A colorimetric chemosensor for quantification of exchangeable Cu2+ in soil.

Chemosensors have already demonstrated potential for the detection and imaging of metal ions in solutions and biological systems, however, their applications to soil analysis are limited. This study explores the potential of utilizing a chemosensor for the detection of exchangeable Cu2+ in soils via qualitative (solution visual color change) and quantitative (UV-Vis spectrophotometry) approaches. Montmorillonite and kaolin clays were doped with Cu(NO3)2 solutions from 2.5 to 50 mM, and contaminated soil samples were collected from a historic copper mine. The exchangeable Cu2+ was extracted using a standard CaCl2 cation exchange approach, and the Cu2+ concentration in the resulting solutions determined by UV-Vis spectrophotometry, using a chemosensor, and compared to traditional ICP-MS analysis. Analytical results showed that the chemosensor provided a visual response in contaminated soils at concentrations of 25 µM and quantitative detection to concentrations of 1 µM using UV-Vis spectrophotometry. This work demonstrates the first reported chemosensor for exchangeable Cu2+ with application to soil systems.

Geochemical signature of urbanisation in Blue Mountains Upland Swamps.

Urbanisation leaves a geochemical signature on the environment, as weathering of urban materials such as concrete contributes to elevated levels of major ions including calcium, bicarbonate and potassium. However, there is limited research that addresses the ecological consequences of this signature on the biotic community. Blue Mountains Upland Swamps (BMUS), an endangered ecological community with high conservation values, are vulnerable to urban degradation. Chemical properties of water, sediment and foliage from native and exotic species were assessed within two urbanised and two naturally vegetated swamp catchments. Water in urban swamps exhibited elevated pH and electrical conductivity. Non-urban swamps were sodium and chloride dominated, with higher calcium and bicarbonate in urban swamps. Water from urban swamps also exhibited 32 times higher levels of strontium. Calcium concentrations were elevated by 14 times in urban swamp sediment. Foliage from urban catchments exhibited six times greater potassium, and three times higher calcium and bicarbonate compared to foliage in non-urban catchments. Calcium, bicarbonate, potassium and strontium were key parameters that were enriched in the urbanised swamps. However, the ecological implications of these findings for urban wetland communities, including BMUS, remain unclear. Interestingly, the chemical signature of water did not fully represent the signatures of sediment and foliage, highlighting the need to further explore sources and forms of major ions within these ecosystems, particularly in sediment. In an increasingly urban world, enhancing knowledge of drivers of change in endangered ecosystems such as BMUS is crucial to promote conservation and guide the development of sustainable management practices.

Ultrasensitive Colorimetric and Ratiometric Detection of Cu2+: Acid-Base Properties, Complexation, and Binding Studies.

Herein, we report the synthesis and characterization of a chemosensor, 5-(diethylamino)-2-(2,3-dihydro-1H-perimidin-2-yl)phenol (HL), synthesized from a condensation between 4-(diethylamino)salicylaldehyde and 1,8-diaminonaphthalene. Upon investigation of the sensing properties of HL, it was found that this sensor may be employed for simple yet efficient detection of Cu2+ in aqueous methanol solutions. The selective and ratiometric response to Cu2+ yielded an outstandingly low limit of detection of 3.7 nM by spectrophotometry and is also useful as a naked-eye sensor from 2.5 µM. The system was studied by spectrophotometric pH titrations to determine Cu2+ binding constants and complex speciation. Binding of Cu2+ to HL occurs in 1:1 stoichiometry, in good agreement with high-resolution electrospray ionization mass spectrometry (ESI-HRMS) results, Cu2+ titrations, and Job's plot experiments, while the coordination geometry was tentatively assigned as square pyramidal by spectroscopic studies.

Self-assembly of an imidazolate-bridged Fe(III)/Cu(II) heterometallic cage.

A rare, discrete, mixed-valent, heterometallic Fe(III)/Cu(II) cage, [Cu6Fe8L8](ClO4)12·χsolvent (H3L = tris{[2-{(imidazole-4-yl)methylidene}amino]ethyl}amine), was designed and synthesized via metal-ion-directed self-assembly with neutral tripodal metalloligands. The formation of this coordination cage was demonstrated by X-ray crystallography, ESI mass spectrometry, FT-IR, and UV-vis-NIR spectroscopy.