A selective colorimetric chemosensor for detecting Ni(II) in aqueous solutions based on 4-[{[4-(3-chlorophenyl)-1,3-thiazol-2-yl]hydrazono}methyl]phenyl 4-methyl benzene sulfonate (CTHMBS)

Among the toxic heavy metals, Ni(II) can cause a variety of side effects on human health, such as allergy, cardiovascular and kidney diseases, lung fibrosis, lung, and nasal cancer. It is therefore critical from a public health and environmental perspective to determine and monitor Ni(II) ions in drinking water, foods, and environmental samples. In this study, a novel selective chemosensor (4-[{[4-(3-Chlorophenyl)-1,3-Thiazol-2-yl]Hydrazono}Methyl]phenyl4-methylBenzene Sulfonate (CTHMBS) was developed for the colorimetric detection of Ni(II) in aqueous medium. The presence of Ni(II) led to a distinct naked-eye color change from yellow to reddish-brown in aqueous solution. To examine the binding mechanism of CTHMBS to Ni(II), UV-vis spectroscopy analysis and DFT calculations were conducted. The detection limit of CTHMBS for Ni(II) was 11.87 µM, and the sensing ability of CTHMBS for Ni(II) was successfully carried out in real water samples.

Highly sensitive and specific detection of Ni2+ using a novel fluorometric probe in the DMSO-H2O system

The rapid detection of Ni ions has important research and application value. This paper presents a novel specific turn-off fluorescence probe PCTMP-FS for detecting Ni2+ ions. The carbazole-based compound PCTMP is first synthesized via a two-step reaction. PCTMP-FS comprises PCTMP dispersed into a DMSO-H2O (fw = 30% v/v) mixed solvent. The probe demonstrates prominent selectivity and anti-interference abilities for detecting Ni2+ with a limit of detection (LOD) of 0.233 μM. The probe exhibits good applicability over a wide range of acidities. The detecting mechanism of the probe is due to the complex formed by PCTMP and Ni2+ (2:1), which destroys intramolecular charge transfer in the compound. The probe has good repeatability and demonstrates excellent stability and sensitivity for the detection of Ni2+ in real water samples.

Solvent-regulated fluorescence off-on signaling of Ni(II) and Zn(II) with the formation of two mononuclear complexes with an ATP detection ability by Zn(II) assembly

The current study shows that Schiff base HL, (Z)-2,4-dibromo-6-(((piperidin-2-ylmethyl)imino)methyl)phenol, can be used successfully as a selective chemosensor for Zn(II) and Ni(II) among several competing cations in purely aqueous and semi-aqueous media. Under UV light in methanol-water (9 : 1) HEPES buffer, the receptor gives its response by changing its color to cyan color in the presence of Zn(II) and to bluish cyan color in the presence of Ni(II). Surprisingly, the chemosensor can only reliably identify Zn(II) in a hundred percent aqueous medium by changing its color to light yellow. UV and fluorescence studies in both aqueous and semi-aqueous media are used to further investigate this Zn(II) and Ni(II) recognition phenomenon. The high values of the host-guest binding constants, obtained by electronic and fluorescence titration, ensure that a strong bond exists between HL and Ni(II)/Zn(II). As anticipated, two highly luminescent mononuclear, crystalline compounds, complexes 1 and 2, have been developed by a separate reaction of HL and Zn(II)/Ni(II), and the high luminous properties are due to the occurrence of Chelation Enhanced Fluorescence (CHEF). According to the single crystal structure, the asymmetric units of both complexes consist of two deprotonated chemosensor units and one Zn(II)/Ni(II), leading to the formation of an octahedral complex. For Ni(II) and Zn(II) sensing, the predicted LOD is in the nanomolar range. Both complexes 1 and 2 are fluorescence active and studies to check their ATP detection ability, but intriguingly, only complex 2 is capable of detecting ATP in a fully aqueous solution. Finally, the live cell imaging study validates the two sensors' biosensing functionality.

Using Smartphone APP To Determine the CN- Concentration Quantitatively in Tap Water: Synthesis of the Naked-Eye Colorimetric Chemosensor for CN- and Ni2+ Based on Benzothiazole

A naked-eye colorimetric chemosensor DK based on benzothiazole could recognize CN^- effectively. When DK interacted with CN^- in the aqueous solution, the obvious color change of the solution was directly observed by the naked eye. Other anions did not cause any interference. It is interesting that DK could also discriminate Ni²⁺ from other cations, and the possible interaction mode between them was verified based on the Job's plot, ¹H nuclear magnetic resonance titration, infrared , electrospray ionization mass spectrometry, scanning electron microscopy analysis, and density functional theory calculation methods. As a result, it is clear that the mode of action between DK and CN^- was different from that between DK and Ni²⁺. Meanwhile, the limit of detection of DK toward CN^- and Ni²⁺ was calculated to be 1.7 × 10^-8 or 7.4 × 10^-9 M, respectively. In addition, CN^- was recognized qualitatively by a test paper and silica gel plates made from DK. DK was able to detect CN^- in tap water quantitatively, rapidly, and on-site by the use of a smartphone APP. All results implied that DK has certain prospects for practical application to identify CN^- in water.

A highly selective chromogenic sensor for Mn2+, turn-off fluorometric for Hg2+ ion, and turn-on fluorogenic sensor for F- ion with the practical application

A colorimetric and fluorometric probe (E)-2-((8-hydroxy-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-9-yl)methylene)hydrazinecarbothioamide based on thiosemicarbazide and julolidine moieties has been synthesised in pure crystalline form and characterized by ¹H NMR, UV-vis, elemental analysis and single crystal XRD. The probe functioned as multitarget ion sensor, detect biologically important metal ions Hg²⁺ and Mn²⁺ in dual channel mode. Meanwhile, in mixed solvent media DMF/H₂O [8:2], probe displayed selectivity for Hg²⁺ over other cations by the emission spectrum. Interestingly probe has been explored to recognize F^- anion in DMF through ESIPT mechanism. The 1:1 binding stoichiometry of probe with Hg²⁺ and Mn²⁺ is confirmed by Job's plot through emission titration and UV-vis titration respectively. Probe is selective and sensitive to Hg²⁺ and Mn²⁺ with detection limit as low as 15μM and 0.2μM respectively. The sensing mechanism for selective ions was also scrutinized using ¹H NMR experiments and computational studies.

Fluorescent sensor for Al3+ ion in partially aqueous media using julolidine based probe

A novel chemosensor was synthesised and used as a selective fluorescent sensor for aluminium ions.