Detection Of Ions In Water Research Articles

Efficient Mercury Ion Detection in Water: CdTe/CdS/ZnS Quantum Dots as a Simple, Sensitive, and Rapid Fluorescence Sensor.

Mercury (Hg), a notorious heavy metal with detrimental impacts on human health and the environment, necessitates the development of precise measurement methods. This study introduces an expeditious and straightforward photochemical approach to synthesize thioglycolic acid (TGA)-stabilized CdTe/CdS/ZnS core/multi-shell quantum dots (QDs). The synthesized CdTe/CdS/ZnS QDs were comprehensively characterized using fluorescence spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), Field Emission Scanning Electron Microscopy (FESEM), and X-Ray diffraction (XRD). XRD and EDS results confirmed the successful formation of CdTe/CdS/ZnS structure. Also, FESEM and TEM results showed that CdTe/CdS/ZnS QDs were spherical. Results showed that synthesized Exhibiting vibrant green fluorescence and notable quenching in the presence of Hg2+ ions, these QDs emerge as promising candidates for fabricating a fluorescent sensor. The proposed sensor demonstrates notable sensitivity to Hg2+, featuring a detection limit of 16.32 nM and a linear range from 20 nM to 70 nM. The sensor's selectivity was confirmed by analyzing various anions and cations. Moreover, when tested with tap water, river water, and agricultural samples, the sensor exhibited reliable performance, validated by Inductively Coupled Plasma (ICP) analysis. Additionally, CdTe/CdS/ZnS QDs immobilized on micro pads proved effective for on-site water sample analysis, presenting a versatile solution for environmental monitoring.

Innovative indenone-derivative colorimetric fluorescent probe: A approach for copper ion detection in water.

Copper (Cu2+) is a metal chemical element closely related to human life and is widely used in many fields. However, with the discharge of copper wastewater, the water quality will be seriously affected, leading to excessive intake of Cu2+ and a variety of diseases. Hence, there is a pressing need for an effective detection method for Cu2+ in aqueous environments. Leveraging the remarkable attributes of GFP chromophores and indenone derivatives, we have created a novel colorimetric fluorescent probe P-Cu2+, tailored for efficient copper ion detection. The addition of Cu2+ causes the solution to visibly change from colorless to a pronounced yellow, enabling naked-eye detection and offering promise for real sample analysis.

Chronoamperometric Ammonium Ion Detection in Water via Conductive Polymers and Gold Nanoparticles.

Monitoring of ammonium ion levels in water is essential due to its significant impact on environmental and human health. This work aims to fabricate and characterize sensitive, real-time, low-cost, and portable amperometric sensors for low NH4+ concentrations in water. Two strategies were conducted by cyclic voltammetry (CV): electrodeposition of Au nanoparticles on a commercial polyaniline/C electrode (Au/PANI/C), and CV of electropolymerized polyaniline on a commercial carbon electrode (Au/PANIep/C). Au NPs increase the electrical conductivity of PANI and its ability to transfer charges during electrochemical reactions. The electrode performances were tested in a concentration range from 0.35 µM to 7 µM in NH4+ solution. The results show that the Au/PANI/C electrode performs well for high NH4+ concentrations (0.34 µM LoD) and worsens for low NH4+ concentrations (0.01 µM LoD). A reverse performance occurs for the electrode Au/PANIep/C, with a 0.03 µM LoD at low NH4+ concentration and 0.07 µM LoD at high NH4+ concentration. The electrodes exhibit a good reproducibility, with a maximum RSD of 3.68% for Au/PANI/C and 5.94% for Au/PANIep/C. In addition, the results of the repeatability tests show that the electrochemical reaction of sensing is fully reversible, leaving the electrode ready for a new detection event.

Flexible electronics for heavy metal ion detection in water: a comprehensive review.

Flexible electronics offer a versatile, rapid, cost-effective and portable solution to monitor water contamination, which poses serious threat to the environment and human health. This review paper presents a comprehensive exploration of the versatile platforms of flexible electronics in the context of heavy metal ion detection in water systems. The review overviews of the fundamental principles of heavy metal ion detection, surveys the state-of-the-art materials and fabrication techniques for flexible sensors, analyses key performance metrics and limitations, and discusses future opportunities and challenges. By highlighting recent advances in nanomaterials, polymers, wireless integration, and sustainability, this review aims to serve as an essential resource for researchers, engineers, and policy makers seeking to address the critical challenge of heavy metal contamination in water resources. The versatile promise of flexible electronics is thoroughly elucidated to inspire continued innovation in this emerging technology arena.

