Optical Detection of Fe3+ Ions in Aqueous Solution with High Selectivity and Sensitivity by Using Sulfasalazine Functionalized Microgels.
ABSTRACT: A highly selective and sensitive optical sensor was developed to colorimetric detect trace Fe3+ ions in aqueous solution. The sensor was the sulfasalazine (SSZ) functionalized microgels (SSZ-MGs), which were fabricated via in-situ quaternization reaction. The obtained SSZ-MGs had hydrodynamic radius of about 259 ± 24 nm with uniform size distribution at 25 °C. The SSZ-MG aqueous suspensions can selectively and sensitively response to Fe3+ ions in aqueous solution at 25 °C and pH of 5.6, which can be quantified by UV-visible spectroscopy and also easily distinguished by the naked eye. Job's plot indicated that the molar binding ratio of SSZ moiety in SSZ-MGs to Fe3+ was close to 1:1 with an apparent association constant of 1.72 × 104 M-1. A linear range of 0-12 μM with the detection limit of 0.110 μM (0.006 mg/L) was found. The obtained detection limit was much lower than the maximum allowance level of Fe3+ ions in drinking water (0.3 mg/L) regulated by the Environmental Protection Agency (EPA) of the United States. The existence of 19 other species of metal ions, namely, Ag+, Li+, Na+, K+, Ca2+, Ba2+, Cu2+, Ni2+, Mn2+, Pb2+, Zn2+, Cd2+, Co2+, Cr3+, Yb3+, La3+, Gd3+, Ce3+, and Bi3+, did not interfere with the detection of Fe3+ ions.
Project description:Electrospun nanofiber membrane (ENM) with huge specific surface area is an ideal solid substrate for sensors. However, only a few ENMs are developed into colorimetric sensors and it is even more challenging to fabricate multiple-ion-responsive ENM-based colorimetric sensor. In this study, benefiting from the excellent metal ion adsorption ability of poly(aspartic acid) (PASP) and high specific surface area of nanofibers, a reusable colorimetric sensor utilizing PASP electrospun nanofiber hydrogel membrane (ENHM) was designed to detect Cu2+ and Fe3+ in aqueous solution with simple filtration. The sensor based on PASP-ENHM exhibited high sensitivity and selectivity, and colorimetric responses for Cu2+ and Fe3+ detection could be observed by the naked eye. Upon exposure to Cu2+ aqueous solution, the color of the sensor changed from white to blue with a naked eye detection limit of 0.3 mg/L, while it turned from white to yellow with a detection limit of 0.1 mg/L for Fe3+ detection. Furthermore, this sensor was reusable after metal ion extraction by the desorption process.
Project description:In this work, an aggregation-induced emission (AIE) sensor for the detection of Fe3+ ions was fabricated through the electrostatic interaction between 1,1,2-triphenyl-2-[4-(3-sulfonatopropoxyl)-phenyl]-ethene sodium salt (SPOTPE) and quaternized cellulose (QC). The structure and properties of the SPOTPE/QC nanocomplex were studied by using ¹H NMR, spectrofluorophotometer, transmission electron microscopy (TEM), and dynamic laser light scattering (DLS). An aqueous solution of SPOTPE and QC resulted in a remarkably enhanced cyan fluorescence in comparison to that of the SPOTPE solution. Strong through-space electrostatic interaction between SPOTPE and QC is the main cause for the fluorescence emerging. The fluorescence of the SPOTPE/QC solutions show good stability over a wide pH range of 5.0⁻10.0. When introducing Fe3+ ions into the SPOTPE/QC solution, the fluorescence quenched within 5 s. SPOTPE/QC solutions exhibited high selectivity and sensitivity for the detection of Fe3+ ions with ignored interferences from other ions, and the detection limit was determined to be 2.92 × 10-6 M. The quenching mechanism was confirmed to be the consequence of the binding interactions between Fe3+ ions and SPOTPE/QC complex.
Project description:A fluorescent optical fiber sensor for the detection of mercury (Hg2+) ions in aqueous solutions is presented in this work. The sensor was based on a fluorophore-labeled thymine (T)-rich oligodeoxyribonucleotide (ON) sequence that was directly immobilized onto the tip of a tapered optical fiber. In the presence of mercury ions, the formation of T-Hg2+-T mismatches quenches the fluorescence emission by the labeled fluorophore, which enables the measurement of Hg2+ ions in aqueous solutions. Thus, in contrast to commonly designed sensors, neither a fluorescence quencher nor a complementary ON sequence is required. The sensor presented a response time of 24.8 seconds toward 5 × 10-12 M Hg2+. It also showed both good reversibility (higher than the 95.8%) and selectivity: the I0/I variation was 10 times higher for Hg2+ ions than for Mn2+ ions. Other contaminants examined (Co2+, Ag+, Cd2+, Ni2+, Ca2+, Pb2+, Mn2+, Zn2+, Fe3+, and Cu2+) presented an even lower interference. The limit of detection of the sensor was 4.73 × 10-13 M Hg2+ in buffer solution and 9.03 × 10-13 M Hg2+ in ultrapure water, and was also able to detect 5 × 10-12 M Hg2+ in tap water.
