Detection Of Ions In Water Research Articles

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. 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.

Synthesis of Carbon Dots from Pear Juice for Fluorescence Detection of Cu2+ Ion in Water.

In this work, a facile green hydrothermal method was developed for the synthesis of carbon dots with fluorescent property using pear juice as raw materials. The synthesized carbon dots were characterized by UV-vis, fluorescence and transmission electron microscopic techniques. The synthesized conditions were optimized and the obtained carbon dots exhibited an average size at 10 nm with bright emission centered at 455 nm (blue color) under UV light with the excitation wavelength at 360 nm. The as-prepared carbon dots exhibited quenching effect in the presence of Cu2+ ion and a method for Cu2+ ion detection in water was developed with acceptable selectivity. The synthesized fluorescent carbon dots showed advantages like easy preparation, low cost and environmental friendly. It could be useful in chemical and biochemical detection.

A porous Zn(II)-based metal–organic framework for highly selective and sensitive Fe3+ ion detection in water

A new highly porous metal–organic framework, namely {[Zn3(bpydb)2(atz)2(DMF)](DMF)6}n, was solvothermally synthesized using 4,4′-(4,4′-bipyridine-2,6-diyl) dibenzoic acid (bpydbH2), 3-amino-1,2,4-triazole (Hatz) and Zn(NO3)2·6H2O as the starting materials. Single crystal X-ray structural analysis shows that compound 1 is composed of 1D helical Zn-triazolate chain building units that connected by the deprotonated bpydbH2 ligand to form a (3,4,6)-connected net. Due to its strong fluorescent emission and high porosity, compound 1 could behave as a chemosensor for selective detection of Fe3+ ion with high selectivity and sensitivity in water. In connection to this, the detection mechanism and the host–guest interaction have also been investigated via computational analysis.

Design and Fabrication of a Highly Stable Polymer Carbon Nanotube Nanocomposite Chemiresistive Sensor for Nitrate Ion Detection in Water

Agricultural and industrial wastes cause contamination of groundwater by the accumulation of various organic, inorganic and metallic pollutants including nitrate ions. In this work, a conducting polymer is designed and synthesized to interact specifically with nitrate ions in water. This designed molecule has conjugation in the backbone, also thiourea moiety which interacts and complexes with the analyte nitrate ions by hydrogen bonding. This binding with nitrate ion perturbs the electron distribution along conjugated polymer backbone which translates to change in conductivity of the polymer. This response of the change in conductivity is used as chemosensing. The sensor exhibited stability, repeatability and reproducibility for more than 20 months. The sensor performance is further compared with a nitrate ion selective electrode for real-world sample applications. The electronic property of the polymer and complex and interaction mechanism is elucidated using UV-Visible spectroscopy, dynamic light-scattering analysis and density functional theory calculations. A practically useful lower limit of detection by the present method is ∼14 ppm NO3−- N in pH 7 water.

Improved Synthesis Method of SiO<sub>2</sub>@Ag Core-Shell for Detection of Toxic Metals in Water

Silvernanoshell consisting of Ag coated on SiO2 core was synthesized and employed as a colorimetric probe for detection of toxic metals ions in water. The SiO2@Ag Core-Shell preparation method was fine-tuned and adjusted to prepare a mono-dispersed and fully encapsulated Ag nanoshell. Silica core spheres with the average diameter of 100 nm was prepared by Stöber method and subsequently coated with AgNPs by Seed-Mediated Growth Technique using NaBH4 as a reducing agent and PVA as a stabilizer. The resulting Ag nanoparticles tethered on silica spheres were found to serve as nucleation sites for the further growth of a silver nanoshell overlayers. The SiO2@Ag was characterized by UV-Visible Spectroscopy and Transmission Electron Microscopy. It was found that the AgNPs was successfully coated on the surface of silica spheres with the average thickness around 20 nm. The adsorptivity of metal ions onto the surface of Ag nanoshell were tested and calibrated using series of Hg2+ and Pb2+ ions with various concentrations. The changes in the band intensity of the surface plasmonresonance (SPR) band, which correspond to the changes in the concentration of ions in model waste water, were evident.

Simultaneous Enrichment and On-line Detection of Low-Concentration Copper, Cobalt, and Nickel Ions in Water by Near-Infrared Diffuse Reflectance Spectroscopy Combined with Chemometrics.