Hectorite/Phenanthroline-Based Nanomaterial as Fluorescent Sensor for Zn Ion Detection: A Theoretical and Experimental Study

The development of fluorescent materials that can act as sensors for the determination of metal ions in biological fluids is important since they show, among others, high sensitivity and specificity. However, most of the molecules that are used for these purposes possess a very low solubility in aqueous media, and, thus, it is necessary to adopt some derivation strategies. Clay minerals, for example, hectorite, as natural materials, are biocompatible and available in large amounts at a very low cost that have been extensively used as carrier systems for the delivery of different hydrophobic species. In the present work, we report the synthesis and characterization of a hectorite/phenanthroline nanomaterial as a potential fluorescent sensor for Zn ion detection in water. The interaction of phenanthroline with the Ht interlaminar space was thoroughly investigated, via both theoretical and experimental studies (i.e., thermogravimetry, FT-IR, UV-vis and fluorescence spectroscopies and XRD measurements), while its morphology was imaged by scanning electron microscopy. Afterwards, the possibility to use it as sensor for the detection of Zn2+ ions, in comparison to other metal ions, was investigated through fluorescent measurements, and the stability of the solid Ht/Phe/Zn complex was assessed by different experimental and theoretical measurements.

Ag-Loaded WS2-Based Pb2+ Ion Detection in Water

Ag-Loaded WS₂-Based Pb²⁺ Ion Detection in Water

An Electrolyte-Gated Graphene Field-Effect Transistor for Detection of Gadolinium(III) in Aqueous Media

In this work, an electrolyte-gated graphene field-effect transistor is developed for Gd3+ ion detection in water. The source and drain electrodes of the transistor are fabricated by photolithography on polyimide, while the graphene channel is obtained by inkjet-printing a graphene oxide ink subsequently electro-reduced to give reduced graphene oxide. The Gd3+-selective ligand DOTA is functionalized by an alkyne linker to be grafted by click chemistry on a gold electrode without losing its affinity for Gd3+. The synthesis route is fully described, and the ligand, the linker and the functionalized surface are characterized by electrochemical analysis and spectroscopy. The as functionalized electrode is used as gate in the graphene transistor so to modulate the source-drain current as a function of its potential, which is itself modulated by the concentration of Gd3+captured on the gate surface. The obtained sensor is able to quantify Gd3+ even in a sample containing several other potentially interfering ions such as Ni2+, Ca2+, Na+ and In3+. The quantification range is from 1 pM to 10 mM, with a sensitivity of 20 mV dec-1 expected for a trivalent ion. This paves the way for Gd3+ quantification in hospital or industrial wastewater.

Highly stable multi-encapsulated red-emitting cesium lead halide nanocrystals for efficient copper ion detection and imaging in live cells

Recently, cesium lead halide (CsPbX3: X = Cl, Br, I) perovskite nanocrystals (NCs) have shown potentiality in the detection of different heavy metal ions and bioimaging applications for their smaller particle size, tunable emission spectra, high luminescent intensity, narrow emission spectra, multiphoton absorption property, etc. CsPbBr3 NCs are explored extensively in bioimaging applications for their comparatively higher stability in water. A longer wavelength excitation light source is recommended due to less scattering of light results in deeper penetration in living cells. However, imaging in live cells with red-emitting perovskite NCs is not suitable because of their poor structural stability, low emission intensity, and complex synthesis process. To tackle these issues, we introduce a specific halide exchange to the NCs and then multi-encapsulation shelling techniques that eventually improve the structural and environmental stability of the red-emitting NCs. Here, we synthesized Zn-doped CsPbBr3 NCs via the ligand-assisted reprecipitation (LARP) synthesis method in an open atmosphere. Then the highly luminescent red emitting CsPbBrxI3−x NCs with Zn doping were grown via the exchange of halide ions from pre-synthesized Zn-doped CsPbBr3 NCs to maintain the stable perovskite crystal structure in the nanoscale regime. Such NCs were further encapsulated with different shelling materials and then compared their photophysical properties. Among them, n-isopropyl acrylamide passivated Zn-doped CsPbBrxI3−x/SiO2/polyvinylpyrrolidone core/shell/shell NCs showed the highest stability against water and UV-irradiation. These NCs efficiently detect Cu2+-ions in water and achieved a detection limit of around 9.68 µM. The NCs were also tested for their compatibility as a fluorescent probe for live cell imaging using mammalian Chinese Hamster Ovary cells. As a proof-of-principle, we demonstrate both the efficient uptake and biocompatibility of the perovskite NCs. This work provides insight for expanding research activities on red-emitting perovskite NCs by developing a new strategy to improve the stability of the NCs, which is beneficial for both cost-effective bioimaging applications and heavy metal ion detection in water.