Project description:A facile, economical, and one-step hydrothermal method was used to prepare highly luminescent nitrogen-doped carbon quantum dots (N-CQDs) with chitosan as both carbon and nitrogen sources. The as-prepared N-CQDs have an average size of 2 nm and exhibit excitation wavelength-dependent fluorescence with a maximum excitation and emission at 330 and 410 nm, respectively. Furthermore, due to the effective quenching effect of Fe3+ ions, the prepared N-CQDs can be used as a fluorescent sensor for Fe3+ ion-sensitive detection with a detection limit of 0.15 ?M. The selectivity experiments revealed that the fluorescent sensor is specific to Fe3+ even with interference by high concentrations of other metal ions. Most importantly, the N-CQD-based Fe3+ ion sensor can be successfully applied to the determination of Fe3+ in real water samples. With excellent sensitivity and selectivity, such stable and cheap carbon materials are potentially suitable for the monitoring of Fe3+ in environmental application.
Project description:Anthropogenic copper pollution of environmental waters from sources such as acid mine drainage, antifouling paints, and industrial waste discharge is a major threat to our environment and human health. This study presents an optical sensing system that combines self-assembled glutaraldehyde-cross-linked double-layered polyethylenimine (PEI-GA-PEI)-modified nanoporous anodic alumina (NAA) interferometers with reflectometric interference spectroscopy (RIfS) for label-free, selective monitoring of ionic copper in environmental waters. Calibration of the sensing system with analytical solutions of copper shows a linear working range between 1 and 100 mg L-1, and a low limit of detection of 0.007 ± 0.001 mg L-1 (i.e., ?0.007 ppm). Changes in the effective optical thickness (?OTeff) of PEI-GA-PEI-functionalized NAA interferometers are monitored in real-time by RIfS, and correlated with the amount of ionic copper present in aqueous solutions. The system performance is validated through X-ray photoelectron spectroscopy (XPS) and the spatial distribution of copper within the nanoporous films is characterized by time-of-flight-secondary ion mass spectroscopy (TOF-SIMS). The specificity and chemical selectivity of the PEI-GA-PEI-NAA sensor to Cu2+ ions is verified by screening six different metal ion solutions containing potentially interfering ions such as Al3+, Cd2+, Fe3+, Pb2+, Ni2+, and Zn2+. Finally, the performance of the PEI-GA-PEI-NAA sensor for real-life applications is demonstrated using legacy acid mine drainage liquid and tap water for qualitative and quantitative detection of copper ions. This study provides new opportunities to develop portable, cost-competitive, and ultrasensitive sensing systems for real-life environmental applications.
Project description:Furocoumarin (furo[3,2-c]coumarin) derivatives have been synthesized from single step, high yielding (82-92%) chemistry involving a 4-hydroxycoumarin 4?+?1 cycloaddition reaction. They are characterized by FTIR, 1H-NMR, and, for the first time, a comprehensive UV-Vis and fluorescence spectroscopy study has been carried out to determine if these compounds can serve as useful sensors. Based on the fluorescence data, the most promising furocoumarin derivative (2-(cyclohexylamino)-3-phenyl-4H-furo[3,2-c]chromen-4-one, FH), exhibits strong fluorescence (?F?=?0.48) with long fluorescence lifetime (5.6?ns) and large Stokes' shift, suggesting FH could be used as a novel fluorescent chemosensor. FH exhibits a highly selective, sensitive and instant turn-off fluorescence response to Fe3+ over other metal ions which was attributed to a charge transfer mechanism. Selectivity was demonstrated against 13 other competing metal ions (Na+, K+, Mg2+, Ca2+, Mn2+, Fe2+, Al3+, Ni2+, Cu2+, Zn2+, Co2+, Pb2+ and Ru3+) and aqueous compatibility was demonstrated in 10% MeOH-H2O solution. The FH sensor coordinates Fe3+ in a 1:2 stoichiometry with a binding constant, Ka?=?5.25 × 103?M-1. This novel sensor has a limit of detection of 1.93?µM, below that of the US environmental protection agency guidelines (5.37?µM), with a linear dynamic range of ~28 (~2-30?µM) and an R2 value of 0.9975. As an exemplar application we demonstrate the potential of this sensor for the rapid measurement of Fe3+ in mineral and tap water samples demonstrating the real-world application of FH as a "turn off" fluorescence sensor.
