found to be 48.1mgg−1. Finally, the proposed analytical procedure was successfully applied to monitoring lead in human hair and water samples with satisfactory results for the spiked samples.

A novel biomimetic logic gate for sensitive and selective detection of Pb(II) base on porous alumina nanochannels

A novel biomimetic logic gate sensor for Pb2 + is established using porous alumina membrane nanochannels modified with morpholino and DNA. It is based on electrochemical detection, and the current response from the diffusion flux of Fe(CN)63 − is influenced by the steric blockage and charge repulsion in nanochannels. A limit of detection (0.1 nM) and good linear range (0.1 nM–5 μM) for Pb2 + analysis are achieved in the tenth cycle. The sensing strategy shows prospective application in drug release, artificial ion channels, DNA logic gates for controlling biomolecule, and ion translocation.

Dansylamide derivatives of 1,8-anthraquinone-18-crown-5: synthesis, characterization and selective detection of Pb(II)

Dansylamide derivatives of an 1,8-anthraquinone-18-crown-5 anthracenone macrocycle have been synthesized by acid catalyzed nucleophilic substitution followed by reduction with sodium borohydride to yield new fluorosensors, 2 and 3, as characterized by elemental analyses, 1H and 13C NMR, ESI–MS, and X-ray crystallography. The optical properties of 2 and 3 were investigated with various metal cations and found to be selective for Pb(II) ion. Substantial ON-OFF quenching of the dansylamide fluorescence was observed after addition of Pb(II). Competition studies with other metal ions were conducted with Pb(II) and ESI–MS, UV/Vis and NMR titrations were carried out to determine a 1:1 binding stoichiometry and association constants with Pb(II) (7.5 × 103 M−1) and compared to fluorescence quenching of the free dansylamide fluorophore (80 M−1). While Pb(II) binding is reversible, as determined by addition of EDTA in an aqueous solution, cations with higher oxidation potentials quench fluorescence via a different mechanism involving oxidation of the macrocycle in a chemodosimeter type response.

Highly sensitive and selective detection of Pb2+ ions using a novel and simple DNAzyme-based quartz crystal microbalance with dissipation biosensor.

A novel, label-free DNAzyme-based quartz crystal microbalance with dissipation monitoring (QCM-D) biosensor was developed for the highly sensitive and specific detection of Pb(2+) ions. To enhance the performance of the sensor, oligonucleotide-functionalized gold nanoparticles were used for both frequency and dissipation amplification. This sensor was developed by immobilizing Pb(2+)-specific DNAzymes onto the QCM-D sensor surface and allowing them to hybridize with substrate-functionalized AuNPs. The DNAzyme catalyzed the cleavage of the substrate in the presence of Pb(2+) ions, causing the cleaved substrate-functionalized AuNPs to be removed from the sensor surface. Thus, Pb(2+) ions can be determined on-line by monitoring the change in frequency and dissipation signals. The results revealed that the sensor showed a sensitive response to Pb(2+) ions with detection limits of 14 nM and 20 nM for frequency and dissipation, respectively. This QCM-D biosensor also exhibited excellent selectivity toward Pb(2+) ions in the presence of other divalent metal ions. In addition, the approach was able to detect Pb(2+) in tap water, demonstrating its great potential for monitoring drinking water quality. The proposed sensor system described here represents a new class of lead ion sensor. Its simple detection strategy makes it feasible for 'pollution-free' detection; thus, the approach could have applications in on-line water quality monitoring.