MIL-88B(Fe)-NH2: an amine-functionalized metal-organic framework for application in a sensitive electrochemical sensor for Cd2+, Pb2+, and Cu2+ ion detection.

We propose here an electrochemical platform for multi-heavy metal ion detection in water based on MIL-88B(Fe)-NH2, an amine-functioned metal-organic framework (MOF) for modifying the surface of a glassy carbon electrode (GCE). Herein, MIL-88B(Fe)-NH2 with abundant functionalized amine groups can play the role of capture sites for the enrichment of metal ions before electrochemical oxidation sensing. MIL-88B(Fe)-NH2 was synthesized under optimized conditions through a solvothermal method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transition electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. MIL-88B(Fe)-NH2 was then drop-casted on GCE to electrochemically determine the Cd2+, Pb2+ and Cu2+ ion concentrations by differential pulse voltammetry (DPV). The electrochemical sensor exhibits excellent electrochemical performance toward Cd2+, Pb2+ and Cu2+ ions in the large linear ranges of 0.025-1.000 μM, 0.3-10.0 μM and 0.6-10.0 μM with limits of detection that are 2.0 × 10-10 M, 1.92 × 10-7 M and 3.81 × 10-7 M, respectively. The fabricated sensor also shows high reliability and good selectivity. This MIL-88B(Fe)-NH2 application strategy is promising for the evaluation of various heavy metal ions in water.

Recent advances in photoelectrochemical sensors for detection of ions in water

Over the last 50 years, the explosive adoption of modern agricultural practices has led to an enormous increase in the emission of non-biodegradable and highly biotoxic ions into the hydrosphere. Excess intake of such ions, even essential trace elements such as Cu2+ and F−, can have serious consequences on human health. Therefore, to ensure safe drinking water and regulate wastewater discharge, photoelectrochemical (PEC) online sensors were developed, with advantages such as low energy consumption, inherent miniaturization, simple instrumentation, and fast response. However, there is no publicly available systematic review of the recent advances in PEC ion sensors available in the literature since January 2017. Thus, this review covers the various strategies that have been used to enhance the sensitivity, selectivity, and limit of detection for PEC ion sensors. The photoelectrochemically active materials, conductive substrates, electronic transfer, and performance of various PEC sensors are discussed in detail and divided into sections based on the measurement principle and detected ion species. We conclude this review by highlighting the challenges and potential future avenues of research associated with the development of novel high-performance PEC sensors.

Synthesis of highly stable double-coated Zn-doped cesium lead bromide nanocrystals for indium ion detection in water

Double-coated CsPbBr3@SiO2@PVP perovskite NCs exhibit higher luminous intensity and better structural stability than those without PVP, enabling indium ion detection in water.

Graphene oxide modified tilted fiber Bragg grating for 10<sup>–12</sup> level heavy metal ion sensing

Graphene oxide (GO) is an ideal label-free sensing material with its super large specific surface area and abundant surface functional groups. Considering its insulating characteristic, the GO is suitable for optics-based heavy metal ion sensing. However, given the large surface tension of water and the hydrophilicity of GO, the agglomeration or wrinkles of GO nanosheets is usually inevitable during coating with aqueous dispersion. This reduces the accessible surface area and surface functional groups of GO, thereby degrading the sensing performance. Here, an ultra-sensitive GO functionalized tilted fiber Bragg grating (TFBG) sensor is designed to detect heavy metal ions in aqueous solutions. Firstly, a strategy of free energy manipulation is employed to avoid the wrinkles and agglomeration of GO nanosheets. In the scenario of aqueous dispersion, the GO nanosheets will wrinkle as the water droplets evaporate and shrink. In contrast, using the lower-surface-tension ethanol as the dispersant and a high-surface-energy substrate processed by oxygen plasma, the dispersion will evenly spread on the substrate instead of forming droplets. When ethanol evaporates, GO nanosheets are attached to the substrate in largest possible area to reduce the free energy of the system, by which a GO film without agglomeration or wrinkles can be obtained. Secondly, the intrinsic sensitivity of TFBG is conducive to the detection of heavy metal ions in water. Mode interference occurs between the cladding mode and the core mode in the TFBG, and the wavelength and intensity of the interference are highly sensitive to the surrounding temperature, stress, and refractive index. Combining the above characteristics, the GO functionalized TFBG is highly sensitive to Pb<sup>2+</sup>, Cd<sup>2+</sup>, and Cu<sup>2+</sup> ions in water. These heavy metal ions are adsorbed by the GO, and thus causing the effective refractive index to increase. The results show that the adsorption of heavy metal ions makes the interference peaks red-shifted in the transmission spectrum. The lowest detection limit for Pb<sup>2+</sup> and Cd<sup>2+</sup> can reach 10<sup>–10</sup> mol/L (ng/L level), and the corresponding sensitivities are 0.426 and 0.385 dB/(nmol·L<sup>–1</sup>) (2.06 and 3.43 dB/(μg·L<sup>–1</sup>)), respectively. These superior sensing performances benefit from the high specific surface area and accessible carbonyl groups of the unfolded GO, and also rely on the excellent intrinsic sensitivity of TFBG. The GO functionalized TFBG sensor has a promising potential application in environment monitoring.

