A highly selective ratiometric fluorescent sensor for Hg2+ based on 1,8‐naphthalimide

A sulfur probe based on 1,8‐naphthalimide was designed and synthesised, and its sensing behaviour towards a mercury ion was investigated by fluorescence spectroscopy. The probe showed higher selective recognition towards Hg²⁺ than towards other metal ions in methanol solution. Compared with 4‐amino‐substituted naphthalimide derivatives, the probe exhibited different fluorescent characteristics for sensing Hg²⁺. The novel, reaction‐based probe is recommended for selective recognition of Hg²⁺ with significant fluorescence change.     

A highly selective turn-on sensor for Hg2 + based on a phosphorescent iridium (III) complex

A highly selective phosphorescent chemosensor for Hg^2 + based on the iridium (III) complex Ir(DTBT)₂(acac) (DTBT = 2-(5-(1,2 dihydroacenaphthylen-5-yl)thiophen-2-yl)benzothiazole, acac = acetylacetone) was synthesized and characterized. Ir(DTBT)₂(acac) exhibited relatively weak fluorescenceat at about 700 nm. Ir(DTBT)₂(acac) displayed a dramatic color change from near-infrared to yellow-green with the addition of Hg^2 +. More significantly, the chemosensor performed “turn-on” phosphorescent responses toward Hg^2 +.     

Highly luminescent Ag+ nanoclusters for Hg2+ ion detection

A simple, low-cost and label-free Hg(2+) ion sensor has been developed by using novel luminescent Ag(+) nanoclusters (NCs) with an excellent optical property (quantum yield = 15%), an ultra-high ratio of active Ag(+) species in the NC surface (~100%), and an ultra-short diffusion path length of Hg(2+) ions to access the NC surface (~0.5 nm).     

A colorimetric sensor for Fe2 + ion

A simple Schiff-based receptor 1 was synthesized and investigated its binding properties toward various metal ions in polar solvent (MeOH). Receptor 1 showed a dramatic color change from colorless to black which could easily be detected by the naked-eye upon binding with Fe^2 +.     

Synthesis of Starch-Stabilized Ag Nanoparticles and Hg2+ Recognition in Aqueous Media

The starch-stabilized Ag nanoparticles were successfully synthesized via a reduction approach and characterized with SPR UV/Vis spectroscopy, TEM, and HRTEM. By utilizing the redox reaction between Ag nanoparticles and Hg²⁺, and the resulted decrease in UV/Vis signal, we develop a colorimetric method for detection of Hg²⁺ ion. A linear relationship stands between the absorbance intensity of the Ag nanoparticles and the concentration of Hg²⁺ ion over the range from 10 ppb to 1 ppm at the absorption of 390 nm. The detection limit for Hg²⁺ ions in homogeneous aqueous solutions is estimated to be ~5 ppb. This system shows excellent selectivity for Hg²⁺ over other metal ions including Na⁺, K⁺, Ba²⁺, Mg²⁺, Ca²⁺, Fe³⁺, and Cd²⁺. The results shown herein have potential implications in the development of new colorimetric sensors for easy and selective detection and monitoring of mercuric ions in aqueous solutions.     

A highly selective and sensitive benzothiazole‐based ‘turn‐on’ fluorescent sensor for Hg2+ ion

A simple benzothiazole‐based fluorescent probe (TDA) for the determination of Hg²⁺ ion in aqueous solutions was synthesised in one step and characterised by ¹H NMR, ¹³C NMR, APT, COSY, FTIR, and elemental analysis. TDA shows a significant fluorescence change upon the interaction of Hg²⁺ ion in DMF–water (v/v = 1/1), while only minor changes in fluorescence intensity are observed with 18 other metal ions. Fluorescence enhancement by a factor of 15 is achieved upon selective interaction with Hg²⁺ ion. The Hg²⁺ ion detection process is found to be pH dependent; therefore, TDA could be feasible within a pH range of 4.0–7.0.     