Project description:A novel conjugated polymer (PDBDBM) was developed by the polymerization of 1,4-dioctyloxy-2,5-diethynylbenzene with 1,3-bis(4-bromophenyl)propane-1,3-dione based on Pd-catalyzed Sonogashira-coupling reaction. The obtained polymer PDBDBM exhibited bright green photoluminescence under UV irradiation. According to the metal ion titration experiments, PDBDBM showed high sensitivity and selectivity for detection of Cu2+ and Fe3+ over other metal ions. The fluorescent detection limits of PDBDBM were calculated to be 5 nM for Cu2+ and 0.4 μM for Fe3+ and the Stern⁻Volmer quenching constant for Cu2+ and Fe3+ were found to be 1.28 × 10⁸ M-1 and 2.40 × 10⁴ M-1, respectively. These results indicated that the polymer can be used as a potential probe for Cu2+ and Fe3+ detection.
Project description:Ferric ions (Fe3+ ions) and l-cysteine (( l-Cys) in the human body have always played an irreplaceable role in biological processes, and overload or deficiency of Fe3+ ions and l-Cys in the biological system leads to various diseases. In this work, N,S-co-doped red-emitting carbon dots (R-CDs) were synthesized by a facile hydrothermal method. Because the doping of N and S gives a unique functional group distribution on the surface of R-CDs, it can be complexed with Fe3+ ions to construct an energy transfer quenching system. However, the presence of l-Cys competitively binds to Fe3+ ions, thus resulting in the photoluminescence recovery of R-CDs. Therefore, a "switch-on" dual function sensing platform has successfully been developed based on R-CDs for rapid identification and quantification of Fe3+ ions and l-Cys. The linear detection range of Fe3+ ions is 0-30 ?M (limit of detection (LOD): 0.27 ?M) and that of l-Cys is 0-24 ?M (LOD: 0.14 ?M). The sensor platform was used to detect Fe3+ ions and l-Cys in human serum samples with satisfactory results. Compared with traditional detection methods, this method is more time-saving and efficient and can be completed in 3 min. It is worth mentioning that the R-CDs not only has high optical stability but also has negligible cytotoxicity and has been successfully applied to in vitro/vivo imaging, indicating that R-CDs have excellent tissue penetration and biomarker potential. More interestingly, the switch-on fluorescence behavior for stepwise detection of Fe3+ ions and l-Cys can also be observed in cell imaging, which provides the possibility of visual detection of the probe to be applied in vivo.
Project description:Biomass as sustainable and renewable resource has been one of the important energy sources for human life. Herein, luminescent nano-biomass dots (NBDs) have been extracted from soybean through ultrasonic method, which endows biomass with fluorescence property. The as-prepared NBDs are amorphous in structure with an average diameter of 2.4 nm and show bright blue fluorescence with a quantum yield of 16.7%. Benefiting from the edible raw materials and heating-free synthesis process, the cytotoxicity test shows that the cell viability still keeps 100% even if the concentration of the NBDs reaches 800 μg/ml, indicating the good biocompatibility of the NBDs. In addition, the fluorescence of the NBDs is very sensitive to Fe3+, which can be used for Fe3+ detection in terms of their health superiority. The limit of detection (LOD) of the proposed sensor was determined as 2.9 μM, which is lower than the maximum allowable level of Fe3+ (5.37 μM) in drinking water.
Project description:The current work deals with fabrication and validation of a new highly Fe3+ selective sensor based on benzo-18-crown-6 (b-18C6) using the potentiometric method. The proposed sensor revealed satisfactory performance for quantitative evaluation of Fe3+ trace amount in environmental samples. The ratio of membrane ingredients optimized and the membrane with the composition of 4:30:65.5:0.5 mg of b-18C6:PVC:o-NPOE:KTpClPB exhibited the desirable Nernstian slope of 19.51?±?0.10 (mV per decade of activity) over the pH range from 2.5 to 5.7 with an acceptable dynamic concentration range of 1.0?×?10-6 M to 1.0?×?10-1 M and lower detection limit of 8.0?×?10-7 M. The proposed sensor demonstrated an appropriate reproducibility with a rapid response time of 12 s and the suitable lifetime of 10 weeks. To validate the accurate response of the proposed sensor, AAS technique applied for the determination of Fe3+ in real aqueous mediums such as drinking tap water and hospital wastewater sample after treatment by electrocoagulation process. Theoretical studies carried out using DFT/B3LYP computational level with 6-311G basis set to optimize the adsorption sites of Fe+3 cationic species by b-18C6. The obtained adsorption energy with large negative value confirmed the formation of a stable complex.