Multi-stimuli responsive fluorescence of amphiphilic AIEgen copolymers for ultrafast, highly sensitive and selective copper ion detection in water

Novel multi-stimuli responsive fluorescence sensors based on amphiphilic copolymers containing hydrophilic N-isopropylmethacrylamide (NIPAM) and AIEgenic tetraphenylethylene-dipicolylamine (TPEDPA) monomers attached to side-chains of copolymers are synthesized. Two copolymers poly(NIPAM)x-co-(TPEDPA)y prepared by free radical polymerization with different molar ratios of monomers NIPAM and TPEDPA (i.e., x:y = 60:1 and 175:1 for P1 and P2, respectively) show good solubilities in organic solvents and water, which exhibit strong cyan fluorescence at 466 nm in aggregation and solid states due to AIE behaviors of TPE units. Upon various external stimuli (temperatures and acid/base conditions), P1 and P2 possess excellent reversible thermo- and pH-responsive fluorescence turn-off/on cyan emissions of TPE units. In addition, with DPA receptor, P1 and P2 are applied as ultrafast, selective and sensitive fluorescence probes for copper ion detection in water based on the TPE fluorescence quenching via photoinduced electron transfer (PET) phenomena, which can be recovered by the addition of disodium ethylenediaminetetraacetate solution. Owing to good water solubilities, amphiphilic copolymers P1 and P2 (containing only 1.6 and 0.6 % molar ratios of AIEgen) exhibit significant sensing towards Cu2+ with very prominent limit of detection values (LOD = 57 and 72 nM, respectively), which are much better than that of hydrophobic monomer TPEDPA (590 nM). Moreover, the fluorescence quenching of TPE units due to PET phenomena is further confirmed by theoretical calculations. Additionally, as an excellent quenching fluorescence sensor with good biocompatibility of P1, its recognition of copper ion and bio-imaging applications in living cells are also reported in this research.

A three-component copper phosphonate complex as a sensor platform for sensitive Cd2+ and Zn2+ ion detection in water via fluorescence enhancement

A three-component molecular copper phosphonate [Cu2(H4tpmm)2(Hpybim)2]·H2O (1·H2O), where H6tpmm ​= ​2,4,6-tris(phosphorylmethyl)mesitylene and Hpybim ​= ​2-(2-pyridyl)benzimidazole, showing high thermal stability up to approximately 370 ​°C has been prepared. Complex 1·H2O has a dinuclear structure symmetry-related by a crystallographic inversion center, in which the Cu(II) center suits a highly distorted square pyramidal geometry. Complex 1·H2O shows two extremely weak emission bands in both solid state and H2O suspension phase. However, as Cd2+ and Zn2+ were added into the H2O suspension of 1·H2O, the fluorescence intensity would be remarkably enhanced by 11.1 and 25.2 times, respectively, with a dramatic change in the emission band shape. The fluorescence enhancement sensing of 1·H2O toward Cd2+ and Zn2+ in H2O is highly sensitive with limit of detection (LOD) values of 1.35 and 0.89 ​μM, respectively. Such sensing performances are negligibly interfered by most perturbed metal ions but largely affected by Fe3+, Ni2+, and Co2+. EDX and XPS analyses show the occurrence of weak binding interactions between the Cd2+/Zn2+ ions and the structure of 1·H2O, resulting in fluorescence enhancement. This work demonstrates a highly water stable molecular copper phosphonate behaving as a sensor platform suitable for Cd2+ and Zn2+ ion detection in water via remarkable fluorescence enhancement, providing a new method for metal phosphonate complexes.