A selective sulphur‐containing colorimetric chemosensor for Cu2+

A highly selective sulphur‐containing colorimetric chemosensor APTS ((E)‐2‐(tert‐butyl)‐6‐(((2‐(phenylthio)phenyl)imino)methyl)phenol) was synthesised for detecting Cu²⁺. APTS showed a clear colour change from colourless to yellow with Cu²⁺. The detection limit of APTS for Cu²⁺ was 0.52 μmol/L. APTS could also be used as a test strip for detecting Cu²⁺. To understand the binding mode of APTS with Cu²⁺, ultraviolet‐visible spectroscopy and electrospray ionisation‐mass spectrometry analyses were conducted. The sensing mechanism of sensor APTS towards Cu²⁺ was proposed to be the combination of intramolecular charge transfer and ligand‐to‐metal charge‐transfer through theoretical calculations.     

Two-photon ratiometric sensing of Hg2+ by using cysteine functionalized Ag nanoparticles

We have demonstrated a novel two-photon sensing strategy to detect mercury ions with high selectivity and sensitivity. This sensing approach is based on the observation that addition of Hg(2+) into a cysteine functionalized Ag nanoparticle solution could significantly enhance their two-photon emission. An enhancement factor of up to 100 fold was obtained when mercury was added. A detection limit of as low as 65 nM could be achieved. The sensitivity and sensing range can be easily tuned. Compared to the conventional colorimetric or extinction spectrum based methods, this scheme offers improved sensitivity, quantitative detection of Hg(2+) with a larger dynamic range, and allows detection deep into biological environments such as cells and tissues where deep penetration is required. The sensitivity could be further improved by using two-photon microscopy with the additional advantages of 3D detection and mapping.     

A polyamidoamine dendrimer as a selective colorimetric and ratiometric fluorescent sensor for Li+ cations in alkali media

In a DMF + NaOH medium, a polyamidoamine dendrimer having sixteen 1,8-naphthalimide fragments in its periphery, formed a complex only with Li⁺ ions, detected by a colour change from red to yellow and by a significant increase in fluorescence intensity. The dendrimer can be used as a selective sensor for Li⁺ ions in the presence of other alkali ions such as Na⁺ or K⁺.     

Conformation-switched chemosensor for selective detection of Hg2+ in aqueous media

A conformation flexible chemosensor for selective detection of Hg²⁺ in aqueous media was achieved by incorporating two well-known rhodamine-6G dyes and a ferrocene group within one molecule. Distinguished from the monosubstituted ferrocene derivative which is previously reported a lack of interaction with Hg²⁺, the title compound was characteristic of two-armed bidendate binding unit. The Hg²⁺ sensing behavior can be switched via the conformation flexibility. The 1:1 sensor/Hg²⁺ binding mode was proposed and supported by the titration experiment and ESI mass spectrum. The fluorescent sensor can display a highly selective response of fluorescence enhancement toward Hg²⁺ and detect the parts per billion (ppb) level of Hg²⁺ in aqueous environment.     

A highly selective fluorescent sensor for Hg based on the water-soluble poly(p-phenyleneethynylene)

The conjugated polymer P-1 could be synthesized by the polymerization of 4,7-diethynyl-benzo[2,1,3]thiadiazole (M-1) and 1,4-bis[3′-(N,N-diethylamino)-1′-oxapropyl]-2,5-diiodobenzene (M-2) via Pd-catalyzed Sonogashira reaction. The water-soluble conjugated polyelectrolyte P-2 could be obtained by the reaction of P-1 with ethyl bromide. Both P-1 and P-2 can emit orange fluorescence. The responsive optical properties of P-1 and P-2 on Hg²⁺ were investigated by fluorescence spectra. Hg²⁺ can lead to nearly complete fluorescence quenching of P-1. On the contrary, Hg²⁺ can show the most pronounced fluorescence enhancement response of P-2 in aqueous solution without interference from those coexistent ions, such as K⁺, Mg²⁺, Pb²⁺, Co²⁺, Ni²⁺, Ag⁺, Cd²⁺, Cu²⁺, Fe³⁺ and Zn²⁺. The results also exhibit that this kind of water-soluble conjugated polyelectrolyte can be used as a highly sensitive and selective fluorescence sensor for Hg²⁺ detection in water.     

