Unusual Specificity of a Receptor for Nd3+ Among Other Lanthanide Ions for Selective Colorimetric Recognition

Colorimetric recognition of lanthanide ions with a complexometric indicator array

A colorimetric sensor array based on complexometric indicators is proposed for pattern recognition of lanthanide ions. The complexometric indicators have abundant functional groups and can act as a platform for chromogenic reaction with various metal ions, including lanthanide ions. The subtle difference of the lanthanide ions' structure results in the difference of absorbance response between lanthanide ions and two chromogenic indicators (Alizarin Red and Erichrome Black T) in Tris-HCl buffer with two different pHs (i.e., pH 7.4 and pH 8.5, colorimetric sensor array). Fourteen lanthanide ions were distinguished well with the newly designed colorimetric sensor array. The sensor array has the potential to distinguish between different concentrations of lanthanide ions and their mixtures. Moreover, the results in actual samples indicate the future practical applications of this sensor array in environmental analysis.

Naked eye detection of moisture in organic solvents and development of alginate polymer beads and test cassettes as a portable kit

New dabsyl-thiophene based receptor DABT and its mercury complex DABT-Hg is reported as a colorimetric sensor for rapid and sensitive detection of trace amount of water in aprotic solvents. Based on intramolecular charge transfer in the excited state, the receptor dabsyl-thiophene (yellow color) binds with the mercury ions (magenta color) to stimulate a colorimetric response. The mercury complex is used as a moisture sensor in THF, acetone, and acetonitrile due to its instability in moisture containing organic solvents. The probe exhibits higher sensitivity towards water in THF (LOD = 0.0041% w/w), acetone (LOD = 0.0144% w/w) and acetonitrile (LOD = 0.1008% w/w). The dissociation of mercury from probe DABT-Hg in the presence of water is accountable for the colorimetric response as proven by the ¹H NMR and ESI-MS studies. DABT-Hg is the first mercury based complex for the detection of moisture in organic solvents. Test paper strip and PVA thin film doped with the probe were successfully used to detect moisture content in organic solvents. DABT-Hg incorporated alginate beads are prepared to determine the water content in triethylamine and ethylene glycol. Portable test cassettes are developed for the on-site detection of distilled and undistilled wet solvents in the chemical laboratory through naked-eye detection.

Oxidative cyclization of thiosemicarbazide: a chemodosimetric approach for the highly selective fluorescence detection of cerium(iv)

A simple thiosemicarbazide-based chemodosimeter was employed to detect Ce⁴⁺ ion through turn-on fluorescence.

Photochromic Lanthanide(III) Materials with Ion Sensing Based on Pyridinium Tetrazolate Zwitterion

Lanthanide(III) ion (Ln(III)) sensing has become a major research area owing to its intriguing prospect in clinic, biology, and environmental studies. However, the existing methods have limitations like requirement of expensive instrumentation, long analytical times, and sample pretreatments, revealing the necessity of other methods. In this work, by using N-methyl-4-pyridinium tetrazolate (mptz) zwitterion as an electron acceptor, we obtained several new Ln(III) compounds with electron-transfer (ET) photochromic properties: [Ln(NO₃)₃(H₂O)₄]·mptz [Ln = Sm (1), Eu (2), Gd (3), La (4), Ce (5), Pr (6), Nd (7), Tb (8), Dy (9), Ho (10), Er (11), Tm (12), Yb (13), Lu (14)]. Notably, different Ln(III) ions in these compounds can be visually identified by their different photoinduced color changes related to the ET process. This work may not only contribute to the more understanding of the structure-photosensitivity relationships of pyridinium-based compounds, but also provide a new approach for Ln(III) ion sensing.

A Minimalist Approach for Distinguishing Individual Lanthanide Ions Using Multivariate Pattern Analysis

To discriminate among the 14 trivalent lanthanide ions, curcumin, a naturally occurring, nontoxic, off-the-shelf, commercially available compound containing a single fluorophore, was chosen as a probe in the water media at pH 6.8 and pH 8.2. By measuring the emission and absorption spectra of the probe, under the different pH conditions, and by performing linear discriminant analysis on the data, 14 Ln³⁺ ions were discriminated. Additionally, an easy tool for the nonspecialists was developed with easily available household substances, using a smartphone app, which added an extra advantage to this single probe. This probe possesses advantageous features in terms of low-cost and instant on-site detection of the lanthanide ions.