Two Zn(II)-based Coordination Polymers: Fe3+ Ion and Prevention Activity Detection On Postpartum Hemorrhage By Regulating Anticoagulant Factor Activity.

Two new Zn(II)-based coordination polymers {[Zn3(L1)6(H2O)]∙(H2O)4}n (1, HL1 = 4-(tetrazol-5-yl)phenyl-4,2':6',4″-terpyridine) and [Zn2Cl2(L2)2H2O]n (2, HL2 = 4-([2,2':6',2″'-terpyridin]-4'-yl)benzoic acid) have been successfully prepared using two similar organic ligands with distinct donor groups under similar reaction conditions. The distinct structural features and donor atoms make the two complexes show different water stability, and the complex 1 with good water stability, which can be utilized as the sensor for Fe3+ ion detection in water. The value of Stern-Volmer quenching constant of 1 to the Fe3+ is 5.77 × 104 M- 1, which lies in the top region of the reported CP-based sensors. The mechanism investigation reveals that the energy transfer of resonance from the complex 1 to the Fe3+ ion can account for its fluorescent quenching behavior. The treatment activity of compounds 1 and 2 on the postpartum hemorrhage (PPH) was assessed. First, the cytotoxicity of compounds 1 and 2 on human umbilical vein endothelial cells was assessed with Cell Counting Kit-8 detection kit. Then, to evaluate the prevention of compounds 1 and 2 on the PPH, we conducted the Lowry method and detected the clotting factor IX and anticoagulant factor III contents after the indicated treatment. Finally, the inflammatory response in mice was determined by ELISA method, and the IL-6 and IL-8 levels were determined.

Blue-emitting fluorescent carbon quantum dots from waste biomass sources and their application in fluoride ion detection in water

Carbon quantum dots (CQDs) are among the most feasible allotropes of carbon-based nanomaterials with unique characteristics of photoluminescence, bio-compatibility, and high stability. Herein, a green and eco-friendly approach has been propagated for the fabrication of CQDs from different biomass waste materials including sugarcane bagasse (SCB), garlic peels (GP), and taro peels (TP) by using ultrasonic-assisted wet-chemical-oxidation method. This top-down approach involves oxidation of the carbonized biomass wastes by H2O2. Another purpose of our work is to make a comparative study on the three CQDs produced from the three different biomass wastes. The properties of the fabricated CQDs were evaluated by using High Resolution-Transmission Electron Microscopy (HR-TEM), Fourier Transform-Infrared (FT-IR) spectroscopy, X-ray Diffraction (XRD), and X-ray Photoelectron spectroscopy (XPS), respectively. The CQDs showed the characteristic photo-physical behaviours as evident from the UV–visible and fluorescence (FL) spectroscopic analyses. The CQDs are found to be highly water soluble possessing strong blue-fluorescence under UV light with excellent quantum yield around 4–27%. The comparative study on the different physico-chemical properties of the three wastes biomass-derived CQDs are also discussed in the paper. The FL properties of CQDs derived from taro peels waste shows the best fluorescence quantum yield among the three and keeping in view of this, an on−off−on fluorescence nanoprobe was designed by using taro peels-derived CQDs (i.e. T-CQDs) and Eu3+ ion. The FL emission of T-CQDs was observed to be significantly quenched by Eu3+ leading to the formation of a CQDs-Eu3+ nanoprobe. The CQDs-Eu3+ nanoprobe was promisingly used for sensing of fluoride ions in water.

Off/On Amino-Functionalized Polyhedral Oligomeric Silsesquioxane-Perylene Diimides Based Hydrophilic Luminescent Polymer for Aqueous Fluoride Ion Detection.

Fluoride ion detection in water focuses much attention due to the serious healthy impact in human pathologies. For fluoride recognition, the chemical affinity between fluoride and silicon has been developed on the basis of the degradation mechanism. However, most fluorescent probes are the "turn off" type due to the aggregation of the degradational products. Herein, we first developed an "off-on" hydrophilic luminescent polymer composed of amino-functionalized polyhedral oligomeric silsesquioxane (AE-POSS) and perylene diimides (PDIs) for fluoride ion in water. The AE-PDI polymer was "turned off" because of the photoinduced electron transfer (PET) between PDI and AE-POSS, and then after reaction with F-, the fluorescent emission could "turn on" obviously because the PET was blocked by the degradation of the cage. The PET from amino-POSS to PDI was proved by FL spectrum and energies of HOMO and LUMO orbitals. 29Si, 19F NMR, and 1H NMR titration, XRD, FTIR, size analysis, and ion chromatography were applied to demonstrate the degradation mechanism. These results indicated that the higher quantum yield could be obtained by introducing the amide group in the PDI and the products of AE-PDI polymer might exist in the form of complex compounds with partial condensation of organosiloxane. With high selectivity and sensitivity (detection limit of 16.2 ppb), this probe was successfully applied for F- detection in actual water samples.