Sensitive detection of heavy metal ions in water is of great importance considering the effects that heavy metals have on public health. A developed fluidized bed enrichment technique was used to concentrate and detect low concentrations of Cu2+, Co2+, and Ni2+ in water samples by near-IR diffuse reflectance (NIDR) spectroscopy (NIDRS) directly without using any chemicals or reagents. The NIDR spectra of adsorbent were measured on-line, and quantitative detection was achieved by applying a built partial least-squares chemometric model. Sensitivity and accuracy was improved significantly because large-volume mixture solutions were used in the enrichment process. Root mean square error of cross-validation values for Cu2+, Co2+, and Ni2+ were 0.29, 0.41, and 0.35 μg/mL, respectively, with mean relative error values in the acceptable range of 6.56-10.27%. This study confirms the potential application of fluidized bed enrichment combined with NIDRS and chemometrics for the simultaneous detection of trace heavy metal ions in water, with low relative error.

White light emission by controlled mixing of carbon dots and rhodamine B for applications in optical thermometry and selective Fe3+detection

Controlled mixing of rhodamine B with fluorescent carbon dots derived from β-carotene resulted in a white light emitting mixture that could be used for optical thermometry and Fe3+ion detection in water.

A catalytic chemodosimetric approach for detection of nanomolar cyanide ions in water, blood serum and live cell imaging.

Naphthimidazolium based monocationic chemodosimeters CD-1 and CD-2 undergo cyanide mediated catalytic transformation in the presence of cyanide ions (0.01% to 1% of CD-1/CD-2 concentrations) with a turnover number from 70 to 360. These chemodosimeters can detect as low as 0.5 nM and 1 nM cyanide ions under nearly physiological conditions (HEPES buffer-DMSO (5%), pH 7.4). The structures of CD-1 and its cyanide induced hydrolyzed product 4 have been confirmed by single crystal X-ray crystallography. CD-1 can also be used for the determination of 2 nM cyanide in the presence of blood serum. CD-1 and CD-2 also find applications in live cell imaging of 10 nM cyanide ions in rat brain C6 glioma cells. To the best of our knowledge, this is the first report where high sensitivity towards cyanide ions has been achieved through catalytic hydrolysis of the fluorescent chemodosimeter.

CdTe QDs functionalized mesoporous silica nanoparticles loaded with conjugated polymers: A facile sensing platform for cupric (II) ion detection in water through FRET

This paper reported a facile method for fabricating CdTe quantum dots decorated fluorescent mesoporous silica nanoparticles containing poly(p-phenylenevinylene) by electrostatic interaction in aqueous solution. The resulted fluorescent hybrid nanomaterials showed the dual-emission centered at 500 nm and 717 nm, which can be used as a fluorescent probe to detect Cu2+ in water through fluorescence resonance energy transfer. Cu2+ can be captured by the amino groups of the polyethyleneimine to form an absorbent complex, resulting in a strong quenching of red-emission from CdTe quantum dots on the surface of nanoparticles via energy transfer. However, the green-emission of poly(p-phenylenevinylene) remained. Therefore the addition of Cu2+ induced the fluorescent evolution of the nanoprobe from red to green. The nanoprobe provided an efficient platform for the sensing of Cu2+ with a detection limit of 31.2 nM. Compared with pure quantum dots, the nanoprobe can distinguish Cu2+ from Hg2+.

Ratiometric Fluorescent Ion Detection in Water with High Sensitivity via Aggregation‐Mediated Fluorescence Resonance Energy Transfer Using a Conjugated Polyelectrolyte as an Optical Platform

A cationic conjugated polyelectrolyte was designed and synthesized based on poly(fluorene-co-phenylene) containing 5 mol% benzothiadiazole (BT) as a low energy trap and 15-crown-5 as a recognizing group for potassium ions. A potassium ion can form a sandwich-type 2:1 Lewis acid-based complex with 15-crown-5, to cause the intermolecular aggregation of polymers. This facilitates inter-chain fluorescence resonance energy transfer (FRET) to a low-energy BT segment, resulting in fluorescent signal amplification, even at dilute analyte concentrations. Highly sensitive and selective detection of K(+) ions was demonstrated in water. The linear response of ratiometric fluorescent signal as a function of [K(+) ] allows K(+) quantification in a range of nanomolar concentrations with a detection limit of ≈0.7 × 10(-9) M.

A fluorescent probe for the selective detection of sulfate ions in water

A nicotinamide–anthracene conjugate based fluorescent probe 1 exhibits highly selective fluorescence enhancement at 535 nm only with sulfate in HEPES buffer–DMSO (9:1) at pH 7.4. The other anions viz. F−, Cl−, Br−, I−, AcO−, HSO4−, H2PO4−, CN−, OH−, NO3−, ClO4−, SCN−, even if present in excess, do not interfere in the estimation of sulfate. The limit of detection for sulfate ions by probe 1 is 0.5 μM. Probe 1 can also be used to determine the sulfate ions in tap water using EDTA as a metal ion masking agent. Titration experiments and Job's plot reveal the formation of a 1:1 stoichiometric complex between the probe 1 and sulfate ions and DFT studies show the electron transfer from SO42− to anthracene moiety responsible for the observed optical changes.