Thenoyltrifluoroacetone (TTA)-Carbon Dot/Aerogel Fluorescent Sensor for Lanthanide and Actinide Ions

Contamination of groundwater with radioactive substances comprising actinides and lanthanides is a significant environmental hazard and thus the development of selective, sensitive, and easy-to-apply sensors for water-soluble actinide and lanthanide ions is highly sought. We constructed a new selective fluorescent sensor for UO2 2+, Sm3+, and Eu3+ based on a carbon dot (C-dot)-aerogel hybrid prepared through in situ carbonization of 2-thenoyltrifluoroacetone (TTA), a high-affinity heavy metal chelator. The TTA-C-dot-aerogel enabled the detection of UO2 2+ ions, which induced a significant red fluorescence shift, whereas Eu3+ and particularly Sm3+ ions gave rise to pronounced fluorescence quenching. Importantly, the lanthanide/actinide ion-selective TTA-C-dots could be synthesized only in situ inside the aerogel pores, indicating the crucial role of the aerogel host matrix both in enabling the formation of the C-dots and in promoting the adsorption and interactions of the lanthanide and actinide metal ions with the embedded C-dots.

Highly selective colorimetric bacteria sensing based on protein-capped nanoparticles

A rapid and cost effective colorimetric sensor has been developed for the detection of bacteria, and Bacillus subtilis was selected as an example to demonstrate the feasibility of the sensing system.

Bispyrene/surfactant-assembly-based fluorescent sensor array for discriminating lanthanide ions in aqueous solution

Lanthanides are valuable nonrenewable resources and widely used in a variety of industries. Detection and identification of lanthanide ions are in high demand but challenging because of the similarity among lanthanide ions. In the present work, a fluorescent sensor array of three cationic bispyrene derivatives mixed with anionic surfactant assemblies was developed. The sensor array exhibits cross-reactive responses to lanthanide ions when tested in aqueous solution. The combination of fluorescence variations at both monomer and excimer emission of each of the bispyrene sensor elements provides a six-signal recognition pattern for lanthanide ions. Principle component analysis illustrates that the sensor array could at least identify 6 of the 14 similar lanthanide ions including La(3+), Pr(3+), Nd(3+), Eu(3+), Ho(3+), and Er(3+). UV-vis absorption measurements rule out the possibility of binding lanthanides with fluorophores. Fluorescence titration experiments in both cationic and neutral surfactant aqueous solutions reveal that the three fluorophores show slight fluorescence responses to the lanthanide ions, indicating that electrostatic attraction between lanthanide ions and anionic surfactant plays an important role in the sensing behavior of the sensor array. Control experiments with divalent metal ions find no cross-reactive responses, suggesting that the stronger electrostatic interaction with trivalent lanthanide ions is responsible for the multiple fluorescence responses.

Zn(II)-cyclam based chromogenic sensors for recognition of ATP in aqueous solution under physiological conditions and their application as viable staining agents for microorganism

Two chromogenic complexes, L.Zn (where L is (E)-4-((4-(1,4,8,11-tetraazacyclotetradecan-1-ylsulfonyl)phenyl)diazenyl)-N,N-dimethylaniline) and its [2]pseudorotaxane form (α-CD.L.Zn), were found to bind preferentially to adenosine triphosphate (ATP), among all other common anions and biologically important phosphate (AMP, ADP, pyrophosphate, and phosphate) ions in aqueous HEPES buffer medium of pH 7.2. Studies with live cell cultures of prokaryotic microbes revealed that binding of these two reagents to intercellular ATP, produced in situ, could be used in delineating the gram-positive and the gram-negative bacteria. More importantly, these dyes were found to be nontoxic to living microbes (eukaryotes and prokaryotes) and could be used for studying the cell growth dynamics. Binding to these two viable staining agents to intercellular ATP was also confirmed by spectroscopic studies on cell growth in the presence of different respiratory inhibitors that influence the intercellular ATP generation.