Field-Effect Transistor Based on Percolation Network of Reduced Graphene Oxide for Real-Time ppb-Level Detection of Lead Ions in Water

Real-time lead ion monitoring for drinking water is in an urgent demand, due to the high biotoxicity of lead. We fabricated a reduced graphene oxide (rGO) percolation network based field-effect transistor (FET) by using an easy and scalable micromolding-in-capillary method for lead ion detection in water. The percolation theory analysis elucidates that the required GO mass concentration for a 2D continuum connection converges at a predictable value. Guided by the theoretical analysis, the prepared rGO network was constructed with 1–4 layers of rGO flakes and exhibits comparable electrical properties with single-layer rGO devices. A thin Al2O3 layer was deposited on the device to isolate the analyte from the FET device. With the specific L-Glutathione reduced (GSH) probe, the sensor can reach a limit of detection (LOD) in ppb-level to lead ions. In addition, good selectivity and the high sensing response to Pb2+ concentrations around 15 ppb (maximum contaminant level of lead for drinking water, US Environmental Protection Agency) suggest our sensor holds great potential for lead ion monitoring in drinking water.

Zinc-Adeninate Metal-Organic Framework: A Versatile Photoluminescent Sensor for Rare Earth Elements in Aqueous Systems.

Rare earth elements (REEs) are strategically important for national security and advanced technologies. Consequently, significant effort has been devoted towards increasing REE domestic production, including the extraction of REEs from coal, coal combustion byproducts, and their associated waste streams such as acid mine drainage. Analytical techniques for rapid quantification of REE content in aqueous phases can facilitate REE recovery through rapid identification of high-value waste streams. In this work, we show that BioMOF-100 can be used as a fluorescent-based sensitizer for emissive REE ion detection in water, providing rapid (<10 min) analysis times and sensitive detection (parts-per-billion detection limits) for terbium, dysprosium, samarium, europium, ytterbium, and neodymium, even in the presence of acids or secondary metals.

High Field Modulated Field Effect Transistors Coated By Ion Selective Membrane for Cadmium Ion Detection in Water

Cadmium is one among the most hazardous heavy metals. Heavy metal cannot be metabolized or digested by human body, therefore, heavy metal accumulates in our body through time. Cadmium in human body causes lung cancer, osteomalacia and even proteinuria. Mostly cadmium ions get in to human body by ingestion, so detecting cadmium ion in drinking water, tap water and liquid form of food is very important. However, traditional laboratory detection methods of cadmium ion are complex and time consuming and requires heavy and expensive machinery. Though the electrochemical ion selective electrode is easy to use, its poor stability and larger detection limit are huge disadvantages. In this research, we devised a small size, high sensitivity, low detection limit, short response time and easy to fabricate cadmium ion selective membrane field effect transistor (ISMFET). This device is easy to use and can measure the cadmium concentration in water quickly with the combination of ion-selective membrane and field effect transistor. The sensing mechanism depends on electrical double layer (EDL) gating coupled with high electric field to enhance the sensitivity of ISHEMT beyond the limit of ideal Nernst sensitivity. World Health Orgnization (WHO) suggests that cadmium ion in drinking water should be lower than 3 ppb, equal to 2.68 10-8 M. This device can detect cadmium ion concentration form 10-7 M to 10-11 M, covering the wide dynamic range according to WHO’s suggestion. Such high sensitivity and low detection limits devices are highly desirable for consumers who intend to regularly monitor the water quality, for food and environmental safety. In contrast, testing cadmium ion in water by ICP-MS takes several hours and the instrument occupies larger space. To improve the yield and sensitivity of our sensor, we are studying on different condition of ISM. With this cadmium, ISMFET, we can determine the cadmium concentration in water in 15 minutes and even higher sensitivity and lower detection limit, in comparison with conventional laboratory based techniques. Not only Cadmium, but also other heavy metals, for example lead and mercury, can use similar methodology to get better detection time and detection limit. This design makes quality monitoring of water we consume in daily life become much easier and convenient.