Highly sensitive C2H2 gas sensor based on Ag modified ZnO nanorods

The sliver (Ag) modified zinc oxide (ZnO) nanorods were successfully obtained with a simplified and environmentally friendly solvothermal method. Materials characterization indicated that the metallic Ag was located on the outside of ZnO nanorods after annealing. In comparison with ZnO nanorods, Ag modified ZnO (Ag–ZnO) nanorods exhibited a considerably enhanced response to C₂H₂. The response of the 3 at% Ag–ZnO based sensor operating at 175 °C is 539 (R_a/R_g), which is the highest value among all the sensors in detecting 100 ppm C₂H₂. The Ag–ZnO based sensors exhibited fast response speed, lower operation temperature and higher selectivity.     

Synthesis and application of ion‐imprinted resin based on modified melamine–thiourea for selective removal of Hg(II)

A novel Hg(II) ion‐imprinted resin based on thiourea‐modified melamine was manufactured for selective elimination of Hg²⁺ from aqueous solutions. The polymerizable thiourea–melamine ligand together with its Hg(II) complex were extensively investigated using elemental analysis, Fourier transform infrared (FTIR) and ¹H NMR spectroscopies. The Hg(II) complex was used in a condensation polymerization in the presence of formaldehyde crosslinker and then the Hg(II) ions were leached out from the crosslinked polymeric network to finally leave the ion‐imprinted Hg‐PMTF resin. Both ion‐imprinted Hg‐PMTF and non‐imprinted resins were examined utilizing scanning electron microscopy and FTIR spectroscopy. The potential of the prepared resin for selective separation of Hg(II) ions from aqueous solutions was then evaluated by performing a series of batch experiments. Hg‐PMTF displayed an obvious rapid removal of Hg(II) ions with a pseudo‐second‐order kinetic pattern. In addition, the Langmuir adsorption isotherm model exhibited the best fit with the experimental data with comparatively high maximum adsorption capacity (360.5 mg g^?1). © 2015 Society of Chemical Industry     

Design and production of Hg0 calibrator,Hg2+ calibrator,and Hg2+ to Hg0 converter for a continuous Hg emission monitor

Hg calibration and conversion systems, which are integral parts of a continuous emission monitor for were designed, produced, and tested. First, both Hg⁰ and Hg²⁺ calibrators showed less than 10% difference between measured and theoretical values. Next, a Hg²⁺ to Hg⁰ thermal converter with a scrubber and heated gas lines showed a conversion efficiency higher than 95%. Finally, the laboratory-prepared Hg converter was tested at a full-scale medical waste incinerator. The Ontario Hydro Method was used for measurement and speciation of Hg. The results showed that the laboratory-prepared Hg converter was highly effective with highest conversion efficiency close to 94%.     

Highly sensitive colorimetric phosphorescent chemodosimeter for Hg2 + based iridium(III) complex with (Ph2PS)2N auxiliary ligand

A colorimetric phosphorescent iridium(III) complex chemodosimeter (Ir1) for Hg^2 + has been prepared and confirmed by NMR, MS, and crystal data, which displays a high selectivity and antidisturbance for Hg^2 + detection among relevant metal ions. Phosphorescent studies show that the luminescence intensity at 598 nm decreased to ca. 12%, while the luminescence intensity in 441 nm increased to ca. 195%. The ratio of Ir1 responding to Hg^2 + was determined to be 1:1 by UV–vis absorption and phosphorescent emission measurements. Further study demonstrates that the detection limit on phosphorescent response of the sensor to Hg^2 + is down to 10^− 6 M range. The mechanism study shows that the interaction between the S atom of ancillary ligand and Hg^2 + is responsible for the highly selective and sensitive phosphorescent senor for Hg^2 +.     

A NBD-based highly sensitive and selective colorimetric chemosensor for Ni2 + and Cu2 +

A new colorimetric chemosensor 1, containing the 7-nitrobenzo-2-oxo-1,3-diazolyl (NBD) moiety and the phenol one connected through Schiff-base linkage, has been synthesized. Sensor 1 showed remarkable color changes from pink to orange and pale brown, respectively, upon selective binding to Ni^2 + and Cu^2 + that can be identified by the naked-eye. The binding modes of sensor 1 to Ni^2 + and Cu^2 + were determined to be 1:1 stoichiometries using a Job plot and ESI-mass analysis. The sensor 1 showed high sensitivity toward Ni^2 + and Cu^2 + with the detection limits of 0.48 μM and 0.26 μM, respectively. The recognition properties of the sensor 1 toward Ni^2 + and Cu^2 + were explained by using photophysical experiments and theoretical calculations. Practically, sensor 1 functioned as a visible test strip for Ni^2 + and Cu^2 +.     

A fluorescein derivative FLTC as a chemosensor for Hg2 + and Ag+ and its application in living-cell imaging

FLTC was synthesized and used as a fluorescent chemosensor to detect Hg^2 +. It showed high selectivity toward Hg^2 + over many heavy metal ions in an ethanol–H₂O (3:2, v/v, HEPES buffer, 0.5 mM, pH 7.15) solution with a detection limit of 0.21 μM. After complexation with Hg^2 +, FLTC showed extremely high selectivity toward Ag⁺ with a detection limit of 0.009 μM. Therefore, detection of Hg^2 + and Ag⁺ could be realized using FLTC and the FLTC–Hg^2 + complex, respectively. Cytotoxicity assays and fluorescence microscopy analysis showed that FLTC could be used as a fluorescent probe to detect Hg^2 + and Ag⁺ in L-02 human liver cells.     

一种新型耐尔蓝衍生物的合成及其对Hg~(2+)识别研究

设计合成了一种新型耐尔蓝衍生物2-{9-(二甲基氨基)-10-甲基-9H-苯并[a]吩嗪-5-羰基}-N-苯基肼硫代酰胺盐酸盐(EPNH),其结构得到了1HNMR、ESI-MS和元素分析的确认。实验结果表明,该化合物在p H 7.4的HEPES缓冲液中,对Hg2+表现出高选择性和高灵敏度的荧光和显色传感;当Hg2+浓度在0.02~0.25μmol/L范围内时,线性相关系数R=0.997 7,最低检出限为0.01μmol/L(n=6)。     

Dual-emission carbon dots-copper nanoclusters ratiometric photoluminescent nano-composites for highly sensitive and selective detection of Hg2+

A novel dual-emission photoluminescent (PL) nano-materials of carbon dots-copper nanoclusters (CDs-CuNCs) nano-composites is prepared for excellent sensitivity and selectivity toward Hg²⁺. The nano-composites are composed of blue photoluminescent CDs and red photoluminescent CuNCs with similar excitation wavelengths through the electrostatic assembly. The red photoluminescence of CuNCs was inhibited by the nano-composites exposed to Hg²⁺, while the blue photoluminescence of CDs remained stable. The color of the nano-composites slowly changed from pink to blue with the added of Hg²⁺ concentration. The limit of detection (LOD) of the nano-composites is 0.31 nmol/L (nM) toward Hg²⁺ in aqueous solution, when the signal to noise ratio is 3. In addition, a visual PL test paper is prepared. When the Hg²⁺ solution is added, the color of test paper transforms from pink to blue immediately. Therefore, the nano-composites are very important for efficient and sensitive detection of Hg²⁺, which show broad application prospects in environmental analysis, food safety detection, biological detection and medical diagnosis in daily life.